UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Electrospinning of lignin based composite nanofibres with nanocrystalline cellulose Cho, Mijung 2018

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
24-ubc_2018_may_cho_mijung.pdf [ 6.54MB ]
Metadata
JSON: 24-1.0364563.json
JSON-LD: 24-1.0364563-ld.json
RDF/XML (Pretty): 24-1.0364563-rdf.xml
RDF/JSON: 24-1.0364563-rdf.json
Turtle: 24-1.0364563-turtle.txt
N-Triples: 24-1.0364563-rdf-ntriples.txt
Original Record: 24-1.0364563-source.json
Full Text
24-1.0364563-fulltext.txt
Citation
24-1.0364563.ris

Full Text

ELECTROSPINNING OF LIGNIN BASED COMPOSITE NANOFIBRES WITH NANOCRYSTALLINE CELLULOSES by  Mijung Cho    A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Forestry)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)   March 2018  © Mijung Cho, 2018 ii  Abstract In this study, composite nanofibres were fabricated from solvent fractionated softwood kraft lignin (SKL), NCC and polyethylene oxide (PEO) by electrospinning. The molecular organization of lignin was investigated in the form of spun fibres and films with and without NCC. Subsequently, the as-spun composite nanofibre mats were thermally stabilized in the air under controlled conditions. The chemical and mechanical properties were studied as a function of the processing conditions. The oxidized nanofibres were then carbonized at 1000 ºC in inert nitrogen atmospheres. The responses investigated include changes in yield, diameter/distribution of nanofibres, thermal stability, elemental composition, the molecular structure and mechanical properties. Lastly, effects of NCCs on lignin structure in the fibres at different stages of heat treatments were determined.   Lignin molecules demonstrated organization within aligned electrospun fibres and within solvent cast lignin films. The nanofibres and films of lignin with and without NCC had birefringence as revealed with polarized optical microscope.  Also, through heat treatment, the lignin-based nanofibres mats with or without NCC, showed improved mechanical and thermal-chemical properties after thermal stabilization and carbonization processes. Specifically the properties of thermally stabilized samples were more variable than carbonized samples. Furthermore, NCC loadings gave a significant reduction in mobility of lignin molecules during heat treatment allowing for direct carbonization for lignin carbon fibres production with NCC loadings for 5 wt.%. NCC overall did not enhance the mechanical properties of the electrospun fibre. However significant interactions between the NCC and lignin were revealed with FTIR spectroscopy and thermal rheological analysis.       iii  In summary, the work investigated how thermal treatments can enhance the performance of lignin-based materials and further enhanced by the presence of nanofillers. This study investigated extensively the effect of NCC in lignin-based composite nanofibres through fundamental understanding of the interaction between lignin and NCC during the different heat treatment stages for carbon fibre production.          iv  Lay Summary Carbon fibres can be extremely lightweight and strong materials to replace metal alloys. The demand for carbon fibres is expected to increase over the next 5 years for the next decade to a market of 200 % due to its versatile applications from vehicles to electrodes. It is highly encouraged to develop carbon fibres with low cost and non-toxic precursor to expanding the use of carbon fibres. Lignin is a co-product of pulp and paper industry nowadays and has been seriously considered as an alternative precursor material to replace current petroleum-based precursor materials. In this research, lignin-based composite carbon nanofibres mats were studied with nanocrystalline cellulose (NCC) as reinforcement to improve physical and chemical properties of nanocomposite system. Here, this study highlighted the effect of NCC in lignin-based composite nanofibres through extensive fundamental understanding of the interaction between lignin and NCC within fibres during the different heat treatment stages for carbon fibre production.         v  Preface I did most of the experimental work for chapter 4 and Dr.Hee-Jae Yang in Advanced Fibrous Materials Lab., helped me to operate the polarized optical microscope. A version of chapter 5 and 6 published in Journal of Materials Science (Mijung Cho, Muzaffer Karaaslan, Scott Renneckar and Frank Ko, J.Mat.Sci.,2017, 52(16), 9602-9614). I conducted all experimental work, analyzing data and wrote the manuscript. Prof. Scott Renneckar and Dr.Muzaffer Karaaslan gave valuable comments and corrections to improve the manuscripts.    In Chapter 7, Dr. Andrew Lewis at Simon Fraser University (SFU) run 13C solid-state NMR. I did most other of experimental work and analysis data in Chapter 7. Also, this chapter has been prepared for publication (Mijung Cho, Frank Ko and Scott Renneckar, 2018).      Chapter 8 has been submitted for publication (Mijung Cho, Muzaffer Karaaslan, Sudip Chowdhury, Frank Ko and Scott Renneckar, ACS Sustainable Chemistry & Engineering.,2018). I did most of the experimental work and analysis data. Dr. Muzaffer Karaaslan helped to operate the rheometer (AR2000) for the thermo-rheological analysis for section 8.3. Dr.Sudip Chowdhury helped to describe data for section 8.3 and the manuscript. Prof. Scott Renneckar and Dr. Muzaffer Karaaslan gave the advice to modify the manuscript.   vi  Table of Contents Abstract .......................................................................................................................................... ii Lay Summary ............................................................................................................................... iv Preface .............................................................................................................................................v Table of Contents ......................................................................................................................... vi List of Tables ................................................................................................................................ xi List of Figures ............................................................................................................................. xiii List of Symbols and Abbreviations .......................................................................................... xxi Acknowledgements ................................................................................................................... xxii Dedication ................................................................................................................................. xxiii Chapter 1: Introduction ................................................................................................................1 1.1 Lignin .............................................................................................................................. 1 1.1.1 Lignin biosynthesis and structure ............................................................................... 1 1.1.2 Delignification and recovery lignins from black liquor .............................................. 4 1.1.2.1 Kraft lignin ...................................................................................................... 5 1.1.2.2 Lignosulfonates ............................................................................................... 6 1.1.2.3 Alkali (soda) lignin ......................................................................................... 6 1.1.2.4 Organosolv lignin............................................................................................ 7 1.1.3 Additional fractionation process for narrowing polydispersity of lignin.................... 7 1.1.3.1 Organic solvent fractionation .......................................................................... 8 1.1.4 Utilization of lignin ................................................................................................... 13 1.1.5 Lignin based carbon fibres (LCFs) ........................................................................... 13 1.2 Carbon fibres ................................................................................................................. 21 vii  1.2.1 Markets for carbon fibres .......................................................................................... 21 1.2.2 Spinning technique.................................................................................................... 24 1.2.2.1 Melt spinning ................................................................................................ 24 1.2.2.2 Dry spinning.................................................................................................. 25 1.2.2.3 Wet spinning ................................................................................................. 25 1.2.2.4 Jet spinning ................................................................................................... 26 1.2.2.5 Electrospinning ............................................................................................. 26 1.2.3 Stabilization process ................................................................................................. 30 1.2.4 Carbonization process ............................................................................................... 32 1.3 Nanocrystalline Cellulose (NCCs) ................................................................................ 32 1.3.1 Nanocomposites reinforced with NCCs.................................................................... 34 1.3.2 Electrospun composite nanofibres reinforced with NCCs ........................................ 36 Chapter 2: Hypothesis and objectives ........................................................................................40 Chapter 3: Materials and experimental methods .....................................................................44 3.1 Materials ....................................................................................................................... 44 3.2 Statistical analysis of the data ....................................................................................... 44 3.3 Organic solvent fractionation of softwood kraft lignin (SKL) ..................................... 44 3.4 Isolation of nanocrstalline celluloses (NCCs)............................................................... 45 3.4.1 Atomic force microscopy (AFM) of nanocrystalline cellulose (NCCs) ................... 46 3.5 Preparation of lignin-NCC-PEO solutions for electrospinning .................................... 46 3.6 Electrospinning of lignin-PEO solutions with various NCC loadings for random fibre mats …………………………………………………………………………………………47 3.7 Electrospinning of lignin-PEO solutions for aligned fibres .......................................... 47 3.8 Oxidative stabilization process of as spun lignin composite fibre mats ....................... 47 3.9 Carbonization process of stabilized lignin composite fibre mats ................................. 48 3.10 Characterization of electrospun lignin composite fibre mats ....................................... 48 viii  3.10.1 Scanning electron microscopy of as spun, stabilized and carbonized composite fibres ……………………………………………………………………………………48 3.10.2 Polarized optical microscopy of aligned lignin fibres .......................................... 48 3.10.3 Thermal analysis of as spun and stabilized composite fibres mats ....................... 49 3.10.4 Molecular structure analysis of composite fibres ................................................. 49 3.10.4.1 Fourier-transform infrared (FTIR) spectroscopy of as spun and stabilized composite fibres ................................................................................................................ 49 3.10.4.2 Polarized fourier-transform infrared (FTIR) spectroscopy of aligned fibres 50 3.10.4.3 Characterization of stabilized composite fibres after various treatment conditions by solid state 13C nuclear magnetic resonance (NMR) spectroscopy ............. 50 3.10.5 Elemental analysis for stabilized and carbonized composite fibres after various treatment conditions .............................................................................................................. 51 3.10.6 Thermorheological analysis of as spun composite fibre mats with NCCs loadings ………………………………………………………………………………………………51 3.10.7 Tensile properties of as spun, stabilized and carbonized composite fibres mats .. 51 3.10.8 Characterization of carbonized composite fibre mats with Raman spectroscopy 52 3.10.9 Electrical conductivity of carbonized composite fibre mats ................................. 53 3.11 Characterization of lignin films .................................................................................... 53 3.11.1 Polarized optical miscoscopy of lignin films ........................................................ 53 3.11.2 Scanning electron microscopy of lignin films ...................................................... 53 Chapter 4: Molecular orientation and organization of lignin based composite nanofibres and lignin film ..............................................................................................................................55 4.1 Introduction ................................................................................................................... 55 ix  4.2 Aligned lignin nanofibres and orientation of lignin ...................................................... 55 4.3 Orientation of lignin molecules chains in lignin film state ........................................... 69 4.4 Conclusions ................................................................................................................... 76 Chapter 5: Optimization of electrospinning process for forming lignin based composite fibres with nanocrystalline celluloses (NCCs) ...........................................................................77 5.1 Introduction ................................................................................................................... 77 5.2 Morphology of isolated-nanocrystalline celluloses (NCCs) ......................................... 78 5.3 Study of electro-spinnability of lignin-NCC-PEO solutions from various electro-spinning conditions ................................................................................................................... 79 5.4 Conclusions ................................................................................................................... 84 Chapter 6: Effects of nanocrystalline celluloses (NCCs) on the structure and properties of electrospun lignin composite fibre mats ....................................................................................85 6.1 Introduction ................................................................................................................... 85 6.2 FTIR study of lignin composite fibre mats with NCCs loadings.................................. 86 6.3 Thermal properties of as spun lignin composite fibre mats .......................................... 89 6.4 Effects of NCC loadings on morphology and fibre diameter of lignin based composite nanofibres .................................................................................................................................. 91 6.5 Mechanical properties of lignin based composite fibre mats with different NCC loadings ..................................................................................................................................... 93 6.6 Conclusions ................................................................................................................... 96 Chapter 7: Impact of thermal oxidation process on the performance of lignin based composite carbon nanofibres ......................................................................................................98 7.1 Introduction ................................................................................................................... 98 7.2 Influence of process parameters on yield after the thermal oxidation process ............. 99 7.3 Effects of stabilization temperatures on chemical composition and structure of lignin composite fibres ...................................................................................................................... 104 7.4 Thermal properties of stabilized lignin fibre mats treated under various stabilization temperatures ............................................................................................................................ 110 x  7.5 Mechanical properties of stabilized and carbonized fibre mats as functions of stabilization temperature ......................................................................................................... 114 7.6 Raman spectroscopy and electrical conductivity of carbonized composite fibre mats as functions of stabilization temperatures ................................................................................... 116 7.7 Conclusion .................................................................................................................. 120 Chapter 8: Direct carbonization process by adding nanocrystalline celluloses (NCCs) for lignin based carbon nanofibres .................................................................................................121 8.1 Introduction ................................................................................................................. 121 8.2 Morphology of lignin carbon fibres with NCCs loadings by skipping stabilization process………………………………………………………………………………………..122 8.3 Electrical conductivity and Raman spectroscopy of carbonized fibre mats ............... 128 8.4 Thermorheological analysis of lignin based composite nanofibres mats ................... 132 8.5 Mechanical properties of carbonized lignin based nanofibre mats with  and without stabilization process ................................................................................................................ 136 8.6 Conclusions ................................................................................................................. 137 Chapter 9: Conclusions and future work ................................................................................138 Reference: ...................................................................................................................................142  xi  List of Tables Table 1.1 Proportional inter-linkages and lignin functional groups in lignins from different wood species 3 ........................................................................................................................................... 4 Table 1.2 Summary of organic solvent fractionation of lignins ................................................... 10 Table 1.3 Summary of lignin based nanofibres with or without binder and nanofillers from various lignin sources by electrospinning ..................................................................................... 17 Table 1.4 Comparison of average fibre diameter and tensile properties of softwood kraft lignin based carbon nanofibre mats with and without reinforcement for different heat treatments ....... 20 Table 1.5 Summary of the electrospun composite nanofibres reinforced with nanocrystalline celluloses (NCCs) ......................................................................................................................... 38 Table 6.1 TGA results for temperature at 5 % weight loss temperature (T5), maximum weight loss temperature (Tmax), maximum weight loss rate (R), and yield % at 600 °C (Y) for as-spun lignin composite nanofibre mats with different NCC loadings .................................................... 91 Table 6.2 . Average fibre diameter and change (%) of average fibre diameter before (as spun and stabilized) and after carbonization as functions of NCC loadings, ± one standard deviation ...... 92 Table 7.1 Experimental design with the various, temperature (X1), holding time (X2), heating rate (X3) and the response, yield (%) for oxidation experiments of lignin based composite fibre mats. ............................................................................................................................................ 100 Table 7.2 Elemental composition of lignin powder (MWL,SKLand F4SKL), as spun lignin fibre and thermally oxidized lignin fibres after various heat temperature. ......................................... 106 Table 7.3 TGA results for thermostabilized lignin fibre mats under different oxidation final temperatures ................................................................................................................................ 111 xii  Table 8.1 Elemental contents with various NCC loadings of carbonized* lignin based composite fibres with and without thermal stabilization process ................................................................. 132 Table 8.2 Maximum tan delta peak and peak temperature as functions of NCC loadings ......... 134  xiii  List of Figures Figure 1.1 Monomers of lignin2 ...................................................................................................... 2 Figure 1.2 Enzymatic generation of resonance stabilized monolignol radicals .............................. 2 Figure 1.3 Structures of the three monolignols and the units derives from them 7 ........................ 3 Figure 1.4 SEM images of lignin fibres (a) overview image, (b) fused fibres, (c) voids at the fibre edge, (d) pores at the surface61. ..................................................................................................... 15 Figure 1.5 Global demand for carbon fibres in 1000 tons(in y-axis) from 2010 to 2022 96 ......... 22 Figure 1.6 Separation of cost elements in the manufacture of carbon fibre from PAN 56 ............ 23 Figure 1.7 Potential lignin market value and sales value as functions of production volume (kt/year)52 ...................................................................................................................................... 23 Figure 1.8 Illustration of the typical set up for electrospinning .................................................... 29 Figure 1.9 Formation of cross linkages61 ...................................................................................... 31 Figure 1.10 Shear moduli Gʹ of cellulose whisker nanocomposite with EO-EPI as a function of composition. The nanocomposites were fabricated by either solution casting (open symbols) or the template approach (filled symbols). Shear moduli were determined by DTMA at 25 °C. Data are for nanocomposites comprising cellulose whiskers isolated from tunicate whiskers (circles), cotton (squares) and microcrystalline cellulose (triangles), respectively. Solid lines represent prediction by the percolation model133. ........................................................................................ 36 Figure 4.1 Photographs of (a) the electrospinning process set up for fabricating aligned lignin fibres (b) mounted aligned electrospun fibres on a rubber o-ring ................................................ 57 Figure 4.2 SEM images of collected aligned lignin nanofibres (a) 0 % and (b) 5 % NCC loadings (scale bar (a) 10 um and (b) 20 um) .............................................................................................. 57 xiv  Figure 4.3 POM images of electrospun lignin based nanofibres (a) randomly collected with 0 wt.% NCC loading (b) aligned with 0 wt.% NCC and (c) aligned with 5 wt.% NCC ................. 58 Figure 4.4 The normalized spectra of polarized FTIR in the 4000 cm-1 to 2000 cm-1 regions with rotating polarizing angles (non : no polarizer) for electrospun lignin nanofibres with (a) 0 wt.% NCC and (b) 5 wt.% NCC loadings (a: 0° and 180 ° at 3330  cm-1 and b: 80°  and 100° at 3340  cm-1 and c: range in 3100-3000 cm-1) ........................................................................................... 60 Figure 4.5 (a) Normalized intensity of aliphatic hydroxyl OH band as functions of rotating degree for both 0wt.% NCC (NCC0) and 5 wt.% NCC loading (NCC5) and (b) change in peak intensity at 3270 cm-1 and 3410 cm-1 as functions of rotating angle with 5 wt.% NCC loading (NCC5) .......................................................................................................................................... 61 Figure 4.6 Intensity at wavenumber 3050 cm-1 as functions of rotating angles for aligned lignin electrospun fibres with and without NCC loadings ...................................................................... 61 Figure 4.7 Normalized intensity at 2930 cm-1 (νC-H) as functions of degree with and without NCC loadings in the fibres ............................................................................................................ 63 Figure 4.8 The normalized spectra of polarized FTIR in the range from 1800 to 1300 cm-1 region for lignin nanofibres (a) without (b) with 5 wt.% NCC loadings with different angles (non: no polarizer). ...................................................................................................................................... 64 Figure 4.9 Normalized intensity at (a) ~ 1598 cm-1(aromatic skeletal vibration + νC=O) (b) 1510 cm-1 (aromatic skeletal vibration) (c) 1710 cm-1 (νC=O) and (d) 1430 cm-1  (C-H in plane deformation with ν-aromatic ring) in normalized polarized FTIR spectra as functions of rotating angles with and without NCC loadings. Inserted graphs are having smaller scale. ..................... 65 xv  Figure 4.10 The normalized spectra of polarized FTIR in the range from 1300 cm-1 to 800 cm-1 regions for electrospun lignin nanofibres (a) without (b) with 5 wt.% NCC loadings with different angles. (a: 0°  and 180 °  and b: 80°  and 100°, non : no polarizer ) .............................. 67 Figure 4.11 Normalized intensity at (a) ~ 1214 cm-1 (b) 1030 cm-1  (ν C6-O of C6H2-O6H) for normalized polarized FTIR spectra as functions of rotating angles with and without NCC loadings. ........................................................................................................................................ 68 Figure 4.12 Normalized intensity at ~ 1034 cm-1 (ν C6-O of C6H2-O6H), 1056 cm-1 (νO-H of C3-O3H) and 1154 cm-1 (glycosidic ether νC1-O-C4) for normalized polarized FTIR spectra of aligned lignin based composite nanofibres with 5 wt % NCC as functions of rotating angles. ... 69 Figure 4.13 Lignin film dried from lignin/NCC/PEO solution in DMF under the circularly polarized optical microscope with reflective light and bright field by changing polarizer orientation from lateral to verical direction from up left to right left (scale bar : 10 um) ............ 70 Figure 4.14 A picture of lignin fime and polarized optical microscope images of lignin based film from lignin in DMF solution and indicating different part of the film have different optical properties (a) mid (b) edge part of the film under the lower magnification (x5, scale bar : 500 µm) and (c) edge part of the film under the higher magnification (x20, scale bar : 100 µm) ...... 70 Figure 4.15 Polarized optical microscope images of lignin based film from lignin in DMF solution with 5 wt.% NCC and indicating different part of the film have different optical properties (a) the lignin film under the lower magnification (x5, scale bar : 500 µm) indicating (I) centre(innermost) (II) mid and (III) edge part, (b) polarized optical microscope images of centre part of film, (c) middle part of the film and (d) edge part of the film under the higher magnification (x20, scale bar : 100 µm) ....................................................................................... 72 Figure 4.16 SEM images of fracture surface of the lignin film without NCC loadings. .............. 74 xvi  Figure 4.17 SEM images of fracture surface of the lignin film with 5wt.% NCC loadings. ........ 75 Figure 4.18 SEM images of the fracture surface of the lignin film with 5 wt.% NCC loadings .. 75 Figure 5.1 AFM images of isolated NCC by sulfuric acid hydrolysis,......................................... 78 Figure 5.2 SEM images for as spun lignin based composite nanofibres with various concentrations of lignin solution (a :25 wt.%, b:27 wt.% and c: 30 wt.% ) and different NCC loadings (0,1,3 and 5 wt.%) .......................................................................................................... 82 Figure 5.3 Average fibre diameter with (a) various spinning conditions with 20 – 30 cm collecting distance, 0.01 or 0.03 ml/min feed speed and 22 G or 25G of needle size (b) different concentration of lignin solutions from 25 to 30 wt.% and NCC loadings from 0-5 wt.% ........... 83 Figure 5.4 SEM images of lignin based nanofibres with (a) 7 wt.% and (b) 10 wt.% NCC loadings. Real fibre mats images were inserted with SEM images respectively. ......................... 83 Figure 6.1 (a) DRIFT-FTIR spectra for lignin based composite nanofibre mats with different NCC loadings; (1) 0 wt.%, (2) 1 wt.%, (3) 3 wt.%, (4) 5 wt.% and (5) NCC film. (b) and (c) are relative intensity of functional groups with different NCC loadings. ........................................... 88 Figure 6.2 DRIFT-FTIR spectra for thermally stabilized lignin based composite nanofibre mats with different NCC loadings; (1) 0 wt.%, (2) 1 wt.%, (3) 3 wt.%, (4) 5 wt.% and (5) thermally oxidized NCC film. ....................................................................................................................... 90 Figure 6.3 (a) TGA curves and (b) derivatives for freeze dried NCC and as-spun lignin composite nanofibre mats with different NCC loadings under nitrogen flow. ............................. 90 Figure 6.4 SEM images of carbonized lignin composite nanofibres with different NCC loadings. (scale bars = 10 um) (a) 0 wt.%, (b) 1wt.%, (c) 3 wt.% and (d) 5 wt.% NCC loadings. .............. 92 xvii  Figure 6.5 (a) Tensile strength, (b) tensile modulus and (c) strain at break of lignin based composite nanofibres at different heat treatment stages with various NCC loadings. (p < 0.05 , except carbonized samples) .......................................................................................................... 96 Figure 7.1 Effects of oxidation parameters (3 various) and their interactions on their response, yield (X1: temperature, X2: holding time, and X3: heating rate). .............................................. 101 Figure 7.2 SEM images of of espun lignin fibres after thermal oxidation process under different heating rates heating rate = 1 and 5 °C/min) final temperatures 200 °C,230 °C,250 °C,280 °C,300 °C and 350 °C, 60 min holding time (scale bar = 10 um). ............................................. 103 Figure 7.3 (a) Average fibre diameter of as spun and oxidized composite nanofibres with various final temperatures and heating rates and (b) yield after stabilization process with various final temperatures with 5 C/min  (p value < 0.05) ............................................................................. 104 Figure 7.4 Contents change of elemental composition for thermally stabilized lignin fibre mats as functions of final temperature. .................................................................................................... 106 Figure 7.5 13C CP/MAS NMR spectra of as spun lignin and stabilized fibre mats after different TS temperatures .......................................................................................................................... 108 Figure 7.6 FT-IR spectrum of thermally stabilized lignin based composite fibre mats after different final temperature .......................................................................................................... 109 Figure 7.7 Change in relative intensity of functional groups of as spun and stabilized lignin fibre mats under various final temperature in FTIR spectra as function of various final temperature showing decreasing intensity of C-H aromatic ring at 1500 cm-1, C-H deformation in primary alcohol at 1260 cm-1 and increasing intensity of unconjugated carbonyl group at 1710 cm-1.... 110 xviii  Figure 7.8 SEM images of carbonized lignin fibres after various final temperatures of oxidation process (a) 200 °C (b) 230 °C (c) 250 °C (d) 280 °C (e) 300 °C and (f) 350 °C (heating rate = 10 °C/min, holding time 60 min at 1000 °C) (scale bar = 10 um) ................................................... 112 Figure 7.9 Average fibre diameters after stabilization process under various final temperature and carbonized fibres as function of final temperature of stabilization process. ........................ 113 Figure 7.10 Elemental analysis of carbonized lignin fibre mats with different final temperature (a) carbon content and (b) contents of hydrogen, oxygen and nitrogen. .................................... 114 Figure 7.11 Tensile properties of lignin based composite nanofibre mats after (a) thermo-stabilization and (b) carbonization under various stabilization temperatures (p value < 0.05 for stabilized samples, but p value > 0.05 for carbonized samples) ................................................. 116 Figure 7.12 Raman spectra of lignin carbon nanofibre mats after various thermal stabilization (TS) temperatures in the range from 900 to 1800 cm-1. .............................................................. 117 Figure 7.13 (a) ID/IG ratio and crystallite size from Raman spectra of carbonized lignin nanofibre mats as functions of thermal stabilization temperature and (b) relationship between the ratio and crystallite sizes    (La, nm) ........................................................................................................... 118 Figure 7.14 Electrical conductivity of carbonized lignin nanofibre mats as functions of thermal stabilization temperatures (P value > 0.05 : statistically same) .................................................. 119 Figure 7.15 Relationship between electrical conductivity and crystallite sized of carbonized lignin nanofibre mats after various thermal stabilization temperatures ...................................... 119 Figure 8.1 SEM images of carbonized lignin based composite nanofibres with various NCC loadings (a) 0 wt.%,(b) 1 wt.%, (c) 3 wt.%, and (d) 5 wt.% at x3k (Scale bar = 10 um), (e) 0 wt.% and (f) 5 wt.% NCC loadings at x10k magnification (Scale bar = 5 m) ......................... 124 xix  Figure 8.2 Electrospun lignin composite nanofibre mats with 5 wt.% NCC loading as spun(left) and after(right) carbonization without stabilization process. ...................................................... 126 Figure 8.3 Average fibre diameter for lignin based composite fibres with various NCC loadings with and without thermal stabilization (TS) process. ................................................................. 126 Figure 8.4 SEM images of carbonized lignin based composite nanofibres with 5 wt.% NCC loadings after various carbonization process (a) 800 °C (b) 900 °C (c) 1000 °C with 10 °C/min for 60 min, (d) 1000 °C with 10 °C/min for 180 min, (e) 1000 °C with 1 °C/min for 60 min and (f) 1000 °C with 5 °C/min for 60 min (scale bar : 10 µm) ......................................................... 127 Figure 8.5 Electrical conductivity of lignin based composite carbon nanofibre mats (5 wt.% NCC loading) for with and without thermal stabilization process (carbonized at 1000 C for 60 min with 10 C/min) .......................................................................................................................... 128 Figure 8.6 SEM images of the cross section of carbonized lignin nanofibre mats with 5 wt.% NCC loadings (a) with thermal stabilization (scale : 20 m) (b) without thermal stabilization process (scale : 10 m) (carbonized at 1000 C for 60 min with 10 C/min) ............................ 129 Figure 8.7 (a) Raman spectra of carbonized lignin based composite nanofibre mats (5 wt.% NCC loading) with or without thermal stabilization (TS) process (b) the ratio of intensity of D band (1360 cm-1) and the intensity of G band (1650 cm-1) on the raman spectra of carbonized lignin based composite as functions of NCC loadings and carbonized neat NCC film (referred as 100 on the X axis) .............................................................................................................................. 131 Figure 8.8 Full width at half maximum (FWHM) at (a) D band (b) G band from Raman spectra of lignin carbon fibre mats as a function of NCC loadings and carbonized neat NCC film (referred as 100 on the X axis) for with (black, square) and without (red, round) stabilization (TS) process. ............................................................................................................................... 131 xx  Figure 8.9 Dynamic rheology of the lignin based composite as spun fibre mats with various NCC loadings (a) storage modulus (top), tan delta (bottom) as functions of temperature and (b) tan delta in the range of 200 °C to 300 °C. ....................................................................................... 134 Figure 8.10 Tan delta curves of lignin based composites fibre mats with (a) various heating rates (1,3 and 5 C/min) with 5 wt.% NCC loading and (b) different NCC loadings with 1 C/min heating rate. ................................................................................................................................. 135 Figure 8.11 (a) Stress and strain curves and (b) average strength and modulus for tensile tests of lignin based composite carbon nanofibre mats after stabilization and without stabilization (direct carbonization) process ................................................................................................................ 136             xxi  List of Symbols and Abbreviations CF = Carbon fibre LCF = Lignin carbon fibre SKL = Softwood Kraft Lignin NCC = Nanocrystalline Cellulose PEO = Poly(ethylene oxide)  TS = Thermal stabilization  CB = Carbonization  F4SKL = 4th fractionated softwood kraft lignin AFM = Atomic Force Microscopy POM = Polarized Optical Microscopy  FTIR = Fourier-transform infrared  NMR = Nuclear Magnetic Resonance SEM = Scanning Electron Microscopy TGA = Thermogravimetric analyzer  DSC = Differential Scanning Calorimeter SEC = Size Exclusion Chromatography       xxii  Acknowledgements Firstly, I would like to thank my co-supervisors, Prof. Scott Renneckar and Prof. Frank Ko for their wise advising and generous mind. Prof. Frank Ko kindly accepted me as his new student unexpectedly when I transferred after 1st year of my Ph.D. He has encouraged me to continue my study with positive thinking and made me not giving up my plan whenever I had the difficult time. Prof. Scott Renneckar also has shown a great model as a supervisor. He always makes time for me and discusses regarding lab work, personal issues and other many things. Even I involved in his group during the middle of my journey, he has given right direction to complete this long journey. Also, I am really thankful to Dr. Muzaffer Karaaslan who has helped me for entire my PhD life from the beginning to the end. I cannot imagine how I could work and study in the lab without him. He has taught me many things from the basic lab skill to scientific research. It was very helpful to build up my knowledge for 6 years. Moreover, I would like to thank Dr. John Kadla who brought me to UBC and involved in LIGNOWORKS(NSERC) for this research funding.  Also, I would like to thank all friends in Advanced fibrous materials lab. They always give positive energy along the way whenever I had difficulties. We have had lots of conversation to get over our uneven pathway for 5 years. I could not complete my long journey without my awesome colleagues in Advanced renewable materials lab. They have given consistently supporting and feeling like as a family for staying we have worked together.    Finally, I also would like to thank and give best wishes to everyone in Department of Wood Science who gave me their kind support for last years.       xxiii  Dedication  To my parents, my brother and my other family members for their loving and unconditional supporting from Korea. Thanks and best wishes to all my friends who have given their continuous cheering massages.     1  Chapter 1: Introduction 1.1 Lignin  1.1.1 Lignin biosynthesis and structure      Lignin is one of the three main components within the cell wall of terrestrial plants. Lignin serves as a structural matrix and aids in stress transfer to the cellulose microfibril reinforcement agent in plant stems helping to support a crown many meters above ground level1. In addition, lignified tissue facilitates the transport of water, nutrients and provides resistance against decay and fire, in part due to their thermal stability from their aromatic structure. Different species of plants have various contents of lignin. Softwood, hard wood and grasses contain 27-33 wt.%, 18-25 wt % and 17-24 wt.% lignin, respectively1.  These lignin types in different species have various structure, molecular weight and macromolecular interactions.  Lignification occurs after polysaccharide scaffolding is in place1. Three primary monomers, or precursors lignin “ monolignols” are coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol as shown in Figure 1.12.   These monolignols undergo polymerization through free radical coupling initiated by enzymes such as peroxidase or laccase as shown in Figure 1.23 . These enzymes (dehydrogenase) lead to removal of a hydrogen atom from the monolignol at the expense of H2O2 or O2 as oxidant for peroxidase or laccase, respectively. Peroxidases are monomeric, heme-containing glycoproteins4 utilizing H2O2 for monolignol oxidation5. Laccases (p-diphenol:O2 oxidoreductases) are copper-containing, cell wall-localized glycoproteins that are encoded by multigene families in plants5. Hydrogen abstraction on the phenolic hydroxyl of the monolignol leads to free radical formation; the radical is not stable and with the conjugated system can move around the phenylpropane unit, called the resonance stabilization providing a number of active sites for lignin polymerization. Polymerization of lignin occurs when another 2  activated monolignol or growing lignin chain with radical couples to form a new linkage1. Polymerization of monolignols creates the different (residues) units of lignin called hydroxyphenyl residue (H-lignin), guaiacyl residue (G-lignin) and syringyl residue (S-lignin) from p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol respectively (Figure 1.3).     Figure 1.1 Monomers of lignin2   Figure 1.2 Enzymatic generation of resonance stabilized monolignol radicals    3  As mentioned above, different plant species contain different concentrations and types of lignin. Softwood lignin is primarily derived from coniferyl alcohol and some p-coumaryl alcohol6.  However, hardwood lignin has both coniferyl and sinapyl alcohols with some p-coumaryl alcohol6. In grasses, lignin is derived from 10-20 % p-coumaryl alcohol along with a mixture of coniferyl and sinapyl alcohols6. Consequentially, softwood lignins are mostly composed of guaiacyl lignin (G-lignin) with very low hydroxyphenyl lignin (H-lignin) content7. Hardwood lignins mainly consist of G and S lignin, with low amount of H-lignin7. Grass lignins have comparable amount of S- and G-lignins, with higher amount of H-lignin compared to hardwoods and softwoods7. Further this G:S ratio largely impact on lignin properties such as thermal behavior which is most important properties for carbon fibre production.           Figure 1.3 Structures of the three monolignols and the units derives from them 7  As shown in Figure 1.3, S-lignin “repeat units” has one additional methoxyl group (-OCH3) than G-lignin. This structure results in lower possibility of branching and crosslinking 4  with C-C condensed structures. As a result, softwood lignins contains more carbon-carbon bonds, and hence, lower ether bonds compared with those of hardwood lignins. This phenomenon leads to various inter-unit linkages of lignin in different wood species. As shown in Table 1.1, both wood species have alkyl-aryl ether (-O-4) linkages over 50 % of total proportional inter unit linkages of lignins3.   Table 1.1 Proportional inter-linkages and lignin functional groups in lignins from different wood species 3 Name Bonds Frequency in Softwood (%) Frequency in Hardwood (%) Ether bonds   β-aryl ether β -O-4’ 35 -60 50-70 Diaryl ether 4-O-5’ <4 ~7 Carbon-carbon bonds (condensed bonds)  Dihydroxybiphenyl 5-5’ 10 ~5 Phenyl coumarane β -5’ 11-12 4-9 Pinoresinol β β’ 2-3 3-4  1.1.2 Delignification and recovery lignins from black liquor   For the pulp and paper industry, lignin is the unwanted component of wood that causes coloration and interferes with interfibre bonds in paper. The primary objective of chemical pulping is the production of high purity cellulosic fibres by maximizing lignin removal from the plant cell wall. In the pulping process, strong alkaline or acidic reagents are applied to wood in order to obtain pulp by the partial degradation and solubilization of lignin. Furthermore, lignin undergoes severe chemical changes relative to the cellulose. In the process of removing lignin, pulping chemicals disrupt native linkages and create new linkages in isolated lignin from the repolymerization. Various pulping processes have been applied and these different techniques 5  impact properties of isolated lignins, especially, chemical group functionality and molecular weight and molecular size distribution.   1.1.2.1 Kraft lignin   Kraft pulping is the most common chemical pulping process in North America. Over 130 million tons are produced annually from softwood, presently more than 50 % of total Kraft lignin production8. In this process, sodium hydroxide and sodium sulfide solutions react with wood chips at approximately 170 C for 2 hours 2. After this process, 90% of total lignin is removed from wood chips and dissolved into the solution known as black liquor.    During this process, alkyl-aryl ether (-O-4) linkages are disrupted and generate small compound degradation products although broken linkages can repolymerize through the free phenolic unit8. Compared with ether linkages, C-C bonds such as -5 and - are relatively stable and minimal fragmentation occurs during this process8. Therefore, Kraft lignin has a high percentage of phenolic hydroxyl groups and more condensed carbon-carbon structure. It is also soluble in aqueous alkaline solutions via deprotonation of the phenolic groups, contains some low molecular mass fragments creating a high polydispersity index (PDI), and has a portion of sulfur (1-3%) chemically bonded to it, and contains a relatively high ash content6. These attributes of inorganic contaminate along with high polydispersity makes it difficult to utilize lignin.  Black liquor with a pH 12-13 is acidified to recover the Kraft lignin as a precipitant. Around 20 years ago, a new process for lignin recovery was developed from Innventia, Sweden for high quality lignin production called LignoBoost9. In this process, lignin in black liquor was precipitated with carbon dioxide (CO2) by lowering the pH down to 9. After precipitation the 6  filtered lignin slurry was washed with sulfuric acid twice at this stage10. Precipitated lignin was crushed and dried to powder form. Now, Domtar Inc, in North Carolina, has licensed the technology and produces commercialized lignin, BioChoice at 75 tons/day11. Another process, LignoForce, has been developed by FPInnovations in Canada for isolating Kraft lignin by first oxidizing the lignin in the black liquor prior to precipitation. In this process, black liquor is first oxidized with oxygen (O2) and acidified to pH 9 by carbon dioxide (CO2)10. After coagulation, lignin is filtered, washed with sulfuric acid and formed into powder. Their oxidized black liquor gave higher content of lignin and lower ash content than without oxidation10. West Fraser Inc. in Alberta, Canada licenses the technology and produces Kraft lignin, LignoForceTM, with yields of process with 30 tons/day 11.  1.1.2.2 Lignosulfonates    Lignin sulfonate is produced by sulfite pulping process involving the reaction of an alkali metal sulfite and sulfur dioxide. The reactions are conducted between 140 °C and 160 °C and the pH of the acid sulfite process is between 1.5 and 2.012.  The lignosulfonate lignin is typically higher in molecular weight and contains 3-5 % sulfur contents, while also is highly soluble in water because of the sulfate ester formed on the propyl side-chain of lignin12.   1.1.2.3 Alkali (soda) lignin  Soda pulping is now the predominant process for non-woody such as bagasse, wheat straw, hemp and jute or some hardwood12. Biomass is heated at 140 – 170 C with 13-16 wt.% sodium hydroxide solutions in the pressurized chamber 12.  Soda lignin is sulfur free and the 7  resulting isolated lignin has higher carboxylic acid content than other technical lignins isolated through industrial processes.   1.1.2.4 Organosolv lignin     Organosolv lignin is produced by organic solvents such as ethanol, methanol, formic acid and acetic acid mixed with water and some acid catalyst13. This has been suggested as more environmental friendly than alkaline or sulfite processes, as all effluent is captured13. Moreover, this lignin is higher purity because it contains no sulfur and much less carbohydrate and ash than other technical lignin. Also, it is generally has lower molecular weight with smaller polydispersity, a lower glass transition temperature (Tg) and typically is more hydrophobic12. Currently, Fibra Innovations in Burnaby, British Columbia in Canada produces organosolv lignin at a pilot scale level.                      1.1.3 Additional fractionation process for narrowing polydispersity of lignin   Several fundamental studies on lignin fractionation were performed in the early 1960’s and 1980’s. Furthermore, lignin has been used as a precursor of carbon fibre and the quality of the precursor for fibre spinning and carbonization requires high purity to avoid defects in the finished product. Nowadays, higher quality of lignin is available through novel lignin recovery processes, as described above, such as LignoBoost with very low ash content and sulfur content. Past research demonstrated that lignin could be further purified by acid precipitation at select pH14,15, ultrafiltration16,17 and organic solvent fractionation18. Fractionated lignins were characterized with respect to functional groups (ie., aliphatic hydroxyl group, phenolic hydroxyl 8  groups and carboxylic acid groups), molecular weight distribution, thermal properties (ie., glass transition temperature, Tg) and elemental composition.  1.1.3.1 Organic solvent fractionation   In the early 1980’s, organic solvent fractionation were applied to get homogenous fraction of lignin molecular weight19. This fractionation process was developed based on the relation of lignin solubility with hydrogen-bonding capacities and solvent solubility parameters. However, very little studies showed practical application of fractionated lignin. However, there were a few studies on the advantages of producing lignin based carbon fibre from organic solvent fractionated lignin (reviewed below in Table 1.2).  Firstly, Sudo and Shimizu separated steam-exploded lignin with chloroform (CHCl3) soluble and carbon disulfide (CS2) insoluble fraction. Those lignins were heated at different temperature before spinning. They evaluated spinnability of lignin and in their thermosetting properties in the fibre form20. Kubo et al. produced softwood lignin through acetic acid pulping21. By adding various acetic acid concentrations, acetic acid lignin was separated into 5 fractions.  They removed an “infusible fraction” of lignin which had high molecular mass and melt spun with fusible fraction of the lignin which had lower molecular weight. The researchers carbonized the melt spun softwood lignin without thermal stabilization. Recently, Baker et al., applied the successive solvent extraction process for purifying hardwood organosolv lignin and softwood kraft lignin for carbon fibre production by melt spinning22,23. Moreover, organic solvent fractionation process was introduced by Dallmeyer24 to achieve higher quality softwood kraft lignin based carbon fibres using an electrospinning process. Since then, many works have been published for solvent fractionation of lignin as seen in the Table 1.2.  The organic solvent 9  fractionation methods have been modified/developed for using non-toxic solvent, simplified and economical processes developed to get high purity and yield of fractionated lignin. Table 1.2 shows the summary of solvent fractionation of lignin with various lignin and variety of solvent types for the last few decades.   10  Table 1.2 Summary of organic solvent fractionation of lignins Lignin Solvents Characterization Properties / application Ref Softwood kraft lignin (SKL)  4 steps – 5 fractions Methylene chloride, n-propanol, Methanol, Methanol/methylene chloride (7/3) Elemental analysis Molecular weight (Mw) 13C NMR  TGA, DSC  Viscosity N/A 19,25 Harwood Kraft lignin(HKL,birch)  2 steps – 3 fractions Methylene chloride, Methanol Elemental analysis Molecular weight (Mw) 13C NMR N/A 26 Alcell hardwood lignin 2 steps – 3 fractions Ether, Methanol (repeating) Molecular weight (Mw) 1H, 13CNMR Polyurethane films 27,28 Hardwood (Eucalyptus) kraft AQ pulping lignin 6 steps - 7 fractions Ethyl ether, methane chloride,              n-propanol, ethanol, methanol and dioxane UV, FTIR Molecular weight(Mw) TGA 1H, 13C NMR N/A 29,30 SKL Soda lignin (grass, wheat straw, hardwood) Organosolv lignin (hardwood) Milled wood lignin 4 steps – 5 fractions Methylene chloride, n-propanol, Methanol, Methylene chloride/Methanol(3/7) Mw with SEC Carbohydrates contents Degree of condensation 31P NMR  Plywood bonding test Binders for PF resin  31 Organosolv lignin (Birch, Alcell) Steam exploded lignin (pine, eucalyptus) 3 steps – 4 fractions Ether, Ether/acetone (4/1,v/v), Acetone 31P NMR  Molecular weight  Enzyme reactivity  4 different Laccase enzyme treated 32 SKL,HKL Organosolv lignin (birch,spruce,chips) 3 steps – 4 fractions Diethyl ether, Diethyl ether/acetone (4/1), Acetone Carbohydrate composition Ash contents 31P NMR  GC/MS  Molecular weight (SEC) DSC Produced most fractioned lignin after 3rd/residue 33 11  Lignin Solvents Characterization Properties / application Ref SKL (Indulin-AT) Methanol (3times) Methanol/methylene chloride (7/3) Molecular weight(Mw) 13C and 1H NMR  Rheology  Fabricating of nanofibres from fractionated lignin by electrospinning Shape memory film and carbon fibres  34–36 Three SKL precipitated by using carbon dioxide Acetone, Acetone/Hexane (4:1, 5:5, 1:4) Yield,  GPC-UV 31P-NMR  N/A 37 SKL(Indulin AT) HKL/Organosolv HW L Soda Grass Lignin Soda wheat straw lignin Acetone/water  (10,30,50 70 and 90 %, v/v), Ethyl acetate Mw (polydispersity) FTIR 31P NMR  Principal component analysis (PCA) Low Mw extracted from Acetone(30, 50%)/Water and ethyl acetate High Mw extracted from insoluble part in Acetone(50,70 and 90 %) /Water 38 SKL (Kruger)  Methanol  (Centrifuged 3 times – decanted soluble part and added MeOH) 4th washing by mixer Mw (SEC in DMF) DSC/TGA  31P , 13C NMR  XPS analysis  High Mw extracted from insoluble part after repeating MeOH washing  (50% yield) 39 Soda lignin (Protobind) Kraft SWL (indulin AT) Corn stover lignin (from bioethanol prcess)  Methanol   : stirring for 5 h at 60 C Divided by soluble and in soluble Klason  Mw   FTIR(S/G ratio)  GC-MS  DSC /TGA TMA,Rheology Soluble lignin= Low Mw : fewer condensed, low aromatic/aliphatic OH, low Tg,  40 Two Industrial SKL (Weyerhaeuser, Backhammar)  4 steps , 5 fractions Dichloromethane, n-propanol, Methanol, Dichloromethane/methanol (7/3) Mw,  DSC/TGA Sugar analysis  Elemental analysis(sulfur) 31P ,13C NMR    N/A 41 SKL (LignoBoost)  100 g/L at 40 C for 2 h Washing 2 times with Methanol, Ethanol 1-propanol, iso-propanol, tert-butanol, Acetone, methyl ethyl ketone, Ethyl acetate Solubility test  SEC  Klason  UV vis spectroscopy   N/A 42 12  Lignin Solvents Characterization Properties / application Ref Then, Sequential fractionation 4 steps, 5 fractions Ethyl acetate,ethanol,methanol, acetone SKL (Indulin AT) : 4g single step / a solvent – 2 fractions THF, Methanol,2-butanone Soxhlet extractor : 150 ml at 66, 65 and 80 C for 8 h Solubility test in DMSO  GPC FTIR 13C NMR  UV-vis (in DMSO)  DSC/TGA Highest yield from THF extraction   43 SKL (BioChoice lignin, Domtar Inc. by LignoBoost) 5g Methanol-acetone mixture (7:3,v/v) Ethyl acetate Ethyl acetate/petroleum ether (1:1) Petroleum ether - 4 fractions GPC Elemental analysis  Methoxyl content by GC  UV spectroscopy  31P NMR,  2D HSQC NMR  TGA,DSC   Similar sulphur contents Polysaccharide existed in highest Mw fraction  Decreasing Tg / decomposition temperature with decreasing Mw   44 Wheat straw organosolv lignin Binary system : Acetone Acetone/hexane (4/1,1/1,1/4) Antioxidant assays,  GPC  31P NMR,  2D HSQC NMR  XPS DSC, TGA  Biomedical application Correlations with Tg and antioxidant activities.  45 SKL by Metsa Fibre Various concentration of Ethanol, acetone and propyleneglycol monomethyl ether (PGME) by adding water Klason lignin  Elemental analysis  UV SEC  31P NMR  Fractionated lignin produced from different solvent showed similar structures.  46 Switchgrass & Pine organosolv lignin 100g Acetone(60 – 30 %)/water :1 L Separated insoluble part and added water to acetone solution Solubility test Mw – GPC 31P NMR  Antioxidant activity  100 % solubility in 60% acetone  HMw ->> More AlOH, less PhOH LMW ->> better antioxidant activity 47 13  1.1.4 Utilization of lignin   For the past few decades, numerous studies have been published for value added applications of lignins for chemicals, polymers and materials to replace with petroleum based products48–52. Not only the increasing interest in replacing non-renewable petroleum based products but also the emerging bioeconomy requires expanding marketplace for traditional forestry industry sector. Forestry industries will need to create new business markets by developing innovative products from forestry biomass resources.       Only a small percentage, less than 2 % of the 70 million tons of lignin produced from the pulp and paper industry is utilized with the remainder used as fuel and waste53. Current applications of industrial lignins include relatively dispersants, emulsion stabilizers, concrete additives, surfactants, and binders50.  However, several decades of research has allowed improvements in properties of lignin-based materials by investigating the relationship between the complex structure and molecular properties of different lignins, processability, and materials properties54.   1.1.5 Lignin based carbon fibres (LCFs)    Transforming to carbon materials such as carbon fibre (CF) and activated carbon (AC) and activated CF from lignin are particularly promising potential application for value adding to lignin due to their high market value.  Carbon fibres have numerous potential applications, including not only structural applications such as aviation, aerospace, automotive industry and wind power, but also, non-structural applications including thermal insulator, catalyst supports, electrodes for batteries (Li-14  ion batteries, fuel cells), supercapacitors55. Lignin based carbon fibres has been widely studied for last 40 years with various lignin types and these studies have been reviewed papers56–58. Both melt and dry spinning have produced precursor fibres for carbon fibres.  Detailed processing methods will be described in the section 1.2.2. Carbon nanofibres prepared by electrospinning are being intensively investigated for potential applications as listed in Table 1.359. Lignin is considered not only inexpensive precursor, but also lignin has shorter crosslinking stage than pitch for carbon fibre production due to lignin’s chemical structure i.e., thermal sensitivity to rearrangement due to a free radical mechanism. Also, relative high carbon yield results in reducing processing cost and a better atom economy. Unfortunately, lignin is relatively difficult to process into high strength CF, with continued research resulting in mechanical properties unsuitable for structural composites materials. Lignin based CF presents a few challenges compared to synthetic polymers (i.e, PAN) because of the complex, branched, heterogeneous, and widely varying lignin structure. Lignin based carbon fibres with sub-micron sized showed lack of homogeneity and orientation between crystalline planes60. As shown in the Figure 1.4, also, some spun fibres showed fusion after heat treatments, while difficulty in fibre formation created issues to optimize spinnability. Overall, these caused lower mechanical properties with more defects than commercial PAN based CF. Also, due to spinnability of difference of technical lignin, there was limited to specific lignins (mostly hardwood lignin) to transform into carbon fibres. It has also been noted that different lignins show a propensity toward molecular orientation in melt state via thermotropic liquid crystal formation, which may be exploited to achieve high mechanical properties60.  15   Figure 1.4 SEM images of lignin fibres (a) overview image, (b) fused fibres, (c) voids at the fibre edge, (d) pores at the surface61. To reduce micron sized defects as seen in Figure 1.4(c), one suggested solution is to make fibres smaller than micron-sized diameter. Reduction of the fibre diameter below that of traditional micron-sized fibres through electrospinning process could improve the material properties and expand the applications of lignin-based CFs. It is reported that the mechanical properties of CF increased with decreasing diameter62. Furthermore, the increased specific surface area provided by a reduction in the fibre diameter can benefit the numerous non-structural applications of CF mentioned above. While lignin-based CF properties must be improved further to compete with PAN and pitch-based CF in terms of mechanical properties, combining an understanding of lignin properties with novel processing strategies such as electrospinning may allow further improvement of properties and expansion of the potential applications of lignin-based CFs to the other areas listed above.    As shown in Table 1.3, electrospinning of various lignin solutions has been reported. However, pure lignin solution usually does not have enough fibre forming capacity for 16  continuous electrospinning without forming beads or going to higher concentrations leading to microscale diameter fibre63. Therefore, it is blended with another polymer, named binder such as poly(ethylene oxide)(PEO), poly(vinyl alcohol)(PVA), and poly acrylonitrile (PAN). Fibre with a low content of additive polymer is required for lignin based carbon fibre production to prevent fusion of the fibres and large mass loss 64,65.   It is known that phenolic hydroxyl groups of lignin and ether oxygen of PEO in alkaline solutions create an association induced complex formation66. When PEO and lignin are mixed together in the presence of salts and water, the chain entanglements of PEO trap the lignin molecules and eventually the bridging of PEO chains creates an association induced complex66. Recently published papers demonstrate the role of PEO chain on forming lignin based fibres by electrospinning process with various molecular weight of PEO and different ratio of PEO with lignin63,66–68.  Table 1.3 summarized electrospun lignin-based fibres with or without binder and nanofillers from various lignin sources. Also, this table contains fibre producing parameters, thermal treatments for carbon fibre production as well as their related applications. Organic solvent fractionation process was applied only for softwood kraft lignin34,36,69–71  for carbon fibre production for electrospinning. Modification of lignin was used for carbonization of lignin based fibres72.  Additionally, Table 1.4 showed comparison between published results for mechanical properties of electrospun softwood kraft lignin based fibres with different heat treatment stages. There is a small difference between materials since they were prepared from different concentration of lignin solution as well as their fibres have various diameters dependent upon the various parameters.  17  Table 1.3 Summary of lignin based nanofibres with or without binder and nanofillers from various lignin sources by electrospinning Lignin Source Solvent/Binder Nanofillers/Particles Conditions* (heating rate, °C/min) Properties (diameter or mechanical properties) Application Ref. Organosolv (Alcell) Ethanol (1:1) - TS; 200 C(0.25) CF; 900 C (10) AS; 400 nm – 2 um CF: 200 nm N/A 73 Organosolv (Alcell) Ethanol (1:1) Doping platinum (platinum acetyl acetonate 0.2-0.4 wt.%) TS; 200 C(0.05) CF; 600- 900 C (10) 800 nm – 3 um  CF: 400 nm-1 um Catalysts 74 SKL, 40 wt.% HKL,40 wt.% SL,30 wt.% Alcell(HOL),40% SOL, 50 wt.% Pyrolytic L, 40 % Lignosulfonate,30 % DMF or Water / PEO, 6  105 g/mol , 99:1  1 mL syringe 18G needle 9- 14kV 14-20 cm 0.03 mL/min   1318 nm  1085 nm 702 nm 1135 nm 1517 nm 912 nm 1645 nm N/A 63 Lignin Alkali  (60,000 g/mol) DMF/PAN(150,000 g/mol, 0-80 %  15 kv 10 cm  Cured by E beam irradiation CF 1000 C (10) 300 nm for 50 wt.% N/A 75 SKL  (Alkali Lignin,10 kDa) Water/PVA,  125 kDa 75:25, 20:80 CNCs from Cotton (0-15 %) 10 mL,22 G  19 kV 15 cm 0.008 ml/min  N/A 76–78 F4 Fractionated SKL DMF/PEO 1106,  99:1 PNIPAM Brushes from surface of modified lignin by SI-ATRP initiator TS : 250 C (5) 653-867 nm Ionic Responsive Platform 69 Sodium Carbonate Lignin Water/ PEO,  2 105 ,1106 Mw   300 nm for the 10-30 % lignin content N/A 79 Fractionated SKL F13:F4, 50:50 DMF/PEO 1106,  99:1  22G  15kV, 20 cm TS : 250 C (5)  Moisture Responsive Film 34 Alkali lignin,60 kDa Water/PEO, 600 kDa  CF. Activated CF without TS at 600 or 850 C (10)  Supercapacitors 80,81 Fractionated SKL F13:F4, 70:30   DMF/PEO 1106,  99:1  TS : 250 C  (5) for 1h  CF : 1000 C (10) Strength ; TS 31 MPa to CF 74 MPa, modulus ; 1.3 GPa to 4 GPa  Flexible (inter fibre bonding) CF  36  18  Lignin Source Solvent/Binder Nanofillers/Particles Conditions* (heating rate, °C/min) Properties (diameter or mechanical properties) Application Ref. up to 19.6 S/cm of electrical conductivity F4 Fractionated SKL DMF/PEO 1106,  99:1 MWNT(multiwalled carbon nanotubes) TS : 250 C  (5) for 1h  CF : 1000 C (10)   82 F4 Fractionated SKL DMF/PEO 1106,  99:1 Iron(3) acetylacetonate (AAI), SWNT(single walled carbon nanotubes)  18 cm  15 kV 0.03 mL/min TS: 250 C (5)1h) CF: 800-1000 C (10) Aligned= 66 MPa 17 GPa compared with random 11 MPa , 6 GPa EMI shielding 70 Organosolv (Alcell) DMF/PEO  600K, 90:10  6.5-7 kV 1 mL/h 10 cm  TS: 200C (1) 2h CF: 500-900C (5-10) 2h    Nitrogen dope fused CF for anode Lithium Ion Batteries  83 Alkali lignin (10k) 4% sulfur Water/PVA (85k-124k) 30/70,50/50,70/30  25 cm, 26 kV, 1.2 ml/h TS 1 (180C, (1) 16h TS 2 (220C, (0.5) 8h CF (1200 C, (5) 1h in Ar 220 nm, 170nm, 140m (30/70,50/50,70/30)   30% reduction after CB Supercapacitors  84 SKL  Water/PEO,  2 105, 5106,   95:5 and 97:3  22 cm  20 kV 0.2 mL/h  N/A 66 Hardwood Organosolv lignin  PAN (150 K)/DMF 90:10 – 0 :100  15 cm,  0.6-4 ml/h,  10 – 15 kV   N/A 85 Sulphur-free anionic sodium carbonate lignin (SCL) Water/ PEO,  5 106, 0.6 % 1.5 % Chitosan (CS) in acetic acid 14 kV 0.1 ml/h  N/A 86 Hardwood Organosolv L Acetone/DMAc Cellulose Acetate (LL:CA=2:1, 4:1) Iodine treatment  22.5 cm 0.7 mL/h  16-18 kV TS : 300C (2),2h CF : 600-1200 C (2),1h Iodine treatment enhanced the morphology retention. Cheap and green carbon fibres 87 Methanol soluble KL DMF/Grafted onto PAN   18G 0.85-10.5 uL/min 15 cm TS250 : 30 MPa  in strength, 0.4 GPa in modulus Electrode 88 19  Lignin Source Solvent/Binder Nanofillers/Particles Conditions* (heating rate, °C/min) Properties (diameter or mechanical properties) Application Ref. 8.5 – 10 kV TS : 250C (10)2h CF: 600-1400 (10) 0.5h CB1000:62.5 MPa in strength , 2.5 GPa in modulus   Electrical Conductivity  :7.1 to 21.3 Scm-1  (1000-1400 C) Lignosulfonate Water/PEO  (97:3)   Various conditions   N/A 89, 90 Butyrated organosolv L DMF/PAN 20 wt.% (50:50) Esterification =improve the miscibility of lignin with low polar solvents, monomer, plasticizing polymer 22 G 5 uL/min 15 kV 20 cm  TS:200C(0.2),12h CF:1000C(5)0.5h L/PAN = 22 MPa,  2.4 GPa BL/PAN= 83 MPa,  6.1 GPa  Fibre junctions for BL-PAN CF 72 Sulfur free softwood lignin DMF / PEO (1106 or 3106)  20G, 20 cm,   Study for role of PEO, Effects of PEO Mw 68,91 Olganosolv NaOH/Ethanol (8:2)/PEO  2106, (95:5)  24G 20kV, 22 cm , 0.7 mL./h) TS;250(0.5) 2h CF ;800 and 1100 C at (2) and (7) for 3 and 10 h   Analysis of CB parameters on structure of carbon fibres 92 Softwood alkali lignin (10k) Water/PVA  (125 kDa, 98%) (L:PVA=75:25)  22G, 20 cm, 17 kV, 8-10 ul/min TS : 250 C (4) 1or 2h   -> 600 C (2 h) -> impregnated in KOH -> CF : 900 C (4) 2h  Supercapacitance 93 Fractionated soft wood kraft lignin Indulin AT DMF /PEO (1106)   NCC from cotton 25G, 20cm, 20kV 0.01 ml/min  TS:250 C (5) 1h CF:1000 C (10) 1h   N/A 71 FPInnovations DMF/PEO  (1106) Zeolite (1-5 wt.%) 18-25 G, 15 cm, 12 kV, 0,02 mL/min TS : 250 C (5) 1h  Filteration 94 *Conditions indicating spinning condition or heating parameters 20  Table 1.4 Comparison of average fibre diameter and tensile properties of softwood kraft lignin based carbon nanofibre mats with and without reinforcement for different heat treatments. Solution concentration Average fibre diameter Average carbonized fibre diameter  Mechanical Properties Ref Strength (MPa) Modulus (MPa) Strain at break (%) 25 wt.% 977 ± 112 nm 639  ± 75 nm AS* 5.13 ± 0.64 514 ± 70.93 1.73 ± 0.45 82 TS* 23.86 ± 2.55 918.05 ± 132.31 3.12 ± 0.61 CF* 45.03 ± 9.93 6238.35 ± 1307.74 0.76 ±0.17 1wt.%  MWCNT loading 930 ± 98 nm 596 ± 65 nm AS 4.16 ± 0.78 566.25 ± 69.51 1.21 ± 0.33 TS 23.34 ± 3.46 1113.68 ± 118.88 2.21 ± 0.41 CF 36.85 ± 10.31 4648.21 ± 755.17 0.97 ± 0.21 25 wt.% 667 ± 111 nm 474 ± 81 nm AS 5.5 - - 70 TS - - - CF 50 6300 ± 1230 2.0 ± 1.2 28 wt.% 875 ± 111 nm 634 ± 87 nm AS - - - 36 TS 17.2 ± 3.4 800 ±60 2.3 ± 0.5 CF 32.0 ± 9.0 4800 ± 600 0.9 ± 0.3 27 wt.% 578 ± 69 nm 319 ± 34 nm AS 8.35 ± 1.15 709 ± 57 1.5 ± 0.2 71 TS 25.5 ± 4.55 1907 ± 226 1.75 ± 0.3 CF 53 ± 22 6865 ± 1013 1.5 ± 0.2 5wt.% NCC loading 783 ± 157 nm 406 ± 51 nm AS 3.6 ±0.57 447 ± 81.6 1.27 ±0.3 TS 18 ±2 1087 ± 129 1.9 ± 0.2 CF 33.7 ± 6 7970.3 ± 1418.5 1.5 ± 0.2 * : AS : as spun , TS : thermal stabilized and CF: carbon fibres 21  1.2 Carbon fibres 1.2.1 Markets for carbon fibres     One key driving force for the carbon fibre (CF) market is the potential application in light weighting automobiles to reduce energy consumption and carbon emissions. All new vehicles in the Europe Union (EU) have been required to meet new carbon dioxide (CO2) emission standards since 2014. Also, a significant reduction in emission of carbon dioxide is needed to achieve the set value in USA and EU by 2020. These limits can be met, by not only improving the efficient engine and driving technologies, but also reducing the automobile weight95. Lightweight construction of cars can be the key factor to achieve the target as for each 10 % (140 kg) of car weight (about 1400 kg) reduced, fuel efficiency increases by 5 % in mile per gallon95.  An estimated CF market value on the automotive industry will be USD $125 million by 2020 compared with USD$ 16 million in 2012.    Markets for CF are not only automobile industry applications, but also include non-structural materials such as sports equipment, leisure goods, and energy storage devices. Therefore, the demand volume of CF is expected to increase to 120,000 tons in 2022 compared to about 58,000 tons in 2015 96 as shown in Figure 1.5. 22  Figure 1.5 Global demand for carbon fibres in 1000 tons(in y-axis) from 2010 to 2022 96    However, CFs are produced from petroleum-based precursors of polyacrylonitrile (PAN) and pitch. These materials are highly dependent on oil price, accounting for around 51 % of manufacturing costs (Figure 1.6)56. Moreover, the high cost of CFs prevents their utilization for commercial products limiting expanded market demands.    Therefore, low cost and non-toxic precursor alternatives have the ability to expand use of carbon fibres in various applications by lowering the overall cost of production. One route proposed is forming carbon fibre from lignin, which has the highest economic value for lignin applications. By replacing CFs precursor resources to lignin from PAN, the price of CFs is expected to decrease to $5-7/lb from $20/lb97.     23   Figure 1.6 Separation of cost elements in the manufacture of carbon fibre from PAN 56    As shown in Figure 1.7, if  lignin converts into various products, carbon fibre is potentially large sales value and large lignin market value. Carbon fibre is only lower in value after monomer chemicals like vanillin and phenol derivatives (Figure 1.7). However, the market volume is an order of magnitude larger than these specialty compounds.     Figure 1.7 Potential lignin market value and sales value as functions of production volume (kt/year)52  24  1.2.2 Spinning technique 1.2.2.1 Melt spinning Compared with other spinning processes, melt technique is relatively simple, with high spinning speeds and does not require solvent. Therefore, it is the most economical technique for producing polymeric fibres. This spinning technique typically requires mixing a polymer with a plasticizer to prevent degradation of polymers during processing in the melt. Polymer pellets or granules are added into an extruder set at a temperature greater than their melting/flow temperature and extruded through narrow channel from a pressure built in the chamber (e.g., screw). The extruded fibres are pulled by a uniaxial drawing process where it elongates the fibre and the filaments are collected on a roll 98.  Traditionally, fibres of nylon and polypropylene (PP) have been produced by this spinning process99.  Moreover, most works for producing carbon fibre precursor from lignin or pitch have been used a melt spinning process100.  Fibres produced by this technique shows surface defects and internal voids, which cause low quality of the final carbon fibres.  Also, melt spun fibres possess many types of cross-sections, like non-circular geometry, and also show heterogeneous textures of cross sections due to voids. Currently, Oak Ridge National Laboratory (ORNL) has produced precursor fibre webs from hardwood lignin with a melt blow spinning batch system at a 15 kg/h semi-industry production scale101. Unfortunately, not all lignin can be melt spun readily due to the nature of lignin from different species and isolation processes.    25  1.2.2.2 Dry spinning Polymer is dissolved in a volatile solvent such as acetone and a high concentrated polymer dope is extruded out of a spinneret nozzle. The solvent evaporates, solidifying the polymer into its fibre form. Additional steps of stretching and crimping can modify the fibre properties. Mostly, cellulose acetate fibres have been produced by dry spinning process for filtration application102.  1.2.2.3 Wet spinning      Compared with dry spinning, the spinneret of wet spinning is located in a coagulation bath. Therefore, the fibres are extruded directly in the bath. These formed fibres experience homogeneous conditions until drawing process of fibres. Wide range of variations in the properties of wet spun fibres are possible by varying the spinning parameters like, the spinneret’s orifice diameter, the throughput rate, the take up velocity, the conditions of coagulation bath and stretching parameters. With the dry-wet (jet) spinning process, lignin-PAN based fibres were produced to be used as carbon fibre precursors103. Lignin and PAN copolymer solution in DMSO was extruded through a spinneret (0.1 mm diameter of hole size) into a DMSO/H2O mixture in the coagulation bath. The extruded fibres were washed and stretched in water at 70 and 80 °C with 2.4 draw ratio. Finally, the fibres were dried on hot rollers at 110 – 120 °C. Also, one of the re-generated cellulose fibres, viscose rayon is produced by wet spinning for carbon fibre precursor57,103. Also, recently, regenerated cellulose phosphonate fibres prepared from ionic liquid were studied for carbon fibre production using a wet spinning technique104.      26  1.2.2.4 Jet spinning    This spinning technique is similar with wet spinning. However, this process produces smaller diameter filaments with few millimeters with higher spinning speed than wet spinning. Therefore, extruded fibres show higher molecular orientation of fibres. Lyocell fibres are spun using this method by dissolving cellulose cellulose in N-methylmorpholine N-oxide (NMMO) and have been studied for carbon fibre production105.  Final characteristics of the fibres produced by above wet techniques are highly dependent on not only the spinning dope but also the coagulation bath which makes for complicated system. After the coagulation bath the fibres go through washing of residue solvent with water during the drawing of fibres, and finally relaxation process followed by drying.    Using these spinning methods, the micron-sized fibres produced have potential for inhomogeneity like wide range of fibre diameters, disrupted surface with pores, and voids on cross section of fibres. These defects causes lower mechanical properties of carbon fibres.   To overcome the drawbacks mentioned above for traditional technique for spinning fibres, electrostatic spinning or electrospinning process has been investigated to produce sub-micron scale fibres. Electrospinning process can be similar to dry spinning or dry-wet spinning but it forms continuous fibres with diameter ranging from single digit nanometers up to a micron.   1.2.2.5 Electrospinning   Electrospinning has been considered as a promising strategy to produce novel materials106,107. Electrospinning is capable of producing continuous fibres with very small diameters from a variety of polymeric materials.  27  By reducing fibre diameters down to the nanoscale, an enormous increase in specific surface area to the level of 1000 m2/g is possible. Moreover, increasing the surface area greatly affects the chemical, biological reactivity and electro-activity of polymeric fibres. By reducing the fibre diameter from 10 um to 10 nm, a million times increase in flexibility is expected as well108. Especially, materials in fibre form are unique in that they are stronger than bulk materials because of orientation of the molecules. Additionally as the fibre diameter decrease, it has been well established in glass fibre science that the strength of the fibre increases exponentially due to the reduction of the probability of including flaws or defects62.   As shown in Figure 1.8, the electrospinning process consists of a polymer solution, needle, a high voltage supply and a collector. Briefly, when differential voltage is applied, a portion of the droplet of the polymer solution overcomes the surface tension at the tip of the needle forming Taylor cone. From the Taylor cone, jet stretched to a smaller diameter and jet instability causes it to have a whipping motion. At this point, the solvent rapidly evaporate and the jet solidifies to form thinner fibres while deposited on the collector109. The electrospinning process is governed by two sets of parameters. One set is polymer solution properties such as surface tension, viscosity, and conductivity arising from polymer concentration, solvent power and additives. The electrospinning process is governed by two sets of parameters. One set is the polymer solution properties that includes surface tension, viscosity, and conductivity arising from polymer concentration, solvent power and additives such as salts. Electrospinning of a polymer solution of various conditions can produce a variety of structures in the mat, including beads, beaded fibres and bead free-fibres depending on the rheological characteristics of the solution, such as molecular weight, polydispersity, the degree of branching and chain entanglement111–113. The proper polymer concentrations allow the formation of adequate chain 28  entanglement, which results in continuous uniform nanofibres114. If the concentration of the polymer solution will electrospin, the concentration usually will have a dominant effect on the fibre diameter and fibre morphology114. The polymer concentration is directly related to the viscosity of the polymer solution109. Higher concentrations generally produce larger average diameter fibres at the given molecular weight of polymer.    Also, spinning parameters related to collecting distance between a needle tip and a collector, feed speed and applied voltage impacts spinnability and fibre dimensions. Using needles with smaller tip diameters was reported to enhance the uniformity of electrospun fibre mats115. Some recent studies have also showed that needles with a smaller diameter tip resulted in smaller fibre diameters115. The feed speed or rate and the electric field make the polymer solution that is pumped into the needle tip to form a Taylor’s cone114. This rate should match the rate of removal of solution from the tip to form continuous fibres114. The collecting distance from the needle tip to the collector impacts the strength of the electric field, jet length as well as the time available for evaporation of the solvent before the nanofibre reaches the collector114. Usually, thinner diameters of fibres are produced with longer spinning distances.  Also, spinning parameters related to collecting distance between a needle tip and a collector, feed speed and applied voltage impacts spinnability and fibre dimensions.Using needles with smaller tip diameters has been reported to enhance the uniformity of electrospun fibre mats110. Some recent studies have also showed that needles with smaller diameter tip resulted in smaller fibre diameters110. The feed speed or rate make the polymer solution pumped into the tip to form the Taylor’s cone111. This should match the rate of removal of solution from the tip to form continuous fibres111. The collecting distance from the needle tip to the collector defines the strength of the electric field, jet length as well as the time available for evaporation of 29  the solvent before the nanofibre reach the collector111. Usually, thinner diameter of fibres are produced with longer the distance.     Figure 1.8 Illustration of the typical set up for electrospinning    Due to its enormous versatility for processing a wide variety of polymers, electro-spinning is a promising method to produce a variety of nanofibre-based materials, including nanocomposites, fibrous catalyst substrates, drug delivery devices, tissue engineering scaffolds, and nanowires112. Electrospun PAN and pitches have been mainly studied as carbon fibre precursors since 2002113.   Since then, numerous studies have been shown fundamental structure and properties of electrospun carbon nanofibres, their performance in potential applications such as energy storage devices, lithium-ion batteries, supercapacitors and composite nanofibres114. 30  Lallave et al., firstly reported filled and hollow lignin based carbon nanofibres produced by co-axial electrospinning and showed catalysts application as support by doping platinum on the surface of nanofibres74,115. For the past decade, studies on lignin based carbon nanofibres by electrospinning have attracted attention related to alternative resources for carbon fibre production and lignin valorization. More details show in section 1.1.5 and Table 1.3.          1.2.3 Stabilization process  For carbon fibre production, stabilization is key processing step to ensure the fibres do not lose their shape during carbonization. The stabilization process involves heat treatment at lower temperature (200 ~ 300 C) under tension in an oxidative atmosphere and produces changes in chemical structure of the fibres. As spun thermoplastic fibres are converted to condensed thermosetting fibres under complex chemical reaction during this stage116. These changes prevent deformation at subsequent high temperature treatments. Moreover, the stabilization process is considered to be the most critical step because it largely governs the final structure of the carbon fibre and hence its ultimate mechanical properties. There are just a few studies that show the effects of stabilization process parameters on properties of lignin powder117 or lignin based fibres 118–120. Additionally there is lack of studies that show how the stabilization process affects properties of the final carbonized lignin fibres. Lignin structure is known to be thermally sensitive to temperatures in the 180 – 250 °C temperature region. Four chemical reactions are observed which are formation of ketone functionality on the side chains, formation of carboxylic acid, autoxidation of aldehydes, and formation of cross-linkages61. The evidence of all functional groups can be found in the IR spectra and solid-state NMR measurements. The formation of ketone is detectable in the IR spectra at 1700 - 1750 cm-1. The formation of 31  carboxylic acids and aldehydes is shown in the region between 190 and 200 ppm in the 13C CP/MAS NMR measurements 22,121. The formation of cross linkages can be detected in the IR spectra at such anhydride formation at 1800-1850 cm-1. The intensity of 1218, 1081 and 1033 cm-1 nearly disappear and these bands correspond to C-O of guaiacyl ring, secondary alcohols and primary alcohols, respectively122. Overall, the region from 1400 to 1000 cm-1 typically became very broad without individual peaks61 after stabilization process indicating the formation of cross linkages. More stable oxygen-bridge structures such as anhydride and carbonyl structures, along with aromatic ethers is formed in the process as shown in Figure 1.9. The elemental analysis shows a decrease in hydrogen and an increase of oxygen content64. Slower heating rates favor reactions that increase oxygen content at low temperature, but faster rates lead to oxygen loss at higher temperature64. It is recommended that precursor fibre is heated slowly (e.g. 0.5 °C/min)123 to get well stabilized fibres to prevent fusion and get homogeneous cross section.     Figure 1.9 Formation of cross linkages61 32  1.2.4 Carbonization process    Stabilized fibres are converted into carbon fibres through the carbonization process, which involves heat treatment in an inert atmosphere such as nitrogen or argon flow under low tension up to 1500 °C. During this process, most elements other than carbon are removed and graphite like structure is formed. When the fibre is made of at least 92 wt.% carbon contents it is classified as carbon fibre100. Graphitization of the fibre requires higher temperatures and longer heating times than carbonization process.  1.3 Nanocrystalline Cellulose (NCCs)    Natural fibres in aquatic and terrestrial plants are pervasive throughout the world. They are also referred to as cellulosic fibres, related to the main chemical and structural component cellulose in lignocellulosic fibres. Cellulose in the cell walls of plants occurs in combination with hemicelluloses, lignin, waxes, and pectins. Cellulose consists of D-anhydroglucose (C6H11O5) repeating units joined by 1, 4-β-D-glycosidic linkages at C1 and C4 position. The degree of polymerization (DP) is around 10,000 but is dependent upon species124. Each repeating unit contains three hydroxyl groups at C-2, C-3 and C-6 positions, and the intra-molecular and the inter-molecular hydrogen bond system of cellulose is in the solid state. Cellulose is further composed of regions of high order i.e. crystalline regions and regions of less ordered which may occur because of amorphous regions or less ordered surfaces. Cellulose supramolecular structure forms slender rod like microfibrils. The crystal nature of naturally occurring cellulose in woods and cotton is known as the polymorph, cellulose І. Because of the intra- and intermolecular hydrogen bond system of celluloses, they have an extremely high structural strength and stiffness with measurements of 150 GPa125. 33  The use of lignocellulosic fibres as a reinforcing phase in polymeric matrix composites provides positive environmental benefits with respect to ultimate disposability and raw material use. Compared to inorganic fillers, there many advantages to use lignocellulosics fibres. Because of their abundance, renewability and nonabrasive nature in damaging processing equipment, it makes significant cost saving. Also, Cellulosic fibre are nonfood sources for a bioeconomy and have low density compared to silica/glass based fillers, which allows high filling levels, and relatively reactive surface resulting in using for grafting specific groups126. Nanocrystalline cellulose (NCC) or cellulose nanocrystal (CNC) with rod-like shape and obtained from acid hydrolysis of cellulose, has been realized as a new class of nanomaterials. Almost any cellulosic material could be considered as a potential source for the isolation of NCC. Commonly studied source materials have included not only wood but also crop residues, sugar beet, the marine animal tunicates and bacterial cellulose. Delignified pulp is hydrolyzed by mineral acid at conditions that partially erode the accessible areas of the cellulose surface and then the reaction is quenched and acid removed through dialysis.  Compared to cellulose fibres, NCC has many advantages, such as nanoscale dimension, low density, high specific strength and modulus, high surface area and unique optical properties. NCCs have a surface composed of primary hydroxyl group at the C6 position, which can also be exploited for grafting specific hydrophobic or hydrophilic region, and secondary hydroxyl groups from C2/3127. NCC derived from sulfuric acid hydrolysis can be readily dispersed in water due to its negatively charged surfaces, as sulfate esters form on the surface. At low concentration, NCC particles are randomly oriented in aqueous suspension as an isotropic phase, and when the concentration reaches a critical value, they form a chiral nematic ordering, where NCC suspensions transform from an isotropic to an anisotropic chiral nematic liquid crystalline phase128.  34  These amazing physicochemical properties have attracted significant interest from both scientists and industrialists125,129–131. Among these properties, in this study, NCC will be considered as a nano-reinforcement in lignin matrix and will investigate the effects of NCC on physical and mechanical properties of lignin based nanocomposite.   1.3.1 Nanocomposites reinforced with NCCs In the past three decades, significant attention toward the development of polymer nanocomposites by incorporation of nano-reinforcement has been studied to significantly improve mechanical properties compared to the neat polymer, matrix or conventional composite materials. Nanoscale materials such as, silver nanoparticles, nano-clay, carbon nanotubes(CNT), silica(SiO2) have been widely investigated. Due to environmental concern and emerging of bioeconomy concept, nanofillers from renewable resources have attracted researchers from both industry and academia. Twenty years ago, Favier et al., showed significant improvement of mechanical properties of synthetic latex (polystyrene-co-butyl acrylate) reinforced with small amount of tunicate cellulose whiskers, up to 6 wt.%, especially when the composite materials were heated above the glass transition temperature of the matrix (Tg=0 °C)132,133. The researchers explained this mechanical enhancement using a percolation model that the tunicate whisker formed networks facilitated by hydrogen bonding between the whiskers132–134 and stress transfer occurred across the composite. The mechanical properties of nanocomposites can be predicted by a percolation model, which expressed Gʹc (expressed below).  Since then, extensive studies have been done with a broad range of polymeric matrices130,135,136.   35  𝐺′𝑐 =(1−2𝜓+ 𝜓𝑋𝑟)𝐺′𝑠𝐺′𝑟+(1−𝑋𝑟)𝜓𝐺′𝑟2(1−𝑋𝑟)𝐺′𝑟+(𝑋𝑟−𝜓)𝐺′𝑠          (1) With  𝜓 = 𝑋𝑟 (𝑋𝑟−𝑋𝑐1−𝑋𝑐)0.4                                  (2)  Where Gʹs and Gʹr are the shear moduli of the neat soft (polymer) and rigid constituents, and 𝜓 is the volume fraction of NCC (or nanowhiskers). Xr is the volume fraction of the randomly oriented rigid component (NCC, nanowhiskers), Xc is the critical NCC percolation volume fraction calculated by 0.7/A where A is the aspect ratio of the filler.  Capadona et al. reported percolating nanocomposites with ethyleneoxide/epichlorohydrin copolymer (EO-EPI) matrix and investigated materials of nanowhiskers isolated from tunicates, cotton or microcrystalline cellulose by two different film fabricating methods (Figure 1.10)137. As shown in Figure 1.10, the predicted percolation model fit the experimental data, especially for solution casting method (open symbols).  36   Figure 1.10 Shear moduli Gʹ of cellulose whisker nanocomposite with EO-EPI as a function of composition. The nanocomposites were fabricated by either solution casting (open symbols) or the template approach (filled symbols). Shear moduli were determined by DTMA at 25 °C. Data are for nanocomposites comprising cellulose whiskers isolated from tunicate whiskers (circles), cotton (squares) and microcrystalline cellulose (triangles), respectively. Solid lines represent prediction by the percolation model135.     1.3.2 Electrospun composite nanofibres reinforced with NCCs  As a result of their distinctive properties, NCC has the potential of becoming an important class of renewable nanomaterials, which could find many useful applications. The main application reported in the literature of NCC is for the reinforcement of polymeric matrix in nanocomposites materials. Many different approaches to fabricate polymer/NCC nanocomposite have been reported like film casting, hydrogels and electrospun nanofibres138,139. During the past decade, NCCs have been used as nano-reinforcement for preparing of nanocomposite fibres by electrospinning process, Table 1.5 with increases in mechanical properties of the nanocomposite ranging from 17-770%. Further this unique material also is expected to give higher performance to lignin-based materials, which together are found in nature blended together in elegant nanocomposite system. Even though studies on electrospun lignin based nanofibres reinforced 37  with NCC were published76–78, they did not report for carbon fibres production, as well as their methodology used a higher percentage of binder. Therefore, they have not shown the effects of NCCs on lignin based carbon nanofibres for improving their properties.      38  Table 1.5 Summary of the electrospun composite nanofibres reinforced with nanocrystalline celluloses (NCCs) Matrix Solvent NCCs origin & size (nm) NCCs wt.% Diameter (nm) Modulus % increase Strength % increase Elongation % increase Ref. PEO water Bacteria cellulose, 420 ±190 in length , 11 ± 4  in width 0-0.4 140 ± 20 to 300 ± 40 + 193.9 + 72.3 + 233.3 140 PAA Ethanol Cotton cellulose 0-20 349 to 69 + 350 + 770 (cross linked) + 160 + 580 (cross linked)  141 PCL DMF Ramie, 100-250 nm in length, 3-10 nm in width 0-7.5  +64.3 +37.2 +49 142 PLA DMF MCC, 124 ±35 in length, 9 ± 2 in width 0-10 500 to 300 +37 +31  143 PS THF Cellulose filter papers 200 nm and 10-20 nm 6, 9 600-5400 - - - 144 Alginate water Cellulose filter , 130 nm , 20.4 nm in width and 6.8 nm in height 0 - 50  +123   145–147 PVA  water Ramie , 100-250 nm in length, 3-10 nm in width 0-15 235 ± 64 to 188 ± 41 274 ± 54 to 295 ± 83 + 300   148,149 Silk Formic acid-water Mulberry branch bark, 400-500 in length, 20-40 in width 0-4 250 to 77 + 400 +300 - 55 150 PEO water MCC, 112 ± 26 nm, 10 ± 3 nm 0-20 154 ± 70  to 149 ± 49 +193.9 + 72.3  110,151 PMMA DMF Softwood dissolving pulp, 380 nm in length,  17 nm in width 0-41 459 to 182 +17 (nano-indentation)   152 SKL/PVA water Pure cotton, 100-150 in length, 10-20 nm  0-15 73 to 114 nm    76–78 39  Matrix Solvent NCCs origin & size (nm) NCCs wt.% Diameter (nm) Modulus % increase Strength % increase Elongation % increase Ref. PLA Chloroform /toluene (7:3)/water BSKP, 100-500 nm in length, 5-20 nm in diameter 0-10 590 to 1000 +147 +70 -82 153 Acronyms: PEO, poly(ethylene oxide); PVA, poly(vinyl alcohol); PAA, poly(acrylic acid); PCL, poly(Ɛ-caprolactone); PLA, poly(lactic acid); PS, polystyrene; EVOH, Ethylene–vinyl alcohol copolymer; PMMA, poly(methyl methacrylate); DMF ,Dimethyl formamide; SKL, softwood kraft lignin; 40  Chapter 2: Hypothesis and objectives    Based upon the literature, lignin derived carbon fibres require improvement in physical or mechanical properties to meet the performance in various commercial applications. Heterogeneous structure and lack of molecular orientation of lignin in the fibres leads to defects and lower mechanical properties in lignin derived carbon fibres. Moreover, fusion and spinnability issues of softwood lignin create limitation where hardwood lignin is primarily used for carbon fibre production.   This study applied organic solvent fractionation to achieve a homogenous fraction of softwood kraft lignin that had higher molecular weight useful for spinning fibres. From composite theory and the mechanics of the materials, it is hypothesized that the addition of reinforcement and smaller diameter fibre will lead to improvement of the mechanical properties of lignin derived carbon fibre and reduce the amount of defects.  To test this hypothesis, one approach is to add reinforcement agents, such as nanocrystalline cellulose (NCCs) to form stronger fibre. The other approach is to apply a novel spinning technique like electrospinning to produce nano-sized fibres with less defects in fibre cross-sections and on surfaces. Moreover, electrospinning produces highly oriented molecular organization within the fibres. Lastly, better carbon structure may be achieve by optimizing the oxidative thermo stabilization process before carbonization. It is been known the stabilization process plays an important role to control carbon structure of the carbon fibres. Although, a considerable number of studies have been focused on micro-sized lignin fibres produced by melt spinning or gel spinning to achieve uniform structure of the carbon fibres, very little is known on the understating relationship 41  between structure and properties of lignin based nano-sized fibre.  For this reason, the following objectives for the PhD research were developed and provided below.   Softwood kraft lignin was successfully converted into continuous composite fibre mats by electrospinning lignin with NCC as a reinforcement and small amount of polyethylene oxide (PEO) as a carrier providing a pathway to study the augmentation of mechanical properties based on the hypothesis above. The influence of NCC loading on lignin composite carbon fibres was the main parameter investigated to determine their effectiveness in achieving higher performance of lignin carbon fibres. Lignin based carbon fibre performance was studied by adding varying amounts of NCC; details are described in the following 4 sections.   Objective 1: Investigate how electrospinning impacts composite nanofibre formation by studying morphology of fibres and orientation of molecules in the fibres. Determine interactions between NCC and lignin in electrospun fibre systems and NCC orientation to understand the composite fibre properties. Firstly, lignin solutions with NCC loaded up to 5% by mass will be electrospun resulting in non-woven random mats with fibre diameters in the 100’s of nanometer range. Further studies of the morphology and internal microstructure of the composite nanofibres using scanning electron microscopy and molecular spectroscopy will reveal changes as a function of NCC loading and further changes connected to nanofibre performance. With microscopy and polarized FTIR spectroscopy, a fundamental understanding on the influence of electrospinning on morphology of fibres will be revealed including the orientation of NCC in the fibre.   42  Objective 2: Determine the effect of NCC on electrospun lignin fibre systems thermal and mechanical properties as a function of NCC content and thermal treatment    The properties of the materials will be studied for both lignin and lignin composite fibre mats with varying levels of thermal treatments (thermal oxidative conditioning and thermal carbonization) to evaluate the impact of the temperature treatment on fibre properties.  This work will highlight an alternative route for the utilization of technical kraft lignin through simple means of thermal treatment.   Objective 3: Elucidate the thermal stabilization process on lignin based carbon fibre structure and performance.  Third, extensive studies for the influence of thermal stabilization process on lignin based composite nanofibres will be completed in order to understand the impact of this important processing step on structure and performance. Understanding this process will be key to understanding the synergy of the manufacturing processing steps on final properties of lignin based composite fibres. A design of experiment approach will be used to reveal the impact of heating rate and heating hold time on fibre yield and properties.  Further lignin based composite fibres will be investigated for chemical, physical, mechanical and electrical properties from macro- to nanoscale level. This chapter will be significant for understanding how stabilization impacts the carbonized lignin based nanofibres during/after the processing.   Objective 4: Measure the impact of nano-reinforcement on the thermal rheological properties of lignin to expand processing options of lignin-based carbon fibre production.  43   Lastly, the research will investigate how the incorporation of NCCs allows for lignin based carbon fibre to retain their shape and create interconnected bonding morphology even when the thermal oxidation step is skipped, which is a step before the carbonization process. The stabilization process has been considered as a critical process to prevent fusion of fibres and to create homogeneous cross section of a carbon fibre. However, by adding NCC, we can exclude the stabilization step and directly apply the carbonization process to produce lignin based carbon nanofibres. This phenomenon will be analyzed by advanced dynamic rheology to understand the fundamental principle of the role of NCC in lignin based composite nanofibres. As a result, it is expected that NCC will have a role of restriction on lignin chain mobility, similar to the crosslinking of rubber. Therefore, the impact will not only potentially reduce manufacturing cost for carbon fibre production but also produce stronger carbon nanofibres materials by NCC addition. Moreover, this interconnected lignin based composite carbon fibre mats may have commercial level of electrical conductivity for electronic device applications.44  Chapter 3: Materials and experimental methods 3.1 Materials    Softwood kraft lignin (SKL) was obtained from Indulin-AT, Meadwestvaco, Glen Allen, VA, USA. Poly(ethylene oxide) (PEO) with average molecular weight of 1 × 106 g/mol was obtained from Sigma-Aldrich and used as received. N,N-dimethylformamide (DMF), methanol, methylene chloride, and sulfuric acid of 98 % were all ACS reagent grade and cellulose filter papers (Whatman No 1001 110) were also purchased from Fisher Scientific and used as received.   3.2 Statistical analysis of the data  Data was collected from repeated experiments with reasonable number of samples determined by prescreening experimental methods and analyzing the variance of the samples. All values were analyzed as mean or average values and data was plotted with one standard deviation error bars. In order to assess the difference between various parameters or experimental conditions, ANOVA with alpha level of 0.05 was used with Excel was applied to compare means.    3.3 Organic solvent fractionation of softwood kraft lignin (SKL)   Solvent fractionation of commercially available softwood kraft lignin (SKL, Indulin-AT, Meadwestvaco, Glen Allen, VA, USA) was carried out by sequential extraction with organic solvents based on a published procedure34,35. In details, impurities in lignin were removed with acidic water washing. First (1st) to third (3rd) lignin fractions (F13 SKL) were obtained through repeated methanol washing. Undissolved lignin from methanol extraction was treated with mixture of methanol and dichloromethane (7:3) to obtain dissolved lignin portion indicated as 45  the 4th fractionated lignin (F4 SKL). The mixture of methanol/dichloromethane soluble part was concentrated on a rotary evaporator and removed the solvent, methanol. The isolated F4 was then grounded with a mortar and a pestle to get a fine powder and subsequently dried in the vacuum oven at 40 °C until further using.       3.4 Isolation of nanocrstalline celluloses (NCCs)   Cellulose filter paper was Wiley milled to pass a 60 mesh screen. The milled cellulose powder was then hydrolyzed with 64 wt.% sulphuric acid at 45 °C for 45 min 154,155. The acid hydrolyzed suspension was then repeatedly washed with water by centrifugation, and finally dialyzed against distilled water using a cellulose membrane (Mw 12.400, D9652-100FT, Sigma-Aldrich, USA). The purified suspension was filtered through a syringe filter (GD/X syringe filters PTFE membrane, pore size 0.45um, Whatman, USA). Water in NCC suspension was exchanged to DMF by the vacuum rotary evaporator152. A 200 mL of the aqueous NCC was added to a 1000 mL round-bottom-flask. Then 200 mL of DMF was added in the flask and the mixture was vigorously agitated to get homogeneous dispersion of DMF in the NCC aqueous suspension. About 200 mL of the liquid was collected in the trap under vacuum and added 200 mL of DMF. This process of adding DMF and evaporation was repeated 3-4 times to ensure all water removed. The final concentration of NCC suspension in DMF was determined by weighing before and after drying 100 µl of suspension in a vial. The average value was obtained from 5 replicates.         46  3.4.1 Atomic force microscopy (AFM) of nanocrystalline cellulose (NCCs)     Morphological characterization of the NCC was carried out using a Multimode AFM Nanoscope-III from Veeco Instruments (Santa Barbara, CA, USA) using the ScanAsyst™ tapping mode. A freshly cleaved mica was washed with sulphuric acid and then rinsed with deionized water. 100 ul of 0.05 wt.% NCC suspension was dropped on the mica and left for 5-10 min for NCC particles to settle down and the water was removed using compressed air. AFM images were captured using RTESPA, Veeco Inst. silicon cantilever with scan rate of 0.383 Hz and at a scan size of 3 x 3 um. The average length and height value of NCC were determined by measuring 50 individual NCC rods from AFM images using NanoScope Software8.10 (Veeco, Santa Barbara, CA, USA).      3.5 Preparation of lignin-NCC-PEO solutions for electrospinning  The 4th fractionated SKF (F4SKL), which was obtained by washing with methanol/ methylene chloride (70/30,v/v) mixed solvent, was used as the raw material for electrospinning. F4SKL/NCC suspension/PEO solutions in DMF were prepared without and with NCCs at 80 °C for 3-4 hours. NCC suspension in DMF were mixed at loadings of 0, 1, 3 and 5 wt.% with respect to lignin solid weight after ultrasound treatment (sonication, Branson) of NCC suspension for 2 min. The lignin solution concentration was kept constant at 25 – 30 wt.% for all the dispersions. 1 wt.% PEO was added to the solution based on lignin solid weight to help form consistent uniform fibres.   47  3.6 Electrospinning of lignin-PEO solutions with various NCC loadings for random fibre mats    Electrospinning was carried out in a vertical orientation using a 1 mL syringe fitted with a 25G needle as a spinneret connected to the positive terminal of a high DC voltage power supply (Glassman HighVoltage, Inc., HighBridge, NJ). The operating voltage was +20 kV. The collecting distance was also varied from 20-30 cm. An aluminum foil sheet was used as the collector, and was connected to ground. A syringe pump (New Era Pump Systems, Inc. Wantagh, NY) operating at a flow rate of 0.01-0.03 mL/min supplied the lignin solution to the spinneret.   3.7 Electrospinning of lignin-PEO solutions for aligned fibres Lignin-PEO solutions without and with 5 wt.% NCC addition in using a 1 mL syringe with a 25G needle were electrospun with the +20 kV applied voltage, 20 cm collecting distance and 0.01 ml/min feed speed as described in section 3.6. Two counters charged metallic plates were used as a fibre collector with 1.5 cm gaps between the plates. 0.15 mL of lignin solution was spun into aligned fibres assemblies.   3.8 Oxidative stabilization process of as spun lignin composite fibre mats Neat NCC films and electrospun F4SKL/NCC/PEO composites nanofibre mats (0 - 5 wt.% NCC loading) were stabilized at 1or 5 °C/min to 200 - 350 °C from 30 °C in a gas chromatography oven (Hewlett Packard 5890 Series II) and held isothermally for 30 - 60 min in air. After treatment, the yield after oxidization was calculated by weighing the mats.  48  2FD3 (2 level Factorial Design with 3 variables) experiments were performed at 2 levels (LOW and HIGH level, often coded as -1 and +1) with the variables of final temperature (X1), holding time (X2) and heating rate (X3). The effect of any factors is calculated by summing a response (yield after thermal stabilization, %) for the factor at a HIGH (+1) level, and subtracting all responses for the factor at a LOW (-1) level.   3.9 Carbonization process of stabilized lignin composite fibre mats  Thermally stabilized lignin/NCC/PEO composite nanofibre mats with different NCC loadings were carbonized at 1000 °C with 10 °C/min and held isothermally for 60 min in the nitrogen atmosphere using a GSL-1100X tube furnace (MTI Corp., Richmond, CA).  3.10 Characterization of electrospun lignin composite fibre mats 3.10.1 Scanning electron microscopy of as spun, stabilized and carbonized composite fibres To study the nanofibre morphology, Hitachi S3000N scanning electron microscope (SEM) was used. The electrospun nanofibre mats were directly deposited onto the sample stages using conductive carbon tapes and characterized at 5 kV with working distance of 15 mm after sputter coating with 15 nm thickness of gold (Au). The mean diameter and standard deviation were calculated from several SEM images, and 100 fibres were analyzed with a ImageJ software.  3.10.2 Polarized optical microscopy of aligned lignin fibres  Collected aligned fibres as prepared in section 3.7 were mounted on a round microscope cover slide with a adhesive. Images of aligned lignin espun fibres with and without NCC were 49  taken in reflective light and dark field mode with a Nikon Eclipse LV100POL optical microscope equipped with a camera and NIS microscope imaging software. The polarizer slider was rotated for changing polarization direction from vertical to lateral direction and showing birefringence of the fibres.   3.10.3 Thermal analysis of as spun and stabilized composite fibres mats     Thermogravimetric analysis (TGA) was performed to characterize thermal properties of as-spun and thermally stabilized fibre mats using Q500 TA instruments (New Castle, DE). 2 ~ 3 mg of the composite nanofibre mats were heated to 600 °C and 1000 °C for as spun fibre mats and stabilized mats, respectively at a heating rate at 10 C/min under nitrogen flow. All runs were triplicate to get average values for 5% loss temperature (T5), maximum weight loss temperature (Tmax), maximum weight loss rate (R) and residue (%).    3.10.4 Molecular structure analysis of composite fibres  3.10.4.1 Fourier-transform infrared (FTIR) spectroscopy of as spun and stabilized composite fibres Evidence of the intermolecular structure change before and after stabilization process with various NCC loadings was analyzed by DRIFT-FTIR. Each of the samples dried in a vacuum oven for overnight before measurements. IR spectra were collected using a Spectrum One FT-IR Spectrometer (Perkin Elmer instrument, spectrometer equipped with spectrum software, 32 scans were collected with spectral resolution of 4 cm-1. The spectra were normalized at 1600 cm-1 for lignin based fibre mats and measured the relative intensity of absorption bands.  50  3.10.4.2 Polarized fourier-transform infrared (FTIR) spectroscopy of aligned fibres Study of lignin molecular alignment with or without NCC loading was conducted using a Spectrum One FT-IR Spectrometer (Perkin Elmer instrument) equipped with an infrared ZeSe polarizer (PIKE technologies) and a Spectrum software. 64 scans were collected with the spectral resolution of 8 cm-1. The infrared ZeSe polarizer mounted before the sample holder for measuring the dichroism of aligned fibres. The spectra for aligned as spun lignin fibres with or without NCC were collected by rotating the polarizer angles recording spectra every 20 from 0 to 180.  The collected spectra were analyzed after baseline collected and the intensity of absorbance was normalized as 0 to 1 with Origin 85 software.    3.10.4.3 Characterization of stabilized composite fibres after various treatment conditions by solid state 13C nuclear magnetic resonance (NMR) spectroscopy  To investigate the chemical structure change in lignin after various thermal stabilization process, solid state 13C NMR samples were prepared in D2O for as spun fibre mats and in DMSO for stabilized fibre mats. Solid-state NMR measurements were carried out on a Bruker Advance-400 spectrometer operating at frequencies of 100.61 MHz for 13C and 400.09 MHz for 1H NMR in a Bruker double resonance MAS probe head at spinning speeds of 16kHz for all experiments. 13C CP/MAS experiments utilized a 3 µs (90 °) 1Hz pulse, 2 ms contact pulse, 4s delay and 2K scans.      51  3.10.5 Elemental analysis for stabilized and carbonized composite fibres after various treatment conditions   Elemental analysis was conducted with a Carlo Erba Elemental Analyzer EA 1108 with stabilized lignin fibre mats after various stabilization conditions and carbonized fibre mats.    3.10.6  Thermorheological analysis of as spun composite fibre mats with NCCs loadings  Thermorheological analysis was performed under dynamic compressive-torsion mode on a TA instruments (New Castle, DE, USA) AR2000 rheometer. Circular discs of 25 mm diameter were cut of the mats, and three of them were stacked and held between two parallel stainless steel plates (25 mm dia.) with a normal force of 3 ± 1 N (strain: 0.1 %, frequency: 1 Hz). Samples were heated at 3 °C/min from 30 °C to 300 °C under nitrogen flow. The experiment was controlled such that the step controlled under normal force was terminated prior to sample softening below a critical modulus (using temperature termination at 190 °C) and switched over gap control once the modulus dropped below 190 °C to eliminate sample compression. The data curves were generated after calculating average values and one standard deviation using Origin 85 software.             3.10.7 Tensile properties of as spun, stabilized and carbonized composite fibres mats  Tensile properties of the electrospun fibre mats were measured using Katotech KES-G1 micro tensile tester equipped with various load cells (200-500 g) and LabVIEW software (National Instruments) for test control and data acquisition. A tensile specimen was cut into 5 mm in width and 37 ~ 50 mm in length size and mounted onto a paper frame. The paper frame was loaded onto the tester and the side of the frame was clipped before the tension was applied. 52  The specimens were deformed with a rate of 0.01 cm/sec. The load with 20-50 g/V sensitivity in grams was measured as functions of time. The time was converted to deformation in cm by multiplying by the deformation rate. The measured load (g) was converted to specific stress (g/tex) with the equation (1).  𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑆𝑡𝑟𝑒𝑠𝑠 (𝑔𝑡𝑒𝑥) =𝐿𝑜𝑎𝑑(𝑔)𝑊𝑖𝑑𝑡ℎ(𝑚𝑚)×𝐴𝑟𝑒𝑎𝑙 𝑑𝑒𝑛𝑠𝑖𝑡𝑦(𝑔𝑚2) -----(1) Where the areal density is the measured mass of the test sample divided by its area.111 The specific stress was then converted to N/tex by multiplying by 9.81 and further to MPa by multiplying by the bulk density of lignin which is assuming 1.35 g/ml.24   5 replicates were tested for each sample group and represent their mean and one standard deviation. ANOVA tests were performed to compare the mean values between samples with NCC loadings.       3.10.8 Characterization of carbonized composite fibre mats with Raman spectroscopy  Raman spectra of carbonized fibre mats were recorded on a RM1000 Raman Microscope system (Renishaw, Gluocestershire, UK) equipped with a 785 nm diode laser. A total of 2 scans per sample at 1 % laser power were collected in the range of 800 - 2000 cm-1 using an X20 microscope objective. Baseline correction between data points in the range was applied before curve fitting. The D-band was fitted with a Lorentzian line shape and the G band was fitted with a Breit-Wigner-Fano (BWF) line shape. The ratio of two bands, ID/IG was calculated as the ratio of the intensities (heights) of the D and G band.   53  3.10.9 Electrical conductivity of carbonized composite fibre mats The direct current (DC) resistance R (ρ, Ω) of carbon nanofibres mats was measured by 2- point probe using a multimeter (Agilent U1272A). Samples approximately cut into 1.5 cm in length and 0.5 cm in width and were painted at each end with silver paint on clean glass slides. DC conductivity (σ) was calculated based on the measure R in Ω and the dimensions of the samples using the following equation: (S/cm) = L/(w*t*R), where L is the distance between the non-painted part in cm, w is the sample width in cm, and t is the thickness in cm of the sample. 3 replicates were prepared and measured for each sample and the results were showed as an average with one standard deviation.   3.11 Characterization of lignin films  3.11.1 Polarized optical microscopy of lignin films 0.15 - 0.2 ml of the lignin-PEO solutions with or without NCC were dropped on glass microscope slides and allowed to evaporate DMF under ambient conditions for overnight. Images of the lignin film were collected in reflective mode under the bright field with a Nikon Eclipse LV100POL optical microscope equipped with a ¼ λ plate and a camera and NIS microscope imaging software. The polarizer slider was rotated for changing polarization directions from vertical to lateral to observe the birefringence of the lignin film.     3.11.2 Scanning electron microscopy of lignin films  Lignin film was mounted on a carbon tape and coated with a 15 nm thickness of gold (Au). Since the film was very fragile, the particles were separated on the carbon tape. Images of 54  a fracture surface of the lignin film were taken with Hitachi S3000N scanning electron microscope (SEM) at 5 kV accelerating voltage with the working distance of 15 mm.      55  Chapter 4: Molecular orientation and organization of lignin based composite nanofibres and lignin film 4.1 Introduction Nano- to sub-micron scale fibres can be produced by electrospinning polymer solutions. Final microstructure and properties of electrospun fibres are governed by the simultaneous solvent evaporation and rapid elongation of the solidifying fibre jets on very short time range(< 0.5 µs)156,157. Moreover, mechanical properties are affected by orientation of polymer chains in the fibres. Therefore, by controlling the orientation of polymer chains, the mechanical properties of polymer can be improved if chain alignment is parallel to the fibre axis158, as found in Spectra™ fibres, polyethylene fibres, which is about 15 times stronger than steel.  In this chapter, the orientation of lignin molecular chains within the aligned fibres was evaluated by polarized light optical microscope (POM). Furthermore, the functional groups of lignin that had preferred alignment along the fibre axis were studied with polarized FTIR. Polarized FTIR has been used for dichorism measurement for electrospun polymer nanofibres159–165 . In addition, nanoscale additives were added, nanocrystalline cellulose (NCC), and the impact of these functional particles on the orientation of lignin molecular chains within the aligned fibres was also investigated utilizing polarized FTIR analysis, providing additional insight to the alignment of nano additives within electrospun fibres.        4.2 Aligned lignin nanofibres and orientation of lignin  Macroscopically aligned nanofibres were fabricated by electrospinning with two counters charged metallic plates with a 1.5 cm gap as shown in Figure 4.1. The charged plate method was 56  chosen to collect fibres instead of using a rotating drum collector to ensure high fibre orientation. Although electrospun fibres can be aligned macroscopically through both collector types, one study showed that polymer chains within the fibres were not oriented when fibres were collected with a rotating drum160. The collected aligned lignin nanofibres were mounted on a rubber ring with an adhesive. Also, the aligned nanofibres were mounted to carbon tape for SEM observation and a round cover glass for the polarized optical microscope (POM). SEM images of fibres show significant alignment that runs diagonally through the image (Figure 4.2).  For both samples, lignin and lignin with NCC had fibre with preferred orientation. As noted, previously fibres had a diameter near nanometer (nm) indicating alignment did not impact diameter, as noted in other studies utilizing a rotating drum collector. However, the SEM image appeared cluster of 2-6 fibres in a small bundle in both set of samples indicating with arrows (Figure 4.2). Some bundling of the fibre was also noted in the polarized optical microscope (POM) images for the aligned fibre (Figure 4.3).  POM was widely used to observe the optical anisotropy associated with either crystalline or ordered structures. In Figure 4.3, electrospun lignin fibres showed bright contrast under the reflective light in dark field mode under POM. Degree of alignment of fibres could be varied with the collecting methods on the glass slides. As seen in the Figure 4.3, it is clearly shown that electrospun lignin-based fibres had birefringence between the crossed polarizers. Previously it was reported for other polymeric systems that electrospinning oriented polymeric chains when fibres were collected randomly or aligned166. This birefringence for lignin was a new discovery, as there has been almost no report for technical lignin molecular organization through the observation with optical microscopes. Further lignin’s structure was noted in the literature as amorphous with the absence of atomic symmetry, however amorphous material can undergo 57  orientation and a few studies have shown preferred orientation of lignin in the native state using polarized Raman or infrared spectroscopy167,168.   (a)   (b) Figure 4.1 Photographs of (a) the electrospinning process set up for fabricating aligned lignin fibres (b) mounted aligned electrospun fibres on a rubber o-ring     (a)  (b) Figure 4.2 SEM images of collected aligned lignin nanofibres (a) 0 % and (b) 5 % NCC loadings (scale bar (a) 10 um and (b) 20 um)  58   (a)  (b)  (c) Figure 4.3 POM images of electrospun lignin based nanofibres (a) randomly collected with 0 wt.% NCC loading (b) aligned with 0 wt.% NCC and (c) aligned with 5 wt.% NCC  To understand lignin orientation within electrospun fibres, polarized FTIR was used with a rotating polarizer recording spectra every 20 from 0 to 180. Aligned electrospun fibres (Figure 4.1(b)) were placed in the FTIR sample holder such that 0 and 180 indicated the parallel direction to the fibre axis. Figure 4.4 shows the normalized FTIR spectra of aligned lignin-based electrospun fibres with and without NCC loadings in the range of 4000 to 2000 cm-1 highlighting the 3600-3100 cm-1 hydroxyl stretching (νO-H), 3100-3000 cm-1 methine stretching (=CH-,νC-H), and 3000-2800 cm-1 aliphatic –CH2/CH3 (methylene/methyl) stretching (νC-H) with different polarization angles. In both cases with and without NCC as seen in Figure 4.4 (a) and (b), there was a significant difference in the wavenumbers where there was maximum absorption for the hydroxyl stretching region. For lignin, Kubo and Kadla used model compounds to analyze the complex hydrogen bonding region of lignin, distinguishing amongst aliphatic, phenolic, and biphenolic structures169. The latter represents the 5-5’ biphenol structure of condensed softwood lignins and these linked phenolics had a distinctive absorption in the region of ~3240 to 3219 cm-1. In Figure 4.4(a), it is clearly shown that a shift in peak intensity 59  was away from the higher wavenumbers when the polarizer was rotated perpendicular to the fibre axis. Hence, the 5-5 linkages may be responsible for allowing lignin to elongate along the fibre direction. Moreover, the difference between rotating angles for this region was also intensified with 5 wt.% NCC loading than spectra with no NCC loading (Figure 4.4 a&b). Two key areas of interest related to divergent cellulose 1 absorbance bands were found in the sharp peak at 3270 cm-1 and 3410cm-1, which bands did not have commonality when the polarizer is rotated from parallel to perpendicular to the fibre axis as shown in Figure 4.4(a).  Maréchal and Chanzy assigned the 3270 cm-1 to the hydroxyl stretching of the C2 (νO-H-C2) on the glucose ring that runs parallel with the cellulose chain axis170. Further the peak at 3410 cm-1 was assigned the predominate C6 conformation with hydroxyl stretching near perpendicular to the cellulose chain axis170. Analysis of the shift of the two peaks suggested a significant degree of orientation of the NCC particles within the electrospun fibres. Further, the normalized intensity of each band in the spectra represent as functions of rotating degree with NCC and without NCC loading (Figure 4.5).   60    Figure 4.4 The normalized spectra of polarized FTIR in the 4000 cm-1 to 2000 cm-1 regions with rotating polarizing angles (non : no polarizer) for electrospun lignin nanofibres with (a) 0 wt.% NCC and (b) 5 wt.% NCC loadings (a: 0° and 180 ° at 3330  cm-1 and b: 80°  and 100° at 3340  cm-1 and c: range in 3100-3000 cm-1) 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 20000.00.20.40.60.81.0a  AbsorbanceWavenumbers (cm-1) non 0 20 40 60 80 100 120 140 160 180bc4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 20000.00.20.40.60.81.0Absorbance   Wavenumbers (cm-1) non 0 20 40 60 80 100 120 140 160 180abca b 61       (a)   (b) Figure 4.5 (a) Normalized intensity of aliphatic hydroxyl OH band as functions of rotating degree for both 0wt.% NCC (NCC0) and 5 wt.% NCC loading (NCC5) and (b) change in peak intensity at 3270 cm-1 and 3410 cm-1 as functions of rotating angle with 5 wt.% NCC loading (NCC5)    Figure 4.6 Intensity at wavenumber 3050 cm-1 (νC-H) as functions of rotating angles for aligned lignin electrospun fibres with and without NCC loadings   0 20 40 60 80 100 120 140 160 1800.500.550.600.650.700.750.80Angle ()  Intensity in 3330-3390 cm-1 NCC0 NCC50 20 40 60 80 100 120 140 160 1800.450.500.550.600.650.700.750.80 Intensity at 3270 (cm-1)Angle ()3270 cm-13410 cm-10.450.500.550.600.650.700.750.80Intensity at 3410 (cm-1)0 20 40 60 80 100 120 140 160 1800.200.250.300.350.400.450.500.550.60  Intensity at 3050 (cm-1)Angle () NCC0 NCC562  As shown in Figure 4.5(a), both samples have “w” shape of intensity change i.e, the intensity was decreased – increased- decreased and increased repeatedly. The intensity is slightly decreased from 0 to 40 and increased to 100 as the similar intensity at 0 and then decreased to 140 and finally, increased to 180 for aligned lignin fibres without NCC loading.  The ratio of the intensity (R) was simply calculated by I0°/I100°. As mentioned above, the intensity of OH stretching was higher with NCC loadings (Figure 4.5 (a) than the intensity for without NCC loadings. This increase was in part due to the additional hydroxyl groups as well as shifts relate to the interaction between lignin and NCC. Also, there is more difference in intensity between 0 and 100 with NCC loading (R= 1.15). For 5 wt.% NCC loadings, the intensity was dropped to 60 and slightly increased to 100 and then decreased to 140 as the same intensity at 60 and finally increased to 180. It was noted that the 0 and 180 intensities for NCC5 were not perfectly symmetrical (Figure 4.5a) and this may arise from a slight deviation in fibre alignment during the mounting of the sample.  In summary, νOH in electrospun lignin fibres had a more preferred orientation along the fibre axis of lignin fibres with NCC loadings, with only a slight deviation in absorbance for hydroxyl stretching. Figure 4.6 shows the intensity of peak at 3050 cm-1 which is the centre of the range from 3100 to 3000 cm-1. This is benzene ring νC-H of the SP2 carbon. This showed that aromatic rings of lignin aligned along the fibre direction. Moreover, this result was enhanced by incorporation of NCC.  Figure 4.7 shows the normalized intensity of the band at 2930 cm-1 (νC-H) as functions of rotation angle for electrospun lignin fibres with and without NCC loading. For both samples, the intensity is decreased from 0 to 100 and increased to 180. Therefore, aliphatic SP3 carbon, CH3- groups preferred to align along with fibre axis for both samples. 63  Especially notable, the dichroic ratio (R) between 0 and 100 was 1.89, which showed significant dependence on direction with the presence of NCC. Also, the intensity plot for NCC loaded sample had a more symmetrical distribution as a function of polarizer angle than that of samples without NCC. This is possible that guaiacyl lignin have only one methoxyl on C3 (C3-OCH3-). This might have preferred orientation along the fibres so this region is more sensitive at certain polarization angles. Also this may be causes by shifts by neighboring bands. Overall, the CH3 stretching(νC-H3-) data for both sample revealed preferred alignment along the fibre axis.   Figure 4.7 Normalized intensity at 2930 cm-1 (νC-H) as functions of degree with and without NCC loadings in the fibres   Figure 4.8 shows that the normalized spectra of polarized FTIR of electrospun lignin nanofibres with and without NCC loadings with different polarizer rotating angles. In this fingerprint region, 1800 – 1300 cm-1, the different spectra for both samples did not have significant differences in intensity as a function of analyzer angles when compared with the region of 3600 – 2900 cm-1 (Figure 4.4). Detailed comparisons for each band were shown in Figure 4.9 (a)-(d). These intensity plots contained slight, yet consistent changes in intensity as a function of polarizer angle.  0 20 40 60 80 100 120 140 160 1800.300.350.400.450.500.550.600.650.70  Intensity at 2930 (cm-1)Angle() NCC0  NCC564     Figure 4.8 The normalized spectra of polarized FTIR in the range from 1800 to 1300 cm-1 region for lignin nanofibres (a) without (b) with 5 wt.% NCC loadings with different angles (non: no polarizer). 1800 1700 1600 1500 1400 13000.00.20.40.60.81.0  AbsorbanceWavenumbers (cm-1) non 0 20 40 60 80 100 120 140 160 1801800 1700 1600 1500 1400 13000.00.20.40.60.81.0Absorbance   Wavenumbers (cm-1) non 0 20 40 60 80 100 120 140 160 180a b 65   (a)  (b) (c) (d) Figure 4.9 Normalized intensity at (a) ~ 1598 cm-1(aromatic skeletal vibration + νC=O) (b) 1510 cm-1 (aromatic skeletal vibration) (c) 1710 cm-1 (νC=O) and (d) 1430 cm-1  (C-H in plane deformation with ν-aromatic ring) in normalized polarized FTIR spectra as functions of rotating angles with and without NCC loadings. Inserted graphs are having smaller scale.       0 20 40 60 80 100 120 140 160 1800.250.300.350.400.45  Intensity in 1710 cm-1Angle () NCC0 NCC50 20 40 60 80 100 120 140 160 1800.550.600.650.700.75   Angle ()Intensity in 1508-1510 cm-1 NCC0 NCC50 20 40 60 80 100 120 140 160 1800.670.680.690.700.710.72   Angle ()Intensity in 1508-1510 cm-1 NCC0 NCC50 20 40 60 80 100 120 140 160 1800.500.550.600.650.70  Intensity in 1430 (cm-1)Angle () NCC0 NCC50 20 40 60 80 100 120 140 160 1800.500.510.520.530.540.55  Intensity in 1430 (cm-1)Angle () NCC0 NCC566  As mentioned above, there was very little difference between polarizer angles and NCC loading as shown in Figure 4.9 (a)-(d). In this region, functional groups preferred to align perpendicularly to the fibre axis. The alignment of the band at 1710 cm-1 region, C=O stretch (νC=O) in Figure 4.9(c) is more angle dependent than aromatic mode, 1594 cm-1 as shown in Figure 4.9(a) and 1508 cm-1 in Figure 4.9(b). An interesting finding was that there is almost no change with angles at 1430 cm-1 in Figure 4.9(d) due to overlapping with cellulose band, δO-H(in-plane bending) of C-O-H alcohol163. This indicated that C-H in-plane deformation in lignin aromatic combined with C6-OH group in cellulose.    Figure 4.10 showed that the normalized spectra of polarized FTIR of electrospun lignin nanofibres without (a) and with (b) NCC loadings with different rotating angles. In this region, 1300 – 800 cm-1 showed significant differences in intensity not only between angles but also with NCC loadings obviously compared with the region of 1800 – 1300 cm-1 as shown in Figure 4.8. Most of the bands in this region preferred to align to the fibre axis except a band at 860 cm-1 which is C-H out of plane in position 2,5 and 6 carbons on lignin. Detailed comparisons for each band were shown in Figure 4.11 (a)-(b).  67    Figure 4.10 The normalized spectra of polarized FTIR in the range from 1300 cm-1 to 800 cm-1 regions for electrospun lignin nanofibres (a) without (b) with 5 wt.% NCC loadings with different angles. (a: 0°  and 180 °  and b: 80°  and 100°, non : no polarizer ) 1300 1200 1100 1000 900 8000.00.20.40.60.81.0  AbsorbanceWavenumbers (cm-1) non 0 20 40 60 80 100 120 140 160 180baab1300 1200 1100 1000 900 8000.00.20.40.60.81.0Absorbance   Wavenumbers (cm-1) non 0 20 40 60 80 100 120 140 160 180abbaa b 68     (a)  (b) Figure 4.11 Normalized intensity at (a) ~ 1214 cm-1 and (b) 1030 cm-1  (ν C6-O of C6H2-O6H) for normalized polarized FTIR spectra as functions of rotating angles with and without NCC loadings.         As shown in Figure 4.11(a), the band at 1214 cm-1 referring νC-O in both lignin and cellulose showed strong angular dependence suggesting the molecular bonds related to methoxy groups on the ring preferred to align to the fibre axis. However, there was no difference in the change of intensity as a function of angles between samples that included NCC with samples that did not have NCC. Figure 4.11(b) showed variation with both the polarization degree and also with the inclusion of NCC in the system. The band at 1030 cm-1, νC6-O deformation was more aligned to the fibre axis when NCC was loaded in lignin fibres. The bands at 1154 cm-1, also showed the same trend as 1030 cm-1 as this band corresponds to the glycosidic ether νC1-O-C4 stretch (Figure 4.12).    0 20 40 60 80 100 120 140 160 1800.650.700.750.800.85Angle ()  Intensity at 1214 (cm-1) NCC0 NCC50 20 40 60 80 100 120 140 160 1800.400.450.500.550.600.650.700.750.800.850.90 Intensity in 1030-1032 cm-1Angle () NCC0 NCC569   Figure 4.12 Normalized intensity at ~ 1034 cm-1 (ν C6-O of C6H2-O6H), 1056 cm-1 (νO-H of C3-O3H) and 1154 cm-1 (glycosidic ether νC1-O-C4) for normalized polarized FTIR spectra of aligned lignin based composite nanofibres with 5 wt % NCC as functions of rotating angles.       In summary, there was a preferred alignment of each functional group in the fibres. There was a effect of NCC loadings on the alignment of lignin’s functional group in the lignin fibres. 4.3 Orientation of lignin molecules chains in lignin film state Previous work was performed for the study of thermotropic lignin molecular organization during the heating process with polarized optical microscope(POM)60. Lignin films were prepared from lignin solution in DMF, similar to the electrospinning solution above, and observed under the POM to reveal if the lignin molecules also had an ordered structure when dried after slow solvent evaporation at room temperature. As shown in Figure 4.13, the solvent cast lignin film showed a unique response under the POM by rotating polarizer slider for adjusting polarizer orientation for lateral(red) and vertical direction(green). The lignin-based film demonstrated birefringence, which would arise from an organized structure, formed during drying.     0 20 40 60 80 100 120 140 160 1800.40.50.60.70.80.91.0  Intensity  Angle () 1034 cm-1  1056-1058 cm-1  1154-1158 cm-170   Figure 4.13 Lignin film dried from lignin/NCC/PEO solution in DMF under the circularly polarized optical microscope with reflective light and bright field by changing polarizer orientation from lateral (ll) to vertical direction from up left to right left (scale bar : 10 um)   Figure 4.14 A picture of lignin film and polarized optical microscope images of lignin based film from lignin in DMF solution and indicating different part of the film have different optical properties (a) mid (b) edge part of the film under the lower magnification (x5, scale bar : 500 µm) and (c) edge part of the film under the higher magnification (x20, scale bar : 100 µm)    c  a b 71  Further, to demonstrate if this birefringence was caused by additive, PEO, a film was prepared from lignin solution dissolved in DMF without adding PEO. As shown in Figure 4.14(a), the thickness section of the film in the centre, there were no separated pieces of colour found clearly. However, near the film’s edge, Figure 4.14(b), there was obvious iridescent colour under low magnification but mostly colours under the higher magnification by circularly polarized light as shown in Figure 4.14(c). Liquid crystal like phenomenon of the lignin showed during the heating by lignin model compounds60. This works showed possibility of forming molecular organization in lignin during the heating for carbonization process60.               72   (b)   (a)  (c)  (d)  Figure 4.15 Polarized optical microscope images of lignin based film from lignin in DMF solution with 5 wt.% NCC and indicating different part of the film have different optical properties (a) the lignin film under the lower magnification (x5, scale bar: 500 µm) indicating (I) centre(innermost) (II) mid and (III) edge part, (b) polarized optical microscope images of centre part of film, (c) middle part of the film and (d) edge part of the film under the higher magnification (x20, scale bar : 100 µm)   III16  I II II I III 73  Another interesting result was found with a lignin film with the inclusion of NCC. As shown in Figure 4.15, dependent upon the location of the film, the number of colours are different under the circular polarized microscope. This is also effect of a thickness in the film. Therefore, we could tailor the colour pattern of the film by controlling thickness of the film. The centre of the film contained a single-colour, which was green or red. On the other hand, the middle or edge part of the film showed 3-4 colours under the POM. This multidomain formation can be compared with the optical investigation of NCC film work by Dumanli et al171 ; they found that colour difference from the ordering layers in microstructure observed by SEM. However, in this study, because the lignin film, itself was very fragile so, it was hard to observe the microstructure under the SEM with the same sample’s state.   As shown in Figure 4.16, fractured surface of the lignin film had clean and uniform layers formed and regular parallel lines show under the top surface of the film. Individual lignin clusters were not distinguished. The length between lines was hard to determine due to sample’s inclined plane but was estimated to be on the order of microns. The same phenomenon was observed with the lignin film with 5 wt.% NCC loadings as shown in Figure 4.17. The film with NCC also contained regular parallel lines under film top surface, but the roughness was different with non-NCC samples. Rough surface shows with NCC, which was also observed under the polarized microscope (Figure 4.13). The surfaces were evenly textured across the edge along with zones of intense clustering. Further, it appeared that NCC particles may have distributed in lines, seen in SEM image with higher magnification in Figure 4.18. It seems NCC particles aligned between layers as shown in earlier work172.  74       a b c Figure 4.16 SEM images of fracture surface of the lignin film without NCC loadings. (Scale bar;(a) 50 m (b) 20 m and (c) 30 m) 75   Figure 4.17 SEM images of fracture surface of the lignin film with 5wt.% NCC loadings.  (Scale bars; (a) 100 m,(b) 20m and (c) 10m)   (a)  (b) Figure 4.18 SEM images of the fracture surface of the lignin film with 5 wt.% NCC loadings (scale bars;(a) 20 m , (b) 5 m) a b c 76  The fractured surface of the SEM films revealed that the lignin was not a monolithic structure. The smallest consistent patterns for films, with and without NCC, were on the scale of single digit micrometers. Complex processes must occur at the film surface where a change in localized concentration may lead to self association of the lignin molecules into specific patterns. Albeit technical lignin was heavily modified during delignification, native lignin has been reported to be able to assemble into a replicating like pattern173. Based on this data it is suggested that technical lignin may still retain some structures that allow them to become organized and oriented based on solvent removal conditions.     4.4 Conclusions Because electrospinning causes rapid elongation of the polymer jet, the orientation of lignin molecules within aligned electrospun fibres were studied along with solvent cast lignin films. The samples were analyzed for their anisotropy polarizabilities resulting in birefringence in the fibres and films of lignin with and without NCC. The birefringence in lignin films indicated that lignin molecules can be organized during the slow evaporation at room temperature. SEM images of the microstructure of the cross-section of the lignin film showed regular patterns under the top surface of the film for both samples, with and without NCC. This result reported was one of the first times for multi-micron thick films based on lignin to develop structural features from self-organization. In addition to organization, orientation of the molecular chains within fibres with polarized FTIR. Spectra of the fibre materials as a function of polarizer angle contained differences that suggested orientation of lignin molecules within the fibres. NCC within the fibre was also oriented along the fibre axis, and this resulted in enhanced lignin orientation. 77  Chapter 5: Optimization of electrospinning process for forming lignin based composite fibres with nanocrystalline celluloses (NCCs) 5.1 Introduction Electrospinning is a simple and effective process to produce continues fibres from a polymer solution or suspension with sub micron-sized to nano-sized in diameter. Electro-spinnability for forming fibres is mostly governed by solution properties and/or spinning processing parameters. Solution parameters could be viscosity, surface tension, a conductivity of solutions etc. Also, parameters of the spinning set up are the collecting distance between the tip of the needle to the target, the feed speed and the applied voltage etc. By controlling these parameters mentioned above, different properties of fibres could be produced with various fibre diameters, morphology and other microstructure of fibres.  Electro-spinnability of lignin solutions was studied to form new composite system consisting of over 95% lignin with 1- 5 wt.% nanocrystalline cellulose (NCC) and 1wt.% poly(ethylene oxide)(PEO) as a supporting material. This similar system was already shown in the previous work76 but their composite contains more than 25 wt.% of another synthetic polymer, poly(vinyl alcohol)(PVA).  This chapter was focused on the production of uniform and the smallest continues nanofibres with defects free and droplet free non-woven fibre mats by controlling electrospinning processing parameters with collecting distance, feed speed, applied voltage and the inner diameter of needles. As a response to these controlled parameters, average diameters of fibres were measured from scanning electron microscopy (SEM) images to select uniform 78  electrospun lignin-based fibres with the smallest fibre diameter with the lowest standard deviation.  5.2 Morphology of isolated-nanocrystalline celluloses (NCCs)  Nanocrystalline cellulose (NCC) is readily dispersed in water but must be carefully exchanged with organic solvents in order to maintain uniform dispersions 174,175. Dimethylformamide (DMF) is a water miscible, aprotic solvent that disperses NCC and was used in this study for this purpose, as it is also a good solvent for lignin. Figure 5.1 reveals an atomic force microscope (AFM) image of NCC. NCC, derived from cotton sources, averages thickness of 8 nm ± 2 and 322 nm in length. These thickness values correspond closely to the values obtained by Elazzouzi-Hafraoui et al. which measured 7 nm, however the length of the nanocrystals are greater than the 141 nm for length176.    Figure 5.1 AFM images of isolated NCC by sulfuric acid hydrolysis,  Average length ≈ 322 nm and height ≈ 8.5 nm  79  5.3 Study of electro-spinnability of lignin-NCC-PEO solutions from various electro-spinning conditions    NCC was mixed with fractionated F4 kraft lignin at various concentrations (0-5 wt.%) and different lignin solution concentrations (25-30 wt.%) with 1 wt.% PEO added based on lignin solid weight. Mixtures of solutions formed composite fibres using fixed electrospinning parameters (i.e., applying voltage of 20 kV, 0.01ml/min feed speed and the collecting distance of 25 cm). SEM analysis (Figure 5.2) revealed that all 9 combination of conditions formed random fibre mats of various quality and dimensions.  Further investigation of the effects of electrospinning parameters on the fibre diameter was performed where lignin/NCC composite fibre mats were produced from 27 wt.% lignin solution with 1wt.% NCC. Applied voltage was maintained at 20 kV and the feed speed (0.03 or 0.01 ml/min), collecting distance (20, 25 and 30 cm) and needle gauge (22G ,0.019 inch=0.482 mm and 25 G, 0.012 inch=0.304 mm) was varied to optimize these parameters on creating uniform fibres with the smallest diameters.  Using needles with smaller tip diameters has been reported to enhance the uniformity of electrospun fibre mats110. Some recent studies have also showed that needles with smaller diameter tip resulted in smaller fibre diameters110. However, the results in this study (Figure 5.3) showed a reversed trend for the lignin nanofibres with 1 wt.% NCC loading. Other study showed similar phenomenon with this current study; the researchers reported a lack of correlation between the needle diameter used and the resulting nanofibre diameter177. The feed speed or rate make the polymer solution pumped into the tip to form the Taylor’s cone111. This should match the rate of removal of solution from the tip to form continuous fibres111. In this study, there is not clear relationship between the speed and the 80  diameter of the fibres. The larger fibre diameters showed at higher speed at same needle size with 27 wt.% lignin solution (Figure 5.3 a).  The collecting distance from the needle tip to the collector defines the strength of the electric field as well as the time available for evaporation of the solvent before the nanofibre reach the collector111. In this study, there was no clear relationship between the distance and the diameter. The diameter decreased and increased from 20 cm to 30 cm of the distance (Figure 5.3a).           Electrospun fibres, which were produced from 25 cm collecting distance and 0.01 ml/min feed speed showed the smallest average fibre diameter values with smallest standard deviations for both needle sizes relative to the other spinning conditions at the same lignin concentration.   The proper concentrations allow adequate chain entanglement, continuous uniform nanofibres. If the concentration of polymer solution will electrospin, it usually has a dominant effect on the fibre diameter and fibre morphology. For low lignin solution concentrations, some fibres contained defects such as spindles. (Figure 5.2 a-1, a-3 and a-5). These spindles were increased at higher NCC loadings which may be related to localized changes in viscosity. According to Ago et al., the viscosity of the spinning dope increased with addition of NCC and showed non-Newtonian behavior76. In this study with specific polymer/solvent system, there generally agree that the fibre diameter increases with increasing polymer concentration (Figure 5.3). A summary of some recent studies was highlighted in Table 1.4 as mentioned earlier, showing the differences at various spinning conditions of solvent fractionated lignin.  In Table 1.4, the fibre diameter for these samples has matched with Dallmeyer et al., which had 875 nm with 28 wt.%36 lignin concentration, however, differed from Lin et al., which had 667 nm with 81  25 wt.% lignin concentration70. Also, high variability was shown in lignin fibre diameter at 25 wt.% lignin without NCC loading. With addition of NCC, uniformity of fibre diameter was improved and increased 40 % from 1 wt.% to 5 wt.% NCC loadings. For both 27% and 30% lignin solutions, uniform fibres were created with NCC addition. A general trend emerged for the fibre diameter, which increased as the concentration of lignin increased. The impact of NCC loadings on the fibre diameter showed no trends when taken into the account of the variation of the fibre size at higher lignin concentration.  Other researchers reported a decrease in electrospun fibre diameter when nanoparticles are added to the spinning solution110,140.  Figure 5.4 shows SEM images and pictures of as spun fibre mats from 7 and 10 wt.% NCC loadings in F4SKL solutions. Morphology of fibres in the SEM images shows the mixing with beaded and large spinndle formed. Also, spinability was unstable with droplets and spray on the mats. Therefore, it was decided that 5 wt.% is maximum loading in this study.   82   Figure 5.2 SEM images for as spun lignin based composite nanofibres with various concentrations of lignin solution (a :25 wt.%, b:27 wt.% and c: 30 wt.% ) and different NCC loadings (0,1,3 and 5 wt.%) (Scale bars = 10 um)  a-0 b-0 c-0 a-1 b-1 c-1 c-3 c-5 a-3 b-3 a-5 b-5 83   (a)  (b) Figure 5.3 Average fibre diameter with (a) various spinning conditions with 20 – 30 cm collecting distance, 0.01 or 0.03 ml/min feed speed and 22 G or 25G of needle size (b) different concentration of lignin solutions from 25 to 30 wt.% and NCC loadings from 0-5 wt.%     (a)   (b) Figure 5.4 SEM images of lignin based nanofibres with (a) 7 wt.% and (b) 10 wt.% NCC loadings. Real fibre mats images were inserted with SEM images respectively.  84  5.4 Conclusions  This chapter showed the feasibility of forming nanofibres from various lignin solution concentrations with different NCC loadings. As a result, the concentration of the lignin solution and NCC loadings impacted the fibre quality and the ability to spin uniform fibre mats. Lignin concentrations of at least 27% formed defect-free nanofibres with NCC and PEO. More than 5 wt.% of NCC loading in lignin solution was unable to form continuous and uniform composite nanofibres due to inhomogeneity of solutions with high viscosity.  85  Chapter 6: Effects of nanocrystalline celluloses (NCCs) on the structure and properties of electrospun lignin composite fibre mats  6.1 Introduction  Limiting the adoption of lignin as a carbon fibre precursor, the mechanical properties of lignin-based carbon fibres still cannot compete with those made from PAN178. Therefore, further mechanical property improvement of the fibre not only is needed for automobile applications, but also may offer other possible applications for both lignin materials as bioplastics and lignin-derived carbon fibre. The mechanical properties of the material can be improved in various ways, such as reducing the fibre diameters, therefore limiting defects. Electrospinning is a simple and effective method of forming a continuous fibre with submicrometer to nanometer scale diameter from polymer solutions106. Another method of enhancing properties is increasing the molecular weight of lignin, either through selective fractionation42,43 or cross-linking179. Further incorporation of nanofillers, or reinforcement, such as organoclay180, carbon nanotubes (CNTs) 35,70 into lignin matrices has been investigated to show improvement in properties. Another nanoparticle reinforcement that has been produced at demonstration scale is nanocrystalline cellulose (NCC). This material has generated a great deal of interest as a source of nanoscale reinforcement in nanocomposites because of high mechanical properties and low density compared to inorganic nanoparticles. Further it has shown to be an effective additive in electrospun lignin and polyvinyl alcohol (PVA) polymer blends with enhanced interaction with lignin76–78. Yet, this is the only composite system that reporting NCC and lignin carbon nanofibres although lignin and cellulose are found as a natural mixture all over the world in plants.  86  In this study, the impact of nano-reinforcement was investigated to determine the impact of the NCC on the chemical, thermal and mechanical behavior of the high lignin content fibre with different levels of thermal treatments. This study provides insight into tailoring the mechanical properties of lignin nanofibre reinforced with NCC as well as the relative improvement in lignin properties through simple thermal stabilization and carbonization processes.  6.2 FTIR study of lignin composite fibre mats with NCCs loadings   Electrospun fibre mats were evaluated using FT-IR spectroscopy in order to reveal indication of interactions between NCC and the lignin. The electrospun lignin material showed typical lignin adsorption bands for O-H stretching of the aliphatic hydroxyl groups at 3400 cm-1, C-H stretching of the methylene and methyl groups of the side chains and aromatic methoxy groups at 2900 cm-1 and C-H vibration of the aromatic rings at 1600 and 1500 cm-1. When NCC was added to the fibres, there was an increase in the relative intensity for the peaks related to cellulose, such at cellulose’s most intense absorbance band at 1033 cm-1. This absorbance band increased linearly with increasing NCC content (Figure 6.1). In addition, the O-H stretching band significantly shifted from 3410 cm-1 to 3336 cm-1 with 1 wt.% NCC loading, and this shift became more pronounced at 5 wt.% NCC loading.  This data suggested that the presence of the NCC had significantly altered the hydrogen-bonding environment of the electrospun lignin fibres. These peak shifts indicated a simple harmonic oscillator model of increased bonding through a shift to lower wavenumbers.  In other words, intermolecular hydrogen bonding weakens the O-H absorption, thereby shifting the band to lower frequency. Based on this insight, there appears to be the intermolecular interaction between lignin and NCC; both surface 87  hydroxyl groups and sulfate esters from the NCC would interact with phenolic and aliphatic hydroxyl groups of lignin through these types of secondary interactions. Recent studies on NCC reinforced polymer nanocomposites have also revealed that NCC strongly interacts with matrix. For example, Ago et al. described a shift of the main OH stretching peak to lower wavenumbers due to the strong hydrogen bonding between the NCC particles and lignin/poly(vinyl alcohol) (PVA)76. Also, Zhou et al, showed that cellulose O-H peak strengthened gradually with increased NCC contents in the PEO/NCC composite nanofibre mats110.  (a) 88   (b)  (c) Figure 6.1 (a) DRIFT-FTIR spectra for lignin based composite nanofibre mats with different NCC loadings; (1) 0 wt.%, (2) 1 wt.%, (3) 3 wt.%, (4) 5 wt.% and (5) NCC film. (b) and (c) are relative intensity of functional groups with different NCC loadings. (No detected peaks at 1082 cm-1 for 3 and 5 wt.% NCC loadings and no detected at 1057 cm-1 for 0 and 1 wt.% NCC loading.)  Figure 6.2 shows FTIR spectra for the thermally stabilized lignin fibre mat with different NCC loadings and NCC film at 250 °C for 1 hour in the air. Compared with the spectrum of NCC in Figure 6.1(a)-(5), the C-O stretching region (~1060 cm-1) related to cellulose completely disappeared and new peaks were found at 1712 cm-1 attributed to νC=O, and 1610 cm-1 for νC=C stretching bands for significantly oxidized NCC in Figure 6.2(5).  This new peak at 1712 cm-1 also is seen in lignin fibre mats even without NCC, but the majority of the signature fingerprint for lignin below 1600 cm-1 still retained even after heat treatment. This suggest that NCC already partially degraded, while the lignin is still structurally intact, and that degradation of the NCC may have played a role as defects after heat treatment in decreasing the tensile strength of the oxidized mats.   89  6.3 Thermal properties of as spun lignin composite fibre mats    Electrospun fibre mats were analyzed using thermogravimetric analysis in nitrogen environments. Similar to prior study76, both NCC and lignin have significantly different degradation profiles, with NCC being more thermally sensitive, with an onset temperature degrading around 230 °C (Figure 6.3). This arises from the sulfate  ester groups  that reside on the NCC surface when hydrolyzed by sulfuric acid181.  In contrast, lignin alone has a broad degradation profile with a derivative peak (dTGA) near 375 °C.  The addition of NCC did not significantly impact the degradation profile of the lignin, however it did shift the intensity of the derivative peak from 1.4 to 2 °C/% loading of NCC, following a rule of mixture. This finding suggested that NCC and the resulting degradation products did not have a catalytic effect on the lignin degradation. This result, however, differs from the findings reported in Ago et al., which showed the addition of NCCs improved the thermal properties of the composite fibres in the presence of PVA76. However, NCC is less thermally stable than lignin so, the shift in composite samples is in line with their individual behavior. Moreover, there was only a minor impact of NCC loading on the residual mass of the electrospun mats, decreasing from 43.6% to 40.8 % without any specific trends. As a result, intermolecular interactions between NCC and lignin had no synergistic influence on thermal stability of composite nanofibres.  90   Figure 6.2 DRIFT-FTIR spectra for thermally stabilized lignin based composite nanofibre mats with different NCC loadings; (1) 0 wt.%, (2) 1 wt.%, (3) 3 wt.%, (4) 5 wt.% and (5) thermally oxidized NCC film.    (a)  (b) Figure 6.3 (a) TGA curves and (b) derivatives for freeze dried NCC and as-spun lignin composite nanofibre mats with different NCC loadings under nitrogen flow.    91  Table 6.1 TGA results for temperature at 5 % weight loss temperature (T5), maximum weight loss temperature (Tmax), maximum weight loss rate (R), and yield % at 600 °C (Y) for as-spun lignin composite nanofibre mats with different NCC loadings   Samples T5 °C Tmax °C R  %/°C Y % NCC 154.1 234.32 0.476 23.69 0 wt.% 112.1 376.36 0.296 43.60 1 wt.% 137.7 375.80 0.335 41.14 3 wt.% 117.9 370.63 0.322 40.79 5 wt.% 131.8 367.45 0.328 41.91  6.4 Effects of NCC loadings on morphology and fibre diameter of lignin based composite nanofibres    Figure 6.4. shows SEM images of lignin based composite nanofibres with different NCC loadings after the carbonization process. Carbonized lignin based composite nanofibres showed distinct differences in their morphology, especially with 3 and 5 wt. % NCC loadings. In Figure 6.4, the fibres with 3 and 5 wt.% NCC prior to carbonization appeared to have very gradually bended structure along their axis as compared to fibres without NCC. During post carbonization, fibre morphology significantly deviated from the fibre axis, appearing as a sinusoidal pattern (wavy) of fibres draped across supporting fibres as seen in Figure 6.4 (c) and (d). This observation was in accordance with an earlier study on electrospun lignin carbon nanofibres with multiwall carbon nanotubes (MWCNTs) and the formation were ascribed to differential shrinkage and degradation of two components, lignin and MWCNTs 82. The wavy fibre structure has also been reported for carbon nanotubes182, however the mechanism was ascribed to catalyst sliding effect during synthesis. Other a work on carbon nanotube fibres has described the presence of oxygen that creates discontinuities in the carbon structure changing the 92  growth rate of fibres183. The other change in the fibre after carbonization treatment contains substantial reduction in fibre diameter as the average diameter of lignin based composite nanofibres significantly decreased after carbonization between 20 and 40% as shown in Table 6.2.  Figure 6.4 SEM images of carbonized lignin composite nanofibres with different NCC loadings. (scale bars = 10 um) (a) 0 wt.%, (b) 1wt.%, (c) 3 wt.% and (d) 5 wt.% NCC loadings.   Table 6.2 . Average fibre diameter and change (%) of average fibre diameter before (as spun and stabilized) and after carbonization as functions of NCC loadings, ± one standard deviation NCC loadings 0 wt.% 1 wt.% 3 wt.% 5 wt.% As spun (nm) 578 ± 69 676 ± 74 672 ±143 783 ± 157 Stabilized (nm) 537 ± 77 609 ± 75 609 ± 74 693 ± 93 Carbonized (nm) 319 ±34 487 ±63 444 ± 44 406 ±51 Change (%) 40.6 20.0 27.1 41.4  a b c d 93  6.5 Mechanical properties of lignin based composite fibre mats with different NCC loadings Figure 6.5(a)-(c) shows the average tensile strength, Young’s modulus, and strain at break values for as-spun, oxidized and carbonized electrospun nanofibres with different NCC contents. There are numerous studies on lignin-based carbon fibres and it has been shown that carbonization greatly improved the mechanical properties of lignin fibres, however, only limited number of studies have reported the properties of thermally stabilized lignin36,82. There was a dramatic increase in both strength and modulus of lignin nanofibre mats with different NCC loadings after thermal stabilization at 250 °C. It has been shown that lignin forms cross-linked structures and behaves as a thermosetting material at elevated temperature184. Argyropoulos et al., reported that MW of softwood kraft lignin was increased 70 fold after heating at 173 °C for 30 min under nitrogen flow. In addition, Cui et al. reported this highly cross-linked lignin could not be dissolved in common organic solvents185 similar to our observations with the thermally stabilized electrospun mats.  While the strain at break values are relatively low (1-2%), tensile strength and modulus values of oxidized lignin nanofibres are in the range of 30 MPa and 1.5 GPa, respectively, which are equivalent to modest performing renewable polymers such as polyhydroxybutylate186 suggesting that controlled thermal processing may greatly improve the performance of technical lignin. It appears there is a marginal effect of NCC content on the performance of the fibres for both the lignin and thermally stabilized lignin samples. Typically, the greatest impact of NCC on mechanical performance of nanocomposites is seen when the matrix polymer is above its glass transition temperature (Tg) in the rubbery plateau132. Normally there is little notable difference in the modulus of glassy materials with nano-reinforcement. In this study, 5 wt.% NCC loading was maximum amount to form uniform electrospun fibres and 94  spinning dope with above 5 wt.% NCC loading showed droplets on the collector with very high viscosity as shown in Figure 5.4. Fractionated soft wood kraft lignin used in this study has a Tg near 209 °C, well above room temperature at which the tensile tested were conducted. Thermally stabilized fibre mats showed decreasing trend on tensile properties with increasing NCC loadings. There was a 40 % and 45 % decrease in strength and modulus, respectively from 0 wt.% to 5 wt.% NCC loadings as shown in Figure 6.5(a). To suggest reason for these differences, the samples were analyzed with FTIR shown in Figure 6.2. Further heat treatment in an inert atmosphere led to carbonization of the lignin mats. The carbonization process dramatically improved the mechanical performance of the electrospun fibre mats in terms of both strength and modulus (Figure 6.5.) from 8 MPa to 52 MPa and 0.71 GPa up to 6.87 GPa, respectively. These values are quite comparable with published values of electrospun PAN fibre by Ding et al 72. They reported tensile strength and Young’s modulus to 41 MPa and 6.4 GPa, respectively for PAN carbon fibre mats. With the increasing NCC content, the tensile modulus of composite lignin carbon nanofibre slightly increased from 6.51 GPa to 8.10 GPa. However, the result values were statistically similar indicating modulus values were not changed by NCC loading. It is important to note that further orientation of the reinforcement phase along the fibre axis plays an important role in enhancing the mechanical properties of nanofibres. A recent study has noted that in most cases NCC has only a marginal degree of orientation along the fibre axis187. Along with the fibre mat being randomly oriented, the wavy morphology has also enhanced random orientation of the fibre in the Z-plane of the mats. Hence, the carbon fibre is remarkable in that the tensile modulus appeared to increase at higher NCC loading although there is significant structural change. It is reasonable to assume that tensile modulus would increase greater without the wavy morphology. This result is in contrast with the 95  electrospun lignin fibre mats reinforced with multi-walled carbon nanotube (MWCT) that led to significant decrease in the modulus of electrospun nanofibres82. Poor interfacial adhesion between the lignin and MWCNT resulted in about 25-60% decrease in modulus when this type of nano-reinforcement was used in lignin, although CNTs have extremely high modulus, up to 1 TPa.     Other studies have shown a significant increase of the electrospun mat modulus contributed by the high level of orientation of the nanofiller, especially NCC 110,166  and fabricating fibres by using different collectors165, applying magnetic field188. This might impact the molecular orientation of polymer chains and result in increased mechanical properties of composite nanofibre mats. Also, It is well known that improving mechanical properties of nanofibres is related to decreasing the fibre diameter62,161 at the single fibre level. The average fibre diameter of individual lignin based-composite nanofibres increased with NCC loading as shown in Table 6.2. This might have affected the mechanical properties of composite nanofibre mats. Also, in this study, mechanical tests were conducted on random fibre mats, not at single fibre level. Therefore, the tensile deformation of a fibre mat is considered more complicated than that of a single fibre tests. During the tensile testing, the nanofibre mats are experienced with non-uniform stresses being developed resulting in the rearrangement of nanofibres within the mat to accommodate the strain111.Therefore, strain-dependent changes in the concentration of stress loading on nanofibres and eventually only a few fibres break from the mat prior to the overall failure of the testing sample111.   96   (a)  (b)  (c)  Figure 6.5 (a) Tensile strength, (b) tensile modulus and (c) strain at break of lignin based composite nanofibres at different heat treatment stages with various NCC loadings. (p < 0.05 , except carbonized samples)  6.6 Conclusions  In this chapter, the extensive studies were conducted for understanding interaction between lignin and NCC in fibrous form and as non-woven fibrous mats state. FTIR analysis for interaction between lignin and NCC indicated a peak shift at the aliphatic hydroxyl region related to interactions between the two phases although there was no synergistic impact on the thermal stability of the material in an inert atmosphere as results of the thermal analysis. Thermally stabilized and carbonized nanofibre had a significant reduction in the overall fibre diameter. 97  With the addition of NCC, the fibre was transformed into a wavy structure indicating a loss of in-plane orientation after carbonization. Thermal treatment of lignin led to a dramatic increase in lignin mechanical properties regardless of the presence of NCC. After thermal stabilization, mechanical properties of electrospun fibre mats increased 400 % and 143% for strength and modulus, respectively. As expected, the carbonization dramatically improved the mechanical properties as well as stiffness by eightfold and strength by twofold. This provides insight into tailoring the mechanical properties of lignin nanofibre reinforced with NCC as well as the relative improvement in lignin properties through simple thermal stabilization and carbonization processes.    98  Chapter 7: Impact of thermal oxidation process on the performance of lignin based composite carbon nanofibres 7.1 Introduction In the previous two chapters, the influence of electrospinning parameters on the formation of precursor nanofibres for carbon nanofibres composed of a mixture of lignin, nanocrystalline cellulose (NCC), and polyethylene oxide (PEO) in dimethylformamide (DMF) were studied to form composite nanofibre mats. Also, the mechanical performance of spun fibre as a function of loading of nanofiller, NCC, was determined for the lignin-based materials after different heat treatment stages. Furthermore, as shown in the previous chapter, thermo-stabilization (TS) was required prior to the carbonization process. This TS step was critical for carbon fibre production to prevent softening and loss of morphological structure of precursor fibres during the carbonization stage56,119. As a result of the TS process, the precursor fibres became more resistant to dimensional change and, therefore, the fusion of individual fibres during the carbonization process was prevented. Further, some studies on the optimization of the TS process with lignin powder or lignin-based fibres had been done for stabilized micro-sized lignin-based fibres to investigate changes in lignin molecular structure after various TS conditions117,118,120. However, there has not been a comprehensive study on properties of lignin based carbon nanofibres with optimizing thermal stabilization from structural view in nano-sized fibre. Especially, the formation of carbon textures in lignin based carbon nanofibres and their change in structure and physical properties might be different from micro sized carbon fibres due to the surface area to volume differences in these systems. In this chapter, extensive studies were conducted to investigate the effects of the thermo-stabilization process on properties of 99  nanofibres and/or nanofibre mats. Yield, change in fibre diameter/distribution, contents of elemental composition and mechanical properties were explored on both stabilized and carbonized nanofibres and/or nanofibre mats. Also, vibrational spectroscopy and solid state 13C nuclear magnetic resonance spectroscopy were used to analyze the change in lignin molecular structure after exposure to various heating conditions. Furthermore, studies were focused on the effects of thermo-stabilization conditions on the resulting carbon structure of carbonized lignin nanofibres and/or nanofibre mats through Raman spectroscopy and electrical conductivity tests.                           7.2 Influence of process parameters on yield after the thermal oxidation process Among different design of experiments based techniques, two-level factorial experiments (2FD) are the most effective in engineering applications for the optimization of parameters189. This analysis can help to identify the effects and interactions of relatively few variables (2-4 variables) or to analyze the most significant one from many variables (over 5 variables).  In the current study, a 2-level factorial design with 3 variables (2FD3, 23) that included final temperature, holding time, and heating rate was studied to determine the impact on yield after thermo-stabilization process. Ranges for these experiments were chosen such that final hold temperature was high enough to cause some degradation to the lignin185, while not too significant to cause serious weight loss based on TGA data as shown in Chapter 5. Holding time was chosen based on literature for thermal-oxidation of softwood lignin, while heating rate was analyzed from previous lignin based fibre studies36,56. Based on this analysis, the most influential parameter on the yield after the thermal oxidation process was found to be the final temperature (Table 7.1). Experimental data showed that mass loss after the oxidative process increased with increasing final temperature for both heating rates (Figure 7.1). Furthermore, holding time had a 100  greater impact on mass loss than heating rate. This data was different from the literature for materials without NCC additives, as Brodin et al. reported that holding time was the most influential factor on yield after thermo-stabilization process120. Moreover, there was minimal influence on the interaction amongst the parameters on yield, as the dominant effect was the single parameter of final holding temperature.  Temperatures used in this study were similar to torrefaction temperatures in the literature, which were great enough to cause some decomposition with loss of water (dehydration) as well as carbonaceous gas (CO and CO2) along with compounds such as methane from loss of methoxy groups190.     Table 7.1 Experimental design with the various, temperature (X1), holding time (X2), heating rate (X3) and the response, yield (%) for oxidation experiments of lignin based composite fibre mats. Experimental  number Final Temperature (°C),  X1 Holding Time   (min), X2 Heating Rate     (°C/min), X3 Yield (%) 1 200 30 1 88.9* 2 200 60 1 91.2 3 250 30 5 80.0 4 250 60 5 76.0 5 200 30 5 93.5 6 200 60 5 90.0 7 250 30 1 81.4* 8 250 60 1 78.0 *: single measurement but other value were average from triplicates 101   Figure 7.1 Effects of oxidation parameters (3 various) and their interactions on their response, yield (X1: temperature, X2: holding time, and X3: heating rate).  As expected, removal of substances like gases at higher temperatures causes mass loss during the thermal stabilization process, and this affected the morphology of fibres. As seen in the SEM images in Figure 7.2 (f) and (k) and l of oxidized lignin fibres under various final temperatures, the morphology of fibres changed, forming a curved-liked shape along the fibre axis. The curved fibres were formed above 250 °C with 5 °C/min (Figure 7.2 i), but the morphological changes were not evident for the lower heating rate, 1 °C/min (Figure 7.2 c).  The average fibre diameter and yield also decreased as a function of increasing final temperature as shown in Figure 7.3(a) and (b). As shown in Figure 7.3(b), yield after stabilization process with various final temperatures decreased by increasing final temperature. The massive changes in yield around 37% occurred between 300 °C and 350 °C than other temperatures. Only 10% yield change occurred between 200 °C and 250 °C and more decreasing between 250 °C to 300°C for 23 %.     102  According to TGA results, lignin based fibre mat showed around 15 % mass loss at 300 °C  then large mass loss was observed above 300 °C (Figure 6.3a). This TGA data would suggest with the smaller fibre diameter would result in a smaller total volume, which may have affected the density dependent upon the reduction in mass.   Based on the thermal analysis studies in Chapter 8, the lower heating rate allows sufficient time for cross-linking of the lignin to occur prior to significant softening, while the higher heating rates allow for greater mobility of the chains prior to thermally induced cross-linking. The fibre diameter decreased further for samples that were stabilized at 1 °C/min compared to 5 °C/min heating rate, beyond 300 °C, as indicated in Figure 7.3(a). This result suggested that longer heating time, by increased total time for heat exposure, affected the morphology of fibres. This result was primarily seen for the samples heated above the 2FD experiments hold temperature of 300 °C, based on TGA data this should have been the dominate factor for yield with degradation occurring in this region as shown in Chapter 571.         103   Temperature Heating rate, 1C/min Heating rate, 5 C/min 200C   230C   250C   280C   300C   350C   Figure 7.2 SEM images of of espun lignin fibres after thermal oxidation process under different heating rates heating rate = 1 and 5 °C/min) final temperatures 200 °C, 230 °C, 250 °C ,280 °C, 300 °C and 350 °C, 60 min holding time (scale bar = 10 um).104   (a)  (b) Figure 7.3 (a) Average fibre diameter of as spun and oxidized composite nanofibres with various final temperatures and heating rates and (b) yield after stabilization process with various final temperatures with 5 C/min  (p value < 0.05)  7.3 Effects of stabilization temperatures on chemical composition and structure of lignin composite fibres  Thermo-stabilization process induce oxygen in the lignin and changes the lignin structure. Elemental analysis is effective way to study the effect of stabilization temperature on change in lignin structure of stabilized fibres. Table 7.2 shows the elemental composition, i.e., carbon, hydrogen, oxygen and nitrogen for the lignin composite nanofibres stabilized at different temperatures. No nitrogen was detected except for the stabilized sample at 350 °C (0.48%) and the non-stabilized control sample. For the control sample, either residual protein in the lignin or residual solvent (DMF) would impact this value. Further, while nitrogen which was purging gas during the carbonization process, is inert, the samples heated at higher temperature may have reacted to a minimal degree with nitrogen present in the air atmosphere. At temperature above 250 °C, the oxygen content increased with increasing temperature of thermal stabilization. Braun 105  et al.118 also reported that the effect of stabilization parameters (temperature and heating rate) on elemental composition of lignin. They reported that increased oxygen contents occurred at treatment temperatures up to 250°C, followed by decreasing oxygen contents beyond 250 °C.  However, in the current case, oxygen content increased even above 250 °C, but both carbon and hydrogen contents decreased with increasing temperature. This result suggested that thermo-stabilization proceeded beyond 250 °C (as opposed to combustion and carbonization).  Also, as seen in Figure 7.4, the effect of stabilization temperature on the change in each element of stabilized lignin fibre mats (E) was shown as a ratio to the control mat (E0) (i.e. as spun is referred as 1). As the oxidation process proceeded at higher temperatures, the loss of carbon content was up to 7 % and the hydrogen content decreased significantly to about 60 % loss. The oxygen content increased by 20 % up to 350 °C compared to the initial content of as spun lignin fibres. The data indicated in Figure 7.4 that even at lower temperature of 200 °C, reactive processes with bond cleavage proceeded that would form radicals, which for lignin leads to depolymerization, but also will lead to significant repolymerization of the lignin in a crosslinked structure191.                106  Table 7.2 Elemental composition of lignin powder (MWL,SKLand F4SKL), as spun lignin fibre and thermally oxidized lignin fibres after various stabilization temperatures as noted below.    Carbon Hydrogen Oxygenc Nitrogen Pine MWLa 65.00 5.80 29.20 0.02 SKLb 65.50 5.60 25.20 0.40 SKL 62.21 5.86 31.30 0.63 F4SKL 65.12 5.79 29.09 0 As Spun 62.45 5.82 31.73 0 TS200 64.96 5.22 29.82 0 TS230 63.98 4.68 31.34 0 TS250 63.10 3.87 33.03 0 TS280 60.87 3.03 36.10 0 TS300 59.23 2.77 38.00 0 TS350 58.57 2.10 38.85 0.48 a Pine MWL measured by Hu et al.192 , b SKL, Indulin AT measured by Hu et al.11, c oxygen content calculated by subtracting the sum of the other composition fraction (C,H and N).                    Figure 7.4 Contents change of elemental composition for thermally stabilized lignin fibre mats as functions of final temperature.  107  Because thermal oxidation causes lignin to undergo cross-linking reactions, lignin was no longer soluble for many characterization methods, so solid state nuclear magnetic resonance (SS NMR) was used to determine chemical changes in the lignin composite nanofibres. As shown in Figure 7.5, 13C CP/MAS SS NMR spectra showed a significant decrease at ~147 ppm region for the various heat treatments, which indicated aryl-ether linkage cleavage, while the region for aliphatic side-chain inter-unit carbon (61-83 ppm) almost disappeared under various heat treatments. The relative intensity of a peak at 55 ppm decreased significantly after 280 °C as major reaction occurring in stabilization (-OCH3) attributing to demethoxylation.  After continued heating at higher temperatures, the signal completely disappeared after 350 °C treatment. The region from 160 to 170 ppm increased slightly after stabilization at 250 °C and showed a broad band at 350 °C. This region was related with esters and anhydrides121 attributed to oxygenation, as found in the elemental analysis, and crosslinking121. At 350 °C, the spectrum showed a broad resonance from 100 to 140 ppm, centred around 124 ppm. These results were similar with other reports with the loss of significant peak signatures121. NCC material in the system at 1% did not show any peaks in the spectra that related to carbohydrate structures.  Often different technical lignins have carbohydrate contents greater than 1%, and the corresponding analysis with solid state NMR did not reveal these peak signatures193. 108   Figure 7.5 13C CP/MAS NMR spectra of as spun lignin and stabilized fibre mats after different TS temperatures    As shown in Figure 7.6 and Figure 7.7, the intensity of various absorbance bands decreased with increasing TS temperature. In detail, the intensity of the O-H stretching band (νO-H, ~ 3600 cm-1) and C-H stretching bands (νC-H~ 2800 cm-1) decreased with increasing final temperature for thermo-stabilization. This result was interpreted because of significant loss of gamma carbons, typical released as formaldehyde with loss of hydroxyls, formation of enol ethers, ketone products, along with loss of hydrogen that was reflected in the elemental analysis194. Also, 1510 -1500 cm-1 decreased and nearly disappeared at 300 °C, suggesting the oxidation of aryl groups as an aromatic breathing mode assignment. At these higher stabilization temperatures, aromatic ring structures had to be significantly modified after losing 60% of hydrogen based on the elemental analysis as shown in Figure 7.4. Also, the intensity of 1218, 1081 and 1033 cm-1 nearly disappeared beyond 300 °C and these bands correspond to C-O of 109  guaiacyl ring, secondary alcohols and primary alcohols, respectively. The intensity of the carbonyl region was increased with increasing temperature and shifted to higher frequency from 1707 to 1725 cm-1 and these bands corresponded to the formation of unconjugated carbonyl which may explain the increase in oxygen content with the loss of some hydroxyl. As temperature was raised to 300 °C, a new band appeared at ~1831 cm-1 which indicated the formation of anhydride linkages118,191.  For these materials, changes to the aromatic signal began at stabilization temperatures of 230 °C, while carbonyl signals rapidly increased above 250 °C. In similar fashion the guiacyl ring stretching stayed nearly constant up to 250 °C, which dramatically decreased at higher temperatures.  This data corresponds with the loss of methoxy groups at these higher temperatures, as seen for the 13C NMR data (Figure 7.5).     Figure 7.6 FT-IR spectrum of thermally stabilized lignin based composite fibre mats after different final temperature  4000 3500 3000 2000 1500 10001800 1600 1400 1200 1000TS 350TS 300TS 280TS 250TS 200TS 230 Abs (a.u) Abs (a.u)  Wavenumber (cm-1)As spun1260   Wavenumber (cm-1)17101500 10301830110   Figure 7.7 Change in relative intensity of functional groups of as spun and stabilized lignin fibre mats under various final temperature in FTIR spectra as function of various final temperature showing decreasing intensity of C-H aromatic ring at 1500 cm-1, C-H deformation in primary alcohol at 1260 cm-1 and increasing intensity of unconjugated carbonyl group at 1710 cm-1.  7.4 Thermal properties of stabilized lignin fibre mats treated under various stabilization temperatures  TGA analysis of the heat-treated lignin revealed that the derivative peak temperature and residue increased with increasing final temperature as shown in Table 7.3. As the samples were heated to relatively higher TS temperatures, the labile linkages would have off-gassed which would suggest the remaining materials would have improved thermal stability of the lignin fibre mat, as evidenced by the increase in the derivative peak temperature from 382°C to 518°C.  Statistical analysis of the results did not reveal a significant difference for the residue (%) remaining at 1000 °C, with a P-value above 0.05 (one way ANOVA), which means that all values are in same range with the large variance. This result was further correlated with uniformity and stability of composite nanofibres after the carbonization process. Yield (%) in Table 7.3 indicated the weight difference before and after the carbonization process for stabilized 111  lignin fibre mats, which demonstrated varied responses with the stabilization temperature. Hence, while hold temperature had a significant impact on yield after stabilization, this parameter did not impact yield for the carbonized samples.   Table 7.3 TGA results for thermostabilized lignin fibre mats under different oxidation final temperatures  and measured yield (%) after carbonization process (heating rate : 5 °C/min for TS process)        Temperature C Deriv. peak temp, Ca Residue at 1000 C, %by TGAb Yield % by weighing before and after carbonization AS Spun 382 ± 1 23 ± 10 N/A 200 369 ± 9 36 ± 26 38.4 230 421 ± 5 34 ± 7 44.4 ± 4.7 250 424 ± 2 40 ± 14 47.9 ± 1.3  280 428 ± 8 47 ± 6 49.1 ± 4.4   300 436 ± 3 43 ± 9 44.8 350 518 ± 12 60 ± 13 46.9 a : p value < 0.05(statistically different) , b : p value > 0.05 (statistically same)  Carbonized nanofibres with the different thermo-stabilization temperatures showed similar morphology as shown by the SEM images in Figure 7.8. All the samples were predominately consisted of uniform individualized nanofibres; some slightly curved fibres could also be seen.  The carbonization process decreased the average fibre diameter compared to the as-spun fibre as shown in Figure 7.9.  Further, there was scatter amongst the average values that revealed different dimensions for oxidized fibres with different final temperatures during the oxidation. However, with the variance it was not clear if individual heating temperatures impacted the carbonized average fibre diameter. It was noteworthy to compare differences amongst heat stabilized and carbonized samples. As compared with values in Figure 7.9, the nanofibres oxidized at 200 °C showed the largest diameter change, about 28% before and after 112  the carbonization followed with the 230 °C samples. Also, 200 °C thermal stabilization gave the lowest yield after carbonization and this is constant with the yield value for TGA results shown in Table 7.3. The smallest average change for the diameter of carbonized nanofibres was shown for the nanofibres oxidized at 250°C, however there was significant variance for all the nanofibres.   (a) (b) (c) (d) (e) (f) Figure 7.8 SEM images of carbonized lignin fibres after various final temperatures of oxidation process (a) 200 °C (b) 230 °C (c) 250 °C (d) 280 °C (e) 300 °C and (f) 350 °C (heating rate = 10 °C/min, holding time 60 min at 1000 °C) (scale bar = 10 um)  113   Figure 7.9 Average fibre diameters after stabilization process under various final temperature and carbonized fibres as function of final temperature of stabilization process.  As shown in Figure 7.10, elemental analysis of carbonized lignin fibre mats showed that the thermal stabilization had a minor impact on carbon content. Overall, compared with Table 7.2 with Figure 7.10, carbon and nitrogen contents in the carbonized lignin nanofibres were increased after carbonization process from 58-65 % to 83-88 % and from 0 % up to 0.4-0.7 %, respectively.  Especially, increased nitrogen content was suggested by nitrogen flow during the carbonization process. Also, oxygen and hydrogen contents decreased to from 30-39 % to 10-15 % and from 2-6 % to 0.4-0.9 %, respectively. Through the carbonization process, carbon content was increased, but was below 92 % as reported for carbon based materials57. Most likely, the final carbonization temperature of 1000 °C was not high enough to completely deoxygenate the material. Moreover, it was reported that the inert gas can impact the carbon content and graphitization process, as argon has been used for PAN based carbon fibre production195.  Based 114  on the elemental analysis of the thermo-stabilized fibres, it is unknown why there was a peak in carbon content of 88% at the 250 °C oxidation temperature.     (a) (b) Figure 7.10 Elemental analysis of carbonized lignin fibre mats with different final temperature (a) carbon content and (b) contents of hydrogen, oxygen and nitrogen.     7.5 Mechanical properties of stabilized and carbonized fibre mats as functions of stabilization temperature    The overall tensile properties of as spun samples improved after heat treatment in the air. The ultimate tensile strength (UTS) was increased from 7 MPa to up to 29 MPa and modulus was 1.6 GPa from 741 MPa. In Figure 7.11(a), samples oxidized at 250 °C showed the highest value of UTS at 29 MPa and decreased above 250 °C with increased standard deviation. Based on the FTIR and NMR data, significant chemical changes such as the formation of carbonyl group occurred to the lignin at above 250 °C, which appeared to impact the strength of the material. The stiffness of the material showed minimal difference between the samples after various heat treatment conditions.  Further, the modulus value showed improved values for 115  different final temperatures after oxidative stabilization and, also showed the highest value at 250 °C.  For tensile tests of carbonized samples, carbon nanofibre mats stabilized at 230 °C were chosen instead of samples stabilized at 200 °C because of ease of handling related to the fragility of the 200 °C samples. The carbon fibres mats stabilized at 200 °C and 350 °C were too brittle to prepare specimens for the tensile tests. As shown in Figure 7.11(b), lignin carbon nanofibre mats after stabilization at various temperatures showed little difference in tensile strength and modulus but statistically no difference analyzed by one-way Anova (p- value > 0.05). These samples had significant variance, especially at the highest thermal stabilization temperature. This result indicated that carbon yield and carbon contents maybe the most critical parameter when evaluating the effect of thermal stabilization temperature as it had minimal impact on the final properties of the carbonized samples for samples heated between 230-300 °C. This observation provided a critical finding that there was flexibility in designing the thermo-stabilization process when creating lignin based carbon nanofibres, as stabilization was not strongly linked to carbon fibre performance.        116   (a) (b) Figure 7.11 Tensile properties of lignin based composite nanofibre mats after (a) thermo-stabilization and (b) carbonization under various stabilization temperatures (p value < 0.05 for stabilized samples, but p value > 0.05 for carbonized samples)  7.6 Raman spectroscopy and electrical conductivity of carbonized composite fibre mats as functions of stabilization temperatures      Figure 7.12 shows Raman spectra of the carbonized mats for different samples after various stabilization conditions. It was revealed the intensity ratio (ID/IG) between D (disordered) band and G (graphitic) band changed with changing TS temperature. As shown in Figure 7.13, the ID/IG ratio was significantly decreased after stabilization at 250 C, indicating graphitic structure (G band) was more developed after this temperature than that of carbonized samples stabilized at 200 and 230 C. The ID/IG ratio was similar for carbonized samples after thermal stabilization between 250 and 300 C. Higher thermal stabilization temperatures led to a further decrease in the ratio, suggesting that higher order for carbon mats stabilized at 350 C. These results indicated that higher stabilization temperature helped to develop the graphitic clusters in the carbonized nanofibres. Moreover, the crystallite size (La) was calculated from Raman spectra using the following equation (1) :  117  𝐿𝑎 =  𝐶(𝜆)𝑅 ………………………………eq(1) where R is ID/IG , C is a function of laser wavelength  : (2.4  10-10)  4 and  is the wavelength of the incident laser (here is 785 nm wavelength)196. As shown in Figure 7.13(a), the higher temperature for stabilization produced the larger La of the carbonized lignin nanofibres and values were significantly increased after stabilized at 250 C. The Calculated La values in this study showed little lager or similar than reported data (25 nm – 45 nm) for lignin based carbon fibres with same laser wavelength87,197. As shown in Figure 7.13 (b), the ID/IG ratio is inversely proportional to the La. This relationship was constant with a reported paper eariler196,198 although the difference in ID/IG values order did not greatly impact the mechanical properties of the carbonized nanofibre mats, for this range of ID/IG values. Based on previous analysis the larger crystallites was expected to have higher electrical conductivity199.    Figure 7.12 Raman spectra of lignin carbon nanofibre mats after various thermal stabilization (TS) temperatures in the range from 900 to 1800 cm-1. 118    (a)  (b) Figure 7.13 (a) ID/IG ratio and crystallite size from Raman spectra of carbonized lignin nanofibre mats as functions of thermal stabilization temperature and (b) relationship between the ratio and crystallite sizes    (La, nm)  A multimode device was used to measure the resistance of thermally stabilized and subsequently carbonized mats as a function of thermal stabilization temperature. The carbonized mats had an electrical conductivity value of near 6 S/cm, with a relatively large variance for the measurements. Statistical analysis showed no difference amongst the mean values. This result demonstrated that the changes in carbon structure did not lead to a uniform path, where most likely there were still resistive carbon structures along the individual nanofibres.  The values of conductivity were comparable to other studies with lignin based carbon nanofibre mats. Carbon fibre mats from kraft lignin grafted with acrylonitrile showed 7.1 S/cm88 and carbon nanofibres from softwood kraft lignin had 2.3 S/cm 36,200.  Figure 7.15 shows there was no strong relationship between the electrical conductivity and the crystalline size of carbon of lignin based carbon fibre mats after various TS conditions, which was different from previously reported data199. The difference was supported with 200 250 300 350505254565860 Crystallite size(La,nm)Final temperature (C) La1.451.501.551.601.651.701.751.801.85 ID/IGI D/IG119  previous reported conductivity data analysis, which showed that no statistically difference occurred on electrical conductivity for carbonized lignin nanofibre mats from various TS conditions.              Figure 7.14 Electrical conductivity of carbonized lignin nanofibre mats as functions of thermal stabilization temperatures (P value > 0.05 : statistically same)   Figure 7.15 Relationship between electrical conductivity and crystallite sized of carbonized lignin nanofibre mats after various thermal stabilization temperatures  120  7.7 Conclusion The thermo-stabilization processing conditions (especially the final TS temperature) greatly affected the properties of stabilized composite lignin-based fibre mats, however, did not have significant impact on the properties of carbonized composite lignin-based fibre. Changes were observed extensively for chemical, structural and mechanical properties of stabilized lignin-based nanofibres/nanofibre mats related to the addition of oxygen and the loss of hydrogen. Loss of methoxy groups occurred at temperatures above 280 °C. However, additional heat treatment of the sample towards carbonization temperatures caused the differences that arose in thermally stabilized lignin performance to disappear. There was only a minor effect of thermo-stabilization conditions on the structure of carbonized lignin nanofibres and/or nanofibre mats and these differences did not correlate with changes in mechanical performance. While surprising, this observation demonstrated that there was flexibility in the thermo-stabilization process when creating lignin-based carbon nanofibres in the range from 230 °C to 300 °C.    121  Chapter 8: Direct carbonization process by adding nanocrystalline celluloses (NCCs) for lignin based carbon nanofibres 8.1 Introduction As shown in previous chapter, the thermal oxidation process was critical for carbonization and it effected on the morphology and properties of carbonized fibres. However, Kubo et al. reported they produced lignin carbon fibres from softwood lignin extracted by acetic acid pulping without the thermal oxidative stabilization process21. However, the as spun fibres that carbonized without stabilization had lower mechanical properties than that of carbon fibres that included stabilization. With the reduced mechanical properties, the authors suggested that the directly carbonized lignin fibres would be a promising source of activated carbon fibre for non-structural applications. Although considerable studies have been focused on micro-sized lignin fibres produced by melt spinning or gel spinning to achieve uniform structure of the carbon fibres, very little is known on the structure and properties of lignin based carbon nano-sized fibres reinforced with nanofillers. Studies had been done with carbon nanotubes within the electrospun linin based carbon nanofibres70,200. However, they could not show impressive reinforcement effect on lignin based carbon nanofibres based on their significant individual mechanical properties (such as 1TP Young’s modulus201). Moreover, even though studies on electrospun lignin based nanofibres reinforced with NCC were published76, they did not report data for carbon fibres production, as well as their methodology used with a higher percentage of another additive . Therefore, previous studies did not show the effects of NCCs on lignin based carbon nanofibres for improving their carbon fibre’s properties. It was hypothesized the role of nanofillers in nanocomposite is to reinforce the matrix by transferring stress and affecting the 122  thermal mobility of polymer17. Therefore, tensile elastic modulus above the glass transition temperature is expected to increase with adding nanofillers. In this chapter, lignin nanofibres were carbonized directly under the nitrogen flow up to 800 - 1000 °C with and without NCC, skipping the thermal stabilization process to investigate the effect of NCC on the mobility of matrix, lignin, during the heat treatment. SEM was used to analyze fibre’s morphology and diameters. Thermal properties of samples were studied with TGA, DSC, and dynamic torsion compression tests with the rheometer. Also, carbon structures were studied with Raman spectroscopy and electrical conductivity property measured for the different samples. Lastly, microtensile tests were conducted to evaluate mechanical properties of carbonized lignin fibre mats.   8.2 Morphology of lignin carbon fibres with NCCs loadings by skipping stabilization process   As mentioned above, typically, the thermal stabilization process was reported as a critical step for the manufacture of carbon fibre. This process induced crosslinking into the lignin structure and aided in creating uniform chemical modification throughout the cross-section of the fibre202. Importantly, for carbon fibre production, thermal stabilization prevented the fusion of fibres into large fibre clusters. Electrospinning carbon fibre precursors yielded sub-micrometer diameter fibres that appeared as overlapping rods. Directly heating the fibre during the carbonization process, the lignin macromolecules underwent a certain level of mobility that allowed the lignin to flow and the fibre structures to deform into a structure that resembled a porous membrane with minimal fibre geometries readily noticeable in the images. An example of fused lignin fibres after direct carbonization without thermal stabilization process was shown in Figure 8.1(a). The majority of the mat structure was destroyed in this carbonization process 123  without thermal stabilization, but surviving pieces of the mat were isolated and analyzed with microscopy. SEM images of the electrospun lignin mat heated up to 1000 °C, in an inert atmosphere, revealed the loss of fibre geometry. Because there was no stabilization step, the fibres morphed into a porous membrane structure where it was difficult to identify separate fibre samples. This mat structure appeared as two or three fibres connected together, but the overall mat still retained a certain level of porosity, on the micron scale range (Figure 8.1a). However, by NCC inclusion in the lignin structure, and without thermal stabilization, lignin carbon nanofibres showed an interconnected network that still maintained the fibrous form by direct carbonization as shown in Figure 8.1(b)-(d). In detail, as shown in Figure 8.1(e) and (f), the interconnected nanofibres formed where one fibre only partially joined with another fibre at contact points; this phenomenon was clearly shown for samples with higher NCC content, compared to one without NCC loading in Figure 8.1(a). Also, this was significant difference with the same sample type relative to the samples that underwent thermal stabilization. This interconnected lignin based fibrous structure was reported earlier, when Wang et al. showed fused electrospun carbon fibrous mats from organosolv lignin83. They reported that the fused structure formed when addition of polyethylene oxide (PEO) was over 10 % due to lower melting point of PEO than that of lignin83. However, they did not report the morphology of fibres after thermal stabilization process to know when this phenomenon was occurred (prior to carbonization or after thermal stabilization). Also, Dallmeyer et al. showed the formation of interconnected carbon fibrous materials from mixture of softwood kraft lignin fractions that contained both low and higher molecular weight samples with different Tg36. They described that two different fractions have different thermal mobility and gave various degree of interconnected bonding structure.  124        Figure 8.1 SEM images of carbonized lignin based composite nanofibres with various NCC loadings (a) 0 wt.%,(b) 1 wt.%, (c) 3 wt.%, and (d) 5 wt.% at x3k (Scale bar = 10 um), (e) 0 wt.% and (f) 5 wt.% NCC loadings at x10k magnification (Scale bar = 5 m)   a b c d e f 125  In addition to the micro-level changes as seen in the SEM, there was macroscale difference for samples that were carbonized without thermal stabilization as a function of NCC loadings. The samples with 5 wt.% NCC loadings were able to be handled without breakage and maintained near original shape after carbonization (Figure 8.2). When NCCs were added to the sample, the carbonized sample shrunk, mainly in length, but remained intact with a frayed edge (Figure 8.2). There was about 14 % shrinkage in length and less than 10 % change in width and a 32% yield in weight after direct carbonization. This value of yield was slightly lower than the value 35 % carbonized samples that included the thermal stabilization process. In contrast, control samples without NCC were highly deformed when heated to maximum temperatures without any thermal stabilization. In addition, samples without NCC showed very fragile behavior after the carbonization process and could not be handled without breakage. Fibre diameter was measured from SEM images and the results showed the average fibre diameter decreased with smaller variation with increasing NCC loadings (Figure 8.3). This result might arise from NCCs serving as physical cross-link for the structure and preventing lignin to flow during heating in the carbonization process. The fibre diameter value for 5 wt.% NCC loading have 500  150 nm and this was a higher value than that of fibre with stabilization process.   126   Figure 8.2 Electrospun lignin composite nanofibre mats with 5 wt.% NCC loading as spun(left) and after(right) carbonization without stabilization process.   Figure 8.3 Average fibre diameter for lignin based composite fibres with various NCC loadings with and without thermal stabilization (TS) process.  Electrospun lignin based nanofibre mats containing 5 wt.% NCC were further studied to investigate how the carbonization condition could be systematically controlled to improve fibre dimensional stability. Various carbonization temperatures, heating rates and holding times were applied in order to optimize the resulting fibre structure. SEM images of carbonized lignin based composite nanofibres (Figure 8.4) varied in structure after various carbonization conditions, i.e. 1 wt% 3 wt% 5 wt%02004006008001000 Average fiber diameter (nm)NCC loadings  AS spun with TS without TS127  final temperature of 800, 900 and 1000 C, holding time (60 and 180 min) and heating rate (1,5 and 10 C/min). The interconnected fibrous structure was formed for certain samples after different carbonization temperature shown in Figure 8.4 (a), (b) and (c). Also, jointed morphology of fibres formed under longer holding time as shown in Figure 8.4(d) at same final temperature of 1000 C. These changes were also accompanied with a small variation of carbon yield from 28 to 33 % weight change. Interestingly, slower heating rate at 1 C/min gave non-interconnected structure as shown in Figure 8.4(e). This was similar approach to prevent forming fused fibres under competing conditions of thermal softening and heat induced cross-linking reactions.              Figure 8.4 SEM images of carbonized lignin based composite nanofibres with 5 wt.% NCC loadings after various carbonization process (a) 800 °C (b) 900 °C (c) 1000 °C with 10 °C/min for 60 min, (d) 1000 °C with 10 °C/min for 180 min, (e) 1000 °C with 1 °C/min for 60 min and (f) 1000 °C with 5 °C/min for 60 min (scale bar : 10 µm) a b c d e f 128  8.3 Electrical conductivity and Raman spectroscopy of carbonized fibre mats     Conductivity tests were performed for interconnected carbon fibres structures with 5 wt.% NCC loadings compared to non-bonded fibres that used thermal oxidation stabilization, shown in Figure 8.5. Non-bonded fibre mats (with stabilization) with 5 wt.% NCC loading had conductivity values around 5 S/cm, while interconnected fibre mats showed electrical conductivity values of 34 S/cm. Hence, bonded carbon fibres structure showed 7 times higher value of the electrical conductivity than that of the non-bonded samples. This improved electrical properties for other systems that showed inter-bonded fibre morphology was reported from earlier studies for supercapacitance83,199 and electrical conductivity36.   Figure 8.5 Electrical conductivity of lignin based composite carbon nanofibre mats (5 wt.% NCC loading) for with and without thermal stabilization process (carbonized at 1000 C for 60 min with 10 C/min)    One possible reason why the bonded fibre mats showed higher electrical conductivity than that of samples that were carbonized after thermal stabilization was enhanced electron transportation through interconnected fibres199,203 that had linked 3D networks as seen in Figure 8.6(b). SEM analysis of the thermally stabilized sample as shown in Figure 8.6(a) revealed the mat with a distinct layered structure after the carbonization process. By skipping the thermal 129  stabilization step it was clear that interconnected fibres structure not only occurred in the x-y axis but also z direction (between layers) as shown in Figure 8.6(b).  (a)  (b) Figure 8.6 SEM images of the cross section of carbonized lignin nanofibre mats with 5 wt.% NCC loadings (a) with thermal stabilization (scale: 100 m) (b) without thermal stabilization process (scale : 10 m) (carbonized at 1000 C for 60 min with 10 C/min)     Raman spectroscopy was used as a means to understand the carbon structural organizational changes as a function of NCC loadings with and without thermal stabilization process for the carbonized samples. As shown in Figure 8.7, Raman spectroscopy analysis showed that the intensity of G band (~1580 cm-1) for direct carbonized lignin fibre mats was lower than that of carbonized lignin fibre mat with the stabilization process. As plots of the ID/IG ratio, a curious difference of the ratio value between samples with and without stabilization process was revealed in Figure 8.7(a). The ID/IG values for carbonized lignin fibres all increased at first and then slightly decreased as a function of NCC loading from 1.40 to 1.6 and 1.55 at 0, 1 and 5 wt. % NCC loading, respectively. NCC can act as a nucleating agent in semi-crystalline polymers to increase the crystallinity of nanocomposite system 129,204–208and also nanocarbon materials such as carbon nanotubes also as a role of a nucleating agent for formation ordered 130  graphitic structure during the carbonization process209,210leading to higher modulus of carbon fibres 211. However, this study showed that NCC did not help to develop graphitic carbon as results as Raman spectroscopy (Figure 8.7b). This result is related to mechanical properties of carbon fibre mats shown in section 6.5. Modulus of carbon fibre mats was not influenced by NCC loadings. Moreover, since lignin has heterogeneous, amorphous and nonlinear structure200; it would be hard to develop ordered carbon crystallite layers with a small amount of nucleating agents at these carbonization temperatures.  Direct carbonized lignin based nanofibres without the stabilization process have much higher ID/IG values (from 2.3 to 2.5) than those of carbonized samples followed by stabilization process. Less developed highly ordered graphitic crystallite (sp2 carbon) of carbon structure for the non-thermally oxidized samples were revealed for these samples. Therefore, it appeared that the thermal stabilization process helped to develop more sp2 carbon clusters in the carbonized samples. For the same reason, values for full width at half maximum (FWHM) at G band were much lower for carbonized lignin fibre mats with stabilization than that of direct carbonized lignin fibre mats as shown Figure 8.8(b) although the latter samples are more electrically conductive.   Neat NCC film samples were also carbonized at 1000 °C with and without the thermal stabilization and were analyzed with Raman spectroscopy for their carbon structure. The spectra were processed in exactly the same manner as those for the lignin based composite fibres. As shown in, the ID/IG values showed 1.64 and 1.61 for without and with thermal stabilization, respectively. Hence, there was not a significant different between two samples groups when there is only cellulose present. This difference indicated that thermal stabilization process for 131  carbon fibre production was critical to control carbon structures of lignin materials, where preheating the material in air enhanced the degree of ordered carbon.   (a) (b) Figure 8.7 (a) Raman spectra of carbonized lignin based composite nanofibre mats (5 wt.% NCC loading) with or without thermal stabilization (TS) process (b) the ratio of intensity of D band (1360 cm-1) and the intensity of G band (1650 cm-1) on the raman spectra of carbonized lignin based composite as functions of NCC loadings and carbonized neat NCC film (referred as 100 on the X axis)  (a)  (b) Figure 8.8 Full width at half maximum (FWHM) at (a) D band (b) G band from Raman spectra of lignin carbon fibre mats as a function of NCC loadings and carbonized neat NCC film (referred as 100 on the X axis) for with (black, square) and without (red, round) stabilization (TS) process.  132  In Table 8.1, elemental composition analysis revealed a difference in carbon content for the directly carbonized samples. Similar to the Raman data with a higher degree of order for the carbon, carbon content was enhanced for the thermally stabilized samples. Carbonized after stabilization samples have 3-5% more carbon than directly carbonized samples. The main difference seems to be the amount of oxygen as contents of hydrogen and nitrogen were similar between two samples. Overall, the thermal oxidation process provided a route for additional oxygen (chapter 6) but it also served to ensure additional total carbon content.      Table 8.1 Elemental contents with various NCC loadings of carbonized* lignin based composite fibres with and without thermal stabilization process TS with without NCC(wt.%) 0 1 3 5 0 1 3 5 Carbon 88.53 88.33 87.95 86.76 82.39 85.61 83.31 83.49 Hydrogen 4.7 0.8 0.71 1.23 0 0.81 0.47 0.59 Nitrogen 0.57 0.5 0 0.57 0.69 0.53 0.57 0.45 Oxygen 6.2 10.37 11.34 11.44 16.92 13.05 15.65 15.47 *Carbonization process : heating rate 10 °C/min up to 1000 °C and holding for 60 min 8.4 Thermorheological analysis of lignin based composite nanofibres mats    Thermorheological analysis of lignin samples was performed under dynamic compressive-torsion mode. Based on previous work with this system34, the experiment was controlled such that the sample was held under normal force and the experiment was switched to a controlled gap mode prior to sample softening below a critical modulus (using temperature termination at 190 °C). Hence the sample was switched over to gap control once the modulus dropped corresponding to 190 °C to eliminate sample compression. Shown in Figure 8.9, a 133  typical response occurred with the sample increasing in storage modulus with increased temperature, initially due to densification of the fibre mats samples and/or sample cross-linking. There was decreased modulus value at 190 °C, due to the softening of lignin up to 240 °C, corresponding with the polymer going through its glass transition (Tg). Above 250 °C, modulus increased due to cross-linking of lignin. With the addition of NCC, there was a similar storage modulus increase as a function of temperature with thermal softening and further crosslinking.  However, the major difference was seen in the tan delta peak, with a subsequent decrease in peak area with additional NCC content. The data suggested during the transition there was reduced mobility of the lignin polymer chains, arising from intermolecular interactions such as hydrogen bonding between lignin and NCCs78 that may serve as physical crosslinks.  This response was similar to what was observed for cross-linking rubber133.  The impact of the NCC’s was further illustrated by comparing the area under the curves, as shown in Table 8.2 with Tandelta area declining as a function of NCC addition. The values were also normalized for the lignin content and this further verified the impact of the nanofiller on the response of the lignin. However, there was no significant difference in the peak temperature of the tan delta curves, which suggested the glass transition temperature (Tg) shift was not observed for the system. It was clear that impact of the nano-reinforcement, NCC and no role in cross-linking reactions that also occur with the normal lignin system. Further modulated DSC tests are recommended to decode these complicated high temperatures changes to lignin reactions (cross-linking and softening).  Regardless of the analysis, the thermal rheological tests demonstrated significant impact of the nanofiller on the lignin thermal properties, suggesting NCC was distributed within and interacted with lignin to impact its bulk properties. 134   (a)  (b) Figure 8.9 Dynamic rheology of the lignin based composite as spun fibre mats with various NCC loadings (a) storage modulus (top), tan delta (bottom) as functions of temperature and (b) tan delta in the range of 200 °C to 300 °C.   Table 8.2 Maximum tan delta peak and peak temperature as functions of NCC loadings NCC loadings (wt %) Max. Tan delta peak Peak temp. (°C ) 0 0.724 ± 0.09 231.07 1 0.670 ± 0.02 233.79 3 0.569 ± 0.03 236.50 5 0.539 ± 0.02 233.79     135  As shown in Figure 8.4 in section 7.2, the different heating rate for carbonization gave various types of morphology of carbonized fibres. Slower heating rate, 1°C/min showed much less interconnected bonded structure after carbonization than 5 or 10 °C/min. This result was correlated with thermal rheological analysis shown in Figure 8.10 where lignin mats were heated at three different rates. As described in earlier work for effects of heating rate1, when lignin was heated two major phenomena occurred, softening and stiffening in sequence. Further, at the slower heating rate, the softening occurred earlier showing a lower Tg. For the samples at 1°/min the lignin fibre mats underwent a reduced softening and resulted in much less interconnected morphology of fibres than that of faster heating rate. Samples heated at 5 and 10 °C/min revealed the results of physical softening in SEM images in Figure 8.4 as well as thermal rheological analysis. Moreover, the addition of NCCs at the slowest heating rate resulted in less mobility of lignin as shown in Figure 8.10(b). The analysis shows why there was potential for some fibres to have any interconnected morphology with such a sharp reduction in mobility.    (a)  (b) Figure 8.10 Tan delta curves of lignin based composites fibre mats with (a) various heating rates (1,3 and 5 C/min) with 5 wt.% NCC loading and (b) different NCC loadings with 1 C/min heating rate.   50 100 150 200 250 3000.00.20.40.60.81.0   1 C/min 3 C/min 5 C/mintan delta ()Temperature (C)217 C233 C50 100 150 200 250 3000.00.10.20.30.40.5   tan delta () 0 wt% 5 wt%Temperature (C)136  8.5 Mechanical properties of carbonized lignin based nanofibre mats with  and without stabilization process  Tensile tests for carbonized lignin based nanofibre mats with and without stabilization were conducted to determine the impact of skipping stabilization on the mechanical properties. As shown in Figure 8.11, directly carbonized samples had lower strength at break and modulus values. It appeared overall that the sample was more brittle than those of carbonized samples with the stabilization process. More the samples heated at this particular rate, this result may have arisen from the continuous crack propagation path of the interconnected fibre-fibre morphology. This result showed a similar trend with previous work on carbonization of lignin fibres from the acetic pulping process21. The authors were able to skip the thermal stabilization process to produce non-fused carbon fibres. The tensile properties of directly carbonized lignin fibre were much lower than that of in-directly carbonized lignin fibres21. However it should be noted that samples without NCC that had skipped the thermal stabilization process could not be evaluated because they were too fragile.   (a)     (b) Average value of tensile strength at break and modulus   Strength at break (MPa) Tensile modulus (GPa) With TS 33.7 ± 6 7.97 ± 1.42 Without TS 20.68 ± 11 6.89 ± 2.21 Figure 8.11 (a) Stress and strain curves and (b) average strength and modulus for tensile tests of lignin based composite carbon nanofibre mats after stabilization and without stabilization (direct carbonization) process 137  8.6 Conclusions The addition of NCC impacted the fibre morphology of the lignin carbon fibre for samples that did not undergo thermal stabilization prior to carbonization.  This impact was clearly seen with the electrospun nanofibres retaining their fibre geometry after heating. The degree was related to the presence of NCC and the heating conditions. Dependent upon these parameters, the electrospun fibres could form interconnected structures. These structures enhanced overall conductivity of the carbon mat while reducing its mechanical properties. The area of the tan delta peak was greatly reduced with the addition of the nanofiller, suggesting significantly restriction to the mobility of lignin chains.  Further, the heating rate also impacted this peak, and the two parameters, NCC loading and heating rate, could be used to control final morphology of the lignin based electrospun nanofibre mats. Moreover, further studies are required to optimize carbonization process to control the quality of carbon nanofibres that not thermally stabilized.            138  Chapter 9: Conclusions and future work The transformation of technical lignin into carbonaceous fibrous materials has been shown in this research through various heat treatment conditions and the addition of a nano-reinforcement additive. Organic solvent fractionated softwood kraft lignin solutions combined with nanocrystalline cellulose (NCC) were electrospun into nanofibres; these fibres consisted nearly entirely of pure lignin/NCC, with only a small quantity of poly(ethylene oxide)(PEO) (1 wt.% based on lignin weight) which was used to help form continuous nano-sized fibres during the electrospinning process.  Because electrospinning causes rapid elongation of the polymer jet, the orientation of lignin molecules within aligned electrospun fibres were studied along with solvent cast lignin films. The samples were analyzed for their anisotropic polarizabilities resulting in birefringence within the fibres and films of lignin with and without NCC. The birefringence in lignin films indicated that lignin molecules can be organized during the slow evaporation at room temperature. It was clearly shown that orientation of the molecular chains occurred within electrospun fibres by using polarized FTIR. Absorbances for each functional group of the lignin based electrospun fibre materials, as a function of polarizer angle, contained differences that suggested orientation of lignin molecules within the fibres. NCC within the fibre was also oriented along the fibre axis, and this resulted in enhanced lignin orientation within the fibre. SEM images of the microstructure of the cross-section of the lignin film showed regular patterns under the top surface of the film for both samples, with and without NCC. This result reported one of the first time for multi-micron thick films based on lignin to develop structural features from self-organization        139  Chapter 5 showed the feasibility of forming nanofibres from various lignin solution concentrations with different amounts of NCC by electrospinning. As a result, spinning conditions, the concentration of the lignin solution and NCC loadings impacted the fibre quality and the ability to electrospin uniform fibre mats. 27 % lignin concentrations formed the smallest sized and defect-free nanofibres with NCC and PEO as a reinforcement additive and spinning aid, respectively.  In chapter 6, extensive studies were conducted for understanding interaction between lignin and NCC in fibrous form and as non-woven fibrous mats state under different heating stages. FTIR analysis of as spun composite fibre mats showed that a peak shift at the aliphatic hydroxyl region related to interactions between lignin and NCC. However, there was no synergistic impact on the thermal stability of the material in an inert atmosphere. Further, thermally stabilized and carbonized nanofibre had a significant reduction in the overall fibre diameter. With the addition of NCC, the fibre was transformed into a wavy fibre geometry indicating a loss of in-plane orientation after carbonization due to their difference in thermal stability. This understanding would be improved by studying interfacial properties of NCC and lignin as a function of temperature. Thermal treatment of lignin led to a dramatic increase in lignin mechanical properties regardless of the presence of NCC. This resulted indicated the possibility of tailoring the mechanical properties of lignin nanofibre mats reinforced with NCC, as well as the relative improvement in lignin properties, through simple thermal stabilization and carbonization processes.  In Chapter 7, studies were focused on the effects of thermal stabilization temperature on the resulting stabilized and carbonized lignin nanofibres and/or nanofibre mats. The thermo- stabilization processing conditions greatly affected the properties of stabilized composite lignin-140  based nanofibre mats, however, the parameters did not have significant impact on the properties of carbonized composite lignin-based fibre after various stabilization process. It was clearly shown which temperature induced the cross-linking of lignin during the stabilization process. 250 °C started significant changes and 280 °C was maximized for thermo-oxidative stabilization. This temperature impacted the physical properties of samples. However, additional heat treatment of the sample towards carbonization temperatures at 1000 °C caused the differences that arose in thermally stabilized lignin performance to disappear, especially in mechanical performance tests. While surprising, this observation demonstrated that there was flexibility in the thermal stabilization process when creating lignin-based carbon nanofibres in the range from 230 °C to 300°C. This study broadened the fundamental understanding for chemical and physical properties of lignin after exposure to various heat treatment conditions and the resulting carbon fibre.   In Chapter 8, an obvious reinforcement effect was shown by skipping the stabilization process. This impact was clearly seen with the electrospun nanofibres retaining their fibre geometry after the carbonization process for samples with NCC. The degree of mobility of lignin was closely related to the presence of NCC and the carbonization conditions. Dependent upon these parameters, the electrospun fibres formed inter- and intra-connected fibre structures especially when nanofibres contained NCC. These structures dramatically enhanced the overall electrical conductivity of the carbonized fibre mats, while mechanical properties were reduced compared to the carbonized fibre mats with the thermo-stabilization process. These results suggested an appropriate application for direct carbonized lignin-based fibre mats for electrical devices, related to non-structural applications. Further study of thermo-rheological testing suggested significant restriction to the mobility of lignin chains due to strong interactions with 141  NCC additives.  Further, the heating rate also greatly impacted the mobility of lignin chains as demonstrated in the thermo-rheological analysis. These the two parameters, NCC loading and heating rates, could be used to control the final morphology of the lignin-based electrospun nanofibres. This analysis showed the possibility of lignin-based carbon fibre production by excluding the stabilization process by adding a nanofiller, NCC, useful for electrical applications. Further, skipping stabilization would reduce the manufacturing processing energy and energy costs of carbon fibre production. Therefore, further studies will be required to optimize and characterize the directly carbonized lignin nanofibres and nanofibre mats in their performance for the electrical devices.  As a whole, this research demonstrated the performance of lignin-based nanofibres with or without NCC for a better understanding of an impact of heat treatment and nanofiller, NCC. The presence of NCC impacted the morphology of electrospun fibre along with the viscoelastic response of nanocomposite fibre materials.  NCC was shown to align along the electrospun fibre axis and this promoted organization of the lignin molecular chains. Based on the carbonization temperatures, there was a significant impact of the NCC on the carbon structure within the nanofibres. Moreover, the research showed how thermal treatment of technical lignin can enhance its performance. Future studies should focus on selected thermal treatments for lignin and drawing methods to tailor properties to selectively substitute certain petroleum based polymeric fibres.  142  Reference: (1)  Glasser, W. G. 2 Lignin. In Pulp and Paper: Chemistry and Chemical Technology; P.Casey, J., Ed.; 1977; pp 39–111. (2)  Chakar, F. S.; Ragauskas, A. J. Review of Current and Future Softwood Kraft Lignin Process Chemistry. Ind. Crops Prod. 2004, 20 (2), 131–141. (3)  Henriksson, G. 6. Lignin. In Wood Chemistry and Wood Biotechnology; Ek, M., Gellerstedt, G., Henriksson, G., Eds.; Walter de Gruyter: Berlin, New York, 2009; pp 121–146. (4)  Ralph, J.; Lundquist, K.; Brunow, G.; Lu, F.; Kim, H.; Schatz, P. F.; Marita, J. M.; Hatfield, R. D.; Ralph, S. A.; Christensen, J. H.; et al. Lignins: Natural Polymers from Oxidative Coupling of 4-Hydroxyphenyl- Propanoids. Phytochem. Rev. 2004, 3 (1–2), 29–60. (5)  Boerjan, W.; Ralph, J.; Baucher, M. Lignin Biosynthesis. Annu. Rev. Plant Biol. 2003, 54 (1), 519–546. (6)  Sjostrom, E. Wood Chemistry (Second Edition) Fundamentals and Applications; Elsevier, 2013. (7)  Whetten, R. W.; Mackay, J. J.; Sederoff, R. R.; Street, N. W. Recent Advances in Understanding Lignin Biosynthesis. Annu. Rev. Plant Physiol. Plant Mol. Biol. 1998, 49, 585–609. (8)  Gellerstedt, G. Softwood Kraft Lignin: Raw Material for the Future. Ind. Crops Prod. 2015, 77, 845–854. (9)  Tomani, P. The Lignoboost Process. Cellul. Chem. Technol. 2010, 44 (1–3), 53–58. (10)  Fatehi, P.; Chen, J. Extraction of Technical Lignins from Pulping Spent Liquors, 143  Challenges and Opportunities. In Production of Biofules and Chemicals from lignin; Fang, Z., Smith, R. L., Eds.; Biofuels and Biorefineries; Springer Singapore: Singapore, 2016; pp 35–54. (11)  Hu, Z.; Du, X.; Liu, J.; Chang, H.; Jameel, H. Structural Characterization of Pine Kraft Lignin: BioChoice Lignin vs Indulin AT. J. Wood Chem. Technol. 2016, 36 (6), 432–446. (12)  Doherty, W. O. S.; Mousavioun, P.; Fellows, C. M. Value-Adding to Cellulosic Ethanol : Lignin Polymers. Ind. Crop. Prod. 2011, 33 (2), 259–276. (13)  Johansson, A.; Aaltonen, O.; Ylinen, P. Organosolv Pulping - Methods and Pulp Properties. Biomass 1987, 13 (1), 45–65. (14)  García, A.; Toledano, A.; Serrano, L.; Egüés, I.; González, M.; Marín, F.; Labidi, J. Characterization of Lignins Obtained by Selective Precipitation. Sep. Purif. Technol. 2009, 68 (2), 193–198. (15)  Lourençon, T. V.; Hansel, F. A.; Da Silva, T. A.; Ramos, L. P.; De Muniz, G. I. B.; Magalhães, W. L. E. Hardwood and Softwood Kraft Lignins Fractionation by Simple Sequential Acid Precipitation. Sep. Purif. Technol. 2015, 154, 82–88. (16)  Humpert, D.; Ebrahimi, M.; Czermak, P. Membrane Technology for the Recovery of Lignin: A Review. Membranes (Basel). 2016, 6 (3), 1–13. (17)  Giummarella, N.; Lindgren, C.; Lindström, M. E.; Henriksson, G. Lignin Prepared by Ultrafiltration of Black Liquor : Investigation of Solubility, Viscosity, and Ash Content. Bioresources 2016, 11 (2), 3494–3510. (18)  Sabormin Chatterjee and Tomonori Saito. Solvent Fractionation of Lignin. In ACS symposium Series 1173; ACS Division of Polymer Chemistry, 2014; pp 153–168. (19)  Mörck, R.; Reimann, A.; Kringstad, K. P. Fractionation of Kraft Lignin by Successive 144  Extraction with Organic Solvents. I. Functional Groups, 13C-NMR-Spectra and Molecular Weight Distributions. Holzforschung 1986, 40 (Suppl), 51–60. (20)  Sudo, K.; Shlmlzu, K. A New Carbon Fiber from Lignin. J. Appl. Polym. Sci. 1992, 44 (1), 127–134. (21)  Kubo, S.; Uraki, Y.; Sano, Y. Preparation of Carbon Fibers from Softwood Lignin by Atmospheric Acetic Acid Pulping. Carbon N. Y. 1998, 36 (7–8), 1119–1124. (22)  Baker, D.A., Haper, D.P., Bozell, J. J. International Symposium on New Frontiers in Fiber Materials Science,The Fiber Society 2011. In Rapid Manufacture of Cabon Fiber from Organosolv Lignins; 2011. (23)  Baker, D.A., Haper, D.P., Rials, T. G. The Fiber Society 2012 Fall Meeting and Technical Conference. In Carbon fiber from extracted commercial softwood lignin; 2012. (24)  Dallmeyer, J. I. Preparation and Characterization of Lignin Nanofibre-Based Material Obtained by Electrostatic Spinning, University of British Columbia, 2013. (25)  Yoshida, H.; Mörck, R.; Kringstad, K. P. Fractionation of Kraft Lignin by Successive Extraction with Organic Solvents. II. Thermal Properties of Kraft Lignin Fractions. Holzforschung 1987, 41 (3), 171–176. (26)  Mörck, R.; Reimann, A.; Kringstad, K. P. Fractionation of Kraft Lignin by Successive Extraction with Organic Solvents. III. Fractionation of Kraft Lignin from Birch. Holzforschung 1988, 42 (2), 111–116. (27)  Thring, R. W.; Vanderlaan, M. N.; Griffin, S. L. Fractionation Of Alcell® Lignin By Sequential Solvent Extraction. J. Wood Chem. Technol. 1996, 16 (2), 139–154. (28)  Vanderlaan, M. N.; Thring, R. W. Polyurethanes from Alcell Lignin Fractions Obtained by Sequential Solvent Extraction. Biomass and Bioenergy 1998, 14 (5–6), 525–531. 145  (29)  Yuan, T. Q.; He, J.; Xu, F.; Sun, R. C. Fractionation and Physico-Chemical Analysis of Degraded Lignins from the Black Liquor of Eucalyptus Pellita KP-AQ Pulping. Polym. Degrad. Stab. 2009, 94 (7), 1142–1150. (30)  Wang, K.; Xu, F.; Sun, R. Molecular Characteristics of Kraft-AQ Pulping Lignin Fractionated by Sequential Organic Solvent Extraction. Int. J. Mol. Sci. 2010, 11 (8), 2988–3001. (31)  Gosselink, R. J. a.; van Dam, J. E. G.; de Jong, E.; Scott, E. L.; Sanders, J. P. M.; Li, J.; Gellerstedt, G. Fractionation, Analysis, and PCA Modeling of Properties of Four Technical Lignins for Prediction of Their Application Potential in Binders. Holzforschung 2010, 64 (2), 193–200. (32)  Van De Pas, D.; Hickson, A.; Donaldson, L.; Lloyd-Jones, G.; Tamminen, T.; Fernyhough, A.; Mattinen, M.-L. Characterization of Fractionated Lignins Polymerized by Fungal Laccases. Bioresources 2011, 6 (2), 1105–1121. (33)  Ropponen, J.; Räsänen, L.; Rovio, S.; Ohra-Aho, T.; Liitiä, T.; Mikkonen, H.; Van De Pas, D.; Tamminen, T. Solvent Extraction as a Means of Preparing Homogeneous Lignin Fractions. Holzforschung 2011, 65 (4), 543–549. (34)  Dallmeyer, I.; Chowdhury, S.; Kadla, J. F. Preparation and Characterization of Kraft Lignin-Based Moisture-Responsive Films with Reversible Shape-Change Capability. Biomacromolecules 2013, 14 (7), 2354–2363. (35)  Teng, N.-Y.; Dallmeyer, I.; Kadla, J. F. Effect of Softwood Kraft Lignin Fractionation on the Dispersion of Multiwalled Carbon Nanotubes. Ind. Eng. Chem. Res. 2013, 52 (19), 6311–6317. (36)  Dallmeyer, I.; Lin, L. T.; Li, Y.; Ko, F.; Kadla, J. F. Preparation and Characterization of 146  Interconnected, Kraft Lignin-Based Carbon Fibrous Materials by Electrospinning. Macromol. Mater. Eng. 2014, 299 (5), 540–551. (37)  Cui, C.; Sun, R.; Argyropoulos, D. S. Fractional Precipitation of Softwood Kraft Lignin: Isolation of Narrow Fractions Common to a Variety of Lignins. ACS Sustain. Chem. Eng. 2014, 2 (4), 959–968. (38)  Boeriu, C. G.; Fiţigău, F. I.; Gosselink, R. J. a.; Frissen, A. E.; Stoutjesdijk, J.; Peter, F. Fractionation of Five Technical Lignins by Selective Extraction in Green Solvents and Characterisation of Isolated Fractions. Ind. Crops Prod. 2014, 62, 481–490. (39)  Saito, T.; Perkins, J. H.; Vautard, F.; Meyer, H. M.; Messman, J. M.; Tolnai, B.; Naskar, A. K. Methanol Fractionation of Softwood Kraft Lignin: Impact on the Lignin Properties. ChemSusChem 2014, 7 (1), 221–228. (40)  Li, H.; McDonald, A. G. Fractionation and Characterization of Industrial Lignins. Ind. Crops Prod. 2014, 62, 67–76. (41)  Dodd, A. P.; Kadla, J. F.; Straus, S. K. Characterization of Fractions Obtained from Two Industrial Softwood Kraft Lignins. ACS Sustain. Chem. Eng. 2015, 3 (1), 103–110. (42)  Duval, A.; Vilaplana, F.; Crestini, C.; Lawoko, M. Solvent Screening for the Fractionation of Industrial Kraft Lignin. Holzforschung 2015, 70 (1), 11–20. (43)  Passoni, V.; Scarica, C.; Levi, M.; Turri, S.; Griffini, G. Fractionation of Industrial Softwood Kraft Lignin: Solvent Selection as a Tool for Tailored Material Properties. ACS Sustain. Chem. Eng. 2016, 4 (4), 2232–2242. (44)  Jiang, X.; Savithri, D.; Du, X.; Pawar, S.; Jameel, H.; Chang, H.-M.; Zhou, X. Fractionation and Characterization of Kraft Lignin by Sequential Precipitation with Various Organic Solvents. ACS Sustain. Chem. Eng. 2017, 5 (1), 835–842. 147  (45)  Lange, H.; Schiffels, P.; Sette, M.; Sevastyanova, O.; Crestini, C. Fractional Precipitation of Wheat Straw Organosolv Lignin: Macroscopic Properties and Structural Insights. ACS Sustain. Chem. Eng. 2016, 4 (10), 5136–5151. (46)  Jääskeläinen, A.-S.; Liitiä, T.; Mikkelson, A.; Tamminen, T. Aqueous Organic Solvent Fractionation as Means to Improve Lignin Homogeneity and Purity. Ind. Crops Prod. 2017, 103, 51–58. (47)  Sadeghifar, H.; Wells, T.; Le, R. K.; Sadeghifar, F.; Yuan, J. S.; Jonas Ragauskas, A. Fractionation of Organosolv Lignin Using Acetone:Water and Properties of the Obtained Fractions. ACS Sustain. Chem. Eng. 2017, 5 (1), 580–587. (48)  Graichen, F. H. M.; Grigsby, W. J.; Hill, S. J.; Raymond, L. G.; Sanglard, M.; Smith, D. A.; Thorlby, G. J.; Torr, K. M.; Warnes, J. M. Yes, We Can Make Money out of Lignin and Other Bio-Based Resources. Ind. Crops Prod. 2017, 106, 74–85. (49)  Duval, A.; Lawoko, M. A Review on Lignin-Based Polymeric, Micro- and Nano-Structured Materials. React. Funct. Polym. 2014, 85, 78–96. (50)  Kai, D.; Tan, M. J.; Chee, P. L.; Chua, Y. K.; Yap, Y. L.; Loh, X. J. Towards Lignin-Based Functional Materials in a Sustainable World. Green Chem. 2016, 18 (5), 1175–1200. (51)  Lora, J. H. Lignin: A Platform for Renewable Aromatic Polymeric Materials. In Quality Living Through Chemurgy and Green Chemistry; Lau, P. C. K., Ed.; Springer Berlin Heidelberg, 2016; pp 221–261. (52)  Gosselink, R. J. A. Lignin as a Renewable Aromatic Resource for the Chemical Industry, Wageningen University, 2011. (53)  Gosselink, R. J. A.; De Jong, E.; Guran, B.; Abächerli, A. Co-Ordination Network for 148  Lignin - Standardisation, Production and Applications Adapted to Market Requirements (EUROLIGNIN). Ind. Crops Prod. 2004, 20 (2), 121–129. (54)  Constant, S.; Wienk, H. L. J.; Frissen, A. E.; Peinder, P. de; Boelens, R.; van Es, D. S.; Grisel, R. J. H.; Weckhuysen, B. M.; Huijgen, W. J. J.; Gosselink, R. J. A.; et al. New Insights into the Structure and Composition of Technical Lignins: A Comparative Characterisation Study. Green Chem. 2016, 18 (9), 2651–2665. (55)  Titirici, M.-M.; White, R. J.; Brun, N.; Budarin, V. L.; Su, D. S.; Del Monte, F.; Clark, J. H.; MacLachlan, M. J. Sustainable Carbon Materials. Chem. Soc. Rev. 2014, 44, 250–290. (56)  Baker, D. A.; Rials, T. G. Recent Advances in Low-Cost Carbon Fiber Manufacture from Lignin. J. Appl. Polym. Sci. 2013, 130 (2), 713–728. (57)  Frank, E.; Steudle, L. M.; Ingildeev, D.; Spörl, J. M.; Buchmeiser, M. R. Carbon Fibers: Precursor Systems, Processing, Structure, and Properties. Angew. Chem. Int. Ed. Engl. 2014, 53 (21), 5262–5298. (58)  Fang, W.; Yang, S.; Wang, X.-L.; Yuan, T.; Sun, R.-C. Manufacture and Application of Lignin-Based Carbon Fibers (LCFs) and Lignin-Based Carbon Nanofibers (LCNFs). Green Chem. 2017, 19 (8), 1794–1827. (59)  Inagaki, M.; Yang, Y.; Kang, F. Carbon Nanofibers Prepared via Electrospinning. Adv. Mater. 2012, 24 (19), 2547–2566. (60)  Davé, V.; Prasad, A.; Marand, H.; Glasser, W. G. Molecular Organization of Lignin during Carbonization. Polymer. 1993, pp 3144–3154. (61)  Mainka, H.; Hilfert, L.; Busse, S.; Edelmann, F.; Haak, E.; Herrmann, A. S. Characterization of the Major Reactions during Conversion of Lignin to Carbon Fiber. J. Mater. Res. Technol. 2015, 4 (4), 377–391. 149  (62)  Otto, W. H. Relationship of Tensile Strength of Glass Fibers to Diameter. J. Am. Ceram. Soc. 1954, 38 (3), 122–125. (63)  Dallmeyer, I.; Ko, F.; Kadla, J. F. Electrospinning of Technical Lignins for the Production of Fibrous Networks. J. Wood Chem. Technol. 2010, 30 (4), 315–329. (64)  Kubo, S.; Kadla, J. F. Lignin-Based Carbon Fibers: Effect of Synthetic Polymer Blending on Fiber Properties. J. Polym. Environ. 2005, 13 (2), 97–105. (65)  Kubo, S.; Kadla, J. F. Kraft Lignin/poly(ethylene Oxide) Blends: Effect of Lignin Structure on Miscibility and Hydrogen Bonding. J. Appl. Polym. Sci. 2005, 98 (3), 1437–1444. (66)  Poursorkhabi, V.; Mohanty, A. K.; Misra, M. Electrospinning of Aqueous Lignin/poly(ethylene Oxide) Complexes. J. Appl. Polym. Sci. 2015, 132 (2), 41260(1-9). (67)  Imel, A. E.; Naskar, A. K.; Dadmun, M. D. Understanding the Impact of Poly(ethylene Oxide) on the Assembly of Lignin in Solution toward Improved Carbon Fiber Production. ACS Appl. Mater. Interfaces 2016, 8 (5), 3200–3207. (68)  Aslanzadeh, S.; Zhu, Z.; Luo, Q.; Ahvazi, B.; Boluk, Y.; Ayranci, C. Electrospinning of Colloidal Lignin in Poly(ethylene Oxide) N , N -Dimethylformamide Solutions. Macromol. Mater. Eng. 2016, 301 (4), 401–413. (69)  Gao, G.; Dallmeyer, J. I.; Kadla, J. F. Synthesis of Lignin Nanofibers with Ionic-Responsive Shells: Water-Expandable Lignin-Based Nanofibrous Mats. Biomacromolecules 2012, 13 (11), 3602–3610. (70)  Lin, L.; Li, Y.; Ko, F. K. Fabrication and Properties of Lignin Based Carbon Nanofiber. J. Fiber Bioeng. Informatics 2013, 6 (4), 335–347. (71)  Cho, M.; Karaaslan, M. A.; Renneckar, S.; Ko, F. Enhancement of the Mechanical 150  Properties of Electrospun Lignin-Based Nanofibers by Heat Treatment. J. Mater. Sci. 2017, 52 (16), 9602–9614. (72)  Ding, R.; Wu, H.; Thunga, M.; Bowler, N.; Kessler, M. R. Processing and Characterization of Low-Cost Electrospun Carbon Fibers from Organosolv Lignin/polyacrylonitrile Blends. Carbon N. Y. 2016, 100, 126–136. (73)  Lallave, M.; Bedia, J.; Ruiz-Rosas, R.; Rodríguez-Mirasol, J.; Cordero, T.; Otero, J. C.; Marquez, M.; Barrero,  a.; Loscertales, I. G. Filled and Hollow Carbon Nanofibers by Coaxial Electrospinning of Alcell Lignin without Binder Polymers. Adv. Mater. 2007, 19 (23), 4292–4296. (74)  Ruiz-Rosas, R.; Bedia, J.; Lallave, M.; Loscertales, I. G.; Barrero,  a.; Rodríguez-Mirasol, J.; Cordero, T. The Production of Submicron Diameter Carbon Fibers by the Electrospinning of Lignin. Carbon N. Y. 2010, 48 (3), 696–705. (75)  Seo, D.; Jeun, J.; Kim, H.; Kang, P. Preparation and Characterization of the Carbon Nanofiber Mat Produced from Electrospun PAN/lignin Precursors by Electron Beam Irradiation. Rev. Adv. Mater. Sci. 2011, 28 (1), 31–34. (76)  Ago, M.; Okajima, K.; Jakes, J. E.; Park, S.; Rojas, O. J. Lignin-Based Electrospun Nanofibers Reinforced with Cellulose Nanocrystals. Biomacromolecules 2012, 13 (3), 918–926. (77)  Ago, M.; Jakes, J. E.; Johansson, L.-S.; Park, S.; Rojas, O. J. Interfacial Properties of Lignin-Based Electrospun Nanofibers and Films Reinforced with Cellulose Nanocrystals. ACS Appl. Mater. Interfaces 2012, 4 (12), 6849–6856. (78)  Ago, M.; Jakes, J.; Rojas, O. Thermomechanical Properties of Lignin-Based Electrospun Nanofibers and Films Reinforced with Cellulose Nanocrystals: A Dynamic Mechanical 151  and Nanoindentation Study. ACS Appl. Mater. Interfaces 2013, 5 (22), 11768–11776. (79)  Schreiber, M.; Vivekanandhan, S.; Mohanty, A. K.; Misra, M. A Study on the Electrospinning Behaviour and Nanofibre Morphology of Anionically Charged Lignin. Adv. Mater. Lett. 2012, 3 (6), 476–480. (80)  Hu, S.; Hsieh, Y.-L. Ultrafine Microporous and Mesoporous Activated Carbon Fibers from Alkali Lignin. J. Mater. Chem. A 2013, 1 (37), 11279–11288. (81)  Hu, S.; Zhang, S.; Pan, N.; Hsieh, Y.-L. High Energy Density Supercapacitors from Lignin Derived Submicron Activated Carbon Fibers in Aqueous Electrolytes. J. Power Sources 2014, 270, 106–112. (82)  Teng, N.-Y.; Dallmeyer, I.; Kadla, J. F. Incorporation of Multiwalled Carbon Nanotubes into Electrospun Softwood Kraft Lignin-Based Fibers. J. Wood Chem. Technol. 2013, 33 (4), 299–316. (83)  Wang, S.; Yang, L.; Stubbs, L. Lignin-Derived Fused Electrospun Carbon Fibrous Mats as High Performance Anode Materials for Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2013, 5, 12275–12282. (84)  Lai, C.; Zhou, Z.; Zhang, L.; Wang, X.; Zhou, Q.; Zhao, Y.; Wang, Y.; Wu, X. F.; Zhu, Z.; Fong, H. Free-Standing and Mechanically Flexible Mats Consisting of Electrospun Carbon Nanofibers Made from a Natural Product of Alkali Lignin as Binder-Free Electrodes for High-Performance Supercapacitors. J. Power Sources 2014, 247, 134–141. (85)  Oroumei, A.; Fox, B.; Naebe, M. Thermal and Rheological Characteristics of Biobased Carbon Fiber Precursor Derived from Low Molecular Weight Organosolv Lignin. ACS Sustain. Chem. Eng. 2015, 3 (4), 758–769. (86)  Schreiber, M.; Vivekanandhan, S.; Cooke, P.; Mohanty, A. K.; Misra, M. Electrospun 152  Green Fibres from Lignin and Chitosan: A Novel Polycomplexation Process for the Production of Lignin-Based Fibres. J. Mater. Sci. 2014, 49 (23), 7949–7958. (87)  Schreiber, M.; Vivekanandhan, S.; Mohanty, A. K.; Misra, M. Iodine Treatment of Lignin–Cellulose Acetate Electrospun Fibers: Enhancement of Green Fiber Carbonization. ACS Sustain. Chem. Eng. 2015, 3 (1), 33–41. (88)  Youe, W.-J.; Lee, S.-M.; Lee, S.-S.; Lee, S.-H.; Kim, Y. S. Characterization of Carbon Nanofiber Mats Produced from Electrospun Lignin- G -Polyacrylonitrile Copolymer. Int. J. Biol. Macromol. 2016, 82, 497–504. (89)  Chang, F.; Chan, K.; Chang, C. The Effect of Processing Parameters on Formation of Lignosulfonate Fibers Produced Using Electrospinning. Bioresources 2016, 11 (2), 4705–4717. (90)  Yen, S.-H.; Chang, F.-C. Effects of Fiber Processing Conditions on the Yield, Carbon Content, and Diameter of Lignosulfonate-Based Carbon Fibers. BioResources 2016, 11 (4), 10158–10172. (91)  Aslanzadeh, S.; Ahvazi, B.; Boluk, Y.; Ayranci, C. Morphologies of Electrospun Fibers of Lignin in Poly(ethylene oxide)/N,N-Dimethylformamide. J. Appl. Polym. Sci. 2016, 133 (44), 44172(1-10). (92)  Poursorkhabi, V.; Mohanty, A. K.; Misra, M. Statistical Analysis of the Effects of Carbonization Parameters on the Structure of Carbonized Electrospun Organosolv Lignin Fibers. J. Appl. Polym. Sci. 2016, 133 (45), 44005(1-17). (93)  Ago, M.; Borghei, M.; Haataja, J. S.; Rojas, O. J. Mesoporous Carbon Soft-Templated from Lignin Nanofiber Networks: Microphase Separation Boosts Supercapacitance in Conductive Electrodes. RSC Adv. 2016, 6 (89), 85802–85810. 153  (94)  Bahi, A.; Shao, J.; Mohseni, M.; Ko, F. K. Membranes Based on Electrospun Lignin-Zeolite Composite Nanofibers. Sep. Purif. Technol. 2017, 187, 207–213. (95)  Mayyas, A.; Qattawi, A.; Omar, M.; Shan, D. Design for Sustainability in Automotive Industry: A Comprehensive Review. Renew. Sustain. Energy Rev. 2012, 16 (4), 1845–1862. (96)  Witten, E.; Kraus, T.; Kühnel, M. Composites Market Report 2016; 2016. (97)  Gallego, N. C.; Baker, D. A.; Baker, F. S. SAMPE Conference 2009. In Low cost production of carbon fibers from lignin materials; 2009; pp 1–6. (98)  Gupta, V. B. Melt-Spinning Processes. In Manufactured Fibre Technology; Springer Netherlands: Dordrecht, 1997; pp 67–97. (99)  Spruiell, J. E.; Bond, E. Summary for Policymakers. In Climate Change 2013 - The Physical Science Basis; Intergovernmental Panel on Climate Change, Ed.; Cambridge University Press: Cambridge, 1999; Vol. 2, pp 1–30. (100)  Frank, E.; Hermanutz, F.; Buchmeiser, M. R. Carbon Fibers: Precursors, Manufacturing, and Properties. Macromol. Mater. Eng. 2012, 297 (6), 493–501. (101)  Eberle, Cliff, Albers, T., Chen, C., Webb, D. Commercialization of New Carbon Fiber Materials Based on Sustainable Resources for Energy Applications; 2013. (102)  Accociation, A. F. M. Acetate http://www.fibersource.com/fiber-products/acetate-fiber/. (103)  Plaisantin, H.; Pailler, R.; Guette, A.; Daudé, G.; Pétraud, M.; Barbe, B.; Birot, M.; Pillot, J. .; Olry, P. Conversion of Cellulosic Fibres into Carbon Fibres. Compos. Sci. Technol. 2001, 61 (14), 2063–2068. (104)  Spörl, J. M.; Ota, A.; Son, S.; Massonne, K.; Hermanutz, F.; Buchmeiser, M. R. Carbon Fibers Prepared from Ionic Liquid-Derived Cellulose Precursors. Mater. Today Commun. 154  2016, 7, 1–10. (105)  Peng, S.; Shao, H.; Hu, X. Lyocell Fibers as the Precursor of Carbon Fibers. J. Appl. Polym. Sci. 2003, 90 (7), 1941–1947. (106)  Doshi, J.; Reneker, D. H. Electrospinning Process and Applications of Electrospun Fibers. Jounal Electrost. 1995, 35, 151–160. (107)  Reneker, D.; Yarin, A.; Zussman, E.; Xu, H. Electrospinning of Nanofibers from Polymer Solutions and Melts. Adv. Appl. Mech. 2007, 41, 43–195. (108)  Ko, F. K.; Wan, Y. Introduction to Nanofiber Materials; Cambridge University Press: Cambridge, 2014. (109)  Reneker, D. H.; Yarin, A. L. Electrospinning Jets and Polymer Nanofibers. Polymer (Guildf). 2008, 49 (10), 2387–2425. (110)  Zhou, C.; Chu, R.; Wu, R.; Wu, Q. Electrospun Polyethylene Oxide/cellulose Nanocrystal Composite Nanofibrous Mats with Homogeneous and Heterogeneous Microstructures. Biomacromolecules 2011, 12 (7), 2617–2625. (111)  Andrady, A. L. Science and Technology of Polymer Nanofibers; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2008. (112)  Huang, Z.-M.; Zhang, Y.-Z.; Kotaki, M.; Ramakrishna, S. A Review on Polymer Nanofibers by Electrospinning and Their Applications in Nanocomposites. Compos. Sci. Technol. 2003, 63 (15), 2223–2253. (113)  Wang, Y.; Serrano, S.; Santiago-Aviles, J. J. Conductivity Measurement of Electrospun PAN-Based Carbon Nanofiber. J. Mater. Sci. Lett. 2002, 21 (13), 1055–1057. (114)  Inagaki, M.; Yang, Y.; Kang, F. Carbon Nanofibers Prepared via Electrospinning. Adv. Mater. 2012, 24 (19), 2547–2566. 155  (115)  Lallave, M.; Bedia, J.; Ruiz-Rosas, R.; Rodríguez-Mirasol, J.; Cordero, T.; Otero, J. C.; Marquez, M.; Barrero, A.; Loscertales, I. G. Filled and Hollow Carbon Nanofibers by Coaxial Electrospinning of Alcell Lignin without Binder Polymers. Adv. Mater. 2007, 19 (23), 4292–4296. (116)  Liu, C. K.; Lai, K.; Liu, W.; Yao, M.; Sun, R. J. Preparation of Carbon Nanofibres through Electrospinning and Thermal Treatment. Polym. Int. 2009, 58 (12), 1341–1349. (117)  Li, Y.; Cui, D.; Tong, Y.; Xu, L. Study on Structure and Thermal Stability Properties of Lignin during Thermostabilization and Carbonization. Int. J. Biol. Macromol. 2013, 62, 663–669. (118)  Braun, J. L.; Holtman, K. M.; Kadla, J. F. Lignin-Based Carbon Fibers: Oxidative Thermostabilization of Kraft Lignin. Carbon N. Y. 2005, 43 (2), 385–394. (119)  Brodin, I.; Sjöholm, E.; Gellerstedt, G. The Behavior of Kraft Lignin during Thermal Treatment. J. Anal. Appl. Pyrolysis 2010, 87 (1), 70–77. (120)  Brodin, I.; Ernstsson, M.; Gellerstedt, G.; Sjöholm, E. Oxidative Stabilisation of Kraft Lignin for Carbon Fibre Production. Holzforschung 2012, 66 (2), 141–147. (121)  Foston, M.; Nunnery, G. a.; Meng, X.; Sun, Q.; Baker, F. S.; Ragauskas, A. NMR a Critical Tool to Study the Production of Carbon Fiber from Lignin. Carbon N. Y. 2013, 52, 65–73. (122)  Schultz, Tor P., Glasser, W. Quantitative Structural Analysis of Lignin by Diffuse Reflectance Fourier Transform Infrared Spectrometry. Holzforschung 1986, 40 (suppl), 37–44. (123)  Uraki, Y.; Kubo, S.; Nigo, N.; Sano, Y.; Sasaya, T. Preparation of Carbon Fibers from Organosolv Lignin Obtained by Aqueous Acetic Acid Pulping. Holzforschung 1995, 49 156  (4), 343–350. (124)  John, M. J.; Thomas, S. Biofibres and Biocomposites. Carbohydr. Polym. 2008, 71 (3), 343–364. (125)  Eichhorn, S. J. Cellulose Nanowhiskers: Promising Materials for Advanced Applications. Soft Matter 2011, 7 (2), 303–315. (126)  Azizi Samir, M. A. S.; Alloin, F.; Dufresne, A. Review of Recent Research into Cellulosic Whiskers, Their Properties and Their Application in Nanocomposite Field. Biomacromolecules 2005, 6 (2), 612–626. (127)  Peng, B. L.; Dhar, N.; Liu, H. L.; Tam, K. C. Chemistry and Applications of Nanocrystalline Cellulose and Its Derivatives: A Nanotechnology Perspective. Can. J. Chem. Eng. 2011, 89 (5), 1191–1206. (128)  Revol, J. F.; Bradford, H.; Giasson, J.; Marchessault, R. H.; Gray, D. G. Helicoidal Self-Ordering of Cellulose Microfibrils in Aqueous Suspension. Int. J. Biol. Macromol. 1992, 14 (3), 170–172. (129)  Habibi, Y.; Lucia, L. a; Rojas, O. J. Cellulose Nanocrystals: Chemistry, Self-Assembly, and Applications. Chem. Rev. 2010, 110 (6), 3479–3500. (130)  Klemm, D.; Kramer, F.; Moritz, S.; Lindström, T.; Ankerfors, M.; Gray, D.; Dorris, A. Nanocelluloses: A New Family of Nature-Based Materials. Angew. Chem. Int. Ed. Engl. 2011, 50 (24), 5438–5466. (131)  Miao, C.; Hamad, W. Y. Cellulose Reinforced Polymer Composites and Nanocomposites: A Critical Review. Cellulose 2013, 20 (5), 2221–2262. (132)  Favier, V.; Chanzy, H.; Cavaille, J.-Y. Y. Polymer Nanocomposites Reinforced by Cellulose Whiskers. Macromolecules 1995, 28, 6365–6367. 157  (133)  Favier, V.; Canova, G. R.; Cavaillé, J. Y.; Chanzy, H.; Dufresne, A.; Gauthier, C. Nanocomposite Materials from Latex and Cellulose Whiskers. Polym. Adv. Technol. 1995, 6 (5), 351–355. (134)  Favier, V.; Cavaille, J. Y.; Canova, G. R.; Shrivastava, S. C. Mechanical Percolation in Cellulose Whisker Nanocomposites. Polym. Eng. Sci. 1997, 37 (10), 1732–1739. (135)  Eichhorn, S. J.; Dufresne, A.; Aranguren, M.; Marcovich, N. E.; Capadona, J. R.; Rowan, S. J.; Weder, C.; Thielemans, W.; Roman, M.; Renneckar, S.; et al. Review: Current International Research into Cellulose Nanofibres and Nanocomposites. J. Mater. Sci. 2010, 45 (1), 1–33. (136)  Dufresne, A. Cellulose Nanomaterial Reinforced Polymer Nanocomposites. Curr. Opin. Colloid Interface Sci. 2017, 29, 1–8. (137)  Capadona, J. R.; Van Den Berg, O.; Capadona, L. a; Schroeter, M.; Rowan, S. J.; Tyler, D. J.; Weder, C. A Versatile Approach for the Processing of Polymer Nanocomposites with Self-Assembled Nanofibre Templates. Nat. Nanotechnol. 2007, 2 (12), 765–769. (138)  Lin, N.; Huang, J.; Dufresne, A. Preparation, Properties and Applications of Polysaccharide Nanocrystals in Advanced Functional Nanomaterials: A Review. Nanoscale 2012, 4 (11), 3274–3294. (139)  Zhou, C.; Wu, Q. Recent Development in Applications of Cellulose Nanocrystals for Advanced Polymer-Based Nanocomposites by Novel Fabrication Strategies. Nanocrystals – Synth. Charact. Appl. Prop. 2012, 103–120. (140)  Park, W.-I.; Kang, M.; Kim, H.-S.; Jin, H.-J. Electrospinning of Poly(ethylene Oxide) with Bacterial Cellulose Whiskers. Macromol. Symp. 2007, 249–250 (1), 289–294. (141)  Lu, P.; Hsieh, Y.-L. Cellulose Nanocrystal-Filled Poly(acrylic Acid) Nanocomposite 158  Fibrous Membranes. Nanotechnology 2009, 20 (41), 415604. (142)  Zoppe, J. O.; Peresin, M. S.; Habibi, Y.; Venditti, R. A.; Rojas, O. J. Reinforcing Poly(epsilon-Caprolactone) Nanofibers with Cellulose Nanocrystals. ACS Appl. Mater. interfaces 2009, 1 (9), 1996–2004. (143)  Xiang, C.; Joo, Y.; Frey, M. Nanocomposite Fibers Electrospun from Poly (Lactic Acid)/cellulose Nanocrystals. J. Biobased Mater. … 2009, 3 (2), 147–155. (144)  Rojas, O. J.; Montero, G. A.; Habibi, Y. Electrospun Nanocomposites from Polystyrene Loaded with Cellulose Nanowhiskers. J. Appl. Polym. Sci. 2009, 113 (2), 927–935. (145)  Ureña-Benavides, E. E.; Brown, P. J.; Kitchens, C. L. Effect of Jet Stretch and Particle Load on Cellulose Nanocrystal-Alginate Nanocomposite Fibers. Langmuir 2010, 26 (17), 14263–14270. (146)  Ureña-Benavides, E. E.; Kitchens, C. L. Wide-Angle X-Ray Diffraction of Cellulose Nanocrystal−Alginate Nanocomposite Fibers. Macromolecules 2011, 44 (9), 3478–3484. (147)  Ureña-Benavides, E. E.; Kitchens, C. L. Cellulose Nanocrystal Reinforced Alginate Fibers—Biomimicry Meets Polymer Processing. Mol. Cryst. Liq. Cryst. 2012, 556 (1), 275–287. (148)  Peresin, M. S.; Habibi, Y.; Vesterinen, A.-H.; Rojas, O. J.; Pawlak, J. J.; Seppälä, J. V. Effect of Moisture on Electrospun Nanofiber Composites of Poly(vinyl Alcohol) and Cellulose Nanocrystals. Biomacromolecules 2010, 11 (9), 2471–2477. (149)  Peresin, M. S.; Habibi, Y.; Zoppe, J. O.; Pawlak, J. J.; Rojas, O. J. Nanofiber Composites of Polyvinyl Alcohol and Cellulose Nanocrystals: Manufacture and Characterization. Biomacromolecules 2010, 11 (3), 674–681. (150)  Huang, J.; Liu, L.; Yao, J. Electrospinning of Bombyx Mori Silk Fibroin Nanofiber Mats 159  Reinforced by Cellulose Nanowhiskers. Fibers Polym. 2011, 12 (8), 1002–1006. (151)  Zhou, C.; Wang, Q.; Wu, Q. UV-Initiated Crosslinking of Electrospun Poly(ethylene Oxide) Nanofibers with Pentaerythritol Triacrylate: Effect of Irradiation Time and Incorporated Cellulose Nanocrystals. Carbohydr. Polym. 2012, 87 (2), 1779–1786. (152)  Dong, H.; Strawhecker, K. E.; Snyder, J. F.; Orlicki, J. a.; Reiner, R. S.; Rudie, A. W. Cellulose Nanocrystals as a Reinforcing Material for Electrospun Poly(methyl Methacrylate) Fibers: Formation, Properties and Nanomechanical Characterization. Carbohydr. Polym. 2012, 87 (4), 2488–2495. (153)  Li, Y.; Ko, F. K.; Hamad, W. Y. Effects of Emulsion Droplet Size on the Structure of Electrospun Ultrafine Biocomposite Fibers with Cellulose Nanocrystals. Biomacromolecules 2013, 14 (11), 3801–3807. (154)  Dong, X. M.; Kimura, T.; Revol, J.-F.; Gray, D. G. Effects of Ionic Strength on the Isotropic−Chiral Nematic Phase Transition of Suspensions of Cellulose Crystallites. Langmuir 1996, 12 (8), 2076–2082. (155)  Dong, X.-M.; REVOL, J.-F.; GRAY, D. G. Effect of Microcrystallite Preparation Conditions on the Formation of Colloid Crystals of Cellulose. Cellulose 1998, 5 (1), 19–32. (156)  Wendorff, J. H. Nanofiber Properties. In Electrospinning; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2012; pp 69–104. (157)  Greenfeld, I.; Fezzaa, K.; Rafailovich, M. H.; Zussman, E. Fast X-Ray Phase-Contrast Imaging of Electrospinning Polymer Jets: Measurements of Radius, Velocity, and Concentration. Macromolecules 2012, 45 (8), 3616–3626. (158)  Lin, D. Y.; Martin, D. C. Orientation Development in Electrospun Liquid—Crystalline 160  Polymer Nanofibers. In Polymeric Nanofibers; Reneker, Darrell H.Fong, H., Ed.; 2006 American Chemical Society, 2006; pp 330–342. (159)  Fennessey, S. F.; Farris, R. J. Fabrication of Aligned and Molecularly Oriented Electrospun Polyacrylonitrile Nanofibers and the Mechanical Behavior of Their Twisted Yarns. Polymer (Guildf). 2004, 45 (12), 4217–4225. (160)  Kakade, M. V.; Givens, S.; Gardner, K.; Lee, K. H.; Chase, D. B.; Rabolt, J. F. Electric Field Induced Orientation of Polymer Chains in Macroscopically Aligned Electrospun Polymer Nanofibers. J. Am. Chem. Soc. 2007, 129 (10), 2777–2782. (161)  Pai, C. L.; Boyce, M. C.; Rutledge, G. C. Mechanical Properties of Individual Electrospun PA 6(3)T Fibers and Their Variation with Fiber Diameter. Polymer (Guildf). 2011, 52 (10), 2295–2301. (162)  Ma, X.; Liu, J.; Ni, C.; Martin, D. C.; Chase, D. B.; Rabolt, J. F. Molecular Orientation in Electrospun Poly(vinylidene Fluoride) Fibers. ACS Macro Lett. 2012, 1 (3), 428–431. (163)  Yano, T.; Higaki, Y.; Tao, D.; Murakami, D.; Kobayashi, M.; Ohta, N.; Koike, J.; Horigome, M.; Masunaga, H.; Ogawa, H.; et al. Orientation of Poly(vinyl Alcohol) Nanofiber and Crystallites in Non-Woven Electrospun Nanofiber Mats under Uniaxial Stretching. Polymer (Guildf). 2012, 53 (21), 4702–4708. (164)  Ma, X.; Liu, J.; Ni, C.; Martin, D. C.; Bruce Chase, D.; Rabolt, J. F. The Effect of Collector Gap Width on the Extent of Molecular Orientation in Polymer Nanofibers. J. Polym. Sci. Part B Polym. Phys. 2015, 617–623. (165)  Song, W.; Liu, D.; Prempeh, N.; Song, R. Fiber Alignment and Liquid Crystal Orientation of Cellulose Nanocrystals in the Electrospun Nanofibrous Mats. Biomacromolecules 2017, 18 (10), 3273–3279. 161  (166)  Richard-Lacroix, M.; Pellerin, C. Molecular Orientation in Electrospun Fibers: From Mats to Single Fibers. Macromolecules 2013, 46 (24), 9473–9493. (167)  Atalla, Rajai H .and Agarwal, U. P. Raman Microprobe Evidence for Lignin Orientation in the Cell Walls of Native Woody Tissue. Science (80-. ). 1985, 227 (4687), 636–638. (168)  Åkerholm, M.; Salmén, L. The Oriented Structure of Lignin and Its Viscoelastic Properties Studied by Static and Dynamic FT-IR Spectroscopy. Holzforschung 2003, 57 (5), 459–465. (169)  Kubo, S.; Kadla, J. F. Hydrogen Bonding in Lignin: A Fourier Transform Infrared Model Compound Study. Biomacromolecules 2005, 6 (5), 2815–2821. (170)  Maréchal, Y.; Chanzy, H. The Hydrogen Bond Network in I β Cellulose as Observed by Infrared Spectrometry. J. Mol. Struct. 2000, 523 (1–3), 183–196. (171)  Dumanli, A. G.; van der Kooij, H. M.; Kamita, G.; Reisner, E.; Baumberg, J. J.; Steiner, U.; Vignolini, S. Digital Color in Cellulose Nanocrystal Films. ACS Appl. Mater. Interfaces 2014, 6 (15), 12302–12306. (172)  Majoinen, J.; Kontturi, E.; Ikkala, O.; Gray, D. G. SEM Imaging of Chiral Nematic Films Cast from Cellulose Nanocrystal Suspensions. Cellulose 2012, 19 (5), 1599–1605. (173)  Chen, Y. ru; Sarkanen, S. Macromolecular Replication during Lignin Biosynthesis. Phytochemistry 2010, 71 (4), 453–462. (174)  Azizi Samir, M. A. S.; Alloin, F.; Sanchez, J. Y.; El Kissi, N.; Dufresne, A. Preparation of Cellulose Whiskers Reinforced Nanocomposites from an Organic Medium Suspension. Macromolecules 2004, 37 (4), 1386–1393. (175)  Viet, D.; Beck-Candanedo, S.; Gray, D. G. Dispersion of Cellulose Nanocrystals in Polar Organic Solvents. Cellulose 2006, 14 (2), 109–113. 162  (176)  Elazzouzi-Hafraoui, S.; Nishiyama, Y.; Putaux, J.-L.; Heux, L.; Dubreuil, F.; Rochas, C. The Shape and Size Distribution of Crystalline Nanoparticles Prepared by Acid Hydrolysis of Native Cellulose. Biomacromolecules 2008, 9 (1), 57–65. (177)  Macossay, J.; Marruffo, A.; Rincon, R.; Eubanks, T.; Kuang, A. Effect of Needle Diameter on Nanofiber Diameter and Thermal Properties of Electrospun Poly(methyl Methacrylate). Polym. Adv. Technol. 2007, 18 (3), 180–183. (178)  Baker, D. A.; Gallego, N. C.; Baker, F. S. On the Characterization and Spinning of an Organic-Purified Lignin toward the Manufacture of Low-Cost Carbon Fiber. J. Appl. Polym. Sci. 2012, 124 (1), 227–234. (179)  Sadeghifar, H.; Sen, S.; Patil, S. V; Argyropoulos, D. S. Toward Carbon Fibers from Single Component Kraft Lignin Systems: Optimization of Chain Extension Chemistry. ACS Sustain. Chem. Eng. 2016, 4 (10), 5230–5237. (180)  Qin, W.; Kadla, J. F. Effect of Organoclay Reinforcement on Lignin-Based Carbon Fibers. Ind. Eng. Chem. Res. 2011, 50 (22), 12548–12555. (181)  Roman, M.; Winter, W. T. Effect of Sulfate Groups from Sulfuric Acid Hydrolysis on the Thermal Degradation Behavior of Bacterial Cellulose. Biomacromolecules 2004, 5 (5), 1671–1677. (182)  Zheng, L. X.; O’Connell, M. J.; Doorn, S. K.; Liao, X. Z.; Zhao, Y. H.; Akhadov, E. A.; Hoffbauer, M. A.; Roop, B. J.; Jia, Q. X.; Dye, R. C.; et al. Ultralong Single-Wall Carbon Nanotubes. Nat. Mater. 2004, 3 (10), 673–676. (183)  Zheng, L.; Sun, G.; Zhan, Z. Tuning Array Morphology for High-Strength Carbon-Nanotube Fibers. Small 2010, 6 (1), 132–137. (184)  Sen, S.; Patil, S.; Argyropoulos, D. S. Thermal Properties of Lignin in Copolymers, 163  Blends, and Composites: A Review. Green Chem. 2015, 17, 4862–4887. (185)  Cui, C.; Sadeghifar, H.; Sen, S.; Argyropoulos, D. S. Toward Thermoplastic Lignin Polymers; Part II: Thermal & Polymer Characteristics of Kraft Lignin & Derivatives. BioResources 2013, 8 (1), 864–886. (186)  Singh, S.; Mohanty, A. K.; Sugie, T.; Takai, Y.; Hamada, H. Renewable Resource Based Biocomposites from Natural Fiber and Polyhydroxybutyrate-Co-Valerate (PHBV) Bioplastic. Compos. Part A Appl. Sci. Manuf. 2008, 39 (5), 875–886. (187)  Wanasekara, N. D.; Santos, R. P. O.; Douch, C.; Frollini, E.; Eichhorn, S. J. Orientation of Cellulose Nanocrystals in Electrospun Polymer Fibres. J. Mater. Sci. 2016, 51 (1), 218–227. (188)  Pullawan, T.; Wilkinson, A. N.; Eichhorn, S. J. Influence of Magnetic Field Alignment of Cellulose Whiskers on the Mechanics of All-Cellulose Nanocomposites. Biomacromolecules 2012, 13 (8), 2528–2536. (189)  Charles Robert Hicks, K. V. T. Fundamental Concepts in the Design of Experiments, 5th ed.; Oxford University Press, 1999, 1999. (190)  van der Stelt, M. J. C.; Gerhauser, H.; Kiel, J. H. A.; Ptasinski, K. J. Biomass Upgrading by Torrefaction for the Production of Biofuels: A Review. Biomass and Bioenergy 2011, 35 (9), 3748–3762. (191)  Sun, Q.; Khunsupat, R.; Akato, K.; Tao, J.; Labbé, N.; Gallego, N. C.; Bozell, J. J.; Rials, T. G.; Tuskan, G. A.; Tschaplinski, T. J.; et al. A Study of Poplar Organosolv Lignin after Melt Rheology Treatment as Carbon Fiber Precursors. Green Chem. 2016, 18 (18), 5015–5024. (192)  Hu, Z.; Yeh, T. F.; Chang, H. M.; Matsumoto, Y.; Kadla, J. F. Elucidation of the Structure 164  of Cellulolytic Enzyme Lignin. Holzforschung 2006, 60 (4), 389–397. (193)  Holtman, K. M.; Chen, N.; Chappell, M. A.; Kadla, J. F.; Xu, L.; Mao, J. Chemical Structure and Heterogeneity Differences of Two Lignins from Loblolly Pine as Investigated by Advanced Solid-State NMR Spectroscopy. J. Agric. Food Chem. 2010, 58 (18), 9882–9892. (194)  Zhang, W.; Sathitsuksanoh, N.; Simmons, B.; Frazier, C.; Barone, J.; Renneckar, S. Revealing the Thermal Sensitivity of Lignin during Glycerol Thermal Processing through Structural Analysis. RSC Adv. 2016, 6, 30234–30246. (195)  Rahaman, M. S. A.; Ismail, A. F.; Mustafa, A. A Review of Heat Treatment on Polyacrylonitrile Fiber. Polym. Degrad. Stab. 2007, 92 (8), 1421–1432. (196)  Caņado, L. G.; Takai, K.; Enoki, T.; Endo, M.; Kim, Y. A.; Mizusaki, H.; Jorio, A.; Coelho, L. N.; Magalhães-Paniago, R.; Pimenta, M. A. General Equation for the Determination of the Crystallite Size La of Nanographite by Raman Spectroscopy. Appl. Phys. Lett. 2006, 88 (16), 1998–2001. (197)  Poursorkhabi, V.; Mohanty, A. K.; Misra, M. Statistical Analysis of the Effects of Carbonization Parameters on the Structure of Carbonized Electrospun Organosolv Lignin Fibers. J. Appl. Polym. Sci. 2016, 133 (45), 44005(1-17). (198)  Tuinstra, F.; Koenig, L. J. Raman Spectrum of Graphite. J. Chem. Phys. 1970, 53 (5), 1126–1130. (199)  Niu, H.; Zhang, J.; Xie, Z.; Wang, X.; Lin, T. Preparation, Structure and Supercapacitance of Bonded Carbon Nanofiber Electrode Materials. Carbon N. Y. 2011, 49 (7), 2380–2388. (200)  Teng, N.-Y.; Dallmeyer, I.; Kadla, J. F. Incorporation of Multiwalled Carbon Nanotubes into Electrospun Softwood Kraft Lignin-Based Fibers. J. Wood Chem. Technol. 2013, 33 165  (4), 299–316. (201)  Qi, H. J.; Teo, K. B. K.; Lau, K. K. S.; Boyce, M. C.; Milne, W. I.; Robertson, J.; Gleason, K. K. Determination of Mechanical Properties of Carbon Nanotubes and Vertically Aligned Carbon Nanotube Forests Using Nanoindentation. J. Mech. Phys. Solids J. Mech. Phys. Solids 2003, 51 (51), 2213–2237. (202)  Norberg, I.; Nordström, Y.; Drougge, R.; Gellerstedt, G.; Sjöholm, E. A New Method for Stabilizing Softwood Kraft Lignin Fibers for Carbon Fiber Production. J. Appl. Polym. Sci. 2013, 128 (6), 3824–3830. (203)  Wu, N.; Wang, Y.; Lei, Y.; Wang, B.; Han, C.; Gou, Y.; Shi, Q.; Fang, D. Electrospun Interconnected Fe-N/C Nanofiber Networks as Efficient Electrocatalysts for Oxygen Reduction Reaction in Acidic Media. Sci. Rep. 2015, 5 (1), 17396. (204)  Xu, X.; Wang, H.; Jiang, L.; Wang, X.; Payne, S. A.; Zhu, J. Y. Comparison between Cellulose Nanocrystal and Cellulose Nanofibril Reinforced Poly ( Ethylene Oxide ) Nanofibers and Their Novel Shish- Kebab-Like Crystalline Structures. Macromolecules 2014, 47, 3409–3416. (205)  Xiang, C.; Frey, M. W. Hydrolytic Degradation of Nanocomposite Fibers Electrospun from Poly(Lactic Acid)/Cellulose Nanocrystals. In Cellulose Based Composites; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2014; pp 117–136. (206)  Ten, E.; Bahr, D. F.; Li, B.; Jiang, L.; Wolcott, M. P. Effects of Cellulose Nanowhiskers on Mechanical, Dielectric, and Rheological Properties of Poly(3-Hydroxybutyrate- Co -3-hydroxyvalerate)/Cellulose Nanowhisker Composites. Ind. Eng. Chem. Res. 2012, 51 (7), 2941–2951. (207)  Pei, A.; Zhou, Q.; Berglund, L. A. Functionalized Cellulose Nanocrystals as Biobased 166  Nucleation Agents in Poly(l-Lactide) (PLLA) - Crystallization and Mechanical Property Effects. Compos. Sci. Technol. 2010, 70 (5), 815–821. (208)  Ten, E.; Turtle, J.; Bahr, D.; Jiang, L.; Wolcott, M. Thermal and Mechanical Properties of poly(3-Hydroxybutyrate-Co-3-Hydroxyvalerate)/cellulose Nanowhiskers Composites. Polymer (Guildf). 2010, 51 (12), 2652–2660. (209)  Matsumoto, H.; Imaizumi, S.; Konosu, Y.; Ashizawa, M.; Minagawa, M.; Tanioka, A.; Lu, W.; Tour, J. M. Electrospun Composite Nanofiber Yarns Containing Oriented Graphene Nanoribbons. ACS Appl. Mater. Interfaces 2013, 5 (13), 6225–6231. (210)  Prilutsky, S.; Zussman, E.; Cohen, Y. The Effect of Embedded Carbon Nanotubes on the Morphological Evolution during the Carbonization of Poly(acrylonitrile) Nanofibers. Nanotechnology 2008, 19 (16), 165603. (211)  Deng, L.; Young, R. J.; Kinloch, I. a.; Zhu, Y.; Eichhorn, S. J. Carbon Nanofibres Produced from Electrospun Cellulose Nanofibres. Carbon N. Y. 2013, 58 (0), 66–75.  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.24.1-0364563/manifest

Comment

Related Items