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Structure and properties of lignin-based composite carbon nanofibres

University of British Columbia

This research investigates the feasibility of developing value-added products from lignin in nanofibre form for structural and functional applications. Specifically, softwood Kraft lignin (SKL) was used as the precursor to fabricate nanofibres via the electrospinning process and then converted into carbon nanofibres (CNF). The mechanical properties of SKL nanofibres were characterized for structural applications at the nanofibre mat level and the single nanofibre level. The electrochemical performance of SKL CNFs was characterized for functional applications at the nanofibre mat level. This research harnessed different processing methods through hierarchical improvements of the mechanical properties of SKL CNF. The mechanical properties of SKL nanofibre mats were improved by the reduction of nanofibre diameter through the optimization of electrospinning process. The mechanical properties of SKL nanofibres gained an order of magnitude improvement through heat treatment processes of thermo-stabilization and carbonization. Aligned nanofibre mats were successfully fabricated via the rotating drum method resulting in further enhancement of the mechanical properties of SKL CNF. Single-walled carbon nanotube (SWNT)-SKL core-shell composite nanofibres were successfully fabricated via the emulsion electrospinning process. The mechanical properties of the SWNT/SKL composite nanofibres were found to increase as the percent of SWNT increases. This research also investigated the mechanical properties translation between SKL single nanofibres and their fibre assemblies. The mechanical properties of the SKL single nanofibres were characterized and then analyzed by the statistical Weibull distribution. The experimental results were in good agreement with the analytical values. A prototype supercapacitor (SC) cell using SKL-based CNF as binder-free electrodes was constructed to demonstrate the feasibility of the SKL CNF for functional applications. The electrochemical performance of the SC cell was characterized and the energy density and power density of the SC cell were found to meet the requirement for commercial products. In summary, this research sheds light on our understanding of the mechanism of the mechanical properties improvement of SKL CNF, which helps guide the tailoring of the mechanical performance of SKL CNF. Moreover, the electrochemical performance of SKL-based CNFs demonstrated that they are promising candidates as electrode materials for SC and a wide range of energy storage devices.

Text

2017-10-23

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/63417

Materials Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/