UBC Theses and Dissertations
Structures, properties and applications of multifunctional lignin nanofibres Li, Yingjie
This study explored the feasibility of creating multifunctional lignin materials in nanofibre form to establish a material platform for the development of value-added products. Specifically, softwood kraft lignin was electrospun, thermostabilized and carbonized into carbon nanofibres. Subsequently, functionalization of lignin based carbon nanofibres were conducted by (1) designing lignin-based composite carbon nanofibre; (2) preparing architecturally-designed lignin-based nanofibres and (3) preparing architecturally-designed lignin-based composite nanofibres. Examples of the advanced applications of the functionalized lignin based nanofibres were demonstrated such as electromagnetic interference shielding, energy storage and actuator. Flexible composite carbon nanofibres were embedded with functional fillers e.g. flexible electromagnetic lignin carbon nanofibres embedded with magnetic nanoparticles was developed. The amorphous structure of lignin and the addition of functional fillers impart the mechanical flexibility to lignin carbon nanofibre mats. By combining the magnetic permeability of magnetic nanoparticles and the electrical conductivity of lignin carbon nanofibre, flexible multifunctional lignin composite carbon nanofibres were created. Electromagnetic shielding effectiveness (SE) of lignin-based carbon nanofibres was comparable to that of the petroleum-based (such as polyacrylonitrile (PAN)-based) nanofibres. The feasibility of using above flexible composite carbon nanofibres from lignin as the lithium ion battery anode was demonstrated. This anode is free-standing, binder-free and mechanically flexible mats. Using lignin nanofibres electrodes and solid electrolytes, flexible solid-state lithium ion batteries were successfully assembled and characterized. Moreover, functions were added to electrospun lignin nanofibres by developing architecturally-designed lignin based thermostabilized nanofibres. A unique actuating phenomenon in thermostabilized lignin nanofibres was observed. It exhibits fast, reversible and dramatic mechanical deformation and recovery in response to environmental moisture gradient at milliseconds level. The actuation mechanism was investigated at the molecular level, and fibre assembly level. In summary, this study demonstrated that renewable biomaterials such as lignin has the potential for adding value through multifunctionalization in nanofibres form, thus creating a promising material platform for petroleum free feedstock for advanced applications.
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