MSE Ph.D. Proposal – H. Clive Liu
Prof. Satish Kumar, Advisor, MSE
Prof. Fred Cook, MSE
Prof. Donggang Yao, MSE
Prof. Meisha Shofner, MSE
Prof. Yulin Deng, CHBE/RBI
Title: PROCESSING, STRUCTURE, AND PROPERTIES OF LIGNIN, AND CARBON NANOTUBES CONTAINING GEL SPUN POLYACRYLONITRILE BASED CARBON FIBERS
Carbon fibers (CF) are considered as ideal reinforcing materials due to high mechanical properties, good thermal and electrical conductivities, and low density. Throughout the development and increasing market demand of carbon fibers, polyacrylonitrile (PAN) based fibers are the most predominant precursors of high performance carbon fibers. Significant component of the PAN-based carbon fiber cost is attributed to the cost of the PAN precursor fiber. Manufacturing infrastructure, and energy used in the conversion process are the other cost drivers. Increasing interest and demand for low-cost carbon fibers have called for investigations for alternative processing methods and precursor materials for carbon fibers, especially in the last decade.
As the byproduct of the pulp and paper industry, and also as the second most abundant bio-macromolecule on earth, lignin has been proposed as a cost-effective alternative for carbon fiber precursor as a renewable feedstock. However, mechanical properties of the lignin based carbon fibers are relatively low compared to the PAN based carbon fibers. Carbon nanotubes (CNT) have been widely proposed as ideal fillers for polymers due to the excellent mechanical properties and thermal/electrical conductivities. Literature shows that CNTs enhance PAN ordering in fiber structure to improve precursor fiber mechanical properties, and enhance resulting PAN/CNT carbon fiber thermal and electrical conductivities due to the development of the graphitic structure template on CNTs.
To fully integrate the advantages of good mechanical performance of PAN-based carbon fibers, low cost of lignin-based carbon fibers, and the favorable properties of CNTs, this study focuses on the processing, structures, and properties of gel-spun PAN/lignin and PAN/lignin/CNT composite carbon fibers. Lignin/polymer and lignin/polymer/CNT interactions in solutions will be investigated by rheological studies. Effects of lignin and CNT on PAN precursor fiber structure are identified to allow further stress-transfer studies of CNT in composite systems. Lignin is shown to alter PAN reaction kinetics with decreased activation energies and enhanced reaction rate constants during carbon fiber conversion process. Raman spectra of carbonized fibers suggest that CNT promotes refining of turbostratic carbon structure and polyaromatic carbon stack of lignin. With research areas pertaining to lignin-polymer and lignin/polymer/CNT interactions for processing optimization, and reaction kinetics toward composite carbon fiber conversion process, this study seeks to elucidate the industrial potential of incorporating renewable biorefinery feedstock to value-added nano-composites.