Abstract: Graphitic materials possess unique properties due to the unique combination of layered crystalline structure and carbon’s low atomic weight. High performance carbon fiber is one such example, displaying exceptional strength-to-weight ratios, stiffness and thermal and chemical resistance. These properties render high performance carbon fiber a critical structural reinforcement material in the manufacture of composites across industries, including automotive and aerospace applications. Balancing fiber performance with precursor and processing costs, however, remains a challenge. As alternative carbonaceous feedstocks are explored, coal has gained interest for use in graphitic products as a relatively abundant and low-cost source of aromatic carbon.
This work broadly covers the process of using coal for high performance carbon fiber. First, coal extracts are obtained through direct coal liquefaction in petroleum-derived fluid catalytic cracking decant oil. The efficacy of the process and the suitability of the coal extract as a precursor to graphitic products is assessed through comprehensive solubility testing, chemical and thermal characterization and polarized optical microscopy. The thermal conversion of coal extracts to mesophase pitch is then examined, and process development, optimization and methods for real-time reaction progress monitoring are described. Additionally, a general framework for understanding the isotropic-mesophase phase transition from a colloidal perspective is proposed.
The production of high performance carbon fiber from a coal extract-derived mesophase pitch is then successfully demonstrated, and mesophase pitch properties impacting melt-spinning stability are discussed. Finally, coal contribution to carbon fiber was quantitatively determined via stable carbon isotope analysis. The investigations detailed in this work provide in-depth understanding of co-processing coal and decant oil system via direct coal liquefaction, the impact of processing steps on chemical and material properties, mesophase pitch processability and carbon fiber performance.
