Formation of microstructure of mesophase pitch-based carbon fibers and its effect on mechanical properties

摘要

The influence of spinning and thermal treatment conditions on formation of the crystallitic structure and mechanical properties of mesophase pitch-based carbon fibers(MPCFs) was studied. The pitch was melt-spun at suitable temperature under various pressure and elongation rates. Then the as-spun pitch fibers were stabilized and carbonized. XRD was used to measure the preferred orientation, single yarn tensile tester was used to measure the tensile strength and modulus, and SEM was applied to observe the cross section of the carbon fiber. As the crystallitic orientation increasing from 77.3% to 83.1%, the tensile strength of MPCFs increased from 1.001GPa to 1.842GPa and modulus increased from 94GPa to 246GPa respectively. The results showed that the tensile strength and modulus of MPCFs increased with crystallite preferred orientation increasing. Moreover, the skin-core structure was easy to form for the fiber with larger diameter, which was also a crucial factor to influence the mechanical properties of carbon fibers.