Analyses of oxidation process for isotropic pitch-based carbon fibers using model compounds

Isotropic pitch-based carbon fiber has been utilized for various applications such as thermal insulation materials for high-temperature furnace and additives for slide member, but the structure of the carbon fiber is still under debate. This is because the precursor pitch contains various aromatic compounds in addition to the complicated oxidation and carbonization reaction during production process of carbon fiber. In this work, oxidation processes of model compounds of pitch such as pyrene (sp2CH with zigzag-like edges), triphenylene (sp2CH with armchair edges), fluorene (pentagon with sp3CH2), and 9-methylanthracene (hexagon with sp3CH3) were analyzed using mass spectrometry, elemental analysis, infrared (IR), Raman, and X-ray photoelectron spectroscopy (XPS) in addition to calculation such as molecular dynamic simulation with a reactive force field (ReaxFF) and simulation of IR, Raman, and XPS spectra (Gaussian09). Combination of calculations and experiments revealed that oxidation proceeded in the order of zigzag-like edges > sp3CH3 > sp2CH2 > armchair edges, and the quinone formed by oxidation worked as a precursor for a crosslinking reaction. It is expected that the results of this work, which revealed the origin of the crosslinking, could lead to improve properties as well as to estimate the detailed structures of isotropic pitch-based carbon fiber. [Display omitted]