Radial stacking arrangement of polycyclic aromatic hydrocarbon molecules influences the oxidation of mesophase pitch-based precursor fibers

Stabilization process during fabrication of mesophase pitch-based carbon fiber has a significant impact on its ultimate performance. Notably, the radial arrangement of polycyclic aromatic hydrocarbon (PAH) molecules influences the stabilization of mesophase pitch-based precursor fibers. Thus, it is crucial to understand the relationship between the microcrystalline arrangement and oxidation process to enhance the properties of carbon fibers. In this study, four types of mesophase pitch-based precursor fibers with distinct section structures and PAH arrangements were prepared, and their oxygen diffusion routes were investigated at two oxidation temperatures. The oxygen distributions in D-type and R-type oxidized fibers are mostly uniform, resulting in optimal oxidation levels. In contrast, Y-type oxidized fibers have anisotropic oxygen distribution across different cross-sectional directions, and C-type oxidized fibers exhibit a pronounced skin-core structure. Analyzing the stabilization process as a function of the microcrystalline arrangement of various precursor fibers indicates that oxygen preferentially diffuses along the microcrystalline orientation direction of the PAHs. In general, fiber diameter and PAH arrangement along the radial direction have significant effects on the oxidation process. Therefore, selectively optimizing the oxidation process according to cross-sectional structural characteristics may enhance homogeneous oxidation, maximize oxidation efficiency, and ensure consistent performance stability of carbon fibers.