中间相沥青碳纤维的氧化行为OA

Mesophase pitch-based carbon fibers(MPCF)possess excellent properties,such as high modulus and high thermal conductivity,making them key strategic materials for national defense security and advanced equipment development.However,their oxidation behavior in high-temperature aerobic environments remains poorly understood.This study investigates the oxidation behaviors and the evolution of mechanical and thermal properties of two types of MPCF,namely split-structured(CF-A)and round-structured(CF-B),in both carbonized(1600℃)and graphitized(3000℃)states.The results show that CF-A-1600 exhibits preferential core oxidation during the 600℃oxidation process,leading to a tensile strength retention of only 34.93%,which is lower than that of CF-B-1600(51.79%).Conversely,the CF-A-3000 achieves tensile strength retention of 79.64%and thermal conductivity retention of 94.36%,respectively,higher than those of CF-B-3000(77.46%and 90.93%).For carbonized MPCF,the oxidation behavior is dominated by diffusion-controlled reactions,where structural morphology plays a decisive role,and CF-B fibers exhibit superior oxidation resistance.For graphitized MPCF,oxidation behavior is governed by chemical-controlled reactions,in which intrinsic crystallite activity becomes dominant.For comparison,CF-A fibers show superior performance due to their better-developed crystallites and consequently higher oxidation activation energy.This study reveals the coupled mechanism between structural morphology and intrinsic crystallite activity of MPCF,providing a theoretical reference for reliability assessment and material optimization design of MPCF and their composites in extreme thermal service conditions.