Influence of graphitization on oxidation resistance of carbon/carbon composites prepared by high pressure impregnation and carbonization

Felt-based carbon/carbon (C/C) composites were prepared by a super high pressure impregnation and carbonization process (SPIC) and graphitization at high temperatures. The oxidation kinetics of the C/C composites was investigated at different temperatures (773-1173 K). The oxidation morphology and microstructure of the C/C composites before and after graphitization were investigated by means of SEM and X-ray diffraction (XRD) technology. The experimental results show that the oxidation resistance of the C/C composites can be dramatically improved by graphitization, oxidation reactions always begin from the carbon matrix and the oxidation rate increases with the increase of oxidation temperatures. When the oxidation temperature is below or above 973 K, the corresponding apparent active energies are 7.91 × 10⁴ J/mol and 2.80 × 10⁴ J/mol before graphitization and the corresponding apparent active energies are 1.08 × 10⁵ J/mol and 4.42 × 10⁴ J/mol after graphitization, which indicates that two different oxidation mechanisms occur below and above 973 K.