Improving the oxidation resistance under thermal shock condition of SiC-coated C/C composites with refined SiC grain size using ferrocene

To improve the oxidation resistance under thermal shock condition of SiC-coated carbon/carbon (C/C) composites, ferrocene ((C₅H₅)₂Fe) was introduced in the SiC coatings during the pack cementation process. The microstructure and oxidation resistance under thermal shock condition of modified SiC coated C/C composites were studied. The HNO₃ treatment and the introduction of (C₅H₅)₂Fe could raise the nucleation point and the decomposition of (C₅H₅)₂Fe can slow down the sintering process, which helps to decreased the sizes of SiC particles and micro-defects (including micro-cracks and micro-holes) and resulted in a relatively dense structure. Thermal shock test revealed that the mass change rate of C/C composites decreased from 18.25% to 10.08% after thermal cycle test between 1773 K and room temperature for 25 times, suggesting a better shock resistance for the modified SiC coating compared with the base coatings (without modification). This work provides a novel way to modify the SiC coating capable of releasing the thermal residual stress and decreasing the oxygen diffusion channels and then further increasing the oxidation resistance under thermal shock condition of C/C composites without other supplementary protective coatings.