Improved ablation resistance of C/SiC-ZrB₂ composites via polymer precursor impregnation and pyrolysis

Carbon fiber-reinforced silicon carbide (C/SiC) composites modified with ZrB₂-SiC ceramics of different compositions were prepared via polymer impregnation and pyrolysis. The ablation behaviors of the composites were systematically studied using an oxy-acetylene torch. The oxidation/ablation mechanisms related to the evolution of the surface morphologies are also discussed on the basis of thermodynamics. The results indicate that the decomposition of the SiC matrix was mainly responsible for the failure of the C/SiC materials. For C/SiC-ZrB₂, the gaseous reactants and products flowed through the micropores of the ZrO₂ skeleton obeying the Knudsen diffusion law. This retarded the elimination process of SiC, resulting in the formation of a ZrO₂-SiO₂ protective layer, and finally the C/SiC-ZrB₂ materials showed good ablation resistance.