Microstructure, thermophysical properties, and ablation resistance of C/HfC-ZrC-SiC composites

Carbon/carbon composites modified by HfC-ZrC-SiC were fabricated by reactive melt infiltration with the aim of improving their ablation resistance for application in aerothermal environments. Their microstructure, thermophysical and ablation properties were investigated. Results show that the thermal diffusivity decreases with increasing temperature for all composites. The thermal conductivity of the C/HfC-ZrC-SiC composites decreasing with increasing HfC molar fraction is related to decreased grain size and increased porosity, which impede phonon interaction and increase the phonon scattering. High HfC content effectively improves the oxidation and ablation resistance of the composites. C/HfC-ZrC-SiC composites containing 8.8 mol.% HfC exhibited the best ablation resistance owing to a compact and continuous HfO2-ZrO2 mixed layer that formed on the ablated surface.