Long-time ablation protection of carbon/carbon composites with different-La2O3-content modified ZrC coating

Long time oxidation protection at ultra-high temperatures or ablation protection has been a choke point for C/C composites. In this study, long time ablation protection of different-La2O3-content (5-30 vol.%) modified ZrC coating for SiC-coated carbon/carbon (C/C) composites was investigated. Results showed that ZrC coating with 15 vol.% La2O3 had good ablation resistance and could protect C/C composites for at least 700 s at 2160 degrees C. A high-thermal-stability and low-oxygen-diffusivity oxide scale containing m-ZrO2 particles and molten phases with La0.1Zr0.9O1.95 and La2Zr2O7 was formed during ablation, offering the ablation protection. La could erode grain boundaries of ZrO2 to refine ZrO2 by short-circuit diffusion and m-ZrO2 particles were retained due to less bulk diffusion than grain-boundary diffusion of La into ZrO2. The erosion resulted in the formation of molten phases containing fine nano-ZrO2, which served as viscous binder among m-ZrO2 particles and crack sealer for the oxide scale.