Ablation-resistant Ta_0.78Hf_0.22C solid solution ceramic modified C/C composites for oxidizing environments over 2200 °C

Ta_0.78Hf_0.22C solid solution ceramic was synthesized and introduced into carbon/carbon (C/C) composites by polymer infiltration and pyrolysis (PIP). Effect of the introduction of Ta_0.78Hf_0.22C on the microstructure, ablation resistance, and flexural performance of C/C composites were investigated. Results showed that the flexural strength and modulus of the composites were increased by 108 % and 117 %, respectively, after adding Ta_0.78Hf_0.22C solid solution into C/C composites. In addition, the introduction of Ta_0.78Hf_0.22C improved the ablation resistance of C/C composites under oxyacetylene ablation environment, over 2200 °C. The linear and mass ablation rates were decreased 73 % and 70 %, respectively. The oxide with low melting point, Ta₂O₅, exhibited good sealing and oxygen-barrier capacity, and the formation of new solid solution oxide particles, Hf₆Ta₂O₁₇, could pin cracks during ablation, both of them were contributed to better ablation resistance of modified C/C composites.