Long-term ablation resistance above 2500 °C in (Hf_0.75Ta_0.25)C-(Hf_0.75Ta_0.25)B₂-SiC composite ceramics

To improve the ablation resistance of materials across a wide temperature range, (Hf_0.75Ta_0.25)C-(Hf_0.75Ta_0.25)B₂-SiC composite ceramics were prepared by introducing SiB₆ into the 3HfC-1TaC system. The borides formed by in situ reaction can promote the formation of dense oxide layer and release thermal stress, significantly improving the ablation resistance. Hf₆Ta₂O₁₇ with high melting point and low thermal conductivity plays a critical role in blocking the transfer of heat while repairing the oxidation defects. Therefore, excellent ablation resistance under ablation above 2500 °C for ∼1800 s is achieved, featuring linear ablation rate ( R _l ) and mass ablation rate ( R _m ) of −0.1 μm/s and −0.14 g/m²·s, respectively. This work provides an effective strategy to design advanced ultra-high temperature ceramics compositions with excellent long-term ablation resistance.