High-entropy (Ta0.2Nb0.2Ti0.2Hf0.2Zr0.2)C-SiC Ceramics: Achieving Superior Ablation Resistance through SiC Particle Size Optimization

To enhance ablation resistance in (Ta₀.₂Nb₀.₂Ti₀.₂Hf₀.₂Zr₀.₂)C–SiC (HEC–SiC) ceramics, the influence of SiC particle size on microstructure and ablation behavior was examined. With the addition of 20   wt% fine SiC particles, its relative density increases from 91.23% to 97.79%, and the grain size of the HEC phase decreased from 3.58 to 0.79 μm. The fine SiC particles facilitated the formation of a continuous SiC network, thereby enhancing the thermal conductivity from 6.94 to 22.35   W/mK. This enhanced thermal conductivity contributed to reducing the ablation temperature from 2358 to 1721 °C during the ablation. The HEC-SiC sample with 0.5 μm fine SiC particles added exhibits a mass and linear ablation rate of 0.05   mg/s and 0.67   µm/s. The superior ablation resistance can be attributed to the reduced ablation temperature, altering the preferential oxidation sequence. This change in preferential oxidation led to the formation of a compact oxide scale with a multi-layer structure.