Ablation behavior of UHTCs carbide-modified C/C composites in extreme aerobic environments (3000℃): Evolution mechanisms of oxides film structure

To mitigate ablation loss in carbon/carbon (C/C) composites under extreme thermal conditions (>3000℃), a novel analytical framework of “extreme environment - microstructure evolution - ablation resistance” was developed via two-way coupled simulation and multi-scale characterization. C/C-MeC-SiC (Me: Hf, Zr, Ti, Ta, Nb, W) composites were prepared by reactive melt infiltration, and the oxide film evolution of the composites under oxyacetylene ablation (4.2 MW/m²) was investigated. HfC and ZrC exhibit excellent ablation resistance by virtue of high melting points and stable oxide films (HfO₂/ZrO₂), but are porous due to phase transition cracks. TiC/NbC has a highly dense ceramic layer but suffers from severe ablation due to low melting point oxide loss. WC has a loose and porous oxide film due to the volatility of the oxidation products. TaSi₂ is difficult to penetrate into the matrix and causes serious ablation loss. The optimized design of C/C-HfC-ZrC-TaC-SiC composites, the mass/linear variation rate were 0.175 mg/s and 0.701 μm/s after long-time ablation (1000 s, 40 s × 25 cycle), provides theoretical foundations and experimental support for the design of UHTCs modified C/C composites in extreme high-temperature environment.