Single‐Source Polymer‐Derived SiC/HfC Composites: Cross‐Linking Mechanism, Microstructure, and Oxy‐Propane Ablation Resistance

A single‐source SiC/HfC‐containing precursor was synthesized using polysiloxane as a precursor and hafnium acetylacetonate (Hf(acac) 4 ) as a metallic modifier. Dense SiC/HfC composites were prepared via precursor pyrolysis combined with spark plasma sintering. The cross‐linking mechanism, microstructural phase evolution, and ablation resistance were systematically studied, and the role of Hf modification in enhancing oxy‐propane ablation resistance was revealed. Results show that the densification of the ceramics is significantly improved with Hf(acac) 4 content. After oxy‐propane ablation at 1600 °C for 120 s, the SiC/HfC composites modified with 20 wt% Hf(acac) 4 exhibit superior linear (0.008 µm/s) and mass ablation rates (−0.478 mg/s). Under high‐temperature ablation, HfC was oxidized into HfO 2 , which subsequently reacted with SiO 2 to form a dense HfSiO 4 layer. This oxide scale inhibits SiO 2 volatilization and oxygen diffusion, providing effective protection for the SiC matrix. This study provides a feasible route for fabricating high‐performance SiC‐based ultrahigh‐temperature ceramics for thermal protection systems.