Preparation of SiC/TiC composite ceramics by precursor conversion method and their oxy-propane ablation behavior at 1600 ℃

To address the issues of volatile oxide scale and insufficient oxidation/ablation resistance of monolithic SiC ceramics in extreme environments, this study employs polysiloxane as a ceramic precursor and titanium acetylacetonate (TiO(acac)₂) as a modifier. SiC/TiC composite ceramics are prepared via a precursor conversion method combined with spark plasma sintering. The cross-linking and curing mechanism of the precursor, as well as the high-temperature pyrolysis behavior, are systematically investigated, and the influence mechanism of Ti doping on the oxidation/ablation resistance of the composite ceramics is elucidated. The results show that Ti promotes precursor cross-linking through the formation of Si―O―Ti bonds, achieving a ceramic yield as high as 79.18%. When the TiO(acac)₂ mass content reaches 20%, the TiC mass content in the composite increases to 19%, and the densification of the sintered ceramic is significantly improved. Oxy-propane ablation tests at 1600 ℃ demonstrate that the 20% modified sample exhibits greatly enhanced ablation resistance, with linear and mass ablation rates of 0.017 μm/s and −0.140 mg/s, respectively. This superior ablation resistance is attributed to the formation of a continuous composite oxide layer consisting of TiO₂ and SiO₂, which suppresses the volatilization of SiO₂ and further oxygen diffusion.