Single-source-precursor synthesis of dense monolithic SiC/ (Ti0.25Zr0.25Hf0.25Ta0.25)C ceramic nanocomposite with excellent high-temperature oxidation resistance

A dense monolithic SiC/(Ti0.25Zr0.25Hf0.25Ta0.25)C ceramic nanocomposite containing high-entropy carbide phase was prepared using a single-source-precursor method combined with spark plasma sintering. The nanocomposites were characterized by a unique microstructure with a homogeneous dispersion of (Ti0.25Zr0.25Hf0.25Ta0.25)C@C core-shell nanoparticles within a beta-SiC matrix. The atomic ratios of transition metal elements within the in situ generated (Ti0.25Zr0.25Hf0.25Ta0.25)C nanoparticles can be controlled precisely by molecular design of the preceramic precursors. Oxidation behavior of the SiC/(Ti0.25Zr0.25Hf0.25Ta0.25)C nanocomposite was investigated as well. The SiC/(Ti0.25Zr0.25Hf0.25Ta0.25)C exhibit excellent oxidation resistance between 1200 degrees C and 1500 degrees C due to the in situ generated continuous multiphase scales consisting of beta-SiO2, HfTiO4, ZrSiO4, HfSiO4, and Ta2O5 that can be rapidly sintered during oxidation. Particularly, at 1200 degrees C, the parabolic oxidation rate constant (Kp) value is 1-2 orders of magnitude lower than that of similar SiC/HfC, SiC/ (Hf, Ta)C, SiC/(Hf, Ti)C and SiC/(Hf, Zr, Ti)C nanocomposites.