Oxidation Resistance and Microstructural Analysis of Polymer‐Derived (HfₓTa₁₋ₓ)C/SiC Ceramic Nanocomposites

The oxidation behavior of polymer‐derived (HfₓTa₁₋ₓ)C/SiC nanocomposites at 1200 °C and 1400 °C for up to 100 h is investigated in this work. Overall, the chemical modification of the polycarbosilane‐based precursor with Hf and Ta leads to an improved oxidation behavior due to an increased densification. Shifting the Hf/Ta ratio from (Hf₀.₂Ta₀.₈)C/SiC to (Hf₀.₇Ta₀.₃)C/SiC results in an improved oxidation behavior due to Hf₆Ta₂O₁₇ formation and the reduction of Ta₂O₅ formation, which reduces cracking of the samples. The formation and microstructure of SiO₂ as well as the internal oxidation of (HfₓTa₁₋ₓ)C precipitates is explained by thermodynamic and kinetic considerations.