Solid‐Solution Effects on the High‐Temperature Oxidation Behavior of Polymer‐Derived (Hf,Ta)C/SiC and (Hf,Ti)C/SiC Ceramic Nanocomposites

In the present study, two concepts to improve the oxidation resistance at high‐temperatures of ceramic nanocomposites consisting of 85–90 vol% SiC, 5–8 vol% group IV metal carbides (i.e., HfC, TaC), and 5–7 vol% carbon are introduced and discussed. First improvement concept relates to the passivation of the samples upon short‐term oxidation at 1400 °C (30 min). This is a critical step, especially with respect to silica formation, which is relatively sluggish at temperatures lower than 1000–1200 °C. Moreover, solid‐solution metal carbides (Hf,Ta)C and (Hf,Ti)C are shown to be clearly more oxidation resistant than the binary HfC and TaC phases. Whereas, the solid‐solution effect contributes to a significant improvement of the short‐term oxidation resistance of the studied nanocomposites, the passivation of the materials prior exposure of high‐temperature oxidation conditions provides a remarkably improved long‐term behavior thereof. Possible mechanisms involved in the oxidation processes of (Hf,Ta)C/SiC and (Hf,Ti)/SiC ceramic nanocomposites are highlighted and critically assessed.