Comparison of oxidation resistance of high-entropy (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC composites prepared by different methods at 1300-1600 ° C

Dense monolithic (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC (HEC/SiC) composites were prepared via single-sourceprecursor (SSP) and solid-state reaction (SSR) method, respectively. The SSP-method nanocomposite features HEC nanoparticles uniformly dispersed within beta-SiC, while the SSR-method composite is a microcomposite containing micro-sized HEC and beta-SiC particles. The oxidation tests at 1300-1600 degrees C show that the HEC/SiC nanocomposites exhibit much better oxidation resistance than that of the HEC/SiC microcomposites. Firstly, the generated metal-containing complex oxides ((Zr,Hf)6Ta2O17, Ti(Ta,Nb)2O7, and Ta-doped rutile TiO2) become more facile for sintering due to the nano-scaled HEC phase. Secondly, the cracks resulting from the oxidation of HEC nanoparticles are fewer and smaller, decreasing the number of channels for oxygen to pass through and channels need to be healed by SiO2. Finally, the homogeneous distribution of the HEC nanoparticles within beta-SiC ensures the homogeneity of the complex oxide layer, significantly reducing the cracks caused by volume expansion and preventing the oxide layer from peeling off.