Preparation of (Ti,Zr,Hf,Nb,Ta)C high-entropy carbide ceramics through carbosilicothermic reduction of oxides

Fully dense high-entropy carbide (HEC) ceramic has been prepared from a mixture of the group IV and V transition metal oxides by a two-step technique, which involved the vacuum carbosilicothermic reduction (VCSTR) synthesis of a composite powder containing 75 vol.% HEC, 20 vol.% (Nb 1-x Me x )Si 2 (where Me = Ti, Zr, Hf, Ta), and 5 vol.% SiC followed by hot pressing of the as-synthesized product. It was found that the reaction between (Nb 1-x Me x )Si 2 and HEC took place during hot pressing, thereby allowing effective sintering to occur. The mechanical properties of the obtained nearly single-phase HEC ceramic were comparable to or even slightly better than those of HEC ceramics prepared by other methods. The use of VCSTR synthesis as a key step in the preparation of fully dense HEC ceramic was concluded to be effective both in lowering the sintering temperature and in improving the mechanical properties.