Synthesis, densification, and microstructure of TaC‐TaB2‐SiC ceramics

The usual way to prepare TaC-TaB2 ceramics by adding B4C to TaC leads to formation of residual C, which degrades samples' mechanical properties. To eliminate the residual C, we suggest incorporating Si together with B4C into TaC ceramics, resulting in new ultrahigh-temperature ceramics (TaC-TaB2-SiC). Dense ceramics (>99%) with SiC volume fraction ranging from 15.86% to 41.04% were fabricated by reactive spark plasma sintering at 1900 degrees C for 5minutes. The formation of SiO2-based transient liquid phase was evidenced by the film in intermediate products, which can promote densification. The fine-grained microstructure in final products was found to be associated with the insitu formed SiC, which impeded TaC and TaB2 grains from coarsening by the pinning effect. Besides, ultrafine TaB2 grains (similar to 100nm) produced during the reaction and then rearranged in liquid also contributed to grain refinement. Compared to TaC-TaB2(-C) ceramics prepared from TaC and B4C, the acquired composites exhibit better mechanical properties, due to their fine-grained microstructures and the elimination of residual C.