Synthesis, densification, and microstructure of TaC‐TaB ₂ ‐SiC ceramics

Abstract

Abstract The usual way to prepare TaC‐TaB 2 ceramics by adding B 4 C to TaC leads to formation of residual C, which degrades samples’ mechanical properties. To eliminate the residual C, we suggest incorporating Si together with B 4 C into TaC ceramics, resulting in new ultrahigh‐temperature ceramics (TaC‐TaB 2 ‐SiC). Dense ceramics (>99%) with SiC volume fraction ranging from 15.86% to 41.04% were fabricated by reactive spark plasma sintering at 1900°C for 5 minutes. The formation of SiO 2 ‐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 in situ formed SiC, which impeded TaC and TaB 2 grains from coarsening by the pinning effect. Besides, ultrafine TaB 2 grains (~100 nm) produced during the reaction and then rearranged in liquid also contributed to grain refinement. Compared to TaC‐TaB 2 (‐C) ceramics prepared from TaC and B 4 C, the acquired composites exhibit better mechanical properties, due to their fine‐grained microstructures and the elimination of residual C.