Low‐temperature reactive hot‐pressing of Ta 0.2 Hf 0.8 C–SiC ceramics at 1700°C

Temperature above 2000°C and additional pressure is generally required to achieve the full densification of Ta x Hf 1− x C‐based ceramics. This work proposed a novel method to fabricate dense Ta 0.2 Hf 0.8 C ceramics at relatively low temperature. Using a small amount of Si as a sintering aid, Ta 0.2 Hf 0.8 C was densified at 1700°C by reactive hot‐pressing (RHP), with SiC formed in situ. Microstructure evolution mechanisms of the ceramics during RHP were investigated. The effect of silicon content on the densification and mechanical properties of the ceramics was revealed. It is indicated that the apparent porosity of the Ta 0.2 Hf 0.8 C–SiC ceramics was as low as 0.5%, whereas bending strength and fracture toughness of the ceramics were as high as ∼637 MPa and 6.7 MPa m 1/2 , respectively, when the silicon content was 8 wt.%. This work provides a new idea for the low‐temperature densification of Ta x Hf 1− x C and other ultrahigh temperature ceramics with high performance.