Low-temperature reactive hot-pressing of Ta0.2Hf0.8C-SiC ceramics at 1700°C

Temperature above 2000 degrees C and additional pressure is generally required to achieve the full densification of TaxHf1-xC-based ceramics. This work proposed a novel method to fabricate dense Ta0.2Hf0.8C ceramics at relatively low temperature. Using a small amount of Si as a sintering aid, Ta0.2Hf0.8C was densified at 1700 degrees 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 Ta0.2Hf0.8C-SiC ceramics was as low as 0.5%, whereas bending strength and fracture toughness of the ceramics were as high as similar to 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 TaxHf1-xC and other ultrahigh temperature ceramics with high performance.

Automated summary

This study proposes a novel method to fabricate dense Ta0.2Hf0.8C ceramics at low temperature using Si as a sintering aid. Reactive hot-pressing was used to densify Ta0.2Hf0.8C at 1700 degrees C, resulting in the formation of SiC. The microstructure evolution mechanisms and the effect of silicon content on the densification and mechanical properties of the ceramics were investigated. The results show that the Ta0.2Hf0.8C-SiC ceramics have a low apparent porosity of 0.5% and high bending strength and fracture toughness of 637 MPa and 6.7 MPa m(1/2), respectively, when the silicon content is 8 wt.%. This work provides new insights for the low-temperature densification of TaxHf1-xC and other high-performance ultrahigh temperature ceramics.