Microstructure and mechanical behavior of TaxHf1-xC-SiC fabricated by reactive hot-pressing: Effect of Ta:Hf ratio

TaxHf1-xC are promising candidates for many applications under harsh environments due to their unique properties. Up until now, low-temperature densification is still a big challenge for these ceramics. Moreover, the effect of Ta:Hf ratio on microstructure development and mechanical behavior of the ceramics is not clear. In this work, highly dense TaxHf1-xC-SiC ceramics (x = 0.2, 0.4, 0.6, 0.8) were fabricated at 1700 degrees C by a novel reactive hot-pressing processing with 8 wt% Si as sintering aid, which present excellent mechanical properties. Fracture toughness of the ceramics is higher than 6.3 MPa<middle dot>m(1/2), with the highest toughness achieved in Ta0.6Hf0.4C-SiC (8.5 MPa<middle dot>m(1/2)). With the increase of Ta content, hardness of the ceramics tends to increase, while the bending strength tends to decrease. The highest bending strength is achieved in Ta0.2Hf0.8C-SiC (637 MPa), and the highest hardness is achieved in Ta0.8Hf0.2C-SiC (17.6 GPa). This work lays the foundation for the composition design of TaxHf1-xC-based ceramics and composites.