In situ synthesis mechanism and characterization of ZrB₂-ZrC-SiC ultra high-temperature ceramics

The synthesis route, microstructure and properties of ZrB₂-ZrC-SiC composites prepared from a mixture of Zr-B₄C-Si powders by in situ reactive synthesis were investigated. The reactive path and synthesized mechanism of ZrB₂-ZrC-SiC composite were studied through series of pressureless heat treatments ranging from 800 °C to 1700 °C in argon. The in situ ZrB₂-ZrC-SiC composites were fabricated under different synthesis processing. The one with 88.4% relative density performed poorly in mechanical properties due to the occurring of self-propagating high-temperature synthesis (SHS). The fully dense ZrB₂-ZrC-SiC composite was obtained under the optimized synthesis processing without SHS reactions. Its Vickers hardness, flexural strength and fracture toughness were 20.22 ± 0.56 GPa, 526 ± 9 MPa and 6.70 ± 0.20 MPa m^1/2, respectively.