Microstructure and mechanical properties of ZrB2-SiC composites prepared by gelcasting and pressureless sintering

ZrB2-SiC ceramic composites were prepared through water-based gelcasting and pressureless sintering. Effects of the pressureless sintering temperature (1500-2000 °C), heating rate (5-15 °C/min) and soaking time (0.5-2 h) on the relative density, microstructure and mechanical properties of the ZrB2-SiC composites were investigated in detail. A sintering temperature of 2000 °C, a heating rate of 5 °C/min and a soaking time of 2 h were found to be the optimal pressureless sintering procedure. The relative density, flexural strength and fracture toughness of the ZrB2-SiC composite prepared under the optimum condition were 97.8%, 403.1 ± 27.8 MPa and 4.05 ± 0.42 MPa·m1/2, respectively.