SPS densification and ablative performance of ZrB2-SiC-ZrC composites derived from the ternary powders by sol-gel

ZrB2-SiC-ZrC (ZSZ) composite ceramics were successfully prepared by sol-gel method combined with spark plasma sintering (SPS) technology. ZrB2-SiC-ZrC multiphase powders with a scale of about 100 nm were firstly synthesized by sol-gel method at 1500 degrees C. The sintering performance of the sol-gel powders was compared with compositionally similar commercial powders mixture by SPS. The relative densities of the corresponding target composite (ZSZ1) and reference composite (ZSZ2) were reached to 96.2% and 92% under 2000 degrees C/40 MPa, respectively. The densification curves indicated that the residual SiO2 and B2O3 oxides derived from the pre-cursor triggered the liquid phase sintering mechanism of sol-gel powders above 750 degrees C. The removal of oxide impurities through carbothermal reduction, and the diffusion and attachment of the liquid phase at the grain boundary jointly promote the densification of ZSZ1. ZSZ1 presented better oxidation/ablation resistance than ZSZ2 during the oxyacetylene ablation tests for 200 s. The mass and line ablation rate of ZSZ1 were only-4.268 x 10-4 g/s and-8.32 x 10-3 mm/s, respectively, which is attributed to be the structure of ZrO2 fine particles uniform distributed in SiO2 melt.