Abstract: Pressureless sintered ZrB₂-SiC ceramics can be prepared as complex shaped component. But they are challenging to densify and have poor anti-ablation resistance. Therefore, there is an urgent need to investigate effective sintering aids to improve the densification of ceramics. ZrB₂-SiC ceramics were prepared by pressureless sintered at 1 850 ℃ for 1 h using CeO₂ and MoSi₂ as sintering aids. The effects of CeO₂ and MoSi₂ on sintering properties and anti-ablation resistance of ZrB₂-SiC ceramics were investigated. The results show that sintering properties and anti-ablation resistance of ZrB₂-SiC ceramics are best when the ratio of CeO₂ and MoSi₂ in 5% (volume fraction) sintering aid is 1∶1. Sintering aids form a Ce-Mo liquid phase during the sintering process. Ceramic particles are rearranged and mass transferred under the surface tension of the liquid phase. The Ce-Mo liquid phase promotes the formation of sintered necks under capillary forces, filles the interstices of the ceramic particles and reduces the grain boundary energy of the ceramic grains to facilitate the densification process. ZrB₂-SiC ceramics are ultimately obtained with an density of 5.02 g/cm³, a relative density of 89.71%, and a Vickers hardness of 14.04 GPa. The actual density and Vickers hardness increases by 53% and 43%, respectively, compared to when no sintering aid is added. During the ablation process, CeO₂ and MoSi₂ supplemented SiO₂ in appropriate amounts to promote self-healing of the glassy phase with suitable viscosity and improve the stability of ZrO₂. The mass ablation rate and the line ablation rate are -1.62 mg/s and 0.33 μm/s, respectively.

Key words: ZrB₂-SiC, CeO₂/MoSi₂ modification, sintering property, anti-ablation resistance, pressureless sintering, slip casting