Sintering Property and Anti-Ablation Resistance of ZrB2-SiC Ceramics Modified by CeO2/MoSi2
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.
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