Effect of SiO2/AlOOH double-coated SiC powders on the properties of SiC ceramics by vat photopolymerization

Vat Photopolymerization (VPP) technology is expected to address the challenges of preparing high-strength, precise, and complex SiC ceramics. However, the poor printability of SiC powders and the low strength of the resulting SiC ceramics remain significant obstacles. To overcome these issues, this study proposes a SiO₂/AlOOH double-coating method for modifying SiC powders. The effects of AlOOH content in the double coating on the properties of SiC powders, slurries, and ceramics were investigated. Additionally, the impact of sintering additives on the densification behavior and mechanical properties of SiC ceramics was examined. The results indicated that increasing the AlOOH content in the double coating decreased the UV absorption of the powders and increased the curing depth of the slurries, but also increased the viscosity of the pastes. Moreover, while increasing the AlOOH content in the double coating improved the densification and flexural strength of the ceramics, the effect was significantly less compared to optimizing the sintering additive. Using SiO₂/AlOOH double-coated SiC powders containing 2.5 wt% AlOOH and 10 wt% Al₂O₃-Y₂O₃-MgO (mass ratio 1:8:1) sintering additives, SiC ceramics were prepared with a relative density of 91.1 ± 3.5 %, a Vickers hardness of 1685.6 ± 86.4 HV, and a flexural strength of 281.7 ± 14.4 MPa, much higher than that of other SiC ceramic prepared using the same process. This represents the highest flexural strength of SiC ceramics prepared by VPP technology to date, providing a new method for the preparation of high-strength SiC ceramics via VPP.