Particle surface oxidation modification and particle gradation strategy for the preparation of high-strength SiC ceramics via vat photopolymerization

The high refractive index, high absorbance, and low sintering activity of SiC powders pose challenges in achieving sufficient curing depth of SiC slurries and achieving densification of SiC ceramics. Hence, the preparation of high-strength SiC ceramics by vat photopolymerization is a challenge. This study proposes a strategy of particle surface oxidation modification and particle gradation to address this difficulty. Specifically, the surface of micron and submicron SiC particles is oxidatively modified to enhance the curing depth of SiC slurry, and the gradation of these particles is optimized to improve the sintering activity of the SiC particle system. The percentage of oxidized micron and submicron SiC particles is carefully adjusted to meet the requirements of both vat photopolymerization preparation and sintering. It found that increasing the percentage of sub-micron particles in the particle grade system had a negative impact on the rheological and curing properties of the slurry but contributed to the stability of the slurry and the performance of the sintered ceramic parts. Ensuring that the percentage of sub-micron particles reaches 50% or higher and reducing direct contact between micron particles to form sintered necks are two key conditions for the preparation of high-strength SiC ceramics. Additionally, it found that interlayer bonding location is the pore defects concentrated in the sintered ceramic parts, providing direction for further optimization of ceramic properties. By implementing the oxidation modification and particle gradation optimization strategy, the densification and three-point flexural strength of SiC ceramic parts were improved significantly. The relative density and three-point flexural strength of SiC increased from 65.7 ± 5.3% to 86.8 ± 3.7% and from 75.0 ± 2.1 to 170.9 ± 11.6 MPa, respectively. This approach provides a simple and effective method to prepare high-strength SiC ceramics by vat photopolymerization.