Low-temperature fabrication of high-specific strength SiC-based ceramics via photopolymerization 3D printing with controllable anisotropy

The combination of silicon carbide (SiC) ceramics and stereolithography technology shows promise for manufacturing complex-shaped SiC components, expanding application possibilities. However, high sintering temperature and structural-performance anisotropy limit the practical use of 3D-printed SiC components. Herein, a novel method is introduced to produce high-specific-strength SiC-based ceramics at a relatively low temperature of 1100 ℃. A mixed SiC/SiO₂ slurry (30% SiO₂ and 70% SiC by volume) with a solid loading of up to 40% was prepared to improve UV light penetration and printability. Additionally, incorporating a high content of methyl-phenyl-polysiloxane (PSO) solution (75% by weight) enabled low-temperature pyrolysis of SiC/SiO₂/PSO ceramics. The SiC/SiO₂/PSO ceramic lattices after pyrolysis achieved a specific strength as high as (1.03 × 10⁵) N·m·kg⁻¹ and a density of 1.75 g·cm⁻³, outperforming similar SiC-based lattices structures of similar porosities. The bending strength of (95.49 ± 8.79) MPa was comparable to that of ceramics sintered at 1400 ℃ or higher. Notably, the addition of the silicon carbide oxide (SiOC) phase reduced anisotropy, lowering the transverse and longitudinal compression strength ratios from 1.87 to 1.08, and improving mechanical properties by 79%. This improvement is attributed to SiOC shrinkage, promoting a uniform distribution of sintered components, resulting in a more robust and balanced material structure. This method offers valuable insight into the additive manufacturing (AM) of SiC-based ceramics at lower temperatures and provides new guidance for controlling anisotropy in 3D-printed ceramic parts.