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 has the potential to manufacture complex-shaped SiC components, thereby expanding application possibilities. However, the high sintering temperature and structural-performance anisotropy of three dimensional (3D)-printed SiC components have limited their practical use. Herein, a novel method is introduced to produce high-specific-strength SiC-based ceramics at a relatively low temperature of 1100 °C. To enhance ultra violet (UV) light penetration in the SiC slurry, a mixed SiC/SiO2 slurry (30% SiO2 and 70% SiC by volume) with a solid loading of up to 40% was prepared, improving printability. Additionally, a high methyl-phenyl-polysiloxane (PSO) solution content (75% of liquid resin weight) was incorporated to enable the low-temperature pyrolysis of SiC/SiO2/PSO ceramics. The resulting pyrolyzed SiC/SiO2/PSO lattice ceramic exhibited a high specific strength of 1.03 × 105 N·m/kg with a density of 1.75 g/cm3, outperforming other SiC-based lattice structures with similar porosity. The bending strength of SiC/SiO2/SiOC ceramics reached 95.49 ± 8.79 MPa, close to some of those prepared at temperatures of 1400 °C and above). Notably, the addition of the silicon carbide oxide (SiOC) phase to the SiC/SiO2 ceramics significantly reduces anisotropy, lowering the transverse and longitudinal compression strength ratios from 1.87 to 1.08, achieving 79% compensation in mechanical properties. This improvement is attributed to the cohesive force of 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.