Stereolithographical fabrication of dense Si3N4 ceramics by slurry optimization and pressure sintering

Photocurable gray-colored Si 3 N 4 ceramic slurry with high solid loading, suitable viscosity and high curing depth is critical to fabricate dense ceramic parts with complex shape and high surface precision by stereolithography technology. In the present study, Si 3 N 4 ceramic slurry with suitable viscosity, high solid loading (45 vol %) and curing depth of 50 μm was prepared successfully when surface modifier KH560 (1 wt%) and dispersant Darvan (1 wt%) were used. The slurry exhibits the shear thinning behavior. Based on the Beer-Lambert formula, D p ( the attenuation length) and E c (the critical energy dose) of Si 3 N 4 ceramic slurry with solid loading of 45 vol % were derived as 0.032 mm and 0.177 mJ/mm 2 , respectively. Si 3 N 4 ceramic green parts with complex shape and high surface precision were successfully fabricated by stereolithography technology. After optimizing the debinding and sintering process for green parts, dense Si 3 N 4 ceramics with 3.28 g/cm 3 sintering density were fabricated. The microhardness and fracture toughness of as-sintered Si 3 N 4 ceramics are ~14.63 GPa and ~5.82 MPa m 1/2 , respectively, which are comparable to those of the samples by traditional dry-pressed and pressureless sintering technology. These results show that ceramic stereolithography technology could be promising to fabricate high performance ceramics, especially for gray-colored monolithic Si 3 N 4 ceramics.