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

Abstract

Photocurable gray-colored Si3N4 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, Si3N4 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, Dp(the attenuation length) and Ec (the critical energy dose) of Si3N4 ceramic slurry with solid loading of 45 vol % were derived as 0.032 mm and 0.177 mJ/mm2, respectively. Si3N4 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 Si3N4 ceramics with 3.28 g/cm3 sintering density were fabricated. The microhardness and fracture toughness of as-sintered Si3N4 ceramics are ~14.63 GPa and ~5.82 MPa m1/2, 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 Si3N4 ceramics.