Improved Mechanical Properties of Porous Si3N4 Ceramics Strengthened by Β-Si3n4 Seeds Fabricated by Vat Photopolymerization

Porous Si3N4 ceramics are widely applied in aerospace and mechanical fields owing to their excellent properties. Furthermore, vat photopolymerization (VPP) technology can fabricate Si3N4 components with complicated structures and high precision, but its layer-by-layer printing method leads to poor mechanical properties of ceramics. In this study, porous Si3N4 ceramics with a porosity of 28.41% strengthened by directional β-Si3N4 were fabricated by combining VPP technology and seeding method. Rheological behavior and curing properties of the slurry were explored, and the influence of β-Si3N4 content on the mechanical properties of printed Si3N4 ceramics was investigated systematically. With the increase of β-Si3N4 content, the orientation degree of β-Si3N4 grains increased gradually, while fracture toughness and flexural strength of the ceramics exhibited a trend of increased first and then decreased and Vickers hardness gradually decreased. As β-Si3N4 content increased to 5 wt%, the fracture toughness and flexural strength of porous Si3N4 ceramics were improved from 4.23 MPa·m1/2 and 214.7 MPa to 5.65 MPa·m1/2 and 272.0 MPa, respectively. Therefore, this work indicates that vat photopolymerization combined with seeding method is a promising approach for the fabrication of porous Si3N4 ceramics with high performance and complex structures.