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 m^1/2 and 214.7 MPa–5.65 MPa m^1/2 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.