Vat Photopolymerization-Based Additive Manufacturing of Si3N4 Ceramic Structures: Printing Optimization, Debinding/Sintering, and Applications

Si3N4 ceramics and composites stand out for their exceptional mechanical and thermal properties. Compared with conventional ceramic forming processes, 3D printing via vat photopolymerization not only ensures high geometric precision but also improves the forming efficiency and strength of green body. Nevertheless, the grayish appearance of Si3N4 and its relatively high refractive index can adversely affect the photocuring behavior in ceramic slurries. The primary objectives focus on enhancing the curing performance and rheological properties of slurries, minimizing defects during post-processing, and improving the relative density and mechanical properties of Si3N4 ceramics. Key advancements include slurry optimization via refractive index matching, biomodal particle gradation and surface modification, while the integration of whisker/fiber additions or polymer-derived ceramic strategies enhances mechanical properties. In addition, controlling the atmosphere and heating rate of the post-processing innovations can achieve a relative density of more than 95%. This paper introduces the mechanisms of vat photopolymerization and then summarizes the strategies for improving Si3N4 ceramic slurries as well as controlling the printing and debinding/sintering processes. It further highlights the ways in which different approaches can be used to enhance the properties of Si3N4 slurries and ceramic parts. Finally, applications of Si3N4 ceramics and composites via vat photopolymerization in various fields such as aviation, aerospace, energy, electronics, chemical processes, and biomedical implants are also presented to point out future opportunities and challenges.