Additive Manufacturing of Silicon Nitride

Abstract: This study aims to investigate the fabrication of silicon nitride ceramics via additive manufacturing method. Silicon nitride exhibits excellent thermo-mechanical properties and it is one of the main structural ceramics. The excellent properties of silicon nitride are obtained through densification via liquid phase sintering. The shaping limitations engendered by conventional manufacturing method of ceramics, such as those in powder pressing, give additive manufacturing a promising potential for fabrication of complex geometrical shapes and small-scale production. Three-dimensional ceramic components can be produced via lithography-based additive manufacturing technique. Due to issues associated with light absorption, lithography-based additive manufacturing has mainly been focused on oxide ceramics, known for their low light-absorption properties. On the other hand, silicon nitride exhibits very high light absorption level. In this study, the possibility to additively manufacture silicon nitride ceramics via the lithography-based ceramic manufacturing technique was presented. Photocurable suspensions with dispersed silicon nitride powder were formulated. The influence of the powder composition was investigated by varying the sintering additives content and silicon nitride powder grade. The suspensions were characterized, and the photo-reactivity effects on the printability were investigating by measuring the cure depth, while also considering the rheological behavior and thermal decomposition of the various photocurable suspensions. Additive manufacturing of silicon nitride ceramic components was successfully achieved. By formulating various suspension compositions, suitable viscosity and cure depth were achieved with 43 vol.% solids loading. Cure depth of 40 µm was found to be sufficient to allow the shaping process, and complex geometrical shapes were fabricated at small-scale. The microstructure and physical properties of additive manufactured parts were similar to those of conventionally made parts. These results suggest that new possibilities with respect to the fabrication of complex geometrical shapes and small-scale series silicon nitride ceramics can be accomplished via lithography-based additive manufacturing.