Large-size Si₃N₄ ceramic fabricated by additive manufacturing using long-term stable hydrogel-based suspensions

Additive manufacturing of ceramic materials has gained the significant attention due to its ability to flexibly fabricate customizable ceramics with complex structures. However, large-size advanced ceramics are still difficult to be fabricated by additive manufacturing, especially for the thin-wall structures. Here, a strategy for fabricating large-size Si₃N₄ ceramic via the materials extrusion process using the long-term stable hydrogel-based suspensions is reported. We establish a mechanism to analyze the rheology relation between the ceramic suspensions and the carboxymethyl cellulose (CMC) hydrogels. The deformation of filaments under gravity is simulated by the computational fluid dynamics (CFD) model, further the effects of the shear-thinning behavior close to the filament surface and the evaporation rate for suspensions with different solid content on the final shape of the filaments are investigated. We finally printed a single-wall cone component with a height of 180 mm, a diameter of 90 mm, and a wall thickness of 1.8 mm by the suspension containing a pseudoplastic CMC hydrogel.