Rapid debinding and sintering of alumina ceramics fabricated by direct ink writing

Direct ink writing (DIW) is a widely used additive manufacturing technique to fabricate complex-shaped ceramics. Unlike vat photopolymerization or fused filament fabrication, the limited amount of binder in DIW facilitates rapid debinding. In this study, alumina inks with suitable rheology were prepared with two different ceramic loadings (42.8 vol% and 48.1 vol%). Subsequently, log-pile structures were printed using two different nozzle diameters (0.41 mm and 0.84 mm). The fabricated samples were dried at room temperature and subjected to different rapid sintering procedures: ultra-fast high temperature sintering (UHS), pressureless spark plasma sintering (PSPS) and fast-firing (FF). Both UHS and PSPS successfully densified the samples in Ar without any defects. Conversely, the fast-firing in air resulted in some cracks, with the intensity of failures increasing with the nozzle size. UHS and PSPS allowed for nearly fully dense materials with refined microstructure which are not achievable by conventional heating.