Rheology and Printability of Alumina-toughened Zirconia Pastes for High-density Strong Parts via Direct Ink Writing

Direct ink writing (DIW) is a promising additive manufacturing technique for fabricating structural ceramics, including alumina-toughened zirconia (ATZ), heavily reliant on the rheological properties of the paste. The rheological properties of aqueous ATZ pastes with 25wt% Pluronic® F127 hydrogel and solid loadings of 28 to 44vol% were investigated, complemented by characterization of the parts, including relative density and shrinkage measurements, to assess the printability. The 42vol% paste was identified as most suitable for producing high-density parts with minimal shrinkage. A controlled drying process gradually decreased humidity from 90% to 30% while raising temperature from 25 to 60°C over 4 days to prevent drying defects. Mechanical testing showed DIW-printed high-density (97.2±2.2%) parts with a mean flexural strength of 670±270MPa, Vickers hardness of 13.6±2.8GPa, and fracture resistance of 4.4±0.2MPa, highlighting the potential for DIW to create high-density ATZ ceramic parts with favorable mechanical properties.