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 25 wt% Pluronic (R) F127 hydrogel and solid loadings of 28 - 44 vol% were investigated, complemented by characterization of the parts, including relative density and shrinkage measurements, to assess the printability. The 42 vol% 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 degrees 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 +/- 270 MPa, Vickers hardness of 13.6 +/- 2.8 GPa, and fracture resistance of 4.4 +/- 0.2 MPa, highlighting the potential for DIW to create high -density ATZ ceramic parts with favorable mechanical properties.