UV-Curing Assisted Direct Ink Writing of Dense, Crack-Free, and High-Performance Zirconia-Based Composites With Aligned Alumina Platelets

Additive manufacturing (AM) of high-performance structural ceramic components with comparative strength and toughness as conventionally manufactured ceramics remains challenging. Here, a UV-curing approach is integrated in direct ink writing (DIW), taking advantage from DIW to enable an easy use of high solid-loading pastes and multi-layered materials with compositional changes; while, avoiding drying problems. UV-curable opaque zirconia-based slurries with a solid loading of 51 vol% are developed to fabricate dense and crack-free alumina-toughened zirconia (ATZ) containing 3 wt% alumina platelets. Importantly, a non-reactive diluent is added to relieve polymerization-induced internal stresses, avoid subsequent warping and cracking, and facilitate the de-binding. For the first time, UV-curing assisted DIW-printed ceramic after sintering reveals even better mechanical properties than that processed by a conventional pressing. This is attributed to the aligned alumina platelets, enhancing crack deflection and improving the fracture toughness from 6.8 +/- 0.3 MPa m0.5 (compacted) to 7.4 +/- 0.3 MPa m0.5 (DIW). The four-point bending strength of the DIW ATZ (1009 +/- 93 MPa) is also higher than that of the conventionally manufactured equivalent (861 +/- 68 MPa). Besides homogeneous ceramic, laminate structures are demonstrated. This work provides a valuable hybrid approach to additively manufacture tough and strong ceramic components. A hybrid 3D printing by coupling UV-curing with direct ink writing is proposed to fabricate dense and crack-free ceramics. Non-reactive diluent relieves polymerization-induced stress, avoiding warpage and cracking, and facilitates de-binding. Benefiting from aligned platelets, this work highlights the possibilities of additively fabricating ceramics that are stronger than conventionally manufactured ceramics, along with the unprecedented potentials of locally tunable compositions.image