Direct ink writing of ATZ composites based on inks prepared by colloidal or hydrogel route: Linking inks rheology with mechanical properties

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The Direct Ink Writing (DIW) technique stands out due to its fast processing, low amounts of additives demanded for the ink’s preparation and, consequently, the relatively quickly thermal post-processing cycles. On this behalf, the development of inks for DIW is usually based on colloidal or hydrogel-based processing routes, which derive from interparticle interactions or gel-particle interactions, respectively. The aim of this work was to evaluate the impact of colloidal or hydrogel-based ceramic inks processing routes in the properties of Alumina Toughened Zirconia (ATZ) composites prepared by DIW. It was found that the alumina grains were homogeneously dispersed into the zirconia matrix on samples derived from the colloidal ink, while big agglomerates could be found on those derived from the hydrogel ink. The good homogeneity observed on the colloidal route is related with the particle-particle (electrosteric) stabilization mechanism that induced an efficient dispersion of the starting powders, in contrast with the hydrogel route where the steric stabilization mechanism is dominant. Given the high interest of these composites as biomaterials, the achievements here attained open future opportunities for the near-net-shape processing of geometrically complex and customized dense and tough prosthesis and implants by DIW with mechanical performance comparable with conventional processing routes.