Direct ink writing of alumina toughened zirconia composites ; Direct Ink Writing de compósitos de zirconia tenacificada com alumina

Robocasting, commonly referred as Direct Ink Writing, is an additive manufacturing technique that stands out for printing ceramic materials starting from pastes/inks with high concentrations of solids (> 30 vol.%) and low amount of additives (< 15 vol.%), making the thermal post-processing relatively fast, when compared to other technologies such as photopolymerization. The development of ceramic inks for robocasting can be done by different routes such as (i) colloidal processing or (ii) hydrogel. The first is based on interparticle interactions in a suspension medium and meanwhile the second is related with gel-particle interactions. Although both methodologies have been studied for the development of monolithic ceramic material pastes, the manufacture of composite ceramic materials has been scarcely explored. The aim of the present work was to evaluate the impact of the dispersion and stabilization method of pastes based on Alumina Toughened Zirconia (ATZ) on the microstructural and mechanical properties of pieces obtained by robocasting. Alumina Toughened Zirconia was selected as the object of study due to its potential as a biomaterial in dental implants. Ceramic pastes were obtained by both routes (colloidal and hydrogel). Optimization was done through rheological characterization achieving good printability. For the colloidal route, Duramax D3005 was used as dispersant, carboxymethylcellulose as thickener agent and polyethyleneimine as coagulant agent. Meanwhile, for the hydrogel system Pluronic F127 was used as a gelling agent. After printing and sintering, the samples were characterized by density, microstructure, and mechanical properties. From the sintered samples it was found that alumina grains were homogeneously dispersed within the zirconia matrix in the samples derived from the colloidal paste, while big agglomerates and abnormal zirconia grain growth were found on those derived from the hydrogel paste. The homogeneity between alumina and zirconia grains observed in the colloidal route is ...