Effect of filling strategy on surface topography and strength of 3D–printed dense zirconia ceramics

A novel 3D printing process based on material extrusion has recently been developed for the preparation of high-quality zirconia-based ceramics with complex configurations. Nevertheless, the attainment of the optimal mechanical properties of 3D-printed zirconia ceramics for advanced engineering applications remains a significant challenge, largely due to the considerable variability in process conditions. In this study, zirconia ceramics with different filling strategies were prepared using direct ink writing technology. The impact of various filling parameters, including nozzle diameter and printing direction, on the sintering shrinkage evolution, surface topography and mechanical properties was examined. To ensure the accuracy of mechanical tests, all the zirconia ceramics were densely sintered to a relative density of above 98 %. The utilization of thinner needles and printing along short distances has been demonstrated to markedly reduce the surface roughness of the printed ceramics. Furthermore, the flexural strength of the ceramics printed along the long-distance direction was found to be the highest, while all the ceramics printed with a medium diameter of nozzle achieved the optimal flexural strength under the same printing paths. These results suggest that optimizing the printing accuracy and path is an effective method for obtaining dense ceramics with superior surface topography and mechanical performance through direct ink writing technology.