Kinetic stability and rheological properties of photosensitive zirconia suspensions for DLP printing

Digital light processing (DLP) is a rapidly developing technology accessing the opportunity to print complex ceramics objects. The main prerequisite for successful printing is the preparation of kinetically stable suspension with low viscosity and homogenous distribution of perfectly dispersed particles. All three mentioned assumptions could be fulfilled by a selection of a suitable dispersant and starting zirconia powder. In this paper, a commercial agent Disperbyk-103 was used to create a highly stable suspension with 30 vol% of zirconia powder with appropriate viscosity (0.93 Pa s at a shear rate of 10 s-1). The optimal concentration of the agent was set not only by rheological measurements but also with the help of measurement of the kinetic stability over time using an analytical centrifuge. Stability measurement was evaluated as an appropriate supplementary analysis to the conventional viscosimetric analysis. Furthermore, the predictive viscosity models were tested either as a tool how to estimate the maximum solid volume fraction for the ceramic suspensions as well as for the prediction of suspension dynamic viscosity according to the used solid content in the prepared suspension. Finally, the suspension with the most suitable physicochemical properties was printed, sintered, and subsequently characterized using the analysis of mechanical properties by the Vickers hardness (1315 HV), relative density (98.2%) and shrinkage. The presented work points to the excellent possibility of using stability analysis as a complementary ceramic suspension analysis.