Microstructure and mechanical properties of 3D printed ceramics with different vinyl acetate contents

Stereolithography (SL)-based three-dimensional (3D) printing technique is an efficient method for the fabrication of alumina ceramics. The alumina slurry is difficult to obtain due to the barrier between hydrophilic alumina and oleophilic resin. It not only requires that the ceramic slurry possessed low viscosity and uniformity, but also requires that the slurry could complete the photocuring process. In this study, vinyl acetate was added in the ceramic slurry as a bridge to connect alumina and resin, and the effects of vinyl acetate content on the microstructure and mechanical properties of the alumina ceramics were systematically investigated. The results showed that the alumina ceramics were composed of three types of particles which included large aggregates, individual particles, and long-column-shaped particles. The shrinkage, bulk density, and crystallite size of the ceramics increased with the increase in vinyl acetate content. The open porosity decreased with the increase in vinyl acetate content. The flexural strength of the ceramics first increased and subsequently decreased with the increase in vinyl acetate content. The shrinkage in Z direction was much greater than that in X or Y direction. Based on the above results, the optimum vinyl acetate content for alumina slurry was 10 wt%, which resulted in sintered ceramic with the shrinkage of 15.6% in X direction, 13.5% in Y direction, 21.9% in Z direction, bulk density of 1.9 g·cm−3, open porosity of 50.1%, and flexural strength of 24.4 MPa. The sintered ceramics satisfy the requirement of alumina ceramic cores.