Additive manufacturing of zirconia and its composites via digital light processing

Zirconia (ZrO2) exhibits a particularly high flexural strength and other advantages such as biocompatibility and high chemical resistance. Consequently, it is used in a vast range of applications, making zirconia an excellent candidate for digital light processing (DLP) due to high printing resolution, good surface finish and fast building process. To achieve highly-dense zirconia parts via DLP, first, a suitable suspension with high solid loading (>55 vol.%) and low viscosity (<2 Pa s) was prepared with the addition of the best dispersant, BYK. Meanwhile, the effect of photoinitiator (PI) concentration and exposure energy on cure depth was investigated. Moreover, two main challenges, the precise control of exposure parameters and optimisation of the thermal debinding process, have been addressed. Finally, the characterisation of the as-sintered dense zirconia parts was comprehensively evaluated, the performance of the DLP-produced zirconia is comparable to that of conventionally fabricated zirconia. Monolithic zirconia, despite its high strength and modulus, is limited in many structural applications due to inherent brittleness and low toughness. Nevertheless, ceramic-based composites, in nacre, overcome this limitation using bottom-up complex hierarchical assembly of hard ceramic and soft polymer interlayers. In this project, two nacre-inspired composites, zirconia / epoxy interpenetrating phase composite (IPC) and layered zirconia / poly (methyl methacrylate) (PMMA) composite, were fabricated via DLP printing and polymer infiltration method. Experimentally, the mechanical test shown that these two composites exhibited a non-catastrophic failure and the IPC showed remarkable energy absorption efficiency, whilst the latter composite displayed an excellent combination of strength, fracture toughness and work of fracture.