Fabrication of alternating layers of multimaterial ceramics with bioinspired microstructures

Abstract

Ceramics are known for their high strength, stiffness, and hardness. However, they usually show poor toughness, which limits their use in applications that need to withstand damage. Previous studies have shown that bioinspired designs, such as the nacre-inspired layered arrangement of hard and soft layers (inspired by nacre in abalone shell), can help mitigate poor toughness. In particular, a layered arrangement to combine alumina and zirconia as hard and soft layer, respectively, could be interesting for structural, transport, energy absorption, biomedical applications, etc. However, the precise microstructural control and the interpenetrating distribution of alumina and zirconia is challenging.

Therefore, in this study, precise composition and microstructural control are carried out to create nacre-inspired alumina-zirconia composites. To do so, first, commercially available plate-shaped microparticles (microplatelets) of alumina are magnetized with superparamagnetic iron-oxide nanoparticles (SPIONs). A slurry is then prepared consisting of alumina nanoparticles (np), zirconia nanoparticles, and magnetized alumina microplatelets in varying ratios to control the composition precisely. Thereafter, the magnetically assisted slip casting (MASC) process is applied using a rotating magnetic field to orient the magnetized alumina microplatelets in the in-plane direction with the nanoparticles of alumina and zirconia trapped in between in a layer-by-layer fashion until complete drying to control the microstructure precisely. Next, sintering is conducted to densify the samples using a templated grain growth (TGG) process, where the nanoparticles of alumina are consumed into the platelets to promote anisotropic grain growth while the zirconia particles remain in between the grown microplatelets. The microstructural, physical and mechanical property measurements indicate an optimum composition for a precise microstructural arrangement with high density that also provides high strength and toughness.