Ultrafast High-Temperature Sintering of Dense Alumina with Bioinspired Microstructures

Bioinspired microstructures in ceramics have the potential to fulfil combined unusual properties such as local anisotropy with high hardness, stiffness and toughness, but their current fabrication methods remain challenging due to the time-consuming, energy-extensive sintering method. Here, we report a strategy to sinter dense ceramics with bioinspired heterogeneous microstructures that have tunable stiffness and toughness within seconds. This strategy combines a colloidal directed assembly i.e., magnetic assisted slip casting (MASC) with templated grain growth (TGG) using ultrafast high-temperature sintering (UHS). The hierarchical microstructural designs result from the local orientation of alumina microplatelets coated with Fe₃O₄ nanoparticles dispersed in a matrix of alumina nanoparticles. After UHS, the presence of Fe₃O₄led to ceramics with about 98% density and a toughness (K_I0) of 5.89 MPa.m^0.5 in nacre-like orientations. We further explored periodically oriented and multi-layered microstructured ceramics using different compositions to attain an overall toughness (K_I0) of about 5.73 MPa.m^0.5 combined with enhanced energy dissipation rates of ~200 J. m^-2 that can exhibit high local stiffness and toughness across multiple directions. Our proof-of-concept specimens demonstrate that MASC and UHS can fabricate dense, tough and preferentially textured ceramic in time-saving, cost-effective and energy-efficient ways, opening the design space for achieving ceramic parts with local structural properties.