A simple approach to bulk bioinspired tough ceramics

The development of damage-resistant structural materials that can withstand harsh environments is a major issue in materials science and engineering. Bioinspired brick-and-mortar designs have recently demonstrated a range of interesting mechanical properties in proof-of-concept studies. However, reproducibility and scalability issues associated with the actual processing routes have impeded further developments and industrialization of such materials. Here we demonstrate a simple approach based on uniaxial pressing and field assisted sintering of commercially available raw materials (alumina, silica, calcium carbonate) to process bioinspired ceramic/ceramic composites of larger thickness than previous approaches, with a sample thickness up to 1 cm. The ceramic composite retains the strength typical of dense alumina (430 ± 30 MPa) while keeping the excellent damage resistance demonstrated previously at the millimeter scale. These properties validate the potential of these all-ceramic composites, previously demonstrated at lab scale only. The R−curves obtained here on samples with a thickness up to 1 cm demonstrate that size effects resulting in an overestimation of the toughness appear much earlier than expected from the commonly used approaches. The maximum toughness of this new class of materials have thus probably been overestimated so far, albeit being high for an all-ceramic composite material. The results could enable the optimization, scale-up, and industrialization of these composites.