Making Ultra‐Tough Nanoceramics by Columnar Submicrocrystals with Three‐Level Micro‐Nano Structures

Abstract The low fracture toughness of equiaxed nanocrystalline ceramics is the main bottleneck of its wide range of commercial applications. Here, the authors report a method to overcome this limitation for preparing ultra‐tough nanoceramics from using amorphous and supersaturated Al 2 O 3 /ZrO 2 solid solution micro‐powders, which is fabricated by Al–O 2 ultrahigh‐temperature combustion synthesis assisted rapid water cooling. The Al 2 O 3 /ZrO 2 micro‐powders containing amorphous and metastable dendritic solid solutions can induce the three‐level micro‐nano structure (submicro/nano/supra‐nano) of the high‐content (up to 70–90%) columnar submicro‐crystals accompanied with high‐density nanoprecipitation after sintering or annealing, which makes the fracture toughness of Al 2 O 3 /ZrO 2 ceramics with a unique combination of high‐strength and high‐hardness increased by 50–100%. This method is beneficial to microstructural design of high‐performance ceramics and can be widely applied to various ceramic systems, coupled with simplicity, low‐cost, and high‐efficiency, making it suitable to industrially produce large‐sized nanoceramics with specific grain geometry in large quantities.