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 Al2 O3 /ZrO2 solid solution micro-powders, which is fabricated by Al-O2 ultrahigh-temperature combustion synthesis assisted rapid water cooling. The Al2 O3 /ZrO2 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 Al2 O3 /ZrO2 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.
Keywords: columnar crystals; combustion synthesis; microstructural design; nanoprecipitation; rapid solidification; supra-nanostructures; three-level structures.
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