Enhanced properties of nanocrystalline alumina ceramic with compressive prestress and coherently aligned nanograins

Prestress strategy is effective to inhibit crack advancement and toughen structural materials such as concrete and glass. However, it is difficult to be utilized in ceramic because of the solid-state processing. In this work, nanocrystalline alumina ceramic with high compressive prestress and coherently aligned nanograins were successfully prepared by the ultra-high pressure sintering technology. The as-prepared ceramics exhibited remarkably enhanced mechanical properties, including hardness of 25.9 GPa and fracture toughness of 3.2 MPa center dot m1/2, which were respectively 36% and 51% higher than corresponding parameters of sapphire. Ultra-high pressure generated compressive prestress as large as several hundred megapascal, and coherent nanograins in the dimensions of 10-15 nm, which markedly contributed to the simultaneously enhancement in toughness and hardness for ceramic materials. The prestressing strategy provides a new opportunity for fabricating advanced ceramics with high failure resistance.