A novel processing route to develop a dense nanocrystalline alumina matrix (< 100 nm) nanocomposite material

A dense 3-mol%-yttria-stabilized tetragonal zirconia polycrystalline (3Y-TZP) toughening alumina matrix nanocomposite with a nanocrystalline (<100 nm) matrix grain size has been successfully developed by a novel processing method. A combination of very rapid sintering at a heating rate of 500degreesC/min and at a sintering temperature as low as 1100degreesC for 3 min by the spark-plasma-sintering technique and mechanical milling of the starting gamma-Al2O3 nanopowder via a high-energy ball-milling process can result in a fully dense nanocrystalline alumina matrix ceramic nanocomposite. The grain sizes for the matrix and the toughening phase were 96 and 265 nm, respectively. A great increase in toughness almost 3 times that for pure nanocrystalline alumina has been achieved in the dense nanocomposite. Ferroelastic domain switching without undergoing phase transformation in nanocrystalline t-ZrO2 is likely as a mechanism for enhanced toughness.