Disperse fine equiaxed alpha alumina nanoparticles with narrow size distribution synthesised by selective corrosion and coagulation separation

Disperse fine equiaxed alpha-Al2O3 nanoparticles with narrow size distribution are important materials in nanotechnology and nanomaterials, but syntheses of disperse fine equiaxed alpha-Al2O3 nanoparticles usually result in fine gamma-Al2O3 nanoparticles or large alpha-Al2O3 nanoparticles larger than 15 nm. alpha-Al2O3 has a higher surface energy than gamma-Al2O3 and becomes thermodynamically not stable with respect to gamma-Al2O3 at specific surface areas larger than 100 m(2)/g (at sizes smaller than 15 nm for spherical particles) at room temperature. So disperse fine equiaxed alpha-Al2O3 nanoparticles smaller than 15 nm with narrow size distribution are extremely difficult to synthesise. Here we show the successful synthesis of disperse fine equiaxed alpha-Al2O3 nanoparticles with average sizes below 10 nm and narrow size distribution by selective corrosion and refined fractionated coagulation separation. An almost fully dense nanocrystalline alpha-Al2O3 ceramic with a relative density of 99.5% and an average grain size of 60 nm can be sintered from disperse fine equiaxed alpha-Al2O3 nanoparticles with narrow size distribution.