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

Disperse fine equiaxed α-Al(2)O(3) nanoparticles with narrow size distribution are important materials in nanotechnology and nanomaterials, but syntheses of disperse fine equiaxed α-Al(2)O(3) nanoparticles usually result in fine γ-Al(2)O(3) nanoparticles or large α-Al(2)O(3) nanoparticles larger than 15 nm. α-Al(2)O(3) has a higher surface energy than γ-Al(2)O(3) and becomes thermodynamically not stable with respect to γ-Al(2)O(3) 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 α-Al(2)O(3) nanoparticles smaller than 15 nm with narrow size distribution are extremely difficult to synthesise. Here we show the successful synthesis of disperse fine equiaxed α-Al(2)O(3) nanoparticles with average sizes below 10 nm and narrow size distribution by selective corrosion and refined fractionated coagulation separation. An almost fully dense nanocrystalline α-Al(2)O(3) ceramic with a relative density of 99.5% and an average grain size of 60 nm can be sintered from disperse fine equiaxed α-Al(2)O(3) nanoparticles with narrow size distribution.