Preparation and modification of nano-sized Al2O3 powders through addition of oxide
(School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China)
Abstract: Ammonium aluminum carbonate hydroxide（AACH）, the precursor of α-Al2O3, was fabricated with NH4Al（SO4）2 and NH4HCO3 via a precipitation method. During the heat treatment AACH undergoes such a phase transformation process: amorphous（350℃）→γ（700℃）→γ+θ（1050℃）→θ+α （1100℃）→α （1200℃）. Oxides, such as TiO2 sol and MgO sol were introduced into the precursor. Then both the α transformation temperature and the particle sizes of α-Al2O3 are decreased. The microstructures and its surface electronic properties of the powders are modified, and its dispersion property is improved. Doping TiO2 sol grains, AACH completes α phase transformation nearly at 1100℃, its first-order diameter is about 120nm. Doping with MgO sol grains, α phase transformation completes after being sintered at 1100℃.
Key words: ammonium aluminum carbonate hydroxide； nano α-Al2O3； α phase transformation； doping； TiO2 sol