Preparation of Nano-sized Alumina Powders at Low Temperatures

Alpha alumina nanocrystalline powders, with mean particle size less than 50nm, were prepared by a novel synthesis process using Al(NH3)3.9H2O and NH3.H2O solutions as raw materials. The process mainly utilized a seed-effect of fine grains worn from the milling mediums and also utilized ZnF2 or AlF3 additives. The phase transformation temperatures to alpha alumina can be reduced dramatically to 900-920℃ by improving the homogeneity of seeds with the hydrous alumina and accelerating the mass diffusivity and transportation in the transformation process.