A simple procedure to prepare spherical α-alumina powders

Spherical alpha-alumina powders were prepared by the controlled hydrolysis of aluminum isopropoxide in a hydrolysis system consisting of octanol and acetonitrile. Diverse solvents to dissolve reactant formed diverse hydrolysis systems and affected particle shape of alpha-alumina powders. The precursors crystallized to gamma-alumina at 1000 degrees C and converted to alpha-alumina at 1150 degrees C without intermediate phases. The particle morphology of precursor was retained after it crystallized to alpha-alumina. The heating rate influenced the particle shape and the state of agglomeration during calcination process. The thermal properties of the precursors were characterized by thermal gravimetric and differential thermal analysis. X-ray diffraction technique was used to confirm the conversion of crystalline phase of alumina powders from amorphous to alpha-phase. Transmission electron microscopy was used to investigate the morphologies and size of the precursors and products. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.