The Preparation of Boehmite and a-Alumina Powders by Hydrothermal Synthesis from Aluminium Metal

Hydrothermal oxidation of aluminium metal has been effected in the temperature and pressure ranges of 300-550°C and 10-120 MPa respectively. While boehmite and a-alumina form at the extremities of these temperatures and pressures respectively, at intermediate temperatures their mixtures are obtained. The products which had average particle sizes in the range of 4-15 pm were further characterised by XRD, IR spectroscopy, and6y SEM observations. The quantity of metal reacting with unit volume of water shows three regions\ud having distinctly different slopes in the temperature ranges of 300- 350°C, 350-450°C and 450-550'~ corresponding to the formation of fully crystalline forms of boehmite, boehmite + a-alumina and a-alumina respectively