Economic preparation of alumina suitable for isostatic pressing and

Abstract

Method for preparing finely divided high purity alumina doped with a small predetermined percentage of magnesia. In the preparation, there is first formed a mixed clear solution of aluminum alkoxide and a small amount of magnesium in the form of alkoxide or water soluble magnesium salt. There is then included with the clear solution a substantial excess of water over that required to completely hydrolyze the alkoxide and there is added thereto a small amount of selected acid which is effective to peptize the resulting slurry. The formed milky slurry is then allowed to become fully peptized to form a clear sol. The clear sol is converted to a finely divided and dried powder either by forming the sol into a gel, which is then dried, and mechanically reduced to a powder status or by spray drying the sol at elevated temperatures which produces the dried powder. Thereafter, the finely divided and dried powder is calcined at a temperature of from about 700.degree. C. to about 900.degree. C., with the crystalline structure of the powder predominately being that of a delta alumina. The preparation of this alumina is very economic and the resulting material is suitable for being isostatically pressed into a tubular form and then sintered to translucent tubular form to a density which closely approaches theoretical.