Effect of seeding on alpha -Al sub 2 O sub 3 powder formation from bayerite and bohemite

• Published in: Key engineering materials 1997-06, Vol.132-136 (1), p.69-72
• Main Authors: Balmori-Ramirez, H, Salvador-Morales, A
• Format: Article
• Language: English
• ISSN: 1013-9826

The production of alpha-alumina from aluminum hydroxides involves the formation of several alumina intermediates whose nature depends on the characteristics of the precursors. The influence of seeding on the production of alpha -Al sub 2 O sub 3 powders from different hydroxides obtained by the precipitation method of AlCl sub 3 6H sub 2 O with NH sub 4 Cl was studied. A bayerite-bohemite mixture and single bayerite wree obtained, depending on the process pH. The transformation sequence for each hydroxide and the transformation kinetics were characterized by thermal analysis and x-ray diffraction. The alpha -Al sub 2 O sub 3 seeds lower the theta - > alpha -Al sub 2 O sub 3 transformation temperature and accelerate the transformation rate, but the transformation is more difficult when single bayerite is the precursor. It is suggested that the characteristics of the theta / alpha Al sub 2 O sub 3 interface depend on the hydroxide precursor.