Preparation And Characterization Of Nanometer-sized α-Al₂O₃ And γ-Al₂O₃ Powders And AAO Membranes

Nanometer-sized α - Al₂O₃ powders have been prepared by solid-state method in the present paper, relatively cheap AlCl₃·6H₂O and (NH₄)₂SO₄·Al₂(SO₄)₃·24H₂O were used as raw materials respectively, soluble starch and active carbon were used as dispersant medium respectively. Effects of dispersants and condition in the processing of crystal transformation and ultrasound on performance of product were studied and technology of preparation was optimized. TEM, SEM and XRD techniques were used to characterize the products, the results show: the particle sizes of the product using AlCl₃·6H₂Oas raw material and soluble starch as dispersant medium are about 80-100 nm, and the particle sizes of the product using AlCl₃·6H₂O as raw material and active carbon as dispersant medium are about 70-90 nm, and the particle sizes of the product using (NH₄)₂SO₄·Al₂(SO₄)₃·24H₂O as raw material and soluble starch as dispersant medium are about 30-40 nm; all the particles are ball-like shape.Nanometer-sized γ - Al₂O₃ powder has been prepared by mechanical chemical synthesis method, relatively cheap AlCl₃·6H₂O and NH₄HCO₃ were used as raw materials, soluble starch was used as dispersant medium. XRD analysis shows that the powder is γ -phase, TEM measurement shows that the particles are about 30-40 nm in sizes with a ball-like shape, TG-DTA analysis shows that the precursor prepared is NH₄AlO(OH)HCO₃.In the processing of preparing Anodic Aluminum Oxide (AAO) membranes, factors that affect the sizes and the order of porosities of AAO membranes were researched. The results show: compared with one-step oxidization processing, two-step oxidization processing is more advantageous to the order of porosities; the sizes of porosities of the product prepared using H₂C₂O₄ solution as electrolyte is larger than the sizes of porosities of the product prepared using H₂SO₄ solution as electrolyte.