Research On α-Al₂O₃ Preparation Technology Of Wet Pretreatment And Low Temperature Mineralization Calcination

The a-alumina has excellent physical and chemical properties, using extensively in ceramic, refractory, polishing and abrasive fields. The single-dry-high-temperature method is usually adopted as the present technology of a-alumina production. The raw material of aluminum hydroxide or aluminum oxide is calcined with a phase inversion process at temperature up to 1300℃, adding appropriate amount of mineralization additives.A new a-alumina production process is introduced in this article. The process, technology parameters and kind of additives are determined by the research of the wet pretreatment and low temperature mineralization calcining process. The raw materials of this technology is aluminum oxide and the parameters are as follow:liquid to solid ratio for 2:1, reaction temperature at between 40 and 50℃, reaction time about 20 minutes, the addition quantity of F1 about 0.2%(mass fraction), and the volume of addition of glacial acetic acid about 0.03%(mass fraction). After pretreatment, the calcination-temperature of alumina of a-alumina generation is 1150℃,which is reduced at least 200℃compared with dry pretreatment.The a-alumina production typical physical and chemical indexes with wet pretreatment and low temperature mineralization calcining method are as follows:the content of a-alumina is equal or greater than 95%, the grain size is between 1 and 2 u m, the absolute grave density is equal or greater than 3.96g/cm3, the quantity of sodium oxide is less than or equal to 0.08%. The SEM result shows that the grain of alumina produced by the new method is existed in the form of platelike.By comparing with a-alumina produced by the single-dry-high-temperature method under the same specification, the new production of grinding technology and the application value in ceramics, refractory castable and polishing field are also evaluated. The test shows:the alumina produced by the new technology has not only better grind-ability but also finer grain fine distribution, which grinding time is 70% of that of single-dry-high-temperature method; the a-alumina is suited to application in ceramics, refractory castable and polishing field. Consequently,the wet pretreatment and low temperature mineralization calcining process can be utilized in industrial production.