Effects of Ultrasonic on Preparation of Alumina Powder by Wet Chemical Method

Effects of ultrasonic on preparation of alumina powder by wet chemical method were researched in the paper. The formation, aggregation, aging, drying and sinter of the precursor in the ultrasonic field were investigated. The results of the research show that ultrasonic energy is able to speed up the nucleation of the precursor and produce enough ultrafine crystal nucleuses at the moment of nucleation. Ultrasonic vibration can stir fierce the reaction solution and promote the diffuse of the reaction system, which makes it possible for the unstable nucleus to transform stable by growing into a particle with the captured ionogen in the reaction solution by diffusion. All the spherical precursor particles have the tendency of translating to the shape of rod or flake during the process of aging. But the translation of the precursor which prepared in ultrasonic field becomes slower. A loose three-dimensional network structure of the precursor without much water can be obtained by the ultrasonic method. Drying the precursor with this structure is very fast and it is favorable to the preparation of nano alumina powder with small size and less conglobation. In addition, ultrasonic dispersion can control the agglomerate of the crystal nucleus effectively, and ultrasonic frequency influences the crystal transformation of the powder actively during the sinter process, the crystallization of alpha alumina is higher with the ultrasonic frequency increasing.