Study On Preparation Of Nanosize Alumina Powder By Precipitation

The preparation, properties and applications of nanosize alumina have been reviewed in this paper. First, the preparation of ultrafine powder was studied, and the factors and mechanisms of reaction by microemulsion were discussed. The particles of CaCO3 are spherical, with an average diameter of 100nm, and well dispersed. It's distributing of particles size is symmetrical. However, because the mass organic agents are used during preparation and washing, it is not only make pollution probably, but also increase the cost. It would be an obstacle for preparation of nanosize powder by microemulsion to reuse organic agents.It can be avoided the above problems to prepare nanosize materials by precipitation. Nevertheless, there are new problems to agglomeration of nanosize powder. One of the goals of this study is to solve agglomeration of nanosize Al2O3 powder prepared by precipitation. AlCl3 and NH4HCO3 were selected as starting materials, the optimum condition of preparation was determined and agglomeration was controlled.First, the influence to preparation by experiments of single factor was discussed. And the operation conditions are optimized by orthogonal design. The optimization parameters are [Al3+] = 1.5mol/L, [NH4HCO3] = 6.75mol/L, time of reaction = 60min, pH=7.5. The surface areas of Al2O3 powders prepared under the optimum condition can achieve to 280m2/g. Furthermore, due to the application of ceramic membrane while washing precipitation, the yield of Al2O3 could achieve to 97.2% and purity could was 99.8%.Second, through the comparison of three drying methods that drying directly, washing by alcohol and distilling, it was found that washing by alcohol and distilling can avoid agglomeration of powder effectively. However, both of them are cost much, so it is hard to use drying methods in industry.In order to decrease the cost, surfactant was added for solving the problem of agglomeration. According to the results of experiment, when the HLB of surfactant is 10, the effect of prevention of agglomeration is best, the powder is loose. It is feasible...