A Study On Preparation And Sintering Of High Purity Alumina Powders

Alumina ceramic is a kind of very important ceramic materials, it is main raw with highpure Al₂O₃and （α-Al₂O₃） as the main mineral composition. The Alumina ceramic is apromising ceramic applied as high mechanical strength, insulation resistance, hightemperature resistance and other excellent properties, so it is widely used in electronic,chemical, military and other fields. Alumina ceramic performance mainly depends on thepowder properties, at present, preparation of high purity alumina ceramic materials mainlycome from the French BAIKOWSKI, the chemical industry of Wang You in the Japan and Daming chemical company. Their preparation of the high purity alumina powder can achievehigh purity superfine, narrow of particle size distribution and with hard agglomeration. Inrecent years, in general the preparation of α-Al₂O₃powder by Sol-gel and alcohol salt solutionmethod in china. Although the above method in determination of the trace elements toachieve a breakthrough, but also has high cost, complex process route, to obtain the powderparticle size distribution is wide and easy agglomeration problems. Thus, the study of powderproperties is become a hot-issue.The mechanical ball milling method has been commonly used in the preparation ofα-Al₂O₃powder, because of low cost, high output, simple preparation. But, because of itsproduct particle size and purity is not enough, with wide size distribution, particle easilyoxidized deformation shortcomings, so that the final performance is not ideal for aluminaceramics. This paper discusses the effect of the milling time, amount of dispersing agent,mineralizer, calcination temperature and other factors on the properties of α-Al₂O₃powder.From the SEM and Particle size analysis results, we can conclude choose of ball milling timeand dispersant dosage, can obtain α-Al₂O₃powder of average particle size <4μm, the narrowerof particle size distribution and better dispersion. And through the control of mineralizationagent dosage, can obtain α-Al₂O₃powder of different morphology.In this work, powder forming by the dry pressing, sintered by atmospheric pressuresintering and liquid phase sintering. Effect of pressure of forming process and sinteringtemperature on product density properties were studied, the layered reason of forming processwas discussed and analysis the kinetic in the sintering process. We determined as follow: Inthe initial stage of sintering, the grain growth is a main process; in the middle and final ofsintering, surface diffusion and grain grow are very important process.