Preparation And Sintering Properties Of Submicron Alumina Ceramic Powder

High purity AI2O3 ceramic material has excellent physical properties and chemical stability, so it is widely used. To prepare high purity Al2O3 ceramics with excellent performance, the Al2O3 powders used must meet the requirements of high purity, good dispersion, narrow particle size distribution, small particle size, high activity and easy sintering. There are many methods to product the Al2O3 powders, but the performance of the prepared powders is unsatisfactory. The purity of Al2O3 powders prepared in some methods was high, but the particle size was large and the distribution of the size was inhomogeneous. The granularity of Al2O3 powders prepared in other methods was ultrafine, but the purity of the powders was low and the powder had poor dispersion. For this reason, this paper prepared the high purity submicron Al2O3 powders with better performance by mechanical milling physical method and sol-gel chemical method. And then through the gel casting molding and atmospheric sintering to prepare high purity submicron Al2O3 ceramic, the specific work is as follows:Firstly, high purity submicron Al2O3 was largely prepared by mechanical milling physical method. The process conditions of preparing high purity submicron Al2O3 and the drying process of Al2O3 particles size were studied. The preparation of high purity submicron Al2O3 was characterized. The results show that freeze drying is the most ideal drying method, the particle size distribution is uniform (narrow) with an average particle size (dso) of 240 nm, and the morphology is pseudo-spherical. Products with high purity after ball milling maintain the alpha phase of the raw material and do not introduce other impurities.Secondly, submicron Al2O3 was prepared successfully by sol-gel method with deionized water, ethanol as the solvent, aluminum nitrate, aluminum isopropoxide as the Al source, pyrocatechol, resorcinol, gelatin as the crosslinking agent, polyvinylpyrrolidone, PEG-1000 as the dispersant respectively. Gelatin as the carbohydrate molecules is non-toxic, environment friendly. The use of gelatin simplifies the preparation process of Al2O3 and provides an economical, environmentally friendly and non-toxic sol-gel method. Using resorcinol as crosslinking agent can successfully obtain submicron α-Al2O3 at 1000℃, provides a method for preparing α-Al2O3 superfine powder in the low temperature.In the end, the Al2O3 ceramics with homogeneous structure were prepared by gel casting using the acrylamide system and the carboxymethyl chitosan system. In the process of acrylamide forming, the solid content of Al2O3 powders was between 40vol%-53vol%, the strength of the green body is about 25MPa, which is satisfied with the mechanical processing performance. After sintering at 1600℃, the solid content of 50vol% Al2O3 ceramics has high density. The density of Al2O3 ceramics formed by acrylamide system is 3.85g/cm3, the relative density is 96.7%, the linear shrinkage rate is 19.11%, and the density of alumina ceramics formed by carboxymethyl chitosan system is 3.71g/cm3, the relative density is 93.2%, the linear shrinkage rate is 20.65%.