Alumina Ceramic Gelcasting Forming Process

The ceramics of alumina, especially the engineering ceramics, is not only the important basic materials for the development of economy, but also high add-ons value for long time. It can be show that the hotspots of research of ceramics go through the sinter to the powder and now to the forming process of ceramics in the history of the development of ceramics in recent half century. The gelcasting is one of the colloidal processing, and a slurry made form ceramic is poured into a mold, ploymerized in-situ to immobilize the particles in a gelled part, removed from the mold while still wet, then dried and fired. Now gelcasting become the focus of attention because the processing additives are all organic and leave no cation impurities behind in the fired part and it can be quickly adapted for use with new materials and new applications.Some research and the process of gelcasting is reviewed in this paper. Some theorys which include the dispersal of ceramic powder in the medium, the stable suspending slurry, the rheological behavior of suspending slurry and the experimentation design— second-order orthogonal designs of regression and stepwise analysis is also reviewed.The rheological behavior of the suspending slurry of gelcasting alumina was researched. The amount of dispersant, the value of pH, the time of ballmill was select as the variable in the experiment. The result of viscosimeter was curvefited using power model and Herschel-Bulkley model by the orthogonal test of L₈(2⁷), which can be show the Herschel-Bulkley model is more suitable. The second-order orthogonal design of regression has been done. Then the analysis of variance, the both equation of regression, the comparison between them and the optimization of coefficient of equation also has been done. It can be show that yield stress of suspending slurry was markedly affected by dispersant, the exponent of Herschel-Bulkley model was mainly affected by the time of ballmill and the interaction among each factor was not ignored. The stepwise analysis is better than orthogon of regression. The optimum technics...