Preparation of Gel-casting Slurry to Fabricate Large Scale Green Body

Abstract

In this study, a gel-casting has been optimized to fabricate larger scale ceramic products. An aqueous alumina slurries with different powder mixing ratio of larger (18 μm) and smaller (0.4 μm) alumina powder, and the initiator which generates the common free radical (Ammonium persulfate) or thermal radical (2, 2' -Azobis [2-(2-imidazolin-2-yl)-propane] dihydrochloride) were prepared to investigate the effect of the gelation time on the structure of the resulting green body. Results showed that the common radical generator (Ammonium persulfate) took longer gelation time, resulting in the distorted green body due to the different shrinkage behavior in upper and lower part of green body. While thermal radical generator (2, 2'-Azobis [2-(2-imidazolin-2-yl)-propane] dihydrochloride) accelerated the polymerizing rate to exhibit uniform shrinkage behavior without cracking in the green bodies because of the uniform density especially for the case of large size powders. As a result, large-scale ceramic green body with uniform packing density was successfully prepared by optimizing the gel-casting conditions, showing the advantage of the gel-casting using starting reagent of thermal radical generator and the raw powders of the mixture of larger and smaller size powders.