Grouting molding is the earliest molding method used for alumina ceramics. Due to the use of gypsum molds, the cost is low and it is easy to form large-sized and complex-shaped parts. The key to grouting is the preparation of alumina slurry. Usually water is used as the flux medium, and then the degumming agent and the binder are added. After fully grinding, the gas is exhausted, and then poured into the gypsum mold. Due to the absorption of moisture by the capillary of the gypsum mold, the slurry then solidifies in the mold. During hollow grouting, the excess slurry needs to be poured out when the slurry absorbed by the mold wall reaches the required thickness. In order to reduce the shrinkage of the green body, high-concentration slurry should be used as much as possible.
Organic additives need to be added to the alumina ceramic slurry to form an electric double layer on the surface of the slurry particles so that the slurry is suspended in a stable manner without precipitation. In addition, binders such as vinyl alcohol, methyl cellulose, alginate, and dispersants such as polyacrylamine, gum arabic, etc. need to be added in order to make the slurry suitable for injection molding operations.
