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The molding method of zirconia ceramics

The molding of zirconia ceramics includes dry pressing molding, isostatic pressing molding, grouting molding, hot die casting molding, casting molding, injection molding, plastic extrusion molding, colloidal solidification molding and so on.

1. Grouting

Grouting molding is the earliest molding method used for zirconia ceramics. The molding process of grouting includes physical dehydration process and chemical coagulation process. Physical dehydration removes the water in the slurry through the capillary action of the porous plaster mold. The chemical coagulation process is because the Ca2+ generated by the dissolution of CaSO4 on the surface of the plaster mold increases the slurry. The ionic strength in the material causes the slurry to flocculate. Under the action of physical dehydration and chemical coagulation, ceramic powder particles are deposited and formed on the wall of the plaster mold. Grouting is suitable for the preparation of large ceramic parts with complex shapes, but the quality of the green body, including shape, density, strength, etc., is poor, and the labor intensity of workers is high and it is not suitable for automated operations.

2. Hot die casting molding

For products with complex shapes, hot die casting is generally used. Hot die casting is to mix ceramic powder and binder (paraffin) at a higher temperature (60-100°C) to obtain slurry and slurry for hot die casting Under the action of compressed air, it is injected into a metal mold, pressure-maintained and cooled, and demolded to obtain a wax blank. The wax blank is dewaxed under the protection of inert powder to obtain a green body, which is then sintered into porcelain at high temperature. The green body formed by hot die-casting has accurate dimensions, uniform internal structure, less mold wear, and high production efficiency

3. Isostatic pressing

Isostatic pressing is mainly used for zirconia structural ceramics with special shapes and large sizes. Because the pressure of the isostatically formed body is uniform and equal in all directions, and the pressure is large, the formed body has high density, good uniformity, small firing shrinkage, and is not easy to deform, crack, and layer. The molding method can avoid delamination that is easy to occur during dry pressing, especially for forming thicker zirconia products, so the molding method is a commonly used method for producing zirconia products. However, the blank after isostatic pressing needs to be processed, so a part of the raw materials will be wasted. At the same time, the blank processing is more troublesome, and the processing speed is slow, and the production efficiency is not high.


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