Pressure slip casting process for making hollow-shaped ceramics

A method of making a green ceramic article by pressure slip casting, comprising the steps of:

• a) providing a slip casting mold including porous mold part means having a molding-cavity-defining surface and porosity channels opening thereto having a given average cross-sectional channel dimension;
• b) providing a slip composition comprising a liquid vehicle, a binder, solid phase particulate components with an average particle size distribution less than said porosity channel dimension and a flocculating agent to cause agglomeration of said solid component particles into floccules larger than said channel dimension;
• c) flowing the slip via a molding cavity inlet into the molding cavity to fill the molding cavity with the slip composition;
• d) hydrostatically pressurizing the slip composition in the molding cavity while withdrawing slip filtrate from the molding cavity via the mold porosity channels at a pressure and for a time sufficient to deposit to a desired thickness a layer of solids from slip on a molding cavity surface-deposit layer interface;
• e) removing excess slip from the molding cavity via a molding cavity outlet to provide a surface on said deposit layer exposed to the interior of the molding cavity;
• f) applying air under pressure to the exposed interior surface of said deposit layer while withdrawing slip filtrate via the mold porosity channels from the molding and cavity surface-deposit layer interface for a time and at sufficient air pressure differential to cause the air to effect a liquid vehicle drying action on said interface by flow of the air therealong and to rupture the liquid vehicle-solid particle bonds so that the liquid vehicle molecules may be forced by the use of the air under pressure from within the deposit layer to the molding cavity surface-deposit layer interface to cause liquid vehicle to be forced from within said deposit layer to said interface for withdrawal therefrom;
• and
• g) removing the slip casted green ceramic article from the mold after sufficient liquid vehicle has been removed from the article to cause the same to be self-supporting.