Method for producing silicon nitride molded bodies by means of pseudoisostatic hot pressing

US4264546A · kind A · utility

Assignee

• Kernforschungszentrum Karlsruhe GmbH · DE

Inventor

• Rudolf Becker · Ingolstadt, DE

Key dates

• Filing date: Mar 19, 1979
• Grant date: Apr 28, 1981
• Expiry date: Mar 19, 1999

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C04B35/6455
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

Method and apparatus for producing silicon nitride molded bodies by means of a pseudoisostatic hot pressing process. Silicon nitride is initially ground in a grinding vessel with grinding elements wherein the vessel is lined with the same material from which the grinding elements are made, e.g., hot pressed silicon nitride. Grinding is continued until a specific surface area greater than 15 m.sup.2 is obtained. The grinding takes place in the presence of a grinding liquid to prevent oxidation of the freshly ground silicon nitride. The silicon nitride suspension is then treated in a pressure vessel to remove the grinding liquid therefrom and form a blank. The blank is thereafter embedded within a pressure transfer medium, e.g., boron nitride, and inserted into the die of a hot pressing furnace to obtain the desired hot pressed silicon nitride. The pressure vessel used in this method comprises a chamber for the silicon nitride suspension, an outlet means connected to the bottom of the chamber to permit the vacuum removal of the grinding fluid from said suspension; and an inlet means connected to the chamber for admitting an inert gas, e.g., nitrogen, into the chamber.