Al.sub.2 O.sub.3 and Y.sub.2 O.sub.3 containing silicon nitride having high mechanical strength at high temperatures

US5720919A · kind A · utility

Assignee

• Hoechst GmbH · DE

Inventors

• Cornelia Boberski · Hofheim, DE
• Hartmut Kruner · Eppstein, DE
• Gunter Riedel · Kelkheim, DE
• Rainer Hamminger · Mannheim, DE

Key dates

• Filing date: Jun 2, 1995
• Grant date: Feb 24, 1998
• Expiry date: Jun 2, 2015

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C04B35/5935
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

A method of making a shaped part of sintered silicon nitride is disclosed which includes preparing a mixture of Si.sub.3 N.sub.4 having a BET specific surface area in the range of from 2 to 15 m.sup.2 /g, having an O.sub.2 content of <1.5% by weight, a .beta.-form content of <2% by volume with finely divided Y.sub.2 O.sub.3, Al.sub.2 O.sub.3 or HfO.sub.2 and/or ZrO.sub.2, the total additive content being in the range of from 6 to 13% by weight, based on the total weight of the mixture, then mixing and milling mixture in a liquid dispersion medium, drying and agglomerating the suspension so produced, subsequently pressing, injection molding or redispersing and casting the agglomerated material obtained to make shaped parts, and finally sintering the shaped parts at temperatures between 1725.degree. and 1850.degree. C. under nitrogen for a period of up to 2 hours. The shaped parts produced according to the method have high mechanical strength and include at least 87% by weight Si.sub.3 N.sub.4 in the crystalline phases of the .alpha.- and/or .beta.-form, up to 13% by weight of an additive combination of Al.sub.2 O.sub.3 and Y.sub.2 O.sub.3, the Y.sub.2 O.sub.3 /Al.sub.2 O.sub.3 weigh…