The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 09, 1990
Filed:
Jul. 29, 1986
Makoto Yoshida, Kokubu, JP;
Kiyoshi Yokoyama, Kokubu, JP;
Kyocera Corporation, Kyoto, JP;
Abstract
Disclosed is a process for the preparation of a silicon nitride sintered body, which comprises steps of (i) molding a composition comprising (a) 87 to 98% by weight of silicon nitride and (b) 2 to 13% by weight of a sintering aid comprising an oxide or nitride of aluminum or an element of the group IIIa of the Periodic Table and an inorganic oxide capable of forming a liquid phase component having a melting point lower than that of silicon nitride, the inorganic oxide being present in an amount of 1 to 7% by weight based on the composition, (ii) sintering the molded body in a nitrogen atmosphere at a temperature forming a liquid phase containing said liquid phase component having a low melting point, and (iii) heat-treating the resulting sintered body in a nitrogen atmosphere at a temperature higher than the sintering temperature to volatilize the liquid phase component having a low melting point from the liquid phase. In the obtained sintered body, the oxygen content in the surface layer is controlled below 3% by weight, and the flexural strength at 1300.degree. C. of the surface layer is higher than that of the inner portion.