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:
Dec. 05, 1995
Filed:
Nov. 03, 1994
Nissan Motor Co., Ltd., Yokohama, JP;
National Institute for Research in Inorganic Materials, Tsukuba, JP;
Abstract
A high strength and toughness .beta.-silicon nitride sintered body suitable for the material of a variety of structural parts. The sintered body contains .beta.-silicon nitride (Si.sub.3 N.sub.4) in an amount not less than 95% by weight of total silicon nitride; oxygen in a total amount not more than 3% by weight of the sintered body; and columnar grains each of which has a diameter not less than 5 .mu.m and an aspect ratio not less than 5, the columnar grains being in an amount not less than 0.5% by volume of total of raw materials in the sintered body; the sintered body having a bulk density not less than 96% of a theoretical density. Such a sintered body is produced by a method comprising the following steps in the sequence set forth: preparing powder of a starting material including .beta.-silicon nitride in an amount not less than 80% by weight of the starting material; adding oxide of at least one element selected from the group IIIa of the periodic table of elements in an amount ranging from 0.2% to 6% by weight (as a sintering assistant) to the starting material powder to form a mixture powder; compacting the mixture powder to form a compact; firing the compact under a nitrogen gas pressure ranging from 1 to 500 atm. at a temperature ranging from 1700.degree. to 2100 .degree. C. to form the sintered body; and continuing the firing step until a bulk density of the sintered body reaches a value not less than 96% of a theoretical density of the sintered body.