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:
Jul. 09, 1991
Filed:
Sep. 04, 1990
Applicant:
Inventors:
Assignee:
Bayer Aktiengesellschaft, Leverkusen, DE;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
C01B / ; C01B / ;
U.S. Cl.
CPC ...
423344 ; 501 97 ;
Abstract
Si.sub.3 N.sub.4 powders having a total oxygen content of less than 1.8% by weight with the proportion of surface oxygen content of more than 65% of the total oxygen content, and having a fluorine content of less than 35 ppm are prepared by annealing Si.sub.3 N.sub.4 powders having a total oxygen content of less than or equal to 0.4% by weight in an oxygen-containing atmosphere at temperatures of 700.degree. C. to 1200.degree. C. for 15 to 90 minutes or by grinding Si.sub.3 N.sub.4 powders having a total oxygen content of less than or equal to 0.4% by weight in water, alcohol or aqueous alcohol 15 to 120 minutes.