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. 05, 1988
Filed:
Oct. 01, 1986
Toshihiko Funahashi, Chiba, JP;
Ryoji Uchimura, Chiba, JP;
Yukio Oguchi, Chiba, JP;
Kenichi Ueda, Chiba, JP;
Kawasaki Steel Corporation, Hyogo, JP;
Abstract
In producing zirconia powder by desiliconizing heat treatment of a mixture of zircon powder and a powdery carbon-containing material, optionally with addition of a zirconia stabilizing oxide such as calcia or yttria, in a nonoxidizing atmosphere the conversion of silica into SiO and dissipation of gaseous SiO are promoted and completed by performing the heat treatment under reduced pressure, viz. at a pressure not higher than 0.6 atm. Zirconia powder of very high purity can surely be obtained, even when a large batch of the raw material mixture is treated, by performing the reduced pressure desiliconizing heat treatment in two stages: first at 1200.degree.-1550.degree. C. until almost complete conversion of silica to SiO and then at 1550.degree.-2000.degree. C. The mole ratio of C to SiO.sub.2 in the raw material mixture must be 0.4-2.0. For further enhancement of purity, zirconia powder obtained by the desiliconizing treatment may be subjected to oxidation heat treatment. Efficiency of the desiliconizing heat treatment can be enhanced by precedingly forming the raw material mixture into porous lump(s) whose bulk density is in the range from 0.7 to 2.0.