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. 01, 1997
Filed:
Jun. 02, 1995
Takao Kaga, Funabashi, JP;
Yutaka Kimura, Funabashi, JP;
Fumio Saito, Sodegaura, JP;
Hiroaki Tanaka, Tokyo, JP;
Nissan Chemical Industries, Ltd., Tokyo, JP;
Abstract
A stable aqueous sol of colloidal zirconia having lowered surface activity and useful for polishing semiconductors and the like, is prepared by a process comprising calcining a colloidal zirconia having a specific surface area of 10 to 400 m.sup.2 /g, a particle size of 20 to 500 nm and a dehydratable water content of 4 to 15% by weight at 400.degree. to 1,000.degree. C. to form a calcined zirconia having a dehydratable water content of 0.1 to 2% by weight, and pulverizing the calcined zirconia in the presence of a water-soluble acid or alkali in water, to form the stable sol of colloidal zirconia having a specific surface area of 5 to 200 m.sup.2 /g, a particle size of 20 to 1,500 nm and a dehydratable water content of 0.1 to 3% by weight. The stable sol of colloidal zirconia has a ZrO.sub.2 concentration of 5 to 80% by weight.