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:
Aug. 22, 1978
Filed:
Sep. 23, 1977
Nikki-Universal Co., Ltd., Tokyo, JP;
Abstract
Substantially spherical alumina particles are obtained by a process comprising ageing substantially spherical alumina hydrogel particles obtained by the oil-drop method in an ammonium hydroxide solution wherein the concentration of ammonia changes continuously from an initial concentration in the range of from about 0.05 wt.% to about 0.5 wt.% to a final concentration in the range of from about 0.8 wt.% to about 2.5 wt.%. Alumina particles obtained by this process possess improved physical strength. Alumina particles which are obtained by calcining alumina particles aged in an ammonium hydroxide solution, wherein the concentration of ammonia increases continuously, at a temperature in the range of from 650.degree. to 800.degree. C in an atmosphere containing 30 mol.% or more of H.sub.2 O possesses a further improved thermal stability.