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:
Apr. 18, 1978
Filed:
Jan. 07, 1977
Ronald L Andrus, Elmira, NY (US);
Richard F Reade, Corning, NY (US);
Corning Glass Works, Corning, NY (US);
Abstract
The present invention is concerned with the production of glass-ceramic articles, wherein the predominant crystal phase consists of beta-spodumene solid solution or nepheline, but which have integral surface films containing alpha-iron. The method for producing such articles comprises two general steps. First, a glass article having a composition within a particularly-defined area within the Li.sub.2 O-FeO-Al.sub.2 O.sub.3 -SiO.sub.2 -TiO.sub.2 field or within the Na.sub.2 O-FeO-Al.sub.2 O.sub.3 -SiO.sub.2 -TiO.sub.2 field is heat treated under oxidizing conditions at temperatures of at least about 1000.degree. C. to cause crystallization in situ of the glass to a glass-ceramic article wherein beta-spodumene solid solution or nepheline crystals constitute the predominant crystal phase in the interior of the article and, at the same time, an integral surface layer containing hematite crystals is developed. Thereafter, second, the glass-ceramic article is exposed to an essentially dry reducing atmosphere at a temperature between about 500.degree.-800.degree. C. to effect the conversion of the hematite crystals to alpha-iron. The resulting surface layers can be highly electrically conductive and may demonstrate magnetic properties suitable for the recording, storage, and erasing of information.