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. 11, 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 instant invention relates to the production of glass-ceramic articles, wherein the predominant crystal phase is beta-quartz solid solution and/or beta-spodumene solid solution, but which have a thin, integral, tightly-bonded surface film containing crystals exhibiting the structure of magnetite. The preferred method of production for such articles requires three general steps. First, a glass article having a particular composition within the Li.sub.2 O--FeO--Al.sub.2 O.sub.3 --SiO.sub.2 field nucleated with TiO.sub.2 is heat treated in air or other oxidizing atmosphere to yield a glass-ceramic article through the crystallization in situ of beta-quartz solid solution and/or beta-spodumene solid solution crystals. Simultaneously during this heat treatment, a surface layer containing hematite is developed. Second, the glass-ceramic article is subjected to a hot acid bath. Third, the acid-washed article is heat treated in a H.sub.2 O-containing reducing atmosphere to convert the hematite crystals to magnetite. The resulting films demonstrate high coercive forces and saturation magnetization comparable to that of magnetite and other ceramic ferrite materials.