| 摘要 |
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 Li2O-FeO-Al2O3-SiO2-TiO2 field or within the Na2O-FeO-Al2O3-SiO2-TiO2 field is heat treated under oxidizing conditions at temperatures of at least about 1000 DEG 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 DEG -800 DEG 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.
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