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. 27, 1982
Filed:
Aug. 20, 1981
George H Beall, Big Flats, NY (US);
Joseph E Pierson, Painted Post, NY (US);
Corning Glass Works, Corning, NY (US);
Abstract
The present invention is concerned with glass-ceramic articles which are extremely resistant to impact and spontaneous delayed breakage, are capable of being sawn with a diamond wheel to a depth of over one-third the cross section thereof without breakage, and exhibit modulus of rupture values of at last 150,000 psi. The articles consist of a body portion and an integral surface compression layer having a depth of at least 0.005'. The body portion consists essentially, in weight percent, of about 8-13% Na.sub.2 O, 7-13% K.sub.2 O, 30-36% Al.sub.2 O.sub.3, 35-43% SiO.sub.2, and 6-10% RO.sub.2, wherein RO.sub.2 consists of 6-10% TiO.sub.2 and 0-4% ZrO.sub.2, wherein the molar ratio Al.sub.2 O.sub.3 :SiO.sub.2 is >0.5 but <0.6 and the molar ratio K.sub.2 O:Na.sub.2 O is >1:3 but <1 and contains nepheline solid solution crystals corresponding to the formula Na.sub.8-x K.sub.x Al.sub.8 Si.sub.8 O.sub.32, with x varying from 0.25-4.73, as the predominant crystal phase. The surface layer contains kalsilite as the predominant crystal phase and is produced by subjecting the base glass-ceramic article to an ion exchange reaction wherein K.sup.+ ions replace at least part of the Na.sup.+ ions in the nepheline solid solution crystals to convert those crystals to kalsilite.