Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Patent
1980-10-31
1982-01-12
Robinson, Ellis P.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
65 3014, 65 33, 428325, 428334, 428410, 428428, 501 6, B32B 1706, C03C 2100
Patent
active
043105955
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 least 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.
REFERENCES:
patent: 2920971 (1960-01-01), Stookey
patent: 3573073 (1971-03-01), Duke
Beall George H.
Pierson Joseph E.
Corning Glass Works
Janes Jr. Clinton S.
Robinson Ellis P.
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