Glass manufacturing – Processes – With chemically reactive treatment of glass preform
Patent
1981-08-20
1982-07-27
Fisher, Richard V.
Glass manufacturing
Processes
With chemically reactive treatment of glass preform
65 33, C03B 2702, C03B 3200, C03C 322
Patent
active
043415440
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.
REFERENCES:
patent: 2920971 (1960-01-01), Stookey
patent: 3573072 (1971-03-01), Duke et al.
patent: 3573073 (1971-03-01), Duke et al.
patent: 3720526 (1973-03-01), Duke et al.
Beall George H.
Pierson Joseph E.
Corning Glass Works
Fisher Richard V.
Janes Jr. Clinton S.
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