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US 4,396,720 AGranted
Transparent glass-ceramics containing mullite
AssigneeCorning Glass Works
InventorsGeorge H. Beall, John F. MacDowell, Mark P. Taylor
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AssigneeCorning Glass Works
InventorsGeorge H. Beall, John F. MacDowell, Mark P. Taylor
Estimating the term…
This invention is concerned with the production of substantially transparent glass-ceramic articles containing mullite as the predominant crystal phase which can be prepared by crystallizing in situ precursor glasses capable of being melted at temperatures no higher than 1650.degree. C. The inventive articles consist essentially, in weight percent, of 1070% SiO.sub.2, 7-40% B.sub.2 O.sub.3, 14-50% Al.sub.2 O.sub.3, 0-35% RO, wherein RO consists of at least one member of the group in the indicated proportions of 015% MgO, 0-20% CaO, 0-30% SrO, 0-30% BaO, and 0-30% PbO, and 0-30% R.sub.2 O, wherein R.sub.2 O consists of at least one member of the group in the indicated proportions of 0-10% Li.sub.2 O, 0-15% Na.sub.2 O, 0-25% K.sub.2 O, 0-25% Rb.sub.2 O, and 0-25% Cs.sub.2 O, the mole ratio Al.sub.2 O.sub.3 :RO+R.sub.2 O>1.3. Where 0.01-1% Cr.sub.2 O.sub.3 is included in the composition, the glass-ceramic will exhibit broad absorption over the visible region of the radiation spectrum, strong fluorescence in the red and near infrared portions of the spectrum where exposed to ultraviolet and/or visible radiation, and relatively little overlap of the absorption and fluorescent spectra.
A substantially transparent glass-ceramic article containing mullite as the predominant crystal phase which can be prepared from a precursor glass capable of being melted at temperatures no higher than 1650.degree. C. and which can be crystallized at high viscosities, i.e., about 10.sup.9 -10.sup.12 poises, said glass-ceramic article consisting essentially, expressed in terms of weight percent on the oxide basis, of 40-60% SiO.sub.2, 12-30% B.sub.2 O.sub.3, 17.5-27.5% Al.sub.2 O.sub.3, and 3-13% Na.sub.2 O and/or K.sub.2 O, and wherein the mole ratio Al.sub.2 O.sub.3 :Na.sub.2 O+K.sub.2 O 1.75.
A substantially transparent glass-ceramic article containing mullite as the predominant crystal phase which can be prepared from a precursor glass capable of being melted at temperatures no higher than 1650.degree. C. and which can be crystallized in situ at high viscosities, i.e., about 10.sup.9 -10.sup.12 poises, said glass-ceramic article consisting essentially, expressed in terms of weight percent on the oxide basis, of 15-45% SiO.sub.2, 20-30% B.sub.2 O.sub.3, 20-40% Al.sub.2 O.sub.3, and 5-30% RO, wherein RO consists of at least one member of the group in the indicated proportions of 0-15% MgO, 0-20% CaO, 0-30% SrO, and 0-30% BaO, and wherein the mole ratio Al.sub.2 O.sub.3 :RO<1.75.
Dependencies are inferred from the claim text.