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US 5,476,821 AGranted
High modulus glass-ceramics containing fine grained spinel-type crystals
AssigneeCorning Incorporated
InventorsGeorge H. Beall, Linda R. Pinckney
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AssigneeCorning Incorporated
InventorsGeorge H. Beall, Linda R. Pinckney
Estimating the term…
This invention is directed at glass-ceramic articles, and methods for producing such articles, exhibiting Young's modulus between about 14 to 24.times.10.sup.6 psi and a fracture toughness in excess of 1.0 MPa.sqroot. in. The crystal phase assemblage is comprised predominately of generally uniformly-sized spinel-type crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase. The composition of these glass-ceramic articles is consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 20-35% Al.sub.2 O.sub.3, 0-25% MgO, 0-25% ZnO, at least about 10% MgO+ZnO, 0-20% TiO.sub.2, 0-10% ZrO.sub.2, 0-2% Li.sub.2 O and 0-8% NiO. However, if the Al.sub.2 O.sub.3 constituent is present in an amount less than about 25%, the TiO.sub.2 +ZrO.sub.2 +NiO amount should be at least 5%. The composition may also contain up to 5% of optional constituents selected from the group consisting of BaO, CaO, PbO, SrO, P.sub.2 O.sub.5, B.sub.2 O.sub.3, Ga.sub.2 O.sub.3, 0-5% R.sub.2 O and 0- 8% of a transition metal oxide; the R.sub.2 O selected from the group consisting of Na.sub.2 O, K.sub.2 O, Rb.sub.2 O and C.sub.2 O.
A glass-ceramic article exhibiting Young's modulus between about 14 to 24.times.10.sup.6 psi and a fracture toughness in excess of 1.0 MPa.multidot.m.sup.1/2, wherein the crystal phase assemblage is comprised predominately of generally uniformly-sized spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the article having an overall composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 20-35% Al.sub.2 O.sub.3, 7-25% MgO, 0-25% ZnO, at least about 10% MgO+ZnO, 0-20% TiO.sub.2, 0-10% ZrO.sub.2, 0-2% Li.sub.2 O, 0-8% NiO, with the proviso that, if the Al.sub.2 O.sub.3 amount is less than about 25%, the TiO.sub.2 +ZrO.sub.2 +NiO amount is at least 5%, and up to 5% of optional constituents selected from the group consisting of BaO, CaO, PbO, SrO, P.sub.2 O.sub.5, B.sub.2 O.sub.3, Ga.sub. 2 O.sub.3, 0-5% R.sub.2 O, wherein R.sub.2 O is selected from the group consisting of Na.sub.2 O, K.sub.2 O, Rb.sub.2 O, and Cs.sub.2 O and 0-8% of a transition metal oxide.
A method for making a glass-ceramic article which comprises the steps of
A magnetic memory storage device comprised of a head pad and rigid information disk, the disk comprising a rigid disc substrate having a layer of magnetic media on the surface thereof, wherein the substrate is comprised of a glass-ceramic exhibiting Young's modulus between about 14 to 24-10.sup.6 psi and a fracture toughness in excess of 1.0 MPa.multidot.m.sup.1/2, wherein the crystal phase assemblage is comprised predominately of generally uniformly-sized spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the article having an overall composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 20-35% Al.sub.2 O.sub.3, 0-25% MgO, 0-25% ZnO, at least about 10% MgO+ZnO, 0-20% TiO.sub.2, 0-10% ZrO.sub.2, 0-2% Li.sub.2 O, 0-8% NiO, with the proviso that, if the Al.sub.2 O.sub.3 amount is less than about 25%, the TiO.sub.2 +ZrO.sub.2 +NiO amount is at least 5%, and up to 5% of optional constituents selected from the group consisting of BaO, CaO, PbO, SrO, P.sub.2 O.sub.5, B.sub.2 O.sub.3, Ga.sub.2 O.sub.3, 0-5% R.sub.2 O, wherein R.sub.2 O is selected from the group consisting of Na.sub.2 O, K.sub.2 O, Rb.sub.2 O, and Cs.sub.2 O and 0-8% of a transition metal oxide.
A rigid information disk for use in a magnetic memory storage device consisting essentially of a substrate with a coating of magnetic media on a surface thereof, wherein the substrate is comprised of a glass-ceramic material exhibiting Young's modulus between about 14 to 24.times.10.sup.6 psi and a fracture toughness in excess of 1.0 MPa.multidot.m.sup.1/2, wherein the crystal phase assemblage is comprised predominately of generally uniformly-sized spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the article having an overall composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 20-35% Al.sub.2 O.sub.3, 0-25% MgO, 0-25% ZnO, at least about 10% MgO+ZnO, 0-20% TiO.sub.2, 0-10% ZrO.sub.2, 0-2% Li.sub.2 O, 0-8% NiO, with the proviso that, if the Al.sub.2 O.sub.3 amount is less than about 25%, the TiO.sub.2 +ZrO.sub.2 +NiO amount is at least 5%, and up to 5% of optional constituents selected from the group consisting of BaO, CaO, PbO, SrO, P.sub.2 O.sub.5, B.sub.2 O.sub.3, Ga.sub.2 O.sub.3, 0-5% R.sub.2 O, wherein R.sub.2 O is selected from the group consisting of Na.sub.2 O, K.sub.2 O, Rb.sub.2 O, and Cs.sub.2 O and 0-8% of a transition metal oxide.
Dependencies are inferred from the claim text.