Fine-grained glass-ceramics
AssigneeCorning Incorporated
InventorsGeorge H. Beall, Linda R. Pinckney
Life of this patent
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Abstract
A glass-ceramic article, such as an information disk substrate, and a method of making the article. The glass-ceramic has Mg-rich pyroxene and spinel-type predominate crystal phases and a composition at least 92% of which consists essentially of 35-60% SiO.sub.2, 10-30% Al.sub.2 O.sub.3, 12-30% MgO, 0-10% ZnO, 5-20% TiO.sub.2, and 0-8% NiO.
Claims24
A glass-ceramic article exhibiting an MOR of at least about 15,000 psi, a Knoop hardness value of greater than at least about 760 KHN, a Young's modulus about 20.times.10.sup.6 psi and a fracture toughness in excess of 1.0 MPa.m.sup.1/2, wherein the crystal phase assemblage is comprised predominately of magnesium containing crystals having a pyroxene structure represented by the formula (M.sub.2)(M.sub.1)Si.sub.2 O.sub.6 where M.sub.2 has a coordination of 6-8 oxygen atoms and M.sub.1 is octahedrally coordinated and spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the article having an overall composition at least 92 % of which consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 10-30% Al.sub.2 O.sub.3, 12-30% MgO, 0-10% ZnO, 5-20% TiO.sub.2, and 0-8% NiO.
A method for making a glass-ceramic article which comprises the steps of
- a. melting a batch for a glass composition at least 92% of which consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 10-30% Al.sub.2 O.sub.3, 12-30% MgO, 0-10% ZnO, 5-20% TiO.sub.2, and 0-8% NiO,
- b. heating the glass article to a temperature range of about 750.degree.-850.degree. C.,
- c. maintaining the temperature for a time sufficient to cause the article to obtain a high degree of nucleation,
- d. heating the glass article to a temperature range about 900.degree.-1100.degree. C. and,
- e. maintaining the temperature for a time sufficient to cause the article to crystallize in situ forming a crystallized glass article which exhibits crystal phase assemblage comprised predominately of generally uniformly-sized magnesium containing crystals having a pyroxene structure represented by the formula (M.sub.2)(M.sub.1)Si.sub.2 O.sub.6 where M.sub.2 has a coordination of 6-8 oxygen atoms and M.sub.1 is octahedrally coordinated and spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase.
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 an MOR of at least about 15,000 psi, a Knoop hardness value of greater than at least about 760 KHN, a Young's modulus about 20.times.10.sup.6 psi and a fracture toughness in excess of 1.0 MPa.m.sup.1/2, wherein the crystal phase assemblage is comprised predominately of magnesium containing crystals having a pyroxene structure represented by the formula (M.sub.2)(M.sub.1)Si.sub.2 O.sub.6 where M.sub.2 has a coordination of 6-8 oxygen atoms and M.sub.1 is octahedrally coordinated and spinel crystals which are uniformly dispersed within a highly siliceous residual glass matrix phase, the substrate having an overall composition at least 92 % of which consists essentially, expressed in terms of weight percent on the oxide basis, of 35-60% SiO.sub.2, 10-30% Al.sub.2 O.sub.3, 12-30% MgO, 0-10% ZnO, 5-20% TiO.sub.2, and 0-8% NiO.
Dependencies are inferred from the claim text.