Chemically strengthenable machinable glass-ceramics
AssigneeCorning Incorporated
InventorsGeorge Halsey Beall, John Philip Finkeldey, Charlene Marie Smith
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Abstract
A glass-ceramic comprising, in weight percent on an oxide basis, of 50 to 70% SiO2, 0 to 20% Al2O3, 12 to 23% MgO, 0 to 4% Li2O, 0 to 10% Na2O, 0 to 10% K2O, 0 to 5% ZrO2, and 2 to 12% F, wherein the predominant crystalline phase of said glass-ceramic is a trisilicic mica, a tetrasilicic mica, or a mica solid solution between trisilicic and tetrasilicic, and wherein the total of Na2O+Li2O is at least 2 wt. %; wherein the glass-ceramic can be ion-exchanged.
Claims33
A glass-ceramic comprising, in weight percent on an oxide basis, of 50 to 70% SiO2, 0 to 20% Al2O3, 12 to 23% MgO, 0 to 4% Li2O, 0 to 10% Na2O, 0 to 10% K2O, 0 to 5% ZrO2, and 2 to 12% F, wherein the predominant crystalline phase of said glass-ceramic is a trisilicic mica, tetrasilicic mica, or a mica solid solution between trisilicic and tetrasilicic, and wherein the total of Na2O+Li2O is at least 2 wt. %;
- wherein the glass-ceramic can be ion-exchanged.
A glass-ceramic comprising, by weight percent on an oxide basis, 60 to 70% SiO2, 0 to 2% Al2O3, 15 to 20% MgO, 2 to 10% Na2O, 0 to 10% K2O, 0 to 3% Li2O, 0 to 5% ZrO2, and 3 to 7% F, wherein the predominant crystalline phase of said glass-ceramic is a tetrasilicic mica;
- wherein the glass-ceramic can be ion-exchanged.
A glass-ceramic comprising, by weight percent on an oxide basis, 50 to 65% SiO2, 9 to 16% Al2O3, 13 to 21% MgO, 0 to 3% Li2O, 1.5 to 8% Na2O, 0 to 6% K2O, 0 to 3% ZrO2, and 3 to 10% F, wherein the predominant crystalline phase of said glass-ceramic is a trisilicic mica;
- wherein the glass-ceramic can be ion-exchanged.
A glass-ceramic comprising:
- a silicate glass phase;
- and
- a crystalline phase predominantly consisting of a trisilicic mica, a tetrasilicic mica, or a mica solid solution between trisilicic and tetrasilicic.
The glass-ceramic according to any one of the preceding claims, having an average grain size of 20 microns or less.
The glass-ceramic according to any one of the preceding claims, having an average grain size of 2 microns or less.
The glass-ceramic according to any one of the preceding claims, comprising from about 30 wt. % to about 80 wt. % crystalline phase.
The glass-ceramic according to any one of the preceding claims, having a density of about 2 g/cc to about 3 g/cc.
The glass-ceramic according to any one of the preceding claims, having a Young's modulus of about 60 GPa to about 70 Gpa.
The glass-ceramic according to any one of the preceding claims, having a Shear modulus of about 18 GPa to about 30 Gpa.
The glass-ceramic according to any one of the preceding claims, having a fracture toughness of about 1 MPa·m0.5 to about 5.0 MPa·m0.5.
The glass-ceramic according to any one of the preceding claims, having a Vickers hardness of about 100 kgf to about 400 kgf.
The glass-ceramic according to any one of the preceding claims, having a Knoop hardness of about 150 kg/mm2 to about 300 kg/mm2.
The glass-ceramic according to any one of the preceding claims, having a Moh's hardness of about 3 to about 7.
The glass-ceramic according to any one of the preceding claims, having an opacity of ≥80% for a 1 mm thickness over the wavelength range from about 380 nm to about 740 nm.
The glass-ceramic according to any one of the preceding claims, having a Poisson's ratio of about 0.2 to about 0.3.
The glass-ceramic according to any one of the preceding claims, having a mechanical strength greater than 100 MPa.
The glass-ceramic according to any one of the preceding claims, having a porosity of 0% to 10%.
The glass-ceramic according to any one of the preceding claims, wherein the glass-ceramic is machinable.
The glass-ceramic according to any one of the preceding claims, which is ion-exchanged.
An article comprising the glass-ceramic of any one of the preceding claims.
A method for forming a glass ceramic comprising:
- melting a batch and forming a precursor glass comprising, in weight percent on an oxide basis, of 50 to 70% SiO2, 0 to 20% Al2O3, 12 to 23% MgO, 0 to 4% Li2O, 0 to 10% Na2O, 0 to 10% K2O, 0 to 5% ZrO2, and 2 to 12% F;
- wherein the total of Na2O+Li2O is at least 2 wt. %;
- annealing the precursor glass at a suitable temperature and for a suitable period of time;
- ceramming the precursor glass at suitable ceramming schedules and cooling to room temperature;
- optionally machining the resulting glass ceramic into the desired form;
- ion exchanging the glass-ceramic by placing the glass article in an alkali ion-containing salt bath exhibiting a temperature sufficiently below the glass strain point and holding it in the salt bath for time sufficient to complete ion exchange of ions in the glass-ceramic;
- and
- cooling the machinable glass-ceramic to room temperature.
Dependencies are inferred from the claim text.