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US4083709A
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Method for making glass-ceramics with ferrimagnetic surfaces
Assignee: Corning Glass Works
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Filing: 1977-01-07
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Granted: 1978-04-11
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Expires: 1997-01-07
Abstract
Abstract This invention relates to the manufacture of glass-ceramic articles having integral surface layers exhibiting ferrimagnetic behavior. More specifically, this invention is directed to glass bodies having compositions within the Li 2 O-Al 2 O 3 -Fe 2 O 3 -SiO 2 -TiO 2 base system, and that additionally contain NiO and/or CoO, which, when heat treated under oxidizing conditions to effect crystallization in situ to glass-ceramic articles, spontaneously develop crystallites of NiFe 2 O 4 and/or CoFe 2 O 4 in the surfaces thereof. The ferrite surfaces can be magnetized in a strong magnetic field and demonstrate magnetic properties eminently suitable for the recording, storage, and erasing of information.
Inventors
- 👤 Richard F. Reade
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:13
CPC Classifications
H; H01; H01F; H01F10/00; H01F10/08; H01F10/10; H01F10/18; H01F10/20; C; C03; C03C; C03C10/00; C03C10/0018; C03C10/0027; C03C10/0081; Y; Y10; Y10T; Y10T428/00; Y10T428/31; Y10T428/315
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
241 words
A method for making a glass-ceramic article composed of a body portion and a thin integral surface layer demonstrating ferrimagnetic properties, said body portion consisting essentially of beta-spodumene solid solution crystals dispersed within a glassy matrix and said surface layer consisting essentially of NiFe 2 O 4 and/or CoFe 2 O 4 crystallites dispersed within a glassy matrix, consisting of the steps of: (a) melting a batch for a glass consisting essentially, in weight percent on the oxide basis, of about 2.5-5.5% Li 2 O, 16-27% Al 2 O 3 , 1-3% Fe 2 O 3 , 40-75% SiO 2 , 1.75-6% TiO 2 , 0.5-3% NiO, and/or 1-3% CoO, the sum NiO + CoO not exceeding about 4%, said Li 2 O, Al 2 O 3 , and SiO 2 being present in a molar ratio of about Li 2 O.Al 2 O 3 . nSiO 2 , wherein n ranges between about 2-8; (b) simultaneously cooling the melt to at least within the transformation range and shaping a glass article therefrom; and (c) exposing said glass article only in an oxidizing atmosphere to a temperature between about 900°-1300° C. for a period of time sufficient to cause the growth in situ of beta-spodumene solid solution crystals in the body portion of said glass article and of NiFe 2 O 4 and/or CoFe 2 O 4 crystallites in an integral surface layer on said article thereby producing a glass-ceramic article.
Claim 2
Independent Claim
241 words
A method for making a glass-ceramic article composed of a body portion and a thin integral surface layer demonstrating ferrimagnetic properties, said body portion consisting essentially of beta-spodumene solid solution crystals dispersed within a glassy matrix and said surface layer consisting essentially of NiFe 2 O 4 and/or CoFe 2 O 4 crystallites dispersed within a glassy matrix, consisting of the steps of: (a) melting a batch for a glass consisting essentially, in weight percent on the oxide basis, of about 2.5-5.5% Li 2 O, 16-27% Al 2 O 3 , 1-3% Fe 2 O 3 , 40-75% SiO 2 , 1.75-6% TiO 2 , 0.5-3% NiO, and/or 1-3% CoO, the sum NiO + CoO not exceeding about 4%, said Li 2 O, Al 2 O 3 , and SiO 2 being present in a molar ratio of about Li 2 O.Al 2 O 3 . nSiO 2 , wherein n ranges between about 2-8; (b) simultaneously cooling the melt to at least within the transformation range and shaping a glass article therefrom; and (c) exposing said glass article only in an oxidizing atmosphere to a temperature between about 900°-1300° C. for a period of time sufficient to cause the growth in situ of beta-spodumene solid solution crystals in the body portion of said glass article and of NiFe 2 O 4 and/or CoFe 2 O 4 crystallites in an integral surface layer on said article thereby producing a glass-ceramic article.
Claim 3
Dependent Claim
23 words
A method according to claim 1 wherein said glass article is heated to a temperature between about 900°-1300° C. for about 0.25-24 hours.
Claim 4
Dependent Claim
39 words
A method according to claim 1 wherein said glass article is heated to a temperature between about 700°-850° C. for a period of time sufficient to cause the development of nuclei therein and is thereafter heated to 900°-1300° C.
Claim 5
Dependent Claim
33 words
A method according to claim 3 wherein said glass article is heated to a temperature between about 700°-850° C. for about 1-6 hours and thereafter heated to 900°-1300° C. for about 1-8 hours.
Claim 6
Dependent Claim
19 words
A method according to claim 1 wherein said surface layer is no more than about several thousand angstroms thick.
References Cited (Backward Citations)
US3962514A
Cited
US4030903A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-04-10 | 1981-10-10 | 1982-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-04-10 | 1985-10-10 | 1986-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-04-10 | 1989-10-10 | 1990-04-11 | $7700.00 | Window Closed / Lapsed |