Patent US4308088A successfully refreshed from Google Patents.
US4308088A
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Macrocrystalline aluminum oxide and method for its manufacture
Assignee: Almatis Chemie GmbH
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Filing: 1979-11-19
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Granted: 1981-12-29
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Expires: 1999-11-19
Abstract
Abstract A method for producing hexagonal, laminar, alpha aluminum oxide monocrystals having a grain size of about 16 to about 250 microns, and a diameter to thickness ratio of about 3:1 to about 7:1. Aluminum hydroxide of particle size greater than 60 microns is calcined in the presence of a fluorine-containing mineralizer at a temperature of greater than 1200° C. but no more than 1450° C., and the desired grain size is separated from the calcinate.
Inventors
- 👤 Egon Cherdron
- 👤 Heinz Hellinghausen
- 👤 Alois Kramer
- 👤 Horst Pohland
- 👤 Avraham Metzer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 18:15
CPC Classifications
C; C01; C01F; C01F7/00; C01F7/02; C01F7/44; C01F7/441; C01F7/442; C30; C30B; C30B1/00; C30B1/10; C30B29/00; C30B29/10; C30B29/16; C30B29/20; C01P; C01P2004/00; C01P2004/20; C01P2004/22; C01P2004/54; C01P2004/60; C01P2004/61
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
71 words
Lapping material comprising hexagonal, laminar alpha aluminum oxide monocrystals containing at least 99% alpha Al 2 O 3 and having a grain size of about 16 to 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, at least about 40.5% by weight of said monocrystals having a grain size of at least 60 microns.
Claim 2
Dependent Claim
71 words
Lapping material comprising hexagonal, laminar alpha aluminum oxide monocrystals containing at least 99% alpha Al 2 O 3 and having a grain size of about 16 to 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, at least about 40.5% by weight of said monocrystals having a grain size of at least 60 microns.
Claim 3
Dependent Claim
72 words
Lapping material comprising hexagonal, laminar alpha aluminum oxide monocrystals containing at least 99% alpha Al 2 O 3 , and having a grain size of about 16 to 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, at least about 56.5% by weight of said monocrystals having a grain size of at least 40 microns.
Claim 4
Dependent Claim
72 words
Lapping material comprising hexagonal, laminar alpha aluminum oxide monocrystals containing at least 99% alpha Al 2 O 3 , and having a grain size of about 16 to 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, at least about 56.5% by weight of said monocrystals having a grain size of at least 40 microns.
Claim 5
Dependent Claim
20 words
The material of claim 1 or 2, wherein the monocrystals have a grain size of 26 to about 250 microns.
Claim 6
Dependent Claim
26 words
The material of claim 1 or 2 wherein at least about 79.5% by weight of said monocrystals have a grain size of at least 32 microns.
Claim 7
Dependent Claim
89 words
Method for producing hexagonal, laminar, alpha aluminum oxide monocrystals having a grain size of about 16 to about 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, comprising: calcining aluminum hydroxide of a grain size greater than 60 microns at a temperature greater than 1200° C. but no more than 1450° C., in the presence of at least one fluorine-containing mineralizer compound, and separating a desired grain fraction from the resulting calcinate.
Claim 8
Dependent Claim
89 words
Method for producing hexagonal, laminar, alpha aluminum oxide monocrystals having a grain size of about 16 to about 250 microns, as measured by the diameter of the hexagon, and a ratio of said diameter to the crystal thickness of about 3:1 to about 7:1, comprising: calcining aluminum hydroxide of a grain size greater than 60 microns at a temperature greater than 1200° C. but no more than 1450° C., in the presence of at least one fluorine-containing mineralizer compound, and separating a desired grain fraction from the resulting calcinate.
Claim 9
Dependent Claim
19 words
Method of claim 5 wherein the aluminum hydroxide has an average particle size of about 70 to 100 microns.
Claim 10
Dependent Claim
31 words
Method of claim 5 wherein the calcination is performed in the presence of seed crystals in a quantity of about 5 to about 50% by weight with respect to the monocrystals.
Claim 11
Dependent Claim
26 words
Method of claim 7 wherein the seed crystals are present in a quantity of about 20 to about 30% by weight with respect to the monocrystals.
Claim 12
Dependent Claim
27 words
Method as defined in claim 7 wherein aluminum oxide monocrystals which are the end product of the present process or are separately produced, are the seed crystals.
Claim 13
Dependent Claim
20 words
Method as defined in claim 5, 6, 7, 8 or 9 wherein calcination is effected in a reducing furnace atmosphere.
Claim 14
Dependent Claim
24 words
Method as defined in claim 10, wherein the reducing furnace atmosphere is produced by adjusting the ratio of fuel to primary and secondary air.
Claim 15
Dependent Claim
38 words
Method as defined in claim 10 wherein the reducing furnace atmosphere is produced in the calcination furnace by the addition of aluminum sulfate in quantities of about 1 to about 10 weight percent with respect to the monocrystals.
Claim 16
Dependent Claim
19 words
Method as defined in claim 12 wherein about 3 to about 5 weight percent of aluminum sulfate is added.
Claim 17
Dependent Claim
19 words
Method as defined in claim 10 wherein calcination is effected in the presence of scrapings from aluminum metal recovery.
Claim 18
Dependent Claim
27 words
Method as defined in claim 14 wherein the scrapings are added in an amount of about 0.3 to about 5 weight percent with respect to the monocrystals.
Claim 19
Dependent Claim
25 words
Method as defined in claim 5 wherein the mineralizer compound is present in a quantity of 0.001 to 1% by weight of the aluminum oxide.
References Cited (Backward Citations)
US2538959A
Cited
US3011870A
Cited
DE1092457B
Cited
US3121623A
Cited
US3175883A
Cited
DE1767511A1
Cited
US3718494A
Cited
US4019914A
Cited
US4130402A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-12-28 | 1985-06-29 | 1985-12-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-12-28 | 1989-06-29 | 1989-12-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-12-28 | 1993-06-29 | 1993-12-29 | $7700.00 | Window Closed / Lapsed |