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US3884823A
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US
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Ceramic permanent magnet
Assignee: Shell USA Inc
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Filing: 1971-09-27
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Granted: 1975-05-20
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Expires: 1991-09-27
Abstract
Abstract Magnetoplumbites having the formula MO.nFe203, wherein M is strontium and n is from about 3 to about 6.5, having densities of not less than 95% of the theoretical maximum, having average crystallite sizes of less than about 2.0 microns, preferably having at least 90% of their crystallites less than 2.5 microns in diameter and having crystallite orientations of not less than about 95%, yield permanent ceramic magnets having both high coercive forces and remanences.
Inventors
- 👤 Ronald L Clendenen
- 👤 Eugene E Olson
- 👤 Charles M Schlaudt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:16
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/01; C04B35/26; C04B35/2683
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
91 words
A PERMANENT CERAMIC MAGNET HAVING A NORMAL COERCIVE FORCE OF NOT LESS THAN 3600 OERSTEDS AND A REMANENCE OF NOT LESS THAN 3600 GAUSS CONSISTING ESSENTIALLY OF A MAGNETOPLUMBITE OF THE FORMULA MO.NFE2O3 WHEREIN M IS STRONTIUM AND N HAS A VALUE OF FROM 3 TO 6.5; AND HAVING A DENSITY OF NOT LESS THAN 95% OF THE THEORETICAL MAXIMUM, AN AVERAGE GRAIN SIZE OF LESS THAN 2.0 MICRONS, NOT LESS THAN 90% OF ITS GRAINS LESS THAN 2.5 MICRONS IN DIAMETER AND A CRYSTALLITE ORIENTATION OF NOT LESS THAN 95%.
Claim 2
Dependent Claim
91 words
A PERMANENT CERAMIC MAGNET HAVING A NORMAL COERCIVE FORCE OF NOT LESS THAN 3600 OERSTEDS AND A REMANENCE OF NOT LESS THAN 3600 GAUSS CONSISTING ESSENTIALLY OF A MAGNETOPLUMBITE OF THE FORMULA MO.NFE2O3 WHEREIN M IS STRONTIUM AND N HAS A VALUE OF FROM 3 TO 6.5; AND HAVING A DENSITY OF NOT LESS THAN 95% OF THE THEORETICAL MAXIMUM, AN AVERAGE GRAIN SIZE OF LESS THAN 2.0 MICRONS, NOT LESS THAN 90% OF ITS GRAINS LESS THAN 2.5 MICRONS IN DIAMETER AND A CRYSTALLITE ORIENTATION OF NOT LESS THAN 95%.
Claim 3
Dependent Claim
21 words
The magnet in accordance with claim 1 wherein M is strontium and n has a value of from 5.0 to 6.5.
Claim 4
Dependent Claim
30 words
The magnet in accordance with claim 2 having a density of not less than 98% of the theoretical maximum and an average grain size of from 0.6 to 1.5 micron.
References Cited (Backward Citations)
US3597357A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-05-19 | 1978-11-18 | 1979-05-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-19 | 1982-11-18 | 1983-05-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-19 | 1986-11-18 | 1987-05-20 | $7700.00 | Window Closed / Lapsed |