US4268540A
Expired / Lapsed
US
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Particles for magnetic recording
Assignee: QUANTEGY MEDIA Corp
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Filing: 1980-02-13
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Granted: 1981-05-19
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Expires: 2000-02-13
Abstract
Abstract Improved particles for magnetic recording are provided by coating gamma ferric oxide with a mixture of barium, strontium, lead or calcium and a trivalent iron oxide. The particles have enhanced coercivity and the coercivity is relatively unaffected by elevated temperatures.
Inventors
- 👤 Lawrence M. Scott
- 👤 Irving W. Wolf
- 👤 Yu C. Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 05:50
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70657
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
126 words
The process of making magnetic particles consisting essentially of the following steps: a. forming a suspension of acicular gamma ferric oxide in an aqueous solution of a salt of a metal selected from the group consisting of barium, strontium, lead and calcium, and a soluble trivalent iron salt, adding an alkali to form a precipitate and drying the resulting mixture of the precipitated decomposition products of said salts and acicular gamma ferric oxide, b. heating said dry mixture in an atmosphere containing oxygen at a temperature of at least 300° F. to produce a magnetic particle having a core of acicular gamma ferric oxide and a coating comprising a mixture of an oxide of metal selected from barium, strontium, lead and calcium and trivalent iron oxide.
Claim 2
Dependent Claim
126 words
The process of making magnetic particles consisting essentially of the following steps: a. forming a suspension of acicular gamma ferric oxide in an aqueous solution of a salt of a metal selected from the group consisting of barium, strontium, lead and calcium, and a soluble trivalent iron salt, adding an alkali to form a precipitate and drying the resulting mixture of the precipitated decomposition products of said salts and acicular gamma ferric oxide, b. heating said dry mixture in an atmosphere containing oxygen at a temperature of at least 300° F. to produce a magnetic particle having a core of acicular gamma ferric oxide and a coating comprising a mixture of an oxide of metal selected from barium, strontium, lead and calcium and trivalent iron oxide.
Claim 3
Dependent Claim
87 words
The process of claim 1 wherein quantities of the starting materials are selected to yield a product having the composition (MO).sub.x (Fe.sub.2 O.sub.3).sub.y (Fe.sub.2 O.sub.3).sub.z wherein M is the metal selected from barium, strontium, lead and calcium, (Fe 2 O 3 ) y is the oxide formed by the trivalent iron salt and (Fe 2 O 3 ) z is the gamma ferric oxide and wherein the ratio of x to z is from 0.04 to 0.2 and the ratio of x+y/z is from 0.1 to 0.4.
References Cited (Backward Citations)
US4125474A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-05-18 | 1984-11-17 | 1985-05-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-05-18 | 1988-11-17 | 1989-05-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-05-18 | 1992-11-17 | 1993-05-19 | $7700.00 | Window Closed / Lapsed |