US4296149A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Manufacture of acicular cobalt-containing magnetic iron oxide
Assignee: Emtec Magnetics GmbH
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Filing: 1980-01-29
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Granted: 1981-10-20
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Expires: 2000-01-29
Abstract
Abstract A process for the manufacture of acicular magnetic iron oxide consisting of a core of gamma-iron(III) oxide and a ferrite shell which contains, based on the total amount of magnetic material, from 0.2 to 12 percent by weight of cobalt(II) ions and from 0.1 to 15 percent by weight of iron(II) ions, wherein a solution containing cobalt(II) hydroxide and iron(II) hydroxide is applied to acicular gamma-iron(III) oxide particles and the latter are heated at 100°-220° C.
Inventors
- 👤 Peter Rudolf
- 👤 Werner Steck
- 👤 Helmut Jakusch
- 👤 Guenter Vaeth
- 👤 Christof Jaeckh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:48
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: 2
Claim 1
Independent Claim
163 words
A process for the manufacture of acicular, magnetic iron oxide consisting of a core of gamma-iron(III) oxide surrounded by a ferrite shell which contains, based on the amount of magnetic material, from 0.2 to 12 percent by weight of cobalt(II) ions and from 0.1 to 15 percent by weight of iron(II) ions, which process comprises: suspending acicular gamma-iron(III) oxide in water, adding to said suspension an aqueous solution containing cobalt(II) ions, followed by the addition of an aqueous base to bring the pH to not less than 10, both additions being made at room temperature, thereafter introducing an aqueous solution containing iron(II) ions under an inert gas atmosphere, with continued stirring, and after the cobalt(II) hydroxide and iron(II) hydroxide has precipitated under the inert gas atmosphere, the solid product is filtered off, washed neutral with water and heated at from 100° to 200° C. for from one to seven hours, the steps of stirring, precipitating and filtering all taking place at room temperature.
Claim 2
Dependent Claim
163 words
A process for the manufacture of acicular, magnetic iron oxide consisting of a core of gamma-iron(III) oxide surrounded by a ferrite shell which contains, based on the amount of magnetic material, from 0.2 to 12 percent by weight of cobalt(II) ions and from 0.1 to 15 percent by weight of iron(II) ions, which process comprises: suspending acicular gamma-iron(III) oxide in water, adding to said suspension an aqueous solution containing cobalt(II) ions, followed by the addition of an aqueous base to bring the pH to not less than 10, both additions being made at room temperature, thereafter introducing an aqueous solution containing iron(II) ions under an inert gas atmosphere, with continued stirring, and after the cobalt(II) hydroxide and iron(II) hydroxide has precipitated under the inert gas atmosphere, the solid product is filtered off, washed neutral with water and heated at from 100° to 200° C. for from one to seven hours, the steps of stirring, precipitating and filtering all taking place at room temperature.
References Cited (Backward Citations)
US3081264A
Cited
US3573980A
Cited
GB1268458A
Cited
GB1318579A
Cited
DE2100390A1
Cited
GB1432643A
Cited
GB1441183A
Cited
US4188302A
Cited
DE2811473A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-10-19 | 1985-04-20 | 1985-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-10-19 | 1989-04-20 | 1989-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-10-19 | 1993-04-20 | 1993-10-20 | $7700.00 | Window Closed / Lapsed |