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US4457982A
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Acicular ferrimagnetic iron oxide and its preparation
Assignee: Emtec Magnetics GmbH
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Filing: 1983-01-28
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Granted: 1984-07-03
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Expires: 2003-01-28
Abstract
Abstract A modified acicular ferrimagnetic iron oxide which consists of a core of gamma-iron(III) oxide and a surrounding shell of gamma-iron(III) oxide modified by tin dioxide and carbon, and a process for its preparation.
Inventors
- 👤 Peter Rudolf
- 👤 Jenoe Kovacs
- 👤 Guenter Vaeth
- 👤 Manfred Ohlinger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 09:32
CPC Classifications
C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70657; C01P; C01P2002/00; C01P2002/50; C01P2002/52; C01P2002/54; C01P2004/00; C01P2004/10; C01P2004/80; C01P2004/82; C01P2004/84; C01P2006/00; C01P2006/42; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
70 words
A modified acicular ferrimagnetic iron oxide which consists of a core of gamma-iron(III) oxide and a surrounding shell of gamma-iron(III) oxide modified by tin dioxide and carbon, and wherein the amount of tin dioxide is from 0.15 to 1.5% by weight and the amount of carbon is from 0.1 to 1% by weight, the percentages in each case being based on the total amount of the modified ferrimagnetic iron oxide.
Claim 2
Dependent Claim
70 words
A modified acicular ferrimagnetic iron oxide which consists of a core of gamma-iron(III) oxide and a surrounding shell of gamma-iron(III) oxide modified by tin dioxide and carbon, and wherein the amount of tin dioxide is from 0.15 to 1.5% by weight and the amount of carbon is from 0.1 to 1% by weight, the percentages in each case being based on the total amount of the modified ferrimagnetic iron oxide.
Claim 3
Dependent Claim
112 words
A process for the preparation of a modified acicular ferrimagnetic iron oxide as claimed in claim 1, comprising depositing tin dioxide and an organic compound on a synthetic lepidocrocite, or an alpha-iron (III) oxide obtained therefrom by dehydration, said organic compound being liquid at room temperature and decomposable in the presence of iron oxide at from 350° to 500° C., reducing the synthetic lepidocrocite, or alpha-iron (III) oxide obtained therefrom by dehydration containing deposited tin dioxide and said organic compound, at from 350° to 500° C., to magnetite and then oxidizing the magnetite by means of oxygen-containing gases at from 200° to 450° C. to give said modified acicular ferrimagnetic iron oxide.
Claim 4
Dependent Claim
94 words
A process for the preparation of a modified acicular ferrimagnetic iron oxide as claimed in claim 1, comprising depositing an organo-tin compound which is decomposable at from 350° to 500° C. on a synthetic lepidocrocite, or an alpha-iron (III) oxide obtained therefrom by dehydration, reducing the synthetic lepidocrocite or an alpha-iron (III) oxide obtained therefrom by dehydration containing said deposited organo-tin compound, at from 350° to 500° C., to magnetite and then oxidizing the magnetite by means of oxygen-containing gases at from 200° to 450° C. to give said modified acicular ferrimagnetic iron oxide.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-07-03 | 1988-01-02 | 1988-07-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-07-03 | 1992-01-02 | 1992-07-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-07-03 | 1996-01-02 | 1996-07-03 | $7700.00 | Window Closed / Lapsed |