US4224175A
Expired / Lapsed
US
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Process for the preparation of magnetic powders based on γ-Fe2 O3
Assignee: Montedison SpA
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Filing: 1979-04-13
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Granted: 1980-09-23
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Expires: 1999-04-13
Abstract
Abstract A process is disclosed for obtaining acicular magnetic particles of gamma -Fe2O3 modified with Fe++ and Co++ ions. The product thus obtained and magnetic tapes containing said product are also disclosed. A suspension of acicular gamma -Fe2O3 in an aqueous solution of soluble Fe++ and Co++ salts is prepared. NH3 is then added in such quantity that the molar ratio NH3/(Fe+++Co++) is between 2.1 and 3, and the whole mass is then heated up to 100 DEG -200 DEG C. When the molar ratio Fe++/Co++ is greater than about 2.5, it is necessary to operate in the presence of a metered quantity of oxygen or of an oxygen-containing gas; when the ratio is smaller or equal to about 2.5, the presence of a metered quantity of oxygen is optional.
Inventors
- 👤 Franco Montino
- 👤 Ariello R. Corradi
- 👤 Erminio Nonato
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 12:17
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70668; G11B5/70673
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
214 words
A process for preparing acicular magnetic particles consisting essentially of γ-Fe 2 O 3 modified with Fe 2+ and Co 2+ ions, by treating hydrothermally, and in the presence of an alkali, a suspension of acicular γ-Fe 2 O 3 in an aqueous solution of soluble Fe 2+ and Co 2+ salts, characterized in that as an alkali there is used NH 3 in such a quantity that the molar ratio NH.sub.3 /(Fe.sup.++ +Co.sup.++) is between 2.1 and 2.3; that the molar ratio Fe ++ /Co ++ in said solution is between 2 and 3; that the treatment is conducted at a temperature between 140° C. and 180° C.; and that when the molar ratio Fe ++ /Co ++ is greater than about 2.5 the process is conducted in the presence of oxygen or of an oxygen-containing gas, the quantity of oxygen not exceeding 28% of the stoichiometric amount required for oxidizing all the ferrous iron to the ferric state, while, when the ratio Fe ++ /Co ++ is less than or equal to about 2.5, the process is conducted either in the absence or in the presence of oxygen or of an oxygen-containing gas, the quantity of oxygen in that event being between 0% and 28% with respect to the above-defined stoichiometric amount.
Claim 2
Dependent Claim
214 words
A process for preparing acicular magnetic particles consisting essentially of γ-Fe 2 O 3 modified with Fe 2+ and Co 2+ ions, by treating hydrothermally, and in the presence of an alkali, a suspension of acicular γ-Fe 2 O 3 in an aqueous solution of soluble Fe 2+ and Co 2+ salts, characterized in that as an alkali there is used NH 3 in such a quantity that the molar ratio NH.sub.3 /(Fe.sup.++ +Co.sup.++) is between 2.1 and 2.3; that the molar ratio Fe ++ /Co ++ in said solution is between 2 and 3; that the treatment is conducted at a temperature between 140° C. and 180° C.; and that when the molar ratio Fe ++ /Co ++ is greater than about 2.5 the process is conducted in the presence of oxygen or of an oxygen-containing gas, the quantity of oxygen not exceeding 28% of the stoichiometric amount required for oxidizing all the ferrous iron to the ferric state, while, when the ratio Fe ++ /Co ++ is less than or equal to about 2.5, the process is conducted either in the absence or in the presence of oxygen or of an oxygen-containing gas, the quantity of oxygen in that event being between 0% and 28% with respect to the above-defined stoichiometric amount.
Claim 3
Dependent Claim
50 words
A process according to claim 1, characterized in that when the molar ratio Fe ++ /Co ++ is greater than 2.5 the quantity of oxygen present in the reaction is equal to 10% to 28% of the stoichiometric value required for oxidizing all the ferrous iron to the ferric state.
Claim 4
Dependent Claim
30 words
A process according to claim 1, characterized in that the soluble salts of Fe 2+ and Co 2+ are selected from the group consisting of sulphate, nitrate, chloride and acetate.
Claim 5
Dependent Claim
25 words
A process according to claim 1, characterized in that the concentration of γ-Fe 2 O 3 in the suspension is between 50 and 100 g/liter.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-09-23 | 1984-03-24 | 1984-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-09-23 | 1988-03-24 | 1988-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-09-23 | 1992-03-24 | 1992-09-23 | $7700.00 | Window Closed / Lapsed |