US4133676A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Acicular ferromagnetic metal particles and method for preparation of the same
Assignee: Maxell Ltd
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Filing: 1977-12-16
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Granted: 1979-01-09
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Expires: 1997-12-16
Abstract
Abstract Acicular ferromagnetic metal particles having a particle size of 0.1 to 1 μm and a dimension of crystallite-size of not more than about 215 A in the effective thickness of the crystallite in the direction perpendicular to the reflecting plane (110), which have a high coercive force, preferably not less than 1,400 oersteds and are useful for a high-density magnetic recording tape, video mother tape, or permanent magnet material, and a method for the preparation of the ferromagnetic metal particles comprising reducing with heating goethite particles which are prepared by treating a ferrous salt with a large amount of a basic agent, particularly an alkali metal hydroxide.
Inventors
- 👤 Masakazu Oshimura
- 👤 Kenichi Yokoyama
- 👤 Yukihiro Hayashi
- 👤 Akira Miyake
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:36
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065; B; B22; B22F; B22F9/00; B22F9/16; B22F9/18; B22F9/20; B22F9/22
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
52 words
An acicular ferromagnetic metal particle comprising iron element as the essential component, which has a particle size of 0.1 to 1 μm and a dimension of crystallite-size of not more than 215 A in the effective thickness of the crystallite in the direction perpendicular to the reflecting plane (110) (D 110 ).
Claim 2
Dependent Claim
52 words
An acicular ferromagnetic metal particle comprising iron element as the essential component, which has a particle size of 0.1 to 1 μm and a dimension of crystallite-size of not more than 215 A in the effective thickness of the crystallite in the direction perpendicular to the reflecting plane (110) (D 110 ).
Claim 3
Dependent Claim
22 words
The acicular ferromagnetic metal particle according to claim 1, wherein the D 110 is in the range of 140 to 200 A.
Claim 4
Dependent Claim
20 words
The acicular ferromagnetic metal particle according to claim 1, which has a coercive force of not less than 1,400 oersteds.
Claim 5
Dependent Claim
22 words
The acicular ferromagnetic metal particle according to claim 3, wherein the coercive force is in the range of 1,400 to 1,700 oersteds.
Claim 6
Dependent Claim
21 words
The acicular ferromagnetic metal particle according to claim 1, which has a maximum magnetization (δs) of not less than 120 emu/g.
Claim 7
Dependent Claim
22 words
The acicular ferromagnetic metal particle according to claim 5, wherein the maximum magnetization is in the range of 129 to 150 emu/g.
Claim 8
Independent Claim
86 words
A method for preparation of an acicular ferromagnetic metal particle having a high coercive force, which comprises adding an aqueous solution of a ferrous salt to an aqueous solution of a basic agent for precipitating ferrous hydroxide or insoluble ferrous salt, passing through an oxygen-containing gas to the mixture to produce an α-ferric oxyhydroxide, and reducing the α-ferric oxyhydroxide with heating with a reducing gas, said basic agent being used in an amount of not less than 6 mol per 1 mol of the ferrous salt.
Claim 9
Independent Claim
86 words
A method for preparation of an acicular ferromagnetic metal particle having a high coercive force, which comprises adding an aqueous solution of a ferrous salt to an aqueous solution of a basic agent for precipitating ferrous hydroxide or insoluble ferrous salt, passing through an oxygen-containing gas to the mixture to produce an α-ferric oxyhydroxide, and reducing the α-ferric oxyhydroxide with heating with a reducing gas, said basic agent being used in an amount of not less than 6 mol per 1 mol of the ferrous salt.
Claim 10
Dependent Claim
15 words
The method according to claim 7, wherein the basic agent is an alkali metal hydroxide.
Claim 11
Dependent Claim
24 words
The method according to claim 8, wherein the basic agent is a member selected from the group consisting of sodium hydroxide and potassium hydroxide.
Claim 12
Dependent Claim
27 words
The method according to claim 8, wherein the basic agent is used in an amount of 8 to 30 mol per 1 mol of the ferrous salt.
Claim 13
Dependent Claim
29 words
The method accoding to claim 10, wherein the ferrous salt is used in an amount of 0.2 to 0.5 mol/l based on the whole volume of the reaction mixture.
Claim 14
Dependent Claim
23 words
The method according to claim 7, wherein the reduction of α-ferric oxyhydroxide is carried out at a temperature of 340 to 420° C.
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) | 1982-01-08 | 1982-07-10 | 1983-01-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-01-08 | 1986-07-10 | 1987-01-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-01-08 | 1990-07-10 | 1991-01-09 | $7700.00 | Window Closed / Lapsed |