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US4539129A
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Barium ferrite particles and process for producing said particles
Assignee: Toda Kogyo Corp
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Filing: 1983-08-23
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Granted: 1985-09-03
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Expires: 2003-08-23
Abstract
Abstract Barium ferrite particles of a coercive force of not more than 1,000 Oe suitable for use as a magnetic material for magnetic recording and a process for producing said particles are disclosed herein.
Inventors
- 👤 Norimichi Nagai
- 👤 Nanao Horiishi
- 👤 Masao Kiyama
- 👤 Toshio Takada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:40
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
38 words
Barium ferrite particles in a form of plate-like having a specific surface area of 0.5 to 5.0 m 2 /g, a maximum magnetization of 35 to 60 emu/g and a coercive force of not more than 1,000 Oe.
Claim 2
Dependent Claim
38 words
Barium ferrite particles in a form of plate-like having a specific surface area of 0.5 to 5.0 m 2 /g, a maximum magnetization of 35 to 60 emu/g and a coercive force of not more than 1,000 Oe.
Claim 3
Dependent Claim
17 words
The particles of claim 1, wherein their specific surface area is 2 to 4 m 2 /g.
Claim 4
Dependent Claim
14 words
The particles of claim 1, wherein their maximum magnetization is 42 to 47 emu/g.
Claim 5
Dependent Claim
14 words
The particles of claim 1, wherein their coercive force is 600 to 800 Oe.
Claim 6
Dependent Claim
14 words
The particles of claim 1, wherein they are in a form of hexagonal plate-like.
Claim 7
Dependent Claim
47 words
A process for producing barium ferrite particles in a form of plate-like, comprising subjecting an alkaline suspension containing acicular particles of α-FeO(OH) with a specific surface area of 10 to 25 m 2 /g and barium ions to autoclaving at a temperature of 250° to 360° C.
Claim 8
Dependent Claim
47 words
A process for producing barium ferrite particles in a form of plate-like, comprising subjecting an alkaline suspension containing acicular particles of α-FeO(OH) with a specific surface area of 10 to 25 m 2 /g and barium ions to autoclaving at a temperature of 250° to 360° C.
Claim 9
Dependent Claim
23 words
The process of claim 6, wherein the acicular particles of α-FeO(OH) have the specific surface area of 15 to 18 m 2 /g.
Claim 10
Dependent Claim
23 words
The process of claim 6, wherein the acicular particles of α-FeO(OH) have an apparent density of not more than 0.08 g/cm 3 .
Claim 11
Dependent Claim
23 words
The process of claim 6, wherein the acicular particles f α-FeO(OH) have a tap density of not more than 0.2 g/cm 3 .
Claim 12
Dependent Claim
34 words
The process of claim 6, wherein the acicular particles of α-FeO(OH) have the apparent density of not more than 0.08 g/cm 3 and the tap density of not more than 0.2 g/cm 3 .
Claim 13
Dependent Claim
13 words
The process of claim 6, wherein the temperature is 280° to 320° C.
Claim 14
Dependent Claim
42 words
The process of claim 6, wherein the acicular particles of α-FeO(OH) are present in the suspension in an amount of at least 6 times based on the amount of the barium ions and calculated as the atomic ratio of Fe(III) to Ba.
Claim 15
Dependent Claim
42 words
The process of claim 12, wherein the acicular particles of α-FeO(OH) are present in the suspension in an amount of 6 to 8 times based on the amount of the barium ions and calculated as the atomic ratio of Fe(III) to Ba.
References Cited (Backward Citations)
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Cited
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Cited
EP0039773A1
Cited
US4401643A
Cited
JPS57198607A
Cited
US4425250A
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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) | 1988-09-02 | 1989-03-04 | 1989-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-09-02 | 1993-03-04 | 1993-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-09-02 | 1997-03-04 | 1997-09-03 | $7700.00 | Window Closed / Lapsed |