US4548801A
Expired / Lapsed
US
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Plate-like barium ferrite particles for use in magnetic recording and process for producing the same
Assignee: Toda Kogyo Corp
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Filing: 1984-02-02
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Granted: 1985-10-22
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Expires: 2004-02-02
Abstract
Abstract Disclosed herein are the plate-like barium ferrite particles for use in magnetic recording, showing a specific surface area of 11 to 50 m 2 /g, a value of magnetization of higher than 25 emu/g in a magnetic field of 10 KOe and a coercive force of 600 to 1100 Oe, and a process for producing the same.
Inventors
- 👤 Norimichi Nagai
- 👤 Nanao Horiishi
- 👤 Masao Kiyama
- 👤 Toshio Takada
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:57
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/10; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; B; B82; B82Y; B82Y30/00; C; C01; C01G; C01G49/00; C01G49/0018; C01G49/0036; C01P; C01P2004/00; C01P2004/01; C01P2004/04; C01P2004/20; C01P2004/60; C01P2004/62; C01P2004/64; C01P2006/00; C01P2006/12; C01P2006/42
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
52 words
Plate-like barium ferrite particles of the formula BaO.6 Fe 2 O 3 for use in magnetic recording, exhibiting a specific surface area of 11 to 50 m 2 /g, a magnetization of higher than 25 emu/g in a magnetic field of 10 kOe and a coercive force of 600 to 1100 Oe.
Claim 2
Dependent Claim
52 words
Plate-like barium ferrite particles of the formula BaO.6 Fe 2 O 3 for use in magnetic recording, exhibiting a specific surface area of 11 to 50 m 2 /g, a magnetization of higher than 25 emu/g in a magnetic field of 10 kOe and a coercive force of 600 to 1100 Oe.
Claim 3
Dependent Claim
23 words
Plate-like barium ferrite particles according to claim 1, exhibiting a specific surface area in a range of 15 to 40 m 2 /g.
Claim 4
Dependent Claim
23 words
Plate-like barium ferrite particles according to claim 1, exhibiting a magnetization of higher than 45 emu/g in a magnetic field of 10 KOe.
Claim 5
Dependent Claim
20 words
Plate-like barium ferrite particles according to claim 1, exhibiting a coercive force in a range of 600 to 800 Oe.
Claim 6
Dependent Claim
143 words
A process for producing plate-like barium ferrite particles of the formula BaO.6Fe 2 O 3 for use in magnetic recording exhibiting a specific surface area in a range of 11 to 50 m 2 /g, a magnetization of higher than 25 emu/g and a coercive force in a range of 600 to 1100 Oe, comprising the steps of autoclaving an aqueous alkaline suspension of pH of higher than 11 which contains Fe(III) and Ba ions at an atomic ratio of Fe(III) to Ba ions of 6:1 to 8:1 at a temperature of 110° to 190° C., to form fine particles of 2BaO.9Fe 2 O 3 ,and then autoclaving said aqueous suspension containing the thus formed 2BaO.9Fe 2 O 3 at a temperature of 280° to 320° C., thereby converting said fine particles of 2BaO.9Fe 2 O 3 into said plate-like barium ferrite particles.
Claim 7
Dependent Claim
143 words
A process for producing plate-like barium ferrite particles of the formula BaO.6Fe 2 O 3 for use in magnetic recording exhibiting a specific surface area in a range of 11 to 50 m 2 /g, a magnetization of higher than 25 emu/g and a coercive force in a range of 600 to 1100 Oe, comprising the steps of autoclaving an aqueous alkaline suspension of pH of higher than 11 which contains Fe(III) and Ba ions at an atomic ratio of Fe(III) to Ba ions of 6:1 to 8:1 at a temperature of 110° to 190° C., to form fine particles of 2BaO.9Fe 2 O 3 ,and then autoclaving said aqueous suspension containing the thus formed 2BaO.9Fe 2 O 3 at a temperature of 280° to 320° C., thereby converting said fine particles of 2BaO.9Fe 2 O 3 into said plate-like barium ferrite particles.
Claim 8
Dependent Claim
18 words
A process according to claim 5, wherein the source of Fe(III) is ferric chloride, ferric nitrate or gamma-FeOOH.
Claim 9
Dependent Claim
18 words
A process according to claim 5, wherein the source of Ba ions is Ba (OH) 2 or BaO.
Claim 10
Dependent Claim
147 words
Plate-like barium ferrite particles of the formula BaO.6Fe 2 O 3 for use in magnetic recording exhibiting a specific surface area in a range of 11 to 50 m 2 /g, a magnetization of higher than 25 emu/g in a magnetic field of 10 KOe and a coercive force in a range of 600 to 1100 Oe, produced by a process comprising the steps of autoclaving an aqueous alkaline suspension of pH of higher than 11, containing Fe(III) and Ba ions at an atomic ratio in a range of 6:1 to 8:1 at a temperature of 110° to 190° C., to form particles of 2BaO.9Fe 2 O 3 , and then autoclaving the aqueous suspension containing the thus formed 2BaO.9Fe 2 O 3 at a temperature of 280° to 320° C. thereby converting said fine particles of 2BaO.9Fe 2 O 3 into said plate-like barium ferrite particles.
Claim 11
Dependent Claim
147 words
Plate-like barium ferrite particles of the formula BaO.6Fe 2 O 3 for use in magnetic recording exhibiting a specific surface area in a range of 11 to 50 m 2 /g, a magnetization of higher than 25 emu/g in a magnetic field of 10 KOe and a coercive force in a range of 600 to 1100 Oe, produced by a process comprising the steps of autoclaving an aqueous alkaline suspension of pH of higher than 11, containing Fe(III) and Ba ions at an atomic ratio in a range of 6:1 to 8:1 at a temperature of 110° to 190° C., to form particles of 2BaO.9Fe 2 O 3 , and then autoclaving the aqueous suspension containing the thus formed 2BaO.9Fe 2 O 3 at a temperature of 280° to 320° C. thereby converting said fine particles of 2BaO.9Fe 2 O 3 into said plate-like barium ferrite particles.
Claim 12
Dependent Claim
23 words
Plate-like barium ferrite particles according to claim 8, exhibiting a specific surface area in a range of 15 to 40 m 2 /g.
Claim 13
Dependent Claim
23 words
Plate-like barium ferrite particles according to claim 8, exhibiting a magnetization of higher than 45 emu/g in a magnetic field of 10 KOe.
Claim 14
Dependent Claim
20 words
Plate-like barium ferrite particles according to claim 8, exhibiting a coercive force in a range of 600 to 800 Oe.
References Cited (Backward Citations)
JPS56155023A
Cited
US4414124A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-10-21 | 1989-04-22 | 1989-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-21 | 1993-04-22 | 1993-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-21 | 1997-04-22 | 1997-10-22 | $7700.00 | Window Closed / Lapsed |