Patent US4318735A successfully refreshed from Google Patents.
US4318735A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing magnetic particles with metallic region therein, and magnetic particles prepared by the process
Assignee: Toda Kogyo Corp
•
Filing: 1980-06-06
•
Granted: 1982-03-09
•
Expires: 2000-06-06
Abstract
Abstract Fine magnetic particles with high saturation magnetization (over 140 emu/g) as well as high stability against oxidation in air, are produced by a process which comprises the first stage of oxidizing the surfaces of metallic particles consisting mainly of iron in an atmosphere containing both H 2 O and H 2 gases at an oxidizing temperature below 900° C., and the second stage of further oxidizing the surfaces of the particles produced at the first stage in an atmosphere containing O 2 gas.
Inventors
- 👤 Akio Mishima
- 👤 Hiroyuki Kondo
- 👤 Akira Mukaizaka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 02:22
CPC Classifications
H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/09; H01F1/04; H01F1/06; H01F1/061
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
80 words
A process of preparing a magnetic particle having a metallic region therein, comprising a first stage of oxidizing a surface of a particle of a metal selected from the group consisting of iron and iron alloys in an atmosphere containing both H 2 and H 2 O gases at an oxidizing temperature below 900° C. and a second stage of further oxidizing the surfaces of the particles formed at the first oxidation stage in an atmosphere containing O 2 gas.
Claim 2
Dependent Claim
80 words
A process of preparing a magnetic particle having a metallic region therein, comprising a first stage of oxidizing a surface of a particle of a metal selected from the group consisting of iron and iron alloys in an atmosphere containing both H 2 and H 2 O gases at an oxidizing temperature below 900° C. and a second stage of further oxidizing the surfaces of the particles formed at the first oxidation stage in an atmosphere containing O 2 gas.
Claim 3
Dependent Claim
35 words
The process according to claim 1, wherein a H 2 O gas concentration at the first oxidation stage defined as (H 2 O partial pressure×100)/(H 2 O partial pressure+H 2 partial pressure) is above 10%.
Claim 4
Dependent Claim
19 words
The process according to claim 2, wherein the oxidizing temperature at the first oxidation stage is above 150° C.
Claim 5
Dependent Claim
19 words
The process according to claim 3, wherein the oxidizing temperature at the second oxidation stage is below 100° C.
Claim 6
Dependent Claim
20 words
The process according to claim 4, wherein the oxidizing temperature at the first oxidation stage is 300° to 700° C.
Claim 7
Dependent Claim
27 words
The process according to claim 5, wherein the metal particle is prepared by reducing a particle of an oxide of the metal in a reducing gas atmosphere.
Claim 8
Dependent Claim
21 words
The process according to claim 5, wherein the H 2 O concentration at the first oxidation stage is 50 to 95%.
Claim 9
Dependent Claim
21 words
The process according to claim 6, wherein the H 2 O concentration at the first oxidation stage is 50 to 95%.
Claim 10
Dependent Claim
24 words
The process according to any one of claims 5 to 8, wherein the oxidizing temperature at the second oxidation stage is below 50° C.
Claim 11
Dependent Claim
14 words
The process according to claim 5, wherein the metal particle is acicular in shape.
Claim 12
Dependent Claim
20 words
The process according to claim 10, wherein the H 2 O concentration at the first oxidation stage is below 90%.
Claim 13
Dependent Claim
20 words
The process according to claim 10, wherein the oxidizing temperature at the first oxidation stage is 300° to 550° C.
Claim 14
Dependent Claim
20 words
The process according to claim 11, wherein the oxidizing temperature at the first oxidation stage is 300° to 550° C.
Claim 15
Dependent Claim
24 words
The process according to any one of claims 10 to 13, wherein the oxidizing temperature at the second oxidation stage is below 50° C.
Claim 16
Dependent Claim
120 words
A fine magnetic particle having a maximum size less than 10 μm, a saturation magnetization over 140 emu/g and high stability against oxidation in air, obtained by a process which comprises a first stage of oxidizing a surface of a fine particle of a metal selected from the group consisting of iron and iron alloys in an atmosphere containing both H 2 and H 2 O gasses at an oxidizing temperature below 900° C., the maximum size of said metallic particle being less than 10 μm, and a second stage of further oxidizing the surface of the particle formed in the first oxidation stage in an atmosphere containing O 2 gas, thus leaving a metallic core region in said particle.
Claim 17
Dependent Claim
120 words
A fine magnetic particle having a maximum size less than 10 μm, a saturation magnetization over 140 emu/g and high stability against oxidation in air, obtained by a process which comprises a first stage of oxidizing a surface of a fine particle of a metal selected from the group consisting of iron and iron alloys in an atmosphere containing both H 2 and H 2 O gasses at an oxidizing temperature below 900° C., the maximum size of said metallic particle being less than 10 μm, and a second stage of further oxidizing the surface of the particle formed in the first oxidation stage in an atmosphere containing O 2 gas, thus leaving a metallic core region in said particle.
Claim 18
Dependent Claim
62 words
The magnetic particle according to claim 15, wherein the H 2 O concentration at the first oxidation stage, defined as (H 2 O partial pressure×100)/(H 2 O partial pressure+H 2 partial pressure), is 50 to 95%, the oxidizing temperature in the first oxidation stage is 300° to 700° C., and the oxidizing temperature in the second oxidation stage is below 50° C.
Claim 19
Dependent Claim
20 words
The magnetic particle according to claim 15 or 16, wherein the magnetic particle is a particle for a magnetic toner.
Claim 20
Dependent Claim
20 words
The magnetic particle according to claim 17, wherein the maximum size of the magnetic particle is less than 1 μm.
Claim 21
Dependent Claim
62 words
The magnetic particle according to claim 15, wherein the H 2 O concentration at the first oxidation stage, defined as (H 2 O partial pressure×100)/(H 2 O partial pressure+H 2 partial pressure), is 50 to 90%, the oxidizing temperature in the first oxidation stage is 300° to 550° C., and the oxidizing temperature in the second oxidation stage is below 50° C.
Claim 22
Dependent Claim
15 words
The magnetic particle according to claim 19, wherein the magnetic particle is acicular in shape.
Claim 23
Dependent Claim
18 words
The magnetic particle according to claim 20, wherein the magnetic particle is a particle for magnetic recording medium.
Claim 24
Dependent Claim
20 words
The magnetic particle according to claim 21, wherein the maximum size of said metallic particle is less than 1 μm.
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) | 1985-03-08 | 1985-09-07 | 1986-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-03-08 | 1989-09-07 | 1990-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-03-08 | 1993-09-07 | 1994-03-09 | $7700.00 | Window Closed / Lapsed |