US4309459A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing SiO2 coated iron oxide powder for use in the preparation of acicular magnetic iron or iron oxide powder
Assignee: TDK Corp
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Filing: 1980-11-25
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Granted: 1982-01-05
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Expires: 2000-11-25
Abstract
Abstract An SiO 2 coated iron oxide powder used for the preparation of an acicular metallic iron powder or an acicular magnetic iron oxide powder, is produced by forming a slurry of hydrated iron oxide as a starting material or a iron oxide powder having pH of 8 to 14; admixing a water soluble silicate at a ratio of 0.1 to 10 mol % as SiO 2 based on Fe; hydrothermally reacting said mixed slurry at 100° to 250° C. for 5 minutes or longer in a closed reactor, and washing, filtering and drying the product.
Inventors
- 👤 Yasumichi Tokuoka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:59
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; H; H01; H01F; H01F1/00; H01F1/01; H01F1/03; H01F1/032; H01F1/04; H01F1/06; H01F1/065
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
110 words
A process for producing SiO 2 -coated iron oxide powder, for use in the preparation of acicular magnetic iron powder or acicular magnetic iron oxide powder, comprising: forming an aqueous slurry of an iron oxide selected from the group consisting of acicular goethite, acicular lepidocrosite and alpha-Fe 2 O 3 , having a pH of 8-14; admixing a water-soluble silicate in an amount of 0.1-10 mole percent, as SiO 2 based on Fe; charging the resultant mixture into an autoclave at 100°-250° C. for at least 5 minutes, to effect hydrothermal reaction at high pressure, the pressure in the autoclave being self-generative; and washing, filtering and drying the resulting product.
Claim 2
Dependent Claim
110 words
A process for producing SiO 2 -coated iron oxide powder, for use in the preparation of acicular magnetic iron powder or acicular magnetic iron oxide powder, comprising: forming an aqueous slurry of an iron oxide selected from the group consisting of acicular goethite, acicular lepidocrosite and alpha-Fe 2 O 3 , having a pH of 8-14; admixing a water-soluble silicate in an amount of 0.1-10 mole percent, as SiO 2 based on Fe; charging the resultant mixture into an autoclave at 100°-250° C. for at least 5 minutes, to effect hydrothermal reaction at high pressure, the pressure in the autoclave being self-generative; and washing, filtering and drying the resulting product.
Claim 3
Dependent Claim
33 words
The process according to claim 1, wherein the SiO 2 component is partially doped in the inner part of the iron oxide and partially adsorbed on the surface thereof in said hydrothermal reaction.
Claim 4
Dependent Claim
16 words
The process according to claim 1 wherein said water soluble silicate is an alkali metal silicate.
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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) | 1985-01-04 | 1985-07-06 | 1986-01-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-01-04 | 1989-07-06 | 1990-01-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-01-04 | 1993-07-06 | 1994-01-05 | $7700.00 | Window Closed / Lapsed |