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Patent US4473542A successfully refreshed from Google Patents.
US4473542A
Expired / Lapsed
US
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Production of microcrystalline ferrimagnetic spinels
Assignee: Celanese Corp
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Filing: 1983-05-23
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Granted: 1984-09-25
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Expires: 2003-05-23
Abstract
Abstract This invention provides an improved process for producing a microcrystalline ferrimagnetic spinel via an amorphous organometallic precursor. The process produces a high purity ferrite powder such as Ni 0 .7 Zn 0 .3 Fe 2 O 4 which has an average particle size less than about 1000 angstroms.
Inventors
- 👤 Lawrence D. David
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 19:47
CPC Classifications
B; B82; B82Y; B82Y30/00; C; C01; C01G; C01G53/00; C01G53/40; C01G49/00; C01G49/0018; C01G49/0063; C01P; C01P2002/00; C01P2002/30; C01P2002/32; C01P2004/00; C01P2004/30; C01P2004/32; C01P2004/60; C01P2004/62; C01P2004/64; C01P2006/00; C01P2006/42; C01P2006/60
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
112 words
A process for the production of a microcrystalline ferrimagnetic spinel which comprises (1) forming an aqueous solution containing a surfactant and water-soluble alpha-hydroxycarboxylate salts of nickel, zinc and iron metals in quantities and with metal valences that subsequently yield a spinel composition corresponding to the formula: M.sub.1 Fe.sub.2 O.sub.4 where M is nickel, zinc, or a combination thereof; (2) removing the aqueous medium to provide a solid-phase spinel precursor; and (3) pyrolyzing the spinel precursor in the presence of molecular oxygen at a temperature in the range between about 300°-900° C. to form a M 1 Fe 2 O 4 spinel composition having an average particle size less than about 1000 angstroms.
Claim 2
Dependent Claim
112 words
A process for the production of a microcrystalline ferrimagnetic spinel which comprises (1) forming an aqueous solution containing a surfactant and water-soluble alpha-hydroxycarboxylate salts of nickel, zinc and iron metals in quantities and with metal valences that subsequently yield a spinel composition corresponding to the formula: M.sub.1 Fe.sub.2 O.sub.4 where M is nickel, zinc, or a combination thereof; (2) removing the aqueous medium to provide a solid-phase spinel precursor; and (3) pyrolyzing the spinel precursor in the presence of molecular oxygen at a temperature in the range between about 300°-900° C. to form a M 1 Fe 2 O 4 spinel composition having an average particle size less than about 1000 angstroms.
Claim 3
Dependent Claim
29 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate salt content of the step (1) aqueous solution is above about 50 weight percent, based on total solution weight.
Claim 4
Dependent Claim
31 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate salt content contains less than about 0.1 weight percent of metal salts other than those of nickel, zinc and iron metals.
Claim 5
Dependent Claim
15 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate in step (1) is citrate.
Claim 6
Dependent Claim
15 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate in step (1) is malate.
Claim 7
Dependent Claim
15 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate in step (1) is tartrate.
Claim 8
Dependent Claim
15 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate in step (1) is lactate.
Claim 9
Dependent Claim
15 words
A process in accordance with claim 1 wherein the alpha-hydroxycarboxylate in step (1) is glycolate.
Claim 10
Dependent Claim
23 words
A process in accordance with claim 1 wherein the solid-phase spinel precursor produced in step (2) is in the form of a gel.
Claim 11
Dependent Claim
44 words
A process in accordance with claim 1 wherein the pyrolysis in step (3) is at a temperature between about 300°-900° C. for a period between about 0.1-2 hours until the conversion of spinel precursor to M 1 Fe 2 O 4 spinel is completed.
Claim 12
Dependent Claim
29 words
A process in accordance with claim 1 wherein the pyrolysis in step (3) is conducted until the resultant M 1 Fe 2 O 4 spinel is substantially carbon free.
Claim 13
Dependent Claim
24 words
A process in accordance with claim 1 wherein the spinel product has a Ni 0 .7 Zn 0 .3 Fe 2 O 4 composition.
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) | 1987-09-25 | 1988-03-26 | 1988-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-09-25 | 1992-03-26 | 1992-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-09-25 | 1996-03-26 | 1996-09-25 | $7700.00 | Window Closed / Lapsed |