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US5316699A
Expired / Lapsed
US
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Process for the controlled preparation of a composite of ultrafine magnetic particles homogeneously dispersed in a dielectric matrix
Assignee: United States Department of Commerce
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Filing: 1990-03-28
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Granted: 1994-05-31
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Expires: 2010-03-28
Abstract
Abstract A chemical process for producing bulk quantities of an iron-silica gel composite in which particle size, form, and magnetic state of the iron can be selected. The process involves polymerizing an ethanolic solution of tetraethylorthosilicate, ferric nitrate and water at low temperature under the influence of an HF catalyst. The chemical and magnetic states of the iron in the resultant composite are modified in situ by exposure to suitable oxidizing or reducing agents at temperatures under 400° C. Iron-containing particles of less than 200 Å diameter, homogeneously dispersed in silica matrices may be prepared in paramagnetic, superparamagnetic, ferrimagnetic and ferromagnetic states.
Inventors
- 👤 Joseph J. Ritter
- 👤 Robert D. Shull
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:06
CPC Classifications
B; B82; B82Y; B82Y25/00; C; C08; C08K; C08K3/00; C08K3/02; C08K3/08; G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; H; H01; H01F; H01F1/00; H01F1/0036; H01F1/0045; H01F1/0063; H01F1/0009
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
109 words
A process for synthesizing a bulk material having magnetic particles dispersed in an non-magnetic matrix, comprising the steps of: a) polymerizing silicon alkoxide in solution with at least one iron compound to form a gel; b) curing said gel to form a porous hydrolyzed silicon product which contains iron; c) subsequently contacting the porous hydrolyzed silicon product with an oxidizing agent at a temperature below 400° C. to convert said iron to a ferrimagnetic state; and d) after exposing said product to said oxidizing agent, contacting said product with a reducing agent to convert said iron to a paramagnetic state, wherein said reducing agent is hydrogen gas and water.
Claim 2
Dependent Claim
109 words
A process for synthesizing a bulk material having magnetic particles dispersed in an non-magnetic matrix, comprising the steps of: a) polymerizing silicon alkoxide in solution with at least one iron compound to form a gel; b) curing said gel to form a porous hydrolyzed silicon product which contains iron; c) subsequently contacting the porous hydrolyzed silicon product with an oxidizing agent at a temperature below 400° C. to convert said iron to a ferrimagnetic state; and d) after exposing said product to said oxidizing agent, contacting said product with a reducing agent to convert said iron to a paramagnetic state, wherein said reducing agent is hydrogen gas and water.
Claim 3
Dependent Claim
12 words
The process of claim 1, wherein said silicon alkoxide is a teraalkylorthosilicate.
Claim 4
Dependent Claim
12 words
The process of claim 1, wherein said iron compound is ferric nitrate.
Claim 5
Dependent Claim
10 words
The process of claim 2, wherein said tetraalkylorthosilicate is tetraethylorthosilicate.
Claim 6
Dependent Claim
18 words
The process of claim 1, wherein said process further comprises forming said bulk material into a shaped monolith.
Claim 7
Dependent Claim
11 words
The process of claim 1, wherein said oxidizing agent comprises oxygen.
Claim 8
Dependent Claim
16 words
The process of claim 1, wherein said polymerizing is conducted in the presence of a catalyst.
Claim 9
Dependent Claim
10 words
The process of claim 7, wherein said catalyst comprises HF.
Claim 10
Dependent Claim
100 words
A process for synthesizing a bulk material having magnetic particles dispersed in an non-magnetic matrix, comprising the steps of: a) polymerizing silicon alkoxide in solution with at least one iron compound to form a gel; b) curing said gel to form a porous hydrolyzed silicon product which contains iron; c) subsequently contacting the porous hydrolyzed silicon product with a reducing agent at a temperature below 400° C. to convert said iron to a superparamagnetic state; and d) after contacting said product with said reducing agent, contacting said product with a nitriding agent to convert said iron to a ferromagnetic state.
Claim 11
Dependent Claim
100 words
A process for synthesizing a bulk material having magnetic particles dispersed in an non-magnetic matrix, comprising the steps of: a) polymerizing silicon alkoxide in solution with at least one iron compound to form a gel; b) curing said gel to form a porous hydrolyzed silicon product which contains iron; c) subsequently contacting the porous hydrolyzed silicon product with a reducing agent at a temperature below 400° C. to convert said iron to a superparamagnetic state; and d) after contacting said product with said reducing agent, contacting said product with a nitriding agent to convert said iron to a ferromagnetic state.
Claim 12
Dependent Claim
11 words
The process of claim 9, wherein said reducing agent is hydrogen.
Claim 13
Dependent Claim
11 words
The process of claim 9, wherein said nitriding agent comprises ammonia.
Claim 14
Dependent Claim
12 words
The process of claim 9, wherein said silicon alkoxide is a tetraalkylorthosilicate.
Claim 15
Dependent Claim
10 words
The process of claim 12, wherein said tetraalkylorthosilicate is tetraethylorthosilicate.
Claim 16
Dependent Claim
12 words
The process of claim 9, wherein said iron compound is ferric nitrate.
Claim 17
Dependent Claim
16 words
The process of claim 9, wherein said polymerizing is conducted in the presence of a catalyst.
Claim 18
Dependent Claim
10 words
The process of claim 15, wherein the catalyst comprises HF.
Claim 19
Dependent Claim
18 words
The process of claim 9, wherein the process further comprises forming said bulk material into a shaped monolith.
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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) | 1997-05-30 | 1997-11-29 | 1998-05-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-05-30 | 2001-11-29 | 2002-05-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-05-30 | 2005-11-29 | 2006-05-31 | $7700.00 | Window Closed / Lapsed |