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US4156661A
Expired / Lapsed
US
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Method of modifying electrical properties of rare-earth chromite material
Assignee: General Refractories Co
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Filing: 1978-03-13
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Granted: 1979-05-29
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Expires: 1998-03-13
Abstract
Abstract A method of decreasing the electrical resistivity of a rare-earth chromite material by substituting bivalent metal ions for some of the chromium or rare-earth ions therein. The method includes applying a solution containing the bivalent metal ions to the rare-earth chromite under vacuum conditions, drying the solution on the chromite, and diffusing the bivalent metal ion into the rare-earth chromite by firing the chromite in a controlled atmosphere.
Inventors
- 👤 Franz J. Brodmann
- 👤 Ronald Staut
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 07:00
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/009; C04B35/00; C04B35/01; C04B35/42; C04B41/45; C04B41/50; C04B41/80; C04B41/81; C04B41/85; H; H01; H01B; H01B1/00; H01B1/06; H01B1/08
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
81 words
A method of forming a rare-earth chromite element having a portion thereof of decreased electrical resistivity from pre-sintered element, comprising the steps of: applying a vacuum to said rare-earth chromite element; contacting the rare-earth chromite element with a solution containing a bivalent metal ion selected from the group consisting of magnesium, calcium, strontium, and barium; drying said solution on said chromite element; and diffusing said bivalent metal ion into said rare-earth chromite element by firing said chromite in a controlled atmosphere.
Claim 2
Independent Claim
81 words
A method of forming a rare-earth chromite element having a portion thereof of decreased electrical resistivity from pre-sintered element, comprising the steps of: applying a vacuum to said rare-earth chromite element; contacting the rare-earth chromite element with a solution containing a bivalent metal ion selected from the group consisting of magnesium, calcium, strontium, and barium; drying said solution on said chromite element; and diffusing said bivalent metal ion into said rare-earth chromite element by firing said chromite in a controlled atmosphere.
Claim 3
Dependent Claim
10 words
The method of claim 1 wherein said rare-earth is lanthanum.
Claim 4
Dependent Claim
14 words
The method of claim 2 wherein said firing is conducted in an oxidizing atmosphere.
Claim 5
Dependent Claim
18 words
The method of claim 3 wherein said firing step is at a temperature in excess of 1500° C.
Claim 6
Dependent Claim
15 words
The method of claim 4 wherein said firing step is approximately 3 hours in length.
Claim 7
Dependent Claim
27 words
The method of claim 1 wherein said chromite is repeatedly contacted with said solution to increase the total amount of bivalent metal ions applied to said chromite.
Claim 8
Dependent Claim
60 words
The method of claim 6 wherein said solution is applied sequentially to partially overlapping areas on said element to provide a sequential variation in the amount of solution applied to said element resulting in a sequential variation of the electrical resistivity of said element after said element is dried and said bivalent metal ion is diffused into said chromite element.
Claim 9
Dependent Claim
32 words
The method of claim 7 wherein said sequential variation results in the electrical resistivity of said element varying from a maximum to a minimum value over the total length of said areas.
Claim 10
Dependent Claim
47 words
The method of claim 1 also including the step of impregnating at least a portion of the rare-earth chromite element with an oil insoluble in the bivalent metal ion solution before the step of contacting the rare-earth chromite element with a solution containing a bivalent metal ion.
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) | 1982-05-28 | 1982-11-27 | 1983-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-28 | 1986-11-27 | 1987-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-28 | 1990-11-27 | 1991-05-29 | $7700.00 | Window Closed / Lapsed |