Patent US4426405A successfully refreshed from Google Patents.
US4426405A
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Method for producing improved silicon carbide resistance elements
Assignee: Emerson Electric Co
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Filing: 1981-02-20
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Granted: 1984-01-17
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Expires: 2001-02-20
Abstract
Abstract Silicon carbide shapes of the general type shown and described in U.S. Pat. No. 4,125,756 are densified and nitrided in such a way as to produce shapes with improved durability and reduction in temperature span in response to voltage changes.
Inventors
- 👤 Frank J. Hierholzer, Jr.
- 👤 Gerald L. Shelton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 11:50
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/009; C04B35/00; C04B35/515; C04B35/56; C04B35/565; C04B35/571; C04B41/45; C04B41/52; C04B41/80; C04B41/81; C04B41/89
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
86 words
The process of forming a silicon carbide resistance element by chemical vapor deposition comprising forming a porous, partially bonded granular silicon carbide shape of precisely controlled electrical resistance; placing said shape in a furnace; heating said shape to a temperature of between 1000° and 1400° C.; exposing said heated shape to a gas containing a reducing agent, carbon, silicon and between about 0.01 and 3.0%, by weight of the gas, nitrogen to penetrate the shape and produce a dense coating of silicon carbide containing co-deposited nitrogen.
Claim 2
Dependent Claim
86 words
The process of forming a silicon carbide resistance element by chemical vapor deposition comprising forming a porous, partially bonded granular silicon carbide shape of precisely controlled electrical resistance; placing said shape in a furnace; heating said shape to a temperature of between 1000° and 1400° C.; exposing said heated shape to a gas containing a reducing agent, carbon, silicon and between about 0.01 and 3.0%, by weight of the gas, nitrogen to penetrate the shape and produce a dense coating of silicon carbide containing co-deposited nitrogen.
Claim 3
Dependent Claim
29 words
The process of claim 1 wherein the reducing agent is hydrogen and the carbon and silicon are introduced to the gas in the form of a gaseous chloro silane.
Claim 4
Dependent Claim
19 words
The process of claim 1 wherein the gas is preheated to a temperature in the range of 300°-800° C.
Claim 5
Dependent Claim
25 words
The process of claim 2 wherein the chloro silane is methyl trichloro silane and it comprises on the order of 0.0025 lbs/liter of the gas.
Claim 6
Dependent Claim
32 words
The process of claim 1 wherein a plurality of shapes are placed in the furnace for concurrent treatment, and said shapes are moved within the furnace during their exposure to said gas.
Claim 7
Dependent Claim
40 words
The process of claim 1 wherein the shapes are two-ended and are formed with metal contacts embedded in the two ends, and the area of the shape around said contacts is spray metallized after the CVD coating process is complete.
Claim 8
Dependent Claim
30 words
The process of claim 1 plus the additional steps of thereafter heating the shape to a temperature above 1600° C. and while so heated, exposing said shape to gaseous nitrogen.
Claim 9
Dependent Claim
37 words
The process of claim 6 including passing current through the said metal contacts, hence the shape, to heat the shape to above 1600° C., and while said shape is so heated, exposing said shape to gaseous nitrogen.
Claim 10
Dependent Claim
11 words
The process of claim 6 wherein the metal contacts are molybdenum.
References Cited (Backward Citations)
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US3895219A
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US3875477A
Cited
US4125756A
Cited
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Cited
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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) | 1987-01-16 | 1987-07-18 | 1988-01-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-01-16 | 1991-07-18 | 1992-01-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-01-16 | 1995-07-18 | 1996-01-17 | $7700.00 | Window Closed / Lapsed |