US4668452A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing silicon carbide heating elements
Assignee: Niterra Co Ltd
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Filing: 1985-03-01
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Granted: 1987-05-26
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Expires: 2005-03-01
Abstract
Abstract A process for producing a silicon carbide heating element is disclosed comprising: adding boron or a boron compound in an amount corresponding to from 0.3 to 3.0% by weight as boron, and carbon or a carbon compound in an amount corresponding to from 0.1 to 6.0% by weight as carbon, to a SiC powder having an average particle size of 1.0μ or less; blending and molding the mixture; conducting a primary sintering in vacuum or in an inert atmosphere, except nitrogen; and thereafter conducting a secondary sintering at from 1500° to 2300° C. in a pressurized nitrogen atmosphere to produce a silicon carbide heating element having a density of at least 80% based on the theoretical density and an electrical resistivity of 1.0 Ω-cm or less.
Inventors
- 👤 Masakazu Watanabe
- 👤 Akiyasu Okuno
- 👤 Shunkichi Nozaki
- 👤 Yasushi Matsuo
- 👤 Isamu Fukuura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 07:56
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565; C04B35/575; C04B35/5755
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
164 words
A process for producing a silicon carbide heating element comprising: (A) adding boron or a boron compound in an amount corresponding to from 0.3 to 3.0% by weight as boron, and carbon or a carbon compound in an amount corresponding to from 0.1 to 6.0% by weight as carbon, to a SiC powder having an average particle size of 1.0μ or less; blending and molding the mixture, wherein said SiC powder is a mixture of at least 10% by weight α-SiC powder and the balance β-SiC powder; (B) conducting a primary sintering at a temperature of from 1850° to 2050° C. in vacuum or in an inert atmosphere, except nitrogen; and thereafter (C) conducting a secondary sintering at from 1500° to 2300° C. in a pressurized nitrogen atmosphere of more than 5 to about 500 atmospheres to produce a silicon carbide heating element having a density of at least 80% based on the theoretical density and an electrical resistivity of 1.0 Ω-cm or less.
Claim 2
Dependent Claim
164 words
A process for producing a silicon carbide heating element comprising: (A) adding boron or a boron compound in an amount corresponding to from 0.3 to 3.0% by weight as boron, and carbon or a carbon compound in an amount corresponding to from 0.1 to 6.0% by weight as carbon, to a SiC powder having an average particle size of 1.0μ or less; blending and molding the mixture, wherein said SiC powder is a mixture of at least 10% by weight α-SiC powder and the balance β-SiC powder; (B) conducting a primary sintering at a temperature of from 1850° to 2050° C. in vacuum or in an inert atmosphere, except nitrogen; and thereafter (C) conducting a secondary sintering at from 1500° to 2300° C. in a pressurized nitrogen atmosphere of more than 5 to about 500 atmospheres to produce a silicon carbide heating element having a density of at least 80% based on the theoretical density and an electrical resistivity of 1.0 Ω-cm or less.
Claim 3
Dependent Claim
31 words
A process for producing silicon carbide heating elements as in claim 1, wherein the sintering density produced in the primary sintering is from 70 to 95% based on the theoretical density.
Claim 4
Dependent Claim
29 words
A process for producing a silicon carbide heating element as in claim 1, wherein the pressure of the atmosphere in the secondary sintering is from 5 to 100 atmospheres.
Claim 5
Dependent Claim
31 words
A process for producing silicon carbide heating elements as in claim 1, wherein the sintering density produced in the primary sintering is from 80 to 95% based on the theoretical density.
Claim 6
Dependent Claim
30 words
A process for producing a silicon carbide heating element as in claim 1, wherein said boron compound contains B, B 4 C, BN, BP, AlB 2 or SiB 6 .
Claim 7
Dependent Claim
26 words
A process for producing a silicon carbide heating element as in claim 1, wherein said carbon compound contains a phenol resin, carbon black, polyphenylene, or polymethylphenylene.
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) | 1990-05-25 | 1990-11-24 | 1991-05-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-05-25 | 1994-11-24 | 1995-05-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-05-25 | 1998-11-24 | 1999-05-26 | $7700.00 | Window Closed / Lapsed |