US4336216A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing silicon carbide heating elements
Assignee: Niterra Co Ltd
•
Filing: 1980-06-09
•
Granted: 1982-06-22
•
Expires: 2000-06-09
Abstract
Abstract A process for producing silicon carbide heating elements is described comprising: a primary sintering wherein a mixture including SiC powder, boron or a boron compound, and carbon or a carbon compound in specific proportions, is molded and sintered to obtain a sintered product having from 70 to 95% of the theoretical density; and a secondary sintering wherein the sintered product obtained in the primary sintering is further sintered at each temperature from 1,600° C. to 2,200° C. to obtain a sintered product having a density of at least 80% of the theoretical density and a specific resistivity of not more than 1.0 Ω-cm.
Inventors
- 👤 Masakazu Watanabe
- 👤 Akiyasu Okuno
- 👤 Yasushi Matsuo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:45
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
166 words
A process for producing a silicon carbide heating element comprising: a primary sintering wherein a mixture including (1) beta-SiC powder having an average particle diameter of not more than 1.0μ, (2) from 0.3 to 3.0% by weight, based on the weight of the beta-SiC powder, of boron or a corresponding amount of a boron compound, and (3) from 0.1 to 3.0% by weight, based on the weight of the beta-SiC powder, of carbon or a corresponding amount of a carbon compound is molded and sintered in vacuum or in a non-nitrogen inert atmosphere to obtain a sintered product having from 70 to 95% of the theoretical density; and a secondary sintering wherein the sintered product obtained in the primary sintering is further sintered in an atmosphere of nitrogen gas at a temperature from 1,600° C. to 2,200° C. to obtain a silicon carbide heating element having a density of at least 80% of the theoretical density and a specific resistivity of not more than 1.0 Ω-cm.
Claim 2
Dependent Claim
166 words
A process for producing a silicon carbide heating element comprising: a primary sintering wherein a mixture including (1) beta-SiC powder having an average particle diameter of not more than 1.0μ, (2) from 0.3 to 3.0% by weight, based on the weight of the beta-SiC powder, of boron or a corresponding amount of a boron compound, and (3) from 0.1 to 3.0% by weight, based on the weight of the beta-SiC powder, of carbon or a corresponding amount of a carbon compound is molded and sintered in vacuum or in a non-nitrogen inert atmosphere to obtain a sintered product having from 70 to 95% of the theoretical density; and a secondary sintering wherein the sintered product obtained in the primary sintering is further sintered in an atmosphere of nitrogen gas at a temperature from 1,600° C. to 2,200° C. to obtain a silicon carbide heating element having a density of at least 80% of the theoretical density and a specific resistivity of not more than 1.0 Ω-cm.
Claim 3
Dependent Claim
29 words
A process for producing a silicon carbide heating element as in claim 1, wherein the boron compound is boron carbide, AlB 2 , BN, BP and SiB 6 .
Claim 4
Dependent Claim
29 words
A process for producing a silicon carbide heating element as in claim 1 or 2, wherein the temperature of the primary sintering is from 1,750° C. to 2,050° C.
Claim 5
Dependent Claim
28 words
A process for producing a silicon carbide heating element as in claim 1, wherein the primary sintering is conducted for a period of from 10 to 60 minutes.
Claim 6
Dependent Claim
21 words
The process of any of claims 1 through 4, inclusive, wherein the primary sintering is carried out in an argon atmosphere.
Claim 7
Dependent Claim
25 words
The process of any claims 1 through 4, inclusive, wherein the sintered product from the primary sintering has at least 90 percent of theoretical density.
Claim 8
Dependent Claim
21 words
The process of claim 5 wherein the sintered product from the primary sintering has at least 90 percent of theoretical density.
References Cited (Backward Citations)
US3998646A
Cited
US4031178A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-06-21 | 1985-12-21 | 1986-06-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-06-21 | 1989-12-21 | 1990-06-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-06-21 | 1993-12-21 | 1994-06-22 | $7700.00 | Window Closed / Lapsed |