US4530825A
Expired / Lapsed
US
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Process for the production of silicon nitride
Assignee: Kemanord AB
•
Filing: 1984-04-12
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Granted: 1985-07-23
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Expires: 2004-04-12
Abstract
Abstract A process for the production of silicon nitride by reaction of silicon dioxide, carbon and nitrogen at temperatures above about 1300° C. whereby a partial pressure of nitrogen above 1 bar is maintained during the reaction.
Inventors
- 👤 Thomas Johansson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 02:48
CPC Classifications
C; C01; C01B; C01B21/00; C01B21/06; C01B21/068; C01B21/0685
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
49 words
A process for the production of silicon nitride by reaction of silicon dioxide, carbon and nitrogen under heat supply in an endothermic process at temperatures in the raw material mixture above 1300 degrees centigrade, comprising the steps of maintaining a nitrogen partial pressure above 5 bars during the reaction.
Claim 2
Dependent Claim
49 words
A process for the production of silicon nitride by reaction of silicon dioxide, carbon and nitrogen under heat supply in an endothermic process at temperatures in the raw material mixture above 1300 degrees centigrade, comprising the steps of maintaining a nitrogen partial pressure above 5 bars during the reaction.
Claim 3
Dependent Claim
57 words
A process according to claim 1 wherein in a first step a part of the silicon dioxide is reacted to carbide with carbon in a mole ratio of 3 moles for each mole of reacted silicon dioxide and in a second step the nitrogen gas is supplied to nitridate the formed carbide and the remaining silicon dioxide.
Claim 4
Dependent Claim
16 words
A process according to claim 1, characterized in that the pressure is kept above 20 bars.
Claim 5
Dependent Claim
21 words
A process according to claim 1, characterized in that the temperature is kept below the fusion temperature for the silicon dioxide.
Claim 6
Dependent Claim
30 words
A process according to claim 4, characterized in that the temperature is kept below the threshold temperature for conversion of silicon nitride to silicon carbide at the pressure in question.
Claim 7
Dependent Claim
24 words
A process according to claim 5 wherein the temperature is above 90% of the threshold temperature, in degrees centigrades, at the selected nitrogen pressure.
Claim 8
Dependent Claim
26 words
A process according to claim 1, characterized in that the mole ratio of silicon dioxide to carbon in the reactor is kept between 1.9:1 to 10:1.
Claim 9
Dependent Claim
18 words
A process according to claim 7, characterized in that the mole ratio is kept between 1.95:1 to 2.2:1.
Claim 10
Dependent Claim
54 words
A process according to claim 1, characterized in that the reaction atmosphere, containing carbon monoxide, is mixed with air in such an amount and under such conditions that the carbon monoxide is oxidized into carbon dioxide, that the carbon dioxide is removed and that the remaining gas is used for further silicon nitride manufacture.
Claim 11
Dependent Claim
43 words
A process for the production of silicon nitride comprising reacting a mixture consisting of silicon dioxide and carbon at temperatures above 1407 degrees C. with nitrogen at a partial pressure above atmospheric pressure to yield a solid product consisting essentially of silicon nitride.
Claim 12
Dependent Claim
43 words
A process for the production of silicon nitride comprising reacting a mixture consisting of silicon dioxide and carbon at temperatures above 1407 degrees C. with nitrogen at a partial pressure above atmospheric pressure to yield a solid product consisting essentially of silicon nitride.
Claim 13
Dependent Claim
28 words
A process according to claim 10 wherein the temperature is kept below the threshold temperature for conversion of silicon nitride to silicon carbide at the pressure in question.
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) | 1988-07-22 | 1989-01-21 | 1989-07-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-07-22 | 1993-01-21 | 1993-07-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-07-22 | 1997-01-21 | 1997-07-23 | $7700.00 | Window Closed / Lapsed |