US4122155A
Expired / Lapsed
US
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Preparation of silicon nitride powder
Assignee: Carboloy Inc
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Filing: 1977-01-03
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Granted: 1978-10-24
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Expires: 1997-01-03
Abstract
Abstract A gas mixture of silane and ammonia is heated at temperatures between about 600° C and 1000° C producing an amorphous powdery reaction product which, when heated at a calcination temperature of at least 1100° C yields ultrafine Si 3 N 4 powder of high purity.
Inventors
- 👤 Svante Prochazka
- 👤 Charles D. Greskovich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 08:21
CPC Classifications
C; C01; C01B; C01B21/00; C01B21/06; C01B21/068; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/5935; C01P; C01P2006/00; C01P2006/12; C01P2006/60; C01P2006/80
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
161 words
A process for producing an amorphous silicon nitride powder free of metallic and non-metallic impurities except for oxygen, which consists essentially of reacting a gaseous mixture of silane and anhydrous ammonia at a reaction temperature ranging from about 600° C. to about 1000° C. producing an amorphous powdery reaction product in an amount of at least about 90% of theoretical yield based on silane, said anhydrous ammonia being used in an amount ranging from about 15 times to about 25 times in excess of the stoichiometric amount, calcining said amorphous powdery reaction product at a temperature ranging from about 1100° C. to 1480° C. for a period of time sufficient to convert at least a substantial amount thereof to amorphous, stoichiometric Si 3 N 4 powder ranging in surface area from about 5m 2 /g to about 20m 2 /g, said calcining being carried out in an atmosphere selected from the group consisting of argon, helium, nitrogen, hydrogen and mixtures thereof.
Claim 2
Dependent Claim
161 words
A process for producing an amorphous silicon nitride powder free of metallic and non-metallic impurities except for oxygen, which consists essentially of reacting a gaseous mixture of silane and anhydrous ammonia at a reaction temperature ranging from about 600° C. to about 1000° C. producing an amorphous powdery reaction product in an amount of at least about 90% of theoretical yield based on silane, said anhydrous ammonia being used in an amount ranging from about 15 times to about 25 times in excess of the stoichiometric amount, calcining said amorphous powdery reaction product at a temperature ranging from about 1100° C. to 1480° C. for a period of time sufficient to convert at least a substantial amount thereof to amorphous, stoichiometric Si 3 N 4 powder ranging in surface area from about 5m 2 /g to about 20m 2 /g, said calcining being carried out in an atmosphere selected from the group consisting of argon, helium, nitrogen, hydrogen and mixtures thereof.
Claim 3
Dependent Claim
68 words
A process according to claim 1 wherein said amorphous Si 3 N 4 powder is calcined in an atmosphere of nitrogen at a temperature ranging from about 1400° C. to about 1600° C. for a period of time sufficient to convert at least a substantial amount thereof to crystalline α-Si 3 N 4 powder ranging in surface area from about 5m 2 /g to about 15m 2 /g.
Claim 4
Dependent Claim
18 words
A process according to claim 1 wherein said reaction temperature ranges from about 650° C. to 850° C.
Claim 5
Dependent Claim
16 words
A process according to claim 1 wherein said reaction is carried out in a non-metallic chamber.
Claim 6
Dependent Claim
30 words
A process according to claim 1 wherein said amorphous stoichiometric Si 3 N 4 powder contains excess silicon in an amount of less than 1% by weight of the powder.
Claim 7
Dependent Claim
149 words
A process for producing crystalline α-Si 3 N 4 powder free of metallic and non-metallic impurities except for oxygen, which consists essentially of reacting a gaseous mixture of silane and anhydrous ammonia at a reaction temperature ranging from about 600° C. to about 1000° C. producing an amorphous powdery reaction product in an amount of at least 90% of theoretical yield based on silane, said anhydrous ammonia being used in an amount ranging from about 15 times to about 25 times in excess of the stoichiometric amount, calcining said amorphous powdery reaction product at a temperature ranging from about 1400° C. to 1600° C. for a period of time sufficient to convert at least a substantial amount thereof to crystalline α-Si 3 N 4 powder ranging in surface area from about 5m 2 /g to about 15m 2 /g, said calcining being carried out in an atmosphere of nitrogen.
Claim 8
Dependent Claim
149 words
A process for producing crystalline α-Si 3 N 4 powder free of metallic and non-metallic impurities except for oxygen, which consists essentially of reacting a gaseous mixture of silane and anhydrous ammonia at a reaction temperature ranging from about 600° C. to about 1000° C. producing an amorphous powdery reaction product in an amount of at least 90% of theoretical yield based on silane, said anhydrous ammonia being used in an amount ranging from about 15 times to about 25 times in excess of the stoichiometric amount, calcining said amorphous powdery reaction product at a temperature ranging from about 1400° C. to 1600° C. for a period of time sufficient to convert at least a substantial amount thereof to crystalline α-Si 3 N 4 powder ranging in surface area from about 5m 2 /g to about 15m 2 /g, said calcining being carried out in an atmosphere of nitrogen.
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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) | 1981-10-23 | 1982-04-24 | 1982-10-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-10-23 | 1986-04-24 | 1986-10-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-10-23 | 1990-04-24 | 1990-10-24 | $7700.00 | Window Closed / Lapsed |