US4455275A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of manufacturing bodies of silicon nitride
Assignee: ABB Norden Holding AB
•
Filing: 1980-10-10
•
Granted: 1984-06-19
•
Expires: 2000-10-10
Abstract
Abstract Bodies of silicon nitride are produced by enclosing a silicon nitride powder in a gas-tight glass casing and subjecting the casing to isostatic pressure using gas as a pressure medium at a temperature of at least 1600° C. and a pressure of at least 100 MPa. The casing is a glass having a high softening point. The casing is evacuated and sealed before compressing. The product may be pre-formed by isostatic compacting at a pressure of at least 100 MPa at a temperature considerably below the sintering temperature. The casing is cooled at a rate of at most 1000° C. per hour and at a pressure of not over 10 MPa.
Inventors
- 👤 Jan Alderborn
- 👤 Hans Larker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 18:39
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
119 words
A method of manufacturing a body of silicon nitride having improved strength at elevated temperatures and substantially the same strength in all directions which comprises first enclosing a quantity of silicon nitride material in the form of a powder or a product preformed from such powder in a gas-tight casing comprising glass that is yelding at the temperatures used for sintering silicon nitride, and only thereafter heating said casing with the silicon nitride material encased thereby to a temperature of at least 1600° C. and subjecting the casing and thereby the silicon nitride material to isostatic pressing at a pressure of at least 100 MPa using a gaseous pressure medium to form said silicon nitride body within said casing.
Claim 2
Independent Claim
119 words
A method of manufacturing a body of silicon nitride having improved strength at elevated temperatures and substantially the same strength in all directions which comprises first enclosing a quantity of silicon nitride material in the form of a powder or a product preformed from such powder in a gas-tight casing comprising glass that is yelding at the temperatures used for sintering silicon nitride, and only thereafter heating said casing with the silicon nitride material encased thereby to a temperature of at least 1600° C. and subjecting the casing and thereby the silicon nitride material to isostatic pressing at a pressure of at least 100 MPa using a gaseous pressure medium to form said silicon nitride body within said casing.
Claim 3
Dependent Claim
22 words
A method as set forth in claim 1 wherein said isostatic pressing is conducted at a pressure of 150 to 1500 MPa.
Claim 4
Dependent Claim
22 words
A method as set forth in claim 2 wherein said isostatic pressing is conducted at a pressure of 200 to 300 MPa.
Claim 5
Dependent Claim
21 words
A method as set forth in claim 1 wherein said temperature is in the range of from 1600 to 1900° C.
Claim 6
Dependent Claim
21 words
A method as set forth in claim 4 wherein said temperature is in the range of from 1700 to 1800° C.
Claim 7
Dependent Claim
18 words
A method as set forth in claim 1 wherein the casing is evacuated prior to said isostatic pressing.
Claim 8
Dependent Claim
54 words
A method as set forth in claim 6 wherein said silicon nitride material is in the form of a predetermined shape created by the isostatic molding of a silicon nitride powder at a pressure of at least 100 MPa and at a temperature less than the temperature at which said powder will become sintered.
Claim 9
Dependent Claim
21 words
A method as set forth in claim 1 wherein said casing is formed of a glass having a high softening temperature.
Claim 10
Dependent Claim
30 words
A method as set forth in claim 8 wherein after said isostatic pressing said casing and its contents are cooled at a rate no greater than 1000° C. per hour.
Claim 11
Dependent Claim
25 words
A method as set forth in claim 9 wherein during said cooling the casing is subjected to a pressure of not greater than 10 MPa.
Claim 12
Dependent Claim
29 words
A method as set forth in claim 1 wherein said silicon nitride material contains no more than 0.6% by weight of impurities in the form of foreign metal oxides.
Claim 13
Dependent Claim
40 words
A method as set forth in claim 1 wherein said silicon nitride material is a silicon nitride powder which initially has a grain size of less than 100 μ m and a crystal size of less than 5 μ m.
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) | 1987-06-19 | 1987-12-19 | 1988-06-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-06-19 | 1991-12-19 | 1992-06-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-06-19 | 1995-12-19 | 1996-06-19 | $7700.00 | Window Closed / Lapsed |