US4997604A
Expired / Lapsed
US
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Method for production of molded articles of silicon nitride
Assignee: HTM AG
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Filing: 1989-12-27
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Granted: 1991-03-05
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Expires: 2009-12-27
Abstract
Abstract A reactively combined silicon nitride is produced in which the starting material is pure silicon powder or a powder mixture of pure silicon and its nitride. This material is subjected to cold isostatic pressing or a slip casting or diecasting process before it is brought into a hot isostatic mold. The reaction is triggered under a nitrogen pressure of initially 0.5-2.0 MPa and at a starting temperature of 1000° C. During the reaction the pressure is raised to 4.9 MPa and the temperature to at most 1420° C. This raising of pressure and temperature is carried out at least partially stepwise. Obtained thereby is a product having a degree of nitriding greater than 92%. With a cycle time of less than 24 hours, the process permits molded articles to be produced which have a wall thickness of more than 10 mm, the material being uniformly nitrided.
Inventors
- 👤 Beat Hofer
- 👤 Bernhard Einstein
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 12:13
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/591; C04B35/593; C04B35/5935
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
141 words
A method of producing a molded article of reactively combined silicon nitride comprising: (a) bringing pure silicon powder or a powder mixture of pure silicon and its nitride into a desired shape having a thickness of greater than 10 mm through cold isostatic pressing, slip casting or diecasting; (b) heating the obtained body in a nitrogen atmosphere, reacting the body with nitrogen starting at a nitrogen pressure of 0.5-2.0 MPa and a temperature of 1000° C.; (c) raising the temperature and the pressure at least in part step-by-step to a final pressure of 4.9 MPa and a final temperature of at most 1420° C. for a reaction time to obtain said molded article of silicon nitride with a uniform degree of nitriding of at least 92%; (d) the entire cycle time of said process without cooling being less than 24 hours.
Claim 2
Independent Claim
141 words
A method of producing a molded article of reactively combined silicon nitride comprising: (a) bringing pure silicon powder or a powder mixture of pure silicon and its nitride into a desired shape having a thickness of greater than 10 mm through cold isostatic pressing, slip casting or diecasting; (b) heating the obtained body in a nitrogen atmosphere, reacting the body with nitrogen starting at a nitrogen pressure of 0.5-2.0 MPa and a temperature of 1000° C.; (c) raising the temperature and the pressure at least in part step-by-step to a final pressure of 4.9 MPa and a final temperature of at most 1420° C. for a reaction time to obtain said molded article of silicon nitride with a uniform degree of nitriding of at least 92%; (d) the entire cycle time of said process without cooling being less than 24 hours.
Claim 3
Dependent Claim
31 words
The method of claim 1, wherein the whole raising of the pressure and the temperature takes place step-by-step, the pressure and temperature values being kept constant during a pause between steps.
Claim 4
Dependent Claim
14 words
The method of claim 1, wherein the entire cycle time amounts to 10 hours.
Claim 5
Dependent Claim
20 words
The method of claim 2, wherein the ratio of the heating periods to the pauses amounts to 1:1.8 to 2.2.
Claim 6
Dependent Claim
13 words
The method of claim 1, wherein the reaction time amounts to 3-20 hours.
Claim 7
Dependent Claim
13 words
The method of claim 3 wherein the reaction time amounts to 8 hours.
Claim 8
Dependent Claim
17 words
The method of claim 1, wherein the raising of pressure and temperature takes place in 5-15 steps.
Claim 9
Dependent Claim
51 words
The method of claim 1, wherein the reaction starts at a furnace temperature of at least 1000° C., the reaction rate controlled first by the pressure, and the furnace temperature and pressure being raised by intervals of about 10° C. or about 0.2 MPa, respectively, only when the reaction is advanced.
Claim 10
Dependent Claim
20 words
The method of claim 1, wherein said pure silicon powder has a density of 1.3 to 2.3 kg/dm 3 .
Claim 11
Dependent Claim
25 words
The method of claim 1, wherein said powder mixture of pure silicon and its nitride contains 1-30% by weight of Si 3 N 4 .
Claim 12
Dependent Claim
25 words
The method of claim 1 wherein said powder mixture of pure silicon and its nitride contains 20% by weight of Si 3 N 4 .
Claim 13
Dependent Claim
19 words
The method of claim 1, wherein further nitrides and oxides are added to said silicon powder or powder mixture.
Claim 14
Dependent Claim
21 words
The method of claim 1, wherein said silicon powder or powder mixture has a particle size of less than 15 microns.
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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) | 1994-03-04 | 1994-09-03 | 1995-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-03-04 | 1998-09-03 | 1999-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-03-04 | 2002-09-03 | 2003-03-05 | $7700.00 | Window Closed / Lapsed |