US4734234A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Preparation of very strong and very heat-stable ceramic moldings of silicon nitride
Assignee: BASF SE
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Filing: 1986-01-21
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Granted: 1988-03-29
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Expires: 2006-01-21
Abstract
Abstract Pore-free, compact moldings of silicon nitride are produced by a method in which amorphous silicon nitride powder is compressed in a first stage at from 1200° to 1350° C. and from 50 to 600 kp/cm 2 to give a glassy molding, and the silicon nitride is converted in a second stage to crystalline silicon nitride at from 1400° to 1800° C. without the use of pressure.
Inventors
- 👤 Hans-Josef Sterzel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 04:01
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
82 words
A process for the production of compact, pore-free moldings of silicon nitride by sintering amorphous silicon nitride powder which comprises: compressing amorphous silicon nitride powder in the absence of sintering assistants in a first stage at from 1200° to 1350° C. and from 50 to 600 kp/cm 2 to give a compact glassy molding; and converting the compact glassy molding in a second stage to crystalline silicon nitride at a temperature of from 1400° to 1800° C. without the use of pressure.
Claim 2
Dependent Claim
82 words
A process for the production of compact, pore-free moldings of silicon nitride by sintering amorphous silicon nitride powder which comprises: compressing amorphous silicon nitride powder in the absence of sintering assistants in a first stage at from 1200° to 1350° C. and from 50 to 600 kp/cm 2 to give a compact glassy molding; and converting the compact glassy molding in a second stage to crystalline silicon nitride at a temperature of from 1400° to 1800° C. without the use of pressure.
Claim 3
Dependent Claim
21 words
The process of claim 1, wherein the amorphous silicon nitride powder has a particle size of from 0.001 to 10 μm.
Claim 4
Dependent Claim
28 words
A process as claimed in claim 1, wherein the amorphous silicon nitride powder contains from 0.0001 to 1% weight of α- and/or β-silicon nitride as a nucleating agent.
Claim 5
Dependent Claim
27 words
The process of claim 1, wherein the amorphous silicon nitride powder is heated in the first stage at a pressure of 100 to 300 kp/cm 2 .
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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) | 1991-03-29 | 1991-09-28 | 1992-03-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-03-29 | 1995-09-28 | 1996-03-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-03-29 | 1999-09-28 | 2000-03-29 | $7700.00 | Window Closed / Lapsed |