US4376742A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fugitive liquid phase densification of silicon nitride
Assignee: Systems Research Laboratories Inc
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Filing: 1981-02-23
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Granted: 1983-03-15
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Expires: 2001-02-23
Abstract
Abstract Dense silicon nitride bodies are fabricated using conventional hot-pressing techniques using cerium oxide as a densification aid. The bodies are then further treated in a flowing inert atmosphere at a temperature of from 1400°-1600° C. for from several hours to 48 hours to remove all or substantially all of the densification aid from grain boundaries. Silicon nitride bodies so treated exhibit superior elevated temperature slow crack growth resistance and strength properties and are suitable for use as structural components in high temperature environments such as jet and internal combustion engines, rockets, atomic power generation, and the like.
Inventors
- 👤 Tai-Il Mah
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 00:20
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
100 words
In a method of fabricating a silicon nitride body including the steps of mixing silicon nitride powder with from 1.0 to 2.5% by weight cerium oxide powder and compressing the mixture in an inert atmosphere at a pressure of from 4000-7000 psi and at a temperature of from 1650°-1800° C. for a time sufficient to produce a body having a density substantially equal to the theoretical density of silicon nitride, the improvement comprising: further treating said silicon nitride body at a temperature of from 1400°-1600° C. for from 4-48 hours in an insert atmosphere to improve slow crack growth resistance.
Claim 2
Dependent Claim
100 words
In a method of fabricating a silicon nitride body including the steps of mixing silicon nitride powder with from 1.0 to 2.5% by weight cerium oxide powder and compressing the mixture in an inert atmosphere at a pressure of from 4000-7000 psi and at a temperature of from 1650°-1800° C. for a time sufficient to produce a body having a density substantially equal to the theoretical density of silicon nitride, the improvement comprising: further treating said silicon nitride body at a temperature of from 1400°-1600° C. for from 4-48 hours in an insert atmosphere to improve slow crack growth resistance.
Claim 3
Dependent Claim
22 words
The method of claim 1 in which said silicon nitride body is covered with silicon nitride powder during the further treating step.
Claim 4
Dependent Claim
21 words
The method of claim 1 in which during said further treating step said body is maintained in a flowing inert atmosphere.
Claim 5
Dependent Claim
12 words
The method of claim 1 in which said inert atmosphere is nitrogen.
Claim 6
Dependent Claim
19 words
The method of claim 1 in which during said further treating step said body is maintained in a vacuum.
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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) | 1986-03-14 | 1986-09-13 | 1987-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-03-14 | 1990-09-13 | 1991-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-03-14 | 1994-09-13 | 1995-03-15 | $7700.00 | Window Closed / Lapsed |