US4209478A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of sintering ceramics
Assignee: Boeing North American Inc
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Filing: 1978-08-16
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Granted: 1980-06-24
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Expires: 1998-08-16
Abstract
Abstract A compact is surrounded by a compatible, nonsinterable powder within a container with a layer of sinterable powder disposed on top of the nonsinterable powder and placed in a sintering oven. During sintering, the sinterable powder forms a cover that retards decomposition of the compact and serves to enhance densification of the compact.
Inventors
- 👤 John R. Wooten
- 👤 Harry W. Carpenter
- 👤 Edwin F. C. Cain
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:14
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/5935; C04B35/622; C04B35/64
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
73 words
A method of manufacturing ceramic articles, said method comprising the steps of: forming a compact comprising a ceramic material and a sintering aid; surrounding said compact with powder comprising a nonsinterable material, which is compatible with the material of said compact; disposing above said powder a cover layer; composed of a sinterable material, which is compatible with the material of said compact; and sintering said compact under a pressure of about 0.5-2 atmospheres.
Claim 2
Independent Claim
73 words
A method of manufacturing ceramic articles, said method comprising the steps of: forming a compact comprising a ceramic material and a sintering aid; surrounding said compact with powder comprising a nonsinterable material, which is compatible with the material of said compact; disposing above said powder a cover layer; composed of a sinterable material, which is compatible with the material of said compact; and sintering said compact under a pressure of about 0.5-2 atmospheres.
Claim 3
Dependent Claim
61 words
The method of claim 1 wherein said sintering step comprises: initially heating said materials to a first temperature above the fusion temperature of said sinterable material, maintaining said first temperature for a period sufficient to cause at least partial sintering of said sinterable material, and subsequently reducing the heat applied to said materials to a suitable sintering temperature for said compact.
Claim 4
Dependent Claim
22 words
The method of claim 1 wherein said sintering step is performed in an inert environment at a pressure of about one atmosphere.
Claim 5
Dependent Claim
11 words
The method of claim 3 wherein said inert environment is nitrogen.
Claim 6
Dependent Claim
11 words
The method of claim 3 wherein said inert environment is argon.
Claim 7
Dependent Claim
18 words
The method of claim 1 wherein said compact is formed of a covalent compound which decomposes during heating.
Claim 8
Dependent Claim
13 words
The method of claim 1 wherein said compact is a silicon-based, nonoxide ceramic.
Claim 9
Dependent Claim
29 words
The method of claim 1 wherein said compact consists of about 80 weight percent of a silicon-based, nonoxide ceramic and to about 20 weight percent of a sintering aid.
Claim 10
Dependent Claim
14 words
The method of claim 7 wherein said ceramic is Si 3 N 4 .
Claim 11
Dependent Claim
10 words
The method of claim 7 wherein said ceramic is SiC.
Claim 12
Dependent Claim
46 words
The method of claim 8 wherein said sintering aid is selected from the group consisting of CeO 2 , MgO, SiO 2 , Y 2 O 3 , ZrO 2 , Al 2 O 3 , AlN, Mg 3 N 2 , and BeN 2 .
Claim 13
Dependent Claim
18 words
The method of claim 1 wherein said nonsinterable powder is a silicon-based, nonoxide ceramic containing no sintering aid.
Claim 14
Dependent Claim
22 words
The method of claim 1 wherein said cover layer is composed of uncompacted powder having a composition substantially identical to said compact.
Claim 15
Independent Claim
121 words
The method of manufacturing ceramic articles, said method comprising the steps of: forming a compact comprising about 80 weight percent Si 3 N 4 and about 20 weight percent CeO 2; surrounding said compact with Si 3 N 4 powder containing no CeO 2; disposing above said powder a cover layer composed of uncompacted powder having a composition substantially identical with said compact; maintaining a pressure of about 0.5-2 atmospheres about said materials; heating said materials to a first temperature of about 1770 C.; maintaining said first temperature for about five minutes to cause at least partial fusion of said cover layer; and reducing the temperature to about 1750 C. for a period of about one hour to sinter said compact.
Claim 16
Independent Claim
121 words
The method of manufacturing ceramic articles, said method comprising the steps of: forming a compact comprising about 80 weight percent Si 3 N 4 and about 20 weight percent CeO 2; surrounding said compact with Si 3 N 4 powder containing no CeO 2; disposing above said powder a cover layer composed of uncompacted powder having a composition substantially identical with said compact; maintaining a pressure of about 0.5-2 atmospheres about said materials; heating said materials to a first temperature of about 1770 C.; maintaining said first temperature for about five minutes to cause at least partial fusion of said cover layer; and reducing the temperature to about 1750 C. for a period of about one hour to sinter said compact.
Claim 17
Dependent Claim
36 words
The method of claim 1 wherein said sintering step comprises: heating said materials to the fusion temperature of said sinterable material; and maintaining said temperature for a period sufficient to cause suitable densification of said compact.
Claim 18
Independent Claim
62 words
A method of manufacturing ceramic articles, said method comprising the steps of: forming a compact comprising a ceramic material and a sintering aid; placing said compact in a crucible; placing a cover, composed of a material which is compatible with said compact, as a lid on said crucible above said compact; and sintering said compact at a pressure of about 0.5-2 atmospheres.
Claim 19
Independent Claim
62 words
A method of manufacturing ceramic articles, said method comprising the steps of: forming a compact comprising a ceramic material and a sintering aid; placing said compact in a crucible; placing a cover, composed of a material which is compatible with said compact, as a lid on said crucible above said compact; and sintering said compact at a pressure of about 0.5-2 atmospheres.
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) | 1983-06-24 | 1983-12-24 | 1984-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-06-24 | 1987-12-24 | 1988-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-06-24 | 1991-12-24 | 1992-06-24 | $7700.00 | Window Closed / Lapsed |