US5164130A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of sintering ceramic materials
Assignee: Lockheed Martin Energy Systems Inc
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Filing: 1990-04-20
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Granted: 1992-11-17
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Expires: 2010-04-20
Abstract
Abstract A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.
Inventors
- 👤 Cressie E. Holcombe
- 👤 Norman L. Dykes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 02:14
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
74 words
A method of sintering a ceramic article comprising the following steps: Step 1--providing a protective coating to a ceramic article to form a coated ceramic article; Step 2--embedding said coated ceramic article in a container containing refractory metal oxide granules; and Step 3--heating said coated ceramic article embedded within said container containing refractory metal oxide granules by microwave energy to a temperature and for a period of time sufficient to sinter said ceramic article.
Claim 2
Independent Claim
74 words
A method of sintering a ceramic article comprising the following steps: Step 1--providing a protective coating to a ceramic article to form a coated ceramic article; Step 2--embedding said coated ceramic article in a container containing refractory metal oxide granules; and Step 3--heating said coated ceramic article embedded within said container containing refractory metal oxide granules by microwave energy to a temperature and for a period of time sufficient to sinter said ceramic article.
Claim 3
Dependent Claim
62 words
A method in accordance with claim 1 wherein said protective coating comprising a first layer of boron nitride covering said ceramic article, a layer of flexible graphite foil covering said first layer of boron nitride, a second layer of boron nitride covering said layer of flexible graphite foil, and a layer of a refractory metal covering said second layer of boron nitride.
Claim 4
Dependent Claim
23 words
A method in accordance with claim 2 wherein said refractory metal is selected from the group consisting of niobium, tungsten, and mixture thereof.
Claim 5
Dependent Claim
35 words
A method in accordance with claim 1 wherein said protective coating consists essentially of a layer of a refractory metal selected from the group consisting of niobium, tungsten, and mixture thereof covering said ceramic article.
Claim 6
Dependent Claim
16 words
A method in accordance with claim 1 wherein said ceramic article is a boron carbide article.
Claim 7
Dependent Claim
12 words
A method in accordance with claim 5 wherein about 2,100 degrees centigrade.
Claim 8
Dependent Claim
16 words
A method in accordance with claim 1 wherein said ceramic article is a titanium diboride article.
Claim 9
Dependent Claim
19 words
A method in accordance with claim 7 wherein said temperature of Step 3 is greater than 2,100 degrees centigrade.
Claim 10
Dependent Claim
19 words
A method in accordance with claim 2 wherein said temperature of Step 3 is greater than 2,000 degrees centigrade.
Claim 11
Dependent Claim
29 words
A method in accordance with claim 1 wherein said refractory metal oxide granules comprise fused yttria granules having a granular size ranging from about microns to about 2,000 microns.
Claim 12
Dependent Claim
31 words
A method in accordance with claim 1 wherein said container comprises a boron nitride case having a minimum wall thickness of 0.06 inches and alumina bricks surrounding said boron nitride case.
Claim 13
Dependent Claim
23 words
A method in accordance with claim 1 wherein said period of time in Step 3 is equal to or less than 60 minutes.
Claim 14
Independent Claim
130 words
A method of sintering a ceramic article comprising the following steps: Step 1--providing a protective coating to a ceramic article to form a coated ceramic article, said protective coating consisting essentially of a first layer of boron nitride covering said ceramic article, a layer of flexible graphite foil covering said first layer of boron nitride, a second layer of boron nitride covering said layer of flexible graphite foil, and a layer of a refractory metal covering said second layer of boron nitride; Step 2--embedding said coated ceramic article in a container containing refractory metal oxide granules; and Step 3--heating said coated ceramic article embedded within said container containing refractory metal oxide granules by microwave energy to a temperature and for a period of time sufficient to sinter said ceramic article.
Claim 15
Independent Claim
130 words
A method of sintering a ceramic article comprising the following steps: Step 1--providing a protective coating to a ceramic article to form a coated ceramic article, said protective coating consisting essentially of a first layer of boron nitride covering said ceramic article, a layer of flexible graphite foil covering said first layer of boron nitride, a second layer of boron nitride covering said layer of flexible graphite foil, and a layer of a refractory metal covering said second layer of boron nitride; Step 2--embedding said coated ceramic article in a container containing refractory metal oxide granules; and Step 3--heating said coated ceramic article embedded within said container containing refractory metal oxide granules by microwave energy to a temperature and for a period of time sufficient to sinter said ceramic article.
Claim 16
Independent Claim
98 words
A method of preparing a protective coating for a boron carbide article comprising the following steps: Step 1--providing a solid cylinder containing 97 wt.% boron carbide and 3 wt.% carbon; Step 2--coating said solid cylinder with a paint of niobium to form a coated boron carbide article. Step 3--embedding said coated boron carbide article in a container containing refractory metal oxide granules; and Step 4--heating said coated boron carbide article embedded within said container containing refractory metal oxide granules by microwave energy to a temperature and for a period of time sufficient to sinter said boron carbide article.
Claim 17
Independent Claim
98 words
A method of preparing a protective coating for a boron carbide article comprising the following steps: Step 1--providing a solid cylinder containing 97 wt.% boron carbide and 3 wt.% carbon; Step 2--coating said solid cylinder with a paint of niobium to form a coated boron carbide article. Step 3--embedding said coated boron carbide article in a container containing refractory metal oxide granules; and Step 4--heating said coated boron carbide article embedded within said container containing refractory metal oxide granules by microwave energy to a temperature and for a period of time sufficient to sinter said boron carbide article.
Claim 18
Dependent Claim
93 words
A method in accordance with claim 14 wherein said solid cylinder of Step 1 was prepared by blending boron carbide particulates having an average size of 5 microns with particles of phenolic resin in acetone, evaporating said acetone forming boron carbide particulates coated with phenolic resin, undirectionally pressing said coated particulates of boron carbide at 10,000 psi to form a solid cylinder having 1-inch diameters and a height of 1 inch, and carbonizing said phenolic resin at temperatures ranging from 850°-950° C. for a period of about 1 hour in an argon atmosphere.
Claim 19
Dependent Claim
60 words
A method in accordance with claim 14 wherein said coating is prepared by blending niobium powder having an average size of 5 microns with an aqueous solution containing 3 wt.% of carboxymethylcellulose and a binder/suspension agent to form a niobium paint, said niobium paint consists essentially of 58 wt.% niobium powder and 42 wt.% of the aqueous solution of carboxymethylcellulose.
Claim 20
Dependent Claim
19 words
A method in accordance with claim 14 wherein said temperature of Step 3 is greater than 2,000 degrees centigrade.
Claim 21
Dependent Claim
30 words
A method in accordance with claim 14 wherein said refractory metal oxide granules comprise fused yttria granules having a granular size ranging from about 150 microns to about 2,000 microns.
Claim 22
Dependent Claim
31 words
A method in accordance with claim 14 wherein said container comprises a boron nitride case having a minimum wall thickness of 0.06 inches and alumina bricks surrounding said boron nitride crucible.
Claim 23
Dependent Claim
23 words
A method in accordance with claim 14 wherein said period of time in Step 3 is equal to or less than 60 minutes.
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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) | 1995-11-17 | 1996-05-18 | 1996-11-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-11-17 | 2000-05-18 | 2000-11-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-11-17 | 2004-05-18 | 2004-11-17 | $7700.00 | Window Closed / Lapsed |