US5449887A
Expired / Lapsed
US
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Thermal insulation for high temperature microwave sintering operations and method thereof
Assignee: Lockheed Martin Energy Systems Inc
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Filing: 1993-03-25
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Granted: 1995-09-12
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Expires: 2013-03-25
Abstract
Abstract Superior microwave transparent thermal insulations for high temperature microwave sintering operations were prepared. One embodiment of the thermal insulation comprises granules of boron nitride coated with a very thin layer of glassy carbon made by preparing a glassy carbon precursor and blending it with boron nitride powder to form a mixture. The blended mixture is granulated to form a grit which is dried and heated to form the granules of boron nitride coated with a glassy carbon. Alternatively, grains of glassy carbon are coated with boron nitride by blending a mixture of a slurry comprising boron nitride, boric acid binder, and methyl alcohol with glassy carbon grains to form a blended mixture. The blended mixture is dried to form grains of glassy carbon coated with boron nitride. In addition, a physical mixture of boron nitride powder and glassy carbon grains has also been shown to be an excellent thermal insulation material for microwave processing and sintering.
Inventors
- 👤 Cressie E. Holcombe
- 👤 Norman L. Dykes
- 👤 Marvin S. Morrow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 18:13
CPC Classifications
H; H05; H05B; H05B6/00; H05B6/64; H05B6/80
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
174 words
A thermal insulation for high temperature microwave sintering operations comprising a material selected from the group consisting of a grit of boron nitride coated with a coating of glassy carbon, a grit of boron nitride coated with a coating of coke, a grit of boron nitride coated with a coating of carbon fibers, a grit of boron nitride coated with a coating of boric acid non-carbon binder, a grit of glassy carbon coated with a coating of boron nitride, a grit of coke coated with a coating of boron nitride, carbon fibers coated with a coating of boron nitride, a grit of boron carbide coated with a coating of boron nitride, a mixture of a grit of glassy carbon and boron nitride powder, a mixture of a grit of coke and boron nitride powder, a mixture of carbon fibers and boron nitride powder, a mixture of a grit of boron carbide and boron nitride powder, and combinations thereof, said thermal insulation being an electrical and thermal insulator and being essentially a noncoupler with microwaves.
Claim 2
Dependent Claim
174 words
A thermal insulation for high temperature microwave sintering operations comprising a material selected from the group consisting of a grit of boron nitride coated with a coating of glassy carbon, a grit of boron nitride coated with a coating of coke, a grit of boron nitride coated with a coating of carbon fibers, a grit of boron nitride coated with a coating of boric acid non-carbon binder, a grit of glassy carbon coated with a coating of boron nitride, a grit of coke coated with a coating of boron nitride, carbon fibers coated with a coating of boron nitride, a grit of boron carbide coated with a coating of boron nitride, a mixture of a grit of glassy carbon and boron nitride powder, a mixture of a grit of coke and boron nitride powder, a mixture of carbon fibers and boron nitride powder, a mixture of a grit of boron carbide and boron nitride powder, and combinations thereof, said thermal insulation being an electrical and thermal insulator and being essentially a noncoupler with microwaves.
Claim 3
Dependent Claim
36 words
A thermal insulation for high temperature microwave sintering operations in accordance with claim 1 wherein said grit of boron nitride comprises boron nitride granules having a particle size ranging from about 150 to about 1400 microns.
Claim 4
Dependent Claim
50 words
A thermal insulation for high temperature microwave sintering operations in accordance with claim 1 wherein said grit of glassy carbon comprises granules having a particle size ranging from about 430 to about 2,000 microns and said coating of boron nitride has a thickness of about 25 to about 200 microns.
Claim 5
Dependent Claim
28 words
A thermal insulation for high temperature microwave sintering operations in accordance with claim 1 wherein said boron nitride powder has a particle size of less than 5 microns.
Claim 6
Dependent Claim
211 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article comprising a container made from a material essentially transparent to microwaves; and thermal insulation contained in said container, said thermal insulation comprising a material selected from the group consisting of a grit of boron nitride coated with a coating of glassy carbon, a grit of boron nitride coated with a coating of coke, a grit of boron nitride coated with a coating of carbon fibers, a grit of boron nitride coated with a coating of boric acid non-carbon binder, a grit of glassy carbon coated with a coating of boron nitride, a grit of coke coated with a coating of boron nitride, carbon fibers coated with a coating of boron nitride, a grit of boron carbide coated with a coating of boron nitride, a mixture of a grit of glassy carbon and boron nitride powder, a mixture of a grit of coke and boron nitride powder, a mixture of carbon fibers and boron nitride powder, a mixture of a grit of boron carbide and boron nitride powder, and combinations thereof, said thermal insulation being an electrical and thermal insulator and being essentially a noncoupler with microwaves, said thermal insulation surrounding and intimately contacting a ceramic article inside said container.
Claim 7
Dependent Claim
211 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article comprising a container made from a material essentially transparent to microwaves; and thermal insulation contained in said container, said thermal insulation comprising a material selected from the group consisting of a grit of boron nitride coated with a coating of glassy carbon, a grit of boron nitride coated with a coating of coke, a grit of boron nitride coated with a coating of carbon fibers, a grit of boron nitride coated with a coating of boric acid non-carbon binder, a grit of glassy carbon coated with a coating of boron nitride, a grit of coke coated with a coating of boron nitride, carbon fibers coated with a coating of boron nitride, a grit of boron carbide coated with a coating of boron nitride, a mixture of a grit of glassy carbon and boron nitride powder, a mixture of a grit of coke and boron nitride powder, a mixture of carbon fibers and boron nitride powder, a mixture of a grit of boron carbide and boron nitride powder, and combinations thereof, said thermal insulation being an electrical and thermal insulator and being essentially a noncoupler with microwaves, said thermal insulation surrounding and intimately contacting a ceramic article inside said container.
Claim 8
Dependent Claim
39 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article in accordance with claim 5 wherein said grit of boron nitride comprises boron nitride granules having a particle size ranging from about 150 to about 1400 microns.
Claim 9
Dependent Claim
24 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article in accordance with claim 5 wherein said container is made from alumina.
Claim 10
Dependent Claim
25 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article in accordance with claim 5 wherein said container is made from boron nitride.
Claim 11
Dependent Claim
51 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article in accordance with claim 5 wherein said grit of glassy carbon has a grain size ranging from about 430 to about 2,000 microns and said coating of boron nitride has a thickness of about 25 to about 200 microns.
Claim 12
Dependent Claim
32 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article in accordance with claim 5 wherein said boron nitride powder has a particle size of less than about 5 microns.
Claim 13
Dependent Claim
47 words
An enclosure apparatus for high temperature microwave sintering of a ceramic article in accordance with claim 5 wherein said material of said container is selected from the group consisting of fused silica, clay-bonded-fused silica, sintered fused silica, alumina 10 w/o silica composite, alumina, yttria, and boron nitride.
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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) | 1998-09-11 | 1999-03-13 | 1999-09-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-09-11 | 2003-03-13 | 2003-09-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-09-11 | 2007-03-13 | 2007-09-12 | $7700.00 | Window Closed / Lapsed |