Patent US5131992A successfully refreshed from Google Patents.
US5131992A
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Microwave induced plasma process for producing tungsten carbide
Assignee: United States Department of the Interior
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Filing: 1991-05-20
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Granted: 1992-07-21
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Expires: 2011-05-20
Abstract
Abstract A method of heating reactant materials in a plasma chamber to achieve a reaction temperature by enveloping the materials in a microwave induced electric plasma. The plasma chamber positioned in the microwave waveguide is filled with a gas and predetermined quantities of the reactant materials are placed in the chamber or reactor. A microwave produced electric field is passed through the gas to ionize it and produce an electric plasma that envelopes the reactant materials. The process may be used in a variety of high temperature chemical processes such as the production of tungsten carbide.
Inventors
- 👤 Ronald H. Church
- 👤 Johanna B. Salsman
- 👤 Bobby J. Hamner
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 18:14
CPC Classifications
H; H01; H01J; H01J37/00; H01J37/32; H01J37/32009; H01J37/32192; H01J37/32211; H01J37/32229; H05; H05H; H05H1/00; H05H1/24; H05H1/46; H01J2237/00; H01J2237/32; H01J2237/33; H01J2237/338
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
162 words
A method of rapidly producing tungsten carbide particles in a microwave induced plasma to provide a higher distribution of particle sizes wherein one hundred percent of the particles are less than 7.46 μm, 83 percent of the particles are less than 5.27 μm, 69 percent of the particles are less than 3.73 μm, 45 percent of the particles are less than 2.63 μm, 19 percent of the particles are less than 1.69 μm, 7 percent of the particles are less than 1.01 μm, and 2 percent of the particles are less than 0.66 μm, comprising: filling a plasma chamber with a gas selected from argon, carbon monoxide, carbon dioxide, helium and butane; charging a mixture of tungsten and carbon powders into the plasma chamber; passing a microwave produced electric field through the gas to ionize the gas and produce a microwave induced electric plasma to uniformly envelop the powders and cause the powders to react and yield a resultant tungsten carbide product.
Claim 2
Independent Claim
162 words
A method of rapidly producing tungsten carbide particles in a microwave induced plasma to provide a higher distribution of particle sizes wherein one hundred percent of the particles are less than 7.46 μm, 83 percent of the particles are less than 5.27 μm, 69 percent of the particles are less than 3.73 μm, 45 percent of the particles are less than 2.63 μm, 19 percent of the particles are less than 1.69 μm, 7 percent of the particles are less than 1.01 μm, and 2 percent of the particles are less than 0.66 μm, comprising: filling a plasma chamber with a gas selected from argon, carbon monoxide, carbon dioxide, helium and butane; charging a mixture of tungsten and carbon powders into the plasma chamber; passing a microwave produced electric field through the gas to ionize the gas and produce a microwave induced electric plasma to uniformly envelop the powders and cause the powders to react and yield a resultant tungsten carbide product.
Claim 3
Dependent Claim
19 words
The method of claim 1 wherein envelopment of the powders includes heating the powders conductively through the electric plasma.
Claim 4
Dependent Claim
19 words
The method of claim 1 wherein envelopment of the powders includes heating the powders by absorption of microwave energy.
Claim 5
Dependent Claim
11 words
The method of claim 1 wherein the gas is carbon monoxide.
Claim 6
Dependent Claim
30 words
The method of claim 4 wherein the tungsten is present in an amount of about 93.5 weight percent, and carbon is present in an amount of about 6.5 weight percent.
Claim 7
Dependent Claim
25 words
The method of claim 5 wherein said carbon monoxide is provided at a flow rate sufficient to maintain a positive pressure in the plasma chamber.
References Cited (Backward Citations)
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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) | 1995-07-21 | 1996-01-20 | 1996-07-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-07-21 | 2000-01-20 | 2000-07-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-07-21 | 2004-01-20 | 2004-07-21 | $7700.00 | Window Closed / Lapsed |