US3720499A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for producing pyrolytic graphite
Assignee: Westinghouse Electric Corp
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Filing: 1970-03-06
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Granted: 1973-03-13
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Expires: 1990-03-06
Abstract
Abstract A hydrocarbon is pyrolyzed to produce a stream of gas having a preselected average gas temperature. An electric arc heater may be employed having an elongated exhaust nozzle, which may be fluid cooled or not fluid cooled, and carbon in the form of soot and/or crystalline graphite may be deposited on the inside wall of the exhaust nozzle, depending on the temperature difference between the gas and the inside surface of the nozzle. Alternatively, an object to be coated with carbon in the form of soot and/or pyrolytic graphite may be mounted in the stream of gas exhausted from the nozzle. The processes may be carried on at atmospheric pressure. The desired average gas temperature may be obtained by adjusting arc power, adjusting the mass flow rate of the hydrocarbon gas, passing a selected portion of the hydrocarbon gas through the arc path to be pyrolyzed and mixing it with another selected portion not passed through the arc path, or utilizing instant variations in current of an alternating current source as the current varies during each alternation between zero and a peak value. An object placed in the gas stream to be coated may be composed of a refractory metal, a refractory non-metal, or may be fluid cooled. Vacuum pump means is used where desired to maintain a pressure at or near atmospheric pressure in the area where an object to be coated comes in contact with the stream of hot gas.
Inventors
- 👤 C Hirayama
- 👤 D Maniero
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:58
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/52; C04B35/522; C01; C01B; C01B32/00; Y; Y10; Y10T; Y10T428/00; Y10T428/30
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
160 words
A process for producing pyrolytic graphite comprising the steps of causing a hydrocarbon gas to flow in a predetermined path without reducing the pressure of said gas in said path below atmospheric pressure, producing a substantially continuously moving electric arc at a predetermined position in said path, the arc heating the gas and pyrolyzing the same and producing an average gas temperature of at least 1500 * C, and at a position in said path downstream of the arc position placing an object having a melting temperature higher than the average gas temperature at that portion of the path and a cooled surface at an operating temperature below the sublimation temperature of carbon and less than the temperature of the heated gas to cause the carbon which is formed as a decomposition product to be precipitated in the form of amorphous carbon to form a thermal barrier and thereafter substantially all of the carbon formed being precipitated as pyrolytic graphite.
Claim 2
Dependent Claim
160 words
A process for producing pyrolytic graphite comprising the steps of causing a hydrocarbon gas to flow in a predetermined path without reducing the pressure of said gas in said path below atmospheric pressure, producing a substantially continuously moving electric arc at a predetermined position in said path, the arc heating the gas and pyrolyzing the same and producing an average gas temperature of at least 1500 * C, and at a position in said path downstream of the arc position placing an object having a melting temperature higher than the average gas temperature at that portion of the path and a cooled surface at an operating temperature below the sublimation temperature of carbon and less than the temperature of the heated gas to cause the carbon which is formed as a decomposition product to be precipitated in the form of amorphous carbon to form a thermal barrier and thereafter substantially all of the carbon formed being precipitated as pyrolytic graphite.
Claim 3
Dependent Claim
29 words
The process according to claim 1 including the additional step of periodically removing pyrolytic graphite from said object to provide a continuous process for the formation of pyrolytic graphite.
Claim 4
Independent Claim
139 words
A method of coating an object with a layer of pyrolytic graphite comprising the steps of utilizing an electric arc to pyrolyze a hydrocarbon gas in the absence of oxygen without reducing the pressure below atmospheric pressure in a chamber having a well defined exhaust area for heated gas, the average temperature of the heated gas being at least 1500* C, and disposing a cooled object to be coated at the exhaust area and in the hot gas stream, the object to be coated having a melting temperature greater than the temperature of the gas and being maintained at an operating temperature less than the sublimation temperature of carbon and less than the temperature of the heated gas, the object to be coated having amorphous carbon first deposited thereon and thereafter having a coating of pyrolytic graphite deposited thereon.
Claim 5
Independent Claim
139 words
A method of coating an object with a layer of pyrolytic graphite comprising the steps of utilizing an electric arc to pyrolyze a hydrocarbon gas in the absence of oxygen without reducing the pressure below atmospheric pressure in a chamber having a well defined exhaust area for heated gas, the average temperature of the heated gas being at least 1500* C, and disposing a cooled object to be coated at the exhaust area and in the hot gas stream, the object to be coated having a melting temperature greater than the temperature of the gas and being maintained at an operating temperature less than the sublimation temperature of carbon and less than the temperature of the heated gas, the object to be coated having amorphous carbon first deposited thereon and thereafter having a coating of pyrolytic graphite deposited thereon.
Claim 6
Dependent Claim
63 words
A process according to claim 3 in which the gas is heated to an average temperature substantially above 1500* Centigrade and including the additional step of maintaining the object to be coated at a temperature of at least 1500*C but less than the temperature of the gas whereby the pyrolytic graphite is deposited in a manner to adhere very strongly to the object.
Claim 7
Dependent Claim
101 words
A process for continuously obtaining pyrolytic graphite which comprises utilizing an electric arc in a confined space to decompose a hydrocarbon gas filling said confined space and produce an average gas temperature of at least 1500* C, causing the decomposed gas to flow in a stream through a well defined path wHile at at least said average temperature, inserting a continuously cooled member cooled below 1500* C in the hot gas stream to produce a deposit thereon including a first layer of amorphous carbon adjacent the surface of the cooled member and pyrolytic graphite deposited on the layer of amorphous carbon.
Claim 8
Dependent Claim
101 words
A process for continuously obtaining pyrolytic graphite which comprises utilizing an electric arc in a confined space to decompose a hydrocarbon gas filling said confined space and produce an average gas temperature of at least 1500* C, causing the decomposed gas to flow in a stream through a well defined path wHile at at least said average temperature, inserting a continuously cooled member cooled below 1500* C in the hot gas stream to produce a deposit thereon including a first layer of amorphous carbon adjacent the surface of the cooled member and pyrolytic graphite deposited on the layer of amorphous carbon.
Claim 9
Dependent Claim
21 words
A process according to claim 3 in which the object is substantially cylindrical and a cylinder of pyrolytic graphite is formed.
Claim 10
Dependent Claim
169 words
A process for producing pyrolytic graphite which comprises producing an arc which follows a predetermined path in an arc chamber having a well defined exhaust area, passing a first portion of a hydrocarbon gas into the arc chamber by a path which causes at least a substantial part of the gas of said first portion to pass through the arc path and to be pyrolyzed, passing a second portion of the hydrocarbon gas into said chamber by a different path whereby the second portion of the gas does not pass through the arc path, the first portion and the second portion being mixed by turbulent mixing after the first portion has passed through the arc path and producing an average gas temperature of at least 1500* C in the gas exhausted through the exhaust area, and placing an object to be coated with carbon in the path of gas exhausted from the exhaust area, the object having a temperature below 1500* C and below the sublimation temperature of carbon.
Claim 11
Dependent Claim
169 words
A process for producing pyrolytic graphite which comprises producing an arc which follows a predetermined path in an arc chamber having a well defined exhaust area, passing a first portion of a hydrocarbon gas into the arc chamber by a path which causes at least a substantial part of the gas of said first portion to pass through the arc path and to be pyrolyzed, passing a second portion of the hydrocarbon gas into said chamber by a different path whereby the second portion of the gas does not pass through the arc path, the first portion and the second portion being mixed by turbulent mixing after the first portion has passed through the arc path and producing an average gas temperature of at least 1500* C in the gas exhausted through the exhaust area, and placing an object to be coated with carbon in the path of gas exhausted from the exhaust area, the object having a temperature below 1500* C and below the sublimation temperature of carbon.
References Cited (Backward Citations)
US3009783A
Cited
US3107180A
Cited
US3168592A
Cited
US3179733A
Cited
US3297406A
Cited
US3288696A
Cited
US3318791A
Cited
US3445191A
Cited
US3554715A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-03-12 | 1976-09-11 | 1977-03-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-12 | 1980-09-11 | 1981-03-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-12 | 1984-09-11 | 1985-03-13 | $7700.00 | Window Closed / Lapsed |