CA2652428A1 - Highly ordered structure pyrolitic graphite or carbon-carbon composite cathodes for plasma generation in carbon containing gases - Google Patents
Highly ordered structure pyrolitic graphite or carbon-carbon composite cathodes for plasma generation in carbon containing gases Download PDFInfo
- Publication number
- CA2652428A1 CA2652428A1 CA002652428A CA2652428A CA2652428A1 CA 2652428 A1 CA2652428 A1 CA 2652428A1 CA 002652428 A CA002652428 A CA 002652428A CA 2652428 A CA2652428 A CA 2652428A CA 2652428 A1 CA2652428 A1 CA 2652428A1
- Authority
- CA
- Canada
- Prior art keywords
- carbon
- electrode
- surface region
- planar outer
- chamber
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
- H05H1/26—Plasma torches
- H05H1/32—Plasma torches using an arc
- H05H1/34—Details, e.g. electrodes, nozzles
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
- H05H1/00—Generating plasma; Handling plasma
- H05H1/24—Generating plasma
- H05H1/26—Plasma torches
- H05H1/32—Plasma torches using an arc
- H05H1/34—Details, e.g. electrodes, nozzles
- H05H1/3436—Hollow cathodes with internal coolant flow
Abstract
A DC plasma torch which includes a long lasting thermionic cathode and has a high thermal efficiency. The DC plasma torch employs a solid cathode made of graphite with highly ordered structure such as Pyrolitic Graphite or Carbon-Carbon composites. Furthermore, carbon containing gases will be used as plasma gas. The cathode will allow for theoretically an unlimited lifetime of the cathode.
Description
01 Apri1 2008 01-. _008 HIGHLY ORDERED STRUCTURE PYROLITIC GRAPHITE OR
CARBON-CARBON COMPOSITE CATHODES FOR PLASMA
GENERATION IN CARBON CONTAINING GASES
s FIELD OF THE INVENTION
The present invention relates generally to carbon based cathodes for DC plasma torches which includes a long lasting thermionic cathode and a high thermal efficiency.
BACKGROUND OF THE INVENTION
Industrial types of direct current (DC) thermal spray plasma torches are built with a water-cooled tungsten cathode and a copper anode. Main plasma gas is argon. The use of argon is dictated by its inertness at high temperatures to the thermionic tungsten cathode. Thermionic cathodes emit electrons from their surface since their temperature is high enough for easy emission of electrons. Tungsten is the preferred cathode material since it is a refractory metal with high melting point temperature. It is however, highly reactive to oxygen at high temperatures. During the operation of the torch, cathode tip is melted and tungsten evaporates. The cathode erosion rate is ALII:NDED $HEET
CARBON-CARBON COMPOSITE CATHODES FOR PLASMA
GENERATION IN CARBON CONTAINING GASES
s FIELD OF THE INVENTION
The present invention relates generally to carbon based cathodes for DC plasma torches which includes a long lasting thermionic cathode and a high thermal efficiency.
BACKGROUND OF THE INVENTION
Industrial types of direct current (DC) thermal spray plasma torches are built with a water-cooled tungsten cathode and a copper anode. Main plasma gas is argon. The use of argon is dictated by its inertness at high temperatures to the thermionic tungsten cathode. Thermionic cathodes emit electrons from their surface since their temperature is high enough for easy emission of electrons. Tungsten is the preferred cathode material since it is a refractory metal with high melting point temperature. It is however, highly reactive to oxygen at high temperatures. During the operation of the torch, cathode tip is melted and tungsten evaporates. The cathode erosion rate is ALII:NDED $HEET
directly dependent on its temperature. Cathode lifetime and consistency of its performance is an important issue in this technology.
One disadvantage of argon is its low thermal conductivity and its low enthalpy which results in reduced thermal efficiency of the DC plasma torches. The low thermal efficiency limits powder feed rate, deposition efficiency and coating quality. To enhance thermal conductivity and thermal efficiency, small amounts of hydrogen or helium are normally mixed with argon.
It is known that to reduce the erosion of the graphite cathodes, they must be cooled either by encasing them in a water-cooled metal jacket (see for example U.S. Patent Nos. 4,490,825 and 4,304,980) or by external water spraying directly onto the electrode (U.S. Patent No. 5,795,539). Direct internal water cooling of graphite electrodes is not practical since the cathode is normally made of polycrystalline graphite which has open porosity and, compared to metals, lower thermal conductivity. This leads to the infiltration of the cooling water through the electrode as well as a less effective heat removal. The latter imposes limits on power generated by the plasma torch.
It would be very advantageous to provide a DC plasma torch which has a long lasting thermionic cathode having a high thermal efficiency.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a DC plasma torch embodiments of which employ a carbon cathode made of graphite with highly ordered structure such as pyrolitic graphite or carbon-carbon composites.
01 April 2008 01-, .008 Furthermore, carbon containing gases are used as the plasma gas to give a long lifetime of the cathode since by using carbon the cathode is regenerated.
The present invention provides a cathode electrode for plasma generation, comprising:
a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18 and a liquid inlet 22 for admitting liquid coolant to said chamber 20 to cool said interior surface region 16, and wherein a region 24 of said carbon electrode 10 between said planar outer electrode surface region 18 and said interior surface 16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18 such that when in operation as a cathode in a plasma torch, a plasma arc is formed adjacent to said planar outer electrode surface region 18.
The present invention also provides embodiments of a plasma torch, comprising:
a) a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18, and wherein a region 24 of said carbon electrode 10 between said planar outer electrode surface region 18 and said interior surface.16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18;
One disadvantage of argon is its low thermal conductivity and its low enthalpy which results in reduced thermal efficiency of the DC plasma torches. The low thermal efficiency limits powder feed rate, deposition efficiency and coating quality. To enhance thermal conductivity and thermal efficiency, small amounts of hydrogen or helium are normally mixed with argon.
It is known that to reduce the erosion of the graphite cathodes, they must be cooled either by encasing them in a water-cooled metal jacket (see for example U.S. Patent Nos. 4,490,825 and 4,304,980) or by external water spraying directly onto the electrode (U.S. Patent No. 5,795,539). Direct internal water cooling of graphite electrodes is not practical since the cathode is normally made of polycrystalline graphite which has open porosity and, compared to metals, lower thermal conductivity. This leads to the infiltration of the cooling water through the electrode as well as a less effective heat removal. The latter imposes limits on power generated by the plasma torch.
It would be very advantageous to provide a DC plasma torch which has a long lasting thermionic cathode having a high thermal efficiency.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a DC plasma torch embodiments of which employ a carbon cathode made of graphite with highly ordered structure such as pyrolitic graphite or carbon-carbon composites.
01 April 2008 01-, .008 Furthermore, carbon containing gases are used as the plasma gas to give a long lifetime of the cathode since by using carbon the cathode is regenerated.
The present invention provides a cathode electrode for plasma generation, comprising:
a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18 and a liquid inlet 22 for admitting liquid coolant to said chamber 20 to cool said interior surface region 16, and wherein a region 24 of said carbon electrode 10 between said planar outer electrode surface region 18 and said interior surface 16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18 such that when in operation as a cathode in a plasma torch, a plasma arc is formed adjacent to said planar outer electrode surface region 18.
The present invention also provides embodiments of a plasma torch, comprising:
a) a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18, and wherein a region 24 of said carbon electrode 10 between said planar outer electrode surface region 18 and said interior surface.16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18;
AMENDED SHEET
b) an anode 42 including an interior chamber 46 in communication with an exit channel 48;
c) an outer mounting tube 50 having a first end portion to which cathode 10 is attached, said outer mounting tube 50 being inserted into said interior chamber 46 of said anode 42 with said planar outer electrode surface region 18 being spaced from and symmetrically aligned with said exit passageway 48;
d) an inner tube 52 inserted into said chamber 20 of the electrode 10 with one open end of the inner tube 52 being adjacent to a space from the interior surface 16 and having a diameter smaller than diameter of the chamber 20 so that an annular passageway 58 is formed between an interior side wall of the chamber 20 and an outer surface of the inner tube 52, a second open end of the inner tube 52 being a fluid inlet for cooling fluid to flow down through the inner tube 52 to contact interior surface 16 after which the fluid flows back through the annular passageway 58 and out of the plasma torch, said anode including ports 44 for introducing plasma gas into said interior chamber 46; and e) wherein in operation a gas mixture comprised of one or more carbon containing gases is flowed into said interior chamber 46 through said ports 44 and a plasma arc is formed in said interior chamber 46 and discharged through said exit passageway 48.
A further understanding of the functional and advantageous aspects of the invention can be realized by reference to the following detailed description and drawings.
b) an anode 42 including an interior chamber 46 in communication with an exit channel 48;
c) an outer mounting tube 50 having a first end portion to which cathode 10 is attached, said outer mounting tube 50 being inserted into said interior chamber 46 of said anode 42 with said planar outer electrode surface region 18 being spaced from and symmetrically aligned with said exit passageway 48;
d) an inner tube 52 inserted into said chamber 20 of the electrode 10 with one open end of the inner tube 52 being adjacent to a space from the interior surface 16 and having a diameter smaller than diameter of the chamber 20 so that an annular passageway 58 is formed between an interior side wall of the chamber 20 and an outer surface of the inner tube 52, a second open end of the inner tube 52 being a fluid inlet for cooling fluid to flow down through the inner tube 52 to contact interior surface 16 after which the fluid flows back through the annular passageway 58 and out of the plasma torch, said anode including ports 44 for introducing plasma gas into said interior chamber 46; and e) wherein in operation a gas mixture comprised of one or more carbon containing gases is flowed into said interior chamber 46 through said ports 44 and a plasma arc is formed in said interior chamber 46 and discharged through said exit passageway 48.
A further understanding of the functional and advantageous aspects of the invention can be realized by reference to the following detailed description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention are described in greater detail with reference to the accompanying drawings.
Figure 1 shows a cross sectional view of a plasma torch cathode electrode constructed in accordance with the present invention; and Figure 2 shows a plasma torch containing the cathode electrode of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
Generally speaking, the systems described herein are directed to cathodes for DC plasma torches and plasma torches containing same. As required, embodiments of the present invention are disclosed herein.
However, the disclosed embodiments are merely exemplary, and it should be understood that the invention may be embodied in many various and alternative forms. The Figures are not to scale and some features may be exaggerated or minimized to show details of particular elements while related elements may have been eliminated to prevent obscuring novel aspects.
Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention. For purposes of teaching and not limitation, the illustrated embodiments are directed cathodes for DC plasma torches and DC plasma torches containing same.
Embodiments of the present invention are described in greater detail with reference to the accompanying drawings.
Figure 1 shows a cross sectional view of a plasma torch cathode electrode constructed in accordance with the present invention; and Figure 2 shows a plasma torch containing the cathode electrode of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
Generally speaking, the systems described herein are directed to cathodes for DC plasma torches and plasma torches containing same. As required, embodiments of the present invention are disclosed herein.
However, the disclosed embodiments are merely exemplary, and it should be understood that the invention may be embodied in many various and alternative forms. The Figures are not to scale and some features may be exaggerated or minimized to show details of particular elements while related elements may have been eliminated to prevent obscuring novel aspects.
Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention. For purposes of teaching and not limitation, the illustrated embodiments are directed cathodes for DC plasma torches and DC plasma torches containing same.
As used herein, the term "about", when used in conjunction with ranges of dimensions of particles or other physical properties or characteristics, is meant to cover slight variations that may exist in the upper and lower limits of the ranges of dimensions so as to not exclude embodiments where on average most of the dimensions are satisfied but where statistically dimensions may exist outside this region. It is not the intention to exclude embodiments such as these from the present invention.
Embodiments of the present invention relate to cathodes for DC
plasma torches which includes a long lasting thermionic cathode and has a high thermal efficiency. Specifically, the new design employs a solid cathode made of graphite with highly ordered structure such as pyrolitic graphite or Carbon-Carbon composites. Furthermore, carbon containing gases will be used as plasma gas. As it will be shown in the following paragraphs description, the above combination will allow for theoretically an unlimited lifetime of the cathode.
In order to improve the graphite electrode cooling and increase torch power, a graphite electrode made of high thermal conductivity pyrolitic graphite or of a carbon fiber-carbon matrix composite is used as the cathode electrode. Pyrolitic graphite structure has low crystal lattice defects and carbon atoms planes are placed parallel to each other, therefore the structure and its properties closely match those of the ideal graphite crystal. This specific crystal structure results in significant electrical and thermal properties anisotropy. Particularly, thermal conductivity varies considerably from 1100-1500 W/mK when measured within the plane compared to only 2 W/mK when measured perpendicular to the plane. Graphite fibers also have high thermal conductivity of up to 1200 w/mK which is four times higher than copper.
Referring to Figure 1, the cathode disclosed herein is shown generally at 10 and is made in the shape of a cylindrical cup 12 from graphite with a highly ordered, low defect crystal structure such as obtained using for example pyrolitic graphite or carbon fibers. The graphite structure has an orientation in such a way that the maximum thermal conductivity plane coincides with the axis 14 of the electrode from inner surface 16 to the outer surface 18. For the electrode made of a carbon fiber -carbon composite, the fibers must be aligned longitudinally along the electrode axis 14 as well. In other words the carbon fibers are parallel to axis 14 to give the optimum thermal conductivity from inner surface 16 to outer surface 18. This ensures the highest heat removal from area of the arc attachment. The density of pyrolitic graphite is high; it is close to the theoretical density of carbon (2.25 g/cm3) which makes it essentially non-porous (Table 1). This allows for direct water cooling of the electrode 12 by flowing water into chamber 20 through the chamber opening 22 without infiltration of water through the cathode 10.
Although graphite is evaporated during the torch operation, its erosion will be compensated by the precipitation of carbon ions on the graphite cathode. This reconstruction of the cathode 10 is only possible if the arc is operated in carbon containing gases. Figure 2 shows a plasma torch 40 with graphite cathode 10, an anode 42 including an interior chamber 46 in communication with an exit passageway 48 and ports 44 for introducing plasma gas into chamber 46. Cathode 10 is preferably cylindrically shaped having an inner threaded portion and is threaded onto the end of an outer threaded mounting tube 50. An inner tube 52 is inserted into chamber 20 with one open end of the inner tube 52 being adjacent to and spaced from the interior surface 16 of cathode 10 and having a diameter smaller than diameter of the chamber 20 so that an annular passageway 58 is formed between an interior side wall of the chamber 20 and an outer surface of the inner tube 52.
The second open end of the inner tube 52 is a fluid inlet for cooling fluid to flow down through inner tube 52 to contact interior surface 16 after which the fluid flows back through annular passageway 58 and out of the plasma torch.
The anode includes ports 44 for introducing plasma gas into the interior chamber 46.
Cooling water to cool cathode 10 flows through the outer end of inner tube 52 and down central channel 56 around the end of inner tube 52 over the inner surface 16 (Figure 1) of cathode 10 thereby cooling it, and out through annular channel 58 between inner tube 52 and outer tube 50. Because the molecular orientation of the constituent components of electrode 10 (whether graphite planes or longitudinal fibers) which run parallel to axis 14, so that the region 24 between inner surface 16 and the outer surface 18 of electrode 10 form planes of maximum thermal conductivity parallel to axis 14 so that surface 18 is cooled. In operation a sufficiently high DC voltage is applied between the cathode and anode electrodes and a gas mixture comprised of one or more carbon containing gases is flowed into the interior chamber 46 through the ports 44 and a plasma arc is formed in the chamber 46 and discharged through the passageway 48.
The gas mixture will be composed from hydrocarbons (methane, ethylene, propane, etc.) and carbon dioxide. Because of the high plasma temperature, hydrocarbons dissociate into free carbon and hydrogen. They are then ionized. Subsequently positive carbon ions move from the gas phase to the cathode emissive surface, where dynamic equilibrium between carbon evaporation and precipitation takes place. This process compensates cathode erosion and ensures long operation life.
As used herein, the terms "comprises", "comprising", "including" and "includes" are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in this specification including claims, the terms "comprises", "comprising", "including" and "includes" and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.
The foregoing description of the preferred embodiments of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.
Embodiments of the present invention relate to cathodes for DC
plasma torches which includes a long lasting thermionic cathode and has a high thermal efficiency. Specifically, the new design employs a solid cathode made of graphite with highly ordered structure such as pyrolitic graphite or Carbon-Carbon composites. Furthermore, carbon containing gases will be used as plasma gas. As it will be shown in the following paragraphs description, the above combination will allow for theoretically an unlimited lifetime of the cathode.
In order to improve the graphite electrode cooling and increase torch power, a graphite electrode made of high thermal conductivity pyrolitic graphite or of a carbon fiber-carbon matrix composite is used as the cathode electrode. Pyrolitic graphite structure has low crystal lattice defects and carbon atoms planes are placed parallel to each other, therefore the structure and its properties closely match those of the ideal graphite crystal. This specific crystal structure results in significant electrical and thermal properties anisotropy. Particularly, thermal conductivity varies considerably from 1100-1500 W/mK when measured within the plane compared to only 2 W/mK when measured perpendicular to the plane. Graphite fibers also have high thermal conductivity of up to 1200 w/mK which is four times higher than copper.
Referring to Figure 1, the cathode disclosed herein is shown generally at 10 and is made in the shape of a cylindrical cup 12 from graphite with a highly ordered, low defect crystal structure such as obtained using for example pyrolitic graphite or carbon fibers. The graphite structure has an orientation in such a way that the maximum thermal conductivity plane coincides with the axis 14 of the electrode from inner surface 16 to the outer surface 18. For the electrode made of a carbon fiber -carbon composite, the fibers must be aligned longitudinally along the electrode axis 14 as well. In other words the carbon fibers are parallel to axis 14 to give the optimum thermal conductivity from inner surface 16 to outer surface 18. This ensures the highest heat removal from area of the arc attachment. The density of pyrolitic graphite is high; it is close to the theoretical density of carbon (2.25 g/cm3) which makes it essentially non-porous (Table 1). This allows for direct water cooling of the electrode 12 by flowing water into chamber 20 through the chamber opening 22 without infiltration of water through the cathode 10.
Although graphite is evaporated during the torch operation, its erosion will be compensated by the precipitation of carbon ions on the graphite cathode. This reconstruction of the cathode 10 is only possible if the arc is operated in carbon containing gases. Figure 2 shows a plasma torch 40 with graphite cathode 10, an anode 42 including an interior chamber 46 in communication with an exit passageway 48 and ports 44 for introducing plasma gas into chamber 46. Cathode 10 is preferably cylindrically shaped having an inner threaded portion and is threaded onto the end of an outer threaded mounting tube 50. An inner tube 52 is inserted into chamber 20 with one open end of the inner tube 52 being adjacent to and spaced from the interior surface 16 of cathode 10 and having a diameter smaller than diameter of the chamber 20 so that an annular passageway 58 is formed between an interior side wall of the chamber 20 and an outer surface of the inner tube 52.
The second open end of the inner tube 52 is a fluid inlet for cooling fluid to flow down through inner tube 52 to contact interior surface 16 after which the fluid flows back through annular passageway 58 and out of the plasma torch.
The anode includes ports 44 for introducing plasma gas into the interior chamber 46.
Cooling water to cool cathode 10 flows through the outer end of inner tube 52 and down central channel 56 around the end of inner tube 52 over the inner surface 16 (Figure 1) of cathode 10 thereby cooling it, and out through annular channel 58 between inner tube 52 and outer tube 50. Because the molecular orientation of the constituent components of electrode 10 (whether graphite planes or longitudinal fibers) which run parallel to axis 14, so that the region 24 between inner surface 16 and the outer surface 18 of electrode 10 form planes of maximum thermal conductivity parallel to axis 14 so that surface 18 is cooled. In operation a sufficiently high DC voltage is applied between the cathode and anode electrodes and a gas mixture comprised of one or more carbon containing gases is flowed into the interior chamber 46 through the ports 44 and a plasma arc is formed in the chamber 46 and discharged through the passageway 48.
The gas mixture will be composed from hydrocarbons (methane, ethylene, propane, etc.) and carbon dioxide. Because of the high plasma temperature, hydrocarbons dissociate into free carbon and hydrogen. They are then ionized. Subsequently positive carbon ions move from the gas phase to the cathode emissive surface, where dynamic equilibrium between carbon evaporation and precipitation takes place. This process compensates cathode erosion and ensures long operation life.
As used herein, the terms "comprises", "comprising", "including" and "includes" are to be construed as being inclusive and open ended, and not exclusive. Specifically, when used in this specification including claims, the terms "comprises", "comprising", "including" and "includes" and variations thereof mean the specified features, steps or components are included. These terms are not to be interpreted to exclude the presence of other features, steps or components.
The foregoing description of the preferred embodiments of the invention has been presented to illustrate the principles of the invention and not to limit the invention to the particular embodiment illustrated. It is intended that the scope of the invention be defined by all of the embodiments encompassed within the following claims and their equivalents.
Table 1:GRAPHITE MATERIALS
DENSITY THERMAL REFER-TYPE OR BRAND [g/c3 ] CONDUCTIVITY ENCE
NAME [W/mK]
APG Pyrolitic 2.3 Graphite 1700 1 Annealed Pyrolitic Graphite 2.22 1100-1300 2 Carbon Fiber 1.8-2.2 1100 1,5 Graphite electrodes for steelmaking 1.6-1.75 2.20-300 3,4 References 1. Website of k-Technology Corporation (www.k-technology.com) 2. Website of Pyrogenics Group (www.pyrographite.com) 3. Website of SGL Carbon AG (www.spicarbon.com) 4. Pierson, H.O. "Handbook of Carbon, Graphite, Diamond and Fullerenes-Properties, Processing and Applications", William Andrew Publishing, 2001, pp 399.
5. Dresselhaus, M.S. "Graphite fibers and filaments", Springer-Veriag, 1988, 382 p.
DENSITY THERMAL REFER-TYPE OR BRAND [g/c3 ] CONDUCTIVITY ENCE
NAME [W/mK]
APG Pyrolitic 2.3 Graphite 1700 1 Annealed Pyrolitic Graphite 2.22 1100-1300 2 Carbon Fiber 1.8-2.2 1100 1,5 Graphite electrodes for steelmaking 1.6-1.75 2.20-300 3,4 References 1. Website of k-Technology Corporation (www.k-technology.com) 2. Website of Pyrogenics Group (www.pyrographite.com) 3. Website of SGL Carbon AG (www.spicarbon.com) 4. Pierson, H.O. "Handbook of Carbon, Graphite, Diamond and Fullerenes-Properties, Processing and Applications", William Andrew Publishing, 2001, pp 399.
5. Dresselhaus, M.S. "Graphite fibers and filaments", Springer-Veriag, 1988, 382 p.
Claims (10)
1. A cathode electrode for plasma generation, comprising:
a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18 and a liquid inlet 22 for admitting liquid coolant to said chamber 20 to cool said interior surface region 16, and wherein a region 24 of said carbon electrode between said planar outer electrode surface region 18 and said interior surface 16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18 such that when in operation as a cathode in a plasma torch, a plasma arc is formed adjacent to said planar outer electrode surface region 18.
a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18 and a liquid inlet 22 for admitting liquid coolant to said chamber 20 to cool said interior surface region 16, and wherein a region 24 of said carbon electrode between said planar outer electrode surface region 18 and said interior surface 16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18 such that when in operation as a cathode in a plasma torch, a plasma arc is formed adjacent to said planar outer electrode surface region 18.
2. The cathode electrode according to claim 1 wherein said carbon electrode 10 has a generally cylindrical shape having a planar end coinciding with said planar outer electrode surface region 18, said carbon electrode 10 including a cylindrical axis 14 which extends symmetrically through said planar outer electrode surface region 18 and said interior surface 16, and wherein said maximum thermal conductivity occurs parallel to said cylindrical axis 14.
3. The cathode electrode according to claim 2 wherein said carbon electrode 10 is made of pyrolitic graphite having highly ordered, low defect crystal structure, and an orientation such that a maximum thermal conductivity plane of the pyrolitic graphite is parallel with the cylindrical axis 14 of the carbon electrode 10 from said interior surface 16 to the planar outer electrode surface 18.
4. The cathode electrode according to claim 2 wherein said carbon electrode 10 is made of carbon fibers, wherein the carbon fibres are aligned longitudinally along the cylindrical axis 14 of the carbon electrode 10 parallel thereto.
5. The cathode electrode according to claim 1, 2, 3 or 4 wherein said carbon electrode 10 is for use for plasma generation in carbon containing gases.
6. A plasma torch, comprising:
a) a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18, and wherein a region 24 of said carbon electrode 10 between said planar outer electrode surface region 18 and said interior surface 16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18;
b) an anode 42 including an interior chamber 46 in communication with an exit channel 48;
c) an outer mounting tube 50 having a first end portion to which cathode 10 is attached, said outer mounting tube 50 being inserted into said interior chamber 46 of said anode 42 with said planar outer electrode surface region 18 being spaced from and symmetrically aligned with said exit passageway 48;
d) an inner tube 52 inserted into said chamber 20 of the electrode 10 with one open end of the inner tube 52 being adjacent to a space from the interior surface 16 and having a diameter smaller than diameter of the chamber 20 so that an annular passageway 58 is formed between an interior side wall of the chamber 20 and an outer surface of the inner tube 52, a second open end of the inner tube 52 being a fluid inlet for cooling fluid to flow down through the inner tube 52 to contact interior surface 16 after which the fluid flows back through the annular passageway 58 and out of the plasma torch, said anode including ports 44 for introducing plasma gas into said interior chamber 46; and e) wherein in operation a gas mixture comprised of one or more carbon containing gases is flowed into said interior chamber 46 through said ports 44 and a plasma arc is formed in said interior chamber 46 and discharged through said exit passageway 48.
a) a carbon electrode 10 having a chamber 20 and a substantially planar outer electrode surface region 18, said chamber 20 having an interior surface region 16 spaced from said planar outer electrode surface region 18, and wherein a region 24 of said carbon electrode 10 between said planar outer electrode surface region 18 and said interior surface 16 has a molecular orientation such that maximum thermal conductivity occurs between said interior surface 16 and said planar outer electrode surface region 18 for dissipation of heat at said planar outer electrode surface region 18;
b) an anode 42 including an interior chamber 46 in communication with an exit channel 48;
c) an outer mounting tube 50 having a first end portion to which cathode 10 is attached, said outer mounting tube 50 being inserted into said interior chamber 46 of said anode 42 with said planar outer electrode surface region 18 being spaced from and symmetrically aligned with said exit passageway 48;
d) an inner tube 52 inserted into said chamber 20 of the electrode 10 with one open end of the inner tube 52 being adjacent to a space from the interior surface 16 and having a diameter smaller than diameter of the chamber 20 so that an annular passageway 58 is formed between an interior side wall of the chamber 20 and an outer surface of the inner tube 52, a second open end of the inner tube 52 being a fluid inlet for cooling fluid to flow down through the inner tube 52 to contact interior surface 16 after which the fluid flows back through the annular passageway 58 and out of the plasma torch, said anode including ports 44 for introducing plasma gas into said interior chamber 46; and e) wherein in operation a gas mixture comprised of one or more carbon containing gases is flowed into said interior chamber 46 through said ports 44 and a plasma arc is formed in said interior chamber 46 and discharged through said exit passageway 48.
7. The plasma torch according to claim 6 wherein said carbon electrode has a generally cylindrical shape having an outer part of which is threaded and being threaded onto the end of the outer mounting tube 50, said cathode having a planar end coinciding with said planar outer electrode surface region 18, said carbon electrode 10 including a cylindrical axis 14 which extends symmetrically through said planar outer electrode surface region 18 and said interior surface 16, and wherein said maximum thermal conductivity occurs parallel to said cylindrical axis 14.
8. The plasma torch according to claim 7 wherein said carbon electrode 10 is made of pyrolitic graphite having highly ordered, low defect crystal structure, and an orientation such that a maximum thermal conductivity plane of the pyrolitic graphite is parallel with the cylindrical axis 14 of the carbon electrode 10 from said interior surface 16 to the planar outer electrode surface 18.
9. The plasma torch according to claim 7 wherein said carbon electrode
10 is made of carbon fibers, wherein the carbon fibres are aligned longitudinally along the cylindrical axis 14 of the carbon electrode 10 parallel thereto.
10. The plasma torch according to claim 6, 7, 8 or 9 wherein including a DC power supply connected between said anode electrode and said cathode electrode.
10. The plasma torch according to claim 6, 7, 8 or 9 wherein including a DC power supply connected between said anode electrode and said cathode electrode.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US80110106P | 2006-05-18 | 2006-05-18 | |
| US60/801,101 | 2006-05-18 | ||
| PCT/CA2007/000846 WO2007134432A1 (en) | 2006-05-18 | 2007-05-16 | Highly ordered structure pyrolitic graphite or carbon-carbon composite cathodes for plasma generation in carbon containing gases |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2652428A1 true CA2652428A1 (en) | 2007-11-29 |
Family
ID=38722891
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002652428A Abandoned CA2652428A1 (en) | 2006-05-18 | 2007-05-16 | Highly ordered structure pyrolitic graphite or carbon-carbon composite cathodes for plasma generation in carbon containing gases |
Country Status (3)
| Country | Link |
|---|---|
| US (2) | US8148661B2 (en) |
| CA (1) | CA2652428A1 (en) |
| WO (1) | WO2007134432A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2796062A1 (en) * | 2010-03-26 | 2011-09-29 | Perfect Point Edm Corporation | Hand tool centering devices and methods |
| US9144148B2 (en) | 2013-07-25 | 2015-09-22 | Hypertherm, Inc. | Devices for gas cooling plasma arc torches and related systems and methods |
| EP3563399A4 (en) * | 2016-12-29 | 2020-07-29 | The University of British Columbia | Optically addressed, thermionic electron beam device |
| JP6800780B2 (en) * | 2017-03-07 | 2020-12-16 | 日鉄エンジニアリング株式会社 | Plasma torch, molten metal heating device and molten metal heating method |
| US10429026B2 (en) * | 2017-06-16 | 2019-10-01 | GM Global Technology Operations LLC | Lamp assembly with anisotropic heat spreader and vehicle having the same |
| CN109401786A (en) * | 2018-11-08 | 2019-03-01 | 山西普皓环保科技有限公司 | A kind of plasma device handling clinical waste |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3410746A (en) * | 1964-03-12 | 1968-11-12 | Space Age Materials Corp | Grain-oriented pyrolytic graphite forms and method of making same |
| US3324333A (en) * | 1965-06-18 | 1967-06-06 | Curtiss Wright Corp | Arc plasma device having a thimble-shaped electrode of pyrolytic graphite |
| US3569661A (en) * | 1969-06-09 | 1971-03-09 | Air Prod & Chem | Method and apparatus for establishing a cathode stabilized (collimated) plasma arc |
| SE426215B (en) * | 1978-05-11 | 1982-12-20 | Vni Pk I Tech Inst Elektrosvar | NON-MELTING ELECTRODES FOR PLASMA BAKING WELDING AND PROCEDURES FOR PRODUCING THEREOF |
| US4954683A (en) * | 1989-05-26 | 1990-09-04 | Thermal Dynamics Corporation | Plasma arc gouger |
| FR2662020B1 (en) | 1990-05-11 | 1996-04-19 | Thomson Tubes Electroniques | ELECTRONIC TUBE WITH CYLINDRICAL GRID. |
| US6466605B1 (en) * | 2000-06-20 | 2002-10-15 | Electro-Pyrolysis, Inc. | Concentric electrode DC arc system and their use in processing waste materials |
| AU2003251307A1 (en) * | 2002-09-10 | 2004-04-30 | The Trustees Of The University Pennsylvania | Carbon nanotubes: high solids dispersions and nematic gels thereof |
| US7049614B2 (en) | 2003-03-10 | 2006-05-23 | Intel Corporation | Electrode in a discharge produced plasma extreme ultraviolet source |
| US7375303B2 (en) * | 2004-11-16 | 2008-05-20 | Hypertherm, Inc. | Plasma arc torch having an electrode with internal passages |
-
2007
- 2007-05-16 US US12/227,439 patent/US8148661B2/en active Active
- 2007-05-16 WO PCT/CA2007/000846 patent/WO2007134432A1/en active Application Filing
- 2007-05-16 CA CA002652428A patent/CA2652428A1/en not_active Abandoned
-
2012
- 2012-04-03 US US13/438,664 patent/US8642917B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| US8642917B2 (en) | 2014-02-04 |
| US20120201718A1 (en) | 2012-08-09 |
| US20090206063A1 (en) | 2009-08-20 |
| WO2007134432A1 (en) | 2007-11-29 |
| US8148661B2 (en) | 2012-04-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US8642917B2 (en) | Highly ordered structure pyrolitic graphite or carbon-carbon composite cathodes for plasma generation in carbon containing gases | |
| US8387561B2 (en) | Method and apparatus for cathodic arc ion plasma deposition | |
| US2951143A (en) | Arc torch | |
| US7309404B2 (en) | Manufacturing apparatus and method for carbon nanotube | |
| CN102217428B (en) | Electrode for a plasma burner | |
| Ng et al. | Self-organisation processes in the carbon arc for nanosynthesis | |
| CN102271451B (en) | A kind of cathode construction of laminar flow electric arc plasma generator | |
| EP1256123B1 (en) | Low input power schottky emitter | |
| US6245280B1 (en) | Method and apparatus for forming polycrystalline particles | |
| US6936228B2 (en) | Manufacturing apparatus for carbon nanotube | |
| US10354845B2 (en) | Atmospheric pressure pulsed arc plasma source and methods of coating therewith | |
| US20160360603A1 (en) | Multi-component electrode for a plasma cutting torch and torch including the same | |
| Tang et al. | Two possible emission mechanisms involved in the arc discharge method of carbon nanotube preparation | |
| BR102014026134B1 (en) | PLASMA PROCESS AND REACTOR FOR THERMOCHEMICAL TREATMENT OF SURFACE OF METALLIC PARTS | |
| US6869574B2 (en) | Apparatus and method of generating charged particles | |
| US5196273A (en) | Tantalum carbide composite materials | |
| JP7212664B2 (en) | Metal refining method and metal refining apparatus | |
| CN112352063B (en) | Vacuum arc source | |
| RU2505882C1 (en) | Composition of material for making electrodes of low-temperature plasma generators | |
| JP3885715B2 (en) | Method for producing carbon nanotubes by arc discharge | |
| RU2336591C1 (en) | Plasma generator cathode component | |
| KR20030018816A (en) | Graphite electrode and Flat-coil type Graphite heater for Device of high temperature X-ray experiments | |
| Melnyk et al. | Recent Progress in Development of Gas-Discharge Electron Beam Guns Providing Extension of their Technological Capabilities | |
| JP2005005236A (en) | Plasma generator | |
| PL117985B1 (en) | Arc plasma generator |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request |
Effective date: 20130326 |
|
| FZDE | Discontinued |
Effective date: 20160506 |