US3852061A - Process and equipment for the treatment of a material by means of an arc discharge plasma - Google Patents

Process and equipment for the treatment of a material by means of an arc discharge plasma Download PDF

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Publication number
US3852061A
US3852061A US00307838A US30783872A US3852061A US 3852061 A US3852061 A US 3852061A US 00307838 A US00307838 A US 00307838A US 30783872 A US30783872 A US 30783872A US 3852061 A US3852061 A US 3852061A
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Prior art keywords
plasma
discharge
region
magnetic field
electrodes
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US00307838A
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English (en)
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H Wulff
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Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
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Max Planck Gesellschaft zur Foerderung der Wissenschaften eV
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
    • H01J37/32055—Arc discharge
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
    • C22B9/16—Remelting metals
    • C22B9/22—Remelting metals with heating by wave energy or particle radiation
    • C22B9/226—Remelting metals with heating by wave energy or particle radiation by electric discharge, e.g. plasma
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32431—Constructional details of the reactor
    • H01J37/32623—Mechanical discharge control means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/32—Gas-filled discharge tubes
    • H01J37/32431—Constructional details of the reactor
    • H01J37/3266—Magnetic control means
    • 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
    • H05H1/3431—Coaxial cylindrical electrodes
    • 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
    • H05H1/40—Details, e.g. electrodes, nozzles using applied magnetic fields, e.g. for focusing or rotating the arc

Definitions

  • ABSTRACT A process is described wherein a material, such as particulate metal oxides, is treated with an arc discharge plasma under vacuum in the presence of a magnetic field running axially between the arc electrodes, wherein the plasma rotates symmetrically about a middle magnetic field, under conditions such that in a region the product of the electron gyration frequency Q and time 7, within which the average electron trans-' mits its impulse to the plasma ions, is 07 1 at about the middle of the magnetic field, and treated material, i.e., reduced metal, is recovered radially outside the region.
  • a material such as particulate metal oxides
  • Apparatus for carrying out the process, including a discharge vessel, two spaced annular electrodes arranged symmetrically to the axis of the vessel, a magnetic coil enclosing coaxially the space between the electrodes, and means to introduce material axially through one electrode into the space.
  • the present invention relates to a process and equipment for the treatment of a material, such as the reduction of metal oxides, by means of an arc discharge plasma burning in a discharge space.
  • Inductive plasma burners for the heating of finegrained material which contain a cylindric discharge vessel into whose front side streams a mixture of a gas and the fine-grained material in axial direction.
  • the stabilization of the discharge plasma is achieved through a tangentially introduced auxiliary current of gas.
  • Such plasma burners are especially used for the melting of powdery or granular materials of high fusing temperatures, such as fireproof oxides or carbides as well as for flame spraying (See German patent publication No. 1,286,241).
  • US. Pat. No. 3,051,639 discloses equipment for hydrocarbon reactions, which employs an arc discharge I between a rod-shaped central electrode and an annular' electrode arranged at an axial distance from its point. No magnetic field is, however, provided.
  • US. Pat. No. 2,944,140 discloses plasma burners in which the plasma is produced through an arc discharge between a rod-shaped or platelike first electrode, and an annular electrode arranged at a distance from this. In the space between the two electrodes, enclosed by a cylindrical wall, a current of gas is tangentially introduced.
  • a magnetic nozzle which is formed through a magnetic coil that may be arranged either between the electrodes or on the side of the annular electrode that is facing away from the platelike electrode.
  • the cross-section of the coil consisting of a tube, through which flows a cooling agent, may at first somewhat diminish and then again gradually enlarge with increasing distance from the annular electrode.
  • the material that is to be treated is introduced through a laterally obliquely inserted tube approximately between the axis and the circumference of the anode into the upper part of the space enclosed by it. Underneath the anode is provided a freezing device.
  • the present invention has as a major objective to obtain a process and equipment for the treatment of material by means of an arc discharge plasma, whereby a contamination of the material with electrode material is prevented and a stable discharge is assured, in the presence of a zone of uniform, very high temperature.
  • the average pressure in the discharge space containing the electrodes is kept below atmospheric pressure
  • a magnetic field is produced which runs substantially parallel to the axis forming the connection line between the electrodes, and which has in at least one part of a region of such a high value that the product 01 of the electron gyration frequency in the plasma Q and the time -r within which on an average an electron c. the material to be treated is brought into a part of the region close to the central 'magnetic field line in which is fulfilled the condition of 01- 1;
  • the treated material is recovered from the space lying radially outside of this region.
  • the material introduced into the space between the electrodes preferably at an axial distance from them in the proximity of the axis, is actually not transported in axial direction, but it permeates the rotating discharge in radial direction, so that the treated material is obtained in pure state from the part of the discharge space which lies outside of the plasma, e.g. after it has been centrifuged onto the inside wall of the discharge vessel.
  • the discharge is also not so strongly disturbed by the foreign or untreated material as to cause instabilities.
  • the relatively high electron temperature in the uninfluenced discharge to be sure, decreases with the introduction of foreign material, but that the electron density which is required for the stability and existence of the discharge is hardly influenced by the introduction of the material.
  • FIGURE shows in cross-sectional elevation the preferred apparatus of the invention, an arc discharge plasma vessel for treatment of particulate material in accordance with the present process.
  • a preferred application of the present process is for the reduction of metal oxides, such as tantalum oxide, titanium oxide, aluminum oxide for recovery of the pure metal.
  • metal oxides such as tantalum oxide, titanium oxide, aluminum oxide
  • a relatively coarse-grained starting material e.g., with particle size up to 100 um and more, preferably between 20 and 80 um, such as 50 pm
  • the particle size is preferably also relatively uniform.
  • Preferred apparatus for executing the process of the invention contains a discharge vessel-connected with a vacuum pump system, including: an annular first electrode; a second electrode, substantially symmetrical to the vessel axis and arranged at a distance from the first electrode, a magnetic coil coaxially enclosing the space between the electrodes, which is capable of producing in the range of the vessel axis a magnetic field of at least kg (kilo-Gauss); and means for introducing material to be treated through the annular, first electrode into the region of the discharge space between the two electrodes, near the vessel axis preferably at distance axially from the electrodes.
  • a vacuum pump system including: an annular first electrode; a second electrode, substantially symmetrical to the vessel axis and arranged at a distance from the first electrode, a magnetic coil coaxially enclosing the space between the electrodes, which is capable of producing in the range of the vessel axis a magnetic field of at least kg (kilo-Gauss); and means for introducing
  • the apparatus schematically presented in the drawing including a substantially cylindric vacuum vessel 10 composed, for example, of quartz, ceramic, or any other non-magnetic material.
  • the vacuum vessel 10 is closed at one end, and connected at theother end through a connecting duct 12 with a vacuum system (not shown) which permits evacuation of the vacuum vessel 10, or alternatively to fill it with a desired gas under a specified pressure, to drain the accumulating inner and outer rim of the electrodes 16 and 18 project each approximately tapered conical walls 20a, 20b, and 22a, 2219, respectively, of insulating material, e.g., quartz or ceramic, which define a channel of annular cross section.
  • each inner wall 20b or 22b axially projects farther toward the center of the discharge vessel than its respective outer wall, 20a or 22a.
  • the feeding is preferably achieved axially symmetrically with respect to axis 14 of the vessel 10 in order to assure uniform influence on the material through the discharge plasma.
  • the means for feeding the material in the illustrated embodiment may be needle valve 26, adjustable through an electro-magnetic or other control means 28, and permits measured introduction of the material 24 into a region near the axis of the vacuum vessel 10. Since wall 20b projects axially from the electrode 16 into the discharge space enclosed of the vacuum vessel 10, the material to be treated may be introduced into the plasma at considerable axial interval from the electrodes 16 and 18. This, together with the special kind of discharge, help to prevent contamination of the material with electrode material, as will be further explained.
  • the central part of the vacuum vessel 10 lying between the electrodes 16 and 18 is enclosed by a cylindric magnetic coil 30, which permits the production of a relatively strong magnetic field B.
  • the intensity of the magnetic field should be at least so great that the product Or, of the gyration frequency 0 of the free electrons in the plasma and the time 1 within which on an average an electron transmits its impulse to the ions of the plasma, is greater than 1 at the pressure condition existing in the discharge space, In practice the intensity of the magnetic field will be at least 10 k6, preferably at least 20 k0; good results were obtained at field intensities between 30 and 60 k6.
  • the magnetic coil terminates preferably bilaterally at an axial distance from the electrodes, so that the magnetic field lines diverge in the region of the electrodes as indicated through dash-lines.
  • the walls 20a, 20b, and 22a, 22b are preferably so shaped (thus tapered conically and similar to a rotated hyperbola), that they follow substantially the course of the magnetic field lines, and that the charge carriers in the discharge are therefore compelled onto paths which run parallel to the electrode walls.
  • the electrodes 16 and 18 are provided with corresponding terminals 32 and 34, respectively, which are connected with a current source (not shown), preferably a direct-current source that is capable to supply sufficient current for the discharge.
  • a current source not shown
  • the magnetic coil 30 in operation is connected with an energy supply (not shown).
  • the magnetic coil 30 may be'a superconductive coil so that it will not require any energy supply in continuous service.
  • the material to be treated 24 e.g., finely granular or powdery tantalum oxide (or titanium oxide or the like) which is to be reduced, is placed within the space enclosed by the wall 20b.
  • the vacuum vessel is then evacuated through the pump duct 12, and subsequently filled with a desired gas (e.g., hydrogen, air or an inert gas) under an inflation pressure between about 1 and torr/preferably between about 3 and 5 torr (measured at room temperature).
  • a desired gas e.g., hydrogen, air or an inert gas
  • an inflation pressure between about 1 and torr/preferably between about 3 and 5 torr (measured at room temperature).
  • the magnetic field B cut in there is then ignited between the electrodes 16 and 18 an arc discharge by means of a high-tension impulse.
  • the needle valve 26 is opened and material 24 is fed in measured doses into a region of the discharge near the vessel axis.
  • the material is driven radially outward through the hot, current-carrying plasma tube which arises between the electrodes due to the discharge. There results an extremely intense and a uniform reciprocal action with the plasma, and the material is centrifuged against the outside wall of the vacuum vessel 10.
  • the treated material e.g., reduced metallic tantalum, is thereby accumulated at the inside wall of the vacuum vessel 10, as shown at 36.
  • the magnetic coil 30 had a length of about 30 cm; the magnetic field B produced through the coil 30 had a field intensity of about 50 k0 and between the electrodes 16 and 18 burned a tubular, stable arc discharge with a current of about 2 kA and an approximate arc-drop-voltage of about 300 V.
  • the distance of the electrodes was about 60 cm, the average diameter of the electrodes was about 6 cm.
  • the work was done in pulsed operation, the duration of the impulses was of the order of milliseconds.
  • the described process and apparatus have particular only in the upper part. In principle, it is also possible to application in the preparation of chemical elements from their compounds, particularly for the recovery of metals. Those metals which cannot be produced from their ores through reduction with carbon, therefore are of particular significance, such as titanium, zirconium, vanadium, tantalum, and aluminum.
  • the present process and apparatus can also be used for the preparation of chemical compounds, especially when these can be produced only through strongly endothermic reactions.
  • various materials which exist in fusible form can be treated; also liquids of low vapor pressure; or vapors, gases, and mixtures or dispersions of such materials.
  • annular electrode is meant herein to comprise also electrode forms which topologically are equivalent to a circular ring, thus e.g., perforated electrodes which substantially have the form of a disc, a rectangle, an ellipse, a triangle, and so on.
  • annular electrode 18 there may be used a coaxial rod-shaped electrode.
  • the developing plasma discharge is then hollow make both electrodes compact, e.g., rod-shaped, and even to arrange them unsymmetrically with respect to the cylindric magnetic coil 30.
  • the electrodes may also be arranged at a relatively great distance from the magnetic coil. In this case the essential conditions for the present process of QT 1 will only be fulfilled in a part of the range lying between the electrodes, and will develop only there the'plasma discharge which rotates around its axis in the form of a column.
  • the plasma discharge is then not hollow, it is not possible to introduce the material to be treated on a burning discharge into the region of the axis of rotation of the plasma discharge, but it becomes first necessary to bring a certain quantity of the material into the region of the axis of rotation, e.g., letting it drop and then only ignite the discharge around the free-falling material.
  • This requires necessarily a relatively complicated control of the course of the process, and the magnetic field is not utilized to its maximum, which fact may lead to quite substantial decreases in efficiency, particularly on account of the high field intensities.
  • the upper electrode-as shown in the drawing is annular and coaxial to the magnetic field, but arranged so far from this that the conduct of the arc current through the magnetic field is not yet incurred in the proximity of the electrode, and that at the electrode is then initiated a discharge channel, which passes over into discharge form used for treating the material only in the'region in which the condition of QT 1 is fulfilled.
  • the desired discharge is not hollow, the discharge is preferably only ignited when the material is already in the range on the axis around which then is formed the ignited, desired discharge.
  • a process for the treatment of material by means of an arc discharge plasma in a region of a discharge vessel between two axially spaced electrodes comprising the following steps:
  • the discharge is produced between an annular first electrode and a second electrode arranged substantially symmetrical to the axis of said annular electrode and spaced at an axial distance therefrom.
  • said magnetic field is substantially symmetrical to the axis of said annular electrode

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)
  • Arc Welding In General (AREA)
  • Chemical Vapour Deposition (AREA)
  • Plasma Technology (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US00307838A 1971-11-20 1972-11-20 Process and equipment for the treatment of a material by means of an arc discharge plasma Expired - Lifetime US3852061A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2157606A DE2157606C3 (de) 1971-11-20 1971-11-20 Verfahren und Einrichtung zur Wärmebehandlung eines Materials durch ein Bogenentladungsplasma
DE2237378A DE2237378A1 (de) 1971-11-20 1972-07-29 Verfahren zur gewinnung eines metalles durch reduktion einer metallverbindung in einem bogenentladungsplasma

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US00360967A Expired - Lifetime US3851136A (en) 1971-11-20 1973-05-16 Process and equipment for the treatment of a material by means of an arc discharge plasma

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US (2) US3852061A (xx)
JP (1) JPS4863941A (xx)
BE (1) BE791550A (xx)
DE (2) DE2157606C3 (xx)
FR (1) FR2160519B1 (xx)
GB (1) GB1418641A (xx)
IT (1) IT973517B (xx)
LU (1) LU66498A1 (xx)
NL (1) NL7215108A (xx)
NO (1) NO131795C (xx)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936586A (en) * 1974-05-07 1976-02-03 Tetronics Research And Development Co. Ltd. Arc furnaces and to methods of treating materials in such furnaces
US3944412A (en) * 1974-09-18 1976-03-16 Hsin Liu Method for recovering metals
US3974245A (en) * 1973-12-17 1976-08-10 Gte Sylvania Incorporated Process for producing free flowing powder and product
US3980467A (en) * 1973-02-16 1976-09-14 Camacho Salvador L Method of operating a batch type annealing furnace using a plasma heat source
US3989511A (en) * 1975-03-10 1976-11-02 Westinghouse Electric Corporation Metal powder production by direct reduction in an arc heater
US4002466A (en) * 1975-11-03 1977-01-11 Bethlehem Steel Corporation Method of reducing ores
US4169962A (en) * 1974-10-02 1979-10-02 Daidoseiko Kabushikikaisha Heat treating apparatus
US4234334A (en) * 1979-01-10 1980-11-18 Bethlehem Steel Corporation Arc control in plasma arc reactors
US4361441A (en) * 1979-04-17 1982-11-30 Plasma Holdings N.V. Treatment of matter in low temperature plasmas
US4431612A (en) * 1982-06-03 1984-02-14 Electro-Petroleum, Inc. Apparatus for the decomposition of hazardous materials and the like
US4670047A (en) * 1986-09-12 1987-06-02 Gte Products Corporation Process for producing finely divided spherical metal powders
US4711661A (en) * 1986-09-08 1987-12-08 Gte Products Corporation Spherical copper based powder particles and process for producing same
US4711660A (en) * 1986-09-08 1987-12-08 Gte Products Corporation Spherical precious metal based powder particles and process for producing same
US20050035085A1 (en) * 2003-08-13 2005-02-17 Stowell William Randolph Apparatus and method for reducing metal oxides on superalloy articles
US20100252411A1 (en) * 2009-04-02 2010-10-07 Toshio Awaji Control method of plasma by magnetic field in an exhaust gas treating apparatus and an exhaust gas treating apparatus using the same

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1055884B (it) * 1976-02-17 1982-01-11 Montedison Spa Procedimento ad arco plasma di prodotti ceramici metallici e simili
FR2446324A1 (fr) * 1979-01-15 1980-08-08 Karlovitz Bela Procede de reduction thermique d'oxydes metalliques tels que l'aluminium
US5135565A (en) * 1991-04-16 1992-08-04 The Boc Group, Inc. Recovery of aluminum from dross using the plasma torch
US5984444A (en) * 1997-06-26 1999-11-16 James M. Hawley Electrostatic three dimensional printer
AT414215B (de) 2003-02-12 2006-10-15 Peter Ziger Anlage zur plasmaprozessierung
CN114433804B (zh) * 2022-04-08 2022-07-05 北京奥邦新材料有限公司 中间包等离子加热电弧控制方法、装置及控制系统

Citations (6)

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US3005859A (en) * 1958-04-24 1961-10-24 Nat Res Corp Production of metals
US3080626A (en) * 1960-05-27 1963-03-12 Stauffer Chemical Co Electron-beam furnace with magnetic guidance and flux concentrator
US3304169A (en) * 1960-08-01 1967-02-14 Union Carbide Corp Method of deoxidizing metals
US3547622A (en) * 1968-06-12 1970-12-15 Pennwalt Corp D.c. powered plasma arc method and apparatus for refining molten metal
US3628948A (en) * 1964-10-29 1971-12-21 Westinghouse Electric Corp Electric arc vacuum melting processes
US3771585A (en) * 1971-03-04 1973-11-13 Krupp Gmbh Device for melting sponge metal using inert gas plasmas

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Publication number Priority date Publication date Assignee Title
US3361927A (en) * 1963-04-22 1968-01-02 Giannini Scient Corp Plasma generating apparatus having an arc restricting region
DE1220058B (de) * 1965-06-28 1966-06-30 Kernforschung Gmbh Ges Fuer Verfahren und Vorrichtung zur Waermebehandlung pulverfoermiger Stoffe, insbesondere zum Schmelzen der Koerner hochschmelzender Stoffe, mittels eines Hochtemperaturplasmas
CH525705A (de) * 1968-12-24 1972-07-31 Lonza Ag Verwendung von vortex-stabilisierten Plasmabrennern zur Durchführung von chemischen Reaktionen
US3671220A (en) * 1969-05-19 1972-06-20 Nordstjernan Rederi Ab Process for the production of powdered metals

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3005859A (en) * 1958-04-24 1961-10-24 Nat Res Corp Production of metals
US3080626A (en) * 1960-05-27 1963-03-12 Stauffer Chemical Co Electron-beam furnace with magnetic guidance and flux concentrator
US3304169A (en) * 1960-08-01 1967-02-14 Union Carbide Corp Method of deoxidizing metals
US3628948A (en) * 1964-10-29 1971-12-21 Westinghouse Electric Corp Electric arc vacuum melting processes
US3547622A (en) * 1968-06-12 1970-12-15 Pennwalt Corp D.c. powered plasma arc method and apparatus for refining molten metal
US3771585A (en) * 1971-03-04 1973-11-13 Krupp Gmbh Device for melting sponge metal using inert gas plasmas

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3980467A (en) * 1973-02-16 1976-09-14 Camacho Salvador L Method of operating a batch type annealing furnace using a plasma heat source
US3974245A (en) * 1973-12-17 1976-08-10 Gte Sylvania Incorporated Process for producing free flowing powder and product
US3936586A (en) * 1974-05-07 1976-02-03 Tetronics Research And Development Co. Ltd. Arc furnaces and to methods of treating materials in such furnaces
US3944412A (en) * 1974-09-18 1976-03-16 Hsin Liu Method for recovering metals
US4169962A (en) * 1974-10-02 1979-10-02 Daidoseiko Kabushikikaisha Heat treating apparatus
US3989511A (en) * 1975-03-10 1976-11-02 Westinghouse Electric Corporation Metal powder production by direct reduction in an arc heater
US4002466A (en) * 1975-11-03 1977-01-11 Bethlehem Steel Corporation Method of reducing ores
US4234334A (en) * 1979-01-10 1980-11-18 Bethlehem Steel Corporation Arc control in plasma arc reactors
US4361441A (en) * 1979-04-17 1982-11-30 Plasma Holdings N.V. Treatment of matter in low temperature plasmas
US4431612A (en) * 1982-06-03 1984-02-14 Electro-Petroleum, Inc. Apparatus for the decomposition of hazardous materials and the like
US4711661A (en) * 1986-09-08 1987-12-08 Gte Products Corporation Spherical copper based powder particles and process for producing same
US4711660A (en) * 1986-09-08 1987-12-08 Gte Products Corporation Spherical precious metal based powder particles and process for producing same
US4670047A (en) * 1986-09-12 1987-06-02 Gte Products Corporation Process for producing finely divided spherical metal powders
US20050035085A1 (en) * 2003-08-13 2005-02-17 Stowell William Randolph Apparatus and method for reducing metal oxides on superalloy articles
US20100252411A1 (en) * 2009-04-02 2010-10-07 Toshio Awaji Control method of plasma by magnetic field in an exhaust gas treating apparatus and an exhaust gas treating apparatus using the same
US9675930B2 (en) * 2009-04-02 2017-06-13 Clean Technology Co., Ltd. Control method of plasma by magnetic field in an exhaust gas treating apparatus and an exhaust gas treating apparatus using the same

Also Published As

Publication number Publication date
DE2157606C3 (de) 1974-04-04
IT973517B (it) 1974-06-10
DE2157606B2 (de) 1973-08-30
DE2157606A1 (de) 1973-05-24
US3851136A (en) 1974-11-26
BE791550A (fr) 1973-03-16
NO131795B (xx) 1975-04-21
NO131795C (xx) 1975-07-30
LU66498A1 (xx) 1973-02-01
JPS4863941A (xx) 1973-09-05
NL7215108A (xx) 1973-05-22
FR2160519B1 (xx) 1978-04-21
DE2237378A1 (de) 1974-02-14
GB1418641A (en) 1975-12-24
FR2160519A1 (xx) 1973-06-29

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