Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/14—Making metallic powder or suspensions thereof using physical processes using electric discharge
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/12—Making metallic powder or suspensions thereof using physical processes starting from gaseous material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J12/00—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor
  • B01J12/002—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor carried out in the plasma state
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J12/00—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor
  • B01J12/02—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor for obtaining at least one reaction product which, at normal temperature, is in the solid state
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00051—Controlling the temperature
  • B01J2219/00121—Controlling the temperature by direct heating or cooling
  • B01J2219/00123—Controlling the temperature by direct heating or cooling adding a temperature modifying medium to the reactants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/00049—Controlling or regulating processes
  • B01J2219/00051—Controlling the temperature
  • B01J2219/0015—Controlling the temperature by thermal insulation means
  • B01J2219/00155—Controlling the temperature by thermal insulation means using insulating materials or refractories
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J2219/0803—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy
  • B01J2219/0805—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges
  • B01J2219/0807—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges involving electrodes
  • B01J2219/0809—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges involving electrodes employing two or more electrodes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J2219/0803—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy
  • B01J2219/0805—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges
  • B01J2219/0845—Details relating to the type of discharge
  • B01J2219/0847—Glow discharge
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J2219/0873—Materials to be treated
  • B01J2219/0879—Solid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J2219/0894—Processes carried out in the presence of a plasma
  • B01J2219/0898—Hot plasma
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

• the present invention relates to a method for the production of fine and ultrafine powders of various materials such as metals, alloys, ceramics, composites and the like with controlled physical properties.
• a novel and flexible transferred arc plasma system providing the ability to control powder properties with a high production rate has been developed.
• the transferred arc plasma system comprises a transferred arc plasma reactor and a separate quench system within which powder condensation occurs.
• Fine powders of metals, alloys, ceramics, composites and the like have a wide variety of applications in various fields such as aeronautics, electronics, microelectronics, ceramics and medicine.
• generation of fine powder i.e.,
• Thermal plasma based vapor condensation methods have demonstrated their ability to generate average particle sizes below 100 nm without the handling and environmental problems associated with hydrometallurgical and spray pyrolysis
• feed materials are generally inert. Examples of such materials include pure metals, alloys, oxides, carbonates etc.
• plasma methods are able to vaporize or decompose these feed materials because of the high-energy input that can be achieved.
• Thermal plasma generation is typically accomplished via 2 methods, i.e., high intensity DC arcs which uses currents higher than 50 A and pressures higher than 10 kPa, or high frequency discharges such as an RF plasma. Because of their high-energy efficiency, DC arcs are generally preferred. DC arcs are classified as transferred when one of the electrodes is a material being processed, and non-
• the powder product is then typically recovered in a filtration unit.
• transferred arc plasma systems can also be used for the production of fine
• transferred arc plasma systems can operate batchwise, it is preferred that they be operated in a continuous manner.
• the material to be vaporized or decomposed can be fed continuously in the reactor in several manners. For example, it can be fed into a crucible either from the top thereof by a side tube in the reactor wall. The material can also be pushed upward underneath the plasma in a continuous manner, or fed directly into the plasma torch. Depending on the powder to be produced, the operator will select the appropriate method. Generally, the preferred feeding method is through one or more tubes located in the upper portion of the reactor.
• the feed materials can be in solid (wire, rod, bar, chunks, shots etc.) or liquid form. When in liquid form, the feed material can also be pumped into the reactor.
• U.S. Patent No. 4,376,740 discloses a method for producing fine metal powders which involves reacting a molten metal or alloy with hydrogen using an arc or plasma discharge, or an infrared radiation which dissolves the hydrogen in the metal. When the dissolved hydrogen is released from the molten metal, fine metal powders are generated. Using this method, a low production rate and yield is attained because of the use of a cold-walled reactor and a water-cooled copper mold which is used to support the material being processed. The maximum production rate reported is less than 240 g/hr. Further, there is no mention or suggestion of control of powder properties.
• a critical aspect of transferred arc plasma systems is that they consume a lot of energy. It is therefore imperative to maximize its efficiency to have a viable commercial method. This means that the temperature within the reactor must be maintained as high as possible to prevent condensation of the vaporized or
• aluminium nitride (A1N) powder using a transferred arc thermal plasma based vapor condensation method. Vaporizing aluminium and reacting it with nitrogen and
• Aluminium is vaporized by using it as the anode material in a transferred arc configuration that employs a thoriated tungsten tip cathode.
• the aluminium being
• vaporized is in the form of an ingot placed in a graphite crucible surrounded by a water-cooled stainless steel support. Because of the presence of that water-cooled
• the aluminium nitride powders generated with this method have a mean particle size of approximately 20 nm.
• the reactor exit gas containing the aluminium vapor is quenched at a single point
• silver/tin anode is vaporized by striking an arc to it while it is contained in a graphite
• a reactive gas i.e., oxygen, is added to the plasma chamber,
• the vaporization and reactive steps in the production of the powder compound are separated to better control the particle formation process.
• silica powders are produced.
• the silica raw material is vaporized
• a particulate form i.e., sand with a particle size of 100 - 315 ⁇ m
• the method comprises the steps of:
• quench tube comprising a first section for indirectly cooling or heating the vapor and any particle present therein, to substantially control particle growth and crystallization; and a second section coupled to the first section for directly cooling the vapor and
• the diluting gas is heated to a temperature corresponding to that of the vapor, or at least 1000 K, before being injected continuously or semi-continuously in the plasma chamber.
• the injection flow rate of the diluting gas can be varied depending on several parameters such as production rate, powder properties, plasma gas flow rate, vapor concentration etc. Any operator
• the liquid material in the crucible is the anode
• the electrode is the cathode.
• the electrode is non-consumable and is
• the quench tube suitable for the condensation of vapor such as that produced from a transferred arc reactor. More specifically, the quench tube comprises a first section with an
• the second section comprises an extension of the tubular body of the first section, and the direct cooling is done by injecting a
• tube can be varied depending on various parameters, such as powders to be produced, properties desired for these powders, flow rate of the carrier gas, particle size desired, etc. Any experienced engineer or operator skilled in the art may adjust these parameters according to powder properties desired. IN THE DRAWINGS
• FIG. 1 illustrates the components of a typical transferred arc plasma
• Figure 2 illustrates a transferred arc plasma chamber suitable for the
• Figure 3 illustrates preferred embodiments of transferred arc
• Figure 4 illustrates a preferred embodiment of a quench tube according to the present invention.
• FIG. 5 illustrates another embodiment of the quench tube according to the present invention.
• Figure 6 illustrates the size distribution of copper particles produced in accordance with the method of the present invention.
• Figure 8 illustrates the crystallinity obtained for copper and nickel powders produced in accordance with the present method.
• cooling or heating can be defined as cooling or heating means wherein the coolant or heating does not come in direct contact with the vapor and condensed particles therein,
• cooling means wherein the coolant is directly contacted with the material's
• the present method comprises striking an arc between an electrode
• a non-consumable electrode inside the torch preferably a non-consumable electrode inside the torch, and a material acting as the
• the material vaporized or decomposed acts as the anode and the non-consumable electrode acts as the cathode.
• the material vaporized or decomposed is therefore in a liquid state.
• suitable materials for the method include any electrically conductive material, such as pure metals, alloys, ceramics, composites etc. Examples of metal powders that can be
• Ceramic powders include, without being restricted thereto,
• composite or coated powders include, without being restricted thereto, powders of SiC/Si, SisN Si, NiO/Ni, CuO/Cu etc.
• a non-electrically conductive crucible which does not have these limitations can be used along with an auxiliary electrode connection.
• the feed material it can be in any form including solid particles, wire, rod, liquids etc.
• Typical plasma torch feed gas flow rates vary depending on the power
• plasma chamber may be required. Dilution reduces the concentration of the vapor and prevents significant condensation of the vapor, which would lead to the formation of
• the diluting gas can be added directly to the plasma gas, but this method is usually limited to the maximum operating flow rate of the plasma torch. This is why it is necessary to have additional means for injecting diluting gases in the plasma chamber. Also, such diluting gas
• At least one gas port is installed to allow additional hot gas to be
• the plasma chamber pressure is preferably maintained
• the fine or ultrafine powder product o can then be collected through any conventional collection/filtration equipment.
• the method of the present invention provides an energy efficient method for producing fine and ultrafine powders at a production rate of about at least 0.5 kg/h while avoiding the handling and environmental problems associated with conventional hydrometallurgical and spray pyrolysis methods.
• Current transferred arc systems can only produce at a rate not exceeding 0.2 kg/h, and lack extensive control of powder properties.
• the present method permits the relatively simple and cost effective production of fine and ultrafine powders of materials like pure metals, alloys, ceramics, composites etc. with the ability to substantially control the properties of the powders.
• a plasma system 10 comprising a transferred arc plasma reactor 12 insulated with an insulating material 13 such as alumina felt, a quench tube 14, and a powder collection unit 16.
• Reactor 12 is coupled to a power supply 11, which is itself coupled to a control panel 15.
• a supply control unit 19 is also provided for controlling the supply of gases and water in reactor 12.
• a heat exchanger 21 may optionally be inserted between unit 16 and quench tube 14 to further lower the temperature of the powder before collecting it.
• a feeder 23 is provided to feed the material inside plasma chamber 17.
• Figure 2 illustrates the interior of plasma reactor 12, which comprises a plasma chamber 17.
• An arc 18 is struck between an electrode 33, preferably non- consumable, located inside torch 20 and material 22 contained in a ceramic crucible 24.
• electrode 33 preferably non- consumable
• material 22 is vaporized or decomposed, further material is added continuously or semi-continuously in the crucible, for example through at least one
• a heated diluting gas preferably argon, helium, hydrogen, nitrogen,
• ammonia, methane or mixtures thereof is injected through a pipe 28 into chamber 17
• exiting the quench tube 14 can be recovered in any suitable solid/gas or solid/liquid separator, such as a particle filtration unit, a scrubber or the like.
• decomposing material 22 is supplied by arc 18 maintained between material 22, which
• gas is continuously or semi-continuously injected into plasma chamber 17 in addition to the feed gas of plasma torch 20, this at least one diluting gas being heated to a temperature preferably corresponding to the temperature of the vapor exiting the plasma chamber, or at least higher than 1000 K, to minimize localized condensation of the vapor.
• electrode 33 acts as the cathode and liquid material 22
• Preferred arc lengths are from about 2 to 20 cm, but the operator, depending on the material to be produced, can vary the length at will. Pressure inside
• chamber 17 is preferably maintained between 0.2 - 2.0 arm, the most preferred
• FIG. 3 illustrates various alternative transferred arc arrangements
• Figure 3A illustrates a preferred crucible arrangement
• FIGS. 3B and 3C illustrate configurations wherein an
• auxiliary electrode 32 is used. Such configuration is suitable when the electrical
• auxiliary electrode may be used even when the crucible is electrically conductive at the operating temperature.
• connection 32 may or may not be in direct contact with material 22.
• contact to material 22 can be either from the top ( Figure 3C), bottom or side.
• auxiliary electrode 32 can be a plasma torch, as per Figure 3B, a water-cooled probe or the feed material.
• Preferred materials of construction for crucible 24 include high melting point materials such as graphite, carbides such as tantalum carbide, silicon carbide, titanium carbide etc.; oxides such as magnesia, alumina, zirconia etc.; nitrides such as titanium nitride, tantalum nitride, zirconium nitride, boron nitride etc.; borides such as titanium diboride, tantalum diboride, zirconium diboride etc.; as well as refractory metals such as tungsten, tantalum, molybdenum, niobium etc.
• Figure 4 illustrates a preferred embodiment of a quench tube according to the present invention.
• the vaporized or decomposed material exits chamber 17 in the form of vapor combined with the diluting gas and the plasma gas, and enters into the first section 34 of quench tube 14.
• First section 34 allows an indirect controlled cooling or heating of the vapor to nucleate the desired product and control the particle growth and crystallization.
• the indirect heating or cooling can be done using a heating or cooling fluid that is circulated in channel 29 which is formed by the inner surface of an external coaxial tube 36 and the external surface of tube 38.
• Tube 36 can also be replaced or combined with one or more heating or cooling elements 40 also
• Tube 36 includes at least one inlet 42 and an at least one outlet 44 to allow fluid circulation therein.
• the reagent may be introduced in the form of a hot reactive gas at one or more points in the first section 34, for example through an inlet 46.
• reactive gases include nitrogen, hydrogen, ammonia, methane, oxygen, water, air, carbon monoxide or mixtures thereof.
• the hot reactive gas is also injected at a temperature preferably close to the temperature of the vapor exiting the plasma reactor, or at least higher than 1000 K, to minimize direct cooling of the vapor. Most preferably, the temperature of the injected hot reactive gas is higher than or at least equal to the temperature of the vapor exiting chamber 17.
• the inner tube of the quench tube should be constructed from a material that can support the temperature of the vapor exiting the plasma chamber. A preferred material is graphite.
• a second section 50 provided for the
• Direct cooling is performed by injecting a fluid
• particles include argon, nitrogen, helium, ammonia, methane, oxygen, air, carbon monoxide, carbon dioxide or mixtures thereof.
• Preferred liquids include water, methanol, ethanol or mixtures thereof, which are typically injected as a spray.
• the cross-section of the inner tube 38 can be any shape. As an example,
• tube 38 is an annular design with the vapor flowing through the annular
• tube 38 is provided inside tube 38 to form a channel between the inner surface of body 38 and the external surface of body 27.
• Fine metal powder production was carried out using a transferred arc thermal plasma system as illustrated in Figure 1 comprising a reactor as illustrated in Figure 2, and a quench tube as illustrated in Figure 4.
• a transferred arc thermal plasma system as illustrated in Figure 1 comprising a reactor as illustrated in Figure 2, and a quench tube as illustrated in Figure 4.
• any conventional plasma torch can be used.
• the crucible can be graphite or any suitable ceramic.
• the material to be vaporized was fed into the crucible in the form of pellets or shots through a port in the upper section of the
• Fine copper powders with controlled mean particle size and distribution were produced.
• Tests 1 and 2 the control of mean particle size is demonstrated using different quench tube operating conditions.
• Test 3 control of the size distribution is demonstrated.
• the size distribution was increased in Test 3 compared to Tests 1 and 2 (see Figure 7).
• the reactor conditions were substantially the same.
• the degree of crystallinity was measured by the maximum peak count in the X-ray diffraction

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Powder Metallurgy (AREA)
• Discharge Heating (AREA)

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Cited By (15)

Families Citing this family (110)

Citations (4)

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• 1998
  • 1998-08-18 US US09/136,043 patent/US6379419B1/en not_active Expired - Lifetime
• 1999
  • 1999-08-16 DE DE69907933T patent/DE69907933T2/de not_active Expired - Lifetime
  • 1999-08-16 AT AT99938107T patent/ATE240177T1/de not_active IP Right Cessation
  • 1999-08-16 KR KR1020017002087A patent/KR100594562B1/ko not_active Expired - Lifetime
  • 1999-08-16 CA CA002340669A patent/CA2340669C/en not_active Expired - Lifetime
  • 1999-08-16 EP EP99938107A patent/EP1115523B1/en not_active Expired - Lifetime
  • 1999-08-16 JP JP2000566062A patent/JP3541939B2/ja not_active Expired - Lifetime
  • 1999-08-16 AU AU52752/99A patent/AU5275299A/en not_active Abandoned
  • 1999-08-16 WO PCT/CA1999/000759 patent/WO2000010756A1/en not_active Ceased
• 2003
  • 2003-10-27 JP JP2003366114A patent/JP2004036005A/ja active Pending
• 2005
  • 2005-02-10 JP JP2005034922A patent/JP2005163188A/ja active Pending

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