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
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
  • B01J19/087—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy
  • B01J19/088—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

Definitions

• the present invention relates mainly to a process for manufacturing fine or ultrafine particles, in particular metallic particles, and to a reactor for the production of such particles.
• the main object of the invention is a method for manufacturing a powder of ultrafine particles comprising the steps consisting in:
• - have in a plasma oven comprising a sealed enclosure a metal anode preferably vaporizable, and a cathode;
• the enclosure comprises two diaphragms comprising openings aligned on an axis connecting the anode to the cathode, these diaphragms delimiting a chamber for receiving the anode, a reaction chamber and a chamber for receiving the cathode.
• the invention also relates to a method, characterized in that it comprises a step of injecting at least one point with an inert gas creating in the chambers a vortex flow and a step of evacuation by a gas pipeline inert pneumatically carrying fine and / or ultrafine particles.
• the invention also relates to a method, characterized in that it comprises a step of opening a pipe arranged in the enclosure so as to promote the evacuation of the enclosure of large undesirable particles.
• the invention also relates to a method, characterized in that it comprises a step consisting in introducing into the enclosure an organic product allowing the formation of metallocarbon particles, in particular ferrocarbon particles by transcondensation of the material which must constitute the base of the particles to be obtained. and organic product upon cooling of the transcondensation product when it leaves the plasma.
• the invention also relates to a process, characterized in that the organic product is a hydrocarbon, in particular petrol.
• the subject of the invention is also a method, characterized in that it comprises a step of pneumatically supplying powders of materials to the plasma to form fine or ultrafine particles.
• the invention also relates to a reactor for the production of fine or ultrafine particles comprising a sealed enclosure comprising an anode and a cathode connected to an electrical supply allowing the formation of a plasma and a source of inert gases opening into the enclosure , characterized in that it further comprises two diaphragms arranged in the enclosure between the anode and the cathode limiting the extent of the plasma, and in that an opening is made in each diaphragm, the electrodes and said openings being aligned.
• the subject of the invention is also a reactor, characterized in that the anode is a vaporizable anode and in that it comprises means for displacing the anode as it sublimates in order to maintain a constant gap between the electrodes as well as rotation of the anode around its axis preventing the undesired flow of the material constituting the anode.
• the invention also relates to a reactor, characterized in that it comprises means for supplying the enclosure with hydrocarbon.
• the invention also relates to a reactor, characterized in that it comprises means for pneumatically supplying the enclosure with powders intended to form fine or ultrafine particles.
• FIG. 1 is a general block diagram of an installation according to the present invention for producing particles
• FIG. 2 is a diagram of the preferred embodiment of a reactor of the installation of FIG. 1.
• FIGS. 1 and 2 the same references have been used to designate the same elements.
• Figures 1 and 2 one can see an installation for producing ultrafine particles according to the present invention.
• the installation according to the invention makes it possible to produce a wide variety of particles.
• the material which is introduced into the reactor is first chosen. Excellent results have been obtained, in particular with iron.
• Fine and ultrafine particles are normally hydrophilic.
• a possible introduction of a hydrocarbon or a hydrocarbon product into the reactor can modify the characteristics of the particles and mainly make them hydrophobic.
• the method makes it possible to constantly obtain particles of regular shape.
• such particles are obtained by sudden condensation of vapor, in particular metallic, or by transcondensation of a material and an organic product.
• the device according to the invention comprises a plasma oven in the enclosure of which two diaphragms provided with openings aligned with the ends of the electrodes limit the extent of the plasma and, consequently, create around the plasma a much cooler concentric zone.
• the geometry of the reactor and of the means for injecting a neutral gas favor the creation of a vortex flow ensuring the circulation of elements of the material or materials intended to form the ultrafine particles.
• This or these gaseous materials in the plasma undergo a abrupt phase change when it (s) is (are) driven by the vortex flow in the cold region of the reactor. This results in condensation and / or solidification of the ultrafine particles or, in the presence of an organic compound, the transcondensation of the vapors of these materials with the vapors of the organic compound.
• the particles are passivated to ensure their stability and thus avoid the risk of fire.
• the size of the particles obtained depends on the temperature conditions, the cooling rates and the gas circulation rates in the reactor. In addition, it is possible, at the outlet of the reactor, to sort or select the particles according to their size.
• the hydrocarbon supply device comprises a set of valves 38c and a flow meter 38d blowing the neutral gas into a mixer 38e, for example by bubbling.
• the gas saturated with hydrocarbon in the mixer 38e is injected into reactor 35.
• the liquid hydrocarbon contained in a container 38g is directly injected into reactor 35 by means of a pump 3 8f.
• the device also comprises means for receiving particles 39, means 40 for cooling particles, means 41 to 43 for particle size selection of the powder particles, means 44 for receiving large particles, means 45 and 46 for receiving fine and ultrafine particles, means 47 for evacuating and / or eliminating the reaction gases and, advantageously, pneumatic means 48 for supplying metal to the reactor 35.
• the electric supply 36 provides a unidirectional electric current allowing the formation in reactor 35 of an electric arc (for example 100 to 150 V or more) symbolized in FIG. 2 by the arrow 49 between an anode 51 and a cathode 48.
• the inert gas supply device comprises a source of pressurized gas supplying via a flow meter 53 and valves 54 and 55, the reactor 35 and by means of a flow meter 56 and valves 57 and 58, a tank 59 in which the means 45 and 46 for receiving fine and ultrafine particles are immersed in order to prevent their oxidation by oxygen in the air.
• the supply of hydrocarbon has been described previously.
• the means 39 advantageously arranged in the lower part of the reaction chamber 64 collect the particles from the reactor 35 entrained by the inert gas.
• the cooling means 40 comprise, for example, an exchanger cooled by circulation 40a of a fluid refrigerating the particles and the inert gas at a temperature below 70 ° C.
• the means 41 to 43 for particle size selection comprise for example three cyclonic separators placed in series and bag filters.
• the first separator 41 ensures the elimination of large particles corresponding to the unreacted particles, as well as to the amalgamated fine particles.
• the large particles are collected in the reception means 44.
• the particles of desired particle size are collected in the reception means 45 and / or 46.
• the residual gases 47 if they are loaded with hydrocarbon vapor can be eliminated by combustion.
• Means 60 measure the pressure difference between the means 42 and 43, allowing the control of the capture of the particles of desired sizes.
• the reactor 35 comprises a sealed enclosure 61 in which circular diaphragms 62 define a chamber 63 for receiving the anode 51, a reaction chamber 64 and a chamber 65 for receiving the cathode 48.
• the chambers 63 to 65 communicate by openings aligned in the diaphragms 62.
• the ends of the electrodes 48 and 51, between which the arc 49 is established are aligned with the openings in the diaphragms 62.
• Lines 66 for supplying inert gas open into the chambers 63 and 65.
• a pipe 67 allows, thanks to the overpressure and to the cyclonic ventilation created by the injection of the inert gas, a selection of the largest particles considered undesirable.
• a hydrocarbon supply line 68 opens into the reaction chamber 64.
• An opening 39 made in the lower part of the reaction chamber 64 makes it possible to collect the treated particles.
• a pipe of the powder supply means 50 opens into the chamber 65 near the cathode 48.
• motorized means 70 ensure the advancement and rotation of the cathode 51 as it sublimates.
• a bellows 71 seals the reactor 35 enclosure. The material or materials intended to form fine or ultrafine particles can be supplied by sublimation of a cathode and / or by pneumatic injection of powders into the reactor 35.
• the cathode actuated by a longitudinal movement of displacement by mechanical means makes it possible to keep constant the gap between the anode and the cathode as and when the sublimation of said cathode.
• the anode rod is made of the material which one wishes to sublimate in order to obtain fine or ultrafine particles.
• the tungsten anode can be used.
• a vaporizable anode 51 is put in place, the inert gas, for example argon, is injected via lines 66, hydrocarbon, for example petrol or other possible reactants via line 68, and metallic particles via the supply means 50.
• the reactor 35 is cooled by circulation of water 40a.
• An electric arc 49 is created using a generator between the anode 51 and the cathode 48.
• the plasma formed by the arc 49 is channeled by the diaphragms 62.
• the plasma of the arc provides, share, the sublimation of the vaporizable anode 51, and carries the powder coming from the supply means 50 at high temperature. It is extremely important to avoid the fusion of the end of the vaporizable anode 51, which, if it flows, could damage the reactor 35.
• the product additions can be influenced by the quantity of powders injected.
• the condensation chamber there is an extremely high temperature in the plasma, for example between 5,000 and 6,000 K, in which the particles of the sublimated anode or the powder of injected material pass through. They are brought to very high temperature and rotated perpendicularly to the axis of the plasma. They are projected by centrifugal force towards the periphery of the condensation chamber 64 containing hydrocarbon vapors.
• the meeting of the two products causes in reaction the formation of hydrophobic particles in the case of the example described.
• the reactor 35 enclosure is made of materials which withstand high temperatures, such as, for example, tungsten, refractory steel, alumina, etc.
• the diaphragms can be made, for example, of non-conductive material which withstands high temperatures, such as in vitro-ceramic, quartz, alumina, etc.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

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Cited By (5)

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Citations (4)

• 1994
  • 1994-12-02 FR FR9414525A patent/FR2727635A1/fr active Granted
• 1995
  • 1995-12-01 AU AU43070/96A patent/AU4307096A/en not_active Abandoned
  • 1995-12-01 WO PCT/FR1995/001592 patent/WO1996016731A1/fr active Application Filing

Patent Citations (4)

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