JP2002263474A - Manufacturing device and manufacturing method for superfine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacturing device and manufacturing method of superfine particles by which productivity is improved, a manufacturing cost is reduced, energy efficiency is improved, the manufacturing device is simplified, reliability is improved, the restrictions of a raw material are reduced and impurities are reduced. SOLUTION: This manufacturing device of the superfine particles is provided with a plasma arc generation means 6a having two shifting type plasma torches 4a and 4b provided with acting gas blow-off nozzles 2a and 2b and electrodes 22 and 23, a current power source 5 disposed in a circuit 21 connected to the electrodes 22 and 23, a short-circuit body 24 mutually short-circuiting the electrodes 22 and 23 and a short-circuit body moving means 25 and which a reacting/cooling gas blow-off nozzle 9 for blowing reacting/cooling gas to evaporative gas generated by exposing a plasma arc generated from the shifting type plasma torches 4a and 4b to a raw material body 3 to be the raw material of the superfine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing ultra-fine particles which has high productivity, low production cost, high energy efficiency, simplification of production equipment and improvement in reliability, has few restrictions on raw materials, and has few impurities. The present invention relates to a manufacturing apparatus and a manufacturing method.

[0002]

2. Description of the Related Art As a conventional apparatus and method for producing ultrafine particles, a transfer DC plasma arc method, a non-transfer DC plasma arc method, a high-frequency plasma method, a hybrid plasma method and the like are exemplified. Here, the transition type is a type in which electrons are transferred between the electrode of the plasma torch and an electrode installed outside the plasma torch to generate a plasma arc, and the non-transition type is a type in which the plasma torch electrode is formed. It has two electrodes, a negative electrode and a positive electrode, and generates a plasma arc even if there is no transfer of electrons outside the plasma torch. Regarding the transfer type DC plasma arc method, for example, Japanese Patent No. 2980980 discloses a manufacturing apparatus and a manufacturing method. This apparatus for producing ultrafine particles is as shown in FIG. This ultrafine particle manufacturing apparatus has a chamber 31 for isolating it from the outside.
, A plasma torch 33 having a cathode 32, a source body 34 as an anode, and a power source 3 for generating a plasma arc between the plasma torch 33 and the source body 34.
5, a raw material holding / sending device 36 for holding and sending the raw material 34, a working gas blowing nozzle 38 for blowing the working gas supplied from the working gas tank 37 around the cathode 32, and the raw material 34 being evaporated by the plasma arc. Reaction and cooling gas tank 3
It has a reaction / cooling gas spray nozzle 40 for blowing the reaction / cooling gas supplied from 9 to the evaporative gas, an evaporative gas cooling tank 41 for cooling the evaporative gas, and a collector 42. The cathode 32 is a non-consuming electrode, and the raw material body 34 is a consuming electrode. Further, the plasma torch 33 is disposed at a certain distance from the surface of the raw material body 34 at an oblique angle.

In the case of this apparatus, first, argon, nitrogen,
While flowing a working gas composed of hydrogen and a mixed gas thereof from the working gas spray nozzle 38, the cathode 3
2 and the raw material 34 are energized by a power supply 35 to generate a plasma arc. This allows electrons to enter the cathode 3
2 to the raw material body 34. The raw material body 34 is heated by the plasma arc thus generated, and evaporates from the surface. Evaporated gas evaporated from the surface of the raw material body 34 is blown toward the front side of the plasma torch 33 by a plasma arc. Then, a reaction composed of oxygen, nitrogen, air and their mixed gas
The cooling gas flows out of the reaction / cooling gas spray nozzle 40 installed near the raw material body 34. The metal vapor contained in the vaporized gas stream reacts with the reaction / cooling gas or is cooled to form ultra-fine particles such as nano-sized metal oxide fine particles. The gas flow containing the ultrafine particles moves to the evaporative gas cooling tank 41 and is separated by the collector 42 in the evaporative gas cooling tank 41.

[0004]

However, in the above-described method, a current is applied between the cathode 32 and the raw material 34 to generate a plasma arc. Therefore, the material applicable to the raw material 34 is limited to a conductor. Was. For this reason, it has not been possible to evaporate the non-conductive raw material or powder as it is (it may be burned when the formed ultra-fine particles are oxides). Therefore, in order to use a non-conductive raw material or powder as the conductive raw material, a non-metallic conductive material (for example, a carbon material) or the like is mixed and molded to form the raw material 34.
Requires a pre-process to produce Also, conductive materials,
Particularly, impurities contained in a carbon material and the like sometimes mixed into the ultrafine particles. When a non-conductor is used as a raw material as described above, the cost of a conductive material is increased, and thus the production cost of ultrafine particles is high. Further, the number of manufacturing steps is increased, so that the productivity is low. Further, in the case of the carbon material-containing molding raw material, a considerable amount of the applied energy is consumed for burning the carbon material, resulting in energy loss.

[0005] Further, although the cross-sectional area of the high-temperature portion of the plasma arc method of the transfer method is narrow, it is difficult to obtain and manufacture a thin raw material, so that the cross-sectional area of the raw material may be large and the evaporation surface may be uniform. Is not heated. In order to uniformly heat the raw material 34, it is necessary to rotate the raw material 34. In this case, after heating and melting, the raw material 34 is cooled away from the high-temperature portion of the arc without being evaporated, resulting in a raw material loss and energy loss. .

In the case of the transfer method, when the distance between the plasma torch 33 serving as the positive electrode and the raw material body 34 serving as the negative electrode changes, the electrical conditions (current value and voltage) fluctuate. In the means for correcting the above, a complicated mechanism is required for controlling the feed amount of the raw material body 34, and the cost of the apparatus is high. In addition, if the oxide adheres and accumulates on the evaporation surface of the raw material body 34, poor conductivity will result.
The production had to be interrupted once and the sediment removed, reducing productivity.

Further, the non-transfer type DC plasma arc method is
As shown in FIG. 7, one plasma torch 43 has a center electrode 44 and an outer peripheral electrode 45, which are energized to generate a plasma arc, and to melt and evaporate the raw material body 46. It is not necessary to energize 46, but since the temperature of the plasma arc rapidly decreases as the distance from the plasma torch 43 increases, a large amount of energy is required to evaporate the raw material, and the energy efficiency is low. In the high-frequency plasma method, a working gas is caused to flow in the center of an induction coil to generate plasma, and further, a raw material is caused to flow and evaporate. The raw material needs to be a powder in order to flow and evaporate the raw material in the center of the coil. The hybrid method can generate high-temperature, high-energy plasma, but the raw material must be powder.

[0008] The present invention has been made in view of the above circumstances, it is possible to achieve high productivity, low manufacturing cost, high energy efficiency, simplification of manufacturing equipment and improvement of reliability, and the restriction of raw materials It is an object of the present invention to provide an apparatus and a method for producing ultrafine particles having a small amount of impurities.

[0009]

According to a first aspect of the present invention, there is provided an apparatus for producing ultrafine particles comprising the following (A) and (B). (A) two transition type plasma torches each including a working gas blowing nozzle for blowing a working gas and an electrode for generating a plasma arc; a current power supply provided in a circuit connecting the electrodes; A short-circuiting body for electrically short-circuiting the two, and a short-circuiting body moving means for moving the short-circuiting body and / or a plasma torch moving means for moving at least one of the two transition type plasma torches. A plasma torch is a plasma arc generating means installed such that two plasma arcs generated from the tip thereof come into contact with each other. (B) A reaction / cooling gas spray nozzle for spraying a reaction / cooling gas to an evaporative gas generated by applying a plasma arc generated from the transfer type plasma torch to a raw material material serving as a raw material of ultrafine particles.

An apparatus for producing ultrafine particles according to claim 2 includes the following (C) and (D). (C) two transfer-type plasma torches including a working gas blowing nozzle for blowing a working gas and an electrode for generating a plasma arc; a current power supply provided in a circuit connecting the electrodes; Plasma torch moving means for moving at least one of the transition type plasma torches, wherein the transition type plasma torch is installed so that plasma arcs generated from the tips thereof come into contact with each other. (D) A reaction / cooling gas spray nozzle for spraying a reaction / cooling gas to an evaporative gas generated by applying a plasma arc generated from the transfer type plasma torch to a raw material serving as a raw material of ultrafine particles. In the apparatus for producing ultrafine particles of the present invention, it is preferable that the current power supply includes a DC power supply and a high-frequency arc generating means having an AC power supply, and the high-frequency AC voltage is superimposed on the DC voltage.

According to a fourth aspect of the present invention, in the method for producing ultrafine particles, the electrodes of the two transition type plasma torches are energized by a DC power supply while blowing a working gas to thereby form a V-shaped plasma arc or a Y-shaped plasma arc. The V-shaped plasma arc or the Y-shaped plasma arc is applied to a raw material as a raw material of ultrafine particles, and the raw material is vaporized to generate an evaporative gas. Is sprayed to react and / or cool the evaporative gas and the reaction / cooling gas to form ultrafine particles.

According to a fifth aspect of the present invention, in the method for producing ultrafine particles, the electrodes of two transfer-type plasma torches close to a short-circuit body for electrically short-circuiting the electrodes are energized while blowing a working gas. A pilot arc is generated between an electrode and the short-circuit body, a distance between the short-circuit body and the electrode is increased, and the pilot arc is grown to form a V-shaped plasma arc or a Y-shaped plasma arc.
The V-shaped plasma arc or the Y-shaped plasma arc is applied to a raw material as a raw material of the ultrafine particles, and the raw material is vaporized to generate an evaporative gas.
A method of spraying a cooling gas to react and / or cool the evaporating gas and the reaction / cooling gas to form ultrafine particles.

In the method for producing ultrafine particles according to a sixth aspect of the present invention, the two transfer-type plasma torch electrodes which are in contact with the short-circuit body for electrically short-circuiting the electrodes are energized while blowing the working gas. A pilot arc is generated by separating the electrode and the short-circuit body, a distance between the short-circuit body and the electrode is widened, and the pilot arc is grown to form a V-shaped plasma arc or a Y-shaped plasma arc. The V-shaped plasma arc or the Y-shaped plasma arc is applied to a raw material as a raw material of ultrafine particles, the raw material is vaporized to generate an evaporative gas, and a reaction / cooling gas is sprayed on the evaporative gas. And reacting and / or cooling the vaporized gas with the reaction / cooling gas to form ultrafine particles.

According to a seventh aspect of the present invention, there is provided a method for producing ultrafine particles, wherein a pilot arc is generated by energizing electrodes of two transition type plasma torches whose electrodes are close to each other while blowing a working gas. By moving at least one of the plasma torches and growing the pilot arc, a V-shaped plasma arc or a Y-shaped plasma arc is formed. The raw material body is vaporized, the raw material body is vaporized to generate an evaporative gas, and a reaction / cooling gas is sprayed on the evaporative gas to react and / or cool the evaporative gas with the reaction / cooling gas. This is a method of forming ultrafine particles. In the method for producing ultrafine particles of the present invention, it is preferable that a DC voltage and a high-frequency AC voltage are applied between the electrodes and superimposed to generate a pilot arc.

[0015]

1 and 2 show an example of an ultrafine particle producing apparatus according to the present invention. This apparatus for producing ultrafine particles includes a chamber 1 for shutting off an external atmosphere, a plasma arc generating means 6a having a transition type plasma torch 4 and a current power supply 5, and an operation filled with an operation gas supplied to the transition type plasma torch 4. A gas tank 7, a reaction / cooling gas spray nozzle 9 for spraying the reaction / cooling gas filled in the reaction / cooling gas tank 8 onto an evaporative gas generated by evaporating the raw material body 3, and a raw material body 3 connected to the chamber 1. And an evaporative gas cooling tank 10 for expanding and cooling the evaporative gas that has evaporated and separating the evaporative gas and the generated ultrafine particles. In this apparatus, the transfer type plasma torch 4 is arranged such that the axial direction of the generated plasma arc is oblique to the evaporation surface of the raw material body 3. The reaction / cooling gas spray nozzle 9 is provided so that the raw material body 3 is disposed between the nozzle body 9 and the plasma torch 4.

Further, a raw material holding / sending device 1 which holds the raw material 3 from outside the chamber 1 and sends out the raw material 3
2, a position where the raw material 3 is evaporated, the information is analyzed, and a signal is output to the raw material holding / delivery device 12 to determine a feed speed of the raw material 3. And Here, the reaction / cooling gas refers to a reaction gas that evaporates the raw material body 3 and reacts with the generated evaporative gas, and / or a cooling gas that cools the evaporative gas. For example, when forming metal oxide ultrafine particles or metal nitride ultrafine particles, oxygen or nitrogen used as a reaction / cooling gas becomes a reaction / cooling gas, and when forming metal ultrafine particles, it becomes a reaction / cooling gas. The inert gas used is a cooling gas. Such a reaction
As the cooling gas, oxygen, nitrogen, helium, air or a mixture thereof is preferably used. Further, the particle size and particle size distribution of the ultrafine particles can be controlled by the flow rate of the reaction / cooling gas and the position of the reaction / cooling gas spray nozzle 9.

The plasma arc generating means 6a in the present embodiment is a working gas blowing nozzle 2a for blowing working gas which is argon, nitrogen, hydrogen or a mixture thereof.
And a transfer type plasma torch 4a having an electrode 22 for generating a plasma arc, a transfer type plasma torch 4b having a working gas blowing nozzle 2b and an electrode 23, and a current provided in a circuit 21 connecting the electrodes 22 and 23. The power supply 5 includes a short-circuiting body 24 for electrically short-circuiting the electrodes 22 and 23, and a short-circuit moving means 25 for moving the short-circuiting body 24. The two transfer-type plasma torches 4a and 4b are installed so that a plasma arc generated from the tip comes into contact when not in proximity to the short-circuit body 24. Further, the transfer type plasma torches 4a, 4
It is preferable that b has a nozzle-like tip.

The shape of the raw material body 3 may be a round bar or a square bar. In the case of a round bar, its diameter is preferably 20 to 100 mm. Such a rod-shaped raw material 3 may be obtained and used, or a rod-shaped raw material 3 may be prepared by mixing a granular or powdery raw material with a resin binder. The mixing ratio of the resin binder is preferably 10 to 50% by weight of the whole raw material body. When these resin binders are burned by a plasma arc in the presence of oxygen, they become carbon dioxide and water, and do not affect the ultrafine particles and the production thereof. In addition, powdered, granular, or lump-shaped raw materials can also be used. In that case, it is preferable to fill the raw material into a crucible for evaporation, and the raw material holding / delivery device 12 is not used.

The current power supply 5 preferably includes a DC power supply and high-frequency arc generating means (not shown) having an AC power supply, and is preferably capable of superimposing a high-frequency AC voltage on the DC voltage.
With such a current power supply 5, a DC voltage and a high-frequency AC voltage are applied and superimposed between the electrode 22 and the electrode 23,
By inducing a high-frequency arc, pilot arcs A and B can be generated between the electrode 22 and the short circuit 24 and between the electrode 23 and the short circuit 24. A specific example of generating a pilot arc in this manner will be described. The working gas is blown out from the working gas blowing nozzles 2a, 2b into the transfer type plasma torches 4a, 4b, and while the working gas is caused to flow out from the transfer type plasma torches 4a, 4b,
A DC voltage is applied to the electrodes 22 and 23 by the current power supply 5 to conduct electricity. A high-frequency AC voltage is superimposed on the DC voltage by high-frequency arc generating means to generate a high-frequency arc. Then, the electrode 2 is induced by induction of a high-frequency arc.
Pilot arcs A and B are generated between the short circuit 2 and the short circuit 24 and between the electrode 23 and the short circuit 24. Thereafter, the superposition of the high-frequency AC voltage by the high-frequency arc generating means is stopped, and the generation of the high-frequency arc is stopped.

The electrodes 22, 23 are non-consumable. For example, a material mainly containing tungsten is used. The short-circuit body 24 has electrical conductivity, and the electrodes 22 and 23
The shape is not limited as long as it is close to the shape, but a metal or carbon material such as tungsten or copper is preferably used. Further, it is preferable to have a cooling means such as a water cooling jacket. Further, a voltage required for generating a pilot arc is previously input to the short-circuiting body 24 and the short-circuiting body moving means 25, and the short-circuiting body moving means 25 moves based on the input voltage.
It is preferable to have a function of automatically adjusting the distance between a, 4b and the short-circuit body 24.

The evaporating surface position detecting device 13 detects the position of the evaporating surface of the raw material, and keeps the distance between the plasma arc end and the surface of the raw material constant. In the above-described example, the evaporating surface position detecting device 13 includes a CCD camera, analyzes an image of the evaporating surface input from the CCD camera by an image processing system, and outputs a signal to the raw material body holding / delivery device 12. The material holding / sending device 12 is operated according to the signal. Collector 11
Is not particularly limited as long as it can separate the ultrafine particles and the gas, and examples thereof include a filter.

In the apparatus for producing ultrafine particles according to the first embodiment, the plasma arc generating means 6a
Is a transfer type plasma torch 4a having a working gas blowing nozzle 2a and an electrode 22;
and a transfer type plasma torch 4b having an electrode 23 and a current source 5 provided in a circuit 21 connecting the electrodes 22 and 23, and a short-circuiting body 24 for electrically short-circuiting the electrodes 22 and 23. And the transfer type plasma torch 4a, 4
b is installed so that the plasma arcs generated from the tips come into contact with each other. Therefore, while blowing the working gas from the working gas blowing nozzle 8, the electrodes 22 and 23 adjacent to the short-circuit body 24 are energized by the current power supply 5,
By inducing the high-frequency arc, pilot arcs A and B can be generated between the electrode 22 and the short circuit 24 and between the electrode 23 and the short circuit 24, as shown in FIG.

Further, since the short-circuit moving means 25 for moving the short-circuit 24 is provided, the pilot arcs A, B
Is generated, the short-circuit moving means 25 causes the short-circuit 2
By expanding the distance between the electrode 4 and the electrodes 22 and 23 and growing the pilot arcs A and B, a V-shaped plasma arc C in which electrons move between the electrodes 22 and 23 can be formed. Further, depending on the plasma gas flow, a Y-shaped plasma arc is formed. Further, the electrodes 22, 23 in contact with the short-circuit body 24 are energized by the current power supply 5 to
Are separated from the electrodes 22 and 23 by the short-circuit moving means 25 to generate pilot arcs A and B, and the short-circuit 24 is moved as it is to grow the pilot arcs A and B, thereby forming the V-shaped plasma arc C. May be formed.

The intermediate point of such a V-shaped plasma arc C can be regarded as a virtual electrode point having an intermediate potential between the plasma torches. Therefore, there is no need to transfer electrons to the raw material 3, and the raw material 3 is not limited to a conductive material such as a metal, and may be a nonconductive material such as a metal oxide. Therefore, when the raw material is non-conductive, there is no need to mix a conductive substance such as a carbon material, which has been conventionally performed, and the raw material cost can be reduced.
Further, the energy used for burning the carbon material can be reduced. In addition, contamination of impurities contained in a carbon material or the like can be eliminated. In addition, restrictions as a raw material are reduced, and a wide range of raw materials can be selected.

Further, since it is not necessary to supply electricity to the raw material body 3, the raw material body 3 does not melt or undergo oxidative collapse. In addition, power supply to the raw material holding / delivery device 12 is not required, and the structure of the equipment is simplified, and the reliability is improved. Further, it is not necessary to provide a holding electrode, which is a consumable product, in the raw material body holding / sending device 12, and the cost can be reduced. In addition, leakage of electricity can be prevented. In addition, because it is a non-consumable electrode, there is little electrical fluctuation,
It is easy to automate the feeding of the raw material body 3.

The above-described plasma arc generating means 6
In (a), a V-shaped plasma arc C is formed after the pilot arcs A and B come into contact with each other, so that the plasma concentration becomes high near the V-shaped tip and an arc high-temperature portion H having a higher temperature than the surroundings is formed. Can be. From these facts, since the arc high-temperature portion H has a long length and a large cross-sectional area, the amount of evaporation of the raw material 3 can be increased. As a result, the productivity of the ultrafine particles is improved. Further, not only can the raw material 3 be evaporated at the optimum position of the plasma arc, but also the degree of freedom in setting the position of the evaporation position is large, so that the particle size of the ultrafine particles can be easily controlled. In addition, even if the oxide adheres to the evaporating surface, since the evaporating surface is wide, the conduction does not become poor, and the operation of temporarily stopping the production and removing the deposit is not required. Further, since the output efficiency is excellent, the power consumption required for the production of ultrafine particles can be significantly reduced.

The apparatus for producing ultra-fine particles according to the first embodiment has the reaction / cooling gas spray nozzle 9, so that the reaction / cooling gas is blown to the evaporative gas so that the reaction / cooling gas is blown. In the case of oxygen or nitrogen, ultrafine metal oxide particles or ultrafine metal nitride particles can be formed, and when the reaction / cooling gas is an inert gas, ultrafine metal particles can be produced. Further, the productivity is further improved. The evaporative gas flow containing the ultrafine particles thus formed moves to the evaporative gas cooling tank 10 connected to the chamber 1 and is further cooled. The ultrafine particles entering the evaporative gas cooling tank 10 are separated from the evaporative gas by the collector 11 and fall to the lower part of the evaporative gas cooling tank 10. Then, it is extracted from the lower part of the evaporative gas cooling tank 10 and collected.

Further, in the above-described apparatus for producing ultrafine particles, the current power supply 5 includes a DC power supply and a high-frequency arc generating means having an AC power supply. The pilot arc can be more easily generated. As a result, it becomes easier to generate the high-temperature portion H of the V-shaped plasma arc C. Further, the transfer type plasma torches 4a, 4
b is that the tip has a nozzle-like shape,
The plasma concentration in the plasma arc can be higher and the temperature can be higher.

The apparatus for producing ultrafine particles according to this embodiment is not limited to the above embodiment. For example, in the above-described embodiment, the short-circuit moving means 25 is provided to move the short-circuit 24, and the electrodes 22, 23 and the short-circuit 2
4, the distance between the electrodes 22, 23 and the short-circuiting body 24 may be increased by moving at least one of the two transition type plasma torches 4a, 4b by the plasma torch moving means. Using both the short-circuit body moving means 25 and the plasma torch moving means, the electrodes 22, 23 are used.
The distance between the short-circuit body 24 and the short-circuit body 24 may be increased. Further, the raw material holding / sending device 12 is provided below the chamber 1 in the illustrated example, but may be provided beside the chamber 1 to hold the raw material and send it out in the lateral direction. In addition, when the raw material is powder, granular, or massive, the raw material holding / sending device 12 cannot be used, and therefore, a crucible for evaporation can be used instead.

Next, an apparatus for producing ultrafine particles according to a second embodiment of the present invention will be described with reference to FIGS. This ultrafine particle production apparatus is the same as the ultrafine particle production apparatus of the first embodiment described above except for the plasma arc generating means 6b, and includes a chamber 1, a working gas tank 7, a reaction / cooling gas tank 8, It has a cooling gas spray nozzle 9, an evaporative gas cooling tank 10, a collector 11, a raw material holding / sending device 12, and an evaporating surface position detecting device 13.

The plasma arc generating means 6b in this embodiment comprises a working gas blowing nozzle 2a for blowing a working gas and an electrode 22 for generating a plasma arc.
, A transfer type plasma torch 4b having a working gas blowing nozzle 2b and an electrode 23, a current power supply 5 provided in a circuit 21 connecting the electrodes 22, 23, and two transfer type plasma torches. 4
a torch moving means 26 for moving at least one of a and 4b. In addition, the transfer type plasma torches 4a and 4b are installed so that plasma arcs generated from the tips come into contact with each other. Further, it is preferable that the transition type plasma torches 4a and 4b have a nozzle-shaped tip.

Although the plasma torch moving means 26 is provided in both of the two transition type plasma torches 4a and 4b in the illustrated example, the present invention is not limited to this, and at least one of the transition type plasma torches is used. What is necessary is just to be provided. The moving method is not particularly limited as long as a V-shaped plasma arc can be finally formed. In addition, it is not preferable that the tips of the transfer-type plasma torch face each other during the movement because the electrodes 22 and 23 may be melted or damaged.

The current power supply 5 preferably includes a DC power supply and a high-frequency arc generating means (not shown) having an AC power supply, and is preferably capable of superimposing a high-frequency AC voltage on the DC voltage.
With such a current power supply 5, a DC voltage and a high-frequency AC voltage are applied and superimposed between the electrode 22 and the electrode 23,
By inducing a high-frequency arc, pilot arcs A and B can be generated between the electrode 22 and the short circuit 24 and between the electrode 23 and the short circuit 24. A specific example of generating a pilot arc in this manner will be described. The working gas is blown out from the working gas blowing nozzles 2a, 2b into the transfer type plasma torches 4a, 4b, and while the working gas is caused to flow out from the transfer type plasma torches 4a, 4b,
A DC voltage is applied to the electrodes 22 and 23 by the current power supply 5 to conduct electricity. A high-frequency AC voltage is superimposed on the DC voltage by high-frequency arc generating means to generate a high-frequency arc. Then, the electrode 2 is induced by induction of a high-frequency arc.
A pilot arc is generated between electrode 2 and electrode 23.
Thereafter, the superposition of the high-frequency AC voltage by the high-frequency arc generating means is stopped, and the generation of the high-frequency arc is stopped.

In the apparatus for producing ultrafine particles according to the second embodiment, the plasma arc generating means 6b
Is a transition type plasma torch 4a having a working gas blowing nozzle 2a and an electrode 22, and a transition type plasma torch 4 having a working gas blowing nozzle 2b and an electrode 23.
b, a current power supply 5 provided in a circuit 21 connecting the electrodes 22 and 23, and two transfer-type plasma torches 4a and 4b.
And the plasma torch moving means 26 for moving at least one of them, and the transfer type plasma torches 4a and 4b are installed so that the plasma arc generated from the tip comes into contact therewith. Therefore, while blowing the working gas, the electrodes 22 and 23 are close to each other.
By energizing 23, a pilot arc can be generated between the electrodes 22 and 23.

Since the plasma torch moving means 26 for moving the transfer type plasma torches 4a and 4b is provided, the plasma torches 4a and 4b are moved by the plasma torch moving means 26 after a pilot arc is generated. By growing the arc, a V-shaped plasma arc C in which electrons move between the electrode 22 and the electrode 23 can be formed. Also, a Y-shaped plasma arc may be formed depending on the plasma gas flow.

The intermediate point of such a V-shaped plasma arc C can be regarded as a virtual electrode point having an intermediate potential between the plasma torches. Therefore, there is no need to transfer electrons to the raw material 3, and the raw material 3 is not limited to a conductive material such as a metal, and may be a nonconductive material such as a metal oxide. Therefore, when the raw material is non-conductive, there is no need to mix a conductive substance such as a carbon material, which has been conventionally performed, and the raw material cost can be reduced.
Further, the energy used for burning the carbon material can be reduced. In addition, contamination of impurities contained in a carbon material or the like can be eliminated. In addition, restrictions as a raw material are reduced, and a wide range of raw materials can be selected.

Further, since it is not necessary to supply electricity to the raw material body 3, the raw material body 3 does not melt or undergo oxidative collapse. In addition, power supply to the raw material holding / delivery device 12 is not required, and the structure of the equipment is simplified, and the reliability is improved. Further, it is not necessary to provide a holding electrode, which is a consumable product, in the raw material body holding / sending device 12, and the cost can be reduced. In addition, leakage of electricity can be prevented. In addition, because it is a non-consumable electrode, there is little electrical fluctuation,
It is easy to automate the feeding of the raw material body 3.

The above-described plasma arc generating means 6
b, the transfer type plasma torches 4a and 4b are moved by the plasma torch moving means 26 while blowing the working gas from the working gas blowing nozzles 2 and 2b.
By growing the pilot arc generated between 2, 23,
Since the V-shaped plasma arc C is formed, the plasma concentration increases near the V-shaped tip, and an arc high-temperature portion H having a higher temperature than the surroundings can be formed. From these facts, since the arc high-temperature portion H has a long length and a large cross-sectional area, the amount of evaporation of the raw material 3 can be increased. As a result, the productivity of the ultrafine particles is improved.

Further, since the arc high-temperature portion H is large, not only can the raw material 3 be evaporated at the optimum position of the plasma arc, but also the degree of freedom in setting the position of the evaporation position is large, so that the particle size of the ultrafine particles can be controlled. It's easy to do. Also,
Even if the oxide adheres to the evaporating surface, the evaporating surface is wide, so that the conduction does not become poor. Therefore, it is not necessary to temporarily stop the production and remove the deposit. Further, since the output efficiency is excellent, the power consumption required for the production of ultrafine particles can be significantly reduced.

The apparatus for producing ultra-fine particles according to the second embodiment has the reaction / cooling gas spray nozzle 9, so that the reaction / cooling gas is blown to the evaporative gas so that the reaction / cooling gas is blown. In the case of oxygen or nitrogen, ultrafine metal oxide particles or ultrafine metal nitride particles can be formed, and when the reaction / cooling gas is an inert gas, ultrafine metal particles can be produced. Further, the productivity is further improved. The evaporative gas flow containing the ultrafine particles thus formed moves to the evaporative gas cooling tank 10 connected to the chamber 1 and is further cooled. The ultrafine particles entering the evaporative gas cooling tank 10 are separated from the evaporative gas by the collector 11 and fall to the lower part of the evaporative gas cooling tank 10. Then, it is extracted from the lower part of the evaporative gas cooling tank 10 and collected.

In the above-described apparatus for producing ultrafine particles, the current power supply 5 includes a DC power supply and a high-frequency arc generating means having an AC power supply, and the high-frequency AC voltage is superimposed on the DC voltage. The pilot arc can be more easily generated. As a result, it becomes easier to generate the high-temperature portion H of the V-shaped plasma arc C. Further, the transfer type plasma torches 4a, 4
b is that the tip has a nozzle-like shape,
The plasma concentration in the plasma arc can be higher and the temperature can be higher.

Further, in the above-described apparatus for producing ultrafine particles, the current power supply 5 includes a DC power supply and a high-frequency arc generating means having an AC power supply. The pilot arc can be more easily generated. As a result, it becomes easier to generate the high-temperature portion H of the V-shaped plasma arc C. Further, the transfer type plasma torches 4a, 4
b is that the tip has a nozzle-like shape,
The plasma concentration in the plasma arc can be higher and the temperature can be higher.

[0043]

EXAMPLES (Example 1) Method for Producing Ultrafine Particles of SiO _{2 In} this example, the apparatus for producing ultrafine particles shown in FIGS. 1 and 2 was used. First, metal silicon coarse particles (crushed product, particle size 1
mm or less) and a resin binder, and compression-molded into a round bar shape having a diameter of 50 mm to prepare a raw material body containing coarse particles of metallic silicon. The raw material body is held and sent out by the raw material body 12
Attached to. Next, the transfer type plasma torches 4a, 4
Tungsten was used for the electrodes 22 and 23 of b, and a short bar 24 in the shape of a round bar was brought close to the electrodes 22 and 23. Then, argon as a working gas is blown out from the working gas blowing nozzles 2a and 2b into the transfer type plasma torches 4a and 4b, and further, the working gas flows out from the transfer type plasma torches 4a and 4b. A voltage was applied and electricity was supplied. Next, a high-frequency arc was generated by superimposing a high-frequency AC voltage on the DC voltage by high-frequency arc generating means. And, by induction of the high-frequency arc,
Electrode 22 and short circuit 24, and electrode 23 and short circuit 24
And pilot arcs A and B were generated.

Next, the gap between the electrodes 22 and 23 and the short-circuiting body 24 was widened by using the short-circuiting body moving means 25, and the pilot arcs A and B were gradually extended and grown. And
The two pilot arcs come into contact, and the electrodes 22 and 23
A V-shaped plasma arc C was formed between the two. An arc high-temperature portion H was formed near the V-shaped tip of the V-shaped plasma arc C.

The plasma arc containing the high-temperature arc portion H was applied to the tip of the round bar of the raw material to evaporate the raw material. Although the tip of the raw material body is consumed, in order to keep the evaporation of the raw material body optimally, the distance between the plasma arc tip and the raw material body tip is kept constant by providing an evaporation surface position detecting device 13. The evaporating surface position detecting device 13 includes a CCD camera, analyzes an image input from the CCD camera by an image processing system, outputs a signal to the raw material body holding / delivery device 12, and outputs the raw material according to the signal. The body holding / delivery device 12 was operated to keep the distance constant.

The silicon vapor generated from the raw material flowed forward of the plasma arc due to the gas pressure of the plasma arc. Oxygen gas was blown from the reaction / cooling gas spray nozzle 9 across the silicon vapor to rapidly oxidize the silicon vapor to form SiO ₂ ultrafine particles. The formed SiO ₂ ultrafine particles and the oxidized evaporative gas were moved to the evaporative gas cooling tank 10, and after being cooled, were separated into SiO ₂ ultrafine particles and a gas by the collector 11. The separated SiO ₂ ultrafine particles are collected by a collector 11
It collected in the collection container installed in the lower part.

In the present embodiment, the current value and the arc shape can always be operated stably, and the yield of the raw material is remarkably improved. The productivity per unit time of the present embodiment was about 2 to 10 times that of the conventional transfer method. Nevertheless, gas flow per unit time did not need to be increased in proportion to productivity, and gas and electricity costs were significantly reduced. In the method of the present embodiment, when the cross section of the high-temperature arc portion is compared with the same electric energy, the high-temperature arc portion of the present embodiment has a diameter of about 1.10 in comparison with the conventional transition type method.
It was 5 times and the cross-sectional area was about 2 times. For this reason, the evaporation area was increased in the cross section of the raw material, and the energy loss was significantly reduced. In addition, the method of this example also improved the purity of the ultrafine particles, and was able to increase the purity to 99.995% by weight.

Example 2 Method for Producing Ultrafine Particles Using a Pulverized Silicon Single Crystal First, a silicon single crystal was pulverized to obtain a granular raw material having a side of about 10 mm. The evaporating crucible was placed at a position where the high-temperature arc portion H hit. The evaporating crucible is a hemisphere having a diameter of 100 mm, and a jacket for water cooling is provided on the outside. The material of the evaporation crucible is made of copper, and zirconia is sprayed on the surface to prevent impurities.

After the pulverized silicon single crystal was put into the evaporation crucible, the electrodes 22 and 23 were treated in the same manner as in Example 1.
, A V-shaped plasma arc C was formed. This V
High-temperature portion H near the V-shaped tip of the V-shaped plasma arc C
Was applied to a crushed silicon single crystal in an evaporation crucible and evaporated. Silicon vapor generated from the raw material flowed forward of the plasma arc due to the gas pressure of the plasma arc. Oxygen gas was blown from the reaction / cooling gas spray nozzle 9 across the silicon vapor to rapidly oxidize the silicon vapor to form SiO ₂ ultrafine particles. The formed SiO ₂ ultrafine particles and the oxidized evaporative gas were moved to the evaporative gas cooling tank 10, and after being cooled, were separated into SiO ₂ ultrafine particles and gas by the collector 11. The separated ultrafine particles of SiO ₂ were collected in a collecting container installed below the evaporative gas cooling tank 10.

Example 3 Method for Producing Ultrafine Particles by Direct Evaporation of Metal Bismuth Particles Metal bismuth particles having a particle size of 5 mm were used as a raw material.
After charging the metal bismuth particles into the same crucible as in Example 2, a V-shaped plasma arc C was formed between the electrodes 22 and 23 in the same manner as in Example 1. Arc high temperature portion H near the V-shaped tip of this V-shaped plasma arc C
Was applied to a crushed bismuth single crystal in an evaporation crucible and evaporated.

The bismuth vapor generated from the raw material flowed forward of the plasma arc due to the gas pressure of the plasma arc. Oxygen gas was blown from the reaction / cooling gas blowing nozzle 9 across the bismuth vapor to rapidly oxidize the bismuth vapor to form Bi ₂ O ₃ ultrafine particles. The formed Bi ₂ O ₃ ultrafine particles and the oxidized evaporative gas were moved to the evaporative gas cooling tank 10 and cooled, and then separated into Bi ₂ O ₃ ultrafine particles and gas by the collector 11. The separated Bi ₂ O ₃ ultrafine particles were collected in a collection container installed at the lower part of the evaporative gas cooling tank 10.

In this embodiment, since the area of the arc high-temperature portion H is large and the entire evaporating crucible can be heated, the molten metal bismuth in the evaporating crucible as seen in the conventional transfer type method can be heated. Above, there was no possibility that the powder that had already evaporated and oxidized fell to form a non-conductive film. Therefore, there was no conduction failure due to the non-conductive oxide film, and there was no need to stop the operation to remove the non-conductive oxide film, and continuous operation was possible.

Example 4 Method for Producing SiO ₂ Ultrafine Particles In this example, the apparatus for producing ultrafine particles shown in FIGS. 4 and 5 was used. First, metal silicon coarse particles (crushed product, particle size 1
mm or less) and a resin binder, and compression-molded into a round bar shape having a diameter of 50 mm to prepare a raw material body containing coarse particles of metallic silicon. The raw material body is held and sent out by the raw material body 12
Attached to. Next, the transfer type plasma torches 4a, 4
The electrodes 22 and 23 of b are brought close to each other, and argon as a working gas is blown from the working gas blowing nozzles 2a and 2b into the transfer type plasma torches 4a and 4b, and while the working gas flows out from the transfer type plasma torches 4a and 4b,
A DC voltage was applied to the electrodes 22 and 23 to conduct electricity. Next, a high-frequency arc was generated by superimposing a high-frequency AC voltage on the DC voltage by high-frequency arc generating means. Then, the induction of the high-frequency arc causes the electrode 2
A pilot arc was generated between electrode 2 and electrode 23.

Next, using the plasma torch moving means 26, the two plasma torches 4a and 4b are moved,
The pilot arc was gradually extended and grown. Then, a V-shaped plasma arc C was formed between the electrodes 22 and 23. An arc high-temperature portion H was formed near the V-shaped tip of the V-shaped plasma arc C.

The plasma arc including the high-temperature arc portion H was applied to the tip of the round bar of the raw material to evaporate the raw material. Although the tip of the raw material body is consumed, in order to keep the evaporation of the raw material body optimally, the distance between the plasma arc tip and the raw material body tip is kept constant by providing an evaporation surface position detecting device 13. The evaporating surface position detecting device 13 includes a CCD camera, analyzes an image input from the CCD camera by an image processing system, outputs a signal to the raw material body holding / delivery device 12, and outputs the raw material according to the signal. The body holding / delivery device 12 was operated to keep the distance constant.

The silicon vapor generated from the raw material flowed forward of the plasma arc due to the gas pressure of the plasma arc. Oxygen gas was blown from the reaction / cooling gas spray nozzle 9 across the silicon vapor to rapidly oxidize the silicon vapor to form SiO ₂ ultrafine particles. The formed SiO ₂ ultrafine particles and the oxidized evaporative gas were moved to the evaporative gas cooling tank 10, and after being cooled, were separated into SiO ₂ ultrafine particles and a gas by the collector 11. The separated SiO ₂ ultrafine particles are collected by a collector 11
It collected in the collection container installed in the lower part.

In the present embodiment, the current value and the arc shape can always be operated stably, and the yield of the raw material is remarkably improved. The productivity per unit time of the present embodiment was about 2 to 10 times that of the conventional transfer method. Nevertheless, gas flow per unit time did not need to be increased in proportion to productivity, and gas and electricity costs were significantly reduced. In the method of the present embodiment, when the cross section of the high-temperature arc portion is compared with the same electric energy, the high-temperature arc portion of the present embodiment has a diameter of about 1.10 in comparison with the conventional transition type method.
It was 5 times and the cross-sectional area was about 2 times. For this reason, the evaporation area was increased in the cross section of the raw material, and the energy loss was significantly reduced. In addition, the method of this example also improved the purity of the ultrafine particles, and was able to increase the purity to 99.995% by weight.

Example 5 Method for Producing Ultrafine Particles Using a Pulverized Silicon Single Crystal First, a silicon single crystal was pulverized to obtain a granular raw material having a side of about 10 mm. The evaporating crucible was placed at a position where the high-temperature arc portion H hit. The evaporating crucible is a hemisphere having a diameter of 100 mm, and a jacket for water cooling is provided on the outside. The material of the evaporation crucible is made of copper, and zirconia is sprayed on the surface to prevent impurities.

After the pulverized silicon single crystal was put into the evaporation crucible, the electrodes 22 and 23 were treated in the same manner as in Example 4.
, A V-shaped plasma arc C was formed. This V
High-temperature portion H near the V-shaped tip of the V-shaped plasma arc C
Was applied to a crushed silicon single crystal in an evaporation crucible and evaporated. Silicon vapor generated from the raw material flowed forward of the plasma arc due to the gas pressure of the plasma arc. Oxygen gas was blown from the reaction / cooling gas spray nozzle 9 across the silicon vapor to rapidly oxidize the silicon vapor to form SiO ₂ ultrafine particles. The formed SiO ₂ ultrafine particles and the oxidized evaporative gas were moved to the evaporative gas cooling tank 10, and after being cooled, were separated into SiO ₂ ultrafine particles and gas by the collector 11. The separated ultrafine particles of SiO ₂ were collected in a collecting container installed below the evaporative gas cooling tank 10.

Example 6 Method for Producing Ultrafine Particles by Direct Evaporation of Metal Bismuth Particles Metal bismuth particles having a particle diameter of 5 mm were used as raw materials.
After charging the metal bismuth particles into the same crucible as in Example 5, a V-shaped plasma arc C was formed between the electrodes 22 and 23 in the same manner as in Example 4. Arc high temperature portion H near the V-shaped tip of this V-shaped plasma arc C
Was applied to a crushed bismuth single crystal in an evaporation crucible and evaporated.

The bismuth vapor generated from the raw material flowed forward of the plasma arc due to the gas pressure of the plasma arc. Oxygen gas was blown from the reaction / cooling gas blowing nozzle 9 across the bismuth vapor to rapidly oxidize the bismuth vapor to form Bi ₂ O ₃ ultrafine particles. The formed Bi ₂ O ₃ ultrafine particles and the oxidized evaporative gas were moved to the evaporative gas cooling tank 10 and cooled, and then separated into Bi ₂ O ₃ ultrafine particles and gas by the collector 11. The separated Bi ₂ O ₃ ultrafine particles were collected in a collection container installed at the lower part of the evaporative gas cooling tank 10.

In this embodiment, since the area of the arc high-temperature portion H is large and the entire evaporating crucible can be heated, the molten metal bismuth in the evaporating crucible as seen in the conventional transfer type method can be heated. Above, there was no possibility that the powder that had already evaporated and oxidized fell to form a non-conductive film. Therefore, there was no conduction failure due to the non-conductive oxide film, and there was no need to stop the operation to remove the non-conductive oxide film, and continuous operation was possible.

[0063]

According to the present invention, there is no need to supply electricity to the raw material, it is not necessary to mix a conductive material, and there are few restrictions on the raw material and ultrafine particles with few impurities can be produced with high energy efficiency and low cost. Can be manufactured. Further, simplification and reliability of the manufacturing apparatus can be improved.
Further, since the arc high-temperature portion becomes large, the productivity can be increased.

[Brief description of the drawings]

FIG. 1 is a top view illustrating an apparatus for producing ultrafine particles according to a first embodiment of the present invention.

FIG. 2 is a side view showing an apparatus for producing ultrafine particles according to the first embodiment of the present invention.

FIG. 3 is a top view showing a state where the electrodes are short-circuited by a short-circuit body in the ultrafine particle manufacturing apparatus according to the first embodiment.

FIG. 4 is a top view illustrating an apparatus for manufacturing ultrafine particles according to a second embodiment of the present invention.

FIG. 5 is a side view showing an apparatus for producing ultrafine particles according to a second embodiment of the present invention.

FIG. 6 is a side view showing an example of an apparatus for producing ultrafine particles used in a transfer type DC plasma arc method which is a conventional method for producing ultrafine particles.

FIG. 7 is a diagram illustrating an example of an ultrafine particle manufacturing apparatus used for a non-transfer type direct current plasma arc method, which is a conventional ultrafine particle manufacturing method.

[Explanation of symbols]

 2a, 2b Working gas blowing nozzle 3 Raw material 4a, 4b Transition type plasma torch 5 Current power supply 6a, 6b Plasma arc generating means 9 Reaction / cooling gas blowing nozzle 10 Evaporation gas cooling tank 22, 23 Electrode 24 Short circuit 25 Short circuit moving Means 26 Plasma torch moving means A, B Pilot arc C V-shaped plasma arc H Arc high temperature part

Claims (8)

[Claims] 1. An apparatus for producing ultrafine particles, comprising the following (A) and (B). (A) 2 provided with a working gas blowing nozzle for blowing working gas and an electrode for generating a plasma arc
Two transfer-type plasma torches, a current power supply provided in a circuit connecting the electrodes, a short-circuit body for electrically short-circuiting the electrodes, a short-circuit moving means for moving the short-circuit, and / or the two A plasma torch moving means for moving at least one of the transition type plasma torches, wherein the two transition type plasma torches are arranged such that two plasma arcs generated from the tips thereof come into contact with each other. Means of generation. (B) A reaction / cooling gas spray nozzle for spraying a reaction / cooling gas to an evaporative gas generated by applying a plasma arc generated from the transfer type plasma torch to a raw material material serving as a raw material of ultrafine particles. 2. An apparatus for producing ultrafine particles, comprising the following (C) and (D). (C) two transfer-type plasma torches including a working gas blowing nozzle for blowing a working gas and an electrode for generating a plasma arc; a current power supply provided in a circuit connecting the electrodes; Plasma torch moving means for moving at least one of the transition type plasma torches, wherein the transition type plasma torch is a plasma arc generation means arranged so that a plasma arc generated from a tip of the transition type plasma torch comes into contact. (D) A reaction / cooling gas spray nozzle for spraying a reaction / cooling gas to an evaporative gas generated by applying a plasma arc generated from the transfer type plasma torch to a raw material serving as a raw material of ultrafine particles. 3. The current power supply includes a DC power supply and high-frequency arc generating means having an AC power supply, and superimposes a high-frequency AC voltage on the DC voltage.
3. The apparatus for producing ultrafine particles according to claim 1. 4. An electrode of the two transfer type plasma torches is energized by a DC power supply while blowing out a working gas,
A V-shaped plasma arc or a Y-shaped plasma arc is formed, and the V-shaped plasma arc or the Y-shaped plasma arc is applied to a raw material as a raw material of ultrafine particles, and the raw material is vaporized to evaporate gas. A method for producing ultrafine particles, comprising: generating and blowing a reaction / cooling gas onto the evaporative gas to react and / or cool the evaporative gas with the reaction / cooling gas to form ultrafine particles. 5. An electric current is supplied to two transfer-type plasma torch electrodes close to a short-circuit body for electrically short-circuiting the electrodes while blowing a working gas, and a pilot arc is generated between the electrodes and the short-circuit body. Generating a V-shaped plasma arc or a Y-shaped plasma arc by growing a distance between the short-circuit body and the electrode and growing the pilot arc; Is applied to a raw material body that is a raw material of ultrafine particles, and the raw material body is vaporized to generate an evaporative gas.
A method for producing ultrafine particles, comprising spraying a cooling gas to react and / or cool the evaporative gas with the reaction / cooling gas to form ultrafine particles. 6. An electric current is supplied to two electrodes of a transition type plasma torch in contact with a short-circuit body for electrically short-circuiting the electrodes while blowing a working gas, and the pilot arc is separated by separating the electrodes from the short-circuit body. Generating a V-shaped plasma arc or a Y-shaped plasma arc by growing a distance between the short-circuit body and the electrode and growing the pilot arc; Is applied to a raw material body that is a raw material of ultrafine particles, and the raw material body is vaporized to generate an evaporative gas.
A method for producing ultrafine particles, comprising spraying a cooling gas to react and / or cool the evaporative gas with the reaction / cooling gas to form ultrafine particles. 7. An electric current is supplied to the electrodes of two transition type plasma torches whose electrodes are close to each other while a working gas is blown out to generate a pilot arc, and at least one of the two transition type plasma torches is moved. Growing the pilot arc,
A V-shaped plasma arc or a Y-shaped plasma arc is formed. The V-shaped plasma arc or the Y-shaped plasma arc is applied to a raw material to be a raw material of ultrafine particles, and the raw material is vaporized to form an evaporative gas. And reacts with the evaporative gas.
A method for producing ultrafine particles, comprising spraying a cooling gas to react and / or cool the evaporative gas with the reaction / cooling gas to form ultrafine particles. 8. The method for producing ultrafine particles according to claim 5, wherein a DC voltage and a high-frequency AC voltage are applied and superimposed between the electrodes to generate a pilot arc. .