JP2002241812A - Method and equipment for manufacturing metallic ultrafine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide equipment and a method for manufacturing metallic ultrafine particles which enable formation of high-quality metallic ultrafine particles having smaller article size and minimal variance in particle size by suppressing the agglomeration and growth of the metallic ultrafine particles in forming the metallic ultrafine particles using arc discharge. SOLUTION: For example, an ultrafine-particle-introducing pipe 38 is provided in the transfer path for the resultant metallic ultrafine particles, and further a pipe-cooling part 51 and a part 52 for cooling the inside of the pipe which are used to cool the atmospheric gas flowing through the ultrafine-particle- introducing pipe 38 are provided. Because the metallic ultrafine particles formed by arc discharge can be cooled thereby in the formed stage of recovery, the growth of the metallic ultrafine particles can be suppressed and finer particles can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for producing ultrafine metal particles, and more particularly to a method and apparatus for effectively controlling the particle diameter of ultrafine metal particles produced by utilizing arc discharge. The present invention relates to an apparatus and a method for producing ultrafine metal particles.

[0002]

2. Description of the Related Art Conventionally, it has been known to use arc discharge as a technique for producing ultrafine metal particles having a diameter of nm units among metal fine particles. In this technique, generally, a voltage is applied between a discharge electrode (cathode) arranged in close proximity and a metal base material (anode) serving as a target to generate an arc discharge, whereby metal ultrafine particles are formed. Further, by using hydrogen gas or a mixed gas of hydrogen gas and an inert gas as an atmospheric gas (this method is referred to as a hydrogen arc method), a metal particle having a particle size of about several tens nm is obtained. Fine particles can be obtained.

[0003] In recent years, in particular, there has been a trend in recent years to demand high quality ultrafine metal particles having a smaller particle size and a small variation in particle size (small particle size distribution). For this reason, various techniques for more effectively controlling the particle size have been proposed in the field of manufacturing ultrafine metal particles.

Generally, in the production of ultrafine metal particles by arc discharge, it is known that the particle diameter of the generated ultrafine metal particles mainly depends on the evaporation rate of the metal by arc discharge. Therefore, in order to control the particle size,
Although it is conceivable to control the evaporation rate, with such a method, although some control of the particle size is possible, it is impossible to satisfy both requirements of reducing the particle size and reducing the particle size distribution. Inability to do so. If the particle size is further reduced, the ability to generate ultrafine metal particles is reduced.

For example, Japanese Patent No. 2980987 discloses a technique for cooling ultrafine particles immediately after generation by injecting a cooled atmosphere gas into an arc flame generated by arc discharge. In this technique, the ultrafine particles in a liquid state immediately after generation are solidified by the cooled atmosphere gas (abbreviated as cooling gas). As a result, even if the solid ultrafine particles collide with each other, they hardly aggregate, so that the aggregation and growth of the ultrafine particles can be suppressed, and an increase in the particle diameter of the ultrafine particles can be avoided. In addition, the particle size can be controlled by the injection position and the injection amount of the cooling gas.

[0006]

However, in the above-mentioned conventional technique, since the cooling gas is directly applied to the arc flame tail, it is actually difficult to reliably avoid an increase in the particle size of the ultrafine particles. There is a problem that is.

Specifically, by injecting the cooling gas into the arc flame tail, the flow of the atmosphere gas for transporting the generated ultrafine particles is disturbed by the cooling gas. Such turbulence in the flow of the atmosphere gas not only prevents the generated ultrafine particles from being stably transported, but also increases the frequency of collision between the ultrafine particles during the transport, and as a result, In addition, the number of collisions between the ultrafine particles before solidification increases, and the possibility that the ultrafine particles grow into particles increases.

Further, the turbulence of the flow of the atmosphere gas is as follows.
Since the retention of the atmospheric gas or the like is caused, the frequency of a large amount of ultrafine particles adhering to the inner wall surface of the chamber in which arc discharge is generated increases. As a result, the possibility of lowering the recovery rate of the generated ultrafine particles also increases.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress aggregation and growth of ultrafine metal particles when producing ultrafine metal particles by using arc discharge. It is an object of the present invention to provide an apparatus and a method for producing ultrafine metal particles which can produce high-quality ultrafine metal particles having a smaller particle size and less variation in the particle size.

[0010]

In order to solve the above-mentioned problems, an apparatus for producing ultrafine metal particles according to the present invention is provided with a discharge electrode and a metal base material provided at a position close to the discharge electrode. Metal having a particle generating means for generating an arc discharge by applying a voltage between the discharge electrode and the holding electrode from the arc power supply. In the ultrafine particle manufacturing apparatus, further, the metal ultrafine particles to be conveyed are cooled by a particle collecting means for collecting the generated metal ultrafine particles and a conveying path of the metal ultrafine particles from the particle generating means to the particle collecting means. And cooling means.

[0011] According to the above configuration, the cooling means cools the ultrafine metal particles in the transport path at the stage prior to collecting the generated ultrafine metal particles. Therefore, immediately after generation, the ultrafine metal particles, which are liquids, also solidify into solids. Also,
Since the ultrafine metal particles are cooled in the transport path, the generation of the ultrafine metal particles by arc discharge is hardly hindered. As a result, even if metal ultrafine particles collide at high frequency, since the metal ultrafine particles are already solid, there is no aggregation and particle growth, and it is possible to produce finer metal ultrafine particles than before. Can be.

The apparatus for producing ultrafine metal particles according to the present invention has, in addition to the above configuration, a particle introduction pipe arranged in the transport path, for sucking the ultrafine metal particles generated by the arc discharge and leading it to the particle collecting means. The cooling means cools at least the particle introduction tube.

According to the above configuration, the particle introducing pipe is disposed in the transport path of the ultrafine metal particles between the particle generating means and the particle collecting means. Therefore, the atmospheric gas containing the ultrafine metal particles is reliably introduced into the particle collecting means, and the ultrafine metal particles are surely cooled during the introduction process.
Therefore, the metal ultrafine particles can be intensively cooled without hindering the generation of the ultrafine metal particles by the arc discharge, and the suppression of the particle growth can be further improved. As a result, finer metal ultrafine particles can be produced.

Alternatively, in the apparatus for producing ultrafine metal particles according to the present invention, in addition to the above configuration,
At least a chamber in which the discharge electrode and the holding electrode are arranged is provided, and the cooling means cools only a portion of the chamber corresponding to the transport path.

According to the above configuration, since the portion serving as the transport path is specifically cooled, it is possible to reliably cool the atmosphere gas flowing through the transport path and the ultrafine metal particles contained therein. it can. Therefore, the generation of ultrafine metal particles by arc discharge is hardly hindered, and the suppression of particle growth can be further improved. As a result, finer metal ultrafine particles can be produced.

In order to solve the above-mentioned problems, another apparatus for producing ultrafine metal particles according to the present invention is provided with a discharge electrode and a holding member provided at a position close to the discharge electrode for holding a metal base material. Production of metal ultrafine particles comprising an electrode and an arc power supply connected thereto, and having a particle generating means for generating an arc discharge by applying a voltage between the discharge electrode and the holding electrode from the arc power supply. In the apparatus, the particle generation means further includes a chamber in which at least a discharge electrode and a holding electrode are arranged, and further, a gas supply means for supplying an atmosphere gas to the chamber, And gas cooling means for cooling the atmospheric gas before being supplied.

According to the above configuration, since the atmospheric gas supplied to the chamber has already been cooled, the ultrafine metal particles generated by the arc discharge are also cooled immediately. As a result, suppression of particle growth can be further improved, and finer metal ultrafine particles can be manufactured. In addition, when combined with each of the above-described configurations, the metal ultrafine particles are cooled in two stages, that is, the vicinity of the generation site of the metal ultrafine particles and the transport path, so that the metal ultrafine particles can be more reliably cooled. Can be.

In order to solve the above-mentioned problems, the method for producing ultrafine metal particles according to the present invention comprises disposing a discharge electrode and a metal base material in close proximity to each other, and applying a voltage between the electrodes to form an arc. A method for producing metal ultrafine particles for generating electric discharge is characterized in that metal ultrafine particles generated by arc discharge are cooled at a stage prior to recovery.

According to the above method, immediately after generation, ultrafine metal particles, which are liquid, are solidified into a solid and then recovered. Therefore, even if the metal ultra-fine particles collide at a high frequency, since the metal ultra-fine particles are already solid, they do not aggregate and grow. As a result, the generation of ultrafine metal particles by arc discharge is hardly hindered, and finer ultrafine metal particles than before can be produced.

In order to solve the above-mentioned problems, another method for producing ultrafine metal particles according to the present invention is to dispose a discharge electrode and a metal base material close to each other and apply a voltage between them. The method for producing ultrafine metal particles for generating arc discharge is characterized in that the arc discharge is generated in the presence of an atmosphere gas, and that the atmosphere gas has high thermal conductivity.

According to the above method, since a gas having a high thermal conductivity is used as the atmosphere gas, the generated ultrafine metal particles are deprived of more heat from the surrounding atmosphere gas. Therefore, the metal ultrafine particles are more easily cooled, and the generation of the metal ultrafine particles by the arc discharge is almost not hindered, and the particle growth can be further suppressed to obtain extremely fine metal ultrafine particles. .

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The first embodiment of the present invention will be described below with reference to FIGS. Note that the present invention is not limited to this.

The apparatus and method for producing ultrafine metal particles according to the present invention are characterized in that a cooling means for generating ultrafine metal particles by generating an arc discharge and then cooling the ultrafine metal particles before collecting the ultrafine metal particles Particularly, in the present embodiment, an arc discharge is generated in the chamber, and the cooling unit cools a portion corresponding to a transport path of the ultrafine metal particles in the chamber. It has become.

More specifically, as shown in FIG. 2, the apparatus for producing ultrafine metal particles according to the present embodiment includes a particle generation section (particle generation means) 10 for generating ultrafine metal particles by arc discharge, A gas supply unit (gas supply unit) 20 for supplying an atmosphere gas containing hydrogen gas to the generation unit 10 and a particle recovery unit (particle recovery unit) 30 for recovering the generated ultrafine metal particles are provided.

The particle generator 10 includes a chamber 11
, A torch (electrode supporting frame / torch mechanism) 12, a discharge electrode 13, a holding base (hearth / holding electrode) 14, and an arc power supply 16.

The chamber 11 is a box having a space where an arc discharge can be generated between the discharge electrode 13 and the target (metal base material) 5. The specific configuration is not particularly limited, and a conventionally known configuration can be preferably used. However, in the present invention, as shown in FIG. An atmosphere gas is supplied from the particle generation chamber 19 side and the atmosphere gas is discharged from the particle collection chamber 37 side.

Specifically, the chamber 11 is provided with an atmosphere gas pipe 23 to be described later with respect to the particle generation chamber 19.
And a shield gas pipe 24. Therefore, the atmospheric gas is supplied into the chamber 11 from the atmospheric gas pipe 23 and the shield gas pipe 24, while the atmospheric gas in the chamber 11 is discharged from the particle recovery chamber 37. Therefore, the atmosphere gas is
As shown by an arrow A in the figure, a flow is formed from the particle generation chamber 19 to the particle recovery chamber 37 via the ultrafine particle introduction pipe 38.

The particle generation chamber 1 in the chamber 11
In 9, the torch 12, the discharge electrode 13, and the holder 14 are arranged. The discharge electrode 13 is fixedly supported at the end of the torch 12, and the holding table 14 is arranged at a position near the discharge electrode 13, and allows the target 5 to be mounted thereon. It has a trapezoidal shape.

The torch 12 has a substantially rod shape having a length in the primary direction. The torch 12 can stably hold the discharge electrode 13 at an end thereof while being connected to an arc power supply 16. ing. The specific configuration of the torch 12 is not particularly limited as long as the discharge electrode 13 can be stably held.

As shown in FIG. 3, the torch 12 may be provided with a shield gas pipe 24 and a shield gas nozzle 25 for forming a shield gas around the discharge electrode 13. The shield gas is formed around the discharge electrode 13 after the arc discharge is stabilized in order to prevent the ultrafine metal particles from adhering to the discharge electrode 13. This is because, when the metal ultrafine particles adhere to the tip of the discharge electrode 13, the discharge electrode 13 is excessively consumed due to deformation, melting, and the like.

In FIG. 3, since the shield gas nozzle 25 is arranged around the discharge electrode 13 in the torch 12, the atmosphere gas flows out from around the discharge electrode 13 along its axial direction (longitudinal direction). (Arrow B in the figure), a shielding gas is formed. In addition, the ultrafine metal particles generated by the arc discharge at this time, as shown by arrow C in the figure,
It blows out to the side opposite to the discharge electrode 13 arranged diagonally above the target 5. Note that the shield gas pipe 24 and the shield gas nozzle 25 are not necessarily provided in the torch 12, and may be provided near the discharge electrode 13 as another configuration.

The discharge electrode 13 is an electrode for generating an arc discharge between the discharge electrode 13 and a target (metal base material) 5 which is a precursor of ultrafine metal particles, and usually contains tungsten (W) as a main component. Is preferably used. A metal oxide is often added to the tungsten electrode, and generally, a material called “tritan” containing thorium oxide (ThO ₂ ) in a range of about 1 to 2% is preferable. Used for

The shape of the discharge electrode 13 is not particularly limited, but usually, as shown in FIG. 4, a shape having a sharpened tip is preferable in order to easily generate arc discharge. Used. The length and diameter are not particularly limited either. For example, length L = 35 mm, diameter φ =
Those having a size of about 4 mm are preferably used.

The holding table 14 holds the target 5 in a state of being placed thereon, and applies a voltage to the target 5 from an arc power supply 16. The specific shape is not particularly limited as long as it has a trapezoidal shape and is configured to apply a voltage to the target 5 placed above. The material is not particularly limited as long as a voltage can be applied to the target 5, but copper is generally preferably used.

This holding table 14 is used for arc discharge.
The cooling is performed by cooling means (not shown) such as water cooling. Therefore, as shown in FIG. 2 and FIG. 3, usually, the metal particles are slightly crushed by their own weight and are rounded into a substantially elliptical sphere, so that ultrafine metal particles can be stably generated.

As means for holding the target 5, if the holding electrode is a holding electrode capable of applying a voltage to the target 5 while holding the target 5, the holding table 1
It is not limited to four.

In this embodiment, as shown in FIG. 2 and FIG. 3, the discharge electrode 13 is applied to the target 5 placed and held on the holding table 14 in the direction of the flow of the atmosphere gas. It is preferable that arc discharge is performed in a state of being disposed obliquely upward on the upstream side in the direction of arrow A). Thereby, the metal ultrafine particles generated in the particle generation chamber 19 can be efficiently conveyed to the particle collection chamber 37 side along with the flow of the atmospheric gas. Note that the specific arrangement of the “diagonally above” is not particularly limited, but, for example,
In the present embodiment, the torch 12 is set at about 45 ° from the horizontal direction.
It is arranged to be inclined.

The arc power supply 16 applies a high-frequency voltage (start voltage) to the discharge electrode 13 and the target 5, that is, the target 5 that is to be electrically connected to the holding table 14 in order to produce ultrafine metal particles. Voltage) to cause an arc discharge between them. In the present embodiment, since the discharge electrode 13 is used as an anode (cathode) and the target 5 is used as a cathode (anode), the arc power source 1 is used.
The negative electrode 6 is connected to the discharge electrode 13 and the positive electrode is connected to the holder 14.

As the target 5, any metal can be used. Generally, nickel (Ni), iron (Fe), and the like are often used. The shape of the target 5 is not particularly limited, and a desired metal may be formed into an appropriate shape so as to enable arc discharge. The metal ultrafine particles generated from the target 5 are as follows:
It is preferable that the average particle size is in the range of 1 nm to 100 nm.

The gas supply section 20 includes a gas tank 21a.
And 21b, gas supply valves 22a and 22b, an atmosphere gas pipe 23, and a shield gas pipe 24, and supply an atmosphere gas for arc discharge including hydrogen gas into the chamber 11 (arrow A in the figure). ).

In the present embodiment, two types of atmosphere gas are used: hydrogen (H ₂ ) gas and argon (Ar). Therefore, a gas tank 21a for hydrogen gas and a gas tank 21b for argon gas are provided to supply these atmospheric gases. These gas tanks 21a and 21b are connected to the chamber 11 by an atmosphere gas pipe 23 and a shield gas pipe 24, and further provided with gas supply valves 22a and 2 provided corresponding to the gas tanks 21a and 21b, respectively.
The supply amount of each atmosphere gas can be adjusted by 2b.

The gas used as the atmospheric gas is not particularly limited, but it is very preferable to use hydrogen gas in the production of ultrafine metal particles. In addition, a gas other than hydrogen gas is not particularly limited, but usually, various inert gases are preferably used. Specifically, a helium gas or the like may be used in addition to the argon gas.

The composition of the above-mentioned atmosphere gas is not particularly limited.
It is preferably at least volume%. Hydrogen gas concentration is 50
If it is at least% by volume, the production efficiency of ultrafine metal particles tends to be improved. In addition, the composition of an inert gas such as an argon gas is not particularly limited. In addition,
In the present invention, a gas having a high thermal conductivity is particularly preferably used as the atmosphere gas. This point will be described in detail in Embodiment 3.

The atmosphere gas pipe 23 and the shield gas pipe 24 are connected to the particle generation chamber 19 in the chamber 11 as described above. Here, the atmosphere gas is mainly supplied through the atmosphere gas pipe 23, and the shield gas pipe 24 is supplied with the shield gas atmosphere gas formed by the shield gas nozzle 25 arranged near the discharge electrode 13. Supply.
Therefore, the shield gas pipe 24 may be configured to branch off from the atmosphere gas pipe 23.

The atmosphere gas pipe 23 not only branches the shield gas pipe 24 but is also connected to the particle recovery section 30 so that the supplied atmosphere gas is circulated by the gas circulation pump 35. It has become. The material and shape of each of the pipes 23 and 24 are not particularly limited, and a conventionally known gas stainless steel pipe or the like can be suitably used.

The pressure of the atmospheric gas in the chamber 11 is not particularly limited, but is generally preferably in the range of 40 kPa to 100 kPa. Further, the flow rate of the atmosphere gas supplied to the chamber 11 is not particularly limited, but the atmosphere gas pipe 2 which is a main supply pipe of the atmosphere gas is used.
In general, when supplied from 3, the gas flow rate for transport is preferably about 0.7 m / s or more.

Further, the flow rate of the atmosphere gas supplied from the shield gas pipe 24 is not particularly limited as long as the shield gas can be formed. For example, a flow rate of about 5 L / min is exemplified. Can be. Normally, the supply amount of the atmosphere gas from the shield gas pipe 24 is an amount within an error range with respect to the supply amount of the atmosphere gas from the atmosphere gas pipe 23.

The particle collecting section 30 includes a collecting filter 3
2. It includes a gas circulation pump 35, a particle recovery chamber 37, and an ultrafine particle introduction pipe (particle introduction pipe) 38.
It also includes a pipe cooling section 51 and an in-pipe cooling section 52 (each a cooling means). The particle recovery unit 30 recovers ultrafine metal particles generated in the chamber 11 using the flow of the atmospheric gas.

The ultrafine particle introduction tube 38 is provided in the chamber 1
1 is arranged so as to connect the particle generation chamber 19 and the particle recovery chamber 37, and introduces the ultrafine metal particles generated by the arc discharge into the recovery filter 32. In particular,
In the chamber 11, one end of the ultrafine particle introduction tube 38 is disposed near the discharge electrode 13 and the holding table 14 (target 5) in the particle generation chamber 19,
The other end is connected to the partition wall 11 a so as to face the particle collection chamber 37. By using the ultrafine particle introduction tube 38, the recovery rate of the generated ultrafine metal particles can be improved.

The shape of the ultrafine particle introduction tube 38 is cylindrical, protruding from the particle recovery chamber 37, in the vicinity of the discharge electrode 13 and the holding table 14 in the particle generation chamber 19 (the generation site 19).
a)), the shape is not particularly limited, but preferably has a bent shape as shown in FIG. 1.

In the ultrafine particle introduction tube 38, a main portion 38d, which is a large portion from the particle discharge port 38b to the particle suction port 38a, is substantially straight, and the tip 38c near the particle suction port 38a is connected to an arc flame tail. So as to be along the same direction as the blowing direction (the direction of arrow C in FIG. 1)
The tip 38c is inclined.

The blowing direction of the arc flame tail corresponds to the tail when the arc column formed by the inclined arc discharge is pulled along the flow of the atmospheric gas, and the blowing direction of the generated ultrafine metal particles. Is almost the same as Therefore, the particle suction port 38a is disposed closer to the position where the metal ultrafine particles are blown out, so that the recovery rate can be further improved.

Needless to say, the shape of the ultrafine particle introducing tube is not limited to the above-mentioned bent shape. For example, even if the shape from the particle suction port to the particle discharge port is substantially straight and not bent or curved. Good.

The diameter R ₁ of the ultrafine particle introduction tube 38 is not particularly limited. By varying this tube diameter R _1, for changing the flow velocity of the atmospheric gas that passes through the ultrafine particles introducing pipe 38, the suction rate of the metal ultrafine particles may be changeable. Therefore, for the specific pipe diameter R _1, it is appropriately set depending on the configuration and arcing conditions of the manufacturing apparatus.

The material of the ultrafine particle introduction tube 38 is as follows.
The material is not particularly limited, and may be a material having heat resistance and durability enough to withstand high temperatures radiated to the surroundings by arc discharge. For example, ceramics and stainless steel are preferably mentioned. In addition, it is preferable that the surface of the ultrafine particle introduction tube 38, particularly the inner wall surface 38e, is such that metal ultrafine particles are hardly adhered as much as possible. More specifically, it is preferable to form the mirror surface or a smooth surface (approximately a mirror surface) to a degree close to the mirror surface by using a buff polishing method or the like. Thereby, the collection rate of the ultrafine metal particles can be further improved.

The apparatus for producing ultrafine metal particles according to the present embodiment is provided with a tube cooling section 51 for cooling the ultrafine particle introduction tube 38. The tube cooling unit 51 is capable of cooling the atmospheric gas flowing through the ultrafine particle introduction tube 38 by sufficiently cooling the ultrafine particle introduction tube 38, and finally cooling the ultrafine metal particles. In this case, the specific configuration is not particularly limited. For example, as shown in FIG.
A configuration in which a layer for circulating a cooling medium is integrally formed around the periphery of 8.

In the configuration shown in FIG. 1, a cooling layer for circulating a cooling medium (refrigerant) is formed around the ultrafine particle introduction tube 38 as the tube cooling section 51, so that the ultrafine particle introduction tube 38 itself has a multilayer structure. And In FIG. 1, the refrigerant layer (tube cooling unit 51) is schematically shown, but as a specific configuration of the refrigerant layer, a pipe through which the refrigerant flows is wound around the ultrafine particle introduction pipe 38. And a configuration in which it is bent and arranged so as to be in close contact with each other. Alternatively, although not shown, the ultrafine particle introduction tube 38 itself may have a double structure, a space may be formed between the outer wall and the inner wall by a spacer or the like, and the refrigerant may flow into this space.

Further, although not shown, in the present embodiment, a heat insulating layer covering the above-mentioned refrigerant layer may be provided. That is, the tube cooling unit 51 has a two-layer structure of a refrigerant layer and a heat insulating layer, and may have a three-layer structure when viewed as the ultrafine particle introduction tube 38. The material and thickness of the heat insulating layer are not particularly limited as long as the heat insulating layer has a structure capable of insulating the refrigerant layer so that the cooling effect is not reduced by the arc heat in the chamber 11. Of course, when the influence of the arc heat is small due to various conditions such as the shape of the chamber 11, the heat insulating layer may not be particularly provided.

The ultrafine particle introduction tube 38 integrated with the tube cooling section 51 may be formed with another layer to have a multilayer structure of three or four or more layers.

The material of the above-mentioned refrigerant is not particularly limited as long as it has a cooling capacity capable of finally cooling the ultrafine metal particles by cooling the ultrafine particle introduction pipe 38. . In the present embodiment, it is particularly preferable to use water from the viewpoints of cost when operating the manufacturing apparatus and safety when the refrigerant leaks. The water may be general industrial water, and its purity and the like are not particularly limited.

In the process of producing ultrafine metal particles by arc discharge, the target 5 is melted by arc discharge,
After the metal forming the target 5 evaporates (vaporizes), it is liquefied and solidified to obtain ultrafine metal particles. Here, the solidified ultrafine metal particles hardly agglomerate even if they collide with each other, so that they do not grow. However, if they collide in a liquid state, they easily aggregate and grow.

Therefore, the cooling temperature of the ultrafine particle introduction tube 38 by the tube cooling unit 51 is appropriately set according to the solidification temperature of the metal to be the target 5.
There is no particular limitation. However, in general, when the temperature of a metal decreases to a normal temperature level, almost all of the metal is solidified. Therefore, in practice, for example, when water (cooling water) is used as a refrigerant, the temperature of the cooling water is set within a range of normal temperature. If the temperature is set within the range (in the present embodiment, within the range of 10 ° C. or more and 30 ° C. or less), the metal ultrafine particles passing through the ultrafine particle introduction pipe 38 can be sufficiently cooled until solidified.

Further, in the present embodiment, as shown in FIG. 1, it is more preferable that an in-tube cooling unit 52 is provided in the ultrafine particle introduction tube 38. Since the pipe cooling section 51 cools the ultrafine particle introduction pipe 38 itself, the atmosphere gas containing the metal ultrafine particles is sufficiently cooled if it flows near the inner wall of the ultrafine particle introduction pipe 38, Atmosphere gas flowing through the portion flows through a portion away from the inner wall of the ultrafine particle introduction pipe 38, and therefore may not be sufficiently cooled.

Therefore, as shown in FIG. 1, for example, an in-pipe cooling section 52 formed by bending a metal pipe is disposed in the ultrafine particle introduction pipe 38, and a cooling medium (cooling water or the like) is supplied to the in-pipe cooling section 52. ) Can sufficiently cool the atmosphere gas flowing in the central part of the tube cross section.

The specific configuration of the in-pipe cooling section 52 is not limited to the configuration, and the
It is sufficient that the atmosphere gas flowing in the central portion of the pipe cross section can be sufficiently cooled in the state where the gas is disposed in the inside of the pipe 8. In the present embodiment, the metal pipe is bent as described above, but with this configuration, the inside of the ultrafine particle introduction pipe 38 can be sufficiently cooled with a simple structure. It is preferred.

The above-mentioned pipe is not necessarily made of metal as long as it has high thermal conductivity, but usually, a pipe made of metal such as copper is preferably used. Its tube diameter is not particularly limited as R _2, it may be a little disturbed not constitute a flow of the ambient gas while located in the ultrafine particle inlet tube 38. In the present embodiment, the pipe diameter R ₂ = 1/4 ″
(About 6 mm). Further, the bent structure of the pipe is not particularly limited.

The method of supplying the cooling water to the pipe cooling section 51 and the in-pipe cooling section 52 is not particularly limited. Cooling water is supplied from one end using a pump (not shown), and the other end is supplied. It is sufficient that the cooling water is discharged from the section. In FIG. 1, the cooling water is supplied from below and the cooling water is discharged from above with respect to the pipe cooling unit 51, and the cooling water is supplied from the upper pipe of the bent pipes with respect to the in-pipe cooling unit 52. The cooling water is supplied and discharged from the lower pipe (arrow F in the figure), but the method of supplying the cooling water is not limited to this.

The collecting filter 32 is arranged in the particle collecting chamber 37 in FIG. Specifically, the particle recovery chamber 37 is configured such that the discharge electrode 1
3. The holder 14 (the generation part 19a) is disposed at a position facing the holding table 14 via the ultrafine particle introduction pipe 38,
Further, a collection filter 32 is provided in the particle collection chamber 37. Therefore, in the chamber 11, the particle recovery chamber 37 is connected to the particle generation chamber 19 via the ultrafine particle introduction pipe 38.
The flow of the atmosphere gas is formed toward the recovery filter 32 in the inside (arrow A in the figure). As a result, the collection filter 32 collects the metal ultrafine particles introduced from the ultrafine particle introduction pipe 38.

The collection filter 32 includes, for example, a membrane filter, a HEPA filter, and a UL filter.
A PA filter or the like is preferably used, but is not particularly limited as long as it has a filter structure capable of reliably collecting ultrafine metal particles. Further, the means for collecting the ultrafine metal particles is not limited to the filter structure, and a configuration such as a cyclone may be used.

The vacuum pump 33 is connected to the chamber 11 (particle recovery chamber 37) via the main valve 34, and sucks and discharges the atmospheric gas from the inside of the chamber 11. Therefore, the vacuum pump 33 and the main valve 3
Reference numeral 4 functions as gas suction means for sucking the atmospheric gas from the chamber 11. Of course, the gas suction means is not limited to this.

The atmosphere gas discharged from the chamber 11 returns to the atmosphere gas pipe 23 through the gas circulation pump 35, and is returned to the chamber 11 and the pipes 23 and 24.
(Arrow A in the figure). This makes it possible to improve the utilization efficiency of the atmospheric gas, and to suppress an increase in the cost for producing the ultrafine metal particles.

Next, the method for producing ultrafine metal particles according to the present embodiment, that is, cooling the ultrafine metal particles generated by arc discharge in a transport path up to transport to the particle collecting section 30 to reduce the particle size A method for suppressing the increase will be described.

First, in this embodiment, the arc power supply 16
The discharge electrode 13 and the target 5 (that is, the holding table 1)
When a high-frequency voltage is applied between step 4), arc discharge is started due to electrostatic breakdown, and an arc column is formed. With the formation of the arc column, a current (arc current) flows between the discharge electrode 13 and the target 5. After the start of the arc discharge, the high-frequency voltage is switched to a DC voltage (arc voltage / discharge voltage).

Due to the heat generated by the arc discharge, the target 5
It melts and eventually becomes substantially spherical / substantially elliptical, and becomes stable in terms of surface tension (see FIGS. 2 and 3). In this state, since the arc discharge is also stable, the ultrafine metal particles are stably generated and blow out along the flow of the atmospheric gas (arrow A in the figure) (arrow C in the figure).

The range of the high frequency voltage for starting arc discharge is not particularly limited. For example, in this embodiment, it is set to about 7 kV. The range of the DC voltage (arc voltage / discharge voltage) after the start of arc discharge is not particularly limited, but is preferably in the range of 30 V to 50 V, and more preferably in the range of 20 V to 30 V. . Similarly, the range of the arc current associated with the arc discharge is not particularly limited, but is generally preferably in the range of 100A or more and 400A or less.

As shown in FIG. 1, the metal ultrafine particles generated by the arc discharge are blown out to the opposite side of the discharge electrode 13 arranged diagonally above the target 5 (arrow C in the figure), and the ultrafine particle introduction tube is formed. The particles are sucked from the particle suction port 38a and discharged to the particle collection chamber 37 from the particle discharge port 38b. Then, in the particle collection chamber 37, the collection filter 32
Thereby, ultrafine metal particles are collected.

Here, a tube cooling unit 51 is provided integrally with the ultrafine particle introduction tube 38, and an in-tube cooling unit 52 is disposed inside the ultrafine particle introduction tube 38.
Therefore, the atmosphere gas flowing through the ultrafine particle introduction pipe 38 is sufficiently cooled, and the metal ultrafine particles contained in the atmosphere gas are also cooled until solidifying from liquid to solid. In addition, since both the tube cooling unit 51 and the in-tube cooling unit 52 cool the atmospheric gas and the ultrafine metal particles at a position distant from the generation part 19a, the cooling operation hardly hinders the arc discharge.

As a result, even if the metal ultra-fine particles collide frequently, the metal ultra-fine particles are already solid, so that they do not agglomerate and grow, and a finer metal ultra-fine particle than before can be obtained. Can be manufactured,
Since the flow of the atmospheric gas containing the ultrafine metal particles can be prevented from staying in the chamber 11, the recovery rate can be improved.

In particular, since the ultrafine particle introduction pipe 38 is disposed in the transport path of the ultrafine metal particles between the particle generation unit 10 and the particle collection unit 30, the atmosphere gas containing the ultrafine metal particles can be reliably sent to the particle collection unit 30. In the process of introduction,
The ultrafine metal particles are surely cooled. for that reason,
The cooling of the ultrafine metal particles can be performed intensively, and as a result, the suppression of the particle growth can be further improved.

As described above, in the present invention, before collecting the generated ultrafine metal particles, the ultrafine metal particles are cooled by the cooling means. In the present embodiment, at least the ultrafine particle introduction pipe is used as the cooling means. It includes a tube cooling unit that cools itself, and preferably includes an in-tube cooling unit that directly cools the atmosphere gas flowing in the tube. therefore,
The metal ultrafine particles in a liquid state can be reliably and efficiently cooled without substantially hindering the arc discharge, and the particle growth can be suppressed to produce finer metal ultrafine particles.

[Embodiment 2] The following will describe a second embodiment of the present invention with reference to FIG. Note that the present invention is not limited to this. Further, for convenience of explanation, members having the same functions as those used in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

In the first embodiment, the ultrafine particle introduction pipe is disposed on the transport path between the particle generation section and the particle collection section.
By cooling the ultrafine particle introduction tube, the atmospheric gas and the metal ultrafine particles contained therein were cooled, but in the present embodiment, the ultrafine particle introduction tube is not disposed, and the air path corresponds to the above-described transport path. By cooling a part of the chamber, the atmospheric gas and the ultrafine metal particles contained therein are cooled.

More specifically, as shown in FIG. 5, the manufacturing apparatus according to the present embodiment has almost the same configuration as the manufacturing apparatus according to the first embodiment. Are not partitioned into the particle generation chamber 19 and the particle recovery chamber 37 by the
8 is not provided. In this configuration, a portion from the generation portion 19a to the collection filter 32 in the chamber 11 corresponds to the transport path.

Therefore, a chamber cooling section 53 is arranged around the chamber 11 corresponding to the transfer path, as shown in FIG. As the chamber cooling unit 53,
The specific configuration of the chamber 11 is not particularly limited as long as it can cool the atmosphere gas at a portion corresponding to the transfer path in the chamber 11 and can finally cool the ultrafine metal particles. In practice, the tube cooling unit 5
1 can be cited.

The coolant used in the chamber cooling section 53 is not particularly limited, but water (cooling water) is used similarly to the first embodiment from the viewpoint of cost and safety. Is particularly preferred. further,
The cooling temperature of the chamber 11 by the chamber cooling unit 53 is not particularly limited as long as the temperature range is such that the liquid metal ultrafine particles contained in the internal atmosphere gas are solidified, as in the first embodiment. Absent.

As described above, depending on the configuration of the manufacturing apparatus,
In some cases, it is more preferable to cool the chamber 11 itself without providing the ultrafine particle introduction pipe 38 to cool the atmospheric gas flowing through the transport path and the metal ultrafine particles contained therein.

In the conventional apparatus for producing ultrafine metal particles, it is known to cool the chamber. However, this is to avoid a decrease in safety caused by the high temperature of the apparatus. It is a passive type aimed at and cannot suppress the particle growth of ultrafine metal particles as in the present invention.

More specifically, the arc discharge is extremely high temperature, so that the chamber and the like which are the exterior of the manufacturing apparatus are also very high temperature. For this reason, there is a high possibility that the operator will burn when the operator touches the chamber or the like carelessly. Therefore, conventionally, for the purpose of improving safety, it has been practiced to cool the chamber and other parts that can be easily touched by an operator.

However, such a conventional technique is as follows.
The purpose is to cool only the chamber, and not to cool the inside of the chamber in order to cool the ultrafine metal particles generated by arc discharge as in the present invention. Particularly, in the present embodiment, in order to suppress the particle growth, only the portion serving as the transport path of the generated ultrafine metal particles is actively cooled, which is fundamentally different from the conventional technology.

[Third Embodiment] The following will describe a third embodiment of the present invention with reference to FIG. Note that the present invention is not limited to this. Further, for convenience of explanation, members having the same functions as those used in the first or second embodiment are given the same numbers, and explanations thereof are omitted.

In the first or second embodiment, the ultrafine metal particles are cooled by providing a separate cooling means for the transport path. In this embodiment, however, the atmosphere gas is used for cooling the ultrafine metal particles. are doing. Specifically, at least one of a technique of cooling the atmosphere gas supplied to the chamber 11 and a technique of using a gas having a high thermal conductivity as the atmosphere gas is preferably used.

Specifically, as shown in FIG. 6, the manufacturing apparatus according to the present embodiment has almost the same configuration as the manufacturing apparatus according to the first embodiment. A gas cooling section (gas cooling means) 54 is further provided for the atmosphere gas pipe 23 to be formed.

The gas cooling section 54 is provided in the chamber 11
Immediately before the supply of the atmosphere gas to the (particle generation chamber 19), the atmosphere gas flowing through the atmosphere gas pipe 23 is cooled. Therefore, as shown in FIG. 6, the atmosphere gas for the shielding gas supplied from the shielding gas pipe 24 is also cooled.

The specific configuration of the gas cooling unit 54 is not particularly limited. Practically, similarly to the tube cooling unit 51 and the chamber cooling unit 53, a configuration in which a pipe through which the refrigerant flows is wound or bent along the atmosphere gas pipe 23 and arranged so as to be in close contact with each other. No. Further, the coolant used for the gas cooling unit 54 is not particularly limited, but water (cooling water) is also used from the viewpoint of cost, safety, and the like, similarly to the first and second embodiments. It is particularly preferred to use.

The cooling temperature of the atmosphere gas by the gas cooling section 54 is not particularly limited, either. The atmosphere gas supplied into the chamber 11 is supplied to the generation portion 19a.
Even after passing through (see FIG. 1), the temperature may be set to a temperature range in which the ultrafine metal particles generated by the arc discharge can be cooled.

The gas cooling unit 54 in the present embodiment is
Although a sufficient cooling effect can be obtained by itself, a further excellent cooling effect can be obtained by combining with the structure of the first or second embodiment.

That is, since the supplied atmospheric gas has already been cooled, the ultrafine metal particles generated by the arc discharge are also cooled immediately, but in practice, all the generated ultrafine metal particles cannot be sufficiently cooled. there is a possibility. On the other hand, when the configuration of the present embodiment is combined with the configuration of the first or second embodiment, the metal ultrafine particles are cooled in two stages, that is, the vicinity of the generation part 19a and the transport path, so that The metal ultrafine particles can be cooled more reliably.

Further, in this embodiment, it is very preferable to select and use a gas having a high thermal conductivity as the atmosphere gas. Specifically, in the present embodiment, since ultrafine metal particles are produced by the hydrogen arc method, hydrogen gas is indispensable as an atmosphere gas. It is preferable to use helium gas instead of the argon gas used in 2. Therefore, in the manufacturing apparatus according to the present embodiment, the gas tank 21b for argon gas (and the gas supply valve 2) is used.
Gas tank 21c for helium gas instead of 2b)
(And the gas supply valve 22c).

When a gas having a high thermal conductivity is used as the atmosphere gas, the atmosphere gas takes more heat from the metal ultra-fine particles generated in the chamber 11, so that the metal ultra-fine particles are very easily cooled. . Therefore, even if this method is used alone, sufficiently fine metal ultrafine particles can be obtained. In addition, the method of cooling the transport path as in the first or second embodiment, and the above-described atmosphere gas When used in combination with a method of cooling itself, very fine metal ultrafine particles can be obtained.

The atmospheric gas having a high thermal conductivity used in the present embodiment is not particularly limited,
For example, helium gas or neon (Ne) gas is preferably used. Specifically, when the thermal conductivity at T / K = 300 (unit: k / 10 ⁻⁴ Wm ⁻¹ K ⁻¹ ) is listed, argon is 177.2, whereas neon is 493.
Since helium is 1499 (from Maruzen Chemical Handbook, Basic Edition, 3rd revised edition), it has a much higher thermal conductivity than argon.

As described above, when the thermal conductivity of the atmosphere gas itself is high, the generated ultrafine metal particles lose more heat from the surrounding atmosphere gas. It is easier to cool than in comparison.
As a result, extremely fine metal ultrafine particles can be obtained by further suppressing the particle growth.

In FIG. 6, the shielding gas piping 24
Is also cooled, but as is clear from FIG. 3, this atmosphere gas does not inject the cooled atmosphere gas into the arc flame tail generated by the arc discharge. This is for forming a shield near the discharge electrode 13. Therefore, the technique is fundamentally different from the technique disclosed in Japanese Patent No. 2980987 as a conventional technique.

[0103]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples and FIG. 7, but the present invention is not limited to these.

Example 1 Nickel was used as the target 5, and a tungsten electrode containing 1 to 2% thorium oxide was used as the discharge electrode 13, and the target 5 was held on the holding table 14. Then, as viewed from the holding table 14, about 45
In a state where the torch 12 was disposed above (see FIG. 2), arc discharge was generated between the target 5 on the holding table 14 and the discharge electrode 13 to generate ultrafine metal particles.

The arc discharge conditions at this time are as follows: arc current 150 A, starting voltage (high-frequency voltage) 7 kV, arc voltage 30 V, composition of atmosphere gas Ar: H ₂ = 4:
6. Atmospheric gas pressure 60 kPa, atmospheric gas flow rate 2
00 L / min. At this time, the flow rate of the atmosphere gas is the amount of the atmosphere gas supplied from the atmosphere gas pipe 23. Separately, the atmosphere gas is supplied at a rate of 5 L / min from the shield gas pipe 24 to the shield gas. A shielding gas was formed around the discharge electrode 13 by the gas nozzle 25. The evaporation rate (evaporation amount) of the target 5 under the above conditions was about 50 g / h.

In the manufacturing apparatus of this embodiment, a tube cooling section 51 was used as a cooling means, and a tube having a diameter R ₁ = 43 mm was used as the ultrafine particle introduction tube 38. That is, the generated ultrafine metal particles were sucked by the ultrafine particle introduction tube 38 having only the tube cooling section 51 and introduced into the particle collection chamber 37. As the refrigerant at this time, chiller circulating water at 15 ° C. was used, and the flow rate of the atmosphere gas was 0.7 m / s as a calculated value. Then, as the atmospheric gas was discharged from the chamber 11 (particle recovery chamber 37), the ultrafine metal particles were recovered by the recovery filter 32.

For the generated ultrafine metal particles, the specific surface area diameter was calculated by the BET method, and this was defined as the particle diameter. The results are shown in the graph of FIG. The vertical axis in FIG. 7 indicates the particle size (unit: nm), and the horizontal axis indicates each example or comparative example.

Comparative Example Ultrafine metal particles were produced in the same manner as in Example 1 except that the tube cooling section 51 was not used in the above production apparatus. Then, the particle size of the metal ultrafine particles was calculated in the same manner as in Example 1. The results are shown in the graph of FIG.

[Embodiment 2] As a cooling means, a pipe cooling unit 5
Ultrafine metal particles were produced in the same manner as in Example 1 except that the in-pipe cooling unit 52 was used in addition to 1. Then, the particle size of the metal ultrafine particles was calculated in the same manner as in Example 1. The results are shown in the graph of FIG.

Example 3 As an atmosphere gas, a composition H was used.
e: H ₂ = 4: except for using 6 mixed gas, in the same manner as in Comparative Example, i.e. to produce a metal ultrafine particles without the use of cooling means. Then, the particle size of the metal ultrafine particles was calculated in the same manner as in Example 1. The results are shown in the graph of FIG.

[Example 4] As in Example 3, except that a mixed gas having a composition of He: H ₂ = 4: 6 was used as the atmosphere gas, ie, the cooling means was used. Ultrafine metal particles were produced by using the tube cooling unit 51 as a sample. Then, the particle size of the metal ultrafine particles was calculated in the same manner as in Example 1. The results are shown in the graph of FIG.

As is apparent from the results shown in FIG. 7, in the comparative example using no argon gas having a high thermal conductivity and no cooling means, the particle diameter of the ultrafine metal particles was 55.6 in specific surface area.
Example 1 provided with a pipe cooling unit 51
52.5 nm, the pipe cooling section 51 and the pipe cooling section 5
In Example 2 including No. 2, the particle size was 49.6 nm, and it was found that the grain size growth could be clearly suppressed by providing the cooling means.

Further, in Example 3 in which helium gas was used as the atmosphere gas, the particle size of the ultrafine metal particles was 32.1 nm in specific surface area. As described above, it was found that the grain growth could be suppressed. In addition, the pipe cooling unit 5 as a cooling means
In Example 4 provided with No. 1, as is clear from the fact that the particle diameter becomes 27.9 nm, the combination of the cooling means and the method of using a gas having a high thermal conductivity as the atmosphere gas,
It was found that grain growth could be further suppressed.

[0114]

As described above, the apparatus for producing ultrafine metal particles according to the present invention cools the ultrafine metal particles to be transported in the transport path of the ultrafine metal particles from the particle generation means to the particle recovery means. This is a configuration having cooling means.

In the above configuration, since the metal ultrafine particles are cooled in the transport path after the generation and before the collection, the metal ultrafine particles which are liquid immediately after generation are solidified into a solid, and the metal ultrafine particles are formed by arc discharge. It hardly hinders the generation of ultrafine particles. As a result, even if the metal ultra-fine particles collide at a high frequency, there is an effect that the metal ultra-fine particles can be produced finer than before without agglomeration and particle growth.

The apparatus for producing ultrafine metal particles has, in addition to the above-described configuration, a particle introduction tube arranged in the transport path, for sucking the ultrafine metal particles generated by the arc discharge and guiding the particles to the particle collection means. In addition, it is preferable that the cooling means cools at least the particle introduction tube.

In the above configuration, since the particle introduction tube is arranged in the transport path, the atmospheric gas containing the ultrafine metal particles is reliably introduced into the particle collection means, and the ultrafine metal particles are surely introduced during the introduction process. It will cool down. Therefore, it is possible to intensively cool the ultrafine metal particles without hindering the generation of the ultrafine metal particles by the arc discharge, and it is possible to further improve the suppression of the particle growth. As a result, there is an effect that even finer metal ultrafine particles can be manufactured.

Alternatively, in addition to the above configuration, the apparatus for producing ultrafine metal particles has a configuration in which the particle generating means includes a chamber in which at least a discharge electrode and a holding electrode are arranged, and the cooling means includes Only the portion of the chamber corresponding to the transfer path may be cooled.

In the above configuration, since the portion serving as the transport path is specifically cooled, the ultrafine metal particles contained in the atmospheric gas flowing through the transport path can be reliably cooled. Therefore, the generation of ultrafine metal particles by arc discharge is hardly hindered, and the suppression of particle growth can be further improved. As a result, there is an effect that even finer metal ultrafine particles can be manufactured.

[0120] In the other apparatus for producing ultrafine metal particles according to the present invention, as described above, the particle generating means is provided with a chamber in which at least a discharge electrode and a holding electrode are arranged, and the chamber further comprises And a gas cooling means for cooling the atmosphere gas before being supplied to the chamber.

In the above configuration, since the atmospheric gas supplied to the chamber has already been cooled, the ultrafine metal particles generated by the arc discharge are also cooled immediately. As a result, it is possible to further improve the suppression of particle growth, and it is possible to produce finer metal ultrafine particles. In addition, when combined with each of the above-described configurations, the metal ultrafine particles are cooled in two stages, that is, the vicinity of the generation site of the metal ultrafine particles and the transport path, so that the metal ultrafine particles can be more reliably cooled. It also has the effect that it can be done.

As described above, the method for producing ultrafine metal particles according to the present invention is a method of cooling ultrafine metal particles generated by arc discharge at a stage prior to recovery.

In the above method, immediately after the production, the ultrafine metal particles, which are liquids, are also solidified and then collected, so that even if the ultrafine metal particles collide with the fuel at a high frequency, the ultrafine metal particles are aggregated into particles. Does not grow. as a result,
There is an effect that it is possible to produce finer metal ultra-fine particles than before, with almost no inhibition of generation of metal ultra-fine particles by arc discharge.

As described above, another method for producing ultrafine metal particles according to the present invention is to produce an arc discharge in the presence of an atmospheric gas and to use a gas having a high thermal conductivity as the atmospheric gas. It is.

In the above method, since a gas having a high thermal conductivity is used as the atmosphere gas, the generated ultrafine metal particles are easily cooled by the surrounding atmosphere gas. As a result, there is an effect that the generation of ultrafine metal particles by arc discharge is substantially not hindered, and the particle growth is further suppressed, so that ultrafine ultrafine metal particles can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a cooling unit provided in an apparatus for producing ultrafine metal particles according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a schematic configuration of an apparatus for producing ultrafine metal particles provided with the cooling means shown in FIG.

FIG. 3 is an explanatory diagram showing a configuration for forming a shielding gas provided in the manufacturing apparatus shown in FIG. 2;

FIG. 4 is an explanatory view showing a shape of a discharge electrode used in the manufacturing apparatus shown in FIG.

FIG. 5 is a schematic diagram showing a schematic configuration of an apparatus for producing ultrafine metal particles according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram showing a schematic configuration of an apparatus for producing ultrafine metal particles according to a third embodiment of the present invention.

FIG. 7 shows Examples 1 to 4 in which ultrafine metal particles were produced using the production apparatus shown in FIG. 1, FIG. 5, or FIG.
4 is a graph showing the results of the specific surface area diameters in a comparative example in which ultrafine metal particles were produced using a production apparatus without the cooling means.

[Explanation of symbols]

 Reference Signs List 5 Target (metal base material) 10 Particle generator (particle generator) 11 Chamber 13 Discharge electrode 14 Holder (holding electrode) 16 Arc power supply 20 Gas supply unit (gas supply unit) 30 Particle recovery unit (particle recovery unit) 38 Ultrafine particle introduction tube (particle introduction tube) 51 Tube cooling unit (cooling means) 52 In-tube cooling unit (cooling unit) 53 Chamber cooling unit (cooling unit) 54 Gas cooling unit (gas cooling unit)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G075 AA27 CA17 CA62 DA01 EB01 EC21 4K017 AA02 CA08 EF02 FA01 FA23 FA29

Claims (6)

[Claims] A discharge electrode, a holding electrode provided at a position close to the discharge electrode for holding a metal base material, and an arc power supply connected thereto; An apparatus for producing ultrafine metal particles having a particle generating means for generating an arc discharge by applying a voltage between the electrode for use and the holding electrode, further comprising: a particle collecting means for collecting the generated ultrafine metal particles; and a particle generating means. And a cooling means for cooling the ultrafine metal particles to be conveyed in a transportation path of the ultrafine metal particles from the device to the particle collection means. 2. The apparatus according to claim 1, further comprising: a particle introduction pipe disposed on the transport path, for attracting ultrafine metal particles generated by arc discharge and guiding the metal ultrafine particles to particle collection means. 2. The apparatus for producing ultrafine metal particles according to claim 1, wherein the introduction pipe is cooled. 3. The particle generation means includes a chamber in which at least a discharge electrode and a holding electrode are disposed, and the cooling means cools only a portion of the chamber corresponding to the transport path. Claim 1.
An apparatus for producing ultrafine metal particles according to the above. A discharge electrode, a holding electrode provided at a position close to the discharge electrode for holding a metal base material, and an arc power supply connected thereto; In the apparatus for producing ultrafine metal particles having a particle generating means for generating an arc discharge by applying a voltage between the electrode for use and the holding electrode, the particle generating means further includes at least a discharge electrode and a holding electrode inside. A chamber for disposing the chamber; a gas supply unit for supplying an atmosphere gas to the chamber; and a gas cooling unit for cooling the atmosphere gas before being supplied to the chamber. An apparatus for producing ultrafine metal particles. 5. A method for producing metal ultrafine particles in which a discharge electrode and a metal base material are arranged close to each other and a voltage is applied between the electrodes and the metal base material, the method comprising the steps of: A method for producing ultrafine metal particles, comprising cooling the fine particles before collecting them. 6. A method for producing ultrafine metal particles in which a discharge electrode and a metal base material are arranged close to each other and a voltage is applied therebetween to generate an arc discharge. A method of producing ultrafine metal particles, wherein a gas having a high thermal conductivity is used as the atmospheric gas.