JPS60228608A - Method and device for producing ultrafine particles - Google Patents

Abstract

PURPOSE:To produce efficiently ultrafine metallic particles by forming a local high-temp. part by the other heat source to the arc concentrating surface of the metal to be evaporated to accelerate evaporation and concentrating the arc to said part by the vapor of the generated ultrafine particles. CONSTITUTION:The inside of a chamber 2 is evacuated to a vacuum and thereafter an atmosphere of argon or a gaseous mixture composed of hydrogen and argon is maintained therein. An arc 10 is then generated with a tungsten electrode 3 as a cathode and the base metal 4 on a water cooled copper crucible 5 as an anode. Carbon dioxide laser light 7 is projected locally on the part where the arc 10 and the base metal 4 contact with each other via a germanium lens 6 after generation of the arc to heat locally said part. The evaporation of the base metal 4 in said part is thereby accelerated and the arc 10 is concentrated to said part by the vapor of the ultrafine particles generated therefrom, by which the amt. of the ultrafine particles to be formed is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) [Field of Application of the Invention] The present invention relates to a method and apparatus for efficiently producing ultrafine particles, particularly ultrafine metal particles of 1 μm or less.

[Background of the invention]

Currently, there is no established method for inexpensively producing large quantities of ultrafine particles with a particle size of 1 μm or less. As conventional manufacturing methods, methods such as Japanese Patent Publication No. 55-44123 and Japanese Patent Publication No. 57-44725 are known, and these are effective methods called evaporation in gas method and hydrogen arc heating method, respectively. However, the in-gas evaporation method requires large-scale production equipment, and it is difficult to reduce the price of ultrafine particles.

Although the hydrogen arc heating method has excellent efficiency, it does not take advantage of the characteristics of the hydrogen arc and the arc concentration phenomenon.

[Purpose of the invention]

An object of the present invention is to provide a method and apparatus capable of efficiently and inexpensively producing ultrafine particles, particularly ultrafine metal particles having a particle size of 1 μm or less.

[Summary of the invention]

(2) Hydrogen gas or a mixed gas of hydrogen gas and inert gas,
Alternatively, in a method of producing ultrafine particles by generating an arc between the base material to be evaporated and an electrode in an inert gas, a localized high-temperature area is formed by another heat source on the surface of the metal to be evaporated where the arc is concentrated. The method is characterized in that the evaporation of the base material is promoted in that part, and the arc is concentrated in the part by the vapor of ultrafine particles generated therefrom.

Heating by arc can easily achieve high temperatures and is an effective method for evaporating base materials, such as metals.

However, a large amount of current is required to evaporate a large amount of metal. Generally, an arc in an inert gas has a shape that is wider at the base than the discharge electrode, but if this arc is concentrated at the periphery of the metal surface, a high temperature region can be formed, and the metal surface can be more efficiently can be evaporated.

Metal atoms require much less energy to ionize than the surrounding gas, so once metal vapor is generated, the arc concentrates there, and the vaporization becomes more active at higher temperatures (3). The present invention is based on this principle, and discloses a method in which a localized high-temperature area is formed on the surface where the base material and the arc are in contact with each other by a heat source other than the arc, or the arc is concentrated by magnetic force.

First, FIG. 1 shows an example in which local heating was performed using another heat source to create arc concentration.

(2) is a torch, which cools the tungsten electrode 3 with cooling water W1. 2 is the vacuum chamber, 4 is the base material, 5
is a water-cooled copper crucible. 6 is a germanium lens, which focuses the carbon dioxide laser 7 on one point on the base material 4. 8
, 9 are a carrier gas nozzle and a suction nozzle, which carry away ultrafine particles generated by the carrier gas G1. 10 indicates an arc.

First, the inside of the chamber 2 is evacuated to an argon or hydrogen-argon mixed gas atmosphere. Thereafter, an arc 10 is generated using the tungsten electrode 3 as a cathode and the base material 4 of the water-cooled copper crucible 5 (4) as an anode.

After the arc is generated, the carbon dioxide laser beam 7 is applied to a local part of the contact area between the arc 10 and the base material through the germanium lens 6 to locally heat it. In this example, a carbon dioxide laser that can obtain high output was used.

First, the results in an Ar-50% H2 atmosphere will be shown.

For reference, Figure 2 shows the relationship between arc shape, arc current, and distance between electrodes when laser heating is not applied. In this figure, the general region is the region produced by the conventional method where an arc spreading from the tungsten electrode exists, and the high efficiency region is the region produced by the manufacturing method of the present invention where there is a locally concentrated arc on the base material, and the transition The term "region" refers to a region where an arc exists between the regions and which includes the method of the present invention.

The production efficiency of ultrafine particles in the high-efficiency range is far higher than that in the general range; when the base material is iron, the amount produced is approximately 6 times that of the general range; shows excellent efficiency of about 20 times.

(5) When carbon dioxide laser heating was applied, the high efficiency region shown in Figure 2 shifted to the high current side, and the amount of ultrafine particles produced increased significantly as the current increased.

Next, the results in an argon atmosphere are shown below. In an argon atmosphere, the arc concentration phenomenon does not occur easily as in a mixed gas of argon and hydrogen.

However, when laser heating is applied, Ar −50%H
Although the current was on the lower side compared to the No. 2 atmosphere, a phenomenon of arc concentration occurred. The amount of ultrafine particles produced at this time is Ar-50
Although the amount of ultrafine particles produced in a %H2 atmosphere was smaller, it was significantly higher than the amount produced in an argon atmosphere without laser heating.

Next, FIGS. 3 and 4 show another embodiment in which the arc is concentrated by magnetic force.

In FIGS. 3 and 4, 2 indicates the vacuum chamber 1 and the torch. Reference numeral 11 indicates a suction cover, which prevents the generated ultrafine particles from scattering and increases collection efficiency. Reference numeral 12 indicates an electromagnet, which is arranged as shown in FIG. Figure 4 shows the base material 4° water-cooled copper crucible 5. shown in Figure 3. FIG. 6 is a diagram of the arrangement of the electromagnets 12 viewed from above. 13 is a suction nozzle, and 14 is a gas passage for carrier gas. Ultrafine particles generated by the carrier gas G2 blown upward from the gas passage 14 are carried to the suction nozzle 13.

First, the inside of the chamber 2 is evacuated to create an argon or argon hydrogen mixed gas atmosphere. An arc is generated using the discharge tungsten electrode 3 as a cathode and the base material 4 on the water-cooled copper crucible 5 as an anode.

After the arc is generated, the magnet 12 concentrates the arc in the shape of a base material 4 on a local area on the base material 4. The generated ultrafine particles pass through the suction cover 11 by the carrier gas G2, are sucked into the suction nozzle 13, and are transported to a collector (not shown).

When a magnetic force that restrained the arc was applied in an Ar-50% H2 atmosphere, the high efficiency region shown in FIG. 2 shifted to the higher position side, and the amount of ultrafine particles produced increased as the current increased.

In the argon atmosphere, the arc concentration phenomenon unlike in the Ar-50%H2 atmosphere is not observed. When the arc is concentrated on the base metal by magnetic force, the amount of ultrafine(7) particles produced is smaller than the amount produced when the arc is concentrated by magnetism in an Ar-50%H2 atmosphere, but when the arc is constricted in an argon atmosphere, Compared to the state without it, the amount produced was a huge +11.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to manufacture economically because large-scale manufacturing equipment is not required as in the case of the in-gas evaporation method, and compared to the conventional hydrogen arc heating method, It can also be manufactured with extremely high efficiency.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the ultrafine particle manufacturing apparatus according to the present invention, and FIG.
Fig. 3 is an explanatory diagram of the relationship between arc current, interelectrode distance, and arc shape, Fig. 3 is an explanatory diagram of the ultrafine particle production apparatus according to the present invention, and Fig. 4 is an explanatory diagram of the ultrafine particle production equipment according to the present invention. FIG. 4 is an explanatory diagram showing the arrangement of materials and magnets. ■...Torch, 2...Vacuum chamber, 3...Tungsten electrode, 4...Base material, 5...Water-cooled copper crucible, 6...Ga lens, 7...CO2 laser beam, 8
... Gas nozzle (8) Zuru, 9... Suction nozzle, 10... Arc, 11.
... Suction cover, 12... Electromagnet, 13... Suction nozzle, 14... Gas passage. (9) ■ 1 Figure 2 0 0' Introduction /shi';° -Ikunami Ebisu -2゜4 104 Shukoshiri/0. Wealth 0 7, / Ding 1 1 ■3 Figure 4 Tomi 4 Figure 0 24681ρ between electrodes y Kyoshima ILL (riyi x-) 62-

Claims (1)

[Claims] 1. A method for producing ultrafine particles by generating an arc between a base material to be evaporated and an electrode in hydrogen gas, a mixed gas of hydrogen gas and an inert gas, or an inert gas. A heat source other than the arc is used to form a localized high-temperature area on the concentrated surface of the metal mark to be evaporated, the evaporation of the base metal is promoted in that area, and the vapor of ultrafine particles generated from the area causes the arc to be activated. A method for producing ultrafine particles, characterized by concentrating them in the above portion. 2. The method for producing ultrafine particles according to claim 1, characterized in that the arc is concentrated locally on the base material to be evaporated by magnetism. 3. An apparatus for producing ultrafine particles, characterized in that a discharge electrode and a base material on a receiving stand are arranged facing each other in a sealed capacity, and an electromagnet is further arranged to surround the space between the electrode and the base material.