JPS61253307A - Production of ultra-fine particles - Google Patents

Abstract

PURPOSE:To obtain efficiently ultra-fine metallic particles by disposing one or both of electrodes in the form of ultra-fine particle raw material so as to face each other, inclining one electrode and generating the vapor flame of a base material in the magnetic blow direction. CONSTITUTION:The electrode 1 is disposed by inclining the same at 15-45% in the horizontal direction. The electrode 1 is acted as a cathode and a holding base 2 as an anode. An inert gas, gaseous hydrogen or gaseous hydrogen-contg. compd. is passed between the electrode 1 and the base material 3 on the base 2 and an arc is generated by current 6. The arc 7 and the arc 8 contg. metallic vapor are generated and a metallic vapor group 9 is conveyed by gaseous plasma flow 5. The electromagnetic force in the right direction shown in the figure is generated in this stage and the plasma flame flows in the same direc tion. The vapor group 9 is quickly conveyed. The efficiency for forming the ultra-fine particles in the entire current region is thus increased.

Description

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

[Background of the invention]

There is no established method to inexpensively produce large quantities of ultrafine particles with a particle size of 1 μm or less.
Methods such as No. 44123 and Japanese Patent Publication No. 57-44725 are known, each of which is an evaporation method in gas.

This method is called hydrogen arc heating and is an effective method for producing ultrafine particles. However, the in-gas evaporation method requires large-scale production equipment and has poor thermal efficiency and low production efficiency, making it difficult to reduce the price of ultrafine particles.

On the other hand, the latter hydrogen arc heating method has a higher production rate of ultrafine particles than the in-gas evaporation method, and requires only a small scale production apparatus, so that ultrafine particles can be economically produced. However, the hydrogen arc heating method uses gas containing hydrogen,
Although this method utilizes a mechanism in which this gas is dissolved in the molten metal, convected, and released, no consideration was given to arc characteristics and manufacturing efficiency.

[Purpose of the invention]

An object of the present invention is to provide a method 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]

The present invention generates an arc between a base material to be evaporated and an electrode in an atmosphere of one, two, or three of (1) inert gas, (2) hydrogen gas, and (3) hydrogen-containing compound gas. The method for producing ultrafine particles is characterized in that one or both of the electrodes are arranged facing each other as ultrafine particle raw materials, and the electrodes are tilted with respect to the horizontal direction to generate a vapor flame of the base material in the magnetic blowing direction. It is something.

Heating with an arc can easily achieve a high temperature and is an effective method for evaporating the base material 1, such as metal.

However, a large amount of current is required to evaporate a large amount of metal6.
Generally, an arc in an inert gas with vertically arranged electrodes takes on a bell-like shape with the base wider than the discharge electrode, making it impossible to efficiently generate ultrafine particles.

By concentrating this arc on a localized portion on the metal surface, a higher temperature region can be formed and generation efficiency can be increased.

In the present invention, when base material vapor is generated by an arc on the surface of the base material, which becomes ultrafine particles, the energy required for ionization is much lower than that of a countersunk. is concentrated there, becomes even hotter, and evaporates more actively. Furthermore, it is based on the phenomenon that by actively utilizing electromagnetic force, it is possible to efficiently produce a large amount of ultrafine particles generated by plasma airflow.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the electrode 1 is tilted with respect to the horizontal direction, the electrode 1 is used as a cathode, the holding table 2 is used as an anode, and Ar + 50% H2 gas 4 is placed between the electrode 1 and the base material 3 on the holding table 2. When an arc is generated by the power source 6, an arc 7 and an arc 8 containing metal vapor are generated, and the metal vapor group 9 is transported by the plasma air flow 5.

The phenomenon at this time is as follows. That is, when an arc is generated between the electrode 1 and the base material 3 at an angle with respect to the horizontal direction, the arc is generated at the shortest distance between the two, and an anode point is formed on the surface of the base material.

Since the anode point is heated to a high temperature, metal vapor is generated from there, and its ionization voltage is low, so the current of the contracting arc subjected to the thermal pinch force of gas 4 and the electromagnetic pinch force of the current flows to this point. and promotes the generation of metal vapor. Furthermore, depending on the composition of the gas, the bonding energy of the dissociated gas is given to the base material, which likewise promotes the generation of metal vapor. Furthermore, since the current density is high in the cathode part of the electrode 1 and the anode point part of the base material 3, the pressure in these parts increases, and a gas flow is generated toward the center part between the electrodes. When this gas stream is generated, a plasma stream 5 is generated from the surroundings in the direction of the arrow to supplement the gas at both poles. In addition to these phenomena, an electromagnetic force is generated in the right direction in the figure due to the current flowing through the electrode, arc, and base metal, and as a result, the plasma flame flows as shown in the figure. Therefore, the generated metal vapor group 9 is rapidly transported from the vicinity of the arc by electromagnetic force and plasma airflow.

According to the present invention, when the current is increased, the amount of ultrafine particles produced increases in proportion. This is because as the heat input increases, the generation of metal vapor increases, and as the electromagnetic force increases, the electromagnetic force generated by the plasma stream itself also becomes stronger, making it possible to obtain a stable metal vapor group 9. Therefore, it has become possible to dramatically increase the efficiency of producing ultrafine particles in the entire current range, something that could not be achieved in the past.

In addition, since the electrode 1 of the present invention is tilted, ultrafine particles generated from the base material 3 are difficult to adhere to the electrode 1.
It also has the effect of preventing wear and tear and allowing arc generation for a long time.

The present invention is based on the electromagnetic force caused by tilting the electrodes and the effect of squeezing the arc itself. Hydrogen gas, water vapor, helium gas, etc., which have a large thermal pinch effect, can also be used as the atmospheric gas, and a cooled atmosphere can be used. If a gas is used or if atmospheric gas is made into a swirling flow and blown onto the arc, the arc will be concentrated at the anode point on the surface of the base material, making it possible to efficiently generate ultrafine particles.

Figure 2 shows the relationship between the amount of ultrafine particles produced as the arc current increases in the conventional method and the present method. The curve (a) in the figure is for the conventional method, and the curve (b) is for the present method. The atmospheric gas used was Ar + 50% H2 gas, and when the arc current was varied, the amount of ultrafine particles produced was small with the conventional method, but the amount of ultrafine particles produced with this method increased dramatically. I understand.

Figure 3 shows arc current 150A, atmospheric gas Ar+50%
H2, electrode is tungsten with 2% sodium, outer diameter 4
This figure shows the relationship between the electrode angle and the production ratio when metal vapor is generated under the conditions of using a voltage of 35 V and a base material of nickel. If the electrode angle is 90 degrees, that is, the production ratio is 1 when installed vertically, the electrode angle is 40 degrees.
The production amount ratio shows a peak value of 2.8 at the position of 2.5 degrees. The reason for the peak value is that when the electrode angle is 40 degrees or less, the arc becomes rigid due to the electromagnetic pinch force, and the electromagnetic force due to changes in the current flow path increases, increasing the force that causes metal vapor to fly horizontally.As a result, a large amount of of metal vapor is conveyed. Furthermore, even when the hydrogen concentration is increased, the amount generated can be increased due to the increase in thermal pinch force. However, if the electrode angle is less than 15 degrees, it will be very difficult to start the arc, and it will be difficult and unstable to maintain the arc due to minute changes in the melting surface when the arc is generated, and the arc will break easily. The above is good.

In this method, from high melting point material, W, Ta to low melting point material, Sn.
, Zn, and various alloys.When manufacturing ultrafine particles of high melting point materials, the electrode angle should be around 40 degrees, and when manufacturing ultrafine particles of low melting point materials, the electrode angle should be adjusted to around 40 degrees. It is preferable to set the temperature to around 30 degrees. When a low melting point material is used as a raw material and an arc is generated, the raw material melts and spreads uniformly on the holding table at the same time as the arc is generated, so a low electrode angle is more efficient.

To further increase the amount produced, arrange a plurality of electrodes, set one of the electrodes to a common potential, and generate an arc to increase the amount produced in proportion to the number of electrodes.

〔Effect of the invention〕

As explained above, according to the present invention, when one or both of the electrodes are arranged facing each other as raw materials for producing ultrafine particles, the electrodes are tilted with respect to the horizontal direction, and an arc is generated, plasma airflow, electromagnetic force, and arc Due to the effect of squeezing, a method for producing ultrafine particles can be obtained that is more efficient than the conventional hydrogen arc heating method.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the manufacturing method of the present invention, and Figure 2 is a diagram showing the amount of ultrafine particles produced due to changes in arc current.Curve (a) is the production amount by the conventional method, and curve (b) is the manufacturing method of the present invention. FIG. 3, which is an explanatory diagram of the amount produced by the method, is a diagram showing the electrode angle with respect to the horizontal direction and the ratio of the amount produced. 1... Electrode, 2... Raw material holding stand, 3... Base material (
(pair electrode), 4... Atmosphere gas, 5... Plasma air flow.

Claims (1)

[Claims] 1. Ultrafine particles are generated by generating an arc between a base material to be evaporated and an electrode in an atmosphere of one, two, or three of inert gas, hydrogen gas, and hydrogen-containing compound gas. In the manufacturing method, one or both of the electrodes are arranged facing each other as ultrafine particle raw materials, and the electrodes are arranged horizontally at 1
A method for producing ultrafine particles characterized by arranging the base material at an angle of 5 to 45 degrees and generating a steam flame in the direction of magnetic blowing. 2. A method for producing ultrafine particles according to claim 1, characterized in that a plurality of electrodes are used and one of the electrodes is set at a common potential.