JPS627804A - Production of hyperfine particle - Google Patents

Abstract

PURPOSE:To safely produce hyperfine metallic or alloy particles with high production efficiency by feeding a gas provided with a whirling flow to the inside of a torch for an arc heat source for melting a metal or alloy. CONSTITUTION:When hyperfine particles are produced from a molten metal or alloy with an arc heat source, gaseous He, CO2, N2, Ar or a mixture thereof is fed to a gas path 3 on the inside of the cover 2 of a torch for the arc heat source in the direction of an arrow 4 and is spouted from gas holes 5 to form a whirling flow 6. Arc generated from the electrode 1 of the torch is centered on a part of the surface of a material to efficiently melt the material and hyperfine particles are efficiently produced. Since the gas contg. no H2 is provided with a whirling flow so as to center arc, high safety operation can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for producing ultrafine particles, and an object of the present invention is to provide a method for producing ultrafine particles with high production efficiency and safety.

[Background of the invention]

Regarding the manufacturing method of ultrafine particles, see Japanese Patent Publication No. 55-4412.
Methods such as No. 3 and Japanese Patent Publication No. 57-44725 are known. These are respectively called the in-gas evaporation method and the hydrogen aeration heating method, and are effective methods for producing ultrafine particles.

However, in the in-gas evaporation method, since the metal to be evaporated is melted in a refractory crucible by high-frequency induction heating, cooling of the refractory crucible is essential, and a large amount of heat is taken away by this cooling water. Therefore, the thermal efficiency is low, and the generation efficiency is also low. Furthermore, it is impossible to produce ultrafine particles of metals that react with a refractory crucible, and it is impossible to produce ultrafine particles of high melting point metals (Nb, Ta, etc.). In addition, the entire device becomes large and requires a lot of installation space, which increases the price of ultrafine particles.

On the other hand, the latter hydrogen arc heating method has a higher generation efficiency 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, in the hydrogen arc heating method, hydrogen or hydrogen-containing compound gas components are mixed in the atmosphere, and since it is usually produced in a closed system, if outside air or oxygen gets into the system, the arc heat source becomes an ignition source. This poses a problem for production equipment as it has the potential to cause an explosion.

[Purpose of the invention]

An object of the present invention is to provide a method for producing ultrafine particles with high safety and high production efficiency.

[Summary of the invention]

The present invention relates to a method for producing ultrafine particles from molten pure metal or molten alloy using an arc heat source, in which gas is flowed inside a torch for the arc heat source, and the gas flow has a structure that imparts a swirling flow. It is characterized by:

As described in Japanese Patent Application No. 59-83711, this method concentrates the arc as locally as possible on the surface of the material, thereby increasing the efficiency of producing ultrafine particles. In this method, instead of using hydrogen or a hydrogen-containing compound gas, a gas swirling flow is applied to the inside of the arc heat source torch in order to concentrate the arc as locally as possible on the surface of the material. As a gas that gives a swirling flow, it is a gas that has a strong effect of concentrating the arc, and in addition to hydrogen or hydrogen-containing compound gas, there are helium, carbon dioxide, nitrogen, argon, etc., and a mixture of these gases is used. Also good. Hydrogen or hydrogen-containing compound gas is very effective in concentrating the arc, but there are safety issues. Therefore, as a method of concentrating the arc using a gas other than hydrogen or hydrogen-containing compound gas, helium is used.

Carbon dioxide, nitrogen, argon gas, or a mixture of these gases is used, but these gases are not as effective in concentrating the arc as hydrogen or hydrogen-containing compound gases, so these gases are not used inside the arc heat source torch. sink,
The purpose is to enhance the effect of concentrating the arc by imparting a swirling flow to the gas flow. As a result, the arc emitted from the arc heat source torch is concentrated locally on the material surface, making it safer and more efficient.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Figures 1 (a) and (b) show an apparatus for producing ultrafine particles using the present invention, which has a structure in which gas is flowed inside an arc heat source torch and a swirling flow is imparted to the gas flow. This is an example of a manufacturing method. Reference numeral 1 denotes an electrode, which is usually made of tungsten or tungsten doped with a small amount of doria. Reference numeral 2 indicates a cover of the torch, and reference numeral 3 indicates a gas passage inside the torch, through which gas is supplied as shown by arrow 4.

The gas supplied from the arrow 4 passes through the holes 5 (in this example, six holes are shown) installed at angles and sizes that provide a plurality of swirling flows, as shown by the arrow 6. The gas flows, swirling around the electrode, and the arc generated from the electrode tip is contracted by thermal pinch force.
The arc can be concentrated locally on the material surface. The structure of the torch is not limited to the illustrated example, but may be any structure that allows gas to flow inside the torch, and the size, shape, number, and angle of the holes 5 that provide swirling flow do not need to be particularly limited. It is related to the gas flow rate determined by the type of gas flowing through this hole 5. This point will be explained using FIG. 2. FIG. 2 shows the relationship between the flow velocity of the swirling flow shown by the arrow 6 in FIGS. 1(a) and (b) and the amount of ultrafine particles produced, and shows an example in which three types of gas are used. Curve (1) is an example in which 100% helium (He) gas is used as the gas for generating the swirling flow, and shows that as the flow rate of the swirling flow is increased, the amount of ultrafine particles produced increases. Curves (2) and (3) are helium-de-nitrogen gas (N2) and helium-1, respectively, as the gases that generate the swirling flow.
This is an example using a 100% helium gas (Ar) mixed gas, and the amount of ultrafine particles produced is not larger than the example of 100% helium gas shown in curve (1), but if the flow velocity of the swirling flow is increased, the amount of ultrafine particles produced shows that the number is increasing. In addition, helium, carbon dioxide (CO2), nitrogen, argon, and other gases such as these may be used, and if each has a structure that provides an appropriate swirling flow velocity, ultrafine particles can be generated safely and efficiently. I can do it.

〔Effect of the invention〕

As explained above, according to the present invention, since hydrogen or hydrogen-containing compound gas is not used, even if air or oxygen gets mixed into the system of the ultrafine particle production device, an explosion using the arc heat source as the ignition source can occur. It is a safe device that does not have any harmful effects, and it has the effect of being highly efficient in producing ultrafine particles.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a torch for arc heat source, (a) shows a cross-sectional view, and (b) shows a longitudinal cross-sectional view. Fig. 2 shows the swirling flow velocity and the amount of ultrafine particle generation when using the present invention. It is a figure showing a relationship. 1... Electrode, 3... Gas passage, 5... First port (Q) that provides swirling flow.

Claims (1)

[Claims] 1. In a method for producing ultrafine particles from a pure metal or a metal alloy using an arc heat source, a gas is caused to flow inside a torch for the arc heat source, and a swirling flow is created in the gas flow. A method for producing ultrafine particles, characterized in that they have a structure. 2. The manufacturing method according to claim 1, wherein the gas providing the swirling flow is helium, carbon dioxide, nitrogen, argon, or a mixture of these gases.