JPH04280906A - Manufacture of ultra-fine particle - Google Patents

Abstract

PURPOSE:To generate a continuous wire exploring phenomenon and to obtain ultra-fine particles small in the mixing of impurities and having arranged particle size and a shape close to that of a spherical one by jetting a molten metal or semiconductor in contact with electrodes from a nozzle. CONSTITUTION:A fixed electrode 2a is arranged on the face opposite to a nozzle 1, and the part of the nozzle 1 is formed into an electrode 2b. An electrode 2c having an area wider than that of the diameter of the nozzle 1 is brought into contact with an molten metal 4 in a raw material puddle 3. By compressed air 7, the internal pressure of the raw material puddle 3 is increased, and the molten metal 4 is jetted from the nozzle 1. Particles formed between the electrodes begin to be brought into a rapid oxidation reaction to generate a continuous wire exploring phenomenon, and they are formed into ultra-fine particles and are adhered to a collecting board 8. In this way, powder particles of various components can be mass-produced at low cost.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for producing fine particles of metal powders, metal compounds, ceramics, etc.
In particular, the present invention relates to a manufacturing method that is more efficient than conventional methods and can produce quenched fine particles with good properties.

0002

2. Description of the Related Art Conventionally, methods such as an atomization method, a spray method, and a cavitation method have been used to produce fine metal powder. In these conventional manufacturing methods, the kinetic energy of a gas, solid, or itself is physically applied to a pre-molten metal to break it up into minute droplets and scatter them, and then a medium with cooling capacity is used. Metal powder is obtained by contacting with When metal is pulverized by such a method, there is a very limited amount of energy that can be used directly to break up the molten metal. For example, even if the flow velocity of the ejected body is increased in the atomization method, It is difficult to reduce the particle size of the metal powder to 10 microns or less.

[0003] In addition to the above-mentioned manufacturing method, a method for manufacturing fine metal powder called the in-gas evaporation method has been proposed, which utilizes the reactivity of plasma hydrogen gas toward metal and heats the metal with plasma. This is a method in which metal is plasma heated in a hydrogen gas atmosphere and metal smoke generated from the surrounding area of the molten metal is collected, but this method has problems with the productivity of the resulting metal fine powder.

[0004] A method of obtaining fine metal powder using the radiation bombing phenomenon has also been devised, and it is possible to obtain powder with a smaller particle size than the atomization method, etc., but the productivity is still very low. Unfortunately, the process for producing powder in practical terms had not yet been achieved.

[0005]

[Problems to be solved by the invention] The present invention is a powder manufacturing method with high productivity and simple steps, unlike conventional methods.
Furthermore, the resulting powder can be used to produce metal or ceramic particles with less contamination of impurities, uniform particle size, nearly spherical shape, and particle size controllable over a wide range.

[0006]

[Means for Solving the Problems] The gist of the present invention is that the electrode 2
A metal or semiconductor 4 in a molten state that is in contact with the metal or semiconductor is ejected from a nozzle, and the material closes the gap between the electrode and the opposing electrode, and a large current flows through the material that closes the electrode. If it heats up rapidly and scatters explosively, or if an arc or plasma is generated at that time,
This has the characteristic of further making the material droplets finer or vaporizing them.

[0007]

[Function] As mentioned above, the fine metal powder obtained by wire bombing has an excellent property of being smaller in particle size than conventional methods, making it possible to obtain metal powder of 5 to 10 microns or less. , the production efficiency was very low and it could not be called a practical manufacturing method. In other words, in the conventional wire bombing method, a solid metal wire is stretched between electrodes, and then a momentary large current is passed through the electrodes to instantaneously heat the metal body, which is converted into a high-speed flow of fine metal droplets. Since powder was obtained by scattering, there was a fatal drawback that the raw metal wire could not be continuously replenished. The present invention solves the above problems by continuously supplying the raw material metal or semiconductor in a molten state between the electrodes, thereby making it possible to continuously generate and maintain the radiation explosion phenomenon. . As shown in the above explanation, in the manufacturing process of the present invention,
Powder can be generated by the radiation bombing phenomenon even without the action of water or plasma. However, the arc or plasma generated near the area where the radiation bomb phenomenon occurs is
It has a more effective effect on metal droplets that have been pulverized by the radiation explosion phenomenon. Conventionally, there are many metal powder manufacturing devices that utilize arc or plasma. These methods apply the heat generated by an arc or plasma to a metal object, causing rapid melting or vaporization, and pulverizing the metal. In this method, an arc or plasma was applied to the metal in a state where it was processed sequentially starting from the surface. In these methods, a considerable portion of the applied heat is spent raising the temperature of the raw metal material in the lump state, and the extremely high temperature energy of the arc and plasma cannot be used effectively. There wasn't. When micronizing metals using arc or plasma, how efficiently and uniformly the energy is applied to the metal body is an important aspect to obtain microscopic metal powder. be able to. In the case of the present invention,
As mentioned above, the molten metal or semiconductor becomes fine droplets due to the radiation explosion, and when the arc or plasma generated near the same part acts on these, energy is transferred very efficiently. , the metal droplets are characterized by being further miniaturized or vaporized.

[0008] Furthermore, the arc or plasma generated at the electrode portion has the effect of promoting the reaction between the raw material and these gases when a gas active with respect to the raw material is used as the atmospheric gas, as will be described later. In the present invention, all metals and semiconductors such as silicon-germanium can be treated because the material used as the raw material must generate heat when energized.

[0009]

[Examples] Next, regarding specific examples of the present invention,
The explanation will be based on the drawings. In the device shown in FIG. 1, a fixed electrode 2a is placed on the opposite surface of a nozzle 1 from which molten metal 4 is spouted in contact with the electrode. In the case of this example, the nozzle portion 1 may be made of a conductive material such as tungsten or copper, and the nozzle portion may be used as the electrode 2b, or the nozzle portion may be made of ceramic or the like and a It is also possible to make the electrode 2c contact the molten metal 4 in the raw material reservoir 3 so that the molten metal itself has the function of the electrode. In this case, the cross-sectional shape of the cavity of the ceramic nozzle is tapered as shown in Figure 2, so that the smallest cross-sectional area of the molten metal 4 becomes the tip of the nozzle 1, thereby preventing excessive temperature rise inside the nozzle. It can be prevented. When using the fixed electrode 2a as in this example, the electrode portion may be constantly cooled with a cooling medium to prevent the electrode portion from being excessively heated and melted.

In FIG. 3, nozzles 1 having electrodes 2c inside are disposed facing each other, and molten metals 4a and 4b are ejected.
This is an example in which the nozzles are configured to collide. In this example, since the nozzle portion can be made of ceramic, it is possible to prevent the nozzle and electrode from melting away. The molten metal is highly reactive and may combine with the electrode 2c inside the nozzle. As a method to prevent this, a temperature gradient is provided in the raw material reservoir part 3 to form a solid metal part 5, and the electrode 2 is formed in the same part.
It is also possible to bring c into contact with the metal 5. Note that the molten metals 4a and 4b that are ejected oppositely may have different components.

FIG. 4 shows an arrangement in which the electrode 2a facing the nozzle 1 is rotated to prevent a portion of the electrode 2a from being heated in a concentrated manner. The melted electrodes may mix with the metal particles that are generated, causing problems such as a decrease in purity, or changes in the properties of the particles due to changes in the distance between the electrodes. This was a problem that had to be solved in order to produce powder. Figure 3 and
What is shown in Fig. 4 is a configuration that can solve this problem. In particular, the method shown in Fig. 3 fundamentally prevents the melting of the electrode.
This is an epoch-making device that enables stable continuous operation.

The area around the nozzle where metal droplets are generated is
It is filled with gases such as argon, helium, nitrogen, hydrogen, carbon dioxide, oxygen, etc., or in the atmosphere or vacuum, and powder particles are generated according to each atmosphere. When a gas inert to the raw material metal is used, quenched metal powder in which metal droplets solidify as they are can be obtained. When a reactive gas is used, the metal droplets react with these gases, so it is also possible to generate fine particles of metal compounds such as oxides, nitrides, and carbides. This is because the metal droplets at the scattering stage are at a very high temperature, and if an arc or plasma is generated, the reaction is likely to be accelerated. In addition to the generation of alumina fine particles shown in the examples described later, it is also possible to generate various types of fine particles such as aluminum nitride, titanium carbide, iron oxide, silicon nitride, and the like.

[0013] Conventionally, in the metal powderization method using plasma, there have been cases where the effect is improved by supplying a gas such as hydrogen from the surroundings, but in this method as well, the Injecting cooling gas is effective in promoting the generation of plasma and rapidly solidifying the generated particles. In addition to hydrogen, the cooling gases used include argon, helium, nitrogen, and the like used as atmospheric gases.
Examples include carbon dioxide and oxygen, but if a reactive gas is used, it is possible to obtain intermetallic compounds and ceramics as described above.

Next, an example of processing aluminum alloy using the apparatus of the present invention will be explained based on FIG. The hole diameter of the nozzle 1 used was 1.1 mm, and the distance from the nozzle to the electrode 2 was 1.1 mm.
The distance to a is 2 mm, and the voltage applied between the electrodes is 200
Volt AC 60 Hz, compressed air 7 to create raw material reservoir 3
The internal pressure is increased to eject molten metal from the nozzle. The area around the electrode where the powder is generated is exposed to the atmosphere.

With the above configuration, a voltage was applied to the electrodes 2a and 2b, and then molten metal was ejected from the nozzle 1 to generate powder. Approximately 0.5 seconds after the start of generation, the aluminum particles generated between the electrodes begin a rapid oxidation reaction, and within 1.5 seconds, approximately 5 grams of the raw material aluminum alloy is completely oxidized. It turned into smoke-like ultrafine particles. The aluminum alloy powder obtained immediately after the experiment adhered to a collection plate 8 located 10 cm away from the electrode, and the metal oxide particles generated thereafter adhered to a collection plate 9 installed approximately 1 m above the device. It was collected in the same condition.

The particles obtained by the collecting plate 8 are aluminum alloy powder, and the particle size is smaller than the raw material aluminum alloy powder, with an average particle size of about 25 microns, and the particle size is uniform even in an unclassified state. Most of the particles were spherical in shape. The metal oxide particles obtained on the upper collecting plate 9 were fine particles of alumina, and had an average particle size of about 0.2 microns, which was also very uniform in size.

In this experiment, the generated aluminum alloy powder was successively regenerated into alumina, but by shielding the area around the electrode with an inert gas, oxidation of aluminum can be prevented and other reactivity can be prevented. When gases are used, different compounds can be used. In the case of this example, a stable arc was generated at the electrode portion, but this worked in the direction of making the metal droplets scattered by the radiation explosion even finer. This is because the flying metal droplets are minute, so they have a large surface area per weight and have high energy pickup efficiency. The generated droplets or particles may be collected in a quenched state by a cooling plate or liquid.

In the method of the present invention, the nozzle diameter, the electrode spacing,
The particle size of the powder obtained depends on factors such as voltage, direct current, alternating current, frequency in the case of alternating current, ejection speed of molten material, generation state of arc or plasma, type and ejection state of cooling gas or reactive gas, etc. , properties, cooling rate, etc. can be adjusted.

[0019]

[Effects of the Invention] Metal or ceramic powder particles have recently been in the spotlight as structural materials, magnetic substances, and functional materials. According to the method of the present invention, it is possible to produce powder particles of various components in large quantities at a very low cost, with uniform particle diameters that are close to spherical diameters, and with little contamination of impurities.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the device of the present invention.

FIG. 2 is a sectional view showing an example of a nozzle portion.

FIG. 3 is a sectional view of the device of the present invention in which nozzles are opposed to each other.

FIG. 4 is a sectional view of the device of the present invention in which the electrodes are rotated.

[Explanation of symbols]

1...Nozzle 2a...Fixed electrode 2b...Nozzle electrode 2c...raw material reservoir partial electrode 3...Raw material storage part 4... Molten metal or semiconductor 5...Solid metal or semiconductor 6...Cooling gas, reactive gas 7...Compressed air 8...Collection plate 9...Collection plate 10...Power supply 11...Motor 12...Insulator, 13...Sliding contact 14...Code

Claims (5)

[Claims] Claim 1: A molten metal or semiconductor 4 is ejected from the nozzle while being in contact with an electrode 2 in a liquid or solid state in a nozzle 1 or a raw material reservoir 3 inside the nozzle, and can be regarded as an opposing electrode 2 or an electrode. By closing the gap between the molten metal or semiconductor 4 that has a potential difference, the molten substance is energized and a continuous radiation explosion phenomenon occurs between the nozzle and the electrode or between the nozzles, and the molten substance A method for producing powder particles, which comprises scattering and pulverizing the particles as fine droplets or vapor. 2. Powder characterized in that the metal or semiconductor serving as the raw material receives an induced electromotive force from the outside in the raw material reservoir portion 3, thereby receiving an effect similar to that when the metal or semiconductor is in contact with an electrode. Body particle manufacturing method. 3. A driving means for rotating the electrode 2;
A method for producing powder particles, characterized in that the point of approach with the opposing nozzle 1 moves continuously. 4. A method for producing powder particles, characterized in that a cooling gas or a gas reactive with the molten substance is supplied from the surroundings between the electrodes. 5. A method for producing powder particles, characterized in that arc or plasma is generated between electrodes.