JP3254278B2 - Method for producing mixed / composite ultrafine particles and apparatus for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a metal, an intermetallic compound,
The present invention relates to a method and an apparatus for producing uniform ultrafine particles of ceramics or the like, or composite ultrafine particles in which plural kinds of substances are mixed in one particle by mutual reaction, coalescence, alloying or the like.

[0002]

2. Description of the Related Art Conventionally, methods for producing ultrafine particles include physical methods such as a pulverizing method and an atomizing method, chemical methods such as a sol-gelling method, and physical methods such as a thermal plasma method and an active hydrogen molten metal reaction method. Chemical methods and the like are known. Among these manufacturing methods, the physical method has a problem that it is difficult to reduce the particle diameter of the ultrafine particles, and the chemical method has a problem that it is difficult to obtain the activity of the surface of the ultrafine particles. On the other hand, the physicochemical method can produce ultrafine particles having a very high purity, a clean surface and a small particle size. Therefore, fine ultrafine particles obtained by a physicochemical method have useful properties such as low-temperature sinterability and high catalytic activity. In the production of ultrafine particles by a physicochemical method, a substance as a raw material is put into a heat source, evaporated, reacted with a reactive gas or the like as needed, and then rapidly cooled to obtain ultrafine particles.

[0003] When producing mixed / composite ultrafine particles in which a plurality of substances are mixed or compounded, generally, a plurality of types of ultrafine particles obtained by the above method are dispersed and mixed in a mortar or liquid. Processing such as mixing / compositing a plurality of types of ultrafine particles is performed. However, it is impossible to obtain complete composite ultrafine particles in which a plurality of materials are composited in one particle by this method. In addition, even if a mixed ultrafine particle obtained by simply mixing a plurality of types of ultrafine particles is obtained, since the ultrafine particles produced and collected by the ultrafine particle manufacturing apparatus form an aggregate, they are individually redispersed. It is extremely difficult to mix uniformly, and uniform mixing in units of ultrafine particles is almost impossible. For this reason, recently, it has been attempted to produce uniform mixed / composite ultrafine particles by simultaneously micronizing a plurality of types of raw materials at the time of production. For example, in the above-mentioned physicochemical method, a mixed powder of a plurality of types of raw materials is mixed. A method has been proposed in which a composite ultrafine particle is placed on a melting table in a closed vessel and is evaporated, quenched, and re-agglomerated in nitrogen or a mixed gas of nitrogen and hydrogen gas by thermal plasma (Japanese Patent Publication No. Hei 3-). 276
No. 01).

[0004]

However, since the above-mentioned conventional method for producing composite ultrafine particles uses a single heat source, it is possible to set the composite state in accordance with the characteristics of each material to be composited. There is a problem that cannot be done. In addition, with a single heat source, the plasma frame has a uniform shape including a high-temperature portion, an intermediate portion, and a tail flame portion, and cannot disturb the frame to form a plasma frame having a temperature range different from the above. . Therefore, the physical properties of each raw material, especially the melting point,
If the boiling point is significantly different, the composition of the composite ultrafine particles obtained with a single heat source must be unique according to the physical property values of each raw material and the characteristic values of the heat source, and the composition can be controlled arbitrarily. I can't. Therefore, it was impossible to produce uniform mixed ultrafine particles or composite ultrafine particles from a plurality of kinds of raw materials, and it was impossible to arbitrarily select and control the mixing / compositing.

An object of the present invention is to solve the above-mentioned problems of the prior art when producing mixed / composite ultrafine particles of a plurality of substances by a physicochemical method.
Efficiently produce mixed / composite ultrafine particles by controlling the shape of the plasma flame for evaporating the raw materials of intermetallic compounds, ceramics, etc., or a plurality of these materials. A method for producing composite ultrafine particles, which is capable of controlling the state of mixing or compounding, and capable of arbitrarily selecting and producing uniform mixed / composite ultrafine particles of any composition, and a method thereof It is intended to provide a device.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems and obtain uniform mixed / composite ultrafine particles of an arbitrary composition. As a result, a sharp temperature gradient in the temperature distribution of the plasma flame has been found. By controlling the superimposed state of a plurality of plasma frames by using the above, it is possible to obtain a disturbed frame that cannot be obtained by a single plasma torch, and to efficiently control the state according to the raw material to efficiently obtain the disturbed frame. Ultrafine particles can be produced, and the raw material is supplied to the high-temperature portion of each plasma frame to arbitrarily select three modes of vapor, cluster, and ultrafine particle generation of each raw material, and in any state. It has been found that a plurality of materials can be combined or mixed, and uniform mixed / composite ultrafine particles having an arbitrary composition can be obtained, and the present invention has been achieved.

That is, the method for producing mixed / composite ultrafine particles of the present invention is a method for producing mixed / composite ultrafine particles by producing the mixed / composite ultrafine particles by thermal plasma. Causes
By controlling the plurality of plasma frames in a superimposed state or a non-contact state, ultrafine particles in which a plurality of material substances are mixed or combined are manufactured.
Further, by charging each raw material into each plasma frame, controlling the plurality of plasma frames in a superimposed state or a non-contact state, and selecting a state at the time of contact of a plurality of types of raw material, a plurality of It is characterized by mixing or compounding material substances.

[0008] The manufacturing apparatus for implementing the method is as follows.
A composite ultrafine particle device for producing composite ultrafine particles by supplying a raw material into a thermal plasma flame generated in an airtight reaction vessel, and evaporating and condensing the raw material, comprising: The plasma torch is provided so as to be swingable with respect to the reaction vessel so that the generated plasma frame can be controlled to move to a superimposed position and a non-contact position with respect to each other. are doing. Each plasma torch is desirably capable of setting heating conditions for each raw material by being able to arbitrarily control the amount of heat and the gas composition of the plasma frame generated by each plasma torch. Furthermore, continuous production is possible by providing a raw material supply device for supplying a raw material to a plasma frame generated by each plasma torch for each plasma frame.

[0009]

The temperature distribution of the plasma flame in the thermal plasma method is as shown in FIG.
There is a high temperature part a reaching 00K, a tail flame part c of about 3,000K, and an intermediate part b between 5,000 and 6,000K in between. Therefore, by controlling the superimposed state of the plasma frames generated from a plurality of torches, it is possible to increase the output and generate a disturbed frame in a different temperature range that cannot be obtained by a single frame, and it is possible to generate a disturbed frame corresponding to the raw material. Ultrafine particles can be efficiently produced by generating a plasma frame in an optimum state.

On the other hand, the raw material charged into the high temperature section of the plasma frame evaporates and is in a vapor state in the high temperature section,
It is considered that the tail portion c and the outer peripheral portion thereof react with the atmospheric gas through the cluster state in the intermediate portion b to become ultrafine particles from nucleation. Therefore, by superimposing a plurality of plasma frames in various states, a plurality of substances can be mixed / combined in a combination of vapor, cluster, or ultrafine particles in various states. FIG. 3 shows a superposed state of plasma frames generated from two plasma torches and a mixed state of materials. That is, in FIG. 3A, since only the tail flame portions of the two plasma frames are overlapped, the material supplied to each of the plasma frames is mixed in a state of being ultra-fine particles. Becomes
In the state of (2), the two materials overlapping in the middle part contact each other in a cluster state to generate composite ultrafine particles. Hereinafter, similarly, when two kinds of substances come into contact with each other in a (3) vapor state, (4) in a cluster state with ultrafine particles,
(5) In the case of contact with the cluster in a vapor state, (6)
In the case of contact with steam in the state of ultrafine particles, furthermore, (4)
In the case of the state opposite to the state of (6), it can be arbitrarily selected according to the characteristics of each material or according to the purpose of the obtained mixed / composite ultrafine particles, whereby the mixture / composite of an arbitrary composition is obtained. Ultra fine particles are obtained. For example, if the high temperature sections of multiple frames are superimposed on each other, a mixed vapor of multiple substances is obtained, and in that state, ultratrace particles are generated at the tail flame, so that multiple substances are completely Ultrafine particles of a novel compound are obtained. On the other hand, when the plurality of plasma frames are in the above-mentioned state (1) or completely in a non-contact state, each substance floats and mixes in the collection area in a state where the ultrafine particles are generated. An ultrafine particle mixture of the substance is obtained.

Further, by increasing the number of torches and the types of raw materials, more complex composite ultrafine particles can be obtained, and it is also possible to synthesize a new material which has not been obtained conventionally. Then, by connecting a plurality of plasma torches to individual plasma power sources and enabling the plasma gas supply system to be individually set and controllable, the gas composition, gas flow rate, and heat amount of the plasma frame generated by each plasma torch are controlled. Can be controlled individually. further,
At the same time, by individually controlling the source supply system, the carrier gas composition, the carrier gas flow rate, the source supply speed, and the type of the source can be individually set and controlled for each plasma frame.

In the present invention, each of the plasma torches is supported by a ball joint or the like so as to be capable of turning motion on the upper part of the reaction vessel.
The projection area of the plasma frame can be arbitrarily controlled. This turning motion has a large degree of freedom, and (a) the position where each plasma frame is in a parallel state without intersecting;
Various positions can be selected, such as (b) a position where they intersect completely and (c) a position where they intersect without contact. This makes it possible to arbitrarily select not only the position in the reaction vessel but also the position to be superimposed in the plasma frame in the above-described states (1) to (7). The raw material can be controlled to any of a vapor state, a cluster state, and an ultrafine state.

[0013]

FIG. 3 shows an embodiment of an apparatus for producing composite ultrafine particles for carrying out the present invention. The apparatus for manufacturing composite ultrafine particles shown in FIG. 3 includes a reaction vessel 1, two plasma torches 2, 2 'hermetically mounted on the upper part of the reaction vessel, and plasma power supplies 3, 3' connected to the plasma torch. A plasma forming gas source 4, raw material feeders 5 and 5 ′ for supplying a powder raw material into a plasma frame, a carrier gas source 6 for supplying a carrier gas to the raw material feeder, an ultrafine particle collector 7 connected to a reaction vessel, It comprises a gas circulation path including a gas circulator 8 for circulating gas between the ultrafine particle collector and the reaction vessel, and an exhaust device 9 for discharging gas in the collector to the outside. The ultrafine particle collector has an inlet 11 connected to the reaction vessel and a gas outlet 12 connected to a gas circulation path and an exhaust device at an upper part.
Is provided, and a filter 13 is provided at the gas outlet, and when the gas passes through the filter from the collection cylinder, the filter captures the ultrafine particles.

Each of the plasma torches 2, 2 'is attached to the reaction vessel so as to be able to swing together with a small amount. In this embodiment, the plasma torches are attached via spherical ball joints 15, 15' so as to maintain airtightness. You can turn around. The ball joint holding portions 16 and 16 ′ holding the ball joints 15 and 15 ′ have a center axis q at the neutral position of each of the plasma torches 2 and 2 ′ which is θ with respect to a vertical center line p of the reaction vessel. At a certain angle, it is attached to the reaction vessel at an angle (FIG. 2).
reference). Thereby, each ball joint 15, 15 '
However, by making it movable within an angle range of maximum θ from the central axis q at the neutral position, the plasma frame projection angle can be set in parallel with the reaction vessel central axis. In the apparatus of this embodiment, θ is set to 20 °, but the set angle of θ can be arbitrarily changed by replacing the ball joint holding portion.

The production of composite ultrafine particles is carried out as follows using the apparatus configured as described above. First, after the inside of the reaction vessel is depressurized by using the exhaust device 9, the atmosphere is adjusted to a predetermined atmosphere, and then the plasma frames F, F 'are generated by each of the plasma torches 2, 2' arranged as shown in the figure. In this state, each of the plasma torches 2, 2 'is turned to form a necessary plasma frame overlap region as illustrated in FIG. Next, the inside of the reaction vessel is set to a predetermined pressure (0.03 to 0.1MP) by the gas circulator 8 and the exhaust device 9.
a is preferable), and a plurality of raw material powders are supplied from one raw material feeder 5 into the plasma frame F, or different raw material powders 20 and 21 ′ are supplied from both raw material feeders 5 and 5 ′. Both plasma frames F,
Put into the high temperature part of F '. Feeding of the raw material into the plasma frame is performed by vibrating the raw material with a vibrating feeder and transporting the raw material with a carrier gas. The powdered raw material is instantaneously melted and vaporized by being injected into the high temperature part of the plasma frame and gasified, and reacts with the atmospheric gas in the reaction vessel while passing through the middle part and tail flame part of the plasma frame to form a cluster. When the raw material is supplied to both plasma torches, the two raw materials come into contact with each other in a selected state due to the overlapping angle of the two plasma frames in the process. It is compounded to form composite ultrafine particles, and the atmosphere gas is converted into a fume-like form, moved into the collection tube, captured by a filter, and collected and collected at a lower portion of the collection tube. Although the apparatus of the above embodiment is an apparatus provided with two plasma torches, the number of plasma torches can be increased to three or more as necessary. Further, the collection of the generated ultrafine particles is not necessarily limited to a filter, and an electrostatic collection method or a collection method using a liquid is also possible.

Next, an example in which Cu / AlN composite ultrafine particles are produced by two plasma torches by the above apparatus will be described. Implementation conditions Only one of the plasma torches (first torch), AlxCu
y (x = 50-90, y = 100-x), and feed a powdered raw material in which Cu and Al are weighed and mixed, and supply the other plasma torch (second
No raw material is supplied to the torch. Reaction vessel internal pressure: 0.07 MPa Reaction vessel atmosphere: Ar gas atmosphere Number of torches: 2 Torch facing angle: Approximately 80 degrees (two plasma frames overlap at high temperature part) First torch operating condition Current: 200 A Voltage: 60 V Gas: Ar = 0.133 l / s N ₂ = 0.116 l / s Raw material supply rate: 0.18 g / s Second torch operating condition Current: 250 A Voltage: 40 V Gas: Ar = 0.166 l / s N ₂ = 0.050 l / s No raw material supplied. TEM observation was performed on the obtained composite ultrafine particles.
As a result, as shown in the TEM photographs of FIGS. 5 and 6, x
With a composition of = 70 or more, Cu-Al composite ultrafine particles having a hexagonal disk-like Al surface having a length of 50 to 100 nm and 10 to 20 hemispherical particles considered to be Cu having a diameter of about 10 nm were confirmed on the surface. . As described above, according to the present embodiment, it is possible to obtain composite ultrafine particles in a state where two kinds of raw materials are completely composited in one particle, and it has been impossible or difficult to achieve uniform mixing / composite superfine particles by the conventional method. It was confirmed that the fine particles could be easily produced.

The apparatus for producing mixed / composite ultrafine particles of the present invention is not necessarily limited to the above embodiment, and various design changes can be made within the scope of the technical idea. For example, in the above embodiment, the raw material powder is supplied to the ball joint portion of the plasma torch. However, in some cases, the raw material powder may be supplied from the center of the top plate of the reaction vessel to the frame overlapping portion. If a hearth that can move up and down is installed in the reaction vessel, a bulk material can be used. Also,
In the above embodiment, the plasma torch is a DC plasma torch, but a high frequency plasma torch can also be used.

[0018]

The present invention has the following special effects. By having a plurality of plasma torches, a high output can be obtained, and by controlling the superposed state of the plasma frames generated from each plasma torch, a disturbed frame having a temperature range that cannot be obtained by a single frame. Can be generated, so that an ultrafine particle can be efficiently produced by generating a plasma flame in an optimum state according to the raw material. Since a plurality of plasma frames can be superimposed in various states, a plurality of substances can be brought into contact with any state of vapor, cluster, or ultrafine particles,
By selecting those combinations, it is possible to control the mixing / compositing of a plurality of substances. This makes it possible to produce uniform mixed / composite ultrafine particles of any composition using metals, intermetallic compounds, ceramics, etc., or a plurality of these materials as raw materials. Synthesis is also possible. The plurality of plasma torches are connected to individual power sources, and the raw material supply system and the plasma gas supply system can be individually controlled, so that the gas composition, gas flow rate, and heat amount of each plasma frame are individually controlled. be able to. In addition, by separately mounting the raw material supply system to the plasma frame, the carrier gas composition, the carrier gas flow rate, the raw material supply speed, and the type of the raw material can be individually set and controlled. The state of ultrafine particle generation can be set, and complete compounding is possible even with a plurality of raw materials having remarkably different melting points and boiling points.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a composite ultrafine particle manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory view of an installation mode of a plasma torch in the apparatus of FIG.

FIG. 3 is an example of a superimposed state of a plasma frame in the apparatus of FIG. 1;

FIG. 4 is a schematic view of a plasma frame.

FIG. 5 is a TEM (transmission electron microscope) photograph showing the particle structure of the composite ultrafine particles manufactured by the apparatus according to the example of the present invention.

6 is a TEM (transmission electron microscope) photograph showing a particle structure in which a main part of the composite ultrafine particle shown in FIG. 5 is enlarged.

Continuing on the front page (72) Inventor Isao Okane 2-1 Higashiura, Kitayama-cho, Toyohashi-shi, Aichi Prefecture Joint Dormitory Takashi Housing 5-201 (72) Inventor Minoru Umemoto 2-9-1-14 Hirakawa Honmachi, Toyohashi-shi, Aichi (72) Inventor Hiroki Kamikita 1-1, Hibarigaoka, Tenhaku-cho, Toyohashi-shi, Aichi Pref. Toyohashi University of Technology (56) References JP-A-3-226509 (JP, A) JP-A-63-221842 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22F 9/04-9/14

Claims (5)

(57) [Claims] 1. A method for producing mixed / composite ultrafine particles by producing mixed / composite ultrafine particles by thermal plasma, wherein a plurality of plasma frames are generated by a plurality of plasma torches, and the plurality of plasma frames are superposed or overlapped. By controlling to a non-contact state, a plurality of material substances are mixed or compounded to produce ultrafine particles.
A method for producing composite ultrafine particles. 2. A method for producing mixed / composite ultrafine particles by producing mixed / composite ultrafine particles by thermal plasma, wherein a plurality of plasma frames are generated by a plurality of plasma torches, and a raw material is placed in each plasma frame. Throwing, controlling the plurality of plasma frames in a superimposed state or a non-contact state, and selecting a state at the time of contact of a plurality of types of raw materials, thereby mixing or complexing a plurality of material substances. To produce mixed / composite ultrafine particles. 3. A mixed / composite in which a raw material is supplied into a thermal plasma flame generated in an airtight reaction vessel, and the raw material is evaporated and condensed to produce mixed / composite ultrafine particles. An apparatus for producing ultrafine particles, comprising a plurality of plasma torches, the plasma torches being at least swingably mounted on a reaction vessel so that generated plasma frames can be controlled to move to a superimposed position and a non-contact position. An apparatus for producing mixed / composite ultrafine particles, characterized in that: 4. The mixing / mixing apparatus according to claim 3, wherein a raw material supply device for supplying a raw material to a plasma frame generated by each plasma torch is provided for each plasma frame.
Composite ultrafine particle manufacturing equipment. 5. The apparatus for producing mixed / composite ultrafine particles according to claim 3, wherein each plasma torch can arbitrarily control a calorific value and a gas composition of a plasma frame generated by each plasma torch.