JPS6376802A - Preparation of fine particle stuck with heterogeneous film on surface - Google Patents

Abstract

PURPOSE:To stick uniform films to the entire area around respective fine particles by entraining the fine particles and the fine particles for a heterogeneous film having the m.p. lower than the m.p. of the fine particles in a carrier gas and passing the gas through a plasma forming region, thereby forming the heterogeneous film on the fine particles. CONSTITUTION:The inside of a flow pipe 16 is evacuated to a vacuum through a suction port 29 and the gaseous Ar for carrying is continuously supplied from a supplying means A thereto and is passed through the plasma forming region 31. On the other hand, microwaves are applied to the inside of a cavity resonator 18 by a microwave oscillator 21 to convert the gaseous Ar to plasma in the region 31. For example, fine Al2O3 particles and fine Al particles are respectively supplied from supplying means B, C to the pipe 16 in this state. When the respective particles arrive at the plasma region, the fine Al particles are heated to melt and evaporate by the plasma to the m.p. or above. Since the fine Al2O3 particles are controlled in the temp. so as to maintain the form of this time as it is, the A&l film is evenly stuck onto the fine Al2O3 particles. Then the fine Al2O3 particles sticking to the film arrive at a recovering device 26 and are captured by the filter 28 thereof.

Description

[Detailed description of the invention] The present invention aims to solve the following problems.

(Industrial Application Field) The present invention relates to a method for producing fine particles having a foreign coating attached to their surfaces.

(Prior art) When producing the above-mentioned fine particles,
For example, by placing a large amount of fine particles in a container placed in a heating furnace, and heating raw materials for coating in the furnace and bringing the vapor into contact with the fine particles, the desired fine particles can be obtained. An idea has been devised to do so. However, according to such means, since the fine particles are in contact with each other in the container, there is a problem that the fine particles agglomerate with each other during the heating in the container, and the particle size increases significantly. there were. There was also the problem that the coating adhered unevenly to the fine particles inside the container.

(Problems to be Solved by the Invention) This invention, except for the above-mentioned conventional problems, can produce fine particles having a coating without significantly increasing the particle size. It is an object of the present invention to provide a method for producing fine particles having a different kind of coating attached to the surface thereof, thereby making it possible to produce fine particles having a coating evenly attached to the entire circumference of the particle.

The configuration of the present invention is as follows.

(Means for Solving the Problems) The present invention takes the measures as described in the claims above, and its effects are as follows.

(Function) The particles carried by the carrier gas passing through the plasma region pass through the plasma region in a suspended state. Further, the gas containing coating particles or coating components carried on the carrier gas passing through the plasma generation region is evaporated or decomposed in the plasma generation region. Then, the vapor of the coating particles or the coating component of the gas adheres to the surface of the floating particles as a coating.

(Embodiments) The drawings showing the embodiments of the present application will be described below. In the fine particle manufacturing apparatus shown in FIG.
is a carrier gas supply means, B is a particulate supply means, and C is a target J1.
The particulate supply means for 9 are shown respectively, and 16 is a flow pipe, one end of which is commonly connected to each of the above-mentioned supply means. This flow pipe 1
Reference numeral 6 is made of a material such as a glass tube, a quartz tube, etc., which allows microwave energy to be passed from outside the tube into the tube to convert the gas inside the tube into plasma. 31 is the flow pipe 16
31a and 31b respectively indicate the inlet and outlet of the plasma generation region set within the plasma chamber.

Next, reference numeral 17 denotes a microwave application device exemplified as a plasma generation means attached to the plasma generation region 31.

In this, 18 is a cavity resonator, and its size is such that microwave resonance occurs inside and a standing wave is generated therein, for example, the size is about the same as or twice the wavelength of the microwave. It's just formed. A power unit 20 includes a microwave oscillator 21 and an output control section 22 for adjusting the output of the oscillator. A magnetron is used as an example of the microwave oscillator.

An isolator 23 is provided to absorb reflected microwaves and prevent damage to the oscillator 21, and is designed to allow water to flow as shown by the arrow. 24
A power monitor is used to monitor the power of each of the incident wave heading from the oscillator 21 toward the flow pipe 16 and the reflected wave heading in the opposite direction.

25 is a matching box (referred to as a three-stub tuner);
It is provided to obtain resonance in the cavity resonator 18. The oscillation frequency of the microwave oscillator is, for example, 2.45.
GHz, and the resonance mode of the cavity resonator is, for example, HO
It is I.

Next, reference numeral 26 denotes a recovery device, which is constructed by providing a filter 28 in a case 27 that communicates with the other end of the flow pipe 16. It should be noted that as this recovery device 26, one having any conventionally known configuration can be used. 29 is a suction port connected to a vacuum pump. 30 indicates a valve.

Next, as an example of manufacturing fine particles using the apparatus with the above configuration,
A procedure for producing fine particles of aluminum oxide with an aluminum film attached to the surface will be described. First, the inside of the flow pipe 16 is evacuated by a vacuum pump through the suction port 29, and when a predetermined degree of vacuum is reached, an inert gas such as argon or helium, or a mixture thereof is supplied as a carrier gas from the carrier gas supply means A. It is continuously supplied to the flow pipe 16. Then, the carrier gas flows through the plasma generation region 31 from its inlet 31a to its outlet 31b,
It passes through the recovery device 26 and is drawn through the suction port 29 to the vacuum pump. The supply amount of the carrier gas mentioned above is such that the gas pressure of the carrier gas inside the flow pipe 16 is, for example, 1 to several tens of Torr, and the flow rate of the carrier gas inside the flow pipe 16 is 3 to 30 Torr.
It is preferable to set the speed to about IIl/sec. On the other hand, the microwave oscillator 21 is operated to apply microwaves from the antenna 21a to the inside of the cavity/resonator 18, and the microwaves are applied to the plasma region 31 inside the flow tube 16.

As a result, in the plasma region 31, the carrier gas flowing therethrough is transformed into plasma. In this specification, the region where the carrier gas is turned into plasma by the microwave energy from the plasma-forming means 17 is referred to as the plasma-forming region 31, and in the region 31, the most upstream side with respect to the flow direction of the carrier gas Entrance 31a
The most downstream portions of S are respectively referred to as exits 31b. This plasma region 31 depends on the type and pressure of the gas flowing there,
Depending on the magnitude of the microwave energy exerted from the plasma generation means 17, the magnitude thereof may be large or small. The microwave energy given to the inside of the resonator 18 is controlled by the control unit 2 while being monitored by the monitor 24.
By adjusting 2, the fine particles for coating, which will be described later, are heated to a temperature equal to or higher than their melting point by the plasma of the carrier gas, but the fine particles are set to a value such that they are not heated to a temperature equal to or higher than their melting point.

In the above state, aluminum oxide A1. Fine particles of aluminum are supplied from the coating fine particle supply means C to the flow pipe 16 as coating fine particles that have the property of evaporating at a temperature lower than the melting point of the fine particles and are different from the above fine particles. Then, they flow into the flow pipe 16 in a floating state on the carrier gas, and reach the plasma generation region 31. In this plasma generation region 31, the plasma density is increased to a predetermined density by the microwave applied there, so that the aluminum fine particles are heated to a temperature higher than their melting point by the plasma of the carrier gas. It is heated and melted, resulting in evaporation into its atomic state. On the other hand, aluminum oxide fine particles are not melted and maintain their fine particle form.

In this case, although the carrier gas is turned into plasma in the plasma-forming region 31, the temperature of the gas itself is not so high.

As described above, the aluminum vapor produced by the evaporation of the aluminum fine particles comes into contact with the suspended aluminum oxide fine particles, and forms an aluminum film that is evenly deposited over the entire surface of the aluminum oxide particles. Once the fine particles to which the film has been attached as described above exit the plasma generation region 31, they are cooled by the carrier gas, which is not heated to a very high temperature. The fine particles are then collected by a collection device 26.
and is captured by filter 28 there.

Next, a method for manufacturing fine particles (eg, aluminum oxide) to which a compound coating (eg, titanium nitride TiN) is attached using the above-mentioned apparatus will be described. In this case, the fine particles of aluminum oxide are supplied from the fine particle supply means B to the flow pipe 16.

Further, from the carrier gas supply means A, a gas having a property of decomposing at a temperature lower than the melting point of the fine particles and containing a coating component different from the fine particles, and further acting as a carrier gas, is supplied. Titanium tetrachloride TtC14 and ammonia NHff are continuously supplied to the flow pipe 16 (hydrogen or nitrogen may be mixed or an inert gas such as argon may be mixed to increase the reaction efficiency), and plasma The microwave energy applied to the oxidizing region 31 is the energy necessary to not melt the aluminum oxide fine particles and to turn the gas into plasma and decompose it. By doing as described above, the gas is turned into plasma and decomposed in the plasma formation region 31. Of the decomposed components, the coating components, that is, titanium and nitrogen, combine to form a compound (titanium nitride), and the compound adheres to the surface of the aluminum oxide fine particles as a coating. Or, these coating components are combined on the surface of aluminum oxide fine particles, and a compound (titanium nitride) is formed on the surface.
Forms a film of The aluminum oxide fine particles to which the titanium nitride film has been attached in this way are recovered by the recovery device in the same manner as described above.

Next, another example of the production of film-attached fine particles using the above-mentioned apparatus is shown in Table 1 below. By doing this, the products listed in the table can be obtained.

Table 1 Note 1) It is also a gas containing coating components. Note that both an inert gas such as argon as a carrier gas and nitrogen as a gas containing the coating component may be supplied.

Next, FIG. 2 showing an example of the particulate supply means B will be explained. 1 is a vacuum container, and 1a is an outlet, which is connected to the flow pipe. 2 is connected to a vacuum pump through a suction port. 3
indicates a valve, and 4 is a gas inlet. Reference numeral 5 denotes a raw material support, which consists of pillars 6, 6 made of a conductive material fixed to the container 1 and a raw material support stand 7 attached to the upper end thereof. Raw material support stand 7
is formed using a tungsten plate (referred to as a tungsten boat). Reference numeral 8 indicates the raw material placed on the support stand 7. Reference numeral 9 represents a power supply for electrical heating, which is exemplified as heating means for the raw material, and is connected to the support column 6.

Next, 15 is a mixing chamber, which is connected to the gas inlet 4 via the valve 12. 10 is a carrier gas supply means, 13 is a supply means for a reactive gas for compound formation, and these are connected to the mixing chamber 15 through valves 11 and 14 for adjusting the supply amount, respectively.

With such a configuration, while the inside of the container 1 is at a predetermined degree of vacuum, the carrier gas from the carrier gas supply means 1O, the reactive gas from the reactive gas supply means, or both are mixed. Container 1 through chamber 15 and inlet 4
The liquid is supplied into the container 1 and directed from the outlet 1a of the container to the flow pipe. In addition, electricity is applied from the power source 9 to the raw material support stand 7 via the pillars 6.6, and the support stand 7 generates heat due to its electric resistance, thereby heating the raw material 8. By performing the above operations, the raw material 8 is sequentially evaporated at the place where it is placed (fine particle generation area), and fine particles of the raw material 8 are generated in the vicinity thereof. The generated fine particles are sent out from the outlet 1a to the flow pipe along with the flow of the gas.

As for the coating particulate supply means C, the same structure as the above means B can be used.

In addition, when using the particulate supply means B having the above structure, the carrier gas or the gas containing coating components passed through the flow pipe described above is passed from the gas supply means 10.13 to the container L instead of the supply means A. It may also be supplied to the flow pipe 16.

Next, as the above-mentioned particulate supply means B and C, a particulate generation device using any heating means such as well-known high frequency heating, heating by plasma arc, heating by arc discharge, heating by electron beam, etc. can be used.

Next, FIG. 3 shows another example of means for supplying fine particles and fine particles for coating, and shows an example in which these means are constructed using a common vacuum container.

Such a configuration can be effectively used when the two types of fine particles can be generated in the same atmosphere.

It should be noted that parts that are considered to have the same or equivalent structure as those in the previous figure in terms of function are given the same reference numerals as in the previous figure with the letter e, and redundant explanations are omitted.

(Effects of the Invention) As described above, in the present invention, the coating particles are evaporated or the gas containing coating components is decomposed by the plasma of the carrier gas in the plasma region, and the vapor of the coating particles or the It goes without saying that it is possible to produce fine particles with a foreign film attached to the surface by attaching gas coating components to the surface of fine particles in a suspended state. Since the film is attached to the surface, it is possible to produce fine particles with the above-mentioned film without causing a large increase in particle size due to mutual agglomeration of the fine particles as in the conventional method. This also has the effect of making the particles uniformly coated over the entire periphery of each particle.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and FIG. 1 is a schematic vertical cross-sectional view of a particle production apparatus, FIG. 2 is a schematic vertical cross-sectional view showing an example of a particle supply means, and FIG. 3 is a schematic longitudinal cross-sectional view of a particle supply means. FIG. 7 is a schematic vertical cross-sectional view showing another example. A... Carrier gas supply means, B... Particulate supply means,
C... Coating particle supply means, 31... Plasma generation region. Figure 2 1a Third cause ae 10e /3e

Claims (1)

[Claims] A carrier gas is passed through the plasma generation region, and fine particles are loaded on the carrier gas and passed through the plasma generation region in a suspended state. Fine particles for coating that have the property of evaporating at a temperature lower than the melting point of the fine particles and are different from the above fine particles, or fine particles for coating that have the property of decomposing at a temperature lower than the melting point of the fine particles and different from the above fine particles. A gas containing the components is also loaded, and the coating particles are evaporated or the gas containing the coating components is decomposed by the plasma of the carrier gas in the plasma region, and a vapor of the coating particles or a coating of the gas is formed. A method for producing fine particles having a foreign coating attached to the surface, characterized in that a component for use is attached to the surface of the fine particles in a suspended state.