Manufacturing apparatus of fine particle

Abstract

To provide a manufacturing apparatus of a fine particle with high productivity of the fine particle.SOLUTION: A manufacturing apparatus of a fine particle includes: a raw material supply part configured to supply a raw material for producing a fine particle into a thermal plasma flame; a plasma torch configured to evaporate, by the thermal plasma flame, the raw material supplied by the raw material supply part and with the thermal plasma flame generated inside, to form a mixture in a gaseous state; a plasma generation part configured to generate a modulated induction thermal plasma flame with a temperature condition time-modulated, as the thermal plasma flame inside the plasma torch; a chamber connected to a bottom edge of the plasma torch and configured to generate a fine particle inside; and a flange part provided inside the chamber. The chamber is cylindrical, with an outer shape thereof being circular. The flange part is an annular member having an opening concentric to the outer shape of the chamber.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an apparatus for manufacturing fine particles using plasma generated by high-frequency current, and particularly to an apparatus for manufacturing fine particles in which the temperature field and flow velocity field of the plasma are time-modulated.

Background Art

[0002] Currently, fine particles such as silicon fine particles, oxide fine particles, nitride fine particles, and carbide fine particles are used in a wide variety of fields. As one of the methods for manufacturing such fine particles, there is the thermal plasma method. The thermal plasma method is a method of manufacturing fine particles by instantaneously evaporating a raw material in a thermal plasma flame and then rapidly solidifying the evaporated material. According to the thermal plasma method, it has many advantages such as being clean, highly productive, being able to handle high melting point materials due to its high temperature, and being relatively easy to compound compared to other vapor phase methods. For this reason, the thermal plasma method is actively used as a method for manufacturing fine particles.

[0003] For example, Patent Document 1 describes an apparatus for manufacturing fine particles. The apparatus for manufacturing fine particles in Patent Document 1 includes a raw material supply unit that supplies a raw material for manufacturing fine particles into a thermal plasma flame, an insulator-made plasma torch in which a thermal plasma flame is generated inside and the raw material supplied by the raw material supply unit is evaporated by the thermal plasma flame to form a gaseous mixture, and a plasma generation unit that generates a thermal plasma flame inside the plasma torch. The plasma generation unit includes a first coil that surrounds the plasma torch, a second coil that is installed below the first coil and surrounds the plasma torch, a first power supply unit that supplies a high-frequency current to the first coil, and a second power supply unit that supplies an amplitude-modulated high-frequency current to the second coil. The first coil and the second coil are arranged side by side in the longitudinal direction of the plasma torch.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, fine particles can be manufactured, but at present, further improvement in the productivity of fine particles is desired. An object of the present invention is to provide an apparatus for manufacturing fine particles with high productivity of fine particles.

Means for Solving the Problems

[0006] In order to achieve the above object, Invention [1] is an apparatus for manufacturing fine particles, comprising a raw material supply unit that supplies a raw material for manufacturing fine particles into a thermal plasma flame, a plasma torch in which a thermal plasma flame is generated inside and the raw material supplied by the raw material supply unit is evaporated by the thermal plasma flame to form a gas-phase mixture, a plasma generation unit that generates a modulated induction thermal plasma flame whose temperature state is time-modulated as a thermal plasma flame inside the plasma torch, a chamber that is connected to the lower end of the plasma torch and in which fine particles are generated inside, and a flange portion provided in the chamber. The chamber is cylindrical and has a circular outer shape, and the flange portion is an annular member having an opening concentric with the outer shape of the chamber. Invention [2] is the apparatus for manufacturing fine particles according to Invention [1], wherein the raw material supply unit intermittently supplies the raw material to the thermal plasma flame. Invention [3] is the apparatus for manufacturing fine particles according to Invention [1] or [2], wherein the raw material supply unit supplies the raw material into the thermal plasma flame in a state of being dispersed in particulate form. Invention [4] has a first coil surrounding the plasma torch and a second coil installed below the first coil and surrounding the plasma torch. The first coil and the second coil are arranged side by side in the axial direction of the plasma torch. The plasma generation unit has a first power supply unit that supplies a high-frequency current to the first coil and a second power supply unit that supplies a high-frequency current to the second coil. At least one of the first power supply unit and the second power supply unit amplitude-modulates the high-frequency current. It is the apparatus for manufacturing fine particles according to any one of Inventions [1] to [3]. The invention [5] is a particulate manufacturing apparatus according to any one of inventions [1] to [3], wherein the plasma generation unit includes a coil surrounding the periphery of a plasma torch and a power supply unit that supplies an amplitude-modulated high-frequency current to the coil.

Effect of the Invention

[0007] According to the present invention, it is possible to provide a particulate manufacturing apparatus with high particulate productivity.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying out the Invention

[0009] Hereinafter, based on the preferred embodiments shown in the accompanying drawings, the particle manufacturing apparatus of the present invention will be described in detail. Note that the figures described below are exemplary for explaining the present invention, and the present invention is not limited to the figures shown below. In the following, the "~" indicating a numerical range includes the numerical values described on both sides. For example, if ε is a numerical value ε α ~ numerical value ε β it means that the range of ε is the numerical value ε α and the numerical value ε β and is a range including them. In mathematical notation, it is ε α ≦ ε ≦ ε β is. Also, for various numerical values, unless otherwise specified, they include the error range generally acceptable in the relevant technical field. Hereinafter, a particulate manufacturing apparatus will be described.

[0010] [First Example of Particulate Manufacturing Apparatus] FIG. 1 is a schematic diagram showing a first example of a particulate manufacturing apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic partial cross-sectional view showing an example of a plasma torch of the first example of the particulate manufacturing apparatus according to an embodiment of the present invention. The particulate manufacturing apparatus 10 shown in FIG. 1 (hereinafter simply referred to as the manufacturing apparatus 10) manufactures nano-sized particulates using a raw material for particulate manufacturing. As the raw material for particulate manufacturing, for example, powder is used. Note that the type of the manufacturing apparatus 10 is not particularly limited as long as it is particulates. By changing the composition of the raw material, in addition to metal particulates, particulates such as oxide particulates, nitride particulates, carbide particulates, and oxynitride particulates can be manufactured as particulates.

[0011] [Nano-sized Particulates] Nano-sized particulates are particles having a particle diameter of 200 nm or less. The particle diameter of the nano-sized particulates is preferably 1 to 150 nm, more preferably 1 to 100 nm. Also, the nano-sized particulates are preferably spherical, but are not limited to being spherical. For example, when the diameter of the minor axis of the nano-sized particulates is α and the diameter of the major axis is β, if the ratio β / α is less than 3, they are nano-sized particulates. The particle size of the nano-sized particles is the average value of the particle sizes obtained by measuring the particle sizes of 500 particles randomly extracted in total from 3 to 5 SEM images of the particles acquired using an SEM (scanning electron microscope). It is also possible to perform image analysis on 3 to 5 SEM images, consider the 500 particles randomly extracted as spheres, measure the diameter of the region corresponding to the spheres, and obtain the average value of the particle sizes. The nano-sized particles include those with a β / α ratio of less than 3 as described above. Therefore, for non-spherical particles, the length corresponding to the minor axis and the length corresponding to the major axis are measured, and the β / α ratio is determined.

[0012] The manufacturing apparatus 10 includes a raw material supply unit 12, a plasma torch 14, a chamber 16, a recovery unit 18, a plasma gas supply unit 20, a plasma generation unit 21, a gas supply unit 22, and a control unit 24. <s

[0013] The raw material supply unit 12 is connected to the plasma torch 14 via a hollow supply pipe 13. Also, an intermittent supply unit 15 may be provided in the supply pipe 13 between the raw material supply unit 12 and the plasma torch 14. In the manufacturing apparatus 10, the intermittent supply unit 15 is not an essential component. A chamber 16 is provided below the plasma torch 14, and a recovery unit 18 is provided downstream of the chamber 16. The plasma generation unit 21 is connected to the plasma torch 14, and as will be described later, a thermal plasma flame 100 is generated inside the plasma torch 14 by the plasma generation unit 21.

[0014] The raw material supply unit 12 is for supplying the raw material for manufacturing the particles into the thermal plasma flame 100 generated inside the plasma torch 14. The raw material supply unit 12 is not particularly limited as long as it can supply the raw material into the thermal plasma flame 100. Two methods can be used: supplying the raw material into the thermal plasma flame 100 in a state where the raw material is dispersed in a particulate form, and supplying the raw material in the form of a slurry after atomizing the slurry into droplets into the thermal plasma flame 100.

[0015] For example, when using powder as the raw material for manufacturing fine particles, when the raw material is supplied into the hot plasma flame 100 in the plasma torch 14, the raw material needs to be dispersed in a particulate state. For this reason, for example, the raw material is dispersed in a carrier gas and supplied in a particulate state. In this case, for example, the raw material supply unit 12 quantitatively supplies the powder raw material into the hot plasma flame 100 inside the plasma torch 14 while maintaining the powder raw material in a dispersed state. As the raw material supply unit 12 having such a function, for example, the devices disclosed in Japanese Patent No. 3217415 and Japanese Unexamined Patent Application Publication No. 2007-138287 can be used. For example, the raw material supply unit 12 includes, for example, a storage tank (not shown) for storing the raw material powder, a screw feeder (not shown) for quantitatively conveying the raw material powder, a dispersion unit (not shown) for dispersing the raw material powder conveyed by the screw feeder into a particulate state before it is finally sprayed, and a carrier gas supply source (not shown). The raw material powder is supplied into the hot plasma flame 100 in the plasma torch 14 through the supply pipe 13 together with the carrier gas to which the extrusion pressure is applied from the carrier gas supply source. The configuration of the raw material supply unit 12 is not particularly limited as long as it can prevent aggregation of the raw material powder and spray the raw material powder into the plasma torch 14 in a state where it is dispersed in a particulate state while maintaining the dispersed state. As the carrier gas, for example, an inert gas such as argon gas (Ar gas) or nitrogen gas is used.

[0016] The raw material supply unit 12 that supplies the raw material powder in the form of a slurry can use, for example, the one disclosed in Japanese Patent Application Laid-Open No. 2011-213524. In this case, the raw material supply unit 12 includes a container (not shown) that contains a slurry (not shown) in which the raw material powder is dispersed in a liquid such as water, a stirrer (not shown) that stirs the slurry in the container, a pump (not shown) that applies high pressure to the slurry through the supply pipe 13 and supplies it into the plasma torch 14, and a spray gas supply source (not shown) that supplies a spray gas for atomizing the slurry and supplying it into the plasma torch 14. The spray gas supply source corresponds to a carrier gas supply source. The spray gas is also referred to as a carrier gas. When supplying the raw material in the form of a slurry, the raw material powder is dispersed in a liquid such as water to form a slurry. The mixing ratio of the raw material powder and water in the slurry is not particularly limited. For example, it is 5:5 (50%:50%) by mass ratio.

[0017] When using the raw material supply unit 12 that makes the raw material powder into a slurry and supplies the slurry in an atomized form, the spray gas pressurized by the extrusion pressure from the spray gas supply source is supplied into the hot plasma flame 100 in the plasma torch 14 through the supply pipe 13 together with the slurry. The supply pipe 13 has a two-fluid nozzle mechanism for spraying the slurry into the hot plasma flame 100 in the plasma torch and atomizing it, whereby the slurry is sprayed into the hot plasma flame 100 in the plasma torch 14. That is, the slurry can be atomized. As the spray gas, similar to the above-described carrier gas, for example, an inert gas such as argon gas (Ar gas) or nitrogen gas is used. In this way, the two-fluid nozzle mechanism can apply high pressure to the slurry and spray the slurry with a gaseous spray gas (carrier gas), and is used as one method for atomizing the slurry. Note that the present invention is not limited to the above-described two-fluid nozzle mechanism, and a one-fluid nozzle mechanism may be used. Further, as another method, for example, a method of dropping a slurry onto a rotating disk at a constant speed and atomizing (forming droplets) the slurry by centrifugal force, a method of applying a high voltage to the surface of the slurry to atomize (generate droplets), and the like can be mentioned.

[0018] The plasma torch 14 is cylindrical with a circular outer shape. A thermal plasma flame 100 is generated inside the plasma torch 14, and the raw material supplied by the raw material supply unit 12 is evaporated by the thermal plasma flame 100 to form a gaseous mixture 45. The thermal plasma flame 100 extends in the axial direction D L (longitudinal direction) of the plasma torch 14. As shown in FIG. 2, the plasma torch 14 includes a quartz tube 14a and a high-frequency oscillation coil 14b provided on the outer surface of the quartz tube 14a and surrounding the outside of the plasma torch 14. At the upper part of the plasma torch 14, a supply port 14c into which the supply pipe 13 is inserted is provided at the central part thereof, and a plasma gas supply port 14d is formed at the peripheral part (on the same circumference). Through the supply pipe 13, for example, a powdery raw material and a carrier gas such as argon gas or hydrogen gas are supplied into the plasma torch 14.

[0019] The plasma gas supply port 14d is connected to a plasma gas supply unit 20 by a pipe (not shown), for example. The plasma gas supply unit 20 supplies plasma gas into the plasma torch 14 through the plasma gas supply port 14d. As the plasma gas, for example, argon gas, hydrogen gas, etc. are used alone or in appropriate combinations. In addition to the plasma gas supply unit 20, a sheath gas supply unit (not shown) for supplying sheath gas into the plasma torch 14 may be provided. The same gas as the plasma gas can be used as the sheath gas. Alternatively, instead of the plasma gas supply unit 20, the above-described sheath gas supply unit may be provided.

[0020] Further, the outside of the quartz tube 14a of the plasma torch 14 is surrounded by a concentrically formed quartz tube 14e, and cooling water 14f is circulated between the quartz tubes 14a and 14e to water-cool the quartz tube 14a, preventing the quartz tube 14a from getting too hot due to the hot plasma flame 100 generated inside the plasma torch 14.

[0021] The plasma generation unit 21 generates a hot plasma flame 100 inside the plasma torch 14 as described above. The plasma generation unit 21 includes a first coil 60 surrounding the plasma torch 14 and a second coil 62 installed below the first coil 60 and surrounding the plasma torch 14. The first coil 60 and the second coil 62 are arranged L side by side in the axial direction D of the plasma torch 14. The plasma generation unit 21 further includes a first power supply unit 21a that supplies a first high-frequency current to the first coil 60 and a second power supply unit 21b that supplies a second high-frequency current to the second coil 62. At least one of the first power supply unit 21a and the second power supply unit 21b amplitude-modulates the high-frequency current. That is, at least one of the first high-frequency current from the first power supply unit 21a to the first coil 60 and the second high-frequency current from the second power supply unit 21b to the second coil 62 is amplitude-modulated. For example, the modulation degree of the first high-frequency current is smaller than that of the second high-frequency current. That is, the amplitude change of the first high-frequency current is smaller than the amplitude change of the second high-frequency current. Also, for example, the first high-frequency current and the second high-frequency current are supplied at the same timing. That is, the first high-frequency current and the second high-frequency current have the same phase. Note that the first high-frequency current may be a steady value as described later.

[0022] As described above, the first coil 60 and the second coil 62 are arranged L side by side in the axial direction D of the plasma torch 14, and the second coil 62 is installed below the first coil 60. The first power supply unit 21a and the second power supply unit 21b of the plasma generation unit 21 are both high-frequency power supplies and are independent of each other. Also, in order to reduce the magnetic coupling between the first coil 60 and the second coil 62, it is preferable that the frequency of the high-frequency current of the first power supply unit 21a is different from the frequency of the high-frequency current of the second power supply unit 21b. Thereby, the influence on each other's power supply units can be suppressed. Note that the high-frequency oscillation coil 14b is constituted by the first coil 60 and the second coil 62. The number of turns of the first coil 60 and the number of turns of the second coil 62 are not particularly limited and are appropriately determined according to the specifications of the manufacturing apparatus 10. The materials of the first coil 60 and the second coil 62 are also not particularly limited and are appropriately determined according to the specifications of the manufacturing apparatus 10.

[0023] In the plasma generation unit 21, by using two coils and two independent power supply units, a series structure of inductively coupled plasma can be configured. By configuring a series structure of inductively coupled plasma, a long high-temperature field can be generated in the axial direction D of the plasma torch 14. L By utilizing the above-mentioned long high-temperature field, it is possible to completely evaporate high-melting-point materials. Note that a modulated inductively coupled plasma flame is a thermal plasma flame that is periodically in a high-temperature state and a low-temperature state lower than this high-temperature state at predetermined time intervals, that is, a thermal plasma flame whose temperature state is time-modulated.

[0024] In the plasma generation unit 21, for example, the first power supply unit 21a supplies a first high-frequency current (see FIG. 3) with amplitude modulation to the first coil 60, and the second power supply unit 21b supplies a second high-frequency current (see FIG. 4) with amplitude modulation to the second coil 62. The first high-frequency current supplied to the first coil 60 is also referred to as the first coil current, and the second high-frequency current supplied to the second coil 62 is also referred to as the second coil current. Here, FIG. 3 is a schematic diagram showing an example of the waveform of the high-frequency current of the first power supply unit, and FIG. 4 is a schematic diagram showing an example of the waveform of the high-frequency current of the second power supply unit. FIG. 3 shows the waveform of the above-described amplitude-modulated first high-frequency current, and the amplitude is periodically modulated with respect to time. FIG. 4 shows the waveform of the above-described amplitude-modulated second high-frequency current, and the amplitude is periodically modulated with respect to time. FIG. 4 shows rectangular wave amplitude modulation. Both the first high-frequency current (first coil current) and the second high-frequency current (second coil current) are amplitude-modulated. The amplitude modulation is not limited to the rectangular wave amplitude modulation shown in FIGS. 3 and 4. Needless to say, waveforms composed of repetitive waves including curves such as triangular waves, sawtooth waves, inverse sawtooth waves, or sine waves can be used. Also, the first high-frequency current (first coil current) supplied to the first coil 60 may be unmodulated. In this case, the second high-frequency current (second coil current) is amplitude-modulated, but the first high-frequency current (first coil current) supplied to the first coil 60 may be a steady value, that is, a constant value.

[0025] In the amplitude-modulated first high-frequency current and second high-frequency current, the high value of the current amplitude is defined as HCL (Higher Current Level), the low value of the current amplitude is defined as LCL (Lower Current Level), and in one modulation period, the time when HCL is taken is defined as the on-time, and the time when LCL is taken is defined as the off-time. Further, the ratio of the on-time in one period (on-time / (on-time + off-time) × 100 (%)) is defined as the duty ratio (DF). Also, the ratio of the amplitudes (LCL / HCL × 100 (%)) is defined as the current modulation rate (SCL). The current modulation rate (SCL) indicates the degree of modulation of the current amplitude. 100% SCL indicates an unmodulated state, 50% SCL indicates that the low value of the current amplitude is half of the high value of the current amplitude, and 0% SCL indicates that the current amplitude is most greatly modulated. At 0% SCL, the off-time, that is, the current value of the high-frequency current is 0 A (ampere) in the region where the current amplitude of the high-frequency current is low as described later.

[0026] The amplitude modulation of the first high-frequency current and the amplitude modulation of the second high-frequency current are not particularly limited as long as the modulation degree of the first high-frequency current is smaller than that of the second high-frequency current as described above. The amplitude modulation of the first high-frequency current can be 0% SCL or more and 100% SCL or less. Note that the closer to 0% SCL, the greater the modulation degree, that is, the greater the modulation of the amplitude. Therefore, the amplitude modulation of the second high-frequency current is most preferably 0% SCL. That is, in the region where the current amplitude of the second high-frequency current is low, it is preferable that the current value is 0 amperes. Also, as described above, the first high-frequency current may be a steady value without amplitude modulation. That is, it may be 100% SCL. Note that the on-time (see FIGS. 3 and 4) is the region where the current amplitude of the high-frequency current is high, and the off-time (see FIGS. 3 and 4) is the region where the current amplitude of the high-frequency current is low. The off-time is also referred to as the modulation time. Also, the above-mentioned on-time, off-time, and one cycle are all preferably on the order of microseconds to several seconds.

[0027] In the plasma generation unit 21, for example, when the first power supply unit 21a supplies the amplitude-modulated first high-frequency current (see FIG. 3) to the first coil 60 and the second power supply unit 21b supplies the amplitude-modulated second high-frequency current (see FIG. 4) to the second coil 62, a thermal plasma flame 100 is generated inside the plasma torch 14. The temperature of the thermal plasma flame 100 can be varied with a larger temperature difference by the amplitude-modulated first high-frequency current supplied to the first coil 60 and the amplitude-modulated second high-frequency current supplied to the second coil 62. As a result, the temperature inside the plasma torch 14 can be controlled with a larger temperature difference. Thereby, a variable temperature field with a large temperature difference in which the temperature state of the thermal plasma flame 100 is time-modulated is obtained, and the temperature state of the thermal plasma flame 100 periodically becomes a high-temperature state and a low-temperature state with a temperature lower than the high-temperature state. With the large variable temperature field caused by the thermal plasma flame 100, the particle size of the fine particles can be controlled, and finer particles can be obtained. Further, by setting the first high-frequency current supplied to the first coil 60 to be unmodulated and modulating the second high-frequency current supplied to the second coil 62, the control can be simplified and the temperature of the thermal plasma flame 100 can be varied with a large temperature difference.

[0028] The pressure atmosphere inside the plasma torch 14 is appropriately determined according to the production conditions of the fine particles. For example, it is below atmospheric pressure. Here, the atmosphere below atmospheric pressure is not particularly limited, but for example, it can be set to 5 Torr (666.5 Pa) to 750 Torr (99.975 kPa).

[0029] As shown in FIG. 1, in the chamber 16, from the side closer to the plasma torch 14, the upstream chamber 16a is coaxial with the plasma torch 14 in the direction D L and is connected. A flange portion 17 is provided inside the upstream chamber 16a. Further, a downstream chamber 16b is provided perpendicular to the upstream chamber 16a, and further downstream, a recovery unit 18 having a desired filter 18a for collecting fine particles is provided. In the production apparatus 10, the collection location of the fine particles is, for example, the filter 18a. The chamber 16 (upstream chamber 16a) functions as a cooling tank for generating fine particles, and fine particles are generated inside the chamber 16. The chamber 16 (upstream chamber 16a) is cylindrical and has a circular outer shape. Also, the chamber 16 is made of, for example, stainless steel. In FIG. 1, a gas supply unit 22 is connected to the upstream chamber 16a. Due to the quenching gas supplied from the gas supply unit 22, fine particles of a material corresponding to the raw material (not shown) are generated inside the chamber 16.

[0030] The recovery unit 18 includes a recovery chamber equipped with a filter 18a and a vacuum pump 18b connected via a pipe provided below the recovery chamber. The fine particles sent from the chamber 16 are sucked by the above-mentioned vacuum pump 18b, so that the fine particles are drawn into the recovery chamber and the fine particles are recovered while staying on the surface of the filter 18a.

[0031] The gas supply unit 22 supplies a quenching gas to the thermal plasma flame 100 in the chamber 16. The quenching gas functions as a cooling gas. The gas supply unit 22 includes a gas supply source (not shown) for storing the gas, and a pressure applying unit (not shown) such as a compressor or a blower that applies an extrusion pressure to the quenching gas supplied into the chamber 16. Further, an adjustment valve (not shown) for controlling the gas supply amount from the gas supply source is provided. The gas supply source is selected according to the composition of the quenching gas, and the type of gas is not limited to one kind. When the quenching gas is a mixed gas, a plurality of gas supply sources are prepared. The quenching gas is not particularly limited as long as it exhibits a cooling function. For example, inert gases such as argon gas, nitrogen gas, and helium gas that do not react with the raw materials are used as the quenching gas. In addition to this, the quenching gas may contain hydrogen gas. Further, the quenching gas may contain a reactive gas that reacts with the raw materials. Examples of the reactive gas include hydrocarbon gases such as methane, ethane, propane, butane, acetylene, ethylene, propylene, and butene.

[0032] The gas supply unit 22 supplies the quenching gas (cooling gas) at an angle of, for example, 45° toward the tail portion 100b of the thermal plasma flame 100 (see FIG. 2), that is, the end of the thermal plasma flame 100 on the side opposite to the plasma gas supply port 14d, that is, the terminal end of the thermal plasma flame 100, and supplies the quenching gas (cooling gas) from above to below along the inner wall of the chamber 16. Note that the supply of the quenching gas is not limited to the terminal end of the thermal plasma flame 100.

[0033] The mixture made into the gas phase by the thermal plasma flame 100 is quenched by the quenching gas supplied from the gas supply unit 22 into the chamber 16, and fine particles of the material corresponding to the raw materials are obtained. In addition to this, the above-described quenching gas has additional effects such as contributing to the classification of the fine particles. When particles collide with each other immediately after the generation of fine particles of a material according to the raw material and form aggregates, resulting in non-uniform particle size, it becomes a factor in quality degradation. However, by supplying a quenching gas toward the tail part 100b (termination part) of the thermal plasma flame, the quenching gas dilutes the fine particles, preventing the fine particles from colliding and aggregating with each other. Also, by supplying a quenching gas along the inner wall surface of the chamber 16, adhesion of the fine particles to the inner wall of the chamber 16 is prevented during the process of recovering the fine particles, and the yield of the generated fine particles is improved.

[0034] The method of supplying the quenching gas to the thermal plasma flame 100 of the gas supply unit 22 is not particularly limited, and the quenching gas may be supplied from one direction. Also, the quenching gas may be supplied from a plurality of directions surrounding the thermal plasma flame 100. In this case, the gas supply ports of the quenching gas are provided in a plurality along the circumferential direction on the outer peripheral surface of the chamber 16, for example, at equal intervals, but are not limited to equal intervals. When supplying the quenching gas from a plurality of directions, the supply timing is not particularly limited, and the quenching gas is supplied synchronously from a plurality of directions. In addition to this, for example, the quenching gas may be supplied in the order of clockwise or counterclockwise. In this case, an air flow such as a swirling flow is generated in the chamber 16 by the quenching gas. When supplying the quenching gas from a plurality of directions, it may be supplied randomly without determining the supply order. Note that since fine particles can be generated without using a quenching gas, the gas supply unit 22 is not necessarily required. In the case of a configuration without the gas supply unit 22, the device configuration of the manufacturing apparatus 10 can be simplified, and the manufacturing method of the fine particles can also simplify the process.

[0035] The raw material supply unit 12 supplies the raw material to the thermal plasma flame 100 as described above. For example, the raw material is supplied in a predetermined amount and supplies a constant amount of raw material regardless of time. The raw material supply unit 12 is not limited to supplying a fixed amount of raw material, and may supply the raw material into the thermal plasma flame 100 with the supply amount of the raw material modulated over time. Thereby, a large amount of raw material can be supplied during the on-time shown in FIGS. 3 and 4. Thereby, a large amount of smaller fine particles can be manufactured. In this case, for example, an intermittent supply unit 15 is provided in the supply pipe 13. The intermittent supply unit 15 supplies the raw material into the chamber 16 with time modulation. The change in the supply amount of the raw material is not particularly limited, and may be sinusoidal, triangular, square, or sawtooth, but it is preferably adjusted according to the amplitude modulation of the first high-frequency current supplied to the first coil 60 and the amplitude modulation of the second high-frequency current supplied to the second coil 62. That is, it is preferable that the time change of the amplitude modulation of the first high-frequency current and the amplitude modulation of the second high-frequency current, represented by a function, is the same as the change in the supply amount of the raw material. Thereby, it becomes easier to match the timing between the on-time and the supply of the raw material.

[0036] The intermittent supply unit 15 modulates the supply amount of the raw material over time, for example, by using a solenoid valve (electromagnetic valve) connected to the supply pipe 13. The opening and closing of the solenoid valve are controlled by the control unit 24. Instead of the solenoid valve, a ball valve may be used. Also in this case, the opening and closing of the ball valve are controlled by the control unit 24. The control unit 24 modulates the supply amount of the raw material in a pattern such that, for example, the supply amount of the raw material is increased during the on-time and decreased during the off-time. Thereby, a large amount of smaller fine particles can be manufactured. For this reason, it is preferable that the supply of the raw material increases the supply amount of the raw material during the on-time and decreases the supply amount of the raw material during the off-time. In this way, by supplying the raw material during the on-time, a large amount of the raw material can be evaporated, and as a result, a large amount of fine particles can be generated, and the fine particles can be manufactured efficiently, with high productivity, and in large quantities.

[0037] Inside the chamber 16, as shown in FIG. 2, a flange portion 17 is provided. The flange portion 17 is an annular member having an outer shape of the chamber 16, that is, an opening 17a concentric with a circle. Also, although not shown, the flange portion 17 is cooled, for example, by a water cooling method. For this reason, the flange portion 17 is maintained at approximately the same temperature as the outer wall of the chamber 16. The flange portion 17 is made of, for example, a high melting point metal or stainless steel. When the flange portion 17 is made of a high melting point metal, for example, tungsten is used. The flange portion 17 is joined and fixed inside the chamber 16, for example, by brazing, welding, or the like. Alternatively, for example, the chamber 16 may be divided into upper and lower parts, and a flange may be provided at a portion that abuts against the flange portion 17 and fixed by sandwiching.

[0038] By amplitude modulation of the second high-frequency current, the temperature state of the thermal plasma flame 100 periodically becomes a high temperature state and a low temperature state where the temperature is lower than the high temperature state. Due to this temperature change, in the low temperature state (off time), the temperature inside the chamber 16 at the upper part of the chamber 16 decreases. At this time, the mass density of the gas in the region where the temperature has decreased increases. This increase in mass density is compensated by moving the gas on the outer wall side of the chamber 16 in the radial direction Dw. The gas on the outer wall side of the chamber 16 is relatively low in temperature inside the chamber 16. Due to the above-described increase in mass density, the gas that is relatively low in temperature moves to the center in the radial direction Dw inside the chamber 16. In the manufacturing apparatus 10, this gas flow generates a swirling flow fl in the vicinity of the tail portion 100b of the thermal plasma flame 100 and at the lower surface 17c of the flange portion 17. The swirling flow fl has a cooling effect with a relatively lower temperature than other regions inside the chamber 16. It is considered that due to the swirling flow fl generated in the vicinity of the tail portion 100b of the thermal plasma flame 100, the vapor of the raw material that becomes the source of the fine particles becomes supersaturated, nucleation occurs, and fine particles are generated inside the chamber 16.

[0039] In the manufacturing apparatus 10, a swirling flow fl that travels from below the flange portion 17 toward the center in the radial direction Dw of the chamber 16 is further generated on the lower surface 17c of the flange portion 17. As described above, the swirling flow fl has a relatively low temperature, and nucleation that results in fine particles occurs near the chamber wall on the lower surface 17c of the flange portion 17. It is considered that fine particles are generated near the lower surface 17c of the flange portion 17 of the chamber 16 due to the swirling flow fl. From this, the manufacturing apparatus 10 generates more fine particles than in the case where the flange portion 17 is not present, and as a result, the productivity of the fine particles is increased. Even when the flange portion 17 is not present, a swirling flow fl is generated near the tail portion 100b of the thermal plasma flame 100 as described above. However, compared to the manufacturing apparatus 10, no fine particles are generated near the lower surface 17c of the flange portion 17, so the amount of fine particles generated is small. As a result, when the flange portion 17 is not present, the productivity of the fine particles is low. Note that the swirling flow fl will be described later by showing the results of numerical analysis.

[0040] Note that the position where the flange portion 17 is provided can be a position near the melting point of the fine particles obtained from the position where the raw material vapor exists along the axial direction D in the chamber 16. Further, the position where the flange portion 17 is provided can be, for example, the position of the distance L from the upper portion 16c of the chamber along the axial direction D in the chamber 16 to the upper surface 17b of the flange portion 17. L The distance L is, for example, 60 to 160 mm. L is the position. D The distance L D is, for example, 60 to 160 mm.

[0041] <Method for manufacturing fine particles> Next, a method for manufacturing fine particles using the above-described manufacturing apparatus 10 will be described by taking metal fine particles as an example. First, as the powder of the raw material for the metal fine particles, for example, a powder of Si having a volume average particle diameter of 30 μm or less is put into the raw material supply unit 12. For the plasma gas, for example, argon gas is used. The first power supply unit 21a supplies an unmodulated first high-frequency current to the first coil 60. The second power supply unit 21b supplies an amplitude-modulated second high-frequency current to the second coil 62. Thereby, a thermal plasma flame 100 is generated inside the plasma torch 14. The first high-frequency current supplied to the first coil 60 is not amplitude-modulated and is a constant value. The amplitude modulation of the second high-frequency current supplied to the second coil 62 is, for example, 50% SCL, the modulation period is 20 ms, the on-time is 10 ms, and the off-time is 10 ms.

[0042] Next, as the carrier gas, for example, argon gas is used to pneumatically convey the Si powder and supply it into the thermal plasma flame 100 inside the plasma torch 14 through the supply pipe 13 (first step). The supplied Si powder evaporates in the thermal plasma flame 100 and becomes a gas-phase mixture 45 (see FIG. 2). The gas-phase mixture 45 (see FIG. 2) is cooled by the temperature change of the thermal plasma flame 100 (second step). At this time, as described above, an entrainment flow fl is generated in the chamber 16 by the flange portion 17 from the lower surface 17c of the flange portion 17 toward the center in the radial direction Dw of the chamber 16 from below the chamber 16, and the gas flow enters up to the central portion in the radial direction Dw of the chamber 16, rapidly cooling the surrounding thermal plasma flame. As a result, nucleation of Si fine particles (metal fine particles) occurs even near the central portion in the radial direction of the chamber on the lower surface 17c of the flange portion 17, and a large amount of Si fine particles (metal fine particles) are generated compared to the configuration without the flange portion 17. Then, the Si fine particles (metal fine particles) obtained in the chamber 16 are collected by the filter 18a of the recovery unit 18 by the negative pressure (suction force) from the recovery unit 18 by the vacuum pump 18b. As described above, by providing the flange portion 17, the thermal plasma flame 100 can be periodically changed between a high-temperature state and a low-temperature state with a lower temperature than the high-temperature state in a stable state. Therefore, compared to the case without the flange portion 17, a large amount of fine particles can be generated, and the productivity of the fine particles is high.

[0043] When supplying Si powder into the hot plasma flame 100 inside the plasma torch 14, as described above, it is preferable to increase the supply amount of Si powder during the on-time and decrease the supply amount of Si powder during the off-time. Also, Si powder may be supplied during the on-time and not supplied during the off-time. In any case, since it takes time from when the solenoid valve opens until the raw material is actually conveyed and the supply amount of the raw material in the hot plasma flame 100 increases, it is necessary to control the solenoid valve etc. in consideration of the time taken for the conveyance time. It is carried out at the timing shown in FIGS. 5(a) to (c) described above.

[0044] In the present embodiment, for example, based on the waveform signal 80 whose amplitude is not modulated for the first coil 60 (see FIG. 5(a)) and the waveform signal 82 whose amplitude is amplitude-modulated by a rectangular wave for the second coil 62 (see FIG. 5(a)), the opening and closing timing of the valve is determined in consideration of the conveyance time, and the valve opening and closing timing signal 84 shown in FIG. 5(b) is obtained, and the valve opens and closes at a predetermined time interval. As a result, with the waveform 86 shown in FIG. 5(c), for example, the raw material powder is supplied into the plasma torch 14 during the on-time, and as a result, the raw material can be supplied intermittently. It is preferable to keep the average input power to the first coil 60 and the second coil 62 constant respectively and amplitude-modulate the second high-frequency current to the second coil 62. Also, for example, the pressure inside the plasma torch is kept constant during the production of the fine particles.

[0045] From the above, by the first high-frequency current that is not amplitude-modulated and the second high-frequency current that is amplitude-modulated, a variable temperature field with a large temperature difference due to the thermal plasma flame 100 can be formed. By introducing the raw material during the on-time, more complete evaporation of the raw material can be achieved. Further, the raw material introduced near the on-time is further quenched compared to the non-modulated state, so further suppression of particle growth can be expected. Therefore, by amplitude-modulating the first high-frequency current and the second high-frequency current, an efficient process for generating nano-sized fine particles can be executed. Furthermore, by making the value of the SCL of the second high-frequency current smaller than the value of the SCL of the first high-frequency current, the temperature of the variable temperature field of the thermal plasma flame can be made lower at the off-time. Moreover, due to the entrainment flow fl caused by providing the flange portion 17, more reliable and efficient cooling of the particles is possible. From this, smaller fine particles can be obtained.

[0046] [Second Example of Fine Particle Manufacturing Apparatus] FIG. 6 is a schematic diagram showing a second example of the fine particle manufacturing apparatus according to an embodiment of the present invention, and FIG. 7 is a schematic partial cross-sectional view showing an example of the plasma torch of the second example of the fine particle manufacturing apparatus according to an embodiment of the present invention. In FIGS. 6 and 7, the same components as those in FIGS. 1 to 5 are denoted by the same reference numerals, and detailed descriptions thereof are omitted. The fine particle manufacturing apparatus 10a shown in FIG. 6 (hereinafter simply referred to as the manufacturing apparatus 10a) has a different configuration of the plasma generation unit 21 and the high-frequency oscillation coil 14b compared to the manufacturing apparatus 10 shown in FIG. 1. The manufacturing apparatus 10a does not have a configuration with two coils. As shown in FIG. 7, the high-frequency oscillation coil 14b is constituted by a single coil 63 surrounding the plasma torch 14. Similar to the manufacturing apparatus 10, the manufacturing apparatus 10a has a flange portion 17 provided in the chamber 16.

[0047] The plasma generation unit 21 includes a coil 63 and a power supply unit 21c that supplies a high-frequency current. The power supply unit 21c has a function of supplying an amplitude-modulated high-frequency current to the coil 63 shown in FIG. 7. When a high-frequency current is applied to the coil 63 of the high-frequency oscillation coil 14b, a thermal plasma flame 100 is generated inside the plasma torch 14. The manufacturing apparatus 10a is configured with only one coil 63, and supplies an amplitude-modulated high-frequency current from the power supply unit 21c of the plasma generation unit 21 to the coil 63 to vary the temperature of the thermal plasma flame 100 with a large temperature difference.

[0048] Here, Fig. 8(a) is a graph showing an example of the waveform of the high-frequency current of the power supply unit of the plasma generation unit, (b) is a graph showing the opening and closing timing of the valve, and (c) is a graph showing the supply of the raw material. In the present embodiment, for example, based on the waveform signal 87 with rectangular wave amplitude modulation to the coil 63 shown in Fig. 8(a), considering the conveyance time, the opening and closing timing of the valve is determined, and the opening and closing timing signal 88 of the valve shown in Fig. 8(b) is obtained, and the valve is opened and closed at a predetermined time interval. As a result, with the waveform 89 shown in Fig. 8(c), for example, the raw material powder is supplied into the plasma torch 14 during the on-time, and as a result, the raw material can be supplied intermittently.

[0049] The manufacturing apparatus 10a is configured with only one coil 63, but the temperature state of the thermal plasma flame 100 is time-modulated to vary the temperature of the thermal plasma flame 100. Due to the variation in the temperature of the thermal plasma flame 100, an entrained flow fl is generated on the lower surface 17c of the flange portion 17. This entrained flow fl has a low temperature and a cooling effect. On the lower surface 17c of the flange portion 17, an entrained flow fl with a relatively low temperature is generated, and due to this entrained flow fl, more fine particles are generated in the middle and downstream regions of the chamber 16 compared to the case where there is no flange portion 17. Thereby, the productivity of fine particles is also high in the manufacturing apparatus 10a. The method for manufacturing fine particles of the manufacturing apparatus 10a is the same as the method for manufacturing fine particles using the above-described manufacturing apparatus 10, except that the modulation of the modulated inductive thermal plasma flame is not by the second high-frequency current supplied to the second coil 62, but by the high-frequency current supplied to the coil 63. For this reason, a detailed description thereof is omitted. The method for manufacturing fine particles using the manufacturing apparatus 10a can obtain the same effects as the method for manufacturing fine particles using the manufacturing apparatus 10.

[0050] [Numerical Analysis] The numerical analysis of the manufacturing apparatus will be described below. FIG. 9 is a schematic diagram showing the calculation space for numerical analysis. The unit of the numerical values indicating the dimensions in FIG. 9 is mm. For the numerical analysis, an unsteady electromagnetic thermofluid analysis model was used. The details of the numerical analysis are as described in Ryudai Furukawa, et al., Numerical Study of Nanoparticle Formation in Two-Coil Tandem-Type Modulated Induction Thermal Plasmas with Simultaneous Modulation of Upper- and Lower-Coil Currents, J. Phys. D: Appl. Phys. vol. 55, 044001, 2022 (28pp). FIG. 9 shows the calculation space 90 in the numerical analysis. The calculation space 90 has a plasma torch element 91, a chamber element 92, and a flange element 93. The plasma torch 14 and the chamber 16 extend in the axial direction D L and have a shape symmetric with respect to the radial direction Dw. The calculation space 90 corresponds to one of the regions symmetric with respect to the radial direction Dw about the central axis C. Note that the position in the radial direction Dw is referred to as the radial position.

[0051] The plasma torch element 91 was set to have a length of 440 mm and a radius of 35 mm. The chamber element 92 was set to have a length of 700 mm and a radius of 65 mm starting from the lower end of the plasma torch element 91. It was assumed that sheath gas was introduced into the plasma torch element 91 from the upper part of the plasma torch element 91. Further, a water-cooled tube element 94 representing a water-cooled tube was inserted into the center of the plasma torch element 91. The water-cooled tube element 94 was given as a wall boundary. Outside the torch element, as corresponding to the first coil and the second coil, two 8-turn coil elements 95 and 96 were arranged side by side in the axial direction. The calculation space 90 was discretized by the finite volume method. The plasma torch element 91 and the chamber element 92 were divided in the axial direction D LIt was divided into 115 in the axial direction and 66 in the radial direction Dw. The mesh shape was rectangular, and the mesh size was 10 mm × 1 mm. Also, the flange portion element 93 represents the flange portion provided in the chamber. The temperature condition of this flange portion element 93 was set to 300 K (constant value). In the numerical analysis, the temperature of the flange portion element 93 was numerically analyzed as the same temperature as the outer wall of the chamber, that is, (300 K (constant value)).

[0052] In the numerical analysis, the time-averaged power was set to 10 kW for both the first coil and the second coil. The frequency of the first coil was 420 kHz, and the frequency of the second coil was 210 kHz. The pressure inside the quartz tube was 300 torr. The plasma gas and the quench gas were not supplied. The carrier gas was supplied with Ar at a flow rate of 4 L / min. The sheath gas was supplied with Ar at a flow rate of 90 L / min. The insertion depth of the water-cooled tube element 94 was 150 mm with respect to the torch head (end portion 90a) of the plasma torch element 91. The first high-frequency current supplied to the first coil was unmodulated. That is, it was set to a constant value. The second high-frequency current supplied to the second coil was set to 50% DF (duty ratio) - 50% SCL (current modulation rate). Silicon was used as the raw material, and the raw material was supplied in synchronization with the on-time of the second high-frequency current. The supply of the raw material was 1.0 g / min / rad.

[0053] Condition 1 was that the region of the flange portion element was in the range exceeding 700 mm and less than 730 mm from the end portion 90a of the calculation space 90 and in the range exceeding 35 mm and less than 65 mm from the center plane 90b. . Condition 2 was that the region of the flange portion element was in the range exceeding 800 mm and less than 830 mm from the end portion 90a of the calculation space 90 and in the range exceeding 35 mm and less than 65 mm from the center plane 90b. Condition 3 was a configuration without a flange portion element.

[0054] Figs. 10(a) to (d) are schematic diagrams showing the temperature distributions in the plasma torch and the chamber in the case of Condition 1. Figs. 11(a) to (d) are schematic diagrams showing the temperature distributions in the plasma torch and the chamber in the case of Condition 2. Figs. 12(a) to (d) are schematic diagrams showing the temperature distributions in the plasma torch and the chamber in the case of Condition 3. Fig. 10(a), Fig. 11(a), and Fig. 12(a) show the temperature distributions at the 5.0 ms time points, respectively. Fig. 10(b), Fig. 11(b), and Fig. 12(b) show the temperature distributions at the 10.0 ms time points, respectively. Fig. 10(c), Fig. 11(c), and Fig. 12(c) show the temperature distributions at the 15.0 ms time points, respectively. Fig. 10(d), Fig. 11(d), and Fig. 12(d) show the temperature distributions at the 20.0 ms time points, respectively.

[0055] As a result of the numerical analysis, as shown in Figs. 10(a) to (d) to Figs. 12(a) to (d), it can be seen that the temperature distribution changes temporally with the modulation of the second high-frequency current. In the plasma torch 14 (plasma torch element 91), donut-shaped eddy currents are generated in the thermal plasma flame by electromagnetic induction from the coil. Due to the Joule heat generated by these eddy currents, a high-temperature field of 10,000 K or more is generated during the on-time of the lower coil (coil element 96) corresponding to the second coil, and the temperature decreases during the off-time of the lower coil (coil element 96). Since the boiling point of the silicon used as the raw material is 2800 K, it is considered that the raw material evaporates efficiently during the on-time. Also, in the region directly below the plasma torch 14 (plasma torch element 91), gas flows in in the radial direction Dw. Regarding the cause of the generation of this gas entrainment flow, since the gas temperature at the upper part of the chamber decreases during the off-time of the lower coil (coil element 96), the mass density ρ of the gas at this position increases. Although it tries to replenish the mass to increase the mass density ρ from the surroundings, the gas flowing in from the upper part of the plasma torch 14 (plasma torch element 91) has a fast flow rate and a very low mass density, so it is supplemented with low-temperature gas from the radial direction Dw. The flow of the low-temperature gas thus generated is the entrainment flow fl (see Fig. 2). When the flange portion 17 (flange portion element 93) is provided as in Condition 1 and Condition 2, a gas flow similar to this entrainment flow enters up to the center of the radial direction Dw at a position directly below the flange portion 17 (flange portion element 93), and quenches the surrounding thermal plasma flame. As a result, it is considered that supersaturation occurs in the vapor of the raw material that becomes the source of the fine particles existing in the quenched region, and nucleation occurs to generate fine particles.

[0056] Figs. 13(a) to (d) are schematic diagrams showing the spatial distribution of the zero-order moment in the plasma torch and the chamber in the case of Condition 1. Figs. 14(a) to (d) are schematic diagrams showing the spatial distribution of the zero-order moment in the plasma torch and the chamber in the case of Condition 2. Figs. 15(a) to (d) are schematic diagrams showing the spatial distribution of the zero-order moment in the plasma torch and the chamber in the case of Condition 3. Here, the zero-order moment is the zero-order moment of the particle size distribution and refers to the number density of fine particles in space. The zero-order moment is an equivalent expression of the number density of all nanoparticles. That is, the zero-order moment indicates how many particles exist in a space of 1 m 3 and shows the degree of particle presence. From this, FIGS. 13(a)-(d) to FIGS. 15(a)-(d) show the distribution of the number density of substantially nano-sized total fine particles. From FIGS. 13(a)-(d) to FIGS. 15(a)-(d), the amount of generation of nano-sized fine particles is large in the vicinity of the flange portion. From this, it is shown that the configurations (conditions 1 and 2) provided with the flange portion have a larger amount of generation of nano-sized fine particles than the configuration (condition 3) without the flange portion.

[0057] FIG. 16(a) is a schematic diagram showing the temperature distribution when the input current of condition 1 is at the maximum value, (b) is a schematic diagram showing the temperature distribution when the input current of condition 2 is at the maximum value, and (c) is a schematic diagram showing the temperature distribution when the input current of condition 3 is at the maximum value. FIG. 17(a) is a schematic diagram showing the spatial distribution of the zero-th moment when the input current of condition 1 is at the maximum value, (b) is a schematic diagram showing the spatial distribution of the zero-th moment when the input current of condition 2 is at the maximum value, and (c) is a schematic diagram showing the spatial distribution of the zero-th moment when the input current of condition 3 is at the maximum value. When the input current is at the maximum value, it is the above-mentioned time point of 10.0 ms. FIGS. 16(a), (b) and (c) correspond to FIGS. 10(b), 11(b) and 12(b) respectively. FIGS. 17(a)-(c) show the distribution of the number density of nano-sized total fine particles. FIGS. 17(a), (b) and (c) correspond to FIGS. 13(b), 14(b) and 15(b) respectively.

[0058] The temperature distribution and the number density of nano-sized total fine particles do not show a large difference among conditions 1 to 3 at the position Q2 which is 500 mm from the lower end Q1 of the coil and 90a. The entrainment flow fl is generated at the position Q3 on the lower surface of the flange portion element 93 (flange portion 17), and the temperature decreases at the lower surface of the flange portion element 93. The range extends to the region Q4 below the opening of the flange portion element 93. From this, as shown in FIGS. 17(a) and (b), a large amount of nano-sized fine particles are generated in the region Q4 below the opening of the flange portion element 93.

[0059] Next, the particle size distribution of the fine particles generated under Conditions 1 to 3 will be described. The particle size distribution at each position was assumed to be a lognormal distribution. In addition, the particle size distribution was calculated for each mesh in the region Dc shown in FIG. 9, and the sum of these values was obtained. Note that the particle size distribution in which fine particles having a particle size of 5 nm or less exist was not added. The results are shown in FIGS. 18(a) to (c). The curve 110a shown in FIG. 18(a), the curve 110b shown in FIG. 18(b), and the curve 110c shown in FIG. 18(c) indicate the number of fine particles, respectively. FIG. 18(a) is a graph showing the particle size frequency distribution of the fine particles under Condition 1, (b) is a graph showing the particle size frequency distribution of the fine particles under Condition 2, and (c) is a graph showing the particle size frequency distribution of the fine particles under Condition 3. FIG. 19 is a graph showing the average particle size and the number of fine particles under Conditions 1 to 3. In FIG. 19, the hatched bar indicates the count, and the white bar indicates the average particle size.

[0060] From FIGS. 18(a) to (c) and FIG. 19, under Conditions 1 to 3, Conditions 1 and 2 having a flange portion have a larger amount of fine particle generation than Condition 3 without a flange portion. As shown in FIG. 18(a), Condition 1 had an average diameter d of 54.1 nm, d 50 was 51.2 nm, and the standard deviation σ was 26.5 nm. As shown in FIG. 18(b), Condition 2 had an average diameter d of 44.7 nm, d 50 was 39.8 nm, and the standard deviation σ was 24.9 nm. As shown in FIG. 18(c), Condition 3 had an average diameter d of 49.1 nm, d 50 was 43.6 nm, and the standard deviation σ was 25.2 nm. Note that the above d 50 is the median of the particle size frequency distribution.

[0061] The present invention is basically configured as described above. Although the apparatus for producing fine particles of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various improvements or modifications may of course be made without departing from the gist of the present invention.

Explanation of Signs

[0062] 10, 10a Manufacturing Apparatus 12 Raw Material Supply Section 13 Supply Pipe 14 Plasma Torch 14a Quartz Tube 14b Coil for High - Frequency Oscillation 14c Supply Port 14d Plasma Gas Supply Port 14e Quartz Tube 14f Cooling Water 15 Intermittent Supply Section 16 Chamber 16a Upstream Chamber 16b Downstream Chamber 16c Upper Part of Chamber 17 Flange Section 17a Opening 17b Upper Surface 17c Lower Surface 18 Recovery Section 18a Filter 18b Vacuum Pump 20 Plasma Gas Supply Section 21 Plasma Generation Section 21a First Power Supply Section 21b Second Power Supply Section 21c Power Supply Section 22 Gas Supply Section 24 Control Section 45 Mixture 60 First Coil 62 Second Coil 63 Coil 80 Waveform Signal 82 Waveform Signal 84 Timing Signal 86 Waveform 87 Waveform Signal 88 Timing Signal 89 Waveform 90 Calculation Space 90a End 90b Central Plane 91 Plasma Torch Element 92 Chamber Element 93 flange element 94 water-cooled tube element 95, 96 coil elements 100 thermal plasma flame 100b tail C central axis D L axial direction Dc region Dw radial direction Q1 coil lower end Q 2、 Q3 position Q4 region fl entrained flow

Claims

1. An apparatus for manufacturing fine particles, comprising: a raw material supply unit configured to supply a raw material for manufacturing fine particles into a thermal plasma flame; a plasma torch having a thermal plasma flame generated therein, configured to evaporate the raw material supplied by the raw material supply unit with the thermal plasma flame to form a gaseous mixture; a plasma generation unit configured to generate a modulated inductively coupled thermal plasma flame having a temperature state modulated with time as the thermal plasma flame inside the plasma torch; a chamber connected to a lower end of the plasma torch, where the fine particles are generated inside; and a flange portion provided in the chamber. The chamber is cylindrical with a circular outer shape, and the flange portion is an annular member having an opening concentric with the outer shape of the chamber. An apparatus for manufacturing fine particles.

2. The raw material supply unit intermittently supplies the raw material to the thermal plasma flame. The apparatus for manufacturing fine particles according to Claim 1.

3. The raw material supply unit supplies the raw material into the thermal plasma flame in a state where the raw material is dispersed in particle form. The apparatus for manufacturing fine particles according to Claim 1 or 2.

4. The plasma generation unit includes a first coil surrounding the plasma torch, a second coil installed below the first coil and surrounding the plasma torch, a first power supply unit configured to supply a high-frequency current to the first coil, and a second power supply unit configured to supply a high-frequency current to the second coil. The first coil and the second coil are arranged side by side in the axial direction of the plasma torch. Among the first power supply unit and the second power supply unit, at least one modulates the amplitude of the high-frequency current. The apparatus for manufacturing fine particles according to Claim 1 or 2.

5. The plasma generation unit includes a coil surrounding the plasma torch and a power supply unit configured to supply an amplitude-modulated high-frequency current to the coil. The apparatus for manufacturing fine particles according to Claim 1 or 2.

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