JP7142241B2 - Microparticle manufacturing apparatus and microparticle manufacturing method - Google Patents

Description

The present invention provides, for example, an electrode material for lithium ion batteries, a catalyst material, a coating material for food packaging film materials, or an ink raw material used for electronic device wiring, etc., and a fine particle production apparatus and fine particle production. Regarding the method.

In recent years, application of nanometer-order fine particles to various devices has been investigated. For example, nickel metal fine particles are currently used in ceramic capacitors, and the use of fine particles having a particle size of 200 nanometers or less and good dispersibility is being studied for next-generation ceramic capacitors.

Furthermore, fine particles of silicon monoxide (SiOx: x = 1 to 1.6), which has a lower oxygen content than silicon dioxide, are utilized as vapor deposition materials for antireflection coatings for optical lenses or gas barrier films for food packaging. there is Recently, it is expected to be applied to negative electrode materials for lithium ion secondary batteries.

As a general method for producing these nanometer-order fine particles, a bulk material as a raw material is introduced together with beads such as ceramic or zirconia, and the material is finely divided by mechanical pulverization, or the material is melted and There are a method of obtaining fine particles by evaporating and injecting into air or water, and a method of chemically obtaining fine particles such as electrolysis or reduction. Among them, there is a method of producing fine particles in a gas phase using thermal plasma (about 10000° C.) such as high-frequency discharge, direct current, or alternating current arc discharge. This method of producing fine particles in the gas phase using this thermal plasma has few impurities (contamination), the produced fine particles have excellent dispersibility, and it is possible to synthesize composite fine particles composed of multiple types of materials. It is very useful from the viewpoint of being easy.

FIG. 4 shows a schematic cross-sectional view of the apparatus for producing fine particles using thermal plasma of Conventional Example 1 as seen from a direction perpendicular to the vertical direction. For the sake of convenience, one direction in the horizontal plane is defined as the x direction, and the vertically upward direction is defined as the z direction.
The reaction chamber 101 includes a material supply device 110, a plurality of electrodes 104 for generating arc discharge, a particle recovery unit 103 for recovering the generated particles 118, and a gas supply pipe (not shown) for supplying gas to the reaction chamber 101. ), a valve for adjusting the pressure, and a pump 113 for exhausting the gas. After argon gas is introduced into the reaction chamber 101 from the gas supply pipe and the pressure is adjusted, AC power is applied to the electrodes 104 from the AC power sources 105 to generate the arc discharge 116 which is thermal plasma. The material particles 117 in the material supply device 110 are introduced together with the carrier gas into the generated arc discharge 116 from the vertically downward direction. The introduced material particles 117 are vaporized and vaporized by the arc discharge 116 , rapidly cooled and solidified in the upper part of the reaction chamber 101 to produce fine particles 118 . The generated fine particles 118 are carried by the gas flow in the reaction chamber 101 and introduced into the fine particle recovery section 103 and recovered by the filter in the fine particle recovery section 103 .

JP-A-2004-263257

5(a) to 5(c) are diagrams schematically showing how the multi-phase AC arc plasma used in Conventional Example 1 is observed by a high-speed camera and how the discharge occurs at certain moments. FIGS. 5A to 5C are cross-sectional views (xy plane) of a portion surrounded by the electrode 104 in FIG. 4 and having an arc discharge 116, viewed from the +z direction. 5(a) to 5(c) represent the tip 120 of the electrode 104 shown in FIG. 4 of Conventional Example 1, and six electrodes 104 are arranged radially at intervals of 60°. is doing. Arc discharge 116 can be generated in the planar direction by applying AC power to the electrodes 104, that is, the electrodes E1 to E6, while shifting the phases by 60°. An arc discharge region 121 at a certain moment shown in FIGS. 5(a) to 5(c) indicates a high temperature region of 5000° C. or higher as a result of gas temperature measurement by spectroscopic analysis. As shown in FIG. 5(a), at a certain moment, an arc discharge D1 is generated from the tip 120 of the electrode E1, and an arc discharge D4 is generated from the tip 120 of the electrode E4. At the next moment (see (b) of FIG. 5), an arc discharge D2 is generated from the electrode E2 and an arc discharge D5 is generated from the electrode E5. Further, at the next instant (see (c) of FIG. 5), an arc discharge D3 is generated from the electrode E3 and an arc discharge D6 is generated from the electrode E6. As shown in FIGS. 5(a) to 5(c), arc discharges D1 to D6 are sequentially generated clockwise from electrode E1 to electrode E6, and discharge is repeatedly generated to electrode E1. At that time, the arc discharge D1 itself also swings from the left to the right with respect to the electrode 104, overlaps with the discharge from the other electrode 104, and the arc discharge area 121 becomes large, and disappears at the next moment. The discharge from the electrode E1 to the electrode E6 is driven at 60 Hz, which is the commercial frequency of AC power, and arc discharge is repeatedly generated with one period of 16.7 ms.

However, the discharge from the electrode E1 to the electrode E6 alone generates a material that is not processed at all (unprocessed) or a material that is melted because the temperature is insufficient to evaporate, and the processing efficiency is low. rice field. It is believed that this is because there is a region 122 where there is no arc discharge temporally and the material slips through it.

SUMMARY OF THE INVENTION In consideration of the conventional problems described above, it is an object of the present invention to provide a fine particle production apparatus and a fine particle production method capable of improving the processing efficiency of material particles and increasing the production amount of fine particles.

In order to achieve the above object, a microparticle production apparatus according to the present invention includes a reaction chamber extending vertically from below to above;
a material supply device connected to a center portion of one end side vertically downward in the reaction chamber and supplying material particles vertically upward into the reaction chamber from a material supply port;
a first electrode placement region having a plurality of lower electrodes to which AC power is applied, protruding radially inward from the inner peripheral wall of the reaction chamber vertically above the material supply device;
a second electrode arrangement area having a plurality of upper electrodes to which alternating current power is applied, protruding radially inward from the inner peripheral wall of the reaction chamber vertically above the first electrode arrangement area;
a recovery unit connected to the other end side vertically above the reaction chamber for recovering fine particles;
a power source capable of changing the frequency of AC power applied to at least one of the lower electrode included in the first electrode placement region and the upper electrode included in the second electrode placement region;
a control unit for setting the frequency of the AC power applied to the lower electrode to a frequency equal to or higher than the frequency of the AC power applied to the upper electrode;
with
An arc discharge is generated by the lower electrode and the upper electrode to generate a plasma in the reaction chamber and produce fine particles from the material particles.

In addition, the method for producing fine particles according to the present invention includes:
supplying material particles from a material supply port vertically upward to a reaction chamber extending along the vertical downward to upward direction;
Alternating current power is applied to a plurality of lower electrodes arranged in the first electrode arrangement region vertically above the material supply port to generate arc discharge, thereby generating plasma in the reaction chamber, and removing at least the material particles. Generate fine particles from a part,
Alternating current power is applied to a plurality of upper electrodes arranged in a second electrode arrangement area vertically above the first electrode arrangement area to generate arc discharge, plasma is generated in the reaction chamber, and the material particles are generating fine particles from at least a portion of
The fine particles are collected vertically above the second electrode arrangement area.

According to the aspect of the present invention, a plurality of electrodes are arranged in a multistage electrode structure, and the frequency of the AC power applied to the lower electrode in the first electrode arrangement region on the material particle supply port side is higher than the commercial frequency. . This increases the probability that the material particles supplied to the central portion of the first electrode arrangement area are processed, and can reduce the amount of unprocessed material. As a result, the evaporation efficiency of the material particles is increased, and a large amount of material particles can be processed, so that the amount of particles generated can be increased, and the production of particles at low cost is possible. can be done.

It is a schematic sectional view seen from a direction perpendicular to the vertical direction of the microparticles|fine-particles manufacturing apparatus which concerns on 1st Embodiment. FIG. 3 is a schematic partial cross-sectional view (xy plan view) of the second electrode arrangement region in the vicinity of the upper electrode of the fine particle manufacturing apparatus of the first embodiment, viewed from the +z direction. FIG. 3 is a schematic partial cross-sectional view (xy plan view) of the first electrode arrangement region in the vicinity of the lower electrode of the fine particle manufacturing apparatus of the first embodiment, viewed from the +z direction. (a) to (c) are schematic diagrams of the existence probability distribution of arc discharge in one cycle of polyphase AC arc plasma measured with a high-speed camera through a bandpass filter. FIG. 2 is a schematic cross-sectional view of the microparticle production apparatus of Conventional Example 1 as seen from a direction perpendicular to the vertical direction; (a) to (c) are cross-sectional views (xy plan views) viewed from the +z direction of a location where arc discharge is generated surrounded by the electrodes in FIG. It is a schematic diagram of the state of discharge for every instant.

A microparticle production apparatus according to a first aspect includes a reaction chamber extending vertically from below to above,
a material supply device connected to a center portion of one end side vertically downward in the reaction chamber and supplying material particles vertically upward into the reaction chamber from a material supply port;
a first electrode placement region having a plurality of lower electrodes to which AC power is applied, protruding radially inward from the inner peripheral wall of the reaction chamber vertically above the material supply device;
a second electrode arrangement area having a plurality of upper electrodes to which alternating current power is applied, protruding radially inward from the inner peripheral wall of the reaction chamber vertically above the first electrode arrangement area;
a recovery unit connected to the other end side vertically above the reaction chamber for recovering fine particles;
a power source capable of changing the frequency of AC power applied to at least one of the lower electrode included in the first electrode placement region and the upper electrode included in the second electrode placement region;
a control unit for setting the frequency of the AC power applied to the lower electrode to a frequency equal to or higher than the frequency of the AC power applied to the upper electrode;
with
A microparticle manufacturing apparatus, wherein arc discharge is generated by the lower electrode and the upper electrode to generate plasma in the reaction chamber, thereby generating microparticles from the material particles.

In the fine particle manufacturing apparatus according to a second aspect, in the above first aspect, the diameter of the circle formed by the tips of the lower electrodes included in the first electrode arrangement area is included in the second electrode arrangement area. The lower electrode and the upper electrode may be arranged so that the diameter of the circle formed by the tip ends of the upper electrode is equal to or less than the diameter of the circle.

In the fine particle manufacturing apparatus according to a third aspect, in the first or second aspect, the lower electrode included in the first electrode arrangement region and the upper electrode included in the second electrode arrangement region are made of the material The lower electrode and the upper electrode may be arranged so as not to overlap each other when viewed vertically from below where the particles flow.

In a fine particle production apparatus according to a fourth aspect, in the third aspect, the lower electrode and the upper electrode may be arranged with a relative displacement of 30° when viewed vertically from above.

A fifth aspect of the microparticle production apparatus according to any one of the first to fourth aspects is that the lower electrode and the upper electrode are projected onto a plane including the direction from the vertically downward direction to the vertically upward direction in which the material particles flow. In this case, the upper electrode and the lower electrode are inclined in the same direction, and the upper electrode may be horizontal or arranged so that the angle with respect to the horizontal plane is smaller than the angle with respect to the horizontal plane of the lower electrode. .

A fine particle manufacturing method according to a sixth aspect supplies material particles from a material supply port vertically upward in a reaction chamber extending vertically downward to upward,
Alternating current power is applied to a plurality of lower electrodes arranged in the first electrode arrangement region vertically above the material supply port to generate arc discharge, thereby generating plasma in the reaction chamber, and removing at least the material particles. Generate fine particles from a part,
Alternating current power is applied to a plurality of upper electrodes arranged in a second electrode arrangement area vertically above the first electrode arrangement area to generate arc discharge, plasma is generated in the reaction chamber, and the material particles are generating fine particles from at least a portion of
The fine particles are collected vertically above the second electrode arrangement area.

A fine particle manufacturing method according to a seventh aspect may be such that, in the sixth aspect, the frequency of the AC power applied to the lower electrode is set to a frequency equal to or higher than the frequency of the AC power applied to the upper electrode. It is desirable to set the frequency to 50 Hz or more and 1000 Hz or less.

Hereinafter, fine particle production apparatuses according to embodiments will be described in detail with reference to the accompanying drawings. In addition, the same code|symbol is attached|subjected about the substantially same member in drawing.

(First embodiment)
FIG. 1 shows a schematic cross-sectional view of a fine particle production apparatus 20 according to the first embodiment as seen from a direction perpendicular to the vertical direction. FIG. 2A is a schematic partial cross-sectional view (xy plan view) of the second electrode arrangement region in the vicinity of the upper electrode in the fine particle manufacturing apparatus according to the first embodiment, viewed from the +z direction. FIG. 2B is a schematic partial cross-sectional view (xy plan view) of the first electrode arrangement region in the vicinity of the lower electrode viewed from the +z direction. For the sake of convenience, one direction in the horizontal plane is defined as the x direction, and the vertically upward direction is defined as the z direction. 1, 2A, and 2B, an example of manufacturing nanometer-order fine particles of silicon will be described.

The microparticle production apparatus 20 according to the first embodiment includes at least a reaction chamber 1 as an example of a reaction chamber, a material supply device 10, a plurality of upper electrodes 4a and lower electrodes 4b that generate an arc discharge 16, and a generation and a fine particle recovery unit 3 as an example of a recovery unit that recovers the fine particles 18 collected therefrom. This fine particle production apparatus 20 can generate an arc discharge 16 in the reaction chamber 1 to produce fine particles 18 from material particles 17 .

Furthermore, in the fine particle manufacturing apparatus 20 according to the first embodiment, in addition to the above configuration, the material supply pipe 11, the discharge gas supply pipe 14 for controlling the flow of the raw material gas in which the material particles 17 and the material are vaporized, and the vaporized A cooling gas supply pipe 15 for cooling the raw material gas is installed. In addition, a pressure control valve 6 and an exhaust pump 7 are provided via a pipe 80 at the rear stage of the fine particle recovery unit 3, so that the pressure in the reaction chamber 1 can be adjusted.

The configuration of this fine particle manufacturing apparatus 20 will be described in detail below.

<Material supply device>
The material supply device 10 is arranged below the bottom portion of the reaction chamber 1 and supplies material particles 17 upward into the reaction chamber 1 from a material supply port 12 at the upper end of the material supply pipe 11 by carrier gas.

A side wall of the reaction chamber 1 has a water cooling mechanism (not shown). Furthermore, the inner surface of the side wall of the reaction chamber 1 is covered with a cylindrical heat insulating member 2 made of a carbon material in order to retain the heat of the arc discharge 16 . As a specific example of the heat insulating member 2, a carbon-based material can be used as the material of the heat insulating member 2. Depending on the type of fine particles to be produced or the type of device to be used, a material ( For example, ceramic-based materials, etc.) may be used.

<Discharge gas supply pipe>
The discharge gas supply pipes 14 are a plurality of discharge gas supply pipes on the lower side of the reaction chamber 1 . They are arranged radially around the circumference at predetermined intervals. Specifically, each discharge gas supply pipe 14 has an opening located on the lower side of the reaction chamber 1 than the material supply port 12, and supplies the discharge gas from the gas supply device 30 via the gas flow rate regulator 31. ing. For example, the discharge gas supply pipe 14 is jetted vertically upward at 30° from the horizontal plane (xy plane) and in a direction inclined at 45° from the radial direction (inward direction) in the horizontal plane as shown in FIG. 2B. , gas can be supplied as a swirling flow. As described above, the discharge gas supply pipe 14 supplies gas in a direction that is vertically upward at 30° and inclined at 45° from the radial direction in the horizontal plane. 4b, the discharge gas supply pipe 14 may generate a gas flow toward the center.

<Cooling gas supply pipe>
The cooling gas supply pipes 15 are a plurality of cooling gas supply pipes on the upper side of the reaction chamber 1. The cooling gas supply pipes 15 are arranged on the upper side of the heat insulating member 2 so that the cooling gas can be supplied toward the center of the reaction chamber 1 around the central axis of the reaction chamber 1. They are arranged radially at predetermined intervals. Specifically, the cooling gas supply pipe 15 has an opening located on the upper side of the reaction chamber 1 from the upper electrode 4a, and supplies the cooling gas from the gas supply device 30 via the gas flow controller 31. . For example, the cooling gas supply pipe 15 ejects the cooling gas vertically upward at 30° from the horizontal plane (xy plane) and radially (inwardly) within the horizontal plane as shown in FIG. 2a. As a result, the gas evaporated and vaporized by the arc discharge 16 can be efficiently cooled, and the particle diameter of the fine particles 18 to be produced can be controlled.

<First electrode placement region and second electrode placement region>
The upper electrode 4a and the lower electrode 4b are arranged above and below the heat insulating member 2 so as to be arranged in two stages vertically with a predetermined interval therebetween. Specifically, the lower electrode 4b is arranged in the first electrode arrangement area (lower electrode arrangement area) 81 on the material supply port side. Further, the upper electrode 4a is arranged in a second electrode arrangement area (upper electrode arrangement area) 82 which is separated from the first electrode arrangement area 81 toward the fine particle collection section. The first electrode arrangement region 81 and the second electrode arrangement region 82 intersect with the direction in which the material particles 17 flow (for example, the upward direction from the bottom) from the vicinity of the material supply port 12 to the fine particle recovery unit 3. (e.g. orthogonal). Each of the regions 81 and 82 is composed of, for example, one plane, and a plurality of electrodes 4b and 4a are arranged in the plane at predetermined angular intervals, respectively, along the plane or inclined at a predetermined angle with respect to the plane. may be

As an example, the metal upper electrode 4a and lower electrode 4b that generate the arc discharge 16 can be arranged in two stages, one above the other, as shown in FIGS. 1, 2A, and 2B. Specifically, for example, the upper electrode 4a is arranged so as to project radially inward while being inclined vertically upward by 5° with respect to the horizontal direction. Six upper electrodes 4a are arranged radially in parallel on the cylindrical inner peripheral wall of the reaction chamber 1 at intervals of 60°. The lower electrode 4b is arranged so as to protrude radially inward while being inclined vertically upward by 30° with respect to the horizontal direction. Six lower electrodes 4b are arranged radially in parallel on the cylindrical inner peripheral wall of the reaction chamber 1 at intervals of 60°. Furthermore, as shown in FIGS. 2A and 2B, the upper electrode 4a and the lower electrode 4b are arranged so as not to overlap each other when viewed from the direction in which the material particles 17 flow (for example, vertically upward from below). . In other words, the upper electrode 4a and the lower electrode 4b are displaced from each other by 30° with respect to the z-axis when viewed from the vertical upper or lower side of the reaction chamber 1 .
Further, by making the upper electrode 4a and the lower electrode 4b horizontal or inclined with respect to the flow direction of the material particles 17, the material particles can be introduced into the plasma without being repelled by the highly viscous thermal plasma. Furthermore, the upper electrode 4a and the lower electrode 4b are inclined in the same direction. , the material can be put on the rising air current in the center, and the spread of the material can be suppressed. These things can raise material processing efficiency.

Further, the diameter of the circle formed between the tips of the lower electrodes 4b is smaller than the diameter of the circle formed between the tips of the upper electrodes 4a. This is because the lower electrode 4b is located very close to the material supply port 12, so that the material particles 17 introduced from the material supply port 12 are introduced into the arc discharge (high temperature region) 16 generated in the lower electrode 4b. high probability. Also, the smaller the discharge area, the higher the power density and the higher the temperature. Conversely, the upper electrode 4a is far from the material supply port 12, and because of the complicated gas flow, the material processed by the arc discharge 16 by the lower electrode 4b and/or the untreated material flowing from the material supply port 12 is removed. It is believed that the distribution of material particles 17 containing the treatment material will be very large. Therefore, it is considered that the larger the diameter of the circle formed between the tips of the upper electrodes 4a, the higher the efficiency of treatment by the arc discharge 16 by the upper electrodes 4a.

The upper electrode 4a and the lower electrode 4b are each composed of a metal electrode, and in order to prevent metal materials from being mixed as impurities in the fine particles 18 to be produced, water cooling and cooling gas are flowed to reduce wear due to evaporation of the metal electrodes. there is As an example of the material of the upper and lower electrodes 4a and 4b, a material obtained by mixing several percent of lanthanum oxide (lanthana) with a tungsten electrode, which is a high-melting-point metal, can be used. Other refractory metals such as tantalum, an electrode material in which several percent of thorium, cerium, yttrium, etc. are mixed with tungsten, or an electrode composed of a carbon material may be used.

As an example, in the embodiment, six upper electrodes 4a and six lower electrodes 4b are arranged radially in two stages, but the present invention is not limited to this. For example, if the number of electrodes is a multiple of 6, the number of electrodes may be increased. Also, 12 electrodes may be arranged on the same plane, a two-stage structure with 6 lower electrodes and 12 upper electrodes, or a multi-stage electrode arrangement of 3 or more stages may be used. Polyphase AC arc plasma, which is an example of plasma generated by electrodes having such a configuration, has a higher degree of freedom in electrode arrangement than other methods of generating thermal plasma. Therefore, the size or shape of the arc discharge (thermal plasma) 16 that evaporates the material particles 17 can be freely designed. Therefore, the multi-phase alternating current arc plasma can be a vertically long discharge, a discharge with a large planar area, or an arbitrary discharge shape according to the treatment, which can improve the treatment efficiency or increase the treatment amount. is possible.

Upper and lower electrodes 4a and 4b are provided with n upper and lower AC power supplies 5a and 5b, respectively (n is an integer of 2 or more; for example, n=6 when each electrode has 6 electrodes). is connected. Specifically, the upper first AC power supply 5a-1, the upper second AC power supply 5a-2, the upper third AC power supply 5a-3, ..., the upper n-th AC power supply 5a-n, are connected to the inverter 40 . In addition, the first AC power supply 5b-1 on the lower side, the second AC power supply 5b-2 on the lower side, the third AC power supply 5b-3 on the lower side, . , are connected to the inverter 41 . Inverters 40 and 41 apply phase-shifted AC power from AC power sources 5a and 5b to the plurality of upper electrodes 4a and the plurality of lower electrodes 4b, respectively, to generate arc discharge 16, which is thermal plasma.

The upper and lower electrodes 4a and 4b are independently movable back and forth in the radial direction with respect to the center of the reaction chamber 1 by an electrode driving device 8 composed of a motor or the like. As an example of the electrode driving device 8, a motor rotates a ball screw forward and backward to axially advance and retreat the electrodes 4a and 4b connected to a nut member screwed onto the ball screw.

<Fine particle recovery part>
The fine particle recovery unit 3 is arranged to be connected to the upper end of the reaction chamber 1 , exhausted by the exhaust pump 7 through the pipe 80 , and recovers the fine particles 18 generated in the reaction chamber 1 . A plurality of electrodes 4a and 4b are arranged in two stages on the side of the middle part of the reaction chamber 1 with a predetermined interval so that the tips protrude inside, and a thermal plasma (that is, An arc discharge) 16 is generated, and the generated thermal plasma 16 produces fine particles 18 from the material particles 17 supplied from the material supply device 10 .

The control device 100 includes the material supply device 10, the fine particle recovery unit 3, the pressure adjustment valve 6, the exhaust pump 7, the gas supply device 30, each gas flow rate regulator 31, and the AC power sources 5a and 5b. , and each electrode driving device 8, respectively. Each operation can be controlled by the control device 100 .

The result of changing the frequency of AC power for generating arc discharge and generating plasma using the above-configured apparatus will be described. FIGS. 3A to 3C are schematic diagrams showing the existence probability distribution of arc discharge in one cycle of multiphase AC arc plasma measured with a high-speed camera through a bandpass filter. Electric power output from the AC power sources 5a-n is applied to the upper electrode 4a of the second electrode arrangement region (upper electrode arrangement region) 82 shown in FIG. was changed to 60 Hz (FIG. 3(a)), 120 Hz (FIG. 3(b)), and 180 Hz (FIG. 3(c)). Plasma light generated by arc discharge was spectroscopically separated by a two-wavelength band-pass filter (675±1.5 nm, 794±1.5 nm) of atomic emission of argon (Ar) and observed with a high-speed camera. . FIG. 3(a) shows the case where the driving frequency of the plasma is 60 Hz, and the black triangular marks "▴" on the periphery indicate the six tips of the upper electrode 4a. The portion colored from gray to black shows the probability distribution that arc discharge existed during one cycle (16.8 ms) in the high temperature range of 7000° C. or higher as a result of gas temperature measurement by spectroscopic analysis. That is, the density corresponds to the degree of probability of existence of arc discharge, and the probability of existence of arc discharge increases as the color becomes darker, that is, closer to black. It can be seen that in FIG. 3(a), the area where the arc discharge existed is larger than when the driving frequency is high in FIGS. 3(b) and 3(c). This indicates that the arc discharge swung significantly to the left and right at a frequency of 60 Hz, as described above. Also, the dark-colored part in the center indicates a probability of 0.7, indicating that 70% of the time in one cycle was 7000° C. or higher. As shown in FIGS. 3(b) and 3(c), when the frequency for driving the plasma is increased, the plasma existence probability distribution concentrates in the central portion. In FIG. 3(c) with a driving frequency of 180 Hz, the spread of the arc discharge near the electrodes is smaller than in the case of FIG. 3(a). The discharge existence probability becomes 1.0, indicating that the arc discharge at 7000° C. or more was continuously present during one cycle.

Based on the results of FIG. 3, by installing the inverter 41 connected to the lower electrode 4b of the first electrode arrangement area (lower electrode arrangement area) 81 on the material supply port side, the output from the AC power supply 5b-n The applied AC power can be applied at a frequency higher than 60 Hz, which is the commercial frequency. Although 60 Hz was used as the commercial frequency this time, 50 Hz may be used. Moreover, it is desirable to set the frequency to 50 Hz or more and 1000 Hz or less. At frequencies over 300 Hz, the discharge concentrates in the center as shown in FIG. Therefore, it is particularly preferable to select a frequency of 50 Hz or more and 300 Hz or less. By adopting this configuration, the material particles 17 that have not spread near the material supply port 12 can be efficiently introduced into the arc discharge, and the processing efficiency can be improved. In addition, even when a large amount of material is introduced, the arc discharge always stays in the central part, so the percentage of particles that pass through without hitting the arc discharge can be extremely reduced, and the treatment efficiency can be improved. In addition, an inverter 40 connected to the upper electrode 4a of the second electrode arrangement area (upper electrode arrangement area) 82 on the fine particle collecting section side is installed. In this way, the AC power output from the AC power supplies 5a-n is converted into the AC power output from the AC power supplies 5b-n by the inverter 41 connected to the lower electrode 4b of the first electrode placement area (lower electrode placement area) 81. It can be set to a frequency equal to or lower than the power frequency. A second electrode placement region (upper electrode placement region) 82 on the fine particle collecting section side is far away from the material supply port 12 and passes through a first electrode placement region (lower electrode placement region) 81 . Therefore, the material particles 17 and the material in the process of being processed spread widely compared to the first electrode placement region (lower electrode placement region) 81 .
Therefore, the frequency of the AC power applied to the upper electrode 4a of the second electrode placement region (upper electrode placement region) 82 by the control unit 100 is changed to the AC power applied to the lower electrode 4b of the first electrode placement region (lower electrode placement region) 81. The frequency is below the power frequency. As a result, the area of the arc discharge by the upper electrode 4a in the second electrode placement region (upper electrode placement region) 82 can be widened, and the processing efficiency of the material particles can be improved.

In this embodiment, the inverters 40 and 41 are installed to make the output frequency of the AC power sources 5a-n and 5b-n higher than the commercial frequency of 60 Hz. An AC power supply with a variable function may be used.

The fine particle recovery unit 3 is arranged to be connected to the upper end of the reaction chamber 1 , exhausted by the exhaust pump 7 through the pipe 80 , and recovers the fine particles 18 generated in the reaction chamber 1 . A plurality of electrodes 4a and 4b are arranged vertically in two stages on the side of the middle portion of the reaction chamber 1 with a predetermined gap therebetween so that their tips protrude inward. A thermal plasma (that is, an arc discharge) 16 is generated in the reaction chamber 1 by the upper electrode 4a and the lower electrode 4b. are manufacturing.

<Fine particle production method>
A fine particle manufacturing method using the fine particle manufacturing apparatus according to the above configuration includes:
generating a thermal plasma 16 by arc discharge;
supplying material particles 17 to the thermal plasma 16;
generating microparticles 18;
It consists of at least three steps. These operations can be automatically performed under the control of the control device 100 .

First, in the reaction chamber 1, AC power is applied to each of the upper electrode 4a and the lower electrode 4b which are arranged in parallel so as to form two or more stages in the direction in which the material particles 17 flow. As a result, arc discharge is generated by each of the upper electrode 4a and the lower electrode 4b, and a vertically long thermal plasma 16 is generated in the direction in which the material particles 17 flow (that is, from vertically downward to vertically upward, z-direction).

Next, material particles 17 are supplied from the material supply port 12 of the material supply device 10 into the area of the thermal plasma 16 .

Next, when the material particles 17 pass through the area of the thermal plasma 16, they evaporate or vaporize into a material gas, and the moment the material gas leaves the area of the thermal plasma 16, the material gas is rapidly cooled. to generate fine particles 18 .

In the following, this fine particle production method will be described in detail along with the actual procedure.

First, the reaction chamber 1, the fine particle recovery section 3, and the material supply device 10 are evacuated to several tens of Pa by the exhaust pump 7, thereby reducing the influence of atmospheric oxygen.

Next, gas is supplied from the gas supply device 30 to the material supply device 10, the discharge gas supply pipe 14, and the cooling gas supply pipe 15 through the gas flow rate regulator 31, and the pressure applied to the front stage of the exhaust pump 7 is The pressure inside the reaction chamber 1 is adjusted by the adjustment valve 6 . From the discharge gas supply pipe 14 on the lower side of the reaction chamber 1, the gas is supplied from a plurality of supply ports, vertically upward from the horizontal plane at 30° and radially inward from the horizontal plane as shown in FIG. ° Spray in a slanted direction. This allows the gas to be supplied as a swirling flow.

The cooling gas supply pipe 15 on the upper side of the reaction chamber 1 supplies gas into the reaction chamber 1 from a plurality of supply ports, and is vertically upward 30° from the horizontal plane (xy plane) and the horizontal plane as shown in FIG. 2a. The cooling gas is jetted radially inward. As a result, the gas evaporated and vaporized by the arc discharge 16 can be efficiently cooled, and the particle diameter of the fine particles 18 to be produced can be controlled.

As an example, in one example of the first embodiment, in order to produce fine silicon particles, gas is supplied from the gas supply device 30 into the reaction chamber 1 through the discharge gas supply pipe 14 and the cooling gas supply pipe 15. Argon is supplied respectively. Specifically, the inside of the reaction chamber 1 was maintained at a desired pressure of 0.3 to 1.2 atmospheres of an inert gas atmosphere of argon, and the following fine particle production process was performed. Here, inert gas is used as the discharge gas and the cooling gas, but both gases may be argon, for example. In order to accelerate the reduction of the material, a trace amount of hydrogen gas and a trace amount of carbonaceous gas are mixed and introduced from the gas supply device 30 into the reaction chamber 1 through the discharge gas supply pipe 14 and the cooling gas supply pipe 15. You may Also, a trace amount of oxygen gas, nitrogen gas, or carbonization-based gas may be mixed to similarly oxidize, nitride, or carbonize the material, or to coat the material with a carbon film.

An arc discharge 16 is then caused to generate a thermal plasma. As an example, the metal upper electrode 4a and lower electrode 4b that generate the arc discharge 16 are arranged in two stages vertically, as shown in FIGS. 1, 2A, and 2B. Specifically, for example, the upper electrode 4a is arranged so as to protrude horizontally or radially inward at 5° vertically upward with respect to the horizontal direction. Six upper electrodes 4a are arranged radially in parallel on the cylindrical inner peripheral wall of the reaction chamber 1 at intervals of 60°. The lower electrode 4b is arranged so as to protrude radially inward at an angle of 30 degrees vertically upward with respect to the horizontal direction in the same direction as the upper electrode 4a. Six lower electrodes 4b are arranged radially in parallel on the cylindrical inner peripheral wall of the reaction chamber 1 at intervals of 60°. Furthermore, as shown in FIGS. 2A and 2B, the upper electrode 4a and the lower electrode 4b are arranged so as not to overlap each other when viewed from the direction in which the material particles 17 flow (for example, vertically upward from below). . In other words, the upper electrode 4a and the lower electrode 4b are arranged with a 30° shift from each other about the z-axis when viewed from the vertical upper or lower side of the reaction chamber 1 .

Alternating current power is applied from upper and lower alternating current power sources 5a and 5b to adjacent electrodes of the upper and lower electrodes 4a and 4b, respectively. As an example, AC power of 60 Hz whose phase is shifted by 60° is applied to six upper electrodes 4a and six lower electrodes 4b from six AC power sources 5a and 5b, respectively, and a thermal plasma of about 10000° C. is generated. A vertically elongated arc discharge 16 was generated. As an example, when there are six upper electrodes 4a and six lower electrodes 4b, it is possible to apply AC power with a phase difference of 60°. Alternating current power of 60 Hz with a phase difference of 30° may be applied to the total of 12 wires. As a result, the upper and lower arc discharges 16 are easily connected, forming the arc discharges 16 that are longer in the vertical direction, and the in-plane distribution is also improved.

When the arc discharge 16 is ignited after the application of the AC power, any two or three of the upper and lower electrodes 4a and 4b are moved toward the center of the reaction chamber 1 by the electrode driving device 8. FIG. After the arc discharge 16 is ignited, the current applied to the upper and lower electrodes 4a and 4b is adjusted to be constant, and the upper and lower electrodes 4a and 4b are arranged in the radial direction (radially arranged upper and lower electrodes). The electrodes 4a and 4b are moved outward from the center of the circle formed by the tip ends of the electrodes 4a and 4b by the electrode driving device 8 to bring the upper and lower electrodes 4a and 4b to desired positions.

Next, the supply of material to be processed is started. As an example, the material particles 17 that are the raw material of the fine particles 18 are placed in the material supply device 10 using silicon powder of about 16 microns. In the first embodiment, particles of 16 microns were used, but depending on the plasma conditions, particles with a diameter of 100 microns or less are evaporated by the thermal plasma 16 to produce fine particles 18 of nanometer order. It is possible to If a material with a particle size greater than 100 microns is used, the material may not be completely evaporated, resulting in micron-sized particles.

As an example of the material supply device 10, a local fluidized powder supply device can be used. In this local fluidization type powder feeder, the feed amount of the material is controlled by the flow rate of the carrier gas and the rotation speed of the vessel into which the material is introduced, and the powder material can be fed to the material feed pipe 11 at a constant rate. Other examples of the material feeder 10 include a surface scanning powder feeder that uses a laser or the like to control the distance between the surface of the powder material and the nozzle, or a hopper that feeds a fixed amount of powder material into the groove. There is also a quantitative powder feeder that sucks with Although any type of powder material supply device may be used, the type of powder material supply device is selected according to the amount of powder material to be supplied, the type of powder material, or the particle size.

As shown in FIG. 1, material particles 17 are sent from material supply device 10 to material supply pipe 11 and introduced into reaction chamber 1 from material supply port 12 . The material particles 17 introduced into the reaction chamber 1 evaporate and vaporize when passing through the arc discharge 16, and the material particles 17 are gasified.

Based on the results of FIG. 3, the inverter 41 connected to the lower electrode 4b of the first electrode arrangement area (lower electrode arrangement area) 81 on the material supply port side causes the AC power output from the AC power supply 5b-n to be converted to the commercial frequency. It is better to apply a frequency higher than 50 Hz or 60 Hz. In particular, it is desirable to set the frequency to 50 Hz or more and 1000 Hz or less. This is because the first electrode placement region is close to the material supply port 12 and the material particles 17 do not spread, so the material concentrates in the central portion of the first electrode placement region 81 . In particular, by setting the frequency of the AC power supply 5b-n to 50 Hz or more and 300 Hz or less, the high temperature region of 7000° C. or more of the arc discharge always exists in the central portion, thereby increasing the processing efficiency. Also, even when a large amount of material is introduced, the arc discharge always exists in the central portion, so the processing efficiency can be improved. When the frequency exceeds 300 Hz, the discharge distribution does not change significantly, so even if the frequency is changed, the treatment efficiency does not change. As an example, here, the frequency of the AC power supply 5b-n is set to 180 Hz by the inverter 41 connected to the lower electrode 4b.

In addition, the inverter 40 connected to the upper electrode 4a of the second electrode arrangement area (upper electrode arrangement area) 82 on the side of the fine particle collecting section converts the AC power output from the AC power supplies 5a-n into the first electrode arrangement area (lower electrode arrangement area). It is desirable that the frequency be equal to or lower than the frequency of the AC power output from the AC power supply 5b-n by the inverter 41 connected to the lower electrode 4b of the electrode arrangement area) 81. The second electrode placement region (upper electrode placement region) 82 on the fine particle collecting section side is far away from the material supply port 12 . Furthermore, since the material particles 17 and the material in process pass through the first electrode arrangement area (lower electrode arrangement area) 81 , the material particles 17 and the material in process spread farther than the first electrode arrangement area (lower electrode arrangement area) 81 . Therefore, as shown in FIG. 3A, by lowering the frequency of the AC power output from the AC power supplies 5a-n, the arc discharge area can be widened and the processing efficiency can be improved. As an example, here, the frequency of the AC power sources 5a-n is set to 60 Hz by an inverter 40 connected to the upper electrode 4a.

Generally, in the arc discharge (thermal plasma) at the location where the material is supplied, the heat of the plasma is taken away by the evaporation of the material particles 17, so the temperature of the plasma at the location where the material is evaporated decreases. Conventionally, when materials are continuously supplied to a continuous discharge with a high frequency of 1 kHz or more such as a general inductively coupled plasma (ICP) torch, the temperature of the plasma drops due to the evaporation of the materials, and the materials completely disappear. It cannot be evaporated and relatively large fine particles are produced, resulting in a poor particle size distribution. In addition, in order to produce fine particles having a desired particle size and to improve the particle size distribution of the produced fine particles, there is no choice but to limit the input amount of the material, resulting in a decrease in throughput.

On the other hand, the arc discharge (polyphase alternating current arc plasma) 16 generated by the upper and lower electrodes 4a and 4b used in the first embodiment is applied to the upper electrode 4a and the lower electrode 4b with alternating currents of different phases. It is generated by applying electric power. Therefore, the arc discharge is pulsed, and high-temperature thermal plasma can be generated at all times.

Since the arc discharge 16 or a thermal plasma such as an ICP torch is a viscous gas, only material particles 17 with a certain velocity are introduced into the arc discharge 16 and treated. Therefore, if the upper electrode 4a or the lower electrode 4b is inclined in the direction in which the gas or the material particles 17 flow, the material particles 17 can be easily introduced into the arc discharge 16 by the flow of the gas or the discharge, thereby improving the treatment efficiency. can be done.

The material supply device 10 and the material supply port 12 are installed below the arc discharge 16 in the vertical direction (z direction). In this fine particle manufacturing apparatus, the material particles 17 are supplied from below the arc discharge 16 in the vertical direction. There, untreated material particles repelled by the arc 16 fall vertically downward by gravity and can be separated from the treated particles 18 located above the arc 16 . These untreated material particles accumulate in an untreated material reservoir 86 partitioned by the cover 13 at the bottom of the reaction chamber 1 and below the material supply port 12 . The material accumulated in the unprocessed material storage section 86 can be returned to the material supply device 10 and reused, thereby increasing material utilization efficiency.

Finally, as shown in FIG. 1, the fine particles 18 generated by the arc discharge 16 are separated from the fine particles by the gas flow from the discharge gas supply pipe 14 and the ascending current or gas exhaust flow caused by the arc discharge 16. transported to 3. Although not shown, the particle recovery unit 3 may be provided with, for example, a cyclone capable of classifying particles having an arbitrary particle diameter or larger and a bag filter capable of recovering desired particles. In addition, when taking out the collected fine particles into the atmosphere, there is a risk of ignition, so leave them in an atmosphere containing about 1% of the atmosphere (oxygen-containing gas) for several hours, perform a slow oxidation treatment, and release them into the atmosphere. preferably taken out. As a result, since the surface of the silicon fine particles has a surface oxide film of several nanometers, it can be taken out safely. By these processes described above, it is possible to recover silicon microparticles of 10 nm or more and 300 nm or less from the bag filter.

In the first embodiment, a method for producing nanometer-order fine particles of silicon (Si) has been described, but the fine particles to be produced are not limited to silicon. For example, carbon materials such as fullerenes or nanotubes, or metals such as nickel (Ni), silver (Ag), copper (Cu), iron (Fe), or glass (SiO ₂ ), silicon nitride (SiN), Fine particles may be generated using an inorganic material such as silicon carbide (SiC), alumina (Al ₂ O ₃ ), or boron nitride (BN) as a fine particle generating material. In addition, by reacting with the gas introduced into the reaction chamber 1, for example, silicon monoxide (SiOx: x=1 to 1.6), silicon nitride (SiNx: x=0.1 to 1 .3) or fine particles of silicon carbide (SiCx: x=0.1-1) may be produced. Furthermore, it can be used to produce composite materials composed of multiple materials, such as having a core of silicon on the inside and covered with amorphous silicon oxide, alumina, or silicon carbide on the outside. can.

It can also be used for the spheroidizing treatment of the materials described above and other materials. By increasing the supply speed of the material or increasing the particle size of the material particles 17, the surfaces of the material particles 17 can be raised to a temperature above the melting point and cooled, so that spherical particles can be formed.

According to the first embodiment, with respect to the direction in which the material particles 17 flow from the vicinity of the material supply port 12 to the recovery unit 3 (the direction from vertically downward to vertically upward, z direction), the material supply port side and an upper electrode placement region 82 separated from the lower electrode placement region 81 toward the collecting section side in the intermediate portion of the reaction chamber 1 . The lower electrode placement region 81 and the upper electrode placement region 82 intersect with each other. A plurality of lower electrodes 4b are arranged in the lower electrode arrangement region 81, and a plurality of upper electrodes 4a are arranged in the upper electrode arrangement region 82, thereby forming a multistage configuration. Furthermore, the inverter 41 connected to the lower electrode 4b of the first electrode arrangement area (lower electrode arrangement area) 81 on the material supply port side can apply power of a commercial frequency of 50 Hz or 60 Hz or higher. In particular, it is desirable to set the frequency to 50 Hz or more and 1000 Hz or less. Further, a frequency lower than that of the first electrode arrangement region (lower electrode arrangement region) 81 can be applied by the inverter 40 connected to the upper electrode 4a of the second electrode arrangement region (upper electrode arrangement region) 82 . With the above configuration, it can be expected that the processing efficiency of the material is increased in both the lower electrode arrangement region 81 and the upper electrode arrangement region 82, and the material processing speed is also greatly improved.

The polyphase AC arc plasma used in the first embodiment is also the same as the polyphase AC arc plasma of Conventional Example 1 shown in FIG. The arc discharge area 121 with arc discharge and the area 122 with no discharge are mixed. In FIG. 5, for ease of understanding, arc discharge areas 121 that are discharging are shown as hatched areas, and areas 122 that are not discharging are shown as areas without hatching. Due to such a discharge form, the material particles 17 introduced from the material supply port 12 into the arc discharge 16 by the lower electrode 4b are repelled by the wall side of the heat insulating member 2 due to the presence or absence of the arc discharge region 121 or due to the complicated rising air current. There are many things. That is, since the discharge of the multiphase AC arc plasma is complicated, the gas flow in the vicinity of the arc discharge region 121 due to the ascending current caused by the arc discharge 116 is also complicated, and the arc discharge 16 is simply moved in the direction in which the material particles 17 pass. It may be difficult to greatly improve the processing efficiency and processing speed as expected only by generating multiple stages.
Therefore, in the first embodiment, it is important to control the drive frequency of the arc discharge in the lower electrode placement region 81 and the upper electrode placement region 82 in order to more reliably improve the processing efficiency and processing speed.

In the first embodiment, the lower electrode 4b of the first electrode arrangement region 81 is applied with power having a commercial frequency of 60 Hz or higher, and the upper electrode 4a of the second electrode arrangement region 82 is applied with the first electrode arrangement region. 81 frequency or less is applied. By configuring in this way, considering the spread of the material particles 17 introduced from the material supply port 12, the arc discharge concentration region and the spread of the arc discharge in the lower electrode arrangement region 81 and the upper electrode arrangement region 82 are controlled. By doing so, the probability that the material particles 17 or the gas from which the material particles 17 are evaporated is introduced into the arc discharge increases, and the evaporation efficiency of the material can be increased.

By appropriately combining any of the various embodiments or modifications described above, the respective effects can be obtained. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, as well as combinations of features in different embodiments or examples.

According to the fine particle production apparatus and the fine particle production method according to the present invention, it is possible to improve the processing efficiency of the material particles, process a large amount of the material particles, and produce the fine particles at a low cost. Therefore, the microparticle production apparatus and microparticle production method according to the present invention are useful as a microparticle production apparatus and microparticle production method used in devices such as lithium ion secondary batteries and ceramic capacitors that require mass production.

Reference Signs List 1, 101 Reaction Chamber 2 Heat Insulating Member 3, 103 Fine Particle Recovery Portion 4a Upper Electrode 4b Lower Electrode 5a, 5b, 105 AC Power Supply 6 Pressure Regulating Valve 7, 113 Exhaust Pump 8 Electrode Drive Device 10, 110 Material Supply Device 11 Material Supply Pipe 12 Material supply port 13 Cover 14 Discharge gas supply pipe 15 Cooling gas supply pipe 16, 116 Arc discharge 17, 117 Material particles 18, 118 Fine particle 20 Fine particle production device 40, 41 Inverter 80 Pipe 81 Lower electrode arrangement area 82 Upper electrode arrangement area 86 Untreated material storage unit 100 Control device 104 Electrode 120 Electrode tip 121 Area of arc discharge (high temperature area)
122 non-arcing area

Claims (6)

a reaction chamber extending along the vertical direction from below to above;
a material supply device connected to a center portion of one end side vertically downward in the reaction chamber and supplying material particles vertically upward into the reaction chamber from a material supply port;
a first electrode placement region having a plurality of lower electrodes to which AC power is applied, protruding radially inward from the inner peripheral wall of the reaction chamber vertically above the material supply device;
a second electrode arrangement area having a plurality of upper electrodes to which alternating current power is applied, protruding radially inward from the inner peripheral wall of the reaction chamber vertically above the first electrode arrangement area;
a recovery unit connected to the other end side vertically above the reaction chamber for recovering fine particles;
a power source capable of changing the frequency of AC power applied to at least one of the lower electrode included in the first electrode placement region and the upper electrode included in the second electrode placement region;
a control unit for setting the frequency of the AC power applied to the lower electrode to a frequency equal to or higher than the frequency of the AC power applied to the upper electrode;
with
A microparticle manufacturing apparatus, wherein arc discharge is generated by the lower electrode and the upper electrode to generate plasma in the reaction chamber, thereby generating microparticles from the material particles. The diameter of the circle formed between the tips of the lower electrodes included in the first electrode placement region is set to be equal to or less than the diameter of the circle formed between the tips of the upper electrodes included in the second electrode placement region. 2. The fine particle manufacturing apparatus according to claim 1, wherein said lower electrode and said upper electrode are arranged in the . The lower electrode included in the first electrode arrangement area and the upper electrode included in the second electrode arrangement area are such that the lower electrode and the upper electrode are aligned when viewed vertically upward from the vertically downward direction through which the material particles flow. 3. The fine particle production apparatus according to claim 1, which is arranged so as not to overlap each other. 4. The fine particle production apparatus according to claim 3, wherein said lower electrode and said upper electrode are arranged with a relative displacement of 30[deg.] when viewed vertically from above. When the lower electrode and the upper electrode are projected onto a plane including the direction from the vertically downward direction to the vertically upward direction in which the material particles flow, the angle of the upper electrode with respect to the horizontal plane is smaller than the angle of the lower electrode with respect to the horizontal plane. The fine particle manufacturing apparatus according to any one of claims 1 to 4, which is installed. supplying material particles from a material supply port vertically upward to a reaction chamber extending along the vertical downward to upward direction;
Alternating current power is applied to a plurality of lower electrodes arranged in the first electrode arrangement region vertically above the material supply port to generate arc discharge, thereby generating plasma in the reaction chamber, and removing at least the material particles. Generate fine particles from a part,
Alternating current power is applied to a plurality of upper electrodes arranged in a second electrode arrangement area vertically above the first electrode arrangement area to generate arc discharge, plasma is generated in the reaction chamber, and the material particles are generating fine particles from at least a portion of
recovering the fine particles vertically above the second electrode arrangement region;
A fine particle manufacturing method ,
A fine particle production method , wherein the frequency of the AC power applied to the lower electrode is set to a frequency equal to or higher than the frequency of the AC power applied to the upper electrode .

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