Apparatus for producing mixture and method for producing mixture

Abstract

To provide an apparatus and a method for producing a mixture for producing a mixture of nano-sized fine particles and nanowires.SOLUTION: An apparatus for producing a mixture of fine particles and nanowires includes: a raw material supply part for supplying a raw material for the mixture to a thermal plasma flame; a plasma torch in which a thermal plasma flame is generated internally and the raw material supplied by the raw material supply part is evaporated by the thermal plasma flame to form a mixture in a vapor phase state; a plasma generation part for generating the thermal plasma flame at the internal of the plasma torch; and a gas supply part for supplying a quenching gas to the thermal plasma flame. The raw material is silicon. The plasma generation part generates a modulation induction thermal plasma flame whose temperature state is time-modulated as a thermal plasma flame, and periodically changes the modulation induction thermal plasma flame into a high temperature state and a low temperature state. The raw material supply part increases the supply amount of the raw material when the modulation induction thermal plasma flame is in a high temperature state. The gas supply part increases the supply amount of the quenching gas when the modulation induction thermal plasma flame is in a high temperature state.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an apparatus for producing a mixture of fine particles and nanowires and a method for producing the mixture, and in particular to an apparatus for producing the mixture and a method for producing the mixture that time-modulates the temperature state of a thermal plasma flame, the supply of raw materials, and the quenching gas used to cool the thermal plasma flame. [Background technology]

[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. Nanowires are also attracting attention as a material that can improve the performance of semiconductor devices, sensors, solar cells, lithium ion batteries, etc. The above-mentioned fine particles and nanowires are used for a variety of purposes. For example, Patent Document 1 describes an electrode material for an electrochemical element in which a plurality of silicon nanowires containing silicon are arranged on a plurality of independent particles containing silicon, the silicon nanowires are entangled with each other to form a silicon nanowire network, and lithium is absorbed into the independent particles and the silicon nanowire network. The silicon nanowire network exists by connecting independent particles with each other, the diameter of the independent particles being about 0.5 to 10 μm, and the diameter of the silicon nanowire being about 10 nm to 500 nm. Patent Document 1 also describes a method for producing an electrode material for an electrochemical element, which includes a step of forming a thermal plasma by applying high-frequency power using a gas containing an inert gas, a step of introducing a raw material containing silicon into the thermal plasma, and a step of sending the raw material that has been exposed to the thermal plasma atmosphere to a support.

[0003] Patent Document 2 discloses a substrate and a first ++ a first polycrystalline silicon layer; ++The present invention relates to a solar cell comprising a first type silicon nanowire layer including first type silicon nanowires grown from a polycrystalline silicon layer, an intrinsic layer provided on a substrate provided with the first type silicon nanowire layer, and a second type doped layer provided on the intrinsic layer. In addition, in Patent Document 2, a first ++ Forming a first polycrystalline silicon layer ++ forming a first polycrystalline silicon layer; ++ The present invention describes a method for forming silicon nanowires, the method including: forming a metal thin film layer on a 1++ type polycrystalline silicon layer; forming a metal nanoparticle layer on the metal thin film layer; forming a metal nanoparticle from the metal thin film layer into metal nanoparticles; and growing a first type silicon nanowire from the 1++ type polycrystalline silicon layer using the metal nanoparticles as seeds. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-269827 A [Patent Document 2] JP 2010-192870 A Summary of the Invention [Problem to be solved by the invention]

[0005] The silicon nanowire network of Patent Document 1 has large independent particle diameters of about 0.5 to 10 μm. Since silicon expands when it is charged, by having silicon nanowires coexist with silicon nanowires and creating space, the volume of the expanded silicon can be absorbed when a solid electrode is formed. However, if the silicon particles have a large particle diameter, a large space is required around the silicon particles, and cracks cannot be suppressed. When the silicon nanowire network of Patent Document 1 is used as an electrode material, it cannot fully function. Furthermore, the method for manufacturing an electrode material in Patent Document 1 does not disclose a method for manufacturing independent particles with a small particle diameter. In Patent Document 2, a first type silicon nanowire layer is formed on a substrate, but there is no description of nanoparticles, nor of a method for producing nanoparticles. Thus, at present, no method for producing a mixture of nano-sized particles and nanowires has been disclosed.

[0006] An object of the present invention is to provide an apparatus and method for producing a mixture of nano-sized particles and nanowires. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, one aspect of the present invention provides an apparatus for producing a mixture of microparticles and nanowires, the apparatus comprising: a raw material supply unit that supplies raw material for the mixture to a thermal plasma flame; a plasma torch in which a thermal plasma flame is generated and the raw material supplied by the raw material supply unit is evaporated by the thermal plasma flame to produce a gas-phase mixture; a plasma generation unit that generates the thermal plasma flame inside the plasma torch; and a gas supply unit that supplies a quenching gas to the thermal plasma flame, the raw material being silicon; the plasma generation unit generates a modulated induction thermal plasma flame as the thermal plasma flame, the temperature state of which is time-modulated, and the modulated induction thermal plasma flame is periodically switched between a high-temperature state and a low-temperature state that is lower than the high-temperature state; the raw material supply unit increases the supply amount of raw material when the modulated induction thermal plasma flame is in a high-temperature state, and the gas supply unit increases the supply amount of quenching gas when the modulated induction thermal plasma flame is in a high-temperature state.

[0008] The raw material supply unit preferably supplies the raw material in a particulate dispersed state into the thermal plasma flame. The difference between the timing when the modulated induction thermal plasma flame reaches a high temperature and the timing when the quenching gas is supplied is δ g The timing when the modulated induction thermal plasma flame switches from a high temperature state to a low temperature state is t e Then, 0<δ g ≦t e It is preferable that:

[0009] Another aspect of the present invention provides a method for producing a mixture of microparticles and nanowires, comprising a first step of supplying a raw material for the mixture to a thermal plasma flame, and a second step of evaporating the raw material in the thermal plasma flame to form a gas-phase mixture and supplying a quenching gas to the thermal plasma flame, wherein the raw material is silicon, and in the first step, a temperature state of the thermal plasma flame is time-modulated to generate a modulated induction thermal plasma flame, the modulated induction thermal plasma flame is periodically switched between a high-temperature state and a low-temperature state that is lower than the high-temperature state, the raw material is intermittently supplied to the modulated induction thermal plasma flame in the high-temperature state, and the supply amount of the raw material is increased when the modulated induction thermal plasma flame is in the high-temperature state, and in the second step, the supply amount of the quenching gas is increased when the modulated induction thermal plasma flame is in the high-temperature state.

[0010] In the first step of supplying the raw material, it is preferable that the raw material is supplied in a dispersed particulate state. The difference between the timing when the modulated induction thermal plasma flame reaches a high temperature and the timing when the quenching gas is supplied is δ g The timing when the modulated induction thermal plasma flame switches from a high temperature state to a low temperature state is t e Then, 0<δ g ≦t e It is preferable that: Effect of the Invention

[0011] According to the present invention, a mixture of particles and nanowires can be produced. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of an apparatus for producing a mixture of fine particles and nanowires according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic partial cross-sectional view showing an example of a plasma torch of an apparatus for producing a mixture of fine particles and nanowires according to an embodiment of the present invention. [Diagram 3] 11 is a graph illustrating a change over time in a coil current during pulse modulation. [Figure 4]Graph (a) is a graph showing a pulse control signal for modulating the coil current, graph (b) is a graph showing the timing of supplying the quenching gas, graph (c) is a graph showing the timing of opening and closing the valve for supplying the raw material, and graph (d) is a graph showing the supply of the raw material. [Diagram 5] FIG. 2 is a schematic diagram showing an SEM image of Experimental Example 1. [Figure 6] FIG. 2 is a schematic view showing an SEM image of Experimental Example 2. [Figure 7] FIG. 13 is a schematic view showing an SEM image of Experimental Example 3. [Figure 8] FIG. 13 is a schematic view showing an SEM image of Experimental Example 4. [Figure 9] FIG. 13 is a schematic view showing an SEM image of Experimental Example 5. [Figure 10] FIG. 13 is a schematic view showing an SEM image of Experimental Example 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the mixture manufacturing apparatus and the mixture manufacturing method of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings. It should be noted that the drawings described below are illustrative for explaining the present invention, and the present invention is not limited to the drawings shown below.

[0014] (Mixture manufacturing equipment) Fig. 1 is a schematic diagram showing an example of an apparatus for producing a mixture of fine particles and nanowires 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 apparatus for producing a mixture of fine particles and nanowires according to an embodiment of the present invention. Fig. 3 is a graph illustrating the time change of the coil current during pulse modulation. 1 shows an apparatus 10 for producing a mixture of fine particles and nanowires (hereinafter, simply referred to as the apparatus 10), which produces a mixture of silicon fine particles and silicon nanowires by using silicon as a raw material for the mixture of fine particles and nanowires. For example, silicon powder is used as the raw material for the mixture.

[0015] [Mixture] Here, the fine particles are nano-sized fine particles with a particle diameter of about 10 to 200 nm. The particle diameter of the fine particles is preferably 10 to 150 nm. The particle diameter of the fine particles is the average particle diameter of the fine particles in the 10 field images obtained by acquiring images of the fine particles in 10 fields of view using an SEM and measuring the particle diameter of the fine particles in each field image. The silicon fine particles are made of silicon. The fine particles may have a surface supported or coated with a substance other than the fine particles, such as carbon. A nanowire is one with a diameter of about 20 to 50 nm and a length of 10 times or more of the diameter. As long as the length of the nanowire is 10 times or more of the diameter, there is no particular upper limit to the length, and it is subject to restrictions such as manufacturing conditions. A silicon nanowire is one made of silicon. Note that, like the above-mentioned fine particles, the surface of the nanowire may be supported or coated with a substance other than the one that constitutes the nanowire, such as carbon. The mixture includes the above-mentioned particles and nanowires.

[0016] The manufacturing apparatus 10 shown in FIG. 1 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. The raw material supply section 12 is connected to a plasma torch 14 via a hollow supply pipe 13 . In addition, an intermittent supply unit 15, which will be described later, is provided in the supply pipe 13 between the raw material supply unit 12 and the plasma torch 14. The raw material supply unit 12 is connected to a valve 30c of the intermittent supply unit 15 provided above the plasma torch 14. A chamber 16 is provided below the plasma torch 14, and a recovery section 18 is provided in the chamber 16. A plasma generating section 21 is connected to the plasma torch 14, and a thermal plasma flame 100 is generated inside the plasma torch 14 by the plasma generating section 21, as described below.

[0017] The raw material supply unit 12 is for supplying raw materials for the mixture into a 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 for the mixture into the thermal plasma flame 100, and two types of methods can be used: one in which the raw material for the mixture is supplied to the thermal plasma flame 100 in a particulate dispersed state, and one in which the raw material for the mixture is made into a slurry and the slurry is supplied to the thermal plasma flame 100 in the form of droplets. For example, the raw material for the mixture is silicon, and for example, silicon powder is used. The average particle size of the silicon powder is appropriately set so that it can be easily evaporated in the thermal plasma flame. The average particle size of the silicon powder is, for example, 100 μm or less, preferably 10 μm or less, and more preferably 5 μm or less, in terms of BET diameter.

[0018] For example, when silicon powder is used as the raw material for the mixture (hereinafter, the raw material for the mixture is also simply referred to as raw material), the raw material needs to be dispersed in a particulate form when it is supplied to the thermal plasma flame 100 in the plasma torch 14. For this reason, for example, the raw material is supplied in a particulate form by being dispersed in a carrier gas. In this case, for example, the raw material supply unit 12 quantitatively supplies the raw material in a particulate form to the thermal plasma flame 100 inside the plasma torch 14 while maintaining the powder raw material in a dispersed state. For example, the devices disclosed in Japanese Patent No. 3217415 and Japanese Patent Laid-Open No. 2007-138287 can be used as the raw material supply unit 12 having such a function. For example, the raw material supply unit 12 includes a storage tank (not shown) for storing raw material powder, a screw feeder (not shown) for transporting a fixed amount of the raw material powder, a dispersion unit (not shown) for dispersing the raw material powder transported by the screw feeder into particles before it is finally dispersed, and a carrier gas supply source (not shown). The raw material powder is supplied, together with carrier gas under extrusion pressure from a carrier gas supply source, through a supply pipe 13 into a thermal plasma flame 100 in a plasma torch 14 . The configuration of the raw material supply unit 12 is not particularly limited as long as it can prevent the raw material powder from agglomerating, maintain the dispersed state, and spray the raw material powder in a particulate dispersed state into the plasma torch 14. As the carrier gas, for example, an inert gas such as argon gas (Ar gas) or nitrogen gas is used.

[0019] The raw material supplying section 12 that supplies the raw material powder in the form of a slurry can be, for example, that disclosed in JP 2011-213524 A. In this case, the raw material supplying section 12 has a container (not shown) for containing a slurry (not shown) in which the raw material powder is dispersed in a liquid such as water, an agitator (not shown) for agitating the slurry in the container, a pump (not shown) for applying high pressure to the slurry through a supply pipe 13 and supplying it into the plasma torch 14, and a spray gas supply source (not shown) for supplying a spray gas for turning the slurry into droplets and supplying them into the plasma torch 14. The spray gas supply source corresponds to a carrier gas supply source. The spray gas is also called a carrier gas. When the raw material is supplied in the form of a slurry, the raw material powder is dispersed in a liquid such as water to form a slurry. The mixture ratio of the raw material powder to water in the slurry is not particularly limited, and is, for example, 5:5 (50%:50%) by mass.

[0020] When using a raw material supply unit 12 that turns raw material powder into a slurry and supplies the slurry in the form of droplets, the spray gas that is extruded and pressurized from the spray gas supply source is supplied together with the slurry through the supply pipe 13 into the thermal plasma flame 100 in the plasma torch 14. The supply pipe 13 has a two-fluid nozzle mechanism for spraying the slurry into the thermal plasma flame 100 in the plasma torch and turning it into droplets, and this allows the slurry to be sprayed into the thermal plasma flame 100 in the plasma torch 14. In other words, the slurry can be turned into droplets. As with the above-mentioned carrier gas, an inert gas such as argon gas (Ar gas) or nitrogen gas is used as the spray gas. In this way, the two-fluid nozzle mechanism can apply high pressure to the slurry and spray the slurry using an atomizing gas (carrier gas), and is used as one method for turning the slurry into droplets. The method is not limited to the two-fluid nozzle mechanism described above, and a one-fluid nozzle mechanism may also be used. Other methods include, for example, a method in which the slurry is dropped onto a rotating disk at a constant speed to form droplets (form droplets) by centrifugal force, and a method in which a high voltage is applied to the surface of the slurry to form droplets (generate droplets).

[0021] The plasma torch 14 generates a thermal plasma flame 100 therein, and the raw material supplied by the raw material supply unit 12 is evaporated by the thermal plasma flame 100 to form a mixture 45 in a gas phase state. 2, the plasma torch 14 is composed of a quartz tube 14a and a high-frequency oscillation coil 14b that is provided on the outer surface of the quartz tube 14a and surrounds the outside of the plasma torch 14. A supply port 14c into which the supply tube 13 is inserted is provided in the center of the upper part of the plasma torch 14, and a plasma gas supply port 14d is formed around the periphery (on the same circumference). A supply pipe 13 supplies, for example, a powdered raw material and a carrier gas such as argon gas or hydrogen gas into a plasma torch 14 .

[0022] The plasma gas supply port 14d is connected to a plasma gas supply unit 20, for example, by a pipe (not shown). The plasma gas supply unit 20 supplies a 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 combination.

[0023] In addition, 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 and prevent the quartz tube 14a from becoming too hot due to the thermal plasma flame 100 generated inside the plasma torch 14.

[0024] The plasma generating unit 21 has a high-frequency power source (not shown) and applies a high-frequency current to the high-frequency oscillation coil 14b. When a high-frequency current is applied to the high-frequency oscillation coil 14b, a thermal plasma flame 100 is generated inside the plasma torch 14. The plasma generating unit 21 has a high frequency modulated induction thermal plasma generating unit 26 . A thermal plasma flame 100 is generated inside the plasma torch 14 by the high frequency modulated induction thermal plasma generator 26, and the temperature state of the thermal plasma flame 100 is time modulated so that the temperature state of the thermal plasma flame 100 periodically changes between a high temperature state and a low temperature state that is lower than the high temperature state. A thermal plasma flame that is periodically changed between a high temperature state and a low temperature state that is lower than the high temperature state at a specified time interval, i.e., a thermal plasma flame whose temperature state is time-modulated, is called a modulated induction thermal plasma flame.

[0025] The high frequency modulated induction thermal plasma generator 26 supplies a high frequency current to the high frequency oscillation coil 14b (see FIG. 2) for generating the thermal plasma flame 100, and can modulate the amplitude of the high frequency current to the high frequency oscillation coil 14b at predetermined time intervals. Hereinafter, the high frequency current supplied to the high frequency oscillation coil 14b for generating the thermal plasma flame 100 is referred to as the coil current. High frequency modulated induction thermal plasma generator 26 has high frequency inverter power supply 28a, impedance matching circuit 28b, pulse signal generator 28c, and FET gate signal circuit 28d.

[0026] The MOSFET inverter power supply constituting the high frequency inverter power supply 28a has a function capable of modulating the amplitude of a current, and can amplitude modulate the coil current. The high frequency inverter power supply 28a includes, for example, a rectifier circuit and a MOSFET inverter circuit. In the high frequency inverter power supply 28a, the rectifier circuit uses, for example, three-phase AC as an input power supply, and after AC-DC conversion is performed by a three-phase full-wave rectifier circuit, the output voltage value is changed by a DC-DC converter using an IGBT (insulated gate bipolar transistor).

[0027] The MOSFET inverter circuit is connected to a rectifier circuit and converts the direct current obtained by the rectifier circuit into alternating current, which causes the inverter output, i.e., the coil current, to be amplitude modulated (AM modulated). An impedance matching circuit 28b is connected to the output side of the high frequency inverter power supply 28a. This impedance matching circuit 28b is configured with a series resonant circuit consisting of a capacitor and a resonant coil, and performs impedance matching so that the resonant frequency of the load impedance including the plasma load is within the driving frequency range of the high frequency inverter power supply 28a.

[0028] The pulse signal generator 28c generates a pulse control signal for applying square wave modulation to the amplitude of the coil current that maintains the high frequency modulated induction thermal plasma. The FET gate signal circuit 28d supplies a modulated signal based on the pulse control signal generated by the pulse signal generator 28c to the gate of the MOSFET of the MOSFET inverter circuit of the high frequency inverter power supply 28a. This allows the coil current to be amplitude-modulated by the pulse control signal from the pulse signal generator 28c to relatively increase or decrease the amplitude, for example, to pulse-modulate the coil current like a square wave 102 shown in FIG. 3. By pulse-modulating the coil current, the thermal plasma flame 100 can be periodically changed to a high temperature state and a low temperature state lower than the high temperature state at a predetermined time interval. In the high frequency modulation induction thermal plasma generating unit 26, a thermal plasma flame whose temperature does not change can also be generated by simply supplying a high frequency current to the high frequency oscillation coil 14b. In FIG. 3, the vertical axis represents current and the horizontal axis represents time. When the raw material is supplied intermittently, the raw material is supplied in synchronization with the high temperature state of the thermal plasma flame 100, and the raw material is completely evaporated at the high temperature to form a gaseous mixture 45 (see FIG. 2). Furthermore, when the thermal plasma flame 100 is in a low temperature state, the raw material is supplied and a quenching gas is supplied to quench the gaseous mixture 45 (see FIG. 2).

[0029] In the square wave 102 shown in FIG. 3, the high value (HCL) and the low value (LCL) of the current amplitude are defined for the coil current, and the period of the time modulation, that is, the modulation period T p The time to remove HCL is called the on time t p1 , the time to take off LCL is the off time t p2 Furthermore, the on-time in one period is defined as t p1 The ratio of ON time to OFF time (ON time / (ON time + OFF time) x 100(%)) is defined as the duty ratio (DF). The ratio of the coil current amplitudes (LCL / HCL x 100(%)) is defined as the current modulation rate (SCL). In addition, in the square wave 102, the on-time t p1 , off time t p2 , and the modulation period T p It is preferable that each of the modulation periods (one period) is on the order of milliseconds. For example, when the duty ratio (DF) is 80%, the modulation period T p When the on time t p1 is 12ms, and the off time t p2 The modulation period T p is the period of the time modulation of the modulated induction thermal plasma flame.

[0030] Furthermore, when the coil current is amplitude modulated using the pulse control signal, it is preferable to use a predetermined waveform, for example, a square wave, for amplitude modulation. Note that the amplitude modulation of the coil current is not limited to a square wave, and a waveform consisting of a repeating wave including a triangular wave, a sawtooth wave, an inverse sawtooth wave, or a curve including a sine wave can be used. In time modulation, it is preferable that the changes in the high temperature and low temperature states of the thermal plasma flame, the supply of the quenching gas, and the supply of the raw material have the same time changes expressed by functions, which makes it easier to synchronize the timing of the supply of the quenching gas, the supply of the raw material, and the temperature state of the thermal plasma flame. The pressure atmosphere in the plasma torch 14 is appropriately determined according to the production conditions of the mixture, and is, for example, atmospheric pressure or less. Here, the atmosphere below atmospheric pressure is not particularly limited, but can be, for example, 5 Torr (666.5 Pa) to 750 Torr (99.975 kPa).

[0031] 1, in the chamber 16, an upstream chamber 16a is attached coaxially with the plasma torch 14 from the side closer to the plasma torch 14. A downstream chamber 16b is provided perpendicular to the upstream chamber 16a, and a collection section 18 equipped with a desired filter 18a for collecting the above-mentioned mixture is provided further downstream. In the production apparatus 10, the mixture is collected at, for example, the filter 18a. A gas supply unit 22 is connected to the top of the chamber 16 . A mixture (not shown) of fine particles (not shown) and nanowires (not shown) is generated in the chamber 16 by the quenching gas Qg (see FIG. 2) supplied from the gas supply unit 22. The chamber 16 also functions as a cooling tank.

[0032] The collection unit 18 includes a collection chamber equipped with a filter 18a, and a vacuum pump 18b connected via a tube provided below the collection chamber. The mixture sent from the chamber 16 is sucked by the vacuum pump 18b, so that the mixture is drawn into the collection chamber, and the mixture is collected while remaining on the surface of the filter 18a. That is, the fine particles and nanowires are collected.

[0033] 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 for the mixture 45 (see FIG. 2). The gas supply unit 22 has a gas supply source (not shown) such as a cylinder in which gas is stored, a regulator (pressure regulator) connected to the gas supply source, and an adjustment valve (not shown) for controlling the amount of gas supplied. The regulator and the adjustment valve are connected by a tube, and the adjustment valve and the chamber 16 are also connected by a tube. When the quenching gas is supplied from multiple directions as described below, the adjustment valve and the chamber 16 are connected by multiple tubes. The gas supply source used depends on the composition of the quenching gas, and the type of gas is not limited to one. When the quenching gas is a mixed gas, multiple gas supply sources are prepared and each of the multiple gas supply sources is connected to a regulator using a tube. The quenching gas is not particularly limited as long as it has the function of cooling the mixture 45 (see FIG. 2). A mixed gas of argon gas (Ar gas) and methane gas (CH4 gas) is used as the quenching gas. The quenching gas may be an inert gas such as argon gas, nitrogen gas, or helium gas that does not react with the raw materials. The quenching gas may also contain hydrogen gas. The quenching gas may also contain a reactive gas that reacts with the raw materials. Examples of the reactive gas include various hydrocarbon gases with a carbon number of 4 or less, such as methane, ethane, propane, butane, acetylene, ethylene, propylene, and butene.

[0034] The gas supply section 22 supplies the quenching gas Qg (cooling gas), for example, from a lateral direction, i.e., horizontally, toward the tail 100b (see FIG. 2) of the thermal plasma flame 100, and also supplies the quenching gas (cooling gas) from above to below along the inner wall of the chamber 16.

[0035] The mixture 45 (see FIG. 2) that has been put into a gaseous state by the thermal plasma flame 100 is quenched by the quenching gas supplied from the gas supply unit 22 into the chamber 16, to obtain a mixture of silicon microparticles and silicon nanowires. When silicon is used as the raw material and a mixed gas of argon gas and methane gas is used as the quenching gas, a mixture of silicon microparticles with carbon supported or coated on their surfaces and silicon nanowires with carbon supported or coated on their surfaces is obtained. In addition, by supplying a quenching gas along the inner wall surface of chamber 16, adhesion of the particles to the inner wall of chamber 16 is prevented during the particle recovery process, improving the yield of the mixture of the above-mentioned silicon particles and silicon nanowires produced.

[0036] The gas supply unit 22 supplies the quenching gas to the thermal plasma flame 100 as described above, but the amount of quenching gas supplied is not constant, and the quenching gas is supplied with a time-modulated rectangular wave shape, similar to the thermal plasma flame 100. This allows the gas supply unit 22 to increase the amount of quenching gas supplied when the thermal plasma flame 100 is in a high temperature state. The change in the amount of quenching gas supplied over time will be described later. The time modulation of the quenching gas in the gas supply unit 22 is performed, for example, by keeping the supply amount from the gas supply source constant and time-modulating the supply amount using an adjustment valve, for example, a ball valve.

[0037] The method of supplying the quenching gas from the gas supply unit 22 to the thermal plasma flame 100 is not particularly limited, and the quenching gas may be supplied from one direction. Also, the quenching gas may be supplied from multiple directions surrounding the thermal plasma flame 100. In this case, multiple quenching gas supply ports are provided on the outer circumferential surface of the chamber 16 along the circumferential direction, for example, at equal intervals, but are not limited to being at equal intervals. When the quenching gas is supplied from a plurality of directions, the supply timing is, for example, such that the quenching gas is supplied from the plurality of directions in a synchronized manner.

[0038] As described above, the raw material supply unit 12 supplies a predetermined amount of raw material to the thermal plasma flame 100. The raw material supply unit 12 supplies the raw material into the thermal plasma flame 100 by time-modulating the amount of the raw material supplied into the thermal plasma flame 100 . In this case, for example, an intermittent supply unit 15 is provided in the supply pipe 13. The intermittent supply unit 15 is for intermittently supplying the raw material into the plasma torch 14. The intermittent supply unit 15 supplies the raw material into the chamber 16 in a time-modulated manner. The change in the supply amount of the raw material is not particularly limited, and may be, for example, a rectangular wave shape. In addition, the time modulation of the supply rate of the quenching gas and the time modulation of the supply rate of the raw material are not limited to a rectangular wave, as in the amplitude modulation of the coil current described above, and waveforms consisting of repeating waves including curves such as a triangular wave, a sawtooth wave, an inverse sawtooth wave, or a sine wave can be used.

[0039] 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 is controlled by the control unit 24. Instead of the solenoid valve, a ball valve may be used. In this case, the opening and closing of the ball valve is also controlled by the control unit 24.

[0040] The intermittent supply unit 15 may also have a configuration including a trigger circuit 30a, an electromagnetic coil 30b, and a valve 30c. The trigger circuit 30a is connected to the pulse signal generator 28c, receives a pulse control signal from the pulse signal generator 28c, and generates a TTL (Transistor Transistor Logic) level signal in synchronization with the input pulse control signal. The electromagnetic coil 30b is connected to a trigger circuit 30a, and opens and closes the valve 30c based on a TTL level signal from the trigger circuit 30a.

[0041] The valve 30c controls the entry of the raw material for the mixture, which is supplied from the raw material supply unit 12 together with, for example, a carrier gas, into the plasma torch 14, and as described above, its opening and closing is controlled by the electromagnetic coil 30b. This makes it possible to change the supply amount of the raw material in accordance with the time modulation of the thermal plasma flame 100. For example, when the thermal plasma flame 100 is in a high temperature state, that is, during the on-time (t p1 ) the supply of raw materials can be increased.

[0042] As described above, the manufacturing apparatus 10 is capable of time-modulated supply of the thermal plasma flame 100, feedstock material, and quench gas. The plasma generating unit 21 generates a modulated induction thermal plasma flame whose temperature state is time-modulated as the thermal plasma flame, and periodically switches the modulated induction thermal plasma flame between a high temperature state and a low temperature state whose temperature is lower than the high temperature state. The raw material supplying unit 12 increases the supply amount of raw material when the modulated induction thermal plasma flame is in the high temperature state, and the gas supplying unit 22 increases the supply amount of quenching gas when the modulated induction thermal plasma flame is in the high temperature state. In this way, the above-mentioned silicon microparticles and silicon nanowires can be produced from silicon powder. It is presumed that after the silicon powder evaporates in the thermal plasma flame, the nucleated particles undergo different quenching processes to produce the microparticles and nanowires. In the manufacturing apparatus 10, since the microparticles can be reduced to nano-sized particles, when a mixture of silicon microparticles and silicon nanowires coexisting is used, for example, as an electrode material, cracks can be suppressed even if the microparticles expand, and the material can function sufficiently as an electrode material.

[0043] Next, the temperature state of the thermal plasma flame, the supply of the quenching gas, and the timing of the supply of the raw material will be described. Figure 4(a) is a graph showing a pulse control signal for modulating the coil current, (b) is a graph showing the timing of supplying the quenching gas, (c) is a graph showing the timing of opening and closing the valve for supplying the raw material, and (d) is a graph showing the supply of the raw material. When manufacturing nanowires, with regard to the supply of quenching gas, a pulse control signal 104 shown in Fig. 4(a) is output from pulse signal generator 28c to gas supply unit 22, and a timing signal 106 shown in Fig. 4(b) is generated in synchronization with this pulse control signal 104. The quenching gas is supplied based on timing signal 106.

[0044] Regarding the supply of raw material, in this embodiment, a pulse control signal 104 shown in Fig. 4(a) is output from the pulse signal generator 28c, and a TTL level signal synchronized with this pulse control signal 104 is generated by the trigger circuit 30a. Based on this TTL level signal, the valve 30c is opened and closed at a predetermined time interval by a timing signal 108 shown in Fig. 4(c). As a result, for example, raw material powder is intermittently supplied into the plasma torch 14, and raw material powder is intermittently supplied to the thermal plasma flame 100, with a waveform 109 shown in Fig. 4(d).

[0045] The pulse control signal 104 shown in Fig. 4(a) corresponds to the square wave 102 shown in Fig. 3. When the signal value of the pulse control signal 104 is high, the thermal plasma flame 100 is in a high temperature state, and when the signal value is low, the thermal plasma flame 100 is in a low temperature state that is lower than the high temperature state. p1 is the high temperature state of the thermal plasma flame 100, and the off time t p2 The timing at which the modulated induction thermal plasma flame switches from a high temperature state to a low temperature state is called t e In other words, the on-time t p1 From off time t p2 The timing to switch to is t e It is. When the signal value of the timing signal 106 shown in FIG. 4(b) is high, the quenching gas is supplied, and when the signal value is low, the quenching gas is not supplied. The timing signal 106 has one period T g In the on-time t g1 and the off time t g2 and has an on-time t g1 Quenching gas is supplied to the When the signal value of the timing signal 108 shown in FIG. 4(c) is high, the raw material is supplied, and when the signal value is low, the raw material is not supplied. The timing signal 108 has one period T f In the on-time t g1 and the off time t f2 and has an on-time t f1 Raw materials are supplied to As described above, the temperature state of the thermal plasma flame, the supply of the quenching gas, and the timing of the supply of the raw material can be synchronized with high precision based on the TTL level signal.

[0046] In the manufacturing apparatus 10, the difference δ between the timing when the modulated induction thermal plasma flame reaches a high temperature state and the timing when the quenching gas is supplied g (See Fig. 4(b)) is the timing when the modulated induction thermal plasma flame switches from a high-temperature state to a low-temperature state. e Then, 0<δ g ≦t e It is preferable that the above difference δ g is 0<δ g ≦t e If so, it will be easy to manufacture a mixture of silicon particles and silicon nanowires. In addition, the timing when the modulated induction thermal plasma flame reaches a high temperature state is when the time is zero or when the off time t p2 Immediately after. The difference δ g When the rising edge of the pulse control signal 104 shown in FIG. 4A is t=0, the time from t=0 to the rising edge of the timing signal 106 shown in FIG. 4B is t=t g It is time until. Modulation period T of modulated induction thermal plasma flame p is 15 ms, and the timing t e If is 12 ms, the difference δ g (See Fig. 4(b)) is 0 to 12 ms (0<δ g ≦12 ms). gWhen the time t is greater than 0 and less than or equal to 12 ms, a mixture of silicon fine particles and silicon nanowires can be easily produced.

[0047] In addition, δ shown in FIG. f represents the amount of deviation in the supply of raw material, from t=0 to t=t f For example, the modulation period T p If is 15 ms, δ f is 6 ms. In the manufacturing apparatus 10, the above-mentioned difference δ g By adjusting the production conditions, such as changing the amount of silicon nanoparticles and silicon nanowires, it is possible to obtain a mixture of silicon nanoparticles and silicon nanowires, and it is also possible to change the composition ratio of silicon nanoparticles and silicon nanowires in the mixture.

[0048] In the manufacturing apparatus 10, the timing of the high temperature and low temperature states of the thermal plasma flame 100 may be feedback controlled as described above. The opening and closing timing of the valve 30c may also be controlled. In this case, a TTL level signal generated by the trigger circuit 30a, i.e., a signal that shifts the phase of the input signal to the electromagnetic coil 30b, is generated and supplied to the trigger circuit 30a. This allows the timing of the supply of the raw material to be set so that the thermal plasma flame is in a high temperature state, a low temperature state, or a state that straddles the high temperature and low temperature states. As described above, in the manufacturing apparatus 10, the temperature of the thermal plasma flame, the time modulation of the quenching gas, and the supply of the raw material can be time modulated. Nanowires can be manufactured by adjusting the timing of the time modulation. The timing of the change in the temperature state of the thermal plasma flame, the timing of the supply of the quenching gas, and the timing of the supply of the raw material are adjusted by the control unit 24.

[0049] In addition, in the manufacturing apparatus 10, the temperature of the thermal plasma flame is time-modulated, but spectroscopic analysis may also be used, for example, as described in Japanese Patent No. 5564370. In this case, the modulated induction thermal plasma flame is spectroscopically analyzed, and the temperature state of the modulated induction thermal plasma flame is time-modulated by the high-frequency modulated induction thermal plasma generating unit based on the intensity of light of a wavelength originating from the raw material among the light emitted from the modulated induction thermal plasma flame.

[0050] The manufacturing apparatus 10 of this embodiment can manufacture a mixture of silicon fine particles and silicon nanowires by using, for example, silicon powder as a raw material. In this case, the mixture of silicon fine particles and silicon nanowires can also be manufactured by forming the silicon powder into a slurry.

[0051] (Method of producing the mixture) Next, a method for producing a mixture of fine particles and nanowires using the above-mentioned production apparatus 10 will be described. First, for example, silicon powder having an average particle size of 10 μm or less is fed into the raw material supply unit 12 as raw material powder for the mixture of fine particles and nanowires. For example, argon gas and hydrogen gas are used as the plasma gas, and a high-frequency voltage is applied to the high-frequency oscillation coil 14b (see FIG. 2) to generate a thermal plasma flame 100 in the plasma torch 14.

[0052] Next, silicon powder is gas-transported using, for example, argon gas as a carrier gas, and is supplied into the thermal plasma flame 100 in the plasma torch 14 via the supply pipe 13 (first step). A thermal plasma flame is generated within the plasma torch 14, and at this time, the temperature state is time-modulated to periodically switch between a high temperature state and a low temperature state that is lower than the high temperature state, thereby forming a modulated induction thermal plasma flame.

[0053] In the first step, the temperature state of the thermal plasma flame is modulated over time to generate a modulated induction thermal plasma flame, the modulated induction thermal plasma flame (thermal plasma flame) is periodically switched between a high temperature state and a low temperature state that is lower than the high temperature state, and the raw material is intermittently supplied to the thermal plasma flame. When the raw material is supplied, the amount of raw material supplied is increased when the modulated induction thermal plasma flame is in a high temperature state. In the first step, the supplied silicon powder is evaporated in the thermal plasma flame 100 to become a gas-phase mixture 45 (see FIG. 2). Next, the raw material is evaporated in the thermal plasma flame to form a gaseous mixture, and a quenching gas is supplied to the thermal plasma flame (second step). As the quenching gas, a mixed gas of argon gas and methane gas, for example, is supplied from the gas supply unit 22 to the tail 100b of the thermal plasma flame 100 (see FIG. 2).

[0054] In the second step, the quenching gas is supplied to the thermal plasma flame at a periodically changing rate. In the second step, the rate of quenching gas is increased when the modulated induction thermal plasma flame is in a high temperature state. This produces a mixture of the above-mentioned silicon microparticles and silicon nanowires through mixture 45 (see FIG. 2). It is presumed that after silicon powder evaporates in the thermal plasma flame, the nucleated particles undergo different quenching processes to produce the microparticles and nanowires. The mixture of silicon microparticles and silicon nanowires obtained in the chamber 16 is collected in the filter 18a of the collection unit 18 by the negative pressure (suction force) from the collection unit 18 by the vacuum pump 18b as described above. The manufacturing method also makes it possible to reduce the size of the particles to nanometer size, so that when a mixture of silicon particles and silicon nanowires coexisting is used as an electrode material, for example, cracks can be suppressed even if the particles expand, and the material can function sufficiently as an electrode material.

[0055] In the manufacturing method, as in the above-mentioned manufacturing apparatus, the difference δ between the timing when the modulated induction thermal plasma flame reaches a high temperature state and the timing when the quenching gas is supplied is also set. g(See Fig. 4(b)) is the timing when the modulated induction thermal plasma flame switches from a high-temperature state to a low-temperature state. e Then, 0<δ g ≦t e It is preferable that the above difference δ g is 0<δ g ≦t e If so, it will be easy to manufacture a mixture of silicon particles and silicon nanowires. Modulation period T of modulated induction thermal plasma flame p is 15 ms, and the timing t e If is 12 ms, the difference δ g 0 to 12 ms (0<δ g ≦12 ms). g When the time t is greater than 0 and less than or equal to 12 ms, a mixture of silicon fine particles and silicon nanowires can be easily produced. In addition, in the method for producing the mixture, the above-mentioned difference δ g By adjusting the production conditions, such as changing the amount of silicon nanoparticles and silicon nanowires, it is possible to obtain a mixture of silicon nanoparticles and silicon nanowires, and it is also possible to change the composition ratio of silicon nanoparticles and silicon nanowires in the mixture.

[0056] The present invention is basically configured as described above. Although the mixture manufacturing apparatus and mixture manufacturing method of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiment, and various improvements and modifications may be made without departing from the spirit and scope of the present invention. EXAMPLES

[0057] The method for producing a mixture of fine particles and nanowires according to the present invention will now be described in more detail. In the present embodiment, an attempt was made to manufacture a mixture of silicon microparticles and silicon nanowires (Experimental Examples 1 to 6). A manufacturing apparatus 10 shown in Fig. 1 was used to manufacture the mixture of microparticles and nanowires. The manufacturing conditions are as follows:

[0058] The production conditions were as follows: average input to the plasma was constant at 20 kW, Ar gas and H2 gas were used as plasma gas, the flow rate of Ar gas was 90 L / min (standard condition conversion), and the flow rate of H2 gas was 1 L / min (standard condition conversion). The pressure inside the plasma torch was fixed at 300 torr (≒40 kPa). For the raw material supply, Ar gas was used as the carrier gas, and Si powder with an average particle size of 19.2 μm was supplied at 3 g / min along with the carrier gas. The flow rate of the carrier gas was 4 L / min (standard state conversion). The average particle size of the Si powder was measured with a particle size distribution analyzer. The quenching gas used was a mixture of argon gas (Ar gas) and methane gas (CH4 gas). The average flow rate of the mixed gas was set to 25 L / min (standard state conversion).

[0059] Regarding the modulation of the plasma, the current modulation rate (SCL) is defined as the ratio of the coil current amplitude (LCL / HCL×100(%)), and SCL=80%. The duty ratio was also set to 80%. For the intermittent supply of the raw material, the on-time was set to 12 ms and the off-time to 3 ms, with one cycle being 15 ms. The time difference between the modulation signal and the valve opening / closing signal, the shift amount δ f (See Figure 4(b)) was set to 6 ms. In the gas supply section, the tube between the regulator and the control valve was 1090 cm long and had a tube diameter of 10 mm (inner diameter 6.5 mm). The tube between the control valve and the chamber was 110 cm long and had a tube diameter of 6.35 mm (inner diameter 4 mm).

[0060] 5 to 10 are schematic diagrams showing SEM images of Experimental Examples 1 to 6. FIG. As shown in Figs. 5 to 10, in each of Experimental Examples 1 to 6, a mixture 110 of particles 111 and nanowires 112 was produced. 50 The average particle size of the particles in Experimental Examples 1 to 6 and the standard deviation of the particle size are shown in Table 1 below. 50was obtained by taking images of the microparticles in 10 fields of view using an SEM, in the same manner as the above-mentioned particle diameter measurement, and measuring the particle diameter in each field of view. In the first experimental example, the difference δ between the timing when the modulated induction thermal plasma flame reaches a high temperature and the timing when the quenching gas is supplied g (See FIG. 4(c)) is 2.5 ms. In the second experimental example, the difference δ g In the experimental example 3, the difference δ g In the experimental example 4, the difference δ g In the fifth experimental example, the difference δ g The difference δ in Experimental Example 6 is 12.5 ms. g The difference δ in Experimental Example 6 is 15.0 ms. g 15.0ms is the difference δ g is the same as 0ms.

[0061] [Table 1]

[0062] In Experimental Examples 1 to 6, the above-mentioned difference δ g When d is between 2.5 and 10.0 ms, the average particle size and d 50 The standard deviation also showed a similar tendency. In the mixture of particles and nanowires, the particle size of the resulting particles changed depending on the manufacturing conditions. [Explanation of symbols]

[0063] 10 Mixture manufacturing equipment (manufacturing equipment) 12 Raw material supply department 13 Supply pipe 14 Plasma Torch 14a quartz tube 14b High frequency oscillation coil 14c supply port 14d Plasma gas supply port 14e quartz tube 14f cooling water 15 Intermittent supply section 16 Chambers 16a Upstream chamber 16b Downstream chamber 18 Collection Department 18a Filter 18b Vacuum pump 20 Plasma gas supply unit 21 Plasma generating unit 22 Gas supply section 24 Control Unit 26 High frequency modulated induction thermal plasma generator 28a High Frequency Inverter Power Supply 28b Impedance matching circuit 28c Pulse signal generator 28d FET gate signal circuit 30a Trigger circuit 30b Electromagnetic coil 30c valve 45 Mixture 100 Hot Plasma Flame 100b Tail 102 square wave 104 Pulse control signal 106, 108 Timing signals 109 Waveform 110 mixture 111 Fine particles 112 Nanowires Qg Quenching gas T f one cycle T g one cycle T p Modulation Period t f1 , t g1 , t p1 On Time t f2 , t g2 , t p2 Off Time δf deviation amount δg difference

Claims

1. An apparatus for producing a mixture of fine particles and nanowires, comprising: a raw material supplying section for supplying raw materials for the mixture to the thermal plasma flame; a plasma torch in which the thermal plasma flame is generated and the raw material supplied by the raw material supply unit is evaporated by the thermal plasma flame to form a mixture in a gas phase state; a plasma generating unit that applies a high-frequency current to a high-frequency oscillation coil surrounding the outside of the plasma torch to generate the thermal plasma flame inside the plasma torch; a gas supply unit for supplying a quenching gas to the thermal plasma flame; The raw material is silicon, the plasma generating unit amplitude-modulates the high frequency current with a pulse control signal to generate, as the thermal plasma flame, a modulated induction thermal plasma flame whose temperature state is time-modulated, and periodically switches the modulated induction thermal plasma flame between a high temperature state and a low temperature state whose temperature is lower than the high temperature state; When the signal value of the pulse control signal is high, the current amplitude is high and the thermal plasma flame is in a high temperature state, and when the signal value of the pulse control signal is low, the current amplitude is low and the thermal plasma flame is in a low temperature state that is lower than the high temperature state. the raw material supply unit starts supplying the raw material when the modulated induction thermal plasma flame is in the high temperature state, and supplies the raw material until the raw material changes from the low temperature state to the high temperature state; The gas supply unit starts supplying the quenching gas when the modulated induction thermal plasma flame is in the high temperature state, and supplies the quenching gas until the modulated induction thermal plasma flame reaches the low temperature state.

2. 2. The apparatus for producing a mixture according to claim 1, wherein the raw material supply unit supplies the raw material into the thermal plasma flame in a particulate dispersed state.

3. The difference between the timing when the modulated induction thermal plasma flame reaches the high temperature state and the timing when the quenching gas is supplied is defined as δ ｇ The timing at which the modulated induction thermal plasma flame switches from the high temperature state to the low temperature state is t ｅ Then, 0 < δ ｇ ≦t ｅ The apparatus for producing the mixture according to claim 1 or 2,

4. A method for producing a mixture of microparticles and nanowires, comprising the steps of: The plasma torch has a plasma generating unit that applies a high-frequency current to a high-frequency oscillation coil surrounding the outside of the plasma torch to generate a thermal plasma flame inside the plasma torch, A first step of supplying raw materials for a mixture to the thermal plasma flame; a second step of evaporating the raw material in the thermal plasma flame to form a gas-phase mixture, and supplying a quenching gas to the thermal plasma flame; The raw material is silicon. In the first step, the high frequency current is amplitude modulated by a pulse control signal to time-modulate the temperature state of the thermal plasma flame to generate a modulated induction thermal plasma flame, and the modulated induction thermal plasma flame is periodically switched between a high temperature state and a low temperature state having a temperature lower than that of the high temperature state, and when the signal value of the pulse control signal is high, the current amplitude is high and the thermal plasma flame is in the high temperature state, and when the signal value of the pulse control signal is low, the current amplitude is low and the flame is in the low temperature state having a temperature lower than that of the high temperature state, The raw material is intermittently supplied to the modulated induction thermal plasma flame in the high temperature state, and when the modulated induction thermal plasma flame is in the high temperature state, the supply of the raw material is started, and the raw material is supplied until the raw material changes from the low temperature state to the high temperature state; In the second step, when the modulated induction thermal plasma flame is in the high temperature state, the supply of the quenching gas is started and the quenching gas is supplied until the modulated induction thermal plasma flame reaches the low temperature state.

5. The method for producing a mixture according to claim 4 , wherein in the first step of supplying the raw material, the raw material is supplied in a dispersed, particulate state.

6. The difference between the timing when the modulated induction thermal plasma flame reaches the high temperature state and the timing when the quenching gas is supplied is defined as δ ｇ The timing at which the modulated induction thermal plasma flame switches from the high temperature state to the low temperature state is t ｅ Then, 0 < δ ｇ ≦t ｅ The method for producing the mixture according to claim 4 or 5,

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