Microparticle manufacturing device, microparticle manufacturing method, microparticle property control method, and plasma state analysis method

Abstract

To provide a fine particle production device and a fine particle production method capable of stably maintaining a plasma state for a long term and stabilizing the quality of produced fine particles, and a method of controlling physical properties of fine particles and a plasma state analysis method.SOLUTION: On the basis of an output value with respect to a plurality of wavelengths which appear in a plasma light emission spectrum, at least any of a supply amount of a plasma gas, plasma output being generated, and a supply amount of a raw material is controlled.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a particle manufacturing apparatus and method for manufacturing particles using plasma, and more particularly to a particle manufacturing apparatus and method that maintain a stable plasma state over a long period of time and produce particles with stable quality, as well as a method for controlling the physical properties of particles and a method for analyzing the state of plasma. [Background technology]

[0002] Conventionally, vapor phase growth methods such as physical vapor deposition and chemical vapor deposition have been known as methods for producing fine particles. For example, Patent Document 1 discloses a technique for producing metal powder that includes a step of heating and spraying raw material powder using a direct current thermal plasma device, in which a mixed gas of argon and nitrogen is used as the plasma gas and the mixture ratio of argon and nitrogen in the plasma gas is controlled to a specific value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-28176 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a method for producing fine particles using plasma, it is difficult to maintain a stable plasma state over a long period of time. In particular, when two or more types of raw materials are used or when the raw materials have multiple valences, the plasma emission state tends to become unstable. This makes it difficult to stabilize the quality of the produced fine particles, and in some cases, production may have to be stopped.

[0005] In view of the current situation, the present invention aims to provide a particle manufacturing apparatus and method, a method for controlling the physical properties of particles, and a method for analyzing the state of plasma that can maintain a stable plasma state over the long term and stabilize the quality of the particles manufactured. [Means for solving the problem]

[0006] The present invention has been made to solve the problems in the prior art as described above, and includes, for example, the following aspects.

[0007] The particle manufacturing apparatus of the present invention is an apparatus for manufacturing particles including a chamber, a raw material supply device, a plasma gas supply device, a voltage application device, a plasma emission analysis device, and a control device, The plasma supplied from the raw material supply device is generated by applying a predetermined voltage to the plasma gas supplied from the plasma gas supply device using the plasma generated by the voltage application device. Multiple species By heating the raw material, Multiple species configured to produce particulates by gasifying a feedstock and cooling it in the chamber; the plasma optical emission analyzer analyzes the optical emission of the plasma after the raw material is introduced, The control device detects the amount of light that appears in the emission spectrum of the plasma measured by the plasma emission analyzer. A ratio is calculated which is a normalized time average value obtained by dividing the time average value of the emission wavelengths of the emission wavelengths of a predetermined raw material among the plurality of raw materials by the time average value of the emission wavelengths of the other raw materials, or a normalized second-order derivative time average value obtained by second-order differentiation of the normalized time average value with respect to the wavelength, and when the ratio exceeds a predetermined raw material ratio threshold value, The amount of plasma gas supplied, the generated plasma of The present invention is characterized in that it controls at least one of the output and the supply amount of the raw material.

[0008] In addition, the method for producing fine particles of the present invention includes applying a predetermined voltage to a plasma gas using a voltage application device to generate plasma, and using the plasma, Multiple species By heating the raw material, Multiple species The raw material is gasified and then cooled to produce fine particles. Appears in the emission spectrum of the plasma A ratio is calculated which is a normalized time average value obtained by dividing the time average value of the emission wavelengths of the emission wavelengths of a predetermined raw material among the plurality of raw materials by the time average value of the emission wavelengths of the other raw materials, or a normalized second-order derivative time average value obtained by second-order differentiation of the normalized time average value with respect to the wavelength, and when the ratio exceeds a predetermined raw material ratio threshold value, the supply amount of the plasma gas; The said occurrence plasma of The present invention is characterized in that at least one of the output and the supply amount of the raw material is controlled.

[0009] The method for controlling the physical properties of fine particles of the present invention includes applying a predetermined voltage to a plasma gas using a voltage application device to generate plasma, and Multiple species By heating the raw material, Multiple species The raw material is gasified and then cooled to produce fine particles. Appears in the emission spectrum of the plasma A ratio is calculated which is a normalized time average value obtained by dividing the time average value of the emission wavelengths of the emission wavelengths of a predetermined raw material among the plurality of raw materials by the time average value of the emission wavelengths of the other raw materials, or a normalized second-order derivative time average value obtained by second-order differentiation of the normalized time average value with respect to the wavelength, and when the ratio exceeds a predetermined raw material ratio threshold value, the supply amount of the plasma gas; The said occurrence plasma of At least one of the output and the supply amount of the raw material is adjusted to control the physical properties of the particles so as to obtain good results during the production of the particles. [Effects of the Invention]

[0011] According to the present invention, by controlling the flow rate of plasma gas, plasma output, and raw material supply amount using output values ​​for multiple wavelengths that appear in the emission spectrum of the plasma flame, it is possible to maintain a stable plasma state and produce microparticles with the desired performance. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram for explaining a typical configuration of a microparticle production apparatus according to this embodiment. [Figure 2] FIG. 2 is a graph showing an example of the spectrum of the time average value B of the light emission output of the plasma flame. [Figure 3] FIG. 3 is a graph showing the relationship between the blending ratio of raw material Y and the time average value B(λY) of wavelength λY. [Figure 4] FIG. 4 is a graph showing an example of the spectrum of the second-order derivative time average value B″ obtained by second-order differentiation of the time average value B with respect to wavelength. [Figure 5]FIG. 5 is a graph showing the relationship between the blending ratio of raw material Y and the second derivative time average value B″(λY). [Figure 6] FIG. 6 is a graph showing an example of the spectrum of the normalized time average value B(λ) / B(λX). [Figure 7] FIG. 7 is a graph showing the relationship between the blending ratio of raw material Y and the normalized time average value B(λY) / B(λX). [Figure 8] FIG. 8 is a graph showing an example of the spectrum of the normalized second derivative time average value B″(λ) / B(λX). [Figure 9] FIG. 9 is a graph showing the relationship between the blending ratio of raw material Y and the normalized second derivative time average value B″(λY) / B(λX). [Figure 10] FIG. 10 is a scatter diagram showing the relationship between the ratio B(λY) / B(λX) when good results were obtained as composite powder particles and the blending ratio of the raw materials during production. [Figure 11] FIG. 11 is a graph for explaining a control method based on the ratio BλY(t) / BλX(t). [Figure 12] FIG. 12 is a graph showing an example of the spectrum of the time average value B of the light emission output of the plasma flame. [Figure 13] FIG. 13 is a calibration curve showing the relationship between the output ratio S(λ1) / S(λ0) and the electron temperature Te. [Figure 14] FIG. 14 is a graph for explaining a control method based on the electron temperature Te. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings. In this embodiment, the production of fine particles using DC plasma will be described as an example, but the type of plasma is not limited to DC plasma, and for example, high frequency plasma can also be used in the same manner.

[0014] FIG. 1 is a schematic diagram for explaining a typical configuration of a microparticle production apparatus according to this embodiment.

[0015] As shown in FIG. 1, the microparticle manufacturing apparatus 10 of this embodiment includes a chamber 12, a collection pot 14, a raw material supply device 15, a plasma gas supply device 18, a DC plasma torch (voltage application device) 20, a plasma emission analysis device 22, and a control device 30.

[0016] In this fine particle manufacturing apparatus 10, the raw material passes from the raw material supply device 15 through the raw material supply nozzle 17 and into the DC plasma torch 20. In this embodiment, the raw material supply amount adjustment means 16 is configured to adjust the amount of raw material supplied from the raw material supply device 15 to the DC plasma torch 20.

[0017] For example, argon (Ar) gas is supplied to the DC plasma torch 20 from the plasma gas supply device 18, and a plasma flame is generated by applying a predetermined voltage to this argon gas (plasma gas) by the DC plasma torch 20. Nitrogen (N2) or the like may then be mixed in.

[0018] In addition, the raw material is gasified in the plasma flame generated by the DC plasma torch 20 and released into the chamber 12, after which it is cooled and converted into fine powder, which is then accumulated and recovered in the recovery pot 14.

[0019] The interior of chamber 12 is controlled by a pressure regulator (not shown) to maintain a negative pressure relative to raw material supply nozzle 17, thereby enabling stable generation of a plasma flame. Note that the interior of chamber 12 can also be kept at atmospheric pressure.

[0020] In the microparticle production apparatus 10 of this embodiment, an observation window 13 is provided in the chamber 12, and the light emitted from the plasma flame is observed through this observation window 13 by a plasma light emission analyzer 22.

[0021] The plasma emission analyzer 22 includes a collimator lens 23, an optical fiber 24, a spectroscope 25, and a spectrum processor 26. When the light emitted from the plasma flame is input to spectrometer 25 via collimator lens 23 and optical fiber 24, spectrometer 25 measures the electromagnetic wave spectrum (emission spectrum) of this light emission. While the electromagnetic waves assumed here are not particularly limited, examples include a wavelength range of 200 nm to 4000 nm, particularly 200 nm to 1700 nm. The measured emission spectrum is sent to spectrum processing unit 26, which obtains an output at a predetermined wavelength, as described below, and transmits this to control device 30.

[0022] The control device 30 is configured to control at least one of the amount of plasma gas supplied by the plasma gas supply device 18 (gas flow rate), the output of the DC plasma torch 20, and the amount of raw material supplied by the raw material supply device 15, based on the output at a predetermined wavelength sent from the spectral processing unit 26.

[0023] The raw material used in such a microparticle production apparatus 10 is appropriately selected depending on the microparticles to be produced and is not particularly limited, but may contain at least one element component selected from, for example, Cu, Si, Ni, Ti, Fe, Co, Cr, Mg, Mn, Mo, W, Ta, In, Zr, Nb, B, Ge, Sn, Zn, Bi, Ag, C, etc. As will be described later, when multiple types of raw materials are used, the raw materials may be composed only of the above-mentioned element components, or may contain other element components.

[0024] The raw material used in the fine particle production apparatus 10 may be in the form of wire, powder, solution, slurry, etc. The following description will be given taking the case where a powder raw material is used as an example.

[0025] From the viewpoint of production, such raw material powder preferably has a volume cumulative particle size D50 of 3.0 μm to 30 μm, and particularly preferably 5.0 μm to 15 μm. The volume cumulative particle size D50 can be measured using a laser diffraction / scattering particle size distribution analyzer.

[0026] The shape of the raw material powder is not particularly limited and may be dendritic, rod-like, flake-like, cubic, spherical or nearly spherical, etc. However, from the viewpoint of stabilizing the efficiency of supply to the plasma torch, a spherical or nearly spherical shape is preferable.

[0027] When heating the raw material powder using the microparticle production apparatus 10, it is preferable to use a mixed gas of argon and nitrogen as the plasma gas and adjust the plasma flame so that it is thick and long in a laminar flow state. By adjusting it in this way, the raw material powder charged is instantly gasified in the plasma flame, and sufficient energy can be supplied within the plasma flame, causing nucleation, cohesion, and condensation toward the plasma tail flame, thereby forming fine particles, especially fine particles on the submicron order.

[0028] Whether the above-mentioned plasma flame is in a laminar flow state can be determined by whether the aspect ratio of the frame length to the frame width (hereinafter referred to as the "frame aspect ratio") is equal to or greater than 3 when the plasma flame is observed from the side where the frame width is widest. Specifically, if the frame aspect ratio is 3 or greater, it can be determined to be in a laminar flow state, while if the frame aspect ratio is less than 3, it can be determined to be in a turbulent flow state.

[0029] Examples of the plasma gas used as the working gas for generating the thermal plasma include argon, hydrogen, nitrogen, and helium, and among these, it is preferable to use a mixed gas of argon and nitrogen as described above.

[0030] Here, if a gas mixture of argon gas and nitrogen gas is used, the nitrogen (diatomic molecule) gas can impart greater vibrational energy (thermal energy) to the raw material powder particles, making the agglomeration state uniform, thereby producing nanoparticles with a sharper particle size distribution.

[0031] The ratio of argon to nitrogen in the plasma gas is preferably 99:1 to 10:90 in terms of flow rate, more preferably 95:5 to 60:40, and even more preferably 95:5 to 80:20. By setting the nitrogen content within this range, the plasma flame is prevented from weakening, and powder with a sharp particle size distribution is more easily obtained.

[0032] Furthermore, from the viewpoint of making the particle size distribution sharper, in other words, making the (D90-D10) / D50 of the produced microparticles smaller, it is preferable to adjust the ratio of argon to nitrogen in terms of flow rate ratio within a range of 99:1 to 50:50, particularly 95:5 to 50:50, in which the flow rate of argon is higher than that of nitrogen.

[0033] When producing oxide particles, oxygen may be contained in the plasma gas. The oxygen content is preferably set appropriately depending on the oxide particles to be produced.

[0034] Here, D10, D50, and D90 of the fine particles are D10, D50, and D90, respectively, based on the volume-based particle size distribution obtained by measurement using a laser diffraction / scattering particle size distribution measurement method. Furthermore, (D90-D10) / D50 of the fine particles is an index showing the sharpness of the particle distribution.

[0035] In the thus configured fine particle production apparatus 10 of this embodiment, the control device 30 controls the plasma gas supply device 18, the DC plasma torch 20, and the raw material supply device 15 in the following manner.

[0036] In this embodiment, the plasma gas supply device 18 has a gas flow rate adjusting means 19 for adjusting the flow rate of the plasma gas supplied to the DC plasma torch 20. The DC plasma torch 20 also has a plasma output adjusting means 21 for adjusting the plasma output. The raw material supply device 15 also has a raw material supply rate adjusting means 16 for adjusting the amount of raw material supplied. In the present invention, the "plasma output" may be a current output, a voltage output, or the magnitude of power, which is the product of the current and the voltage.

[0037] The raw material supply amount adjustment means 16, the gas flow rate adjustment means 19, and the plasma output adjustment means 21 are connected to a control device 30, which adjusts at least one of the flow rate of the plasma gas supplied from the plasma gas supply device 18 to the DC plasma torch 20, the plasma output of the DC plasma torch 20, and the amount of raw material supplied from the raw material supply device 15.

[0038] When producing microparticles using the microparticle production apparatus 10, the control device 30 controls the gas flow rate adjusting means 19 and the plasma output adjusting means 21 to supply a predetermined amount of plasma gas from the plasma gas supply device 18 to the DC plasma torch 20, and sets the DC plasma torch 20 to a predetermined plasma output, thereby generating a plasma flame.

[0039] To ensure that the plasma flame is thick and long in a laminar flow state, the plasma output is preferably 2 kW to 40 kW, more preferably 4 kW to 15 kW, and from the above viewpoint, the gas flow rate of the plasma gas is preferably 0.1 L / min to 20 L / min, more preferably 0.5 L / min to 18 L / min.

[0040] Furthermore, to maintain the plasma flame in a stable laminar flow state, it is preferable to maintain the above-mentioned ranges of plasma output and gas flow rate, and to maintain an appropriate gas flow rate relative to the plasma output (A). For example, when using a mixture of argon and nitrogen as the plasma gas, the ratio of the sum of the Ar gas flow rate (B) and the N2 gas flow rate (C), calculated by the formula (B + C) / A (unit: L / (min kW)), is more preferably 0.50 to 2.00. To obtain the flow rate necessary for gasifying the raw material powder, the (B + C) / A value is preferably 0.50 or greater, and to maintain the plasma flame in a stable laminar flow state, it is preferably 2.00 or less. From this viewpoint, it is particularly preferable to adjust (B+C) / A to be 0.70 to 1.70, and even more preferable to adjust it to be 0.75 to 1.50.

[0041] In this state, raw material powder is supplied from the raw material supply device 15 to the plasma flame through the raw material supply nozzle 17, whereby the raw material powder is gasified and released into the chamber 12, after which it is cooled and turned into fine particles which are accumulated and recovered in the recovery pot 14.

[0042] When producing microparticles in this manner, the state of the plasma flame is analyzed by a plasma emission analyzer 22. Then, based on the output of a wavelength λ having characteristics described below in the emission spectrum of the plasma flame, a control device 30 adjusts at least one of the flow rate of the plasma gas supplied from the plasma gas supply device 18 to the DC plasma torch 20, the plasma output of the DC plasma torch 20, and the supply amount of raw material supplied from the raw material supply device 15. This makes it possible to control the physical properties of the produced microparticles (for example, the raw material powder ratio in the mixed powder, ion state, particle diameter, specific surface area, pore diameter, etc., as described below).

[0043] As the output of wavelength λ, the value output from the spectrometer 25 may be used as is, or a derivative value obtained by differentiating this value with respect to time or a second-order derivative value obtained by second-order differentiation with respect to time may be used. By using such a derivative value or second-order derivative value, the time change of the output of wavelength λ becomes more noticeable. Note that not only first-order and second-order derivatives but also higher-order derivatives (third-order, fourth-order, etc.) may be performed. Also, a derivative value obtained by differentiating the value output from the spectrometer 25 with respect to wavelength or a second-order derivative value obtained by second-order differentiation with respect to wavelength may be used. Also, a value normalized by dividing the output of wavelength λ by the output of another wavelength λ' may be used. Note that such an output of wavelength λ' may be the output at the same time as the output of wavelength λ, or may be, for example, the initial output before the start of raw material supply. Also, a value obtained by moving average of these values ​​with respect to time may be used. In this specification, such derivative values ​​and normalized values ​​are collectively referred to as the "output of wavelength λ."

[0044] (1) When using wavelength outputs derived from multiple types of raw materials When producing fine particles of composite powder made of multiple metals using the fine particle production apparatus 10 of this embodiment, for example, the raw material powder of raw material X and the raw material powder of raw material Y are mixed so as to have a desired mass ratio, and placed in the raw material supply device 15, and the fine particles are produced as described above. Note that the composite powder made of multiple metals described above may be a mixture of multiple metals or may be made of an alloy of multiple metals.

[0045] In this way, when a plurality of types of raw materials are used, the output of the wavelengths derived from each raw material can be regarded as output values ​​for the plurality of wavelengths in the emission spectrum of the plasma flame.

[0046] (1-1) Spectrum during composite powder production Composite powder particles were produced by setting the mass ratio of raw material X and raw material Y as shown in Table 1 below, and the emission spectrum of the plasma flame at that time was observed.

[0047] [Table 1]

[0048] When the time average value B of the change in output for each wavelength at time t during microparticle production (hereinafter referred to as "output Y(t)") is calculated, the spectrum of the time average value B is obtained as shown in Figure 2. Here, the time average value B was calculated over the entire time period during which the microparticles were produced.

[0049] In Figure 2, wavelength λ X is the emission wavelength derived from raw material X, and wavelength λ Y is the emission wavelength originating from the raw material Y. The emission wavelength originating from the raw material metal can be determined from the change in the emission spectrum of the plasma flame immediately after a single raw material metal is supplied to the DC plasma torch 20.

[0050] Figure 3 shows the relationship between the blending ratio of raw material Y and wavelength λ Y The time average value of B[λ Y ] is a graph showing the relationship between the time average value B[λ Y ] was calculated over the entire time period for producing microparticles. As shown in Figure 3, the correlation was low (coefficient of determination R 2 :0.0381), it is difficult to use for control in this state.

[0051] Figure 4 shows the spectrum of the second derivative time average value B'', which is the second derivative of the time average value B with respect to wavelength. Figure 5 shows the spectrum of the second derivative time average value B'' [λ Y ]. Here, the second derivative time average value B''[λ Y ] was calculated over the entire time period for producing the microparticles.

[0052] As shown in Figure 5, the correlation is higher than when the time average value B is used directly (coefficient of determination R 2 :0.6479), but it is still difficult to use for high-precision control.

[0053] Therefore, the time average value B[λ] at each wavelength λ is calculated byX The time average value of B[λ X ]. Figure 6 shows the normalized time-averaged B[λ] / B[λ X ] spectrum, and Fig. 7 shows the normalized time average value B[λ Y ] / B[λ X ] is a graph showing the relationship between the normalized time average value B[λ Y ] / B[λ X ] was calculated over the entire time period for producing microparticles. As shown in Figure 7, a high correlation (correlation coefficient R 2 :0.9465) was obtained.

[0054] Similarly, the time average value B[λ] at each wavelength λ is calculated by X The time average value of B[λ X ] and normalized by dividing by . This is then differentiated twice with respect to wavelength to obtain the normalized second-order differential time average value B''[λ] / B[λ X ] was calculated. Figure 8 shows the normalized second derivative time average value B''[λ] / B[λ X ) spectrum, and Figure 9 shows the relationship between the blending ratio of raw material Y and the normalized second derivative time average value B''[λ Y ] / B[λ X ]. Here, the normalized second derivative time average value B''[λ Y ] / B[λ X ] was calculated over the entire time period for producing microparticles. As shown in Figure 8, a high correlation (coefficient of determination R 2 :0.9618) was obtained.

[0055] In this way, when producing composite powder particles made of multiple metals, a value highly correlated with the mass ratio of the raw metals can be obtained by normalizing the time-averaged value B of the emission wavelengths derived from a given raw metal by the time-averaged value B of the emission wavelengths derived from the other raw metals. Note that the raw metal to be normalized (i.e., the raw metal to be used as the denominator) is preferably a raw metal with a high blending ratio, but is not particularly limited as long as the time-averaged value B[λ] used as the denominator for normalization is not 0.

[0056] Hereinafter, the normalized time average value (hereinafter simply referred to as "ratio") B[λ Y ] / B[λ X ], the flow of adjusting at least one of the flow rate of the plasma gas supplied from the plasma gas supply device 18 to the DC plasma torch 20, the plasma output of the DC plasma torch 20, and the supply amount of the raw material supplied from the raw material supply device 15 by the control device 30 will be described. Note that the normalized second-order differential time average value B''[λ Y ] / B[λ X ] can be used to perform control in the same way.

[0057] (1-2) Setting the raw material ratio threshold In advance, microparticles are produced under conditions where the blending ratio of raw materials is known, and the ratio B[λ Y ] / B[λ X ] is measured. When the produced fine particles are good as composite fine particles, the ratio B[λ Y ] / B[λ X A scatter diagram is then created showing the relationship between the amount of the raw material used and the blending ratio of the raw materials used in the manufacturing process. An example of the scatter diagram obtained in this way is shown in Figure 10.

[0058] As shown in Figure 10, an approximate straight line is calculated for each data, and the upper and lower limits of the raw material ratio threshold are set within a range in which each data falls. In the example shown in Figure 10, when the blending ratio of raw material Y is 6 mass%, the ratio B[λ Y ] / B[λ X The allowable range of [C±Δα] is defined as C±Δα. The control flow when the blending ratio of raw material Y is 6 mass % will be described below.

[0059] The "good result" when producing microparticles can be determined, for example, by the duration of production of the microparticles and the characteristics of the produced microparticles. The characteristics of the microparticles are not particularly limited, but for example, the image analysis particle size D SEMExamples of such parameters include laser diffraction scattering particle sizes D10, D50, and D90, the (D90-D10) / D50 of the microparticles calculated from these, the element content of O2 and N2, etc., the X-ray diffraction crystallite diameter, and the specific surface area SSA.

[0060] (1-3) Control As described above, while a plasma flame is generated, raw material powder is supplied from the raw material supply device 15 to produce particles. In this case, in the emission spectrum of the plasma flame obtained, the emission wavelength λ originating from the raw material X is X and the emission wavelength λ originating from raw material Y Y Based on the output of the plasma flame, the state of the plasma flame is analyzed.

[0061] Specifically, the control device 30 controls the wavelength λ X Output Yλ X (t) and wavelength λ Y Output Yλ Y (t) are acquired at regular intervals, and these outputs Yλ X (t) and output Yλ Y (t) time average value Bλ X (t) and Bλ Y Calculate (t).

[0062] And this time average value Bλ X (t) and Bλ Y (t) ratio Bλ Y (t) / Bλ X (t) and calculate the ratio Bλ Y (t) / Bλ X When (t) exceeds a preset raw material ratio threshold, the flow rate of the plasma gas, the plasma output, and the amount of raw material supplied are increased or decreased to adjust the ratio Bλ Y (t) / Bλ X Control is performed so that (t) falls within the raw material ratio threshold.

[0063] For example, as shown in FIG. 11(a), the ratio Bλ Y (t) / Bλ X When (t) exceeds the raw material ratio threshold C+Δα, the control device 30 adjusts the ratio Bλ Y (t) / BλX The flow rate of the plasma gas, the plasma output, and the supply amount of the raw material are controlled by the gas flow rate control means 19, the plasma output control means 21, and the raw material supply amount control means 16 so that the ratio Bλ Y (t) / Bλ X (t) changes so as to stay within the raw material ratio threshold.

[0064] On the other hand, as shown in Fig. 11(b), the ratio Bλ Y (t) / Bλ X When (t) exceeds the raw material ratio threshold C-Δα, the control device 30 adjusts the ratio Bλ Y (t) / Bλ X The flow rate of the plasma gas, the plasma output, and the supply amount of the raw material are controlled by the gas flow rate control means 19, the plasma output control means 21, and the raw material supply amount control means 16 so that (t) increases. Y (t) / Bλ X (t) changes so as to stay within the raw material ratio threshold.

[0065] Thus, the ratio Bλ Y (t) / Bλ X By controlling at least one of the plasma gas flow rate, plasma output, and raw material supply amount so that (t) falls within the raw material ratio threshold, the plasma state can be stabilized, preventing the production of microparticles from being stopped midway and reducing productivity, and also stabilizing the quality of the produced microparticles.

[0066] In addition, when such control is performed, the ratio Bλ Y (t) / Bλ X Since there is a tendency for variation in (t) to be large, it is preferable to configure the control device 30 so that a predetermined judgment start time is set and the above-described control is started after this judgment start time has passed.

[0067] In the above example, the ratio Bλ Y (t) / Bλ XWhen (t) exceeds the raw material ratio threshold, the plasma gas supply amount, plasma output, and raw material supply amount are controlled. However, it is also possible to configure the plasma gas supply amount, plasma output, and raw material supply amount to be controlled so that the raw material ratio threshold is not exceeded.

[0068] In the above example, the case of producing composite powder particles of two kinds of metals, raw material X and raw material Y, was described, but similar control can be performed when producing composite powder particles of three or more kinds of metals. For example, when producing composite powder particles of three kinds of metals, raw material X, raw material Y, and raw material W, the ratio Bλ Y (t) / Bλ X (t), ratio Bλ W (t) / Bλ X (t), ratio Bλ W (t) / Bλ Y (t) should be controlled so that they do not exceed the raw material ratio thresholds.

[0069] In the above example, the average value over the entire microparticle production time is used to calculate the time average value B, but the average value may be calculated for different time ranges, for example, the early, middle, and late stages of microparticle production. When using multiple time ranges in this way, the allowable width (raw material ratio threshold value) may be different for each time range.

[0070] In the above example, two or more raw materials are supplied from one raw material supply device 15, but it is also possible to produce composite powder particles of two or more metals by providing two or more raw material supply devices and supplying each raw material from each raw material supply device. In this case, the control device 30 is configured to control the supply amount of plasma gas, plasma output, and the supply amount of raw materials from each raw material supply device to achieve a desired ratio of each raw material.

[0071] (2) When using the output of the emission wavelength according to the ionic state of the raw material When producing fine particles using the fine particle production apparatus 10 of this embodiment, the raw material powder is gasified by the plasma flame, and at that time, the ion state (valence) of the raw material changes.

[0072] It is known that the emission wavelength is determined for each valence of a substance. It is also known that the emission output for each valence of a substance changes depending on the temperature of the substance. Based on these facts, by measuring the emission wavelength output for multiple wavelengths in multiple ionic states (valences) of the raw material from the emission spectrum of the plasma flame, it is possible to estimate the plasma temperature as a plasma state.

[0073] (2-1) Spectrum during particle production Fine particles were produced using raw material Z, and the emission spectrum of the plasma flame was observed. When the time average value B of the change in output (output Y(t)) for each wavelength at time t during microparticle production is calculated, the spectrum of the time average value B is obtained as shown in Figure 12. Here, the time average value B was calculated over the entire time period during which the microparticles were produced.

[0074] In FIG. 12, wavelength λ0 is the emission wavelength when the ionic state of raw material Z is zero-valent, and wavelength λ1 is the emission wavelength when the ionic state of raw material Z is mono-valent.

[0075] Meanwhile, using a known database, the relationship between the temperature and the ratio of the luminous output S of zero-valent raw material Z and monovalent raw material Z was obtained. Table 2 summarizes the luminous output S and output ratio S[λ1] / S[λ0] for each emission wavelength, electron temperature Te, of zero-valent raw material Z and monovalent raw material Z.

[0076] [Table 2]

[0077] In this embodiment, the relationship between the ratio of light output power S and electron temperature is obtained using the NIST LIBS Database (https: / / physics.nist.gov / PhysRefData / ASD / LIBS / libs-form.html), but other databases may be used, or the relationship may be obtained by conducting tests in advance. Furthermore, the temperature is not limited to the electron temperature, but may also be an ion temperature or a normal temperature.

[0078] From Table 2, a calibration curve showing the relationship between the output ratio S[λ1] / S[λ0] and the electron temperature Te can be created as shown in FIG.

[0079] In the emission spectrum shown in Figure 12, the time average value B[λ0] of wavelength λ0 is 29223, the time average value B[λ1] of wavelength λ1 is 14849, and the ratio of the time average values ​​B[λ1] / B[λ0] is 0.508.

[0080] From this ratio of time average values ​​B[λ1] / B[λ0]=0.508 and the calibration curve shown in FIG. 13, it can be seen that the electron temperature of the plasma flame during the production of fine particles is 1.25 eV.

[0081] In the above example, when calculating the ratio of the time average values, B[λ1] is used as the numerator and B[λ0] is used as the denominator, but this is not particularly limited as long as the time average value in the denominator is not 0.

[0082] (2-2) Temperature threshold setting In advance, particles are produced from the raw material Z, and the electron temperature Te is calculated as described above. Then, the electron temperature Te can be set based on the electron temperature at which good results are obtained for the produced particles.

[0083] (2-3) Control As described above, while a plasma flame is generated, microparticles are produced by supplying raw material powder from the raw material supply device 15. At this time, the state of the plasma flame is analyzed based on the output of the emission wavelength λ0 derived from the zero-valent raw material Z and the emission wavelength λ1 derived from the monovalent raw material Z in the acquired emission spectrum of the plasma flame.

[0084] Specifically, the control device 30 acquires the output Yλ0(t) of wavelength λ0 and the output Yλ1(t) of wavelength λ1 at regular intervals, and calculates the time average values ​​Bλ0(t) and Bλ1(t) of these outputs Yλ0(t) and Yλ1(t).

[0085] The ratio Bλ1(t) / Bλ0(t) of these time average values ​​Bλ0(t) and Bλ1(t) is calculated, and the electron temperature Te at that time is calculated using the calibration curve shown in Figure 13. If this electron temperature Te exceeds a preset temperature threshold, the flow rate of the plasma gas, the plasma output, and the amount of raw material supplied are increased or decreased to control the electron temperature Te so that it falls within the temperature threshold range.

[0086] 14(a), when the electron temperature Te exceeds the temperature threshold Te1, the control device 30 controls the plasma gas flow rate, plasma output, and raw material supply rate by the gas flow rate adjusting means 19, plasma output adjusting means 21, and raw material supply rate adjusting means 16 so that the electron temperature Te decreases, thereby keeping the electron temperature Te within the temperature threshold.

[0087] 14(b), when the electron temperature Te exceeds the temperature threshold Te2, the control device 30 controls the plasma gas flow rate, plasma output, and raw material supply rate by the gas flow rate adjusting means 19, plasma output adjusting means 21, and raw material supply rate adjusting means 16 so that the electron temperature Te increases. As a result, the electron temperature Te changes so as to fall within the temperature threshold.

[0088] In this way, by controlling at least one of the plasma gas flow rate, plasma output, and raw material supply amount so that the electron temperature Te falls within the temperature threshold range (Te1 to Te2), the plasma state can be stabilized, thereby preventing the production of microparticles from being stopped midway and reducing productivity, and also stabilizing the quality of the microparticles produced.

[0089] When performing such control, since there is a tendency for the electron temperature Te to vary greatly immediately after the start of production of the microparticles (immediately after the raw material is supplied), it is preferable to configure the control device 30 so that a predetermined judgment start time is set and the above-mentioned control begins after this judgment start time has passed.

[0090] In the above example, the plasma gas supply amount, plasma output, and raw material supply amount are controlled when the electron temperature Te exceeds the temperature threshold range (Te1 to Te2). However, the plasma gas supply amount, plasma output, and raw material supply amount can also be configured to be controlled in advance so that the temperature threshold range (Te1 to Te2) is not exceeded.

[0091] In the above example, the electron temperature Te is calculated and control is performed using this electron temperature Te. However, control may also be performed using the ratio Bλ1(t) / Bλ0(t) without converting to electron temperature. In this case, the threshold value can be arbitrarily set as an ion state ratio threshold value for control. Furthermore, the ion state ratio threshold value may be set based on good results from multiple microparticle production runs performed in advance.

[0092] Furthermore, while the above example uses luminescence in two ionic states, luminescence in three or more ionic states can also be used. In this case, for example, if the emission wavelength of trivalent raw material Z is λ3, the temperature corresponding to the ratio Bλ1(t) / Bλ0(t), the temperature corresponding to the ratio Bλ2(t) / Bλ0(t), and the temperature corresponding to the ratio Bλ2(t) / Bλ1(t) should be controlled so that they do not exceed their respective temperature thresholds.

[0093] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible without departing from the scope of the present invention. In addition, methods for controlling the physical properties of fine particles by the above-described control are also included in the embodiments of the present invention. [Explanation of symbols]

[0094] 10 Fine particle production equipment 12 chambers 13 Observation window 14 Collection Pot 15 Raw material supply device 16 Raw material supply amount adjustment means 17 Raw material supply nozzle 18 Plasma gas supply device 19 Gas flow rate adjusting means 20 DC plasma torch (voltage application device) 21 Plasma output adjustment means 22 Plasma emission analyzer 23 Collimating lens 24 Optical Fiber 25 Spectrometer 26 Spectral Processing Section 30 Control device

Claims

1. A microparticle manufacturing apparatus comprising a chamber, a raw material supply device, a plasma gas supply device, a voltage application device, a plasma emission analysis device, and a control device, a predetermined voltage is applied by the voltage application device to the plasma gas supplied from the plasma gas supply device, and plasma is generated by using the plasma to heat a plurality of types of raw materials supplied from the raw material supply device, thereby gasifying the plurality of types of raw materials, and then cooling the raw materials in the chamber, thereby producing fine particles; the plasma optical emission analyzer analyzes the optical emission of the plasma after the raw material is introduced, The control device calculates a ratio which is a normalized time average value by dividing the time average value of the emission wavelengths of a specific raw material among the multiple raw materials appearing in the plasma emission spectrum measured by the plasma emission analysis device by the time average value of the emission wavelengths of the other raw materials, or a normalized second-order derivative time average value obtained by second-order differentiation of the normalized time average value with respect to wavelength, and when the ratio exceeds a predetermined raw material ratio threshold, controls at least one of the supply amount of the plasma gas, the output of the generated plasma, and the supply amount of the raw material.

2. The particle manufacturing apparatus described in claim 1, characterized in that the raw material ratio threshold is set based on the ratio of the output of each wavelength derived from multiple types of raw materials in multiple successful results from previous particle manufacturing operations, and the blending ratio of the multiple raw materials.

3. A method for producing fine particles by applying a predetermined voltage to a plasma gas using a voltage application device to generate plasma, thereby heating a plurality of raw materials and gasifying the raw materials, and then cooling the raw materials, A method for producing fine particles, characterized in that a ratio is calculated by dividing the time average value of the emission wavelengths of a specified raw material among the multiple raw materials appearing in the plasma emission spectrum by the time average value of the emission wavelengths of the other raw materials, or by calculating a normalized time average value, or a normalized second-order derivative time average value obtained by second-order differentiation of the normalized time average value with respect to the wavelength, and when the ratio exceeds a predetermined raw material ratio threshold, at least one of the supply amount of the plasma gas, the output of the generated plasma, and the supply amount of the raw material is controlled.

4. A method for producing fine particles by applying a predetermined voltage to a plasma gas using a voltage application device to generate plasma, thereby heating a plurality of raw materials and gasifying the raw materials, and then cooling the raw materials, A method for controlling the physical properties of microparticles, characterized in that a ratio is calculated by dividing the time average value of the emission wavelengths of a specified raw material among the multiple raw materials appearing in the plasma emission spectrum by the time average value of the emission wavelengths of the other raw materials, or by calculating a normalized time average value, or a normalized second-order derivative time average value obtained by second-deriving the normalized time average value with respect to the wavelength, and when the ratio exceeds a predetermined raw material ratio threshold, at least one of the supply amount of the plasma gas, the output of the generated plasma, and the supply amount of the raw material is adjusted to control the physical properties of the microparticles so as to achieve good results during the production of microparticles.

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