Method for producing fine particles and device for producing fine particles

Abstract

A method for producing fine particles according to one embodiment of the present disclosure comprises: a step for ejecting particles mixed with a solvent as droplets; a step for irradiating the ejected droplets with laser light to form fine particles; and a step for removing the solvent from the droplets to recover the fine particles.

Description

Method for producing fine particles and apparatus for producing fine particles 【0001】 This disclosure relates to a method for producing fine particles and an apparatus for producing fine particles. 【0002】 In conventional technology, iron oxide particles in an organic solvent are irradiated with laser light to reduce iron oxide, process and manufacture spherical particles. The desired composition and shape are obtained by controlling the energy of the irradiated laser (see, for example, Non-Patent Document 1). 【0003】 IEEJ Transaction on Electronics, Information and System Vol. 135 No. 9 pp. 1066-1070 (2015) 【0004】 However, the technology described in Non-Patent Document 1 involves placing an organic solvent mixed with iron oxide particles into a container and processing it by irradiating it with laser light, which presents challenges in terms of productivity and efficiency from an industrial standpoint. Furthermore, the need to separate the processed and generated particles from the solvent increases the number of steps involved. 【0005】 This disclosure has been made in view of the above points, and aims to provide a method for producing processed and modified fine particles that can be manufactured with high productivity and efficiency. 【0006】 A method for producing fine particles according to one aspect of the present disclosure includes the steps of: discharging particles mixed in a solvent as droplets; irradiating the discharged droplets with laser light to form fine particles; and removing the solvent from the droplets to recover the fine particles. 【0007】 According to this disclosure, it is possible to provide a method for producing processed and modified fine particles that can be manufactured with high productivity and efficiency. 【0008】 This figure shows an example of a fine particle manufacturing apparatus according to this embodiment. 【0009】 Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the embodiments described below. 【0010】 FIG. 1 is a diagram showing an example of an apparatus for producing fine particles according to the present embodiment. The apparatus 1 for producing fine particles shown in FIG. 1 includes a droplet discharging unit 10, a laser light irradiation unit 20, and a fine particle collecting unit 30. 【0011】 The droplet discharging unit 10 is a unit that discharges the particles P mixed in the solvent S ０ as droplets D, and includes a nozzle 11 that discharges the droplets D, a container 12 that stores a mixed solution of the solvent S and the particles P ０ and a discharge control unit 13 that controls the discharge of the droplets D. The droplet discharging unit 10 can discharge the particles P mixed in the solvent S ０ as droplets D. 【0012】 As the particles P ０ materials to be processed and modified can be appropriately selected, and examples include metals, metal oxides, ceramics, polymers, and the like. As the size of the particles P ０ those having a number average particle size of several hundred nm to several tens of μm observed by, for example, an electron microscope can be used. 【0013】 Examples of the solvent S include water, organic solvents such as ethanol, and mixed solvents thereof. The content of the particles P with respect to the solvent S ０ can be appropriately selected according to droplet discharge conditions, laser light irradiation conditions, etc., and examples include 5 mg / mL to 100 mg / mL. The container that stores the mixed solution of the solvent S and the particles P ０ preferably further includes a stirring unit that stirs the mixed solution. As the stirring unit, for example, a stirrer, a stirring rod, ultrasonic vibration, etc. can be used. 【0014】 Conditions such as the size, discharge speed, and frequency of the discharged droplets D ０ can be appropriately set according to various conditions such as the type and size of the particles P ０Taking the size into consideration, it can be set to, for example, about 10 μm to 100 μm. 【0015】 The laser beam irradiation means 20 irradiates the ejected liquid droplet with laser light L to form fine particles P １ The means for forming a liquid droplet includes a laser light source 21 that irradiates laser light and an irradiation control unit 22 that controls the irradiation of the laser light. The laser light irradiation means 20 irradiates the ejected liquid droplet with laser light L to form fine particles P １ It is possible to form this. 【0016】 For example, an infrared pulsed laser can be used as the laser light source 21. The conditions for the laser light source and the laser light L to be irradiated are as follows: ０ The type of material and the size of the droplet D can be appropriately selected. The irradiation diameter of the laser beam L is preferably about the same as or larger than the droplet diameter of the droplet D, for example, it can be about 10 μm to several mm. When a pulsed laser is used as the laser beam, the ejected droplet D is irradiated with at least one pulse of laser beam L. The laser beam L may be scanned and irradiated in synchronization with the droplet ejection speed, or multiple laser light sources 21 may be arranged on the path of the droplet D and the laser beam L may be irradiated at the timing when the droplet D passes through each optical path. 【0017】The discharge control unit 13 and the irradiation control unit 22 may receive and transmit control signals to each other to control each other, or they may be controlled as an integrated unit. Specifically, the discharge control unit 13 controls the discharge of droplets D from the nozzle 11 based on set conditions such as the size, discharge speed, and discharge frequency of the droplets D discharged from the nozzle 11, and outputs the set conditions and executed parameters to the irradiation control unit 22. The irradiation control unit 22 irradiates each droplet D with laser light L based on set conditions such as the irradiation intensity, irradiation diameter, and irradiation frequency of the laser light L, and parameters received from the discharge control unit 13. In addition, parameters such as whether the irradiation was performed and the irradiation position on the droplet D may be detected and information such as irradiation accuracy may be analyzed, and image recognition, infrared sensors, etc. can be used for analysis. By feeding back the analysis signal to the discharge control unit 13 and / or the irradiation control unit 22, discharge and / or irradiation can be controlled with greater precision. 【0018】 In droplet D, particles P are in solvent S. ０ By irradiating the particle P with laser light, ０ It is processed into fine particles P １ This can be obtained. The processing involves particles P ０ This involves at least one of the following: miniaturization, modification by reduction of the material, and melting and solidifying at least a portion of the particles, and the target fine particles P １ It can be set appropriately according to the requirements. In one embodiment, the raw material is particle P ０ The molten material absorbs the laser light L, reaching a temperature above its melting point, and the resulting molten droplets are cooled during intermittent laser pulses, forming spherical fine particles P. １ Therefore, relatively uniform sub-μm sized fine particles P are obtained. １ You can obtain this. 【0019】 Laser irradiation and processing can be carried out in the atmosphere, in an inert gas such as nitrogen, or in an environment with a lower pressure than the atmosphere. If the solvent of the droplet is an organic solvent, it is preferable to provide an exhaust system as the solvent removal unit 31. 【0020】 The fine particle recovery means 30 removes the solvent S from the droplet D and collects fine particles P １It is a means for recovering, and includes a solvent removal unit 31 and a fine particle recovery container 32. The fine particle recovery means 30 removes the solvent from the droplet D to obtain the fine particles P １ can be recovered. 【0021】 For example, the solvent removal unit 31 is a chamber that covers the discharge port of the nozzle 11, the irradiation port of the laser light source 21, and the fine particle recovery container 32. The solvent removal unit 31 can be provided with an exhaust pipe for removing the solvent S volatilized by the irradiation of the laser light L, and vaporization and removal of the solvent S in an inert gas or under reduced pressure, and can efficiently remove the solvent S from the droplet after laser light irradiation. 【0022】 As the fine particle recovery container 32, there is no particular limitation as long as it can recover the fine particles P １ and a known container can be used. The fine particle recovery container 32 may further include a filter for classifying the recovered fine particles P, and may also perform suction. Depending on the type of the fine particles P １ the fine particles P may be selectively recovered by an adsorption mechanism such as a magnetic force. １ １ 【0023】 Hereinafter, the steps executed in the method for manufacturing fine particles will be described. The method for manufacturing fine particles of the present embodiment can be preferably implemented by the droplet discharge means 10 in the fine particle manufacturing apparatus 1 of FIG. 1. 【0024】 In step S101, the particles P mixed in the solvent S ０ are discharged as droplets D. Specifically, a container 12 containing the mixed liquid obtained by mixing the solvent S and the particles P ０ and the particles P mixed in the solvent S are discharged as droplets D from the nozzle 11 connected to the container 12. Conditions such as the size, discharge speed, and frequency of the discharged droplets D are controlled by the discharge control unit 13 to perform the discharge of the droplets D. ０ 【0025】 In step S102, the discharged droplets are irradiated with the laser light L to obtain the fine particles P １Forms the laser light L to be irradiated, based on the setting conditions set in advance in the irradiation control unit 22 and the parameters received from the discharge control unit 13. In the droplet D, particles P are formed in the solvent S. ０ By irradiating the particle P with laser light, ０ It is processed into fine particles P １ You can obtain this. 【0026】 In step S103, the solvent S is removed from the droplet D to form fine particles P. １ The solvent S is removed from droplet D by irradiation with laser light, which removes particles P. ０ This may be carried out during the processing stage, or it may be carried out with an additional solvent removal section 31 such as a reduced pressure chamber. 【0027】 As one embodiment, particle P ０ Using metal oxides such as iron oxide particles, and irradiating them with laser light, fine particles P １ As such, a reduced metal (e.g., iron particles) can be obtained. Laser irradiation conditions include, for example, Fe ２ O ３ For this purpose, a high microchip repetition rate Nd:YAG pulse laser (for example, maximum output average laser output: 250 mW, wavelength: 1064 nm, repetition frequency: 18 Hz, pulse width: 8 ns) can be used. The particle size of the metal oxide may be 1 μm to 50 μm in volume-average particle size measured by laser diffraction scattering. The resulting metal particle size can be, for example, 10 nm to 1 μm in number-average particle size observed by an electron microscope. 【0028】 The metal can be appropriately selected depending on the purpose, and examples include Mg, Al, Fe, Co, Ni, Mo, and W. The metal oxide MO can be appropriately selected from oxides corresponding to metal M. Among these, from the viewpoint of safety and availability, it is preferable that the metal is iron (Fe) and the metal oxide is iron oxide. Here, the metal oxide corresponding to metal M can be appropriately selected according to the valence of the target metal. Examples of iron oxides include iron(II) oxide (FeO) and iron(II,III) oxide (Fe). ３ O ４, iron(III) oxide Fe ２ O ３ These are some examples. 【0029】 particle P ０ The metal oxide is reduced to form fine particles P １ There are no particular restrictions on the method for confirming that a metal has been obtained, and any method can be selected as appropriate. For example, the presence of the metal may be identified by X-ray diffraction, and in the case of iron, iron oxide (Fe) ２ O ３ This can be determined by observing the change from reddish-brown to black (reduced iron), or by measuring the reducing ability, such as hydrogen production capacity. 【0030】 According to the fine particle manufacturing method and apparatus of this embodiment, since a laser beam is irradiated onto a droplet to process and modify the particles in the droplet, the productivity of manufacturing the processed and modified fine particles can be increased. Furthermore, since the solvent is removed along with the formation of the fine particles, there is no need to separate and recover the obtained fine particles from the solvent, and the manufacturing process can be simplified, thereby increasing the efficiency of manufacturing the processed and modified fine particles. Therefore, it is possible to provide a fine particle manufacturing method and apparatus that can produce processed and modified fine particles with high productivity and efficiency. 【0031】 The following additional information is disclosed regarding the embodiments described above. 【0032】<Notes> (Note 1) A method for producing fine particles, comprising: a step of discharging particles mixed in a solvent as droplets; a step of irradiating the discharged droplets with laser light to form fine particles; and a step of removing the solvent from the droplets to recover the fine particles. (Note 2) The method for producing fine particles according to Note 1, wherein the particles are selected from the group consisting of metals, metal oxides, ceramics, and polymers. (Note 3) The method for producing fine particles according to Note 1, wherein the particles are iron oxide particles and the fine particles are iron particles. (Note 4) An apparatus for producing fine particles, comprising: means for discharging particles mixed in a solvent as droplets; means for irradiating the discharged droplets with laser light to form fine particles; and means for removing the solvent from the droplets to recover the fine particles. (Note 5) The apparatus for producing fine particles according to Note 4, wherein the particles are selected from the group consisting of metals, metal oxides, ceramics, and polymers. (Note 6) The apparatus for producing fine particles according to Note 4, wherein the particles are iron oxide particles and the fine particles are iron particles. 【0033】 The present invention is not limited to the embodiments specifically disclosed above, and various modifications, changes, and combinations with known technologies are possible without departing from the scope of the claims. 【0034】 1. Apparatus for manufacturing fine particles 10. Droplet dispensing means 11. Nozzle 12. Container 13. Dispensing control unit 20. Laser light irradiation means 21. Laser light source 22. Irradiation control unit 30. Fine particle recovery means 31. Solvent removal unit 32. Fine particle recovery container D. Droplet L. Laser light P ０ particle P １ Fine particles S solvent

Claims

1. A method for producing fine particles, comprising the steps of: discharging particles mixed in a solvent as droplets; irradiating the discharged droplets with laser light to form fine particles; and removing the solvent from the droplets to recover the fine particles.

2. The method for producing fine particles according to claim 1, wherein the particles are selected from the group consisting of metals, metal oxides, ceramics, and polymers.

3. The method for producing fine particles according to claim 1, wherein the particles are iron oxide particles and the fine particles are iron particles.

4. An apparatus for producing fine particles, comprising: means for discharging particles mixed in a solvent as droplets; means for irradiating the discharged droplets with laser light to form fine particles; and means for removing the solvent from the droplets to recover the fine particles.

5. The apparatus for producing fine particles according to claim 4, wherein the particles are selected from the group consisting of metals, metal oxides, ceramics, and polymers.

6. The apparatus for producing fine particles according to claim 4, wherein the particles are iron oxide particles and the fine particles are iron particles.

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