JP2005066557A - Method and apparatus for manufacturing minute particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method and apparatus, in which spherical minute particles of a uniform size can be surely manufactured. <P>SOLUTION: The manufacturing apparatus of the minute particles 100 is composed of an aperture 4 discharging and dropping a molten solution 1 during dropping, and a coil 6 provided below the aperture 4, in which a direction traversing a dropping direction of a molten solution 5 during dropping is an axial direction 7, and which applies an alternating magnetic field to the molten solution 5 during dropping, by which Lorentz force acts on the molten solution 5 during dropping by the alternating magnetic field to be able to produce a droplet 8 segmentalized into a granularity of the uniform size, and to drop the droplet 8 alternately in different directions. Therefore, it is possible to prevent a coalescence of the droplets 8 certainly, and to manufacture minute particles of the uniform size. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus for manufacturing fine particles having a uniform size from a molten liquid.

  Conventionally, as a method and apparatus for producing fine particles of uniform size, a regular vibration is applied to the molten liquid of the raw material discharged from the holes, so that the molten liquid undergoes a knot-like deformation at regular intervals. By generating and spontaneously growing this deformation by the action of the surface tension of the molten liquid, the molten liquid is divided into granular droplets having a uniform size, and these droplets are solidified by cooling. The method is known.

  As means for applying vibration to the molten liquid by this method, there are means for vibrating the holes, means for irradiating the molten liquid discharged from the holes with a sound wave having a constant frequency, etc. .

  However, in the conventional method for producing microparticles, since the droplets generated by being separated from the molten liquid fall one after another in a very close state, the droplets are uniformly sized from the molten liquid. Even if it is divided, the droplets coalesce in the subsequent dropping process and become droplets of different sizes, and there is a problem that the size of the finally produced fine particles becomes non-uniform .

  In order to solve this problem, a regular vibration is applied to the molten liquid discharged from the hole, and the container having the hole in the peripheral wall is rotated at high speed so that the molten liquid is discharged radially. A method for generating droplets toward the surface has been proposed (see Patent Document 2).

According to the method of applying regular vibration to the molten liquid discharged from the hole and generating droplets toward the periphery while rotating the container having the hole in the peripheral wall part, the container rotates and the peripheral wall part As the molten liquid is discharged radially from the holes, the generated droplets follow different parabolic trajectories, effectively preventing the droplets from coalescing and uniform. That is, it is possible to obtain microparticles of various sizes.
U.S. Pat.No. 5,445,666 JP-A-5-154425

  However, in the case where droplets are generated by a method of producing fine particles while rotating a container having a hole in the peripheral wall while applying regular vibration to the molten liquid discharged from the hole, the liquid is discharged radially. The droplets are scattered over a wide range around the rotating container, but the drop process of the droplets also serves as a cooling process for solidifying the droplets, so the droplets do not collide with each other during the fall. As described above, there is a problem that it is necessary to secure a drop drop area with a sufficient width in the apparatus for producing fine particles, and as a result, the apparatus becomes large.

  In addition, in order to produce microparticles having a diameter of less than 1 mm, the diameter of the holes for generating droplets is as small as that. However, since the surface tension of the liquid droplets discharged from the holes increases as the diameter of the holes decreases, it was necessary to increase the pressure in the container having the holes extremely to discharge the molten liquid continuously. . For example, when manufacturing Si microparticles as a granular semiconductor used in a photoelectric conversion device, it is necessary to suppress the material cost of Si and secure the minimum thickness necessary for light absorption. The size is as small as about 300 μm in diameter, and the pressure inside the container having the corresponding hole becomes as high as about 0.1 MPa to 1 MPa. And in order to rotate such a container at high speed, there existed a problem that a large-scale apparatus was needed and it also became expensive.

  The present invention has been devised in order to solve the above-described problems of the prior art. The purpose of the present invention is, for example, to easily obtain fine particles having a uniform size even for fine particles having a diameter of 1 mm or less. An object of the present invention is to provide a method and apparatus for producing fine particles that can be produced.

  In the method for producing microparticles of the present invention, a molten liquid is discharged from a hole and dropped, and the molten liquid that is falling is granulated by applying an alternating magnetic field in a direction crossing the dropping direction. It is characterized by making it a microparticle.

 Further, the apparatus for producing microparticles of the present invention is provided with a hole for discharging and dropping the molten liquid, and a direction crossing the direction in which the molten liquid falls below the hole as the axial direction. And a coil for applying an alternating magnetic field to the molten liquid.

  According to the method for producing microparticles of the present invention, the molten liquid is discharged from the hole and dropped, and the molten liquid being dropped is granulated by applying an alternating magnetic field in a direction crossing the dropping direction. Therefore, the Lorentz force acts on the falling molten liquid by an alternating magnetic field, thereby generating droplets that are divided into particles having a uniform size. Since every other droplet can be dropped in different directions, coalescence of the droplets can be reliably prevented, and microparticles of uniform size can be produced.

 Further, according to the apparatus for producing fine particles of the present invention, a hole for discharging and dropping the molten liquid, and a direction crossing the direction in which the molten liquid falls below the hole is provided as an axial direction. Since the coil for applying an alternating magnetic field to the molten liquid is provided, spherical microparticles of uniform size can be easily manufactured by the method of manufacturing microparticles of the present invention. Further, it is not necessary to ensure a wide drop area for the droplets discharged radially as in the prior art, and there is no need to use a driving device for rotating the container, so that the rotating container has a high pressure. For this reason, it is not necessary to use a large-scale device, so that the device can be downsized.

  Hereinafter, the method and apparatus for producing fine particles of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a schematic configuration in an example of an embodiment of a production apparatus for carrying out the method for producing fine particles of the present invention.

  A fine particle manufacturing apparatus 100 shown in FIG. 1 includes a container 2, a hole 4 formed in the bottom surface of the container 2, and a heater 3 that heats the molten liquid 1 that is disposed on the side surface of the container 2 and is filled in the container 2. And a coil 6 arranged below the bottom surface of the container 2 with the direction crossing the falling direction of the molten liquid 1 discharged from the hole 4 as the axial direction.

  As the raw material to be the molten liquid 1, all materials having conductivity in the liquid state can be used. For example, a metal or a semiconductor material having high conductivity in a liquid state such as Si or Ge can be used.

  The container 2 is preferably made of a material considering the reactivity with the molten liquid 1. For example, if the molten liquid 1 is Si, by using the container 2 made of aluminum oxide, silicon carbide, graphite, etc., it is possible to prevent the components constituting the container 2 from being mixed into the molten liquid 1, And since it is less deteriorated, it can be used for a long time.

  The hole 4 may be formed by drilling or laser processing according to the diameter. A plurality of holes 4 may be provided to improve productivity.

  The coil 6 is a conductive wire wound in a spiral shape.

  Next, a method for producing fine particles having a uniform size using the fine particle production apparatus 100 of the present invention will be described. First, a solid raw material that becomes the molten liquid 1 is charged into the container 2, and the heater 3 is operated to heat the raw material through the container 2 and melt it into the molten liquid 1.

  Next, the molten liquid 1 is discharged from the holes 4 by applying pressure to the molten liquid 1. As the pressurizing means, for example, a means for introducing a gas that does not react with the molten liquid 1 such as an inert gas into the container 2 or a mechanical pressurizing means may be used.

  Here, when an AC voltage is applied to the coil 6 arranged in a direction crossing the direction in which the molten liquid 5 is falling, an AC magnetic field having the same period as the AC voltage is generated in the axial direction 7 of the coil 6. . Here, when the falling molten liquid 5 passes through this alternating magnetic field, the falling molten liquid 5 has conductivity, so that an induced current having the same period as the alternating magnetic field is generated in the falling direction. Due to this induced current and the alternating magnetic field applied by the coil 6, Lorentz force acts on the falling molten liquid 5. Since the Lorentz force is represented by the outer product of the current vector and the magnetic field vector, the period in which the Lorentz force works is half the period of the induced current and the alternating magnetic field.

  Due to the Lorentz force, the surface of the falling molten liquid 5 is distorted at regular intervals, and is divided into granular droplets 8 of a uniform size by the surface tension of the falling molten liquid 5. The Since this hump-shaped deformation interval corresponds to half of the period of the alternating magnetic field, the size of the droplet 8 to be divided is the opening diameter of the hole 4, the velocity of the falling molten liquid 5, and the AC voltage. Determined by the period. Therefore, the frequency of the AC voltage applied to the coil 6 may be determined from the opening diameter of the hole 4, the speed of the molten liquid 5 falling, and the desired size of the droplet 8.

  For example, when the opening diameter of the hole 4 is 100 μm and the speed of the falling molten liquid 5 is 14.4 m / sec, in order to generate 8000 droplets 8 having a particle diameter of 300 μm per second, it is applied to the coil 6. The frequency of the AC voltage is 2 kHz.

  The Lorentz force acts in a direction perpendicular to each of the falling direction of the molten liquid 5 and the axial direction 7 of the coil 6, that is, a direction perpendicular to the paper surface of FIG. The working direction is reversed 180 degrees during one cycle. Accordingly, the direction in which the Lorentz force acts strongly on the falling molten liquid 5 is also reversed 180 degrees every other time when the falling molten liquid 5 is divided into droplets 8. As a result, the dropping trajectories of the divided droplets 8 are 180 degrees different from each other, and the coalescence of the droplets 8 during the dropping process can be reliably prevented.

  At this time, the coil 6 is arranged so that the axis of the coil 6 is located directly below the hole 4 so that the falling molten liquid 5 passes across the central portion of the coil 6, and the axial direction 7 of the coil 6 falls. It is desirable to arrange so as to be orthogonal to the falling direction of the molten liquid 5. By doing so, the droplet 8 passes through a portion where the alternating magnetic field by the coil 6 is strong, and the directions of the induced current and the alternating magnetic field are orthogonal to each other. On the other hand, the Lorentz force can be effectively applied to 8.

  In addition, it is desirable to adjust the winding interval and the arrangement of the coils 6 so that the divided droplets 8 do not collide with the conductors of the coil 6 in the middle of dropping.

  As described above, the droplet 8 divided into a uniform size becomes spherical due to the surface tension, and becomes a spherical minute particle with a uniform size by releasing heat and solidifying in the dropping process.

  According to the microparticle manufacturing apparatus 100 of the present invention as described above, a manufacturing apparatus capable of easily manufacturing spherical microparticles of uniform size is provided with a simple configuration without requiring a large-scale apparatus. It will be possible.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications and improvements can be added without departing from the scope of the present invention.

  For example, in the example of the above embodiment, the raw material to be the molten liquid 1 is heated by the heater 3 in the container 2 to be the molten liquid 1, but is supplied to the container 2 after the raw material is in a molten liquid state. You may make it do.

  In the example of the embodiment described above, the hole 4 is formed on the bottom surface of the container 2. However, the hole may be formed using a tubular member drawn out from the container 2.

It is sectional drawing which shows schematic structure in an example of embodiment of the manufacturing apparatus for enforcing the manufacturing method of the microparticles of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Molten liquid 2 ... Container 3 ... Heater 4 ... Hole 5 ... Falling molten liquid 6 ... Coil 7 ... Coil axial direction 8 ... Droplet
100 ... Microparticle production equipment

Claims (2)

The molten liquid is discharged from a hole and dropped, and the molten liquid that is falling is made into fine particles by applying an alternating magnetic field in a direction crossing the dropping direction to be granulated and solidified. A method for producing fine particles. A hole for discharging and dropping the molten liquid, and a coil for applying an alternating magnetic field to the falling molten liquid provided below the hole with the direction crossing the direction in which the molten liquid falls as an axial direction; An apparatus for producing fine particles, comprising:

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