JPWO2013047678A1 - Fine particle manufacturing method - Google Patents

Abstract

Cutting or polishing comprising a fixed abrasive wire (2) to which abrasive grains are fixed, a support unit (8) for supporting a workpiece (10), and a coolant liquid supply unit (9) for supplying a coolant liquid. Using the crushing device (1), the workpiece (10) is cut or ground by relatively reciprocating or turning the fixed abrasive wire (2) or the workpiece (10) while supplying the coolant liquid. A micronization step, a recovery step in which fine particles (11) are formed by cutting or grinding the workpiece (10) and recovered as a slurry together with the coolant, and submicron from this slurry is taken as the average value of the particle size And a taking-out step of taking out fine particles having a normal distribution.

Description

  The present invention relates to a method for producing fine particles, and more particularly to a method for producing fine particles having a normal distribution in which submicron is an average value of particle diameters.

  In general, it is known that as the particle size of a sintered body or a coating material falls within a submicron range, the sinterability and coating property are improved. For example, the characteristics of a ceramic sintered body or silicon particle coating material made of silicon are improved as the particle size of silicon particles as a raw material falls within a submicron range. Alternatively, the same quality improvement can be seen when silicon particles are used as a negative electrode material for a lithium ion secondary battery. Further, when a silicon alloy such as magnesium silicide or manganese silicide is used as a thermoelectric element, the thermoelectric performance is expected to improve as the particle diameter of the silicon alloy as a material falls within the submicron range.

  Conventionally, as a method for producing such fine particles, there is a breakdown method in which a large lump is pulverized to obtain particles of a desired particle size, and a build that obtains particles of a desired particle size by growing from a raw material having a small molecular level Up method is used.

  For example, as a breakdown method, a method is known in which a large lump is pulverized using a ball mill, a jet mill or the like (see Patent Document 1). However, with the breakdown method, it is said that it is very difficult to produce fine particles having a normal distribution with the average value of submicron particle size. Further, as a build-up method, a CVD method, a sputtering method, and the like are known. However, since the manufacturing cost is expensive and mass production is difficult, it is not suitable for industrial production.

JP 2000-176303 A

  The present invention takes the above-mentioned conventional art into consideration, and can obtain fine particles having a normal distribution in which submicron is the average value of particle diameters by mechanical means (breakdown method). An object is to provide a method for producing fine particles which is excellent in cost and suitable for industrial production.

  In order to achieve the object, in the present invention, a fixed abrasive wire to which abrasive grains are fixed in advance, a support unit that supports a workpiece to be cut or ground and presses against the fixed abrasive wire, and polishing. Using a cutting or grinding device provided with a coolant liquid supply unit for supplying a coolant liquid that does not contain an agent, pressing the workpiece against the fixed abrasive wire using the support unit, and supplying the coolant liquid A refining step of cutting or grinding the workpiece by reciprocating or turning the fixed abrasive wire or the workpiece while supplying a coolant liquid from a unit, and cutting or grinding of the workpiece It comprises a recovery step of recovering the formed fine particles as a slurry together with the coolant, and a take-out step of taking out the fine particles from the slurry. Providing fine particle production process.

  Preferably, the fine particles have a normal distribution in which submicron is an average value of particle sizes.

  Preferably, the fine particles have a particle size of 10 nm to 100 μm and a purity of 99.5% or more.

  Preferably, the fine particles have a particle size of 20 nm to 3 μm and a purity of 99.5% or more.

  Preferably, a plurality of the fixed abrasive wires are arranged in parallel.

  Preferably, the fixed abrasive wire is spirally wound to form a curved portion.

  Preferably, the workpiece is pressed against the fixed abrasive wire while reciprocating in the direction perpendicular to the axial direction of the wire of the fixed abrasive.

  Preferably, the workpiece is pressed against the fixed abrasive wire while rotating the workpiece.

  Preferably, an individual liquid separator is used in the extraction step.

  Preferably, after the removing step, pure water is added to the fine particles and stirred, and then the fine particles are precipitated, and the supernatant is discarded to further improve the purity of the fine particles. .

  Preferably, after the take-out step, pure water is added to the fine particles, and after stirring, the impurities are removed together with the pure water added using the individual liquid separator to further improve the purity of the fine particles. A purity improving step is performed.

  As described above, according to the present invention, the workpiece is cut or ground using the fixed abrasive wire while supplying the coolant liquid that does not contain the abrasive in the miniaturization process. In the process, the desired fine particles can be obtained without going through a complicated post-treatment process such as chemical treatment.

  In addition, since fine particles having a normal distribution with submicron average particle size can be obtained, for example, when producing a magnesium silicide thermoelectric element by sintering, the particle uniformity in the submicron order is obtained. This demand can be met in the required fields.

  In addition, fine particles having a particle size of 10 nm to 100 μm and a purity of 99.5% or more can be obtained.

  Further, fine particles having a particle diameter of 20 nm to 3 μm and a purity of 99.5% or more can be obtained.

  In addition, since a plurality of the fixed abrasive wires are arranged in parallel, the area where the workpiece is pressed against the fixed abrasive wire in one miniaturization step increases, and more fine particles Can be obtained efficiently. When the workpiece is a silicon ingot, the refining process can be performed simultaneously with the slicing process of the silicon wafer by reciprocating the fixed abrasive wire in the axial direction. Silicon sludge discarded by slicing can be used effectively. As an example, a cutting margin necessary for slicing a 180 μm thick silicon wafer from a high-purity silicon ingot is about 150 μm. For this reason, at present, almost half the amount of high-purity silicon is discarded as silicon sludge. However, according to the present invention, it can be effectively used as fine particles, which is preferable from the viewpoint of recycling.

  In addition, since the curved portion is formed by spirally winding the fixed abrasive wire, an area where the workpiece is pressed against the fixed abrasive wire in a single miniaturization process increases, and more Fine particles can be obtained efficiently.

  Further, since the workpiece is pressed against the fixed abrasive wire while reciprocating in the direction perpendicular to the axial direction of the fixed abrasive wire, the workpiece can be made into fine particles without waste.

  Further, since the workpiece is pressed against the fixed abrasive wire while turning, the workpiece can be made into fine particles without waste.

  In addition, since a single liquid separator is used in the extraction step, fine particles can be extracted efficiently in a shorter time.

  Moreover, since finer particles with higher purity can be obtained, they can be used as raw materials for hard ceramics, solar cell materials, thermoelectric conversion element materials, and negative electrode materials for lithium ion secondary batteries that require higher purity. It becomes like this. In addition, unlike complicated post-processing steps such as chemical processing, the operation can be performed with a simple operation, resulting in high work efficiency. Furthermore, in the case where the miniaturization process is performed simultaneously with the slicing process of the silicon wafer, it is also preferable from the viewpoint of recycling because it generally leads to reuse of silicon sludge discarded as cutting waste. .

  In addition, the point that fine particles with higher purity can be obtained is the same as described above, but finer particles with higher purity can be obtained efficiently in a shorter time by using a single-liquid separator. .

It is a schematic perspective view of a cutting or grinding apparatus. It is an expansion schematic of a fixed abrasive wire. It is the schematic of a cutting or grinding apparatus. It is a graph which shows the particle size distribution of the fine particle obtained at the taking-out process. It is the schematic at the time of arranging a plurality of fixed abrasive wires in parallel. It is the schematic at the time of winding a fixed abrasive wire helically and forming a curved part. It is the schematic which shows the flow in a purity improvement process. It is a graph which shows the relationship between the pure water washing | cleaning amount and impurity density | concentration in a purity improvement process.

  Hereinafter, an embodiment of a fine particle manufacturing method according to the present invention will be described using a workpiece as a silicon ingot. Silicon as a workpiece is merely an example, and various brittle materials other than silicon (for example, silicon alloys such as magnesium silicide and manganese silicide) can be applied as the workpiece in the present invention.

  As shown in FIG. 1, a cutting or grinding apparatus 1 as an example used in the fine particle manufacturing method according to the present invention includes a fixed abrasive wire 2 and a wire holding roller 3 around which the fixed abrasive wire 2 is wound. And a slurry tank 4. The wire holding roller 3 protrudes from the apparatus main body 5. Two wire holding rollers 3 are disposed, and the fixed abrasive wire 2 is wound around the two wire holding rollers 3 and continuously wound. At that time, the fixed abrasive wires 2 are wound so as to be spaced apart from each other. In addition, as this apparatus main body 5, you may use a general fixed abrasive wire saw apparatus.

  As shown in FIG. 2, the fixed abrasive wire 2 is formed of a wire 6 and an abrasive grain 7, and the abrasive grain 7 is fixed to the wire 6 in advance. In the present embodiment, as an example when the workpiece is a silicon ingot, the protruding length of the abrasive grains 7 from the wire 6 is 10 μm or less, and the pitch of the abrasive grains 7 is distributed at intervals of several tens of micrometers. A fixed abrasive wire 2 is used. However, the fixed abrasive wire 2 is not limited to this form, and can be changed according to the purpose of the workpiece or the fine particles to be manufactured.

  A method for producing fine particles from a workpiece using such a cutting or grinding apparatus 1 will be described. Here, a case where the workpiece 10 is cut will be described. As shown in FIG. 3, the two wire holding rollers 3 are rotated or reversed in the same direction to cause the fixed abrasive wire 2 to reciprocate or move in one direction in the direction of arrow A. The rotation or reverse rotation of the wire holding roller 3 at this time is performed by the drive unit 13. That is, when one wire holding roller 3 rotates or reversely rotates, the fixed abrasive wire 2 reciprocates or moves in one direction in conjunction with this, and the other wire holding roller 3 rotates or reversely moves according to this. . Then, the workpiece 10 supported by the support unit 8 is moved in the arrow B direction. This movement is performed by a lifting mechanism (not shown) provided in the support unit 8. At this time, the coolant liquid 12 is supplied from the coolant liquid supply unit 9 to the cut portion of the workpiece 10. This coolant liquid 12 contains no abrasive. That is, it only serves as cooling water for cooling the heat generated when the workpiece 10 is cut with the fixed abrasive wire 2. The workpiece 10 is cut only by the abrasive grains 7 fixed to the wire 6. Thereby, since the miniaturization process can be executed simultaneously with the slicing process of the silicon wafer, the silicon sludge discarded in the general slicing process of the silicon wafer can be effectively used.

  Simultaneously with such a miniaturization step, a recovery step is performed. When the workpiece 10 and the fixed abrasive wire 2 come into contact with each other, the workpiece 10 is cut and silicon fine particles 11 are formed. The silicon fine particles 11 are recovered as a slurry in the slurry tank 4 together with the coolant liquid 12.

  Next, a removal process is performed. As a method for extracting fine particles from the slurry, a general solid-liquid separation method may be used. As an example, there are a method of sucking up slurry with a pump and taking out fine particles with a centrifugal separator as the take-out unit 21 and a method of taking out fine particles with a filter press as the take-out unit 21. Thereby, the fine particles 11 are smoothly taken out from the coolant 12 from the slurry. The coolant liquid 12 from which the fine particles have been taken out is returned to the coolant tank. Since the fine particles taken out in this manner contain a small amount of coolant, they are put into a pure water tank and washed. Depending on the application, tap water or well water may be used in addition to pure water. In any case, since the coolant liquid does not contain an abrasive, cleaning with a chemical liquid is unnecessary.

  When the particle size of the silicon fine particles thus obtained was measured, it had a particle size of 10 nm to 100 μm as shown in FIG. More specifically, the obtained silicon fine particles had a normal distribution with an average value of 500 nm within a range of 20 nm to 3 μm. Further, when the silicon purity at this time was analyzed, it was 99.5%.

  Therefore, it is understood that fine particles having a normal distribution with submicron as the average value of the particle diameter can be produced by mechanical means (breakdown method) such as cutting the workpiece 10 using the fixed abrasive wire 2. It was. Furthermore, since the fixed abrasive wire 2 to which the abrasive grains are fixed in advance and the coolant liquid 12 containing no abrasive are used, it is possible to prevent the abrasive grains from being mixed into the silicon fine particles 11. At the same time, it was possible to obtain fine particles of purity.

  By the way, in the above embodiment, the fixed abrasive wire 2 is wound around the two wire holding rollers 3 and continuously wound. However, as shown in FIG. It may be arranged. Fine particles can be produced in the same manner as in the above example by moving the workpiece 10 in the J direction while reciprocating the fixed abrasive wire 2 in the direction of arrow P (the axial direction of the wire 2). On the other hand, fine particles can be produced by moving the workpiece 10 in the J direction while reciprocating the fixed abrasive wire 2 in the direction of arrow I (the direction perpendicular to the axis of the wire 2).

  Alternatively, as shown in FIG. 6, the fixed abrasive wire 2 may be spirally wound to form a curved portion. By moving the workpiece 10 in the arrow H direction while rotating the fixed abrasive wire 2 in the arrow G direction, fine particles can be produced in the same manner as in the above example.

  Moreover, in the said embodiment, although the workpiece 10 is moved to the arrow B direction (refer FIG. 3, the arrow J direction in FIG. 5, the arrow H direction in FIG. 6), in addition to that, fixed abrasive When the workpiece 10 is pressed against the wire 2, the workpiece 10 may be reciprocated in the direction perpendicular to the axial direction of the fixed abrasive wire 2 (in the direction of arrow N in FIG. 5). By providing the support unit 8 not only with an elevating mechanism but also with a moving mechanism to the left and right, more fine particles can be produced more efficiently than in the above example.

  Or you may add the motion (the arrow Q direction in FIG. 5, the arrow M direction in FIG. 6) which rotates the workpiece 10 when pressing the workpiece 10 against the fixed abrasive wire 2. By providing the support unit 8 with not only an elevating mechanism but also a rotating mechanism, more fine particles can be produced more efficiently than in the above-described example.

  Furthermore, a purity improving step may be performed in order to further increase the purity of the silicon fine particles produced in the above embodiment. As shown in FIG. 7, after the take-out step described above, pure water is added to the silicon fine particles and stirred to make a fine particle mixed solution 18 (state (D)), which is left for a while. By precipitating the fine particles 19 (state (E)) and then discarding and drying the supernatant liquid 17, silicon fine particles with higher purity can be obtained as compared with the above example. In addition, you may repeat the said purity improvement process in multiple times by adding the pure water after discarding the supernatant liquid 17, and making it stir (state of (F)).

  The inventors of the present application conducted an experiment using the silicon fine particles 50 g produced in the above-described example in order to confirm the effect of the purity improving step. FIG. 8 shows the relationship between the amount of pure water added (horizontal axis) and the concentration (vertical axis) of impurities K (potassium), Fe (iron), and Ni (nickel) contained in silicon fine particles. is there. The case where the amount of added pure water is 0 liters indicates the concentration of impurities in silicon fine particles that have not been subjected to any purity improvement step. The concentration of K (potassium) as an impurity is 600 ppm, Fe (Iron) was 400 ppm and Ni (nickel) was 120 ppm. When the purity improving step was performed on the silicon fine particles (repeated), when the amount of pure water added exceeded 2 liters, impurities K (potassium), Fe (iron), and Ni (nickel) All the concentrations could be 100 ppm or less.

  In the purity improving step, after the fine particle mixture 18 is made, the fine particle mixture 19 is allowed to stand until the fine particles 19 are precipitated, but the pure water added is added using a solid-liquid separator such as a filter press or a screw press. In addition, it may be a means for removing impurities.

DESCRIPTION OF SYMBOLS 1 Cutting or grinding apparatus 2 Fixed abrasive wire 3 Wire holding roller 4 Slurry tank 5 Apparatus main body 6 Wire 7 Abrasive grain 8 Support unit 9 Coolant liquid supply unit 10 Workpiece 11 Silicon fine particle 12 Coolant liquid 13 Drive unit 17 Supernatant Liquid 18 Slurry 19 Fine particles 20 Curved portion 21 Take-out unit

Claims (11)

A fixed abrasive wire to which abrasive grains are fixed in advance;
A support unit that supports a workpiece to be cut or ground and presses against the fixed abrasive wire;
Using a cutting or grinding device provided with a coolant liquid supply unit that supplies a coolant liquid that does not contain an abrasive,
The workpiece is pressed against the fixed abrasive wire using the support unit, and the fixed abrasive wire and / or the workpiece is reciprocated or swiveled while supplying the coolant liquid from the coolant liquid supply unit. A micronization process for cutting or grinding the workpiece,
A recovery step of recovering fine particles formed by cutting or grinding of the workpiece as a slurry together with the coolant liquid;
A method for producing fine particles, comprising the step of taking out the fine particles from the slurry.   2. The method for producing fine particles according to claim 1, wherein the fine particles have a normal distribution in which submicron is an average value of particle diameters.   3. The method for producing fine particles according to claim 1, wherein the fine particles have a particle diameter of 10 nm to 100 [mu] m and have a purity of 99.5% or more.   3. The method for producing fine particles according to claim 1, wherein the fine particles have a particle diameter of 20 nm to 3 [mu] m and have a purity of 99.5% or more.   The method for producing fine particles according to any one of claims 1 to 4, wherein a plurality of the fixed abrasive wires are arranged in parallel.   The method for producing fine particles according to any one of claims 1 to 4, wherein the fixed abrasive wire is spirally wound to form a curved portion.   6. The micronization process, wherein the workpiece is pressed against the fixed abrasive wire while reciprocating in a direction perpendicular to the axial direction of the fixed abrasive wire. The fine particle manufacturing method in any one of.   The method for producing fine particles according to any one of claims 1 to 6, wherein, in the miniaturization step, the workpiece is pressed against the fixed abrasive wire while rotating.   The method for producing fine particles according to any one of claims 1 to 8, wherein, in the take-out step, the fine particles are taken out by using an individual liquid separator.   After the extraction step, pure water is added to the fine particles, and after stirring, the fine particles are precipitated, and the supernatant is discarded to further improve the purity of the fine particles. The method for producing fine particles according to any one of claims 1 to 8.   Purity improvement that further improves the purity of the fine particles by adding impurities to the fine particles after the extraction step, stirring, and then removing impurities together with the pure water added using the individual liquid separator The method for producing fine particles according to claim 9, wherein the step is performed.

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