JP2020090703A - Metal particle manufacturing device, metal particle manufacturing method, and metal particle classification method - Google Patents

Abstract

To provide a metal particle manufacturing device precisely classifying metal particles according to size; to provide a metal particle manufacturing method: and to provide a metal particle classification method.SOLUTION: A metal particle manufacturing device includes: a raw material crushing part 120 crushing the surface of a metal composition 200 to generate primary metal particles 201; a particle aggregation part 131 aggregating the primary metal particles 201 with each other to generate secondary metal particles 202 larger than the primary metal particles 201; a particle classification part 132 classifying the primary particles 201 from the secondary metal particles 202 by applying a perpendicular magnet field into the flow of solvent 210 containing the primary metal particles 201 and the secondary metal particles 202; and a particle recovery part 133 respectively recovering the classified primary metal particles 201 and the classified secondary metal particles 202.SELECTED DRAWING: Figure 5

Description

The present invention relates to a metal particle production apparatus for metal nanoparticles synthesized by a liquid phase method, a metal particle production method, and a metal particle classification method.

Metal particles having an average particle size of less than 0.5 μm are called metal nanoparticles. Since metal nanoparticles have physical and chemical properties different from those of bulk metals, for example, electrode materials such as conductive paste and transparent conductive film, high-density recording materials, catalyst materials, ink-jet ink materials, solder materials , Is used in various industrial materials for electronic circuit board applications. For example, metal nanoparticles have a high sinterability that is brought about by the fine particle size, and the particles can be sintered at a temperature of 500° C. or lower, which is much lower than the melting point of the metal that constitutes the metal nanoparticles. It has been confirmed. Further, the structural strength of the obtained sintered body is expected to be maintained up to around the melting point of the metal. As a metal constituting the metal nanoparticles, Ag is representative, and in addition, Au, Cu, Ni and the like can be mentioned (for example, Patent Document 1).

The metal nanoparticles are generally covered with an organic substance, whereby self-aggregation of the particles is prevented, and the independently dispersed form of the metal nanoparticles is maintained at room temperature. When using metal nanoparticles, the covering organic material is decomposed and removed, for example by high temperature. For example, when metal nanoparticles are used for joining members to be joined, when the metal composite nanoparticles covered with an organic substance are supplied to the surfaces of the members to be joined and heated to a predetermined temperature and baked, the organic substance Are decomposed and removed, and the active surface of the metal nanoparticles is exposed. Thereby, the metal nanoparticles are bonded to each other, and at the same time, they are bonded to the surface of the member to be bonded, and the members to be bonded are bonded to each other.

The method for producing the metal nanoparticles includes a vapor phase method such as a thermal CVD (chemical vapor deposition) method and a method of synthesizing in a gas by arc discharge, and a metal salt obtained by mixing an aqueous solution of a metal salt and a reducing auxiliary agent. There is a liquid phase method such as a reduction method for reducing an aqueous solution, which is synthesized in a liquid. The liquid phase method is more suitable because it is possible to avoid contact between the surrounding oxygen and the surface of the metal nanoparticles, and to suppress surface oxidation.

By the way, it is required that the metal nanoparticles used for various purposes have a uniform particle size. In order to meet such a demand, it is required to appropriately classify the metal nanoparticles according to the size of the produced particles, that is, to perform classification accurately. As a classification method of metal nanoparticles, for example, a wet centrifugal classification method is known (for example, Patent Document 2). According to this wet centrifugal classification method, a discharge area for fine metal particles is formed at the center of the centrifuge tube, and a discharge area for coarse metal particles is formed at the outer peripheral portion of the centrifuge tube. Thereby, the coarse metal particles and the fine metal particles can be classified by the centrifugal force.

JP, 2013-012693, A JP, 2008-142681, A

However, in the classification method disclosed in the cited document 2, since the discharge port diameter of the metal fine particles is small, the chances that the metal nanoparticles contact and collide with each other increase, and the metal nanoparticles may aggregate during the discharge. is there. In such a case, the size of the produced particles is not the desired size, and thus another classification method is desired.

An object of the present invention is to provide an apparatus for producing metal particles, a method for producing metal particles, and a method for classifying metal particles, which are capable of accurately classifying metal particles according to size.

The apparatus for producing metal particles of the present disclosure is a raw material crushing unit for crushing the surface of a metal composition to generate primary metal particles, aggregating the primary metal particles with each other, and producing secondary metal particles larger than the primary metal particles. A particle aggregating part to generate, a particle classification part for classifying the primary metal particles and the secondary metal particles by applying a magnetic field perpendicular to the flow of a solvent containing the primary metal particles and the secondary metal particles, It has a particle recovery part for recovering the classified primary metal particles and secondary metal particles respectively.

The metal particle manufacturing method according to the present disclosure crushes the surface of the metal composition to generate primary metal particles, agglomerates the primary metal particles with each other, and generates secondary metal particles larger than the primary metal particles, A magnetic field perpendicular to the flow of a solvent containing the primary metal particles and the secondary metal particles is applied to classify the primary metal particles and the secondary metal particles, and the classified primary metal particles and the secondary metal particles are classified. Collect each metal particle.

The method for classifying metal particles according to the present disclosure includes a primary metal particle and a secondary metal particle larger than the primary metal particle, which causes a solvent to flow in one direction, and a magnetic field perpendicular to the flow of the solvent is applied to the solvent. The primary metal particles and the secondary metal particles are classified.

According to the present invention, metal particles can be accurately classified according to size.

The figure which shows the process of the metal particle manufacturing process in Embodiment 1 of this invention. Diagram showing raw material crushing process by ultrasonic vibration Diagram showing particle aggregation process by ultrasonic vibration Diagram showing volume magnetic force acting on metal particles by magnetic field The schematic diagram which looked at the metal particle manufacturing apparatus in Embodiment 1 of this invention from the upper surface. The schematic diagram which shows the cross section of the metal particle manufacturing apparatus in Embodiment 1 of this invention. The schematic diagram which looked at the metal particle manufacturing apparatus in Embodiment 2 of this invention from the upper surface.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Metal particle manufacturing process>
First, a manufacturing process of metal nanoparticles (hereinafter simply referred to as metal particles) according to an embodiment of the present disclosure will be described. FIG. 1 is a diagram showing a metal particle manufacturing process according to the first embodiment of the present invention.

As shown in FIG. 1, the metal particle manufacturing process includes a raw material supplying step S1, a raw material crushing step S2, a particle aggregating step S3, a particle classifying step S4, and a particle collecting step S5.

The raw material supply step S1 is a step of supplying a solid-state metal composition, which is a raw material of metal particles, into a solvent.

The raw material crushing step S2 is a step of irradiating an ultrasonic wave into a solvent and applying impact pressure of cavitation to crush the surface of the metal composition to generate primary metal particles.

The particle aggregating step S3 is a step of irradiating the primary metal particles generated in the raw material crushing step S2 with ultrasonic waves to bring the primary metal particles into contact with each other to agglomerate them to generate secondary metal particles.

In the particle classification step S4, the solvent containing the secondary metal particles generated in the particle aggregation step S3 and the primary metal particles that have finished the particle aggregation step S3 without aggregating flows in one direction, It is a step of applying a magnetic field to the flow and classifying by utilizing the difference in magnetic force due to the difference in particle size.

The particle collecting step S5 is a step of collecting the secondary metal particles classified in the particle classifying step S4.

<Description of raw material crushing step S2>
FIG. 2 is a conceptual diagram for explaining how primary metal particles are generated by ultrasonic vibration in the raw material crushing step S2. Generally, ultrasonic waves propagate as a compressional wave in a liquid. As shown in FIG. 2, when ultrasonic waves are applied to the solvent 210, minute bubbles 211 are generated in the solvent 210 due to the compressional waves. This bubble 211 repeats expansion and contraction due to pressure fluctuations in the solvent 210 due to the compressional wave, and gradually grows. Then, when the large-grown bubble cannot withstand the contraction, the bubble collapses and a high-pressure shock wave 212 is generated. This phenomenon is generally called cavitation. The shock wave 212 acts on the surface of the metal composition 200, so that the surface of the metal composition 200 is crushed and primary metal particles 201 are generated. The primary metal particles 201 are generally about several nm in size.

<Explanation of Particle Aggregation Step S3>
FIG. 3 is a conceptual diagram for explaining how particles are aggregated by ultrasonic vibration in the particle aggregation step S3. As shown in FIG. 3, when a shock wave 212 is generated when a bubble is crushed in a state where the primary metal particles 201 are suspended in the solvent 210, the primary metal particles 201 are repelled and moved by the impact, and another primary metal Contact the particles 201. When the primary metal particles 201 contact with each other, they aggregate. By repeating this a plurality of times, the secondary metal particles 202 are generated.

<About ultrasound>
Regarding the frequency of the ultrasonic waves used in the raw material crushing step S2, the lower frequency is more preferable because the shock wave 212 when the bubbles are crushed becomes larger. The larger the shock wave 212 is, the more efficiently the primary metal particles 201 can be generated in the raw material crushing step S2. Specifically, the frequency of ultrasonic waves is preferably 15 kHz to 100 kHz, and most preferably 20 kHz to 30 kHz.

Regarding the frequency of the ultrasonic waves used in the particle aggregating step S3, since the purpose is not crushing but aggregation, it is more preferable to use high frequency ultrasonic waves than the raw material crushing step S2. In particular, by using a high frequency, the chances of cavitation increase and the secondary metal particles 202 can be efficiently generated.

Regarding the output of ultrasonic waves, the higher output can increase the amplitude of the vibration wave, so that the action of growing bubbles becomes stronger and the shock wave 212 at the time of bubble collapse can be increased. Therefore, in the raw material crushing step S2 and the particle aggregating step S3, the output of ultrasonic waves is most preferably 300W to 1200W. This is because the shock wave 212 becomes small at a low output of about 200 W, and an ultrasonic vibrating device capable of oscillating an ultrasonic wave having a higher output than 1200 W is expensive.

<About the metal composition>
The metal composition 200 which is a raw material of the metal particles may be a metal or an alloy containing at least one element of Sn, Ag, Cu, Sb, Bi, In and Au, and a metal oxide composed of these metals. The thing is good. Further, in order to efficiently generate the primary metal particles 201, it is most preferable that the size of the metal composition 200 is about 10 to 1000 μm in height and width. This is for the following reason. This is because if the thickness is 10 μm or less, the shock wave 212 is repelled by the shock wave 212 when hit and the efficiency with which the primary metal particles 201 can be generated decreases. Further, when it is 1000 μm or more, the surface area becomes small for the volume of the metal composition 200, and the probability of being acted upon by the shock wave 212 becomes low, resulting in a low efficiency of generating the primary metal particles 201.

<Particle classification step S4>
In the particle classification step S4, the magnetic field perpendicular to the flow direction of the solvent 210 is applied to the metal particles (the primary metal particles 201 and the secondary metal particles 202) contained in the flow of the solvent 210 as described above, so that the primary metal The particles 201 and the secondary metal particles 202 are classified. Details of the classification method in the particle classification step S4 will be described later.

FIG. 4 is a conceptual diagram for explaining the magnetic force applied to the metal particles 400 by the magnetic field 300. In the magnetic field 300, the magnetic volume force F _mag acts on the metal particles 400. The magnetic volume force F _mag can be expressed by the following equation (1).

In the formula (1), M is the magnetization [A/m], H is the magnetic field [A/m], χ is the magnetic susceptibility [m ³ /kg] of the metal particle 400 that is a magnetic substance, and ΔH is the magnetic field gradient [ A/m] and V represent the volume [m ³ ] of the metal particles 400. The magnetic volume force F _mag , the magnetization M, and the magnetic field H are vector quantities, and the magnetic susceptibility χ, the magnetic field gradient ΔH, and V are scalar quantities.

As shown in Expression (1), the magnitude of the magnetic volume force F _mag can be represented by the product of the volume V of the metal particle 400, the magnetization M, and the magnetic field gradient ΔH. From equation (1), it can be seen that the larger the volume of the metal particles 400, the greater the magnetic volume force F _mag acts. That is, since the volume of the secondary metal particles 202 is larger than that of the primary metal particles 201 as described above, the magnetic volume force _acting on the secondary metal particles 202 is _larger than the magnetic volume force F _{mag —} 201 acting on the primary metal particles 201. The volume force F _{mag — 202} is larger. In the particle classification step S4, this is utilized to classify the primary metal particles 201 and the secondary metal particles 202.

The direction of the magnetic volume force F _mag is determined by the direction of the magnetization M of the metal particles 400. The magnetization M can be represented by the product of the magnetic field strength H and the magnetic susceptibility χ of the metal particles 400. By controlling the direction of the magnetic field by the positive/negative of the magnetic susceptibility χ of the metal particles 400, the direction of the magnetic volume force F _mag Can be controlled.

Table 1 shows the magnetic susceptibility of the metal materials Sn, Cu, Bi that can be the material of the metal composition 200. As can be seen from Table 1, when the metal particles 400 are composed of Sn, Cu, and Bi, the magnetic susceptibility χ is χ<0 and they are diamagnetic materials. In this case, as shown in FIG. 4, the direction of the magnetic volume force F _mag is opposite to the direction of the magnetic field 300. On the other hand, when the metal particles 400 are a ferromagnetic material (for example, Co, Ni, or an alloy thereof), the magnetic susceptibility χ>0, and thus the direction of the magnetic volume force F _mag is the same as the direction of the magnetic field 300.

<Metal particle manufacturing apparatus 100>
Next, a metal particle manufacturing apparatus 100 capable of carrying out the above-described explanation plate metal particle manufacturing process will be described. FIG. 5 is a schematic view of the metal particle manufacturing apparatus according to Embodiment 1 of the present invention as viewed from above. Further, FIG. 6 is a schematic diagram showing a cross section of the apparatus for producing metal particles according to the first embodiment of the present invention, which is an xx cross section of FIG. 5.

As shown in FIG. 5, the metal particle production apparatus 100 according to the embodiment of the present invention includes a raw material supply unit 110, a raw material crushing unit 120, and a particle production unit 130. The particle manufacturing unit 130 includes a particle aggregating unit 131, a particle classifying unit 132, and a particle collecting unit 133.

As shown in FIGS. 5 and 6, the raw material crushing unit 120 and the particle manufacturing unit 130 are provided on the solvent tank 140. The solvent tank 140 is a tank through which the solvent 210 can flow. As shown in FIG. 6, the solvent tank 140 has a partition 141 that separates the raw material crushing unit 120 and the particle manufacturing unit 130.

The raw material supply unit 110 supplies the metal composition 200, which is a raw material of the metal particles, and the solvent 210 to the raw material crushing unit 120 side of the solvent tank 140. Since the solvent 210 is supplied in a larger amount than the metal composition 200, the solvent tank 140 stores the solvent 210 in an amount higher than that of the partition 141. On the other hand, since the metal composition 200 has a smaller amount than the solvent 210 and has a large specific gravity, it is arranged at the bottom of the raw material supply unit 110. In such a state, the metal composition 200 does not exceed the partition 141 of the solvent tank 140, while the solvent 210 can flow over the partition 141 to the raw material crushing section 120 side and the particle production section 130 side. It has become. In the example described above, the metal composition 200 and the solvent 210 are supplied from the raw material supply unit 110 to the raw material crushing unit 120, but the solvent 210 is stored in advance in the solvent tank 140 to some extent. May be.

The raw material crushing unit 120 crushes the surface of the metal composition 200 in the solvent 210 to generate primary metal particles 201. That is, in the raw material crushing unit 120, the raw material crushing step S2 of the metal particle manufacturing step shown in FIG. 1 is performed. As shown in FIG. 6, in the raw material crushing unit 120, a first vibrator 121 that emits ultrasonic waves is provided above the solvent tank 140. Under the control of a control unit (not shown), the first oscillator 121 irradiates the raw material crushing unit 120 with ultrasonic waves to generate the primary metal particles 201 from the metal composition 200.

The solvent 210 containing the primary metal particles 201 thus generated flows from the raw material crushing section 120, over the partition 141, and into the particle aggregating section 131 of the particle manufacturing section 130. An arrow A shown in FIG. 5 indicates a direction in which the solvent 210 approximately flows. At this time, the metal composition 200 does not exceed the partition 141. The flow of the solvent in the solvent tank 140 is, for example, a flow generated when the solvent 210 (including the metal composition 200) supplied from the raw material supply unit 110 flows into the raw material crushing unit 120. The flow of the solvent in the solvent tank 140 may be generated by a pump (not shown).

The particle aggregating unit 131 aggregates the primary metal particles 201 with each other to generate larger secondary metal particles 202. That is, in the particle aggregating unit 131, the particle aggregating step S3 of the metal particle manufacturing step shown in FIG. 1 is performed. As shown in FIG. 6, in the particle aggregating part 131, a second oscillator 1311 that emits ultrasonic waves is provided below the solvent tank 140. The second oscillator 1311 irradiates the particle aggregating unit 131 with ultrasonic waves to cause the primary metal particles 201 to agglomerate by the control of a control unit (not shown), and generate the secondary metal particles 202.

The solvent 210 containing the secondary metal particles 202 thus generated flows to the particle classification unit 132 along the flow of the solvent (arrow A shown in FIG. 5). In the particle aggregating unit 131, it is difficult to agglomerate all the primary metal particles 201 generated in the raw material crushing unit 120 into the secondary metal particles 202. Therefore, the solvent 210 in a state in which the primary metal particles 201 and the secondary metal particles 202 are mixed flows into the particle classification unit 132.

The particle classifying unit 132 classifies the primary metal particles 201 and the secondary metal particles 202. That is, the particle classifying unit 132 performs the particle classifying step S4 in the metal particle manufacturing step shown in FIG. An electromagnet 135 is installed in the particle classifying unit 132 so as to generate a magnetic field in a direction perpendicular to the flow of the solvent 210. The primary metal particles 201 and the secondary metal particles 202 flowing into the particle classifying unit 132 receive a force in a direction perpendicular to the flow of the solvent 210 due to the magnetic field generated by the electromagnet 135. As described above, this force acts on the secondary metal particles 202 having a relatively large volume more than the primary metal particles 201 having a relatively small volume. Therefore, in the particle classifying unit 132, the primary metal particles 201 and the secondary metal particles 202 move along the different flows of the solvent 210. Specifically, the primary metal particles 201 flow along the original flow direction A of the solvent 210, and the secondary metal particles 202 deviate from the flow direction A of the solvent 210 and turn to the direction B shown in FIG. It begins to flow.

The particle recovery unit 133 recovers the primary metal particles 201 and the secondary metal particles 202. The recovery method is not particularly limited, but in the particle recovery unit 133, for example, the solvent tank 140 has a recovery hole (not shown) on the bottom surface, and the primary metal particles 201 and the secondary metal particles 202 may be recovered from there. ..

In addition, as shown in FIG. 5, in the particle recovery unit 133, the solvent tank 140 has a structure divided into two. A first recovery part 136 for recovering the primary metal particles 201 and a second recovery part 137. As shown in FIG. 5, the first recovery unit 136 is provided at a position where the primary metal particles 201 can be recovered along the flow direction A of the solvent 210. On the other hand, the second collecting unit 137 is provided at a position where the secondary metal particles 202 that have started to move in the direction B due to the magnetic volume force applied by the electromagnet 135 in the particle classifying unit 132 can be collected. Thereby, the primary metal particles 201 and the secondary metal particles 202 can be efficiently and highly accurately classified and collected.

<Action/effect>
The metal particle manufacturing apparatus 100 according to the present disclosure is larger than the primary metal particles 201 by aggregating the raw material crushing unit 120 that crushes the surface of the metal composition 200 to generate the primary metal particles 201 and the primary metal particles 201. A magnetic field perpendicular to the flow of the solvent 210 containing the primary metal particles 201 and the secondary metal particles 202 and the particle agglomeration part 131 that generates the secondary metal particles 202 is applied to the primary metal particles 201 and the secondary metal particles 202. And a particle collecting unit 133 for collecting the classified primary metal particles 201 and the classified secondary metal particles 202, respectively.

With such a configuration, the primary metal particles 201 and the secondary metal particles 202 in the solvent 210 can be classified accurately and efficiently.

<Modification>
Although various embodiments have been described above with reference to the drawings, the present disclosure is not limited to such examples. It is obvious to those skilled in the art that various changes or modifications can be conceived within the scope described in the claims, and naturally, these also belong to the technical scope of the present disclosure. Understood. Further, the constituent elements in the above-described embodiments may be arbitrarily combined without departing from the spirit of the disclosure.

In the above-described embodiment, the raw material crushing unit 120 is one as shown in FIG. However, in the present disclosure, in order to increase the generation amount of the primary metal particles 201, a structure including a plurality of raw material crushing portions may be used.

As a modified example of the metal particle manufacturing apparatus 100 shown in FIG. 5, for example, there is a metal particle manufacturing apparatus 100D having the following configuration. FIG. 7: is a figure for demonstrating the metal particle manufacturing apparatus 100D of a modification. FIG. 7 is a schematic diagram of the metal particle manufacturing apparatus 100D seen from above. The metal particle manufacturing apparatus 100D is different from the metal particle manufacturing apparatus 100 described above in that the re-aggregation flow channel 138 is provided downstream of the particle recovery unit 133. As shown in FIG. 7, the re-aggregation channel 138 connects the downstream side of the first recovery section 136 of the particle recovery section 133 and the upstream side of the particle agglomeration section 131 to each other. As a result, the primary metal particles 201 that cannot be completely collected by the first collecting unit 136 reach the particle aggregating unit 131 again through the re-aggregating channel 138, and the particle aggregating unit 131 causes symmetry of the particle aggregating step. Become. According to such a configuration, loss of metal particles is reduced, which is more preferable.

INDUSTRIAL APPLICABILITY The present disclosure is useful for a method for producing metal particles, which comprises producing metal nanoparticles by a liquid phase method.

100,100D Metal particle production apparatus 110 Raw material supply section 120 Raw material crushing section 121 First oscillator 130 Particle production section 131 Particle aggregating section 1311 Second oscillator 132 Particle classifying section 133 Particle collecting section 135 Electromagnet 136 First collecting section 137th 2 Recovery part 138 Re-aggregation flow path 140 Solvent tank 200 Metal composition 201 Primary metal particle 202 Secondary metal particle 210 Solvent 211 Bubble 212 Shock wave 300 Magnetic field 400 Metal particle

Claims (7)

A raw material crushing unit for crushing the surface of the metal composition to generate primary metal particles,
By aggregating the primary metal particles with each other, a particle aggregating portion for producing secondary metal particles larger than the primary metal particles,
A particle classification unit that classifies the primary metal particles and the secondary metal particles by applying a magnetic field perpendicular to the flow of a solvent containing the primary metal particles and the secondary metal particles,
A particle recovery unit for respectively recovering the classified primary metal particles and the secondary metal particles,
An apparatus for producing metal particles, comprising: The raw material crushing unit crushes the surface of the metal composition by irradiating the solvent containing the metal composition with ultrasonic waves to cause cavitation,
The metal particle manufacturing apparatus according to claim 1. The particle aggregating unit moves the primary metal particles by irradiating the solvent containing the primary metal particles with ultrasonic waves to cause cavitation, thereby aggregating the primary metal particles with each other,
The metal particle manufacturing apparatus according to claim 2. The frequency of ultrasonic waves emitted by the raw material crushing unit is higher than the frequency of ultrasonic waves emitted by the particle aggregating unit,
The metal particle manufacturing apparatus according to claim 3. The particle recovery unit has a first recovery unit for recovering the classified primary metal particles, and a second recovery unit for recovering the classified secondary metal particles,
Further comprising a flow path that connects the downstream side of the first recovery unit in the flow direction of the solvent and the upstream side of the particle aggregation unit,
The metal particle manufacturing apparatus according to claim 1. The surface of the metal composition is crushed to generate primary metal particles,
Aggregating the primary metal particles with each other to generate secondary metal particles larger than the primary metal particles,
A magnetic field perpendicular to the flow of a solvent containing the primary metal particles and the secondary metal particles is applied to classify the primary metal particles and the secondary metal particles,
Respectively collecting the classified primary metal particles and the secondary metal particles,
Metal particle manufacturing method. A solvent containing primary metal particles and secondary metal particles larger than the primary metal particles is caused to flow in one direction,
A magnetic field perpendicular to the flow of the solvent is applied to classify the primary metal particles and the secondary metal particles,
Metal particle classification method.

Images