JP2011089156A - Metal fine particle, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide metal fine particles in which production process is simple and inexpensive, and the separation of the metal fine particles from impurities other than those is facilitated, and further, which can cope with high-mix low-volume production and also can be produced at high efficiency, and to provide a method for producing the same. <P>SOLUTION: The metal fine particles are obtained by cracking a metal lump by ultrasonic cavitation. Further, in the method for producing metal fine particles, a metal lump is arranged in a solvent, ultrasonic waves are emitted to the metal lump using the solvent as a medium, thus the metal lump is cracked by ultrasonic cavitation produced by the emission of the ultrasonic waves so as to obtain metal fine particles. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is, for example, a metal fine particle used for a catalyst for chemical synthesis, an automobile catalyst, a fuel cell catalyst, or the like, or a magnetic metal fine particle, or a metal fine particle for a coloring material or a paint, or for forming an electronic circuit, The present invention relates to fine metal particles suitable for solder materials, metal inks and metal pastes used for forming a wire shield layer, and fine particle materials for molecular detection in the bio field, and a method for producing the same.

  Conventionally, there are three types of methods for producing this kind of fine metal particles: a solid phase method, a gas phase method, and a liquid phase method.

As disclosed in, for example, Patent Document 1 and Non-Patent Document 1, the solid phase method uses a metal powder as a raw material, and performs mechanical milling or mechanical alloying treatment using, for example, a ball mill. By applying, metal fine particles or alloy fine particles are produced.

  In the gas phase method, for example, as disclosed in Patent Document 2, a metal or a metal compound is vaporized in a vacuum chamber, and a vapor of a dispersant is brought into contact with the gas to prevent aggregation of metal fine particles. To produce fine metal particles.

  In the liquid phase method, for example, as described in Non-Patent Document 2, metal ions and complexes are reduced in a solution to grow metal atom nuclei little by little to produce metal fine particles. That's it.

  Further, among the liquid phase methods, particularly in the ultrasonic liquid phase synthesis method, as described in Non-Patent Document 3, metal ions are reduced using ultrasonic waves as an energy source to produce metal fine particles. I have to.

  Further, as a material processing technique and manufacturing technique other than the above-described metal fine particle synthesis method using ultrasonic waves as an energy source, for example, a cleaning technique described in Non-Patent Document 4, for example, Patent Document 3 As described above, activated carbon, oyster shells, etc. are processed objects (raw materials), and particles having a large particle size using simple dispersion or crushing of processed objects by ultrasonic irradiation at a frequency of about 28 kHz are used. There is a manufacturing technique of a slurry and suspension formed by dispersion.

JP-A-2005-314806 Japanese Patent No. 2561537 JP 2000-140677 A

S. Sheibani et al., Mater. Lett., (2006) Inkjet fine wiring of metal nanoparticle paste (CMC Publishing, 2006) R.A.Salkar et al., J. Mater.Chem., 9, 1333 (1999). Ultrasound Handbook (Ultrasonic Handbook Editing Committee, 1999)

However, the above solid phase method has a problem that it takes a very long time to produce metal fine particles or alloy fine particles, making it difficult or impossible to efficiently produce metal fine particles.
The mechanical milling method generally involves mixing metal powder with high-hardness ball-shaped ceramic powder, etc., and rotating the container containing them at high speed or stirring the interior to cause the powder particles to collide with each other. In this case, the powder particles are pulverized by the mechanical energy at that time to make fine particles. In other words, the raw material is mechanically pulverized into fine particles. Then, in order to sufficiently miniaturize the metal, a processing time of at least several tens of hours to about 200 hours is required, which is not practical and is not suitable for production on a commercial line. In addition, since high-speed milling generates high heat, continuous operation is difficult with a low-durability device, and there is a high possibility that the device may be damaged (the possibility of an inconvenient situation; the same applies hereinafter). Moreover, since ceramic powder etc. are grind | pulverized together with the metal powder made into the objective, there also exists a problem that the mixing cannot be prevented fundamentally.

Further, the above gas phase method has a problem that it is not suitable for multi-product / small-volume production.
For example, if the fine metal particles are for a catalyst material, fine particles of platinum (Pt) or palladium (Pd) are required. If the fine metal particles are for a conductive ink or paste material, gold (Au), silver ( Different metal species are required for each industrial application, for example, fine particles such as Ag) and copper (Cu) are required. Therefore, as a process used for producing such metal fine particles for a catalyst material, it is desirable that various types of metal fine particles can be produced on a so-called on-demand basis. However, in general, the gas phase method requires cleaning and replacement of parts in the reaction apparatus for each lot, and the apparatus itself is large, so even if the production amount is small, the running cost is not so low. Therefore, it is not suitable for the production of a variety of products and a small amount of production.
Furthermore, the vapor phase method tends to be expensive in equipment cost and running cost. In order to perform a gas phase reaction, a vacuum system and a sealed chamber are required, and various energy beam irradiation devices such as plasma, electron beam, laser, induction heating are used as an energy source for evaporating a metal lump or metal compound. In general, these are because the apparatus itself and the running cost tend to be expensive.

In addition, the above liquid phase method has a problem that it is difficult to separate impurities and a problem that a manufacturing process becomes complicated.
Compared with the solid phase method, the liquid phase method tends to have a shorter production time, more versatile equipment, and lower initial equipment and running costs. However, the liquid phase method uses metal ions and metal complexes from metal salts as raw materials and reduces them to deposit metal nuclei, in other words, chemically synthesizing metal fine particles. In practice, it is inevitable that metal ions and metal complexes remain in the liquid. In addition, anions derived from raw metal salts (eg, chloride ions, nitrate ions, sulfate ions, carboxylate ions, carbonate ions, etc.), excessive amounts of reducing agents and dispersants are practically inevitable. Therefore, they may deteriorate the characteristics of the metal fine particles as impurities. For this reason, it is necessary to completely separate and remove impurities inevitably remaining as described above from the metal fine particles, but for that purpose, a separate process step for completely removing these impurities is required, which is extended. This complicates the entire manufacturing process of the metal fine particles and increases the manufacturing cost.
Furthermore, although the liquid phase method can synthesize various kinds of fine metal particles with a simple apparatus, there is a problem that the synthesis of fine metal particles other than noble metals is not always easy. The main causes are gold (Au), silver (Ag), platinum (Pt), palladium, which are called noble metals whose standard electrode potential (vs. SHE; Standard Hydrogen Electrode standard, the same applies hereinafter) is high on the positive potential side. Metal fine particles such as (Pd) are chemically stable once generated and do not oxidize again, but are standard electrodes such as copper (Cu), cobalt (Co), iron (Fe), etc. In the case of a metal species whose potential (vs. SHE) is on the negative potential side of the noble metal, water (H ₂ O), atmospheric oxygen (O ₂ ), dissolved oxygen in the solvent, or other various oxidizing agents It is easily oxidized by the presence of a functioning element, making it difficult to synthesize desired metal fine particles.

  In addition, since the ultrasonic liquid phase synthesis method uses ultrasonic waves with high energy efficiency, high-efficiency production of metal fine particles is possible. This ultrasonic liquid phase synthesis method is also the liquid phase synthesis method described above. As in the case of the method, basically the metal fine particles are chemically generated in the liquid phase, so that the desired metal fine particles are caused by the problem of impurities remaining, metal oxidation, etc. There is a problem that the synthesis of is difficult.

  In addition, the cleaning, crushing, and mixing techniques using elastic vibration using the above ultrasonic wave as an energy source means that activated carbon, oyster shells, etc. are made into solid particles and suspended in the liquid to obtain slurry and suspension. It was intended, and it was used only for that purpose. Moreover, as disclosed in Patent Document 3, the particle size of the solid particles crushed using elastic vibration caused by ultrasonic irradiation is a relatively large one having an average of about 29.2 μm. Since it is an order of magnitude larger than extremely fine particles such as metal fine particles having a size of several nanometers, such a conventional technique is used as it is. It was practically impossible to apply to the production of fine metal fine particles. Or examination about the possibility of crushing the metal piece etc. of a raw material and forming metal fine particles using such elastic vibration by ultrasonic irradiation was not performed conventionally.

  The present invention has been made in view of such problems, and its object is that the manufacturing process is simple and inexpensive, the metal fine particles can be easily separated from other impurities, and a wide variety and a small amount. An object of the present invention is to provide metal fine particles that can be produced and that can be produced with high efficiency, and a method for producing the same.

The fine metal particles of the present invention are characterized by crushing a metal lump by ultrasonic cavitation.
According to the method for producing fine metal particles of the present invention, a metal lump is disposed in a solvent, and the metal lump is irradiated with ultrasonic waves using the solvent as a medium, thereby ultrasonic cavitation caused by the ultrasonic irradiation. The method includes a step of crushing the metal lump to obtain metal fine particles.

  According to the present invention, the manufacturing process is simple and inexpensive, the metal fine particles and other impurities can be easily separated, and can be used for a wide variety and a small amount of production, and can be manufactured with high efficiency. It is possible to provide metal fine particles and a method for producing the same.

It is a figure which shows an example of the measurement result of the particle size of the metal fine particle which concerns on the Example of this invention. It is a figure which shows an example of the XRD measurement result of the metal fine particle which concerns on the Example of this invention. The figure which copied the photograph which shows an example of the general view of the state (a) of the metal lump before ultrasonic irradiation of the metal fine particle which concerns on the Example of this invention, and the state (b) of the metal fine particle after irradiation, respectively. is there. It is the figure which copied an example of the FE-SEM photograph of the metal fine particle which concerns on the Example of this invention.

  Hereinafter, metal fine particles and a method for producing the same according to an embodiment of the present invention will be described with reference to the drawings.

The fine metal particles according to the embodiment of the present invention are formed by crushing a metal lump as a raw material by ultrasonic cavitation.
The particle diameter varies depending on the material of the raw material and the frequency and intensity of the ultrasonic wave applied to the raw material, but from the viewpoint that stable production is possible, it may be 1 nm or more and 100 μm or less. Is possible. However, it is not impossible to make the particle diameter less than 1 nm or more than 100 μm. In any case, it is possible to produce metal fine particles having an extremely fine particle size such as nm order.

  According to the manufacturing method according to the embodiment of the present invention, such a metal fine particle having a particle size of the nm (nanometer) order is easily and comparatively obtained by crushing a metal lump as a raw material by ultrasonic cavitation. With an inexpensive manufacturing device, it can be manufactured on demand, with high production efficiency, and for high-mix and low-volume production. That is, the inventors of the present invention have intensively studied, considered, and investigated various experiments and their results, and as a result, the metal mass arranged in the solvent is irradiated with ultrasonic waves through the solvent. The new knowledge that it is possible to generate metal fine particles by crushing a metal lump with high efficiency by cavitation by ultrasonic irradiation. And based on such new knowledge, it came to complete this invention.

  In the method for producing fine metal particles according to the embodiment of the present invention, a metal lump is disposed in a solvent, and the ultrasonic wave is irradiated to the metal lump of the raw material using the solvent as a medium. The method includes a step of crushing a metal lump by ultrasonic cavitation generated by irradiation to obtain extremely fine metal fine particles having a particle size of 1 nm to 100 μm, for example.

The above-mentioned metal lump of raw material includes gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), rhodium (Rh), aluminum (Al), zinc (Zn), tin (Sn), Cobalt (Co), Nickel (Ni), Iron (Fe), Indium (In), Magnesium (Mg), or an alloy composed of these metal species, shall be composed of at least one of them. It is possible.
Moreover, the shape of the metal lump of the raw material can be any one of a metal foil, a metal bar, a metal wire, and a metal particle.

As the above-mentioned solvent, a solvent comprising at least one of water, alcohols, aldehydes, amines, monosaccharides, polysaccharides, linear hydrocarbons, fatty acids and aromatics should be used. Is possible.
The above-mentioned solvent is used as a medium for transmitting ultrasonic waves. However, it is known that the crushing effect of metal lumps by ultrasonic cavitation changes depending on the physical and chemical characteristics of the solvent. ing. For example, in a solvent having a high boiling point or viscosity, although the number of cavitations (or frequency) itself decreases, the individual energy increases, so the crushing effect by cavitation becomes rather high. Further, the temperature and pressure at the time of cavitation collapse also change in accordance with the type of solvent and the type of gas dissolved in the solvent. Further, depending on the solvent, there is a possibility that the metal will react with the fine metal particles generated by crushing the metal lump and cause metal corrosion, and a metal complex may be formed accordingly. For this reason, as a solvent,
The one that can enhance the crushing effect of metal lumps by ultrasonic cavitation to promote the production efficiency of metal fine particles, and does not cause the metal corrosion of the metal fine particles produced or the formation of metal complexes, etc. It is necessary to select In order to meet such conditions, more specifically, heat conduction in the working atmosphere by combining a plurality of types of solvents, further adding a reducing agent or dispersing agent, or substituting with an atmospheric gas. It is effective to improve the degree and chemical reduction ability.

  Further, in the above solvent, as a reducing agent, alcohols, aldehydes, amines, lithium aluminum hydroxide, sodium thiosulfate, hydrogen peroxide, hydrogen sulfide, borane, diborane, hydrazine, potassium iodide, It is a more desirable mode to add at least one chemical species of citric acid, oxalic acid, and ascorbic acid. In this way, for example, when producing fine metal particles such as copper (Cu), which are highly likely to oxidize unless a reducing agent is added, the oxidation can be suppressed or suppressed. it can.

The ultrasonic waves are desirably set so that the frequency is 15 kHz or more and 200 kHz or less and the intensity is 0.5 W / cm ³ or more. This is because, by setting in this way, it is possible to produce finer metal fine particles having a desired particle diameter with higher generation efficiency.

  The metal fine particles and the manufacturing method thereof according to the embodiment of the present invention are as follows in more detail.

  As the metal lump of the raw material, gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), rhodium (Rh), aluminum (Al), zinc (Zn), tin (Sn ), Cobalt (Co), nickel (Ni), iron (Fe), indium (In), magnesium (Mg), or an alloy metal composed of these metal species, and if necessary, It is also possible to select a plurality of types.

  Further, the shape of the metal lump is not particularly limited, but typical shapes include a metal foil, a metal rod, a metal wire, a metal particle, and the like. A material having a shape with a high aspect ratio, such as a foil or a wire, is more suitable because it has a large area to receive ultrasonic cavitation. Moreover, in the case of foil, the thickness is 20 μm or less, and in the case of a strand, the diameter is 20 μm or less, so that the crushing by ultrasonic waves can be further effectively advanced in a short time. Become.

Also, the metal purity and alloy composition of the metal lump are not particularly limited, but in the case of a metal species or alloy having extremely high strength and hardness, the time required for crushing by ultrasonic waves tends to be long. In such a case, it is desirable to further adjust the ultrasonic irradiation conditions, the solvent composition, and the like to further promote crushing by ultrasonic cavitation.
Or conversely, by putting a material that is not crushed under a certain ultrasonic setting condition into the reaction system, the fine material is supported on the material that is not crushed, or the material that is not crushed is a metal. It is also possible to coat with fine particles, or to combine or alloy the non-crushed material and metal fine particles. Such a material that is not crushed may be anything as long as it is not miniaturized by an ultrasonic reaction, but more specific examples include various metals, alloys, ceramics, polymers, and rubbers. Further, the shape is not particularly limited. Moreover, when it is requested | required that coating property should be improved, it is also possible to use electroplating, various surface treatments, etc. together.

The solvent used as the ultrasonic medium can be selected from water, alcohols, aldehydes, amines, monosaccharides, polysaccharides, linear hydrocarbons, fatty acids, and aromatics. . Moreover, if necessary, it is also possible to select a plurality of types and mix and use them.
Further, it is desirable that the viscosity of the solvent when used as the ultrasonic medium is not too high. Specifically, it is preferably 10 c · P or less. If the viscosity becomes too high, cavitation due to ultrasonic irradiation becomes difficult to be generated, and the progress of crushing of the metal mass to generation of the metal fine particles is slowed down.
Moreover, it is desirable that the solvent is one that does not oxidize the metal mass and the metal fine particles obtained by crushing the metal mass as much as possible. More specifically, it is a solvent in which the standard electrode potential (vs. SHE) is higher on the negative potential side than the metal species of the metal mass to be crushed and has reducibility to the metal species. It is desirable to be.

  In addition, when crushing a metal lump composed of a metal species other than a noble metal by ultrasonic cavitation, in order to prevent oxidation of metal fine particles obtained by the crushing, the metal lump is immersed in a solvent before crushing. On the other hand, it is desirable to sufficiently deaerate by irradiating ultrasonic waves to remove dissolved oxygen in the solvent. Further, in the subsequent crushing of the metal lump, it is also a desirable aspect that ultrasonic irradiation is performed while purging the solvent with an inert gas or a reducing gas.

Examples of reducing agents include alcohols, aldehydes, amines, lithium aluminum hydroxide, sodium thiosulfate, hydrogen peroxide, hydrogen sulfide, borane, diborane, hydrazine, potassium iodide, citric acid, oxalic acid, and ascorbic acid. It is possible to select from among them, and if necessary, a plurality of types can be selected and used by mixing them.
The amount of the reducing agent added can be appropriately selected according to the metal species of the metal lump to be crushed, and is not particularly limited. Further, in the case of a metal lump made of silver (Ag), gold (Au), platinum (Pt), palladium (Pd), etc., which is called a noble metal, it is chemically stable from the beginning, so the reducing agent as described above. May not necessarily be added. Moreover, there is almost no possibility that the metal fine particles obtained by crushing are oxidized in the air atmosphere.
However, in the case of a metal whose standard electrode potential (vs. SHE) is on the negative potential side with respect to copper (Cu), there is a risk of oxidation unless a reducing agent is added. Therefore, it is desirable to add a reducing agent when producing metal fine particles using a metal lump comprising such a metal species or an alloy of those metal species as a raw material. In this case, the amount of addition of the reducing agent is preferably 0.001 to 5 in terms of the concentration ratio to the metal (reducing agent / metal). When the concentration of the reducing agent is lower than 0.001, it becomes difficult to suppress oxidation of metal fine particles during or after crushing by ultrasonic cavitation. On the other hand, when the concentration of the reducing agent is higher than 5, there is a high possibility that undesired by-products such as metal salts, precipitates, metal complexes and the like are generated during crushing by ultrasonic cavitation. Therefore, it is desirable that the addition amount of the reducing agent is 0.001 to 5 in terms of the concentration ratio to the metal (reducing agent / metal).

  It is desirable that the mixing ratio of the solvent and the reducing agent is appropriately adjusted in accordance with the metal species of the metal mass to be crushed. Further, in order to efficiently disperse the obtained metal fine particles in the solvent, a surfactant, a protective polymer or the like may be further added. As these surfactants and protective polymers, general materials used as so-called dispersants can be used, but they are chemically used for metal fine particles and alloy fine particles to be dispersed. It is more desirable that it exhibits affinity and adsorbs.

As for the frequency of the ultrasonic wave irradiated with respect to a metal lump, it is desirable to set it as 15 kHz-200 kHz. This is because if the frequency is less than 15 kHz, the wavelength in the solvent becomes long and passes through the metal block, making it difficult to obtain metal fine particles having a desired fine particle size such as nm order. This is because, when the frequency exceeds 200 kHz, the energy of individual cavities generated by ultrasonic waves is reduced, and the ability to crush the metal lump and generate fine metal fine particles is significantly reduced. Therefore, by setting the frequency of the ultrasonic wave within the above range of 15 kHz to 200 kHz (within the frequency region), finer metal fine particles having a desired particle diameter are produced with higher efficiency. It becomes possible. Moreover, by appropriately adjusting the frequency and intensity of the ultrasonic wave within such a frequency region, the crushing speed of the metal mass and the particle diameter of the obtained metal fine particles can be changed. Specifically, the particle diameter of the metal fine particles can be controlled over a wide range such as several nm to several tens of μm (more specific numerical value is 1 nm to 100 μm).

In addition, by appropriately setting the intensity and irradiation time of the ultrasonic wave applied to the metal lump according to the hardness of the metal lump to be crushed, the amount charged, the particle size of the desired metal fine particles, etc. The particle diameter of the metal fine particles obtained can be adjusted to a desired size within the above range.
In general, in addition to functions such as crushing, dispersing, and mixing, ultrasonic irradiation has the function of causing agglomeration due to dispersoids and particle collisions, and the function of causing melting of particles in hot spots and fusion of particles. Etc. Since these multiple functions appear simultaneously, the setting of various process conditions such as intensity and irradiation time differs depending on which one is expected to be the most important one. Generally, when the intensity of ultrasonic waves is increased, the crushing of the metal mass is promoted, but when the intensity exceeds a certain intensity, the reaction rate may be saturated. Alternatively, there are many cases where an optimum intensity exists on the way. In consideration of such various characteristics, it is desirable to appropriately set and change various process conditions for ultrasonic irradiation.

In the method for producing fine metal particles according to the embodiment of the present invention, it is desirable that the intensity of ultrasonic waves be 0.5 W / cm ³ or more. This is because if the intensity of the ultrasonic wave is less than 0.5 W / cm ³ , although depending on the type and shape of the metal, sufficient crushing effect cannot be obtained, and the crushing speed is reduced, resulting in deterioration in production efficiency. Because.

  As for the irradiation time of ultrasonic waves, generally, when it is a short time, the function of crushing, dispersing and mixing appears strongly, and when it is a long time, the function of aggregation appears strongly. Therefore, the ultrasonic irradiation time may be controlled in accordance with the target particle size of the metal fine particles. More specifically, as the crushing of the metal mass proceeds, the metal particles become finer, but eventually the particle size reaches a minimum value. After that, the progress of aggregation becomes dominant, and the particle size becomes coarser again as it progresses. Therefore, when the ultrasonic irradiation time is set to a time shorter than the time when the particle size reaches the minimum value, since the miniaturization is in the process of progressing within that time, it corresponds to the irradiation time. Metal fine particles having a fine particle size can be obtained. Then, by setting the ultrasonic irradiation time exactly to the time when the above minimum value is reached, fine metal particles having a minimum particle size can be obtained. In addition, when the irradiation time of ultrasonic waves is set to a time longer than the time when the above particle size reaches the minimum value, the aggregation proceeds dominantly, so a metal having a large particle size corresponding to the set time. Fine particles will be obtained. This tendency is similar to that of silver (Ag), aluminum (Al), gold (Au), indium (In), magnesium (Mg), palladium (Pd), platinum (Pt), tin (Sn), zinc (Zn), etc. This is particularly true for such relatively soft metal species. Using the phenomenon that the particle size of the metal fine particles obtained corresponding to the ultrasonic irradiation time changes, the metal fine particles and the method for producing the same according to the embodiment of the present invention are manufactured. It is possible to control the particle size of the particles.

  The temperature condition for irradiating with ultrasonic waves is not particularly limited, but is preferably equal to or lower than the boiling point of the solvent, reducing agent, or dispersant. This is because a reflux device or the like is required at a temperature exceeding the boiling point, and ultrasonic irradiation at high temperatures generally has a high risk of increasing the load of ultrasonic waves on the manufacturing system used at the time of irradiation. It is.

  In addition, the oscillation / output method and device structure of the ultrasonic irradiation device can irradiate ultrasonic waves as described above to crush the metal lump to a fine particle state, and the frequency, intensity, irradiation As long as various process conditions such as time can be set and adjusted, for example, a commercially available ultrasonic generator can be appropriately arranged and used.

  Also, in order to be able to produce fine metal particles with higher efficiency, consideration is given so that cavitation is uniformly dispersed in the metal mass in a solvent by using a stirring device or the like. It is desirable.

  Next, the effect | action in the metal fine particle which concerns on embodiment of this invention, and its manufacturing method is demonstrated.

When a metal lump, which is a raw material, is placed in a solvent and irradiated with ultrasonic waves as described above, minute bubbles called ultrasonic cavitation are generated. The ultrasonic cavitation is a heterogeneous interfacial reaction that occurs between the interface of ultrasonic cavitation generated in the solvent and the surface of the metal mass, and finally the crushing is repeated by repeating a quasi-adiabatic compression / expansion cycle. To do. In a series of processes from the generation of the ultrasonic cavitation to the collapse, the ultrasonic cavitation itself is extremely high temperature and high pressure, and a shock wave and a jet flow are also generated during the collapse. Due to the behavior of ultrasonic cavitation, physical crushing of a very small scale and thus high energy density proceeds on the surface of the metal block disposed in the solvent. In other words, the ultrasonic cavitation that contributes to crushing on the surface of the metal lump is a very small scale of several μm or less. It becomes possible to obtain metal fine particles having a diameter. Moreover, metal fine particles can be generated with high efficiency by crushing by ultrasonic cavitation with high energy density.
In fact, as a result of experiments by the present inventors, metal fine particles having a particle size of nm (nanometer) order can be obtained in a short process of about several hours by crushing a metal lump using such ultrasonic cavitation. It has been confirmed that it can be generated with high efficiency (details thereof will be described in the examples described later).

Furthermore, since the ultrasonic wave has a function of dispersing the generated particles in a solvent, it is possible to simultaneously generate and disperse the metal fine particles. Taking advantage of this effect, the production efficiency of fine metal particles can be further increased.
In addition, since the particle size of the metal fine particles obtained changes according to the size of ultrasonic cavitation, the number and size of cavitations that are reaction sites can be adjusted by adjusting the frequency and output of the ultrasonic waves to be irradiated. In addition, by controlling energy and the like, it is possible to control the production rate, production amount, particle size, and the like of the finally obtained fine metal particles. Furthermore, the particle size of the metal fine particles can be controlled by adjusting the irradiation time of the ultrasonic waves.

  In addition, the metal lump that is the raw material exists as a solid, so that compared to the conventional ion source liquid phase method, particle precipitation and particle coarsening due to ion diffusion do not occur, and the raw material concentration is charged at a high concentration. Therefore, according to the manufacturing method according to the embodiment of the present invention using ultrasonic cavitation, it is possible to manufacture metal fine particles with high efficiency.

Further, in the metal fine particles and the manufacturing method thereof according to the embodiment of the present invention, a metal lump such as a copper foil is crushed and refined by ultrasonic cavitation, in other words, in a solvent. Therefore, chemical species such as metal ions and metal complexes are not generated. Therefore, it is possible to omit the process of purifying and purifying the solution after the production of fine metal particles, which could not be omitted or simplified by the conventional liquid phase method. At the same time, it is possible to use general-purpose manufacturing apparatuses and solvent containers, and therefore, from this point, it is possible to adapt to multi-product / small-volume production.

  In addition, the type of solvent and reducing agent can be appropriately selected according to the type of metal fine particles of interest, and by appropriately combining these conditions and ultrasonic conditions, the metal lump of the raw material can be crushed. It can be promoted and the particle size of the metal fine particles obtained can be controlled. Furthermore, by combining metal fine particles to be generated and other materials, it is possible to produce more various metal fine particles and more highly functional metal fine particles.

  As described above, according to the metal fine particles and the method for producing the same according to the embodiment of the present invention, for example, metal fine particles having an extremely fine particle size such as nm order can be produced with high production efficiency. Is possible. In addition, the manufacturing process can be simplified and inexpensive, the target fine metal particles can be easily separated from other impurities, and it can be used for various types and small-scale production. It becomes possible.

  The fine metal particles and the production method thereof according to the embodiment of the present invention are, for example, fine metal particles, magnetic fine metal particles, or coloring materials used in catalysts for chemical synthesis, automobile catalysts, fuel cell catalysts, etc. Fine metal particles for use in coatings and coatings, or for metal circuit formation and solder materials, metal inks and metal pastes used for wire shield layer formation, and molecular detection in bio fields It is possible to apply.

  Metal fine particles were produced by the production method as described in the above embodiment, and used as samples of metal fine particles according to Examples 1-12. For comparison with the above, metal fine particles were produced by a conventional solid phase method and liquid phase method, and used as samples of metal fine particles according to Comparative Examples 1-12. Table 1 summarizes the time required for the manufacturing method and the manufacturing (generation) process for the sample according to the example, data and information such as particle size, and the like. Further, Table 2 summarizes data, information, etc. such as the time and particle size required for the manufacturing method and manufacturing (generation) process for the sample according to the comparative example.

Various physical properties of each sample were measured and analyzed as follows.
(1) Qualitative analysis
For the phase identification of the metal fine particles, a powder X-ray diffractometer “RlNT2000” (manufactured by Rigaku Corporation) was used.
(2) Measurement of average particle size
The metal fine particles were observed using “S-5000” manufactured by Hitachi, Ltd. as an FE-SEM (Field Emission-Scanning Electron Microscope; hereinafter the same). The average particle size was measured using a laser Doppler dynamic light scattering apparatus “UPA-EX150 type” (manufactured by Nikkiso).
(3) Plasmon absorption
It is known that metal nanoparticles having a particle size of about several nanometers to 100 nm generally have a remarkable absorption unevenly distributed corresponding to a specific wavelength by localized surface plasmon resonance. The plasmon absorption was measured using an ultraviolet / visible absorptiometer (V-550; manufactured by JASCO Corporation).
(4) Content of metal component
Using a differential thermothermal gravimetric simultaneous measurement apparatus (TG8120; manufactured by Rigaku Corporation), the content of each metal component was determined by TG-DTA analysis. Nitrogen gas (N ₂ ) was used as the atmosphere during the measurement.

Example 1
In a container, 21.9 mL of triethylamine (milliliter; the same applies hereinafter) and 20 mL of a toluene solvent are mixed, and 1 g of copper foil having a thickness of 11 μm (purity of copper (Cu) = 99.9%) is obtained as a metal lump of raw material. added. An example is shown in FIG. Then, while maintaining the temperature of the solvent at about 40 ° C., an ultrasonic wave with a frequency of 28 kHz in an atmosphere of nitrogen (N ₂ ) is output at about 15 W.
By irradiating at / cm ³ for 5 hours, the metal lump was crushed by the ultrasonic cavitation to obtain a solution in which fine metal particles were dispersed. An example is shown in FIG.
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Further, the metal fine particles were washed with acetone, and then dried at room temperature to obtain a sample of metal fine particles in the form of fine particle powder according to Example 1.
When XRD (X-Ray Diffraction Spectroscopy; hereinafter the same) measurement was performed on the fine metal particles, the measurement results shown in FIG. 2 were obtained. From this measurement result, it was confirmed that the metal fine particle which concerns on Example 1 consists of metal copper which has fcc structure.
As a result of thermogravimetry, the content of copper (Cu) was 96.5 wt%.
Further, when observation was performed by FE-SEM, it was observed that the metal fine particles had a particle size of about 200 nm as shown in FIG.
Further, when the fine metal particles according to Example 1 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, the measurement results shown in FIG. The volume particle diameter was confirmed to be about 220 nm.

(Example 2)
In a container, 21.9 mL of triethylamine and 20 mL of toluene solvent are mixed, and 1 g of copper wire having a diameter of 20 μm (copper (Cu) purity = 99.9%) is added as a raw material metal lump. While maintaining the temperature at 40 ° C., an ultrasonic wave with a frequency of 28 kHz is irradiated in an atmosphere of nitrogen (N ₂ ) at an output of about 15 W / cm ³ for 5 hours, so that the metal lump is crushed by the ultrasonic cavitation. Thus, a solution in which fine metal particles were dispersed was obtained.
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Further, the metal fine particles were washed with acetone and then dried at room temperature to obtain a sample of metal fine particles in the form of fine particle powder.
When XRD measurement was performed on the sample thus obtained, it was confirmed that the metal fine particles according to Example 2 were made of metal copper having an fcc structure.
As a result of thermogravimetry, the content of copper (Cu) was 98.5 wt%.
Moreover, when observation was performed by FE-SEM, it was observed that the metal fine particles had a particle size of about 170 nm.
Further, when the fine metal particles according to Example 2 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, it was confirmed that the average volume particle diameter was about 175 nm. It was done.

(Example 3)
In a container, 21.9 mL of triethylamine and 20 mL of toluene solvent are mixed, and 1 g of 100 μm thick copper foil (copper (Cu) purity = 99.9%) is added as a raw material metal lump, and the temperature of the solvent is adjusted. While maintaining the temperature at about 40 ° C., an ultrasonic wave with a frequency of 28 kHz is irradiated in an atmosphere of nitrogen (N ₂ ) at an output of about 15 W / cm ³ for 5 hours. Thus, a solution in which fine metal particles were dispersed was obtained.
In the sample according to Example 3, a part of the copper foil remained in the solution, and it was confirmed that not all the copper foil as the raw material was crushed.
An acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Moreover, the remaining copper foil was removed. The fine metal particles were washed with acetone and then dried at room temperature to obtain a fine metal powder sample of fine metal particles.
When this sample was observed by FE-SEM, it was observed that the sample was fine metal particles having a particle size of about 200 nm.

Example 4
In a container, 21.9 mL of triethylamine and 20 mL of ethylene glycol solvent are mixed, and 1 g of 11 μm-thick copper foil (purity of copper (Cu) = 99.9%) is added as a metal lump of the raw material, and the temperature of the solvent Is kept at about 40 ° C., and an ultrasonic wave with a frequency of 28 kHz is irradiated for 24 hours in an atmosphere of nitrogen (N ₂ ) at an output of about 5 W / cm ³ , so that a metal lump is formed by the ultrasonic cavitation. By crushing, a solution in which fine metal particles were dispersed was obtained.
In the sample according to Example 4, it was confirmed that part of the copper foil remained in the solution, and not all of the copper foil as the raw material was crushed.
An acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Moreover, the remaining copper foil was removed. The fine metal particles were washed with acetone and then dried at room temperature to obtain a fine metal powder sample of fine metal particles.
When the sample thus obtained was observed by FE-SEM, it was observed that the sample was a fine metal particle having a particle size of about 300 nm.

(Example 5)
In a container, 1 g of 11 μm thick copper foil (purity of copper (Cu) = 99.9%) as a metal lump of raw material was added to 40 mL of toluene solvent, and nitrogen was maintained while maintaining the temperature of the solvent at about 40 ° C. (N ₂ ) Ultrasonic waves with a frequency of 28 kHz are irradiated in an atmosphere at an output of about 15 W / cm ³ for 5 hours, whereby the metal lump is crushed by the ultrasonic cavitation and the metal fine particles are dispersed. Solution was obtained.
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Further, the metal fine particles were washed with acetone and then dried at room temperature to obtain a sample of metal fine particles in the form of fine particle powder.
When XRD measurement of the sample thus obtained was performed, it was confirmed that the metal fine particles according to Example 5 were made of metallic copper having an fcc structure.
As a result of thermogravimetry, the content of copper (Cu) was 99.2 wt%.
Moreover, when it observed by FE-SEM, it was observed that it is a metal fine particle whose particle size is about 1000 nm.
Further, when the fine metal particles according to Example 5 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, it was confirmed that the average volume particle diameter was about 1040 nm. It was done.

(Example 6)
In a container, 21.9 mL of triethylamine and 20 mL of toluene solvent are mixed, and 1 g of 10 μm-thick silver foil (purity of silver (Ag) = 99.98%) is added as a raw material metal lump. While maintaining the temperature at 40 ° C., an ultrasonic wave with a frequency of 50 kHz is irradiated in the atmosphere at an output of about 5 W / cm ³ for 5 hours, so that the metal lump is crushed by the ultrasonic cavitation, and the metal fine particles An orange solution in which was dispersed was obtained.
When the absorbance of the solution was measured, clear plasmon absorption was confirmed in the vicinity of 430 nm indicating fine particles made of silver (Ag).
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Furthermore, the metal fine particles were washed with acetone, and then dried at room temperature to obtain a sample of fine metal powder metal fine particles according to Example 6.
When the XRD measurement of this metal fine particle was performed, it was confirmed that this metal fine particle consists of metal silver which has fcc structure.
As a result of thermogravimetry, the silver (Ag) content was 98.0 wt%.
Moreover, when observation by FE-SEM was performed, it was observed that it was a metal fine particle with a particle size of about 75 nm.
Further, when the fine metal particles according to Example 6 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, it was confirmed that the average volume particle diameter was about 80 nm. It was done.

(Example 7)
In a container, mix 21.9 mL of triethylamine and 20 mL of ethylene glycol solvent, add 1 g of 10 μm-thick silver foil (purity of silver (Ag) = 99.98%) as a raw material metal lump, and adjust the temperature of the solvent. While maintaining the temperature at about 40 ° C., an ultrasonic wave with a frequency of 28 kHz is irradiated in the atmosphere at an output of about 5 W / cm ³ for 24 hours. A solution in which the particles were dispersed was obtained.
In the sample according to Example 7, a part of the silver foil remained in the solution, and it was confirmed that not all of the silver foil as the raw material was crushed.
An acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Moreover, the remaining copper foil was removed. The fine metal particles were washed with acetone and then dried at room temperature to obtain a fine metal powder sample of fine metal particles.
When this sample was observed by FE-SEM, it was observed that the sample was fine metal particles having a particle size of about 150 nm.

(Example 8)
In a container, 1 g of 10 μm-thick silver foil (purity of silver (Ag) = 99.98%) as a metal lump of raw material is added to 40 mL of toluene solvent, and the solvent temperature is kept at about 40 ° C. in the atmosphere. By irradiating an ultrasonic wave having a frequency of 28 kHz with an output of about 15 W / cm ³ for 5 hours, the metal lump was crushed by the ultrasonic cavitation to obtain a solution in which fine metal particles were dispersed.
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Further, the metal fine particles were washed with acetone, and then dried at room temperature to obtain a sample of metal fine particles in the form of fine particle powder according to Example 8.
When the XRD measurement of this metal fine particle was performed, it was confirmed that this metal fine particle consists of metal silver which has fcc structure.
As a result of thermogravimetry, the silver (Ag) content was 99.0 wt%.
Moreover, when observation by FE-SEM was performed, it was observed that it was a metal fine particle with a particle size of about 800 nm.
Further, when the fine metal particles according to Example 8 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, it was confirmed that the average volume particle diameter was about 820 nm. It was done.

Example 9
In a container, 21.9 mL of triethylamine and 20 mL of a toluene solvent are mixed, and 1 g of a 2.5 μm-thick gold foil (gold (Au) purity = 99.9%) is added as a raw material metal lump. By irradiating ultrasonic waves with a frequency of 50 kHz in the atmosphere at an output of about 5 W / cm ³ for 5 hours while maintaining the temperature at about 40 ° C., the metal lumps are crushed by the ultrasonic cavitation, and the metal A red solution in which fine particles were dispersed was obtained.
When the absorbance of the solution was measured, clear plasmon absorption was confirmed in the vicinity of 530 nm indicating fine particles made of gold (Au).
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Furthermore, the metal fine particles were washed with acetone, and then dried at room temperature to obtain a sample of fine metal powder metal fine particles according to Example 9.
As a result of XRD measurement of the metal fine particles, it was confirmed that the metal fine particles were made of metal gold having an fcc structure.
As a result of thermogravimetry, the content of gold (Au) was 98.5 wt%.
Moreover, when observation by FE-SEM was performed, it was observed that it was a metal fine particle with a particle size of about 40 nm.
Further, when the fine metal particles according to Example 9 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, it was confirmed that the average volume particle diameter was about 40 nm. It was done.

(Example 10)
In a container, 21.9 mL of triethylamine and 20 mL of an ethylene glycol solvent are mixed, and 1 g of a 2.5 μm-thick gold foil (gold (Au) purity = 99.9%) is added as a raw material metal lump. While maintaining the temperature at about 40 ° C., an ultrasonic wave with a frequency of 28 kHz is irradiated in the atmosphere at an output of about 5 W / cm ³ for 24 hours, thereby crushing the metal mass by the ultrasonic cavitation, A solution in which metal fine particles were dispersed was obtained.
In the sample according to Example 10, a part of the gold foil remained in the solution, and it was confirmed that not all the gold foil as the raw material was crushed.
An acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Further, the remaining gold foil was removed. The fine metal particles were washed with acetone and then dried at room temperature to obtain a fine metal powder sample of fine metal particles.
When the sample thus obtained was observed with an FE-SEM, it was observed that the sample was fine metal particles having a particle size of about 120 nm.

(Example 11)
In a container, 1 g of 2.5 μm-thick gold foil (purity of gold (Au) = 99.9%) was added as a metal lump of raw material to 40 mL of toluene solvent, while maintaining the temperature of the solvent at about 40 ° C., By irradiating an ultrasonic wave with a frequency of 50 kHz in the atmosphere at an output of about 15 W / cm ³ for 5 hours, the metal lumps are crushed by the ultrasonic cavitation to obtain a solution in which fine metal particles are dispersed. It was.
Then, an acetone solvent was added to the solution to precipitate metal fine particles, and the supernatant was removed. Further, the metal fine particles were washed with acetone, and then dried at room temperature to obtain a sample of metal fine particles in the form of fine particles according to Example 11.
As a result of XRD measurement of the metal fine particles, it was confirmed that the metal fine particles were made of metal gold having an fcc structure.
As a result of thermogravimetry, the content of gold (Au) was 99.2 wt%.
Moreover, when observation was performed by FE-SEM, it was observed that the metal fine particles had a particle size of about 700 nm.
Further, when the fine metal particles according to Example 11 were redispersed in a toluene solvent and irradiated with ultrasonic waves, and the particle size distribution of the dispersion was measured, it was confirmed that the average volume particle diameter was about 710 nm. It was done.

(Example 12)
Inside the container, 21.9 mL of triethylamine and 150 mL of toluene solvent are mixed, and 1 g of silver foil having a thickness of 10 μm is added as a metal lump of raw material, and a nitrile rubber sheet (4 cm × 2 cm × 3 cm) is added to the temperature of the solvent. Was maintained at about 40 ° C., and an ultrasonic wave having a frequency of 28 kHz was irradiated in the atmosphere at an output of about 5 W / cm ³ for 10 hours. As a result, the metal lumps were crushed by the ultrasonic cavitation to produce fine metal particles made of silver (Ag), which could be coated on the surface of the nitrile rubber sheet.

(Comparative Example 1)
5 g of 11 μm-thick copper foil (purity of copper (Cu) = 99.9%) and 50 g of a large number of balls made of Al ₂ O ₃ having a diameter of 5 mm were mixed, and a room temperature of 20 ° C. to A mechanical dry grinding process was performed at 30 ° C. for 48 hours at a rotational speed of 200 rpm. Then, Al ₂ O ₃ balls were separated from the treated solution.
As a result, unground copper foil was confirmed in the solution, but metal fine particles were not generated.

(Comparative Example 2)
A mixture of 109.5 mL of triethylamine and 50 mL of toluene solvent to prepare a solution, and a large number of them consisting of 5 g of 11 μm thick copper foil (copper (Cu) purity = 99.9%) and 5 mm diameter Al ₂ O ₃ Of balls was added. And using the tabletop ball mill device,
Wet grinding was performed at room temperature (20 ° C. to 30 ° C.) for 48 hours at a stirring speed of 200 rpm. Al ₂ O ₃ balls were separated from the solution after the treatment.
As a result, unground copper foil was confirmed in the solution, but metal fine particles were not generated.

(Comparative Example 3)
A mixture of 109.5 mL of triethylamine and 50 mL of toluene solvent to prepare a solution, and a large number of them consisting of 5 g of 11 μm thick copper foil (copper (Cu) purity = 99.9%) and 5 mm diameter Al ₂ O ₃ Of balls was added. Then, using a planetary table-top ball mill apparatus, wet planetary pulverization was performed at room temperature (20 ° C. to 30 ° C.) for 5 minutes at a stirring speed of 500 rpm. Al ₂ O ₃ balls were separated from the solution after the treatment.
As a result, copper foil in the middle of pulverization was confirmed in the solution. Then, the copper foil was removed, and the copper (Cu) particles precipitated in the solution were collected, washed with acetone, and then dried at room temperature to obtain a copper (Cu) powder. When XRD measurement of this powder was performed, it was confirmed to be metallic copper having an fcc structure. Moreover, when observation was performed by FE-SEM, it was confirmed that the particle size was 10 μm to 5000 μm, but the metal fine particles according to the examples of the present invention having a particle size smaller than such a μm order particle size were used. Generation of such fine particles having a particle size of the order of nm was not confirmed.

(Comparative Example 4)
21.9 mL of triethylamine and 20 mL of toluene solvent were mixed, 5 g of 11 μm thick copper foil (copper (Cu) purity = 99.9%) was added thereto, and nitrogen (N ₂₎ was maintained while maintaining the temperature of the solvent at 40 ° C. ) In the atmosphere, the production process of the metal fine particle by the liquid phase method accompanied by a stirring process was carried out with a magnetic steerer at a stirring speed of 100 rpm for 24 hours.
As a result, unground copper foil was confirmed in the solution, but metal fine particles were not generated.

(Comparative Example 5)
5 g of silver foil having a thickness of 10 μm (purity of silver (Ag) = 99.98%) and 50 g of a large number of balls made of Al ₂ O ₃ having a diameter of 5 mm were mixed, and a room temperature of 20 ° C. to 30 ° C. was measured using a table-top ball mill apparatus. Mechanical dry pulverization was performed at a rotational speed of 200 rpm for 48 hours at 0C. Then, Al ₂ O ₃ balls were separated from the treated solution.
As a result, uncrushed silver foil was confirmed in the solution, but metal fine particles composed of silver (Ag) were not generated.

(Comparative Example 6)
Mix 109.5 mL of triethylamine and 50 mL of toluene solvent, and add 50 g of 10 g thick silver foil (purity of silver (Ag) = 99.98%) and a large number of balls of 5 g of Al ₂ O _{3 having a} diameter of 5 mm. Using a table-top ball mill, wet pulverization was performed at a room temperature of 20 ° C. to 30 ° C. for 48 hours at a stirring speed of 200 rpm. Al ₂ O ₃ balls were separated from the solution after the treatment.
As a result, uncrushed silver foil was confirmed in the solution, but metal fine particles were not generated.

(Comparative Example 7)
A solution was prepared by mixing 109.5 mL of triethylamine and 50 mL of toluene solvent, and a plurality of silver foil having a thickness of 10 μm (purity of silver (Ag) = 99.98%) and a large number of Al ₂ O _{3 having a} diameter of 5 mm. 50 g of balls were added. Then, using a planetary table-top ball mill apparatus, wet planetary pulverization was performed at room temperature (20 ° C. to 30 ° C.) for 5 minutes at a stirring speed of 500 rpm. Al ₂ O ₃ balls were separated from the solution after the treatment.
As a result, a silver foil in the middle of pulverization was confirmed in the solution. Then, the silver foil was removed, and silver (Ag) particles precipitated in the solution were collected, washed with acetone, and then dried at room temperature to obtain silver (Ag) powder. When XRD measurement of this powder was performed, it was confirmed to be metallic silver having an fcc structure. Further, when observed by FE-SEM, it was confirmed that the particle size was 10 μm to 3000 μm, but it was smaller than such a particle size on the order of μm, like the metal fine particles according to the example of the present invention. Formation of fine particles having a particle size on the order of nm was not confirmed.

(Comparative Example 8)
A mixture of 21.9 mL of triethylamine and 20 mL of toluene solvent, 1 g of 10 μm-thick silver foil (purity of silver (Ag) = 99.98%) was added thereto, and the magnetic temperature was maintained in the atmosphere while maintaining the temperature of the solvent at 40 ° C. A process for producing fine metal particles by a liquid phase method accompanied by a stirring process was carried out by a steerer at a stirring speed of 100 rpm for 24 hours.
As a result, uncrushed silver foil was confirmed in the solution, but metal fine particles were not generated.

(Comparative Example 9)
5 g of gold foil with a thickness of 2.5 μm (purity of gold (Au) = 99.9%) and a large number of balls of 50 g made of Al ₂ O ₃ with a diameter of 5 mm were mixed, and a room temperature of 20 ° C. was measured by a table-top ball mill apparatus. Mechanical dry pulverization was performed at ˜30 ° C. for 48 hours at a rotational speed of 200 rpm. Then, Al ₂ O ₃ balls were separated from the treated solution.
As a result, uncrushed gold foil was confirmed in the solution, but metal fine particles made of gold (Au) were not generated.

(Comparative Example 10)
A mixture of 109.5 mL of triethylamine and 50 mL of toluene solvent, and 50 g of a large number of balls made of 5 g of gold foil (purity of gold (Au) = 99.9%) having a thickness of 2.5 μm and Al ₂ O _{3 having a} diameter of 5 mm And a wet pulverization treatment was performed at a room temperature of 20 ° C. to 30 ° C. for 48 hours at a stirring speed of 200 rpm using a table-top ball mill. Al ₂ O ₃ balls were separated from the solution after the treatment.
As a result, uncrushed gold foil was confirmed in the solution, but metal fine particles were not generated.

(Comparative Example 11)
A solution was prepared by mixing 109.5 mL of triethylamine and 50 mL of toluene solvent, and consisting of 5 g of gold foil (purity of gold (Au) = 99.9%) 5 g and Al ₂ O _{3 having a} diameter of 5 mm. 50 g of balls were added. Then, using a planetary table-top ball mill apparatus, wet planetary pulverization was performed at room temperature (20 ° C. to 30 ° C.) for 5 minutes at a stirring speed of 500 rpm. Al ₂ O ₃ balls were separated from the solution after the treatment.
As a result, a gold foil in the middle of pulverization was confirmed in the solution. Then, the gold foil was removed, and gold (Au) particles precipitated in the solution were collected, washed with acetone, and then dried at room temperature to obtain gold (Au) powder. When XRD measurement of this powder was performed, it was confirmed that it was metal gold having an fcc structure. Further, when observed by FE-SEM, it was confirmed that the particle size was 10 μm to 3000 μm, but it was smaller than such a particle size on the order of μm, like the metal fine particles according to the example of the present invention. Formation of fine particles having a particle size on the order of nm was not confirmed.

(Comparative Example 12)
Mix 21.9 mL of triethylamine and 20 mL of toluene solvent, and add 2.5
1 g of a gold foil (purity of gold (Au) = 99.9%) was added, and while maintaining the temperature of the solvent at 40 ° C., the magnetic stirrer was used in the atmosphere at a stirring speed of 100 rpm for 24 hours. The production process of metal fine particles by liquid phase method was carried out.
As a result, uncrushed gold foil was confirmed in the solution, but metal fine particles were not generated.

  From the results of generating, analyzing and evaluating the samples according to the examples and the comparative examples as described above, according to the present invention, the metal mass is placed in a solvent, and the solvent is used as a medium to form the metal mass. By irradiating with ultrasonic waves, the metal lumps were crushed by ultrasonic cavitation generated by the irradiation of the ultrasonic waves to obtain fine metal particles. It was confirmed that it can be produced with high efficiency in the processing time. In contrast to this, conventional mechanical crushing methods (solid phase method), chemical reduction synthesis methods (liquid phase method), etc., produce such fine metal particles of nm order with high efficiency. Was found to be difficult in practice.

In the above-described embodiment and each example, the case where high purity copper (Cu), silver (Ag), and other various metals are used as the metal lump of the raw material has been described. However, it goes without saying that, for example, used metal materials or alloy materials can be used.
In addition, the present invention can be applied to a process for recovering each metal species as metal fine particles from a composite metal material such as an electric wire material, or a process for making fine powder of metal resources in a so-called recycling system. Application is also possible.
Further, the present invention is particularly suitable for the production of metal fine particles having an extremely fine particle size such as nm order, and the particle size of the metal fine particles that can be produced is such a particle size of nm order. Of course, it is not limited to only. In addition, the present invention can be applied to the production of fine metal particles having a large particle size, for example, about 1 μm to 100 μm, or more, for example, up to about 1000 nm. Alternatively, it is also possible to produce fine metal particles having a finer particle size, for example, less than 1 nm.
The present invention can also be applied to the coating of metal fine particles on the surface of a metal material or the surface of a non-metal material such as various polymers.

Claims (8)

Metal fine particles obtained by crushing a metal lump by ultrasonic cavitation. In the metal fine particle of Claim 1,
A metal fine particle, wherein the metal fine particle has a particle size of 1 nm or more and 100 μm or less. By placing the metal mass in a solvent and irradiating the metal mass with ultrasonic waves using the solvent as a medium, the metal mass is crushed by ultrasonic cavitation generated by the irradiation of the ultrasonic waves, and fine metal particles are obtained. The manufacturing method of the metal fine particle characterized by including the process to obtain. In the manufacturing method of the metal fine particle of Claim 3,
The metal mass is gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), rhodium (Rh), aluminum (Al), zinc (Zn), tin (Sn), Cobalt (Co), nickel (Ni), iron (Fe), indium (In), magnesium (Mg), or an alloy composed of these metal species, characterized in that it is composed of at least one of them A method for producing fine metal particles. In the manufacturing method of the metal fine particle of Claim 3 or 4,
The shape of the metal lump is any one of a metal foil, a metal rod, a metal wire, and a metal particle. In the method for producing fine metal particles according to any one of claims 3 to 5,
The solvent is composed of at least one of water, alcohols, aldehydes, amines, monosaccharides, polysaccharides, linear hydrocarbons, fatty acids, and aromatics. A method for producing fine metal particles. In the method for producing fine metal particles according to any one of claims 3 to 6,
In the solvent, alcohols, aldehydes, amines, lithium aluminum hydroxide, sodium thiosulfate, hydrogen peroxide, hydrogen sulfide, borane, diborane, hydrazine, potassium iodide, citric acid, A method for producing fine metal particles, comprising adding at least one chemical species of oxalic acid and ascorbic acid. In the method for producing fine metal particles according to any one of claims 3 to 7,
The method for producing fine metal particles, wherein the ultrasonic wave has a frequency of 15 kHz or more and 200 kHz or less and an intensity of 0.5 W / cm ³ or more.