JP6993674B2 - Amorphous nanoparticles manufacturing method, amorphous nanoparticles and amorphous nanoparticles dispersion - Google Patents

Description

The present invention relates to a method for producing amorphous nanoparticles, amorphous nanoparticles and an amorphous nanoparticle dispersion liquid.

Conventionally, as a method for producing amorphous particles containing an amorphous structure, a liquid quenching method for rapidly cooling a liquid metal, an atomizing method such as a gas atomizing method, and the like are known. For example, Japanese Patent Application Laid-Open No. 2010-209409 (Patent). Document 1) describes a method for producing an amorphous soft magnetic alloy powder in which a molten metal primary pulverized by a gas atomizing method is rapidly cooled while being secondary pulverized by a liquid film of a refrigerant formed on the surface of a rotating disk. Are listed. However, these methods have a problem that the obtained amorphous particles have a relatively large particle size of several μm or more, contain an amorphous structure, and it is difficult to obtain amorphous nanoparticles on the order of nanometers. It was.

Further, as a method for producing metal nanoparticles, a method using an arc plasma discharge is known in addition to a chemical method such as a metal salt reduction method and a sol-gel method. However, it is difficult to apply the above chemical method to the formation of amorphous particles, and the method using arc plasma discharge has a problem that secondary particles are easily formed, and is usually 10,000 ° C. or higher. There is a problem that segregation is likely to occur because particles are obtained by cooling from a high arc temperature, and there is also a problem that it is difficult to obtain a large amount of nanoparticles.

Japanese Unexamined Patent Publication No. 2010-209409

The present invention has been made in view of the above-mentioned problems of the prior art, and is a method for producing amorphous nanoparticles, which can easily obtain amorphous nanoparticles having excellent dispersibility at a relatively low temperature, amorphous nanoparticles and amorphous. It is an object of the present invention to provide a nanoparticle dispersion liquid.

As a result of diligent research to achieve the above object, the present inventors have maintained a dispersion liquid containing a solid metal made of an alloy and a reducing dispersion medium at a relatively low temperature (for example, 35 ° C. or lower). It has been found that amorphous nanoparticles containing an amorphous structure can be obtained by irradiating with ultrasonic waves. Further, they have found that such amorphous nanoparticles have excellent dispersibility (suppression of formation of secondary particles and dispersibility in a dispersion medium), and have completed the present invention.

That is, the method for producing amorphous nanoparticles of the present invention is:
A step of obtaining a dispersion liquid containing a solid metal composed of an alloy and a reducing dispersion medium, and
A step of irradiating the dispersion liquid with ultrasonic waves while maintaining the temperature at 35 ° C. or lower to obtain amorphous nanoparticles containing an amorphous structure from the solid metal.
Including
The solid metal is made of an alloy having a lower hardness than iron, copper and nickel metals.
The average particle size of the amorphous nanoparticles is 200 nm or less .
The reducing dispersion medium is at least one selected from the group consisting of hydrocarbons and alcohols.

Further, as a method for producing amorphous nanoparticles of the present invention,
A step of obtaining a dispersion liquid containing a solid metal composed of an alloy and a reducing dispersion medium, and
A step of irradiating the dispersion liquid with ultrasonic waves while maintaining the temperature at 35 ° C. or lower to obtain amorphous nanoparticles containing an amorphous structure from the solid metal.
Is preferable, and it is more preferable to irradiate the dispersion liquid with the ultrasonic wave while maintaining the temperature in the range of −90 to 20 ° C.

Further, as a method for producing amorphous nanoparticles of the present invention, the alloys are Sn—Bi alloy, Sn—Sb alloy, Sn—Ag alloy, Sn—Cu alloy, Zn—Al alloy, Bi—Cu alloy, Au—. It is preferably at least one selected from the group consisting of Sn alloys, Au—Ge alloys and Ag—Cu alloys.

Further, as a method for producing amorphous nanoparticles of the present invention, the average particle size of the amorphous nanoparticles is preferably 1 to 200 nm, and the solid metal is a metal powder having an average primary particle size of 1 to 500 μm. Is preferable.

Further, in the method for producing amorphous nanoparticles of the present invention, the content of the solid metal in the dispersion liquid is preferably 0.1 to 50 parts by mass with respect to 100 parts by mass of the reducing dispersion medium.

Further, as a method for producing amorphous nanoparticles of the present invention, it is preferable that the amorphous nanoparticles do not have an oxide film on the surface thereof.

Further, the amorphous nanoparticles of the present invention are amorphous nanoparticles containing an amorphous structure composed of two or more kinds of metal atoms, and have substantially no oxide film on the surface.
The amorphous nanoparticles are characterized by being made of a solid metal made of an alloy having a hardness lower than that of iron, copper and nickel metals. The amorphous nanoparticles of the present invention preferably contain an amorphous nanocrystal structure. The amorphous nanoparticle dispersion liquid of the present invention is characterized by containing the amorphous nanoparticles of the present invention.

According to the present invention, it is possible to provide a method for producing amorphous nanoparticles, an amorphous nanoparticles and an amorphous nanoparticles dispersion liquid, which can easily obtain amorphous nanoparticles having excellent dispersibility at a relatively low temperature.

It is a schematic diagram conceptually showing the amorphous random structure which concerns on this invention. It is a schematic diagram conceptually showing the amorphous nanocrystal structure which concerns on this invention. It is a scanning electron micrograph of the Sn—Bi alloy powder used in Examples 1 and 2. 6 is a magnified scanning electron micrograph of the Sn—Bi alloy powder used in Examples 1 and 2. 6 is a scanning electron micrograph of the amorphous nanoparticles obtained in Example 1. 6 is a magnified scanning electron micrograph of the amorphous nanoparticles obtained in Example 1. 6 is a transmission electron micrograph of the amorphous nanoparticles obtained in Example 1. It is an electron diffraction image obtained by Fourier transforming the electron micrograph of the amorphous nanoparticles obtained in Example 1. 6 is a transmission electron micrograph of the amorphous nanoparticles obtained in Example 2. 6 is a magnified transmission electron micrograph of the amorphous nanoparticles obtained in Example 2. 3 is a transmission electron micrograph of the amorphous nanoparticles obtained in Example 3. 6 is a magnified transmission electron micrograph of the amorphous nanoparticles obtained in Example 3. 3 is a field emission scanning electron micrograph after heating the amorphous nanoparticles obtained in Example 3. It is a graph which shows the result of the methanol dispersion liquid of the amorphous nanoparticles obtained in Example 3, the thermogravimetric change measurement of methanol, and the differential scanning calorimetry. It is a graph which shows the particle size distribution curve immediately after the production of the amorphous nanoparticle obtained in Example 3. FIG. It is a graph which shows the particle size distribution curve 2 months after the production of the amorphous nanoparticles obtained in Example 3. FIG.

Hereinafter, preferred embodiments of the present invention will be described in detail. The method for producing amorphous nanoparticles of the present invention includes a step of obtaining a dispersion liquid containing a solid metal made of an alloy and a reducing dispersion medium, and irradiating the dispersion liquid with ultrasonic waves to make the solid metal amorphous. It is characterized by including a step of obtaining amorphous nanoparticles containing a structure.

Further, the amorphous nanoparticles of the present invention are characterized by being amorphous nanoparticles containing an amorphous structure composed of two or more kinds of metal atoms and having substantially no oxide film on the surface.

<Amorphous nanoparticles>
The amorphous nanoparticles of the present invention can be obtained by the production method of the present invention. The amorphous nanoparticles of the present invention are nanoparticles containing an amorphous structure, and may be particles containing an amorphous random structure or particles containing an amorphous nanocrystal structure. 1A and 1B show conceptual schematic diagrams of an amorphous random structure and an amorphous nanocrystal structure according to the present invention, respectively. In the following description and drawings, the same or corresponding elements are designated by the same reference numerals, and duplicate description will be omitted.

In the present invention, the "amorphous random structure" refers to a metal nanostructure that is an amorphous (amorphous metal) in which metal atoms are randomly arranged. In the present invention, since an alloy composed of two or more kinds of metals is used as the metal material, the amorphous random structure contains two or more kinds of metal atoms. For example, metal A and metal B are used as the metal materials. When an alloy (AB alloy) is used, in the amorphous random structure, as shown in FIG. 1A, an atom of metal A (first atom 1) and an atom of metal B (second atom 2) are used. Are mixed with each other and arranged randomly.

In the present invention, the "amorphous nanocrystal structure" is an aggregate of a crystal in which metal atoms are regularly arranged (metal crystal) and an amorphous in which metal atoms are randomly arranged (amorphous metal). As shown in FIG. 1B, the crystals (nano crystal grains 4) are dispersed in the amorphous mother phase (amorphous mother phase 3), and the crystals are randomly arranged metal nanostructures. To say. In the present invention, since an alloy composed of two or more kinds of metals is used as the metal material, the amorphous nanocrystal structure contains two or more kinds of metal atoms. When the alloy of (AB alloy) is used, in the amorphous nanocrystal structure, the nanocrystal grains 4 include a crystal (A) composed of an atom of metal A, a crystal (B) composed of an atom of metal B, and the like. In addition, at least one of the crystals composed of the atom of the metal A and the atom of the metal B (AnBm, n and m each independently indicate the number of the metal atom) exists (in FIG. 1B, among these, the metal A (in FIG. 1B). The crystal consisting of the first atom 1) is shown by enclosing it in a circle). In this case, the amorphous matrix 3 is an amorphous in which an atom of metal A (first atom 1) is randomly arranged, and an amorphous in which an atom of metal B (second atom 2) is randomly arranged. In addition, there is at least one of amorphous substances in which an atom of metal A (first atom 1) and an atom of metal B (second atom 2) are mixed and randomly arranged (in FIG. 1B, this atom). Of these, the amorphous material consisting of the atom of metal A and the atom of metal B is shown by enclosing it in a circle).

Therefore, the amorphous nanoparticles of the present invention are nanoparticles containing two or more kinds of metal atoms, that is, an amorphous structure composed of metal atoms constituting the alloy used as the metal material.

In the present invention, it can be confirmed that the metal nanoparticles contain an amorphous structure by observing a halo pattern by an electron diffraction image (Fourier transform image). Further, the fact that the metal nanostructure is an amorphous random structure or an amorphous nanocrystal structure can be confirmed by confirming the halo pattern and the diffraction spot by the electron diffraction image and observing the arrangement state of atoms by a transmission electron microscope (TEM). You can check.

The shape of the amorphous nanoparticles of the present invention is not particularly limited, and examples thereof include a spherical shape, a flat plate shape, a plate shape, and the like, but a spherical shape is preferable. Further, as the amorphous nanoparticles of the present invention, the average particle size (average particle size of the primary particles) is preferably 200 nm or less, more preferably 1.0 to 200 nm, and the formation of secondary particles is more preferable. It is more preferably 1.0 to 80 nm from the viewpoint that it is suppressed and tends to be more excellent in dispersibility in the dispersion medium. According to the production method of the present invention, such amorphous nanoparticles on the order of nanometers can be easily obtained. Therefore, it is also possible to obtain a large amount of the amorphous nanoparticles.

In the present invention, the particle size of each particle (primary particle) can be measured by observation with a scanning electron microscope (SEM), and the particle size is the diameter of a circle when the particles are projected onto a plane. When the projection surface is not circular (when the particles have a flat plate shape, a plate shape, a rod shape, a polygonal shape, etc.), it means the diameter of the circumscribing circle. Further, the average particle size of the particles means the average particle size measured for each of these particles by extracting 100 arbitrary particles.

Further, according to the production method of the present invention, as the amorphous nanoparticles of the present invention, particles having substantially no oxide film on the surface can be obtained. In the present invention, the fact that the particles do not have an oxide film on the surface means that the surface of the primary particles is observed at a magnification of 600,000 with a transmission electron microscope (TEM) and is within the observation field of any 20 points (30 × 30 nm). It means that no oxide film is confirmed on the surface of the primary particles in the region).

Further, since the amorphous nanoparticles of the present invention do not substantially have an oxide film on the particle surface as described above, sintering (or bonding) between the particles occurs at a sufficiently low temperature. Therefore, for example, when the amorphous nanoparticles of the present invention are used for soldering purposes, the bonding force can be expected to be enhanced. Specifically, the temperature is lower than the melting point of an alloy composed of all the metal atoms (two or more kinds of metal atoms) constituting the amorphous structure. In the present invention, the temperature at which sintering (bonding) between particles occurs can be confirmed by observing the sintering peak using differential scanning calorimetry (DSC). More specifically, all the metals constituting the amorphous structure in the thermogram obtained by heating the dispersion liquid in which the particles are dispersed in methanol from 10 ° C. to 75 ° C. at a heating rate of 10 ° C./min. The exothermic peak (temperature) observed at a temperature lower than the melting point of an alloy composed of atoms (two or more kinds of metal atoms) (for example, around 25 ° C.) is defined as the temperature at which sintering (bonding) occurs between the particles according to the present invention. You can ask. Further, in the present invention, the melting point of an alloy can be measured by using thermal weight change measurement (TG) for a powder of a solid metal made of an alloy having an average primary particle diameter of 1.0 to 500 μm. The heat absorption peak (temperature) observed in the thermogram obtained by heating a solid metal composed of 100 ° C. at a heating rate of 10 ° C./min at 1 atm from 0 ° C. to 550 ° C. is determined as the melting point of the alloy according to the present invention. Can be done.

<Amorphous nanoparticles manufacturing method, amorphous nanoparticles dispersion liquid>
In the method for producing amorphous nanoparticles of the present invention, first, a dispersion liquid (reaction dispersion liquid) containing a solid metal made of an alloy and a reducing dispersion medium is obtained.

In the solid metal composed of the alloy according to the present invention, the alloy is a metal in which two or more kinds of metals (more preferably metal crystals) are mixed. In the present invention, the alloys include, for example, Sn—Bi alloy, Sn—Sb alloy, Sn—Ag alloy, Sn—Cu alloy, Sn—Pb alloy, Zn—Al alloy, Bi—Cu alloy, Au—Sn alloy. , Au-Ge alloys, Ag-Cu alloys, and other binary alloys; in the binary alloy, at least one metal selected from the group consisting of Ag, Cu, Ni, Ge, Bi, In, and P is further added. Examples include mixed ternary alloys and quaternary alloys. The solid metal according to the present invention may be a solid metal made of one of these alloys, or a mixture of one or more solid metals made of other alloys. good. Among these alloys, Pb-free, which does not contain Pb, is preferable from the viewpoint of environmental conservation, aggregation of the obtained amorphous nanoparticles is particularly suppressed, and dispersibility in a dispersion medium tends to be maintained for a long period of time. Sn-Bi alloy, Sn-Sb alloy, Sn-Ag alloy, Sn-Cu alloy, Zn-Al alloy, Bi-Cu alloy, Au-Sn alloy, Au-Ge alloy and Ag-Cu alloy. It is more preferably selected from the group consisting of at least one selected from the group consisting of Sn—Bi alloy, Sn—Sb alloy, Sn—Cu alloy, Zn—Al alloy, Au—Sn alloy and Au—Ge alloy. It is particularly preferable that it is one of the above.

The content ratio of each metal contained in the alloy is, for example, in the case of a Sn-based alloy such as a Sn—Bi alloy, a Sn—Sb alloy, or a Sn—Ag alloy, the Sn content and other metals. The ratio to the content of (Sn content: content of other metals) is in the range of 99: 1 to 30:70.

Examples of the shape of the solid metal according to the present invention include flat plates, plates and the like, rods, polygons, spheres and the like, and examples of the solid metal include metal foils, metal rods, metal wires and metals. It is preferably at least one of the powders (metal particles), and the longest diameter is preferably 1.0 μm or more. Among these, the solid metal is preferably a metal powder, the metal powder is preferably microparticles, and the average particle size (average primary particle size) of the primary particles constituting the powder is large. It is preferably 1.0 μm or more, more preferably 1.0 to 500 μm, further preferably 1.0 to 300 μm, and particularly preferably 10 to 100 μm. When the average particle size is less than the lower limit, it tends to be difficult to obtain amorphous nanoparticles, while when the average particle size exceeds the upper limit, the particle size of the obtained amorphous nanoparticles varies widely. There is a tendency for the production efficiency of amorphous nanoparticles to decrease. As such a metal powder, for example, it is preferable to use a metal powder made of the alloy obtained by an atomization method such as gas atomization, centrifugal atomization, water atomization, or oil droplet atomization.

In the production method of the present invention, it is necessary to use a reducing dispersion medium as the medium. Examples of the reducing dispersion medium according to the present invention include at least one selected from the group consisting of hydrocarbons and alcohols, and more specifically, aromatic hydrocarbons (xylene, toluene, styrene, naphthalene, etc.). , Hydrocarbons such as paraffinic hydrocarbons (methane, ethane, propane, butane, etc.); alcohols such as monohydric alcohols (ethanol, methanol, propanol, butanol, etc.), dihydric alcohols (ethylene glycol, etc.). .. The reducing dispersion medium may be one of these alone or a mixture of two or more thereof, but the aggregation of the obtained amorphous nanoparticles is particularly suppressed and the dispersibility in the dispersion medium is particularly suppressed. Is preferably any one selected from the group consisting of ethanol, methanol, aromatic hydrocarbons and paraffinic hydrocarbons, from the viewpoint that it tends to be maintained for a long period of time.

Further, as the reducing dispersion medium according to the present invention, it is preferable to perform a degassing treatment in advance to remove dissolved oxygen from the viewpoint of further preventing the oxidation of the obtained amorphous nanoparticles. Examples of the degassing treatment include a method of irradiating ultrasonic waves, a method of aerating an inert gas and a reducing gas, and the like.

The method for obtaining the dispersion liquid (reaction dispersion liquid) containing the solid metal and the reducing dispersion medium is not particularly limited, and the solid metal can be obtained by adding the solid metal to the reducing dispersion medium. Can be done. In the dispersion liquid, the content of the solid metal is preferably 0.1 to 50 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the reducing dispersion medium. .. According to the production method of the present invention, even if the content of the solid metal is relatively large (for example, 10 parts by mass or more with respect to 100 parts by mass of the reducing dispersion medium), the amorphous nanoparticles can be efficiently obtained. Can be done.

The dispersion liquid (reaction dispersion liquid) according to the present invention may further contain a reducing agent. Examples of such reducing agents include lithium ammonium hydroxide, lithium aluminum hydroxide, sodium thiosulfate, hydrogen peroxide solution, hydrogen sulfide, borane, diborane, hydrazine, potassium iodide, citric acid, oxalic acid, and ascorbic acid. At least one selected from the group consisting of. When such a reducing agent is added, its content in the dispersion liquid is appropriately adjusted depending on the type of alloy used and the reducing dispersion medium. For example, it is added to 100 parts by mass of the solid metal. On the other hand, it is preferably 5 to 20 parts by mass.

Further, the dispersion liquid (reaction dispersion liquid) according to the present invention may contain a surfactant and / or a surface modifier, but in the production method of the present invention, the surfactant and the surface modifier are substantially contained. Amorphous nanoparticles having excellent dispersibility in a dispersion medium can be obtained even if they are not contained therein. In the present invention, "substantially free" means that the total content of the surfactant and the surface modifier in the dispersion is less than 0.1 part by mass with respect to 100 parts by mass of the solid metal. Say something.

Such surfactants and surface modifiers have a function of modifying the surface of the obtained amorphous nanoparticles and the solid metal to further maintain dispersibility in a reducing dispersion medium, and / or these particles. It refers to a substance having a function of further suppressing aggregation between the particles, and examples thereof include those conventionally known as surfactants or surface modifiers. The surface modifier also includes an organic compound chemically bonded to the surface of these particles.

More specifically, examples of the surfactant include cationic surfactants such as benzalkonium chloride, alkyltrimethylammonium salt and dialkyltrimethylammonium salt; sodium dodecylsulfate (SDS), sodium alkylbenzenesulfonate and alkylsulfate. Anionic surfactants such as sodium ester, sodium alkylsulfonate, sodium alphaolefin sulfonate; nonionic surfactants such as polyoxyethylene alkylphenyl ether, alkyl glycoloxide, sucrose fatty acid ester, fatty acid alkanolamide, etc. Examples of the surface modifier include polyethyleneimine; polyvinylpyrrolidone (PVP); polyvinyl alcohol (PVA); organic compounds having an amino group and a carboxy group; and polysaccharides such as starch and sucrose.

In the method for producing amorphous nanoparticles of the present invention, the dispersion liquid (reaction dispersion liquid) is then irradiated with ultrasonic waves to obtain the amorphous nanoparticles from the solid metal.

For the irradiation of the ultrasonic waves, the temperature of the reaction dispersion is preferably maintained at a temperature equal to or lower than the boiling point of the reducing dispersion medium or lower than the melting point of the solid metal, and is maintained at 35 ° C. or lower. Is more preferable. In the production method of the present invention, by irradiating the solid metal with ultrasonic waves using the reducing dispersion medium as a medium, the solid metal is crushed by the cavitation bubbles generated by the irradiation of the ultrasonic waves, and the inside of the cavitation bubbles. By the physicochemical action in the high temperature and high pressure reaction field (hot spot) generated in the above, the amorphous nanoparticles can be easily obtained in the reducing dispersion medium even at a relatively low temperature. The inventors speculate. Further, in the production method of the present invention, the alloy is embrittled by irradiating a solid metal made of an alloy having a hardness lower than that of a metal such as iron, copper, or nickel with ultrasonic waves at such a low temperature. Therefore, the present inventors presume that amorphous nanoparticles having a small particle size and suppressed formation of secondary particles can be obtained.

In the method for producing amorphous nanoparticles of the present invention, the temperature of the reaction dispersion liquid (hereinafter, sometimes referred to as “irradiation temperature”) at the time of irradiation with ultrasonic waves is preferably −90 to 20 ° C. It is more preferably −80 to 10 ° C., and even more preferably −80 to 0 ° C. When the irradiation temperature is less than the lower limit, the production efficiency of the obtained amorphous nanoparticles tends to decrease, while when the irradiation temperature exceeds the upper limit, the obtained amorphous nanoparticles tend to aggregate with each other. It tends to form secondary particles and reduce the dispersibility of amorphous nanoparticles in the dispersion medium.

The frequency of the ultrasonic irradiation is preferably 1 k to 1 MHz, more preferably 15 to 200 kHz, and even more preferably 15 to 100 kHz. When the frequency is less than the lower limit, it becomes difficult to obtain amorphous nanoparticles on the order of nanometers, or the production efficiency of amorphous nanoparticles tends to decrease. On the other hand, even if the upper limit is exceeded, It becomes difficult to obtain amorphous nanoparticles on the order of nanometers, and the production efficiency of amorphous nanoparticles tends to decrease.

Further, as the irradiation of the ultrasonic wave, the irradiation time is preferably 1 to 100 hours, more preferably 10 to 80 hours, and further preferably 24 to 72 hours. When the irradiation time is less than the lower limit, it becomes difficult to obtain amorphous nanoparticles on the order of nanometers, or the production efficiency of amorphous nanoparticles tends to decrease, while when the irradiation time exceeds the upper limit. The obtained amorphous nanoparticles tend to aggregate and become coarse.

Further, for the ultrasonic irradiation, the irradiation intensity is preferably 0.01 to 100 W / cm ² from the viewpoint that amorphous nanoparticles having a small particle size tend to be obtained more efficiently, and is 0. .1 to 50 W / cm ² is more preferable, and 1.0 to 10 W / cm ² is even more preferable.

By such a production method of the present invention, the amorphous nanoparticles can be obtained in the reducing dispersion medium. The obtained amorphous nanoparticles can be dispersed in a dispersion medium to obtain the amorphous nanoparticles dispersion liquid of the present invention containing the amorphous nanoparticles and the dispersion medium.

The amorphous nanoparticle dispersion liquid of the present invention is characterized by containing the amorphous nanoparticles, and preferably further contains a dispersion medium. As the dispersion medium of the amorphous nanoparticles dispersion liquid, in addition to the reducing dispersion medium, for example, alcohols such as propylene glycol and terpineol; ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as tetramethyl benzene; Esters such as ethyl acetate and butyl acetate; aliphatic hydrocarbons such as octane and decane; petroleum-based solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha; acrylic resin, alkyd resin, polyester resin, phthalic acid Examples thereof include resins such as resins, amino resins, urea resins, urethane resins, epoxy resins, butyral resins, phenol resins, hydrocarbon resins, polyamide resins, and melamine resins, and even if one of these is used alone, there are two types. The above mixture may be used.

Further, the content of the amorphous nanoparticles in the amorphous nanoparticles dispersion liquid of the present invention is not particularly limited and can be appropriately adjusted according to the purpose of use. The amorphous nanoparticle dispersion liquid further contains additives such as an oxide film remover, a thickener, a thixo agent, an antifoaming agent, and an antioxidant, as needed, as long as the effects of the present invention are not impaired. You may be doing it.

As such an amorphous nanoparticle dispersion, the dispersion obtained by the production method of the present invention after ultrasonic irradiation can be used as it is as an amorphous nanoparticle dispersion, and the dispersion after ultrasonic irradiation can be used as it is. It can also be obtained by substituting the reducing dispersion medium with an appropriate dispersion medium. Further, the amorphous nanoparticle dispersion liquid of the present invention also includes forms such as solder cream. Therefore, the amorphous nanoparticles and the amorphous nanoparticles dispersion liquid of the present invention can be used for soldered members, electronic members, and electric devices including them.

Since the amorphous nanoparticles obtained by the production method of the present invention have excellent dispersibility in a dispersion medium, even if the above-mentioned surfactant and surface modifier are not substantially contained, the secondary particles due to aggregation of the particles can be obtained. Formation is suppressed. For example, when the amorphous nanoparticles are dispersed in the reducing dispersion medium, the formation of secondary particles is sufficiently suppressed even after being allowed to stand at 25 ° C. for 24 hours, and more specifically, the particle size distribution measurement is performed. The peak position of the particle size distribution curve obtained is in the range of 10 to 300 nm, particularly preferably in the range of 20 to 200 nm. Further, the peak of the particle size distribution curve refers to the maximum peak observed in the particle size distribution curve in the present invention, the peak position indicates the average position of three measurements, and the width (peak width) thereof is measured. The average of 3 times is preferably 200 nm or less, and particularly preferably 5 to 150 nm.

In the amorphous nanoparticles obtained by the production method of the present invention, the effect of suppressing the formation of such secondary particles is maintained even after long-term storage, and after standing for a long period of time, after standing for 24 hours, and after standing for 6 months. The peak position and the peak width hardly change between them, and the particle size of the amorphous nanoparticles before standing is maintained. Further, the amorphous nanoparticles obtained by the production method of the present invention have excellent dispersibility in a dispersion medium, and the precipitation of the particles tends not to be observed even if the dispersion liquid of the amorphous nanoparticles is allowed to stand for a long period of time. be.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples. In each example, the particle size measurement of the metal powder, the particle size measurement of the metal nanoparticles, the observation of the metal nanostructure of the metal nanoparticles, the dispersibility evaluation, and the sintering property evaluation were performed by the following methods, respectively.

<Measurement of particle size>
For the metal powder used in each example and the obtained metal nanoparticles, electron microscope observation of the metal particles was performed using an electro-emission scanning electron microscope (FE-SEM, manufactured by Hitachi High-Tech, model number: SU-70). Then, a scanning electron micrograph (SEM photograph) was taken. In the obtained SEM photograph, 100 metal particles (primary particles) are randomly extracted, and the diameter of the circle when each particle is projected onto a plane, or the circumscribing circle when the projection surface is not circular. The diameter of these particles was measured and used as the particle diameter, and the average of these particle diameters was obtained as the average particle diameter.

<Observation of metal nanostructure>
The metal nanoparticles dispersion obtained in each example was left in the air at 20 ° C. to evaporate the dispersion medium, and then the remaining metal was subjected to a scanning electron microscope (FE-SEM, manufactured by Hitachi, model number: SU8020). , And an electron microscope observation was performed using an electron microscope (TEM / STEM, manufactured by JEOL Ltd., model number: JEM-ARM200F), and a scanning electron micrograph (SEM photograph) and a transmission electron micrograph (TEM photograph) were performed. ) Was taken respectively. In addition, the metal nanostructure was confirmed by observing the arrangement state of the atoms in the obtained TEM photograph. Further, the obtained TEM photograph was Fourier transformed to obtain an electron diffraction image, and the presence or absence of a halo pattern and a diffraction spot was confirmed.

<Dispersity evaluation>
For the metal nanoparticle dispersions obtained in each example, the appearance of the dispersion immediately after production and the appearance of the dispersion after stirring at 25 ° C. for 24 hours were observed, respectively, and the following criteria:
A: Metal particles are dispersed throughout the dispersion medium and no precipitation is observed. B: Metal particles are dispersed only in a part of the dispersion medium and the supernatant is clear, and precipitation is observed. C: Metal particles are observed. The dispersibility of the metal particles in the dispersion medium was evaluated based on the fact that all the particles were precipitated. Further, with respect to the metal nanoparticle dispersion liquid obtained in each example, immediately after production and two months after production, a particle size analyzer (“Zetasizer”, manufactured by Malvern) was used. A particle size distribution curve was obtained by measuring the scattering intensity three times each.

<Evaluation of sintering characteristics>
The metal nanoparticles dispersion obtained in each example was left in the air at 20 ° C. to evaporate the dispersion medium, and then the remaining metal was subjected to a field emission scanning transmission electron microscope (TEM / STEM, manufactured by JEOL Ltd.). , Model number: JEM-2100), electron microscope observation was performed under the conditions of acceleration voltage: 200 kV, magnification: 600,000 times and 800,000 times, and transmission electron microscope photographs (TEM photographs) were taken. With respect to the obtained TEM photograph (magnification: 600,000 times), the presence or absence of an oxide film on the surface of the primary particles was confirmed within the observation field of view (30 × 30 nm region) at any 20 points.

Further, after heating the metal nanoparticles dispersion obtained in each example at 100 ° C. in the air, the remaining metal is subjected to a field emission scanning electron microscope (TEM / STEM, manufactured by JEOL Ltd., model number: JEM). -2100) was used for electron microscopic observation, and field emission scanning electron micrographs (FE-SEM photographs) were taken to confirm the presence or absence of particle growth (stituting).

Further, for the metal nanoparticles dispersion obtained in each example, a thermogravimetric change / differential scanning calorimetry device (TG-DSC measuring device, manufactured by NETZSCH, model number: STA449) was used, and the measurement range was 10 to 75 ° C. Thermogravimetric change measurement (TG) and differential scanning calorimetry (DSC) were performed under the condition of heating rate: 10 ° C./min to obtain a thermogram. The exothermic peak (temperature) confirmed in the obtained DSC thermogram was defined as the temperature at which sintering (bonding) occurred between the metal nanoparticles.

(Example 1)
60 g of Sn—Bi alloy powder (content ratio (Sn: Bi) = 42: 58, average primary particle size measured by the particle size measurement: 25 μm, melting point: 140 ° C.) obtained by the centrifugal atomization method is irradiated with ultrasonic waves in advance. Then, it was added to 1.8 L of degassed ethanol (99%) to obtain a dispersion. Conditions for the obtained dispersion: irradiation temperature (dispersion temperature): -5 ° C, frequency: 20 kHz, irradiation intensity: 1.0 W / cm ² (output intensity: 1200 W / cm ² ), irradiation time: 36 hours. Then, the metal powder was crushed by subjecting it to a treatment of irradiating with ultrasonic waves to obtain a dispersion liquid (metal nanoparticles dispersion liquid) in which metal nanoparticles (Sn-58Bi nanoparticles) were dispersed in ethanol. The scanning electron micrographs obtained by performing the particle size measurement on the Sn—Bi alloy powder used are shown in FIGS. 2A to 2B.

(Example 2)
Metal nanoparticles (Sn-58Bi nanoparticles) were contained in ethanol in the same manner as in Example 1 except that ethanol (99%) was 0.6 L and the irradiation time was 24 hours among the irradiation conditions of ultrasonic waves. A dispersion liquid (metal nanoparticle dispersion liquid) in which ethanol was dispersed was obtained.

For each of the obtained metal nanoparticles, the particle size measurement and the metal nanostructure observation were carried out. Scanning electron micrographs of the amorphous nanoparticles (metal nanoparticles) obtained in Example 1 are obtained in FIGS. 3 to 4A, transmission electron micrographs are obtained in FIG. 4B, electron diffraction images are obtained in FIG. 4C, and Example 2 is obtained. Transmission electron micrographs of the obtained amorphous nanoparticles (metal nanoparticles) are shown in FIGS. 5A to 5B, respectively. 4A to 5B are states after the dispersion medium is evaporated, and the mesh in the photograph of FIG. 4A is a grid used for observation. Further, FIG. 4B shows a part of the observed nanocrystal grains 4 and the amorphous mother phase 3 in circles. Further, in FIG. 4C, the observed diffraction spots are indicated by arrows.

As shown in FIGS. 2A, 2B and 3, it was confirmed that nanometer-order metal nanoparticles can be obtained from the micrometer-order alloy powder by the production method of the present invention. The average particle size of the obtained metal nanoparticles was 20 nm in Example 1 and 30 nm in Example 2.

Further, as shown in FIGS. 2A and 2B, the primary particles constituting the Sn—Bi alloy powder used as the solid metal material are spherical in which the final solidification portion in the atomization method becomes a protrusion due to solidification shrinkage. (FIG. 2A), the Sn moiety (Sn crystal) and the Bi moiety (Bi crystal) formed a eutectic (FIG. 2B). On the other hand, as shown in FIGS. 4B and 5B, in the metal nanoparticles obtained by the production method of the present invention, Sn, Bi, and SnBi crystals (nanocrystal grains 4) are partially present. It was confirmed that these were dispersed with an amorphous portion (amorphous mother phase 3) in which Sn atoms and Bi atoms were randomly mixed as a mother phase, and that they had an amorphous nanocrystal structure. Further, it was clear from the fact that both the halo pattern and the diffraction spot were confirmed in FIG. 4C that the obtained metal nanoparticles had an amorphous nanocrystal structure.

Further, when the dispersibility evaluation was performed on the obtained metal nanoparticle dispersion liquid, the dispersibility evaluation in the dispersion medium was A (metal particles were dispersed in the entire dispersion medium in all of Examples 1 and 2). , No precipitation was observed).

From the results shown above, it was confirmed that the production method of the present invention can obtain amorphous nanoparticles containing an amorphous structure and on the order of nanometers. Further, in the obtained amorphous nanoparticles, even in the dispersion liquid containing no surfactant or surface modifier, the aggregation of the particles is suppressed and the formation of secondary particles is sufficiently suppressed, and the particles are dispersed in the dispersion medium. It was confirmed that it is also excellent in sex.

(Example 3)
A dispersion liquid (metal nanoparticles dispersion liquid) in which metal nanoparticles (Sn-58Bi nanoparticles) were dispersed in methanol was obtained in the same manner as in Example 1 except that methanol was used instead of ethanol.

When the above-mentioned sintering property evaluation was performed on the metal nanoparticles obtained in Example 3, the obtained particles were nanometer-order amorphous nanoparticles containing an amorphous structure in the observation with a transmission electron microscope (TEM), and the particles were obtained. No oxide film was found on the surface of the particle. Transmission electron micrographs of the amorphous nanoparticles obtained in Example 3 are shown in FIGS. 6A to 6B, respectively. Further, FIG. 7 shows a field emission scanning electron micrograph after heating the amorphous nanoparticle dispersion liquid obtained in Example 3 at 100 ° C. As shown in FIG. 7, the amorphous nanoparticles obtained in Example 3 are grown to about 500 nm after heating at 100 ° C., and are grown from the Sn—Bi alloy powder (melting point: 140 ° C.) used as the metal material. It was confirmed that it was sintered at a low temperature.

Further, FIG. 8 shows a graph (thermogram) showing the results of thermogravimetric change measurement (TG) and differential scanning calorimetry (DSC) of the methanol dispersion of the amorphous nanoparticles obtained in Example 3. Further, FIG. 8 also shows the results of thermogravimetric change measurement (TG) and differential scanning calorimetry (DSC) for methanol, which is the dispersion medium used in Example 3. From the DSC graph shown in FIG. 8, the temperature at which sintering (bonding) occurred between the amorphous nanoparticles obtained in Example 3 was 24.8 ° C.

Further, the dispersibility evaluation of the metal nanoparticle dispersion liquid obtained in Example 3 was carried out immediately after production and 2 months after production, and the obtained particle size distribution curves are shown in FIGS. 9A and 9B, respectively (3 respectively). Batch). In FIG. 9A, the peak position of the particle size distribution curve was 193.3 nm on average of three times, and the peak width was 92.3 nm. Further, in FIG. 9B, the peak position of the particle size distribution curve was 244.0 nm on average for three times, and the peak width was 102.2 nm. As described above, the amorphous nanoparticles of the present invention are excellent in dispersibility in the dispersion medium by suppressing the aggregation of the particles and sufficiently suppressing the formation of secondary particles even after a long period of 2 months. Was confirmed. Moreover, after such a long period of time, the thermophysical properties of the amorphous nanoparticles of the present invention did not change.

As described above, according to the present invention, there are provided a method for producing amorphous nanoparticles, an amorphous nanoparticles and an amorphous nanoparticles dispersion liquid, which can easily obtain amorphous nanoparticles having excellent dispersibility at a relatively low temperature. It becomes possible.

1 ... 1st atom, 2 ... 2nd atom, 3 ... amorphous mother phase, 4 ... Nanocrystal grain.

Claims (10)

A step of obtaining a dispersion liquid containing a solid metal composed of an alloy and a reducing dispersion medium, and
A step of irradiating the dispersion liquid with ultrasonic waves while maintaining the temperature at 35 ° C. or lower to obtain amorphous nanoparticles containing an amorphous structure from the solid metal.
Including
The solid metal is made of an alloy having a lower hardness than iron, copper and nickel metals.
The average particle size of the amorphous nanoparticles is 200 nm or less .
A method for producing amorphous nanoparticles, wherein the reducing dispersion medium is at least one selected from the group consisting of hydrocarbons and alcohols. The method for producing amorphous nanoparticles according to claim 1 , wherein the dispersion liquid is irradiated with the ultrasonic waves while maintaining the temperature in the range of −90 to 20 ° C. The alloy is composed of Sn—Bi alloy, Sn—Sb alloy, Sn—Ag alloy, Sn—Cu alloy, Zn—Al alloy, Bi—Cu alloy, Au—Sn alloy, Au—Ge alloy and Ag—Cu alloy. The method for producing an amorphous nanoparticles according to claim 1 or 2 , wherein the alloying material is at least one selected from the group. The method for producing amorphous nanoparticles according to any one of claims 1 to 3 , wherein the average particle size of the amorphous nanoparticles is 1 to 200 nm. The method for producing amorphous nanoparticles according to any one of claims 1 to 4 , wherein the solid metal is a metal powder having an average primary particle diameter of 1 to 500 μm. The item according to any one of claims 1 to 5 , wherein the content of the solid metal in the dispersion is 0.1 to 50 parts by mass with respect to 100 parts by mass of the reducing dispersion medium. The method for producing amorphous nanoparticles according to the above. The method for producing amorphous nanoparticles according to any one of claims 1 to 6 , wherein the amorphous nanoparticles have substantially no oxide film on the surface. Amorphous nanoparticles containing an amorphous structure composed of two or more kinds of metal atoms, and having substantially no oxide film on the surface.
The amorphous nanoparticles are characterized by being made of a solid metal made of an alloy having a hardness lower than that of iron, copper and nickel metals. The amorphous nanoparticles according to claim 8 , wherein the amorphous nanoparticles contain an amorphous nanocrystal structure. An amorphous nanoparticle dispersion liquid containing the amorphous nanoparticles according to claim 8 or 9 .

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