JP2012224885A - Method for producing metal porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal porous body having desired micropores, especially micropores in the order of nanometers by a simple method.SOLUTION: A first metal particle having an average particle size in the range of 50 nm-1 μm and a second metal particle in which the metal particle containing a second metal material has an average particle size in the range of 5-500 nm and not more than the average particle size of the first metal particle are prepared. Then, a mixture is obtained by mixing the first metal particle and the second metal particle, and also the second metal particle is molten. The metal porous body is produced by binding the first metal particle with the obtained molten material.

Description

  The present invention relates to a method for producing a metal porous body that is particularly applicable to energy devices.

  Metal porous bodies having a large specific surface area are used as catalysts, gas storage materials, gas sensors, capacitors, permselective membranes, and the like. In these applications, the higher the specific surface area, the better the functionality in each application.

  Conventionally, when producing a metal porous body, metal particles are likely to aggregate each other during high-temperature firing, which imposes restrictions on the porous structure, and in particular, produces a metal porous body having nanometer-order micropores. Was difficult.

  In view of such a situation, Patent Document 1 discloses that after a nickel compound is dispersed and adsorbed on a polyvinyl alcohol film, the polyvinyl alcohol film disappears by heating in a reducing or non-oxidizing atmosphere. A technique for producing a nickel porous body by reducing the metal to Ni is disclosed. Patent Document 2 discloses a porous metal-containing material in which particles containing a metal base compound and a polymer are dispersed in a solvent, and then the obtained dispersion is applied onto a substrate, and then the solvent is removed. Is disclosed.

  In Patent Document 3, a porous substrate having a predetermined size is prepared in advance, slurry and aerosol containing nanoparticles are supplied to the porous substrate, and porous sintered nanoparticles are supplied to the porous substrate. A method of forming a layer is disclosed. Patent Document 4 discloses a coating film made of a metal nanoparticle colloid solution containing no coupling agent on a base material including a base layer containing a coupling agent or a reaction product of the coupling agent. It is disclosed that a porous film is formed by forming and sintering the coating film.

  In Patent Document 5, a porous film is formed on a porous substrate by applying a suspension of sinterable particles on a porous substrate and then sintering the sinterable particles. It is disclosed. In Patent Document 6, metal powders (large particle size metal powder and small particle size metal powder) having different particle diameters are sintered and an air chamber is formed between the metal powders. To form a porous material.

  However, in the method described in Patent Document 1, no attention is paid to the control of the size of the metal particles used as the base material when the porous body is manufactured, and the metal particles are removed in the process of disappearing the organic film by heating. Since melting may also occur, it becomes difficult to control the melting of the base material, and the size of the micropores formed by the metal particles is limited. Also, in the method described in Patent Document 2, since the polymer is decomposed and removed by heat treatment of the metal-containing polymer particles, and the metal particles as the base material are sintered, in order to control the pore size, There is a problem that the manufacturing method is complicated because it is necessary to strictly control the concentration and temperature of the dispersion.

  In the method described in Patent Document 3, a slurry containing nanoparticles is supplied to a porous substrate to produce a porous body only on the surface layer, so that a metal porous having fine pores on the order of nanometers as a whole. It is difficult to make a body. Also, the method described in Patent Document 4 is not suitable for the production of a porous body having a three-dimensional structure because the porous film is fixed and the pores are formed by the underlayer. The method described in Patent Document 5 is a manufacturing method using a suspension of particles. Therefore, in order to make the porous body have a predetermined thickness, it is necessary to repeat coating and sintering several times to form the porous body. The control of the pore size requires a precise control of the concentration of the dispersion and the temperature, and there is a problem that the manufacturing method becomes complicated.

  Furthermore, in the method described in Patent Document 6, when the metal powder as a raw material for obtaining the target porous body has a particle diameter of about several tens of nm to 1 μm, the metal particles in the sintering process Since melting is likely to occur, it is difficult to control, and it has been difficult to produce a metal porous body having desired micropores.

  In addition, as a method for producing metal particles having a particle size on the order of several tens of nanometers, techniques using a liquid phase reaction have been reported (for example, see Patent Documents 7 to 9). In Patent Document 7, a step of adding a reducing agent, a dispersant, and a nickel salt to a polyol solution to produce a mixed solution, a step of stirring and heating the mixed solution, and reacting the mixed solution to produce nickel nanoparticles. And a step of producing a nickel nanoparticle production method. Patent Document 8 discloses a technique for obtaining nickel nanoparticles by mixing a nickel precursor, an organic amine, and a reducing agent and then heating the mixture. In Patent Document 9, the metal salt is reduced by microwave irradiation. These prior arts do not teach any method for producing a metal porous body.

JP 2003-239028 A Special table 2008-532913 gazette JP-T-2006-509918 JP 2010-37464 A Special table 2010-505043 gazette JP 2010-53414 A JP 2009-024254 A JP 2010-037647 A JP 2000-256707 A

  An object of the present invention is to provide a metal porous body having desired micropores, particularly nanometer-order micropores, by a simple method.

In order to achieve the above object, the method for producing a porous metal body of the present invention comprises:
Metal particles containing a first metal material, wherein the metal particles have an average particle diameter in the range of 50 nm to 1 μm;
Metal particles containing a second metal material having a melting point lower than the melting point of the first metal material, wherein the average particle size of the metal particles is in the range of 5 nm to 500 nm, and the average particle size is Preparing a second metal particle having an average particle diameter equal to or less than the first metal particle;
Mixing the first metal particles and the second metal particles to obtain a mixture;
Heating the mixture to melt the second metal particles, and bonding the first metal particles with the obtained melt to obtain a metal porous body;
It is characterized by comprising.

  Further, the average particle diameter d1 of the first metal particles is in the range of 50 nm to 200 nm, and the ratio d1 / d2 to the average particle diameter d2 of the second metal particles is in the range of 5 to 200. The difference between the melting point of the first metal material and the melting point of the second metal material may be 50 ° C. or higher.

  Further, the ratio of the second metal particles to the first metal particles may be in the range of 5% by mass to 40% by mass.

  Furthermore, the first metal material is at least one selected from the group consisting of nickel, cobalt, iron and copper, or the second metal material is selected from the group consisting of gold, silver and copper. Or at least one of them.

Moreover, the method for producing the porous metal body of the present invention includes:
Dissolving a metal salt that is a precursor of the first metal material and / or the second metal material in an organic solvent to obtain a complexing reaction solution in which a metal complex is formed;
Heating the complexing reaction solution by microwave irradiation to obtain a slurry of the first metal particles and / or a slurry of the second metal particles;
Isolating the first metal particles and / or the second metal particles from the slurry of the first metal particles and / or the slurry of the second metal particles;
It is preferable to comprise.

  The method for producing a porous metal body according to the present invention uses the first metal particles that suppress melting and the second metal particles that enable melting, thereby retaining the original shape of the first metal particles. As a result, the first metal particles can be connected to each other. For example, even if the metal particles that are the base material of the metal porous body easily melt not only to the surface layer portion but also to the inside of the metal particles, the second metal particles intervene. The desired metal porous body can be simply provided without performing the heating control.

  In addition, even when a metal porous body base material is formed using high melting point metal particles, the metal porous body can be formed at a relatively low temperature by interposing the second metal particles. It becomes. Thus, the method for producing a metal porous body according to the present invention can provide a metal porous body having desired micropores, particularly nanometer-order micropores, by a simple method.

  Hereinafter, details of the present invention and other features and advantages will be described based on embodiments.

[Preparation step of first metal particles and second metal particles]
In this embodiment, first, metal particles having a first metal material, and the average particle diameter d1 of the metal particles is in the range of 50 nm to 1 μm, preferably in the range of 50 nm to 500 nm, more preferably. A metal particle comprising a first metal particle in a range of 50 nm to 400 nm, more preferably in a range of 50 nm to 200 nm, and a second metal material having a melting point lower than the melting point of the first metal material. The average particle diameter d2 of the metal particles is in the range of 5 nm to 500 nm, preferably in the range of 5 nm to 200 nm, more preferably in the range of 5 nm to 100 nm, still more preferably in the range of 5 nm to 50 nm, and The average particle diameter is equal to or less than the average particle diameter of the first metal particles, that is, the average particle diameter d1 of the first metal particles and the average particle diameter d2 of the second metal particles The ratio d1 / d2 is prepared and a second metal particles is 1 or more.

(First metal particles)
The first metal particles constitute the base material of the target metal porous body, and it is desirable that the original metal particles can be distinguished even after the metal porous body is formed. By setting the lower limit of the average particle diameter of the first metal particles to 50 nm, it becomes easier to suppress the progress of melting into the first metal particles, and the original shape of the first metal particles constituting the base material is completely Can be prevented from disappearing. On the other hand, when the average particle diameter of the first metal particles exceeds 1 μm, voids formed by the first metal particles are increased, and the bonding function by the second metal particles tends to be lowered.

  In the metal porous body according to the present invention, in order to facilitate the formation of nanometer-order micropores, the upper limit value is preferably 400 nm, and more preferably 200 nm. Here, the average particle diameter is an area average particle diameter of a powder photograph taken by SEM (scanning electron microscope) and randomly extracted 200 particles. The particle size of the metal particles is not only the primary particle size (the particle size of one metal particle that is completely independent without agglomeration), but also the particle size of the agglomerated particles (a plurality of metal particles are aggregated to be one particle). Mean particle diameter).

  The first metal particles contain a first metal material. The first metal material preferably contains a metal element having a melting point of 1000 ° C. or higher at 1 atm (101,325 Pa) as a main component, more preferably 70% by mass or more, and still more preferably 95% by mass. % Or more is preferable.

  Examples of such metal elements include nickel (melting point: 1455 ° C.), cobalt (melting point: 1495 ° C.), iron (melting point: 1535 ° C.), copper (melting point: 1083 ° C.), gold (melting point: 1063 ° C.), platinum ( Melting point: 1770 ° C., palladium (melting point: 1550 ° C.), rhodium (melting point: 1966 ° C.), iridium (melting point: 2454 ° C.), ruthenium (melting point: 2500 ° C.), tungsten (melting point: 3390 ° C.), molybdenum (melting point; 2619 ° C.), vanadium (melting point: 1730 ° C.), niobium (melting point: 2437 ° C.) and the like, and these may be used alone or in combination of two or more.

  Other metal elements may contain, for example, zinc, tin, silver, etc., and may contain elements other than metal elements such as hydrogen element, carbon element, oxygen element, nitrogen element, sulfur element, These alloys may be used. Furthermore, the first metal particles may be composed of a single metal particle or a mixture of two or more metal particles. In particular, when the finally obtained metal porous body is used for applications such as a catalyst, a gas storage material, a gas sensor, and a capacitor, the first metal material is preferably nickel, cobalt, or the like.

  In addition, melting | fusing point which this invention defines can be confirmed from the intrinsic value (for example, literature value) of a metal material (bulk material). Here, the numerical values of the melting points at 1 atm of the metal elements exemplified above are quoted from Basic Handbook of Chemistry II (Revised 3rd edition, Maruzen Publishing).

  The first metal particles may have a core-shell structure composed of two or more kinds of chemical species (Core-shell), or a structure in which two or more kinds of chemical species are combined with each other and combined. For example, in a core-shell structure composed of two kinds of chemical species, the first metal material is a structure surrounding an arbitrary chemical species.

(Second metal particles)
Since the second metal particles function as a binder for the first metal particles serving as a base material of the metal porous body, the second metal material having a melting point lower than the melting point of the first metal material is used. It is necessary to contain. The difference between the melting point of the second metal material and the melting point of the first metal material is preferably 50 ° C. or higher, more preferably 100 ° C. or higher. Thereby, even when the first metal particles and the second metal particles are heated at the same time, only the second metal particles can be easily dissolved, and can easily function as the binder. The upper limit of the difference in melting point is not particularly limited, and is necessarily determined by the type of the first metal material described above and the second metal material described in detail below.

  The second metal material preferably contains a metal element having a melting point lower than that of the main metal element of the first metal material as the main component of the second metal material. It is good to contain 70 mass parts or more with respect to 100 mass parts of 2nd metal materials, Preferably it is 95 mass parts or more.

  The metal element contained as the main component of the second metal particles preferably has a melting point at 1 atm of the metal element of preferably 1100 ° C. or less, more preferably 1000 ° C. or less. Examples of such metal elements include copper (melting point: 1083 ° C.), gold (melting point: 1063 ° C.), silver (melting point: 961 ° C.), indium (melting point: 157 ° C.), tin (melting point: 232 ° C.), zinc ( Melting point; 420 ° C.), etc., and these may be used alone or in combination of two or more. Other metal elements, hydrogen elements, carbon elements, oxygen elements, nitrogen elements, sulfur elements, and other elements other than metal elements may be contained, or alloys thereof may be used. Furthermore, the second metal particles may be composed of a single metal particle or a mixture of two or more kinds of metal particles. In particular, since gold, silver, copper, and the like are good electrical conductors, when the finally obtained metal porous body is used for an electrode, a capacitor, or the like, the first metal particles (for example, the first metal material) that is a base material. This is preferable because the electrical characteristics of nickel, etc.) are not deteriorated.

  The second metal particles can be used without particular limitation as long as they are solid at room temperature. However, when a metal material having a melting point of less than 500 ° C., such as bismuth, antimony, or zinc, is contained as a main component, it is obtained due to a melting point drop due to a quantum effect by forming these metals into nanoparticles. The absolute value of the melting point is greatly reduced. Therefore, in the heat treatment described below, melting occurs even at a relatively low temperature, which may make temperature control difficult. In addition, when the finally obtained metal porous body is used for a predetermined application, it is remelted by the environmental temperature, and the structure of the metal porous body is destroyed, and is used for the application. May become impossible. From such a viewpoint, the lower limit value of the melting point of the second metal material is preferably 500 ° C. or higher.

  The ratio d1 / d2 between the average particle diameter d1 of the first metal particles and the average particle diameter d2 of the second metal particles is 1 or more, preferably within the range of 5 to 200, more preferably 10 to 10. A range of 200 is preferable. As described above, due to the melting point drop based on the quantum effect caused by forming the metal into nanoparticles, the absolute values of the melting points of the first metal particles and the second metal particles are greatly reduced. Therefore, when the average particle diameter d1 of the first metal particles is in the range of 50 nm to 200 nm, d1 / d2 is set to 5 or more, and the melting point drop of the first metal particles is reduced to the second. In comparison with the first metal particles, the second metal particles are dissolved by the heat treatment using the melting point difference between the first metal particles and the second metal particles. It can easily function as a binder.

  In order to obtain a metal porous body having a predetermined, particularly nanometer-order fine pores as a base material without completely erasing the original shape of the first metal particles, the average particle diameter d1 of the first metal particles is The ratio d1 / d2 between the average particle diameter d1 and the average particle diameter d2 of the second metal particles is preferably in the range of 5 to 200, more preferably in the range of 50 to 200 nm. It is good to set so that it is in the range. If it is smaller than 5, the absolute amount of the second metal particles becomes too large, which closes the pores of the formed metal porous body, making it difficult to obtain a metal porous body having fine pores on the order of nanometers. It may become. On the other hand, if it exceeds 200, the absolute amount of the second metal particles decreases, and the first metal particles cannot be bonded.

  Moreover, it is preferable that the ratio with respect to the 1st metal particle of a 2nd metal particle is the range of 5 mass%-40 mass%, More preferably, the range of 5 mass%-20 mass% is good. If it is less than 5% by mass, the absolute amount of the second metal particles becomes small, and the first metal particles cannot be bonded. On the other hand, if it exceeds 40% by mass, the absolute amount of the second metal particles becomes too large, and the pores of the formed metal porous body are blocked, and the metal porous body having fine pores on the order of nanometers is obtained. It can be difficult to obtain.

<Method for producing first metal particles and second metal particles>
The first metal particles and the second metal particles can be produced by a method such as a gas phase method or a liquid phase method, and the method is not particularly limited. In the vapor phase method, for example, a reaction apparatus having a vaporization section, a reaction section, and a cooling section is used, and a metal chloride is used as a raw material. Here, the metal can be deposited in the form of particles by contacting with hydrogen, and then the obtained metal particles can be cooled in the cooling section. For example, when producing nickel metal particles, the reaction temperature is controlled to about 950 ° C to 1100 ° C.

  The particle size control in this method can be carried out, for example, by controlling the flow rate of the carrier gas. Generally, if the flow rate of the carrier gas is increased, the particle size of the obtained metal particles tends to be small.

Further, since the vapor phase method tends to be expensive to produce compared with the liquid phase method, it is advantageous to apply the liquid phase method. Among the liquid phase methods, in order to improve the porosity of the metal porous body, the first metal particles preferably have a narrow particle size distribution, more preferably the first metal particles have a narrow particle size distribution. It is preferable to select the second metal particles having a narrow particle size distribution. As a method for easily producing such metal particles having a narrow particle size distribution in a short time, the following steps A to C;
A) A step of obtaining a complexing reaction solution in which a metal complex is formed by dissolving a metal salt which is a precursor of the first metal material and / or the second metal material in an organic solvent,
B) heating the complexing reaction solution by microwave irradiation to obtain a slurry of the first metal particles and / or a slurry of the second metal particles;
C) isolating the first metal particles and / or the second metal particles from the first metal particle slurry and / or the second metal particle slurry;
It is preferable to comprise.

Step A) Complexation reaction solution generation step:
(Metal salt)
The kind of metal salt is not particularly limited, and can be selected according to the kind of metal material of the obtained metal particles. Examples of the metal salt include hydroxide, halide, nitrate, sulfate, carbonate, carboxylate, β-diketonate salt and the like. Among these, it is preferable to use a carboxylate having a relatively low dissociation temperature (decomposition temperature) in the reduction process.

(Organic solvent)
The organic solvent is not particularly limited as long as it can dissolve the metal salt, and examples thereof include ethylene glycol, alcohols, organic amines, N, N-dimethylformamide, dimethyl sulfoxide, acetone, and the like. On the other hand, organic solvents such as ethylene glycol, alcohols and organic amines having a reducing action are preferred. Among these, primary organic amines (hereinafter abbreviated as “primary amines”) can form a complex with a metal ion by dissolving a mixture with a metal salt. It is easy to effectively exhibit the reducing ability for (or metal ions), and can be advantageously used for metal salts having a high reduction temperature by heating. The primary amine is not particularly limited as long as it can form a complex with a metal ion, and can be a solid or liquid at room temperature. Here, room temperature means 20 ° C. ± 15 ° C.

  The primary amine that is liquid at room temperature also functions as an organic solvent for forming the nickel complex. Even if it is a primary organic amine that is solid at room temperature, there is no particular problem as long as it is liquid by heating or can be dissolved using an organic solvent.

  The primary amine may be an aromatic primary amine, but an aliphatic primary amine is preferred from the viewpoint of easy nickel complex formation in the reaction solution. Aliphatic primary amine can control the particle size of the metal particles produced | generated by adjusting the length of the carbon chain, for example. From the viewpoint of controlling the particle size of the metal particles, the aliphatic primary amine is preferably selected from those having about 6 to 20 carbon atoms. The larger the carbon number, the smaller the particle size of the metal particles obtained. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, and laurylamine.

  The primary amine is preferably liquid at room temperature from the viewpoint of ease of processing operation in the washing step of separating the solid component of the produced nanoparticles after the reduction reaction from the solvent or the unreacted primary amine. Further, the primary amine is preferably one having a boiling point higher than the reduction temperature from the viewpoint of ease of reaction control when the metal complex is reduced to obtain metal particles. The amount of the primary amine is preferably 2 mol or more, more preferably 2.2 mol or more, relative to 1 mol of the metal salt. When the amount of primary amine is less than 2 mol, it is difficult to control the particle size of the resulting metal particles, and the particle size tends to vary. The upper limit of the amount of primary amine is not particularly limited, but is preferably 20 mol or less from the viewpoint of productivity, for example.

  In order to proceed the reaction in a homogeneous solution more efficiently, an organic solvent other than the primary amine may be newly added. The organic solvent that can be used is not particularly limited as long as it does not inhibit the complex formation between the primary amine and the metal ion. For example, the ether-based organic solvent having 4 to 30 carbon atoms and the carbon number having 7 to 30 carbon atoms. A saturated or unsaturated hydrocarbon organic solvent, an alcohol organic solvent having 8 to 18 carbon atoms, or the like can be used. Moreover, from the viewpoint of enabling use even under heating conditions by microwave irradiation, it is preferable to select an organic solvent having a boiling point of 170 ° C. or higher, more preferably in the range of 200 to 300 ° C. It is better to choose one. Specific examples of such an organic solvent include tetraethylene glycol and n-octyl ether.

  Although the complex formation reaction can proceed even at room temperature, in order to perform a sufficient and more efficient complex formation reaction, for example, the reaction is performed by heating within a range of 50 ° C. to 160 ° C. This heating can be appropriately set from the viewpoint of reliably separating the subsequent metal complex (or metal ion) from the process of heat reduction by microwave irradiation and completing the complex formation reaction.

Step B) Metal particle slurry generation step:
In this step, a complexing reaction solution obtained by a complex formation reaction between a metal salt and an organic solvent is heated by microwave irradiation to reduce metal ions in the complexing reaction solution to obtain a slurry of metal particles. The temperature for heating by microwave irradiation is preferably 170 ° C. or higher, more preferably 180 ° C. or higher, from the viewpoint of suppressing variation in the shape of the obtained nanoparticles. The upper limit of the heating temperature is not particularly limited, but is preferably set to 270 ° C. or less, for example, from the viewpoint of efficiently performing the treatment. In addition, the use wavelength of a microwave is not specifically limited, For example, it is 2.45 GHz.

  In this step, since microwaves penetrate into the reaction solution, uniform heating is performed, and energy can be directly applied to the medium, so that rapid heating can be performed. As a result, the entire reaction solution can be made uniform at a desired temperature, and the processes of reduction, nucleation, and nucleation of the metal complex (or metal ions) can occur simultaneously in the entire solution. Narrow monodisperse particles can be easily produced in a short time.

  In order to generate metal particles having a uniform particle size, the heating temperature in the complexing reaction liquid generation step is adjusted within a specific range, and is surely lower than the heating temperature by the microwave in the metal particle slurry generation step. This makes it easy to produce particles having a uniform particle size and shape. For example, if the heating temperature is too high in the complexing reaction liquid generation process, the metal complex formation and the reduction reaction to metal (zero valence) proceed simultaneously to generate different kinds of metal species. There is a possibility that it is difficult to generate particles having a uniform particle shape. In addition, if the heating temperature in the metal particle slurry generation step is too low, the reduction reaction rate to metal (zero valence) is slowed and the generation of nuclei is reduced, so that not only the particles are enlarged, but also from the viewpoint of the yield of metal particles. Is also not preferred.

  In the metal particle slurry generation step, the organic solvent described above may be added as necessary. As described above, it is a preferred embodiment of the present invention to use the primary amine used in the complex formation reaction as an organic solvent as it is.

Step C) Metal particle isolation step:
In this step, the metal particle slurry obtained by heating by microwave irradiation, for example, standing and separating, removing the supernatant liquid, washing with an appropriate solvent, and drying to obtain metal particles. It is done.

  As mentioned above, according to the manufacturing method of the 1st metal particle and 2nd metal particle which concern on this Embodiment, it has a uniform particle diameter by a simple method, without using a lot of reducing agents. Although metal particles can be produced, it is not limited to those obtained by the above-described production method, and commercially available products can be used as appropriate.

[Metallic porous material production process]
In this step, after mixing the first metal particles and the second metal particles, the mixture is heated to melt the second metal particles, and the first metal particles are melted by the obtained melt of the second metal particles. The metal particles are bonded to obtain a porous metal body.

  The mixing method is not particularly limited, and each of the first metal particles and the second metal particles may be mixed in a powder state, mixed in a slurry state, or mixed in a paste state. May be. Moreover, you may use a general purpose kneader, a stirrer, a disperser, an emulsifier, etc. The mixture thus obtained is placed in a predetermined container or heated or deposited on a predetermined substrate before heating in the subsequent step, and dried as necessary. The method for drying is not particularly limited, and for example, drying is preferably performed at a temperature in the range of 30 to 150 ° C.

  In addition, before the mixture is heated to melt the second metal particles, it is preferable to press the pressure within a range of, for example, 0.1 MPa to 10 MPa to form a predetermined molded body. This molded body can be formed, for example, by pressurizing a mixture placed in a predetermined container, or by pressing the mixture deposited on a predetermined substrate. In addition, pressurization can also be performed continuously when the second metal particles are melted by subsequent heating.

  The heat treatment can be performed, for example, within a range of 150 ° C. to 600 ° C., preferably within a range of 170 ° C. to 400 ° C. This temperature may be appropriately set to a temperature at which the second metal particles can be melted without completely melting the first metal particles. The heat treatment can be performed, for example, in an inert gas atmosphere such as nitrogen gas or argon gas, in a vacuum of 1 to 5 KPa, in the air, or in hydrogen gas. What is necessary is just to select suitably according to the use purpose of a mass. Moreover, you may heat using pressurization or a press together as needed.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In the examples of the present invention, various measurements and evaluations are as follows unless otherwise specified.

[Average particle diameter of metal particles]
The average particle size of the metal particles was obtained by taking a photograph of the sample with an SEM (scanning electron microscope), randomly extracting 200 samples from the sample, obtaining each particle size, and calculating the average particle size.

[5% heat shrink temperature]
The 5% heat shrink temperature is obtained by placing a sample in a 5Φ × 2 mm cylindrical molding machine and producing a molded product obtained by press molding, and then heating it in an atmosphere of nitrogen gas (containing 3% hydrogen gas). The temperature was 5% thermal yield measured by an analyzer (TMA).

[Weight loss start temperature]
The weight loss starting temperature is determined by thermogravimetry (TGA) (manufactured by Shimadzu Corporation, trade name: TGA-50) under an atmosphere of nitrogen gas (nitrogen gas flow rate 100 mL / min), at a temperature rising rate of 10 ° C./min. It was set as the starting temperature of the weight change of the sample to be measured.

Example 1
As the first metal particles, 10 g of nickel particles 1a (trade name: NFP201S, nickel content: 99 wt%, average particle diameter: 200 nm, specific surface area: 3.4 m ² / g, 5% heat shrinkage, manufactured by JFE Mineral Co., Ltd. Temperature: 400 ° C., and 2 g of silver particles 1b (manufactured by DOWA Electronics, trade name: DOWA silver nanoparticle dry powder, silver content: 95 wt%, average particle size: 20 nm, ratio) Surface area; 17.5 m ² / g) was prepared.

  20 g of isopropyl alcohol was added to the nickel particles 1a and the silver particles 1b, and the mixture was kneaded for 10 minutes using an automatic revolution mixer manufactured by Sinky Co., Ltd., and then air-dried to remove isopropyl alcohol, whereby a mixture 1 was obtained. This mixture 1 is put into a cylindrical mold container of 10Φ × 2 nm, a molded body is produced under a pressure of 1 MPa with a press machine, and the molded body is 350 in an atmosphere of nitrogen gas (containing 3% hydrogen gas). The objective metal porous body 1 was obtained by heating at 3 ° C. for 3 hours.

It was 0.7 m < ² > / g when the specific surface area was calculated | required by the BET method from the nitrogen absorption isotherm of the metal porous body 1. FIG. Furthermore, it was found from the mesopore distribution obtained by the DH method (Dollimore-Heal method) that the pore diameter is about 45 nm and has a pore distribution of about 1 nm to 85 nm.

(Example 2)
By adding 18.5 g of nickel formate dihydrate to 144.9 g of dimethyl myristylamine and heating at 120 ° C. for 10 minutes under a nitrogen flow, nickel formate was dissolved to obtain complexing reaction solution 2a. Next, 96.6 g of dimethyl myristylamine was further added to the complexing reaction solution 2 and heated at 180 ° C. for 10 minutes using a microwave to obtain a nickel particle slurry 2a.

The nickel particle slurry 2 was allowed to stand and separated, the supernatant was removed, washed with hexane and methanol, and then dried for 6 hours in a vacuum dryer maintained at 60 ° C. to obtain nickel particles 2a (nickel content; 98 wt%, average particle size; 71 nm, specific surface area; 12 m ² / g, 5% heat shrinkage temperature;

  Add 50 g of sodium stearate to 4200 g of ethylene glycol, heat at 85 ° C. for 10 minutes under a nitrogen flow, and then add a solution of 28 g of silver nitrate in 800 g of ethylene glycol to this solution. Heated at 140 ° C. for 1 minute. It was rapidly cooled by putting it in a large amount of methanol solution, the precipitate was decanted, washed twice with methanol, once with acetone, and dried to obtain silver nanoparticles 2b (silver content: 30 wt%, average) Particle diameter: 15 nm, weight loss onset temperature: 200 ° C.).

  10 g of the nickel particles 2a and 2 g of the silver particles 2b were prepared, and kneaded and air-dried in the same manner as in Example 1 to obtain a mixture 2. This mixture 2 is put into a cylindrical mold container of 10Φ × 2 nm, a molded body is produced with a press machine under a pressure of 1 MPa, and the molded body is 250 under an atmosphere of nitrogen gas (containing 3% hydrogen gas). The objective metal porous body 2 was obtained by heating at 3 ° C. for 3 hours.

The specific surface area of the porous metal body 2 determined by the BET method was 2.5 m ² / g. Furthermore, from the mesopore distribution determined by the DH method, it was found that the pore diameter is about 36 nm and has a pore distribution of about 1 nm to 75 nm.

  As is clear from the above-described examples, according to the present invention, if the first metal particles and the second metal particles, which are nanoparticles having different average particle diameters, are prepared, then these metal particles are mixed. And the metal porous body which has the target micropore can be obtained only by using the general purpose sintering technique in what is called normal powder metallurgy etc. of heating. That is, a metal porous body having fine pores can be obtained very easily without using a complicated production method such as a wet method.

  While the present invention has been described in detail based on the above specific examples, the present invention is not limited to the above specific examples, and various modifications and changes can be made without departing from the scope of the present invention.

Claims (7)

Metal particles containing a first metal material, wherein the metal particles have an average particle diameter in the range of 50 nm to 1 μm;
Metal particles containing a second metal material having a melting point lower than the melting point of the first metal material, wherein the average particle size of the metal particles is in the range of 5 nm to 500 nm, and the average particle size is Preparing a second metal particle having an average particle diameter equal to or less than the first metal particle;
Mixing the first metal particles and the second metal particles to obtain a mixture;
Heating the mixture to melt the second metal particles, and bonding the first metal particles with the obtained melt to obtain a metal porous body;
A method for producing a metal porous body, comprising:   The average particle diameter d1 of the first metal particles is in the range of 50 nm to 200 nm, and the ratio d1 / d2 to the average particle diameter d2 of the second metal particles is in the range of 5 to 200. The method for producing a porous metal body according to claim 1, wherein:   The method for producing a metal porous body according to claim 1 or 2, wherein a difference between the melting point of the first metal material and the melting point of the second metal material is 50 ° C or more.   The metal porous according to any one of claims 1 to 3, wherein a ratio of the second metal particles to the first metal particles is in a range of 5% by mass to 40% by mass. Body manufacturing method.   The metal porous body according to any one of claims 1 to 4, wherein the first metal material is at least one selected from the group consisting of nickel, cobalt, iron, and copper. Method.   The method for producing a metal porous body according to any one of claims 1 to 5, wherein the second metal material is at least one selected from the group consisting of gold, silver, and copper. Dissolving a metal salt that is a precursor of the first metal material and / or the second metal material in an organic solvent to obtain a complexing reaction solution in which a metal complex is formed;
Heating the complexing reaction solution by microwave irradiation to obtain a slurry of the first metal particles and / or a slurry of the second metal particles;
Isolating the first metal particles and / or the second metal particles from the slurry of the first metal particles and / or the slurry of the second metal particles;
The method for producing a metal porous body according to any one of claims 1 to 6, further comprising: