JP2013040358A - Method for manufacturing metal porous body - Google Patents

Abstract

Provided is a metal porous body having desired micropores, particularly nanometer-order micropores, by a simple method without using an organic solvent or the like.
First metal particles having an average particle size of 5 nm or more and not more than a particle size at a starting point of a melting point drop due to a quantum effect are prepared. Next, the first metal particles are coated with a second metal having a second melting point lower than the first melting point of the first metal particles, and the second metal is coated on the surface of the first metal particles. A film made of metal is formed. Next, the first metal particles including the coating are heated to dissolve the coating, and the first metal particles are bonded through the obtained dissolved material to produce a metal porous body.
[Selection figure] None

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 sintering 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 porous metal body having desired micropores, particularly nanometer-order micropores, by a simple method without using an organic solvent or the like.

In order to achieve the above object, the present invention provides a first metal particle comprising a first metal material, wherein the first metal particle has an average particle diameter in the range of 10 nm to 500 nm. 1 process,
A second step of coating the first metal particles with a second metal material having a melting point lower than the melting point of the first metal material;
The first metal particles coated with the second metal material are heated to melt the second metal material, and the first metal particles are bonded by the obtained melt, and the metal porous body A third step of obtaining
It is related with the manufacturing method of a metal porous body characterized by comprising.

  In the present invention, the third step can be performed after obtaining the mixture by mixing the first metal particles and the first metal particles coated with the second metal material. In this case, the ratio of the first metal particles coated with the second metal material to the mixture can be in the range of 10% by mass to less than 100% by mass.

  Furthermore, in the present invention, the coating can be performed by electrolytic plating or electroless plating.

  In the present invention, the difference between the melting point of the first metal material and the melting point of the second metal material is preferably 300 ° C. or higher.

  Furthermore, the ratio of the second metal material to the first metal particles in the first metal particles coated with the second metal material is in the range of 5% by mass to 50% by mass. preferable.

  In the present invention, the first metal particles may be at least one selected from the group consisting of nickel, cobalt, and copper, and the second metal particles may be bismuth, tin, zinc, indium, gallium, and antimony. And at least one selected from the group consisting of

  According to the present invention, it is possible to connect the first metal particles while keeping the original shape of the first metal particles. For example, even if the metal particles that are the base material of the metal porous body are likely to melt not only to the surface layer portion but also to the inside of the metal particles, special heating control is performed by the second metal material. Without performing, a desired metal porous body can be provided simply. In addition, even when the base material of the porous metal body is formed using high melting point metal particles, the porous metal body can be formed at a relatively low temperature by interposing the second metal material. 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.

[First Step of Preparing First Metal Particles]
In the present embodiment, first, metal particles containing a first metal material, and first metal particles having an average particle diameter in the range of 10 nm to 500 nm are prepared.

(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 10 nm, the progress of melting of the first metal particles inside the metal porous body can be suppressed, and the first material constituting the base material It is possible to prevent the original shape of the metal particles from completely disappearing.

  In the metal porous body according to the present invention, in order to facilitate the formation of a metal porous body having fine pores on the order of nanometers, the upper limit value needs to be 500 nm, and further 400 nm. It is particularly preferable that the thickness is 200 nm. When the upper limit exceeds 500 nm, it becomes difficult to form a porous metal body having nanometer-order micropores. 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 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. Among these, nickel, cobalt, and copper, which are easily available and inexpensive, are preferable.

  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 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 constituted by two kinds of chemical species, it is a preferable aspect that the first metal material forms a shell surrounding an arbitrary chemical species.

  Further, the first metal particles affect the characteristics of the metal porous body in combination with the characteristics due to the porosity. Therefore, 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.

<The manufacturing method of the 1st metal particle>
The first 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 salt, which is a precursor of the first metal material, is dissolved in an organic solvent to form a metal complex,
B) Heating the complexing reaction liquid by microwave irradiation to obtain a slurry of the first metal particles,
C) isolating the first metal particles from the slurry of the first metal particles;
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 a metal 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 ease of forming a metal complex 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 easy control of the reaction 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 described above, according to the first method for producing metal particles according to the present embodiment, metal particles having a uniform particle diameter can be produced by a simple method without using a large amount of reducing agent. These are not limited to those obtained by the above-described production method, and commercially available products can be used as appropriate.

[Second Step of Coating with Second Metal Material]
In this step, the first metal particles are coated with the second metal material. Since the second metal material functions as a binder for the first metal particles serving as a base material of the metal porous body, only the second metal material is melted in the heat treatment described below, In order to suppress melting of the first metal particles, the melting point of the second metal material needs to be lower than the melting point of the first metal particle material.

  Therefore, the second metal material can be made of any metal as long as the above requirements are satisfied. However, the first metal particles are in the form of nanoparticles, and therefore the melting point thereof is greatly reduced compared to the bulk state. For this reason, the second metal material is a metal having a low melting point in the bulk state and having a second melting point lower than the first melting point even when the first metal particles are made into nanoparticles. It is preferable. From such a viewpoint, the difference between the melting point of the second metal material and the melting point of the first metal material is preferably 300 ° C. or higher. Specifically, the second metal material preferably contains a metal element having a melting point of 700 ° C. or less at 1 atm (101,325 Pa) as a main component, more preferably 70% by mass or more, and further Preferably it is 95 mass% or more. Examples of such metal materials include bismuth (melting point: 271 ° C.), tin (melting point: 232 ° C.), zinc (melting point: 420 ° C.), indium (melting point: 157 ° C.), gallium (melting point: 37 ° C.), and antimony (melting point). At least one selected from the group consisting of: 631 ° C.).

  Moreover, it is preferable that the ratio with respect to the 1st metal particle of the 2nd metal material in the said 1st metal particle coat | covered with the 2nd metal material is the range of 5 mass%-50 mass%. If it is less than 5% by mass, the absolute amount of the second metal is reduced, and the first metal particles cannot be bonded. On the other hand, if it exceeds 50% by mass, the absolute amount of the second metal is excessively large and closes the pores of the formed metal porous body, thereby obtaining a metal porous body having fine pores on the order of nanometers. Can be difficult.

  The method for coating the second metal material on the first metal particles is not particularly limited. For example, the first metal particles can be formed by melting the second metal material and immersing the first metal particles in the obtained molten metal, but the dispersibility is extremely poor because the first metal particles are nanoparticles. In some cases, this method cannot form a uniform film. From such a viewpoint, the coating is preferably performed using so-called electroless plating such as electrolytic plating, immersion plating, or chemical plating.

  The immersion plating method uses the difference in ionization tendency of seed metals, and when a base metal is inserted into a solution containing electrochemically noble metal ions, it is released by dissolution of the base metal. Electrons are transferred to noble metal ions in the solution, and the noble metal is coated on the base metal surface. In the chemical plating method, electrons released by oxidation of the reducing agent are transferred to metal ions, and the metal is coated. The coating defined by the present invention includes the entire or partial coating of the first metal particles, primary particles (one metal particle completely independent without agglomeration), and agglomerated particles (a plurality of metal particles). In a state of all coatings, such as a coating on particles that are aggregated and regarded as one metal particle).

[Third step of obtaining metal porous body]
In this step, the first metal particles coated with the second metal material are heated to melt the second metal material, and the first metal particles are bonded by the obtained melt to form a metal porous material. Get the body.

  The first metal particles coated with the second metal material can be powders, slurries, pastes, etc., and can be put in a predetermined container, or deposited or applied on a predetermined base material, if necessary. ,dry. A drying method in particular is not restrict | limited, For example, it is preferable to dry at the temperature within the range of 30-150 degreeC.

  In this step, the first metal particles coated with the second metal material are used. However, the coated first metal particles may be used alone or the coated first metal particles. And a mixture of first metal particles not coated with a second metal material may be used. When used as a mixture of the first metal particles coated with the second metal material and the first metal particles not coated, the first coated with the second metal material with respect to 100 parts by mass of the mixture. The metal particles are preferably in the range of 10 parts by mass to less than 100 parts by mass.

  The heat treatment can be performed, for example, at a temperature in the range of 150 ° C to 300 ° C. This temperature may be appropriately set to a temperature at which the second metal material 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, and the type of the first metal particles and the metal obtained What is necessary is just to select suitably according to the intended purpose of using a porous body. Moreover, you may perform a hot press or the heating under high pressure as needed.

  The heat treatment is preferably performed in a pressurized atmosphere. As described above, the second metal material is melted by the heat treatment and functions as a binder with respect to the first metal particles. However, the second heat treatment is performed in a pressurized atmosphere. The first metal particles can be more firmly bonded to each other by the metal material, and the first metal particles are also pressed and bonded to each other. That is, the skeleton strength of the metal porous body finally obtained increases, and as a result, the strength of the metal porous body increases.

  The applied pressure can be, for example, 0.1 MPa to 10 MPa. The pressurized atmosphere described above can be realized by filling the reaction vessel with nitrogen gas, hydrogen gas, or the like in a pressurized state. Moreover, it can necessarily carry out by the said heat press.

  In this embodiment, instead of directly using the above-described second metal material, a precursor containing the second metal material that constitutes the second metal material can be used. In this case, the precursor is thermally decomposed by the heat treatment described above to generate the second metal material. Therefore, the generated second metal material is dissolved as described above to form the first metal particles. Can be joined to obtain a porous metal body having the above-mentioned fine pores.

  Examples of the precursor include a hydroxide, a halide, a nitrate, a sulfate, a carbonate, a carboxylate, and a β-diketonate of a metal constituting the second metal material.

  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).

(Synthesis Example 1)
18.5 g of nickel formate dihydrate was added to 125.9 g of laurylamine and heated at 120 ° C. for 10 minutes under a nitrogen flow to dissolve nickel formate to obtain a complexing reaction solution. Next, 83.9 g of laurylamine was further added to the complexing reaction solution, and the mixture was heated at 180 ° C. for 10 minutes using a microwave to obtain a nickel particle slurry 1a.

  The nickel particle slurry 1a was allowed to stand and separated, the supernatant was removed, washed with hexane and methanol, and then dried in a vacuum dryer maintained at 60 ° C. for 6 hours to obtain nickel particles 1 (nickel content; 98 mass%, average particle diameter; 100 nm, CV value; 0.17, 5% heat shrinkage temperature; As a result of elemental analysis, it was C; 0.5, N; 0.026, O; 2.2 (unit: mass%).

(Synthesis Example 2)
To 4280 g of oleylamine, 310 g of nickel formate dihydrate and 181 g of copper formate tetrahydrate are added and heated at 120 ° C. for 40 minutes under a nitrogen flow to dissolve and complex the Ni and Cu salts. The reaction solution was obtained. Next, 3230 g of 1-octanol was further added to the complexing reaction solution, and the mixture was heated at 190 ° C. for 5 minutes using a microwave to obtain a nickel-copper particle slurry 2a.

  The nickel-copper particle slurry 2a was allowed to stand and separated, the supernatant was removed, washed with hexane and methanol, and then dried in a vacuum dryer maintained at 60 ° C. for 6 hours to obtain nickel-copper particles 2 ( Nickel content: 67 mass%, copper content: 33 mass%, average particle diameter: 40 nm, CV value: 0.16, 5% heat shrinkage temperature: 265 ° C.).

Example 1
First, nickel particles 1 (specific surface area: 8.9 m ² / kg) obtained in Synthesis Example 1 were prepared.

  The nickel particles 1 were coated with tin by electrolytic plating to obtain tin-coated nickel particles 1 '. The tin plating amount in the tin-coated nickel particles 1 ′ was 20% by mass with respect to the nickel particles 1 by calculating the tin plating amount from the increase in the weight of the nickel particles 1 before and after tin plating.

  Next, the tin-coated nickel particles 1 ′ are put into a 5Φ × 2 mm cylindrical molding machine, and a molded body is produced under a pressure of 1 MPa with a press machine. The molded body is an atmosphere of nitrogen gas (containing 3% hydrogen gas). Under the condition, heat treatment was performed at 250 ° C. for 1 hour to obtain a target porous metal body 1.

When the specific surface area was determined by the BET method from the nitrogen absorption isotherm of the obtained metal porous body 1, it was found to be 1.5 m ² / g. Furthermore, from the mesopore distribution determined by the DH method (Dollimore-Heal method), it was found that the pore diameter is about 21 nm and the pore distribution is about 1 to 50 nm.

(Example 2)
First, nickel-copper particles 2 (specific surface area: 14.5 m ² / g) obtained in Synthesis Example 2 were prepared.

  The nickel-copper particles 2 were coated with tin by electroless plating to obtain tin-coated nickel-copper particles 2 '. The tin plating amount in the tin-coated nickel-copper particles 2 ′ was 15 mass% with respect to the nickel-copper particles 2, as calculated from the increase in the weight of the nickel-copper particles 2 before and after tin plating.

  Next, 1 part by weight of the tin-coated nickel-copper particles 2 ′ and 3 parts by weight of the nickel particles 1 obtained in Synthesis Example 1 were mixed to obtain a mixture 2.

  The mixture 2 is put into a 5Φ × 2 mm cylindrical molding machine, a molded body is produced with a press machine under a pressure of 1 MPa, and the molded body is heated at 250 ° C. for 1 hour in an atmosphere of hydrogen gas. A porous metal body 2 was obtained.

When the specific surface area was determined by the BET method from the nitrogen absorption isotherm of the obtained metal porous body 2, it was found to be 2.1 m ² / g. Furthermore, it was found from the mesopore distribution obtained by the DH method (Dollimore-Heal method) that the pore diameter is about 30 nm and the pore distribution is about 1 to 46 nm.

  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)

A first step of preparing metal particles containing a first metal material, wherein the metal particles have an average particle diameter in the range of 10 nm to 500 nm;
A second step of coating the first metal particles with a second metal material having a melting point lower than the melting point of the first metal material;
The first metal particles coated with the second metal material are heated to melt the second metal material, and the first metal particles are bonded by the obtained melt, and the metal porous body A third step of obtaining
A method for producing a metal porous body, comprising:   2. The method according to claim 1, wherein the third step is performed after mixing the first metal particles and the first metal particles coated with the second metal material to obtain a mixture. The manufacturing method of the metal porous body of description.   The ratio of the first metal particles coated with the second metal material to the mixture is within a range of 10% by mass to less than 100% by mass. A method for producing a metal porous body.   The said coating is performed by electrolytic plating or electroless plating, The manufacturing method of the metal porous body in any one of Claims 1-3 characterized by the above-mentioned.   The metal porous body according to any one of claims 1 to 4, wherein a difference between a melting point of the first metal material and a melting point of the second metal material is 300 ° C or more. Production method.   The ratio of the second metal material to the first metal particles in the first metal particles coated with the second metal material is in the range of 5% by mass to 50% by mass. The manufacturing method of the metal porous body as described in any one of Claims 1-5.   The first metal particles are at least one selected from the group consisting of nickel, cobalt and copper, and the second metal particles are selected from the group consisting of bismuth, tin, zinc, indium, gallium and antimony. It is at least one, The manufacturing method of the metal porous body as described in any one of Claims 1-6 characterized by the above-mentioned.