Nickel granulated powder manufacturing method

Abstract

To provide a nickel granulated powder production method which does not require an excessively complicated process, and nickel granulated powder which is produced by the production method.SOLUTION: One of the embodiments is a nickel granulated powder production method having the steps of: mixing a nickel raw material, a reductant, a protective agent having a functional group capable of coordinating to nickel and also having a methyl group and a solvent having two or more hydroxy groups to obtain a raw material solution; and irradiating the raw material solution with microwaves to execute heating.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing nickel granulated powder. [Background technology]

[0002] Various studies have been conducted on powders containing metals, such as raw material powders for sintering. For example, Patent Document 1 discloses a raw material powder for sintering that is mainly composed of Fe, 0.8% by weight or less of C, 0.05 to 1.0% by weight of Si, 1.0% by weight or less of Mn, and 1.0 to 10.0% by weight or less of Ni, and that has an average particle size of 8.5 μm or less, and a granulated powder for sintering that is obtained by granulating the raw material powder for sintering using a binder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-154847 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a raw material powder for sintering that has been modified to have a high sintered density and uniform properties when sintered, a granulated powder for sintering obtained by granulating the raw material powder for sintering, and a sintered body obtained using these. However, to obtain the granulated powder for sintering disclosed in Patent Document 1, it is necessary to produce the raw material powder for sintering and then granulate the raw material powder for sintering and a binder, which is a complicated process. Therefore, according to the inventors' investigations, the granulated powder for sintering disclosed in Patent Document 1 tends to be expensive, and there is still room for improvement.

[0005] Therefore, an object of the present disclosure is to provide a method for producing nickel granulated powder that does not require an excessively complicated process, and nickel granulated powder produced by the production method. [Means for solving the problem]

[0006] As a result of intensive research to solve the above problems, the present inventors have found that nickel granulated powder can be produced by irradiating a raw material solution containing specific components with microwaves, and have arrived at the present disclosure.

[0007] An example aspect of this embodiment is described as follows.

[0008] [1] A step of mixing a nickel raw material, a reducing agent, a protecting agent having a functional group capable of coordinating with nickel and having a methyl group, and a solvent having two or more hydroxyl groups to obtain a raw material solution; The method for producing nickel granulated powder comprises a step of irradiating the raw material solution with microwaves to heat it. [2] The method for producing nickel granulated powder according to [1], wherein the protective agent having a functional group capable of coordinating to nickel and having a methyl group is an amine. [3] The method for producing a granulated nickel powder according to [1] or [2], wherein the solvent having two or more hydroxyl groups is a dihydric alcohol. [4] The integrated microwave absorption power of the raw material solution is 5 × 10 nickel atoms. -6 The method for producing a granulated nickel powder according to any one of [1] to [3], wherein the electrical conductivity is 100 W·s or more per mol. [Effects of the Invention]

[0009] The present disclosure provides a novel method for producing nickel granulated powder and nickel granulated powder produced by the method. The method for producing nickel granulated powder according to the present embodiment does not require a step of producing nickel nanoparticles and a step of granulating the nickel nanoparticles using the nickel nanoparticles and a binder, and is therefore advantageous in that an excessively complicated process is not required to obtain the nickel granulated powder, and in terms of cost. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a method for producing nickel granulated powder according to the present embodiment and the nickel granulated powder produced by the production method will be described in detail.

[0011] (Method of manufacturing granulated nickel powder) The method for producing nickel granulated powder of the present embodiment includes a step of mixing a nickel raw material, a reducing agent, a protective agent having a functional group capable of coordinating to nickel and having a methyl group, and a solvent having two or more hydroxyl groups to obtain a raw material solution, and a step of irradiating the raw material solution with microwaves and heating it.

[0012] In the method for producing nickel granulated powder of the present embodiment, nickel ions in a nickel raw material are reduced to obtain metallic nickel particles (nanoparticles) as a granulated powder, rather than as single particles. The nickel raw material is not limited as long as it is a nickel compound that can be reduced to obtain nickel particles. The nickel raw material may be an organic salt of nickel or an inorganic salt of nickel. For example, the following can be used as the nickel raw material, and one type of nickel raw material may be used alone, or two or more types of nickel raw materials may be used.

[0013] Examples of the organic salt include carboxylates and sulfonates. Examples of nickel carboxylates include nickel acetate (Ni acetate), nickel formate (Ni formate), nickel malonate, and nickel succinate. Examples of nickel sulfonates include nickel trifluoromethanesulfonate.

[0014] Examples of the inorganic salt include halides (e.g., chlorides), sulfates, nitrates, phosphates, hydroxides, etc. Examples of inorganic salts of nickel include nickel halides (e.g., nickel chloride (Ni chloride)), nickel sulfate (Ni sulfate), nickel nitrate, nickel hydroxide, etc.

[0015] The nickel raw material is preferably at least one nickel raw material selected from the group consisting of nickel acetate, nickel formate, nickel chloride, and nickel sulfate. The nickel raw material may be an anhydride or a hydrate.

[0016] The reducing agent is not limited as long as it can reduce the nickel raw material to obtain nickel particles. Examples of the reducing agent include hydrazine-based compounds such as hydrazine, hydrazine hydrochloride, and hydrazine sulfate; boron compounds and salts thereof such as sodium borohydride and dimethylamine borane; sulfur oxoacid salts such as sodium sulfite, sodium hydrogen sulfite, and sodium thiosulfate; nitrogen oxoacid salts such as sodium nitrite and sodium hyponitrite; and phosphorus oxoacids and salts thereof such as phosphorous acid, sodium phosphite, hypophosphorous acid, and sodium hypophosphite. The reducing agent may be an anhydride or a hydrate. One reducing agent may be used alone, or two or more reducing agents may be used.

[0017] The protecting agent having a functional group capable of coordinating with nickel and a methyl group is not limited. The protecting agent may be used alone or in combination of two or more types. Examples of the functional group capable of coordinating with nickel include an amino group and a carbonyl group. The amino group is not limited, and examples thereof include -NH 2、 Examples of the amino group include -NHR and -NRR' (R and R' each independently represent an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 12 carbon atoms). Specific examples of the amino group include -NH2, a dimethylamino group, an ethylmethylamino group, and a diphenylamino group, with -NH2 being preferred as it easily coordinates to nickel.

[0018] The protecting agent having a functional group capable of coordinating with nickel and a methyl group is preferably an amine. The amine may be any of a primary amine, a secondary amine, and a tertiary amine, and a primary amine is preferred.

[0019] The methyl group contained in the protective agent may be at least one methyl group present in the molecule of the protective agent, and may also be present as part of another group. In one preferred embodiment, the methyl group contained in the protective agent is contained in the protective agent as part of an alkyl group. The protective agent preferably has an alkyl group having 1 to 20 carbon atoms, preferably an alkyl group having 6 to 18 carbon atoms, and more preferably an alkyl group having 8 to 16 carbon atoms. The alkyl group may be a linear alkyl group or a branched alkyl group, but a linear alkyl group is preferred.

[0020] Examples of the protecting agent having a functional group capable of coordinating to nickel and having a methyl group include hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, and icosylamine, with decylamine, undecylamine, dodecylamine, tridecylamine, and tetradecylamine being preferred.

[0021] In the method for producing nickel granulated powder according to the present embodiment, a protective agent (another protective agent) other than the protective agent having a functional group capable of coordinating with nickel and a methyl group may be mixed with the solvent. Examples of the other protective agent include polyvinylpyrrolidone (PVP) and trioctylphosphine (TOP). The other protective agents may be used alone or in combination of two or more.

[0022] The solvent having two or more hydroxyl groups is not limited, but is preferably a solvent having 2 to 6 hydroxyl groups in the molecule, more preferably a solvent having two hydroxyl groups. Furthermore, the solvent having two or more hydroxyl groups is preferably a polyhydric alcohol, more preferably a dihydric alcohol. The solvent having two or more hydroxyl groups may be used alone or in combination of two or more.

[0023] Examples of the solvent having two or more hydroxyl groups include ethylene glycol, propylene glycol, and diethylene glycol.

[0024] In the step of obtaining the raw material solution, the raw material solution may be obtained by mixing the above-mentioned nickel raw material, a reducing agent, a protecting agent having a functional group capable of coordinating to nickel and having a methyl group, a solvent having two or more hydroxyl groups, and, if necessary, other protecting agents, and the method for obtaining the raw material solution is not limited. In the step of obtaining the raw material solution, the order of addition of the materials, the addition temperature, the mixing method, the mixing time, and the like are not limited, as long as the materials are mixed so as to prepare a uniform raw material solution.

[0025] The amount of each material contained in the raw material solution is preferably 0.1 to 500 mM (mmol / L), more preferably 1 to 20 mM (mmol / L), of the nickel raw material. The raw material solution also contains preferably 1.5 to 50 mol, more preferably 2 to 20 mol, of the reducing agent per mol of the nickel raw material. The raw material solution also contains preferably 2 to 50 mol, more preferably 5 to 20 mol, of the protecting agent having a functional group capable of coordinating with nickel and a methyl group per mol of the nickel raw material. When the raw material solution contains another protecting agent, the amount of the other protecting agent per mol of the nickel raw material is preferably more than 0 mol and 100 mol or less, more preferably 5 to 50 mol. The raw material solution contains a solvent having two or more hydroxyl groups as the balance. Specifically, the raw material solution contains preferably 5 mol or more, more preferably 10 mol or more, of the solvent having two or more hydroxyl groups per mol of the nickel raw material.

[0026] The method for producing nickel granulated powder of this embodiment includes a step of irradiating and heating the raw material solution prepared in the step of obtaining the raw material solution with microwaves. In the method for producing nickel granulated powder of this embodiment, the nickel raw material in the raw material solution is reduced to nickel by a reducing agent through microwave irradiation. The nickel nanoparticles obtained by the reduction are then converted into nickel granulated powder by the action of a protective agent having a functional group capable of coordinating with nickel and a methyl group, a solvent having two or more hydroxyl groups, and the microwaves. More specifically, the inventors speculate that the nickel raw material is reduced by a reducing agent through microwave irradiation to form nickel (nickel nanoparticles). The functional groups of the protective agent coordinate to the nickel nanoparticles. The methyl groups of the protective agent and the hydroxyl groups of the solvent form bonds (e.g., ether bonds) through the action of the microwaves, acting as a binder, and bonding multiple nickel particles together to produce nickel granulated powder.

[0027] In the step of irradiating the raw material solution with microwaves to heat it (also simply referred to as the heating step), the raw material solution is usually heated only by microwaves, but heating by a heater or the like may also be performed in addition to heating by microwaves. In the heating step, the raw material solution is heated preferably to 90 to 190°C, more preferably 120 to 160°C. In the heating step, it is usually preferable to heat within a temperature range below the boiling point of the solvent. Heating by microwaves is performed by heat generation caused by irradiating the raw material solution with microwaves, whereby the nickel raw material, etc., absorbs the microwaves and converts them into thermal energy.

[0028] In the heating step, the integrated microwave absorption power of the raw material solution is 5×10 nickel atoms -6 The integrated microwave absorption power of the raw material solution is preferably 100 W·s or more, more preferably 150 W·s or more, per mol of nickel atoms. -6 It is preferably 2 kW·s or less per mole, and more preferably 600 W·s or less.

[0029] In the heating step, microwave heating is preferably performed for 1 second to 30 minutes, and more preferably for 1 second to 5 minutes from the viewpoint of productivity. In one embodiment, the heating time from the start of microwave irradiation to reaching 140°C is preferably 1 second to 20 seconds, and more preferably 1 second to 10 seconds.

[0030] The amount (volume) of the raw material solution used in the heating step varies depending on the conditions of the microwave irradiation and is not limited, but is usually 0.0001 L to 100 L, and preferably 0.0005 L to 10 L.

[0031] The output of the microwave irradiation source used for microwave irradiation can be appropriately changed depending on the reaction conditions and is not limited, but is usually 100 W / L to 200 kW / L, preferably 1 kW / L to 50 kW / L, based on the volume of the raw material solution.

[0032] As a microwave irradiation source, a microwave oscillator (magnetron) can usually be used, and the microwave irradiation source can be either a single mode system or a multimode system.

[0033] The frequency of the microwaves generated from the microwave irradiation source can be changed as appropriate and is not limited, but is usually 1 GHz to 10 GHz, preferably 2 GHz to 6 GHz. In the present invention, it is more preferable to use, for example, 2.45 GHz, which is the frequency of industrial microwave power sources specified by Japanese regulations.

[0034] The method for producing nickel granulated powder according to the present embodiment is superior to conventional methods for producing nickel granulated powder in that it does not require an excessively complicated process because the heating step simultaneously synthesizes nickel nanoparticles and produces granulated powder. Furthermore, since the process is not excessively complicated, the method is also superior in terms of the production cost of the nickel granulated powder. Furthermore, the method for producing nickel granulated powder according to the present embodiment also makes it possible to control the particle size of the resulting nickel granulated powder. The particle size of the nickel granulated powder can be controlled, for example, by the integrated microwave absorption power. The particle size of the nickel granulated powder tends to decrease as the integrated microwave absorption power increases.

[0035] (Nickel granulated powder) The nickel granulated powder of this embodiment is nickel granulated powder produced by the above-described method for producing nickel granulated powder. The nickel granulated powder of this embodiment is made of fine nickel nanoparticles granulated and thus has the low-temperature sintering properties and flowability improvement effects that are characteristic of granulated powders, and can be used in various applications where nickel nanoparticles are required. For example, the nickel granulated powder can be used as an electrode material for multilayer ceramic capacitors. As another example, the nickel granulated powder can be used in a paste form by kneading it with a resin, or can be made into an ink by combining it with a dispersion medium or the like and used in fine printed wiring applications and bonding agent applications. [Example]

[0036] The present embodiment will be described below with reference to examples, but the present disclosure is not limited to these examples.

[0037] [Examples 1 to 5, Comparative Examples 1 to 3] (Preparation of raw material solution) As shown in Table 1, a Ni raw material, hydrazine hydrate, dodecylamine, and polyvinylpyrrolidone (PVP) were added to a solvent to prepare a raw material solution. As shown in Table 1, Ni acetate, Ni chloride, or Ni formate was used as the Ni raw material. As shown in Table 1, ethylene glycol or dodecylamine was used as the solvent. In all raw material solutions, the Ni raw material was used in an amount of 5 mM and hydrazine hydrate in an amount of 50 mM. In Examples and Comparative Examples (except Comparative Example 3) using dodecylamine, dodecylamine was used in an amount of 45 mM, and in Examples and Comparative Examples using PVP, PVP was used in an amount of 100 mM. In addition, in the Examples and Comparative Examples (except Comparative Example 3), the raw material solutions contained the Ni raw material, hydrazine hydrate, dodecylamine, and PVP (Example 3 and Comparative Example 2) in the amounts described above, with the remainder being ethylene glycol. In Comparative Example 3, dodecylamine was used as a solvent and a protective agent, and specifically, a raw material solution containing 5 mM Ni acetate, 50 mM hydrazine hydrate, and the remainder being dodecylamine was prepared.

[0038] (Microwave irradiation and heating of raw material solution) 1 mL of the raw material solution was irradiated with microwaves at an output of 50 W to 200 W and heated to 140°C to reduce the Ni raw material and produce Ni particles. Note that the integrated microwave absorption power in each example and comparative example means the integrated microwave absorption power of the raw material solution, and is calculated based on the total amount of nickel atoms (5 × 10) contained in the raw material solution. -6 The power per mole (W·s) is shown in Table 1.

[0039] The particles obtained in the examples and comparative examples were dispersed on a Cu150P grid and observed with a JEOL ARM300F transmission electron microscope (TEM) at an accelerating voltage of 200 kV. The particles obtained in the examples were confirmed to be nickel granulated powder in which multiple small particles aggregated to form spherical secondary particles, while the particles obtained in the comparative examples were not confirmed to have been granulated. Table 1 shows the particle sizes (secondary particle sizes in the case of nickel granulated powder) and the presence or absence of granulation of the particles obtained in the examples and comparative examples.

[0040] [Table 1]

[0041] From Table 1, it was confirmed that nickel granulated powder was produced by the method for producing nickel granulated powder of the present embodiment.

[0042] The upper and / or lower limit values ​​of the numerical ranges described herein can be arbitrarily combined to define a preferred range. For example, the upper and lower limit values ​​of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limit values ​​of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limit values ​​of the numerical ranges can be arbitrarily combined to define a preferred range.

[0043] Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope that do not deviate from the gist of this disclosure, they are included in this disclosure.

Claims

1. A step of mixing a nickel raw material, a reducing agent, a protecting agent having a functional group capable of coordinating with nickel and having a methyl group, and a solvent having two or more hydroxyl groups to obtain a raw material solution; The method includes a step of irradiating the raw material solution with microwaves to heat it, the nickel raw material is an organic or inorganic salt of nickel that can be reduced with the reducing agent to obtain metallic nickel particles, the reducing agent is a hydrazine-based compound that reduces the nickel raw material to metallic nickel particles, the protecting agent having a functional group capable of coordinating to nickel and a methyl group is a primary amine; The method for producing nickel granulated powder, wherein the solvent having two or more hydroxyl groups is a dihydric alcohol.

2. A method for producing nickel granulated powder as described in claim 1, wherein the nickel raw material is at least one selected from nickel acetate, nickel formate, nickel chloride, and nickel sulfate, the hydrazine-based compound is hydrazine, hydrazine hydrochloride, or hydrazine sulfate, the primary amine is decylamine, undecylamine, dodecylamine, tridecylamine, or tetradecylamine, and the dihydric alcohol is ethylene glycol, propylene glycol, or diethylene glycol.

3. A method for producing nickel granulated powder as described in claim 2, wherein the nickel raw material is at least one selected from nickel acetate, nickel formate, and nickel chloride, the reducing agent is hydrazine, the primary amine is dodecylamine, and the dihydric alcohol is ethylene glycol.

4. The integrated microwave absorption power of the raw material solution is 5×10 nickel atoms －６ The method for producing nickel granulated powder according to claim 1, wherein the electrical conductivity is 100 W s or more per mol.

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