JP2021188087A - Nickel nanoparticle aggregate, method for producing the same and nickel nanoparticle composite substrate - Google Patents

Abstract

To provide a nickel nanoparticle aggregate that strongly aggregates at a low temperature of 150°C or lower.SOLUTION: A nickel nanoparticle paste having nickel nanoparticles with an average particle size of 5-100 nm and a binder resin dispersed in a nonpolar solvent is brought into contact with water or 1 wt.% or more hydrogen peroxide solution, thereby causing a coat to form on the nickel nanoparticles and causing the nickel nanoparticles to be aggregated directly or through the coat, resulting in a nickel nanoparticle aggregate.SELECTED DRAWING: Figure 2

Description

The present invention relates to a nickel nanoparticle agglomerate capable of low temperature bonding by forming nickel hydroxide on the surface of nickel nanoparticles, a method for producing the same, and a nickel nanoparticle composite substrate.

Since metal nanoparticles have different physical and chemical properties from bulk metals, they are used in various applications such as bonding materials such as semiconductor devices, electromagnetic wave shielding materials, optical materials, and brazing materials. There is.

Nickel nanoparticles are known to be obtained by solid phase reaction or liquid phase reaction. Known solid phase reactions include chemical vapor deposition of nickel chloride and thermal decomposition of nickel formate. As a liquid phase reaction, a method of directly reducing a metal salt with a strong reducing agent such as sodium borohydride (for example, Patent Document 1), or adding a reducing agent such as hydrazine in the presence of a strong alkali to prepare a precursor. A method of thermally decomposing after formation (for example, Patent Document 2), a method of putting a metal complex containing a metal salt or an organic ligand in a pressure vessel together with a solvent and synthesizing by thermal decomposition (for example, Patent Document 3), etc. Can be mentioned.

Generally, when nickel nanoparticles are used, the bonding temperature is 300 ° C. or higher using hydrogen gas (inert gas base) having an explosion limit concentration of 5% or less. Even if ultrafine particles of 10 to 50 nm are used, bonding is difficult unless the temperature is 200 ° C or higher (for example, Patent Document 4), and applications that require a plastic substrate, such as electromagnetic wave shielding materials, optical materials, and bonding materials, etc. Not applicable to.

Further, as a low-temperature bonding method, a method of bonding at 25 ° C to 200 ° C using a complex of metals having different ionization tendencies has been proposed, but not only is it not possible to obtain sufficient bonding strength because it contains a large amount of organic substances, but also, sufficient bonding strength cannot be obtained. It is not preferable because the performance peculiar to the metal is lowered (for example, Patent Document 5).

Japanese Unexamined Patent Publication No. 2003-193118 Japanese Unexamined Patent Publication No. 2008-95146 Japanese Unexamined Patent Publication No. 2010-105149 Patent No. 6061427 Japanese Unexamined Patent Publication No. 2010-29871

An object of the present invention is to provide a nickel nanoparticle agglomerate that strongly agglomerates at a low temperature of, for example, 150 ° C. or lower.

As a result of diligent research, the present inventors have made nickel nanoparticles produced by minimizing contact with water and solvents containing hydroxyl groups, which are strong due to the presence of a very small amount of chemical substances having hydroxyl groups such as water and alcohol. It was found that it is easy to form an agglomerate. In this behavior, when a hydroxyl group such as water or alcohol is present, nickel hydroxide is generated after the hydroxyl group is coordinated with nickel, and further, the generated water is further adjacent due to condensation with the adjacent nickel hydroxide. It is presumed that nickel oxide and nickel hydroxide are produced by coordinating with nickel. It is presumed that strong aggregates are formed by repeating this reaction. Utilizing this phenomenon, we have found that nickel nanoparticles produced by the above method are impregnated with a small amount of water or hydrogen peroxide and dried to form strong aggregates in a short time, and the present invention has been completed. I came to do.

That is, the nickel nanoparticle aggregate of the present invention is prepared by adding water or 1 wt% or more hydrogen peroxide to a nickel nanoparticle paste in which nickel nanoparticles having an average particle diameter of 5 to 100 nm and a binder resin are dispersed in a non-polar solvent. It is obtained by contacting water to form a film on the surface of the nickel nanoparticles and aggregating the nickel nanoparticles directly or through the film.

The nickel nanoparticle aggregate of the present invention may be obtained by drying the nickel nanoparticle paste and then contacting it with the water or a hydrogen peroxide solution of 1 wt% or more.

The nickel nanoparticles of the present invention may be nickel nanoparticles having a calculated value V of 3 or more calculated by the following formula (1).
V = A × D ³ / S / 10000000 ・ ・ ・ (1)
{In the formula, A means the amount of nickel dimethylglyoxime detected by the nickel measurement method specified in JIS K 0102 59.1 [ppm], and S is the ratio of nickel particles measured by the gas adsorption method. It means the surface area [m ² / g], and D means the average particle size [nm] of the nickel particles measured by a scanning electron microscope (SEM). }

In the nickel nanoparticle aggregate of the present invention, the nickel nanoparticles are nickel alone or an alloy of nickel and one or more metals selected from lithium, copper, iron, cobalt, gold, platinum and palladium. May be.

In the nickel nanoparticle aggregate of the present invention, the nickel nanoparticles may contain 99 wt% or more of the metal component contained in the nickel nanoparticles.

The nickel nanoparticle composite substrate of the present invention includes a substrate and the nickel nanoparticle aggregates laminated on the substrate.

The method for producing a nickel nanoparticle aggregate of the present invention includes a step of preparing a nickel nanoparticle paste in which nickel nanoparticles having an average particle diameter of 5 to 100 nm and a binder resin are dispersed in a non-polar solvent.
A step of contacting the nickel nanoparticles paste with water or 1 wt% or more of hydrogen peroxide solution to form a film on the surface of the nickel nanoparticles and agglomerate the nickel nanoparticles directly or through the film. When,
including.

The nickel nanoparticles used in the present invention can easily react with water or hydroxyl groups by producing them in a solution containing a small amount of water or a hydroxyl group so that nickel cations can be easily generated on the surface of the nickel nanoparticles, and the temperature is, for example, 150 ° C. or lower. Drying at low temperatures forms strong aggregates. Therefore, the nickel nanoparticle agglomerates of the present invention have a lower agglomeration temperature than the prior art, and therefore, for example, not only an inorganic substrate having high heat resistance such as a metal substrate, a glass substrate, or a ceramic substrate, but also an inorganic substrate. It can also be formed on a resin substrate, which has poor heat resistance.
Therefore, the nickel nanoparticle aggregate of the present invention is useful as a bonding material for bonding various members. Further, by using the nickel nanoparticle aggregate of the present invention, a composite substrate of nickel nanoparticles and a substrate can be obtained at a low temperature, so that it can be widely used as a material for various electronic components.

It is a scanning electron microscope (SEM) image (50,000 times) of the dry paste prepared in Example 1. FIG. It is an SEM image (50,000 times) of the aggregate prepared in Example 1. FIG. It is an SEM image (50,000 times) of the dry paste prepared in Example 2. FIG. It is an SEM image (50,000 times) of the aggregate prepared in Example 2. FIG. It is an SEM image (100,000 times) of the dry paste prepared in Example 3. FIG. 3 is an SEM image (110,000 times) of the aggregate prepared in Example 3. It is an SEM image (50,000 times) of the aggregate prepared in Example 4. FIG. 6 is an SEM image (50,000 times) of the aggregate prepared in Example 5. 6 is an SEM image (50,000 times) of the dried paste prepared in Comparative Example 1. 6 is an SEM image (50,000 times) of the paste prepared in Comparative Example 1 after the hydrogen peroxide solution treatment. 6 is an SEM image (50,000 times) of the dried paste prepared in Comparative Example 2. 6 is an SEM image (50,000 times) of the paste prepared in Comparative Example 2 after the hydrogen peroxide solution treatment.

Embodiments of the present invention will be described below.
In the nickel nanoparticle aggregate of the present invention, water or 1 wt% or more hydrogen peroxide solution is added to a nickel nanoparticle paste in which nickel nanoparticles having an average particle diameter of 5 to 100 nm and a binder resin are dispersed in a non-polar solvent. By contacting them, a film is formed on the surface of the nickel nanoparticles, and the nickel nanoparticles are agglomerated directly or through the film.

Here, as long as the nickel nanoparticles have the average particle size, particles produced by a known production method such as particles synthesized by the vapor phase method and particles synthesized by the liquid phase method shall be applied. However, the particles are preferably synthesized by the liquid phase method because nickel cations are easily generated.

Further, it is preferable that the nickel nanoparticles have a calculated value V calculated by the following formula (1) of 3 or more.
V = A × D ³ / S / 10000000 ・ ・ ・ (1)
{In the formula, A means the amount of nickel dimethylglyoxime detected by the nickel measurement method specified in JIS K 0102 59.1 [ppm], and S is the ratio of nickel particles measured by the gas adsorption method. It means the surface area [m ² / g], and D means the average particle size [nm] of the nickel particles measured by a scanning electron microscope (SEM). }
Within this range, there is an advantage that nickel cations forming a film are sufficiently generated, and aggregates are easily formed.

Further, in the nickel nanoparticles agglomerates of the present invention, it is necessary for nickel hydroxide to be formed on the surface of the nickel nanoparticles in order to form the agglomerates. Therefore, the material of the nickel nanoparticles is nickel alone or nickel capable of producing nickel hydroxide on the particle surface, and one or more metals selected from lithium, copper, iron, cobalt, gold, platinum and palladium. It is preferably an alloy.
Further, for the above reason, it is preferable that the nickel concentration in the nickel nanoparticles is high, and specifically, it is preferable that 99 wt% or more of the metal component contained in the nickel nanoparticles is nickel.

The following is an example of a preferred method for producing nickel nanoparticles.
The nickel nanoparticles used in this embodiment are the following steps A and B;
A) A step of mixing a nickel salt and a reducing agent to obtain a complexing reaction solution.
B) A step of heating the complexing reaction solution to reduce the nickel component in the complexing reaction solution to obtain a slurry of nickel nanoparticles.
It can be manufactured by a method including. Preferably, the next step C;
C) A step of cleaning the nickel nanoparticle slurry with a cleaning solvent,
May be carried out. Then, for the purpose of controlling the particle size of the nickel nanoparticles to be synthesized, a predetermined amount of the organometallic compound is added at any timing between the step A and the heating of the complexing reaction solution in the step B. Is also good.

[Step A]
Step A is a step of mixing a nickel salt and a reducing agent to obtain a nickel complexing reaction solution.

<Nickel salt>
Examples of the nickel salt include known nickel salts. Here, examples of the nickel salt include organic acid nickel salts such as carboxylic acid nickel salt and inorganic metal salts such as nickel chloride salt, nickel sulfate salt, nickel nitrate salt and nickel carbonate salt, and one or more of these. Selected from metal salts. Among these, nickel carboxylic acid salts having 1 to 12 carbon atoms in the portion excluding the COOH group, which can easily control the particle size and particle size distribution, are preferable, and nickel acetate and nickel formate are preferable.

<Reducing agent>
The reducing agent used in the present embodiment is not particularly limited as long as it can form a complex with a metal, but for example, a primary amine is preferably used. Primary amines are preferable because they can form a complex with a metal and can effectively exert a reducing ability on a nickel complex. On the other hand, since the secondary amine has a large steric hindrance, it may hinder the good formation of the nickel complex, and since the tertiary amine does not have the reducing ability of the metal, neither of them can be used alone, but the primary amine can be used. In use, it is permissible to use them in combination as long as they do not affect the shape of the generated nickel nanoparticles.

The reducing agent can be solid or liquid at room temperature. Here, the normal temperature means 20 ° C ± 15 ° C. The primary amine, which is liquid at room temperature, also functions as an organic solvent when forming a metal complex. Even if it is a primary amine that is solid at room temperature, there is no particular problem as long as it is a liquid by heating at 100 ° C. or higher or is dissolved by using an organic solvent.

The primary amine may be an aromatic primary amine, but an aliphatic primary amine is preferable from the viewpoint of easiness of forming a nickel complex in the reaction solution. Aliphatic primary amines can control the dispersibility of nickel nanoparticles produced, for example, by adjusting the length of their carbon chains, which is advantageous in applications where dispersibility is required. From the viewpoint of controlling the aggregation of nickel nanoparticles in the slurry state, it is preferable to select and use the aliphatic primary amine having a carbon number of about 6 to 20. Examples of such amines include octylamine, trioctylamine, dioctylamine, hexadecylamine, dodecylamine, tetradecylamine, stearylamine, oleylamine, myristylamine, and laurylamine. Oleylamine and dodecylamine are particularly preferable because they exist in a liquid state under the temperature conditions in the nickel nanoparticle formation process and can efficiently proceed with the reaction in a uniform solution. More preferably, it is oleylamine.

Since the primary amine functions as a surface modifier during the formation of nickel nanoparticles, secondary aggregation in the slurry state can be suppressed even after the primary amine is removed. Further, the primary amine is a liquid at room temperature from the viewpoint of ease of treatment in the washing step of separating the solid component of the produced nickel nanoparticles from the solvent or the unreacted primary amine after the reduction reaction in step B. Those are preferable. The amount of the primary amine is preferably used at a magnification of the valence of the metal × 1 times mol or more, more preferably the valence × 1.1 times mol or more, and the valence × 2 with respect to 1 mol of the metal. It is more preferable to use twice mol or more. If the amount of the primary amine is less than the valence of the metal × 1 times mol, it becomes difficult to control the particle size of the obtained nickel nanoparticles, and the particle size tends to vary. The upper limit of the amount of the primary amine is not particularly limited, but for example, from the viewpoint of productivity, it is preferably the valence of the metal × 10 times mol or less.

The conditions for forming the complexing reaction solution in the step A, that is, the mixing conditions for the nickel salt and the reducing agent, will be described by taking as an example the case where nickel carboxylate is used as the nickel salt and primary amine is used as the reducing agent. In this case, the complex formation reaction can proceed even at room temperature, but in order to carry out a sufficient and more efficient complex formation reaction, it is heated to a temperature in the range of, for example, 100 ° C to 165 ° C. It is preferable to carry out the reaction. The heating temperature is preferably a temperature exceeding 100 ° C., more preferably a temperature of 105 ° C. or higher, so that the ligand substitution reaction between the coordinated water coordinated to nickel carboxylate and the primary amine is efficient. This is done, the water molecule as a complex ligand can be dissociated, and the water can be taken out of the system, so that a complex with an amine can be efficiently formed. In addition, when nickel formate dihydrate is used as nickel carboxylate, it has a complex structure in which two coordinated waters and two formicic acids, which are bidentate ligands, are present at room temperature. In order to efficiently form a complex by the ligand substitution of one coordinated water and the primary amine, it is preferable to heat at a temperature higher than 100 ° C. to dissociate the water molecule as a complex ligand. The heating time can be appropriately determined according to the heating temperature and the content of each raw material. There is no particular upper limit to the heating time, but unnecessarily long heat treatment is wasteful from the viewpoint of saving energy consumption and process time.

The heating method in the step A is not particularly limited, and may be heating by a heat medium such as oil temperature control or an electric heater, or heating by microwave irradiation or ultrasonic irradiation.

In step A, an organic solvent other than the primary amine may be newly added in order to allow the reaction in the uniform solution to proceed more efficiently. When an organic solvent is used, the organic solvent may be mixed at the same time as the nickel salt and the reducing agent, but if the nickel salt and the reducing agent are first mixed to form a complex and then the organic solvent is added, the reducing agent efficiently produces nickel atoms. It is more preferable because it coordinates with. The organic solvent that can be used is not particularly limited as long as it does not inhibit the complex formation between the nickel salt and the reducing agent and does not oxidize the produced nickel, and is not particularly limited, and is, for example, saturated or unsaturated with 7 to 30 carbon atoms. Hydrocarbon-based organic solvents and the like can be used. Further, from the viewpoint of enabling use even under heating conditions, it is preferable to select an organic solvent having a boiling point of 170 ° C. or higher. Specific examples of such an organic solvent include paraffin oil.

[Step B]
In step B, the nickel complexing reaction solution obtained by the complexing reaction is heated and the nickel in the complexing reaction solution is reduced to obtain a slurry of nickel nanoparticles. The heating temperature in step B varies depending on the particle size, particle size distribution, etc. of the obtained nickel nanoparticles, but is preferably maintained at a temperature at which a reaction accompanied by endothermic occurs. When the reaction temperature is significantly exceeded and the nickel is sufficiently heated, the hydrocarbon is decomposed by the catalytic action of the generated nickel, and carbon is deposited and covered on the surface of the nickel nanoparticles, so that the generation of nickel ions on the nickel surface is suppressed. , It is not preferable because the bondability is lowered.

The heating time is not particularly limited, but it is preferable to measure the nickel concentration of the reaction solution using, for example, a nickel densitometer Ni-5Z manufactured by Kasahara Kagaku Kogyo Co., Ltd., and heat until nickel is no longer detected. If the heating time is shorter than this, it is difficult to obtain particles having the desired particle size, and the dispersibility tends to decrease, which is not preferable. The upper limit of the heating time is not particularly limited because the heating time changes depending on the particle size, but when the reaction is completed for a long time, carbon is deposited on the nickel surface and the generation of nickel ions is suppressed. This is not preferable because the cohesiveness is reduced.

As a production process in step B, a batch method for heating a stainless steel container or a continuous reactor is used, and as a heating means, a heat medium such as oil temperature control, a heating method using electricity, microwaves, ultrasonic waves, etc. Can be mentioned. From the viewpoint of production cost, a heating method using a heat medium such as oil temperature control and electricity is preferably used. Further, the heating may be performed by microwave irradiation or ultrasonic irradiation.

In step B, in order to improve the dispersibility of the nickel nanoparticles and to impart a function such as a rust preventive to prevent oxidation, a dispersant or an additive for imparting the function hinders the bondability. It can be added within a range that does not exist.

[Addition of organometallic compounds]
The organometallic compound used in the present embodiment has the same properties (nucleophilicity) as the nucleophile, and is not particularly limited as long as it acts on the metal complex. As a preferable organic metal compound, an organic group such as an alkyl group or an alkoxy group is coordinated with the alkali metal from the viewpoints of ease of control of the particle size and particle size distribution of nickel nanoparticles, safety, convenience, and productivity. Examples of the alkali metal-based organic metal compound and the alkaline earth metal obtained are the alkaline earth metal-based organic metal compound in which the organic group is coordinated. Hereinafter, the alkali metal-based organic compound and the alkaline earth metal-based organic compound are collectively referred to as "the present organic metal compound". The present organic metal compound may be an organic metal halide containing a halide such as chlorine, bromine, or iodine. In this case, they are also referred to as an alkali metal-based organic metal halide and an alkaline earth metal-based organic metal halide, respectively. The alkali metal-based organic metal halide is a form of an alkali metal-based organic metal compound, and the alkaline earth metal-based organic metal halide is a form of an alkaline earth metal-based organic metal compound.

Examples of the alkali metal constituting the alkali metal-based organic metal compound include lithium, sodium, potassium, rubidium, and cesium, and organic lithium containing highly reactive lithium is preferably used.
Examples of the alkaline earth metal constituting the alkaline earth metal-based organic metal compound include beryllium, magnesium, calcium, strontium, and barium, and an organic magnesium halide containing magnesium having good reactivity can be mentioned. It is preferably used. Since alkylaluminum in which an alkyl group is coordinated with aluminum has strong ignition properties, alkali metal-based and alkaline earth metal-based organic metal compounds are more preferably used from the viewpoint of safety and convenience. ..

The present organic metal compound is preferably used as a diluted solution diluted with an organic solvent such as tetrahydrofuran, hexane, toluene, cyclohexane, butyl ether, dibutyl ether and the like. The concentration of the diluted solution is not limited, but when a small amount affects the particle size, a low concentration is preferable because it is easy to control.

As the alkali metal-based organometallic compound, inexpensive and general-purpose n-butyllithium and phenyllithium are preferably used, and these toluene solutions and n-hexane solutions are particularly suitable from the viewpoint of safety and convenience. ..
Further, as the alkaline earth metal-based organic metal compound, ethylmagnesium chloride, ethylmagnesium bromide, butylmagnesium chloride, 2-butylmagnesium chloride-lithium chloride complex, and butylmagnesium bromide are preferably used, and these tetrahydrofuran solutions are particularly suitable. Used for.

The amount of the organometallic compound added is not particularly limited because the amount to be added may be selected according to the target particle size. Specifically, the amount of the organometallic compound added is as exemplified below.

The organometallic compound may be added at any timing from step A to heating the complexing reaction solution in step B. For example, the organometallic compound may be added after mixing the nickel salt and the reducing agent in step A to remove excess water, or may be added after preparing the complexing reaction solution. Further, since the organometallic compound is easily deactivated by moisture and loses its effect, it is preferable to add it immediately before heating the complexing reaction solution in step B. By adding the present organometallic compound, the particle size of the nickel nanoparticles can be remarkably reduced. The mechanism of its action is not yet clear, but it is presumed that the nucleophilic organometallic compound acts on the nickel complex and promotes the formation of nickel nuclei. Since the effect is deactivated by the influence of moisture absorption and it becomes difficult to control the particle size distribution, it is preferable to add the organometallic compound immediately before heating the complexing reaction solution in step B.

[Nickel nanoparticles]
As described above, a synthetic liquid slurry containing nickel nanoparticles can be obtained. The obtained nickel nanoparticle synthetic liquid slurry is, for example, statically separated, and after removing the supernatant liquid, it is washed and replaced with a washing solvent in order to suppress the decrease in the activity of nickel ions on the surface of the nickel nanoparticles. Is preferable (step C). It is preferable that the cleaning solvent used in this step C does not contain a hydroxyl group. Therefore, as the cleaning solvent, it is preferable to use a solvent containing 0.1 wt% or more of water, and an organic solvent such as toluene, xylene, hexane, or cyclohexane satisfying this condition can be preferably used. A hydrophilic alcohol having 3 or less carbon atoms is not preferable as a cleaning solvent because it usually contains 0.1 wt% or more of water.
Further, the nickel nanoparticles may contain a small amount of elements other than metal elements such as oxygen, hydrogen, carbon and nitrogen, or may be alloys thereof. Further, it may be composed of a single nickel nanoparticles, or may be a mixture of two or more kinds of nickel nanoparticles.

Further, the metal component contained in the nickel nanoparticles may include an alkali metal such as lithium, sodium, potassium, rubidium and cesium, a base metal such as copper, iron and cobalt, and a noble metal such as platinum, gold, palladium and silver. ..

In the method for producing the present nickel nanoparticles, the average particle size of the obtained nickel nanoparticles is not particularly limited, but by adding the present organic metal compound, the average particle size can be adjusted to a desired size in the range of, for example, 5 nm to 100 nm. Can be controlled.

[Nickel nanoparticle ink or paste composition]
In order to make the obtained slurry containing nickel nanoparticles into an ink or a paste as described above, it is preferable to use a solvent containing no water or a hydrophilic alcohol having 3 or less carbon atoms, for example. , Fat group hydrocarbons such as decane, tetradecane, paraffin oil, petroleum hydrocarbons, alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane, decahydronaphthalene, aromatic hydrocarbons such as toluene, xylene, ethylbenzene, Esters such as ethyl acetate, butyl acetate, dihydroturpinyl acetate, isobonyl acetate, isobonyl proquinate, isobonylbutyrate, isobonylisobutyrate, long chain type such as α-terpineol and butylcarbitol, long A non-aqueous solvent such as an ester of a chain alcohol and a carboxylic acid is preferable. Among these, it is more preferable to use a non-polar solvent such as an aliphatic hydrocarbon or an alicyclic hydrocarbon.

The dispersant used for inking or pasting in the present embodiment is not particularly limited, but a non-aqueous polymer dispersant is preferable because a water-insoluble solvent is preferably used, and it is a commercially available dispersant. May be.

The weight average molecular weight of the non-aqueous polymer dispersant used in the present embodiment is preferably in the range of 1,000 to 200,000, more preferably in the range of 5,000 to 100,000. If the weight average molecular weight is less than the above lower limit, the dispersion stability may not be sufficient for a low polar solvent, and if it exceeds the above upper limit, the viscosity may become too high and handling may be difficult.

Examples of commercially available non-aqueous polymer dispersants that can be suitably used include Solsperse 3000 (trade name), Solsperse 8000 (trade name), Solsperse 9000 (trade name), and Solsperse 11200 (trade name) manufactured by Japan Lubrizol. Solspece13940 (trade name), Solspirase13240 (trade name), DISPERBYK-161 (trade name), DISPERBYK-163 (trade name), DISPERBYK-2164 (trade name), DISPERBYK-2155 (trade name) manufactured by Big Chemie Japan. ) Etc. can be mentioned.

The amount of the non-aqueous polymer dispersant used in the present embodiment varies depending on the particle size, but is in the range of 0.01 to 10 parts by mass, preferably 0.1 with respect to 100 parts by mass of the nickel nanoparticles. It should be in the range of ~ 5 parts by mass. If the amount added is less than the above lower limit, the dispersibility in the paste tends to decrease, and if it exceeds the above upper limit, aggregation tends to occur in the paste.

The binder resin used in this embodiment is not particularly limited as long as it can adjust the viscosity characteristics and can form a good coating film. The type and amount of the binder resin added differ depending on the solvent used, and may be adjusted as appropriate.

[Aggregation method]
The nickel nanoparticle aggregate of the present invention is obtained by contacting the nickel nanoparticle paste obtained as described above with water or a hydrogen peroxide solution of 1 wt% or more (hereinafter referred to as “aggregation liquid”) to obtain nickel nanoparticles. It is obtained by joining them directly or via a film thereof.
The agglomeration solution needs to be a solution that easily reacts with nickel ions on the surface of nickel nanoparticles to generate hydroxyl groups. As the coagulation liquid, for example, water or 1 wt% or more of hydrogen peroxide solution can be used. A film of nickel hydroxide or nickel oxide is formed on the surface of nickel nanoparticles by spraying a coagulation liquid on a film or the like formed by applying the nickel nanoparticles ink or paste on a substrate and contacting the nickel nanoparticles. Can be formed, and nickel nanoparticles can be agglomerated with each other directly or through the film to form a nickel nanoparticle agglomerate. When a hydrogen peroxide solution is used as the aggregating liquid, the concentration may be 1 wt% or more, preferably in the range of 30 wt% to 35 wt%.
Further, it is preferable to dry the nickel nanoparticle paste to reduce the content of the non-polar solvent in the nickel nanoparticle paste before contacting the agglomerating liquid. The nickel nanoparticle paste can be dried at room temperature, but it is preferable to heat-treat it at a temperature in the range of, for example, 150 ° C. or lower, preferably 70 ° C. to 150 ° C.
Agglutination of nickel nanoparticles is possible even at room temperature, but after contact with water or hydrogen peroxide solution of 1 wt% or more, the temperature is, for example, 150 ° C. or lower, preferably 70 ° C. to 150 ° C. By heat-treating with, the time required for aggregation can be shortened. When the nickel nanoparticle aggregates are formed on the resin substrate, the heat treatment temperature is more preferably in the range of 70 ° C. to 120 ° C. in order to suppress damage to the resin substrate.

The method of contacting the aggregating liquid is not particularly limited, but if it is immersed in a large amount for a long time, granular deposits that are considered to be nickel hydroxide are generated on the surface of the nickel nanoparticles, and it becomes difficult to form a film. Further, if the precipitation amount of nickel hydroxide becomes too large, the characteristics peculiar to nickel such as magnetism and conductivity are lost, which is not preferable. Therefore, for example, it is preferable to bring an appropriate amount of agglutinating solution into contact with the nickel nanoparticle paste by a method such as spraying or coating. Further, as described above, it is preferable to heat-treat the agglomeration liquid at 70 ° C. or higher after bringing it into contact with the nickel nanoparticles.

As the substrate, not only an inorganic substrate having high heat resistance such as a metal substrate, a glass substrate, and a ceramic substrate, but also a resin substrate having inferior heat resistance to the inorganic substrate can be applied. A known resin can be applied to the resin substrate, and examples thereof include nylon resin, epoxy resin, acrylic resin, polyethylene terephthalate, polyimide, polycarbonate, and liquid crystal polymer.
The nickel nanoparticle paste is applied and dried on these substrates, and the agglomeration liquid is brought into contact with the substrate and dried to form nickel nanoparticle agglomerates on the substrate, and a composite of the nickel nanoparticles and the substrate ( Nickel nanoparticles composite substrate) can be preferably obtained.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. In the following examples, the measurements and evaluations are as follows unless otherwise specified.

[Measurement of average particle size]
To measure the average particle size, take a picture of the sample with an SEM (scanning electron microscope), randomly select 200 particles from it, determine the area of each, and convert the particle size into a true sphere. The average particle size of the primary particles was calculated as the number standard. The CV value (coefficient of variation) was calculated by (standard deviation) ÷ (average particle size). The smaller the CV value, the more uniform the particle size.

[Applying nickel nanoparticle paste]
Two slide glasses S1112 (76 mm × 26 mm × t1.1 mm) manufactured by Matsunami Glass Industry Co., Ltd. were wiped dry with absorbent cotton moistened with acetone. Approximately 0.05 g of nickel nanoparticle paste is weighed in the center of one slide glass, sandwiched between another slide glass, and then printed while applying pressure so that it does not protrude from the side surface, and the slide glass is spread in the parallel direction. A smooth coating surface can be obtained by sliding.

[Evaluation of cohesiveness]
A solution containing 30-35 wt% hydrogen peroxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) or an isopropanol solution containing 10 wt% water is sprayed on the nickel nanoparticle paste applied to the slide glass by spraying for about 1 minute. After impregnation, the mixture was dried in a tabletop oven at 80 ° C., and the cohesiveness was evaluated using an optical microscope and an electron microscope.

[Quantification of nickel]
The detection amount of nickel dimethylglyoxime to be detected was determined by the nickel measurement method specified in JIS K 0102 59.1, and used as the detection amount of nickel ions.

[Measurement of specific surface area]
The specific surface area [m ² / g] of the nickel particles was measured by the gas adsorption method.

[Elemental analysis]
1. 1. H, C and N were measured by the elemental analysis method using JIS8819 coal and coke-instrumental analyzer.
2. 2. O was measured by JIS8813 coal and coke-elemental analysis method.

[Calculated value V]
The calculated value V was obtained based on the following equation (1).
V = A × D ³ / S / 10000000 ・ ・ ・ (1)
{In the formula, A means the amount of nickel dimethylglyoxime detected by the nickel measurement method specified in JIS K 0102 59.1 [ppm], and S is the ratio of nickel particles measured by the gas adsorption method. It means the surface area [m ² / g], and D means the average particle size [nm] of the nickel particles measured by a scanning electron microscope (SEM). }

[Organometallic compounds]
Organometallic compound (1): Approximately 19% dibutyl ether solution of phenyllithium manufactured by Fuji Film Wako Pure Chemical Industries, Ltd. (approximately 1.9 mol / L)

The materials used to make the nickel nanoparticle slurry and their abbreviations are as follows.

Solvent (1): Decahydronaphthalen (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd .; Grade 1)
Solvent (2): terpineol

Dispersant (1): Aliphatic polymer dispersant (manufactured by Japan Lubrizol Co., Ltd., trade name; Solsperse9000)
Dispersant (2): Polyester-based polymer dispersant (manufactured by Japan Lubrizol Co., Ltd., trade name; Solspecs 13240)

Binder resin (1): Aliphatic saturated hydrocarbon resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name; Archon P-100) / decahydronaphthalene = 2/1 parts by weight Binder resin (2): Cellulosic resin / terpineol = 1/10 parts by weight (manufactured by Nissin Kasei Co., Ltd., trade name; EC-100FTP)

(Synthesis Example 1)
246.8 g of nickel acetate tetrahydrate was added to 600 g of oleylamine, and the mixture was heated at 140 ° C. for 3 hours under a nitrogen flow to obtain a complexing reaction solution 1 (nickel ion concentration; 7.5% by weight). After cooling the complexing reaction solution 1 to about 60 ° C., 0.10 g of the organometallic compound (1) was added, and the mixture was reacted at 215 ° C. for 7 minutes and then rapidly cooled to obtain a nickel nanoparticle slurry 1. The analysis results of the obtained nickel nanoparticle slurry 1 are shown in Tables 1 and 2. In addition, a part of the obtained nickel nanoparticles 1 was dried at 80 ° C. for 1 hour, then sprayed with an isopropanol solution containing 10 wt% of water, dried at 80 ° C. for 1 hour, and then analyzed. Shown in 3.

(Synthesis Example 2)
246.8 g of nickel acetate tetrahydrate was added to 600 g of oleylamine, and the mixture was heated at 140 ° C. for 3 hours under a nitrogen flow to obtain a complexing reaction solution 2 (nickel ion concentration; 7.5% by weight). The complexing reaction solution 2 was cooled to about 60 ° C., 1.10 g of the organometallic compound (1) was added, and the mixture was reacted at 212 ° C. for 5 minutes and then rapidly cooled to obtain a nickel nanoparticle slurry 2. The analysis results of the obtained nickel nanoparticle slurry 2 are shown in Tables 1 and 2. The results of analysis after drying a part of the obtained nickel nanoparticles 2 at 80 ° C. for 1 hour, spraying with an isopropanol solution containing 10 wt% of water by spraying, and drying at 80 ° C. for 1 hour are shown. Shown in 3.

(Synthesis Example 3)
246.8 g of nickel acetate tetrahydrate was added to 600 g of oleylamine, and the mixture was heated at 140 ° C. for 3 hours under a nitrogen flow to obtain a complexing reaction solution 1 (nickel ion concentration; 7.5% by weight). After cooling the complexing reaction solution 1 to about 60 ° C., 3.0 g of the organometallic compound (1) was added, and the mixture was reacted at 212 ° C. for 5 minutes and then rapidly cooled to obtain a nickel nanoparticle slurry 3. The analysis results of the obtained nickel nanoparticle slurry 3 are shown in Tables 1 and 2. The results of analysis after drying a part of the obtained nickel nanoparticles 3 at 80 ° C. for 1 hour, spraying with an isopropanol solution containing 10 wt% of water by spraying, and drying at 80 ° C. for 1 hour are shown. Shown in 3.

(Synthesis Example 4)
246.8 g of nickel acetate tetrahydrate was added to 600 g of oleylamine, and the mixture was heated at 140 ° C. for 3 hours under a nitrogen flow to obtain a complexing reaction solution 1 (nickel ion concentration; 7.5% by weight). After cooling the complexing reaction solution 1 to about 60 ° C., 0.10 g of the organometallic compound (1) was added, and the mixture was reacted at 215 ° C. for 30 minutes and then rapidly cooled to obtain a nickel nanoparticle slurry 4. The analysis results of the obtained nickel nanoparticle slurry 4 are shown in Tables 1 and 2. The results of analysis after drying a part of the obtained nickel nanoparticles 4 at 80 ° C. for 1 hour, spraying with an isopropanol solution containing 10 wt% of water by spraying, and drying at 80 ° C. for 1 hour are shown. Shown in 3.

(Example 1)
The nickel nanoparticle slurry 1 obtained in Synthesis Example 1 is settled with a neodymium magnet, the supernatant is discarded, about 50 g of a toluene washing solvent is added, and the mixture is shaken for 10 minutes using a shaker, and then with a neodymium magnet. The settling and discarding of the supernatant were repeated three times to obtain a nickel nanoparticles toluene slurry. About 1 g of nickel nanoparticles was collected from this slurry liquid, 0.2 g of a dispersant (1) was added, and the mixture was treated with an ultrasonic wave for 10 minutes, the supernatant liquid was discarded using a neodymium magnet, and then the solvent (1) was added. After adding 15 cc, the supernatant was discarded 3 times with ultrasonic waves for 10 minutes to obtain a nickel nanoparticle decahydronaphthalene slurry. After adjusting this slurry liquid so that the solid content of nickel nanoparticles becomes 85%, 0.05 g of the binder resin (1) is added, and the mixture is used with a stirrer (trade name: Neritaro, manufactured by Shinky Co., Ltd.) for 10 minutes. The paste 1 was obtained by stirring. This paste 1 was applied to a slide glass and dried at 80 ° C. The result of observing the state of this dry paste by SEM is shown in FIG.
After drying, a 30-35 wt% hydrogen peroxide solution was sprayed, dried at 80 ° C., and the results observed by SEM are shown in FIG. From the comparison between FIGS. 1 and 2, it was confirmed that in FIG. 2, a film presumed to be nickel hydroxide or nickel oxide was formed around the nickel nanoparticles, and good aggregates were formed.

(Example 2)
A dry paste and an agglomerate were prepared in the same manner as in Example 1 except that the nickel nanoparticle slurry 2 was used, and the results observed by SEM are shown in FIGS. 3 (dry paste) and 4 (aggregate). rice field. From the comparison between FIGS. 3 and 4, it was confirmed in FIG. 4 that a film was formed around the nickel nanoparticles and good aggregates were formed.

(Example 3)
A dry paste and an agglomerate were prepared in the same manner as in Example 1 except that the nickel nanoparticle slurry 3 was used, and the results observed by SEM are shown in FIGS. 5 (dry paste) and 6 (aggregate). rice field. From the comparison between FIGS. 5 and 6, it was confirmed in FIG. 6 that a film was formed around the nickel nanoparticles and good aggregates were formed.

(Example 4)
The solvent (1) of Example 1 was changed to the solvent (2), the dispersant (1) was changed to the dispersant (2), and the binder resin (1) was changed to the binder resin (2). A dry paste and an agglomerate were prepared in the same manner as in Example 1 except that the amount used was 0.03 g. The result of observing the obtained aggregate by SEM is shown in FIG. From FIG. 7, it was confirmed that a film was formed around the nickel nanoparticles and good aggregates were formed.

(Example 5)
Dry pastes and aggregates were prepared in the same manner as in Example 1 except that the 30-35% hydrogen peroxide solution used in the evaluation of the bondability of Example 1 was changed to an isopropanol solution containing 10 wt% of water. The result of observing the obtained aggregate by SEM is shown in FIG. From FIG. 8, it was confirmed that a film was formed around the nickel nanoparticles and good aggregates were formed.

(Comparative Example 1)
Nickel nanoparticles were separately synthesized in the same manner as in Synthesis Example 1 to obtain a nickel nanoparticle slurry having an average particle diameter of 43.5 nm. The analysis results of the obtained nickel nanoparticle slurry 2 are shown in Table 2. Using this nickel nanoparticle slurry, a dry paste was prepared in the same manner as in Example 1 except that the toluene washing solvent was changed to methanol / toluene = 1/4 mixed solvent, and further treated with a hydrogen peroxide solution. I tried to make an aggregate. The results observed by SEM are shown in FIG. 9 (dry paste) and FIG. 10 (after treatment with hydrogen peroxide solution). From the comparison of FIGS. 9 and 10, it was confirmed that no film was formed on the surface of the nickel nanoparticles and no aggregate was obtained.
In addition, a part of the obtained nickel nanoparticles was dried at 80 ° C. for 1 hour, then sprayed with an isopropanol solution containing 10 wt% of water by spraying, dried at 80 ° C. for 1 hour, and then analyzed. Table 3 shows the results of analysis. It was shown to.

(Comparative Example 2)
A dry paste was prepared in the same manner as in Example 1 except that the nickel nanoparticle slurry 4 was used, and further treated with a hydrogen peroxide solution to attempt to prepare an aggregate. The results observed by SEM are shown in FIG. 11 (dry paste) and FIG. 12 (paste after hydrogen peroxide solution treatment). From the comparison of FIGS. 11 and 12, it was confirmed that the part where the film was formed and the part where the film was not formed coexisted and good aggregates could not be obtained.

Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above embodiments.

Claims (7)

The nickel nanoparticles having an average particle diameter of 5 to 100 nm and a binder resin dispersed in a non-polar solvent are brought into contact with water or 1 wt% or more of hydrogen peroxide solution to obtain the nickel nanoparticles. A nickel nanoparticle agglomerate obtained by forming a film on the surface and aggregating nickel nanoparticles directly or through the film. The nickel nanoparticle aggregate according to claim 1, wherein the nickel nanoparticle paste is dried and then contacted with the water or 1 wt% or more of hydrogen peroxide solution. The nickel nanoparticle aggregate according to claim 1 or 2, wherein the nickel nanoparticles are nickel nanoparticles having a calculated value V calculated by the following formula (1) of 3 or more.
V = A × D ³ / S / 10000000 ・ ・ ・ (1)
{In the formula, A means the amount of nickel dimethylglyoxime detected by the nickel measurement method specified in JIS K 0102 59.1 [ppm], and S is the ratio of nickel particles measured by the gas adsorption method. It means the surface area [m ² / g], and D means the average particle size [nm] of the nickel particles measured by a scanning electron microscope (SEM). } One of claims 1 to 3, wherein the nickel nanoparticles are nickel alone or an alloy of nickel and one or more metals selected from lithium, copper, iron, cobalt, gold, platinum and palladium. Nickel nanoparticle agglomerates according to. The nickel nanoparticle aggregate according to any one of claims 1 to 4, wherein the nickel nanoparticles have 99 wt% or more of a metal component contained in the nickel nanoparticles of nickel. With the board
A nickel nanoparticle composite substrate comprising the nickel nanoparticle aggregate according to any one of claims 1 to 5 laminated on the substrate. A step of preparing a nickel nanoparticle paste in which nickel nanoparticles having an average particle diameter of 5 to 100 nm and a binder resin are dispersed in a non-polar solvent, and a step of preparing the nickel nanoparticles.
A step of contacting the nickel nanoparticles paste with water or 1 wt% or more of hydrogen peroxide solution to form a film on the surface of the nickel nanoparticles and agglomerate the nickel nanoparticles directly or through the film. When,
A method for producing a nickel nanoparticle aggregate containing.

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