JP5485122B2 - Sulfur-containing nickel particles and method for producing the same - Google Patents

Description

  The present invention relates to nickel particles containing sulfur, typically sulfur-containing nickel particles that are fine particles having an average particle size of 1 μm or less. Furthermore, it relates to a method for producing such sulfur-containing nickel particles.

  Nickel particle material (powder material) supplied at a relatively low cost compared to noble metal particle material is a metal material used for various applications. For example, a conductor sheet made of nickel (Ni) is prepared by applying a paste or slurry material prepared by dispersing nickel particles in a predetermined dispersion medium to a substrate with a predetermined film thickness and firing the material. (Conductive film) can be formed on the substrate. Nickel particles contained in a paste-like or slurry-like material for forming such a conductor (also called a conductor paste) have an average particle size (or median diameter in the particle size distribution) of 1 μm or less, typically Nickel fine particles (so-called nickel nanoparticles) having a thickness of 10 nm to 1000 nm (for example, 30 nm to 300 nm) are preferable.

  Various techniques have been proposed for producing such nickel fine particles. For example, Non-Patent Documents 1 to 3 disclose a method of generating nickel particles by adding hydrazine to nickel chloride and reducing it under basic conditions. Patent Document 1 discloses that a metal salt such as nickel hydroxide is dissolved or dispersed in an organic solvent such as reducing ethylene glycol together with a solid catalyst such as chloroplatinic acid, and a microwave is added to the solution. A method for producing nickel particles by irradiating is disclosed. Patent Document 2 discloses a method in which nickel hydroxide is produced by reducing nickel hydroxide with hydrogen gas and then crushing it with a jet mill equipped with a high-speed classification rotor to remove coarse particles before reaggregation. ing. In addition, patent documents 3-5 are mentioned as literature relevant to nickel particles, for example.

JP 2000-256707 A JP 2003-89806 A JP-A-11-302709 JP 2010-53409 A JP 2010-185112 A

Chou K., et al., "Studies on the chemical synthesis of nanosized nickel powder and its stability", J. Nanopart. Res., 2001, 3, p.127-132 Duan Y., et al., "Structure study of nickelnanoparticles", Mater. Chem. Phys., 2004, 87, p.452-454 Park J. W., et al., "Preparation of fine Ni powders from nickelhydrazine complex", Mater. Chem. Phys., 2006, 97, p.371-378

By the way, as one of the problems required for the nickel particles used for the above-described uses of the nickel particles, there is a suppression of so-called “necking”. Necking refers to a phenomenon in which adjacent nickel particles adhere to each other and aggregate during firing (typically during calcination). If such necking occurs excessively, the dispersibility of the nickel particles deteriorates, and there is a risk that problems such as the formation of a high-density (dense) conductor film may occur, which is not preferable.
As one means for suppressing necking, it is conceivable to use sulfur-containing nickel particles obtained by adding (doping) sulfur to nickel particles. In order to employ such sulfur-containing nickel particles and obtain a high necking-suppressing effect, it is preferable that sulfur atoms exist almost uniformly over the entire surface of the nickel particles.

However, it has been difficult to produce nickel particles in which sulfur atoms are arranged substantially evenly over the entire surface of the particles depending on the conventional nickel fine particle production method. For example, even if sulfur is supplied after nickel particles are generated, it is difficult to evenly distribute sulfur atoms (sulfur alone or sulfur compounds) to the surface region of the nickel particles.
Therefore, the present invention has been created to solve such a problem, and sulfur is disposed almost uniformly over the entire surface area of nickel particles (preferably nano-sized fine particles having a particle size of 1 μm or less). An object is to provide a method for suitably producing sulfur-containing nickel particles. Another object is to provide sulfur-containing nickel particles produced by such a production method.

In order to achieve the above object, the method for producing nickel fine particles provided by the present invention is a method for producing sulfur-containing nickel particles. Such a manufacturing method is:
(1) preparing a raw material aqueous solution containing nickel ions;
(2) generating a complex of nickel and said compound in the raw material aqueous solution by adding to that of compound functions as a reducing agent solution in,
(3) adding an alkali metal salt of a polyvalent carboxylic acid to the aqueous raw material solution produced by the composite;
(4) adding a sulfur supply material in which sulfur powder is dispersed in the raw material aqueous solution to which the alkali metal carboxylate is added;
(5) adjusting the basic aqueous solution to which the sulfur supply material is added to basic to induce a nickel reduction reaction; and
(6) recovering the sulfur-containing nickel particles generated by the reduction reaction,
Is included.

In the manufacturing method of this structure, upon which has been formed complex between said reducing agent der Ru of compound and nickel (complex) by first adding the reducing agent in the raw material aqueous solution containing nickel ions Add the alkali metal salt of a polyvalent carboxylic acid, followed by the sulfur feed (typically a dispersion containing particles of sulfur alone). Then, the solution to which each substance is added is adjusted to be basic, and nickel particles are generated by inducing a nickel reduction reaction (that is, reduction of nickel ions). Typically, it can be adjusted by adding a sulfur feed adjusted to a high pH or by separately adding an alkaline solution (eg, sodium hydroxide solution) to reach a high pH range (eg, pH 12 or higher). .
According to such a process, sulfur (typically elemental sulfur) contained in a dispersed state in the raw material aqueous solution is spread over the entire surface of the particles in the production process of nickel particles in the solution. They can be arranged almost evenly.
Therefore, according to the production method disclosed herein, it is possible to suitably produce sulfur-containing nickel particles that are effective in suppressing necking by using the above-described series of simple processes and inexpensive raw materials.

  Preferably, sodium citrate (typically trisodium citrate) is used as the alkali metal carboxylate. Preferably, hydrazine or a derivative thereof is used as the reducing agent. Preferably, an aqueous solution of nickel chloride (anhydride or hydrate) is used as the raw material aqueous solution. By using these compounds, it is possible to produce sulfur-containing nickel particles that are more effective in suppressing necking.

Further, a preferred embodiment of the production method disclosed herein is that the sulfur feed material is supplied to the raw material aqueous solution so that an amount of sulfur corresponding to 0.05 to 10% by mass of the nickel amount contained in the raw material aqueous solution is supplied. It is characterized by adding to.
By mixing nickel (Ni) and sulfur (S) at such a ratio, nickel particles in which sulfur is evenly distributed and arranged over the entire surface can be suitably produced.

In another preferred embodiment of the production method disclosed herein, the amount of the alkali metal salt of polyvalent carboxylic acid added to the aqueous raw material solution is 2 to 5% by mass of the amount of nickel contained in the aqueous raw material solution. It is characterized by being defined in a corresponding amount.
By adding the amount of the alkali metal salt of polyvalent carboxylic acid as defined above, the average particle size (typically the average particle size based on either TEM or SEM observation or X-ray diffraction) is 100 nm or less. Sulfur-containing nickel fine particles (nanoparticles) (typically 30 nm to 100 nm, particularly preferably 30 nm to 50 nm) can be suitably produced.

In another preferred embodiment of the production method disclosed herein, the raw material aqueous solution is heated from 50 ° C. to 90 ° C. at least from the formation of the complex to the induction of a nickel reduction reaction. Features.
By performing each of the above treatments on the raw material aqueous solution thus heated, the treatment efficiency can be increased and sulfur-containing nickel particles can be preferably produced.

The present invention also provides sulfur-containing nickel particles and a sulfur-containing nickel powder material comprising the particles. Typically, sulfur-containing nickel particles produced by any of the production methods disclosed herein and a sulfur-containing nickel powder material comprising the particles are provided.
Preferably, the average particle size (typically based on TEM or SEM observation or X-ray diffraction) is 30 nm to 300 nm (for example, 50 nm to 200 nm). Moreover, Preferably, the sulfur content rate with respect to nickel total mass is 0.1-5 mass%.
Such a sulfur-containing nickel powder material has good dispersibility, for example, suppresses necking during firing (or calcination) and forms a conductive film or other highly dense nickel film (sheet) on a predetermined substrate. Can be formed.

It is a graph which shows the relationship between nickel chloride density | concentration (M: horizontal axis) and the reduction process time (minute: vertical axis | shaft) until the nickel particle of a predetermined particle size precipitates. It is a SEM image which shows the state of the sulfur containing nickel particle obtained in one Example. It is a SEM image which shows the state of the sulfur containing nickel particle obtained in one Example. It is a SEM image which shows the state of the nickel particle which does not contain sulfur.

  Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than matters specifically mentioned in the present specification (for example, methods for preparing nickel compounds, polyvalent carboxylic acid alkali metal salts, reducing agents, various solvents, etc., which are raw materials for the produced sulfur-containing nickel particles) Thus, matters necessary for carrying out the present invention (for example, a method of taking out the generated nickel fine particles as a powder) can be grasped as a design matter of a person skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

The method for producing sulfur-containing nickel particles disclosed herein supplies a reducing agent, a polyvalent carboxylic acid alkali metal salt, and sulfur (sulfur feed material) to an aqueous solution containing nickel ions, This is a manufacturing method in which sulfur is taken in in the process of reducing and precipitating nickel particles, and sulfur (typically a simple substance) is distributed almost evenly on the surface of the nickel particles produced.
The raw material aqueous solution used in such a production method is an aqueous solution containing nickel ions for forming nickel particles. The source of nickel ions is not particularly limited as long as it is a compound (salt) that easily dissociates in water to generate nickel ions. Examples thereof include nickel chloride, nickel nitrate, nickel sulfate, nickel acetate (tetrahydrate), nickel sulfamate tetrahydrate, and the like. From the viewpoints of high solubility in water and easy pH adjustment of the raw material aqueous solution, nickel chloride is particularly preferred.

In the manufacturing method disclosed herein, may be used a seed s of a compound as to that of compound functions as a reducing agent. For example, hydrazine, thioglycolic acid, hydroxylamine, dihydric phenol, etc. are mentioned, but hydrazine (typically a hydrated hydrazine hydrate that has been conventionally used for this kind of use) or its Derivatives (for example, organic hydrazines having a hydrazine group) are particularly preferred.

In addition, in the production method disclosed herein, a polyvalent carboxylic acid alkali metal salt (typically a sodium salt) is used.
A polyvalent carboxylic acid alkali metal salt capable of functioning as a complexing agent (or surfactant) is suitable, and examples thereof include alkali metal salts such as citric acid, oxalic acid, tartaric acid, malic acid, and succinic acid. Among these polyvalent carboxylic acid alkali metal salts, sodium citrate is preferable, and trisodium citrate is particularly preferable. By adding such a complexing agent (surfactant), nickel particles can be suitably deposited in the raw material aqueous solution.

In addition, the sulfur supply material used in the production method disclosed herein includes a sulfur powder (typically a powder consisting of simple sulfur) and an appropriate dispersion medium (typically water) in which the sulfur powder can be dispersed. Or a lower alcohol solvent). For example, a sulfur feed material prepared using water, methanol, or ethanol as a dispersion medium can be suitably used. Moreover, in order to improve dispersibility, it is preferable that a sulfur supply material (dispersion) shows basicity. For example, a colloid in which sulfur is highly dispersed can be formed by adding an aqueous solution containing an alkali metal to make the dispersion basic (for example, pH is 12 or more, particularly 13 or more).
The concentration of sulfur contained in the material to be used is not particularly limited, but a material in which 0.1 to 20% by mass of the mass of the entire material is a sulfur concentration is preferable, and a dispersion containing colloidal sulfur in such a concentration range is preferable. Particularly preferred.

The production method disclosed herein can be carried out using a raw material aqueous solution, a polyvalent carboxylate salt, a sulfur feed material, a reducing agent, and the like configured as described above.
First, the raw material aqueous solution to be used is not limited as long as it contains various nickel compounds (that is, nickel ions) as described above, but preferably has a nickel ion concentration of about 0.5 to 2M. When the nickel ion concentration is within such a range, the average particle diameter (typically, the average particle diameter based on either TEM or SEM observation or X-ray diffraction; hereinafter the same) is 200 nm or less (for example, 50 nm to 200 nm). ) Nickel fine particles can be suitably produced. In particular, the nickel ion concentration is preferably about 1 to 2M (for example, 0.7 to 1.5M).
If the nickel ion concentration is too low, the nickel particles are formed for a long time. In addition, the number of generated particles per unit raw material aqueous solution is reduced, and the particle size of each particle tends to increase. On the other hand, even if the nickel ion concentration is too high, the amount of nickel particles formed tends to increase and the particle size tends to increase. Moreover, there exists a possibility that a dispersibility may fall and it may become easy to aggregate.

  The raw material aqueous solution may be used in a normal temperature range (typically 5 to 30 ° C.), but it does not boil (typically 80 ° C. or less, preferably 40 to 80 ° C., for example 50 to 50 ° C. under atmospheric pressure). It is preferably used in a state heated to 70 ° C. For example, a desired raw material aqueous solution is prepared by adding a predetermined amount of a nickel compound such as nickel chloride to water heated to about 60 ° C. and stirring (for example, stirring using a magnetic stirrer), and while being heated, It is preferable to carry out the subsequent steps.

By adding a reducing agent subsequent to the raw solution prepared as described above, it is possible to form a complex with nickel and a reducing agent that make up the reduction compound a (complex). Although it is the addition amount of the reducing agent at this time, it is theoretically preferable to add a reducing agent (for example, hydrazine or a derivative thereof) in an amount capable of reducing the total amount of nickel ions present in the raw material aqueous solution. For example, it is preferable to add a reducing agent (for example, hydrazine) having a molar number of 1 to 5 times or more (for example, 1 to 10 times) the theoretical reaction equivalent (molar conversion) with respect to nickel (II) ions. The form of addition is not particularly limited, but for example, it is preferable to add a predetermined amount dropwise to the stirred raw material aqueous solution. Thus, by adding a reducing agent little by little, the quantity and magnitude | size of a complex produced | generated can be adjusted. That is, aggregation of the generated complexes can be prevented, and a relatively small-sized complex can be generated in a state of being dispersed throughout the raw material aqueous solution.
After adding the reducing agent, preferably the reduction of nickel ions proceeds by maintaining the reaction solution (raw material aqueous solution) in a heated state (for example, 50 to 70 ° C.) for an appropriate time (for example, 0.5 to 6 hours). To generate the complex.

After forming a complex (for example, a complex of nickel and a hydrazine reactant as a reducing agent) in the reaction solution (raw material aqueous solution) by the above reducing agent treatment, an alkali metal salt of a predetermined polyvalent carboxylic acid is added to the raw material aqueous solution ( To the complex-containing reaction solution).
For example, the addition of a polyvalent carboxylic acid alkali metal salt that can function as a complexing agent (or surfactant) is suitable, and the size of the nickel particles to be formed can be adjusted by adjusting the addition amount. .
For example, when adding sodium citrate (especially trisodium citrate) or other alkali metal salt of polyvalent carboxylic acid that can function as a complexing agent (or surfactant), the amount of nickel contained in the raw material aqueous solution is 100 mol. %, It is appropriate to add an amount corresponding to 0.05 to 20 mol%, and an appropriate value corresponding to 0.1 to 10 mol% is preferable, and the value is 0.3 to 1.5 mol%. The degree is particularly preferred. By adding a reducing agent (particularly trisodium citrate) so as to be in such a concentration range, for example, the average particle size is 200 nm or less (for example, 50 nm to 200 nm), more preferably the average particle size is 100 nm or less (for example, 30 nm). Nickel fine particles of ˜100 nm, particularly preferably 30 nm to 50 nm) can be obtained.
Alternatively, in terms of weight, for example, when adding sodium citrate (particularly trisodium citrate) or other polyvalent carboxylic acid alkali metal salt that can function as a complexing agent (or surfactant), an aqueous raw material solution The amount of nickel contained therein is 100% by mass, the addition of an amount corresponding to 0.25 to 100% by mass is appropriate, and the amount corresponding to 0.5 to 50% by mass is preferable. The value is particularly preferably about 1.5 to 7% by mass. By adding a reducing agent (particularly trisodium citrate) so as to be in such a concentration range, for example, the average particle size is 200 nm or less (for example, 50 nm to 200 nm), more preferably the average particle size is 100 nm or less (for example, 30 nm). Nickel fine particles of ˜100 nm, particularly preferably 30 nm to 50 nm) can be obtained.
After adding the polyvalent carboxylic acid alkali metal salt, the reaction solution (raw material aqueous solution) is preferably maintained in a heated state (for example, 50 to 70 ° C.) for an appropriate time (for example, 0.5 to 6 hours).

Next, a sulfur feed material is added to the reaction solution (raw material aqueous solution). The amount of addition is not particularly limited, but the amount of nickel contained in the reaction liquid (raw material aqueous solution) is required to dispose sulfur (typically sulfur alone) almost evenly over the entire surface of the nickel particles to be produced. It is preferable to add a sulfur supply material having a predetermined sulfur concentration so that sulfur corresponding to 0.05 to 10% by mass is contained.
In addition, the reaction solution (raw material aqueous solution) to which the sulfur supply material is added preferably has a basicity of pH 12 or higher (typically pH 13 or higher), and if necessary, an alkaline solution for pH adjustment such as a sodium hydroxide solution. Is preferably added.
After adding the sulfur feed material, the reaction solution (raw material aqueous solution) is preferably maintained in a heated state (for example, 50 to 70 ° C.) for an appropriate time (for example, 0.5 to 6 hours). Thereby, it is possible to produce sulfur-containing nickel particles that are reduced in the reaction solution and into which sulfur is taken in the process of precipitation in the reaction solution.

In the manufacturing method disclosed herein, it is possible to easily prepare sulfur-containing nickel (metal Ni) particles having an average particle diameter of 10 nm to 1000 nm (typically 30 nm to 300 nm) through the above-described processes. it can. Such nickel particles are obtained as precipitates generated in the reaction solution (raw material aqueous solution).
Then, the nickel particles generated as a precipitate are recovered from the reaction solution (raw material aqueous solution) by an appropriate separation / recovery means. For example, after separating the precipitate (solid material) and the solvent, it can be taken out in a powder state by using a method similar to the conventional method for taking out the precipitate. For example, focusing on the magnetism of nickel particles, it can be easily separated and collected by a magnet (magnetic force).
After recovery, the alkaline component is removed until the pH is approximately neutral (around pH 7) by washing, etc., and then dried for an appropriate period of time to obtain the desired sulfur-containing nickel particles (that is, aggregates of the particles). A certain sulfur-containing nickel powder material) can be obtained.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples.

<Example 1: Production of sulfur-containing nickel particles (1)>
Sulfur-containing nickel particles were produced as follows. The used materials (chemicals) are all commercially available products, and can be obtained as products such as Wako Pure Chemical Industries, Ltd., for example.
First, commercially available sulfur powder was added to ethanol to prepare a 10 mass% sulfur-containing ethanol dispersion. An equal amount of 10% by mass sodium hydroxide solution was added to this dispersion to prepare a sulfur feed material (stock solution) containing sulfur at a concentration of about 5% by mass.
On the other hand, a commercially available nickel chloride hexahydrate (NiCl ₂ .6H ₂ O) was used as a Ni source (starting material) to prepare a raw material aqueous solution. Specifically, a 1M nickel chloride aqueous solution was prepared. Then, 50 mL of the prepared 1M nickel chloride aqueous solution was weighed and heated to 60 ° C. on a hot plate.

Subsequently, 5 g of hydrazine hydrate was added dropwise to the 50 mL of the raw material aqueous solution heated to 60 ° C. and stirred using a magnetic stirrer. Stirring was continued for 1 hour after the entire amount of hydrazine was dropped.
Thus, after forming a complex of nickel and hydrazine (complex), the amount corresponding to 0.5% by mass of trisodium citrate as the polyvalent carboxylic acid alkali metal salt with Ni mass of 100 (ie, about Ni The amount corresponding to 0.114 mol%) was added. Stirring was further continued for 1 hour while maintaining the temperature of the reaction solution (raw material aqueous solution) at 60 ° C.

Subsequently, the said sulfur supply material (stock liquid) was added to the said reaction liquid so that the sulfur concentration in the said reaction liquid (raw material aqueous solution) might be 0.05 mass%. In addition, a 50% by mass NaOH aqueous solution in an amount corresponding to 4 g of sodium hydroxide was added to the reaction solution to adjust the reaction solution to basic. After addition of the aqueous NaOH solution, stirring was performed for 1 hour while maintaining the temperature at 60 ° C.
Thereby, the reduction reaction of nickel contained in the complex (complex) in the reaction solution (raw material aqueous solution) was induced, and generation (precipitation) of sulfur-containing nickel particles was observed. In addition, it can visually recognize easily by the change of the color of the reaction liquid accompanying the reduction | restoration of nickel ion.

  Since the sulfur-containing nickel particles thus produced are magnetic, they were recovered using magnetic force. The collected particles were washed with water until the pH reached a neutral range (that is, the pH value of water required for washing was around 7) to remove alkali components, and then dried at 60 ° C. for 2 hours. Such sulfur-containing nickel particles were obtained.

<Example 2: Production of sulfur-containing nickel particles (2)>
Except that the amount of trisodium citrate added was changed to an amount corresponding to 0.75% by mass with respect to Ni as 100 (that is, an amount corresponding to about 0.171 mol% of Ni), and The sulfur-containing nickel particles according to Example 2 were obtained using the same material and the same conditions.

<Example 3: Production of sulfur-containing nickel particles (3)>
The same material as in Example 1 above, except that the amount of trisodium citrate added was changed to an amount corresponding to 1% by mass of Ni (100) (ie, an amount corresponding to about 0.228 mol% of Ni). In addition, sulfur-containing nickel particles according to Example 3 were obtained under the same conditions.

<Example 4: Production of sulfur-containing nickel particles (4)>
The same material as in Example 1 above, except that the amount of trisodium citrate added was changed to an amount corresponding to 2% by mass of Ni (ie, an amount corresponding to about 0.455 mol% of Ni). In addition, sulfur-containing nickel particles according to Example 4 were obtained under the same conditions.

<Example 5: Production of sulfur-containing nickel particles (5)>
The same material as in Example 1 above, except that the amount of trisodium citrate added was changed to an amount corresponding to 5% by mass of Ni (ie, an amount corresponding to about 1.14 mol% of Ni). In addition, sulfur-containing nickel particles according to Example 5 were obtained under the same conditions.

<Example 6: Production of sulfur-containing nickel particles (6)>
The same material as in Example 1 above, except that the amount of trisodium citrate added was changed to an amount corresponding to 10% by mass of Ni (ie, an amount corresponding to about 2.23 mol% of Ni). And under the same conditions, sulfur-containing nickel particles according to Example 6 were obtained.

<Example 7: Production of sulfur-containing nickel particles (7)>
The same material as in Example 1 above, except that the amount of trisodium citrate added was changed to an amount corresponding to 50% by mass of Ni (ie, an amount corresponding to about 11.4 mol% of Ni). And under the same conditions, sulfur-containing nickel particles according to Example 7 were obtained.

<Test Example 1>
The properties of the nickel particles of Examples (Samples) 1 to 7 prepared as described above were examined by X-ray diffraction (XRD) measurement. Table 1 shows the phase state (phase) based on the XRD measurement and the average particle size as main results.
As shown in this table, in the nickel particles of Examples 1 to 3 in which the amount of trisodium citrate added is 1% by mass or less of the amount of Ni, nickel hydroxide may be mixed in addition to metal Ni. Admitted. On the other hand, in the nickel particles of Examples 4 to 7 in which the amount of trisodium citrate added was 2% by mass or more of the amount of Ni, nickel hydroxide was not mixed.
Further, the average particle diameter of the nickel particles was 100 nm or less in all examples, but in Examples 4 and 5 in which the amount of trisodium citrate added was 2 to 5 mass% of the Ni amount, it was 50 nm or less. It was. Therefore, the addition amount of trisodium citrate, which is a kind of alkali metal salt of polyvalent carboxylic acid that functions as a complexing agent or surfactant, is 2 to 5% by mass (generally 0.4 to 1.2 mol%) of the Ni amount. It was confirmed that sulfur-containing nickel particles having an average particle diameter of 100 nm or less (particularly 30 to 50 nm) can be suitably produced. Further, it was confirmed by TEM observation that sulfur was present almost uniformly on the surface of the obtained sulfur-containing nickel particles.

<Test Example 2>
Next, the relationship between the nickel ion concentration in the raw material aqueous solution and the generation time of the sulfur-containing nickel particles was examined. That is, a total of six types of raw material aqueous solutions having a nickel chloride concentration of 0.25M, 0.5M, 0.75M, 1M, 1.5M, and 2M were used as the raw material aqueous solution, respectively. A formation test of sulfur-containing nickel particles was performed under the same conditions as the materials.
Then, the time from when the sulfur supply material and the NaOH aqueous solution were added in a specified amount to when nickel particles having an average particle diameter of approximately 50 to 100 nm were formed was measured. The results are shown in FIG.
As is apparent from the graph of FIG. 1, in the case of using a raw material aqueous solution having a nickel chloride concentration of 0.75 M or more, the average particle size is within 1 hour (especially within 0.5 hour when the nickel chloride concentration is 1 M or more). It was confirmed that nickel particles having a diameter of 50 to 100 nm can be formed.
Accordingly, it is confirmed that if the raw material aqueous solution is 0.75 M or higher (particularly preferably 1 M or higher, for example, 1 to 1.5 M), the nickel ion concentration is sufficient and sulfur-containing nickel particles can be efficiently generated. did it.

<Example 8: Production of sulfur-containing nickel particles (8)>
The same material as in Example 1 above, except that the sulfur supply material (stock solution) was added to the reaction solution so that the sulfur concentration in the reaction solution (raw material aqueous solution) was 0.5 mass% of the total mass of Ni. In addition, sulfur-containing nickel particles according to Example 8 were obtained under the same conditions. SEM images of the obtained sulfur-containing nickel particles are shown in FIGS. Based on the SEM images, the particle size (and hence the average particle size) of most particles was in the range of 50 nm to 200 nm.
For comparison, FIG. 4 shows an SEM image of sulfur-free nickel particles produced in the same manner without supplying a sulfur supply material (stock solution). As is clear from the comparison of these SEM images, the surface of the non-sulfur-containing nickel particles (FIG. 4) is relatively smooth, while the surface of the sulfur-containing nickel particles (FIGS. 2 and 3) is uneven throughout. It is shown that the adsorption of sulfur atoms is performed almost evenly over the entire surface. The specific surface area of the obtained sulfur-containing nickel particles based on the N ₂ gas adsorption method was 15.4 m ² / g.
Further, the sulfur (S) content in the sulfur-containing nickel particles based on ICP (inductively coupled plasma) emission analysis was equivalent to 0.29 mass% of the total mass of Ni.

<Example 9: Production of sulfur-containing nickel particles (9)>
Except having added the said sulfur supply material (stock liquid) to the said reaction liquid so that the sulfur concentration in reaction liquid (raw material aqueous solution) might be 0.25 mass% of Ni total mass, it is the same as that of the said Example 8. The sulfur-containing nickel particles according to Example 9 were obtained. Based on SEM images (not shown), the particle size (and hence average particle size) of most particles was in the range of 50 nm to 200 nm.
The obtained sulfur-containing nickel particles are uneven (non-smooth) over the entire particle surface, similarly to the sulfur-containing nickel particles according to Example 8, and the adsorption of sulfur atoms is almost even over the entire surface. It was shown that it was done without bias. Moreover, the sulfur (S) content rate in the sulfur-containing nickel particle | grains calculated | required based on the ICP emission analysis corresponded to 0.13 mass% of Ni total mass.

<Example 10: Production of sulfur-containing nickel particles (10)>
Except that the sulfur supply material (stock solution) was added to the reaction solution so that the sulfur concentration in the reaction solution (raw material aqueous solution) was 0.15 mass% of the total mass of Ni, the same as in Example 8 above. The sulfur-containing nickel particles according to Example 10 were obtained. Based on SEM images (not shown), the particle size (and hence the average particle size) of most particles was in the range of 100 nm to 200 nm.
The obtained sulfur-containing nickel particles are uneven (non-smooth) over the entire particle surface, similarly to the sulfur-containing nickel particles according to Example 8, and the adsorption of sulfur atoms is almost even over the entire surface. It was shown that it was done without bias. The sulfur (S) content in the sulfur-containing nickel particles based on the ICP emission analysis was equivalent to 0.11% by mass of the total mass of Ni.

<Example 11: Production of sulfur-containing nickel particles (11)>
Example similar to Example 8 above except that the sulfur supply material (stock solution) was added to the reaction solution so that the sulfur concentration in the reaction solution (raw material aqueous solution) was 10% by mass of Ni total mass. No. 11 sulfur-containing nickel particles were obtained. Based on SEM images (not shown), the particle size (and hence the average particle size) of most particles was in the range of 100 nm to 200 nm.
The obtained sulfur-containing nickel particles are uneven (non-smooth) over the entire particle surface, similarly to the sulfur-containing nickel particles according to Example 8, and the adsorption of sulfur atoms is almost even over the entire surface. It was shown that it was done without bias. The sulfur (S) content in the sulfur-containing nickel particles based on the ICP emission analysis corresponded to 2.96% by mass of the total mass of Ni.

  As described above, according to the present invention, sulfur-containing nickel particles can be produced by a simple method. Preferably, a sulfur-containing nickel powder material composed of metallic nickel particles having an average particle size of nano-size (1 μm or less) level can be obtained.

Claims (8)

A method for producing sulfur-containing nickel particles comprising:
Preparing a raw material aqueous solution containing nickel ions;
Generating a complex of nickel and said compound in addition to the solution in to that of compound functions as a reducing agent to the raw material aqueous solution,
Adding an alkali metal salt of a polyvalent carboxylic acid to the aqueous raw material solution produced by the complex,
Adding a sulfur feed material in which sulfur powder is dispersed in the raw material aqueous solution to which the alkali metal salt of polyvalent carboxylic acid is added;
Inducing a nickel reduction reaction by adjusting the aqueous raw material solution to which the sulfur feed material has been added to basicity; and
Recovering the sulfur-containing nickel particles produced by the reduction reaction,
A method for producing sulfur-containing nickel particles.   The manufacturing method of Claim 1 which uses sodium citrate as said polyvalent carboxylic acid alkali metal salt.   The production method according to claim 1 or 2, wherein hydrazine or a derivative thereof is used as the reducing agent.   The manufacturing method as described in any one of Claims 1-3 which uses the aqueous solution of nickel chloride as said raw material aqueous solution.   The sulfur supply material is added to the raw material aqueous solution so that an amount of sulfur corresponding to 0.05 to 10% by mass of nickel contained in the raw material aqueous solution is supplied. The manufacturing method as described in.   The amount of the alkali metal salt of polyvalent carboxylic acid added to the raw material aqueous solution is defined as an amount corresponding to 2 to 5 mass% of the amount of nickel contained in the raw material aqueous solution. The manufacturing method according to one item.   The manufacturing method as described in any one of Claims 1-6 performed in the state which heated the said raw material aqueous solution to 50 degreeC or more and 90 degrees C or less at least from the production | generation of the said composite_body | complex to induction of the reduction reaction of the said nickel. A sulfur-containing nickel powder material comprising sulfur-containing nickel particles produced by the production method according to claim 1,
The average particle size is 30-300 nm,
The sulfur content nickel powder material whose sulfur content rate is 0.1-5 mass% with respect to nickel total mass.