KR100907424B1 - Method of preparation fine nickel powders in aqueous solution under wet chemical process and fine nickel powers prepared by the method - Google Patents

Abstract

The present invention comprises the steps of forming an aqueous solution of nickel sulfide and sodium hydroxide; Adding a nonionic surfactant to the nickel sulfide aqueous solution and the sodium hydroxide aqueous solution; Mixing the two aqueous solutions to prepare an aqueous solution of nickel hydrate, and injecting and stirring the mixture into a reactor; Adding a reducing agent to the mixed reactor and preparing a fine nickel powder by a reduction reaction; And recovering the fine nickel powder, washing with distilled water repeatedly, and then removing and drying the impurities, thereby providing a spherical nickel fine powder prepared by the wet reduction method and the spherical nickel fine powder prepared by the above method. According to the present invention, the use of a nonionic surfactant makes it easy to control the shape and particle size of particles and to produce spherical nickel powder of 100 nm class by an eco-friendly wet reduction method.

MLCC, nickel powder, wet reduction method, nonionic surfactant

Description

Method of preparation fine nickel powder prepared by the wet reduction method and spherical nickel powder prepared by the method {Method of preparation fine nickel powders in aqueous solution under wet chemical process and fine nickel powers prepared by the method}

The present invention relates to a method for producing a spherical nickel fine powder by the wet reduction method and to a spherical nickel fine powder prepared by the method, after the addition of sodium hydroxide (NaOH) to the aqueous nickel sulfide solution to form a nickel hydrate, the hydrazine ( Hydrazine) is sequentially added to extract the nickel powder, but by controlling the initial particles of the nickel hydrate using sugar, an environmentally friendly nonionic surfactant, in the manufacturing method to finally synthesize the spherical Ni powder of 100nm class The present invention relates to a method for producing spherical nickel powders according to size and input amount of sugar in a nickel powder manufacturing process by a wet cyclic method, and to spherical nickel fine powders produced by the method.

Multilayer Ceramic Capacitors (MLCCs) are fabricated by integrating ceramic dielectric materials and internal electrodes alternately, and then integrating the layers together by pressing and attaching these layers and firing the resulting assembly. Condenser.

According to the miniaturization and high capacity of electronic components in recent years, multilayer ceramic capacitors used as electrode materials have to have a large number of stacked layers, so that the use of Pd and Pt has to increase the price of electronic components. Therefore, research is being actively conducted to replace inexpensive nickel or nickel-like electrode materials. The electrode material powder synthesis method is largely divided into gas phase reaction method and liquid phase precipitation method.

Japanese Patent Laid-Open No. Hei 8-246001 discloses a gas phase reaction method for reducing and depositing nickel powder by contacting nickel chloride vapor with a reducing gas such as hydrogen. This method has a problem in that particle size is not easily controlled because particles are formed by instantaneous reactions in a gaseous state, but relatively high in monodispersity, high in production cost, low in productivity, and simultaneously in nucleation and nuclear growth.

On the other hand, Japanese Patent Application Laid-Open No. 7-207307 discloses reaction by treating a reducing agent having a specific temperature and concentration by adding strong alkali to a nickel brine solution having a specific concentration to adjust the temperature and pH of the mixture to a specific value. A liquid precipitation method is disclosed in which the reaction is terminated within a specific reaction time. Since this method causes a reduction reaction in aqueous solution, the produced nickel powder easily aggregates, and once aggregated in the aqueous solution, the cohesive force increases more during filtration and drying. Therefore, the resultant powder has a problem that not only the particles are large and not uniform, but also the dispersibility is not good.

Korean Laid-Open Patent Publication No. 2004-94096 discloses a method for preparing spherical nickel fine powder by adding a dispersant and an organic solvent to a solvent in order to improve particle size distribution and reduce particle size among research methods focusing on liquid precipitation which is capable of mass production. It is starting. However, such a manufacturing method has a problem in that it is not environmentally friendly in the manufacturing process because it is difficult to remove the dispersant and the reaction residue organic solvent is an additive harmful to the human body.

In order to solve the above problems, it is an object of the present invention to provide a method for producing spherical nickel fine powder which is easy to control the shape and size of particles using a nonionic surfactant.

In addition, an object of the present invention is to provide a spherical nickel fine powder prepared by the above production method using a nonionic surfactant in order to solve the above problems.

In order to achieve the above object, the present invention

Forming an aqueous solution of nickel sulfide and sodium hydroxide;

Adding a nonionic surfactant to the nickel sulfide aqueous solution and the sodium hydroxide aqueous solution;

Mixing the two aqueous solutions to prepare an aqueous solution of nickel hydrate, and injecting and stirring the mixture into a reactor;

Adding a reducing agent to the mixed reactor and preparing a fine nickel powder by a reduction reaction; And

After recovering the fine nickel powder and washed repeatedly with distilled water, and removing impurities and drying, it provides a method for producing a spherical nickel fine powder by a wet reduction method comprising a.

The nonionic surfactant is preferably one selected from sugar, polyethylene glycol fatty acid ester, glycerin ester, sorbitan ester, and propylene glycol ester.

The concentration of nickel sulfide is preferably 0.16M to 2.00M.

The temperature of the reactor is preferably adjusted to 50 to 90 ℃.

The concentration of the nonionic surfactant is preferably in the range of 0.005M ~ 0.1M.

In order to achieve the above another object, the present invention

An aqueous solution of nickel sulfide and sodium hydroxide was formed, and a nonionic surfactant was added to the aqueous nickel sulfide solution and an aqueous sodium hydroxide solution. Then, the two aqueous solutions were mixed to prepare an aqueous solution of nickel hydrate, which was then injected into a mixture reactor. After stirring, a reducing agent is added to the mixing reactor, a fine nickel powder is prepared by a reduction reaction, the fine nickel powder is recovered, washed repeatedly with distilled water, and impurities are removed and dried to provide a spherical nickel fine powder.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The present invention comprises the steps of forming an aqueous solution of nickel sulfide and sodium hydroxide; Adding a nonionic surfactant to the nickel sulfide aqueous solution and the sodium hydroxide aqueous solution; Mixing the two aqueous solutions to prepare an aqueous solution of nickel hydrate, and injecting and stirring the mixture into a reactor; Adding a reducing agent to the mixed reactor and preparing a fine nickel powder by a reduction reaction; And recovering the fine nickel powder, washing with distilled water repeatedly, and then removing and drying the impurities, thereby providing a spherical nickel fine powder by the wet reduction method.

The present invention relates to a method for producing spherical nickel powder by the wet reduction method of the novel method. 1 shows the synthesis mechanism of spherical nickel fine powder according to the present invention. Referring to FIG. 1, a nonionic surfactant is added to each of an aqueous nickel sulfide (NiSO ₄ ) solution and sodium hydroxide (NaOH), and both aqueous solutions are mixed to form nickel hydrate, and then a reducing agent is sequentially added to extract nickel powder. can do. According to the present invention, particles of nickel hydrate can be controlled using a nonionic surfactant, and finally, 100 nm-class spherical nickel (Ni) powder can be synthesized by a reduction reaction at an optimum reaction temperature and time. This is because the initial particles of the nickel hydrate can be controlled by the steric stabilization and the hindering action of the nonionic surfactant.

It is preferable that the nonionic surfactant used in order to prevent grain coagulation and aggregation is one selected from sugar, polyethylene glycol fatty acid ester, glycerin ester, sorbitan ester, and propylene glycol ester.

The concentration of nickel sulfide is preferably 0.16M to 2.00M. When the concentration of the nickel sulfide is less than 0.16M, it is not preferable because of the problem of agglomeration of the secondary particles by the remaining filters after the formation of the initial particles, and when the concentration of the nickel sulfide exceeds 2.00M, the particle generation of nickel is limited. And is undesirable due to the problem of residues remaining in the form of nickel salts.

The temperature of the mixed reactor is preferably adjusted to 50 to 90 ℃. If the temperature of the mixed reactor is less than 50 ℃ the reduction reaction by the hydrazine (Hydrazine) is not preferable, and if it exceeds 90 ℃, the secondary particles due to the high temperature in the reaction vessel after the formation of the primary particles are agglomerated It is not desirable to occur.

The concentration of the nonionic surfactant is preferably in the range of 0.005M to 0.1M. If it is less than 0.005M, since the activity of the surfactant for the entrant fish is significantly lowered, it is not preferable. If it exceeds 0.1M, the excessive amount of the surfactant prevents the production of primary particles, so that the formation of nickel powder is appropriate. Because it is not desirable.

According to the present invention, a nickel powder having a particle size of 100 nm class and excellent in particle size distribution having a spherical shape is obtained. The nickel hydrate is formed by mixing the nickel sulfide aqueous solution and the sodium hydroxide aqueous solution to which the nonionic surfactant is added, but the nickel hydrate particles are dispersed well due to the steric hindrance effect of the nonionic surfactant polymer. In this state, a reducing agent is added and reacted at a reduction temperature (60 ° C.) of the nickel powder. At this time, the particle agglomeration due to the collision of the initial nickel fine particles, which may occur in the reduction reaction, may be alleviated by the polymer chain of the nonionic surfactant. In addition, environmental pollution can be reduced by using nonionic surfactants, which are environmentally friendly materials, and refraining from using ionic surfactants, which are environmentally problematic.

Figure 3 shows a process for producing spherical nickel fine powder prepared by the wet reduction method according to an embodiment of the present invention. Referring to FIG. 3, an aqueous nickel sulfide solution of preferably 0.16M to 2.00M concentration is prepared using distilled distilled water as a solvent. A nonionic surfactant was added to the nickel sulfide aqueous solution, and the formation of nickel by the reduction reaction of the reducing agent occurred under conditions of pH 10 or more, so that sodium hydroxide was added so that the pH was 12 or more. In addition to sodium hydroxide, a nonionic surfactant is added in advance and mixed with nickel sulfide.

The mixed reaction suspension is maintained at the desired reaction temperature and then stirred in a stirrer. After stirring for a predetermined time, a reducing agent is added and stirred again. The reaction time is preferably 30 minutes to 2 hours. The filtrate is separated from the obtained precipitate, washed several times with secondary ion distilled water, alcohol and acetone to remove unreacted impurities present in the precipitate, filtered and dried in a drier for 10 to 18 hours to obtain a final product.

According to a preferred embodiment of the present invention, nickel sulfide and sodium hydroxide are each made into an aqueous solution at a constant ratio to synthesize 100 nm-spherical nickel fine powder, and then sugar is added as a nonionic surfactant.

NiSO ₄ 6H ₂ O + H ₂ O + sugar (C ₁₂ H ₂₂ O ₁₁ )

NaOH + H ₂ O + sugar (C ₁₂ H ₂₂ O ₁₁ )

The two mixed aqueous solutions are mixed again to form an aqueous solution of nickel hydrate.

NiSO ₄ 6H ₂ O + NaOH ⇒ Ni (OH) ₂ + NaSO ₄ + 6H ₂ O + sugar

The prepared secondary mixture is injected into the reactor and stirred at a temperature of 50 to 90 ° C. for a predetermined time. After a predetermined time, a certain amount of reducing agent (Hydrazine) is added and stirred at 50 to 90 ° C. for a predetermined time to reduce the reaction.

2Ni (OH) ₂ + NaSO ₄ + 6H ₂ O + N ₂ H ₄ H ₂ O + sugar

⇒ 2Ni + NaSO ₄ + 11 H ₂ O + sugar

Finally, the fine nickel powder produced is washed and dried.

Ni + H ₂ O + sugar ⇒ (washing) Ni + H ₂ O

Ni + H ₂ O ⇒ dry Ni

By the above reaction, a nickel powder having a particle size of 100 nm class and excellent in particle size distribution having a spherical shape is obtained. Nickel hydrate is formed by mixing the nickel sulfide aqueous solution and sodium hydroxide aqueous solution to which sugar is added, but nickel hydrate particles are dispersed well due to the steric hindrance effect of sugar. In this state, a reducing agent is added and reacted at a reduction temperature (60 ° C.) of the nickel powder. At this time, the particle agglomeration due to the collision of the initial nickel fine particles, which may occur in the reduction reaction, may be alleviated by the polymer chain of sugar.

According to the present invention, the use of a nonionic surfactant makes it easy to control the shape and particle diameter of the particles and can produce spherical nickel powder of 100 nm class by an environmentally friendly wet reduction method.

The following experiment was carried out to determine the extent to which the addition of environmentally friendly nonionic surfactants used as surfactants in the synthesis of Ni powder by the wet reduction method affects the shape and size of the particles.

The apparatus used for the synthesis in the present invention is an oil bath [HAN BAEK SCIENTIFIC (Model HB-205WM)] nickel fine powder synthesis apparatus, which is shown in FIG. 2. The flask 4 is equipped with a regulator 1, a thermocouple 2 for controlling temperature and a cooler 3. The flask 4 is contained in an oil bath 6 for controlling the reaction rate. In addition, an agitator 5 is provided inside the flask 4 for smooth mixing.

Example 1

100 ml of nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O, Junsei Chemical Co., Ltd. 98%) with 24% nickel metal content and 100 ml of aqueous solution of sodium hydroxide (NaOH, Kanto Chemical Co., Ltd. 97%) 0.3423 g of 0.001 M sugar (C ₁₂ H ₂₂ O ₁₁ ) was added to each of the two solutions. At a reaction temperature of 60 ° C., 117.7568 ml of hydrazine hydrate (N ₂ H ₄ · H ₂ O, Junsei Chemical Co., Ltd. 80%) as a reducing agent was added to the mixed solution and reduced. At this time, the color of the solution was changed to black after about 10 minutes by stirring in the whole process for a uniform reaction. To remove impurities in the reactants, the precipitated product was washed several times with water and dried to prepare a fine nickel powder. The shape and size of the fine nickel powder particles were observed by scanning electron microscopy (SEM), and the results are shown in FIG. 4A. The shape of the particles showed a shape close to a spherical shape.

Example 2

The same procedure as in Example 1 except that 0.3423g of 0.001M sugar was added and the temperature of the thermostat was set to 50 ° C., 70 ° C., 80 ° C., and 90 ° C., respectively. Nickel fine powder was prepared through. The shape and size of the fine particles of nickel powder were observed by scanning electron microscopy (SEM), and the results are shown in FIGS. 5A to 5D, respectively. The shape of the particles showed a shape close to a sphere.

Example 3

To determine the degree of change of the concentration of the starting material nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) on the shape and size of the particles, fix the sugar concentration to 0.001M at the reaction temperature of 60 ℃. The fine nickel powder was prepared by changing the concentration of phosphorus nickel sulfate hexahydrate to 0.16M, 0.32M, 0.80M, 0.96M, 1.50M, and 2.00M, respectively. Particle shape and size of the prepared powder were observed by scanning electron microscopy (SEM) photographs, and SEM photographs observing the results are shown in FIGS. 6A to 6F, respectively.

Example 4

The reaction temperature was fixed at 60 ° C., and the concentration of the starting material nickel sulfate hydrate was fixed at 0.64M to determine the effect of sugar on the size and shape of the produced nickel particles. Nickel fine powder was prepared while changing to 0.025M, 0.05M, 0.1M. The particle shape and size of the prepared powder were observed by scanning electron microscopy (SEM) photographs, and SEM photographs observing the results are shown in FIGS. 7A to 7D, respectively.

Comparative Example 1

100 ml of nickel sulfate hexahydrate (NiSO ₄ .6H ₂ O) and 100 ml of aqueous sodium hydroxide (NaOH) solution were mixed. At a reaction temperature of 60 ° C., 117.7568 ml of hydrazine hydrate (N ₂ H ₄ · H ₂ O) as a reducing agent was added to the mixed solution to reduce the mixture. At this time, the color of the solution was changed to black after about 10 minutes by stirring in the whole process for a uniform reaction. To remove impurities in the reactants, the precipitated product was washed several times with water and dried to prepare a fine nickel powder. The shape and size of the fine nickel powder particles were observed by scanning electron microscopy (SEM), and the results are shown in FIG. 4B. The shape of the particles was not close to a sphere.

Comparative Example 2

0.36445 g of cationic surfactant CTAB: cetyl trimethyl ammonium bromide (C ₁₉ H ₄₂ BrN) was added to 100 ml of an aqueous solution of nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and 100 ml of an aqueous solution of sodium hydroxide (NaOH). The same process as in Comparative Example 1 was conducted except that the two solutions were mixed. The particle shape and size were observed by SEM photographs and the results are shown in FIG. 4C. The shape of the particles was not close to a sphere.

Comparative Example 3

Into 100 ml of nickel sulfate hexahydrate (NiSO ₄ · 6H ₂ O) and 100 ml of sodium hydroxide (NaOH) aqueous solution, 0.0021M of anionic surfactant SLS: 0.421 g of sodium laury sulfate (Na ₄ O ₇ P ₂ ) was added. It carried out similarly to the comparative example 1 except having mixed the solution. Particle shape and size were observed by SEM photographs, and the results are shown in FIG. 4D. The shape of the particles was not close to a sphere.

Evaluation results

Particle shape and size

The particles according to Examples 1 to 4 were close to a spherical shape, but the particles according to Comparative Examples 1 to 3 had impurities formed around the produced nickel (Ni) particles and were not close to the spherical shape. As a result of comparing the size of the particles, Examples 1 to 4 were added when anionic surfactants (SLS) or cationic surfactants (CTAB) were added (Comparative Examples 2 and 3) or when nothing was added (Comparative Examples). Particles smaller than 1) could be obtained.

Reaction temperature

In the SEM photographs of FIGS. 5A to 5D, it may be observed that the size of the particles increases as the reaction temperature increases. It is believed that the higher the temperature, the larger the particle size because of the higher rate of nuclear growth compared to nucleation. In addition, when compared with FIG. 4 (b), the produced particles were the smallest when the reaction temperature was 60 ° C., and the shape of the particles was the most spherical at the high temperature of 90 ° C. It was. However, as the reaction temperature increased, the particles were close to a spherical shape, but the particles were relatively agglomerated, and the size distribution of the particles was not uniform as compared to 60 ° C.

Concentration of nickel sulfide

As the concentration of the nickel sulfide as a starting material increases, the particle size decreases, and as shown in FIG. 6E, the concentration of nickel sulfide increases again when the concentration of the nickel sulfide is 1.5M or more. When the concentration of the starting material required for the initial reaction is small, the unreacted OH group sticks around the particles which are generated, resulting in relatively large particles, and the particle size of the particles is not uniform due to excessive reaction of the reducing agent.

And if the excess concentration of the starting materials in the initial reaction is expected to be reduced both Ni ^{2 +} ions results in the agglomeration of the particles remain in the generation not generating a Ni particles solution increases the size of the particles. When the concentration of nickel sulfide as the starting material is 0.64M, it can be seen that the reaction most closely matches the initial conditions of the pH adjusting agent NaOH and the reducing agent hydrazine hydrate.

Concentration of sugar

As can be seen in Figure 7 (d), the excessive addition of sugar rather inhibits the production of nickel particles and can lead to aggregation of the produced particles. As a result, the reaction temperature was 60 ° C, the initial concentration of nickel sulfide as the starting material was 0.64M, the concentration of NaOH as the pH regulator was 2.4M, and the concentration of the hydrazine hydrate as the reducing agent was 7: 1 by mass ratio. In addition, the case where the concentration of sugar is 0.025M is considered to be the method having the narrow particle size distribution of monodispersion in the particle generation.

Results of X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) of nickel fine powder by wet reduction method using sugar, an environmentally friendly nonionic surfactant, are shown in FIGS. 8 and 9.

Figure 1 illustrates the synthesis mechanism of the spherical nickel fine powder in the present invention.

Figure 2 shows a schematic diagram of the wet reduction method used in the present invention.

Figure 3 shows a flow chart of the production of spherical nickel fine powder in the present invention.

FIG. 4 shows a scanning electron micrograph (SEM) of spherical nickel fine powder prepared according to Example 1. FIG.

FIG. 5 shows a scanning electron micrograph (SEM) of spherical nickel fine powder prepared according to Example 2. FIG.

6 shows a scanning electron micrograph (SEM) of spherical nickel fine powder prepared according to Example 3. FIG.

FIG. 7 shows a scanning electron micrograph (SEM) of spherical nickel fine powder prepared according to Example 4. FIG.

Figure 8 shows the results of X-ray diffraction analysis (XRD) of the product by the addition of sugar in the production of spherical nickel fine powder using the wet reduction method.

Figure 9 shows the scanning micrograph (SEM) results of the product by the addition of sugar in the production of spherical nickel fine powder using the wet reduction method.

Claims (7)

Forming an aqueous solution of nickel sulfide and sodium hydroxide; Adding 0.005M to 0.1M of sugar to the aqueous nickel sulfide solution and aqueous sodium hydroxide solution; Mixing the two aqueous solutions to prepare an aqueous solution of nickel hydrate, and injecting and stirring the mixture into a reactor; Adding a reducing agent to the mixed reactor and preparing a fine nickel powder by a reduction reaction; And Recovering the fine nickel powder, washing with distilled water repeatedly, and then removing and drying the impurities. The method for preparing the spherical nickel fine powder by the wet reduction method comprising the above. delete The method of claim 1, wherein the nickel sulfide aqueous solution has a concentration of 0.16M to 2.00M. The method of claim 1, wherein the temperature of the mixed reactor is adjusted to 50 to 90 ℃ the method of producing a spherical nickel fine powder by the wet reduction method. delete The method of claim 1, wherein the reducing agent is a hydrazine (hydrazine). delete

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