KR20070101091A - Method for manufacturing nickel nano particle - Google Patents

Abstract

A method for manufacturing nickel nanoparticles is provided to produce nickel nanoparticles with a smooth surface having uniform size and excellent dispersion stability by reducing a nickel-hydrazine complex formed in reverse microemulsion. A method for manufacturing nickel nanoparticles includes the steps of: (a) forming an aqueous solution comprising a nickel precursor, a surfactant, and a hydrophobic solvent; (b) adding a hydrazine-containing compound into the mixed solution to form a nickel-hydrazine complex; and (c) adding a reducing agent into the mixed solution containing the nickel-hydrazine complex to form nickel nanoparticles. The nickel precursor is at least one compound selected from the group consisting of NiCl2, Ni(NO3)2, NiSO4, and (CH3COO)2Ni.

Description

Method for Manufacturing Nickel Nano Particles

1 is a graph of the XRD analysis of the nickel nanoparticles prepared in Example 1 of the present invention;

Figure 2 is a graph of the TGA analysis of the nickel nanoparticles prepared in Example 1 of the present invention;

Figure 3 is a graph of the particle size analysis of the nickel nanoparticles prepared in Example 1 of the present invention;

4 is a SEM photograph of the nickel nanoparticles prepared in Example 1 of the present invention;

5 is a SEM photograph of the nickel nanoparticles prepared in Example 2 of the present invention; And

Figure 6 is a SEM photograph of the nickel nanoparticles prepared in Example 3 of the present invention.

The present invention relates to a method for producing nickel nanoparticles, and more particularly, to a method for producing nickel nanoparticles having excellent dispersion stability of uniform size by nickel nanoparticles.

In recent years, with the miniaturization of electric devices, miniaturization of electronic components is urgently required. Accordingly, miniaturization and high capacity are required in multilayer ceramic capacitors (MLCCs), and high density and high integration multilayer substrates are also required in substrates.

In such multilayer ceramic capacitors and substrates, expensive precious metal materials such as silver, platinum and palladium have been used as internal conductive materials or electrode materials, but they are being replaced by nickel particles in order to reduce manufacturing costs. Among the multilayer ceramic capacitors, the nickel electrode layer is lower than the layer density of the molded body in powder metallurgy, and the shrinkage amount due to sintering during firing is larger than that of the dielectric layer, so that defects due to interlayer short circuit or disconnection of the nickel electrode are likely to occur. There is. To prevent this problem, the nickel powder used as the inner electrode layer should not contain large particles, and should have a narrow and uniform particle size distribution and excellent dispersibility without aggregation. To this end, there is a need for a method for producing nickel particles having excellent nanoscale dispersion stability and uniform size. However, as a conventional method for preparing nickel particles, a method for preparing nanoparticles having excellent uniformity and dispersion stability under 100 nm has not been proposed.

According to one embodiment of the present invention, a method of gas phase reduction with hydrogen at a high temperature of about 1000 ° C. has been proposed, but this method has a thermal history of reaction under high temperature, so that nucleation and growth occur at the same time, thus the particle size distribution is wide and 1 μm Because of the large particles present, it is insufficient to be applied to internal electrodes or internal wiring. In addition, according to another conventional embodiment, it is possible to prepare the fine powder of the submicron unit by the wet reduction method, but due to the variable reaction, the nanoparticles produced may be non-uniform, the surface of the fine powder is not smooth, 200 nm Although it may be prepared to a size of 1㎛, there is a difficult disadvantage of producing uniform particles of less than 100nm.

The present invention to solve the above problems by forming a nickel-hydrazine complex in a reverse microemulsion and then reducing the method for producing nickel nanoparticles of a smooth surface having a good dispersion stability of a uniform size by It provides the prepared nickel nanoparticles.

The present invention also provides a method for producing nickel nanoparticles having a narrow particle size distribution of 100 nm or less, preferably 10 to 50 nm, and nickel nanoparticles prepared thereby.

According to one aspect of the invention, (a) forming an aqueous solution containing a nickel precursor, a surfactant and a hydrophobic solvent, (b) adding a compound containing a hydrazine to the mixed solution to form a nickel-hydrazine complex And (c) adding a reducing agent to the mixed solution including the nickel-hydrazine complex to form nickel nanoparticles.

The nickel precursor may be at least one compound selected from the group consisting of NiCl ₂ , Ni (NO ₃ ) ₂ , NiSO ₄ and (CH ₃ COO) ₂ Ni. In addition, the surfactant is a group consisting of cetyltrimethylammonium bromide, sodium dodecyl sulfate, sodium carboxymethyl cellulose and polyvinylpyrrolidone It may be one or more compounds selected from. In addition, the surfactant may further include one or more auxiliary surfactants selected from the group consisting of ethanol, propanol and butanol. In addition, the hydrophobic solvent is hexane, cyclohexane, heptane, octane, isooctane, decane, tetradecane, hexatecane, toluene, xylene, 1-octadecene and 1-hexadecene It may be one or more compounds selected from the group consisting of

Here, the nickel precursor may be included in 0.1 to 10 parts by weight based on 100 parts by weight of the aqueous solution.

In addition, the surfactant may be included in 0.1 to 20 moles with respect to 1 mole of distilled water added to the aqueous solution.

In addition, the auxiliary surfactant may be included in 20 to 40 parts by weight based on 100 parts by weight of the distilled water.

In addition, the hydrophobic solvent may be included in 30 to 60 parts by weight based on 100 parts by weight of the aqueous solution.

In addition, the compound containing the hydrazine may be one or more compounds selected from the group consisting of hydrazine (hydrazine), hydrazine hydrate (hydrazine hydrate) and hydrazine hyddrochloride. According to a preferred embodiment, the compound containing the hydrazine may be included in 1 to 10 moles with respect to 1 mole of nickel ions provided by the nickel precursor.

In addition, the reducing agent may be sodium borohydride. According to a preferred embodiment, the sodium borohydride may be included in 0.1 to 1 mol relative to 1 mol of nickel ions provided by the nickel precursor.

In addition, wherein step (a) to step (c) may be performed at 25 to 60 ℃, step (c) may be performed for 0.5 to 2 hours.

It is also possible here to form particles of smooth surfaces having good dispersion stability of uniform size of 10 to 50 nm.

According to another aspect of the present invention, a method for preparing nickel nanoparticles by an inverse microemulsion method comprising the steps of: forming a nickel-hydrazine complex using a compound comprising hydrazine; And it can propose a method for producing a nickel nanoparticles of the smooth surface having a good dispersion stability of uniform size including the step of reducing the nickel-hydrazine complex.

According to another aspect of the present invention, it is possible to present the nickel nanoparticles prepared by the method for producing nickel nanoparticles described above.

Here, it is possible to provide nickel nanoparticles having a smooth surface having excellent dispersion stability with a uniform size of 10 to 50 nm, and to provide nickel nanoparticles including 90 to 97 wt% nickel metal.

According to another aspect of the present invention, it is possible to provide a conductive ink including the above-described nickel nanoparticles.

According to another aspect of the present invention, it is possible to provide a multilayer ceramic capacitor including the nickel nanoparticles described above as an electrode material.

Hereinafter, a method for preparing nickel nanoparticles and nickel nanoparticles prepared according to the present invention will be described in detail. In addition, the reverse microemulsion method will be described first before describing the preferred embodiments of the present invention in detail.

When a poorly soluble substance is dissolved in water or a hydrophilic substance by adding a surfactant, the micelle expands as it is solubilized. At this time, the micelle system expanded by solubilization is called a microemulsion. This microemulsion forms a thermodynamically stable system, which contains an oil-in-water type in which the micelle expands in water or a hydrophilic system, and a large amount of reverse micelles in an oil-in-water or hydrophobic system. Water-in-Oil type is obtained by solubilizing water or hydrophilic substances. The method using this water-in-oil type is called a reverse microemulsion method.

The present invention relates to a method of introducing an arbitrary surfactant by this inverse microemulsion method to form nano-sized uniform fine droplets formed by the surfactant.

In the fine droplets, a compound containing hydrazine is added first to form a complex, and the complex is reduced to form uniform nickel particles, while preventing the aggregation with other fine particles, so that the surface is smooth and has excellent dispersion stability. The particles can be produced. To this end, according to an embodiment of the present invention may include a secondary surfactant.

Method for producing nickel nanoparticles according to the present invention comprises the steps of (a) forming an aqueous solution containing a nickel precursor, a surfactant and a hydrophobic solvent, (b) adding a compound containing a hydrazine to the mixed solution to form a nickel-hydrazine complex Forming and (c) adding a reducing agent to the mixed solution containing the nickel-hydrazine complex to form nickel nanoparticles.

Unlike the method of preparing nanoparticles by the conventional inverse microemulsion method, the nickel complex is first formed and then reduced in order to stably produce nanoparticles of uniform size. In addition, there is an advantage that can be prepared through the steps to produce excellent nickel nanoparticles dispersion stability.

Step by step to prepare a reverse microemulsion comprising a nickel precursor and a surfactant containing a nickel ion. As the nickel precursor, any compound containing nickel ions may be used without limitation, but a nickel salt may be preferably used. Examples of nickel salts include NiCl ₂ , Ni (NO ₃ ) ₂ , NiSO ₄ or (CH ₃ COO) ₂ Ni, which may be used by mixing one or more of them. It is preferable that this nickel precursor is contained in 0.1-10 weight part with respect to 100 weight part of total aqueous solutions. If the nickel precursor is contained less than 0.1 parts by weight, the nickel ions provided are not preferable in terms of efficiency. If the nickel precursor is included in an amount of more than 10 parts by weight, the formed nickel particles are not preferably aggregated together to form nanoparticles. Here, the lower the content of the nickel precursor may form nickel nanoparticles of smaller size.

Surfactants include cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), sodium carboxymethyl cellulose (Na-CMC), polyvinylpyrrolidone ( polyvinylpyrrolidone, PVP) or mixtures thereof. In addition to these surfactants, auxiliary surfactants may be further added to stably form fine micelles. Examples of this co-surfactant include alcoholic compounds such as ethanol, propanol or butanol. Herein, the surfactant may be included in an amount of 0.1 to 20 moles with respect to 1 mole of distilled water added to the aqueous solution, and it is preferable that the surfactant be included in such a ratio because the surfactant may sufficiently cover the distilled water droplets. At this time, the higher the content of the surfactant can form a nickel nanoparticles of a smaller size. In addition, the auxiliary surfactant may be included in 20 to 40 parts by weight based on 100 parts by weight of the distilled water, when included in less than 20 parts by weight does not affect the stabilization of the microemulsion, if included in more than 40 parts by weight of the surfactant This is undesirable because it can inhibit and interfere with stable microemulsion formation.

These nickel precursors and surfactants are mixed with a hydrophobic solvent and distilled water, wherein the hydrophobic solvent is hexane, cyclohexane, heptane, octane, isooctane, decane, tetradecane, hexatecane, toluene, xylene, 1-octa Hydrocarbon-based compounds such as decene (1-octadecene) or 1-hexadecene (1-hexadecene) may be used alone or in combination. The hydrophobic solvent may be included in an amount of 30 to 60 parts by weight based on 100 parts by weight of the aqueous solution. This is because the inclusion of a hydrophobic solvent in this ratio can form a stable reverse microemulsion containing nickel ions.

Next, a nickel complex is formed in the reverse microemulsion. To this end, a compound containing hydrazine is added, for example, hydrazine, hydrazine hydrate or hydrazine hyddrochloride may be used alone or in combination. Herein, hydrazine refers to a compound having a structure of NH ₂ NH ₂ , hydrazine hydrate to NH ₂ NH ₂ · nH ₂ O, and hydrazine chloride to NH ₂ NH ₃ Cl. The compound containing this hydrazine may be added in an amount of 1 to 10 moles with respect to 1 mole of nickel ions provided by the nickel precursor, and if it is contained in less than 1 mole, the nickel complex may not be formed sufficiently. Not desirable in

This is followed by the addition of a reducing agent to the reverse microemulsion to form nickel particles. As the reducing agent added here, sodium borohydride, that is, NaBH ₄ , may be preferably used. Wherein sodium borohydride may be included in 0.1 to 1 mole with respect to 1 mole of nickel ions, if less than 0.1 mole can not sufficiently reduce the nickel-hydrazine complex, if more than 1 mole side reaction occurs excessively and 100% nickel More reducing agents necessary for the reduction are added, which is undesirable in terms of efficiency. 0.5 to 2 hours after the addition of the reducing agent to form a nanoparticle having a narrow particle size distribution of less than 100nm. If the reduction reaction time is less than 0.5 hours, sufficient reduction of nickel ions does not occur, and if it exceeds 2 hours, the nickel particles are excessively grown and become uneven, which is not preferable.

According to a preferred embodiment of the present invention, the reaction temperature is preferably carried out at room temperature, that is, 25 ℃ to 60 ℃, it is not preferable because the reaction occurs rapidly at 60 ℃ difficult to form uniform particles and difficult to control the growth of the particles.

Separating the nickel nanoparticles formed by such a step from the reverse microemulsion by a conventional method in the art, and washing and drying the separated nickel nanoparticles may be further included. For example, nickel nanoparticles may be separated from the mixed solution by centrifugation, and the separated particles may be washed with acetone and distilled water and dried in a vacuum dryer to recover the nanoparticles.

The method for producing nickel nanoparticles and the nickel particles produced thereby are described above through the preferred embodiments, which will be described below with reference to more specific examples.

Example 1

18 g of nickel chloride, 18 g of PVP, 150 g of ethanol, and 150 g of toluene were added to 300 g of distilled water, and mixed with a stirrer at 40 ° C. to prepare a reverse microemulsion. 40 g of hydrazine hydrate was added to this reverse microemulsion aqueous solution and stirred for 30 minutes to form a nickel-hydrazine complex. To the reverse microemulsion in which the nickel-hydrazine complex was formed, 0.04 mol of NaBH ₄ was added and stirred for 1 hour to prepare nickel nanoparticles by reduction. Nickel nanoparticles were separated from the reverse microemulsion using a centrifuge. The separated nanoparticles were washed three times with acetone and distilled water, and then dried in a vacuum dryer maintained at 50 ° C. for 3 hours to collect nickel nanoparticles.

X-ray diffraction examination (XRD) analysis of the nickel nanoparticles prepared in Example 1 is a graph showing the results of FIG. 1. Referring to FIG. 1, only pure nickel crystal phases were formed without impurities and oxides.

In addition, the graph of the results obtained by TGA (Thermogravimetric Analysis) analysis of the nickel nanoparticles prepared in Example 1 is shown in FIG. 2. Referring to Figure 2 it can be seen that the content of the organic material in the formed nickel nanoparticles is 3 to 10% by weight. That is, it was found that 90 to 97% by weight of nickel metal contained in the formed nickel nanoparticles.

In addition, the particle size analysis of the nickel nanoparticles prepared in Example 1 is shown in FIG. Referring to FIG. 3, it was found that nanoparticles having a narrow particle size distribution were formed.

In addition, a SEM (Scanning Electron Microscope) photograph of the nickel nanoparticles prepared in Example 1 is shown in FIG. 4. Referring to FIG. 4, it was confirmed that spherical uniform particles of 30 to 40 nm were formed.

Example 2

18 g of nickel chloride, 20 g of CTAB, 150 g of ethanol, and 150 g of toluene were added to 300 g of distilled water and mixed with a stirrer at 40 ° C. to prepare a reverse microemulsion. 30 g of hydrazine hydrate was added to the reverse microemulsion and stirred for 30 minutes to form a nickel-hydrazine complex. To the reverse microemulsion in which the nickel-hydrazine complex was formed, 0.03 mol of NaBH ₄ was added and stirred for 1 hour to prepare nickel nanoparticles by reduction. Nickel nanoparticles were separated from the reverse microemulsion using a centrifuge. The separated nanoparticles were washed three times with acetone and distilled water, and then dried in a vacuum dryer maintained at 50 ° C. for 3 hours to collect nickel nanoparticles.

SEM photographs of the nickel nanoparticles prepared in Example 2 are shown in FIG. 5. Referring to FIG. 5, it was confirmed that spherical uniform particles of 15 to 20 nm were formed.

Example 3

18 g nickel chloride, 12 g Na-CMC, 150 g ethanol, and 150 g toluene were added to 300 g of distilled water. Inverted microemulsion was prepared by mixing with a stirrer at 40 ° C. 30 g of hydrazine hydrate was added to the above reverse microemulsion and stirred for 30 minutes to form a nickel-hydrazine complex. To the reverse microemulsion in which the nickel-hydrazine complex was formed, 0.03 mol of NaBH ₄ was added and stirred for 1 hour to prepare nickel nanoparticles by reduction. Nickel nanoparticles were separated from the reverse microemulsion using a centrifuge. The separated nanoparticles were washed three times with acetone and distilled water, and then dried in a vacuum dryer maintained at 50 ° C. for 3 hours to collect nickel nanoparticles.

SEM photographs of the nickel nanoparticles prepared in Example 3 are shown in FIG. 6. Referring to FIG. 6, it can be confirmed that spherical uniform particles having a thickness of 30 to 40 nm are formed.

Comparative Example 1

18 g of nickel chloride, 60 g of PVP, 150 g of ethanol, and 150 g of toluene were added to 300 g of distilled water. Inverted microemulsion was prepared by mixing with a stirrer at 40 ° C. To this reverse microemulsion, 0.03 mol of NaBH ₄ was added and stirred for 1 hour to prepare nickel nanoparticles by reduction. Nickel nanoparticles were separated from the reverse microemulsion using a centrifuge. The separated nanoparticles were washed three times with acetone and distilled water, and then dried in a vacuum dryer maintained at 50 ° C. for 3 hours to collect nickel nanoparticles.

The nickel particles prepared by Comparative Example 1 were 15 to 20 nm, but irregular shapes and severe aggregation did not form properly dispersed nanoparticles.

About 4 g of nickel nanoparticles were obtained from 18 g of nickel chloride in Example 1. After redispersion in ethanol and centrifugation at 3000 rpm for 5 minutes, the precipitate was removed to obtain nickel nanoparticles having dispersion stability of about 3.5 g. Similar results were obtained in the case of Examples 2 and 3 by the same method.

In contrast, in the case of Comparative Example 1, when re-dispersed in the same manner, when aggregation was severe, centrifugation was performed at 3000 rpm for 5 minutes, and thus, nickel nanoparticles having a dispersion stability could not be obtained.

Meanwhile, in the method for preparing nickel nanoparticles according to the present invention, nickel chloride and each type of surfactant are shown in Table 1 below in order to confirm the relationship between the size of the nickel nanoparticles according to the content of the nickel precursor and the content of the surfactant. The nickel nanoparticles were prepared by performing the same procedure as in Example 1, except that the contents were added in the contents shown in Table 1 below.

TABLE 1

Nickel chloride Surfactants Average particle size (nm) Example 4 7 g PVP 14 g 34 Example 5 7 g PVP 35 g 18 Example 6 40 g PVP 14 g 55 Example 7 2 g Na-CMC 6 g 35 Example 8 7 g Na-CMC 6 g 52 Example 9 2 g CTAB 22 g 8 Example 10 7 g CTAB 22 g 17

As shown in Table 1, the lower the content of the nickel precursor, the higher the content of the surfactant was confirmed to form the nickel nanoparticles of a smaller size.

[Production of Conductive Ink]

20 cps of conductive ink was prepared by dispersing in an aqueous solution of styrene glycol butyl ether acetate and ethanol and dispersing with an ultra sonicator. The conductive ink thus prepared may be printed on a circuit board by an inkjet method to form conductive wiring.

[Laminated Ceramic Capacitor]

The nickel powders prepared in Examples 1 to 3 were dispersed in a binder to prepare a high viscosity nickel paste, which was then screen printed onto a ceramic dielectric layer of barium titanate, dried, and then stacked and pressed into several layers. It is prepared by firing at about 1300 ° C. under a reducing atmosphere.

In addition, the above-mentioned conductive ink may be inkjet printed onto a ceramic dielectric layer of barium titanate, dried, and then fired in a reducing atmosphere to form internal electrodes.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

As described above, the present invention provides a method for preparing nickel nanoparticles having a smooth surface having excellent dispersion stability of uniform size by forming a nickel-hydrazine complex in an inverse microemulsion and then reducing the nickel produced therefrom. Provide nanoparticles. The present invention also provides a method for producing nickel nanoparticles having a narrow particle size distribution of 100 nm or less, preferably 10 to 50 nm, and nickel nanoparticles prepared thereby.

Claims (22)

(a) forming an aqueous solution comprising a nickel precursor, a surfactant and a hydrophobic solvent; (b) adding a compound containing hydrazine to the mixture to form a nickel-hydrazine complex; And (c) adding a reducing agent to the mixed solution containing the nickel-hydrazine complex to form nickel nanoparticles. The method according to claim 1, The nickel precursor is at least one compound selected from the group consisting of NiCl ₂ , Ni (NO ₃ ) ₂ , NiSO ₄ and (CH ₃ COO) ₂ Ni. The method according to claim 1, The surfactant is selected from the group consisting of cetyltrimethylammonium bromide, sodium dodecyl sulfate, sodium carboxymethyl cellulose and polyvinylpyrrolidone. Method for producing nickel nanoparticles that are one or more compounds. The method according to claim 1, The surfactant is a method for producing nickel nanoparticles further comprising at least one auxiliary surfactant selected from the group consisting of ethanol, propanol and butanol. The method according to claim 1, The hydrophobic solvent is hexane, cyclohexane, heptane, octane, isooctane, decane, tetradecane, hexadecane, toluene, xylene, 1-octadecene and 1-hexadecene Method for producing nickel nanoparticles which is at least one compound selected from the group consisting of. The method according to claim 2, The nickel precursor is a method for producing nickel nanoparticles contained in 0.1 to 10 parts by weight based on 100 parts by weight of the aqueous solution. The method according to claim 3, The surfactant is a method for producing nickel nanoparticles contained in 0.1 to 20 moles per 1 mole of distilled water added to the aqueous solution. The method according to claim 4, The auxiliary surfactant is a method for producing nickel nanoparticles contained in 20 to 40 parts by weight based on 100 parts by weight of the distilled water The method according to claim 5, The hydrophobic solvent is a method for producing nickel nanoparticles contained in 30 to 60 parts by weight based on 100 parts by weight of the aqueous solution The method according to claim 1, The compound containing the hydrazine is a method for producing nickel nanoparticles of at least one compound selected from the group consisting of hydrazine (hydrazine), hydrazine hydrate (hydrazine hydrate) and hydrazine chloride (hydrazine hyddrochloride) The method according to claim 10, The compound containing the hydrazine is a method for producing nickel nanoparticles contained in 1 to 10 moles with respect to 1 mole of nickel ions provided by the nickel precursor The method according to claim 1, The reducing agent is a method for producing nickel nanoparticles which is sodium borohydride The method according to claim 12, The sodium borohydride is a method for producing nickel nanoparticles contained in 0.1 to 1 mol relative to 1 mol of nickel ions provided by the nickel precursor The method according to claim 1, Step (a) to step (c) is a method for producing nickel nanoparticles carried out at 25 to 60 ℃ The method according to claim 1, Step (c) is a method for producing nickel nanoparticles is carried out for 0.5 to 2 hours The method according to claim 1, Method for producing nickel nanoparticles to form particles of a smooth surface having excellent dispersion stability of uniform size of 10 to 50nm. In the method for producing nickel nanoparticles by an inverse microemulsion method, Forming a nickel-hydrazine complex using a compound comprising hydrazine; And a method for producing nickel nanoparticles having a smooth surface having excellent dispersion stability of uniform size, comprising the step of reducing the nickel-hydrazine complex. Nickel nanoparticles prepared according to claim 1. The method according to claim 18, Smooth surface nickel nanoparticles having excellent dispersion stability of uniform size of 10 to 50nm. The method according to claim 18, Nickel nanoparticles comprising 90 to 97% by weight of nickel metal. A conductive ink comprising the nickel nanoparticles of claim 18. A multilayer ceramic capacitor comprising the nickel nanoparticles of claim 18 as an electrode material.

Images