KR20090028019A - Preparation of nickel powder using aqueous sodium hypophosphite solution as a reducing agent - Google Patents

Abstract

Preparation of nickel powder using aqueous sodium hypophosphite solution is provided to prepare nickel power by autocatalytic reduction reaction within a short time at the room temperature of 20~30°C without using expensive alkali boron hydride nor explosive hydrazinium compound. Preparation of nickel powder using aqueous sodium hypophosphite solution comprises a step of dissolving nickel chloride hexahydrate in the distilled water at 20~30°C, a step of creating hydroxide nickel by adding NaOH, a step of obtaining nickel powder by reducing the hydroxide nickel with aqueous sodium hypophosphite solution, and a step of filtering, washing, and drying the nickel powder.

Description

Preparation of nickel powder using aqueous sodium hypophosphite solution as a reducing agent}

The present invention relates to a method for producing nickel powder using an aqueous sodium hypophosphite solution, and more particularly, nickel hydroxide and / or nickel produced by dissolving nickel chloride hexahydrate in distilled water and adding sodium hydroxide and / or a complexing agent. A method of producing fine nickel powder at room temperature by adding an aqueous sodium hypophosphite solution as a reducing agent to a complex.

Silver white nickel, which accounts for 0.007% of the earth's crust, is one of the most widely used metals today as a major component of metal alloys. Nickel has FCC crystalline lattice, high ductility and malleability, good corrosion resistance and oxidation resistance in most industrial applications, and because of its thermal conductivity and mechanical strength, it retains its unique mechanical and physical properties in harsh conditions. Easily alloy with metals. Nickel powder is composed of magnetic materials, electrical contact materials, adhesives of metal carbides, catalysts, welding rod coating materials, plasma spray coatings, powder metallurgy, conductive plastic and multilayer ceramic capacitor internal electrode materials (MLCC), porous electrodes of nickel batteries and fuel cells, The range of applications will be further increased, showing various applications such as steam generators, cathode materials, fluorescent lamps, heat exchangers, heat shields, catalysts, etc. (Korean Patent Publication No. 2003-66171).

To date, a method of producing nickel powder is known as a wet reduction method or a gas phase method. The gas phase method is divided into gas phase synthesis method and spray pyrolysis method. Vapor phase synthesis is a technique for producing nickel powder by reducing the vapor of the nickel precursor at a high temperature. Nickel precursors grow particles according to nucleation and growth mechanisms to obtain nickel powders with an average particle size in the range of 0.1-1.0 μm. Spray pyrolysis is a method of generating droplets from a nickel precursor solution and pyrolyzing them into nickel powder. That is, crystalline metal particles are obtained by spraying an aqueous solution or an alcohol solution in which a nickel precursor is dissolved into fine droplets in a droplet generator, and drying and pyrolyzing in a high temperature furnace. Metal powders produced by gas phase synthesis and spray pyrolysis are relatively high in monodispersity, but control of particle size distribution is not easy because high production cost, low productivity, nucleation and growth occur simultaneously.

The wet reduction method is a method of producing metal powder using a reducing agent such as hydrazine (which is used in most reduction reactions) as a nickel precursor, which has the advantages of low production cost and easy mass production on an industrial scale, but strong cohesive strength. It is not easy to prepare a powder with controlled particle size and shape. In order to solve these problems, studies are being actively conducted in the developed countries to prepare metal powders whose composition and microstructure are controlled by an aqueous metal salt solution or a non-aqueous solution process.

Republic of Korea Patent No. 411575 discloses a method for preparing nickel powder after reducing nickel chloride using reducing gas (hydrogen or hydrogen sulfide) and chlorine gas. Korean Patent No. 490678 discloses nickel powder by dissolving a water-soluble nickel compound selected from nickel nitrate, nickel sulfate, and nickel chloride in distilled water and adding hydrazine and sodium hydroxide. Korean Patent No. 10-572742 prepared an aqueous solution by dissolving a nickel salt in an aqueous alcohol solution, followed by adding NaOH, sodium carboxylmethylcellulose (dispersant), and hydrazine hydrate (reducing agent) to obtain a reaction slurry. Nickel powder was recovered from the reaction slurry using a 2.45 GHz (output 700 W) microwave heating apparatus after a reduction reaction at 50 ° C. for 10 minutes. Korean Patent Laid-Open Publication No. 2003-66171 discloses nickel powder by producing a reaction solution by dissolving nickel sulfate, silver nitrate, sodium hydroxide, ammonia water (or sodium carbonate), and hydrazine hydrate in distilled water. The hydrothermal synthesis temperature is 150 ° C., and the reduction time is 2 hours. Korean Patent Laid-Open Publication No. 2006-59018 discloses a method for producing nickel powder by spray pyrolysis. The nickel metal powder manufacturing step includes droplet generation of a nickel precursor solution in which nickel nitrate and nickel acetate are mixed, drying (100 to 700 ° C.) and pyrolysis (900 to 1500 ° C.) of nickel solution droplets. Korean Patent Laid-Open Publication No. 2006-60331 prepared a solution in which sodium hydroxide aqueous solution and nickel chloride were mixed, and then nickel powder was prepared using diethanol amine and triethanol amine as a dispersion medium, hydrazine hydrate or hydrazine as a reducing agent.

As described above, many studies on the production of nickel particles have been conducted. Hydrazine hydrate is mainly used as a reducing agent in a solution in which a water-soluble nickel salt is dissolved. The reduction method is a wet reduction reaction by heating except for special methods such as hydrothermal synthesis, microwave irradiation, and gas phase spraying. PVP, gelatin, and carboxylmethyl cellulose (CMC) are used as surfactants to stabilize the produced nickel particles, and the reduction temperature range is 60 to 80 ° C.

Therefore, the present inventors can replace the hydrazine hydrate or hydrazine which is a risk of explosion, and conducted a series of studies to escape the high temperature reduction conditions (60 ~ 80 ℃) and nickel hydroxide, complexing agent, hypophosphoric acid at 20 ~ 30 ℃ It has been found how nickel powders can be prepared using aqueous sodium solutions.

Accordingly, an object of the present invention is to reduce nickel chloride hexahydrate by dissolving nickel chloride hexahydrate in distilled water at room temperature and adding sodium hypophosphite as an reducing agent to the nickel hydroxide and / or nickel complex formed by adding sodium hydroxide and / or a complexing agent. The nickel powder solution is prepared, and the nickel powder is prepared by filtration, washing, and drying.

In order to achieve the above object,

The present invention

Dissolving nickel chloride in distilled water at 20 ° C to 30 ° C;

Adding sodium hydroxide and / or complexing agent to produce nickel hydroxide and / or nickel complex;

Preparing a nickel powder by reducing the nickel hydroxide and / or nickel complex with an aqueous sodium hypophosphite solution; And

Filtering, washing and drying the precipitated nickel powder

Characterized in that the method for producing a nickel powder comprising a.

As described above, the present invention is a technique for producing a nickel powder by reducing the sodium hydroxide and / or nickel complex compound after the addition of sodium hydroxide and / or a complexing agent to nickel chloride to an aqueous solution of sodium hypophosphite to water-soluble nickel salt Alkali boron hydride and explosive hydrazine compounds, which are expensive reducing agents, are not used, and nickel powder can be produced by autocatalytic reduction in a short time at room temperature (20 to 30 ° C) instead of high reduction temperature (60 to 80 ° C). Do.

Hereinafter, the present invention will be described in more detail.

The present invention

Dissolving nickel chloride in distilled water at 20 to 30 ° C .;

Adding sodium hydroxide and / or complexing agent to produce nickel hydroxide and / or nickel complex;

Preparing a nickel powder by reducing the nickel hydroxide and / or nickel complex with an aqueous sodium hypophosphite solution; And

Filtering, washing and drying the precipitated nickel powder

Characterized in that the method for producing a nickel powder comprising a.

First, nickel chloride is dissolved in distilled water at a water-soluble 20-30 ° C. In addition, the concentration of the water-soluble nickel salt dissolved in the distilled water is preferably 5 to 15% by weight. If it is out of the above range, due to the intense nickel reduction reaction, there is a problem in temperature control or there is a disadvantage that the nickel recovery is lowered.

After dissolving distilled water, sodium hydroxide is added to produce nickel hydroxide. A hydroxyl group (OH ^-) alkali salt to give the sodium hydroxide is preferred when considering solubility in water and economical efficiency.

The weight ratio of nickel chloride hexahydrate to sodium hydroxide is preferably 0.5: 1 to 1.5: 1. This range is a condition under which the production of nickel hydroxide can be optimized, and it is very advantageous to exist in the form of nickel hydroxide rather than nickel ions to prepare nickel particles. This is because there is a great difference between the potential of reduction from nickel ions to nickel metal and the potential of reduction of nickel hydroxide to nickel metal. Nickel metals are produced relatively easily in nickel hydroxide because of their low reduction potential without hydrogen evolution. The pH range required for the conversion of metallic nickel in nickel hydroxide is 9-12. If the pH is less than 9 Nickel is present and if it exceeds a pH 12 as a nickel ion are nickel HNiO ₂ ^- present in the form of so-reduction reaction rate does not become reduced to nickel metal is rapidly decreased.

Nickel hydroxide produced by the reaction of sodium hydroxide with nickel chloride hexahydrate can be mixed with the complexing agent or immediately reduced by an aqueous sodium hypophosphite solution without the complexing agent. In the present invention, an aqueous sodium hypophosphite solution was selected as a reducing agent for process hazards or a reduction reaction in the range of 20 to 30 ° C. The aqueous sodium hypophosphite solution is sold as an industrial grade in the art and the concentration of sodium hypophosphite is 37% or 50% by weight. In the present invention, an aqueous sodium hypophosphite solution having a hypophosphite concentration of 50% by weight was used as the reducing agent. Also, in the present invention, EDTA (ethylenediamine tetraacetic acid) tetrasodium and an aqueous ammonia solution having a relatively high stability constant for a complex compound were selected as the complexing agent. The aqueous ammonia solution is sold as an industrial grade used in the art, and the ammonia concentration is about 28%. Since pure EDTA has low solubility in water, it is difficult to dissolve in an aqueous phase. Thus, tetrasodium EDTA was used in the present invention. When mixed with a complexing agent and then reduced by an aqueous sodium hypophosphite solution, the weight ratio of sodium hydroxide to the complexing agent is preferably 1: 1 to 2: 1, considering the stoichiometric ratio and the reaction conditions. This is because it is the minimum amount to form a nickel complex in nickel. In this case, the weight ratio of the complexing agent to the aqueous sodium hypophosphite solution is maintained as 1: 1 to 1:20, which is to prevent evaporation of distilled water at the same time without vigorously inducing a reduction reaction of the nickel complex formed in the distilled water. to be. When no nickel complexing agent is used and the nickel reduction reaction takes place from the aqueous nickel chloride solution by an aqueous sodium hypophosphite solution, a mixing ratio of nickel hydroxide and aqueous sodium hypophosphite solution is preferably 1:20 to 1:35.

The step of producing nickel hydroxide by adding sodium hydroxide after dissolving the nickel chloride hexahydrate can be omitted, and after the complexing agent is mixed with the dissolved nickel chloride hexahydrate solution in a proportion, an aqueous sodium hypophosphite solution is added. Although nickel powder can be manufactured by reduction of nickel, the weight ratio of nickel chloride hexahydrate and a complexing agent is suitable for the weight ratio of 1: 0.4-1: 4. When the content of the complexing agent is too large, it is difficult to generate a nickel complex compound suitable for the reduction reaction, so that the reduction reaction potential is high, so that the induction time of the reduction reaction may be long. When an aqueous sodium hypophosphite solution is added as the reducing agent, it is preferable to add about 1 to 10 parts by weight of an aqueous sodium hypophosphite solution based on 1 part by weight of nickel chloride hexahydrate. If the sodium hypophosphite aqueous solution is less than 1 part by weight, the reduction reaction is not induced in the range of 20 to 30 ° C and heating is required. On the other hand, when the sodium hypophosphite aqueous solution exceeds 10 parts by weight, coarse particles are generated due to a very rapid reduction reaction and generation of water vapor.

In the present invention, the reduction reaction is started immediately after the sodium hypophosphite aqueous solution is added, and the time point of completion of the reduction reaction is within 30 minutes (5 minutes to 30 minutes) when the sodium hypophosphite aqueous solution is added dropwise.

The nickel powder produced by the reduction reaction is washed, filtered and dried.

As such, alkaline boron hydrides and explosive hydrazine compounds, which are expensive reducing agents, are not used for water-soluble nickel salts. It is possible to produce nickel powder.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

Example 1

2.3 g of nickel chloride hexahydrate was completely dissolved in distilled water at 20 ° C. The amount of distilled water added at this time was 46.4 g. After the nickel chloride hexahydrate was completely dissolved, 2.1 g of sodium hydroxide was added to produce 0.81 g of nickel hydroxide. 1.07 g of EDTA.4Na was added as a complexing agent. A reducing agent of 18.82 g of sodium hypophosphite solution was added. After addition of aqueous sodium hypophosphite solution, the reduction reaction proceeded rapidly (5 minutes), yielding 0.52 g of black nickel powder (yield 91.56%). Nickel powder was filtered, washed and dried.

1 shows the XRD diffraction diagram of the nickel hydroxide produced. Figure 2 shows the XRD diffraction diagram of the nickel powder prepared from the resulting nickel hydroxide. Nickel obtained from the XRD diffraction diagram can be seen that the hexagonal (hexagonal) structure.

Example 2

0.51 g of nickel chloride hexahydrate was completely dissolved in distilled water at 25 ° C. The amount of distilled water added at this time was 4.93 g. After the nickel chloride hexahydrate was completely dissolved, 0.824 g of sodium hydroxide was added. 0.15 g of precipitated nickel hydroxide was produced. 4.67 g of sodium hypophosphite aqueous solution was added. After the addition of aqueous sodium hypophosphite solution, the reduction of nickel proceeded rapidly (21 minutes), yielding 0.05 g of black nickel powder (39.7% yield). Nickel powder was filtered, washed and dried.

3 shows an XRD diffraction diagram of the nickel powder obtained in Example 2. FIG. It can be seen that the nickel recovered from the XRD diffraction diagram has a hexagonal structure.

Example 3

2.47 g of nickel chloride hexahydrate was completely dissolved in distilled water at 25 ° C. At this time, the amount of distilled water added was 21.79 g. To 23.26 g of an aqueous nickel solution in which nickel chloride hexahydrate was completely dissolved, 6.98 g of ammonia water (28%) was added as a complexing agent. 7.92 g of aqueous sodium hypophosphite solution as a reducing agent was added. The reduction of nickel proceeded rapidly after addition of aqueous sodium hypophosphite solution (11 minutes), yielding 0.41 g of black nickel powder (67.22% yield). Nickel powder was filtered, washed and dried.

1 shows an X-ray diffraction diagram of nickel hydroxide obtained when sodium hydroxide is added to an aqueous nickel solution.

2 shows an X-ray diffraction diagram of the nickel powder obtained in Example 1. FIG.

3 shows an X-ray diffraction diagram of the nickel powder obtained in Example 2. FIG.

Claims (4)

Dissolving nickel chloride hexahydrate in distilled water at 20 to 30 ° C; Adding sodium hydroxide to produce nickel hydroxide; Preparing a nickel powder by reducing the product as an aqueous sodium hypophosphite solution; Filtering, washing and drying the nickel powder Nickel powder production method comprising a. Dissolving nickel chloride hexahydrate in distilled water at 20 to 30 ° C; Adding sodium hydroxide and a complexing agent; Preparing a nickel powder by reducing the product as an aqueous sodium hypophosphite solution; Filtering, washing and drying the nickel powder Nickel powder production method comprising a. Dissolving nickel chloride hexahydrate in distilled water at 20 to 30 ° C; Adding a complexing agent to produce a nickel-compound; Preparing a nickel powder by reducing the product as an aqueous sodium hypophosphite solution; Filtering, washing and drying the nickel powder Nickel powder production method comprising a. The method according to any one of claims 1 to 3, wherein the complexing agent is an aqueous solution of EDTA tetrasodium or ammonia.

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