JPS5896802A - Production of fine metallic powder by wet reduction - Google Patents

Abstract

PURPOSE:To produce metallic nickel powder or metallic copper powder surely and safely with simple installations by subjecting the hydroxides or carbonates of nickel or copper obtained from sulfates of nickel or copper to wet reduction. CONSTITUTION:Caustic soda or sodium carbonate or a mixture thereof is added in the form of an aq. soln. to an aq. soln. of nickel sulfate or copper sulfate to allow fine particles or colloidal particles of hydroxides or carbonates of nickel or copper to deposit. Hydrazine or hydrazine hydrate, etc. are added as a reducing agent at about 3-8 equiv. to this slurry-like soln. and the soln. is heated to about 70-90 deg.C under stirring to complete reducing reaction, whereby the precipiate of metallic powder is formed. After standing and cooling, the supernatant liquid is run away, and the resultant precipitate is rinsed and is then vacuum dried, whereby fine metallic nickel powder or metallic copper powder of about 1 micron is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine metallic nickel powder of 1 micron or less and metallic copper powder by wet reduction.

Conventional methods for manufacturing these metal powders include dry methods such as electrolytic method, hydrogen reduction method, pyrolysis method, melt injection method, and evaporation method in gas, but all of them require complicated equipment and advanced technology. technology is required. Compared to these methods, wet reduction is the most convenient and requires the simplest equipment, but in order to obtain metal powder of 1 micron or less using conventional wet reduction methods, pressurization in a closed container is required, or It is necessary not to use large amounts of expensive reducing agents.

This method eliminates these drawbacks and reliably uses simple equipment.
Moreover, it is intended to safely produce metallic nickel and copper fine powders of 1 micron or less.

That is, in this method, caustic soda, soda carbonate, or a mixture thereof is added to a solution in which nickel sulfate and copper sulfate, which are the most easily available nickel and copper compounds, are dissolved, and hydroxide or carbonate is dissolved. Particles containing the metal are poured into a mold. Therefore, very fine particles are produced at this stage. The fineness of the particles is most influenced by the concentration of the liquid, and normally the lower the concentration, the thinner the particles will be.

Next, as a reducing agent, hydrazine or hydrazine hydrate was used in an amount of 3 to 8 equivalents, but this is because if the amount is less than 3 equivalents, the reaction will take a long time or is unstable, and from the economic point of view, about 8 equivalents are used. I was able to hold it down. When heated while stirring after igniting the reducing agent, the reaction will vary depending on the concentration of the liquid, the equivalent amount of reducing agent added, etc., but in the case of nickel, the reaction temperature will be 70 to 90°C.
The reaction starts and becomes more vigorous as the temperature rises until the reaction is complete. In the case of copper, the reaction begins at a much lower temperature, but it is weak at this stage, and complete metallic copper cannot be produced until the final reaction is violent at temperatures above 85°C.

In either case, once the reaction is complete, the bubbles weaken and the liquid becomes transparent. When the metal powder is then left to stand and cooled, it precipitates, so high-quality salt is poured over it, washed with water several times, filtered, and dried to obtain a product. To prevent oxidation, vacuum drying is preferable, and care must be taken especially since copper is easily oxidized.

Next, an explanation will be given according to an example.

Example (1) 1 liter of 500 g of nickel sulfate (NiSO4, 5H2O)
Dissolve in water and use caustic soda (NaOH) as a neutralizing agent.
150 g was dissolved in 1 liter of water. When these two solutions were mixed with stirring, nickel hydroxide immediately started to form and swell. When 450 ml of 60% hydrazine hydrate was added to this suspension and heated while stirring well, a rapid reaction started when the temperature exceeded 80°C and bubbles started to form, so the heating was weakened to prevent overflowing. The reaction continued at 88°C, and after about 1 hour, the liquid became colorless and the generation of bubbles stopped.The nickel powder was allowed to stand still, and the supernatant liquid was poured off. It was decanted twice, washed with water, and finally washed with acetone, filtered, and dried under reduced pressure.

The nickel powder thus obtained weighed about 110 g. Further, as a result of examination using an electron microscope, the grain size was 0.7 microns.

Example (2) Dissolve 500 g of nickel sulfate in 3 liters of water, and use 101 g of caustic soda and 67 g of soda carbonate (NO4CO3) as neutralizing agents.
Using a solution prepared by dissolving 1.5 g in 1 liter of water, the same reducing agent and other methods as in Example (1) were used, and the reduction was maintained at 92°C. The particle size of the resulting nickel powder was 0.3 microns.

Example (3) 500g of copper sulfate (C12SO4.5H2O) to 1.5L
A solution of 160 g of caustic soda dissolved in 2 liters of water was mixed with a solution of 160 g of caustic soda dissolved in 2 liters of water to extract fine particles of copper hydroxide, and after thorough stirring and mixing, 60% hydrazine hydrate 4
When 50 ml of the mixture was added and heated with stirring, the reaction started with bubbles appearing at 50°C, and when the temperature exceeded 90°C, the reaction became more active and was completed in 65 minutes from the start of heating.

The copper powder that settled after standing was thoroughly washed, filtered, and then vacuum dried. The grain size of the copper powder was 0.2 microns.

Example (4) The same procedure as in Example (3) was carried out except that the caustic soda of Example (3) was added to 215 g of soda carbonate.

The reaction became more rapid when the temperature exceeded 85°C, but the reaction time was
Heating was completed in 45 minutes after starting.

The grain size of the copper powder was 0.3 microns.

As mentioned above, unlike conventional wet reduction, this method does not directly reduce the metal from the liquid phase, but first removes fine particles of the metal hydroxide compound or carbonate through neutralization. It can be made into very fine particles, and therefore the metal particles obtained by reducing it can be obtained as even finer particles. Furthermore, for the purpose of standing still, a normal stirring tank and heating device are used for the living body, no special equipment is required, and a normal pressure reaction is sufficient.

In other words, according to this method, it is possible to produce fine powders of metallic nickel and metallic copper of 1 micron or less using extremely simple equipment and operations using industrially easily available nickel sulfate and copper sulfate as raw materials.

Claims (1)

[Claims] When producing the metal fine powder from a nickel or copper sulfate solution, a solution of caustic soda or soda carbonate, or a mixed solution of both is added to the metal-containing solution to form a hydroxide of nickel or copper. A method for producing fine nickel powder and copper powder, characterized by reducing the fine precipitates or colloidal particles of carbonate or carbonate.