KR930003821B1 - Electroless method for coating the hydrogen storage alloy powder of rare earth-nickel metals with a copper - Google Patents

Abstract

The electroless copper plating method of rare earth-nickel based hydrogen storage alloy powder comprises (a) mixing and stirring powder (1) pulverized by hydrogenation reaction or rare earth- nickel based hydrogen storage alloy powder which is machanically obtd. powder (2) at air atmosphere, with 2-20 gm copper sulfate solution or 2-20 gm copper sulfate solution added with less then 2 ml solution of sulphuric acid or hydrochloric acid, (b) reducing copper ions in the plating solution to alloy powder surfaces.

Description

Electroless Copper Plating of Rare Earth-Nickel Hydrogen Storage Alloy Powders

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless copper plating method of rare earth-nickel hydrogen storage alloy powders used in the negative electrode material of a nickel-metal hydride rechargeable battery or a metal hydride heat pump solvent. The electroless copper plating method of the rare earth-nickel hydrogen storage alloy powder which has been used conventionally, first, the alloy powder is mixed with a mixed aqueous solution of palladium chloride and hydrochloric acid [Pdcl ₂ + Hcl] and a mixed aqueous solution of tin chloride and hydrochloric acid [Sncl ₂ + Hcl]. After pretreatment, there is a conventional method of plating in an aqueous solution of copper sulfate, formalin, ethylenediamine tetraacetic acid and sodium hydroxide [CuSO ₄ + CH ₂ O + EDTA + NaOH], but the plating method is (1) plating process. This complex, (2) slow plating rate, (3) toxic palladium chloride, formalin, sodium hydroxide [Pdcl ₂ , CH ₂ O, NaOH], etc. should be used a lot of the (4) excessive plating costs to be.

Accordingly, an object of the present invention is to provide a new electroless copper plating method of a conventional rare earth-nickel hydrogen storage alloy powder in view of the above circumstances.

Selection of the plating liquid used in the present invention is as follows.

① Copper sulfate (CuSO ₄ ) aqueous solution [5 ~ 20g CuSO ₄ 100ml aqueous solution]

② Copper sulfate (CuSO ₄ ) + sulfuric acid (H ₂ SO ₄ ) aqueous solution [plating solution ① + 2.1ml or less H ₂ SO ₄ ]

③ Copper sulfate (CuSO ₄ ) + hydrochloric acid (Hcl) aqueous solution [plating solution ① + 2.0ml or less Hcl]

In general, the rare earth-nickel-based hydrogen resistance alloy powder to be used for electroless copper plating, the degree of oxidation of the surface is greatly different according to the powder manufacturing conditions, classified as follows.

① Alloy powder with less surface oxidation

Pulverized powder by hydrogenation reaction

Hydrogenation reaction + powders mechanically ground in hydrogen or inert gas atmosphere

Mechanically ground powder in hydrogen or inert gas atmosphere

② Alloy powder with heavily oxidized surface

Powder mechanically ground in air

Powders that have been ground by hydrogenation or in an inert gas atmosphere, but have severe surface oxidation due to contact with air

The electroless copper plating method of the rare earth-nickel hydrogen storage alloy powders using the above-mentioned plating solutions (1) to (3) and each alloy powder (1,2) will be described below by way of examples.

Example 1

(1) experimental conditions according to the present invention

Alloy component; (LM) Ni _4.49 Coo _.205 Al _0.205 (LM: La-rich misch metal)

Alloy powder weight; 2.4g

Powder particle size; 100μ or less

Powder production method; Sample (1)-Grinding by Hydrogenation

Sample (2)-mechanical grinding in air

Plating amount adjustment and amount; Plating solution (1) -CuSO ₄ 15g / 100ml aqueous solution

Plating solution (2) -CuSO ₄ 15g + H ₂ SO ₄ 0.8ml / 100ml aqueous solution

Plating temperature; 25 ℃

(2) Each implementation method according to the present invention

a) Sample (1) + Plating Solution (1)

b) Sample (2) + Plating Solution (2)

c) Sample (2) + Plating Solution (1)

In the method a), the sample 1, which is an alloy powder, is placed in a plating solution 1 [CuSO ₄ , 15 g / 100 ml aqueous solution] and agitated while avoiding contact with air.

When the copper in the plating liquid is completely plated on the surface of the alloy powder, the color of the plating liquid changes from blue to green.

The method b) to give the stirring the alloy powders of the sample 2 in a plating solution (2) [CuSO ₄ + H ₂ SO ₄ 15g 0.8ml / 100ml solution.

When the plating is completed, the plating liquid color changes from blue to green.

The amount of sulfuric acid (H ₂ SO ₄ ) or hydrochloric acid (Hcl) in the plating liquid is adjusted according to the degree of surface oxidation of the alloy powder sample (2).

In Example c), the sample (2), which is an alloy powder, is placed in a plating solution (1) [CuSO ₄ 15g / 100ml aqueous solution] and stirred.

The ratio of the amount of the alloy powder and the amount of copper to be plated according to each of the above embodiments is controlled by the amount of the plating liquid or the amount of copper sulfate (CuSO ₄ ) in the plating liquid.

(3) Plating rate measurement experiment of each method [a), b), c)].

In the plating principle of each method [a), b), c)], the rare earth-nickel alloy is dissolved and ionized (oxidized) in each plating solution and copper ions [Cu ²⁺ ] in the plating solution are deposited on the surface of the alloy powder. It is reduced precipitated.

If the surface of the alloy powder is oxidized, the ionization rate of the alloy is very slow. If sulfuric acid (CuSO ₄ ) or hydrochloric acid (Hcl) is dissolved in the plating solution, the ionization of the alloy is accelerated.

The variation of the plating amount according to the plating time of each embodiment of the present invention is shown in the following table.

[Figure 1]

Change of plating amount according to plating time

Therefore, the most ideal embodiment according to the present invention is a) [sample (1) + plating solution (1)], b) [sample (2) + plating solution (2)] copper in the plating solution between 4-5 minutes after stirring Ion (Cu ²⁺ ) was reduced by 90% or more on the surface of the alloy powder, the plating was completed, and after about 10 minutes, the plating rate was measured to approach 100%.

As described above in the above embodiment, the application effect of the present invention is as follows.

(1) simple plating process, (2) low plating cost, (3) use less toxic chemicals, (4) shorter plating time, and (5) especially for nickel-metal hydride rechargeable batteries When applied to copper plating of the rare earth-nickel hydrogen storage alloy powder used, all of the following ① to ⑤ are satisfied.

① Electrical conductivity and thermal conductivity are improved.

② The life of charge and discharge cycle increases.

③ The charging and discharging speed is fast and energy efficiency increases.

④ The autonomous discharge rate is reduced.

⑤ Good compressibility in electrode production.

In addition, when used in the metal hydride heat pulp has a fast heat transfer rate and has the effect of suppressing the dispersion and backflow of the alloy powder.

This effect is a novel useful plating method with almost the same effect when the rare earth-nickel-based hydrogen storage alloy powder is used for other fields such as hydrogen energy storage and hydrogen gas purifier.

Claims (1)

A rare earth-nickel hydrogen storage alloy powder, which is a sample (1) pulverized by a hydrogenation reaction or a mechanical sample (2) in air, is prepared using (5-20 g copper sulfate / 100 ml aqueous solution) or {(5-20 g copper sulfate / 100 ml aqueous solution) + (Less than 2 ml of sulfuric acid or hydrochloric acid aqueous solution)}, the electroless copper plating method of the rare earth-nickel hydrogen storage alloy powder, characterized in that the copper ions (Cu ²⁺ ) in the plating solution are reduced to the surface of the alloy powder. .