JPS5836627A - Production of powder coated with base metal - Google Patents

Abstract

PURPOSE:To produce titled coated powder which is finely granular and uniform easily by dispersing ceramic-base powder in a gellike aq. soln. contg. base metal compds., nonmetallic NH4 salt and aqueous ammonia or caustic alkalis then adding a reducing agent thereto. CONSTITUTION:Base metals alone or their compds. are once dissolved in an arbitrary aq. soln. and nonmetallic NH4 salt such as NH4Cl is mixed with said soln. Aqueous ammonia or an aq. soln. of caustic alkali is added to the mixed solns. to control the pH thereof to 5-10. Powder of ceramic base is added under agitation to the resultant gellike aq. soln., whereby the powder is dispersed uniformly therein. Under agitation, a reducing agent is added to the dispersion to reduce the base metal compd. to the simple substance of the base metal. Then, the gel state of the dispersion is eliminated and at the same time the powder coated with base metal is formed. Said powder is removed by decantation or filtration and is washed and dried.

Description

[Detailed description of the invention] The present invention relates to a method for producing base metal coated powders.

More particularly, the present invention relates to a method for producing a base metal coated powder comprising particles of a substrate material that are substantially completely coated with a coating layer of base metal.

The composite sintered body obtained by molding and sintering metal powders such as steel, nickel, zinc, iron, etc., and the upper 22 Tutas powder has the characteristics of both metals and ceramics, and can be used as a bearing material. Used in various applications such as wear-resistant materials and high-temperature resistant materials. However, in the case of manufacturing metal-to-metal and OS composite sintered bodies, in many combinations, the difference in specific gravity between the metals is not so large, and by normal mixing of one metal powder and the other metal powder, a homogeneous product can be obtained. Mixed powders can be obtained, but since there is generally a large difference in specific gravity between metal and ceramic powders, the preparation of homogeneous and mixed powders and the production of homogeneous fired products require special mixing equipment, molding equipment, etc. It also makes the operation more complicated. The degree of homogeneity of the obtained baked product is also not high.

The present invention provides a method for producing a round metal-coated powder particularly suitable for producing a composite sintered body made of surface metal and ceramics as described above.

The present invention comprises a base metal compound, a nonmetallic ammonium salt, and ammonia water or alkali.
This is a method for producing a base metal-coated powder, which is characterized in that a reducing agent is added to a dispersion in which a ceramic substrate powder is uniformly dispersed in a gel-like aqueous solution under stirring.

The powder produced according to the present invention is a coated powder consisting of composite particles having a ceramic base particle as a core and a coating layer made of a base metal provided around the core. According to the manufacturing method of the present invention, it is possible to provide a homogeneous and strong base metal coating layer on the ceramic particles, and the coating layer is more easily bonded to the substrate unlike the coating layer produced by the conventional chemical plating method. It's going to be AI, make pollution a reality. (For mutual acceptance, it can be formed as a high-purity base metal coating layer.) Furthermore, in the present invention, a thicker, more homogeneous and stronger coating layer can be obtained compared to conventional chemical plating methods. Furthermore, with conventional chemical plating methods, it was difficult to obtain uniform metal coating powder for powders with an average particle size of 1 micron or less; however, the method of the present invention makes it possible to uniformly coat such fine powder particles. You can achieve 1IIK. Therefore, one shot is 1jlK
The base metal coated powder obtained from the method can be used for various O applications in addition to the production of sintered bodies.

Next, the present invention will be explained in detail.

An example of a base metal used in the present invention is titanium.

Panax, aluminum, chromium, manganese, iron, cobalt.

Examples include transition metals belonging to the fourth period of the periodic table, such as nickel, copper, and zinc. Furthermore, lead.

Also base metals that are stable in air, such as molybdenum and tin.

Suitable for forming the coating layer of the present invention. These base metal compounds may be used alone, or two or more of them may be used in combination. It is also possible to mix and use noble metals in a relatively small amount (weight ratio) with respect to base metals. Base metal compounds are dissolved in their aqueous solutions (aqueous solutions,
There is no particular restriction as long as a mineral acid solution, alkaline aqueous solution, etc.) can be prepared. Examples include base metal sulfates, nitrates, halides, and cyanides.

Furthermore, complex compounds of base metals can also be used.

Further, a solution in which a base metal element is dissolved in a mineral acid can also be used.

Examples of nonmetallic ammonium salts include ammonium chloride, ammonium acetate, ammonium sulfate, ammonium nitrate, and ammonium phosphate, with ammonium chloride being particularly preferred.

A gel-like aqueous solution of -5-1O containing a base metal compound, a nonmetallic ammonium salt, and aqueous ammonia or aqueous alkali is prepared, for example, as follows. Once the base metal element or base metal compound is dissolved in any aqueous solvent such as water, dilute acid, dilute acid, mixed acid, or alkaline aqueous solution (a solvent that dissolves the target base metal element or base metal compound), it is mixed with a solution of chloride. By mixing ammonium salts such as ammonium (Nil, ct) and adding aqueous ammonia or aqueous alkaline solutions (aqueous solutions of sodium chloride, potassium chloride, etc.) to the mixture, - of the mixture can be changed to 5-1O ( Preferably e-s)ic adjustment. By adding an ammonium salt to the base metal solution, or by further adding aqueous ammonia or aqueous alkaline solution, the - of the mixture can be reduced to 5-10.
The mixed solution is made into a gel by adjusting the amount. The amount of ammonium salt such as ammonium chloride added is preferably at least three times the amount and three times the amount relative to the base metal of the base metal compound. If ammonium salt is added in an amount less than this range, it becomes difficult to uniformly disperse the ceramic substrate powder in a stable state.

On the other hand, if the amount of ammonium salt is greater than the above range, the viscosity of the gel will become too high, causing the reaction to become uneven. It becomes easier.

The ceramic ivy body used in the present invention is the above-mentioned gel-like aqueous *
*It is not limited to q# as long as it does not show substantial solubility in .An example is silicon oxide.

Oxide ceramics such as zirconium oxide, titanium dioxide, alumina, barium titanate, and titanium carbide,
Examples include ceramics such as non-oxide ceramics such as titanium nitride, tungsten carbide, and silicon carbide.

The ceramic substrate powder usually has an average particle size of about 30 microns or less, but preferably has an average particle size of 10 microns or less.

The particle size does not need to be particularly uniform. Furthermore, as mentioned above, uniform coating of powder with an average particle size of 1 micron or less is also possible.

There is no particular restriction on the ratio of the ceramic base powder and the base metal compound contained in the dispersion liquid, but if the base metal coated powder to be produced is assumed to be used as a composite sintered body, the ratio between the ceramic base powder and the base metal compound may be The ratio to base metals is 289
It is desirable that the ratio is in the range of 8 to 98:2 (weight ratio). A more desirable range is that ceramic substrate: base metal-S
:5S-95:5 (weight ratio).

The dispersion of the present invention is prepared as described above, and ceramic substrate powder is added to a gel-like aqueous solution of -5-1O containing a round ring metal compound, a nonmetallic ammonium salt, and aqueous ammonia or an aqueous alkali under stirring. A uniform dispersion can be obtained by this method. A stirring device that can be used in any manner and at any time.

It can be used regardless of the scissor holder type OII.

The reducing agent is added to the dispersion while stirring. There are no particular restrictions on the stirring method, but since the dispersion of the gel-like aqueous solution and the ceramic base powder is to be stirred, a method that allows for high-power stirring is desirable.

The reducing agent is not particularly limited as long as it can reduce the base metal compound in the gel-like aqueous solution and convert it into a base metal element.

Examples of the reducing agent include lithium arsenium hydride, sodium borohydride, etc., but the reducing agent is not limited to these. A reducing agent is added in an amount sufficient to reduce the base metal compound in the gel-like aqueous solution to a base metal element.

By adding a reducing agent to the stirred dispersion of gel-like aqueous solution and ceramic substrate powder, the gel state of the dispersion disappears and at the same time a base metal-coated powder is produced.

The resulting round metal-coated powder is then decanted and F
It is taken out, washed, dried, and used for various purposes.

Next, examples of the present invention will be shown.

[Example 1] 6 f of cupric chloride (CuC4) was mixed with 45 g of water (1 w + g
Dissolve K, add 5 t of ammonium chloride (1.05 times the equivalent of copper), and then add aqueous ammonia (aqueous solution to 28).
Upon addition of 7.5, a blue gel-like solution (f1 about 7) was obtained. Paryu titanate A (Ba
Ti0. ) powder (average particle size 0.13 microns) 40
Add F and stir thoroughly to obtain a uniform dispersion.9.

While thoroughly stirring this dispersion, 10% of a sodium borohydride aqueous solution (NaBH, 21/100w1 H,O) was added.
When 0- was added, the gel state disappeared and a gray powder was produced. Next, the powder is taken out of the furnace and washed with water and hot water.
By drying at 65° C., 941.12 tons of steel-coated barium titanate powder was obtained. Yield: 96x0 Barium titanate/copper weight ratio in coated powder: 914/6.6゜The nine copper coated barium titanate powder obtained above was placed in a container, and an electrode was inserted into it to measure the resistance value. The resistance value was almost 0, which matched the resistance value of pure copper powder.

The copper-coated barium titanate powder obtained above was pressed into a disk shape at a pressure of 1 ton/-.

When fired for 1 hour at 1150°C under an argon atmosphere, a strong fired product with a homogeneous surface condition was obtained.

[Example 2] Cupric chloride 42.3 F was dissolved in 3 t of water, followed by ammonium chloride 3 & 3 F (1.05 equivalent to copper) and then aqueous sodium chloride solution (NaOH 100 F/!!OOs).
g) A blue gel-like solution (-approx. 7) was obtained by adding 480 mg. Add titanium dioxide (〒io) to this solution.
, ) was added and stirred sufficiently to obtain a uniform dispersion. When this dispersion was thoroughly stirred and 11 g of 70 G of a sodium borohydride aqueous solution (NaBH, 14f/700-10) was added, the gel state disappeared and a gray powder was produced. The powder was then collected, washed with water and hot water, and dried at 65°C to obtain fi 39.2.
A copper-coated titanium dioxide powder of F was obtained. Yield 98%. Titanium dioxide/steel weight ratio in coated powder: 501500 Place the copper coated titanium dioxide powder obtained above in a container,
When I inserted an electrode into the leg and measured the resistance value, the resistance value line was 0, which matched the resistance value of pure copper powder.

In addition, when the copper-coated titanium dioxide powder obtained above was pressed into a disc shape under a pressure of 1 ton/j and fired at 1000°C for 1 hour in an argon atmosphere, a strong fired product with a homogeneous surface condition was obtained. was gotten.

[Example 3] Nickel chloride (NiC4.6 0) 22F to 20% water
0-, and to this was added 16 t of ammonium chloride (1.6 times the amount of sodium chloride) and then aqueous sodium hydroxide solution (Na
By adding OH5Qf/25Gsg H,O) 140-, a blue gel-like solution (-about 7) was obtained. Add 4 titanium dioxide powder (average particle size 2 microns) to this solution.
02 was added and thoroughly stirred to obtain a uniform dispersion. While thoroughly stirring this dispersion, add 250g of sodium borohydride aqueous solution (NaBH, 5f/2S OsgH,O).
When Id was added, the gel-like part disappeared and a gray powder was produced. Next, the powder is taken out in a furnace.

Wash with water and hot water and dry at 65℃.
) 44.54f of nickel-coated titanium dioxide powder was obtained. Yield 98%. Titanium dioxide/nickel weight ratio in coated powder: 88/12° The nickel-coated titanium dioxide powder obtained above was pressed into a disk shape at a pressure of 1 ton/-.

When fired at 1200° C. for 1 hour under an argon atmosphere, a strong fired product with a homogeneous surface condition was obtained.

Patent applicant Shinro Kawakami Agent: Patent attorney Yasuo Yanagawa

Claims (1)

[Claims] 1. Base metal compound, nonmetallic ammonium salt. -5-10 gel-like aqueous solution containing ammonia water or aqueous alkali! A method for producing a base metal-coated powder, which comprises adding a reducing agent to a dispersion liquid in which two ceramic base powders are uniformly dispersed, while stirring. 1. The manufacturing method according to claim 1, wherein the nonmetallic ammonium salt is ammonium chloride. 3. The manufacturing method according to claim 1, characterized in that the content of the nonmetallic ammonium salt is at least an equivalent amount and at most three times the equivalent amount of the base metal of the base metal compound. 4. The manufacturing method according to claim 1, wherein the base metal is a transition metal in the fourth period of the periodic table. 1. The OII manufacturing method according to claim 1, wherein the average particle size of the base material powder is 1 micron or less.