JPH02185901A - Copper-silver-coated metal sulfide powder and manufacture thereof - Google Patents

Abstract

PURPOSE:To easily manufacture copper-silver-coated metal sulfide powder having excellent uniformity and stickability by forming silver supporting layer on the whole surface of the metal sulfide powder with thermal decomposition method of silver salt and forming copper coating layer on the supporting layer with chemical plating method. CONSTITUTION:After executing dipping-treatment to the metal sulfide powder of MoS2, WS2, etc., into alcohol water solution of silver nitrate, this is dried at about 120-170 deg.C. The silver nitrate coating formed with this is heat-treated at <=450 deg.C and further, desirably >= about 200 deg.C and the thermal decomposition is executed. By this method, the silver supporting layer is applied on the surface of the above metal sulfide powder at high density strength. Successively, this powder is charged into alkali water solution of complexing agent, such as Rochelle salt, having pH10-13. Formalin and water solution of copper compound is added to this while stirring the above water solution and keeping the above pH value. By this method, the copper layer is applied on the surface of the above silver supporting layer at good platability and high density strength. After that, if necessary, by executing heat treatment at the prescribed temp., the silver-copper double coating layers are diffused or alloyed and the improvement of detaching resistance can be executed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a copper-silver coated metal sulfide powder and a method for producing the same. A new copper-silver coated metal sulfide powder in which a copper-silver coating layer is uniformly formed and the metal sulfide powder is not consumed even in processes such as sintering and thermal spraying, and the copper-silver coated metal sulfide powder. The present invention relates to a method for producing a copper-silver coated metal sulfide powder that can stably, reliably, and economically obtain a metal powder.

The copper-silver coated metal sulfide powder according to the present invention can be applied to oil-impregnated bearings, carbon brushes, friction materials, thermal spray materials, etc.

[Prior art and its problems] Since metal sulfide P powder has self-lubricating properties, it is used after being mixed with copper powder, tin powder, etc., and then formed into bearings by powder metallurgy or thermal spraying. ing.

However, the metal sulfide powder used here, especially molybdenum disulfide powder, which is a typical example, cannot be mixed with copper powder, etc. due to differences in apparent density and surface condition, making it difficult to obtain a uniform mixed powder. Moreover, it has drawbacks such as being consumed during sintering or thermal spraying. For this reason, metal sulfide powder whose surface is coated with copper has conventionally been used. This copper coating is required to have uniform coating properties and adhesion strength that will not peel off during mixing or thermal spraying.

Conventionally, as a method for coating metal sulfide powder with copper, a method using a cementation reaction (in particular, a method in which an acidic solution containing copper ions is added to a mixture of a metal less base than copper and metal sulfide powder) has been used. Kosho 57-31532.58-3220
1) is known. However, metal sulfide powder whose surface is difficult to activate has the disadvantage that it is difficult to uniformly coat the copper layer and the adhesion strength is low.

In order to improve the above-mentioned drawbacks, a method of pre-activating metal sulfide powder is to coat the surface of the metal sulfide powder with a platinum group coating layer by thermal decomposition of a platinum group compound, and then apply a cementation reaction to the surface. How to coat copper using
Special Publication No. 57-31533) has been proposed. but,
This method is also essentially a substitution reaction between a base metal and copper,
When coating metal sulfide powder, there are problems with uniform coating and adhesion.

Furthermore, a method of immersion treatment using palladium chloride as an activator has been proposed (Japanese Patent Publication No. 55-1321). However, this method has the disadvantage that it is not preferable to add expensive platinum group metals (2 Cg/l) or more, which increases processing costs.

Furthermore, in order to solve these problems, a method has been proposed in which metal sulfide powder is subjected to immersion activation treatment in an aqueous solution of ferrous sulfate, stannous chloride, and silver nitrate (Japanese Patent Publication No. 6O-255902). However, this method has the disadvantage that the processing is complicated and the management of the processing liquid is difficult.

[Means to solve the problem]

As a result of repeated research in order to solve the various problems of the various conventional techniques mentioned above, the present inventor has finally completed the present invention which can achieve the intended purpose.

That is, there are two types of copper-silver-coated metal sulfide powder according to the present invention, one in which the surface of the metal sulfide powder is covered with a silver support layer, and the surface is covered with a copper layer (hereinafter referred to as a type). (simply referred to as "double coating layer type")
The other - is a type in which the surface of the metal sulfide powder is covered with a diffusion layer or an alloy layer of silver and copper (hereinafter referred to as
It is simply called "diffusion/alloy layer type." ).

The method for producing a double coating layer type copper-silver coated metal sulfide powder according to the present invention is to immerse metal sulfide powder in an alcohol aqueous solution of silver nitrate, dry it, and then heat it at 450°C or lower. Silver nitrate is thermally decomposed to coat the surface of the metal sulfide powder with a silver support layer, which is then subjected to pH
A copper layer is coated on the surface of the silver-supporting layer by adding the complexing agent to an aqueous solution of a complexing agent adjusted to a pH of 0 to 13, and adding the aqueous solution of formalin and a copper compound while maintaining the above pH while stirring. That is.

In addition, a method for producing a diffusion/alloy layer type copper-silver coated metal sulfide powder is to heat the copper-silver coated metal sulfide powder obtained by the above method at 250 to 700°C in a reducing atmosphere or an inert atmosphere. The present invention is characterized in that at least a portion of the silver support layer and the copper layer are mutually diffused or alloyed by heat treatment.

Next, the configuration of the present invention will be explained in detail.

The metal sulfide powder in the present invention has self-lubricating properties, and representative examples include molybdenum disulfide and tungsten disulfide.

In the copper-silver coated metal sulfide powder according to the present invention, since silver is present on the surface of the metal sulfide powder, silver reacts with sulfur in the metal sulfide to form a sulfide with silver. Therefore, the adhesion strength between silver and metal sulfide is improved compared to platinum group metals, which have less reactivity with sulfur in this metal sulfide. Also,
Since the price is lower than that of platinum group metals, a large amount can be supported, and therefore the coating becomes more uniform. Furthermore, silver is
Even with copper, it has good coverage and strong adhesion.

Next, a method for manufacturing a double coating layer type copper-coated metal sulfide powder according to the present invention will be described. In this manufacturing method, the surface of the metal sulfide powder is coated with a silver supporting layer. The process is broadly divided into the step of forming a copper layer on top of the copper layer.

The method of supporting silver on the surface of metal sulfide powder (7) Although chemical plating, gas phase plating, etc. can also be applied, the following method is used because it is easy to operate and the amount supported can be easily adjusted. In other words, in the method of the present invention, metal sulfide powder is added to an alcohol aqueous solution of silver nitrate, such as ethyl alcohol or butyral alcohol, which is adjusted to a predetermined supported amount. Mix well to form a paste and coat the surface of the metal sulfide powder with silver nitrate. Next, this is dried at 120 to 170°C, and then heated in an electric furnace at 450°C or lower to thermally decompose the nitric acid. By doing so, a silver supporting layer can be formed on the surface of the metal sulfide powder. Heating temperature is 450°
If it exceeds C, the metal sulfide decomposes and becomes an oxide, which is not preferable. On the other hand, there is no particular restriction on the lower limit of the heating temperature, but in order to sufficiently activate silver, it is necessary to
It is preferable to heat at 00°C or higher. As for the amount supported by the roots, if it is 0.01 wt% or more based on the metal sulfide powder, it is possible to form a uniform copper (M) with good adhesion in the next step. The upper limit is determined by the silver requirements of the end-use field.

Next, for forming the copper layer covering the silver supporting layer, in addition to chemical plating, electroless plating, vapor phase plating, etc. can be applied, but chemical plating is preferable from the viewpoint of stability in repeating.

The copper coating process by chemical plating consists of coating the copper with a silver support layer in an alkaline solution of a complexing agent such as Rothsell salt or ethylenediaminetetraacetic acid (TFT), which causes trade bonding with the copper. Add metal sulfide powder.p
Copper can be easily plated by gradually dropping a 35% formalin solution and an aqueous copper compound solution while maintaining H at 10 to 13. The reaction temperature is preferably 15 to 40 °C in the case of a Rosselle salt bath and 25 to 60 °C in the case of an ethylenediaminetetraacetic acid bath.If the temperature exceeds the upper limit described above, the plating bath is likely to decompose. Abnormally precipitated copper powder exists in the copper-silver coated metal sulfide powder, which may deteriorate the quality of the product.On the other hand, if the temperature does not reach the lower limit mentioned above, the plating reaction will be difficult to proceed. According to the above-mentioned chemical plating method, almost all of the injected copper is plated on the surface of the silver layer, and the desired copper layer can be easily formed with high precision.Furthermore, bath management is extremely easy. It has the characteristic of being Yazui.

Incidentally, after completing the plating described above, washing with water and drying are performed to obtain a double coating layer type copper-silver coated metal sulfide powder according to the present invention.

f + q of the double coating layer Yu-Eve obtained by the above-mentioned method
The silver-coated metal sulfide powder has good uniform coverage and adhesion. However, depending on the field of use, even stronger adhesion may be desired. For example, when used in sintered metals, etc., it is necessary to prevent peeling when mixed with dissimilar metal powder such as copper powder. A copper-silver-coated metal sulfide powder that satisfies these characteristics is the one used in the diffusion alloy layer according to the present invention. The manufacturing method will be explained below. The double coating layer type copper-silver coated metal sulfide powder obtained by the above method was heated for 250 min in a reducing atmosphere such as hydrogen or ammonia decomposition gas, or in an inert gas such as nitrogen argon or helium.
Heat treatment may be performed at ~700°C for 10 minutes to several hours.

If the heat treatment is carried out at 250° C. or lower, diffusion or alloying will not proceed sufficiently, so it will tend to be difficult to improve adhesion. On the other hand, if the temperature is higher than 700°C, sintering of the copper-silver coated metal sulfide powder itself tends to occur.
When the sintered material is processed in a crusher, the coating layer is crushed and metal sulfides are exposed.

When the double coating layer type copper-silver wave) metal sulfide powder is heat treated at a predetermined temperature in this way, the reaction between the metal sulfide and the silver constituting the inner coating layer becomes active. Also,
At the same time, the coating layers (inner silver supporting layer, outer copper layer) shrink due to sintering. During this sintering, a copper-silver mutual diffusion layer or alloy layer is formed on the surface of the metal sulfide powder. It is presumed that this occurs because the silver precipitated particles produced by thermal decomposition of silver nitrate and the copper precipitated particles produced by chemical plating are extremely fine, dense, and highly active. Whether diffusion or alloying occurs is determined by the heat treatment conditions of the double layer type copper-silver coated metal sulfide powder.

The diffusion/alloy layer type copper-silver coated metal sulfide powder according to the present invention obtained in this manner shows almost no peeling of the copper layer even when mixed with a different metal powder.

〔Example] Next, the configuration of the present invention will be explained based on examples.

Example 1 50 g of commercially available molybdenum disulfide powder (manufactured by Sumiko Lubricants θros, trade name "Moly Powder") was mixed with 0.1 g of reagent primary silver nitrate.
Mixed solution of butyl alcohol and water containing 58g 4
Add 0 mN to make a slurry, mix and dry, then heat at 300°
Silver was supported in an electric furnace for C130 minutes to obtain a powder in which the surface of molybdenum disulfide powder was coated with a silver support layer.

Next, after sieving this powder, Rossel salt (10
0 g/42) into 500 ml of solution, and plating by dropping plating solution containing cupric chloride solution (copper 50 g, 10% solution) and formalin 35% solution while adjusting the pH to 12.0 to 12.5. I did it. After filtering and drying, a copper-silver-coated molybdenum disulfide powder having a copper layer coated on the surface of the silver supporting layer was obtained.

The copper ion concentration in the solution after the reaction is 0. O3 ppm, almost all of the implanted copper ions are plated, and the color tone and
The driving ability was also perfect.

Example 2 The copper-silver coated molybdenum disulfide powder obtained in Example 1 was heated to 4% in an atmosphere of 70 VOL% hydrogen and 30 VOL% nitrogen.
A heat treatment was performed at 00°C for 12 hours to obtain a copper-silver alloy coated molybdenum disulfide powder in which the copper layer and the silver support layer were alloyed.

Example 3 In Example 1, 100 mj of a mixed solution of ethyl alcohol, butyl alcohol, and water in which 40 g of molybdenum disulfide powder and 16 g of silver nitrate were dissolved! Example 1 except that
A copper-silver coated molybdenum disulfide powder was obtained in the same manner as above.

Example 4 The copper-silver coated molybdenum disulfide powder obtained in Example 3 was heat-treated at 650°C for 11 hours in a hydrogen atmosphere.
Copper layer and silver support! *A copper-silver alloy coated molybdenum disulfide powder alloyed with was obtained.

Comparative Example 1 In an open rotary drum (3000 mj! capacity), 200 g of molybdenum disulfide powder (manufactured by Sumiko Lubricants 0@: trade name "Molypowder J") and 200 ml of palladium nitrate aqueous solution (palladium O, 15 g/f solution) were added. Add and mix;
After drying with an infrared lamp and dehydrating, heat at 350°C with a gas burner.
Heat treatment was performed for 30 minutes. Next, this and 180 g of reduced iron powder with a particle size of 200 mesh under were placed in a cementation container equipped with a stirrer, and while mixing, an acidic copper sulfate solution (free acid 200 g/j!, copper 50 g/14 I!) was gradually added. and the cementation reaction was carried out for 15 minutes.

The amount of copper deposited after washing with water and drying was 49%. In this way, a copper-palladium-coated molybdenum disulfide powder was obtained, in which the surface of the molybdenum disulfide powder was coated with a palladium layer as an inner layer and a copper layer as an outer layer.

Table 1 shows the peel test results and composition XMA of the coating layer of the copper-silver-coated molybdenum disulfide powder obtained in Examples 1 to 4 and the copper-palladium-coated molybdenum disulfide powder obtained in Comparative Example 1. Shown below.

Table 1 *1: By observation using a stereomicroscope (250x magnification), the percentage of completely covered powder in the total was randomly sampled from 5 fields, and the average value was determined.

*2: The copper-silver-coated molybdenum disulfide powder obtained in Examples 1 to 4 and the copper-palladium-coated molybdenum disulfide powder obtained in Comparative Example 1 were targeted.

*3: 70VOL% of the copper-silver coated molybdenum disulfide powder obtained in Examples 1 to 4 and 70VOL% of the copper-palladium coated molybdenum disulfide powder obtained in Comparative Example 1 were each added to glass beads (diameter 2m+n) 30V leaf%. After rotating and mixing for 1 hour, the mixture was sieved and used as the sample.

*4: Surface composition was analyzed using an X-ray microanalyzer.

〔Effect of the invention〕

Since the present invention has the above configuration, the following effects are achieved. That is, in the copper-silver-coated metal sulfide "5) powder of the double-coated layer quiz according to the present invention, since silver is present on the surface of the metal sulfide powder, this silver is mixed with the sulfur in the metal sulfide. It reacts and forms a large amount of its compounds.Therefore, compared to the case of using platinum group metals that form fewer such compounds, silver has better compatibility with metal sulfide powder and greater adhesion strength.In addition, silver The plating has good throwing power1 and high adhesion strength.In addition, the diffusion/alloy layer type copper-silver coated metal sulfide powder of the present invention has silver and tears integrated. Therefore, stronger adhesion can be provided.

The method for producing the double wave) W layer type copper-silver-coated metal sulfide powder according to the present invention is to form a silver-supported layer on the entire surface of the metal sulfide powder by a silver salt thermal decomposition method, and then use a chemical plating method. Since the 1liI layer is formed on the surface of the root JFI layer, it can be processed easily and inexpensively, and bath management is also easy. In addition, the method for producing the diffusion/alloy layer type copper-silver coated metal sulfide powder according to the present invention involves preparing the copper-silver coated metal sulfide powder of the double coating layer quiz at a relatively low temperature.
Since only a single treatment is required, it is possible to easily obtain a scrap-silver-coated metal sulfide powder having strong adhesion strength.

Therefore, the present invention makes a significant contribution to the industrial production of ceramic powders such as molybdenum disulfide for metallization.

Claims (4)

[Claims] (1) A copper-silver coated metal sulfide powder, characterized in that the surface of the metal sulfide powder is covered with a silver support layer, and the surface is covered with an upper layer. (2) A copper-silver coated metal sulfide powder, characterized in that the surface of the metal sulfide powder is covered with a diffusion layer or an alloy layer of silver and copper. (3) Metal sulfide powder is immersed in an alcohol aqueous solution of silver nitrate, dried, and heated at 450° C. or lower to thermally decompose the silver nitrate and coat the surface of the metal sulfide powder with a silver-supported layer; Next, this is added to an aqueous complexing agent solution adjusted to pH 10 to 13, and an aqueous solution of formalin and a copper compound is added while stirring while maintaining the above pH, thereby coating the surface of the silver support layer with a copper layer. A method for producing a copper-silver coated metal sulfide powder, characterized in that: (4) By heat-treating the copper-silver coated metal sulfide powder obtained by the production method according to claim 3 at 250 to 700°C in a reducing atmosphere or inert atmosphere, the silver support layer and the copper layer are formed. A method for producing a copper-silver coated metal sulfide powder, which comprises diffusing or alloying at least a portion of the powder with the copper-silver coated metal sulfide powder.