JPS5817825B2 - Method for producing metal-coated inorganic fine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing inorganic fine particles such as fine alumina particles coated with a metal, and more specifically, the present invention relates to a method for producing inorganic fine particles such as fine alumina particles coated with a metal, and more specifically, by uniformly coating metals such as nickel, nickel-cobalt, copper, etc. The present invention relates to a method for producing inorganic fine particles of 5 μm or less that have properties such as magnetism.

Conventionally, inorganic particles such as carbon particles or metal particles such as nickel and silver have been known as conductive particles, but there have been few examples of making non-conductive inorganic particles themselves, such as alumina, conductive. unknown.

For this reason, conventionally when imparting electrical conductivity to inorganic fine particles,
It has been attempted to make inorganic particles conductive by mixing fine powders of nickel, silver, etc., but this is because the conductive material is simply dispersed in a matrix of inorganic particles. It had the disadvantage that it was difficult to clean and was not uniform.

In view of the above-mentioned circumstances, the present inventor conducted intensive research on making individual particles of non-conductive inorganic particles or inorganic ceramic particles, such as fine alumina particles with a particle size of 5 μm or less, uniformly conductive. Substance particles or aggregates of fine inorganic particles such as fine alumina particles with a diameter of 5μ or less, which have an average particle size of 10μ or more, are coated with metal by electroless plating and, if necessary, electroplating. By the final grinding of crushed particles or aggregates,
It has been found that inorganic fine particles each having a particle size of 5 μm or less and which are individually uniformly coated with metal can be easily and reliably obtained.

That is, as a result of various studies conducted by the present inventors, it has been found that when applying electroless plating to the inorganic powder itself, precipitation and recovery are not easy if the powder is not rice grains, especially if the powder is not rice grains. It takes time for the material to settle, and if the mesh of the furnace cloth is not very fine, problems such as passing through the furnace cloth will occur, making it less economical and mass-producible.''-1 The resulting electroless plating film is Kokichi and Yaguchi observed that the particles had poor homogeneity as a whole, and therefore it was extremely difficult to apply a homogeneous metal coating directly to individual inorganic fine particles with a particle size of 5 μm or less.

Therefore, as a result of further investigation, we found that by applying electroless plating to the phantom particles or aggregates of inorganic fine particles, these phantom particles or aggregates are uniformly coated with an electroless plating film. By crushing with a ball mill etc., the skeletal particles or aggregates are divided into individual particles to obtain inorganic fine particles homogeneously coated with metal. When this method is used, it can be used as various electronic materials, fillers, etc. It was discovered that homogeneous metal-coated inorganic fine particles that can be suitably used can be produced efficiently, easily, and economically, and that this method is extremely superior as an industrial method for producing metal-coated inorganic fine particles, and the present invention was completed. This is what I came to do.

The present invention will be explained in more detail below.

The method for producing metal-coated inorganic fine particles of the present invention involves subjecting a skeleton particle or aggregate of inorganic fine particles to electroless plating, further electroplating if necessary, and then pulverizing this.

In this case, as the inorganic fine particles, for example, At203°S
i02, TiO2, BaTiOs, MnO2,
Oxides such as Cr2O3 and Fe20B, sulfates such as BaS04, A,/, (OH)s.

Hydroxides such as W(0H)2, Cr(OH)a, C,
W.C.

Carbides such as SiC, nitrides such as TiN, silicides, borides, and other inorganic fine particles used as ceramic materials such as glass may be used.

The present invention is directed to the inorganic fine particles, particularly the particle size of 5 μm or less, usually 1 μm.
The following phantom particles or aggregates of inorganic fine particles are used and electroless plating is applied to these phantom particles or aggregates.
A thickness of μ or more, particularly 20 μ or more, is preferably used.

The skeleton particles or aggregates of the inorganic fine particles can be obtained by calcining an appropriate metal salt or inorganic fine particles at an appropriate temperature.

For example, in the case of fine alumina particles, aluminum sulfate, ammonia carbonate, ammonia sulfate,
One or more of chlorides, fine hydroxides, and nitrates
Those obtained by calcining at a temperature of 000°C or higher, preferably 1000 to 1300°C are used.

The skeleton particles have a spherical or cocoon shape formed by thermal decomposition of the raw material, and are continuous particles of fine alumina with a particle size of 5 μm or less (see Figures 1 and 2).

In addition, in the case of an aggregate of fine alumina, fine alumina of 5μ or less and/or γ alumina produced by a vapor phase method is heated at a temperature of 1100°C or higher, preferably 1200 to 1300°C.
Those obtained by calcining at a temperature of °C can be used.

This aggregate of fine alumina is a combination of grain growth due to re-calcination of fine alumina and aggregates of discontinuous particles, and is an aggregate of fine alumina with a particle size of 5μ or less (see Figures 3 and 4). .

Furthermore, titanium dioxide skeleton particles can be made from titanium sulfate or ammonia sulfate by calcining at 600°C or higher, and aggregates can be made by adding a small amount of alkali salt to titanium dioxide and calcining at 800°C or higher. It can be obtained by

In the present invention, electroless plating is applied to the skeleton particles or aggregates of the inorganic fine particles.

As this electroless plating method, a known method can be adopted, and after attaching a catalyst such as metal palladium to the skeleton particles or aggregates of the inorganic fine particles, it is immersed in the required electroless plating solution. It performs electroless plating.

In this case, methods for attaching the catalyst include, for example, a method in which the skeleton particles or aggregates are immersed in an acidic solution of a stannous salt and then in an acidic solution of a palladium salt (so-called sensitizing-activation process); A method of immersing in a so-called colloidal palladium solution containing a tin salt and a palladium salt and then pickling, a method of immersing in an acidic solution of palladium salt and then immersing in a reducing agent solution, or a method of using a combination of these methods, etc. Although any suitable method may be employed, a sensitizing-activation process is preferred from the viewpoint of coverage, and it is particularly desirable to repeat this method two to three times.

The type of electroless plating is appropriately selected depending on the function required of the product (metal-coated inorganic fine particles), and a desired electroless plating such as copper, nickel, cobalt, nickel-cobalt alloy, etc. is applied.

In addition, in the present invention, electroless plating is acidic, neutral,
It does not matter whether it is alkaline or not, and there are no restrictions on the plating temperature, type of reducing agent, etc.

Further, the thickness of the electroless plating film is also appropriately selected depending on the functions required of the product, but preferably the film thickness is 0.1 μm or more.

After applying the electroless plating, barrel method,
For knitting, electroplating can also be applied using methods such as methods.

In this case, the type of electroplating, film thickness, etc. are selected depending on the functions required for the product.

After plating, the particles or aggregates on which the metal film is formed are crushed.

In this case, a ball mill or the like is used as the crushing means.

Through this crushing process, the particles or aggregates are reduced to 5 μm.
The following individual particles are divided and pulverized to obtain inorganic fine particles having a particle size of 5 μm or less, each homogeneously coated with a metal film.

The metal-coated inorganic fine particles thus obtained are imparted with properties such as conductivity or magnetism, and can be effectively used as electronic materials and as fillers for resins, films, and the like.

According to the present invention, inorganic fine particles having a particle size of 5 μm or less that are homogeneously coated with metals such as nickel and copper can be easily, efficiently, and reliably produced, and the method of the present invention is economical. This is an excellent industrial manufacturing method.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 Fine alumina skeleton particles are degreased by immersion in an alkali, washed with water, and then pickled (concentrated hydrochloric acid 400 ml/l).

Next, the following solution 5nC4・2H2015? /l pH 2.0 (adjusted with hydrochloric acid) was used for sensitizing at room temperature for 5 minutes, and after washing with water, the following solution PdC40.2? /l, H2,0 (adjusted with hydrochloric acid) for 3 minutes at 40°C, followed by water.

Wash.

After repeating the above sensitizing and activation processing again, electroless nickel plating "DEL nickel plating" manufactured by Uezai Kogyo Co., Ltd. (this is electroless nickel plating using dimethylborazane as a reducing agent), This precipitated film is made of nickel-boron containing less than 1% boron) at 60°C for 5 minutes, and the shape of the particles is about 0.
．． A 5μ electroless nickel-boron film is formed.

This is washed with water, then hot water, dried, and finally, the skeleton particles are crushed in a ball mill, divided into 4 individual fine particles, and metal (boron) coated fine alumina particles with a particle size of 5μ or less are prepared. get.

As a result of observing the obtained fine alumina particles under a microscope, it was found that each of the alumina particles was uniformly coated with a nickel-boron electroless plating film.

In the rice grain example, ammonium alum calcined at 1200° C. for 3 hours was used as the fine alumina particles.

This micrograph is shown in Figures 1 and 2.

Figure 1 shows one skeleton particle at 1500x magnification, and the second
The figure is an enlarged photograph of the skeleton particles in Figure 1 at a magnification of 10,000 times.

Example 2 After pretreating an aggregate of fine alumina particles in the same manner as in Example 1, electroless copper plating with the following composition was performed.

Cu SO4.5 H200.03 lumo/l lotusel salt
0.3 “Formalin (37%) 0.3 Stabilizer
Small amount pH (adjusted with NaOH) 12.8 Plating temperature After plating at room temperature, wash with water, wash with hot water, dry, then crush with a ball mill to separate into individual particles, metal (copper) with a particle size of 5μ or less
A coated fine alumina was obtained.

As a result of observing the fine alumina particles under a microscope, it was found that all the fine particles were uniformly coated with copper.

In addition, as an aggregate of fine alumina, fine grain aluminum hydroxide is calcined at 1200°C for 3 hours, and then heated to about 200°C.
The product was cooled to 1300°C and fired again at 1300°C for 3 hours.

Figures 3 and 4 show their microscopic photographs, respectively.

FIG. 3 shows one aggregate at a magnification of 1,500 times, and FIG. 4 is an enlarged photograph of the aggregate in FIG. 3 at a magnification of 6,000 times.

Further, although Examples 1 and 2 have been described with respect to the phantom particles or aggregates of fine alumina, phantom particles or aggregates of other inorganic fine particles can be treated in the same manner.

[Brief explanation of drawings]

Figure 1 is a microscopic photograph of a skeleton particle of fine alumina, Figure 2 is an enlarged microscope photograph of a same-shaped skeleton particle, Figure 3 is a microscope photograph of an aggregate of fine alumina, and Figure 4 is an enlarged microscope photograph of the same aggregate. be.

Claims (1)

[Scope of Claims] 1. Electroless plating is applied to skeleton particles or aggregates of inorganic fine particles to form an electroless plated metal film on these skeleton particles or aggregates, electroplating is performed if necessary, and finally the above-mentioned A method for producing metal-coated inorganic fine particles, which comprises obtaining metal-coated inorganic fine particles by pulverizing skeleton particles or aggregates. 2. The manufacturing method according to claim 1, wherein the inorganic fine particles have a particle size of 5 μm or less. 3. The manufacturing method according to claim 1 or 2, wherein the particle size of one of the skeleton particles or aggregates of inorganic fine particles is 10 μ or more. 4. The manufacturing method according to any one of claims 1 to 3, wherein inorganic fine particles are used as the ceramic material. 5 Inorganic fine particles are oxides, sulfates, hydroxides, carbides,
5. The manufacturing method according to claim 4, wherein the material is selected from nitrides, silicides, borides, and glasses.