JPH0262481B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention easily and efficiently produces extremely fine non-acicular metal oxide particles such as triiron tetroxide, tricobalt tetroxide, and manganese oxide. Relating to a method of manufacturing.

[Prior art and its problems] In general, fine metal oxide particles are useful as pigments, abrasives, electromagnetic materials, and the like. For example, by making iron sesquioxide into fine particles of 0.1 μm or less, it can be used as a special pigment that does not easily transmit ultraviolet rays, increasing its usefulness. In addition, ferrite is generally synthesized by mixing iron oxide with other metal oxides or carbonates and performing a solid-state reaction at high temperatures of 1000°C or higher. Minute iron oxide is desired.

Conventionally, methods for producing fine metal oxide particles generally include (1) a method of precipitating metal cations in the form of hardly soluble hydroxide, carbonate, oxalate, etc., and calcining this; ) A method of calcining the precipitate obtained by hydrolyzing a metal alkoxide, (3) As an iron oxide,
For example, as proposed in JP-A-58-20733, lepidocrocite γ-FeOOH is hydrothermally treated at 200°C for about 30 minutes while stirring in an autoclave to form minute α-type iron sesquioxide. There are ways to get it.

However, in the conventional method as described above, even if the particles are microscopic when forming the precipitate, the particle size may be uneven, or the particles may easily undergo secondary growth in the subsequent firing process and become coarse. The disadvantages include that minute metal oxide particles cannot be easily obtained, and that the process is complicated in industrial operations, such as requiring reactions at high temperatures and under pressure.

[Means for solving the problems] The present inventors solved the problems in the conventional method,
We have conducted extensive research into ways to easily obtain minute metal oxides. As a result, they discovered that metal hydrazine salts can be instantaneously oxidized and decomposed with an oxidizing agent such as hydrogen peroxide, and that minute metal oxide particles with a sharp particle size distribution can be easily obtained, and have thus come to provide the present invention. It is ivy. That is, the present invention is a method for producing minute metal oxide particles, which is characterized by oxidatively decomposing a metal hydrazine salt.

Examples of the metal of the metal hydrazine salt used in the present invention include iron, cobalt, manganese, nickel,
such as tin. Such metal hydrazine salts are generally obtained by reacting at least one corresponding metal salt with hydrazine or a hydrazine compound in an aqueous solution. Therefore, water-soluble metal compounds are generally preferred as metal salts, such as FeCl ₂ ,
Chlorides such as CoCl ₂ , sulfates such as FeSO ₄ and MnSO ₄ , or nitrates are preferably used. The reaction between metal salts and hydrazine is known, for example, as shown in the following formula: FeCl ₂ +2N ₂ H ₄ →FeCl ₂ (N ₂ H ₄ ) ₂ CoCl ₂ +2N ₂ H ₄ →CoCl ₂ (N ₂ H ₄ ) ₂ It will be done.

Next, the oxidative decomposition reaction of the metal hydrazine salt in the present invention can be successfully achieved by adding an oxidizing agent while vigorously stirring the reaction solution of the metal hydrazine salt. Therefore, in the present invention, the synthesis of a metal hydrazine salt and the oxidative decomposition of the hydrazine salt can be carried out continuously in the same reaction vessel. The oxidizing agent is not particularly limited, but from the viewpoint of preventing contamination with impurities, hydrogen peroxide is preferred, but nitrites, hypochlorites, nitric acid, etc. are also applicable.

In the present invention, in order to obtain metal oxide particles with a particularly sharp particle size distribution, the concentration of the metal hydrazine salt is generally 15% by weight or less, particularly 5 to 10% by weight.
It is preferable to carry out oxidative decomposition in an aqueous solution adjusted to That is, since the oxidative decomposition reaction of the metal hydrazine salt is accomplished very instantaneously, if the concentration of the metal hydrazine salt is too high, the reaction will be localized and the particle size distribution of the resulting metal oxide will be uneven. The reaction is also achieved when the concentration of metal hydrazine salt is lower than 5% by weight, but not efficiently. Furthermore, if the reaction temperature is too low, the reaction will not be achieved smoothly and will not be efficient, and as a result, it will be difficult to obtain metal oxide particles having a fine and sharp particle size distribution. Therefore, the reaction temperature is generally preferably in the range of 20 to 100°C, particularly 40 to 90°C.

In the present invention, the oxidative decomposition of the metal hydrazine salt by an oxidizing agent can quickly achieve the reaction as shown in the following formula: 3FeCl ₂ (N ₂ H ₄ ) ₂ +2H ₂ O ₂ →Fe ₃ O ₄ +6NH ₄ Cl+2H ₂ +3N ₂ be done. The generated metal oxide is separated from the reaction solution by a conventional method, washed with water, and then dried to obtain a fine particulate powder.

[Effects] As explained above, the present invention does not require a firing process compared to the conventional method, so there is no coarsening of particles, and non-needle particles with extremely small particles of, for example, 0.05 μm or less and a sharp particle size distribution, are produced. It is possible to obtain metal oxide particles having a shape and a substantially spherical shape. Furthermore, since the present invention does not require a reaction under pressure, it can be carried out quickly, efficiently, and easily with simple steps and operations.
Desired minute metal oxides can be obtained and are extremely useful industrially.

[Examples] Examples of the present invention will be shown below, but the present invention is not limited to these Examples.

Example 1 After heating 600 ml of an aqueous solution of 30 g of ferrous sulfate (heptahydrate) dissolved in water to 50°C, 12 g of saturated hydrazine (N ₂ H ₄ H ₂ O) was gradually added while stirring. As a result, a slightly greenish white precipitate was formed. Next, while stirring, 10 g of hydrogen peroxide solution (15% by weight) was gradually added to proceed with the reaction while generating gas, and the precipitate finally turned black. The generated precipitate was washed with water, filtered and dried to obtain a fine powder.

The powder obtained above was confirmed to be Fe ₃ O ₄ by X-ray diffraction. In addition, the specific surface area of the powder is
As a result of measurement by BET method, it was 74.4 m ² /g. Figure 1 shows an electron micrograph (200,000x magnification) of this powder. Observation of this electron micrograph reveals that the powder particles are approximately spherical with an average diameter of 0.02 μm.

Example 2 30 g of manganese chloride (tetrahydrate) was dissolved in 600° C. of water, heated to 80° C., and then 12 g of saturated hydrazine was gradually added while stirring to form a yellowish white precipitate. . Next, 20 g of hydrogen peroxide solution (15% by weight) was gradually added to the mixture while stirring immediately, thereby producing a precipitate that turned blackish brown in color. The generated precipitate was washed with water, filtered and dried to obtain a fine powder.

The powder obtained above was confirmed to be Mn ₂ O ₃ by X-ray diffraction. Also, the average diameter of the particles is
The specific surface area was 0.04 μm, and the specific surface area was 34.1 m ² /g by BET method.

Example 3 27 g of ferrous sulfate (7 hydrate) and 30 g of cobalt sulfate (7 hydrate) were dissolved in 600 ml of water, heated to 70°C, and then 13 g of saturated hydrazine was added with stirring. Upon gradual addition, an off-white precipitate formed. Then, after raising the temperature to 90℃,
By adding 10 g of hydrogen peroxide solution (15% by weight) while stirring, a black precipitate was formed. The generated precipitate was washed with water, filtered and dried to obtain a fine powder.

As a result of analyzing the powder obtained above by X-ray diffraction,
The peak deviated from the Fe ₃ O ₄ peak, suggesting the presence of an iron-cobalt solid solution. In addition, the presence of cobalt was confirmed as a result of analyzing the powder using fluorescent X-rays.
In addition, the average diameter of the powder particles is 0.02 μm,
When measuring the specific surface area using the BET method, it was 80.7m ² /g.
It was hot.

Example 4 A fine black powder was obtained in the same manner as in Example 1, except that an aqueous sodium nitrite solution (10% by weight) was used as the oxidizing agent instead of aqueous hydrogen peroxide. .

The above powder was confirmed to be Fe ₃ O ₄ by X-ray diffraction, and the average particle diameter was 0.025 μm, and the specific surface area was measured to be 54.6 m ² /g by BET method.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph (200,000 times magnification) showing the shape of the powder obtained in Example 1.

Claims (1)

[Claims] 1. A method for producing minute metal oxide particles, which comprises oxidatively decomposing a metal hydrazine salt.