JPS6227310A - Production of fine metallic oxide particle - Google Patents

Abstract

PURPOSE:To obtain rapidly and efficiently nonacicular and spheroidal hyperfine metallic oxide particles having a sharp particles size distribution with ease at a low cost by decomposing a metallic salt of hydrazine by oxidation with an oxidizing agent. CONSTITUTION:A metallic salt such as FeCl2, CoCl2 or MnSO4 is reacted with hydrazine in water to prepare an aqueous soln. of a metallic salt of hydrazine having <=15wt% concn. An oxidizing agent such as H2O2 is added to the soln. while the soln, is vigorously stirred, they are brought into a reaction at 20-100 deg.C, and a formed precipitate is separated, wasted and dried to obtain the titled particles of magnetic oxide of iron, tricobalt tetroxide, manganese oxide or the like having <=0.05mum average particle size.

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, iron sesquioxide
By making the particles smaller than 0.1 am, they can be used as special pigments that do not easily transmit ultraviolet rays, increasing their 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) converting metal cations into poorly soluble hydroxides, carbonates, #J
A method of precipitating in the form of an acid salt and calcining this, (2)
A method of calcining a precipitate obtained by hydrolyzing a metal alkoxide, (3) as an iron oxide, for example, JP-A-58-
As proposed in No. 20733, levidocrocite γ-Fe00H was stirred in an autoclave.
There is a method of obtaining minute α-type iron sesquioxide by hydrothermal treatment at 200° C. for about 30 minutes.

However, in the conventional method as described above, even if the particles are minute 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. It has drawbacks such as the difficulty in obtaining minute metal oxide particles, and the complicated process in industrial operations, such as the need for reactions at high temperatures and under pressure.

Means for Solving the Problems] The present inventors have conducted intensive research on a method for solving the problems in conventional methods and easily obtaining minute metal oxides.

As a result, they discovered that metal hydrazine salts can be instantly 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.
This has led to the provision of the present invention. 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, and 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 F
Chlorides such as eC12, CoCl2, FeSO4, Mn
Sulfates such as SO4 or nitrates are preferably used. The reaction between a metal salt and hydrazine is known, and is represented by the following formula, for example: FeCl2+2N2H4 +FeCl2(N2H4)2 COCI2+2N2H4-+CoC12(N2H4)2.

Next, the oxidative decomposition reaction of the metal hydrazine salt in the present invention is favorably achieved by adding an oxidizing agent while vigorously stirring the reaction solution of the metal hydrazine salt. Therefore, in the present invention, synthesis of a metal hydrazine salt and 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, it is preferable to carry out oxidative decomposition in an aqueous solution in which the concentration of the metal hydrazine salt is generally adjusted to 15% by weight or less, particularly 5 to 10% by weight. . 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.

Moreover, 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 20-100℃
, particularly preferably in the range of 40 to 90°C.

In the oxidative decomposition of the metal hydrazine salt by an oxidizing agent in the present invention, the reaction is quickly achieved, for example, as shown in the following formula %. 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, for example, 0.
．． It is possible to obtain non-acicular, substantially spherical metal oxide particles that are extremely small, 0.05 μm or less, and have a sharp particle size distribution. Furthermore, since the present invention does not require any reaction under pressure, it is possible to quickly, efficiently, and easily obtain the desired minute metal oxide through simple steps and operations.
It is also 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 Aqueous solution of 30 g of ferrous sulfate (heptahydrate) dissolved in water 60
After heating 0mQ to 50℃, saturated hydrazine (NzH
4.H20) was gradually added with oil while stirring, a slightly greenish white precipitate was formed.

Next, hydrogen peroxide solution (15% by weight) was added to this while stirring.
) By gradually adding 10 g, the reaction proceeded 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 Fe3O4 by X-ray diffraction. Further, the specific surface area of the powder was 74.4 m'/g as measured by the Br':T method. 1st
The figure shows an electron micrograph (200,000 times 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 30g of mankan chloride (tetrahydrate salt) was dissolved in 600ml of water,
After heating to 80°C, add saturated hydrazine 12 without stirring.
A yellowish white precipitate was formed by gradually adding oil. Next, 20 g of hydrogen peroxide solution (15 layers) was gradually added to the mixture while stirring, thereby producing a blackish brown precipitate. Wash the formed precipitate with water, 1! A fine powder was obtained by filtering and drying.

The powder obtained above was confirmed to have M n 203 by X-ray diffraction. In addition, the specific surface area was determined to be 34.1 d1g by BET method.

Example: 3 27 g of ferrous sulfate (7 hydrate) and 30 g of cobalt sulfate (7 hydrate) were dissolved in 600 m of water and heated to 7 g.
After raising the temperature to 0°C, add 13 g of saturated hydrazine without stirring.
By gradually adding , an off-white precipitate was formed. Next, after raising the temperature to 90° C., 10 g of hydrogen peroxide solution (15% by weight) was poured into the solution while stirring, thereby producing a precipitate that turned black. The generated precipitate was washed with water, filtered and dried to obtain a fine powder.

As a result of X-ray diffraction analysis of the powder obtained above, the peak deviated from the Fe3O4 peak, suggesting the presence of an iron-cobalt solid solution. Furthermore, as a result of analyzing the powder using fluorescent X-rays, the presence of cobalt was confirmed. Further, the specific surface area of the powder was measured by FJET method and was 80.7 vn''/g.

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 an oxidizing agent instead of aqueous hydrogen peroxide.

The above powder was confirmed to be Fe3O4 by X-ray diffraction, and the specific surface area was measured to be 54.6 i/g by BET method.

[Brief explanation of the drawing]

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.