JP2003342007A - Method for producing metal oxide fine particle and the metal oxide fine particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nanometer-order crystalline metal oxide and a method for producing whereby the particle size of the obtained metal oxide fine particle can be controlled. <P>SOLUTION: This method comprises hydrolyzing a hydrolyzable metal compound in a polyol solution containing it followed by irradiating with a microwave. The polyol includes polyhydric alcohols such as diols or triols and a mixture of a plurality of polyols. The hydrolyzable metal compound is generally a metal alkoxide, but includes a metal salt such as an acetate, chloride, oxalate, sulfate or nitrate depending on the type of metal. The metal compound may be a hydrate or a non-hydrate, and titanium, silicon, tin and zinc are cited as the metal. In the case of non-hydrated metal compound, hydrolysis is performed by adding water to the polyol solution. In the case of the hydrated compound, the hydrolysis may be performed by irradiating with the microwave having an output not grater than that of the above one. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing metal oxide fine particles, and is particularly suitable for use in the fields of photocatalyst, functional electrode, electrode catalyst, solid catalyst, gas sensor, solar cell, photonic crystal and the like. Can be done.

[0002]

2. Description of the Related Art Metal oxides such as titanium oxide having a size of nanometer order are important materials used as photocatalysts, solar cells, and photonic crystals. A method of hydrolyzing a metal alkoxide in order to obtain fine particles of a metal oxide such as titanium oxide is known. Since this hydrolysis method forms an oxide in a solution,
Compared with solid-phase reaction, it has the advantages that it is easier to make the composition uniform, and the cost is lower than vapor deposition. By the way, the oxide immediately after hydrolysis is often amorphous, and the amorphous is sometimes used, but it is also necessary to crystallize it in order to use it for various purposes.

[0003]

However, in the conventional hydrolysis method, even if the particles are fine particles at the time of hydrolysis, when they are heated to a high temperature of, for example, 500 ° C. or more to crystallize, the particles are bonded to each other and the I was unable to maintain the meter order. Therefore, the first object of the present invention is to provide a crystalline metal oxide on the order of nanometers. The second object is to provide a method capable of controlling the particle size of the obtained metal oxide fine particles.

[0004]

In order to solve the problem, the method for producing the metal oxide fine particles of the present invention is to hydrolyze the metal compound in a polyol solution containing a hydrolyzable metal compound. After that, it is characterized in that a microwave is applied. Here, the polyol includes polyhydric alcohols (whether aliphatic or aromatic) such as diols and triols, and a mixture of plural kinds of polyols.
The hydrolyzable metal compound is generally a metal alkoxide, but depending on the type of metal, acetate, chloride,
Also included are metal salts such as oxalate, lead sulfate, nitrates. Further, the metal compound may be a hydrate or a non-hydrate.
Examples of metals include titanium, silicon, tin, zinc, and the like. When the metal compound is non-hydrated, hydrolysis is done by adding water to the polyol solution. When the metal compound is a hydrate, the hydrolysis is carried out by irradiating with a microwave having an output not higher than the microwave, or water may be added in parallel.

When the metal compound is hydrolyzed in a polyol solution containing a hydrolyzable metal compound, a metal oxide surrounded by the polyol is produced. When microwaves are irradiated in this state, the polyol, which is the solvent, is heated uniformly, and the produced metal oxide crystallizes. Moreover, since the polyol is present around the particles, the particles are not bonded to each other and the fine particle state is maintained. The microwave generally refers to an electromagnetic wave of 1 GHz to 300 GHz, usually 1 GHz.
z to 10 GHz. Polyol as a solvent easily absorbs microwaves and has a high heat generation efficiency, and therefore can be crystallized in a short time. According to the present invention, the particle size of the metal oxide produced can be controlled by changing the total amount of water to be added, the time of microwave irradiation, the type of polyol, and the like. Generally, as the total amount of water, the microwave irradiation time or the carbon number of the polyol increases, the particle size also increases. Therefore, 0.5 nm to 50
In particular, fine particles of metal oxide crystals having a desired particle diameter in the range of 1 nm to 15 nm can be obtained.

[0006]

EXAMPLES Example 1 As a microwave irradiation apparatus, an MMG-213VP microwave apparatus manufactured by Micro Electronics Co., Ltd. equipped with a magnetron having a frequency of 2.45 GHz and a maximum output of 1.3 kW was prepared.

2 mmol of tetraisopropoxide titanium Ti (OiPr) 4 and 50 mL of 1,4-butanediol were placed in a nitrogen atmosphere in a quartz flask having an internal volume of 100 mL. While measuring the temperature of this solution with a thermocouple,
The solution was irradiated with microwave of 200 W for 3 minutes at a temperature of 413K. The temperature of the solution reached 413 K within 2 minutes after irradiation. Then, 1 mL, 2 mL, or 3 mL of pure water was added dropwise and irradiated with a microwave having an output of 900 W, and the temperature of the solution reached 513 K within 1 minute. Subsequently, the microwave was intermittently irradiated for 30 minutes while controlling the temperature of the solution to be maintained at 513K. The amount of added water is 1 mL
Only when the temperature reached 513K, the microwave output was lowered to 700W. The output was maintained during the remaining irradiation time.

Immediately after irradiation, the solution was cooled to 30 m.
A precipitate was generated by diluting with L ethanol and centrifuging at 40000 G for 10 minutes. The obtained precipitate is ultrasonically washed twice with ethanol and then washed at 40,000 G for 10
Centrifuge for minutes and dry. Using an X-ray diffractometer (MultiFlex manufactured by Rigaku Denki Co., Ltd.), 40 kV-40 mA, 1
The precipitate was irradiated with X-rays of Cu-Kα under the condition of ° (2θ) / min. The crystal size was calculated from the full width at half maximum of the [101] diffraction peak of the anatase phase according to the Debye-Scherrer equation.
In the formula, λ _Cu- K α1 = 0.154056 nm and K = 0.9.
The calculation results are shown in Table 1 together with the amount of added water, the temperature during microwave irradiation, and the irradiation time. Regarding the precipitation of sample No. 3, a transmission electron microscope (H-9000 manufactured by Hitachi, Ltd.)
An image of the precipitate was taken with. The photograph taken is shown in FIG. Further, FIG. 2 shows a result of arbitrarily selecting 200 particles from the particles belonging to the range of FIG. 1 and totaling them for each size.

[0009]

[Table 1]

As a result of X-ray diffraction, regardless of the amount of added water, all the precipitates were anatase phase of titanium oxide, and as shown in Table 1, the sample under any condition had a crystal size of nanometer order. When the conditions other than the amount of added water were the same, the crystal grain size increased as the amount of added water increased. It should be noted that among them, the crystal grain size of sample No. 1 of 4.5 nm is found to match the average grain size of 5.8 nm in FIG. Therefore, the crystal grain size by X-ray diffraction can be understood as the average value of the actual crystal grain group.

Example 2 Example 1 was repeated except that 1,5-pentanediol was used as a solvent instead of 1,4-butanediol and the microwave output and irradiation time were changed as shown in Table 2. Similarly, titanium oxide fine particles were synthesized.

[0012]

[Table 2]

It was identified by X-ray diffraction that the precipitate obtained in this example was also in the anatase phase of titanium oxide. Then, the sample numbers 4, 7 and 9 of Table 2 are replaced with the sample numbers 1 and 1 of Table 1.
As can be seen by comparing with 2 and 3, respectively, even if the other conditions were the same, the crystal grain size increased only by changing the solvent from 1,4-butanediol to 1,5-pentanediol. Further, from the sample numbers 4, 7 and 9 in Table 2, the crystal grain size increased with the amount of added water, as in Example 1. Furthermore, as seen in sample numbers 5, 6 and 7 of Table 2,
Even if the amount of added water and the temperature are the same, as the irradiation time increases,
The crystal grain size increased.

[0014]

As described above, according to the present invention, it is possible to quickly and inexpensively obtain metal oxide fine particles having good crystallinity on the order of nanometers. Further, the particle size can be controlled to a desired value. Therefore, it is useful in various fields in which crystalline metal oxide fine particles are used.

[Brief description of drawings]

FIG. 1 is a photograph of Sample No. 3 of Example 1 taken with a transmission electron microscope.

FIG. 2 is a graph showing a particle size distribution obtained based on the above photographs.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayuki Kitamura             3-9-9-203 Onohara East, Minoh City, Osaka Prefecture F-term (reference) 4G042 DA01 DB11 DB15 DB38 DC03                       DD04 DE09 DE14                 4G047 CA02 CB06 CB08 CC03 CD04                       CD07

Claims (4)

[Claims] 1. A method for producing fine metal oxide particles, which comprises hydrolyzing a metal compound in a polyol solution containing a hydrolyzable metal compound and then irradiating with microwaves. 2. The method of claim 1, wherein the metal compound is a non-hydrate and the hydrolysis is done by adding water to the polyol solution. 3. The method according to claim 1, wherein the metal compound is a hydrate, and the hydrolysis is performed by irradiating with a microwave having a power not higher than the microwave. 4. Fine metal oxide particles comprising a metal oxide crystal having an average particle size of 0.5 nm to 50 nm.