Production of monodispersed hyperfine particles of oxide of rare earth element by inverse micelle method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a technique for easily producing ultrafine particles of rare earth oxides and composite oxides having an extremely small average particle size and excellent monodispersity.

【0002】

[Conventional technology]

In the conventional rare earth oxide fine particles, since the particle size is large, the particle size distribution is wide, and the shape of the particles varies, so that electronic materials, functional ceramic materials, phosphor materials, catalyst materials, etc. have been particularly refined in recent years. For use in the required fields, steps such as pulverization and classification are required to make the particle size uniform. For this reason, problems such as complicated operation and complicated operation in the particle manufacturing process and contamination of impurities due to the complicated operation occur.

【0003】

[Problem to Solve the Invention]

An object of the present invention is a monodisperse rare earth oxide ultrafine particles having an extremely small average particle size and a composite, which cannot be achieved by conventional production methods such as a coprecipitation method, a hydrolysis method, a uniform precipitation method and a hydrothermal method. It is an object of the present invention to provide oxide ultrafine particles and a method for producing them.

【0004】

[Means for solving problems]

In order to achieve the above object, it is effective to prevent grain growth by advancing the hydrolysis reaction in a reaction field having a physically limited size. In the present invention, an aqueous solution of a rare earth salt such as a rare earth nitrate is solubilized inside the reverse micelle, and this is similarly solubilized with an aqueous ammonia or a reverse micelle solution of a precipitate such as urea and a room temperature under normal pressure. By reacting with, rare earth oxide ultrafine particles such as yttrium oxide and cerium oxide, and composite oxide ultrafine particles are produced in a monodisperse state.

【0005】

[Action]

In the present invention, it is possible to produce rare earth oxide ultrafine particles and composite oxide ultrafine particles which are monodisperse and have an extremely small average particle size without using a high pressure and high temperature process.

【0006】

In the production, an aqueous solution containing a predetermined amount of rare earth ions is added to a non-polar organic solvent in which a surfactant and, if necessary, a coser factorant are dissolved, and solubilized by forming reverse micelles. This can be easily done by mixing urea with a solution solubilized in reverse micelles. The produced precipitated particles are centrifuged at high speed and washed with hydrocarbons, alcohol, acetone, petroleum ether and the like.

【0007】

Furthermore, since it is possible to use a high-purity reagent as a starting material in the present invention, it is also useful as a means for obtaining extremely high-purity oxide ultrafine particles. Further, by using a solution containing two or more kinds of metal ions as a raw material, monodisperse composite oxide ultrafine particles can be produced in the same manner as a two-component oxide at room temperature under normal pressure.

【0008】

[Example]

By the operation and manufacturing process shown in FIG. 1, monodisperse ultrafine particles of various oxides or composite oxides including rare earth oxides can be manufactured.

【0009】

The operation and manufacture were carried out by the following steps. A surfactant or a mixed solution of a surfactant and a intermediate alcohol having 4 to 8 carbon atoms which is a coser factorant is added to a non-polar organic solvent such as cyclohexane to generate a reverse micelle of the surfactant. An aqueous solution containing various rare earth ions and a precipitate that causes a hydrolysis reaction are solubilized in the above-mentioned reverse micelles, and both are mixed and stirred at room temperature to react, and the resulting precipitate is obtained from hydrocarbons, acetone, and the like. Washed with alcohol. As a result, various rare earth oxide ultrafine particles such as cerium oxide having an extremely small average particle size were obtained.

【0010】

From the transmission type high-resolution electron microscope observation of the obtained ultrafine particles, it was confirmed that nanometer-sized ultrafine particles having very uniform particle sizes were produced. From the selected area electron diffraction ring, it was confirmed that the obtained ultrafine particles were already oxides.

【0011】

FIG. 2 is a particle size distribution diagram of cerium oxide ultrafine particles synthesized by reacting a reverse micelle solution in which an aqueous solution of cerium nitrate is solubilized and a solution in which aqueous ammonia is solubilized in the same manner. From the figure, it was found that the particle size of the produced particles was distributed in the range of 1.6 to 5.6 nm, and the average value was 3.4 nm.

【0012】

Furthermore, the standard deviation of the particle size distribution was 0.72 nm, and it was clarified that the obtained ultrafine particles were extremely excellent in monodispersity.

【0013】

[Effect of the invention]

The present invention is a technique for easily producing monodisperse rare earth oxide ultrafine particles and composite oxide ultrafine particles having an extremely small particle size. Therefore, it is possible to easily produce the desired rare earth oxide ultrafine particles by using various rare earth salt aqueous solutions as a starting material, and various kinds by using a solution containing a plurality of metal ions as a starting material. It also enables the production of composite oxide ultrafine particles.

[Simple explanation of drawings]

[Figure 1]

It is a manufacturing process diagram of the monodisperse rare earth oxide ultrafine particles which made the inside of the reverse micelle a reaction field.

[Figure 2]

It is a particle size distribution map of cerium oxide ultrafine particles produced by the reverse micelle method.