KR100417694B1 - Preparation method of spherical monodispersed bariumtitanate particles - Google Patents

Abstract

The present invention relates to a method for producing monodisperse spherical barium titanate fine particles by alkoxide method, octanol, acetonitrile, which is the higher alcohol among the alcohols present in the liquid phase at room temperature. ) And a barium titanium composite alkoxide in a mixed solution consisting of ethanol (Ethanol) is hydrolyzed to provide a method for producing barium titanate fine particles having a spherical shape, uniform particle size and a size of 1 micron or less.

Description

Preparation method of monodisperse spherical barium titanate particles {Preparation method of spherical monodispersed bariumtitanate particles}

The present invention relates to a method for producing monodisperse spherical barium titanate fine particles, and more particularly to the production of barium titanate fine particles having a spherical particle size and a size of 1 micron (μm) or less by the alkoxide method. It is about how to.

A barium titanate sintered body having a perovskite structure is widely used as a raw material for producing advanced electronic materials such as dielectrics and piezoelectric elements due to its crystal structure.

The raw materials of functional ceramic devices such as barium titanate powder used in such high-tech industries have a high purity of more than 99.0% and a uniform microstructure because the physical properties of devices manufactured from these materials vary greatly depending on their chemical composition and microstructure. It needs to be made into a sphere having a dense, chemically homogeneous and having a particle size of less than 1 micron.

The barium titanate powder is prepared by mixing barium chloride, titanium chloride aqueous solution, and oxalic acid solution to precipitate barium titanyl oxalate, and then pyrolyzing it to prepare a metal, inorganic salt, oxide, or hydrate. The hydrothermal synthesis method, which is put into an autoclave and manufactured under high temperature and high pressure, is known, but the barium titanate powder or crystals prepared by such a method cannot be spherical in form and are not chemically homogeneous. The disadvantage is that the size of the particles cannot be made below 1 micron.

In recent years, the method of hydrolyzing a metal alkoxide in an organic solvent as a means of manufacturing spherical particulate ceramic raw material powder attracts attention.

This method is called alkoxide method or hydrolysis control method. In 1968, Stober was known to produce spherical silica fine particles having a size of 0.5 micron by hydrolyzing silicon alkoxide using ammonia as a catalyst in ethanol. Started.

Thereafter, titania fine particles (JP-A 62-91418, Pyung 1-33939) and zirconia fine particles (JP-A 62-91421) were produced using an ethanol solvent.

However, it is not known to synthesize monodisperse spherical barium titanate particles by the alkoxide method.

The main reason why the barium titanate cannot be synthesized by the alkoxide method is that the hydrolysis rate of the composite alkoxide of barium and titanium, which is a precursor, is very fast. This is because spherical monodisperse fine particles cannot be obtained because the hydrolysis rate of the very fast barium titanium composite alkoxide cannot be properly controlled with a lower alcohol solvent such as ethanol used in the alkoxide method.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing barium titanate fine particles having a spherical shape, a narrow particle size distribution, and a particle size of 1 micron or less using an alkoxide method. .

1 is a scanning electron microscope (SEM) photograph of monodisperse barium titanate particles prepared according to an embodiment of the present invention.

Figure 2 is a scanning electron microscope (SEM) micrograph of the barium titanate fine particles in the form of aggregates synthesized by the comparative example of the present invention.

In order to achieve the above object, the present invention is a method for synthesizing the barium titanium fine particles using the alkoxide method, octanol (Actoniol), acetonitrile which is the highest alcohol among the alcohols present in the liquid phase at room temperature And it provides a method for producing monodispersed spherical barium titanate fine particles by hydrolyzing the barium titanium composite alkoxide in a mixed solvent consisting of ethanol (Ethanol).

The method for producing monodisperse spherical barium titanate fine particles using a mixed solution of octanol, acetonitrile and ethanol

a) dissolving 0.04 to 0.30 mol / l of barium titanium complex alkoxide in 45 to 65% by volume of octanol to prepare an octanol solution;

b) preparing a mixed solution by adding 25 to 45% by volume of acetonitrile to the octanol solution such that the total amount with the octanol solution becomes 90% by volume;

c) preparing a reaction solution by mixing a solution obtained by dissolving 0.04 to 0.45 mol / L of water in 10% by volume of ethanol in the mixed solution; And

d) a method for producing monodisperse spherical barium titanate fine particles, comprising growing the nucleated barium titanate fine particles at the initial stage of the reaction solution formation.

Hereinafter, the present invention will be described in more detail.

In the method for preparing monodisperse spherical barium titanate fine particles according to the present invention, first, dissolving 0.04 to 0.30 mol / l of barium titanium complex alkoxide in 45 to 65 vol% (volume%) octanol to prepare an octanol solution 25 to 45% by volume of acetonitrile is added to the octanol solution so that the combined amount with the obtained octanol solution is 90% by volume to prepare a mixed solution. At this time, in order to completely dissolve the alkoxide in the solvent, it is preferable to heat each solution to a temperature of 21 to 60 ℃ and then mix.

The reaction solution obtained by dissolving 0.04 to 0.45 mol / L of water in 10% by volume of ethanol in the mixed solution was mixed while stirring to proceed the hydrolysis reaction of the alkoxide.

When the ethanol solution is mixed with the mixed solution, the hydrolysis reaction starts immediately, and nuclei of barium titanate fine particles are generated at the beginning of the reaction. The nucleus is grown by initially maintaining the reaction solution in which the nucleus is formed at a constant temperature, and maintaining the nucleus to a desired particle size for a predetermined time, preferably 30 minutes to 3 hours.

According to the method for producing barium titanate according to the present invention, after a certain amount of barium titanate fine particle nucleus is generated, additional nuclei are prevented by controlling the synthesis conditions, and only the nuclei that have already been formed are grown to have high monodispersity. Titanate fine particles are obtained.

In the present invention, when the barium titanium complex alkoxide is dissolved in octanol, it may not be easily dissolved at room temperature, and the mixture is stirred while heating at about 50 ° C.

The concentration of the barium titanium composite alkoxide used to prepare the barium titanate fine particles is preferably 0.04 to 0.30 mol / l, and when the concentration is less than 0.04 mol / l, the concentration of the hydrolyzate is low and the barium titanate fine particles The nucleation of does not occur, and if the concentration exceeds 0.30 mol / l excess nuclei are generated in the solution, there is a problem that agglomerates are generated by sticking to each other during the grain growth process.

In addition, it is preferable that the concentration of water essential for the hydrolysis reaction is 0.04 to 0.45 mol / l, and when the concentration of water is less than 0.04 mol / l, colloidal particles of barium titanate are precipitated in the reaction solution. It takes a long time and is not practical, and when the concentration of water exceeds 0.45 mol / L, the particle size distribution of the barium titanate fine particles is widened, resulting in polydispersion or generation of aggregates other than spherical fine particles.

In order to produce a uniform and monodisperse barium titanate powder, the mixing ratio of the octanol solution and acetonitrile used in the reaction is also an important reaction factor.When the volume is set to 90% by volume after mixing the two solutions, It is preferable that the volume ratio of double acetonitrile is 25 to 45 volume%. If the volume ratio occupied by the acetonitrile is less than 25% by volume or exceeds 45% by volume, spherical barium titanate fine particles are not obtained and barium titanate aggregates are not obtained because of poor mixing of the two solutions.

When acetonitrile is added to and mixed with the octanol solution in which the barium titanium complex alkoxide is dissolved, the barium titanium complex alkoxide dissolved in the octanol is precipitated. Sex should be good. Therefore, in order to improve the mixing of the two solutions, it is preferable to raise the temperature of the octanol solution and the acetonitrile solution to 21 ° C. to 60 ° C., respectively, before mixing the two solutions.

When the temperature of the mixed solution is less than 21 ° C., the octanol solution and acetonitrile are not mixed at all. If the temperature of the solution exceeds 60 ° C., the hydrolysis reaction proceeds too fast after the two solutions are mixed. There is a problem that only the barium titanate aggregate is produced without the titanate fine particles being produced.

In addition, in order to uniformly mix the octanol solution and acetonitrile and to generate the grain growth uniformly throughout the solution, it is preferable to stir the reaction solution, and as a stirring method, a stirring method using a magnetic stirrer, A stirring method using a propeller type stirrer, stirring using ultrasonic waves, etc. may be used, but there is no need to particularly limit the stirring method or apparatus.

The growth rate of the barium titanate particles is very fast up to about 1 minute after adding the ethanol solution to the mixed solution of octanol solution and acetonitrile, but the growth rate becomes slow as the particles grow. Such particle growth lasts up to about 1 hour after mixing the ethanol solution, but the particle size grown for about 5 minutes after the addition of ethanol reaches about 90% of the final particle size. This other barium titanate particle can be obtained. According to one embodiment of the invention, the particle size obtained after one hour of grain growth was about 0.15 microns.

Barium titanate microparticles grown to a desired size according to the barium titanate microparticle manufacturing method of the present invention is centrifuged in a centrifuge to recover only the microparticles and the recovered microparticles are dried at about 200 ℃ in an oven and a vacuum dryer, and finally monodispersed. Spherical barium titanate fine particles can be obtained.

The particle size distribution of the barium titanate fine particles prepared by the method for synthesizing the monodisperse barium titanate fine particles of the present invention has a normal distribution, and includes fine particles of 68% or more of the total particles within ± 10% of the average particle diameter, and thus has a very high monophase. Is obtained. Therefore, the alkoxide method using the mixed solution of the present invention can not only produce fine particles of a size suitable for product use, but also provide suitable barium titanate fine particles which do not have a detrimental effect on products using barium titanate fine particles. .

The following presents preferred examples and comparative examples to aid in understanding the invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples.

(Example 1)

After adding barium titanium complex alkoxide 0.045 mol / l to 45 vol% octanol heated to a temperature of about 50 ℃ to prepare a barium titanium solution, it was maintained at a temperature of about 40 ℃, the temperature was raised to about 40 ℃ 45 Volumetric acetonitrile was added to prepare a mixed solution while stirring. To the mixed solution prepared above, 0.04 mol / l of distilled water dissolved in 10% by volume of ethanol was added with stirring and mixed to perform hydrolysis of the barium titanium composite alkoxide. After maintaining the hydrolysis reaction at room temperature for 1 hour to sufficiently grow the resulting nucleus, the fine particles and the solvent were separated by a centrifuge, and the separated precipitate was dried for 6 hours in a vacuum dryer at 200 ° C. for barium titanate. Fine particles were prepared.

As a result of confirming the prepared barium titanate fine particles by scanning electron microscopy, it was found that monodisperse spherical barium titanate fine particles having an average particle diameter of 0.15 micron and no aggregation were prepared, and the results are shown in FIG. 1.

(Example 2)

0.30 mol / l of barium titanium complex alkoxide was added to 65 vol% octanol heated to a temperature of about 50 ° C. to prepare a barium titanium solution, and then maintained at a temperature of about 40 ° C., and the solution was heated to a temperature of about 40 ° C. 25 Volumetric acetonitrile was added to prepare a mixed solution while stirring. 0.45 mol / l of distilled water dissolved in 10% by volume of ethanol was added to the mixed solution with stirring, followed by hydrolysis of the barium titanium composite alkoxide. After maintaining the hydrolysis reaction at room temperature for 1 hour to sufficiently grow the resulting nucleus, the fine particles and the solvent were separated by a centrifuge, and the separated precipitate was dried for 6 hours in a vacuum dryer at 200 ° C. for barium titanate. Fine particles were prepared.

When the barium titanate particles prepared above were confirmed by scanning electron microscopy, it was found that monodisperse spherical barium titanate particles having an average particle diameter of 1 micron and no aggregation were produced.

(Comparative Example 1)

0.50 mol / l of barium titanium composite alkoxide was added to 70 vol% octanol heated to a temperature of about 50 ° C. to prepare a barium titanium solution, and then maintained at a temperature of about 40 ° C., and the solution was heated to a temperature of about 40 ° C. 20 Volumetric acetonitrile was added to prepare a mixed solution while stirring. To the mixed solution prepared above was added 0.50 mol / l of distilled water dissolved in 10% by volume of ethanol while stirring and mixed to perform hydrolysis of the barium titanium composite alkoxide. After maintaining the hydrolysis reaction at room temperature for 1 hour to sufficiently grow the resulting nucleus, the fine particles and the solvent were separated by a centrifuge, and the separated precipitate was dried for 6 hours in a vacuum dryer at 200 ° C. for barium titanate. Fine particles were prepared.

As a result of confirming the prepared barium titanate microparticles by scanning electron microscope, it was not spherical, unlike Examples 1 and 2, it was found that the particles produced are agglomerated with each other severely, the results are shown in Figure 1 below.

The method for producing the monodisperse spherical barium titanate fine particles of the present invention is hydrolyzed barium titanium composite alkoxide using a mixed solution of octanol, acetonitrile and ethanol to have an average particle size of 1 micron or less and suitable size for use without aggregation. Monodisperse spherical barium titanate fine particles can be prepared, and the prepared monodisperse spherical barium titanate fine particles can be used to prepare advanced electronic materials such as dielectrics or piezoelectric elements, pigments, cosmetics, jewelry or fillers, and the like.

Claims (5)

a) dissolving 0.04 to 0.30 mol / l of barium titanium complex alkoxide in 45 to 65% by volume of octanol to prepare an octanol solution; b) preparing a mixed solution by adding 25 to 45% by volume of acetonitrile to the octanol solution such that the total amount with the octanol solution becomes 90% by volume; c) preparing a reaction solution by mixing a solution obtained by dissolving 0.04-0.45 mol / L of water in 10% by volume of ethanol in the mixed solution; And d) growing the nucleated barium titanate particulate nucleus at the beginning of the reaction solution formation; Method for producing monodisperse spherical barium titanate fine particles comprising a. delete The method for producing monodisperse spherical barium titanate fine particles according to claim 1, wherein the mixed solution of b) is mixed after heating the octanol solution and acetonitrile to 21 ° C to 60 ° C. The monodisperse spherical barium titanate microparticles according to claim 1, wherein the mixed solution is stirred in any one or all of the steps of preparing the mixed solution, preparing the reaction solution and nucleus growth. Way. The method for preparing monodisperse spherical barium titanate fine particles according to claim 1, wherein the nucleus growth step of d) is performed at room temperature for 1 hour.