KR101512359B1 - Manufacturing Methods of Colloidal Cerium Oxides - Google Patents

Abstract

Disclosed is a method for producing colloidal cerium oxide uniformly dispersed in a size of several nanometers without exhibiting aggregation. The present invention relates to a method for preparing a cerium oxide precursor solution, which comprises dissolving a cerium oxide precursor in an organic solvent to prepare a cerium oxide precursor solution; Adjusting the pH of the precursor solution to precipitate the surface-treated cerium oxide with a mixed solvent of alcohol and glycol; Washing the surface-treated cerium oxide precipitate with a mixed solvent of an alcohol and a glycol; And subjecting the cerium oxide precipitate to peptization and spontaneous dispersion. The present invention also provides a method for producing a cerium oxide colloid solution. According to the present invention, it becomes possible to prepare a transparent colloidal solution of cerium oxide spontaneously dispersed at a size of several nanometers.

Description

[0001] Manufacturing Methods of Colloidal Cerium Oxides [

The present invention relates to a process for preparing a colloidal cerium oxide solution, and more particularly, to a process for producing colloidal cerium oxide uniformly dispersed in a size of several nanometers without agglomeration phenomenon.

Cerium oxide has a fluorite structure which is stable compared to other oxides having oxygen ion conductivity such as zirconium oxide or bismuth oxide. Because of these structural characteristics, cerium oxide is currently in the spotlight as a material for glass additives, glass abrasives, phosphors, oxygen gas sensors, catalyst supports for automotive exhaust systems, and solid electrolytes for solid oxide fuel cells. Also, in the field of polymer electrolyte membrane fuel cell, a cerium oxide film is used as a catalyst material for removing carbon monoxide.

Generally, the cerium oxide film is produced by various methods such as chemical vapor deposition, pulse laser vapor deposition, evaporation by electron beam evaporation, and coating using a sol-gel method. Among them, the technique using a solution phase such as a coating method using a sol-gel method is advantageous in that it can be manufactured with easy processes and apparatuses and uniformly coated over a wide area as compared with other methods. In addition, it can easily adjust the film component, thickness and structure, and has a very good advantage in cost competitiveness. The most important technique considered for using such a sol-gel method is to produce a stabilized cerium oxide sol having a high concentration. However, the techniques for producing high concentration cerium oxide sol have so many difficulties, and the main problem is that the nano-sized highly concentrated cerium oxide easily agglomerates in the solution.

Therefore, the inventors of the present invention have studied a method of preparing agglomerated cerium oxide particles having a uniform distribution of water nano in a solution phase and easily agglomerating and covalently dispersing the agglomerated cerium oxide particles. As a result, Of a transparent cerium oxide sol.

In order to solve the problems of the prior art described above, it is an object of the present invention to provide a method for easily producing a cerium oxide sol having a high concentration.

Another object of the present invention is to provide a method for easily producing a large amount of cerium oxide nanoparticles forming weak aggregation.

It is another object of the present invention to provide a method for cleaning manufactured nano-sized cerium oxide particles.

It is another object of the present invention to provide a method for preparing a stabilized colloidal sol by cracking and spontaneous dispersion of agglomerated cerium oxide particles washed nano-sized.

The present invention is not limited to the above-mentioned technical subjects, and other technical subjects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a method for preparing a cerium oxide precursor solution, comprising: dissolving a cerium oxide precursor in an organic solvent to prepare a cerium oxide precursor solution; Preparing a cerium oxide surface-treated with a mixed solvent of an alcohol and a glycol by a precipitation reaction by adjusting the pH of the precursor solution; Washing the precipitated cerium oxide in the precipitation reaction step; And subjecting the cerium oxide precipitate to peptization and spontaneous dispersion. The present invention also provides a method for producing a cerium oxide colloid solution.

In the present invention, the organic solvent is preferably a mixed solvent of a glycol-based solvent and an alcohol-based solvent. At this time, the mixing volume ratio of the alcohol-based solvent to the glycol-based solvent is preferably 0.5: 0.5 to 0.98: 0.02.

In addition, an oxidation promoter may be used in the precipitation reaction step. At this time, the oxidation promoter is preferably oxygen gas, air or hydrogen peroxide.

Also, the precipitation reaction step is preferably carried out at a temperature of 30 to 90 ° C and a pH of 5.0 to 10.0.

Further, in the washing step of the present invention, it is preferable that the cerium oxide precipitate is washed with acetone or alcohol.

In addition, it is preferable that the above-described peptization and spontaneous dispersion of the present invention is performed at a temperature of 30 to 75 ° C and a pH of 0.01 to 4.0 after dispersing the cerium oxide precipitate in water. At this time, in the peptization and spontaneous dispersion step of the present invention, pH is preferably controlled by acetic acid or nitric acid, or a mixture thereof.

According to the present invention, the crystal size and the degree of dispersion of the cerium oxide particles can be controlled according to the ratio of the organic solvent.

According to the present invention, a large amount of transparent cerium oxide colloidal sol that is spontaneously dispersed and stabilized at a high concentration of several nanometers in size can be easily produced.

1 is a graph showing XRD analysis results of cerium oxide particles according to a preferred embodiment of the present invention.
2 is a SEM photograph of colloidal cerium oxide particles according to a preferred embodiment of the present invention.
3 is a graph showing XRD analysis results of cerium oxide particles according to the preferred embodiments and the comparative examples of the present invention.
4 is a graph showing XRD analysis results of cerium oxide particles according to another comparative example of the present invention.

Preferred embodiments of the present invention will be described with reference to the drawings.

The present invention relates to a method of using a mixed organic solvent to adjust cerium oxide particle size to several nanometers in size and avoid aggregation of particles during precipitation reaction of cerium ions, a method of using acetone or ethanol And a method of controlling the pH to stabilize the washed cerium oxide particles at a high concentration. The present invention also provides a method for producing colloidal cerium oxide.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

The cerium oxide of the present invention is prepared by a method of precipitating cerium oxide from a cerium precursor in solution. Typically, distilled water is used as a solvent in the precipitation method. However, distilled water induces intergranular bonds while forming hydrogen bonds on the surface of the particles determined in the precipitation reaction process. As a result, strong agglomerates are formed as the crystallization progresses, resulting in poor dispersion of particles.

Therefore, in the present invention, by using an organic solvent instead of distilled water which has been used as a solvent in the past, a carbonaceous group is formed on the surface during particle formation, and it serves as a dispersing agent for preventing agglomeration between particles.

For example, when cerium nitrate is used as a cerium precursor, ethanol is used instead of water as a solvent, and potassium hydroxide is used as a pH regulator, the reaction formula on the surface of the precipitated cerium is as follows.

As can be seen from the above reaction formula, water nanosized cerium oxide whose surface is modified with cerium alkoxide compound is weakly aggregated and precipitated by ethanol. The cerium oxide surface treated with ethanol has a role as a functional group for dispersing on the surface of the particle because the surface of the particle is modified by bonding a carbon-based compound to the surface rather than a hydrogen bond.

In addition, since the solvent has a unique dielectric constant value, the dielectric constant of the solvent changes the surface energy or the surface charge in the nucleation and crystal growth during the powder synthesis to affect the agglomeration and growth of the nucleus, The size and shape of the substrate.

In the present invention, the cerium precursor is not particularly limited as long as it is a cerium-containing compound, but it is preferably in the form of a salt, and examples thereof include cerium nitride, ammonium cerium nitride, Cerium chloride, cerium acetate, and the like.

As described above, an organic solvent is used as a solvent for these precursors in the present invention in place of conventional distilled water.

Examples of the organic solvent used for preparing the cerium precursor solution in the present invention include ethylene glycol, 1-4, buthanediol, and diethylene glycol in glycol solvents And alcohols such as methanol, ethanol, iso-propanol and buthanol, and preferably at least one glycol-based alcohol and at least one alcohol-based solvent And a cerium precursor solution is prepared by dissolving the cerium precursor in a mixed solvent.

In the present invention, the two kinds of organic solvents are used for the following reasons.

Since cerium oxide nanoparticles surface-modified with cerium alkoxide are very slow in peptization and spontaneous dispersion and it is difficult to cause complete spontaneous dispersion, glycol is mixed with other organic solvent in a volume ratio to precipitate cerium oxide. At this time, cerium oxide nanoparticles surface-treated with cerium alkoxide and cerium glycolate are synthesized on the surface. When the particles are dispersed in water as described later, cerium alkoxide and glycolate are hydrated on the surface of cerium oxide, As a result, it is possible to synthesize a stable and transparent cerium oxide colloidal sol of high concentration because it acts as a dispersing agent simultaneously with peptization and complete spontaneous dispersion.

The present invention has been made to control the crystal growth and coagulation phenomenon of particles by using two or more organic solvents.

In the present invention, at least one glycol-based solvent and at least one alcohol-based solvent are selected and mixed at a ratio of 0.5: 0.5 to 0.98: 0.02 by volume ratio of the alcohol-based solvent to the glycol-based solvent .

If the ratio of the alcoholic solvent is 98% or more of the total solvent, the crystallinity of the cerium oxide precipitate becomes high, and difficulty occurs in the subsequent cracking reaction, making it difficult to form the cerium oxide sol. When the ratio of the alcoholic solvent is lower than 50% of the total solvent, crystallinity of the cerium oxide precipitate is lowered, leading to instability of grain boundaries, which leads to gelation phenomenon.

When preparing the cerium precursor solution in the present invention, the cerium precursor can be dissolved in a mixed solvent by using a strong mixing system, an ultrasonic system or ball milling in consideration of the solubility between the solvent and the cerium precursor.

In the present invention, the concentration of the cerium precursor in the solution is suitably about 0.01M to 3.0M.

If the concentration is lower than 0.01M, there is an advantage in terms of uniformity of the cerium oxide particles morphologically, but the amount of precipitated particles is small, which is disadvantageous in terms of productivity. In addition, when the concentration is higher than 3.0 M, it is difficult to control the pH of the solution, so that a large amount of precipitant is additionally required. Even if the concentration is adjusted, the solubility increases during the reaction, There arises a disadvantageous problem in terms of crystal growth or uniformity.

In the present invention, the precipitation agent for controlling the pH is not particularly limited as long as it is a compound containing a hydroxyl group (OH ^- ), but one of ammonium hydroxide, potassium hydroxide, and sodium hydroxide can be used as a non-limiting example.

In the present invention, the pH of the reaction solution is adjusted to 5.0 to 10.0 using the precipitant. If the pH is lower than 5.0, a small amount of precipitate is formed, which is disadvantageous in terms of productivity. In addition, when the pH is higher than 10.0, the solubility of the reaction solution is lowered to produce uneven crystal grains.

If the precipitant used is a liquid, the pH can be adjusted by adding it directly to the cerium precursor solution. However, when the precipitant is a solid phase, it is preferable to dissolve the precipitant in a part of the solvent to dissolve the cerium precursor, separately prepare the precipitate solution, and then adjust the pH while mixing with the cerium precursor solution. When the solid precipitant can not be dissolved in the mixed solvent, it may be dissolved by using a strong mixing system, an ultrasonic system or ball milling.

In the present invention, an oxidation promoter may be used to control the reaction rate in the precipitation reaction. The oxidation promoter is not particularly limited as long as it is a compound containing oxygen (O2) ions, but a method of adding hydrogen peroxide or mixing oxygen gas or air directly into the reaction can be used as a non-limiting example.

In the present invention, the hydrogen peroxide may also control the size of the cerium oxide. Hydrogen peroxide forms a hydroxide (OH ^- ) layer on the surface during the growth of cerium oxide particles, and tends to prevent the growth of particles. Therefore, in the present invention, a small amount of hydrogen peroxide is used in an amount of about 0.05 to 0.2 wt%, relative to the cerium precursor, and this can be used to adjust the size of the cerium oxide particles.

In the present invention, the temperature of the precipitation reaction is preferably 30 ° C or higher and lower than the breaking point of each solvent. In the present invention, the reaction is carried out at 90 ° C or less in consideration of the breaking point of the alcoholic solvent, and a condenser is used if necessary.

In the present invention, the precipitation reaction time is preferably 2 hours to 36 hours. The reaction time is expected to be related to the yield of the precipitate. If the reaction takes less than 2 hours, the reaction does not proceed completely, which causes a disadvantage in productivity. In addition, pure cerium oxide particles are not produced and an unstable phase is formed. Further, if the reaction is carried out for 36 hours or more, it becomes disadvantageous in terms of process efficiency.

On the other hand, the cerium oxide precipitate prepared by surface-treating with a mixed solvent of alcohol and glycol by the above-described method is characterized in that it is prepared using an organic solvent. Therefore, the surface of the prepared particles and the organic substances and impurities existing therein You need to remove it.

The cerium oxide precipitate prepared in the present invention can be washed by selecting one of decanter and centrifuge processes.

In the present invention, it is preferable to use acetone or ethanol as the washing solution used in the washing process. If distilled water is used in the washing process, the hydration reaction proceeds and intergranular hydrogen bonding is formed, and rapid aggregation may occur.

The washed cerium oxide precipitate is then peptized and spontaneously dispersed using a pH adjuster and distilled water. In the peptization and spontaneous dispersion step of the present invention, any acid may be used when titrating, preferably nitric acid and / or acetic acid. In the peptization step of the present invention, the pH is preferably adjusted in the range of 0.1 to 3.0.

In the present invention, the step of peptizing and spontaneously dispersing may be carried out by adding cerium oxide particles and a pH adjusting agent, mixing the mixture strongly using a paint shaker or a homogenizer, adding water, and adjusting the solid concentration in the solution have. In the above procedure, the mixture is mixed at a volume ratio of 1: 9 to 2: 1 with respect to the volume ratio of the pH adjusting agent to the mixture, and the mixture is strongly mixed using a paint shaker or a homogenizer to prepare yellow transparent colloidal cerium oxide. If not, the cerium oxide particles produced using the mixing reactor and heat may be cracked. In this case, the reaction proceeds slowly at a temperature of 30 ° C to 75 ° C. In some cases, it may take several days or longer to disperse and disperse spontaneously.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited by the following examples.

[Example 1]

 After mixing 60 ml of ethylene glycol (Duksan Co., 99.5%) and 240 ml of ethanol (Ethanol; Duksan CO., 99.5%), 26.04 g of cerium nitrideanhydrate (Aldrich 99.5% And then mixed at 150 rpm for 20 minutes.

1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution and mixed at 150 rpm for 20 minutes. Ammonium hydroxide (Duksan Co.) was added to the solution to adjust the pH to 8.0 to 9.0. After increasing the reaction temperature to 50 ° C, the reaction was allowed to proceed for 24 hours while blowing air into the reaction solution. A yellow precipitate was formed by the above method. As a result of the analysis of the precipitate using XRD, it was confirmed that the precipitate was formed as a cerium oxide particle having a fluorite structure. This is shown in Fig. 1 (a).

The cerium oxide particles prepared by the above method were washed with ethanol (Ethanol; Duksan Co., 99.5%) as a washing solution using centrifugal separation. After washing, a yellow precipitate mass could be obtained. The crystalline size by the Scherrer equation was calculated to be 4.36 nm.

2 ml of acetic acid (Aldrich) was added to 10 g of cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. A homogenizer may be used at this time. After 5 minutes of mixing, a yellow transparent solution can be obtained, which is shown in Figure 1 (b) using XRD. As can be seen from Figs. 1 (a) and 1 (b), there was no change in the crystal structure and size between the two materials. Also, it can be seen from FIG. 2 that cerium oxide particles are well dispersed in colloidal form using HRTEM (high resolution transmission electron microscopy). The solid concentration at this time was 27.3 wt%.

The slide glass was immersed in the prepared colloid solution for 30 seconds and dried at room temperature. On the dried glass surface, a yellow transparent coating layer was formed and maintained its shape without spillage.

[Example 2]

After mixing 90 ml of ethylene glycol (Ethyene glycol; Duksan Co., 99.5%) and 210 ml of ethanol (Ethanol; Duksan Co., 99.5%), 26.04 g of cerium nitrideanhydrate (Aldrich 99.5% And then mixed at 150 rpm for 20 minutes. 1 ml of hydrogen peroxide (Junsel Co., 98.5%) was added to the mixed cerium precursor solution, followed by mixing at 150 rpm for 20 minutes. Ammonium hydroxide (Duksan Co.) was added to the solution to adjust the pH to 8.0 to 9.0. After increasing the reaction temperature to 50 ° C, the reaction was allowed to proceed for 24 hours while blowing air into the reaction solution. A yellow precipitate was formed by the above method. As a result of the analysis of the precipitate using XRD, it was confirmed that the precipitate was formed as a cerium oxide particle having a fluorite structure. The X-ray analysis results are shown in Fig. 3 (a).

The cerium oxide particles prepared by the above method were washed using centrifugation using ethanol (Erhanol; Duksan Co., 99.5%) as a washing solution. At this time, the rotation speed was set at 5,000 rpm for 10 minutes, and washing was repeated three times. After washing, a yellow precipitate mass could be obtained. The formed precipitate mass was found by Scherrer equation to have a crystalline size of 4.02 nm.

2 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. A clear solution of yellow was obtained in one minute.

The slide glass was immersed in the prepared colloid solution for 30 seconds and dried at room temperature.

On the dried glass surface, a yellow transparent coating layer was formed and maintained its shape without spillage.

[Example 3]

After mixing 60 ml of ethylene glycol (Duksan Co., 99.5%) and 240 ml of ethanol (Ethanol; Duksan Co., 99.5%), 26.04 g of cerium nitrideanhydrate (Aldrich 99.5% And then mixed at 150 rpm for 20 minutes. 1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution and mixed at 150 rpm for 20 minutes. To this solution was added ammonium hydroxide (Duksan Co.) to adjust the pH to 8.0 to 9.0. After the reaction temperature was increased to 30 ° C, air was blown into the reaction solution, and the reaction was carried out for 24 hours. The precipitated moles were analyzed by XRD, and it was confirmed that the precipitated moles were formed as cerium oxide particles of a fluorite type structure. This is shown in Fig. 3 (b). Washing was carried out as in Examples 1 to 4 above. 2 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. To this solution, 8 ml of distilled water was added, followed by vigorous mixing with a pate shaker. A clear solution of yellow was obtained in 10 minutes.

[Example 4]

After mixing 30 ml of ethylene glycol (Duksen Co., 99.5%) and 270 ml of ethanol (Ethanol; Duksan Co., 99.5%), 26.04 g of cerium nitrideanhydrate (Aldrich 99.5%) was added And then mixed at 150 rpm for 20 minutes. 1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution, followed by mixing at 150 rpm for 20 minutes. Ammonium hydroxide (Duksan Co.) was added to the solution to adjust the pH to 8.0 to 9.0. After increasing the reaction temperature to 50 ° C, the reaction was allowed to proceed for 24 hours while blowing air into the reaction solution. A yellow precipitate was formed by the above method. As a result of the analysis of the precipitate using XRD, it was confirmed that the precipitate was formed as a cerium oxide particle having a fluorite structure. This is shown in Fig. 3 (c).

The cerium oxide particles prepared by the above method were washed with ethanol (Ethanol; Duksan Co., 99.5%) as a washing solution using centrifugation. At this time, the rotation speed was set at 5,000 rpm for 10 minutes, and washing was repeated three times. After washing, a yellow precipitate mass could be obtained. The crystalline size by the Scherrer equation was 4.16 nm.

2 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 20 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. A clear solution of yellow was obtained in 30 minutes.

The slide glass was immersed in the prepared colloid solution for 30 seconds and dried at room temperature. A yellow transparent coating layer was formed on the dried glass surface, and the shape was maintained without flowing down.

[Example 5]

After mixing 15 ml of ethylene glycol (Duksan Co., 99.5%) and 285 ml of ethanol (Ethanol; Duksan Co., 99.5%), 26.04 g of cerium nitrideanhydrate (Aldrich 99.5%) And then mixed at 150 rpm for 20 minutes. 1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution and mixed at 150 rpm for 20 minutes. Ammonium hydroxide (Duksan Co.) was added to the solution to adjust the pH to 8.0 to 9.0. After increasing the reaction temperature to 50 ° C, the reaction was allowed to proceed for 24 hours while blowing air into the reaction solution. A yellow precipitate was formed by the above method. As a result of the analysis of the precipitate using XRD, it was confirmed that the precipitate was formed as a cerium oxide particle having a fluorite structure. This is shown in Fig. 3 (d).

The cerium oxide particles prepared by the above method were washed with ethanol (Ethanol; Duksan Co., 99.5%) as a washing solution using centrifugation. At this time, the rotation speed was set at 5,000 rpm for 10 minutes, and washing was repeated three times. After washing, a yellow precipitate mass could be obtained. The crystalline size by the Scherrer equation was 4.21 nm.

2 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. A clear solution of yellow was obtained in 20 minutes.

The slide glass was immersed in the prepared colloid solution for 30 seconds and dried at room temperature. On the dried glass surface, a yellow transparent coating layer was formed and maintained its shape without spillage.

 [Example 6]

The cerium oxide particles were prepared and washed in the same manner as in Example 1 above. 1 g of nitric acid (Duksan Co., 68%) of 10 g of cerium oxide prepared by the above method was added thereto, and the mixture was intensely mixed for 5 minutes using a paint shaker. 9 ml of distilled water was added to the solution, and the mixture was vigorously mixed using a paint shaker. A clear solution of yellow was obtained after 1 minute.

[Example 7]

The cerium oxide particles were prepared and washed in the same manner as in Example 1 except that 60 ml of 1,4-butanediol was used instead of ethylene glycol. 2 ml of acetic acid was added to 10 g of the cerium oxide particles prepared by the above method, and the mixture was intensely mixed for 5 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. After 10 minutes, a yellow transparent solution was obtained.

[Comparative Example 1]

Only 300 ml of ethanol (Ethanol; Duksan Co., 99.5%) was used without mixing ethylene glycol (Duksan Co., 99.5%). 26.04 g of cerium nitride hydrate (Aldrich 99.5%) was added to ethanol and mixed at 150 rpm for 20 minutes.

1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution, followed by mixing at 150 rpm for 20 minutes. Ammonium hydroxide (Duksan Co.) was added to the solution to adjust the pH to 8.0 to 9.0. After increasing the reaction temperature to 50 ° C, air was blown into the reaction solution. Yellow precipitate was formed in 3 hours, and reaction was carried out for 12 hours. As a result of the analysis of the precipitate using XRD, it was confirmed that the precipitate was formed as a cerium oxide particle having a fluorite structure. This is shown in Fig. 3 (e). The crystalline size by the Scherrer equation was 8.48 nm.

The cerium oxide particles prepared by the above method were washed with ethanol (Ethanol; Duksan Co., 99.5%) as a washing solution using centrifugation. At this time, the rotation speed was set at 5,000 rpm for 10 minutes, and washing was repeated three times. After washing, a yellow precipitate mass could be obtained.

2 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. It did not become clear and after a few minutes yellow deposits were formed.

[Comparative Example 2]

26.04 g of cerium nitride anhydrate (Aldrich 99.5%) was added to 300 ml of ethylene glycol (Duksan Co., 99.5%) and mixed at 150 rpm for 20 minutes.

1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution, followed by mixing at 150 rpm for 20 minutes. Ammonium hydroxide (Duksan Co.) was added to the solution to adjust the pH to 8.0 to 9.0. After increasing the reaction temperature to 50 ° C, the reaction was allowed to proceed for 24 hours while blowing air into the reaction solution. After the reaction, a dark yellow precipitate was formed. This was washed twice with acetone once with ethanol, then dried and analyzed by XRD. The dried particles are shown in Fig. The crystalline size by the Scherrer equation was 4.38 nm.

The cerium oxide particles prepared by the above method were washed with ethanol (Ethanol; Duksan Co., 99.5%) as a washing solution using centrifugation. At this time, the rotation speed was set at 5,000 rpm for 10 minutes, and washing was repeated three times. 2 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. 8 ml of distilled water was added to this solution, and the mixture was vigorously mixed using a paint shaker. A yellow transparent solution was prepared in one minute, and the solid concentration was 6.8 wt%.

[Comparative Example 3]

After mixing 60 ml of ethylene glycol (Duksan Co., 99.5%) and 240 ml of ethanol (Ethanol; Duksan Co., 99.5%), 26.04 g of cerium nitrideanhydrate (Aldrich 99.5% After the addition, the mixture was mixed at 150 rpm for 20 minutes. 1 ml of hydrogen peroxide (Junsei Co., 98.5%) was added to the mixed cerium precursor solution, followed by mixing at 150 rpm for 20 minutes. The pH of the solution was adjusted to 9.02 by the addition of ammonium hydroxide (Duksan Co.). After the reaction temperature was increased to 75 ° C, air was blown into the reaction solution and reacted for 24 hours. As a result of the analysis of the precipitate using XRD, it was confirmed that the precipitate was formed as a cerium oxide particle having a fluorite structure.

The cerium oxide particles prepared by the above method were washed with ethanol (Ethanol; Duksan Co., 99.5%) as a washing solution using centrifugation. At this time, the rotation speed was set at 5,000 rpm for 10 minutes, and washing was repeated three times. After washing, a yellow precipitate mass could be obtained.

5 ml of acetic acid was added to 10 g of the cerium oxide particles washed by the above method, and the mixture was intensively mixed for 10 minutes using a paint shaker. 5 ml of distilled water was added to the solution, and the mixture was vigorously mixed using a paint shaker. A transparent colloidal cerium oxide solution could be obtained even after mixing for 12 hours.

Claims (9)

delete delete Preparing a cerium oxide precursor solution by dissolving a cerium oxide precursor in an organic solvent comprising a mixed solvent of a glycol solvent and an alcohol solvent;
By adjusting the pH of the precursor solution, cerium alkoxide and cerium glycolate Precipitating the surface-treated cerium oxide;
Washing the precipitated cerium oxide in the precipitation reaction step; And
And subjecting the cerium oxide precipitate to peptization and spontaneous dispersion in an aqueous solution,
The peptizing and spontaneous dispersing step is carried out at a temperature of 30 to 75 DEG C and a pH of 0.01 to 4.0 after dispersing the cerium oxide precipitate in water,
Wherein the mixing volume ratio of the alcohol solvent to the glycol solvent is between 0.5: 0.5 and 0.98: 0.02. The method of claim 3,
Wherein the oxidizing accelerator is used in the precipitation reaction step. 5. The method of claim 4,
Wherein the oxidation promoter is oxygen gas, air or hydrogen peroxide. The method of claim 3,
Wherein the precipitation reaction step is carried out at a temperature of 30 to 90 DEG C and a pH of 5.0 to 10.0. The method of claim 3,
Wherein the precipitate is washed with acetone or an alcohol in the washing step. delete The method of claim 3,
Wherein the pH is controlled by acetic acid or nitric acid, or a mixture thereof, in the step of peptizing and spontaneous dispersion.

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