KR20180086616A - METHOD OF SILICA PARTICLES FROM SODIΜM SILICATE USING ZnO INORGANIC TEMPLATE PARTICLES - Google Patents

Abstract

The present invention provides a method of preparing hollow silica particles, comprising the steps of: applying heat to a solution, in which a Zn precursor is mixed with an alkaline precipitating agent, to prepare ZnO inorganic template particles; making a silica precursor and a salt react with the ZnO inorganic template particles, thereby forming a silica shell on the surface of the ZnO inorganic template particles to prepare ZnO/silica core-shell particles; and removing the ZnO inorganic template particles from the ZnO/silica core-shell particles. The present invention can prevent particle agglomeration and contamination problems generated during a template particle removing process using heat treatment and the organic solvent by producing hollow silica particles with the ZnO inorganic template particles that can be easily removed through an acid treatment process without using separate heat treatment or an organic solvent. Further, the present invention improves hollow efficiency and can provide hollow silica particles required according to application fields by controlling size and shape of the ZnO inorganic template particles, thereby maximizing hollow size of hollow silica particles.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for preparing hollow silica particles from sodium silicate using ZnO inorganic mold particles,

The present invention relates to a method for producing hollow silica particles starting from sodium silicate using ZnO inorganic mold particles, and more particularly, to a method for producing hollow silica particles using ZnO as inorganic mold particles and sodium silicate as a silica precursor ≪ / RTI >

The inorganic particles in the hollow structure have a shape in which the shell containing the nanopore is hollow with particles enclosed by the outer shell. Micro- and nano-sized hollow inorganic particles have high application potential in the academic and industrial fields due to their unique physical properties such as relatively low density, large specific surface area, and surface permeability.

Various methods for synthesizing hollow inorganic particles have been studied by a number of researchers. Currently, a general method for synthesizing hollow silica is to use a polystyrene latex (PSS) organic mold to prepare a hollow silica from TEOS (tetraethylorthosilicate) The synthesis method is known.

When an organic template is used, the silica produced from TEOS is coated on the surface of the organic mold to form the core shell structure, and then the organic silica mold is removed by heat treatment or organic solvent to finally obtain the hollow silica particles.

However, in the case of using the organic mold particles as described above, there is a problem that the problem of the contamination of the hollow silica due to the residual organic template occurring in the process of removing the organic template by using the organic solvent and the washing process of the residue are difficult and cumbersome. Further, when the organic mold is removed by firing at a high temperature, the resultant hollow silica is agglomerated. Also, when the silica precursor is TEOS, alcohol and ammonia water are used as the reaction solvent. Therefore, there is an environmental problem due to the generation of the waste water.

It is an object of the present invention to provide a method for producing hollow silica particles from sodium silicate using a ZnO inorganic mold which can be easily removed through an acid treatment process without using a separate firing step or an organic solvent.

Another object of the present invention is to provide hollow silica particles which are required according to application fields by preparing hollow silica particles having various shapes and various hollow sizes by controlling the shape and size of ZnO inorganic mold particles.

According to an aspect of the present invention, there is provided a ZnO nanoporous inorganic particle according to the present invention, which comprises mixing a Zn precursor and an alkaline precipitant, and applying heat to the solution.

The Zn precursor is characterized by being one of zinc chloride (ZnCl ₂ ) and zinc acetate (Zn (CH ₃ COO) ₂ ).

The Zn precursor is zinc chloride (ZnCl ₂ ), and the alkaline precipitant is NaOH, LiOH, NaCO ₃ , And the ZnO inorganic template particles are spherical with a diameter of 190 nm to 200 nm.

Further, the Zn precursor is zinc chloride (ZnCl ₂ ), the alkaline precipitant is NaOH, and the ZnO inorganic mold particles have a particle size of 200 nm to 300 nm.

Also, the Zn precursor is zinc chloride (ZnCl ₂ ), the alkaline precipitant is NaOH, and the ZnO inorganic mold particles have a columnar shape of 500 nm to 2.0 μm.

The Zn precursor is characterized by zinc chloride (ZnCl ₂ ) and the alkaline precipitant is NH ₄ OH.

And the ZnO inorganic mold particles are in the form of a plate having a thickness of 0.4 mu m to 1.0 mu m.

Further, the ZnO inorganic mold particles are elliptical with a particle length of 2.0 탆 to 3.0 탆.

And further dispersing the ZnO inorganic template particles by applying ultrasonic waves to a solution obtained by mixing the heat-applied Zn precursor and the alkaline precipitant.

The hollow silica particles according to the present invention can be prepared by reacting a solution of a Zn precursor and an alkaline precipitant with heat to form ZnO inorganic template particles (S100), reacting a silica precursor and a salt with the ZnO inorganic template particles A step (S200) of forming a silica shell on the surface of ZnO inorganic mold particles to produce ZnO / silica core-shell particles (S200) and removing the ZnO inorganic mold particles (S300) from the ZnO / And a control unit.

The silica precursor in step S200 may be sodium silicate.

And the concentration of the sodium silicate is 0.2 M to 0.6 M.

In addition, the salt of the step S200 is (NH _{4) 2} SO ₄ Or NaH (CO ₃ ) ₂ .

The reaction temperature for forming the ZnO / silica core-shell particles in step S200 is 60 ° C to 90 ° C.

The removal of the ZnO inorganic mold particles in step S300 may be performed by dispersing the core shell particles of ZnO / silica in distilled water, and then stirring and dissolving an acid solution to dissolve the ZnO inorganic mold particles .

The acid solution may be a hydrochloric acid dilution solution or a sulfuric acid dilution solution.

According to the present invention, hollow silica particles are produced by using ZnO inorganic mold particles which can be easily removed through an acid treatment process without using a heat treatment or an organic solvent. As a result, It is possible to prevent the problem of particle agglomeration and contamination that occur during the mold particle removal process using the mold.

In addition, since the shape and size of the ZnO inorganic mold particles can be easily controlled, the hollow size of the hollow silica can be maximized by controlling the size and shape of the ZnO inorganic mold particles, thereby improving the hollow efficiency. Particles can be provided.

In addition, the manufacturing cost is lower than that of TEOS because sodium silicate is used as a silica precursor.

Further, since the reaction solvent is water, it is more eco-friendly than the hollow silica synthesis method using TEOS as a silica precursor.

However, the effect of the method for producing hollow silica particles from sodium silicate using ZnO inorganic mold particles according to the embodiments of the present invention is not limited to those mentioned above, It will be understood by those skilled in the art that the present invention can be understood by those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a flow chart showing a process for producing hollow silica particles according to the present invention.
2 is a schematic view showing a process of forming hollow silica particles according to the present invention.
FIG. 3 is a flowchart showing a process for preparing a ZnO inorganic template particle according to the present invention.
4 (a) and 4 (b) are SEM images showing ZnO inorganic mold particles according to the kind of ZnO precursor.
5 (a), 5 (b) and 5 (c) are SEM images showing ZnO inorganic mold particles according to the concentration of the ZnO precursor.
6 (a), 6 (b) and 6 (c) are SEM images showing ZnO inorganic mold particles according to kinds of alkaline precipitants.
7 (a), 7 (b) and 7 (c) are SEM images showing ZnO inorganic mold particles according to pH.
8 (a), 8 (b) and 8 (c) are SEM images showing ZnO inorganic mold particles according to the reaction temperature.
9 is an SEM image showing an elliptical ZnO inorganic mold particle according to the present invention.
10 is an SEM image of spherical ZnO inorganic mold particles having a size of 0.1 mu m to 0.2 mu m according to the present invention.
11 is a SEM image of a cross-section of a coating film formed by coating a hollow silica synthesized using spherical ZnO inorganic mold particles having a size of 0.1 m to 0.2 m in size on a substrate.

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor shall appropriately define the concept of the term in order to describe its invention in the best way It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and not all of the technical ideas of the present invention are described. Therefore, It should be understood that various equivalents and modifications may be present. Hereinafter, a method for manufacturing a ZnO inorganic mold particle according to an embodiment of the present invention and a hollow silica particle manufacturing method based thereon will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing a process for producing hollow silica particles according to the present invention.

The hollow silica particles according to the present invention can be prepared by preparing a ZnO inorganic mold particle by heating a solution prepared by mixing a Zn precursor and an alkaline precipitant (S100), adding a silica precursor and a salt to the ZnO inorganic mold particle (S200) of preparing a ZnO / silica core shell particle by forming a silica shell on the surface of the ZnO inorganic mold particle by reacting the ZnO / inorganic core particle with the ZnO / (Step S300).

Referring to FIG. 3, the step (S100) of forming the ZnO inorganic template particles and the factors controlling the size and shape of the inorganic template particles will be described.

ZnO inorganic mold particles become the basic skeleton of the hollow silica particles, and controlling the shape of the ZnO inorganic mold particles affects the shape of the hollow silica particles.

Basically, a Zn precursor and an alkaline precipitant are mixed using a sedimentation method, followed by reaction with heat to form ZnO inorganic mold particles. In this case, the Zn precursor may be zinc chloride (ZnCl ₂ ), zinc acetate (Zn (CH ₃ COO) ₂ ), and the alkaline precipitant may be NaOH, LiOH, NaCO ₃ or NH ₄ OH.

The shape and size of the ZnO inorganic mold particles can be determined by the kind of Zn precursor, the concentration of Zn precursor, the kind of alkaline precipitant, the pH, the reaction temperature and the like. It is important to control and control the shape and size of ZnO inorganic mold particles as they are the most important factors for determining the shape and hollow efficiency of hollow silica.

The size and shape of the ZnO particles can be controlled depending on the kind of the Zn precursor. This is because the reaction mechanism is the same, but the rate of reaction with salt and precipitant formed during the reaction is different. In one embodiment, the zinc chloride has a faster reaction rate with the precipitant than the zinc acetate, so that the particle size is rapidly increased as the particle formation proceeds rapidly.

Also, the higher the Zn precursor concentration in the Zn precursor concentration, the larger the particle size. That is, since the nucleation rate is slower as the concentration is lower, the aggregation of the formed nuclei is less so that the particle size is small. In one embodiment, spherical particles of 100 nm in zinc chloride 0.5 M and spherical particles of 200 nm in 1.5 M of zinc choride are formed.

Depending on the type of alkaline precipitant, the shape and size of the ZnO template particles can be varied. When sodium hydroxide (NaOH), lithium hydroxide (LiOH) and sodium carbonate (Na ₂ CO ₃ ) are used, spherical particles of the order of several nanometers are formed and ammonium hydroxide ((NH ₄ ) OH) Micrometer particles can be formed, and long elliptical or plate-shaped ZnO inorganic mold particles can be obtained.

As the pH of the reaction solvent increases, the particles grow in the direction of the crystal c axis, which is a direction for reducing the surface energy of the particles, so that ZnO near the plate is formed instead of spherical particles. Experimental results show that at pH 12 or higher, a platelet-like particle is formed.

As the reaction temperature increases, the spherical particle size increases. In the case of the plate-like particles, the c-axis grows to form columnar particles. Experimentally, the particle size increases significantly at reaction temperatures above 70 ℃.

The step of forming a silica shell (S200) and the factors controlling the thickness and shape of the silica shell will be described.

In the step of forming the silica shell, the silica precursor and the ammonium salt or the metal salt are simultaneously dropped in a solution in which the ZnO inorganic mold particles are dispersed, after the step (S100) of forming the ZnO inorganic mold particles, And a silica shell is formed on the surface of the particles to obtain core shell particles of ZnO / silica. The silica precursor in one embodiment is a sodium silicate (Sodiμm Silicate) that can be used, ammonium salt or metal salt is ammonium sulfate _{((NH 4) 2 SO 4} ), sodium bicarbonate (NaH (CO _{3) 2)} may be used have.

It is preferable to completely disperse the ZnO inorganic template particles in the solution before starting the silica shell forming reaction because if the ZnO inorganic template particles are aggregated or precipitated, the silica precursor content becomes larger than the surface area of the ZnO inorganic template particles, It is impossible to form a silica shell of one thickness or shape. Accordingly, it is required to apply ultrasonic waves to disperse the ZnO inorganic template particles in the solution so that all the ZnO inorganic template particles are used in the core shell reaction. In one embodiment, the ultrasonic waves may be applied at a frequency of about 40 kHz for about 20 minutes.

The shell thickness and shape of the hollow silica can be controlled by the size and shape of the ZnO inorganic mold particles, the dispersity of the ZnO inorganic mold particles, the concentration of the silica precursor, and the reaction temperature during the shell forming reaction.

In the silica shell forming reaction, the hollow silica can be made thin by reducing the concentration of the silica precursor, thereby increasing the hollow efficiency. However, when the silica precursor concentration is extremely low, the amount of silica produced is insufficient relative to the surface area of the ZnO inorganic mold particle surface, and hollow silica is formed as a broken silica shell. On the other hand, silica shell thickness can be controlled to be high by increasing the silica precursor concentration. However, when the concentration is too high, excess silica is generated and the surface of the inorganic ZnO template is completely coated, Particles are formed. It is preferable that an appropriate concentration of the silica precursor is added according to the surface area of the size and shape of the ZnO inorganic mold particles used.

Experimental shell formation is best formed at about 0.2M sodium silicate when using spherical ZnO inorganic molds of 0.1 to 0.2μm size. At a concentration of 0.2M or less, the shell is formed in a broken shape. At 0.2M or more, the shell thickness gradually increases. At 0.6M or more, unwanted spherical silica particles are formed on the shell surface.

In addition, when the reaction temperature is low based on the same reaction time in the formation of the silica shell, the silica spherical particle size constituting the silica shell is small and the shell thickness can be controlled to be thin. However, when the reaction temperature is too low, the rate of shell formation reaction becomes slow, so that silica is not coated on the surface of ZnO inorganic mold, resulting in the formation of broken hollow silica. On the other hand, when the reaction temperature is high, the shell forming reaction rate is accelerated so that the silica shell can be easily formed on the ZnO inorganic mold surface. However, since the silica spherical particle size constituting the silica shell is increased, a rough silica shell can be formed have. In fact, the shell is broken at a reaction temperature of 60 ° C or less, and the shell is relatively easily formed at a temperature of 60 ° C or more, but the shell surface becomes rough at 90 ° C or more.

The reaction temperature is preferably controlled according to the ZnO inorganic mold size and the silica precursor concentration, and the hollow silica shell thickness can ultimately be controlled by controlling the silica spherical particle size of the silica shell by controlling the reaction temperature.

The step of removing the ZnO inorganic template particles (S300) will be described.

After forming core shell particles of ZnO / silica through step S200, the core shell particles of ZnO / silica are obtained after washing with a filter. After that, the core shell particles of ZnO / silica are dispersed in distilled water, and the acid solution is dropped at room temperature while stirring to dissolve the ZnO inorganic mold particles to form hollow silica. The acid solution may be a hydrochloric acid dilution solution or a sulfuric acid dilution solution.

The hollow silica dispersion from which the ZnO inorganic mold particles have been removed is washed with distilled water using a filter, and finally the hollow silica particles are obtained. Since the core in the silica shell can be easily removed using the acid solution, the hollow silica particles can be prepared by a simple method without using a sintering process or an extraction process using an organic solvent.

2 is a schematic view showing a process of forming hollow silica particles according to the present invention.

(a), (b) and (c) show a process in which a silica precursor forms a silica shell on the surface of a ZnO inorganic mold particle to form a ZnO / silica core shell particle, And hollow silica particles formed by removing ZnO inorganic mold particles from the particles.

4 (a) and 4 (b) are SEM images showing ZnO inorganic mold particles according to the kind of Zn precursor.

Zn precursor, (a) zinc chloride (Zinc chloride) and (b) zinc acetylacetonate. It can be seen that the size of the ZnO inorganic mold particles varies depending on the Zn precursor used. Specific experimental conditions are shown in Table 1 below.

Experimental variable Zn precursor Alkaline precipitant Zn
Molar concentration pH Reaction temperature shape
(size) (a) Zn precursor
Kinds Zinc chloride NaOH 1M 7 80 ℃ Spherical (105 nm) (b) Zinc
actate Spherical (100 nm)

5 (a), 5 (b) and 5 (c) are SEM images showing ZnO inorganic mold particles according to the concentration of the ZnO precursor.

(a), (b) and (c) were tested at molar concentrations of 0.5 M, 1 M and 1.5 M, respectively, using zinc chloride as Zn precursor. As the concentration of Zn precursor increases from 0.5M to 1M or 1.5M, it can be seen that the size of ZnO inorganic mold particle becomes larger. Specific experimental conditions are shown in Table 2 below.

Experimental variable Zn precursor Alkaline precipitant Zn
Molar concentration pH Reaction temperature shape
(size) (a) Zn precursor
density Zinc chloride NaOH 0.5M 7 80 ℃ rectangle
(About 100 nm) (b) 1.0M rectangle
(About 200 nm) (c) 1.5M rectangle
(About 200 nm)

6 (a), 6 (b) and 6 (c) are SEM images showing ZnO inorganic mold particles according to kinds of alkaline precipitants.

As the alkaline precipitant, (a) was NaOH, (b) was LiOH, and (c) was NH ₄ OH. In the case of NaOH and LiOH, there was no difference in shape and size of the ZnO inorganic mold particles. However, when NH ₄ OH was used, the shape was formed in a plate or column shape different from that of NaOH and LiOH and the size was also 0.4 to 1 micrometer ([mu] m). Specific experimental conditions are shown in Table 3 below.

Experimental variable Zn precursor Alkaline precipitant Zn
Molar concentration pH Reaction temperature shape
(size) (a) Alkaline precipitant
Kinds Zinc chloride NaOH 1M 7 80 ℃ rectangle
(About 200 nm) (b) LiOH rectangle
(About 200 nm) (c) NH ₄ OH Plate type
(0.4
To 1 [mu] m)

7 (a), 7 (b) and 7 (c) are SEM images showing ZnO inorganic mold particles according to pH.

At pH 7, the spherical shape was formed to have a size of 200 nm. However, when the pH was increased to 12 or 13, the size was found to be 200 to 300 nm in the plate-like shape. Specific experimental conditions are shown in Table 4 below.

Experimental variable Zn precursor Alkaline precipitant Zn
Molar concentration pH Reaction temperature shape
(size) (a) pH Zinc chloride NaOH 1M 7 30 ℃ rectangle
(200 nm) (b) 12 Plate type
(200 to 300 nm) (c) 13 Plate type
(200 to 300 nm)

8 (a), 8 (b) and 8 (c) are SEM images showing ZnO inorganic mold particles according to the reaction temperature.

Basically, as the temperature increases, the shape changes from a plate-like shape to a columnar shape, and the particle size increases. Specific experimental conditions are shown in Table 5 below.

Experimental variable Zn precursor Alkaline precipitant Zn
Molar concentration pH Reaction temperature shape
(size) (a) Reaction temperature Zinc chloride NaOH 1M 13 30 ℃ Plate type
(200 to 300 nm) (b) 50 ℃ Plate type (300 nm) (c) 70 ℃ The columnar (500 nm) (d) 95 ℃ Columnar
(1 to 2 m)

9 is an SEM image showing an elliptical ZnO inorganic mold particle according to the present invention. The size of the elliptical ZnO inorganic mold particles formed through the experiment was 2 to 3 micrometers (μm). Specific experimental conditions are shown in Table 6 below.

Zn precursor Alkaline precipitant Zn molar concentration pH Reaction temperature shape
(size) Zinc chloride NH ₄ OH 0.2M 7 80 ℃ Oval
(Size 2 to 3 [micro] m)

10 is an SEM image of a ZnO inorganic mold particle according to the present invention, and FIG. 11 is a SEM image of a cross section of hollow silica.

As shown in Fig. 10, the ZnO inorganic mold particles were formed into spherical shapes having a diameter of 0.1 to 0.2 占 퐉. FIG. 11 is a SEM image of the cross-section of the hollow silica formed by using the spherical ZnO inorganic mold particles (0.1 to 0.2 .mu.m) on a substrate.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, . Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the scope of the appended claims, as well as the appended claims.

Claims (16)

Zn precursor and an alkaline precipitant; And
Applying heat to the solution;
≪ / RTI > The method according to claim 1,
Wherein the Zn precursor is any one of zinc chloride (ZnCl ₂ ) and zinc acetate (Zn (CH ₃ COO) ₂ ). The method according to claim 1,
The Zn precursor may be zinc chloride₂), The alkaline precipitant is NaOH, LiOH, NaCO₃ Wherein the ZnO inorganic mold particles are spherical with a diameter of 190 nm to 210 nm. The method according to claim 1,
Wherein the Zn precursor is zinc chloride (ZnCl ₂ ), the alkaline precipitant is NaOH, and the ZnO inorganic mold particle has a particle size of 200 nm to 300 nm in a plate form. The method according to claim 1,
Wherein the Zn precursor is zinc chloride (ZnCl ₂ ), the alkaline precipitant is NaOH, and the ZnO inorganic mold particles have a columnar shape of 500 nm to 2.0 μm. The method according to claim 1,
Wherein the Zn precursor is zinc chloride (ZnCl ₂ ), and the alkaline precipitant is NH ₄ OH. The method according to claim 6,
Wherein the ZnO inorganic template particles are in the form of a plate having a particle size of 0.4 mu m to 1.0 mu m. The method according to claim 6,
Wherein the ZnO inorganic mold particles have an elliptical shape with a particle size of 2.0 占 퐉 to 3.0 占 퐉. The method according to claim 1,
Further comprising the step of dispersing the ZnO inorganic template particles by applying ultrasonic waves to a solution prepared by mixing the heat-treated Zn precursor and the alkaline precipitant. Zn precursor and an alkaline precipitant to prepare a ZnO inorganic template particle (S100);
Reacting a silica precursor and a salt with the ZnO inorganic template particles to form a silica shell on the surface of the ZnO inorganic template particles to produce ZnO / silica core-shell particles (S200); And
Removing the ZnO inorganic template particles from the ZnO / silica core shell particle (S300);
≪ / RTI > 11. The method of claim 10,
Wherein the silica precursor in step S200 is sodium silicate. 12. The method of claim 11,
Wherein the concentration of the sodium silicate is 0.2 M to 0.6 M. 11. The method of claim 10,
The salts of the step S200 is (NH _{4) 2} SO ₄ Or NaH (CO ₃ ) ₂ . 11. The method of claim 10,
Wherein the reaction temperature for forming the ZnO / silica core-shell particles in step S200 is in the range of 60 ° C to 90 ° C. 11. The method of claim 10,
The removal of the ZnO inorganic mold particles in step S300 is performed by dispersing the core shell particles of ZnO / silica in distilled water, and then stirring and dissolving an acid solution to dissolve the ZnO inorganic mold particles. By weight based on the total weight of the hollow silica particles. 16. The method of claim 15,
Wherein the acid solution is any one of a hydrochloric acid dilution solution and a sulfuric acid dilution solution.

Images