KR101692332B1

KR101692332B1 - Method of manufacturing barium titanate nanostructure

Info

Publication number: KR101692332B1
Application number: KR1020150098536A
Authority: KR
Inventors: 이형익; 양성호; 이승준; 배수빈; 박귀일; 이기수
Original assignee: 국방과학연구소
Priority date: 2015-07-10
Filing date: 2015-07-10
Publication date: 2017-01-03

Abstract

The present invention relates to a preparation method of a barium titanate nanostructure. The preparation method of a barium titanate nanostructure comprises the following steps of: synthesizing a TiO3 precursor by dispersing a titanium dioxide (TiO2) powder in an alkaline solution; synthesizing a barium titanate nanostructure by adding an aqueous barium solution to the TiO3 precursor; and cleaning and drying the synthesized barium titanate nanostructure.

Description

TECHNICAL FIELD [0001] The present invention relates to a barium titanate nanostructure,

The present invention relates to a method for producing a highly crystalline barium titanate (BaTiO3) nanostructure.

Barium titanate (BaTiO3, hereinafter referred to as BT) is a material of perovskite structure with a large nonlinear optical constant and a high dielectric constant. It is used in electro-optical devices, microwave absorption, high- dielectrics / materials, capacitors, transducers, transistors, thermistors, actuators, piezoelectric materials, and so on. Particularly, it has been investigated actively because it has perovskite structure with high dielectric constant and has much higher piezoelectric properties than Wurtzite structure materials such as ZnO.

In recent decades, in particular, one-dimensional nanostructured materials such as nanowires, nanorods, and nanotubes have exhibited physicochemical properties far exceeding those of conventional bulk materials, so that the electrical and optical properties of such nanostructured materials , The interest in magnetic properties and research are steadily increasing. The BaTiO3 one-dimensional nanostructure is advantageous in that it has high response and piezoelectric characteristics due to the unidirectionality of the one-dimensional structure compared to the conventional nano-particle type BaTiO3.

Since the unique characteristics of these nanomaterials vary greatly depending on the nanostructure of the material, studies on synthesis methods for controlling such nanostructures are actively under way. This synthesis of one-dimensional BT nanomaterials is mainly applied to two steps of synthesizing NaTiO3 or KTiO3 and then converting it into BT. Direct synthesis using H2TiO3 precursors has also been reported, but based on organic solvents (ethanol) rather than water, there are fatal defects with low crystallinity of the nanowires. Recently, a new direct synthesis method has been reported. However, it is a method to utilize an alkoxide-based Ti precursor, and the cost of the precursor is very high and mass synthesis and application are limited. Recently, a method of replicating with BaTiO3 by using anodized aluminum oxide (AAO) as a template has been suggested. However, it is necessary to perform various steps such as mold making / impregnation heat treatment / mold removal, and only a very small amount of synthesis There was a problem.

The present invention is directed to solving the above-mentioned problems and other problems. Another object of the present invention is to provide a method for producing a barium titanate nanostructure by a direct synthesis method.

According to an aspect of the present invention, there is provided a method for preparing a TiO 3 precursor, comprising the steps of: dispersing titanium dioxide (TiO 2) powder in an alkali solution to synthesize a TiO 3 precursor; and adding a barium aqueous solution to the TiO 3 precursor to form a barium titanate nano- And a step of washing and drying the synthesized barium titanate nano-structure, thereby producing a barium titanate nano-structure.

According to an aspect of the present invention, the alkali solution may be composed of a combination of at least one of NaOH, KOH, LiOH, Ca (OH) 2, and Mg (OH) 2.

According to an aspect of the present invention, the concentration of the alkali solution may be 4M to 15M.

According to an aspect of the present invention, the alkali solution in which the TiO 2 powder is mixed can be hydrothermally synthesized at a temperature ranging from 90 to 150 ° C.

According to an aspect of the present invention, the hydrothermal synthesis may be performed within a range of 24 to 72 hours.

According to an aspect of the present invention, the atomic ratio of barium (Ba) and titanium (Ti) may be 1: 1 to 10: 1 in the synthesis of the barium titanate nanostructure.

According to an aspect of the present invention, in the washing step, the barium titanate nanostructure can be washed with water, an alcohol, or an acidic aqueous solution.

According to one aspect of the present invention, the barium aqueous solution may be composed of Ba (OH) 2, Ba (OH) 2 .8H2O, BaCl2, Ba (NO3) 2, or a combination thereof.

According to an aspect of the present invention, the concentration of the aqueous barium solution may range from 0.01M to 10M.

According to an aspect of the present invention, the barium aqueous solution may be added within a range of 72 to 120 hours after the hydrothermal reaction is started.

According to at least one embodiment of the present invention, a BaTiO3 one-dimensional nanostructure having a high crystallinity and a diameter of 50 nm or less can be easily produced by one hydrothermal synthesis without a post-treatment conversion process.

In addition, according to at least one embodiment of the present invention, in addition to the advantages of direct synthesis, a template material, a structure control agent, an organic solvent, an organic precursor and the like are not used in the process of synthesizing a BaTiO3 one-dimensional nanostructure, Because of its high yield, it has advantages in mass production and its application.

1 is a flow chart of a process for manufacturing a BaTiO3 one-dimensional nanostructure according to an embodiment of the present invention.
2 is an FE-SEM (scanning electron microscope) image of a BaTiO3 one-dimensional nanostructure produced according to an embodiment of the present invention.
3 is a TEM (transmission electron microscope) image of a BaTiO3 one-dimensional nanostructure produced according to an embodiment of the present invention.
4 is an XRD graph of a BaTiO3 one-dimensional nanostructure produced according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The detailed description thereof will be omitted. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , &Lt; / RTI > equivalents, and alternatives.

In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

In one embodiment of the present invention, a method is used in which a cheap TiO 2 powder is used as a precursor, water is used without an organic solvent, a capping agent is not used, a post-treatment is not necessary, Titanate) is provided.

This is a new direct synthesis method. The direct synthesis method in one embodiment of the present invention does not use an expensive precursor, a structure control agent, and an organic solvent. Since it is based on water, mass production is possible. It is expected to be meaningful in future applications because it provides a direct synthesis method free from deterioration of shape and shape damage.

FIG. 1 is a flowchart illustrating a process for fabricating a BaTiO.sub.3 one-dimensional nanostructure according to an embodiment of the present invention. Referring to FIG. 1, a method for fabricating a BaTiO.sub.3 one-dimensional nanostructure will be described in detail.

In the BaTiO3 one-dimensional nanostructure manufacturing process according to an embodiment of the present invention, the anatase type titanium dioxide (TiO2) powder is uniformly dispersed in a strong alkaline aqueous solution to induce a hydrothermal reaction (S11). After completion of the reaction, the TiO3 precursor was synthesized by the hydrothermal reaction and washed with water, an acidic aqueous solution and ethanol, followed by drying (S13), and a BaTiO3 And a process for producing the nanostructure. At this time, the TiO3 precursor is a precursor of a barium titanate nanostructure, and includes TiO3, and the barium titanate nanostructure has a one-dimensional structure.

The strongly alkaline aqueous solution is prepared by dispersing at least one of NaOH, KOH, LiOH, Ca (OH) 2 and Mg (OH) 2 in water. KOH is preferably used. The concentration of the strongly alkaline aqueous solution is preferably maintained at 4 to 15M. If the concentration of the alkali aqueous solution is less than 4M, short alkaline titanic acid nanowires are stuck. On the other hand, if the concentration of the strongly alkaline aqueous solution is more than 15M, it is disadvantageous that the alkaline ions are uniformly distributed and the gell-time becomes too long, so that the synthesis may be inefficient. Accordingly, in one embodiment of the present invention, the concentration of the strongly alkaline aqueous solution is limited to 4 to 15M.

The hydrothermal synthesis preferably proceeds in a Teflon vessel. At this time, a dense structure of BaTiO3 one-dimensional nanostructure can be obtained at a synthesis temperature of 90 ° C or higher. At below 90 ° C, formation of an alkali titanate one-dimensional structure and direct conversion to BaTiO 3 one-dimensional nanostructures can not be achieved, and it can remain as an alkali titanate one-dimensional structure. At temperatures above 150 ° C., transformation of BaTiO 3 into a particle form It is not desirable.

When hydrothermally synthesizing the titanic acid alkali nanowire, the total reaction time is at least 6 hours. Within 6 hours, no nanowires are formed, and spherical particles of alkali titanate can be formed. After 72 hours, the reaction is complete and reaches the phase equilibrium, so no further reaction occurs. Since the reaction time is preferably from 24 hours to 72 hours, the reaction time in hydrothermal synthesis in the embodiment of the present invention is limited to 24 to 72 hours.

BaTiO3 can be transformed into a particle form when the barium aqueous solution is added too quickly within 72 hours of the initiation of the reaction. If the reaction time is more than 120 hours, the particles are excessively entangled and the efficiency of the synthesis is inadequate. The reaction temperature after the addition of the aqueous barium solution is 70 ° C or higher, and 90-120 ° C is suitable. The holding time can be from several minutes to several hours depending on the temperature, and 1 to 3 hours at 90 ° C is suitable.

Meanwhile, in one embodiment of the present invention, the ratio of Na to Ba is limited to 1: 1 to 1:10. Preferably, the ratio of Na to Ba may be 1: 1.05. If the ratio of Na and Ba is lower than 1: 1, the reaction does not occur properly. If the ratio of Na and Ba exceeds 1:10, side reaction occurs vigorously, and other structures other than the one- have. At this time, the concentration of the barium aqueous solution can be adjusted from 0.01M to 10M, preferably from 0.03M to 0.3M. At this time, the barium aqueous solution is composed of Ba (OH) 2, Ba (OH) 2 .8H2O, BaCl2, Ba (NO3) 2, or a combination thereof.

The direct synthesis method for producing the barium titanate one-dimensional nanostructure in one embodiment of the present invention is basically a method in which only water is used as a solvent, but an alcohol solvent (methanol, ethanol, n-propanol, cyclohexanol, iso-propanol, n- butanol, sec-butanol, tertiary-butanol, and iso-butanol) may be combined to change the reaction rate and pattern.

In the washing / separating process of the BaTiO 3 nanowire, filtration, centrifugation, etc. may be used, and water, ethanol, or an aqueous solution is used. The reason why the acidic aqueous solution is used is to remove the byproducts (BaCO3 etc.) produced during the synthesis.

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

In one embodiment of the present invention, a BaTiO3 one-dimensional nanostructure was prepared by a direct synthesis method using the method described with reference to Fig.

First, add 5 g of titanium dioxide powder and 100 ml of 10 M KaOH aqueous solution, stir for 1 hour, and place in a Teflon container. Subsequently, hydrothermal reaction (S11) is carried out in an oil bath at 110 DEG C for 72 hours under stirring. Then, the temperature of the oil bath is lowered to 90 DEG C, and a barium aqueous solution is added (S12) and further reacted for 2 hours.

After the hydrothermal reaction, the solid precipitate is filtered in a cooled reaction vessel, and washed with water, an aqueous acetic acid solution and ethanol to obtain a barium titanate one-dimensional nanostructure (S13).

2 is an FE-SEM (scanning electron microscope) photograph of a barium titanate one-dimensional nanostructure produced by hydrothermal synthesis according to an embodiment of the present invention. As shown in FIG. 2, a uniformly synthesized barium titanate one-dimensional nanostructure having a diameter of 50 nm or less can be identified.

FIG. 3 shows an X-ray diffraction (XRD) pattern of a barium titanate one-dimensional nanostructure produced by hydrothermal synthesis according to an embodiment of the present invention. Referring to FIG. 3, It can be seen that a very narrow intermediate line width is shown. It can be confirmed that the barium titanate one-dimensional nano-structure thus prepared is a cubic barium titanate, and that no by-product (potassium titanate) remains.

4 is a TEM (transmission electron microscope) image of barium titanate nano-wires prepared by ion exchange reaction from a barium titanate one-dimensional nanostructure according to an embodiment of the present invention. It can be confirmed that the barium titanate one-dimensional nanostructure of this embodiment is a barium titanate nano-structure composed of a high-crystalline single crystal.

As described above, according to the present invention, a barium titanate one-dimensional nanostructure can be prepared by a single synthesis process without a post-treatment conversion reaction. The method of manufacturing the barium titanate one-dimensional nanostructure described above is not limited to the configuration and the method of the embodiments described above, but the embodiments may be modified such that all or some of the embodiments are selectively combined .

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims

Dispersing a titanium dioxide (TiO2) powder in an alkali solution to synthesize a TiO3 precursor;
Adding a barium aqueous solution to the TiO3 precursor to synthesize a barium titanate nano-structure; And
And washing and drying the synthesized barium titanate nanostructure,
The concentration of the alkali solution is 4M to 15M,
Wherein the alkali solution mixed with the TiO2 powder is subjected to hydrothermal synthesis within a temperature range of 90 to 150 占 폚 for 24 to 72 hours.

The method according to claim 1,
Wherein the alkali solution is composed of a combination of at least one of NaOH, KOH, LiOH, Ca (OH) 2 and Mg (OH) 2.

delete

The method according to claim 1,
Wherein the atomic ratio of barium (Ba) to titanium (Ti) is 1: 1 to 10: 1 in synthesizing the barium titanate nanostructure.

The method according to claim 1,
Wherein the cleaning step comprises washing the barium titanate nanostructure with water, an alcohol and an acidic aqueous solution.

The method according to claim 1,
Wherein the barium aqueous solution is composed of Ba (OH) 2, Ba (OH) 2 .8H2O, BaCl2, Ba (NO3) 2, or a combination thereof.

9. The method of claim 8,
Wherein the concentration of the barium aqueous solution is in the range of 0.01M to 10M.

The method according to claim 1,
Wherein the barium aqueous solution is added within 72 to 120 hours after the initiation of the hydrothermal reaction.