KR102577100B1 - Method for manufacturing metal oxide nanotube with hollow core and carbon-coated metal oxide nanotube with hollow core - Google Patents

Abstract

The present invention relates to a method for producing a metal oxide nanotube with a hollow core and a metal oxide nanotube with a hollow core formed and coated with carbon.
A method for producing metal oxide nanotubes according to an embodiment of the present invention includes preparing a precursor mixture solution by mixing carbon nanoparticles, a metal oxide precursor, and a solvent; Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles; and manufacturing a metal oxide nanotube structure by baking the coating composite.

Description

Method for manufacturing metal oxide nanotube with hollow core and carbon-coated metal oxide nanotube with hollow core}

The present invention relates to a method for producing a metal oxide nanotube with a hollow core and a metal oxide nanotube with a hollow core formed and coated with carbon.

Metal oxides, which contain multiple types of metal ions and exhibit unique properties, are manufactured by various methods such as solid-phase synthesis, hydrothermal synthesis, sol-gel method, and co-precipitation method.

General metal oxides are synthesized into the most stable phase suitable for that temperature by removing impurities through a sintering process at high temperature, and using the remaining metal ions and oxygen as well as oxygen in the atmosphere. Metal oxides are formed into solid particles through the diffusion process of complex metal ions and oxygen, but the external shape of the particles cannot be controlled, so they are mostly synthesized in spherical particles or in a predominant shape following the crystal system of the original solid phase.

Previously, in order to control the shape of the metal oxide, a method was used to control the shape of the oxide precursor by adjusting the shape of the oxide precursor in the pre-sintering stage and then sintering it under mild conditions.

For example, the precursor of vanadium pentoxide (V ₂ O ₅ ) nanowires grows into a very thin and elongated shape under hydrothermal synthesis conditions. This is because vanadium pentoxide has an orthorhombic crystal system and has a flat structure along the c-axis. It is possible because it has . However, there is a problem with this method that such a shape is not easily formed when the crystal system is cubic or tetragonal.

In addition, in order to manufacture an oxide with a hollow structure, spherical silica (SiO ₂ ) is used as a core template, coated with a carbon precursor, and then heat treated and silica etched. . This structure is difficult to manufacture with metal oxide because other materials are formed by reacting with the silica inside during the firing process. As described above, creating a nanotube or wire shape with a hollow structure is intended to improve characteristics such as catalytic activity and ion movement by utilizing the expanded specific surface area, but there is a problem that such a shape is not easily formed.

Recently, various attempts have been made to control the shape by using carbon black (spherical) and carbon nanotubes as templates, but it was not possible to create a specific shape because the template was not completely surrounded by the metal oxide precursor. This is because the carbon surface is hydrophobic, so no charged metal ions are introduced onto the carbon using conventional methods. To solve this problem, several methods have been proposed to attach metal ions by introducing functional groups such as carboxyl groups to the carbon surface through acid or base treatment, plasma treatment, etc., but they have not been formed to completely surround the entire carbon particle. In the case of coating carbon on oxide, several opposite methods are already being implemented. The present invention proposes a method of controlling the shape of a metal oxide having these characteristics using ultrasonic chemistry and a carbon core template.

Korean Patent No. 10-1466752 (Announcement date: 2014.12.02.) Korean Patent No. 10-1466752 (Announcement date: 2014.12.02.)

Therefore, an embodiment of the present invention is intended to solve the problems of the prior art described above, and utilizes ultrasonic chemistry and a carbon core template to manufacture hollow metal oxide nanotubes in a hollow shape that are difficult to manufacture using existing oxide manufacturing methods. The technical problem to be solved is to provide a method to do so.

In addition, the present invention aims to solve the technical problem of providing a method for producing carbon-coated metal oxide nanotubes that can produce metal oxide nanotubes and then form a thin carbon coating film through hydrothermal synthesis. do.

In order to achieve the above-described technical problem, an embodiment of the present invention includes the steps of mixing carbon nanoparticles, a metal oxide precursor, and a solvent to prepare a precursor mixture solution; Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles; and baking the coating composite to produce a metal oxide nanotube structure.

According to one embodiment, the carbon nanoparticles may include one or more types selected from the group consisting of carbon nanofibers, carbon nanotubes, multilayer graphene, graphite, and partially crystalline carbon.

According to one embodiment, the metal oxide precursor may include one or more selected from the group consisting of metal alkoxide, metal hydroxide, metal hydrate, metal oxide, metal nitride, metal nitrate, metal carbonate, metal sulfate, and metal chloride. there is.

According to one embodiment, the metal oxide precursor is a metal alkoxide containing one or more metals selected from the group consisting of Group 2 metals, Group 3 metals, Group 4 metals, Group 5 metals, Group 13 metals, and Group 14 metals. It may be a mixture.

According to one embodiment, the solvent may include water (H ₂ O) and alcohol at a volume ratio of 1:100 to 10:1, respectively.

According to one embodiment, the precursor mixed solution may include carbon nanoparticles and metal oxide precursors at a weight ratio of 5:1 to 1:10, respectively.

According to one embodiment, the step of manufacturing the coating composite may irradiate the precursor mixture solution with ultrasonic waves with a frequency of 10 to 200 kHz for 1 to 2880 minutes.

According to one embodiment, the step of manufacturing the metal oxide nanotube structure may include heating at a temperature increase rate of 3 to 49 ° C./min and firing at a temperature of 600 to 1,200 ° C. for 1 to 12 hours.

In addition, an embodiment of the present invention includes preparing a precursor mixed solution by mixing carbon nanoparticles, a metal oxide precursor, and a solvent; Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles; manufacturing a metal oxide nanotube structure by baking the coating composite; manufacturing a coating structure by coating the metal oxide nanotube structure with a carbon source solution; and producing a carbon-coated metal oxide nanotube structure by calcining the coated structure in an inert atmosphere.

According to one embodiment, the carbon source solution includes glucose, sucrose, graphite, carbon nanotube, citric acid, carbon black, and diethylene. It may include one or more carbon sources selected from the group consisting of glycol (diethylene glycol) and triethylene glycol (triethylene glycol).

According to one embodiment, the step of manufacturing the coating structure may include applying the carbon source solution to the metal oxide nanotube structure and then heat treating it at a temperature of 180 to 300 ° C. for 0.5 to 12 hours. there is.

According to one embodiment, the step of manufacturing the carbon-coated metal oxide nanotube structure may include baking the coated structure at a temperature of 500 to 1,500° C. for 1 to 24 hours in an atmosphere supplied with an inert gas.

The method for manufacturing hollow metal oxide nanotubes according to an embodiment of the present invention described above includes completely coating metal alkoxide on carbon nanofibers using an ultrasonic chemistry method to produce a coating having a carbon nanoparticle core and a metal alkoxide shell structure. Hollow metal oxide nanotubes can be manufactured by manufacturing and firing the coating to remove the carbon component.

In addition, it was confirmed that a carbon-coated metal oxide nanotube structure capable of exhibiting conductivity could be manufactured by coating the manufactured hollow metal oxide nanotubes with a carbon source and then sintering them.

1 is a process diagram showing a method for manufacturing hollow metal oxide nanotubes according to an embodiment of the present invention.
Figure 2 is a process diagram showing a method of manufacturing hollow metal oxide nanotubes coated with carbon according to an embodiment of the present invention.
Figure 3 is an electron microscope image of (a) a coating composite and (b) TiNb ₂ O ₇ nanotubes prepared by the method according to Example 1.
Figure 4 is a transmission electron microscope image of TiNb ₂ O ₇ nanotubes prepared by the method according to Example 1.
Figure 5 is an electron microscope image of composite particles prepared by the method according to (a) Comparative Example 1 and (b) Comparative Example 2.
Figure 6 is an electron microscope image of nanotubes prepared by the method according to (a) Example 1, (b) Example 2-1, and (c) Example 2-2.
Figure 7 shows the results of XRD pattern analysis of TiNb ₂ O ₇ nanotubes prepared by firing at temperatures of 600°C, 700°C, and 800°C according to Example 1.
Figure 8 is an electron microscope image of a carbon-coated titanium niobate and nanotube composite prepared by the method according to Example 3.

In the following description of the present invention, if a detailed description of a related known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Since embodiments according to the concept of the present invention can make various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the specification or application. However, this is not intended to limit the embodiments according to the concept of the present invention to a specific disclosed form, and the present invention should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between. Other expressions that describe the relationship between components, such as "between" and "immediately between" or "neighboring" and "directly adjacent to" should be interpreted similarly.

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “include” or “have” are intended to indicate the existence of a described feature, number, step, operation, component, part, or combination thereof, but are not intended to indicate the presence of one or more other features or numbers. It should be understood that this does not preclude the existence or addition of steps, operations, components, parts, or combinations thereof.

The inventors of the present invention have developed a method of completely coating metal alkoxide on carbon nanofibers using ultrasonic chemistry to produce a coating having a carbon nanoparticle core and metal alkoxide shell structure, and then calcining the coating to remove the carbon component. It was confirmed that hollow metal oxide nanotubes could be manufactured.

In addition, it was confirmed that a carbon-coated metal oxide nanotube structure capable of exhibiting conductivity could be manufactured by coating the manufactured hollow metal oxide nanotubes with a carbon source and then sintering them.

In the present invention, the ultrasonic chemical method refers to a method of forming a double-layer structure in which a metal precursor shell is coated on a carbon nanofiber core by irradiating ultrasonic waves to a mixed solution containing carbon nanofibers and a metal precursor.

Specifically, when ultrasonic waves are irradiated to a mixed solution, a sonic luminescence phenomenon is induced by bubble cavitation within the ultrasonic wavelength, and the sonic luminescence phenomenon occurs when bubbles rising inside the liquid are synchronized by ultrasonic waves, causing the vibrating gas bubbles to rapidly contract. This refers to the phenomenon of emitting light when In other words, when ultrasonic waves are irradiated to bubbles floating in a liquid, the bubbles repeatedly contract and expand according to the cycle of the ultrasonic waves, and when the bubbles contract, they emit light. When the bubble shrinks around the wall of the bubble where sonic luminescence occurs, a high-temperature and high-pressure liquid reaction area is created at a temperature of approximately 1,000 ℃ and 500 bar, and hydroxyl radicals (OH ^- ) are generated. In this reaction area, high-energy chemical reactions occur due to the high-temperature, high-pressure environment and highly reactive radicals, and high-energy chemical reactions can also occur within bubbles.

Therefore, when a hot spot area around the chemical bubble cavitation phenomenon is formed around the core particle by ultrasonic irradiation, the molecules (metal alkoxide and water (H ₂ O)) dissolved in the liquid are formed. The reaction occurs on the core surface so that the material can be coated on the surface of the core in a form similar to deposition, and the method for producing hollow metal oxide nanotubes of the present invention completely coats metal alkoxide particles on carbon particles using an ultrasonic chemical method. Thus, a coating composite having a carbon nanofiber core and a metal alkoxide shell structure can be manufactured.

It was confirmed that hollow metal oxide nanotubes could be manufactured by firing the prepared coating composite to remove the carbon component.

Additionally, carbon coating can be applied to the hollow metal oxide nanotube structure, making it possible to manufacture a conductive hollow metal oxide nanotube structure. Additionally, carbon coating can be applied to the hollow metal oxide nanotube structure, making it possible to manufacture a conductive hollow metal oxide nanotube structure.

The present invention basically involves a core/shell structure in which a metal precursor is coated on carbon using ultrasonic chemistry, a method of firing the structure to remove the carbon and only metal oxide nanotubes remain, and a method of coating the nanotubes with carbon again. present.

In this specification, the coating composite refers to a composite with a double-layer structure including a core and a shell by coating a metal oxide precursor on the surface of the carbon nanoparticle.

In this specification, the coated structure refers to a metal oxide nanotube structure manufactured by coating a carbon source solution.

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

1 is a process diagram showing a method for manufacturing hollow metal oxide nanotubes according to an embodiment of the present invention.

Referring to FIG. 1, a method for manufacturing hollow metal oxide nanotubes according to an embodiment of the present invention includes the steps of mixing carbon nanoparticles, a metal oxide precursor, and a solvent to prepare a precursor mixture solution; Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles; and manufacturing a metal oxide nanotube structure by baking the coating composite.

First, in the step of preparing a precursor mixed solution, the precursor mixed solution can be prepared by mixing carbon nanoparticles, a metal oxide precursor, and a solvent.

The carbon nanoparticles are a component that forms a core so that metal oxide particles can be coated by ultrasonic irradiation. The carbon nanoparticles may include carbon nanofibers, carbon nanotubes, multilayer graphene, graphite, partially crystalline carbon, or mixtures thereof. In particular, the carbon nanoparticles may be carbon nanofibers having a diameter of 1 to 500 nm and a length of 100 to 9,000 nm.

Carbon nanoparticles can be used immediately without additional pretreatment such as acid treatment or base treatment.

The metal oxide precursor is coated on the carbon nanoparticle core to form a shell, and is a component that forms a nanotube after the core is removed.

The metal oxide precursor can form a metal oxide by heat treatment and can be used without limitation as long as it contains a metal salt containing a metal ion. For example, the metal oxide precursor may include a metal alkoxide, metal hydroxide, metal hydrate, metal oxide, metal nitride, metal nitrate, metal carbonate, metal sulfate, metal chloride, or a mixture thereof.

Preferably, the metal oxide precursor may be a metal alkoxide, and one or more metal alkoxides containing different metals may be mixed and used. More preferably, the metal oxide precursor may be a metal alkoxide containing a Group 2 to Group 5 metal, a Group 13 metal, a Group 14 metal, or a mixture thereof. In particular, group 1 metal alkoxides are not suitable because they induce a substitution reaction that changes other metals into alkoxides in the precursor mixture solution. The alkoxide can be selected from various alkoxides such as methoxide, ethoxide, propoxide, iso-propoxide, and butoxide.

The solvent may be a variety of common solvents that can dissolve and uniformly disperse carbon nanoparticles and metal precursors. In particular, the solvent may be a mixed solvent containing water (H ₂ O) and alcohol. The solvent may be one containing water (H ₂ O) and alcohol in a volume ratio of 1:100 to 10:1, respectively.

The solvent contains water (H ₂ O) and reacts with the metal oxide precursor to form a metal hydroxyl chain. For example, when a metal alkoxide is used as a metal oxide precursor, water (H ₂ O) reacts with the metal alkoxide as shown in Equation 1 below to form a metal hydroxyl chain.

[Equation 1]

Metal-alkoxide + H ₂ O = -M-(OH)-M-(OH)- + alcohol

When the above reaction occurs under a cavitation phenomenon induced by ultrasonic irradiation, metal hydroxyl chains are doped on the surface of the carbon nanofiber to form a complex of the core and the shell surrounding the core.

The alcohol may be methanol, ethanol, propanol, isopropanol, butanol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, or mixtures thereof.

If the content of carbon nanoparticles serving as the core in the precursor mixture solution is less than that of the metal oxide precursor, seeds may be formed somewhere other than the carbon surface during the decomposition reaction of the alkoxide of the metal precursor, resulting in the formation of metal oxide powder particles. Conversely, if the content of carbon nanoparticles is excessive compared to the metal oxide precursor, the amount of core may become too large and the entire core may not be coated, and nanotubes may not be formed during firing. In addition, if the content of carbon nanofibers, which is a core material, is excessive compared to the metal precursor, the thickness of the finally formed metal oxide is reduced.

Therefore, the precursor mixed solution may contain carbon nanoparticles and metal oxide precursors at a weight ratio of 5:1 to 1:10, respectively. Preferably, the precursor mixed solution may be a mixture containing carbon nanoparticles and metal oxide precursors at a weight ratio of 1:5 to 1:15, respectively.

Additionally, the precursor mixed solution may be mixed with a solvent at a ratio of 500 to 2,000 parts by weight based on 1 part by weight of the metal oxide precursor. If the solvent content is less than 500 parts by weight, the specific surface area of the carbon nanofibers is very large, so the carbon nanofibers may not be sufficiently dispersed and may be granulated, and an ultrasonic field may not be formed. Preferably, the solvent may be included in a ratio of 1000 to 1500 parts by weight based on 1 part by weight of the metal oxide precursor.

In this step, in order to prepare the precursor mixed solution as described above, a first mixed solution is prepared by mixing carbon nanoparticles and a solvent, and a metal oxide precursor is mixed into the first mixed solution to prepare a precursor mixed solution. You can.

Additionally, to prepare the first mixed solution, carbon nanoparticles and a solvent may be mixed, and then ultrasonic waves may be irradiated to the first mixed solution to sufficiently disperse the carbon nanoparticles.

Meanwhile, in the step of manufacturing a coating composite including a core and a shell, the metal oxide precursor may be coated on the surface of the carbon nanoparticles by irradiating ultrasonic waves to the precursor mixture solution to produce the coating composite.

The ultrasonic waves can be selectively used, such as bath-type ultrasonic waves or probe-type ultrasonic waves.

In this step, the coating composite can be manufactured by irradiating the precursor mixture solution with ultrasonic waves at a frequency of 10 to 200 kHz for 1 to 2880 minutes. Ultrasonic power can be adjusted in the range of 1 to 1,000 W. If the frequency of ultrasonic waves is less than 10 KHz, there is a risk of insufficient doping reaction due to interference, and if the frequency of ultrasonic waves exceeds 200 KHz, there is a problem that it is difficult to induce a cavitation phenomenon.

Additionally, in this step, the precursor mixed solution can be adjusted to maintain a temperature between the freezing point and the boiling point, and in particular, can be adjusted to maintain a temperature of 35 to 45°C. The ultrasonic irradiation time varies depending on the composition of the components introduced into the precursor mixed solution, and the irradiation time can be selectively adjusted depending on the content.

According to a preferred embodiment of the present invention, a coating composite including a core and a shell can be manufactured by irradiating ultrasonic waves in the range of 20 to 60 KHz with a power of 10 to 50 W for 90 to 180 minutes.

Additionally, this step may further include preparing the coating composite as described above and then recovering the coating composite.

The coating composite can be recovered by filtering the mixed solution containing the coating composite, and the coating composite can be separated from the mixed solution using a filtration filter capable of separating nanometer-sized particles.

The separated coating composite can be cleaned using alcohol such as ethanol, and the cleaning can be repeated one or more times.

Meanwhile, in the step of manufacturing a metal oxide nanotube structure, the coating composite is sintered to remove the carbon component forming the core, and a nanotube structure having a hollow structure formed therein and made of metal oxide can be manufactured.

In this step, the metal oxide nanotube structure can be manufactured by baking the coating composite at a temperature of 600 to 1,200° C. for 1 to 12 hours and then cooling it.

If the firing temperature is less than 600 ℃ or the processing time is less than 1 hour, there is a risk that the removal of carbon components may be insufficient, and if it exceeds 1,200 ℃ or the processing time is more than 12 hours, there is a risk of nanotube aggregation or damage. .

In addition, in this step, the coating composite can be sintered by heating at a temperature increase rate of 3 to 49 ℃/min. If the temperature increase rate is more than 50 ℃/min, agglomeration of metal oxides occurs due to a rapid temperature increase, causing agglomeration in the nanotubes. There is a risk of pinholes being created or damage occurring.

The method for producing hollow metal oxide nanotubes according to the present invention as described above involves completely coating metal alkoxide on carbon nanofibers using an ultrasonic chemistry method to produce a coating having a carbon nanoparticle core and metal alkoxide shell structure. And, hollow metal oxide nanotubes can be manufactured by calcining the coating to remove the carbon component.

Meanwhile, Figure 2 is a process diagram showing a method of manufacturing hollow metal oxide nanotubes coated with carbon according to the present invention.

Referring to Figure 2, the method for producing carbon-coated metal oxide nanotubes according to the present invention includes the steps of mixing carbon nanoparticles, a metal oxide precursor, and a solvent to prepare a precursor mixture solution; Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles; manufacturing a metal oxide nanotube structure by baking the coating composite; manufacturing a coating structure by coating the metal oxide nanotube structure with a carbon source solution; and manufacturing a carbon-coated metal oxide nanotube structure by calcining the coated structure in an inert atmosphere.

In the step of manufacturing the coating structure, the coating structure can be manufactured by coating a carbon source on the metal oxide nanotube structure prepared by the method described above.

Specifically, in this step, the carbon source solution can be applied to the metal oxide nanotube structure and then heat treated to fix the carbon source to the metal oxide nanotube structure to manufacture the coating structure.

The method of applying the carbon source solution to the metal oxide nanotube structure can be performed by mixing the structure and the carbon source solution or using various conventional methods used to apply the solution to particles. Preferably, in this step, the metal oxide nanotube structure and the carbon source solution are mixed and then ultrasonic waves are applied to apply the carbon source to the surface of the metal oxide nanotube structure.

In this step, a coated structure can be manufactured by applying the carbon source solution to the structure in the same manner as above and then heat-treating the structure to fix the carbon source to the metal oxide nanotube structure.

The heat treatment may be performed at a temperature of 180 to 300° C. for 0.5 to 12 hours. Through the above heat treatment, a portion of the carbon source may be carbonized and the carbon source may be fixed to the metal oxide nanotube structure. The above heat treatment can be performed by supplying a structure coated with a carbon source solution to a heat treatment device such as an autoclave, or by using a crucible (furnace).

The carbon source solution may be a mixture containing a carbon source and a solvent. The carbon source solution may include a carbon source in a ratio of 10 to 100 parts by weight based on 10 parts by weight of the metal oxide nanotube structure.

Additionally, the carbon source solution may be prepared by mixing a solvent containing water (H ₂ O), alcohol, or a mixture thereof with the carbon source. Preferably, the solvent may be a mixed solvent containing distilled water and ethanol in a weight ratio of 1:1. The carbon source solution can be prepared by mixing 50 to 200 parts by weight of solvent with 10 parts by weight of carbon source.

Carbon sources include glucose, sucrose, graphite, carbon nanotube, citric acid, carbon black, diethylene glycol, and triethylene glycol. (triethylene glycol) or mixtures thereof.

The carbon source may utilize different carbon sources depending on the heat treatment method used in the step to be described later. For example, in the case of heat treatment using an autoclave, glucose can be used as a carbon source, and the carbon source can be fixed to the surface of the structure by heat treatment at a temperature of 180 to 230 ° C. for 2 to 12 hours to carbonize the glucose.

Alternatively, in the case of heat treatment using a crucible, a high boiling point solvent such as diethylene glycol or triethylene glycol can be used as a carbon source and heat treated at a temperature of 200 to 300 ° C for 0.5 to 63 hours to fix the carbon source on the surface of the structure. there is.

Additionally, this step may further include manufacturing a coating structure by fixing the carbon source to the metal oxide nanotube structure as described above and then washing the manufactured coating structure.

Washing of the coating structure can be performed using a mixed solution containing water, alcohol, or a mixture thereof. The coating structure can be cooled to room temperature and then washed repeatedly one or more times using the mixed solution.

In the step of manufacturing the carbon-coated metal oxide nanotube structure, carbon can be coated on the metal oxide nanotube structure by baking the coating structure in an inert gas atmosphere, and carbonizing the carbon source through heat treatment to apply carbon to the structure. Can be coated on the surface.

In this step, the coating structure can be fired in an atmosphere where an inert gas such as nitrogen, argon, helium, etc. is supplied. The firing treatment can be performed at a temperature of 500 to 1,500° C. for 1 to 24 hours. Accordingly, a carbon-coated metal oxide nanotube structure can be manufactured by completely carbonizing the carbon source fixed to the surface and fixing it to the surface of the structure.

The hollow metal oxide nanotube structure and the carbon-coated metal oxide nanotube structure using the method described above can be easily utilized for purposes such as electrode forming materials, sensors, catalysts, fuel cells, and electrode active materials.

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

The presented examples are only specific examples for explaining the present invention and are not intended to limit the technical scope of the present invention.

<Example 1>

Titanium iso-propoxide and niobium ethoxide were used as metal alkoxide precursors. Carbon nanofibers with a diameter of 100 to 200 nm and a length of 5 ㎛ were used. A mixed solvent containing distilled water and ethanol at a volume ratio of 1:99 was prepared.

A dispersion solution containing carbon nanotube oxide was prepared by mixing 0.15 g of carbon nanofibers in a mixed solvent and radiating ultrasound at 40 kHz and 20 W for 1 hour. A precursor mixed solution was prepared by mixing 0.431 g of titanium iso-propoxide and 0.954 g of niobium ethoxide in the dispersion solution and irradiating ultrasound under the same conditions as above for 2 hours. The temperature of the solution was maintained at 40°C. did.

Afterwards, the precursor mixture solution was filtered using a Buchner funnel to obtain a coating composite, and the obtained coating composite was washed with distilled water and ethanol and then dried.

The dried composite was heated at 5°C per minute, maintained at 600°C, 700°C, and 800°C for 6 hours, respectively, and then cooled to room temperature to prepare a titanium niobate and nanotube composite (TiNb ₂ O ₇ nanotube).

<Example 2>

A titanium niobate and nanotube composite (TiNb ₂ O ₇ nanotube) according to Example 2-1 was prepared in the same manner as in Example 1, except that 0.2 g of each carbon nanofiber was mixed in the mixed solvent.

In addition, a titanium niobate and nanotube composite (TiNb ₂ O ₇ nanotube) according to Example 2-2 was prepared in the same manner as Example 1, except that 0.25 g of each carbon nanofiber was mixed in the mixed solvent. .

<Example 3>

A dispersion solution was prepared by mixing 0.2 g of the nanotube oxide of Example 1 and 1 g of glucose in a mixed solvent containing distilled water and ethanol at a volume ratio of 1:1, and irradiating the mixture with ultrasound for 2 minutes. The dispersion solution was supplied to an autoclave and heat treated at 210°C for 4 hours. The heat-treated dispersion solution was filtered to obtain a composite, and the obtained composite was washed with distilled water and ethanol and then dried. The dried composite was reacted in an argon gas atmosphere at a temperature of 600° C. for 4 hours and cooled to room temperature to prepare a carbon-coated titanium niobate and nanotube composite (TiNb ₂ O ₇ nanotube).

<Comparative Example 1>

A mixed solution was prepared by mixing 0.431 g of titanium iso-propoxide, 0.954 g of niobium ethoxide, and 0.15 g of carbon nanofibers in a mixed solvent containing distilled water and ethanol at a volume ratio of 1:99, and the prepared mixed solution was It was supplied to an autoclave and reacted at 210°C for 4 hours to form a complex. The complex was reacted at a temperature of 600°C for 6 hours.

<Comparative Example 2>

A composite was prepared in the same manner as Example 1, except that carbon nanofibers were not mixed in the mixed solvent.

<Experimental example>

(1) Appearance evaluation of nanotubes and composite particles 1

The external appearance of the coating composite and TiNb ₂ O ₇ nanotubes prepared by the method according to Example 1 was evaluated using an electron microscope, and the results are shown in Figures 3 and 4.

If the carbon nanofiber coated with TiNb ₂ O ₇ as shown in Figure 3(a) is the fired material, it can be seen that hollow TiNb ₂ O ₇ nanotubes were formed as shown in Figure 3(b) and Figure 4. I was able to.

In addition, the external appearance of the composite particles manufactured by the method according to Comparative Example 1 and Comparative Example 2 was evaluated, and the results are shown in FIG. 5.

As shown in Figures 5(a) and 5(b), it was confirmed that none of the manufactured composite particles had a hollow structure.

(2) Appearance evaluation of nanotubes 2

The external appearance of nanotubes manufactured by the method according to Example 1, Example 2-1, and Example 2-2 was evaluated, and the results are shown in FIG. 6.

As shown in Figure 6, it was confirmed that the thickness was 220 nm in Example 1, 150 nm in Example 2-1, and 100 nm in Example 2-2, and accordingly, the content of carbon nanofibers As this increased, it was confirmed that the carbon component was removed by firing and the thickness of the TiNb ₂ O ₇ nanotube decreased.

(3) Evaluation of the effect of firing temperature

In order to evaluate the composition of titanium niobate and nanotube composites (TiNb ₂ O ₇ nanotubes) calcined at temperatures of 600°C, 700°C, and 800°C, respectively, according to Example 1, X-ray diffraction analysis was performed, and the The results are shown in Figure 7.

As shown in Figure 7, as the sintering temperature increases, the strength of the carbon crystals decreases and the strength of the metal oxide tends to increase, confirming that the carbon component is removed and metal oxide nanotubes are formed.

(4) Appearance evaluation of carbon-coated nanotubes

In order to evaluate the appearance of the carbon-coated titanium niobate and nanotube composite prepared by the method according to Example 3, the appearance was evaluated using an electron microscope, and the results are shown in FIG. 8.

As shown in Figure 8, it was confirmed that a carbon coating layer was formed on the surface of the manufactured carbon-coated titanium niobate and nanotube composite.

The technical idea of the present invention described above has been described in detail in preferred embodiments, but it should be noted that the embodiments are for illustrative purposes only and are not intended for limitation. Additionally, those skilled in the art of the present invention will understand that various embodiments are possible within the scope of the technical idea of the present invention. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the attached claims.

Claims (12)

Preparing a precursor mixed solution by mixing carbon nanoparticles, a metal oxide precursor, and a solvent;
Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles; and
Comprising: manufacturing a metal oxide nanotube structure by baking the coating composite,
The solvent contains water and alcohol in a volume ratio of 1:100 to 10:1, respectively,
The precursor mixed solution contains carbon nanoparticles and metal oxide precursors at a weight ratio of 5:1 to 1:10, respectively,
The method of manufacturing a hollow metal oxide nanotube, characterized in that the step of manufacturing the coating composite involves irradiating the precursor mixture solution with ultrasonic waves at a frequency of 10 to 200 kHz for 1 to 2880 minutes. According to paragraph 1,
A method of producing hollow metal oxide nanotubes, wherein the carbon nanoparticles include at least one selected from the group consisting of carbon nanofibers, carbon nanotubes, multilayer graphene, graphite, and partially crystalline carbon. According to paragraph 1,
The metal oxide precursor is a hollow metal oxide nanotube containing at least one member selected from the group consisting of metal alkoxide, metal hydroxide, metal hydrate, metal oxide, metal nitride, metal nitrate, metal carbonate, metal sulfate, and metal chloride. Manufacturing method. According to paragraph 1,
The metal oxide precursor is a hollow metal oxide nano-type metal alkoxide containing at least one metal selected from the group consisting of Group 2 metals, Group 3 metals, Group 4 metals, Group 5 metals, Group 13 metals, and Group 14 metals. Tube manufacturing method. delete delete delete According to paragraph 1,
The step of manufacturing the metal oxide nanotube structure is,
A method of producing hollow metal oxide nanotubes comprising heating at a temperature increase rate of 3 to 49 °C/min and firing at a temperature of 600 to 1,200 °C for 1 to 12 hours. Preparing a precursor mixed solution by mixing carbon nanoparticles, a metal oxide precursor, and a solvent;
Producing a coating composite including a core and a shell by irradiating the precursor mixture solution with ultrasonic waves to coat the metal oxide precursor on the surface of the carbon nanoparticles;
manufacturing a metal oxide nanotube structure by baking the coating composite;
manufacturing a coating structure by coating the metal oxide nanotube structure with a carbon source solution; and
Comprising: manufacturing a carbon-coated metal oxide nanotube structure by calcining the coating structure in an inert atmosphere,
The carbon source solution includes glucose, sucrose, graphite, carbon nanotubes, citric acid, carbon black, diethylene glycol, and Containing at least one carbon source selected from the group consisting of triethylene glycol,
In the step of manufacturing the coating structure, the carbon source solution is applied to the metal oxide nanotube structure and then heat-treated at a temperature of 180 to 300 ° C. for 0.5 to 12 hours to prepare the coating structure,
The step of manufacturing the carbon-coated metal oxide nanotube structure includes baking the coated structure at a temperature of 500 to 1,500 ° C. for 1 to 24 hours in an atmosphere supplied with an inert gas. Method for manufacturing nanotubes. delete delete delete