KR20210054405A - Graphene oxide-carbon nanotube composite, manufacturing method for the same and cement paste comprising the same - Google Patents

Abstract

The present invention relates to a graphene oxide-carbon nanotube composite, a method for preparing the same and cement paste including the same. The method for preparing a graphene oxide-carbon nanotube composite according to the present invention includes the steps of: mixing carbon nanotubes (CNT), graphite, sodium nitrate (NaNO_3) and a solvent to prepare a first solution; agitating the first solution and adding potassium permanganate (KMnO_4) thereto; agitating the first solution containing the potassium permanganate added thereto, and adding distilled water thereto so as to prepare a second solution; heating the second solution; adding hydrogen peroxide (H_2O_2) to the heated second solution to prepare a third solution; adjusting pH of the third solution; and ultrasonicating the pH-adjusted third solution to obtain a graphene oxide-carbon nanotube composite. The graphene oxide-carbon nanotube composite shows improved dispersibility in cement paste, and the cement paste including the graphene oxide-carbon nanotube composite shows improved strength.

Description

Graphene oxide-carbon nanotube composite, manufacturing method thereof, and cement paste containing the same {GRAPHENE OXIDE-CARBON NANOTUBE COMPOSITE, MANUFACTURING METHOD FOR THE SAME AND CEMENT PASTE COMPRISING THE SAME}

The present invention relates to a graphene oxide-carbon nanotube composite, a method of manufacturing the same, and a cement paste including the same.

In general, carbon nanotubes or graphene oxide, which have been mixed and used in building materials, are known to be helpful in the filling effect or hydration acceleration in concrete composite materials, and thus many studies have been conducted in this regard.

As a result of these studies, a method for synthesizing various carbon nanotubes or a method for synthesizing graphene oxide has been suggested, and studies are being conducted in various fields using the same.

Regarding the previous work, the atomic structure and performance of the carbon nanotubes concerned have attracted attention from many scientists since 1991, when Sumio Iijima, a physicist at the NEC Institute in Japan, reported on carbon nanotubes.

Materials related to carbon nanotubes are divided into single-walled carbon nanotubes and multi-walled carbon nanotubes, and carbon nanotubes are known to have very high specific surface area, mechanical properties, excellent thermal conductivity, and electrical properties.

As the most ideal material for improving the mechanical properties of cement pastes in the field of construction, carbon nanotubes have sufficiently shown excellent performance, but they have an elongated shape, so that water due to the strong attraction between carbon nanotube molecules (Van der Waal force) It is easily agglomerated in, and there is a problem that the dispersibility is poor due to the complex structure.

To solve this problem, research has been conducted to disperse carbon nanotubes in a physical or chemical manner, but this method has a disadvantage in that a lot of time and economic cost are spent.

On the other hand, graphene oxide has better dispersibility in water than carbon nanotubes, but it is known that mechanical performance improvement is inferior to carbon nanotubes when used in cement paste.

Because of the structural differences between graphene oxide and carbon nanotubes, there is no known information about the proper synthesis, nor is known about the proper mixing ratio or method.

Republic of Korea Patent Publication No. 10-2017-0027232, "Eco-friendly finishing material additives for buildings, finishing material compositions containing them, and eco-friendly finishing materials for buildings" Republic of Korea Patent Publication No. 10-1425536, "Method of manufacturing cement composite material containing carbon nanotubes"

An embodiment of the present invention is a graphene oxide-carbon nanotube composite capable of improving dispersibility in a cement paste and strength of a cement paste by synthesizing graphene oxide having excellent dispersibility and carbon nanotubes having excellent mechanical properties, and a method for producing the same And it is intended to provide a cement paste containing the same.

According to an embodiment of the present invention, the strength of the cement paste may be improved by including the graphene oxide-carbon nanotube composite having excellent dispersibility in the cement paste, and the graphene oxide-carbon nanotube composite evenly dispersed in the cement paste. It is intended to provide a possible graphene oxide-carbon nanotube composite, a method of manufacturing the same, and a cement paste including the same.

According to an embodiment of the present invention, graphene that can synthesize graphene oxide and carbon nanotubes at a lower temperature than conventional graphene can minimize the weight loss of graphene oxide-carbon nanotube composites due to heat and chemical treatment. It is intended to provide an oxide-carbon nanotube composite, a method for manufacturing the same, and a cement paste including the same.

According to an embodiment of the present invention, a graphene oxide-carbon nanotube composite capable of improving dispersibility by monolayering a multilayer structure of a graphene oxide-carbon nanotube composite through ultrasonic treatment, a method of manufacturing the same, and a cement comprising the same I want to provide a paste.

According to the method for producing a graphene oxide-carbon nanotube composite according to the present invention, a first solution by mixing _{carbon nanotubes (CNT), graphite, sodium nitrate (NaNO 3} ) and a solvent (H ₂ SO ₄₎ Manufacturing a; Adding _{potassium permanganate (KMnO 4} ) after stirring the first solution; Preparing a second solution by stirring the first solution to which potassium permanganate is added and then adding distilled water; Heating the second solution; Preparing a third solution by adding hydrogen peroxide (H ₂ O _{2) to the heated second solution;} Adjusting the pH of the third solution; And ultrasonicating the third solution whose pH is adjusted to prepare a graphene oxide-carbon nanotube composite.

According to the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the weight ratio of the carbon nanotube and graphite may be 1:1 to 1:4.

According to the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the step of heating the second solution may be performed at 90°C to 100°C.

According to the manufacturing method of the graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the step of washing the third solution with hydrochloric acid (HCl) may be further included.

According to the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the pH of the third solution may be adjusted to 6.5 to 7.2.

According to the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the ultrasonic treatment may be performed for 30 to 50 minutes.

According to the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the ultrasonic treatment may be performed at a frequency of 20 kHz to 50 kHz.

The graphene oxide-carbon nanotube composite may be prepared according to the method of manufacturing the graphene oxide-carbon nanotube composite according to an embodiment of the present invention.

According to the graphene oxide-carbon nanotube composite according to an embodiment of the present invention, the graphene oxide-carbon nanotube composite may have a three-dimensional structure by chemically bonding graphene oxide and carbon nanotubes.

The cement paste according to the present invention may include a graphene oxide-carbon nanotube composite, cement, and water according to an embodiment of the present invention.

According to the cement paste according to an embodiment of the present invention, the graphene oxide-carbon nanotube composite may be dispersed in the water by a hydroxyl group (-OH).

According to the cement paste according to an embodiment of the present invention, the graphene oxide-carbon nanotube composite may be included in an amount of 0.01% to 1% by weight based on the total weight of the cement paste.

According to an exemplary embodiment of the present invention, graphene oxide having excellent dispersibility and carbon nanotubes having excellent mechanical properties may be synthesized to improve dispersibility in cement paste and strength of cement paste.

According to an embodiment of the present invention, the strength of the cement paste may be improved by including the graphene oxide-carbon nanotube composite having excellent dispersibility in the cement paste, and the graphene oxide-carbon nanotube composite evenly dispersed in the cement paste. I can.

According to an embodiment of the present invention, graphene oxide and carbon nanotubes can be synthesized at a lower temperature than the conventional one, so that the weight loss of the graphene oxide-carbon nanotube composite due to heat can be minimized.

According to an embodiment of the present invention, dispersibility may be improved by monolayering the multilayer structure of the graphene oxide-carbon nanotube composite through ultrasonic treatment.

1 is a flow chart showing a method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.
2 is a schematic diagram showing a state in which graphite and carbon nanotubes are combined according to an embodiment of the present invention.
3 is a schematic diagram showing a bonding state of graphene oxide and carbon nanotubes according to an embodiment of the present invention.
4 is a schematic diagram showing a state of a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.
5A and 5B are transmission electron microscopy (TEM) images showing the shape of a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.
6A to 6C are graphs showing Fourier transformed infrared spectroscopy (FT-IR) measurement results of Comparative Examples and Examples of the present invention.
7 is a graph showing the heat weight according to the combustion temperature of Comparative Examples and Examples of the present invention.
8 is a graph showing absorbance of ultraviolet-visible light (UV-vis) spectrum of Comparative Examples and Examples of the present invention.
9A is a graph showing the compressive strength according to the application time of the cement paste of Comparative Examples and Examples of the present invention, and FIG. 9B is a graph showing the tensile strength according to the application time of the cement paste of Comparative Examples and Examples of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and contents described in the accompanying drawings, but the present invention is not limited or limited by the embodiments.

The terms used in the present specification are for describing exemplary embodiments and are not intended to limit the present invention. In this specification, the singular form also includes the plural form unless specifically stated in the phrase. As used in the specification, “comprises” and/or “comprising” do not exclude the presence or addition of one or more other elements or steps to the mentioned elements or steps.

As used herein, "an embodiment", "example", "side", "example", etc. should be construed as having any aspect or design described better than or having an advantage over other aspects or designs. It is not.

In addition, the term'or' means an inclusive OR'inclusive or' rather than an exclusive OR'exclusive or'. That is, unless stated otherwise or unless clear from context, the expression'x uses a or b'means any one of natural inclusive permutations.

In addition, the singular expression ("a" or "an") used in this specification and claims generally means "one or more" unless otherwise stated or unless it is clear from the context that it relates to the singular form. Should be interpreted as.

The terms used in the description below have been selected as general and universal in the related technical field, but there may be other terms depending on the development and/or change of technology, customs, preferences of technicians, and the like. Therefore, terms used in the following description should not be understood as limiting the technical idea, but should be understood as illustrative terms for describing embodiments.

In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, detailed meanings of the terms will be described in the corresponding description. Therefore, terms used in the following description should be understood based on the meaning of the term and the contents throughout the specification, not just the name of the term.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used with meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not interpreted ideally or excessively unless explicitly defined specifically.

Meanwhile, in the description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, terms used in the present specification are terms used to properly express an embodiment of the present invention, which may vary depending on the intention of users or operators, or customs in the field to which the present invention belongs. Therefore, definitions of these terms should be made based on the contents throughout the present specification.

The method for preparing a graphene oxide-carbon nanotube composite of the present invention is to prepare a graphene oxide-carbon nanotube composite through chemical treatment using carbon nanotubes and graphite.

The graphene oxide-carbon nanotube composite of the present invention prepared through this may have a three-dimensional structure by chemically bonding graphene oxide and carbon nanotubes, and may be included in the cement paste to improve the strength of the cement paste. .

In addition, the graphene oxide-carbon nanotube composite of the present invention may have better dispersibility than conventional carbon nanotubes in the cement paste, thereby contributing to improving the strength of the cement paste.

Hereinafter, the graphene oxide-carbon nanotube composite of the present invention, a method of manufacturing the same, and a cement paste including the same will be described in detail with reference to the drawings.

1 is a flow chart showing a method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.

The method for preparing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention includes preparing a first solution by mixing _{carbon nanotubes (CNT), graphite, sodium nitrate (NaNO 3 ), and a solvent ( S110), adding potassium permanganate (KMnO 4} ) after stirring the first solution (S120), preparing a second solution by adding distilled water after stirring the first solution to which the potassium permanganate was added ( S130), heating the second solution (S140), _{preparing a third solution by adding hydrogen peroxide (H 2} O ₂ ) to the heated second solution (S150), and adjusting the pH of the third solution A step of controlling (S160) and a step (S170) of preparing a graphene oxide-carbon nanotube composite by ultrasonicating the third solution whose pH is adjusted.

In step S110, a first solution is prepared using carbon nanotubes and graphite, which are carbon raw materials for preparing a graphene oxide-carbon nanotube composite.

Conventionally, graphite. While a composite is manufactured using graphene oxide or carbon nanotubes as a raw material, the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention uses graphite and carbon nanotubes as raw materials to produce graphene oxide-carbon. Nanotube composites can be prepared.

The graphite is a material that becomes graphene oxide contained in the graphene oxide-carbon nanotube composite, and may be graphene oxide by ultrasonic treatment performed in step S170.

The carbon nanotube is a material having very high specific surface area, excellent mechanical properties, excellent thermal conductivity, and electrical properties, and is a material that improves the mechanical properties of a cement paste in the field of construction.

According to an embodiment, the carbon nanotubes may be single-walled or multi-walled carbon nanotubes.

The sodium nitrate is an oxidizing agent, and may generate a hydroxy group (-OH) and a carboxy group (-COOH) by oxidizing graphite and carbon nanotubes, respectively.

The solvent may be a strong acid having a high concentration, and a strong acid condition may be provided to the first solution.

The solvent, which is a high concentration of a strong acid, may provide an environment such that the graphite and the carbon nanotubes in which the hydroxy group (-OH) and the carboxy group (-COOH) are generated are bonded to each other.

2 is a schematic diagram showing a state in which graphite and carbon nanotubes are combined according to an embodiment of the present invention.

Referring to FIG. 2, the hydroxy group and carboxyl group generated in the graphite 111 and the carbon nanotube 110 are a bonding group between the graphite 111 and the carbon nanotube 110, and the graphite 111 and the carbon nanotube ( 110) may be bonded to each other due to hydrogen bonding of the hydroxy group and the carboxy group.

In addition, the solvent of a high concentration strong acid can cut the carbon nanotubes 110.

This is to improve the dispersibility of the graphene oxide-carbon nanotube 110 composite by shortening the length of the carbon nanotube 110.

Depending on the embodiment, the solvent may be 95% or more high concentration sulfuric acid (H ₂ SO ₄ ), but is not limited to the material.

In the description of the present invention, for convenience of explanation, sulfuric acid, which is an embodiment of the solvent, will be described as a representative example.

Referring back to FIG. 1, in step S110, a graphene oxide-carbon nanotube composite having excellent dispersibility in water may be prepared by adjusting the weight ratio of carbon nanotubes and graphite contained in the first solution.

Specifically, the weight ratio of carbon nanotubes and graphite included in the first solution may be 1:1 to 1:4.

When the weight ratio of carbon nanotubes and graphite is less than 1:1, the number of carbon nanotubes in the graphene oxide-carbon nanotube composite increases compared to graphene oxide, resulting in a problem in that dispersibility is deteriorated.

When the weight ratio of carbon nanotubes and graphite exceeds 1:4, the number of graphene oxides compared to carbon nanotubes in the graphene oxide-carbon nanotube composite increases, and due to the lack of carbon nanotubes, graphene oxide-carbon nanotubes There may be a problem in that the mechanical properties and strength enhancement effects of the cement paste using the composite are not sufficiently improved.

In step S120, the first solution may be stirred to evenly mix the graphite and the carbon nanotubes.

Through this, while the potassium permanganate is added, graphite and carbon nanotubes can be oxidized evenly, and a chemical bond between graphite and carbon nanotubes can be induced to occur evenly.

According to an embodiment, the process of stirring the first solution may be performed at a speed of 1,000 rpm using an electromagnetic mixer.

Potassium permanganate added to the stirred first solution may be a strong oxidizing agent to oxidize graphite and carbon nanotubes contained in the first solution.

Specifically, the potassium permanganate may generate a hydroxy group and a carboxyl group by oxidizing graphite and carbon nanotubes like sodium nitrate in step S110.

At this time, in the present invention, carbon nanotubes in which hydroxyl groups and carboxyl groups are generated are also collectively referred to as carbon nanotubes.

Since the sodium nitrate and the potassium permanganate in the step S110 can cause a stronger oxidation reaction under a strong acid condition by the solvent of the first solution prepared in the step S110, the graphite and the carbon nanotubes are oxidized to form a hydroxyl group and a carboxyl group. Can be produced effectively.

As the length of the carbon nanotubes is relatively shortened by the potassium permanganate, the attractive force between molecules is weakened, so that dispersibility in water may be improved than that of the existing carbon nanotubes.

Accordingly, the first solution to which potassium permanganate is added may include graphite and carbon nanotubes bonded by a hydroxyl group and a carboxyl group.

In step S130, the first solution to which potassium permanganate is added is stirred to evenly disperse graphite and carbon nanotubes in the first solution to which potassium permanganate is added, so that the chemical bonding between graphite and carbon nanotubes is evenly generated, so that the dispersibility is High graphene oxide-carbon nanotube composites can be prepared.

According to an embodiment, the stirring of the first solution to which potassium permanganate is added is performed by immersing a container containing the first solution to which potassium permanganate is added to ice water to create an environment of 20° C. or less, and then using an electromagnetic mixer. It can be carried out at a speed of 1,000 rpm for 2 hours.

In addition, according to an embodiment, after the container containing the first solution to which potassium permanganate is added is removed from the ice water, additional stirring may be performed for 30 minutes using an electromagnetic mixer at a temperature of 35°C.

In step S130, after stirring the first solution to which potassium permanganate is added, distilled water may be added to prepare a second solution.

The distilled water is a solvent for discharging sulfuric acid, which is a solvent present between the graphite layers of the graphite, and hydrolyzing sulfate.

The solvent of the strong acid used in the first solution may exist between the graphite layer of the graphite by the steps S110 and S120, and the distilled water may discharge such a solvent of the strong acid from the graphite layer of the graphite.

Further, the solvent is sulfuric acid that is present between the graphite layers of the graphite while being hydrolyzed by the distilled water and the hydroxide ion produced from distilled water (OH ^-) the hydrogen sulfate ion (HSO ₄ ^-) and an exchange of carbon atoms of graphite, the graphite layer And hydroxide ions are combined, and the interlayer spacing of the graphite layer is increased by distilled water, which makes it easier to separate the graphite layer of graphite by the ultrasonic treatment in step S170, which will be described later.

That is, the hydroxide ions remove hydrogen sulfate ions present between graphite layers of graphite and exist between graphite layers of graphite, and the distilled water may serve to increase the distance between layers of graphite.

A detailed description of the separation of the graphite layer of graphite by the ultrasonic treatment will be described in detail in step S170 to be described later.

According to an embodiment, in step S130, the first solution to which potassium permanganate is added is stirred, then distilled water is added, and then a stirring process is further performed to prepare a second solution.

In step S140, by heating the second solution, sulfuric acid, a solvent present between the graphite graphite layers included in the second solution, is sufficiently hydrolyzed by distilled water to facilitate the separation of the graphite layers.

Specifically, in step S140, the second solution may be heated at 90°C to 100°C so that hydrolysis is effectively performed.

Accordingly, the heated second solution may include a graphene oxide-carbon nanotube composite.

In step S150, a third solution may be prepared by adding hydrogen peroxide to remove potassium permanganate remaining in the heated second solution.

Specifically, the hydrogen peroxide may remove potassium permanganate remaining in a supersaturated state in the heated second solution.

Step S160 may adjust the pH of the third solution.

In general, since the cement is in a strongly basic state, in step S160, the pH of the third solution in the acidic state is adjusted to a neutral state, so that the cement paste containing the graphene oxide-carbon nanotube complex, which will be described later, is graphene oxide-carbon nanotubes. The pH condition of the composite can be prevented from affecting the mechanical properties and performance.

Specifically, in the step of adjusting the pH of the third solution, the pH may be adjusted to neutral by adding a basic solution to the third solution.

Depending on the embodiment, the basic solution may be sodium hydroxide (NaOH), but is not limited to the material.

According to an embodiment, in step S160, the pH of the third solution may be adjusted to 6.5 to 7.2 so as to have excellent dispersibility in the cement paste to be described later.

Step S170 may improve the dispersibility of the graphene oxide-carbon nanotube composite in the third solution by ultrasonicating the third solution.

Specifically, in the step S170, a graphene oxide-carbon nanotube composite having improved dispersibility may be prepared by peeling the graphite graphite layer having a multilayer structure through ultrasonic treatment and generating a graphene oxide structure having a single-layer structure.

Depending on the embodiment, the ultrasonic treatment may be performed for 30 to 50 minutes.

If the ultrasonic treatment is performed for less than 30 minutes, the graphite layer does not sufficiently peel off, so that the single-layered graphene oxide-carbon nanotube composite is not well formed, and thus the dispersibility of the graphene oxide-carbon nanotube composite decreases I can.

If the ultrasonic treatment is performed for more than 50 minutes, a problem in that the graphene oxide-carbon nanotube composite is decomposed may occur.

In addition, according to an embodiment, the ultrasonic treatment may be performed at a frequency of 20 kHz to 50 kHz, and preferably, ultrasonic treatment may be performed at 60 to 70 W in units of 20 kHz or more.

In the step S170, the third solution is ultrasonicated, filtered, and dried to finally obtain a graphene oxide-carbon nanotube composite.

The method of manufacturing a graphene oxide-carbon nanotube composite according to an exemplary embodiment of the present invention may further include washing the third solution with hydrochloric acid after step S150 according to an exemplary embodiment.

By washing the third solution with hydrochloric acid, metal ions and the sulfuric acid contained in the third solution may be removed.

Depending on the embodiment, the hydrochloric acid may be dilute hydrochloric acid, but is not limited to the material.

Hereinafter, a graphene oxide-carbon nanotube composite manufactured by a method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention will be described with reference to the drawings.

3 is a schematic diagram showing a bonding state of graphene oxide and carbon nanotubes according to an embodiment of the present invention.

Referring to FIG. 3, graphene oxide and carbon nanotubes including a hydroxy group and a carboxyl group are chemically bonded to each other to form a carbonyl group (C=O), so that a graphene oxide-carbon nanotube composite can be synthesized.

4 is a schematic diagram showing a state of a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.

4, the graphene oxide-carbon nanotube composite 100 according to the embodiment of the present invention may have a three-dimensional structure by chemically bonding the graphene oxide 120 to the surface of the carbon nanotube 110. have.

Specifically, in the graphene oxide-carbon nanotube composite 100 according to an embodiment of the present invention, the graphene oxide 120 and the carbon nanotube 110 are chemically bonded to each other so that the single-layered graphene oxide 120 is carbon It may be connected by the nanotubes 110 to have a three-dimensional structure.

In the prior art, graphene oxide 120 having a two-dimensional structure is prepared by oxidizing graphite, but the graphene oxide-carbon nanotube composite 100 according to an embodiment of the present invention is in a cement paste to be described later due to the three-dimensional structure. It can have high mechanical strength while maintaining excellent dispersibility.

The graphene oxide-carbon nanotube composite according to the embodiment of the present invention can be used in the construction field due to the excellent mechanical properties of the carbon nanotube.

Conventionally, only carbon nanotubes were added to the cement paste and used, but the elongated carbon nanotubes have a complex structure and are easily agglomerated in water due to the strong attractive force between each molecule, Van der Waals force. As a result, there is a problem that the dispersibility in the cement paste is poor.

In addition, graphene oxide has excellent dispersibility, but when used in a cement paste, there is a problem that mechanical properties of the cement paste cannot be improved compared to carbon nanotubes.

However, the graphene oxide-carbon nanotube composite according to an embodiment of the present invention is shorter than the length of the conventional carbon nanotube and chemically bonds with the graphene oxide, so that it receives less Van der Waals force and has excellent dispersibility in water. .

Therefore, the graphene oxide-carbon nanotube composite according to an embodiment of the present invention uses carbon nanotubes and graphene oxide to exhibit both the advantages of graphene oxide having excellent dispersibility and carbon nanotubes having excellent mechanical properties. By synthesizing, it is possible to improve the strength of the cement paste while having excellent dispersibility in the cement paste.

The cement paste according to an embodiment of the present invention may include a graphene oxide-carbon nanotube composite, cement, and water.

At this time, the cement paste according to the embodiment of the present invention may be prepared by first mixing the graphene oxide-carbon nanotube composite and the water to disperse the graphene oxide-carbon nanotube composite, and then mixing the cement. .

In the cement paste containing the graphene oxide-carbon nanotube composite according to an embodiment of the present invention, since the hydroxyl groups contained in the graphene oxide-carbon nanotube composite have high dispersibility in water, as a result, in the cement paste Can be excellently dispersed in.

Depending on the embodiment, the graphene oxide-carbon nanotube composite according to an embodiment of the present invention may be included in an amount of 0.01% to 1% by weight relative to the total weight of the cement, so that the amount of carbon nanotubes contained in the conventional cement paste It can be added in the cement paste in small amounts.

The graphene oxide-carbon nanotube composite according to an embodiment of the present invention is added to the cement paste, and can have excellent dispersibility even if it is added in a smaller amount than before. As the carbon nanotubes of mechanical properties are evenly dispersed, the strength of the cement paste can also be improved.

Hereinafter, a graphene oxide-carbon nanotube composite is prepared through a method of preparing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention, and the properties of a graphene oxide-carbon nanotube composite and a cement paste including the same Evaluation was performed.

Example

[Example 1-1]

Dip a beaker in ice water, 0.5 g of graphite (Alfa aesar: grahite flake natural, 325 mesh, 99.8%), 0.5 g of carbon nanotubes (Hengqiu Graphene Technology (Suzhou), China), 0.5 g of sodium nitrate, 95% sulfuric acid 30 mL was mixed and stirred for 3 minutes to prepare a first solution. At this time, the weight ratio of graphite and carbon nanotubes is 1:1.

After adding potassium permanganate to the first solution, the mixture was stirred at a rate of 1,000 rpm for 2 hours at 20° C., and the temperature was raised to 35° C. and stirred for 30 minutes.

Thereafter, 50 mL of distilled water was added and stirred for 30 minutes to prepare a second solution.

Thereafter, the second solution was heated at 98° C. and stirred for 20 minutes.

A third solution was prepared by adding 5 g of 30% hydrogen peroxide to the heated second solution, followed by washing with a diluted hydrochloric acid solution.

Sodium hydroxide solution was added until the pH of the washed third solution became 7.

Thereafter, after filtering the third solution of pH 7, distilled water was added to the residue, and then ultrasonicated for 30 minutes under the condition of an amplitude of 50% (amplitude range of 22 to 50 μm) and a power of 70 W.

Thereafter, the sonicated solution was filtered and dried to obtain a graphene oxide-carbon nanotube composite.

[Example 1-2]

A graphene oxide-carbon nanotube composite was prepared in the same manner as in Example 1-1, except that 0.666 g of graphite and 0.334 g of carbon nanotubes were used. At this time, the weight ratio of graphite and carbon nanotubes is 2:1.

[Example 1-3]

A graphene oxide-carbon nanotube composite was prepared in the same manner as in Example 1-1, except that 0.8 g of graphite and 0.2 g of carbon nanotubes were used. At this time, the weight ratio of graphite and carbon nanotubes is 4:1.

[Comparative Example 1-1]

Carbon nanotubes (CNT).

[Comparative Example 1-2]

Graphite.

[Comparative Example 1-3]

Graphene oxide (GO) synthesized from graphite (Alfa aesar: grahite flake natural, 325mesh, 99.8%).

[Comparative Example 1-4]

A graphene oxide-carbon nanotube composite was prepared by synthesizing 0.5 g each of functionalized CNTs (FCNTs) obtained by oxidizing carbon nanotubes using graphene oxide and sulfuric acid of Comparative Example 1-3. At this time, the weight ratio of graphene oxide and carbon nanotubes is 1:1. (GO+FCNT=1:1)

[Comparative Example 1-5]

0.666 g of graphene oxide of Comparative Example 1-3 and 0.334 g of functionalized CNT (FCNT) were synthesized to prepare a graphene oxide-carbon nanotube composite. At this time, the weight ratio of graphene oxide and carbon nanotubes is 2:1. (GO+FCNT=2:1)

[Comparative Example 1-6]

0.8 g of graphene oxide of Comparative Example 1-3 and 0.2 g of functionalized CNT (FCNT) were synthesized to prepare a graphene oxide-carbon nanotube composite. At this time, the weight ratio of graphene oxide and carbon nanotubes is 4:1. (GO+FCNT=4:1)

[Comparative Example 1-7]

Functionalized carbon nanotubes (FCNT) of Comparative Example 1-4.

[Example 2-1]

A cement paste was prepared by mixing 0.05 g of the graphene oxide-carbon nanotube composite of Example 1-1, 100 g of cement, and 30 mL of water.

[Example 2-2]

A cement paste was prepared in the same manner as in Example 2-1, except that the graphene oxide-carbon nanotube composite of Example 1-2 was used.

[Example 2-3]

A cement paste was prepared in the same manner as in Example 2-1, except that the graphene oxide-carbon nanotube composite of Example 1-3 was used.

[Comparative Example 2]

Ordinary Portland cement (OPC) purchased from Cheonmapyo Cement.

The materials and weight ratios of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-3 are summarized in the table below.

[table]

Property evaluation

5A and 5B are transmission electron microscopy (TEM) images showing the shape of a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.

5A and 5B, it can be seen that the graphene oxide (GO) of Example 1-1 is connected to each other by carbon nanotubes (CNT).

Therefore, the graphene oxide-carbon nanotube composite may be formed by synthesizing graphene oxide and carbon nanotubes with each other through the method of manufacturing a graphene oxide-carbon nanotube composite according to an embodiment of the present invention.

6A to 6C are graphs showing Fourier transformed infrared spectroscopy (FT-IR) measurement results of Comparative Examples and Examples of the present invention.

When Fig. 6a to refer to Figure 6c, the Example 1-1 (GC1), Example 1-2 (GC2), Example 1-3 (GC3) is that it has a peak between 1900cm ^-1 and 1600cm ^-1 I can confirm.

Accordingly, it can be confirmed that Example 1-1 (GC1), Example 1-2 (GC2), and Example 1-3 (GC3) have a carbonyl group (C=O), through which graphene oxide It can be seen that the graphene oxide-carbon nanotube composite was successfully prepared by combining the carbon nanotubes with each other having a carbonyl group.

In addition, Examples 1-1 (GC1), Example 1-2 (GC2), and Example 1-3 (GC3) included a hydroxy group as a peak was formed between about 3330 cm-1 and 3400 cm-1. You can confirm that.

Accordingly, it can be seen that Examples 1-1 to 1-3 have excellent dispersibility due to a hydroxyl group.

7 is a graph showing the heat weight according to the combustion temperature of Comparative Examples and Examples of the present invention.

Referring to FIG. 7, a mass loss occurs from 500° C. in Comparative Example 1-1 (CNT), but Example 1-1 (GC1), Example 1-2 (GC2), and Example 1-3 (GC4) ), Comparative Example 1-3 (GO) it can be seen that the mass begins to lose less than 100 ℃.

In the case of Comparative Example 1-1 (CNT), since it is composed of only carbon, it is burned at a high temperature to cause mass loss, and the mass is started to be lost at less than 100° C. Example 1-1 (GC1), Example 1 The mass loss of -2 (GC2), Example 1-3 (GC4), and Comparative Example 1-3 (GO) is due to combustion of the hydroxy group and the carboxyl group.

Specifically, in the case of Comparative Example 1-1 (CNT), as the carbon structure was decomposed, a rapid mass decrease occurred after 500°C, but in the case of Comparative Example 1-7 (FCNT), hydroxide ions (-OH) were converted to water by heat. The decomposition is decomposed, and the decomposition of the carboxyl group (COOH-) occurs after the decomposition of hydroxide ions and decomposes in the form of _{CO 2, resulting in weight reduction.}

Weight loss due to decomposition after 200°C is a phenomenon that occurs due to decomposition of the structure of graphene oxide.

Therefore, it can be seen that the graphene oxide-carbon nanotube composite according to an embodiment of the present invention includes a hydroxyl group and a carboxyl group, and thus has excellent dispersibility in water.

8 is a graph showing absorbance of ultraviolet-visible light (UV-vis) spectrum of Comparative Examples and Examples of the present invention.

8 is a result showing an ultraviolet-visible light spectrum after dispersing Examples 1-1 to 1-3 and Comparative Example 1-1 in water.

8, the absorbance of Example 1-1 (GC1), Example 1-2 (GC2), and Example 1-3 (GC4) was greater than that of Comparative Example 1-1 (CNT). I can confirm.

In addition, it can be seen that the value of the absorbance is large in the order of Example 1-2, Example 1-1, and Example 1-3.

When a specific substance is uniformly dispersed in water, ultraviolet rays can be absorbed. In general, the better the dispersion is in water, the greater the absorbance value of the ultraviolet-visible light spectrum.

In view of this phenomenon, in the case of Comparative Example 1-1, the absorbance value was the smallest, and it was found that dispersion in water was not good, and in the case of Examples 1-1 to 1-3, the absorbance value was large. It can be seen that dispersibility in water is excellent, and it can be seen that the dispersibility is excellent in the order of Example 1-2, Example 1-1, and Example 1-3.

9A is a graph showing the compressive strength according to the application time of the cement paste of Comparative Examples and Examples of the present invention, and FIG. 9B is a graph showing the tensile strength according to the application time of the cement paste of Comparative Examples and Examples of the present invention.

9A and 9B, the compressive strength and tensile strength of Example 2-1 (GC1), Example 2-2 (GC2), and Example 2-3 (GC4) were compared with the Comparative Example 2 (OPC). You can see that it is larger.

As a result, it can be seen that Examples 2-1 to 2-3 including the graphene oxide-carbon nanotube composite than Comparative Example 2 enhance the strength of the cement.

In addition, it can be seen that the compressive strength and tensile strength values are high in the order of Example 2-2, Example 2-1, and Example 2-3.

This is related to the excellent dispersibility in the order of Example 1-2, Example 1-1, and Example 1-3 in FIG. 8 described above. It can be seen that it improves the strength of the cement paste containing it.

In addition, even if the content of the graphene oxide-carbon nanotube composite contained in the cement paste is small, it can be seen that the mechanical performance is improved by excellent dispersibility, and this is a relatively small amount compared to the conventional cement paste, which reduces cost. In addition, it can be seen that it greatly contributes to performance improvement.

As described above, although the present invention has been described by limited embodiments and drawings, the present invention is not limited to the above embodiments, and various modifications and variations from these descriptions for those of ordinary skill in the field to which the present invention pertains. This is possible. Therefore, the scope of the present invention is limited to the described embodiments and should not be defined, but should be defined by the claims to be described later as well as those equivalent to the claims.

100: graphene oxide-carbon nanotube composite
110: carbon nanotube
111: graphite
120: graphene oxide

Claims (12)

Preparing a first solution by mixing carbon nanotubes (CNT), graphite, sodium nitrate (NaNO ₃ ), and a solvent;
Adding _{potassium permanganate (KMnO 4} ) after stirring the first solution;
Preparing a second solution by stirring the first solution to which potassium permanganate is added and then adding distilled water;
Heating the second solution;
Preparing a third solution by adding hydrogen peroxide (H ₂ O _{2) to the heated second solution;}
Adjusting the pH of the third solution; And
Producing a graphene oxide-carbon nanotube composite by ultrasonicating the third solution whose pH is adjusted
Graphene oxide, characterized in that it comprises a-method for producing a carbon nanotube composite.
The method of claim 1,
The method of producing a graphene oxide-carbon nanotube composite, characterized in that the weight ratio of the carbon nanotubes and graphite is 1:1 to 1:4.
The method of claim 1,
The step of heating the second solution is a method of producing a graphene oxide-carbon nanotube composite, characterized in that carried out at 90 ℃ to 100 ℃.
The method of claim 1,
Graphene oxide-carbon nanotube composite manufacturing method, characterized in that it further comprises the step of washing the third solution with hydrochloric acid (HCl).
The method of claim 1,
The method of manufacturing a graphene oxide-carbon nanotube composite, characterized in that the pH of the third solution is adjusted to 6.5 to 7.2.
The method of claim 1,
The method of manufacturing a graphene oxide-carbon nanotube composite, characterized in that the ultrasonic treatment is performed for 30 to 50 minutes.
The method of claim 1,
The ultrasonic treatment is a method of producing a graphene oxide-carbon nanotube composite, characterized in that performed at a frequency of 20 kHz to 50 kHz.
Graphene oxide prepared according to claim 1-carbon nanotube composite.
The method of claim 8,
The graphene oxide-carbon nanotube composite is a graphene oxide-carbon nanotube composite, characterized in that the graphene oxide and the carbon nanotube are chemically bonded to each other to have a three-dimensional structure.
A cement paste comprising the graphene oxide-carbon nanotube composite according to claim 8, cement, and water.
The method of claim 10,
Cement paste, characterized in that the graphene oxide-carbon nanotube composite is dispersed in the water by a hydroxy group (-OH).
The method of claim 10,
Cement paste, characterized in that the graphene oxide-carbon nanotube composite is contained in an amount of 0.01% to 1% by weight based on the total weight of the cement.

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