WO2018169249A1

WO2018169249A1 - Carbon nanotube composition, method for manufacturing carbon nanotube composition, reduced oxidized carbon nanotubes, and method for manufacturing reduced oxidized carbon nanotubes

Info

Publication number: WO2018169249A1
Application number: PCT/KR2018/002737
Authority: WO
Inventors: 한중탁; 이건웅; 박종환; 서선희; 정승열; 정희진; 하정선
Original assignee: 한국전기연구원
Priority date: 2017-03-16
Filing date: 2018-03-08
Publication date: 2018-09-20

Abstract

The present invention relates to a carbon nanotube composition, a method for manufacturing a carbon nanotube composition, reduced oxidized carbon nanotubes, and a method for manufacturing reduced oxidized carbon nanotubes, and the technical subject of the present invention comprises: a step of oxidizing carbon nanotubes through an acid treatment to form oxidized carbon nanotubes; and a step of obtaining the carbon nanotube composition by dispersing the oxidized carbon nanotubes in alcohol. As a result, carbon nanotubes having low dispersibility in alcohol can be treated with an oxidation process to improve dispersibility in alcohol to enable easy printing and coating on a substrate, and the shape of carbon nanotubes are recovered through reduction so that the carbon nanotube composition dispersed in alcohol having high electric conductivity can be obtained without a dispersing agent. Also, the shape of carbon nanotubes can be recovered through reduction even when oxidation is performed to improve the dispersibility of carbon nanotubes, enabling recovery of the structure which can maintain electric conductivity of carbon nanotubes through reduction, thus the reduced oxidized carbon nanotubes having high electric conductivity can be obtained.

Description

Carbon nanotube composition, carbon nanotube composition manufacturing method, carbon nanotube reduced product and carbon nanotube reduced product manufacturing method

The present invention relates to a carbon nanotube composition dispersed in alcohol without a dispersant, a method for producing a carbon nanotube composition, a carbon nanotube reduced product having a high electroconductivity by restoring its structure by reduction, and more particularly, In order to improve the dispersibility in alcohol without using a dispersant, carbon nanotubes with low dispersibility in alcohol are treated with carbon nanotubes through easy oxidation and printing and coating on substrates, and carbon nanotubes through reduction process. Is to provide a carbon nanotube composition dispersed in alcohol without a dispersing agent exhibiting a high electroconductivity and a method for producing the same, and also through the reduction process even if the oxidation process to improve the dispersibility of the carbon nanotubes A ring that can restore the shape of nanotubes and maintain the electrical conductivity of carbon nanotubes The structure is restored by a circle, and relates to a carbon nanotube reduced product having a high electroconductivity and a method for producing the same.

Carbon nanotubes (CNTs) are tiny molecules of about 1 to several tens of nanometers in diameter, in which carbons connected by hexagonal rings form a tube shape, and carbon planes in which the carbon planes have a honeycomb structure by combining three carbon atoms each have a tube shape. It is formed by curling. Such carbon nanotubes are expected to have various applications in modern industrial fields based on their excellent mechanical strength, chemical stability, thermal conductivity, and electrical conductivity. That is, carbon nanotubes have electrical resistance ¹⁰ has an electric conductivity comparable to metals to ⁴ Ωcm, the surface area is higher than 1000 times that of the bulk material, in the conductive implemented because the length is long enough to be a thousand times compared with the outer diameter of the ideal material And it has the advantage that can improve the binding force to the substrate through the surface functionalization. In particular, it is expected that the use of the flexible substrate can be infinite. However, in the case of carbon nanotubes, when a large amount is added, the carbon nanotubes are agglomerated with each other, and thus uniform dispersion is difficult.

In the conventional case, a technique of acidifying a carbon nanotube to functionalize a surface with a carboxyl group or a hydroxyl group, and introducing various functional groups to improve the dispersibility of the carbon nanotube is mainly used. In addition, since impurities present in carbon nanotubes are surrounded by a stable carbon layer, it is difficult to physically or chemically purify them. When acid-processing carbon nanotubes, impurities present in carbon nanotubes can be relatively easily removed. have. Such a prior art is a method for purifying carbon nanotubes of Korea Patent Office No. 10-1586155 and a method for manufacturing a transparent electrode using carbon nanotube films of high purity and high density. The technique is known.

However, when carbon nanotubes are excessively acid treated to produce carbon nanotubes, defects that cause the tube shape of the carbon nanotubes to burst occur, and these defects are not restored even when reduced, resulting in defects in the carbon nanotubes. When the conductivity is reduced. That is, when acid treatment is performed by the conventional method to improve the dispersibility of the carbon nanotubes, the electrical conductivity of the carbon nanotubes is greatly reduced. In addition, conventionally, when acid is treated with carbon nanotubes and then additional functional groups are introduced, it is difficult to recover the defective carbon nanotubes to a tube shape having double bonds by using any method.

Accordingly, an object of the present invention is to easily print and coat the substrate by treating the carbon nanotubes through an oxidation process to improve the dispersibility in the alcohol without using a dispersant in the carbon nanotubes having low dispersibility in alcohol, The shape of the carbon nanotubes is restored through a reduction process to provide a carbon nanotube composition dispersed in alcohol without a dispersant exhibiting high conductivity and a method of manufacturing the same, and also performing an oxidation process to improve the dispersibility of the carbon nanotubes. Even though the shape of the carbon nanotubes can be recovered through a reduction process, and the structure is restored by the reduction capable of maintaining the electrical conductivity of the carbon nanotubes, the present invention relates to a carbon nanotube reduced product having high conductivity, and a method of manufacturing the same. .

The above object is to oxidize carbon nanotubes through acid treatment to form carbon nanotubes; Dispersing the carbon nanotubes in alcohol to obtain a carbon nanotube composition is achieved by a method for producing a carbon nanotube composition dispersed in alcohol without a dispersant.

Here, after obtaining the carbon nanotube composition, further comprising the step of reducing after coating or pattern printing on the substrate using the carbon nanotube composition, the reduction is to recover the carbon nanotube double bond Therefore, it is preferable that the electrical conductivity is higher than that of the carbon nanotubes.

In the forming of the carbon nanotubes, the carbon nanotubes may be mixed with the oxidizing agent to form a mixed powder, kneaded with the addition of a strong acid to the mixed powder, and then there is no flowable dough formed through the dough. It is preferable to leave the water to form the carbon nanotubes.

The forming of the carbon nanotubes may include fuming nitric acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and hydrogen peroxide in the carbon nanotubes. peroxide) and a strong acid selected from the group consisting of sodium chlorate (NaClO ₃ ), sodium perchlorate (NaClO ₄ ), potassium chlorate (KClO ₃ ), potassium perchlorate (KClO ₄ ) and mixtures thereof An oxidizing agent is added and left to stir or kneaded at room temperature for 30 minutes to a week, and the oxidizing agent is preferably added in a 0.5 to 10 weight ratio based on the weight of the carbon nanotubes.

The alcohol is selected from the group consisting of primary alcohols, secondary alcohols, tertiary alcohols, alcohol derivatives and mixtures thereof, and the carbon nanotubes are preferably added to the alcohol at 10 to 10,000 mg / L.

The above object is, carbon nanotube oxide in a state in which a double bond is broken to form a surface defect in which the hexagonal carbon structure is broken; It is also achieved by a carbon nanotube composition dispersed in an alcohol without a dispersant, characterized in that the carbon nanotubes contain an alcohol dispersed.

Here, the carbon nanotubes have a high electroconductivity by recovering the double bond through reduction, the carbon nanotubes are preferably added to the alcohol at 10 to 10,000mg / L, the carbon nanotube composition is ink It is preferable that it is an ink or paste.

The above object is also to oxidize carbon nanotubes through a strong acid to form carbon nanotubes; Reducing the carbon nanotubes to reduce the carbon nanotubes, the structure is restored by the reduction, characterized in that it comprises a carbon nanotube reduced product manufacturing method exhibiting high conductivity.

Here, the step of forming the carbon nanotubes, the carbon nanotubes and the oxidizing agent is mixed to form a mixed powder, kneading while adding a strong acid to the mixed powder, the dough having no flow formed through the dough It is preferable to leave the water to form the carbon nanotubes.

In addition, the step of forming the carbon oxide nanotubes, fuming nitric acid (sulfuric acid), sulfuric acid (sulfuric acid), nitric acid (nitric acid), hydrochloric acid (hydrochloric acid), phosphoric acid (phosphoric acid), hydrogen peroxide on the carbon nanotubes (hydrogen peroxide) and a strong acid selected from the group consisting of, sodium chloride (NaClO ₃ ), sodium perchlorate (NaClO ₄ ), potassium chloride (KClO ₃ ), potassium perchlorate (KClO ₄ ) and a group thereof It is preferable to add an oxidizing agent selected from and to stir for 30 minutes to a week at room temperature or to leave it kneaded, and the oxidizing agent is preferably added in a 0.5 to 10 weight ratio based on the weight of the carbon nanotubes.

In the obtaining of the carbon oxide oxide reduction product, the carbon nanotube dispersion is dispersed in a solvent and then reduced by adding a reducing agent through a wet process to obtain the carbon oxide oxide reduction product, and the reducing agent is sodium hydroxide ( NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium borohydride (NaBH ₄ ), hydrazine (N ₂ H ₄ ), iodine hydrochloric acid (HI), ascorbic acid, reducing solvent, It is preferably selected from the group consisting of a reducing organic material and a mixture thereof, and the carbon nanotube reduced product is, the carbon nanotubes by the oxidation of the carbon nanotubes using the strong acid and the oxidizing agent to deform the tube shape, deformed tube shape It is preferable to restore the double bond through reduction to increase the electrical conductivity than the carbon nanotubes.

The above object is also oxidized carbon nanotubes through a strong acid to form carbon nanotubes, and the structure is restored by reduction, characterized in that obtained by reducing the carbon nanotubes, carbon nanooxide having high conductivity. It is also achieved by tube reduction.

Here, the carbon nanotube reduced product, the carbon nanotubes are deformed by the oxidation of the carbon nanotubes using the strong acid, the modified tube shape is restored to the double bond through the reduction of the electric It is desirable to increase the conductivity.

According to the above-described configuration of the present invention, carbon nanotubes having low dispersibility in alcohol can be easily printed and coated on a substrate by treating the carbon nanotubes through oxidation to improve dispersibility in alcohol without using a dispersant. In addition, the shape of the carbon nanotubes is restored through a reduction process, thereby obtaining a carbon nanotube composition dispersed in alcohol without a dispersant having high conductivity.

In addition, even if the oxidation process is performed to improve the dispersibility of the carbon nanotubes, the shape of the carbon nanotubes can be restored through the reduction process, so that the structure is restored by the reduction, which can maintain the electrical conductivity of the carbon nanotubes. It is possible to obtain a carbon nanotube reduction product.

1 is a flow chart of a carbon nanotube composition manufacturing method according to an embodiment of the present invention,

Figure 2 is a flow chart of the carbon nanotube reduction product manufacturing method according to an embodiment of the present invention,

3 is a photograph showing a dispersion state of carbon nanotubes according to the solvent of Example 1,

4 is a graph showing absorbance of visible light region according to the concentration of carbon nanotubes of Example 1. FIG.

5 is a SEM photograph of carbon nanotubes before and after oxidation;

6 is a graph of carbon nanotube X-ray photoelectron spectroscopy analysis results before and after oxidation treatment,

7 is a graph of Raman spectroscopy analysis results of carbon nanotubes of Example 2,

8 is a graph showing the results of electrical conductivity before and after reduction of carbon nanotubes,

9 is a graph showing Raman spectroscopy analysis results of carbon nanotubes of Comparative Example 1.

Hereinafter, a carbon nanotube composition, a carbon nanotube composition manufacturing method, a carbon nanotube reduction product, and a carbon nanotube reduction product manufacturing method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Here, the carbon nanotube composition dispersed in alcohol without a dispersant means an ink or paste that can be used for coating or printing, and the ink or paste has a viscosity adjusted according to the proportion of carbon nanotubes added to the alcohol. A low viscosity composition can be used as an ink and a high viscosity composition can be used as a paste.

In the method for preparing a carbon nanotube composition dispersed in an alcohol without such a dispersant, first, as shown in FIG. 1, carbon nanotubes are oxidized through acid treatment to form carbon nanotubes (S1a).

After oxidation of carbon nanotubes consisting of single wall, double wall or multi-wall through acid treatment, carbon nanotubes are formed by removing impurities by repeated washing of aqueous solution and centrifuge. When the acid treatment is carried out, the double bonds of the carbon nanotubes are broken and the original carbon structures are present in a damaged state. The carbon nanotubes in the damaged state are easily agglomerated and dispersed in a solvent.

Acid treatment is performed on carbon nanotubes with strong acids and sodium chlorates such as fuming nitric acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and hydrogen peroxide. (NaClO ₃ ), sodium perchlorate (NaClO ₄ ), potassium chlorate (KClO ₃ ), potassium perchlorate (KClO ₄ ) and the like are added and stirred at room temperature for 30 minutes to a week, or left to kneaded and carbon nano Oxidize the tube. Here, the oxidizing agent is preferably added in a ratio of 0.5 to 10% by weight based on the weight of the carbon nanotubes. If the oxidizing agent is less than 0.5 weight ratio, the carbon nanotubes are not sufficiently oxidized. If the oxidizing agent is more than 10 weight ratio, the degree of oxidation is excessive, so that the electrical conductivity of the carbon nanotubes is rapidly decreased.

Stirring or kneading of carbon nanotubes can be selected according to the amount of strong acid added. However, the method of kneading with strong acid is most preferred due to the characteristics of carbon nanotubes that are strongly agglomerated. Then, the strong acid is neutralized with distilled water, followed by repeated washing with filtering or centrifugation, and drying yields pure carbon nanotubes without strong acid remaining on the surface.

In the method of kneading the carbon nanotubes, the carbon nanotubes and the oxidizing agent are respectively prepared and mixed to form a mixed powder. At this time, since the carbon nanotubes and the oxidizing agent are present in powder form, they do not react with each other even if they are mixed to form a mixed powder. Then kneading while adding a small amount of strong acid to the mixed powder formed. That is, a small amount of strong acid is added to the mixed powder, followed by kneading, and a small amount of strong acid is added thereto, followed by kneading. For ease of kneading the strong acid is preferably added in small portions of about 2 to 5 times. Finally, the dough is left to form carbon nanotubes. After adding strong acid to the mixed powder, the kneaded non-flowable dough is left for 1 to 10 hours to oxidize carbon nanotubes in the dough to form carbon nanotubes. Even if the formed dough is left as it is without further treatment, carbon nanotubes in the dough may be oxidized to obtain carbon nanotubes. The process of purifying the remaining oxidant and strong acid may then be further subjected.

The amount of strong acid is added in a weight ratio of 0.5 to 7% by weight of the carbon nanotubes. That is, carbon nanotubes: strong acids = 1: 0.5 to 7 is added in a weight ratio. If the amount of strong acid is less than 0.5% by weight, a lot of time is spent kneading and the oxidizing agent is not dissolved in the acid, so that the carbon nanotubes are not completely oxidized and some remain. In addition, when a strong acid is added in excess of 7% by weight, the reaction is excessive, the carbon nanotubes may be damaged by high temperature heat generation, and safety problems may occur.

In addition, the strong acid added in small portions is preferably kneaded while adding to the mixed powder in a ratio of 0.1 to 0.5% by weight based on the carbon nanotube weight. Here, when the kneading is made while the strong acid is added in less than 0.1 weight ratio, a lot of time is consumed when kneading, and when the strong acid is added in excess of 0.5 weight ratio, the reaction may occur excessively and the carbon nanotubes may be damaged by high temperature heating.

Here, the acid treatment is generally used by the Staudenmaier method (L. Staudenmaier, Ber. Dtsch. Chem. Gas., 31, 1481-1499, 1898), the Hummus method (W. Hummers et al., J. Am. Chem) Soc., 80, 1339, 1958) or the Brodie method (BC Brodie Ann. Chim. Phys., 59, 466-472, 1860) or variations thereof. The Steudenmeier method, the Hummus method and its modified oxidation method have been mainly used to prepare graphite oxide by oxidizing graphite or to produce graphene oxide by peeling graphite oxide.

This oxidation method not only introduces an oxidizing functional group, but also has a disadvantage that surface defects in which the hexagonal carbon structure is broken due to strong oxidizing power are simultaneously formed and are not recovered to the hexagonal carbon structure even after reduction. Therefore, when manufacturing carbon nanotubes by this method, there is an advantage in that the carbon nanotubes have excellent dispersibility, but instead of excellent dispersibility, it contains many oxidizing groups and structural defects are formed, thereby improving the quality of carbon nanotubes. This has the disadvantage of falling. In addition, carbon nanotubes are reduced in a later step. In the process, the oxidation functional group and the defect structure interfere with the rearrangement of the carbon nanotubes in the shape of a tube. There is no way to apply it. On the other hand, in the case of brody method, the manufactured carbon nanotube has the advantage that the hexagonal structure is maintained as it is, and thus the quality is excellent due to high purity and low defects. When the carbon nanotube is reduced in a subsequent step, the carbon nanotube is oxidized smoothly. There is an advantage that it is possible to recover the deformation of the tube shape by. Therefore, in the present invention, carbon nanotubes are manufactured by using a brody method rather than a commonly used studenmeier method or a hummus method.

The carbon nanotubes are dispersed in alcohol to obtain a carbon nanotube composition (S2a).

The carbon nanotubes prepared through the step S1a are dispersed in alcohols having low harmfulness and high environmental friendliness, thereby obtaining a carbon nanotube composition which may be coated or printed. In the case of general carbon nanotubes, it is not dispersed in alcohol, so that a dispersant may be used separately or mixed with a harmful solvent such as dimethyl formamide or N-methyl-2-pyrollidone. Got. However, the use of a dispersant not only increases the manufacturing cost but also reduces the content of carbon nanotubes, so that the electrical conductivity cannot be maintained. In addition, dimethylformamide or N-methyl-2-pyrrolidone has a problem that it is not desirable to apply it to a carbon nanotube composition that can be coated or printed because it is not only harmful to the body but also adversely affects the environment. However, carbon nanotubes in which carbon nanotubes are oxidized as in the present invention can be easily dispersed in alcohol without using a dispersant.

The alcohol constituting such a carbon nanotube composition is preferably selected from the group consisting of primary alcohols, secondary alcohols, tertiary alcohols, alcohol derivatives, and mixtures thereof. For example, methyl alcohol, ethyl alcohol ( Any alcohol that is generally used as a solvent, such as ethyl alcohol, isopropyl alcohol, and butyl alcohol, can be applied without limitation.

In the carbon nanotube composition, carbon nanotubes are preferably added in an amount of 10 to 10,000 mg / L using alcohol as a solvent. If the carbon nanotube oxide is less than 10mg / L, it is difficult to show high conductivity, and when the carbon nanotube exceeds 10,000mg / L, the viscosity becomes high, which makes it unsuitable for printing.

The carbon nanotube composition is classified into ink or paste according to the viscosity, and may be used as an ink when the viscosity is 2,000 cps or less and may be used as a paste when it exceeds 2,000 cps.

In order to apply the carbon nanotube composition prepared as described above for coating or printing, the coating or pattern is printed and then reduced (S3a).

After the carbon nanotube composition is selected and coated with an ink or a paste, or printed on a substrate with a desired pattern, the carbon nanotube composition may be reduced. In the case of carbon nanotubes, the shape of the tube is deformed, so the electrical conductivity is present in a very low state. When carbon nanotubes are reduced through the reduction process, the double bonds are restored to increase the electrical conductivity than carbon nanotubes. . As such a process for reducing carbon nanotubes, sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium borohydride (NaBH ₄ ), hydrazine (N ₂ H ₄ ), hydriodine (HI), ascorbic acid, reducing organic solvents and mixtures thereof, and the method of chemical reduction and the drying process such as heat treatment, plasma treatment.

Next, the carbon nanotube reduction product is a carbon nanotube reduction product having a high electroconductivity by restoring its structure by reduction, which oxidizes carbon nanotubes through a strong acid to form carbon nanotube oxides, and the oxidation It is obtained by reducing carbon nanotubes.

The structure is restored by such a reduction, and as a method for producing a carbon nanooxide reduced product having high electroconductivity, as shown in FIG. 2, first, the carbon nanotubes are oxidized to form carbon nanotubes (S1b).

After oxidation of carbon nanotubes consisting of single wall, double wall or multi-wall through acid treatment, carbon nanotubes are formed by removing impurities by repeated washing of aqueous solution and centrifuge. Acid treatment is performed on carbon nanotubes with strong acids and sodium chlorates such as fuming nitric acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and hydrogen peroxide. (NaClO ₃ ), sodium perchlorate (NaClO ₄ ), potassium chlorate (KClO ₃ ), potassium perchlorate (KClO ₄ ) and the like are added and stirred at room temperature for 30 minutes to a week, or left to kneaded and carbon nano Oxidize the tube. Here, the oxidizing agent is preferably added in a ratio of 0.5 to 10% by weight based on the weight of the carbon nanotubes. If the oxidizing agent is less than 0.5 weight ratio, the carbon nanotubes are not sufficiently oxidized. If the oxidizing agent is more than 10 weight ratio, the degree of oxidation is excessive, so that the electrical conductivity of the carbon nanotubes is rapidly decreased.

Here, the acid treatment is generally used by the Staudenmaier method (L. Staudenmaier, Ber. Dtsch. Chem. Gas., 31, 1481-1499, 1898), the Hummus method (W. Hummers et al., J. Am. Chem) Soc., 80, 1339, 1958) or the Brodie method (BC Brodie Ann. Chim. Phys., 59, 466-472, 1860) or variations thereof. The Steudenmeier method, the Hummus method and its modified oxidation method have been mainly used to prepare graphite oxide by oxidizing graphite or to produce graphene oxide by peeling graphite oxide. This oxidation method not only introduces an oxidizing functional group, but also has a disadvantage that surface defects in which the hexagonal carbon structure is broken due to strong oxidizing power are simultaneously formed and are not recovered to the hexagonal carbon structure even after reduction. Therefore, when manufacturing carbon nanotubes by this method, there is an advantage in that the carbon nanotubes have excellent dispersibility, but instead of excellent dispersibility, it contains many oxidizing groups and structural defects are formed, thereby improving the quality of carbon nanotubes. This has the disadvantage of falling. In addition, carbon nanotubes are reduced in a later step. In the process, the oxidation functional group and the defect structure interfere with the rearrangement of the carbon nanotubes into a tube shape. There is no way to apply it. On the other hand, in the case of brody method, the manufactured carbon nanotube has the advantage that the hexagonal structure is maintained as it is, and thus the quality is excellent due to high purity and low defects. When the carbon nanotube is reduced in a subsequent step, the carbon nanotube is oxidized. There is an advantage that it is possible to recover the deformation of the tube shape by. Therefore, in the present invention, carbon nanotubes are manufactured by using a brody method rather than a commonly used studenmeier method or a hummus method.

Reduction of carbon nanotubes results in reduction of carbon nanotubes (S2b).

The carbon nanotubes prepared by the step S1b are dispersed in a solvent, and thereafter, a reducing agent is added thereto to be reduced by a wet process to obtain a carbon nanotube reduced product. The reducing agent here is sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium boron hydroxide (NaBH ₄ ), hydrazine (N ₂ H ₄ ), iodine hydrochloric acid (HI), ascorbic acid (ascorbic) acid), a reducing solvent, a reducing organic material and a mixture thereof.

In addition, the solvent in which carbon nanotubes are reduced is acetone, methyl ethyl ketone, methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol ( butyl alcohol, ethylene glycol, polyethylene glycol, tetrahydrofuran, tetrahydropyran dimethyl formamide, dimethyl acetamide, N-methyl -2-pyrrolidone (N-methyl-2-pyrolidone), hexane, cyclohexanone, toluene, chloroform, dichlorobenzene, dimethyl benzene ), Trimethyl benzene, pyridine, methyl naphthalene, nitromethane, acrylonitrile, octadecylamine, aniline, dimethyl sulfoxide Id (dimethyl sulfoxide), preferably selected from the group consisting of distilled water and the mixture thereof.

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

<Example 1>: method for producing carbon nanotube composition dispersed in alcohol without dispersant

First, 1 g of single-walled carbon nanotubes and 5 g of sodium chlorate (NaClO ₃ ) are mixed in a powder state, and 100 mL of fuming nitric acid is mixed therein to make a dough, and then the prepared mixture is prepared at room temperature. Oxidation reaction is carried out using an altered brody method that is left as it is for 1 to 48 hours or is subjected to shear stress by milling, kneading, or the like. Thereafter, carbon nanotubes are neutralized using distilled water, hydrochloric acid, and hydrogen peroxide, followed by washing, filtration, and drying to remove acids and oxidants to obtain oxidized carbon nanotubes. If necessary, carbon nanotube powder is obtained by performing a drying process using a freeze dryer.

The carbon nanotubes prepared are 30 to 300 mg / L in alcoholic organic solvents such as butyl alcohol and isopropyl alcohol, as well as water and dimethyl formamide as shown in FIG. 3. Carbon nanotubes were added at the concentration of and dispersed using an ultrasonic disperser. In the case of carbon nanotubes, they are originally dispersed in dimethylformamide or N-methyl-2-pyrrolidone, but not in water, butyl alcohol or isopropyl alcohol. However, when the carbon nanotubes are dispersed in an oxidized state as in the present invention, dispersion is easily performed.

This can be seen more clearly through FIG. 4, which is a graph showing absorbance according to carbon nanotube concentration in the visible light region (550 nm wavelength). Absorption is linear as the concentration of carbon nanotubes increases, indicating that the dispersion state is maintained even when the concentration increases. That is, it can be seen that carbon nanotubes are properly dispersed in alcoholic organic solvents such as water, butyl alcohol and isopropyl alcohol as well as dimethylformamide. Therefore, it can be seen that the carbon nanotubes prepared through the present examples generally have a good dispersion state in polar solvents such as water, dimethylformamide and N-methylpyrrolidone in addition to alcohol. In addition, the dispersion is made even at a concentration of 300mg / L or more than 10,000mg / L, can be selectively used depending on the viscosity to suit the purpose. If it is used for applications that have no flow, it can be used at higher concentrations.

After printing the pattern on the substrate using the carbon nanotube composition, the pattern of the carbon nanotubes is evenly dispersed through the process of reducing the pattern. Here, pattern printing is possible by direct printing process such as inkjet, 3D printing, gravure, gravure offset, reverse gravure offset, and applied to the substrate by front coating by coating method such as spray coating, bar coating, knife coating and slot die coating. It is possible. After printing or coating sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium borohydride (NaBH ₄ ), hydrazine (N ₂ H ₄ ), hydriodine (HI), ascorbic acid ( Ascorbic acid), a reducing organic solvent and a compound selected from the group consisting of a mixture of the method of chemical reduction and the reduction process by a dry method such as heat treatment, plasma treatment can be used. As a specific example, after forming a thin film by spray coating a plastic substrate with 100mg / L single-walled carbon nanotube ink, carbon nanotubes were reduced by using hydrazine vapor.

<Example 2>: A method for producing a carbon nanotube reduced product having a high electroconductivity by restoring its structure by reduction

1 g of single-walled carbon nanotubes and 5 g of sodium chlorate (NaClO ₃ ) are mixed in a powder state, and 100 mL of fuming nitric acid is mixed therein to prepare a mixture. The prepared mixture is left at room temperature for about 24 hours to proceed the oxidation reaction using brody method. Thereafter, carbon nanotubes are neutralized using distilled water, hydrochloric acid, and hydrogen peroxide, followed by washing, filtration, and drying to remove acids and oxidants to obtain oxidized carbon nanotubes. If necessary, carbon nanotube powder is obtained by performing a drying process using a freeze dryer.

Disperse the prepared carbon oxide nanotubes at 100mg / L in 100mL of water, add 1mL of hydrazine (N ₂ H ₄ ) to it, and raise the temperature to 80 ° C. After filtering the carbon nanotube dispersion to produce a paper-like film, the produced film may be subjected to chemical reduction using iodine hydrochloric acid (HI) to finally obtain a carbon nanotube reduction product.

Figure 5a shows a SEM picture before the oxidation of the single-walled carbon nanotubes, Figure 5b shows a SEM picture of the carbon nanotubes oxidized through Example 2. 5A and 5B, the bundle size decreases after oxidation of the single-walled carbon nanotubes. In addition, the degree of oxidation of the prepared carbon nanotubes was confirmed by X-ray photoelectron spectroscopy and Raman spectroscopy. As a result of X-ray photoelectron spectroscopy analysis like the carbon nanotubes before the oxidation treatment of FIG. 6A and the carbon nanotubes after the oxidation treatment of FIG. 6B, it was confirmed that functional groups of C-O and C = O forms were introduced by oxidation. In the Raman spectroscopy analysis shown in FIG. 7, the D band indicating the degree of defect increased after oxidizing the carbon nanotubes. This indicates that the carbon nanotubes are changed to carbon nanotubes due to an increase in defects or an increase in the introduction of an oxidative functional group to change a double bond into a single bond.

The results of measuring the electrical conductivity before and after reduction of the carbon nanotubes present in the film prepared through the examples can be confirmed through FIG. 8. First of all, when the carbon nanotubes were prepared, the electrical conductivity of the carbon nanotubes decreased as the mixing ratio (NaClO ₃ / SWCNT ratio) of sodium chloride and single-walled carbon nanotubes added for oxidation increased. Can be. This means that as the amount of sodium chlorate increases, double bonds of carbon nanotubes change into single bonds, and oxidative functional groups are introduced. As shown in FIG. 8, the reduced carbon nanotube reduced product has an electrical conductivity that is increased by three times or more compared with the carbon nanotube before reduction, and the functional group is removed after the reduction as illustrated in FIGS. 5 and 6. And the defects are reduced. In the Raman analysis of the carbon nanotube reduced product of FIG. 7, the significant decrease in the intensity of the D-band peak proves that the structure of the chemically oxidized carbon nanotubes is recovered through reduction.

<Example 3>: Method for producing carbon nanotube reduced product having high electroconductivity by reconstructing structure by reduction

Example 3 is the same as Example 2, but the same oxidation and reduction process was performed using multi-walled carbon nanotubes. As a result of chemically reducing the oxidized multi-walled carbon nanotubes like single-walled carbon nanotubes, it was confirmed that the defect structure of the oxidative functional group was recovered to a double bond, thereby improving the electrical conductivity.

<Example 4>: method for producing carbon nanotubes using dough

After mixing 2g of carbon nanotubes and 15g of sodium chlorate as an oxidizing agent in powder form, 10ml of total nitric acid is added to the mixed powder in small portions several times. At this time, while adding the nitric acid to the mixed powder, mix the mixed powder as if kneaded. In this process, Examples 1 to 3 were made of a flowable slurry, but in the case of the present embodiment, unlike the slurry, the flowability is almost impossible, such as a flour dough, so that stirring is impossible and mixing is possible through the dough.

The soaked dough is then left for 1 to 10 hours to form carbon nanotubes. At this time, as the oxidizing agent is dissolved in the concentrated nitric acid, the local oxidation reaction proceeds rapidly on the surface of the carbon nanotubes, which can drastically shorten the reaction time.

After completion of the reaction, hydrogen peroxide and hydrochloric acid were added to the dough to neutralize the dough, and then excess water was added to remove the acid, and lyophilized to obtain carbon nanotube powder. That is, the oxidation of carbon nanotubes proceeds quickly by the instant strong reaction between the oxidant mixed on the surface of the carbon nanotubes and the strong acid added in small amounts.

Comparative Example 1

In Comparative Example 1, single-walled carbon nanotubes were prepared using sulfuric acid and potassium permanganate (KMnO ₄ ). As a result of reducing the prepared single-walled carbon nanotubes using hydroiodic acid, it was found that the D bands showing defects did not decrease in Raman analysis as shown in FIG. 9. In addition, the electrical conductivity showed only a slight increase. This indicates that the honeycomb carbon nanotube structure is broken and changed into a defect structure that cannot be recovered.

Comparative Example 2

In Comparative Example 2, the single-walled carbon nanotubes were heated to more than 100 ^° C. in nitric acid or nitric acid / sulfuric acid mixture, oxidized by reflux, and chemically reduced. Also in this case, as in Comparative Example 1, as a result of Raman analysis, D bands showing defects did not decrease, and it was confirmed that the structure of the single-walled oxide carbon nanotubes was not restored by chemical reduction.

When coating or printing general carbon nanotubes as in the prior art, when a large amount is added, the carbon nanotubes are agglomerated with each other, which makes it difficult to uniformly disperse them. In particular, when the solvent used with the carbon nanotubes include alcohol, it is particularly difficult to disperse the dispersant. In addition, since alcohol is not properly dispersed in carbon nanotubes, a composition is prepared to prevent agglomeration of carbon nanotubes using mainly harmful solvents such as dimethylformamide or N-methyl-2-pyrrolidone.

However, in the present invention, the carbon nanotubes having low dispersibility in alcohol are treated with carbon nanotubes through an oxidation process in order to improve dispersibility in alcohol without using a dispersing agent, and thus printing and coating on the substrate are easily carried out. Through the restoration of the shape of the carbon nanotubes, it is possible to obtain carbon nanotubes having high conductivity.

Claims

In the method for producing a carbon nanotube composition dispersed in alcohol without a dispersant,

Oxidizing the carbon nanotubes by acid treatment to form carbon nanotubes;

Dispersing the carbon nanotubes in alcohol to obtain a carbon nanotube composition, wherein the carbon nanotube composition is dispersed in alcohol without a dispersant.
The method of claim 1,

After obtaining the carbon nanotube composition,

Reducing after coating or pattern printing on the substrate using the carbon nanotube composition,

The reduction is a method of producing a carbon nanotube composition dispersed in an alcohol without a dispersant, characterized in that the carbon nanotubes are a process of increasing the electrical conductivity than the carbon nanotubes by restoring a double bond.
The method of claim 1,

Forming the carbon oxide nanotubes,

After mixing the carbon nanotubes and the oxidizing agent to form a mixed powder, and kneading while adding a strong acid to the mixed powder, and leaving the flow-free dough formed through the dough to form the carbon nanotubes Method for producing a carbon nanotube composition dispersed in alcohol without a dispersant characterized in that.
The method of claim 1,

Forming the carbon oxide nanotubes,

Strong acid selected from the group consisting of fuming nitric acid, sulfuric acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, hydrogen peroxide, and mixtures thereof on the carbon nanotubes. And an oxidizing agent selected from the group consisting of sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ), potassium chlorate (KClO 3 ), potassium perchlorate (KClO 4 ), and mixtures thereof, for 30 minutes to a week at room temperature. Method for producing a carbon nanotube composition dispersed in alcohol without a dispersant, characterized in that it is left in a stirred or kneaded state.
The method of claim 4, wherein

The oxidizing agent is a carbon nanotube composition manufacturing method dispersed in an alcohol without a dispersant, characterized in that added to the weight ratio of 0.5 to 10% by weight of the carbon nanotubes.
The method of claim 1,

The alcohol is a method of producing a carbon nanotube composition dispersed in an alcohol without a dispersant, characterized in that selected from the group consisting of primary alcohol, secondary alcohol, tertiary alcohol, alcohol derivatives and mixtures thereof.
The method of claim 1,

The carbon nanotubes are carbon nanotube composition prepared by dispersing in alcohol without a dispersant, characterized in that added to the alcohol 10 to 10,000mg / L.
In the carbon nanotube composition dispersed in alcohol without a dispersant,

Carbon nanotubes in which a double bond is broken to form a surface defect in which a hexagonal carbon structure is broken;

Carbon nanotube composition dispersed in alcohol without a dispersant, characterized in that the carbon nanotubes are dispersed in the alcohol.
The method of claim 8,

The carbon nanotubes are carbon nanotube compositions dispersed in alcohol without a dispersant, characterized in that the double bond is recovered through reduction to exhibit high conductivity.
The method of claim 8,

The carbon nanotubes are carbon nanotube composition dispersed in alcohol without a dispersant, characterized in that added to the alcohol 10 to 10,000mg / L.
The method of claim 8,

The carbon nanotube composition is an ink (ink) or paste (paste) characterized in that the carbon nanotube composition dispersed in alcohol without a dispersant.
In the method for producing a carbon nanotube reduced product having a high electroconductivity by restoring its structure by reduction,

Oxidizing the carbon nanotubes through a strong acid to form carbon nanotubes;

Reducing the carbon nanotubes to obtain a carbon nanotube reduced product.
The method of claim 12,

Forming the carbon oxide nanotubes,

After mixing the carbon nanotubes and the oxidizing agent to form a mixed powder, and kneading while adding a strong acid to the mixed powder, and leaving the flow-free dough formed through the dough to form the carbon nanotubes Carbon nanotube reduction product manufacturing method characterized in that.
The method of claim 13,

Forming the carbon oxide nanotubes,

Strong acid selected from the group consisting of fuming nitric acid, sulfuric acid, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, hydrogen peroxide, and mixtures thereof on the carbon nanotubes. And an oxidizing agent selected from the group consisting of sodium chlorate (NaClO 3 ), sodium perchlorate (NaClO 4 ), potassium chlorate (KClO 3 ), potassium perchlorate (KClO 4 ), and mixtures thereof, for 30 minutes to a week at room temperature. Method for producing a carbon nano-oxide reduced product characterized in that it is left in a stirred or kneaded state.
The method of claim 14,

The oxidizing agent is a carbon nanotube reduction product manufacturing method, characterized in that added to the weight ratio of 0.5 to 10% by weight of the carbon nanotubes.
The method of claim 13,

Obtaining the carbon nanotube reduction product,

Dispersing the carbon nanotubes in a solvent and then reducing the carbon nanotube reduction product by adding a reducing agent through a wet process to obtain a carbon nanotube reduced product.
The method of claim 16,

The reducing agent is sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH 4 OH), sodium boron hydroxide (NaBH 4 ), hydrazine (N 2 H 4 ), iodine hydrochloric acid (HI), ascorbic acid ( ascorbic acid), a reducing solvent, a reducing organic material, and a mixture thereof.
The method of claim 13,

The carbon oxide oxide reduction product,

By using the strong acid and the oxidizing agent, the carbon nanotubes are deformed in the shape of a tube through oxidation, and by reducing the deformed tube shape by restoring a double bond, the electrical conductivity of the carbon nanotubes is increased. Carbon nanotube reduction product manufacturing method.
In the carbon nanotube reduction product having a high electroconductivity by restoring the structure by reduction,

A carbon nanotube reduced product obtained by oxidizing carbon nanotubes through a strong acid to form carbon nanotubes and reducing the carbon nanotubes.
The method of claim 19,

The carbon oxide oxide reduction product,

The carbon nanotubes are deformed by oxidation of the carbon nanotubes using the strong acid, and the carbon nanotubes have higher electrical conductivity than the carbon nanotubes by restoring the double bonds through reduction of the deformed tube shapes. Tube reducing material.