KR20100076521A

KR20100076521A - Purification method for carbon structure and purification solution to perform the method

Info

Publication number: KR20100076521A
Application number: KR1020080134601A
Authority: KR
Inventors: 오운수; 이상훈
Original assignee: (주) 나노허브
Priority date: 2008-12-26
Filing date: 2008-12-26
Publication date: 2010-07-06

Abstract

PURPOSE: A purification method of a carbon structure, and a refined solution for operating thereof are provided to remove a metallic catalyst and a carbon impurity generated from a synthesis process of the carbon structure. CONSTITUTION: A purification method of a carbon structure comprises the following steps: producing a purification solution for the carbon structure including trioxidane; dipping the carbon structure into the purification solution; refining the dipped carbon structure for a predetermined temperature and time; washing the carbon structure with distilled water after pulling out from the purification solution; and drying the washed carbon structure. The purification solution contains the trioxidane or trioxidane diluted with water, an acid solution or ammonium hydroxide, and the distilled water.

Description

Purification method for carrying out the carbon structure, and a purification solution for performing the same {PURIFICATION METHOD FOR CARBON STRUCTURE AND PURIFICATION SOLUTION TO PERFORM THE METHOD}

The present invention relates to a method for purifying a carbon structure and a purification solution for carrying out the same, and more particularly, to remove amorphous and crystalline carbon impurities and metal catalysts produced during the synthesis of a carbon structure, and at the same time, The present invention relates to a method for purifying carbon nanotubes capable of obtaining high purity carbon nanotubes having good dispersibility.

Since the synthesis of a large amount of carbon nanotubes (Nanture, Vol. 358 (1992), No. 6383, pp. 220-222), various synthesis methods have been developed.

Carbon nanotubes are generally extremely fine cylindrical materials having an aspect ratio ranging from tens to thousands, with diameters of several nm to several tens of nm and lengths of several to several hundred micrometers. Carbon nanotubes have high theoretical modulus and experimental elastic modulus of about 1.0 ~ 1.8TPa, which is not found in conventional materials, as well as heat resistance that can withstand temperatures up to 2,800 ℃ in vacuum, thermal conductivity nearly twice that of diamond, Potential properties such as 1,000 times higher current transfer capability compared to copper are used as additives for nanoscale electrical, electronic devices, nanosensors, optoelectronic devices, high-performance composites and composites. Methods for manufacturing carbon nanotubes include arc discharge method, laser evaporation method, plasma vapor phase synthesis method, thermophase synthesis method, and the like, although there are some differences depending on these preparation methods, inevitably 5 to 40% of impurities are included. do.

In order to make functional composite materials containing carbon nanotubes, uniform mixing of carbon nanotubes with organic polymers or metals is required, and in order to maintain the strength and intrinsic properties of carbon nanotubes, excessive carbon impurities and metal catalysts must be used. It is important to remove.

These impurities are composed of amorphous carbon, graphite, metal catalyst particles, ellipsoidal fullerene, and the like. The amorphous carbon is easily removed by thermal oxidation and acid solution treatment. To remove this, the carbon nanotube surface is oxidized with a strong acid solution such as sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), nitric acid (HNO ₃ ), and hydrogen peroxide (H ₂ O ₂ ). There is this.

U.S. Patent No. 5,698,175, proposed by Hiura, states that when carbon nanotubes that are not purified with nitric acid or sulfuric acid are mixed, the amorphous impurities are easily oxidized and dissolved by the acid, leaving only carbon nanotubes. The contents are disclosed. In this case, most of the amorphous carbon impurities can be removed, but it is known to partially oxidize the end of the carbon nanotubes or the defective portion in the tube to form a carboxyl group (COOH).

In addition, it is disclosed in U.S. Patent Nos. 6,031,711, 6,099,960, and 6,099,965 that treating the surface of carbon nanotubes with a solution of sulfonic acid, an alkali base metal, and hydrogen peroxide solution may occur.

In addition, after dispersing the carbon nanotubes in the aqueous acid solution and maintaining the appropriate temperature while applying a ultrasonic wave or microwave treatment for a given time is a general method, which is a Korean Patent Application No. 2000-0030351, Korean Patent Application 2001-0047617, Korean Laid-Open Patent Publication No. 2003-0013552, Korean Laid-Open Patent Publication No. 2001-0066815, and Korean Patent Application No. 2004-0068976.

In general, when carbon nanotubes are purified using an aqueous acid solution, the ends of the closed carbon nanotubes are opened. At this time, the activated carbon is oxidized to form functional groups such as carboxyl group (-COOH) or hydroxyl group (-OH). Dispersion with a polymer can be made easy.

However, the purification and surface treatment of carbon nanotubes by the acidic aqueous solution as described above require not only an unnecessary purification process by ultrasonic waves or microwaves in recent applications of carbon nanotubes, but also in most cases by a multi-stage purification method. The purification process is subject to many limitations, and high concentrations of strong acids can rapidly oxidize the defects of carbon nanotubes to form functional groups.However, the defects of carbon nanotubes rapidly increase, reducing the crystallinity of carbon nanotubes. The characteristics of the nanotubes are deteriorated, and a large amount of strong acid wastewater is generated when the carbon nanotubes are washed. On the other hand, in the case of using a low concentration of weak acid, there is a process constraint that the reaction at high temperature for a long time when the purification of carbon nanotubes and the formation of functional groups.

In addition, the purification methods are useful for removing soft amorphous carbon and metal catalysts, but are not preferable as a method for removing even harder amorphous carbon surrounding the metal catalyst. Among the amorphous and crystalline carbons surrounding the core-shell type metal catalyst, crystalline carbon has better thermal and chemical stability than amorphous carbon, so when strong acid is treated to remove crystalline carbon, The damage is severe. The strong acid treatment with hydrogen peroxide (H ₂ O ₂₎ instead of oxidizing the amorphous and amorphous carbon by O ₂ generated from the _{2H 2 O 2 → 2H 2 O} + O 2 sikimeuroseo converted to CO ₂ minimize damage to the carbon nanotubes And the removal of amorphous and crystalline carbon.

In this regard, Japanese Patent Publication No. 2003-89510 uses a mixture of hydrogen peroxide (H ₂ O ₂ ) and nitric acid, and according to Korean Patent Application No. 2004-0068976, hydrogen peroxide (H ₂ O ₂ ) and ammonium hydroxide ( Disclosed is a method of purifying amorphous and crystalline carbon by using NH ₄ OH) mixed solution, and then purifying by converting the metal catalyst into water-soluble metal ions such as metal nitrate or ammonium metal, which are mixed at the same time. have.

However, these methods have some effects on minimizing defects of carbon nanotubes and removing amorphous and crystalline carbon and metal catalysts compared to strong acid treatment methods such as nitric acid and sulfuric acid, but the purification efficiency is insignificant. This is because the oxidation of hydrogen peroxide is intended to oxidize and remove the amorphous carbon, but the removal of the hard crystalline carbon surrounding the catalyst is not efficient. Therefore, if it is not possible to remove the crystalline carbon surrounding the catalyst, it is impossible in principle to remove the gold catalyst, so that it is difficult to obtain high purity carbon nanotubes.

In addition, according to the above method, amorphous and crystalline carbon covering the metal catalyst with hydrogen peroxide are oxidized to expose some metal catalysts. Hydrogen peroxide by the exposed metal is rapidly catalyzed (for example, by water or oxygen, 2H ₂ O ₂ → 2H ₂ O + O ₂ ). For this reason, hydrogen peroxide in the solution is rapidly decomposed, and as a result, the purification process is completed to the extent that the amorphous and crystalline carbon to be removed is partially oxidized, so that the purification remains insufficient.

Accordingly, the present invention is a trioxy group (H ₂ O ₃ ), which can efficiently remove a plurality of carbon and metal impurities generated in the process of manufacturing carbon nanotubes simultaneously and at the same time add a functional group to the surface of the carbon structure, or The object of the present invention is to provide a purification method for a carbon structure comprising preparing a purification solution of a carbon structure containing trioxydan (H ₂ O ₃ ) and an acid or basic mixed solution, and a purification solution for performing the same. have.

The present invention provides a first step of preparing a carbon structure purification solution comprising a trioxy group to remove amorphous or crystalline carbon impurities or metal impurities contained in the carbon structure and to impart functional groups to the carbon structure; Dipping a carbon structure in the refining solution; A third step of purifying the carbon structure contained in the purification solution at a predetermined temperature for a predetermined time; A fourth step of removing the carbon structure to which the purification and functionalization groups are provided from the purification solution and washing in distilled water; And it provides a carbon structure purification method comprising a fifth step of drying the washed carbon structure, and also provides a carbon structure purification solution for performing the same.

According to the present invention, trioxydan (H ₂ O ₃ ) alone, or trioxydan (H ₂ O ₃ ), an acid solution or ammonium hydroxide has a high oxygen concentration and high oxidizing power when decomposed compared to hydrogen peroxide (H ₂ O ₂ ). By purifying the carbon structure using a purification solution containing water, and distilled water, it is possible to easily and efficiently remove amorphous and crystalline carbon impurities and metal impurities on the surface of the carbon structure by the oxidative power of the trioxy group to improve the purification efficiency and at the same time, Forming functional groups such as carboxylic acid groups on the surface of the structure increases dispersibility, and provides the advantage of minimizing defects on the surface of the carbon nanotubes.

The present invention relates to a method for purifying a carbon structure using the purification solution of the carbon structure. 1 is a process chart showing a method for preparing a purification solution and a purification method of carbon nanotubes according to the present invention.

The first step of the purification method of the present invention is a trioxydan (H ₂ O ₃ ) alone, or trioxydan (H ₂ O ₃ ), the acid solution or ammonium hydroxide, and the purification solution of the carbon structure containing distilled water To prepare.

Trioxydans are labile hydrogen polyoxide type molecules. Hydrogen peroxide proceeds from the decomposition process of 2H ₂ O ₂ → 2H ₂ O + O ₂ , while trioxydan is decomposed into H ₂ O ₃ → H ₂ O + O ₂ , which is more easily oxygenated than oxygen peroxide. Excellent removal ability of amorphous and crystalline.

When the carbon structure is purified using trioxydan (H ₂ O ₃ ), which has a higher oxygen concentration and oxidizing power when decomposed than hydrogen peroxide (H ₂ O ₂ ), oxidation of amorphous and crystalline carbon proceeds. When amorphous and crystalline carbon coated with a catalyst metal is oxidized to CO ₂ and the catalyst metal is exposed, the catalyst metal is dissolved by an acid or a basic solution, and oxidation of the catalyst metal is suppressed. In addition, since the dissolution reaction of an acid or a base solution and the decomposition reaction of trioxydans compete, the rapid decomposition of trioxydans is suppressed, and the ratio of trioxydans available for the oxidation of amorphous and crystalline carbon increases. This leads to an improvement in purification efficiency. In addition, functionalized groups such as -COOH, -OH, and -NH ₃ are formed on the surface of the purified carbon nanotubes.

As shown in FIG. 1, the purification solution for refining carbon nanotubes is trioxydan (H ₂ O ₃ ) alone or trioxydan (H ₂ O ₃ ) and an acid solution (hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid) or hydroxide. After mixing with at least one solution such as ammonium (NH ₄ OH) is prepared by adding a certain amount of distilled water to the mixed solution.

In the present invention, 1 to 40% by volume of trioxydan, 2 to 40% by volume of acid solution or ammonium hydroxide, 20 to 97% by volume of distilled water, preferably 2 to 15% by volume of trioxydan, acid solution or Purified solution may be prepared such that ammonium hydroxide is 7-15% by volume and distilled water is 70-91% by volume.

In the second step, carbon nanotubes are added to the prepared carbon structure purification solution. Carbon nanotubes used in the present invention may be a single-walled carbon nanotubes, double-walled carbon nanotubes, or multi-walled carbon nanotubes manufactured using arc discharge, chemical vapor deposition, laser evaporation, plasma vapor phase synthesis, etc. Or carbon nano horn, carbon fiber, and graphene.

The third step is to purify the carbon structure in the purification solution.

In the present invention, the purified amount of carbon nanotubes is 10 to 100 g, preferably 40 g based on 1000 mL of the purification solution.

In addition, this step includes mixing the carbon nanotubes with the refining solution to improve the purification efficiency and forming functional groups, and using a mixer such as a homogenizer, a rotary stirrer or ultrasonic cleaning rather than a simple stirring. It is also possible to increase the purification efficiency by adding a constant temperature to the mixed solution. In general, the purification efficiency is higher at 40 ℃ than 25 ℃.

In the above step, the heating temperature is 5 to 120 ℃, the higher the temperature, the higher the evaporation rate of trioxydan, and the acid solution or ammonium hydroxide, the purification efficiency can be reduced, preferably not exceed 60 ℃, 60 ℃ When refine | purifying above, it is preferable to carry out in a closed reactor.

The reaction time is preferably carried out in the range of 30 minutes to 24 hours, more preferably purified within 3 hours.

In the fourth step, the purified carbon nanotubes to which the functional groups are attached are washed several times with ultrapure water, and when the final washing is performed with a volatile solvent such as ethanol, methanol, acetone, and ether, the pH of the filtrate is 7. Washing step.

Finally, the fifth step of the purification method of the carbon structure of the present invention is a step of drying the purified carbon nanotubes, preferably the drying temperature is 50 to 120 ℃, more preferably at 80 ℃ under vacuum atmosphere do.

In addition, the method may further include a high temperature heat treatment of the carbon structure at 300 to 500 ° C. for 30 minutes to 2 hours before or after the third step.

Purified according to the carbon structure purification method of the present invention, the purity and functional group formation can be confirmed through TGA (thermogravimetric analyzer) and FT-IR (Fourier Infrared Spectrometer) of the carbon nanotubes formed with functional groups on the surface.

As can be seen from the results of the following examples, the carbon nanotubes (refer to FIG. 3) purified with a purification solution containing the trioxydan and ammonium hydroxide aqueous solution disclosed in the present invention are purified using only nitric acid in all regions regardless of the content. Compared to the carbon nanotubes (see FIG. 2), it can be seen that the purification rate and functionalization forming effect of the carbon nanotubes are very effective.

In addition, the carbon nanotubes purified with the purification solution containing the trioxydan and hydrochloric acid solution of the present invention, regardless of the content of the purification rate and functionalization of carbon nanotubes compared to the case of purification using an aqueous solution of hydrogen peroxide and hydrochloric acid in all areas It can be seen that the forming effect is very effective.

On the other hand, the purification efficiency and the functional group formation effect improved as the volume ratio of trioxydan increased in the tablet solution containing trioxydan.

In addition, as a result of thermogravimetric analysis of the carbon structure purification solution of the present invention, the residual amount of impurities was less than 5wt%, the purification effect was very excellent, and the functional group such as -OH or -COOH in the carbon nanotubes by FT-IR measurement. Confirmed its formation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to preferred embodiments, but various modifications and changes of the present invention will be made by those skilled in the art without departing from the spirit and scope of the present invention as set forth in the claims below. You can.

Example 1

After mixing 15 mL of trioxydan and 15 mL of ammonium hydroxide, 70 mL of distilled water was added to prepare a purification solution. 4 g of carbon nanotubes (purity 75%) was added to 100 mL of the purification solution, followed by stirring at 200 rpm for 2 hours at 25 ° C. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The carbon nanotubes purified and the functional group formed on the surface were vacuum dried at 80 ° C.

Impurity residue through TGA (thermogravimetric analyzer) was 3wt%, which was excellent in purifying effect, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that C = O shrinkage vibration coupling of carboxyl group, which is the characteristic peak generated in carbon nanotubes Was found around 1635cm ^-1 , and -OH binding peak was found at 3450cm ^-1 .

[Example 2]

10 mL of trioxydan and 20 mL of ammonium hydroxide were mixed, followed by adding 70 mL of distilled water to prepare a purification solution. Purification, functionalizer formation, washing and drying were carried out in the same manner as in Example 1.

Impurity residue through TGA (thermogravimetric analyzer) was 5wt%, which was excellent in purifying effect, and FT-IR (Fourier Infrared Spectrometer) measurement showed that C = O shrinkage vibration coupling of carboxyl group, which is the functional peak characteristic carbon nanotube produced Was found around 1635cm ^-1 , and -OH binding peak was found at 3450cm ^-1 .

Example 3

20 mL of trioxydan and 10 mL of ammonium hydroxide are mixed, followed by adding 70 mL of distilled water to prepare a purification solution. Purification, functionalizer formation, washing and drying were carried out in the same manner as in Example 1.

Impurity residue through TGA (thermogravimetric analyzer) was 2wt%, which was excellent in purifying effect, and FT-IR (Fourier Infrared Spectrometer) measurement showed that C = O shrinkage vibration coupling of carboxyl group, which is a functional group characteristic peak generated in carbon nanotubes Was found around 1635cm ^-1 , and -OH binding peak was found at 3450cm ^-1 .

Example 4

15 mL of trioxydan and 15 mL of ammonium hydroxide were mixed, and 70 mL of distilled water was added thereto to prepare a purified solution. 4 g of carbon nanotubes were added to the purified solution and stirred at 200 rpm for 2 hours at 40 ° C. Washing and drying process was carried out in the same manner as in Example 1.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 1.5wt%, and the purification effect was excellent, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that the C = O shrinkage vibration of the carboxyl group, the functional peak produced in carbon nanotubes. Coupling appeared around 1635cm ^-1 and -OH binding characteristic peak appeared at 3450cm ^-1 .

Example 5

15 mL of trioxydan and 15 mL of ammonium hydroxide were mixed, and 70 mL of distilled water was added to prepare a purification solution. 4 g of carbon nanotubes were added to the purified solution and reacted for 2 hours in an ultrasonic cleaner at 40 ° C. Washing and drying process was carried out in the same manner as in Example 1.

Impurity residues through TGA (thermogravimetric analyzer) were less than 0.8wt%, and the purification effect was excellent, and the FT-IR (Fourier Infrared Spectrometer) measurement showed that the C = O shrinkage of the carboxyl group, which is a functional group characteristic peak generated in carbon nanotubes Vibration coupling was found around 1635cm ^-1 , and -OH coupling characteristic peak was found at 3450cm ^-1 .

Example 6

20 mL of trioxydan and 80 mL of distilled water were added to prepare a purification solution. 4 g of carbon nanotubes were added to the purified solution and reacted for 2 hours in an ultrasonic cleaner at 40 ° C. Washing and drying process was carried out in the same manner as in Example 1.

Impurity residue through TGA (thermogravimetric analyzer) was 22wt%, and the purification effect was insignificant, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that the C = O shrinkage vibration coupling of the carboxyl group, the functional peak characteristic carbon nanotubes produced. Was found around 1645cm ^-1 and -OH binding peak was found at 3438cm ^-1 .

Example 7

40 mL of trioxydan and 60 mL of distilled water were added to prepare a purification solution. 4 g of carbon nanotubes were added to the purified solution and reacted for 2 hours in an ultrasonic cleaner at 40 ° C. Washing and drying process was carried out in the same manner as in Example 1.

Impurity residue through TGA (thermogravimetric analyzer) was 16wt%, and the purification effect was insignificant, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that C = O shrinkage vibration coupling of carboxyl group, which is the characteristic peak generated in carbon nanotubes Was found around 1645cm ^-1 and -OH binding peak was found at 3438cm ^-1 .

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Trioxydan 15 ml 10 ml 20 ml 15 ml 15 ml 20 ml 40ml Ammonium Hydroxide 15 ml 20 ml 10 ml 15 ml 15 ml - - Distilled water 70ml 70ml 70ml 70ml 70ml 80 ml 60 ml Reaction time 2 hours 2 hours 2 hours 2 hours 2 hours 2 hours 2 hours Reaction temperature 25 ℃ 25 ℃ 25 ℃ 40 ℃ 40 ℃ 40 ℃ 40 ℃ Reaction condition Stirring Stirring Stirring Stirring ultrasonic wave ultrasonic wave ultrasonic wave Thermogravimetric analysis
(Residual impurities wt%) 3wt% 5wt% 2wt% 1.5wt% <0.8 wt% 22wt% 16wt% FT-IR characteristic peak presence U U U U U U U

In Examples 1 to 3 of Table 1, after purifying carbon nanotubes by changing the ratio of trioxydan and ammonium hydroxide at a constant temperature of 25 ° C. and a purification time of 2 hours, impurity residues of carbon nanotubes using TGA Purification efficiency was measured by measuring the concentration of carbon nanotubes, and FT-IR. As a result, it was confirmed that the purification efficiency and the functional group formation effect were improved as the volume ratio of trioxydan in the purification solution increased.

In addition, Examples 4 and 5 fixed the volume ratio and reaction temperature of trioxydan and ammonium hydroxide at 40 ° C., purified carbon nanotubes using agitation and ultrasonic waves, and then the residual impurities of carbon nanotubes using TGA. Purification efficiency was measured by measuring the amount of carbon nanotubes and functional group formation using FT-IR (see FIG. 4). As a result, the temperature of the purification solution at the time of purification at 40 ℃ rather than 25 ℃, purification by ultrasonic rather than simple stirring to improve the purification efficiency and functionalizer formation effect.

In Examples 6 and 7, by varying the dilution ratio with distilled water alone in trioxy group alone, the reaction temperature was fixed at 40 ° C. and sonicated to purify the carbon nanotubes, and the impurity residues of the carbon nanotubes using TGA were used. The preliminary efficiency was measured by measuring and the functional group formation of carbon nanotubes was measured using FT-IR. As a result, as the volume ratio of the trioxy group was increased, the purification efficiency and functional group formation effect of the crystalline and amorphous carbon structures were improved, but the metal catalyst remained.

As shown in Table 1, the residual amount of impurities through thermogravimetric analysis in all given compositions of Examples 1 to 5 was excellent in the purification effect of less than 5wt%, and the functional group characteristics generated in the carbon nanotubes as a result of FT-IR measurement. The C = O contraction vibration coupling of the carboxyl group, which is the peak, was found around 1635cm ^-1 , and the -OH binding characteristic peak was found at 3450cm ^-1 .

Comparative Example 1

30 mL of nitric acid and 70 mL of distilled water were mixed to prepare a purification solution. 4 g of carbon nanotubes were added to 100 mL of the purification solution, and stirred at 200 rpm for 2 hours at 25 ° C. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The purified carbon nanotubes on which the functional group was formed were vacuum dried at 80 ° C.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 10wt%, and the purification effect was not excellent, and the FT-IR (Fourier Infrared Spectrometer) measurement showed that the C = O shrinkage vibration of the carboxyl group, which is the characteristic peak produced in carbon nanotubes. Coupling appeared around 1635cm ^-1 and -OH binding characteristic peak appeared at 3450cm ^-1 .

Comparative Example 2

A purified solution was prepared after mixing 40 mL of nitric acid and 70 mL of distilled water. Purification, functionalizer formation, washing and drying were carried out in the same manner as in Comparative Example 1.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 7wt%, which was not excellent in purification effect, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that C = O shrinkage of carboxyl group, which is the characteristic peak generated in carbon nanotubes Vibration coupling was found around 1635cm ^-1 , and -OH coupling characteristic peak was found at 3450cm ^-1 .

Comparative Example 3

30 mL of nitric acid and 70 mL of distilled water were mixed to prepare a purification solution. Except that the purification temperature is 40 ℃, the purification, functionalizer formation, washing and drying process was carried out in the same manner as in Comparative Example 1.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 5wt%, and the purification effect was not excellent, and the FT-IR (Fourier Infrared Spectrometer) measurement showed that the C = O shrinkage of the carboxyl group, which is a functional group characteristic peak generated in carbon nanotubes. Vibration coupling was found around 1635cm ^-1 , and -OH coupling characteristic peak was found at 3450cm ^-1 .

division Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 3 Example 5 Trioxydan - - - 20 ml 15 ml Ammonium Hydroxide - - - 10 ml 15 ml nitric acid 30 ml 40ml 30 ml - - Distilled water 70ml 60 ml 70ml 70ml 70ml Reaction time 2 hours 2 hours 2 hours 2 hours 2 hours Reaction temperature 25 ℃ 25 ℃ 40 ℃ 25 ℃ 40 ℃ Reaction condition Stirring Stirring Stirring Stirring ultrasonic wave Thermogravimetric analysis
(Residual impurities wt%) 10wt% 7wt% 5wt% 2wt% <0.8 wt% FT-IR characteristic peak presence U U U U U

As shown in Table 2, the carbon nanotubes purified by the trioxydan and ammonium hydroxide aqueous solution presented in the present invention have a purification rate of carbon nanotubes compared to the carbon nanotubes purified using nitric acid in all regions regardless of the content. And it can be seen that the functionalization forming effect is very effective.

Example 8

After mixing 15 mL of trioxydan and 15 mL of hydrochloric acid, 70 mL of distilled water was added to prepare a purification solution. 4 g of carbon nanotubes (purity 75%) was added to 100 mL of the purification solution, followed by reaction for 2 hours in an ultrasonic cleaner at 40 ° C. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The carbon nanotubes purified and the functional group formed on the surface were vacuum dried at 80 ° C.

Impurity residue through TGA (thermogravimetric analyzer) was less than 0.5wt%, and the refining effect was excellent.As a result of FT-IR (Fourier Infrared Spectroscopy) measurement, C = O shrinkage of the carboxyl group, which is a functional group characteristic peak generated in carbon nanotubes Vibration coupling was found around 1635 cm ⁻¹ , and the -OH coupling characteristic peak was found at 3450 cm ⁻¹ (see FIG. 4).

Example 9

After mixing 20 mL of trioxydan and 10 mL of hydrochloric acid, 70 mL of distilled water was added to prepare a purification solution. 4 g of carbon nanotubes (purity 75%) was added to 100 mL of the purification solution, followed by reaction for 2 hours in an ultrasonic cleaner at 40 ° C. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The carbon nanotubes purified and the functional group formed on the surface were vacuum dried at 80 ° C.

Impurity residue through TGA (thermogravimetric analyzer) was less than 0.2wt%, and the purification effect was excellent, and the FT-IR (Fourier Infrared Spectrometer) measurement showed that the C = O shrinkage of the carboxyl group, the functional peak produced in carbon nanotubes. Vibration coupling was found around 1635cm ^-1 , and -OH coupling characteristic peak was found at 3450cm ^-1 .

Comparative Example 4

10 mL of hydrochloric acid, 15 mL of hydrogen peroxide, and 75 mL of distilled water were mixed to prepare a purification solution. 4 g of carbon nanotubes were added to 100 mL of the purification solution and reacted at 40 ° C. for 2 hours in an ultrasonic cleaner. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The purified carbon nanotubes on which the functional group was formed were vacuum dried at 80 ° C.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 7wt%, and the purification effect was not excellent, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that C = O shrinkage vibration of carboxyl group, which is the characteristic peak generated in carbon nanotubes. Coupling appeared around 1635cm ^-1 and -OH binding characteristic peak appeared at 3450cm ^-1 .

Comparative Example 5

15 mL of hydrochloric acid, 15 mL of hydrogen peroxide, and 70 mL of distilled water were mixed to prepare a purification solution. 4 g of carbon nanotubes were added to 100 mL of the purification solution and reacted at 40 ° C. for 2 hours in an ultrasonic cleaner. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The purified carbon nanotubes on which the functional group was formed were vacuum dried at 80 ° C.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 6wt%, and the purification effect was not excellent, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that C = O shrinkage vibration of carboxyl group, which is the characteristic peak generated in carbon nanotubes. Coupling appeared around 1635cm ^-1 and -OH binding characteristic peak appeared at 3450cm ^-1 .

Comparative Example 6

10 mL of hydrochloric acid, 20 mL of hydrogen peroxide, and 70 mL of distilled water were mixed to prepare a purification solution. 4 g of carbon nanotubes were added to 100 mL of the purification solution and reacted at 60 ° C. for 2 hours in an ultrasonic cleaner. The carbon nanotubes were washed with distilled water until the filtrate reached pH 7. The purified carbon nanotubes on which the functional group was formed were vacuum dried at 80 ° C.

The residual amount of impurities through TGA (thermogravimetric analyzer) was 5wt%, which was not excellent in purifying effect, and the result of FT-IR (Fourier Infrared Spectroscopy) measurement showed that the C = O shrinkage vibration of the carboxyl group, the functional peak generated in carbon nanotubes. Coupling appeared around 1635cm ^-1 and -OH binding characteristic peak appeared at 3450cm ^-1 .

division Comparative Example 4 Comparative Example 5 Comparative Example 6 Example 8 Example 9 Trioxydan - - - 15 ml 20 ml Hydrochloric acid 10 ml 15 ml 10 ml 15 ml 10 ml Hydrogen peroxide 15 ml 15 ml 20 ml - - Distilled water 75 ml 70ml 70ml 70ml 70ml Reaction time 2 hours 2 hours 2 hours 2 hours 2 hours Reaction temperature 40 ℃ 40 ℃ 60 ℃ 40 ℃ 40 ℃ Reaction condition ultrasonic wave ultrasonic wave ultrasonic wave ultrasonic wave ultrasonic wave Thermogravimetric analysis
(Residual impurities wt%) 7wt% 6wt% 5wt% <0.5wt% <0.2wt% FT-IR characteristic peak presence U U U U U

As can be seen from Table 3, the carbon nanotubes purified by the aqueous solution of trioxydan and hydrochloric acid presented in the present invention are carbon nanotubes compared to the case of purification using aqueous solutions of hydrogen peroxide and hydrochloric acid in all regions regardless of the content. It can be seen that the purification rate and the functionalization forming effect are very effective.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flowchart illustrating the preparation of a purification solution for a carbon structure of the present invention and a method for purifying the carbon structure using the purification solution.

Figure 2 is a scanning electron micrograph of unpurified carbon nanotubes.

Figure 3 is a scanning electron micrograph of the carbon nanotubes purified with a purification solution of the carbon structure of the present invention.

4 is a spectrum of FT-IR (Fourier Infrared Spectrometer) of carbon nanotubes functionalized with unfunctionalized carbon nanotubes and a purification solution of the carbon structure of the present invention.

Claims

A first step of preparing a carbon structure purification solution containing trioxydan;

A second step of dipping the carbon structure in the purification solution;

And a third step of purifying the carbon structure contained in the purification solution at a predetermined temperature for a predetermined time.

A carbon structure purification method for providing a functional group at the same time as the purification of the carbon structure comprising a.

The method of claim 1, wherein the carbon structure purification solution in the first step comprises trioxydan, trioxydan, acid solution or ammonium hydroxide diluted with water, and distilled water.

The method of claim 2, wherein the acid solution is selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

The method of claim 1 or 2, characterized in that the purification solution comprises 1 to 40% by volume of trioxydan, 2 to 40% by volume of acid solution or ammonium hydroxide, and 20 to 97% by volume of distilled water. Carbon Structure Purification Method.

The method of claim 1, wherein the purification amount of carbon nanotubes in the second step is 10 to 100g with respect to 1000mL of the purification solution.

The method of claim 5, wherein the purification amount of carbon nanotubes in the second step is 40g based on 1000mL of the purification solution.

The method of claim 1, wherein the carbon structure purification method comprises at least one of a method of stirring with a stirrer or mixing by ultrasonic waves in the third step.

The carbon structure of claim 1, wherein the carbon structure comprises at least one selected from the group consisting of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, carbon fibers, and carbon blends. Structure Purification Method.

The method of claim 1, wherein the predetermined temperature of the third step is 5 to 120 ° C., and the predetermined time is 30 minutes to 20 hours.

10. The method of claim 9, wherein the predetermined temperature of the third step is 5 to 60 ℃.

The method of claim 10, wherein the predetermined time of the third step is 30 minutes to 3 hours.

The carbon structure purification method according to claim 1, further comprising a fourth step of removing the carbon structure to which the purification and functionalizing groups are provided from the carbon structure purification solution and washing in distilled water.

The method of claim 12, wherein the fourth step is washed several times with ultrapure water, and at the last wash with volatile solvents such as ethanol, methanol, acetone, ether, and the like until the pH of the filtrate is 7. Carbon structure purification method characterized in that.

The method of claim 1, further comprising a fifth step of drying the washed carbon structure.

15. The method of claim 14, wherein the drying temperature in the fifth step is 50 to 120 ℃.

The method for purifying carbon structures according to claim 15, wherein the fifth step is 80 DEG C in a vacuum atmosphere.

The method of claim 1, further comprising the step of heat-treating the carbon structure at 300 to 500 ° C. for 30 minutes to 2 hours before or after the third step.

Carbon structure purification solution containing trioxydan for carrying out the carbon structure purification method of claim 1.

19. The carbon structure purification solution according to claim 18, wherein the carbon structure purification solution comprises trioxydan or trioxydan diluted with water, an acid solution or ammonium hydroxide, and distilled water.

20. The carbon structure purification solution according to claim 19, wherein the acid solution is selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid.

The method of claim 19 or 20, wherein the purification solution comprises 1 to 40% by volume of trioxydan, 2 to 40% by volume of acid solution or ammonium hydroxide, and 20 to 97% by volume of distilled water. Carbon Structure Purification Solution.