WO2017048053A1 - Carbon nanotube having improved crystallizability - Google Patents

Abstract

The present invention provides a carbon nanotube which is purified through a method including the steps of: reacting metal remaining in a carbon nanotube with a chorine containing compound at a first temperature in a vacuum or inert atmosphere; chlorinating the remaining metal; and evaporating and removing the chlorinated remaining metal at a second temperature that is higher than the first temperature, wherein a carbon nanotube is provided that has an average value of an intensity ratio (I_G/I_D) of a G band and a D band, as measured through Raman spectroscopy, that is increased by 20% or more when compared to the carbon nanotube before purification.

Description

Carbon nanotubes with improved crystallinity

This application was filed on September 15, 2015. Claiming the benefit of priority based on Korean Patent Application No. 10-2015-0130049 dated, all contents disclosed in the literature of that Korean Patent Application are incorporated as part of this specification.

The present invention relates to carbon nanotubes having improved crystallinity by reacting and removing impurities contained in carbon nanotubes with chlorine-containing compounds.

Generally, carbon nanotubes (hereinafter referred to as 'CNT') are cylindrical carbon tubes having a diameter of about 3 to 150 nm, specifically about 3 to 100 nm, and having a length several times the diameter, for example, 100 times or more. Refer. These CNTs consist of layers of aligned carbon atoms and have different types of cores. Such CNTs are also called, for example, carbon fibrils or hollow carbon fibers.

The CNT can be generally manufactured by an arc discharge method, a laser evaporation method, a chemical vapor deposition method, or the like. Among these, the arc discharge method and the laser evaporation method is difficult to mass-produce, there is a problem that the economical efficiency is lowered due to excessive arc production cost or laser equipment purchase cost.

In chemical vapor deposition, carbon nanostructures are typically produced by dispersing and reacting metal catalyst particles with a hydrocarbon-based feed gas in a high temperature fluidized bed reactor. That is, the metal catalyst is suspended in the fluidized bed reactor by the source gas and reacts with the source gas to grow carbon nanostructures.

Carbon nanotubes exhibit non-conductor, conductor or semiconducting properties according to their unique chirality, and the carbon atoms are connected by strong covalent bonds, so that their tensile strength is about 100 times greater than steel, and they have excellent flexibility and elasticity. It is also chemically stable, and because of its size and specific properties, it is industrially important in the manufacture of composites and has high utility in the field of electronic materials, energy materials and many other fields. For example, the carbon nanotubes may be applied to electrodes of an electrochemical storage device such as a secondary battery, a fuel cell or a super capacitor, an electromagnetic shield, a field emission display, or a gas sensor.

However, the catalytic metal used in the carbon nanotube fabrication process is treated as an impurity when attempting to use the carbon nanotubes, and the above-mentioned metal impurities cause a problem that the basic physical properties such as thermal stability and chemical stability are reduced. Therefore, at this time, there is a need for a method of improving the basic physical properties of carbon nanotubes by purifying only carbon nanotubes.

The present invention is to provide a carbon nanotube significantly improved thermal stability by going through the step of removing the residual metal contained in the carbon nanotubes.

In order to solve the problem of the present invention, the present invention comprises the steps of chlorinating the residual metal by reacting the metal remaining in the carbon nanotubes with a chlorine-containing compound at a first temperature (T ₁ ) in a vacuum or inert atmosphere; And

Evaporating and removing the chlorinated residual metal with an inert gas or vacuum at a second temperature (T ₂ ) of a temperature higher than the first temperature (T ₁ );

By refining in a method comprising,

By the average of the G band and the intensity ratio (I _G / I _D) of D-band in a Raman spectroscopy measurement compared to the carbon nanotube before purification provides the carbon nanotube, characterized in that increase of 20% or more.

The second temperature T ₂ may be performed at a temperature of T ₁ + 300 ° C. or more.

The first temperature T ₁ may be selected from 500 ° C. to 1000 ° C., and the second temperature may be selected from 800 ° C. to 1500 ° C.

In addition, the oxidation start temperature of the purified carbon nanotube may be 550 ℃ or more.

In addition, the metal impurity content remaining in the purified carbon nanotubes may be 50 ppm or less.

In addition, the purification step of evaporating the residual metal by reacting with the chlorine-containing compound may be performed in an N ₂ gas or a vacuum atmosphere.

In addition, the carbon nanotubes may be manufactured using a metal catalyst containing cobalt (Co), and at least one metal component of iron (Fe), molybdenum (Mo), vanadium (V) and chromium (Cr). It may be to include more.

In addition, the carbon nanotubes may have a Co content of 40 ppm or less after the purification process.

In addition, the carbon nanotubes may be prepared by chemical vapor deposition (CVD) on a fluidized bed reactor.

In addition, the carbon nanotubes may have an entangled shape or a bundle shape.

In addition, the chlorine-containing compound may be chlorine (Cl ₂ ) gas or trichloromethane (CHCl ₃ ) gas.

In addition, the first temperature may be performed at a temperature condition of 700 ℃ to 900 ℃, the second temperature is 900 ℃ to 1500 ℃.

The carbon nanotubes according to the present invention can remove residual metals generated in the manufacturing process of carbon nanotubes using a metal catalyst by reacting with a chlorine compound at a high temperature, thereby effectively removing impurities such as residual metals. Can be removed. In particular, the chlorine gas treatment process that proceeds at a relatively low temperature of the first temperature and the metal chlorine removal process that proceeds to nitrogen (N ₂ ) or the second temperature in a vacuum atmosphere can increase the metal removal efficiency remaining in the carbon nanotubes. , The second process is carried out in a nitrogen or vacuum atmosphere, the chlorine remaining in the carbon nanotubes can be removed together. Purification process according to the present invention can further improve the physical properties of the carbon nanotubes, in particular, the oxidation stability stability and conductivity is improved by improving the crystallinity can be useful for use as a composite material of the metal composite and the conductive polymer.

Figure 1 shows the SEM images before and after the purification process of the carbon nanotubes of Example 1 and Comparative Example 1.

2 is a graph showing TEM_EDX results of carbon nanotubes before and after the purification process.

3 is a graph comparing G bands and D bands measured by Raman spectroscopy for carbon nanotubes of Example 1 and Comparative Example 1. FIG.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. Based on the principle, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Hereinafter, the present invention will be described in detail.

Carbon nanotubes according to a preferred embodiment of the present invention,

Chlorinating the residual metal by reacting the metal remaining in the carbon nanotubes with a chlorine-containing compound at a first temperature in a vacuum or inert atmosphere; And

Evaporating and removing the chlorinated residual metal at a second temperature (T ₂ ) at a temperature higher than the first temperature (T ₁ );

By purifying by a method comprising a, the average value of the intensity ratio (I _G / I _D ) of the G band and D band measured by Raman spectroscopy is characterized in that 20% or more compared to the carbon nanotubes before purification.

The present invention provides a method for removing residual metal generated from a metal catalyst used in a manufacturing process in a manufactured carbon nanotube, by using a method of reacting at a high temperature with a chlorine-containing compound to chlorinate the residual metal and evaporate it. By refining carbon nanotubes using the method, the physical property degradation due to metal impurities such as residual metals can be improved. In particular, in thermal stability, the oxidation start temperature of purified carbon nanotubes is refined, that is, remaining. Compared to the carbon nanotube containing the metal can exhibit an increase rate of 100 ℃ or more, it can be used more efficiently, such as a flame retardant or metal composite that can be used in high temperature environment.

According to one embodiment, the first temperature may be selected from 500 ℃ to 1000 ℃, the second temperature may be selected from 800 ℃ to 1500 ℃.

In addition, the oxidation start temperature of the purified carbon nanotube may be 550 ℃ or more.

In addition, the metal impurity content remaining in the carbon nanotubes subjected to the purification process may be reduced by 10 to 100 times or more than before purification, that is, almost all of the metal remaining can be removed, which is a boiling point of the chlorinated metal By using a lower characteristic than this metal, it may be to use the principle of evaporating all of the liquefied or gaseous metal to a higher temperature through the chlorination process, which is because the high temperature reaction of the gas phase is used, It has the advantage of not causing physical damage.

Hereinafter, the carbon nanotube purification process will be described in more detail.

Chlorinating the residual metal by reacting the metal remaining in the prepared carbon nanotubes with a chlorine-containing compound at a first temperature in a vacuum or inert gas atmosphere; And evaporating and removing the chlorinated residual metal at a second temperature at a temperature higher than the first temperature.

According to one embodiment, the chlorine-containing compound may be chlorine (Cl ₂ ) or trichloromethane (CHCl ₃ ) gas. Since chlorine-containing compounds have low reactivity with carbon nanotubes, the damage to the manufactured carbon nanotubes can be further reduced.

A first temperature of the metal chlorination takes place (T ₁₎ may be a 500 ℃ to 1000 ℃, may be more preferably 700 ℃ to 900 ℃. At temperatures below 500 ° C, chlorination of metal impurities such as catalyst metals in the carbon material may not be smooth.

The heating process after the chlorination of the metal is performed at a second temperature T ₂ , which is higher than the first temperature T ₁ , and specifically, T ₂ may be a temperature of T ₁ + 300 ° C. or more. The second temperature may range from 800 ° C to 1500 ° C, preferably 900 ° C to 1500 ° C, and more preferably 900 ° C to 1400 ° C. If the reaction proceeds at a temperature below 900 ° C. or lower than the first temperature, the removal reaction of chlorinated metal is not smooth and residual metal and chlorinated metal may remain in the carbon nanotubes to act as impurities. Can be reduced. In addition, the catalyst graphitization by the residual metal occurs at a temperature higher than 1500 ℃, it may not be easy to remove the metal.

In addition, the chlorination reaction carried out at the first temperature may be maintained for about 10 minutes to 1 hour to make the chlorination process of the residual metal more completely, and the total flow rate depends on the size of the charged carbon nanotubes and the reactor. I can regulate it.

After the chlorination process, the metal chlorination evaporation and removal reaction at the second temperature may be performed for 30 minutes to 300 minutes in an inert gas or vacuum atmosphere, and this may remove only the chlorinated residual metal without affecting carbon nanotubes. It should be within the range In addition, the metal chlorine evaporation and removal reaction may proceed while alternately forming a vacuum atmosphere and an inert gas atmosphere, which may further increase the removal efficiency.

In addition, the chlorination reaction of the residual metal may occur in a vacuum or nitrogen gas atmosphere. More specifically, the reaction in which the residual metal is chlorinated by adding a chlorine-containing compound gas after heating the carbon nanotube-filled reactor or reactor to a first temperature in a vacuum or nitrogen atmosphere. In this case, in the chlorination process performed at the first temperature, only the chlorination reaction of the metal may occur, and the removal reaction by evaporation of the chlorinated residual metal may occur mainly at the second temperature. At this time, the step of evaporation and removal of the residual metal is to stop the addition of the chlorine-containing compound and proceed again by converting the reaction furnace or the inside of the reactor into a vacuum atmosphere, the evaporation of the metal chloride may occur more smoothly.

In this case, the vacuum atmosphere means a pressure of 1 torr or less, and the inert gas means an inert gas such as nitrogen (N ₂ ) or argon (Ar). In addition, the second process in which the evaporation and chlorinated metal removal reaction occurs may be performed at a pressure of 500 tortor to 800 tor, preferably 600 to 700 torr. In addition, the metal chloride and chlorine compound removal and evaporation processes proceeding to the second temperature may be alternately applied with a vacuum and an inert gas atmosphere, and may be pressured in the form of a pulse. Specifically, after forming a vacuum to 1torr, after a predetermined time, the inert gas is added again, the pressure is applied to 500torr, and the process of forming a vacuum again may be repeated. Residual metals can also be removed, resulting in higher purification efficiency.

The metal impurity content of the carbon nanotubes from which the residual metal is removed by the above method may be 50 ppm or less, and may be measured through the metal impurity ICP analysis of the carbon nanotubes. According to one embodiment, the carbon nanotubes may be to use a metal catalyst containing a metal such as cobalt (Co), iron (Fe) as a main component, in this case, the content of the main component metal after purification is less than 40ppm each The total content may be 50 ppm or less.

The carbon nanotube purification method as described above can effectively remove residual metals such as catalytic metals while using ultrasonic waves while suppressing damage or cutting of carbon nanotubes or solidifying carbon nanotubes to amorphous carbon materials. It can be purified without being able to suppress the physical damage or cutting of the carbon nanotubes, thereby providing a carbon nanotubes with improved mechanical and physical properties, in particular carbon nanotubes significantly improved in thermal stability Can be provided.

The carbon nanotubes according to the present invention may be prepared by growing carbon nanotubes by chemical vapor deposition (CVD) through decomposition of a carbon source using a supported catalyst, and the catalyst metal supported on the supported catalyst is carbon nanotubes. It will not be restrict | limited in particular, if it is a substance which accelerates growth of.

Examples of such a catalytic metal include at least one metal selected from the group consisting of Groups 3 to 12 of the Group 18 periodic table recommended by IUPAC in 1990. Among them, at least one metal selected from the group consisting of Groups 3, 5, 6, 8, 9, and 10 is preferable, and iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), and molybdenum are preferred. At least one metal selected from (Mo), tungsten (W), vanadium (V), titanium (Ti), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt) and rare earth elements Particularly preferred. Moreover, as a compound containing metal elements which act as these catalysts, ie, a catalyst metal precursor, inorganic salts, such as nitrate, sulfate, and carbonate of a catalyst metal, organic salts, such as acetate, organic complexes, such as an acetylacetone complex, an organometallic compound, etc. It will not specifically limit, if it is a compound containing a catalyst metal.

It is well known to control reaction activity by using 2 or more types of these catalyst metals and catalyst metal precursor compounds. For example, at least one element selected from iron (Fe), cobalt (Co) and nickel (Ni), and an element selected from titanium (Ti), vanadium (V) and chromium (Cr) and molybdenum (Mo) and tungsten What combined the element chosen from (W) can be illustrated. Preferably, it may be a metal catalyst containing cobalt (Co) as a main component and further including at least one metal selected from iron (Fe), molybdenum (Mo), chromium (Cr), and vanadium (V).

The catalyst used in the carbon nanotube generation step is specifically a catalytically active metal precursor, Co (NO ₃ ) ₂ -6H _2O , (NH ₄ ) ₆ Mo ₇ O ₂₄ -4H ₂ O, Fe (NO ₃ ) ₂ -6H ₂ O or _{(Ni (NO 3) 2 -6H} 2 O) was dissolved in distilled water, etc., and then, this Al ₂ O _3, by wet impregnation (wet impregnation) of the support, such as SiO ₂ or MgO may be manufactured.

In addition, the catalyst may be prepared by ultrasonically treating a catalytically active metal precursor with a carrier such as Al (OH) ₃ , Mg (NO ₃ ) _2, or colloidal silica.

In addition, the catalyst is prepared by the sol-gel method using a chelating agent such as citric acid (citric acid), tartaric acid (tartaric acid), so that the catalytically active metal precursor in water can be dissolved smoothly, or a catalyst that is well dissolved It may be prepared by co-precipitation of the active metal precursor.

In the method of the present invention, the supported catalyst and the carbon-containing compound may be prepared by contacting under a heating zone.

In the preparation of the catalyst, it is preferable to use a supported catalyst by impregnation method, in which the bulk density of the catalyst itself is higher than that of the coprecipitation catalyst and fine powder of 10 microns or less unlike the coprecipitation catalyst when the supported catalyst is used. This is because it is possible to reduce the possibility of fine powder due to wear (attrition) that can occur in the fluidization process, and because the mechanical strength of the catalyst itself is also excellent, it has the effect of stabilizing the operation of the reactor.

The aluminum-based support that can be used in the present invention may be one or more selected from the group consisting of Al ₂ O ₃ , AlO (OH) and Al (OH) ₃ , and preferably may be alumina (Al ₂ O ₃ ). In addition, the aluminum (Al) -based support may further include one or more selected from the group consisting of ZrO ₂ , MgO and SiO ₂ . The aluminum (Al) -based support may have a spherical or potato shape, and may be made of a material having a porous structure, a molecular sieve structure, a honeycomb structure, or another suitable structure to have a relatively high surface area per unit mass or volume.

According to one embodiment, the preparation method of the supported catalyst for CNT synthesis according to the present invention,

(1) mixing a support with a metal aqueous solution containing a catalyst component precursor and an active component precursor to form a supported catalyst precursor-containing aqueous solution;

(2) aging and impregnating the supported catalyst precursor-containing aqueous solution to obtain a mixture;

(3) vacuum drying the mixture to coat the catalyst component and active ingredient on the support surface; And

(4) calcining the resultant obtained by the vacuum drying to form a supported catalyst; can be prepared by a method comprising a.

Carbon nanotubes can be prepared by chemical vapor phase synthesis in which carbon nanotubes are grown by chemical vapor phase synthesis through decomposition of a carbon source using the catalyst.

Specifically, the chemical vapor phase synthesis method is a carbon nanotube catalyst is introduced into a fluidized bed reactor and at least one carbon source selected from saturated or unsaturated hydrocarbons having 1 to 4 carbon atoms at 500 ℃ ~ 900 ℃, or the carbon source and hydrogen and nitrogen It can be carried out by injecting a mixed gas. The carbon nanotubes are grown by injecting a carbon source into the catalyst for preparing carbon nanotubes, which may be performed for 30 minutes to 8 hours.

The carbon source may be a saturated or unsaturated hydrocarbon having 1 to 4 carbon atoms, such as ethylene (C ₂ H ₄ ), acetylene (C ₂ H ₂ ), methane (C ₂ H ₄ ), propane (C ₃ H ₈ ), and the like. May be, but is not limited thereto. In addition, the mixed gas of hydrogen and nitrogen transports a carbon source, prevents carbon nanotubes from burning at a high temperature, and assists decomposition of the carbon source.

The carbon nanotubes prepared using the supported catalyst according to the present invention may be obtained in the form of a potato or sphere aggregate having a particle size distribution (D _cnt ) of 0.5 to 1.0. For example, a catalyst obtained by impregnating and calcining a catalyst component and an active ingredient in a spherical or potato granular support also has a spherical or potato form without significant change in shape, and the carbon nanotube aggregates grown on such a catalyst also have a shape. Another feature is to have a spherical or potato shape with only a large diameter without a large change of. Here, the spherical or potato shape refers to a three-dimensional shape such as a spherical and ellipsoidal shape having an aspect ratio of 1.2 or less.

The particle size distribution value (D _cnt ) of the carbon nanotubes is defined by Equation 1 below.

  [Equation 1]

Dcnt = [Dn ₉₀ -Dn ₁₀ ] / Dn ₅₀

Here, Dn ₉₀ is the number average particle diameter measured under 90% in absorbing mode using a Microtrac particle size analyzer after 3 hours of CNT in distilled water, Dn ₁₀ is the number average particle diameter measured under 10%. And Dn ₅₀ is the number average particle diameter measured on a 50% basis.

The particle size distribution value may be preferably 0.55 to 0.95, more preferably 0.55 to 0.9.

In the present invention, the carbon nanotubes may be a bundle type or a non-bundle type having a flatness of 0.9 to 1, and the term 'bundle' used in the present invention, unless otherwise stated, refers to a plurality of carbon nanotubes. It refers to a bundle or rope form, in which the tubes are arranged or intertwined side by side. 'Non-bundle (entangled) type' is a form without a certain shape, such as a bundle or rope shape, in the case of a bundle type CNT bundle may have a diameter of 1 to 50㎛.

The flatness is defined by Equation 2 below.

 [Equation 2]

 Flatness ratio = shortest diameter through the center of CNT / maximum diameter through the center of CNT.

In the present invention, the carbon nanotubes are characterized in that the bulk density (bulk density) is 80 ~ 250kg / m ³ . Specifically, the bulk density is defined by the following Equation 3, the density distribution of the carbon nanotubes can provide a range unique to the present invention.

 [Equation 3]

Bulk Density = CNT Weight (kg) / CNT Volume (m ³ )

 In the present invention, the carbon nanotubes may have an average particle diameter of 100 to 800 µm, and a strand diameter of the carbon nanotubes may be 10 to 50 nm.

 By reacting a metal component remaining in the form of fine powder or impurity in a carbon nanotube having the above properties with a chlorine compound in a high temperature atmosphere to form a metal chlorine, the boiling point can be lowered, and the temperature above the boiling point of the metal chloride The carbon nanotubes may be purified using a process of evaporation and removal under conditions, and the carbon nanotubes manufactured by this method may have improved physical properties, and in particular, thermal stability may be improved, such as high temperature flame retardants and metal composite materials. It can be usefully used for carbon composites used in the environment.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto, and the present invention is merely illustrative for describing the present invention in more detail.

Comparative example  One

Carbon nanotube synthesis was tested in a laboratory scale fixed bed reactor using a Co / Fe-containing metal catalyst for CNT synthesis. Specifically, the catalyst for synthesizing CNT prepared in the above process was mounted in the middle of a quartz tube having an internal diameter of 55 mm, and then heated and maintained at 650 ° C. in a nitrogen atmosphere, while flowing hydrogen gas at a flow rate of 60 sccm. Synthesis was carried out for 2 hours to synthesize an entangled (non-bundle) type carbon nanotube aggregate. The shape of the carbon nanotubes is shown in FIG. 1.

Example  One

20 g of carbon nanotubes prepared in Comparative Example 1 were placed in a firing furnace. The kiln was evacuated to 1 torr and the temperature was raised to 900 ° C inside. Next, chlorine (Cl ₂ ) gas was supplied to 680 torr. Thereafter, the temperature was raised to 1400 ° C. and maintained in a vacuum atmosphere for 2 hours, followed by vacuum cooling. The shape of the purified carbon nanotubes is shown in FIG. 1.

TEM_EDX was measured and observed in FIG. As a result of analyzing the surface elements before and after the purification of carbon nanotubes (Comparative Example 1) and after the purification (Example 1) by means of the TEM-EDX analyzer, no special elements other than carbon were detected on the surface of the purified carbon nanotubes. Could confirm. That is, the peaks detected before and after purification were the same, and no further peaks were generated after purification. Therefore, it can be seen that there is no change of carbon nanotubes by Cl used in the purification.

In addition, I _G / I _D by Raman spectroscopy of carbon nanotubes of Example 1 and Comparative Example 1 was measured at a laser wavelength of 532 nm using DXR Raman Microscope (Thermo Electron Scientific Instruments LLC). Were shown in Figure 3 to the Raman analysis, obtaining the I _G / I _D values are shown in Table 1 below.

division	Cl 2 treatment	I G / I D ratio
		Average	Standard Deviation	Relative standard deviation (%)
Example 1	O	0.99	0.01	1.38
Comparative Example 1	X	0.77	0.02	2.35

From the results of Table 1, the I _G / I _D value of the carbon nanotubes of Example 1 purified by the purification method according to the present invention was increased by more than 20%, which was carbon nano purified by the method according to the present invention It shows that the crystallinity of the tube is significantly improved. In addition, the numerical values of the standard deviation and the relative standard deviation% become smaller, indicating that the purification process was performed uniformly for the entire sample, and secondly, the effect of improving the crystallinity from the purification process was also obtained. It can be shown that the carbon nanotubes having more homogeneous crystallinity can be produced by exhibiting the effect evenly in the first half.

 Accordingly, the method for purifying carbon nanotubes according to the present invention can provide carbon nanotubes having excellent crystallinity without changing the shape and elements of the carbon nanotubes.

The specific parts of the present invention have been described in detail above, and it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

The carbon nanotubes according to the present invention can remove residual metals generated in the manufacturing process of carbon nanotubes using a metal catalyst by reacting with a chlorine compound at a high temperature, thereby effectively removing impurities such as residual metals. Can be removed. In particular, the oxidation stability and conductivity is improved by improving the crystallinity may be useful for use as a composite material of the metal composite and the conductive polymer.

Claims (15)

1. Chlorinating the residual metal by reacting the metal remaining in the carbon nanotubes with a chlorine-containing compound at a first temperature in a vacuum or inert gas atmosphere; And

   Evaporating and removing the chlorinated residual metal at a second temperature (T ₂ ) at a temperature higher than the first temperature (T ₁ );

   By purifying by a method comprising a carbon nanotube characterized in that the average value of the intensity ratio (I _G / I _D ) of the G band and D band measured by Raman spectroscopy increased by more than 20% compared to the carbon nanotube before purification .
2. The method of claim 1,

   Of the G-band and D-band measured in the Raman spectroscopy, the intensity ratio (I _G / I _D) carbon nanotubes, characterized in that an average value of 0.9 to 1.5.
3. The method of claim 1,

   Carbon standard tube characterized in that the standard deviation of the average value of the IG / ID measured by Raman spectroscopy reduced by more than 40% compared to the carbon nanotubes before purification.
4. The method of claim 1,

   Carbon nanotubes, characterized in that the second temperature (T ₂ ) is carried out at a temperature of T ₁ +300 ℃ or more.
5. The method of claim 1,

   Wherein the first temperature is selected from 500 ℃ to 1000 ℃, the second temperature is selected from 800 ℃ to 1500 ℃ carbon nanotubes.
6. The method of claim 1,

   Carbon nanotubes, characterized in that the evaporation at a second temperature and the metal chlorine removal process is carried out in a vacuum or inert gas atmosphere.
7. The method of claim 1,

   Carbon nanotubes, characterized in that the oxidation start temperature of the purified carbon nanotubes is 550 ℃ or more.
8. The method of claim 1,

   Carbon nanotubes, characterized in that the metal impurity content remaining in the purified carbon nanotubes 50ppm or less.
9. The method of claim 1,

   The carbon nanotubes are manufactured using a metal catalyst containing cobalt (Co).
10. The method of claim 9,

    The carbon nanotubes are manufactured using a metal catalyst further comprising at least one metal component of iron (Fe), molybdenum (Mo), vanadium (V) and chromium (Cr).
11. The method of claim 9,

    Carbon nanotubes having a Co content of 40 ppm or less after the purification process of the carbon nanotubes.
12. The method of claim 1,

    The carbon nanotubes are manufactured by chemical vapor deposition (CVD) on a fluidized bed reactor.
13. The method of claim 1,

    Carbon nanotubes, characterized in that the carbon nanotubes are entangled (Entangle) or bundle (Bundle) shape.
14. The method of claim 1,

    Carbon nanotubes, characterized in that the chlorine-containing compound is chlorine (Cl ₂ ) gas or trichloromethane (CHCl ₃ ) gas.
15. The method of claim 1,

    Carbon nanotubes, characterized in that the first temperature is performed at a temperature of 700 ℃ to 900 ℃, the second temperature is 900 ℃ to 1500 ℃.

Images