JP2010132543A - Method for producing and purifying carbon nanotube, carbon nanotube and carbon nanotube element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing/purifying a carbon nanotube without damaging the carbon nanotube, in particular the sidewall thereof. <P>SOLUTION: The method for producing and purifying a carbon nanotube includes (a) a process for producing the carbon nanotube by an arc discharge method in the presence of a catalyst and an optional co-catalyst, (b) a process for obtaining a complex by coordinately bonding a metal element present in the catalyst and/or in the optional co-catalyst, to a substance capable of forming the complex with the metal element in the catalyst and/or in the optional co-catalyst, and (c) a process for removing the complex. The carbon nanotube obtained by the method and an element using the carbon nanotube, are also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing carbon nanotubes (CNT), a method for purifying carbon nanotubes (CNT), carbon nanotubes obtained by these methods, and a carbon nanotube element containing the carbon nanotubes. The present invention relates to a method for producing a nanotube, a method for purifying a carbon nanotube, a carbon nanotube obtained by these methods, and a carbon nanotube element containing the carbon nanotube. Unlike conventional methods, in the production method or purification method of the present invention, the catalyst used in the arc discharge method and any cocatalyst are removed by a coordination bonding step.

  As one-dimensional carbon nanomaterials, carbon nanotubes (CNTs) are attracting increasing attention due to their excellent electrical, mechanical and chemical properties. As research on nanomaterials has become deeper, carbon nanotubes have come to be applied in a wide range of fields such as field emission electron sources, nanofield effect transistors, hydrogen storage materials and high strength fibers.

Carbon nanotubes are divided into single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) depending on the number of carbon atoms that form the tube wall. Multi-walled carbon nanotubes consist of single-walled carbon nanotubes with different diameters You may understand. Single-walled carbon nanotubes and multi-walled carbon nanotubes with a small number of layers occupy important positions in actual research and application because they have excellent performance in electrical properties, thermal properties, mechanical and chemical properties.

Conventional methods for producing carbon nanotubes include arc discharge, chemical vapor deposition (CVD), and laser evaporation. The arc discharge method is one of the most effective methods to date for producing high-quality carbon nanotubes on a large scale.

However, when carbon nanotubes are produced by the arc discharge method, impurities such as graphite fine particles, amorphous carbon, and other forms of carbon nanoparticles are usually generated, and metal catalyst particles and optional promoters are produced. Is also present. These impurities are mixed with the carbon nanotubes, resulting in extreme inconvenience for further research and application on carbon nanotubes. Therefore, in order to obtain carbon nanotubes with higher purity, it is common to purify the manufactured carbon nanotube initial product by each physicochemical method. Commonly used chemical purification methods include a liquid phase oxidation method and a gas phase oxidation method. For example, the hydrothermal method proposed by K. Tohji. T. Goto et al. (K. Tohji. T. Goto et al. J. Phys. Chem. 1996, 101, 1974), the gas proposed by Z. Shi et al. Phase oxidation method (Z. Shi et al. Solid State Commun. 1999, 112, 35), catalytic oxidation method proposed by E. Mizoguti et al. (E. Mizoguti et al. Chem. Phys. Let. 2000, 321,297). There is also extensive research on the nitric acid reflux method, for example, a study by J.L.Zimmerman et al. (J.L.Zimmerman et al. Chem. Mater. 2000, 12, 1361). It has also been discovered that the metal in the reaction product can be effectively removed by a purification method in which amorphous carbon is removed by initial selective oxidation and refluxed with concentrated nitric acid (K. Tohji et al. Nature 1996,383,679).

These purification methods are known in the field, and utilize the characteristics of carbon nanotubes, which are more stable than impurities such as amorphous carbon and metal catalyst particles, and are difficult to oxidize. It can be removed and purified. Examples of the gas phase oxidation method include an oxygen (or air) oxidation method and a carbon dioxide oxidation method depending on the oxidizing atmosphere. Examples of the liquid phase oxidizing agent often used in the liquid phase oxidation method include potassium permanganate, nitric acid solution, potassium dichromate, and the like. In addition, carbon nanotubes are separated by a centrifugal separation method and a physical method such as microfiltration. These methods may be used alone, or one or various combinations thereof may be used. For example, impurities such as amorphous carbon that can be easily removed by gas phase oxidation methods such as air oxidation methods can be removed from carbon nanotubes, and metal catalyst particles that are difficult to remove by liquid phase oxidation methods such as nitric acid oxidation methods. Impurities can be removed from the carbon nanotubes. Moreover, the carbon nanotube after refinement | purification can be obtained by the combination of the said method and centrifugation.

K. Tohji. T. Goto et al. J. Phys. Chem. 1996, 101, 1974 Z. Shi et al. Solid State Commun. 1999, 112, 35 E. Mizoguti et al. Chem. Phys. Let. 2000,321,297 J.L.Zimmerman et al.Chem.Mater.2000,12,1361 K. Tohji et al. Nature 1996,383,679

However, the main problem to date is how to purify the carbon nanotubes produced without destroying the carbon nanotubes. In the prior art, a liquid phase oxidation method is used. For example, the method of purifying by refluxing with nitric acid will destroy the tube wall. Even using the gas phase oxidation method, the carbon nanotubes are also destroyed because the oxidation temperature is high (usually 470 ° C.).

In addition, in the arc discharge method, for example, when a Y-Ni alloy is used as a catalyst, when the reaction is completed, the catalyst remains in or on the surface of the reaction product and is difficult to remove by the inorganic acid reflux method. Even if most of the catalyst particles are removed by a long-time reaction, the carbon nanotubes are also destroyed, and the quality of the carbon nanotubes is lowered, and in particular, the conductivity is lowered.

Moreover, in the case of the strong acid reflux purification method, the obtained carbon nanotubes have the following defects:
A. Carbon nanotubes bend because carbon skeletons have 5 or 7 member rings instead of the usual 6 member rings;
B.Sp ³ hybrid defect (R = H and OH);
C. The carbon structure is destroyed by the oxidation conditions and COOH groups are drawn into the defects; and
D. The end of the carbon nanotube opens, and COOH groups are drawn in and block.
The above defects are shown in FIG.

  Therefore, a method for producing and purifying carbon nanotubes without destroying the carbon nanotubes is required.

By the method of the present invention, carbon nanotubes can be produced and purified without damaging the carbon nanotubes, and particularly without damaging the side walls of the carbon nanotubes.

The first invention of the present invention is:
(A) a step of producing carbon nanotubes by an arc discharge method in the presence of a catalyst and a cocatalyst as necessary;
(B) A complex formed by coordination bonding between a metal element present in the catalyst and / or a necessary co-catalyst and a substance capable of forming a complex with the metal element present in the catalyst and / or the necessary co-catalyst. Obtaining
(C) It aims at providing the manufacturing method of a carbon nanotube including the process of removing the said complex.

In one embodiment of the first invention of the present invention, a promoter is used in the step (a).

In this case, the promoter is preferably FeS.

One aspect of the first invention of the present invention is selected from the group consisting of a lanthanum-based metal oxide, a transition metal, a mixture of nickel and a rare earth element, and a mixture of the catalyst as the catalyst.

In this case, the catalyst is preferably selected from the group consisting of Y—Ni alloy, Fe—Ni alloy, Fe—Co alloy, Co—Ni alloy, Rh—Pt alloy, and Ce—Ni alloy.

In one aspect of the first invention of the present invention, the step (b) comprises:
(D) a step of converting a metal element present in the catalyst and / or a co-catalyst as needed into ions, and (e) forming a complex with the metal element present in the catalyst and / or co-catalyst as needed. A step of coordinating a substance to be obtained with the ion to obtain a complex;
including.

In this case, the step (d)
(F) It is preferable to include a step of oxidizing the catalyst and / or the co-catalyst as necessary to obtain a catalyst and / or an oxide of the co-catalyst as needed.
Further, the substance capable of forming a complex with the metal element present in the catalyst and / or the co-catalyst as required is more preferably selected from aminopolycarboxylic acids.
In this embodiment, the aminopolycarboxylic acid is ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid ( DTPA) and triethylenetetraaminehexaacetic acid (TTHA) are preferred.

At this time, the aminopolycarboxylic acid is more preferably triethylenetetraaminehexaacetic acid (TTHA).

Furthermore, it is more preferable to convert the complex formed by the aminopolycarboxylic acid into a salt form so as to promote the removal of the complex.

In one aspect of the first invention of the present invention, the step (d) further comprises
(G) The process of making the said oxide and an acid react and obtaining the metal element ion of a catalyst and / or a promoter as needed.

  In one aspect of the first invention, the substance capable of forming a complex with a metal element present in the catalyst and / or a co-catalyst as required includes tetrahydrofuran, trialkylphosphine, ε-caprolactone, ε-caprolactam, dimethylformamide, And selected from the group consisting of dimethyl sulfoxide.

In one embodiment of the first invention, the complex includes {M [(NC) ₂ CC (OCH ₂ CH ₂ OH) C (CN) ₂ ] ₂ (4,4′-bPy) (H ₂ O) ₂ }, Binuclear [M ′ {(phen) ₂ } ₂ V ₄ O ₁₂ ] C ₆ H ₁₂ Oki H ₂ O and [Ni (L) (H ₂ O) ₃ 2H ₂ O] M is selected from the group consisting of Ni, Co and Fe, M ′ is selected from the group consisting of Ni and Co, bPy is bipyridine, phen is a phenyl group, and L is (2-methoxycarbonylmethylimino-5 -Methyl-thiazol-3-yl-acetic acid).

As a variant of the above aspect of the invention, the step (f) includes oxidizing the catalyst and / or the co-catalyst as required with an oxygen-containing gas.

In this case, the time and temperature for oxidation with the oxygen-containing gas are preferably sufficient to convert the catalyst and / or the co-catalyst, if necessary, to oxide. More preferably, the oxygen-containing gas is air. Further, the oxidation temperature is preferably 80 to 300 ° C., and the oxidation time is more preferably 1 to 20 hours.

As one aspect of the first invention of the present invention, the method of the present invention further includes a step of centrifuging after removing the complex.

At this time, it is preferable to perform the centrifugation step at 5000 to 30000 rpm for 1 to 20 hours.

In all aspects of the first invention of the present invention, the carbon nanotubes are preferably single-walled carbon nanotubes.

The second invention of the present invention is:
A method for purifying carbon nanotubes produced by an arc discharge method in the presence of a catalyst and a cocatalyst as required,
(I) A complex in which a metal element present in a catalyst and / or a co-catalyst as required and a substance capable of forming a complex with the metal element present in the catalyst and / or a co-catalyst as needed are coordinated. Obtaining
(II) A method for purifying carbon nanotubes comprising the step of removing the complex.

  In one aspect of the second invention of the present invention, a promoter is used in the arc discharge method.

  In this case, the promoter is preferably FeS.

In one embodiment of the second invention of the present invention, the catalyst is selected from the group consisting of lanthanum-based metal oxides, transition metals, a mixture of nickel and rare earth elements, and a mixture of the aforementioned catalysts.

In this case, the catalyst is preferably selected from the group consisting of Y-Ni alloys, Fe-Ni alloys, Fe-Co alloys, Co-Ni alloys, Rh-Pt alloys, and Ce-Ni alloys.

In one aspect of the second invention of the present invention, the step (I) comprises:
(III) a step of converting a metal element present in the catalyst and / or a co-catalyst as needed into ions, and (IV) forming a complex with the metal element present in the catalyst and / or co-catalyst as necessary. A step of coordinating a substance to be obtained with the ion to obtain a complex is included.
At this time, the step (III)
(V) It is preferable to include a step of oxidizing the catalyst and / or the co-catalyst as necessary to obtain a catalyst and / or an oxide of the co-catalyst as necessary.

  At this time, the substance capable of forming a complex with the metal element present in the catalyst and / or the co-catalyst as required is more preferably selected from aminopolycarboxylic acids.

In this embodiment, the aminopolycarboxylic acid is ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid ( DTPA) and triethylenetetraaminehexaacetic acid (TTHA) are preferred.

At this time, the aminopolycarboxylic acid is more preferably triethylenetetraaminehexaacetic acid (TTHA).

Furthermore, it is more preferable to convert the complex formed by the aminopolycarboxylic acid into a salt form so as to promote the removal of the complex.

In one aspect of the second invention of the present invention, the step (III) further comprises
(VI) A step of reacting the oxide with an acid to obtain a metal element ion of a catalyst and / or a promoter as required.

In one aspect of the second invention, as a substance capable of forming a complex with the metal element present in the catalyst and / or a co-catalyst as necessary, tetrahydrofuran, trialkylphosphine, ε-caprolactone, ε-caprolactam, dimethylformamide, And selected from the group consisting of dimethyl sulfoxide.

In one embodiment of the second invention, the complex includes {M [(NC) ₂ CC (OCH ₂ CH ₂ OH) C (CN) ₂ ] ₂ (4,4′-bPy) (H ₂ O) ₂ }, Binuclear [M ′ {(phen) ₂ } ₂ V ₄ O ₁₂ ] C ₆ H ₁₂ Oki H ₂ O and [Ni (L) (H ₂ O) ₃ 2H ₂ O] M is selected from the group consisting of Ni, Co and Fe, M ′ is selected from the group consisting of Ni and Co, bPy is bipyridine, phen is a phenyl group, and L is (2-methoxycarbonylmethylimino-5 -Methyl-thiazol-3-yl-acetic acid).

As a modification of the embodiment of the present invention, the step (f) includes oxidizing the catalyst and / or the co-catalyst as necessary with an oxygen-containing gas.

At this time, the time and temperature for oxidizing with the oxygen-containing gas are preferably sufficient to convert the catalyst and / or the co-catalyst as required to an oxide. More preferably, the oxygen-containing gas is air. Further, the oxidation temperature is preferably 80 to 300 ° C., and the oxidation time is more preferably 1 to 20 hours.

As one aspect of the second invention of the present invention, the method of the present invention further includes a step of centrifuging after removing the complex.

At this time, it is preferable to perform the centrifugation step at 5000 to 30000 rpm for 1 to 20 hours.

In all aspects of the second invention of the present invention, the carbon nanotubes are preferably single-walled carbon nanotubes.

The third invention of the present invention provides a carbon nanotube produced by the method described in the first and second inventions of the present invention. Compared with the carbon nanotubes obtained by the prior art method, the tube wall of the carbon nanotubes obtained by the method of the present invention is not destroyed.

The fourth invention of the present invention provides a carbon nanotube device including the carbon nanotube of the third invention of the present invention.
In each invention of the present invention, the carbon nanotube (CNT) is preferably a single-walled carbon nanotube (SWNT).

Other objects and inventions of the present invention will become apparent from the following detailed description, but the detailed description and specific examples show preferred embodiments of the present invention. The present invention is merely an example, and the present invention can be arbitrarily modified and implemented without departing from the gist thereof.

By the method of the present invention, carbon nanotubes can be produced and purified without damaging the carbon nanotubes, and particularly without damaging the side walls of the carbon nanotubes.

It is a schematic diagram which shows the carbon nanotube obtained by acid reflux. It is a schematic diagram which shows the arc furnace used for manufacture of a carbon nanotube by this invention. It is a schematic diagram which shows refine | purifying a carbon nanotube by CYDTA. It is a figure which shows the Raman spectrum of the carbon nanotube refine | purified by EDTA and CYDTA. FIG. 4 also shows the spectrum of a commercially available P3 carbon nanotube (P3, purity greater than 85% from Carbon Solutions. INC.). It is a figure which shows the XPS spectrum of the carbon nanotube refine | purified by EDTA. It is a figure which shows the SEM photograph of the carbon nanotube which is not refine | purified, and the figure which shows the SEM photograph of the carbon nanotube refine | purified by TTHA. It is a figure which shows the TEM photograph of the carbon nanotube refine | purified with TTHA. In FIG. 7, FIG. 7a and FIG. 7b differ only in the amplification factor. It is a figure which shows the Raman spectrum of the carbon nanotube before and behind refinement | purification by TTHA. It is a figure which shows the XPS spectrum of the carbon nanotube refine | purified with TTHA, and the carbon nanotube processed with the conventional acid. It is a figure which shows the carbon nanotube film manufactured with the carbon nanotube refine | purified by TTHA. It is a figure which shows the sheet resistance of the film manufactured by the carbon nanotube film manufactured by the film-forming example 1 and the comparative example 1. FIG. It is a figure which shows the steam generator used for this invention. It is a schematic diagram which shows the cross section of the structure of the glass casing of the steam generator shown to FIG. 12a.

Exemplary embodiments of the present invention will now be described in detail with reference to the drawings.
First invention of the present invention

The first invention of the present invention is:
(A) a step of producing carbon nanotubes by an arc discharge method in the presence of a catalyst and a cocatalyst as necessary;
(B) A complex formed by coordination of a metal element present in the catalyst and / or a co-catalyst as necessary and a substance capable of forming a complex with the metal element present in the catalyst and / or the co-catalyst as necessary. Obtaining
(C) A method for producing a carbon nanotube including the step of removing the complex is provided.

  Next, each step will be described in detail.

(1) Arc discharge method

The arc discharge method is one of the earliest processes for producing carbon nanotubes. The arc discharge method is not particularly limited as a method for producing the carbon nanotube of the present invention. In the present invention, unpurified carbon nanotubes can be obtained by using a normal arc discharge method. Next, we will briefly explain the equipment, conditions and materials used in the arc discharge method.

FIG. 2 is a schematic view showing an arc furnace 100 for producing carbon nanotubes in the embodiment of the present invention. The arc furnace includes a vacuum chamber 160, a cathode terminal 110, a cathode 120, an anode 130, an anode terminal 140, and a linear motion device 150. The cathode 120 is usually a graphite rod having a large diameter (for example, about 13 mm), but a copper-based metal electrode may be used. The anode 130 is a graphite rod having a small diameter (for example, about 6 mm).

In one embodiment of the present invention, an anode graphite rod used for the anode 130 is manufactured as follows. A hole is made in the center of the anode graphite rod. An anode mixture obtained by crushing a catalyst and a co-catalyst as required and then uniformly mixing with graphite is filled into the pores of the anode graphite rod and packed to form the anode 130 for arc discharge. Further, the anode 130 can be formed by mixing a catalyst and an optional co-catalyst into graphite to obtain an anode mixture, and forming the mixture to form an anode graphite rod.

Prior to arcing, the vacuum chamber 160 is aspirated and an inert gas (eg, helium gas or argon gas), hydrogen, nitrogen or a mixture of these gases is introduced as a protective gas. When the power is connected, the distance between the cathode 120 and the anode 130 is adjusted by the linear motion device 150 so that a stable arc discharge is performed between the anode 130 and the cathode 120 (this distance is usually a predetermined constant value). For example, about 1 to 5 mm). Initially, cathode 120 and anode 130 should not be in contact, so no initial current is generated. Then, the anode 120 is moved and approaches the cathode 130 until an arc is generated. During discharge, a high-speed plasma flow is generated between the anode 130 and the cathode 120, the surfaces of the cathode 120 and the anode 130 reach extremely high temperatures (for example, about 3000 ° C. or more and 5000 ° C. or more, respectively), and the anode 130 is rapidly carbonized. It is evaporated as a cluster and gradually consumed. In the high temperature region between the cathode 120 and the anode 130, the carbon clusters evaporated from the anode 130 can form carbon nanotubes, and these carbon nanotubes fill the vacuum chamber, and the walls of the vacuum chamber 160 and / or Alternatively, it is deposited on the cathode 120. These evaporated carbon clusters can fill the vacuum chamber and nucleate and grow at the cathode 120, the vacuum chamber walls, etc. to obtain carbon nanotubes. The anode generally consumes approximately enough, and after completing the discharge reaction, the vacuum chamber is cooled.

After the reaction is over and fully cooled, the cloth-like soot product on the wall of the vacuum chamber 160, the web-like soot product between the chamber wall and the cathode, the cathode End deposits and “collar-like soot” around the deposits are collected in the vacuum chamber 160. The obtained carbon nanotubes are usually bonded by van der Waals force and are arranged in a hexagonal crystal structure. Carbon nanotubes, especially single-walled carbon nanotubes, appear in three places, for example, mainly cloth soot products, reticulated soot products, and “collar” soot products. Among these three, the purity of carbon nanotubes in reticulated soot products, especially single-walled carbon nanotubes, is the highest, the purity of cloth soot products is the lowest, and the purity of “collar” soot products is between. Carbon nanotubes exist with impurities such as amorphous carbon and metal catalyst particles. These impurities can be removed by subsequent purification steps. This point will be described in detail later.

In the process for producing the carbon nanotube of the present invention, a catalyst is required. The catalyst plays an important role in the growth of carbon nanotubes, especially single-walled carbon nanotubes. The catalyst used in the present invention can be selected from the group consisting of lanthanum-based metal oxides, transition metals, mixtures of nickel and rare earth elements, and mixtures of the aforementioned catalysts. Further, the catalyst may be a mixture of a rare earth element such as Y, Ce, Er, Tb, Ho, La, Nd, Gd, Dy or a mixture thereof and metallic nickel (Ni). In one embodiment of the present invention, the catalyst is preferably selected from the group consisting of Y—Ni alloy, Fe—Ni alloy, Fe—Co alloy, Co—Ni alloy, Rh—Pt alloy, and Ce—Ni alloy.

In the method for producing carbon nanotubes of the present invention, a promoter may be used. In general, cocatalysts also play an important role in the growth of carbon nanotubes, especially single-walled carbon nanotubes, especially in increasing the purity of carbon nanotubes and controlling the diameter distribution of carbon nanotubes. It seems. Therefore, in the present invention, it is preferable to use FeS as a promoter.

In the case of using a cocatalyst in the present invention, the proportion of the catalyst and the cocatalyst may be arbitrarily proportional as long as the growth of the carbon nanotubes and the properties such as the purity and diameter distribution of the carbon nanotubes are not adversely affected. Can be used.

Usually, the weight ratio of the catalyst to the cocatalyst is 1 to 20: 1, preferably 5 to 15: 1, more preferably 10: 1. However, a weight ratio other than the above range may be used depending on specific conditions. Good.

In the process of producing carbon nanotubes by the arc discharge method of the present invention, a carbon source is further required. The carbon source is preferably graphite. In the present invention, the catalyst and the carbon source may be used in any proportion as long as the growth of the carbon nanotubes and the properties such as the purity and diameter distribution of the carbon nanotubes are not adversely affected. it can. In one embodiment, the molar ratio of carbon source to catalyst is 1-50: 1, preferably 5-30: 1, more preferably 15: 1.

In a more preferred embodiment of the present invention, the carbon source is graphite, the catalyst is a Y-Ni alloy, and the promoter is FeS.

In the arc discharge method, a protective gas such as an inert gas (helium gas, argon gas, or a mixed gas thereof), hydrogen, nitrogen, or a mixture of these gases is often used. Argon gas is a common protective gas. The pressure when using hydrogen may be lower than the pressure of argon gas. In addition, since hydrogen has higher thermal conductivity, C—H bonds can be formed with carbon, and amorphous carbon and the like can be etched, so that purer carbon nanotubes can be synthesized. The pressure of the protective gas may be about 6.67 to 203 kPa, preferably 13.3 to 160 kPa, more preferably 66.7 to 120 kPa, for example 80.0 to 93.3 kPa.

In order to generate a discharge between the anode and the cathode, the current is usually 30A to 200A, preferably 70 to 120A, for example 100A. If the current is too small, a stable arc cannot be formed. On the other hand, if the current is too large, impurities such as amorphous carbon and graphite particles increase, and subsequent purification treatment becomes difficult. The DC voltage is about 20-40V, for example, 30V. Carbon nanotubes can sinter together with other by-products like impurities such as amorphous carbon and graphite particles, making subsequent separation and purification difficult, making it more pure with a perfect structure In order to produce carbon nanotubes, the temperature of the graphite cathode is often lowered by a method such as water cooling. For example, the cathode graphite rod can be fixed to a water-cooled copper base so as to lower the temperature of the graphite cathode. In addition, the use of a metal that has a better thermal conductivity, such as copper (Cu), that easily dissipates heat, contributes to the formation of carbon nanotubes. During discharge, the temperature in the vacuum chamber 160 can be further controlled using a temperature control device in order to prevent the temperature in the vacuum chamber 160 from being too low and increasing impurities such as amorphous carbon.

In addition, arc discharge in the arc furnace 100 shown in FIG. 2 occurs between the opposing end faces of the cathode and anode, but the cathode and anode may be placed on the same side. In this case, by placing a certain angle between the cathode and the anode, the discharge between the cathode and the anode becomes a discharge between the points, and the product is in the form of a sheet in the vacuum chamber 160. Since it adheres to a wall etc., productivity of a carbon nanotube can be improved.

After the arc discharge reaction, it is common to collect the reticulated soot product and perform the next purification step. This is because the carbon nanotubes in the product, especially single-walled carbon nanotubes, have the highest purity.

(2) Purification process-complex formation and removal

As described above, high temperature oxidation or strong acid oxidation (reflux) methods are often used to remove impurities in carbon nanotubes, particularly to remove residual catalyst and cocatalyst as needed. However, these methods damage the carbon nanotubes, particularly the sidewalls of the carbon nanotubes.

In order to eliminate the destruction of carbon nanotubes due to high temperature oxidation or strong acid oxidation of the prior art, the inventors of the present invention have studied the carbon nanotubes based on the coordination bond technology without destroying the quality of the carbon nanotubes. It has been discovered that the remaining catalyst and the cocatalyst can be removed if necessary.

Compared with the conventional purification methods, the purification process based on the coordination bond technique is mild and does not damage the side walls of the carbon nanotubes. Therefore, the quality of the carbon nanotubes produced by the method of the present invention is higher than that of carbon nanotubes obtained by the prior art, and the conductivity is remarkably improved.

By coordinating the catalyst and the metal element present in the co-catalyst, if necessary, the catalyst and the metal element present in the co-catalyst as needed, the catalyst and the metal element present in the co-catalyst as needed. It has been discovered by the inventors of the present invention that the cocatalyst can be removed.

The term “substance capable of forming a complex with a metal element present in a catalyst and a co-catalyst as required” means a substance capable of forming a complex with a metal element used in the catalyst or the co-catalyst, or a catalyst and co-catalyst. A substance that can form a complex with a metal element used in a catalyst. As described above, examples of the catalyst used in the present invention include oxides of transition metals or lanthanum metals. The catalyst may be a mixture of a rare earth element such as Y, Ce, Er, Tb, Ho, La, Nd, Gd, Dy, or a mixture thereof and metallic nickel (Ni). Therefore, in order to remove the catalyst from the obtained carbon nanotubes, the above-mentioned transition metals, lanthanum metals, and rare earths can be used as “substances capable of forming a complex with the metal elements present in the catalyst and the promoter as required”. Substances that can form complexes with metals etc. should be used.

In the arc discharge method, a Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy, or Ce-Ni alloy is often used as a catalyst. Therefore, in the present invention, a substance that can form a complex with Y, Ni, F, Co, Rh, Pt, Ce, etc. is a “substance that can form a complex with a metal element present in a catalyst and a co-catalyst as needed”. Is preferable.

When producing a carbon nanotube by the arc discharge method, when using a cocatalyst, the cocatalyst dose may be ignored with respect to the catalyst dose. Similarly, the amount of promoter present in the produced carbon nanotubes is negligibly small relative to the amount of catalyst. Therefore, when selecting the substance, only the metal elements present in the catalyst should be considered.

Nevertheless, it is more preferable to consider the metal elements used for the catalyst and the cocatalyst at the same time. It is further preferred to select a substance that can form a complex with all the metal elements present in the catalyst and the cocatalyst. This is because all the existing catalyst and cocatalyst can be removed with only one substance.

A certain substance can form a complex with a single metal (zero-valent metal), but an alloy material is often used in the arc discharge process, so that it becomes difficult for the substance and the element of the alloy material to form a complex directly. Therefore, in the present invention, it is preferable that the metal element in the catalyst and / or the cocatalyst as necessary is converted into an ionic form and coordinated.

There is no particular limitation on the method for converting the metal element into the ion form, and various methods can be employed. For example, a metal element can be converted into a metal ion by a strong acid oxidation method. However, in order to minimize damage to the generated carbon nanotubes, it is conceivable to first convert the metal element into an oxide by an appropriate oxidation method and obtain a metal ion with an appropriate acid. Since the oxidation method and acid used at this time are milder than the conditions used in the conventional purification method, the quality of the carbon nanotube is not significantly reduced.

In one embodiment, an acidic substance such as an aminopolycarboxylic acid is used as the “substance that can form a complex with the metal element present in the catalyst and the co-catalyst as necessary”, so that the metal oxide is converted into a metal ion. Not only can it be converted, it can also be coordinated with the metal ion to form a complex. In this case, it is not necessary to obtain metal ions with other acids.

In some embodiments, the complex formed may be in other suitable forms, such as salt forms, in order to increase the solubility in a solvent (usually water) to facilitate removal of the complex. Can be converted to In this way, the solubility of the complex is enhanced, and by filtering the carbon nanotubes that are not dissolved by a method such as a filtration method, the complex can be removed and the catalyst and / or promoter can remain as little as possible. . Any filtration media may be used in the filtration method. For example, a polytetrafluoroethylene filtration membrane is used.

For example, when aminopolycarboxylic acid is used as the substance, it is preferable to convert the formed aminopolycarboxylic acid complex into a salt form. At this time, an appropriate alkaline solution such as NaOH or KOH can be added to convert the salt form so that the pH becomes basic.

When aminopolycarboxylic acid is used, the aminopolycarboxylic acid is not particularly limited. For example, ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid (DTPA), and triethylenetetraaminehexa Acetic acid (TTHA) can be used.

Aminopolycarboxylic acids can form complexes with Y. At this time, as aminopolycarboxylic acid, ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid (DTPA) And triethylenetetraamine hexaacetic acid (TTHA) are preferred. These structures are shown below:

The structure of the complex formed by Y and EDTA, CYDTA, DTPA and TTHA is shown below:

Ni can also form complexes with TTHA as follows:

Of these, triethylenetetraamine hexaacetic acid (TTHA) is most preferred. This is because when aminopolycarboxylic acid is used, the purity and transparency of carbon nanotubes purified by TTHA is the best.

FIG. 3 is a schematic view showing carbon nanotubes purified by CYDTA. From FIG. 3, it can be seen that CYDTA can form a complex with Y present on the carbon nanotube and can be separated from the carbon nanotube.

Examples of substances that can form a complex with Y include tetrahydrofuran, trialkylphosphine, ε-caprolactone, ε-caprolactam, dimethylformamide, dimethyl sulfoxide, and the like. However, it is not limited to the substance. Regarding substances that can form complexes with Y and the complexes formed, “Anhydrous scandium, yttrium, lanthanide and actinide halide complexes with neutral oxygen and nitrogen donor ligands” (Shashank Mishra, Coordination Chemistry Review 252 (2008) 1996-2025) You can refer to it. The above document is cited here for reference. Catalysts such as Y in Y-Ni alloys can be removed with any substance listed in the above literature that can form a complex with Y.

As an example of a complex formed with Ni, Co, Fe, {M [(NC) ₂ CC (OCH ₂ CH ₂ OH) C (CN) ₂ ] ₂ (4,4'-bPy) (H ₂ O) ₂ } (M is selected from the group consisting of Ni, Co, and Fe) (Inorganica Chemica Acta, Vol. 361, Issues 14-15, 1 October 2008, Pages 3856-3862). Obtain binuclear [M ′ {(phen) ₂ } ₂ V ₄ O ₁₂ ] C ₆ H ₁₂ O ki H ₂ O (M is selected from the group consisting of Co and Ni) according to the above-mentioned literature by an appropriate substance. (Inorganica Chemica Acta, Vol. 361, Issues 12-13, 1 September 2008, Pages 3681-3689). Substances listed in the above literature for obtaining the complex can also be employed in the present invention.

A substance capable of forming a complex with Ni can be used. As a complex formed, [Ni (L) (H ₂ O) ₃ 2H ₂ O] (L represents (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl-acetic acid)), Ni [ P (Ph ₂ ) —N (H) —CH ₂ Py] ₄ (wherein Ph represents a phenyl group and Py represents pyridine). Other applicable substances include Inorganica Chemica Acta, Vol. 361, Issues 12-13, 1 September 2008, Pages 3723-3729 and Journal of Organometallic Chemistry, Vol. 693, Issue 12, 1, June 2008, Pages 2171- 2176 and the materials listed in Inorganic ChemistRY Communications, In Press, Corrected Proof, Available on line 17, May 2008, and the complexes formed.

Regarding substances that can form complexes with Fe, Inorganica Chimica Acta, Vol 361, Issues 14-15, 1 October 2008, Pages 3926-3930; Coordination Chemistry Reviews, Vol. 229, Issues 1-2, 9, July 2002, Pages 27-35; Coordination Chemistry Reviews, Vol. 232, Issues 1-2, October 2002, Pages 151-171; and Coordination Chemistry Reviews, Vol. 233-234, 1 November 2002, Pages 273-287 can do.

For substances that can form complexes with Fe, Co, Ni, Coordination Chemistry Reviews, Vol. 12, Issue 2 April 1974, Pages 151-184; Coordination Chemistry Reviews, Vol. 11, Issue 4, December 1973, Pages 343-402 And Coordination Chemistry Reviews, Vol. 2, Issue 2, September 1967, Pages 173-193.

The above references are cited here for reference.

The kind of the substance can be selected depending on the form of the catalyst and / or promoter (alloy, simple substance, compound, etc.) and the kind of the metal element present.

In addition, how to perform the coordination and bonding process is determined according to the specific situation of the catalyst and / or the cocatalyst. For example, the specific catalyst and / or cocatalyst determines whether to convert the catalyst and / or cocatalyst to ions. In the case of conversion by an oxidation method, it is further necessary to determine whether the metal elements in the catalyst and / or promoter field need to be converted to ions with an acid other than the above substances.

As described above, in order to convert the metal element in the catalyst and / or the cocatalyst into ions, the metal element can be first converted into an oxide by an appropriate oxidation method. At this time, it is preferable to oxidize the catalyst and / or promoter with an oxygen-containing gas (preferably air). Oxidation conditions using oxygen-containing gases are much milder than conventional gas phase oxidation purification conditions. In general, there is no specific limitation on the time and temperature required to oxidize the catalyst and / or promoter with an oxygen-containing gas, and the time and temperature sufficient to convert the catalyst and / or promoter to its oxide. I just need it. Usually, the oxidation temperature may be 80-300 ° C, more preferably 100-200 ° C, most preferably 150-200 ° C. The oxidation time depends on the oxidation temperature and can vary. In general, the oxidation time may be 1-20 hours, preferably 5-15 hours, more preferably 8-10 hours. In view of the above, the oxidation used in the method for producing carbon nanotubes of the present invention is low-temperature oxidation as compared with a high-temperature oxidation method that is usually used (generally, the oxidation temperature is 470 ° C.). Therefore, this low temperature oxidation does not destroy the carbon nanotubes.

The method for producing a carbon nanotube of the present invention may further include a step of centrifuging after removing the complex. Thereby, the amorphous carbon remaining in the carbon nanotube is removed, and the purity of the carbon nanotube is further increased. The centrifugation step may be any centrifugation speed, but higher speed centrifugation is preferred. For example, a speed of 5000 to 30000 rpm may be used, but a centrifugal speed of 10,000 to 20000 is preferable. The time of centrifugation is related to the speed of centrifugation. In general, centrifugation can be performed in 1 minute to 20 hours, but preferably in 2 to 10 hours, for example, 3 hours.

  The carbon nanotube obtained by the method of the present invention is preferably a single-walled carbon nanotube. The single-walled carbon nanotube is selected from the group consisting of metallic single-walled carbon nanotube (M-SWNT), semiconducting single-walled carbon nanotube (S-SWNT), and combinations thereof.

Second invention of the present invention

The second invention of the present invention is a method for purifying carbon nanotubes produced by an arc discharge method in the presence of a catalyst and optionally a cocatalyst,
(I) a step of obtaining a complex by coordinating a catalyst and a metal element present in a co-catalyst as needed, and a substance capable of forming a complex with the metal element present in the co-catalyst as needed. ,
(II) It aims at providing the method of purifying the carbon nanotube including the process of removing the said complex.

  By the purification method of the second invention of the present invention, the carbon nanotubes can be purified by the arc discharge method, the purity of the carbon nanotubes can be increased, and the characteristics thereof can be improved.

The carbon nanotube applicable to the second invention of the present invention is not particularly limited, and may be a carbon nanotube by an arc discharge method.

As known to those skilled in the art, when producing carbon nanotubes by the arc discharge method, a catalyst and an optional co-catalyst are employed. The catalyst is generally a transition metal, a lanthanum metal oxide, or a mixture thereof. The catalyst may be a mixture of a rare earth element such as Y, Ce, Er, Tb, Ho, La, Nd, Gd, Dy, or a mixture thereof and metallic nickel (Ni). In one embodiment of the present invention, the catalyst is preferably a Y—Ni alloy, a Fe—Ni alloy, a Fe—Co alloy, a Co—Ni alloy, a Rh—Pt alloy, or a Ce—Ni alloy.

In general, a promoter such as FeS is used in the arc discharge method.

By the purification method of the second invention of the present invention, the catalyst and / or promoter remaining in the carbon nanotubes obtained by the arc discharge method can be effectively removed without negatively affecting the quality of the carbon nanotubes, particularly the conductivity. .

In the method of the second invention of the present invention, “a substance capable of forming a complex with a catalyst and a metal element present in a promoter as necessary” is coordinated with a metal element present in a catalyst and a promoter as necessary. Carbon nanotubes are purified by bonding to form a complex and removing the complex.

  In the second invention, in order to remove the catalyst from the obtained carbon nanotube, a substance capable of forming a complex with a transition metal, a lanthanum metal, a rare earth metal, etc. Should be "substances that can form".

In the arc discharge method, a Y—Ni alloy, Fe—Ni alloy, Fe—Co alloy, Co—Ni alloy, Rh—Pt alloy, or Ce—Ni alloy is often used as a catalyst. Therefore, in the present invention, a substance that can form a complex with Y, Ni, F, Co, Rh, Pt, Ce, etc. is referred to as “a substance that can form a complex with a metal element present in a catalyst and an optional cocatalyst. Is preferred.

When producing a carbon nanotube by the arc discharge method, when using a cocatalyst, the cocatalyst dose may be ignored with respect to the catalyst dose. Similarly, the amount of promoter present in the produced carbon nanotubes is negligibly small relative to the amount of catalyst. Therefore, when selecting the substance, only the metal elements present in the catalyst should be considered.

Nevertheless, it is more preferable to consider the metal elements used for the catalyst and the cocatalyst at the same time. It is further preferred to select a substance that can form a complex with all the metal elements present in the catalyst and the cocatalyst. This is because all the existing catalyst and cocatalyst can be removed with only one substance.

A certain substance can form a complex with a single metal (zero-valent metal), but an alloy material is often used in the arc discharge process, so that it becomes difficult for the substance and the element of the alloy material to form a complex directly. Therefore, in the present invention, it is preferable that the metal element in the catalyst and / or the cocatalyst as necessary is converted into an ionic form and coordinated.

There is no particular limitation on the method for converting the metal element into the ion form, and various methods can be employed. For example, a metal element can be converted into a metal ion by a strong acid oxidation method. However, in order to minimize damage to the generated carbon nanotubes, it is conceivable to first convert the metal element into an oxide by an appropriate oxidation method and obtain a metal ion with an appropriate acid. Since the oxidation method and acid used at this time are milder than the conditions used in the conventional purification method, the quality of the carbon nanotube is not significantly reduced.

In one embodiment, an acidic substance such as an aminopolycarboxylic acid is used as the “substance that can form a complex with the metal element present in the catalyst and the co-catalyst as necessary”, so that the metal oxide is converted into a metal ion. Not only can it be converted, it can also be coordinated with the metal ion to form a complex. In this case, it is not necessary to obtain metal ions with other acids.

In some embodiments, the complex formed may be in other suitable forms, such as salt forms, in order to increase the solubility in a solvent (usually water) to facilitate removal of the complex. Can be converted to In this way, the solubility of the complex is enhanced, and by filtering the carbon nanotubes that are not dissolved by a method such as a filtration method, the complex can be removed and the catalyst and / or promoter can remain as little as possible. . Any medium can be used in the filtration method. For example, a polytetrafluoroethylene filtration membrane is used.

For example, when aminopolycarboxylic acid is used as the substance, it is preferable to convert the formed aminopolycarboxylic acid complex into a salt form. At this time, an appropriate alkaline solution such as NaOH or KOH can be added to convert the salt form so that the pH becomes basic.

When aminopolycarboxylic acid is used, the aminopolycarboxylic acid is not particularly limited. For example, ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid (DTPA), and triethylenetetraaminehexa Acetic acid (TTHA) can be used.

Aminopolycarboxylic acids can form complexes with Y. At this time, as aminopolycarboxylic acid, ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid (DTPA) And triethylenetetraamine hexaacetic acid (TTHA) are preferred. These structures are shown below:

The structure of the complex formed by Y and EDTA, CYDTA, DTPA and TTHA is shown below:

Ni can also form complexes with TTHA as follows:

Of these, triethylenetetraamine hexaacetic acid (TTHA) is most preferred. This is because when aminopolycarboxylic acid is used, the purity and transparency of carbon nanotubes purified by TTHA is the best.

Examples of substances that can form a complex with Y include tetrahydrofuran, trialkylphosphine, ε-caprolactone, ε-caprolactam, dimethylformamide, dimethyl sulfoxide, and the like. However, it is not limited to the substance. Regarding substances that can form complexes with Y and the complexes formed, “Anhydrous scandium, yttrium, lanthanide and actinide halide complexes with neutral oxygen and nitrogen donor ligands” (Shashank Mishra, Coordination Chemistry Review 252 (2008) 1996-2025) You can refer to it. The above document is cited here for reference. Catalysts such as Y in Y-Ni alloys can be removed with any substance listed in the above literature that can form a complex with Y.

As an example of a complex formed with Ni, Co, Fe, {M [(NC) ₂ CC (OCH ₂ CH ₂ OH) C (CN) ₂ ] ₂ (4,4'-bPy) (H ₂ O) ₂ } (M is selected from the group consisting of Ni, Co, and Fe) (Inorganica Chemica Acta, Vol. 361, Issues 14-15, 1 October 2008, Pages 3856-3862). Obtain binuclear [M ′ {(phen) ₂ } ₂ V ₄ O ₁₂ ] C ₆ H ₁₂ O-ki H ₂ O (M is selected from the group consisting of Co and Ni) according to the above literature by an appropriate substance. (Inorganica Chemica Acta, Vol. 361, Issues 12-13, 1 September 2008, Pages 3681-3689). Substances listed in the above literature for obtaining the complex can also be employed in the present invention.

Any substance that can form a complex with Ni can be used. Complexes formed include [Ni (L) (H ₂ O) ₃ 2H ₂ O] (L represents (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl-acetic acid)), Ni [ P (Ph ₂ ) —N (H) —CH ₂ Py] ₄ (Ph represents a phenyl group, Py represents pyridine). Other applicable substances include Inorganica Chemica Acta, Vol.361, Issues 12-13, 1 September 2008, Pages 3723-3729 and Journal of Organometallic Chemistry, Vol. 693, Issue 12, 1, June 2008, Pages 2171- 2176 and the materials listed in Inorganic ChemistRY Communications, In Press, Corrected Proof, Available on line 17, May 2008, and the complexes formed.

Regarding substances that can form complexes with Fe, Inorganica Chimica Acta, Vol 361, Issues 14-15, 1 October 2008, Pages 3926-3930; Coordination Chemistry Reviews, Vol. 229, Issues 1-2, 9, July 2002, Pages 27-35; Coordination Chemistry Reviews, Vol. 232, Issues 1-2, October 2002, Pages 151-171; and Coordination Chemistry Reviews, Vol. 233-234, 1 November 2002, Pages 273-287 can do.

For substances that can form complexes with Fe, Co, Ni, Coordination Chemistry Reviews, Vol. 12, Issue 2 April 1974, Pages 151-184; Coordination Chemistry Reviews, Vol. 11, Issue 4, December 1973, Pages 343-402 And Coordination Chemistry Reviews, Vol. 2, Issue 2, September 1967, Pages 173-193.

The above references are cited here for reference.

The kind of the substance can be selected depending on the form of the catalyst and / or promoter (alloy, simple substance, compound, etc.) and the kind of the metal element present.

In addition, how to perform the coordination and bonding process is determined according to the specific situation of the catalyst and / or the cocatalyst. For example, the specific catalyst and / or cocatalyst determines whether to convert the catalyst and / or cocatalyst to ions. In the case of conversion by an oxidation method, it is further necessary to determine whether the metal elements in the catalyst and / or promoter field need to be converted to ions with an acid other than the above substances.

As described above, in order to convert the metal element in the catalyst and / or the cocatalyst into ions, the metal element can be first converted into an oxide by an appropriate oxidation method. At this time, it is preferable to oxidize the catalyst and / or the promoter with an oxygen-containing gas (preferably air). Oxidation conditions using oxygen-containing gases are much milder than conventional gas phase oxidation purification conditions. In general, there is no specific limitation on the time and temperature required to oxidize the catalyst and / or promoter with an oxygen-containing gas, and the time and temperature sufficient to convert the catalyst and / or promoter to its oxide. If it is. Usually, the oxidation temperature may be 80-300 ° C, more preferably 100-200 ° C, most preferably 150-200 ° C. The oxidation time depends on the oxidation temperature and can vary. In general, the oxidation time may be 1-20 hours, preferably 5-15 hours, more preferably 8-10 hours. In view of the above, the oxidation used in the carbon nanotube purification method of the present invention is low-temperature oxidation as compared to the high-temperature oxidation method that is usually used. Therefore, this low temperature oxidation does not destroy the carbon nanotubes.

The method for purifying carbon nanotubes of the present invention may further include a step of centrifuging after removing the complex. Thereby, the amorphous carbon remaining in the carbon nanotube is removed, and the purity of the carbon nanotube is further increased. The centrifugation step may be any centrifugation speed, but higher speed centrifugation is preferred. For example, a speed of 5000 to 30000 rpm may be used, but a centrifugal speed of 10,000 to 20000 is preferable. Centrifugation time is closely related to the speed of centrifugation. In general, centrifugation can be performed in 1 minute to 20 hours, but preferably in 2 to 10 hours, for example, 3 hours.

Third invention of the present invention

  The third invention of the present invention provides the carbon nanotube produced by the first invention of the present invention and the carbon nanotube purified by the second invention of the present invention.

The term “carbon nanotube” as used herein includes any carbon nanotube known to those skilled in the art. Depending on the number of carbon atoms that form the tube wall, for example, single-walled carbon nanotubes, multi-walled carbon nanotubes, and combinations thereof may be included. In addition, metallic carbon nanotubes, semiconducting carbon nanotubes, and combinations thereof may be included depending on their electrical characteristics. However, the carbon nanotube of the present invention is preferably a single-walled carbon nanotube. The single-walled carbon nanotubes include metallic single-walled carbon nanotubes (M-SWNT), semiconducting single-walled carbon nanotubes (S-SWNT), and combinations thereof.

As described above in detail, the carbon nanotube production / purification method of the present invention does not damage the side wall of the carbon nanotube, and does not affect the quality of the carbon nanotube, particularly the conductivity. In this respect, the carbon nanotubes obtained by the first invention and the second invention of the present invention are different from the carbon nanotubes obtained by the prior art.

As shown in FIG. 1, there is a defect in the tube wall of the prior art carbon nanotubes, limited by manufacturing and purification conditions. In contrast, the carbon nanotubes of the third invention of the present invention have smoother side walls and are not broken as shown in FIG. Moreover, as shown in FIGS. 8 and 9, the purity of the carbon nanotubes obtained by the method of the present invention is very high and the quality is also excellent.

Fourth invention of the present invention

The fourth invention of the present invention provides a carbon nanotube device including the carbon nanotube of the third invention of the present invention.

Examples of the carbon nanotube element include a carbon nanotube conductive film, a field emission electron source, a transistor, a conductive wire, an electrode material (for example, a transparent, porous, or gas diffusion electrode material), a nano-electromechanical system (nano-electro -Mechanical system (NEMS), spin conduction device, nano cantilever, quantum computing device, light emitting diode, solar cell, surface conduction electron-emitting device display, optical filter (eg, high frequency) Or optical filters), drug delivery systems, heat transfer materials, nano nozzles, energy storage materials (eg, hydrogen storage materials), space elevators, fuel cells, sensors (eg, gas, glucose, or ion sensors), or Examples thereof include a catalyst carrier. Moreover, it is not limited to these elements.

Next, an example is given about a carbon nanotube. However, the present invention is not limited to these examples.

1. Carbon nanotube conductive film

Since carbon nanotubes have both strength and flexibility, they are extremely applicable to flexible electronic components. In particular, flexible and transparent conductive films made of carbon nanotubes have attracted attention. This is due in part to the applicability to electroluminescence, photoconductors, and photovoltaic devices.

Although transparent and highly conductive indium tin oxide (ITO) is already widely used for photoelectric conversion, the flexibility of the film is severely limited by the brittleness of ITO itself. For example, the carbon nanotube film is suitable for alternation of ITO because it has a characteristic that it is not crushed even if it is repeatedly bent. A carbon nanotube film having a low sheet resistance is transparent in the visible light and infrared regions. In addition, carbon nanotube films are even more advantageous due to their low cost and tunable electronic properties.

The carbon nanotube conductive film of the present invention can be manufactured as follows:

In an ultrasonic bath, 10 mg of carbon nanotubes are dispersed in 200 ml of an aqueous solution of 1 wt.% Octyl-phenol-ethoxylate (referred to as TRitoN X-100) for 20 minutes. In a vacuum filtration apparatus (Millipore), the dispersion is filtered with a mixed cellulose ester (MCE) thin film filter (Millipore, 0.2 μm pore) to form a carbon nanotube film on the thin film filter. After two days, any Triton X-100 of the carbon nanotube film is dialyzed against Tris (hydroxymethyl) aminomethane hydrochloride (Tris-HCl) buffer (50 mm, PH 7.5). Next, after washing the Tris-HCl buffer with pure water, the carbon nanotube film is transferred to a quartz substrate. The sample is dried at 90 ° C. for 1 hour and then the membrane filter is removed with acetone vapor. Finally, the carbon nanotube film is dried at 100 ° C. for 1 hour.

Regarding the method for producing such a carbon nanotube film, in particular, the process of removing the thin film filter with acetone vapor, reference can be made to the related description in the Chinese patent application No. 200810005631.7 filed on Feb. 14, 2008. it can. The patent application is cited here for reference.

For example, the steam generator shown in FIG. 12 is used in the present invention. FIG. 12 (A) is a view showing a steam generator used in the present invention, and (b) is a view showing a cross-sectional structure of a glass casing of the steam generator shown in (A).

The steam generator
A glass casing with a condensing device with the inlet of the condensing medium below the casing and the outlet above;
A container for a solvent (for example, acetone) such as a round bottom flask;
It consists of a heating device for heating a solvent such as a heating jacket capable of adjusting the temperature, and an optional stirring device such as a magnetic stirrer. The casing is attached to the interior of the casing and includes a porous support for placing a sample at a height approximately equal to the entrance of the condensing medium. The porous support base is made of, for example, glass. Although the hole diameter of the support base is not strictly required, it is sufficient if the sample can be supported while a sufficient amount of vapor can pass therethrough. The size of the support base is determined by the inner diameter of the glass casing.

2. Carbon nanotube field effect transistor

A single carbon nanotube and a carbon nanotube bundle can constitute a carbon nanotube field effect tube (carbon nanotube FET) which is a basic element of a nanoelectronic element. The carbon nanotubes of the manufactured products are usually not in a single book but in the form of bundles. That is, several to hundreds of carbon nanotubes are also connected in a direction parallel to the axial direction, and form a carbon nanotube bundle having a diameter of about several nanometers to several tens of nanometers. However, in order to use the carbon nanotube FET in a nanoelectronic device, first, a tube bundle of carbon nanotubes must be separated to obtain single or small-sized carbon nanotubes.

In the tube bundle of carbon nanotubes, the diameters of the carbon nanotubes can be made uniform, and the tubes are arranged in a tightly packed form, so that a certain degree of crystallization may occur in the tube bundle itself. As a separation method, in order to achieve the purpose of separating the carbon nanotubes in the tube bundle or the carbon nanotubes in the tube bundle, the carbon nanotube powder is usually dispersed in an organic solvent and then subjected to ultrasonic treatment for a long time. The effect of separation depends on the type of solvent and the sonication time. Examples of commonly used organic solvents include ethanol, isopropanol, acetone, carbon tetrachloride, dichloroethane, dimethylformamide (DMF), and the like.

3.Transistor-Nanoelectrodynatron

There are currently two types of nanoelectrodynatrons: single electron transistors (SET) and carbon nanotube dynatrons. The latter is also called a field effect transistor (FET), which includes a carbon nanotube between the source and drain, and electron (or hole) transport by the carbon nanotube is controlled by the gate voltage.

One typical method for manufacturing FETs is as follows. As mentioned above, the initial product of the carbon nanotubes is usually a bundle of tubes entangled with each other. This is sufficiently ultrasonically dispersed in an organic solvent (for example, ethanol), and then the liquid is dropped onto a chip whose surface layer is SiO ₂ . A large number of metal electrodes are manufactured on the chip by conventional photoetching, metal evaporation, or screen printing. Then, an atomic force microscope (AFM) is used to confirm whether there is a single carbon nanotube or tube bundle connecting the two electrodes. These two electrodes serve as the source and drain of the manufactured FET. The distance between the two electrodes is usually 100 nm, but varies, for example, in the range of 0.1-1 μm. The other electrode under the SiO ₂ layer, or the topped silicon base, is the gate electrode of the FET, and the gate FET is applied to control the current passing through the carbon nanotubes. is there. Of course, an upper gate FET can also be manufactured. First, a carbon nanotube or tube bundle is manufactured at the base, the source and drain are connected, and a gate insulating layer is deposited in order, and a gate manufactured by screen printing or the like on the gate insulating layer above the carbon nanotube or tube bundle. Pass the electrode. Alternatively, a single carbon nanotube or tube bundle may be first sputtered to the base along a predetermined direction, and electrodes may be deposited on both ends of the carbon nanotube or tube bundle by an electron bundle. The carbon nanotubes in between may be cut off.

Test the relationship between the transport result and gate voltage (I-V characteristics) at room temperature. In the assay, metallic carbon nanotubes display or do not display linear conductivity that is weakly affected by the gate voltage. In contrast, semiconducting carbon nanotubes show a strong demand for gate voltage.

Example

The following examples explain the invention in more detail. Except where otherwise described, all raw materials and reagents used in the present invention are either commercially available or obtainable by conventional techniques in the field.

The main ingredients are as follows:

Y-Ni alloy catalyst (manufactured by Beijing Color Metal Research Institute);

Graphite rod (manufactured by Shanghai Carbon Co., Ltd.);

FeS (manufactured by Beijing Yongli Fine Chemicals Co., Ltd.);

NaOH and o-dichlorobenzene (o-DCB) (manufactured by Beijing Chemical Industry Co., Ltd.);

EDTA (ethylenediaminetetraacetic acid), CYDTA (trans-1,2-diaminocyclohexane-N, N, N ', N'-tetraacetic acid hydrate), DTPA (diethylenetriaminepentaacetic acid), and TTHA (triethylenetetraaminehexa) Acetic acid): made by Alfa Aesar;

Triton X-100, made by Acros;

Tris (hydroxymethyl) aminomethane, Acros, 99%;

Hydrochloric acid, manufactured by Beijing Chemical Industry, HCl content 36-38%.

Feature expression method

The purified carbon nanotubes can be characterized using the following representation:

Raman spectrum: Renishaw 100 micro-Raman system is used;

X-ray photoelectron spectrum: VG Scientific's ESCALAb220i-XL Electron Spectrometer is used, 300W AlKα rays are used;

Scanning electron microscope: JEOL JSM-6700F;

Transmission electron microscope: JEOL-2010, 200kV;

The sheet resistance of the carbon nanotube film is measured with a 4-probe Loresta-EP MCP-T360, and the transparency of the carbon nanotube film is tested with a UV-vis-NIR spectrophotometer (JASCO V-570).

The Raman spectrum is one of the most powerful tools for measuring carbon nanotubes. The purity of the sample can be reflected by reflecting the degree of order of the sample, and the diameter distribution of the carbon nanotube can also be expressed. When performing a Raman spectrum test, in order to eliminate the influence of the bundle of carbon nanotubes on the measurement results, the sample used for Raman measurement was sonicated with ethanol for 5 minutes, and the resulting suspension was A treatment such as dropping on a slide glass and drying in air can be performed.

The Raman spectrum has three regions or peaks: Radial Breathing Mode (RBM) (approximately 100 to 300 cm ^-1 ), D band (~ 1350 cm ^-1 ), and G band (~ 1570 cm ^-1 ). It should be noted (MS Dresselhaus, et al., Raman Spectroscopy of Carbon Nanotubes in 1997 and 2007, J. Phys. Chem. C, 111 (48), 2007, 17887-17893). The RBM peak is one of the characteristic scattering modes of carbon nanotubes, is unique to carbon nanotubes, and is related to the diameter of carbon nanotubes. (See Araujo, PT, et al., Third and fourth optical transitions in semiconducting carbon nanotubes. Phys. Rev. Lett., 98, 2007, 067401) ω _RBM = A / d _t + B (where A = 217.8 ± 0.3 cm ⁻¹ nm, B = 15.7 ± 0.3 cm ⁻¹ , ω _RBM represents the wave number of the RBM peak with the unit cm ⁻¹ , and d _t represents the diameter of the carbon nanotube with the unit nm. The diameter distribution of carbon nanotubes is known. The D and G bands correspond to amorphous carbon and graphitized carbon, respectively. The purity of the carbon nanotube can be estimated from the intensity ratio (G / D) of the G band and the D band. The greater the G / D, the higher the purity because there are more graphite carbons and fewer impurities or defects.

Production Example 1

An arc furnace 100 shown in FIG. 2, an anode 130 which is a graphite rod having a length of 100 mm and a diameter of 6 mm, and a cathode 120 which is a graphite rod having a diameter of 8 mm were used. A small hole with an inner diameter of 4 mm and a depth of 80 mm was drilled at one end of the anode graphite rod. High purity graphite powder, YNi _4.2 alloy powder as metal catalyst, and FeS powder as promoter so that the molar ratio of carbon to catalyst is 15: 1 and the weight ratio of catalyst to promoter is 10: 1 The holes were filled and packed. The cathode was fixed to a water-cooled copper base. Then, after the arc furnace 100 was sucked to 3.0 Pa, the vacuum valve was closed and helium gas was introduced to about 0.07 MPa. When the power supply is connected, the current is controlled to about 80 to 120A, the voltage is controlled to 20 to 25V, and the cathode is manually adjusted so that the distance between both electrodes is maintained at about 3mm, thereby generating stable arc discharge. It was.

Cloth-like soot deposited on the chamber wall, web-like soot between the chamber wall and the cathode, and “collar” soot produced on one end of the cathode A collar-like soot was collected. Among these, the purity of the carbon nanotubes in the reticulated soot product is the highest, the purity in the cloth soot product is the lowest, and the purity in the “collar” soot product is between them.

The following examples are given using the reticulated soot product as an unpurified sample.

Purification example 1

First, 10 mg of an unpurified sample was baked at 200 ° C. with an air flow rate of 20 ml / min for 10 hours, and then the baked sample was dispersed in deionized water and treated with ultrasound for 30 minutes. Then, a 0.5M EDTA aqueous solution is prepared and put into the carbon nanotube dispersion. The mixture was refluxed at 110 ° C. for 18 hours and the pH value was adjusted to about 8 with 1M aqueous NaOH. Next, the dispersion was filtered with a 0.5 μm porous polytetrafluoroethylene filter membrane and washed with hot water many times. Then, the sample was dispersed in o-DCB and centrifuged at 15000 rpm for 3 hours. The supernatant was decanted and collected by filtration through a mixed cellulose ester (MCE) membrane filter.

Purification example 2

Coordination was performed in the same manner as in Purification Example 1 except that 0.5 M EDTA aqueous solution was used instead of 0.5 M CYDTA aqueous solution.

Purification example 3

Coordination was carried out in the same manner as in Purification Example 1 except that 0.5M DTPA aqueous solution was used instead of 0.5M EDTA aqueous solution for coordination.

Purification example 4

Coordination was carried out in the same manner as in Purification Example 1 except that 0.5 M TTTA aqueous solution was used instead of 0.5 M EDTA aqueous solution, and coordination was carried out.

First, the samples purified by EDTA and CYDTA were compared. The Raman spectrum of the purified carbon nanotube is shown in FIG. FIG. 4 also shows commercially available P3 carbon nanotubes (P3, manufactured by the acid reflux method, obtained from Carbon Solutions. INC., Purity greater than 85%).

Fig. 4 shows three characteristics of carbon nanotubes: radial-breathing mode (RBM) (100-250 cm ^-1 ), D-band (1330 cm ^-1 ), and G-band (1520-1600 cm ^-1 ). It is clear that the spectral region is preserved. In addition, it is clear that the G / D of EDTA and CYDTA is larger than that of P3, which indicates that the purity of carbon nanotubes purified by EDTA and CYDTA is higher than that of P3.

It can also be seen that the purity of carbon nanotubes purified by CYDTA is higher than the purity of carbon nanotubes purified by EDTA. This is probably because the complex of CYDTA and Y is more stable than the complex of EDTA and Y.

XPS analysis was performed on the carbon nanotubes purified by EDTA, and the results are shown in FIG.

From FIG. 5, it can be confirmed that the 1s peak of NA exists. This indicates that EDTA sodium salt still remains in the purified carbon nanotube. That is, EDTA is not completely removed.

Although not shown, there is also a 1s peak of NA in the XPS spectrum of the CYDTA purified product.

From this point of view, catalyst impurities are not completely removed in CYDTA and EDTA. This may be because EDTA sodium salt and CYDTA sodium salt have poor solubility in water.

The result of SEM analysis of carbon nanotubes purified by TTHA is shown in FIG. 6 (FIG. 6b). FIG. 6 also shows an SEM of the unpurified carbon nanotubes (FIG. 6a).

Similarly, FIG. 7 shows the result of TEM analysis of carbon nanotubes purified by TTHA. In FIG. 7, FIG. 7a and FIG. 7b differ only in magnification.

Comparing FIG. 6a and FIG. 6b, it can be seen that after purification with TTHA, most of the impurities are removed and only a few amorphous carbons are attached to the carbon nanotubes. The residual impurities can be further removed by ultrasonic and ultracentrifugation techniques.

From FIG. 7a and FIG. 7b, it can be seen that the side walls of the obtained carbon nanotubes are very smooth. This indicates that the carbon nanotube sidewalls were not damaged during the purification process.

FIG. 8 shows Raman spectra of carbon nanotubes before and after purification with TTHA. Comparing the G / D proportions of the two curves before and after purification, it is clear that the purity was remarkably increased when purifying with TTHA. It can also be seen that the quality and purity of the carbon nanotubes are both excellent.

FIG. 9 is a view showing XPS spectra of carbon nanotubes obtained by TTHA-purified carbon nanotubes and carbon nanotubes obtained by conventional acid treatment (P3). From FIG. 9, it can be seen that Y is completely removed by TTHA, whereas a larger amount of Y remains in the acid reflux treatment.

Film formation example 1

In this example, a carbon nanotube film was produced using carbon nanotubes purified by TTHA. The production of the film is based on a filtration method. The manufacturing method is as follows.

In an ultrasonic bath, 10 mg of carbon nanotubes were dispersed in 200 ml of an aqueous solution of 1 wt.% Octyl-phenol-ethoxylate (referred to as Triton X-100) for 20 minutes. In a vacuum filtration apparatus (Millipore), the dispersion was filtered with a mixed cellulose ester (MCE) thin film filter (Millipore, 0.2 μm pore) to form a carbon nanotube film on the thin film filter. After two days, any Triton X-100 of the carbon nanotube film was dialyzed against Tris (hydroxymethyl) aminomethane hydrochloride (Tris-HCl) buffer (50 mm, pH 7.5). Next, the Tris-HCl buffer was washed away with pure water, and then the carbon nanotube film was transferred to a quartz substrate. The sample was dried at 90 ° C. for 1 hour and then the membrane filter was removed with acetone vapor. Finally, the carbon nanotube film was dried at 100 ° C. for 1 hour.

Comparative Example 1

A carbon nanotube film was produced in the same manner as in Production Example 1 except that carbon nanotubes (P3) obtained by conventional nitric acid reflux were used instead of carbon nanotubes purified by TTHA.

FIG. 10 shows a carbon nanotube film made of carbon nanotubes purified with TTHA. The film is covered on a quartz substrate labeled ICCAS. From FIG. 10, it can be seen that the ICCAS characters on the substrate can be clearly seen through the carbon nanotube film (about 70 nanometers). This means that the transparency of the film is very high.

In FIG. 11, the sheet resistance of the carbon nanotube film manufactured in Film Formation Example 1 is compared with the sheet resistance of the carbon nanotube film manufactured in Comparative Example 1. From the carbon nanotube film produced in Comparative Example 1, it can be seen that the sheet resistance of the carbon nanotube film produced in Film Production Example 1 is significantly reduced.

Obviously, the carbon nanotubes produced by the method of the present invention or the carbon nanotubes purified by the method of the present invention have excellent properties because they avoid the destruction of the carbon nanotubes to the tube wall. Can be used extensively.

Sequential numbers such as (a) and (b) in the method of the present invention are merely used to distinguish each other and do not deny that there are other steps between these steps. . For example, there are other steps between steps (a) and (b) and / or (b) and (c). The other steps may be normal steps in this field such as drying and washing as long as the effects of the present invention are not negatively affected.

The expression “as needed” as used in the present invention indicates that there is a subsequent item or item (for example, a processing step), and may or may not exist. The present invention also includes two situations in which the matter or item is present and absent.

All documents cited herein are incorporated into the present invention.

Although the present invention has been described with reference to specific embodiments, it is clear that there are many variations. Such variations do not depart from the spirit and scope of the present invention, and any variations that are apparent to those skilled in the art are within the scope of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Arc furnace, 110 ... Cathode terminal, 120 ... Cathode, 130 ... Anode, 140 ... Anode terminal, 150 ... Linear motion apparatus, 160 ... Vacuum chamber

Claims (46)

(A) a step of producing carbon nanotubes by an arc discharge method in the presence of a catalyst and a cocatalyst as necessary;
(B) A complex formed by coordination of a metal element present in the catalyst and / or a co-catalyst as necessary and a substance capable of forming a complex with the metal element present in the catalyst and / or the co-catalyst as necessary. Obtaining
(C) A method for producing a carbon nanotube, comprising a step of removing the complex.   The method according to claim 1, wherein a promoter is used in the step (a).   The method of claim 2, wherein the promoter is FeS.   The method according to claim 1, wherein the catalyst is selected from the group consisting of lanthanum-based metal oxides, transition metals, mixtures of nickel and rare earth elements, and mixtures thereof.   The catalyst is selected from the group consisting of Y-Ni alloys, Fe-Ni alloys, Fe-Co alloys, Co-Ni alloys, Rh-Pt alloys, and Ce-Ni alloys. the method of. The step (b)
(D) a step of converting a metal element present in the catalyst and / or a co-catalyst as needed into ions, and (e) forming a complex with the metal element present in the catalyst and / or co-catalyst as needed. A step of coordinating a substance to be obtained with the ion to obtain a complex;
The method of claim 1, comprising: The step (d)
7. The process according to claim 6, comprising the step of (f) oxidizing the catalyst and / or an optional promoter to obtain a catalyst and / or an optional oxide of the promoter.   Using a substance capable of forming a complex with a metal element present in the catalyst and / or a co-catalyst as required, a corresponding metal ion is formed from the oxide, and the catalyst and / or co-catalyst as required The method according to claim 7, wherein a substance that can form a complex with a metal element present in the metal is coordinated with the metal ion to obtain a complex.   9. The process according to claim 8, wherein the substance capable of forming a complex with the metal element present in the catalyst and / or optionally the cocatalyst is selected from aminopolycarboxylic acids.   The aminopolycarboxylic acid is ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid (DTPA), and 10. The method of claim 9, wherein the method is selected from the group consisting of triethylenetetraamine hexaacetic acid (TTHA).   The method according to claim 9, wherein the aminopolycarboxylic acid is triethylenetetraaminehexaacetic acid (TTHA).   The method of claim 1, wherein step (c) comprises converting the complex to a salt form to remove the salt form complex. The step (d) further includes
The method according to claim 7, further comprising the step of (g) reacting the oxide with an acid to obtain a metal element ion of a catalyst and / or a promoter as required.   The substance capable of forming a complex with the metal element present in the catalyst and / or optionally the cocatalyst is a group consisting of tetrahydrofuran, trialkylphosphine, ε-caprolactone, ε-caprolactam, dimethylformamide, and dimethylsulfoxide The method according to claim 6, wherein the method is selected. The complex includes {M [(NC) ₂ CC (OCH ₂ CH ₂ OH) C (CN) ₂ ] ₂ (4,4′-bPy) (H ₂ O) ₂ }, dinuclear [M ′ {(phen) _2} is selected from _{2 V 4 O 12] C 6} H 12 O key between H ₂ O and the group consisting of _{[Ni (L) (H 2} O) 3 2H 2 O], M is a group consisting Ni, Co, from Fe M ′ is selected from the group consisting of Ni and Co, bPy represents bipyridine, phen represents a phenyl group, and L represents (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl-acetic acid) The method according to claim 6.   The method according to claim 7, wherein the step (f) includes oxidizing the catalyst and / or the co-catalyst as necessary with an oxygen-containing gas.   The process according to claim 16, characterized in that the time and temperature for the oxidation with the oxygen-containing gas are sufficient to convert the catalyst and / or the optional promoter to oxides.   The method of claim 16, wherein the oxygen-containing gas is air.   The method according to claim 17, wherein the oxidation temperature is 80 to 300 ° C.   The method of claim 17, wherein the oxidation time is 1 to 20 hours.   The method of claim 1, further comprising the step of centrifuging after removing the complex.   The method according to claim 21, wherein the centrifugation is performed at 5000 to 30000 rpm for 1 to 20 hours.   The method according to claim 1, wherein the carbon nanotube is a single-walled carbon nanotube. A method for purifying carbon nanotubes produced by an arc discharge method in the presence of a catalyst and a cocatalyst as required,
(I) A complex in which a metal element present in a catalyst and / or a co-catalyst as required and a substance capable of forming a complex with the metal element present in the catalyst and / or a co-catalyst as needed are coordinated. Obtaining
(II) A method for purifying carbon nanotubes, comprising the step of removing the complex. The step (I)
(III) a step of converting a metal element present in the catalyst and / or a co-catalyst as needed into ions, and (IV) forming a complex with the metal element present in the catalyst and / or co-catalyst as necessary. The method according to claim 24, comprising the step of coordinating a substance to be obtained with the ions to obtain a complex. The step (III)
26. The method according to claim 25, comprising the step of (V) oxidizing the catalyst and / or an optional promoter to obtain an oxide of the catalyst and / or optional promoter. Using a substance capable of forming a complex with a metal element present in the catalyst and / or a co-catalyst as required, a corresponding metal ion is formed from the oxide, and the catalyst and / or co-catalyst as required 27. The method according to claim 26, wherein a complex is obtained by coordinating a substance capable of forming a complex with a metal element present in the metal to the metal ion.   28. Process according to claim 27, characterized in that the substance capable of forming a complex with the metal elements present in the catalyst and / or optionally the cocatalyst is selected from aminopolycarboxylic acids.   The aminopolycarboxylic acid is ethylenediaminetetraacetic acid (EDTA), trans-1,2-diaminocyclohexane-N, N, N ′, N′-tetraacetic acid hydrate (CYDTA), diethylenetriaminepentaacetic acid (DTPA), and 29. The method of claim 28, wherein the method is selected from the group consisting of triethylenetetraamine hexaacetic acid (TTHA).   29. The method of claim 28, wherein the aminopolycarboxylic acid is triethylenetetraamine hexaacetic acid (TTHA).   25. The method of claim 24, wherein step (II) includes converting the complex to a salt form to remove the salt form complex. The step (V) further includes
27. The method according to claim 26, comprising the step of (VI) reacting the oxide with an acid to obtain a metal element ion of a catalyst and / or a promoter as required.   25. The catalyst according to claim 24, wherein the catalyst is selected from the group consisting of Y-Ni alloy, Fe-Ni alloy, Fe-Co alloy, Co-Ni alloy, Rh-Pt alloy, and Ce-Ni alloy. the method of.   The substance capable of forming a complex with the metal element present in the catalyst and / or optionally the cocatalyst is a group consisting of tetrahydrofuran, trialkylphosphine, ε-caprolactone, ε-caprolactam, dimethylformamide, and dimethylsulfoxide 26. The method of claim 25, wherein the method is selected. The complex includes {M [(NC) ₂ CC (OCH ₂ CH ₂ OH) C (CN) ₂ ] ₂ (4,4′-bPy) (H ₂ O) ₂ }, dinuclear [M ′ {(phen) _2} is selected from _{2 V 4 O 12] C 6} H 12 O key between H ₂ O and the group consisting of _{[Ni (L) (H 2} O) 3 2H 2 O], M is a group consisting Ni, Co, from Fe M ′ is selected from the group consisting of Ni and Co, bPy represents bipyridine, phen represents a phenyl group, and L represents (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl-acetic acid) 26. The method of claim 25.   27. The method of claim 26, wherein step (V) comprises oxidizing the catalyst and / or promoter as needed with an oxygen-containing gas.   37. A process according to claim 36, characterized in that the time and temperature of oxidation with the oxygen-containing gas is sufficient to convert the catalyst and / or optional promoter to oxides.   The method of claim 36, wherein the oxygen-containing gas is air.   The method according to claim 37, wherein the oxidation temperature is 80 to 300 ° C.   38. The method of claim 37, wherein the oxidation time is 1 to 20 hours.   The method of claim 24, further comprising the step of centrifuging after removing the complex.   The method according to claim 41, wherein the centrifugation step is performed at 5000 to 30000 rpm for 1 to 20 hours.   43. The method according to any one of claims 24 to 42, wherein the carbon nanotubes are single-walled carbon nanotubes.   The carbon nanotube refine | purified by the method of any one of Claims 1-43.   The carbon nanotube element containing the carbon nanotube of Claim 44.   The carbon nanotube element is a carbon nanotube conductive film, field emission electron source, transistor, lead wire, nanoelectromechanical system, spin conductive device, nanocantilever, quantum computing device, light emitting diode, solar cell, surface conduction electron emission 46. The carbon nanotube of claim 45, wherein the carbon nanotube is selected from the group consisting of an element display, an optical filter, a drug transmission system, a heat conducting material, a nano nozzle, an energy storage system, a space elevator, a fuel cell, a sensor, and a catalyst carrier. element.

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