JP2004224579A - Winding type carbon nanotube and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for manufacturing a carbon nanotube by which the design and the structure control of the carbon nanotube is facilitated. <P>SOLUTION: The winding type carbon nanotube has a structure formed by winding one layer of graphene originating from a graphite material. The method for manufacturing the carbon nanotube having a structure formed by winding one layer of graphene originating from a graphite material is provided with: a process (1) for forming a graphite intercalation compound by intercalating an alkali metal between the graphite layers of the graphite material; a process (2) for forming a high polymer by introducing an unsaturated hydrocarbon between the graphite layers of the graphite intercalation compound obtained in the process (1) and polymerizing the unsaturated hydrocarbon using the alkali metal as a catalyst; and a process (3) for dissolving and removing the high polymer by dipping the graphite material containing the high polymer formed in the process (2) in a solvent. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a carbon nanotube having a novel structure and a method for producing the same.
[0002]
[Prior art]
Conventionally, methods for producing carbon nanotubes include a method of performing arc discharge on a carbon material, a method of performing laser irradiation on a carbon material, and a method of decomposing a hydrocarbon gas by CVD using metal fine particles as a catalyst. . In each of these methods, carbon nanotubes are produced by reconstituting or generating carbon atoms in a nanotube shape by sublimation or thermal decomposition.
[0003]
Conventional methods for producing carbon nanotubes utilize the reconstitution phenomenon of carbon atoms, so the diameter, length, shape, etc. of carbon nanotubes are determined depending on many variables such as the synthesis apparatus and synthesis conditions. . Therefore, it is very difficult to design or control the diameter, length, shape, and the like in advance, and products having limited diameters, lengths, shapes, and the like are manufactured based on empirical rules. Is the current situation.
[0004]
The present inventor previously described, "After introducing unsaturated hydrocarbons between the graphite layers of the alkali metal-graphite intercalation compound and polymerizing the unsaturated hydrocarbons using the alkali metal as a catalyst, the obtained graphite-polymer was obtained. A method for producing a graphite material characterized by heat-treating a composite "(Patent Document 1). However, in the inorganic-organic composite obtained by this method, a polymer remains, and a part of the graphene derived from the graphite material is only wound, and a carbon that can be regarded as a carbon nanotube is obtained. No material has been produced.
[0005]
[Patent Document 1] Japanese Patent Application Laid-Open No. 11-70612
[Problems to be solved by the present invention]
Accordingly, it is a main object of the present invention to provide a technique for manufacturing carbon nanotubes that can easily design and control the structure of carbon nanotubes.
[0007]
[Means for Solving the Problems]
The present inventors have conducted research to achieve the above object, and as a result, polymerized unsaturated hydrocarbons between graphite layers having a structure in which monoatomic layers (graphene) in which carbon atoms are arranged in a plane are stacked. After that, carbon nanotubes having a novel structure were successfully manufactured by a simple chemical technique of removing the generated polymer with a solvent.
[0008]
That is, the present invention provides the following carbon nanotubes and a method for producing the same:
1. A wound carbon nanotube having a structure in which one layer of graphene is wound.
2. (1) a step of intercalating an alkali metal between graphite layers of a graphite material to form a graphite interlayer compound;
(2) a step of introducing an unsaturated hydrocarbon between the graphite layers of the graphite intercalation compound obtained in the step (1), polymerizing the unsaturated hydrocarbon with an alkali metal as a catalyst, and forming a polymer, and (3) A) a step of immersing the graphite material containing the polymer formed in the step (2) in a solvent and dissolving and removing the polymer to form a wound single-layer graphene carbon nanotube; A method for producing rolled carbon nanotubes, which is characterized by the following.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings.
In the present invention, a graphite intercalation compound (Graphite Intercalation Compound: hereinafter referred to as “GIC”) is obtained by intercalating an alkali metal between graphite layers of a graphite material by a known method (for example, see Patent Document 1). (See FIG. 1). Such a GIC is called potassium-GIC (or K-GIC) when the intercalated alkali metal is, for example, potassium (see FIG. 1). When other alkali metals are intercalated, each metal is similarly referred to. Alternatively, from another viewpoint, particularly focusing on the type of intercalated alkali metal and its abundance, it may be called, for example, KC ₈ , KC ₂₄ , KC _36, or the like. In the GIC used in the present invention, the kind of alkali metal and its abundance are not particularly limited. However, in the following, for simplicity of description, “KC ₈ ” is used to represent alkali metal-GIC. Let it.
[0010]
Next, the obtained KC _{8 is} reacted with an easily polymerizable unsaturated hydrocarbon under reduced pressure (under the presence of a polymerization initiator, at room temperature = about 25 ° C., under a mild condition of 1 atmosphere or less). Hydrogen, which includes, for example, liquid styrene, isoprene, and the like at room temperature and atmospheric pressure, and liquid 1,3-butadiene at room temperature and atmospheric pressure. Is introduced. There is no particular limitation on the type and amount of the easily polymerizable unsaturated hydrocarbon as long as a polymer that can be dissolved and removed with an organic solvent is formed. In the following, for simplicity of description, a combination of KC ₈ and styrene is represented, but in the present invention, it is needless to say that a combination of another alkali metal and another unsaturated hydrocarbon can also be used. No.
[0011]
The introduction of the unsaturated hydrocarbon between the graphite layers and the polymerization thereof can be carried out in the same manner as in the method disclosed in Patent Document 1. For example, the decompression container (typically, P ≦ ¹⁰ -2 Torr, and more preferably P ≦ ¹⁰ -3 Torr) for accommodating the KC ₈ when introduced into the styrene monomer, the styrene monomer is inserted between the graphite layers of KC ₈ Thus, the expansion of graphite in the c-axis direction starts very slowly, and the polymerization of styrene monomer starts using K as a polymerization initiator. After a certain period of time, a graphite-styrene polymer composite is formed (see FIG. 1). Styrene introduction amount for KC ₈ is may be at least the amount of expanding the KC ₈ to the extent that may be carried out in the isolation of graphene will be described later, is in the range of about 20 to 1000 fold (weight ratio) of KC _8.
[0012]
Next, the obtained graphite-polymer composite is immersed in a solvent capable of dissolving the polymer, for example, N-methyl-2-pyrrolidone, tetrahydrofuran, nitrobenzene, or the like for a predetermined time, so that the polymer between the graphite layers is formed. The components are dissolved and removed. Among these solvents, N-methyl-2-pyrrolidone which is excellent in dissolving ability of the polymer component is more preferable.
[0013]
Thus, the graphene that was dispersed in the structure of the graphite-polymer composite is isolated by removing the polymer component. Since isolated graphene has a high surface energy when present in a spread state, the graphene tends to bond with itself and become low in surface energy by Van der Waals bonding. That is, the isolated graphene is rolled up, and as a result, a rolled carbon nanotube having a form schematically shown in FIG. 1 is formed.
[0014]
In addition, in order to remove the polymer in the graphite-polymer composite, when the polymer is decomposed and evaporated and removed by heating (Patent Document 1 and Shioyama, J. Mat. Sci. Lett., 20). (2001) 499), although some of the graphene may be rolled up, which is considered to have been caused by exfoliation of graphene, most of the graphene has been re-laminated, and it is not possible to produce carbon nanotubes according to the present invention. Can not.
[0015]
【The invention's effect】
According to the present invention, a novel carbon nanotube having a structure in which graphene is rolled up can be produced by a chemical operation. In this case, the surface energy of the graphene is reduced by winding the graphene. It is considered that the diameter of the obtained nanotube is determined by the balance between the surface energy reduction amount and the energy increase due to bending of one graphene sheet. Since the amount of energy increase is determined by the bending stiffness, the bending stiffness value of one graphene can be estimated by measuring the diameter of the nanotube. That is, according to the present invention, it is possible to measure the mechanical properties of the nanoscale material.
[0016]
In addition, the "tightening degree" (or the degree of winding) of the wound product is assumed to vary depending on the type and temperature of the solvent and the type of the polymer when the nanotube is produced by the chemical treatment. According to the method of the present invention, control of the diameter by changing the solvent used in the treatment and its temperature, etc., nanomachines that perform the operation of winding and unwinding, and unwound nanocomposites by involving other substances, such as new nanotechnology, Deployment is also possible.
[0017]
【Example】
Hereinafter, examples will be shown to further clarify features of the present invention. The present invention is not limited at all by the examples.
Example 1
Using highly oriented pyrolytic graphite (HOPG; manufactured by Advanced Ceramics Corp., U.S.A.), a 2-valve method (see "Introduction to New Carbon Materials", Realize Inc. (1996), pp. 159-160) , was synthesized KC _8, housed in a sealed container, was below the vacuum vessel pressure advance 10 -3 ^Torr, at room temperature (about 25 ° C.), introducing the styrene vapor corresponding to the vapor pressure at room temperature of styrene And reacted. In addition, styrene was previously dehydrated using a molecular sieve 4A, and then purified by vacuum distillation.
[0018]
The graphite-polymer composite obtained 24 hours after the start of the reaction is a black, resilient, expanded graphite-like material in which about 400 times the amount of styrene has been absorbed based on ₈ weights of KC. .
[0019]
50 mg of the obtained graphite-polymer composite was immersed in 100 ml of N-methyl-2-pyrrolidone, and left standing for 8 weeks with occasional stirring. was gotten.
Observation of the obtained black fine powder with a transmission electron microscope revealed that it was a carbon nanotube having a cylindrical shape with an outer diameter of 26 nm and an inner diameter of 16 nm and graphene laminated with 15 layers, as shown in FIG. It was confirmed that.
Example 2
Using highly oriented pyrolytic graphite (HOPG; manufactured by Advanced Ceramics Corp., U.S.A.), a 2-valve method (see "Introduction to New Carbon Materials", Realize Inc. (1996), pp. 159-160) , And KC ₂₄ , and housed in a closed vessel. After the vessel pressure was previously reduced to 10 ⁻³ Torr or less, at room temperature (about 25 ° C.), isoprene vapor corresponding to the vapor pressure of isoprene at room temperature was introduced. And reacted. It should be noted that isoprene was previously dehydrated using a molecular sieve 4A and then purified by vacuum distillation.
[0020]
The graphite-polymer composite obtained 24 hours after the start of the reaction is a black, resilient, expanded graphite-like material, in which about 173 times the amount of isoprene was absorbed based on ₂₄ weights of KC. .
[0021]
50 mg of the obtained graphite-polymer composite was immersed in 100 ml of N-methyl-2-pyrrolidone, and left for 8 weeks with occasional stirring. was gotten.
[0022]
Observation of the obtained black fine powder with a transmission electron microscope confirmed that it was a carbon nanotube.
Example 3
According to the method of Example 2, except that gaseous 1,3-butadiene (purity of 99.5% or more) packed in a cylinder was used as an unsaturated hydrocarbon and the butadiene pressure was set to 500 Torr. A molecular conjugate was prepared.
[0023]
The resulting graphite-polymer composite was a black, resilient, expanded graphite-like material, storing about 153 times the amount of styrene based on ₂₄ weights of KC.
50 mg of the obtained graphite-polymer complex was immersed in 100 ml of N-methyl-2-pyrrolidone and left for 8 weeks with occasional stirring, whereby the polybutadiene component was eluted and a black fine powder was obtained. was gotten.
[0024]
Observation of the obtained black fine powder with a transmission electron microscope confirmed that it was a carbon nanotube.
[Brief description of the drawings]
FIG. 1 is a view schematically showing a method for producing a carbon nanotube according to the present invention.
FIG. 2 is a transmission electron micrograph showing a laminated structure of carbon nanotubes obtained by the method of the present invention.

Claims (2)

A wound carbon nanotube having a structure in which one layer of graphene is wound. (1) a step of intercalating an alkali metal between graphite layers of a graphite material to form a graphite interlayer compound;
(2) a step of introducing an unsaturated hydrocarbon between the graphite layers of the graphite intercalation compound obtained in the step (1), polymerizing the unsaturated hydrocarbon with an alkali metal as a catalyst, and forming a polymer, and (3) A) a step of immersing the graphite material containing the polymer formed in the step (2) in a solvent and dissolving and removing the polymer to form a wound single-layer graphene carbon nanotube; A method for producing rolled carbon nanotubes, which is characterized by the following.

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