JP3735669B2 - Winding carbon nanotube and method for producing the same - Google Patents

Description

[0001]
BACKGROUND 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, as a carbon nanotube production method, a method of performing arc discharge on a carbon material, a method of performing laser irradiation on the carbon material, a method of decomposing a hydrocarbon gas by CVD using metal fine particles as a catalyst, and the like are known. . In any of these methods, carbon nanotubes are produced by reconstituting carbon atoms dissociated or generated by sublimation or thermal decomposition into nanotubes.
[0003]
Since the conventional carbon nanotube manufacturing method uses the carbon atom reconstruction phenomenon, the diameter, length, shape, etc. of the carbon nanotube are determined depending on many variable factors such as the synthesis apparatus and synthesis conditions. . Therefore, it is very difficult to design or control the diameter, length, shape, etc. in advance, and products with limited diameter, length, shape, etc. are manufactured based on empirical rules. Is the current situation.
[0004]
The present inventor previously described, “After introducing unsaturated hydrocarbon between graphite layers of an alkali metal-graphite intercalation compound and polymerizing unsaturated hydrocarbon using an alkali metal as a catalyst, the obtained graphite-polymer A method for producing a graphite material characterized by heat-treating the composite was proposed (Patent Document 1). However, in the inorganic-organic composite obtained by this method, a polymer remains, and only part of the graphene derived from the graphite material is wound, and carbon that can be regarded as a carbon nanotube No material has been produced.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-70612 [0006]
[Problems to be solved by the present invention]
Accordingly, the main object of the present invention is to provide a carbon nanotube production technique that allows simple design and structural control of carbon nanotubes.
[0007]
[Means for Solving the Problems]
As a result of conducting research to achieve the above object, the present inventor polymerizes unsaturated hydrocarbons between graphite layers having a structure in which monoatomic layers (graphene) in which carbon atoms are arranged in a plane are stacked. Then, carbon nanotubes having a novel structure were successfully produced by a simple chemical method of removing the produced polymer with a solvent.
[0008]
That is, the present invention provides the following carbon nanotubes and methods for producing the following:
1. A wound carbon nanotube having a structure in which a single 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) introducing an unsaturated hydrocarbon between graphite layers of the graphite intercalation compound obtained in step (1), using an alkali metal as a catalyst, polymerizing the unsaturated hydrocarbon to form a polymer, and
(3) A step of forming a carbon nanotube made of a wound single-layer graphene by immersing the graphite material containing the polymer formed in step (2) in a solvent and dissolving and removing the polymer A method for producing a wound carbon nanotube, wherein:
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the drawings.
In the present invention, an alkali metal is first intercalated between graphite layers of a graphite material by a known method (for example, see Patent Document 1), and a graphite intercalation compound (hereinafter referred to as “GIC”) is obtained. Form (see FIG. 1). Such GIC is called potassium-GIC (or K-GIC) when the intercalated alkali metal is, for example, potassium (see FIG. 1). In the case of intercalating other alkali metals, each metal is similarly called. Alternatively, from another point of view, focusing on the kind of the 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, there are no particular restrictions on the type of alkali metal and its abundance, but in the following, for the purpose of simplifying the description, “KC ₈ ” is used to represent alkali metal-GIC. Let
[0010]
Next, the obtained KC ₈ was subjected to an easily polymerizable unsaturated hydrocarbon under reduced pressure (unsaturated carbon that reacts under mild conditions of room temperature = about 25 ° C. and 1 atm or less in the presence of a polymerization initiator). Means hydrogen; for example, styrene, isoprene, etc. which are liquid at normal temperature and atmospheric pressure, and liquid 1,3-butadiene which is liquid at normal temperature and atmospheric pressure are brought into contact with each other, and the unsaturated hydrocarbon is interposed between the graphite layers of the former Is introduced. There are no particular limitations on the type and amount of the easily polymerizable unsaturated hydrocarbon as long as a polymer that can be dissolved and removed by an organic solvent is formed. In the following, in order to simplify the description, it is represented by a combination of KC ₈ and styrene, but it goes without saying that combinations of other alkali metals and other unsaturated hydrocarbons can be used in the present invention. Yes.
[0011]
The introduction of unsaturated hydrocarbons between the graphite layers and the polymerization thereof can be performed in the same manner as the method disclosed in Patent Document 1 described above. 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, expansion begins very slowly in the c-axis direction of graphite, and polymerization of styrene monomer begins with 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, etc. for a predetermined time, whereby a polymer between graphite layers The components are dissolved and removed. In these solvents, N-methyl-2-pyrrolidone having excellent solubility 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 it exists in a spread state, it tends to bind to itself by a van der Waals bond and become a low surface energy state. That is, the isolated graphene rolls up, and as a result, a wound carbon nanotube having the form schematically shown in FIG. 1 is formed.
[0014]
In the case of decomposing and evaporating and removing the polymer by heating in order to remove the polymer in the graphite-polymer composite (Patent Document 1 and Shioyama, J. Mat. Sci. Lett., 20 (2001) 499), although some graphene rolls that are thought to have occurred due to the exfoliation of graphene are observed, most of the graphene is re-stacked, and the production of 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 rolling up the graphene. The diameter of the obtained nanotube is considered to be determined by the balance between the amount of surface energy reduction and the increase in energy caused by bending one graphene. Since the amount of increase in energy is determined by the bending rigidity, conversely, the bending rigidity 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 material mechanical properties of the nanoscale material.
[0016]
In addition, the `` clamping 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 polymer when the nanotube is produced by chemical treatment. According to the method of the present invention, the diameter of the solvent can be controlled by changing the solvent used in the treatment and its temperature, the nanomachine can be wound and unwound, and the nano-composite material can be wound by other substances. Deployment is also possible.
[0017]
【Example】
Hereinafter, examples will be shown to further clarify the features of the present invention. The present invention is not limited in any way by the examples.
Example 1
Using highly oriented pyrolytic graphite (HOPG; manufactured by Advanced Ceramics Corp., USA) by the 2-valve method ("Introduction to New Carbon Materials", Realize Inc. (1996), pp159-160) , KC ₈ was synthesized, stored in a sealed container, and after the container pressure was evacuated to 10 ^-3 Torr or less in advance, styrene vapor corresponding to the vapor pressure of styrene at room temperature was introduced at room temperature (about 25 ° C) And reacted. Styrene was previously dehydrated using molecular sieve 4A and then purified by vacuum distillation.
[0018]
The graphite-polymer composite obtained 24 hours after the start of the reaction is black, elastic, expanded graphite-like material, and occluded about 400 times the amount of styrene based on KC ₈ weight. .
[0019]
When 50 mg of the obtained graphite-polymer complex is immersed in 100 ml of N-methyl-2-pyrrolidone and left for 8 weeks with occasional stirring, the polystyrene component elutes and a black fine powder was gotten.
When the obtained black fine powder was observed with a transmission electron microscope, as shown in FIG. 2, it was a carbon nanotube having a cylindrical shape with an outer diameter of 26 nm and an inner diameter of 16 nm and 15 layers of graphene laminated thereon. It was confirmed.
Example 2
Using highly oriented pyrolytic graphite (HOPG; manufactured by Advanced Ceramics Corp., USA) by the 2-valve method ("Introduction to New Carbon Materials", Realize Inc. (1996), pp159-160) , KC ₂₄ was synthesized, stored in a sealed container, the container pressure was previously reduced to a vacuum of 10 ^-3 Torr or less, and isoprene vapor corresponding to the vapor pressure of isoprene at room temperature was introduced at room temperature (about 25 ° C) And reacted. Note that isoprene was dehydrated in advance using molecular sieve 4A and then purified by vacuum distillation.
[0020]
The graphite-polymer composite obtained 24 hours after the start of the reaction is black, elastic, expanded graphite-like material, and about 173 times the amount of isoprene was occluded based on the weight of KC ₂₄ .
[0021]
When 50 mg of the obtained graphite-polymer complex is immersed in 100 ml of N-methyl-2-pyrrolidone and left for 8 weeks with occasional stirring, the isoprene component elutes and a black fine powder was gotten.
[0022]
When the obtained black fine powder was observed with a transmission electron microscope, it was confirmed to be a carbon nanotube.
Example 3
A graphite-polymer composite was used in the same manner as in Example 2 except that gas-filled 1,3-butadiene (purity of 99.5% or more) was used as the unsaturated hydrocarbon, and the butadiene pressure was 500 Torr. The body was prepared.
[0023]
The obtained graphite-polymer composite was a black, elastic, expanded graphite-like material, and occluded about 153 times as much styrene based on ₂₄ weight KC.
When 50 mg of the obtained graphite-polymer composite is immersed in 100 ml of N-methyl-2-pyrrolidone and left for 8 weeks with occasional stirring, the polybutadiene component elutes, resulting in a fine black powder. was gotten.
[0024]
When the obtained black fine powder was observed with a transmission electron microscope, it was confirmed to be a carbon nanotube.
[Brief description of the drawings]
FIG. 1 is a drawing schematically showing a method for producing carbon nanotubes according to the present invention.
FIG. 2 is a transmission electron micrograph showing the laminated structure of carbon nanotubes obtained by the method of the present invention.

Claims (1)

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

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