JPWO2014021257A1 - Method for producing composite film comprising graphene and carbon nanotube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a composite film capable of efficiently and easily producing a composite film having a structure in which graphene and carbon nanotubes are alternately laminated. A method for producing a composite film having a structure in which nanosheet structures 10 and nanocarbon structures 12 are alternately laminated, comprising: a. Functionalizing the nanocarbon structure 12 to be cationic, b. Mixing a dispersion of the functionalized nanocarbon structure 12 and the dispersion of the nanosheet structure 10 to produce a suspension containing the nanocarbon structure and the nanosheet structure; c. Removing the dispersion medium from the suspension to form a film. [Selection] Figure 1

Description

  The present invention relates to a method for producing a composite film made of a composite carbon material in which graphene and carbon nanotubes are alternately laminated.

A carbon nanotube (CNT) is a hollow nano-sized carbon fiber having a high aspect ratio obtained by rounding a graphene sheet into a cylindrical shape. Carbon atoms that make up the carbon skeleton of CNTs are substituted with other atoms called other-atom-doped CNTs, such as nitrogen-doped CNTs and boron-doped CNTs. Type CNT).
Hybrid carbon materials combining CNTs (hereinafter including other-atom doped CNTs and encapsulated CNTs) and graphene (G), graphene oxide (GO) or reduced graphene (RGO) are materials composed of a carbon skeleton and have a specific surface area. It is expected to have excellent physical properties that are not present in conventional materials, such as high mechanical stability, high mechanical stability, and high electrical and thermal conductivity. For example, application to supercapacitors, carbon electrodes, solar cell components, energy storage, sensors, etc. is expected.

What is desired as a method of creating hybrid carbon materials (CNT / G, CNT / GO, CNT / RGO) combining these CNTs with graphene (G), graphene oxide (GO), and reduced graphene (RGO) (1) Introducing CNTs without placing support between the graphene layers, (2) Satisfying the two points of coordinating and orienting CNTs between the graphene layers.
Regarding (1), the stacking interval of G, GO, and RGO is basically 0.335 nm of the interlayer distance of graphite, and is narrower than the minimum diameter of 0.4 nm of CNT. Therefore, CNTs will not be coordinated between the layers unless the G, GO, and RGO layer spacing is increased using some support (support).
Regarding (2), CNT, G, GO, and RGO are all carbon crystals, and CNTs are randomly coordinated on the G, GO, and RGO surfaces. It is not impossible to mechanically or electrically align the direction of CNTs on the G, GO, and RGO planes, but it is not easy to make a laminated composite material.

Methods for overcoming these technical problems include filtration methods (Non-Patent Documents 1 and 2), casting of dispersion liquid (Non-Patent Documents 3), electrophoretic growth methods (Non-Patent Documents 4 and 5), layer-by-layer lamination Methods (Non-Patent Documents 6 and 7) and Langmuir-Blodgett film method (Non-Patent Document 8) have been proposed.
However, these methods are not suitable for mass production practical use because they require a lot of man-hours and take a lot of time or require operation under a microscope.
In order to complete a stack of CNT and graphene by a chemically easy reaction, attempts have been made to obtain a stacked structure by chemically treating and reacting either CNT or graphene or both (non- Patent Documents 9 and 10). However, this method also takes time or is far from practical use due to aggregation of CNT or G, GO, and RGO.

  As a technique for simply combining CNT with G, GO, and RGO, a system in which CNT is cut when CNT is applied to an electrode and G and CNT coexist as a mixture has been proposed (Patent Document 1). ). This is to fix the cylindrical structure of CNT to the current plate (through electrode) using graphene. It cannot be said to be a laminated structure material of CNT and graphene. In addition, although it has been proposed as an electrode material to squeeze CNTs to make graphene and dope lithium (Patent Document 2), it appeals for CNT / G, CNT / GO, and CNT / RGO laminated structures. I don't mean.

A laminate structure in which vapor-grown carbon fibers are laminated and CNTs are arranged in gaps has been reported (Patent Document 3). This structure is a composite having a structure in which a vapor-grown carbon fiber having a diameter of 100 nm or more is a basic skeleton, and the gap is filled with CNTs having a diameter of less than 100 nm. It should be noted that the description describes the rounded graphene but does not form a CNT / G stacked structure.
An electronic material having a structure in which graphite is deposited on the surface centering on CNT has been proposed (Patent Document 4). This material should be understood that the carbon remaining in the CNT manufacturing process has a graphite structure, and is greatly different from the CNT / G laminated structure of the present invention.
As described above, a method for producing a CNT / G, CNT / GO, and CNT / RGO laminated composite carbon material in which CNT and graphene are laminated has not been established so far, and has not yet reached a practical stage.

Table 02/063693 Special table 2011-503804 gazette JP 2008-285745 A JP-T 2009-524567

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  In the present invention, a composite film having a structure in which carbon nanotubes (CNT) are sandwiched between layers made of graphene, and layers made of graphene and layers made of carbon nanotubes are alternately stacked, is applied to a long-time reaction treatment with a large number of steps. It is an object of the present invention to provide a method that enables easy production without performing work under a microscope.

The method for producing a composite film according to the present invention is a method for producing a composite film having a structure in which nanosheet structures and nanocarbon structures are alternately laminated,
a. A step of functionalizing the nanocarbon structure to be cationic,
b. A step of mixing the dispersion of the functionalized nanocarbon structure and the dispersion of the nanosheet structure to produce a mixed suspension;
c. Removing the dispersion medium from the mixed suspension to form a composite film;
It is characterized by providing.

Moreover, as a manufacturing method of the composite film which concerns on this invention, d. It is effective to include a step of reducing the composite film.
As the reduction treatment method, thermal or chemical reduction treatment can be used. As the thermal reduction treatment, a treatment of heating to a high temperature sufficient to reduce the nanosheet structure such as graphene oxide in the atmosphere can be used. As the chemical reduction treatment, treatment using hydrazine monohydrate, hydroquinone, gaseous hydrogen, alkaline solution (NaOH, KOH, etc.), vitamin C, sodium borohydride can be used.
The composite film means a film made of a composite carbon material in which nanosheet structures and nanocarbon structures are alternately laminated. The composite film is subjected to the reduction treatment in step d and the reduction treatment in step d. Includes both not. Usually, a composite film subjected to a reduction treatment is used in order to obtain the conductivity or toughness of the film, but a composite film that has not been subjected to the reduction treatment can be used depending on the application.

  As the nanosheet structure, any one of graphene, graphene oxide, reduced graphene, graphite oxide, or reduced graphite can be used. Graphene oxide (GO) has a structure in which part of carbon in graphene is substituted with oxygen or a structure in which oxygen is bonded to carbon, and can be synthesized by oxidizing graphite. Reduced graphene (RGO) is obtained by reducing graphene oxide. In the reduced graphene obtained by reducing graphene oxide, a portion where graphene is oxidized remains slightly, and in this sense, it is not completely the same as graphene. Graphite oxide is obtained by oxidizing graphite, and reduced graphite is obtained by reducing graphite oxide. Graphite oxide can be obtained by a method of chemically oxidizing graphite. Note that graphite is formed by stacking a plurality of graphenes.

Since graphene used as a nanosheet structure does not have a structure in which carbon and oxygen are combined, its action is different from graphene oxide or the like. However, it can be dispersed in a solvent by a method such as using a surfactant, and a composite film can be formed using the same steps as other nanosheet structures.
When a composite film is manufactured using graphene, the structure is similar to that of graphene oxide in which carbon is replaced with oxygen or bonded to oxygen by passing the treatment process. Therefore, the reduction treatment step d has an effective effect of improving the electrical conductivity of the composite film even when graphene is used as the nanosheet structure.

As the nanosheet structure, a peelable layered material made of a divalent or trivalent chalcogenide of a transition metal can be used instead of graphene, graphene oxide, reduced graphene, or the like. Examples of transition metal chalcogenides include MoS ₂ , WS ₂ , NbS ₃ , and MnPS ₃ . In addition, a layered material such as boron nitride can also be used.

As the nanocarbon structure, carbon nanotubes, other atom-doped carbon nanotubes, encapsulated carbon nanotubes, fullerenes, and graphene nanoribbons can be used. As the carbon nanotubes, single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), triple-walled carbon nanotubes (TWCNT), and multi-walled carbon nanotubes (MWCNT) can be used.
The atoms to be doped as other atom-doped carbon nanotubes are not particularly limited, but single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), triple-walled carbon nanotubes (TWCNT), multi-walled carbon nanotubes (MWCNT) ), Carbon nanotubes doped with nitrogen or boron can be suitably used.
Carbon nanotubes can be synthesized using, for example, a CVD method (Non-patent Documents 17 and 18).

  As the nanocarbon structure, inorganic nanotubes such as boron nitride nanotubes, tungsten disulfide nanotubes, molybdenum disulfide nanotubes, titanium oxide nanotubes, chalcogenide nanotubes, and boron-carbon-nitrogen (BCN) nanotubes can be used.

As a method for functionalizing the nanocarbon structure cationically (step a), the methods already disclosed (Non-Patent Documents 12, 13, 14, and 15) can be used. As a method for functionalizing the nanocarbon structure cationically, there is a method using a surfactant, a polymer, or a polyelectrolyte.
By functionalizing a nanocarbon structure such as a carbon nanotube, the nanocarbon structure can be suitably dispersed in a polar solvent such as water, alcohol, acetone, or aldehydes.

In step b of the method of the present invention, the dispersion liquid of the functionalized nanocarbon structure and the dispersion liquid of the nanosheet structure are mixed to obtain a mixed suspension containing the nanocarbon structure and the nanosheet structure. Make it. The mixed suspension is meant to include both nanocarbon structures and nanosheet structures.
By using a polar solvent as the dispersion, the functionalized nanocarbon structure becomes cationic and is suitably dispersed in the polar solvent, and the nanosheet structure is anionic and suitably dispersed in the polar solvent. . As the polar solvent, a solvent can be appropriately used, and it is of course possible to use water. When water is used, the treatment operation can be easily performed, which is preferable.

To prepare a mixed suspension containing a functionalized nanocarbon structure and nanosheet structure, drop the nanocarbon structure dispersion little by little into the nanosheet structure dispersion. What is necessary is just to mix a nanocarbon structure. Conversely, a method of dropping the nanosheet structure dispersion into the nanocarbon structure dispersion may be used.
In the mixing step, the nanocarbon structure and the nanosheet structure can be effectively dispersed and mixed by mixing the dispersion while applying ultrasonic vibration. Ultrasonic vibration, a stirrer, and a vortex generator can be used in combination.
When the dispersion of nanocarbon structure and nanosheet structure is mixed, the structure in which the nanocarbon structure and nanosheet structure are alternately stacked is gradually increased by the cation-anion action of the nanocarbon structure and nanosheet structure. Will be built.

Step c is a step of removing the dispersion medium from the mixed suspension to form a film.
As a method for forming a film using the mixed suspension, a method of casting the mixed suspension on the surface of the substrate and allowing it to stand to remove a dispersion medium such as moisture from the mixed suspension can be used. After the mixed suspension is cast on the surface of the base material, it is made of a composite carbon material in which nanocarbon structures and nanosheet structures are alternately stacked on the surface of the base material by heating gently to remove the dispersion medium. A film is produced.

  When the mixed suspension is cast on the substrate surface and allowed to stand, the nanocarbon structure and the nanosheet structure are re-coordinated to the alternately stacked arrangement by the cation-anion action (self-assembly). In this state, the film is formed. A composite film is a composite carbon material in which nanocarbon structures and nanosheet structures are alternately laminated in a plurality of layers in a sheet shape, and the composite carbon materials are accumulated in various directions in the film. However, in the vicinity of the surface of the composite film, the composite carbon materials are arranged so that the plane of the nanosheet structure is parallel to the surface of the composite film.

The composite film formed on the substrate surface is used after being detached (peeled) from the substrate surface. Therefore, the substrate on which the mixed suspension is cast is preferably a water-repellent substrate.
The method of forming a film using the mixed suspension is not limited to the casting method, and a method used in the paper manufacturing process can be used. The method of casting the mixed suspension on the surface of the substrate to form a composite film can arbitrarily set the width, length, thickness, etc. of the composite film.

FIG. 1 shows a process of forming a composite carbon material of carbon nanotubes and graphene when carbon nanotubes are used as nanocarbon structures and graphene oxide is used as nanosheet structures.
Steps A and B are processes in which the graphene oxide 10 and the carbon nanotubes 12 are each stably dispersed in the dispersion. Graphene oxide can be dispersed in a dispersion as an anionic polyelectrolyte by addition of carboxylic acid or itself, and carbon nanotubes can be dispersed in a dispersion as a cationic polyelectrolyte by the functionalization treatment described above. .

Next, the graphene oxide dispersion and the carbon nanotube dispersion are mixed to prepare a suspension (mixed suspension) in which the graphene oxide 10 and the carbon nanotubes 12 are mixed with each other (step C). ). In the mixed suspension, the graphene oxide and the carbon nanotubes interact with each other by a cation-anion action, and the graphene oxide and the carbon nanotubes are gradually arranged alternately.
Next, the mixed suspension of graphene oxide and carbon nanotubes is cast into a mold (substrate surface), heated gently to remove the dispersion medium (dispersion), and the graphene oxide and carbon nanotubes are re-coordinated. A structure in which graphene oxide 10 and carbon nanotubes 12 are alternately stacked is constructed (step D). Step D shows one composite carbon material in which graphene oxide 10 and carbon nanotubes 12 have a laminated structure. Step E is a state in which the film is subjected to a reduction treatment to finally obtain a composite film (hybrid film).

  The composite film of graphene oxide and carbon nanotube becomes a film having a structure in which graphene oxide (GO) is reduced to graphene (RGO) by reduction treatment, and reduced graphene and carbon nanotubes are alternately stacked. When this composite film is further reduced to reduce the reduced graphene completely, a composite film of graphene (G) and carbon nanotubes is obtained. Thus, a hybrid film (composite carbon material) composed of graphene and carbon nanotubes can have a laminated structure that is a combination of CNT / GO, CNT / RGO, and CNT / G.

  According to this method, carbon nanotubes and graphene oxide are stacked by the action of Self-Assemble by utilizing the cation-anion reaction between carbon nanotubes (CNT) and graphene oxide (GO). A hybrid laminated structure can be configured easily. This method can be applied not only to carbon nanotubes, but also to other atom-doped carbon nanotubes, encapsulated carbon nanotubes, fullerenes, graphene nanoribbons, etc. that can be modified (functionalized) using a polyelectrolyte. it can.

  The physical properties of CNT / GO hybrid films produced using graphene oxide can be adjusted by adjusting the degree of reduction of GO. Since the hybrid film is basically a carbon composite, it has high heat stability. A fully reduced CNT / G hybrid film is chemically stable. Further, since the composite carbon material is formed by the self-stacking reaction, it is not necessary to form a support structure between the graphene layers, and the number of steps can be significantly reduced as a method of manufacturing the composite carbon material (hybrid film).

The composite film obtained by the method of the present invention is composed of a regular composite, and the fibrous CNT (nanocarbon structure) and the planar G, GO, RGO (nanosheet structure) are in contact at multiple points. Therefore, it exhibits a low electric resistance of 10 ⁻³ Ω · cm or less. In addition, by using other atom-doped CNT such as nitrogen-doped CNT or boron-doped CNT, the band gap can be controlled, so that it can be applied as a carbon semiconductor. On the other hand, since it is made of carbon, it has high heat resistance, chemical resistance, and rust resistance.
Based on these facts, the range of applications includes supercapacitors, fuel cells and other electrochemical fields, metal-free catalyst fields, scaffolding materials and other tissue engineering fields, metal replacement materials such as electric wires, wire harnesses, mobile vehicle bodies, and aircraft. Materials, spacecraft / base materials, electromagnetic shielding materials, carbon semiconductors, electron / electromagnetic emission sources, building structural materials, resin composite materials, metal composite materials, energy storage materials, photovoltaic materials, water treatment adsorbents, conductivity There are fibers, heat-resistant fabrics and the like.

  According to the method for producing a composite film according to the present invention, a composite film having a structure in which nanocarbon structures and nanosheet structures are alternately laminated can be easily and efficiently produced. The composite film which can be utilized for various uses from a physical characteristic can be provided.

It is a conceptual diagram about the manufacturing method of the composite film which has a laminated composite structure of a graphene and a carbon nanotube. It is a photograph of the composite film (before reduction process) produced using the multi-walled carbon nanotube and graphene oxide. It is a photograph which shows the state before and behind reduction processing about the composite film of MWCNT / GO (a), N-MWCNT / GO (b), and B-MWCNT / GO (c). It is a SEM image of the composite film which consists of a multi-walled carbon nanotube (MWNT) and a graphene oxide (GO). It is a SEM image about the composite film which consists of nitrogen dope MWNT and a graphene oxide. It is a SEM image of the composite film which consists of boron dope MWNT and graphene oxide. It is a Raman spectrum about the composite film before and behind a reduction process. It is a graph which shows a thermogravimetric analysis result.

(Synthesis of carbon nanotubes)
Multi-walled CNTs use a mixture of 6 wt% ferrocene and 94 wt% toluene, and CVD (chemical) with argon flow (2.5 L / min), 825 ° C, normal pressure
This was obtained by performing annealing and purification after synthesis by vapor deposition).

  Nitrogen-doped CNTs were synthesized by a CVD (chemical vapor deposition) method using a mixture of 6 wt% ferrocene and 94 wt% benzylamine, flowing through argon (2.5 L / min), 850 ° C, and atmospheric pressure. Obtained by processing.

  Boron-doped CNTs were first synthesized using a continuous reaction vessel using a cylindrical reaction vessel, using a continuous system with ferrocene as a catalyst precursor, toluene as a carbon supply source, and hydrogen as a carrier gas. A toluene solution containing 2-3 wt% of the ferrocene compound was fed into the reaction vessel with a supply pump (25 g / min) and reacted at about 1200 ° C. The obtained carbon nanotubes were mixed with boric acid (5 wt%), and the mixture was heat-treated at 2400 ° C. in an argon atmosphere to obtain boron-doped CNTs.

(Synthesis of graphene oxide)
Graphene oxide was synthesized using commercially available graphite and obtained by chemical oxidation treatment (Non-patent Document 16).
The obtained graphene oxide is thoroughly washed with distilled water, and then freeze-dried to remove moisture trapped in the graphene oxide.

(Modification of carbon nanotube)
As a method for modifying (cation modification) the carbon nanotube (including other atom-doped carbon nanotube), a method using a polyelectrolyte can be used. The carbon nanotube can be functionalized as a cationic polyelectrolyte by a method already disclosed (Non-Patent Documents 12, 13, 14, and 15). By functionalization, the carbon nanotubes are dispersed from a bundled state in a polar solvent such as water, alcohol, acetone, and aldehydes, and are uniformly dispersed in the solvent.

In the examples, the carbon nanotubes were functionalized as follows.
First, 10 mg of carbon nanotubes were heat-treated at 800 ° C. in the presence of oxygen (air flow rate: 0.5 L / min) to remove amorphous carbon on the surface of carbon nanotubes and impurities (solvent, hydrocarbon, etc.) remaining on the surface. By this heat treatment, it becomes possible to slightly oxidize the surface of the carbon nanotube and form an anchor site functionalized by the polyelectrolyte.

The carbon nanotubes subjected to the heat treatment were uniformly dispersed in water by applying ultrasonic waves to form a suspension, and this suspension was applied to the 2 mg / L cationic polyelectrolyte solution while applying ultrasonic waves. It was dripped.
Carbon nanotubes (MWCNT), nitrogen-doped carbon nanotubes, and boron-doped carbon nanotubes can be functionalized cationically with amines or amines, imines or imines, and this operation enables functionalized carbon nanotubes. Is uniformly dispersed in the electrolyte solution. Next, a functionalized carbon nanotube was obtained by removing excess polyelectrolyte using a washing method using a centrifugal separation method.

(Creation of graphene-carbon nanotube composite film)
10 mg of the suspension (dispersion medium: water) of MWCNT, nitrogen-doped MWCNT, and boron-doped MWCNT prepared by the above method was added to the suspension of graphene oxide (dispersion medium: water) at a concentration of 0.05 g / mL, respectively. The solution was dropped while applying sound waves. After dropping, the mixture was further stirred for 30 minutes using ultrasonic waves to uniformly disperse the carbon nanotubes and graphene oxide to obtain a mixed suspension.
Subsequently, this suspension (mixed suspension) containing graphene oxide and carbon nanotubes is cast on the surface of a PTFE (polytetrafluoroethylene) substrate and heated at 60 ° C. to dissipate moisture. A film was formed on the material surface. The obtained film is a composite film made of a composite carbon material in which graphene oxide, multilayer CNT, nitrogen-doped multilayer CNT, and boron-doped multilayer CNT are alternately laminated.
The reduction treatment of the composite film was performed by heating the film detached from the substrate surface to 800 ° C. under Ar flow.

  As a comparative example, a suspension containing only graphene oxide is stirred for 30 minutes using an ultrasonic stirrer, cast on the substrate surface, a film is formed by the same method as described above, and comparative measurement is performed. went.

Table 1 shows carbon, oxygen, and nitrogen before and after reduction treatment by heating at 800 ° C. for 10 minutes in air for a composite film made of multi-walled carbon nanotubes, nitrogen-doped carbon nanotubes, boron-doped carbon nanotubes and graphene oxide. The result of having measured the content of is shown. The content of carbon, oxygen and the like can be measured by obtaining a core level spectrum of each element using XPS.
The measurement results show that oxygen is greatly reduced by reduction treatment for any composite film. However, oxygen is not completely lost by the reduction treatment.
The amount of nitrogen in the sample using nitrogen-doped carbon nanotubes does not change much before and after the reduction treatment. Although the measurement results of boron content are not shown for samples using boron-doped carbon nanotubes, the amount of boron does not change much before and after the reduction treatment, as with samples using nitrogen-doped carbon nanotubes. Depends on the boron content of the boron doped carbon nanotubes.

(Composite film)
FIG. 2 shows a composite film produced by the above-described method using multi-walled carbon nanotubes and graphene oxide. The composite film shown here is the one before the reduction treatment. 2 (a)) shows a state where the composite film is bent, FIGS. 2 (b) and 2 (c) show a state where the composite film is twisted, and FIG. 2 (d) shows a state where the composite film is twisted and further bent. As can be seen from FIG. 2, the composite film is a highly flexible film.

  FIG. 3 (a) shows the state before and after the reduction treatment of the MWCNT / GO, FIG. 3 (b) shows the N-MWCNT / GO, and FIG. 3 (c) shows the B-MWCNT / GO composite film. In any sample, the composite film before the reduction treatment has a darker color than the composite film after the reduction treatment. This is mainly due to the carbon nanotubes present between the graphene oxide sheets. When the reduction treatment is performed, the composite film exhibits a silver metallic color as shown in FIG.

(SEM observation)
4, 5, and 6 show SEM images of a hybrid film (composite carbon material) of multilayer CNT, nitrogen-doped multilayer CNT, boron-doped multilayer CNT, and graphene oxide. In each figure, (a), (b), and (c) are before the reduction treatment and have different magnifications, and (d) is the one subjected to the reduction treatment at 800 ° C. in an argon atmosphere.
In any case, it can be seen that the carbon nanotubes are randomly and uniformly distributed in the film plane and are sandwiched between the graphene oxide layers. It is important that the carbon nanotubes disperse independently within the film and do not agglomerate, and this results in the presence of strong interactions that make up the film, a dispersion (suspension) of graphene oxide and carbon nanotubes It is shown that it is effective to construct a film from
Even when the reduction treatment is performed, the configuration of the laminated composite carbon material is not changed.

(Raman spectroscopy)
FIG. 7 shows the results of Raman spectroscopic analysis before and after the reduction treatment of the composite film of MWCNT / GO, N-MWCNT / GO, and B-MWCNT / GO and the GO film. 7A and 7B show the measurement results before the reduction treatment, and FIGS. 7C and 7D show the measurement results after the reduction treatment. Table 2 shows the peak value of the Raman band.

In all spectra, D (1348 cm ⁻¹ ), G (1588 cm ⁻¹ ), 2D (2724 cm ⁻¹ ), D + G (2918 cm ⁻¹ ), and 2D ′ (3151 cm ⁻¹ ) bands appear. Although the peak shift occurs when the types of carbon nanotubes are different, the shift amount is very small in the result of this experiment. This is based on a strong interaction between the carbon nanotube and the graphene oxide sheet. In addition, since the peak shift before and after the reduction treatment is very slight, it can be seen that the structure of graphene and carbon nanotubes is retained before and after the reduction treatment and does not change significantly, and the laminated structure of graphene and carbon nanotubes is stable.

(Thermogravimetric analysis)
FIG. 8 shows the thermogravimetric analysis results. The first change around 200 ° C indicates an exothermic reaction when GO is reduced. The change around 500 ℃ indicates the oxidation of carbon with graphite structure. The difference in the oxidation reaction temperature of each sample is due to the influence of other atom doping on CNT. That is, other atoms dope a defect in the carbon crystal lattice and shift the oxidation start temperature to the low temperature side. From these results, it can be seen that the graphene-CNT hybrid film (laminated composite carbon material) produced by the method of the present invention has different physical properties from graphene or graphene oxide.

(Electrical resistance measurement)

Table 3 shows the resistance values of CNT / GO and GO. Although the resistance of single-walled CNT has been reported to be 10 ⁻⁴ Ωcm, the effective value is 10 ⁰ Ωcm. The resistance value of graphene oxide was 4.26 × 10 ⁻³ Ωcm. As shown in Table 3, the resistance value of the composite film of carbon nanotubes (MWCNT) and graphene oxide (after reduction treatment) according to the present invention is much smaller than the resistance value of graphene oxide. This means that the electrical conductivity has been improved by the addition of carbon nanotubes.

10 Graphene oxide (nanosheet structure)
12 Carbon nanotubes (nanocarbon structure)

Claims (13)

A method for producing a composite film having a structure in which nanosheet structures and nanocarbon structures are alternately laminated,
a. A step of functionalizing the nanocarbon structure to be cationic,
b. A step of mixing the dispersion of the functionalized nanocarbon structure and the dispersion of the nanosheet structure to produce a mixed suspension;
c. Removing the dispersion medium from the mixed suspension to form a composite film;
A method for producing a composite film, comprising: As a subsequent step of the step c,
d. The method for producing a composite film according to claim 1, further comprising a step of reducing the composite film.   The method for producing a composite film according to claim 2, wherein a thermal or chemical reduction treatment is performed as the reduction treatment in the step d. As the nanosheet structure,
The method for producing a composite film according to any one of claims 1 to 3, wherein any one of graphene, graphene oxide, reduced graphene, graphite oxide, or reduced graphite is used. As the nanocarbon structure,
The method for producing a composite film according to any one of claims 1 to 4, wherein carbon nanotubes, other atom-doped carbon nanotubes, encapsulated carbon nanotubes, fullerenes, and graphene nanoribbons are used. As the carbon nanotube,
6. The method for producing a composite film according to claim 5, wherein single-walled carbon nanotubes (SWCNT), double-walled carbon nanotubes (DWCNT), triple-walled carbon nanotubes (TWCNT), and multi-walled carbon nanotubes (MWCNT) are used. As the other atom-doped carbon nanotube,
A single-walled carbon nanotube (SWCNT), a double-walled carbon nanotube (DWCNT), a triple-walled carbon nanotube (TWCNT), or a multi-walled carbon nanotube (MWCNT), wherein carbon nanotubes doped with nitrogen or boron are used. 5. A method for producing a composite film according to 5.   A method for producing a composite film according to any one of claims 1 to 7, wherein a polar solvent is used as the dispersion.   The method for producing a composite film according to claim 8, wherein water is used as the polar solvent.   The method for producing a composite film according to claim 1, wherein in step a, the nanocarbon structure is functionalized using a surfactant, a polymer, and a polyelectrolyte solution.   2. The method for producing a composite film according to claim 1, wherein in step b, a suspension of the nanocarbon structure and the nanosheet body is produced by utilizing an action of ultrasonic waves. As the nanosheet structure,
2. The method for producing a composite film according to claim 1, wherein a peelable layered material comprising a divalent chalcogenide or a trivalent chalcogenide of a transition metal is used. As the nanocarbon structure,
The method for producing a composite film according to claim 1, wherein boron nitride nanotubes, tungsten disulfide nanotubes, molybdenum disulfide nanotubes, titanium oxide nanotubes, chalcogenide nanotubes, and boron-carbon-nitrogen (BCN) nanotubes are used.

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