JP7305146B2 - Carbon nanostructure production method and carbon nanostructure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a carbon nanostructure and a carbon nanostructure, and more particularly to a method for forming a carbon nanostructure on the surface of a carbon fiber and a carbon fiber surface-coated with the carbon nanostructure. The present invention also relates to a method for producing carbon nanowalls, which are carbon nanostructures.

In recent years, minute carbon structures (carbon nanostructures) having sizes on the order of nanometers, such as carbon nanotubes, carbon nanofibers, carbon nanowalls, fullerenes, and graphenes, have attracted attention. For example, carbon nanofibers are superior in mechanical strength, electrical conductivity, and thermal conductivity to glass fibers and the like, so they are used in a wide range of applications such as plastic reinforcing materials, gas storage materials, and electrode materials.

Here, for the mass production of carbon nanostructures, a vapor phase method is generally used in which a carbon compound is brought into contact with fine metal particles as a catalyst. A problem is that it adversely affects the properties of the nanostructures.

On the other hand, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-212948), by irradiating carbon nanofibers with microwaves, impurities in the carbon nanofibers are removed and the degree of graphitization is improved. A method is proposed.

On the other hand, conventionally known carbon fibers are in increasing demand as reinforcing materials for various matrices, and various surface modification methods have been proposed to enhance interactions with matrices. For example, Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2013-231245) proposes a method of attaching atoms not derived from carbon fibers to the surface by subjecting carbon fibers to mechanochemical treatment. Japanese Unexamined Patent Application Publication No. 2017-193791) proposes a method of forming unevenness on the surface by subjecting carbon fibers to electrolytic oxidation treatment.

JP 2013-212948 A JP 2013-231245 A JP 2017-193791 A

However, the method for producing carbon nanofibers described in Patent Document 1 reduces the metal content of the carbon nanofibers containing the metal catalyst, and it is extremely difficult to completely remove the metal elements. Moreover, the obtained carbon nanofibers cannot be densely arranged on the substrate surface (for example, the carbon fiber surface).

In addition, the surface treatment methods described in Patent Documents 2 and 3 are not sufficient from the viewpoint of increasing the surface area of the carbon fibers, in addition to concerns about contamination of metal impurities and damage to the carbon fibers.

In view of the circumstances as described above, an object of the present invention is to provide a method for easily producing a carbon nanostructure without using a metal catalyst, and a surface modification method for easily converting the surface of a carbon fiber into a carbon nanostructure. is to provide

In order to achieve the above object, the present inventors have made intensive studies on a method for modifying the surface of carbon fibers and a method for producing a carbon nanostructure. However, it is extremely effective in converting the surface of the carbon fiber into a carbon nanostructure, and simultaneous application of microwave heating and gas plasma to the carbon material and the base material is effective for forming carbon nanostructures on the surface of the base material. The inventors have found that it is extremely effective in generating a wall, and arrived at the present invention.

That is, the present invention
Microwave-heating the carbon fiber by irradiating the carbon fiber with microwaves in a gas atmosphere,
inducing an excited state of the gas by the microwave;
cutting the C=C bonds of the carbon fibers with ultraviolet rays generated during the light emission process of the gas;
A carbon fiber surface modification method characterized by:
In the present invention, carbon fiber has a diameter of 1 μm to 20 μm, and is completely different from carbon nanotubes and carbon nanofibers.

In the carbon fiber surface modification method of the present invention, the carbon fiber is microwave-heated and, at the same time, the C=C bonds near the surface are cut by ultraviolet rays generated in the process of gas emission. Structured carbon nanostructures (carbon nanotubes, carbon nanowalls, graphene, graphene oxide, etc.) are densely formed. That is, heating of the carbon fiber by microwave irradiation and ionization (plasma generation) of the gas in the atmosphere are essential conditions.
In the present invention, the graphene structure means a structure including a sheet-like hexagonal lattice structure of sp-bonded carbon atoms with a thickness of one atom.

In the carbon fiber modification method of the present invention, the gas preferably contains at least one of air, argon, helium, nitrogen and carbon dioxide. By irradiating any one of air, argon, helium, nitrogen, and carbon dioxide with microwaves, it is possible to efficiently generate ultraviolet rays that contribute to scission of C═C bonds near the carbon fiber surface.

Further, in the method for modifying carbon fibers of the present invention, it is preferable that the carbon fibers are short fibers. By using short carbon fibers, it becomes easy to arrange them in a microwave irradiation device, and a large amount of processing can be performed at one time.

Moreover, in the method for modifying carbon fibers of the present invention, it is preferable that the carbon fibers are milled fibers. Milled fibers are carbon fibers made into short fibers by mechanical pulverization, and defects and strains are introduced near the surface. can proceed more efficiently.

In addition, the present invention
The surface is covered with a carbon nanostructure having a graphene structure,
that the carbon nanostructure does not contain a metal element;
A carbon fiber, characterized by:

The carbon fiber of the present invention has a diameter of 1 μm to 20 μm, and its entire surface is covered with a carbon nanostructure having a graphene structure. The carbon nanostructure having a graphene structure is not particularly limited as long as it is a nanometer-order carbon structure having a graphene structure. Examples include carbon nanotubes, carbon nanofibers, graphene, and carbon nanowalls. preferably carbon nanotubes and/or carbon nanowalls. In addition, the carbon nanostructure may be oxidized, and graphene oxide can be given as an example of the oxidized carbon nanostructure.

Moreover, in the carbon fiber of the present invention, the carbon nanostructure covering the surface does not contain a metal element. In general, a carbon nanostructure is formed using metal particles as a catalyst in the gas phase method, but the carbon nanostructure in the carbon fiber of the present invention is formed by cutting and recombination of C in the carbon fiber. , does not contain metal elements because it does not use a metal catalyst.

Also, the carbon fibers of the present invention are preferably short fibers. By forming a carbon nanostructure on the surface of short fibers, they can be suitably used for applications such as plastic reinforcing materials, gas storage materials, and electrode materials.

Furthermore, the carbon fibers of the present invention are preferably milled fibers. Milled fibers are carbon fibers made into short fibers by mechanical pulverization, and defects and strains are introduced near the surface. It can proceed more efficiently, and the carbon nanostructures can be formed more densely. The carbon fiber of the present invention can be suitably obtained by the carbon fiber surface modification method of the present invention.

In addition, the present invention
irradiating a carbon material and a base material with microwaves in a gas atmosphere to microwave-heat the carbon material and the base material;
inducing an excited state of the gas by the microwave;
The C=C bond of the carbon material is cut by ultraviolet rays generated during the light emission process of the gas,
forming carbon nanowalls on the surface of the base material using plasma carbon separated from the carbon material as a raw material;
Also provided is a method for producing carbon nanowalls, characterized by:

In the method for producing carbon nanowalls of the present invention, carbon nanowalls can be produced simply and in a short time using various carbon materials as raw materials without using a hydrocarbon-based gas and a metal catalyst. In addition, when carbon nanostructures are formed on the surface of a base material, there are cases in which the temperature of the base material needs to be raised separately. and heating of the substrate are achieved at the same time, so there is no need to separately heat the substrate.

The positional relationship between the carbon material and the substrate is not particularly limited as long as it does not impair the effects of the present invention. For example, the carbon material and the substrate may be arranged side by side in an alumina boat that is generally commercially available.

Moreover, in the method for producing carbon nanowalls of the present invention, it is preferable that the gas contains at least one of air, argon, nitrogen, and carbon dioxide. By irradiating any of air, argon, helium, nitrogen, and carbon dioxide with microwaves, it is possible to efficiently generate ultraviolet rays that contribute to scission of C=C bonds in the carbon material.

Moreover, in the method for producing carbon nanowalls of the present invention, it is preferable that the carbon material is carbon fiber. By using carbon fibers as the carbon material, it is possible to simultaneously achieve the formation of carbon nanowalls on the substrate surface and the coating of the carbon fiber surface with the carbon nanostructures.

Furthermore, in the method for producing carbon nanowalls of the present invention, it is preferable that the carbon nanowalls do not contain a metal element. Since the carbon nanowalls do not contain a metal element, it is possible to prevent the metal element from adversely affecting the electrical conductivity and the like of the carbon nanowalls. Note that the carbon nanowall is a plate-like carbon nanostructure in which several to several hundred graphene sheets are stacked and spread two-dimensionally with a thickness of several nanometers to several tens of nanometers. It has the characteristic that there is

ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing a carbon nanostructure simply can be provided, without using a metal catalyst. Furthermore, according to the present invention, it is possible to provide a surface modification method for easily converting the surface of carbon fibers into a carbon nanostructure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the state of the carbon fiber surface modification method of the present invention. 1 is a schematic cross-sectional view of a carbon fiber (carbon nanostructure-coated carbon fiber) of the present invention; FIG. 1 is a SEM photograph of carbon fibers when the microwave irradiation time was set to 1 minute in Example 1. FIG. 4 is a SEM photograph of carbon fibers when the microwave irradiation time was set to 3 minutes in Example 1. FIG. 4 is a SEM photograph of carbon fibers when the microwave irradiation time was set to 5 minutes in Example 1. FIG. 4 is a high-magnification SEM photograph of the surface of the carbon fiber shown in FIG. 3; 4 is a TEM photograph of the surface of the carbon fiber shown in FIG. 3; 8 is a high-magnification observation image of the region indicated by the ◯ mark in the TEM observation image of FIG. 7 . 1 shows the results of X-ray photoelectron spectroscopy (XPS) of an untreated carbon fiber surface and a carbon fiber surface obtained with a microwave irradiation time of 1 minute. It is the Raman spectroscopic analysis result of the untreated carbon fiber surface and the carbon fiber surface obtained with the microwave irradiation time of 1 minute. 4 is a SEM photograph of carbon fibers irradiated with microwaves for 1 minute in Example 2. FIG. 4 is a SEM photograph of carbon fibers irradiated with microwaves for 5 minutes in Example 2. FIG. 10 is a SEM photograph of carbon fibers irradiated with microwaves for 1 minute in Example 3. FIG. 4 is a SEM photograph of carbon fibers irradiated with microwaves for 5 minutes in Example 3. FIG. 10 is a SEM photograph of carbon fibers irradiated with microwaves for 1 minute in Example 4. FIG. 10 is a SEM photograph of carbon fibers irradiated with microwaves for 5 minutes in Example 4. FIG. 4 is an SEM photograph of carbon fibers obtained in a comparative example. 10 is an appearance photograph showing the arrangement of activated carbon powder and each substrate in an alumina boat in Example 5. FIG. 4 is an appearance photograph of each substrate after treatment in Example 5. FIG. 11 is a SEM photograph of a black deposit peeled off from a Cu substrate in Example 5. FIG. 10 is a SEM photograph of the Al substrate surface after treatment in Example 5. FIG. 11 is a photograph of the appearance of a Si substrate after treatment in Example 6. FIG. 10 is an SEM photograph of the Si base material after treatment in Example 6, observed from the side. 10 is an appearance photograph of a glass substrate after treatment in an alumina boat in Example 7. FIG. 4 is a SEM photograph of the surface of the glass substrate in Example 7. FIG.

Hereinafter, a preferred embodiment of the method for producing a carbon nanostructure of the present invention, the carbon nanostructure obtained by the method, and the carbon fiber coated with the carbon nanostructure will be described in detail. It should be noted that the following description merely shows one embodiment of the present invention, and the present invention is not limited by these, and redundant description may be omitted.

(1) Carbon fiber surface modification method (carbon nanostructure production method)
In the carbon fiber surface modification method of the present invention, the carbon fiber is microwave-heated by irradiating the carbon fiber with microwaves in a gas atmosphere, the excited state of the gas is induced by the microwave, and the It is characterized by cutting the C=C bond of the carbon fiber with ultraviolet rays. Each of these constituent requirements will be described in detail below.

FIG. 1 schematically shows an example of a situation in which carbon fibers are surface-modified. A glass tube 4 is inserted into the microwave generator 2 , and carbon fibers 8 placed in an alumina boat 6 are arranged inside the glass tube 4 . Further, the glass tube 4 is provided with a gas inlet 10 and a gas outlet 12, and the inside of the glass tube 4 is a gas atmosphere.

(1-1) Carbon Fiber The carbon fiber 8 is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known carbon fibers can be used. The carbon fiber 8 has a diameter of 1 μm to 20 μm, and is completely different from carbon nanotubes and carbon nanofibers.

Short fibers are preferably used for the carbon fibers 8, and milled fibers are more preferably used. Milled fibers are carbon fibers made into short fibers by mechanical pulverization, and defects and strains are introduced near the surface. can proceed more efficiently.

(1-2) Gas Atmosphere The surface modification method of the present invention cannot be achieved only by micro-heating the carbon fibers 8, and requires the use of gas plasma. When the carbon fibers 8 are heated by microwaves, ultraviolet rays generated during the light emission process of the gas present inside the glass tube 4 cut the C=C bonds near the surfaces of the carbon fibers 8. As a result, the surfaces of the carbon fibers 8 Carbon nanostructures (carbon nanotubes, graphene, graphene oxide, etc.) having a graphene structure are densely formed.

As long as the C=C bond on the surface of the carbon fiber 8 is cut by the ultraviolet rays generated during the light emission process of the gas, the type of gas filled or circulated in the glass tube 4 is not limited, but air, argon, helium, nitrogen and It preferably contains at least one of carbon dioxide. These gases may be used singly or in combination of two or more. By irradiating any one of air, argon, helium, nitrogen, and carbon dioxide with microwaves, it is possible to efficiently generate ultraviolet rays that contribute to severing the C═C bonds near the surface of the carbon fibers 8 .

The gas pressure and gas flow rate inside the glass tube 4 are not particularly limited as long as they do not impair the effects of the present invention, and may be appropriately adjusted according to the desired surface condition of the carbon fibers 8. The pressure is preferably less than 1000Pa. By setting the inside of the glass tube 4 to 1000 Pa and irradiating microwaves, it is possible to efficiently generate ultraviolet rays that contribute to the breaking of C=C bonds near the surface of the carbon fibers 8 .

(1-3) Microwave Irradiation Conditions Microwaves are generated by the microwave generator 2 to irradiate the gas inside the carbon fiber 8 and the glass tube 4 . Here, the microwave means an electromagnetic wave having a wavelength within the range of 100 μm to 1 m and a frequency of 30 MHz to 3 THz. As the microwave generator 2, for example, a general-purpose microwave oven can be used.

The output of the microwave used for surface modification of the carbon fibers 8 is not particularly limited, and may be appropriately adjusted according to the insertion amount (treatment amount) of the carbon fibers 8, the treatment speed, the desired surface state, etc., but for example When processing 10 mg of carbon fiber 8, the power is preferably 10 W to 1000 W, more preferably 100 W to 800 W.

The microwave irradiation time is also not particularly limited, and may be appropriately adjusted according to the amount of carbon fiber 8 to be inserted (processing amount), processing speed, desired surface condition, etc., but may be 10 seconds to 10 minutes. Preferably, the time is 1 to 5 minutes. When the treatment time is lengthened in the range of 10 seconds to 10 minutes, the amount of carbon nanostructures formed on the surface of the carbon fibers 8 increases and the density increases. In addition to increasing damage to 8, the resulting carbon nanostructures may also be damaged.

(2) Carbon Nanostructure-Coated Carbon Fiber By the carbon fiber surface modification method of the present invention, a carbon fiber surface-coated with a carbon nanostructure can be obtained. FIG. 2 shows a schematic cross-sectional view of the carbon fiber (carbon nanostructure-coated carbon fiber) of the present invention.

The carbon fiber 8 has a diameter of 1 μm to 20 μm, and has a carbon nanostructure 20 formed on its surface. Further, the length of the carbon fibers 8 is not particularly limited, and generally known long fibers, short fibers, or the like can be used. Here, the carbon nanostructures 20 are densely formed and cover the entire surface of the carbon fibers 8 . Here, since the carbon nanostructure 20 is formed of C near the surface of the carbon fiber 8, the carbon fiber 8 and the carbon nanostructure 20 have relatively good adhesion. is used as a reinforcing material for various matrices, the interaction between the carbon fibers 8 and various matrices can be increased (the mechanical properties of the carbon fibers can be better reflected).

The carbon nanostructure 20 is a carbon structure having a nanometer-order size and basically has a graphene structure. The carbon nanostructure 20 is not particularly limited, and examples thereof include carbon nanotubes (single-walled or multi-walled) and carbon nanowalls in which several layers of graphene are laminated. Also, the carbon nanostructure 20 may be oxidized. For example, graphene oxide can be used as the oxidized carbon nanostructure 20 .

Moreover, the carbon nanostructure 20 does not contain any metal element. Generally, in the vapor phase method, a carbon nanostructure is formed using metal particles as a catalyst, and the carbon nanostructure 20 is formed by cutting and recombination of C in the vicinity of the surface of the carbon fiber 8, Metal elements are not included. That is, it has excellent electrical conductivity and the like as compared with carbon nanostructures containing metal elements.

Further, the carbon fibers 8 are preferably short fibers, more preferably milled fibers. Milled fibers are carbon fibers made into short fibers by mechanical pulverization, and defects and strains are introduced near the surface. It can proceed more efficiently and form more carbon nanostructures 20 on the surface.

(3) Method for producing carbon nanowalls The method for producing carbon nanowalls of the present invention comprises irradiating a carbon material and a base material with microwaves in a gas atmosphere, heating the carbon material and the base material with microwaves, and heating the carbon material and the base material with microwaves. The excited state of the gas is induced, and the C=C bond of the carbon material is cut by the ultraviolet rays generated in the light emission process of the gas. is characterized by generating Each of these constituent requirements will be described in detail below.

Carbon nanowalls can be generated in the same manner as the above-described carbon fiber surface modification method, except that the carbon material and the substrate are arranged side by side in the alumina boat 6 shown in FIG.

The carbon material is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known carbon materials such as graphite and activated carbon can be used. Here, by using carbon fibers as the carbon material, it is possible to simultaneously achieve the generation of carbon nanowalls and the coating of the carbon fibers with the carbon nanostructures.

Also, the base material is not particularly limited as long as it does not impair the effects of the present invention, and conventionally known various metal materials, ceramic materials, Si materials, and the like can be used. Examples of metal materials include Al, Cu, and Fe, and examples of ceramic materials include glass.

The carbon nanowalls produced on the substrate surface may be used as they are, but they can be easily recovered by separating them from the substrate, and can be used as carbon nanowalls alone.

Although representative embodiments of the present invention have been described above, the present invention is not limited to these. For example, the carbon nanostructure 20 can be separated and recovered from the surface of the carbon fiber 8 and used only as the carbon nanostructure 20 .

Hereinafter, the method for producing a carbon nanostructure and the carbon nanostructure of the present invention will be further described in Examples, but the present invention is not limited to these Examples.

(1) Coating of carbon fiber with carbon nanostructure and carbon nanostructure <<Example 1>>
A PAN-based milled fiber (manufactured by Toray Industries, Inc., Torayca MLD, diameter 5 μm) was used as the carbon fiber and subjected to surface treatment in the state shown in FIG. Specifically, an alumina boat containing 20 mg of carbon fiber was inserted into a glass tube, and microwaves were irradiated at an output of 700 W using a commercially available microwave oven. Here, the inside of the glass tube was in a carbon dioxide atmosphere of about 100 Pa, and the microwave irradiation time was 1 to 5 minutes. Light emission was observed during microwave irradiation.

FIGS. 3 to 5 show SEM photographs of the carbon fibers after irradiation when the microwave irradiation times were 1 minute, 3 minutes, and 5 minutes, respectively. An extremely fine structure is formed on the surface of all carbon fibers, and its density and amount increase as the irradiation time increases.

High-magnification SEM and TEM photographs of the surface of the carbon fiber shown in FIG. 3 are shown in FIGS. 6 and 7, respectively. Complicated fold-like structures and sheet-like structures can be confirmed, and it is considered that carbon nanowalls in which multiple graphene sheets are laminated are densely generated. A region that is considered to be tubular is also confirmed.

FIG. 8 shows a high-magnification observation image of the region indicated by the ◯ mark in the TEM observation image of FIG. The interplanar spacing (d ₀₀₂ ) of the graphene sheets is approximately 3 angstroms, indicating that carbon nanowalls with extremely high purity are produced.

FIG. 9 shows the results of X-ray photoelectron spectroscopy (XPS) of the untreated carbon fiber surface and the carbon fiber surface obtained with the microwave irradiation time of 1 minute. The microwave irradiation increased the relative intensity of the peak due to the C—O bond, suggesting that the carbon nanostructure formed on the carbon fiber surface has an oxidized region.

FIG. 10 shows the Raman spectroscopic analysis results of the untreated carbon fiber surface and the carbon fiber surface obtained with the microwave irradiation time of 1 minute. Observation of the Raman frequency distribution shows that signals in both the D and G bands grow due to microwave irradiation, and that a carbon structure is formed on the surface of the carbon fiber. In addition, since oxygen was confirmed in the sample after microwave irradiation by XPS analysis, it is considered that a carbon structure similar to graphene oxide is generated on the surface of the carbon fiber.

<<Example 2>>
The carbon fibers were surface-treated in the same manner as in Example 1 except that the inside of the glass tube was made into an air atmosphere of about 100 Pa and the microwave irradiation time was set to 1 minute or 5 minutes. Light emission was observed during microwave irradiation.

SEM photographs of carbon fibers obtained with microwave irradiation times of 1 minute and 5 minutes are shown in FIGS. 11 and 12, respectively. An extremely fine carbon nanostructure is formed on the surface of the carbon fiber, and its density and amount increase as the irradiation time increases.

<<Example 3>>
The carbon fiber was surface-treated in the same manner as in Example 1 except that the inside of the glass tube was in an argon atmosphere of about 100 Pa and the microwave irradiation time was set to 1 minute or 5 minutes. Light emission was observed during microwave irradiation.

SEM photographs of carbon fibers obtained with microwave irradiation times of 1 minute and 5 minutes are shown in FIGS. 13 and 14, respectively. An extremely fine carbon nanostructure is formed on the surface of the carbon fiber, and its density and amount increase as the irradiation time increases.

<<Example 4>>
Carbon fibers were surface-treated in the same manner as in Example 1, except that the inside of the glass tube was in a nitrogen atmosphere of about 100 Pa, and the microwave irradiation time was set to 1 minute or 5 minutes. Light emission was observed during microwave irradiation.

SEM photographs of carbon fibers obtained with microwave irradiation times of 1 minute and 5 minutes are shown in FIGS. 15 and 16, respectively. An extremely fine carbon nanostructure is formed on the surface of the carbon fiber, and its density and amount increase as the irradiation time increases.

≪Comparative example≫
The carbon fiber was surface-treated in the same manner as in Example 2 except that the pressure inside the glass tube was reduced to 1000 Pa and the microwave irradiation time was set to 5 minutes. No luminous phenomenon was observed during microwave irradiation, and it is considered that ultraviolet rays were not generated.

A SEM photograph of the obtained carbon fiber is shown in FIG. Although the carbon fiber surface is rough, no carbon nanostructure formation is observed.

(2) Method for producing carbon nanowall <<Example 5>>
Except that activated carbon powder and base materials (Al base, Cu base and Fe base) are placed in an alumina boat, the inside of the glass tube is argon atmosphere of 1.4 Pa, and the microwave irradiation time is 5 minutes. produced carbon nanowalls on the substrate surface in the same manner as in Example 1. FIG. 18 shows the arrangement of the activated carbon powder and each substrate in the alumina boat. The size of each substrate was 5×5 mm. Light emission was observed during microwave irradiation.

FIG. 19 shows photographs of the appearance of each substrate after treatment. The surface of each substrate is blackened, and it can be confirmed that the carbon separated from the activated carbon powder adheres. Deformation is observed in the Al base material, but the deformation is considered to be caused by temperature rise due to microwave irradiation.

A black deposit was peeled off from the Cu substrate, and SEM observation was performed. The obtained SEM photograph is shown in FIG. A fold-like fine structure was observed, confirming the formation of carbon nanowalls. SEM photographs of the surface of the Al substrate were also taken, and the formation of carbon nanostructures (carbon nanowalls) was confirmed as shown in FIG.

<<Example 6>>
In the same manner as in Example 5, except that the carbon material and the substrate were carbon fiber and the Si substrate, respectively, the inside of the glass tube was a carbon dioxide atmosphere of 8 Pa, and the microwave irradiation time was 3 minutes. generated carbon nanowalls.

FIG. 22 shows a photograph of the appearance of the Si substrate after treatment. The surface is blackened, and it can be confirmed that carbon has adhered. Further, when the Si substrate was observed from the side by SEM, dense carbon nanowalls were confirmed as shown in FIG.

<<Example 7>>
Carbon nanowalls were generated on the substrate surface in the same manner as in Example 6, except that the substrate was a glass substrate.

FIG. 24 shows a photograph of the appearance of the glass substrate after treatment in the alumina boat. The surfaces of the alumina boat and the glass substrate were blackened, and it was confirmed that carbon had adhered. Further, when the surface of the glass substrate was observed with an SEM, dense carbon nanowalls were confirmed as shown in FIG.

2 ... microwave generator,
4... glass tube,
6: Alumina boat,
8 ... carbon fiber,
10... Gas inlet,
12 gas outlet,
20... Carbon nanostructure.

Claims (8)

Microwave-heating the carbon fiber by irradiating the carbon fiber with microwaves in a gas atmosphere,
inducing an excited state of the gas by the microwave;
cutting the C=C bonds of the carbon fibers with ultraviolet rays generated during the light emission process of the gas;
A method for modifying the surface of carbon fibers. said gas comprising at least one of air, argon, helium, nitrogen and carbon dioxide;
The method for modifying the surface of carbon fibers according to claim 1, characterized in that: that the carbon fibers are short fibers;
The method for modifying the surface of carbon fibers according to claim 1 or 2, characterized in that: the carbon fiber being a milled fiber;
The method for modifying the surface of carbon fibers according to any one of claims 1 to 3, characterized by: irradiating a carbon material and a base material with microwaves in a gas atmosphere to microwave-heat the carbon material and the base material;
inducing an excited state of the gas by the microwave;
The C=C bond of the carbon material is cut by ultraviolet rays generated during the light emission process of the gas,
forming carbon nanowalls on the surface of the base material using plasma carbon separated from the carbon material as a raw material;
A method for producing carbon nanowalls, characterized by: said gas comprising at least one of air, argon, nitrogen, carbon dioxide;
The method for producing carbon nanowalls according to claim 5 , characterized in that: the carbon material being carbon fiber;
The method for producing carbon nanowalls according to claim 5 or 6 , characterized by: that the carbon nanowalls do not contain a metal element;
The method for producing carbon nanowalls according to any one of claims 5 to 7 , characterized by:

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