JP2002094283A - Coiled carbon fiber and its manufacturing method and electromagnetic absorption material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide coiled carbon fiber that can efficiently absorb an electromagnetic wave in a high-frequency band, the manufacturing method of the coiled carbon fiber, and an electromagnetic absorption material. SOLUTION: This coiled carbon fiber is made of amorphous carbon fiber in a coil shape. The diameter of a coil is set to 1 nm or more and less than 100 nm. Also, the coiled carbon fiber has spiral structure including single or double spiral structure. In general, the coiled carbon fiber having the single spiral structure becomes a main constituent in one reaction system. In addition, in one reaction system, the coiled carbon fiber with clockwise spiral structure as the winding direction of the spiral of the coil, the coiled carbon fiber with counterclockwise one, or the mixture of them exists. In the mixture, the content of the coiled carbon fiber which has the clockwise spiral structure is different from the content of the coiled carbon fiber which has the counterclockwise one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coiled carbon fiber capable of absorbing electromagnetic waves in a high frequency band, a method for producing the same, and an electromagnetic wave absorbing material.

[0002]

2. Description of the Related Art In recent years, for example, malfunctions of medical equipment due to electromagnetic waves generated from mobile phones, operational obstacles such as aircraft and railway vehicles, and health disorders have been pointed out. Therefore, an electromagnetic wave absorbing material, a shielding material, and the like have been proposed, and examples of the electromagnetic wave absorbing material include coiled carbon fibers. This coiled carbon fiber is formed into a coil shape by carbon fiber, the fiber diameter is 0.01 to 5 μm, and the coil diameter is 0.1.
２０００2000 μm, coil pitch of 0-50 μm, coil length of 100 μm -5 m, containing a coil having a right-handed double helical structure and a left-handed double helical structure It is. The coiled carbon fiber has a coil diameter substantially on the order of microns, and when exposed to electromagnetic waves from the outside and exposed to a fluctuating electric field or magnetic field, an induced current due to induced electromotive force flows in the coil according to Faraday's law and causes joules. Generates heat and absorbs electromagnetic waves. The frequency band of the electromagnetic wave absorbed by the coiled carbon fiber depends on the coil diameter and the like. When the coil diameter is large, the electromagnetic waves in the low frequency band are absorbed, and when the coil diameter is small, the electromagnetic waves in the high frequency band are absorbed.

[0003]

The above-mentioned conventional coiled carbon fiber has a coil diameter on the order of microns.
The frequency band of the electromagnetic wave that can be absorbed is a low frequency band of several GHz. Therefore, frequencies of 0.8 to 1.5 GHz of electromagnetic waves currently used in mobile phones can be absorbed by conventional coiled carbon fibers. However, the frequency band of electromagnetic waves used by the development of automatic transportation systems and satellite broadcasting is expected to shift to a high frequency band of several tens of GHz to several hundred GHz in the future. There is a problem that electromagnetic waves in a high frequency band cannot be absorbed.

[0004] The present invention has been made to solve the problems existing in the prior art. An object of the present invention is to provide a coiled carbon fiber that can efficiently absorb electromagnetic waves in a high frequency band, a method for producing the same, and an electromagnetic wave absorbing material.

[0005]

In order to achieve the above object, the coiled carbon fiber according to the first aspect of the present invention is formed of an amorphous carbon fiber in a coil shape and has a coil diameter of 1 nm. Above is less than 100 nm.

A coiled carbon fiber according to a second aspect of the present invention is the coiled carbon fiber according to the first aspect of the present invention, wherein the coil has a single spiral structure as a main component. According to a third aspect of the present invention, in the coiled carbon fiber according to the first or second aspect, the coil has a right-handed spiral structure, a left-handed spiral structure, or a mixture thereof. In the case of a mixture, the mixture is configured so that the content of the mixture having a right-handed spiral structure is different from that of the mixture having a left-handed spiral structure.

According to a fourth aspect of the present invention, there is provided a method for producing a coiled carbon fiber, wherein a hydrocarbon or carbon monoxide is heated to 600 to 950 ° C. in the presence of a metal catalyst, and the hydrocarbon or carbon monoxide is vapor-phased. When the carbon fiber is grown in a coil shape by a decomposition reaction of carbon, the particle diameter of the metal catalyst is 1 to 1000.
nm.

According to a fifth aspect of the present invention, there is provided the method for producing a coiled carbon fiber according to the fourth aspect, further comprising performing a decomposition reaction in the presence of an electromagnetic field and a static magnetic field. is there.

[0009] The electromagnetic wave absorbing material of the invention according to claim 6 is:
It is made of the coiled carbon fiber according to claim 1, and can absorb electromagnetic waves having a frequency of 1 to 1000 GHz.

[0010]

Embodiments of the present invention will be described below in detail. The coiled carbon fiber is formed in a coil shape from amorphous carbon fiber, and has a coil diameter of 1 nm or more and less than 100 nm. Further, the coiled carbon fiber has a coil pitch of 0 to 50.
μm, and the coil length is 100 μm to 5 m.
Further, the coiled carbon fiber has a helical structure, and the helical structure includes a single helical structure or a double helical structure. In a single reaction system, the one having a single helical structure is mainly used. Has become. That is, in the coiled carbon fiber of the above size, 50% by weight or more of the total weight of the coiled carbon fiber in one reaction system has a single spiral structure.

Furthermore, in one reaction system, a coil having a right-handed spiral structure, a left-handed spiral structure, or a mixture thereof exists as a coil spiral direction. When present as a mixture, the content of the right-handed helical structure and the content of the left-handed helical structure are often different, and may be the same.

[0012] The obtained coiled carbon fiber has a higher flexibility and elasticity than the crystalline coiled carbon fiber because the carbon particles are grown in an amorphous state. As a result, for example, when a composite material such as an electromagnetic wave absorber is manufactured by dispersing amorphous coiled carbon fibers in a polymer material,
The disadvantage that the coiled carbon fiber is broken in the polymer material can be eliminated. Further, the composite material has elasticity, and when the composite material is expanded and contracted, the problem that the coiled carbon fiber is cut can be eliminated. In addition, unlike the crystalline case, the surface area of the carbon particles on the outer surface of the coiled carbon fiber increases. for that reason,
The amount of gas (for example, hydrogen gas) that can be adsorbed on the surface of the coiled carbon fiber is larger than that in the case of crystalline.

[0013] Further, most of the coiled carbon fibers are formed in a state where fine carbon particles are packed up to the center of the fiber, and some are formed to be hollow. The frequency band of the electromagnetic wave absorbed by the coiled carbon fiber depends on the coil diameter, coil pitch and coil length. When the coiled carbon fiber has a large coil diameter, it can effectively absorb electromagnetic waves in a low frequency band, and when the coil diameter is small, it can effectively absorb electromagnetic waves in a high frequency band. can do.

That is, as the coil diameter of the coiled carbon fiber becomes smaller, such as on the order of nanometers, the fiber diameter and the coil pitch become smaller, and it becomes easier to tune with the high frequency band in which the period of the electromagnetic wave is shortened. Can be efficiently absorbed. Therefore, the coiled carbon fiber of the embodiment has a coil diameter of 1 nm or more and less than 100 nm,
Electromagnetic waves in a high frequency band up to GHz can be effectively absorbed. In order to more effectively absorb electromagnetic waves in a high-frequency band, the coil diameter of the coiled carbon fiber is preferably less than 70 to 100 nm, more preferably 20 to 70 nm.
Less than is more preferable. The coil diameter of the coiled carbon fiber is particularly preferably less than 1 to 20 nm.

The electric resistance of the coiled carbon fiber having a single spiral structure is larger than that of the coiled carbon fiber having a double spiral structure. Therefore, when electromagnetic waves are irradiated on these coiled carbon fibers and an induced current due to induced electromotive force flows in the coils according to Faraday's law, the coiled carbon fibers having a single helical structure are more than the coiled carbon fibers having a double helical structure. The electric resistance to the induced current increases. Therefore, the amount of Joule heat generated by the induction current flowing through the coiled carbon fiber becomes large, and the electromagnetic wave absorption becomes larger than that of the coiled carbon fiber having the double helical structure.

Further, in the left-handed or right-handed coiled carbon fiber, for example, the left-handed coiled carbon fiber absorbs a larger amount of electromagnetic waves than the right-handed coiled carbon fiber with respect to left-polarized electromagnetic waves. Become. On the other hand, for right-polarized electromagnetic waves, the right-handed coiled carbon fiber has a larger electromagnetic wave absorption than the left-handed coiled carbon fiber.

The electromagnetic wave absorbing material can be manufactured by dispersing the coiled carbon fiber having the above structure in a base material and molding it into a predetermined shape.
Electromagnetic waves in a high frequency band up to 00 GHz can be effectively absorbed. Examples of the matrix include a polymer,
Examples of the polymer include at least one selected from a thermoplastic resin, a thermosetting resin, a crosslinked rubber, and a thermoplastic elastomer. At least one of these is appropriately selected and used depending on the requirements of electrical characteristics such as hardness, mechanical strength, heat resistance, electric resistance and durability of the obtained radio wave absorber.

Examples of the thermoplastic resin include polyethylene and polypropylene. Examples of the thermoplastic elastomer include a styrene-butadiene or styrene-isoprene block copolymer and a hydrogenated copolymer thereof, a styrene-based thermoplastic elastomer, and the like. Is mentioned. Examples of the crosslinked rubber include natural rubber, butadiene rubber, and isoprene rubber, and examples of the thermosetting resin include an epoxy resin, a phenol resin, and a polyimide resin.

Furthermore, plasticizers, fillers, organic fibers (such as aramid fibers), carbon fibers, inorganic fibers (such as glass fibers),
Natural polymers such as cellulose, silk, cotton, and wool, stabilizers,
A coloring agent may be added as needed. In addition, an organic solvent or water may be added in order to lower the viscosity of the composition comprising the coiled carbon fiber and the polymer to facilitate the incorporation of the coiled carbon fiber in the polymer.

Next, a method for producing the coiled carbon fiber will be described. The method for producing the coiled carbon fiber includes the steps of converting a hydrocarbon or carbon monoxide to 600 to 950
C. is heated to cause a decomposition reaction of hydrocarbons or carbon monoxide in a gas phase to grow carbon fibers into a coil shape.

[0021] The coiled carbon fiber is formed by catalyst activated CVD.
(Chemical vapor deposition) method or the like. For example, a substrate is placed in a horizontal thermochemical vapor synthesis apparatus in which a metal catalyst is present, and a catalyst gas, a hydrogen gas, and a seal gas composed of a compound of Group 5B or 6B of the periodic table are injected, and When a hydrocarbon or carbon monoxide is injected and thermally decomposed at a predetermined temperature, it grows from the crystal plane of the metal catalyst.

As the substrate on which the coiled carbon fiber grows, a substrate formed of graphite, nickel or quartz in a plate shape is used, and nickel is sprayed, sintered or plated on the outer surface of the substrate. May be used. The metal catalyst is at least one compound selected from metal oxides, carbides, sulfides, phosphides, carbonates and carbosulfides, preferably nickel,
Cobalt, niobium, tantalum, titanium, tungsten,
Nickel carbide, nickel sulfide, nickel oxide, nickel carbon sulfide, nickel carbonate and the like can be mentioned. The metal catalyst may be precipitated and carried on the outer surface of the substrate by sublimating and pyrolyzing a metal-containing compound such as nickelocene and metallocene in a reaction vessel. In order to grow the coiled carbon fiber efficiently, it is preferable to use a nickel-based compound of nickel, nickel carbide, nickel sulfide, nickel oxide, nickel carbon sulfide, nickel carbonate, and nickelocene among the metal catalysts.

The coil diameter, coil pitch and coil length of the coiled carbon fiber depend on the anisotropy and the particle size of the catalytic activity on each crystal plane of the metal catalyst. Therefore, in order to form a coil diameter on the order of nanometers, a metal catalyst having a particle diameter of 1 to 1000 nm is used. By using a metal catalyst having a particle diameter within the above range, a coiled carbon fiber having a coil diameter on the order of nanometers can be grown.
Further, since the particle size of the metal catalyst is on the order of nanometers, the amount of the metal catalyst supported on the outer surface of the base material is larger than that of the metal catalyst having a particle size on the order of microns. In addition, the surface area of the metal catalyst on the outer surface of the base material is larger than that of a metal catalyst having a particle diameter on the order of microns, and the contact efficiency with various gases is improved. Therefore, the amount of the growing coiled carbon fiber also increases, and the yield can be improved.

As the hydrocarbon, acetylene, methane, propane or the like is used, and acetylene may contain a small amount of impurities such as sulfur or phosphorus. The catalyst gas is
A gas containing a 5B group element and a 6B group element of the periodic table;
A compound containing a sulfur atom such as thiophene, methyl mercaptan, or hydrogen sulfide, or a compound containing a phosphorus atom such as phosphorus or phosphorus trichloride is used.

During the production of the coiled carbon fiber, the reaction system is placed in a state where at least one of an electromagnetic field and a static magnetic field is generated, and the reaction system is provided with at least one of an electromagnetic wave and a static magnetic wave. One may be irradiated.
Means for generating an electromagnetic field include an AC or DC electric heater, and means for generating a static magnetic field include flowing a DC current through a permanent magnet or a conducting wire (straight or coiled). The frequency of the electromagnetic wave to be irradiated is preferably 1 Hz to 1 GHz, and more preferably 50 to 60 Hz for convenience in irradiating the reaction system with the electromagnetic wave. Further, at least one of the electromagnetic wave and the magnetostatic wave may be irradiated from any direction with respect to the growth direction of the coiled carbon fiber. Therefore, by arranging the reaction system in the presence of at least one of an electromagnetic field and a static magnetic field, particularly in the presence of both an electromagnetic field and a static magnetic field, the anisotropy of the catalytic activity on each crystal plane of the metal catalyst is reduced. As a result, the coil diameter is reduced, and the growth rate of the coiled carbon fiber is improved. Moreover, the particle diameter is 1 to 1000 n.
m nickel as a metal catalyst, and in addition to the electromagnetic field from the electric heater in the reaction system, by generating another magnetic field, for example, a static magnetic field, a coiled carbon fiber having a uniform coil diameter of 1 to 3 μm is obtained. can get.

As the seal gas, an inert gas such as a nitrogen gas and a helium gas, or an inert gas which does not react with a substance of the system or a hydrogen gas is used. When the sealing gas is injected into the horizontal thermochemical vapor synthesis apparatus, it is possible to prevent an extra or harmful influence from being added to the reaction system by oxygen gas or the like.

The effects of the above embodiment will be described below.・ Since the carbon fiber is formed in a coil shape and the coil diameter is formed on the order of nanometers, it can absorb electromagnetic waves in the high-frequency band more effectively than the carbon fiber formed on the order of microns. it can.

Since the coiled carbon fiber is amorphous, the flexibility and elasticity thereof are increased unlike the crystalline coiled carbon fiber. Therefore, it is possible to eliminate such a problem that the coiled carbon fiber in the composite material is broken or cut at the time of manufacturing and using the composite material using the coiled carbon fiber. An effect such as a dependent electromagnetic wave absorption characteristic can be effectively exhibited.

The coiled carbon fiber having a single helical structure has a larger electromagnetic wave absorption than the coiled carbon fiber having a double helical structure. Therefore, when the coiled carbon fiber is grown, the coiled carbon fiber having a single helical structure grows as a main component, so that the obtained coiled carbon fiber can effectively exert an electromagnetic wave absorbing effect.

The left-handed coiled carbon fiber can more effectively absorb left-polarized electromagnetic waves than the right-handed coiled carbon fiber. The right-handed coiled carbon fiber can absorb more effectively than the coiled carbon fiber. Therefore, when the coiled carbon fiber exists as a mixture of a right-handed and a left-handed helical structure, and the content of the right-handed and the left-handed helical structure is different,
Unlike the case where the right-handed and left-handed helical structures have the same content, either right-handed or left-handed polarized electromagnetic waves can be effectively absorbed.

Electromagnetic waves currently used for communication such as radio waves and television waves are converted into signals without distinction between left and right polarized waves. On the other hand, right-handed or left-handed coiled carbon fibers can distinguish right-handed or left-handed polarized waves, so that twice as much information can be transmitted by electromagnetic waves in the radio wave and television wave bands.

The metal catalyst has a particle diameter of 1 to 1000 nm.
Is used, so that a coiled carbon fiber having a coil diameter on the order of nanometers can be surely grown. In addition, the amount of the metal catalyst supported on the outer surface of the base material can be increased, the surface area can be increased, and the yield of the coiled carbon fiber can be improved as compared with a metal catalyst having a particle diameter of the order of microns. .

The use of a nickel-based compound as the metal catalyst allows the coiled carbon fiber to be efficiently grown from the metal catalyst.・ During the production of coiled carbon fibers, the anisotropy of catalytic activity on each crystal plane of the metal catalyst is increased by at least one of the electromagnetic wave and the magnetostatic wave irradiated to the reaction system, and the coil diameter is assured. It is possible to reduce the size and to reliably form a coiled carbon fiber on the order of nanometers. Similarly, the growth rate of the coiled carbon fiber can be improved.

An electromagnetic wave absorbing material can be manufactured by dispersing a coiled carbon fiber capable of absorbing electromagnetic waves in a high frequency band of 1 to 1000 GHz in a base material. Therefore, for example, by manufacturing the main body case of the personal computer using the electromagnetic wave absorbing material, it is possible to effectively absorb the electromagnetic wave generated from the personal computer, particularly, the electromagnetic wave in a high frequency band.

By using nickel having a particle diameter of 1 to 1000 nm as a metal catalyst and generating another magnetic field in the reaction system in addition to the electromagnetic field from the electric heater,
A coiled carbon fiber having a uniform coil diameter of 1 to 3 μm is obtained. for that reason. Coiled carbon fibers having a narrow coil diameter range can be reliably manufactured, and electromagnetic waves in a limited band can be reliably absorbed. Therefore, compared with the case where a large amount of coiled carbon fiber absorbs electromagnetic waves in a wide band, the small amount of coiled carbon fiber can effectively absorb electromagnetic waves in a corresponding frequency band. In addition, by using coiled carbon fibers corresponding to the frequency of the electromagnetic waves generated from each electrical device, it is possible to effectively absorb the electromagnetic waves,

[0036]

The above embodiment will be described more specifically with reference to examples and comparative examples. (Example 1) In Example 1, a metal-containing compound was sublimated and pyrolyzed in a reaction vessel to precipitate a metal catalyst on the outer surface of a substrate, and further, a static magnetic field and an electromagnetic field were generated in the reaction system to grow coiled carbon fibers. I let it. First, inner diameter 100mm, length 1
A reaction vessel consisting of a 000 mm transparent quartz tube was set horizontally, and a graphite substrate (width 40 mm, length 100 mm) was set as a base material in the center of the reaction vessel. Further, a carbon steel pipe (yoke: inner diameter 100 mm, length 50 mm) is installed outside the reaction vessel,
A samarium-cobalt permanent magnet (residual magnetic flux density: 1 Tesla) was set inside the carbon steel pipe, and a static magnetic field was generated in the reaction vessel by the permanent magnet.

Then, acetylene, a catalyst gas, hydrogen gas and nickelocene were introduced into the reaction vessel, heated to 750 to 800 ° C. by a DC nichrome wire electric heater, and added to the static magnetic field in the reaction vessel by applying the static magnetic field. An electromagnetic field (magnetic flux density at the center of the substrate: 0.25 to 0.30 Tesla) was generated, and the reaction was performed at the above temperature for 1 hour. as a result,
The nickelocene is thermally decomposed in the gas phase to become an atomic state having a particle size of about 5 angstroms, and a plurality of the nickelocene in the atomic state assemble on the substrate, and nickel having an average particle size of 1 to 10 nm precipitates on the substrate. It is carried on a substrate.

The nickel served as a metal catalyst, and coiled carbon fibers grew from each crystal face of the nickel. The coiled carbon fiber was obtained in a yield of 40% based on the raw material acetylene, and 89% of the total coiled carbon fiber had a coil diameter on the order of nanometers. Coiled carbon fibers of the order of nanometers have an average coil diameter of less than 1 to 20 nm, a length of 5 to 10 mm, a single helical structure and a double helical structure, a right-handed helical structure and a left-handed helical structure. The ratio with that having the structure was the same.

(Embodiment 2) In Embodiment 2, a permanent magnet is omitted and a static magnetic field is not generated, and only a fluctuating electromagnetic field is generated in the reaction system by an AC nichrome wire electric heater. Carbon fibers were grown. As a result, this coiled carbon fiber was 3% based on the raw material acetylene.
A yield of 5% was obtained, and 80% of the total coiled carbon fibers had a coil diameter on the order of nanometers. Coiled carbon fibers of the order of nanometers have an average coil diameter of less than 20 to 70 nm, a length of 4 to 7 mm, a single helical structure and a double helical structure, a right-handed helical structure and a left-handed helical structure. The ratio with that having the structure was the same.

(Example 3) In Example 3, instead of sublimating and pyrolyzing the metal-containing compound in the reaction vessel in Example 1 to precipitate the metal catalyst on the outer surface of the substrate, the outer surface of the substrate had an average particle diameter of 30 nm. Nickel powder was applied as a metal catalyst, and a static magnetic field and a fluctuating electromagnetic field were generated in the reaction system to grow coiled carbon fibers. As a result, the coiled carbon fiber was obtained in a yield of 20% with respect to the raw material acetylene, and 93% of the total coiled carbon fiber had a coil diameter on the order of nanometers. Nanometer-order coiled carbon fiber has an average coil diameter of 70-100 nm
, Having a single spiral structure and a double spiral structure with a length of 3 to 5 mm, and the ratio of those having a right-handed spiral structure to those having a left-handed spiral structure was the same. Also, 7% of the total amount of the coiled carbon fiber has a coil diameter on the order of micrometers, and the coil diameter is 1.0 to 1.0%.
It was 3.0 μm.

Example 4 A flat annular carbon steel was installed outside the reaction vessel of Example 3 so that it could rotate horizontally at the same height as the substrate, and two carbon steels were placed inside the carbon steel. The permanent magnet was set so that the N pole and the S pole faced each other. Then, the carbon steel is rotated at a rotation speed of 200 rpm to the right as viewed from below the reaction vessel to generate a fluctuating static magnetic field in the reaction vessel, and the coiled carbon fiber is grown in the same manner as in Example 3. I let it.

As a result, the coiled carbon fiber grows on the substrate, and the coiled carbon fiber is 20% of the raw material acetylene.
%, And 75% of the total coiled carbon fibers had a coil diameter on the order of nanometers.
Coiled carbon fibers of the order of nanometers have an average coil diameter of less than 70 to 100 nm, a length of 3 to 5 mm, a single spiral structure, a right-handed spiral structure and a left-handed spiral structure. Was 55:45.

(Example 5) In Example 4, the carbon steel was rotated leftward at a rotational speed of 200 rpm as viewed from below the reaction vessel.
m, a static magnetic field was generated to grow the coiled carbon fiber.

As a result, the coiled carbon fiber grows on the substrate, and the coiled carbon fiber is 20% of the starting acetylene.
%, And 75% of the total coiled carbon fibers had a coil diameter on the order of nanometers.
Coiled carbon fibers of the order of nanometers have an average coil diameter of less than 70 to 100 nm, a length of 3 to 5 mm, a single spiral structure, a right-handed spiral structure and a left-handed spiral structure. Was 39:61.

Comparative Example 1 In Comparative Example 1, instead of sublimating and pyrolyzing a metal-containing compound in a reaction vessel in Example 1 to precipitate a metal catalyst on the surface of a substrate, an average particle size of 2 was formed on the outer surface of the substrate. Nickel powder of about 6 μm was applied as a metal catalyst, and the above-mentioned variable electromagnetic field was generated in the reaction system to grow the coiled carbon fiber. As a result, the coiled carbon fiber is obtained with a yield of 35% based on the raw material acetylene, has a double helical structure with a coil diameter of 50 to 7000 nm and a length of 1 to 3 mm, and has a right-handed helical structure. The ratio between those having the left-handed spiral structure and those having the left-handed spiral structure was the same.

Comparative Example 2 In Comparative Example 2, a coiled carbon fiber was grown by generating an electrostatic magnetic field in the reaction system instead of the fluctuating electromagnetic field in Comparative Example 1. As a result, the coiled carbon fiber was obtained in a yield of 40% based on the raw material acetylene, the coil diameter was 30 to 3000 nm, and the length was 1 to 1
It had a 3 mm single helical structure and a double helical structure, and the ratio between those having a right-handed helical structure and those having a left-handed helical structure was the same.

(Electromagnetic Wave Absorption Test) The coiled carbon fibers obtained in the above Examples 1 to 5 and Comparative Examples 1 and 2 were dispersed in an epoxy resin to produce an electromagnetic wave absorbing material, and 10 GHz and 100 GHz of each electromagnetic wave absorbing material were manufactured. And the electromagnetic wave absorption characteristics in each frequency band of 1000 GHz were evaluated. In addition, the coiled carbon fiber was added so as to be 30% by weight of each electromagnetic wave absorbing material. Table 1 shows the results.

[0048]

[Table 1] As shown in Table 1, the electromagnetic wave absorber using the coiled carbon fiber having a small coil diameter has a higher degree of attenuating electromagnetic waves in a high frequency band such as 1000 GHz, that is,
It was shown that electromagnetic waves in the high frequency band were effectively absorbed.

(Electromagnetic Wave Absorption Test Dependent on Winding Direction) The above-mentioned electromagnetic wave absorbing material manufactured using the coiled carbon fibers obtained in Examples 3 to 5 was 10 GHz and 100 GHz.
The electromagnetic wave absorption characteristics of right and left polarized waves in each frequency band of z and 1000 GHz were evaluated. Table 2 shows the results.
And Table 3.

[0050]

[Table 2]

[0051]

[Table 3] As shown in Tables 2 and 3, when irradiated with right-polarized electromagnetic waves, the electromagnetic wave absorbing material of Example 4 containing a large amount of right-handed coiled carbon fibers contains many left-handed coiled carbon fibers. It was shown that the electromagnetic wave absorbing material of Example 5 and the electromagnetic wave absorbing material of Example 3 in which the same number of right-handed and left-handed coiled carbon fibers are included absorb electromagnetic waves more effectively. On the other hand, when the electromagnetic wave of the left polarization is irradiated, the electromagnetic wave absorbing material of the fifth embodiment is replaced with the electromagnetic wave absorbing material of the fourth embodiment and the third embodiment.
It was shown that the electromagnetic wave absorbing material effectively absorbed electromagnetic waves.

(Electromagnetic wave absorption test depending on the content of coiled carbon fiber) The content of the coiled carbon fiber obtained in Example 3 was 10, 30, 60% by weight based on the total amount.
The electromagnetic wave absorbing materials were manufactured with the following changes, and the electromagnetic wave absorbing characteristics of each electromagnetic wave absorbing material were evaluated. Table 4 shows the results.

[0053]

[Table 4] As shown in Table 4, it was shown that the larger the amount of the coiled carbon fibers, the greater the amount of electromagnetic wave absorption in each frequency band.

(Relationship Test between Particle Size of Metal Catalyst and Yield) In the above-mentioned Example 3, in a state where a static magnetic field was not generated, the particle size of the nickel powder was changed to grow coiled carbon fibers. Was measured for the yield of the coiled carbon fiber. Table 5 shows the results.

[0055]

[Table 5] As shown in Table 5, it was shown that the smaller the particle size of the nickel powder, the higher the yield of coiled carbon fibers.

(Relationship Test between Particle Size of Metal Catalyst and Electromagnetic Field and Static Magnetic Field) Nickel having a particle size on the order of micrometers was used in Example 3 to generate an electromagnetic field, while forming a coil without generating a static magnetic field. When the carbon fiber is grown, the coil diameter of the coiled carbon fiber is 0.1 to 2000 μ.
m. In the case of using nickel having a particle size on the order of micrometers in Example 3 above and generating an electromagnetic field and a static magnetic field to grow the coiled carbon fiber, the coil diameter of the coiled carbon fiber is 0.1 to 500 μm. Met.
In Example 3, 7% of the total amount of the coiled carbon fibers had a coil diameter on the order of micrometers.
The coil diameter was 1.0 to 3.0 μm. Accordingly, by using nickel having a particle diameter of 1 to 1000 nm as a metal catalyst and generating a static magnetic field in addition to the electromagnetic field from the electric heater in the reaction system, a coiled carbon fiber having a narrow coil diameter range can be obtained. It was shown that.

The above embodiment can be modified and embodied as follows. The reaction system may be heated by a gas burner or the like in a state where a static magnetic field is generated in the reaction system, and the coiled carbon fiber may be grown in a state where only the static magnetic field is generated.

Further, a technical idea which can be grasped from the embodiment will be described below. -The static magnetic field is generated by a permanent magnet.
3. The method for producing a coiled carbon fiber according to item 1. With this configuration, a static magnetic field can be generated in a stable state with respect to the reaction system.

The method for producing a coiled carbon fiber according to claim 4, wherein the metal catalyst is a nickel-based compound. With this configuration, the coiled carbon fiber can be grown more efficiently than a metal catalyst other than the nickel-based compound.

[0060]

As described above, the present invention has the following advantages. According to the coiled carbon fiber of the first aspect, electromagnetic waves in a high frequency band can be efficiently absorbed.

According to the coiled carbon fiber according to the second aspect, in addition to the effect of the first aspect, the coiled carbon fiber having a single helical structure is compared with the coiled carbon fiber having a double helical structure. Therefore, the electromagnetic wave absorption amount is large. Therefore, when the coiled carbon fiber having a single helical structure is grown as a main component, the obtained coiled carbon fiber can effectively exert an electromagnetic wave absorbing effect.

According to the coiled carbon fiber of the third aspect, in addition to the effect of the first or second aspect,
When the coiled carbon fiber exists as a mixture of a right-handed and left-handed helical structure and the content of the right-handed and left-handed helical structure is different, the right-handed and left-handed helical structures are used. Unlike the case where the content of the helical structure is the same, the electromagnetic wave of either right or left polarization can be effectively absorbed.

According to the method of manufacturing the coiled carbon fiber according to the fourth aspect, the coiled carbon fiber having a coil diameter on the order of nanometers can be surely grown. According to the method of manufacturing the coiled carbon fiber according to the fifth aspect, in addition to the effects of the fourth aspect, the anisotropy of catalytic activity on each crystal plane of the metal catalyst is increased by electromagnetic waves and magnetostatic waves. As a result, the coil diameter can be reliably reduced, and a coiled carbon fiber of the order of nanometers can be reliably formed.

According to the electromagnetic wave absorbing material of the sixth aspect,
Electromagnetic waves in a high frequency band of 1 to 1000 GHz can be effectively absorbed.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Hishikawa 4-179, Suemachi, Kakamigahara-shi, Gifu Prefecture Techno Plaza CMC Technology Development Co., Ltd. F-term (reference) 4L037 CS03 FA05 PA03 PA06 PA10 PA12 UA02 5E070 AB01 AB10 BB02 CA02 CA16 5E321 BB60 GG11 5J020 EA01

Claims (6)

[Claims] 1. A coiled carbon fiber formed of an amorphous carbon fiber into a coil and having a coil diameter of 1 nm or more and less than 100 nm. 2. The coiled carbon fiber according to claim 1, wherein the coil has a single spiral structure as a main component. 3. The coil has a right-handed helical structure, a left-handed helical structure, or a mixture thereof. In the case of a mixture, the coil has a right-handed helical structure and a left-handed helical structure. The coiled carbon fiber according to claim 1, wherein a content of the coiled carbon fiber is different from a content of the coiled carbon fiber. 4. A method for heating a hydrocarbon or carbon monoxide to 600 to 950 ° C. in the presence of a metal catalyst to cause a decomposition reaction of the hydrocarbon or carbon monoxide in a gas phase to grow carbon fibers into a coil shape. The particle diameter of the metal catalyst is 1 to 1000;
a method of producing a coiled carbon fiber, wherein 5. The method for producing coiled carbon fibers according to claim 4, further comprising performing a decomposition reaction in the presence of an electromagnetic field and a static magnetic field. 6. An electromagnetic wave absorbing material comprising the coiled carbon fiber according to claim 1 and capable of absorbing electromagnetic waves having a frequency of 1 to 1000 GHz.