JP2001146645A - Coiled carbon fiber composite having ferromagnetism, method for producing the same and electric wave absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a coiled carbon fiber composite having ferromagnetism and capable of efficiently absorbing required electric waves propagating only in a prescribed direction or efficiently shielding electromagnetic waves and preventing the production cost thereof from increasing without increasing the amount of the coiled carbon fibers used, to provide a method for producing the carbon fiber composite and to obtain an electric wave absorber. SOLUTION: This coiled carbon fiber composite having the ferromagnetism is obtained by arranging and forming carbon fibers into a micro coiled shape and having a coating layer of a ferromagnetic substance comprising (a) at least one kind selected from nickel, cobalt, chromium, iron, manganese and a rare earth element, (2) a compound thereof or (3) an alloy and having the ferromagnetism in a matrix so as to face a prescribed direction. The content of the coiled carbon fibers having the ferromagnetism is 0.1-50 wt.%.

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 composite having ferromagnetism used for radio wave absorbers, electromagnetic wave shielding materials, magnetic recording materials, various switches, sensors, micromechanical elements, adsorbents, filters and the like. TECHNICAL FIELD The present invention relates to a body, a method for manufacturing the same, and a radio wave absorber.

[0002]

2. Description of the Related Art In recent years, portable telephones, personal computers, and the like have spread throughout daily life, and the radio wave environment has been steadily increasing. On the other hand, malfunctions of medical equipment due to radio waves, operational obstacles of aircraft and railway vehicles, or concerns about health problems have become major social problems. Therefore, many radio wave absorbing materials, electromagnetic wave absorbing materials, shielding materials, and the like have been proposed and put to practical use.

[0003] As a radio wave absorber, for example, a coiled carbon fiber composite obtained by dispersing a coiled carbon fiber in a base material such as synthetic resin or rubber while forming carbon in an extremely fine fibrous form. The body is known.

Further, Japanese Patent Application Laid-Open Nos. 5-21984 and 226876 disclose that the coiled carbon fiber is dispersed in synthetic resin, rubber or the like by utilizing the conductivity of the coiled carbon fiber. Electromagnetic shielding composites have been proposed. Furthermore, the coiled carbon fiber is a material that is expected to be widely applied to various switches, micromechanical elements, adsorbents, filters, packings, three-dimensional reinforced composite materials, and the like.

[0005]

However, in the conventional coiled carbon fiber composite or electromagnetic wave shielding composite material, the direction in which the coiled carbon fibers extend is dispersed in the base material in a random state. Its radio wave absorption characteristics,
Electromagnetic wave shielding properties, electromagnetic properties, thermal properties, and mechanical properties are isotropic. As a result, when a radio wave is applied to the coiled carbon fiber composite, the radio wave is absorbed little by little into the coiled carbon fiber from a random direction. Alternatively, when an electromagnetic wave is applied to the electromagnetic wave shielding composite material, the electromagnetic wave is shielded little by little by the coiled carbon fiber from random directions. As a result, when trying to absorb or shield electromagnetic waves of a required amount of radio waves propagating only in a certain direction, a large amount of coiled carbon fiber is required, and the production cost of the coiled carbon fiber composite increases. there were.

The present invention has been made by paying attention to such problems existing in the prior art. The purpose is to efficiently absorb the required radio wave propagating only in a certain direction or to shield the electromagnetic wave efficiently, without increasing the amount of coiled carbon fiber used. A coiled carbon fiber composite having ferromagnetism that can prevent the production cost from increasing,
An object of the present invention is to provide a manufacturing method and a radio wave absorber. Other objects include a coiled carbon fiber composite having a ferromagnetic property capable of expressing anisotropy in radio wave absorption properties, electromagnetic wave shielding properties, electromagnetic properties, thermal properties, mechanical properties, etc. It is to provide a manufacturing method and a radio wave absorber.

[0007]

In order to achieve the above object, the ferromagnetic coiled carbon fiber composite according to the first aspect of the present invention is formed by a carbon fiber into a micro coil shape. Nickel, cobalt, chrome,
A ferromagnetic coiled carbon fiber having a ferromagnetic coating layer formed of at least one selected from iron, manganese, and rare earth elements (1), a compound (2) or an alloy (3) thereof is oriented in a certain direction. As described above.

According to a second aspect of the present invention, in the method for producing a coiled carbon fiber composite having ferromagnetism, at least one type selected from the group consisting of nickel, cobalt, chromium, iron, manganese, and a rare earth element is provided on the outer peripheral surface. A ferromagnetic coiled carbon fiber having a ferromagnetic coating layer made of the compound (2) or alloy (3) is added to a base material to prepare a composition, and a magnetic field is applied to the composition. When applied, the coiled carbon fibers having ferromagnetism are arranged in the base material so as to be oriented in a certain direction.

According to a third aspect of the invention, there is provided a radio wave absorber, wherein the ferromagnetic coiled carbon fiber composite according to the first aspect is formed in a predetermined shape.

[0010]

Embodiments of the present invention will be described below in detail. The coiled carbon fiber composite having ferromagnetism is formed in a micro coil shape by carbon fiber, and has at least one kind (1) selected from nickel, cobalt, chromium, iron, manganese, and rare earth elements on the outer peripheral surface thereof, It is formed by arranging ferromagnetic coiled carbon fibers having a ferromagnetic coating layer made of the compound (2) or the alloy (3) in a base material so as to face a certain direction.

The coiled carbon fiber has a fiber diameter of 0.1.
01-1 μm, coil diameter 0.1-15 μm, coil pitch 0.01-5 μm, and coil length 1-5
000 μm, the coil having a right-handed double helix structure, the left-handed double helix structure, or the coil having a right-handed single helix structure and a left-handed single helix structure And
In addition, you may use these coiled carbon fibers individually by 1 type or in combination of 2 or more types. The coiled carbon fiber has a coil diameter substantially on the order of micrometers, is capable of absorbing radio waves, and has excellent elastic properties and high strength.

The ferromagnetic coating layer includes at least one kind (1) selected from nickel, cobalt, chromium, iron, manganese and rare earth elements, a compound (2) or an alloy (3) thereof.

At least one kind (1) selected from nickel, cobalt, chromium, iron, manganese and rare earth elements may be used alone or in combination of two or more. As rare earth elements, neodymium,
Gadolinium, terbium, dysprosium, holmium, erbium, thulium, europium and the like can be mentioned. Examples of the at least one compound (2) selected from nickel, cobalt, chromium, iron, manganese and rare earth elements include, for example, ferrite, manganese-ferrite compound, barium-ferrite compound, strontium-ferrite compound, cobalt-ferrite compound, Cobalt oxide, manganese dioxide, europium oxide and the like can be mentioned.

The at least one alloy (3) selected from the group consisting of nickel, cobalt, chromium, iron, manganese and rare earth elements includes a cobalt-boron alloy, a cobalt-boron alloy.
Phosphorus alloy, cobalt-iron alloy, cobalt-iron-chromium alloy, iron-aluminum-nickel alloy, cobalt-iron-
Terbium alloy, cobalt-iron-boron alloy, cobalt-iron-phosphorus alloy, cobalt-samarium alloy, cobalt-tungsten-boron alloy, cobalt-tungsten-phosphorus alloy, nickel-cobalt alloy, nickel-cobalt-boron alloy, nickel- Cobalt-phosphorus alloy, cobalt-nickel-manganese alloy, nickel-boron alloy, nickel-iron-boron alloy, nickel-tungsten-boron alloy, nickel-phosphorus alloy, nickel-iron-
Phosphorus alloys, nickel-tungsten-phosphorus alloys and the like can be mentioned.

Among the coating layers (1) to (3),
Iron, ferrite, cobalt, manganese, nickel-boron alloy, nickel-phosphorus alloy, cobalt-boron alloy,
At least one selected from a cobalt-phosphorus alloy and a rare earth element is preferable from the viewpoint that the magnetic force is strong, the coating layer is easily formed on the outer peripheral surface of the coiled carbon fiber, and the cost is low.

The weight ratio of the coating layer is preferably set to 1 to 50% by weight with respect to the coiled carbon fiber.
The thickness is preferably set to 0.01 to 5 μm, and particularly preferably set to 0.05 to 2 μm.
If the weight ratio and the thickness are out of the above-mentioned ranges, it is not preferable because the electromagnetic wave absorption characteristics of the coiled carbon fiber and the shielding effect of the magnetic field component of the electromagnetic wave cannot be efficiently exhibited.

A ferromagnetic coiled carbon fiber having a coating layer formed on the outer peripheral surface thereof is irradiated with radio waves from the outside, for example, the traveling direction of the magnetic field component of the radio waves and the traveling direction of the magnetic field component of the ferromagnetic material. When they match, the magnetic field component of the radio wave is attracted. Further, compared with the coiled carbon fiber having no coating layer formed thereon, the coating layer increases the magnetic permeability indicating the ratio between the magnetic flux density and the magnetic field. For this reason, the radio wave absorption characteristics are improved, and the shielding effect against the magnetic field component is improved.

Further, when the radio wave passes through the coating layer and reaches the coiled carbon fiber, an induced current due to a dielectric starting force flows in the coil according to Faraday's law, generating Joule heat and absorbing the radio wave. The electric field component is circularly deflected as well as linearly deflected by the coiled carbon fiber. In addition, since the coiled carbon fiber is highly conductive, the coiled carbon fiber is also subjected to reflection, scattering loss, etc., and is rapidly attenuated. Further, the magnetic field component passed through the coiled carbon fiber is absorbed by the coating layer on the back surface of the coiled carbon fiber. Therefore, the radio wave is absorbed by the coiled carbon fiber having the coating layer formed on the outer peripheral surface.

Examples of the base material include thermoplastic polymer materials (thermoplastic resins and thermoplastic elastomers), curable polymer materials, adhesives, paints, inks, metals, alloys, and the like.
Ceramics, cement, gel, paper, fiber, woven fabric,
Nonwoven fabrics and the like can be mentioned. These are at least one of them in accordance with the requirements of electric characteristics such as hardness, mechanical strength, heat resistance, electric resistance, etc., of a radio wave absorber using a coiled carbon fiber composite having ferromagnetism. It is appropriately selected and used. Among these, it is preferable to use a thermoplastic polymer material (thermoplastic resin, thermoplastic elastomer) and a curable polymer material that are easily formed.

As the thermoplastic polymer material, for example,
Polyethylene, polypropylene, ethylene-α olefin copolymer such as ethylene-propylene copolymer, polymethylpentene, polyvinyl chloride, polyvinylidene chloride,
Polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl acetal, fluorine polymers such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene -Acrylonitrile copolymer, ABS resin, polyphenylene ether, modified PPE resin, aliphatic polyamides, aromatic polyamides, polyimide, polyamideimide, polymethacrylic esters, polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone, polyether Thermoplastics such as sulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, silicone resin, ionomer, etc. Resins.

Further, styrene-butadiene, styrene-
Isoprene block copolymer and its hydrogenated copolymer, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, etc. Is mentioned.

Among the curable polymer materials, heat-curable materials include natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-
Propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, halogenated butyl rubber,
Crosslinked rubber such as fluoro rubber, urethane rubber, silicone rubber, epoxy resin, phenol resin, polyimide resin,
Unsaturated polyester resin, diallyl phthalate resin and the like can be mentioned.

In addition, celluloses, cotton, silk, wool and the like can also be used. Further, the polymer material having a cross-linking property is not limited to a heat-curing property, but may be a resin, a rubber, or the like obtained by a cross-linking method such as a normal-temperature curability, a photo-curability, and a moisture-curability. Further, a plasticizer, a filler, an organic fiber (such as aramid fiber), a carbon fiber, an inorganic fiber (such as glass fiber), a stabilizer, and a coloring agent may be added as necessary. Further, by lowering the viscosity of the composition comprising the coiled carbon fiber having a ferromagnetic coating layer and the base material,
Organic solvents and water are added to facilitate the incorporation of ferromagnetic coiled carbon fibers into the base material and to facilitate the alignment of ferromagnetic coiled carbon fibers when a magnetic field is applied. You may.

From the viewpoint of heat resistance, mechanical strength, electrical reliability and the like, it is preferable to use at least one selected from the group consisting of silicone rubber, chlorinated polyethylene, epoxy resin and polyimide resin.

In the coiled carbon fiber composite having ferromagnetism, the ferromagnetic coiled carbon fibers having a coating layer made of a ferromagnetic material formed on the outer peripheral surface extend in a predetermined direction and are arranged in the base material. Being manufactured. In the radio wave, the electric field component and the magnetic field component are each perpendicular to the propagation direction of the radio wave. Therefore, by arranging the coiled carbon fiber composite having ferromagnetism so that the traveling direction of the magnetic field component of the coating layer and the traveling direction of the magnetic field component of the radio wave are the same direction, only the radio wave in a certain direction can be obtained. It is selectively and efficiently absorbed.

The heat conductivity of the coiled carbon fiber having ferromagnetism in the fiber direction is larger than the heat conductivity in the direction perpendicular to the fiber direction. Therefore, for example, when the coiled carbon fiber composite having ferromagnetism is formed into a plate shape and arranged so that the coiled carbon fiber having ferromagnetism extends in the thickness direction, the coiled carbon fiber having ferromagnetism is used. The thermal conductivity in the thickness direction of the composite is higher than the thermal conductivity in a direction orthogonal to the thickness direction. Therefore, in the coiled carbon fiber composite having ferromagnetism, anisotropy of thermal conductivity is developed between the thickness direction and the direction perpendicular thereto.

In addition, as in the case where ferromagnetic coiled carbon fibers are randomly dispersed in a base material, the contact area between adjacent ferromagnetic coiled carbon fibers is reduced. In addition, a base material is interposed between them. Therefore, the electric resistance in the thickness direction of the coiled carbon fiber composite having ferromagnetism is smaller than the electric resistance in the direction substantially orthogonal to the thickness direction. Therefore, in the coiled carbon fiber composite having ferromagnetism, anisotropy of the electric resistance value is developed between the thickness direction and the direction perpendicular thereto.

Further, the elastic property is exhibited only in the thickness direction of the coiled carbon fiber composite having ferromagnetism, and is not exhibited in the direction perpendicular to the thickness direction. Therefore, in the coiled carbon fiber composite having ferromagnetism, anisotropy of elastic properties is developed between the thickness direction and the direction perpendicular thereto. As a result, the coiled carbon fiber composite having ferromagnetism can be used for a pressure-sensitive sensor or a switching element by utilizing the anisotropy of the electric resistance value and the anisotropy of the elastic property.

The frequency range of the electromagnetic wave absorbed by the coiled carbon fiber having ferromagnetism depends on the coil diameter, coil pitch and coil length. If the coil length is long and the coil diameter is large, it is possible to absorb electromagnetic waves in a low frequency range. Therefore, by controlling these,
It can be applied to a wide range of radio wave absorbing materials, magnetic shielding materials, magnetic recording materials, magnetoresistive materials, magnetostrictive materials, magnetic fluids, magnetoelastic materials, magnetic sensors, and magnetic switches. It can also be used as a new electrode material, energy conversion element, microsensor, micromechanical element, microfilter, high temperature / high pressure / corrosion resistant / elastic packing, antibacterial material, adsorbent, etc.

Next, a method for producing a coiled carbon fiber composite having ferromagnetism will be described. First, a method for producing the coiled carbon fiber will be described. The coiled carbon fiber can be obtained by a catalyst activated CVD (chemical vapor deposition) method or the like. For example, JP-A-3-104927, JP-A-3-227412, JP-A-4-222228,
There are manufacturing methods disclosed in JP-A-10-37024, JP-A-11-81051, and the like.

Specifically, a substrate supporting a metal catalyst is placed in a horizontal thermochemical vapor synthesis apparatus, and the fifteenth table of the periodic table is placed.
When a catalyst gas composed of a compound of Group 16 or Group 16, a hydrogen gas and a sealing gas are injected, and a raw material gas for generating carbon by thermal decomposition is injected and thermally decomposed at a predetermined temperature,
It grows from the crystal plane of the metal catalyst.

The metal catalyst is at least one compound selected from oxides, carbides, sulfides, phosphides, carbonates and carbosulfides of transition metals, and is preferably a metal such as nickel, titanium or tungsten. Or a solid solution thereof, an oxide, a carbide, a sulfide, a phosphide, a carbonate or a carbon sulfide with oxygen. The form of the metal catalyst is powder,
Either a metal plate or a powdered sintered plate may be used, and preferably a fine powder or a sintered plate having an average particle size of about 5 μm.

As the raw material gas, a gas containing a carbon element such as acetylene, methane, propane or the like, which is thermally decomposed to generate carbon, or a carbon monoxide gas is used. The catalyst gas is a gas containing an element of Groups 15 and 16 of the periodic table, and sulfur,
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.

As the sealing gas, an inert gas such as a nitrogen gas and a helium gas or a hydrogen gas which does not react with a substance in the system is used. Heating temperature is 600-9
Preferably, the temperature is set within the range of 50 ° C.

Next, a method of forming a coating layer on the outer peripheral surface of the coiled carbon fiber will be described. The coating layer is made of a physical vapor deposition method such as an electroless plating method, an electrolytic plating method, a vacuum vapor deposition method or a sputtering method, a chemical vapor deposition method, a thermal spraying method, a coating method, a dipping method, and a mechanochemical for mechanically fixing fine particles. It is formed by one method selected from methods. In order to uniformly form the coating layer on the outer peripheral surface of the coiled carbon fiber, it is preferable to employ an electroless plating method. In this embodiment, a case where a coating layer is formed on the outer peripheral surface of a coiled carbon fiber by an electroless plating method will be described.

First, the coiled carbon fiber is washed with trichlorethylene, then immersed in a stannous chloride aqueous hydrochloric acid solution for a predetermined time, and further washed with distilled water. Next, the coiled carbon fiber after washing is poured into a palladium chloride-hydrochloric acid aqueous solution to activate the outer peripheral surface of the coiled carbon fiber, and then washed with distilled water. Next, the coiled carbon fibers having the activated outer peripheral surface are put into a plating solution having a predetermined concentration, and heated to a predetermined temperature while stirring. As a result, a coating layer is formed on the outer peripheral surface of the coiled carbon fiber.

A method for producing a coiled carbon fiber composite having ferromagnetism will be described. First, ferromagnetic coiled carbon fibers having a coating layer formed thereon are added to a base material.
At this time, in order to efficiently exhibit a radio wave absorption characteristic, a shielding effect of a magnetic field component of an electromagnetic wave, and the like, a ferromagnetic coiled carbon fiber is added to the ferromagnetic coiled carbon fiber composite in an amount of 0.1 to 50. It is preferred to add by weight. The addition amount is appropriately adjusted according to the type of the base material, the heat resistance, mechanical strength, electrical reliability, and the like of the obtained ferromagnetic coiled carbon fiber composite.

When the base material is a liquid polymer, the composition is prepared by adding a ferromagnetic coiled carbon fiber, followed by mixing using a mixer or a blender. In order to remove air in the composition, it is preferable to degas by vacuum or pressure. When the base material is a solid polymer, the composition is prepared using a kneader such as an extruder, a kneader, a roller or the like after adding the ferromagnetic coiled carbon fiber.

In order to improve the wettability and adhesion between the ferromagnetic coiled carbon fiber and the base material, the surface of the ferromagnetic coiled carbon fiber is previously degreased, washed, irradiated with ultraviolet light, corona-treated. It is preferable to perform an activation treatment such as a discharge treatment, a plasma treatment, a flame treatment, and an ion implantation treatment. Further, after the activation treatment, by treating with a silane-based or aluminum-based coupling agent, a large amount of ferromagnetic coiled carbon fiber can be easily dispersed in the base material, and the resulting ferromagnetic coil is obtained. It is possible to improve the radio wave absorption characteristics of the carbon fiber composite or the radio wave absorber, the shielding effect against magnetic field components, and the like.

Next, the above-described composition is filled in a mold made of metal, ceramics, resin or the like which is hardly affected by a magnetic field. Subsequently, a magnetic field is applied from outside the mold. As a means for generating a magnetic field, a permanent magnet, an electromagnet, a coil, or the like can be used. Then, the direction of the lines of magnetic force is adjusted so that the extending direction of the ferromagnetic coiled carbon fiber is oriented in a desired direction, and the magnetic field generating means is arranged. In addition,
When a magnet is used as the magnetic field generating means, the magnet may be configured so that the N pole and the S pole are opposite, the N pole and the N pole are opposed,
The magnet may be arranged only on one side. Further, the magnetic field atmosphere may be configured such that the magnetic lines of force are not necessarily linear in one direction but linear or curved in two or more directions.

At this time, the applied magnetic field is preferably from 0.05 to 30 Tesla, and preferably from 0.1 to 2 Tesla in terms of magnetic flux density in order to arrange the ferromagnetic coiled carbon fibers in a desired direction without fail. More preferred. Then, by heating and curing the composition to which the magnetic field is applied at a predetermined temperature and for a predetermined time or by cooling and curing, a coiled carbon fiber composite having ferromagnetism can be obtained. Furthermore, the obtained coiled carbon fiber composite having ferromagnetism may be molded into, for example, a body of a mobile phone and used as a radio wave absorber.

As described above, according to this embodiment, the following effects are exhibited. The ferromagnetic coiled carbon fiber composite has a base material such that the ferromagnetic coiled carbon fiber having a coating layer made of a ferromagnetic material having a high magnetic permeability formed on the outer peripheral surface is oriented in an arbitrary direction. Manufactured in an array. Therefore, by arranging the coiled carbon fiber composite having ferromagnetism so that the traveling direction of the magnetic field component of the coating layer is the same as the traveling direction of the magnetic field component of the radio wave, only radio waves in a certain direction are selected. It can be efficiently and efficiently absorbed. Further, the magnetic permeability is higher than that of the coiled carbon fiber having no coating layer. As a result, when used for electromagnetic wave shielding, the effect of shielding against magnetic field components of electromagnetic waves can be enhanced.

When the extending directions of the ferromagnetic coiled carbon fibers are randomly dispersed in the base material, radio waves from random directions are absorbed or electromagnetic waves are shielded. However, when a required amount of radio waves in a specific direction is absorbed or electromagnetic waves are shielded, the coiled carbon fiber having ferromagnetism can be reduced in a small amount as compared with the conventional coiled carbon fiber, and the manufacturing cost is reduced. Reduction can be achieved.

When the coiled carbon fiber composite having ferromagnetism is formed into a plate shape and the coiled carbon fibers having ferromagnetism are arranged in the thickness direction, the coiled carbon fiber composite is disposed between the thickness direction and a direction perpendicular thereto. Anisotropy in electric resistance is exhibited. Therefore, it is preferable to suppress the reflection of radio waves on the surface like a radio wave absorber, and a coiled carbon fiber composite having ferromagnetism is used by installing it near a printed circuit board that requires electrical insulation. can do.

When the coiled carbon fiber composite having ferromagnetism is formed into a plate shape and the coiled carbon fibers having ferromagnetism are arranged in the thickness direction, the coiled carbon fiber composite Anisotropy of thermal conductivity and elastic properties is developed between the thickness direction and the direction perpendicular thereto. As a result, the coiled carbon fiber composite having ferromagnetism can be used for a pressure-sensitive sensor or a switching element by utilizing the anisotropy of the electric resistance value and the anisotropy of the elastic property.

The coiled carbon fiber having ferromagnetism is 0.1% compared to the coiled carbon fiber composite having ferromagnetism.
It is set so as to be contained at ５０50% by weight. Therefore, the radio wave absorption characteristics can be efficiently exhibited.

[0047]

The above embodiment will be described more specifically with reference to examples and comparative examples. (Example 1, Example 2, Comparative Example 1 and Comparative Example 2) In Example 1 and Example 2, a coil-shaped carbon fiber having a ferromagnetic property using a coiled carbon fiber on which a coating layer of a cobalt-phosphorus alloy was formed was used. A carbon fiber composite was manufactured.

First, a method for producing a coiled carbon fiber will be described. A graphite substrate coated with nickel powder having an average particle size of 5 μm was set at the center of a reaction vessel of a horizontal thermochemical vapor phase synthesis device comprising a transparent quartz tube having an inner diameter of 23 mm and a length of 500 mm. 30 ml (min) / min of acetylene containing 1.51 mol% of thiophene impurities and 70 ml of hydrogen gas from the inlet at the upper center of the reaction vessel
/ Minute, argon was introduced at a rate of 40 ml / minute, and nitrogen gas was introduced as a seal gas from the inlet. Then, the reaction was performed at 750 ° C. for 15 minutes under normal pressure.

As a result, a double-helical coiled carbon fiber was obtained, in which two coils grew while being wound. The outer diameter of the coil is 0.1 to 15 μm, and the coil pitch is 0.1 μm.
01 to 5 μm, and the coil length was 1 to 5000 μm. Then, the coiled carbon fiber was heat-treated at 3000 ° C. for 6 hours in a reaction vessel in an argon atmosphere. As a result, all the amorphous portions were graphitized. The coiled shape of the carbon fiber was completely retained.

Next, a coating layer of a cobalt-phosphorus alloy was formed on the coiled carbon fiber. After washing the coiled carbon fiber with trichlorethylene, it was poured into a stannous chloride aqueous hydrochloric acid solution, immersed for about 15 minutes, and further washed with distilled water. Next, the washed coiled carbon fiber was poured into a palladium chloride-hydrochloric acid aqueous solution to activate the outer peripheral surface of the coiled carbon fiber, and then washed with distilled water.

Next, the coiled carbon fiber whose outer peripheral surface has been activated is put into a predetermined concentration of an aqueous solution of cobalt sulfate-sodium hypophosphite-sodium acetate-ammonium sulfate (plating solution), and stirred to about 90 ° C. By heating, a coating layer of a cobalt-phosphorus alloy was formed on the outer peripheral surface of the coiled carbon fiber by an electroless plating method. The coating layer of the cobalt-phosphorus alloy was formed uniformly on the outer peripheral surface of the coiled carbon fiber, and its thickness was about 0.3 μm.

Subsequently, a coiled carbon fiber composite having ferromagnetism was produced. In Example 1, 10% by weight of a coiled carbon fiber having a coating layer of a cobalt-phosphorus alloy was added to a thermosetting silicone rubber (trade name: TSE3033, manufactured by GE Toshiba Silicone) as a base material, and 1% in Example 2.
5% by weight was added. Next, the composition was prepared by stirring and defoaming, and the composition was filled in a Teflon-coated aluminum mold and formed into a thin plate. Next, the magnetic flux density 2 is set so that the magnetic field lines extend in one direction in the length direction of the molded product.
A magnetic field of Tesla was applied and the composition was cured by heating at 85 ° C. for 1 hour to produce a ferromagnetic coiled carbon fiber composite. The resulting ferromagnetic coiled carbon fiber composite had the ferromagnetic coiled carbon fibers oriented in the longitudinal direction. Further, the return loss of the coiled carbon fiber composite having ferromagnetism in radio waves of 50 MHz to 20 GHz was measured by a network analyzer (HP8720 manufactured by Hewlett-Packard Company). Table 1 shows the results.

The return loss is determined by making a radio wave incident on the coiled carbon fiber composite having ferromagnetism and coming out from the back surface of the coiled carbon fiber composite having ferromagnetism. Indicates the amount of attenuated radio waves.

In Comparative Example 1, Comparative Example 2 differs from Example 1.
In Example 2, the molded product was cured without applying a magnetic field to produce a coiled carbon fiber composite having ferromagnetism. Then, the return loss in the radio wave of 50 MHz to 20 GHz was measured in the same manner as in Example 1. Table 1 shows the results.

[0055]

[Table 1] As shown in Table 1, it was shown that Examples 1 and 2 had a larger return loss than Comparative Examples 1 and 2. Further, it was shown that Example 2 in which the amount of the coiled carbon fiber having ferromagnetism was larger than that in Example 1 had a larger return loss.

(Example 3, Example 4, Comparative Example 3 and Comparative Example 4) In Examples 3 and 4, ferromagnetic properties were obtained by using a coiled carbon fiber on which a nickel-boron alloy coating layer was formed. To produce a coiled carbon fiber composite.

The outer peripheral surface of the coiled carbon fiber was activated in the same manner as in Examples 1 and 2, and the activated carbon fiber was treated with a predetermined concentration of nickel sulfate-dimethylamine borane-sodium citrate-ethylenediaminetetraacetic acid aqueous solution (plating solution). ), And heated to about 80 ° C. with stirring to form a nickel-boron alloy coating layer on the outer peripheral surface of the coiled carbon fiber by an electroless plating method. The thickness of the coating layer is about 0.3
μm. Further, at 400 ° C. in an argon atmosphere.
For 20 minutes to magnetize the nickel. A coating layer of a nickel-boron alloy was uniformly formed on the outer peripheral surface of the coiled carbon fiber, and its thickness was about 0.3 μm.

The thermosetting silicone rubber (G
E Toshiba Silicone product name TSE3033)
In Example 3, 10% by weight and in Example 4 15% by weight of the coiled carbon fiber on which the nickel-boron alloy coating layer was formed were added. Next, a composition is prepared by stirring and defoaming,
The composition was cured by applying a magnetic field having a magnetic flux density of 2 Tesla and heating at 85 ° C. for 1 hour in the same manner as in Examples 1 and 2 to cure the composition and to provide a ferromagnetic coiled carbon fiber composite. Was manufactured. The resulting ferromagnetic coiled carbon fiber composite had the ferromagnetic coiled carbon fibers oriented in the longitudinal direction. Further, the coiled carbon fiber composite having the ferromagnetism of 50 MHz to 20 GH
The return loss in the radio wave of z was measured in the same manner as in Examples 1 and 2. Table 1 shows the results.

Comparative Example 3 differs from Example 3 in that Comparative Example 4
In Example 4, the molded product was cured without applying a magnetic field to produce a coiled carbon fiber composite having ferromagnetism. Then, the return loss in the radio wave of 50 MHz to 20 GHz was measured in the same manner as in Example 1. Table 1 shows the results.

As shown in Table 1, Examples 3 and 4
Indicates that the return loss is larger than that of Comparative Examples 3 and 4. It was also shown that the coating layer of the cobalt-phosphorus alloy had a larger return loss than the nickel-boron alloy.

(Example 5 and Comparative Example 5) Thermosetting epoxy resin (EPOXY-T, USA)
ECHNOLOGY, INC. ) Product name EPOTECH 3
To 10), 30% by weight of the coiled carbon fiber on which the coating layer of the cobalt-phosphorus alloy obtained in Example 1 was formed was added. Next, a composition was prepared by stirring and defoaming, filled in the mold used in Example 1, molded, and a magnetic field having a magnetic flux density of 2 Tesla was applied so that the magnetic flux extended in one direction. Then, the molded product was cured by heating at 70 ° C. for 1 hour to produce a coiled carbon fiber composite having ferromagnetism.

In the obtained coiled carbon fiber composite having ferromagnetism, the electric resistance in the direction parallel to the direction parallel to the arrangement direction of the coiled carbon fibers having ferromagnetism and the direction perpendicular thereto were measured. Table 2 shows the results.

In Comparative Example 5, the coiled carbon fiber composite having ferromagnetism was produced by curing the molded product in Example 5 without applying a magnetic field, and the electrical resistance was measured in the same manner as in Example 5. . Table 2 shows the results.

[0064]

[Table 2] As shown in Table 2, as compared with the case where the coiled carbon fibers having ferromagnetism of Comparative Example 5 are randomly arranged, in Example 5, the direction perpendicular to the extending direction of the coiled carbon fibers having ferromagnetism is shown. It was shown that the electrical resistance in the direction became very large. In addition, it was shown that anisotropy of the electric resistance value was exhibited between the direction parallel to the arrangement direction of the coiled carbon fibers having ferromagnetism and the direction perpendicular to the arrangement direction.

Example 6 and Comparative Example 6 The thermosetting epoxy resin used in Example 5 and Comparative Example 5 was coated with the nickel-boron alloy coating layer obtained in Example 2 in the form of a coil. 30% by weight of carbon fiber was added. Next, a coiled carbon fiber composite having ferromagnetism was produced in the same manner as in Example 5. The electrical resistance of the obtained coiled carbon fiber composite having ferromagnetism was measured in the same manner as in Example 5. Table 2 shows the results.

In Comparative Example 6, in Example 6, the composition was cured without applying a magnetic field to produce a coiled carbon fiber composite having ferromagnetism, and the electric resistance was measured in the same manner as in Example 6. . Table 2 shows the results.

As shown in Table 2, the arrangement direction of the coiled carbon fibers having ferromagnetism in Example 6 is different from that in Comparative Example 6 in which the coiled carbon fibers having ferromagnetism are randomly arranged. It was shown that the electric resistance in the direction perpendicular to the direction became extremely large. In addition, it was shown that anisotropy of the electric resistance value was exhibited between the direction parallel to the arrangement direction of the coiled carbon fibers having ferromagnetism and the direction perpendicular to the arrangement direction.

(Example 7 and Comparative Example 7) The thermosetting silicone rubber used in Example 1 was replaced with a coil-shaped carbon fiber having a coating layer of the cobalt-phosphorus alloy obtained in Example 1 for 20 times. % By weight. Next, the composition was prepared by stirring and defoaming, and filled into the mold used in Example 1 to be molded. Next, a magnetic field having a magnetic flux density of 2 Tesla is applied so that the magnetic flux extends in the thickness direction of the molded product, and the molded product is cured by heating at 85 ° C. for 1 hour to form a coiled carbon fiber composite having ferromagnetism. Manufactured.

In the obtained coiled carbon fiber composite having ferromagnetism, the thermal conductivity in the direction parallel to the arrangement direction of the coiled carbon fibers having ferromagnetism, that is, the thickness direction was measured by a laser flash method.

In Comparative Example 7, a coiled carbon fiber composite having ferromagnetism was produced by curing the molded product in Example 7 without applying a magnetic field, and the thermal conductivity was measured in the same manner as in Example 7. .

As a result, in Example 7, the thermal conductivity was 0.6
1 W / (m · K), and the thermal conductivity was 0.37 in Comparative Example 7.
W / (m · K). Therefore, it was shown that when the coiled carbon fibers having ferromagnetism are arranged in a certain direction, the thermal conductivity becomes larger as compared with the case where they are randomly dispersed.

Further, a technical idea which can be grasped from the above embodiment will be described below. The weight ratio of the ferromagnetic coating layer to the coiled carbon fiber is 1 to 50.
The ferromagnetic coiled carbon fiber composite according to claim 1, wherein the carbon fiber composite has a ferromagnetic property and is set to 0.01% to 5 μm by weight.

With this configuration, it is possible to efficiently absorb a required radio wave propagating only in a certain direction or to shield an electromagnetic wave efficiently. The ferromagnetic coiled carbon fiber composite according to claim 1, wherein the ferromagnetic coiled carbon fiber is contained in an amount of 0.1 to 50% by weight.

With this configuration, the coil-like carbon fiber composite having ferromagnetism can efficiently exhibit the radio wave absorption characteristics, the electromagnetic wave shielding effect, and the like. The method according to claim 2, wherein a magnetic field having a magnetic flux density of 0.05 to 30 Tesla is applied to the composition.

With this configuration, the coiled carbon fibers having ferromagnetism can be arranged in the base material in a certain direction.

[0076]

As described above in detail, according to the present invention, the following effects can be obtained. According to the coiled carbon fiber composite having ferromagnetism of the invention according to claim 1, a required radio wave propagating only in a certain direction can be efficiently absorbed,
Electromagnetic waves can be efficiently shielded, and the production cost of the coiled carbon fiber can be prevented from increasing without increasing the usage of the coiled carbon fiber.
Further, anisotropy can be expressed in radio wave absorption characteristics, electromagnetic wave shielding properties, electromagnetic properties, thermal properties, mechanical properties, and the like.

According to the method for manufacturing a coiled carbon fiber composite having ferromagnetism according to the second aspect of the invention, the coiled carbon fibers having ferromagnetism can be arranged in a desired direction. It is possible to efficiently produce a coiled carbon fiber composite having the same.

According to the radio wave absorber of the third aspect of the present invention, radio waves can be efficiently absorbed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Tobita 5-10-5 Tabata, Kita-ku, Tokyo Within Polytec Corporation (72) Inventor Kengo Nishi 5-10-5 Tabata, Kita-ku, Tokyo Polymertec Inc. F Term (reference) 4K030 BA01 BA06 BA07 BA14 BA35 BA59 CA05 CA13 HA08 LA11 4L038 AA28 AA29 AB20 BA02 BB01 CA20 DA04 DA20 5E049 AA01 AA04 AA07 AA09 BA16 BA27 CB10 CC01

Claims (3)

[Claims] 1. A micro-coil formed from carbon fiber, and nickel, cobalt, chromium, iron,
A ferromagnetic coiled carbon fiber having a ferromagnetic coating layer made of at least one selected from manganese and rare earth elements (1), a compound (2) or an alloy (3) thereof is oriented in a certain direction. A ferromagnetic coiled carbon fiber composite formed in a matrix. 2. A ferromagnetic coating layer comprising at least one selected from nickel, cobalt, chromium, iron, manganese, and rare earth elements, and a compound (2) or alloy (3) thereof, on the outer peripheral surface. A composition is prepared by adding the formed ferromagnetic coiled carbon fiber to the base material, and a magnetic field is applied to the composition so that the ferromagnetic coiled carbon fiber is oriented in a certain direction. A method for producing a coiled carbon fiber composite having ferromagnetism arranged therein. 3. A radio wave absorber in which the coiled carbon fiber composite having ferromagnetism according to claim 1 is formed in a predetermined shape.