JP2007138338A - Composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new composite material which maximally utilizes the specific properties of fine carbon fibers. <P>SOLUTION: This composite material has a skeleton structure formed by three-dimensionally binding carbon fiber structures which exhibit a three-dimensional network state composed of carbon fibers having outer diameters of 15 to 100 nm, have granular portions in which the carbon fibers are bound to each other in a form that the carbon fibers are extended, and are formed in a process for growing the carbon fibers, wherein a resin, a rubber, a metal or a carbonaceous material is impregnated into pores formed in the inside of the skeleton structure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composite material using fine carbon fibers (so-called carbon nanotubes).

  Conventionally, a resin composition, so-called composite material, in which desired characteristics (for example, conductivity, mechanical characteristics, etc.) are imparted by blending a filler such as carbon black with a resin has been proposed.

  In recent years, fine carbon fibers (so-called carbon nanotubes) are blended in place of conventionally used carbon black in order to impart further excellent electrical conductivity and mechanical properties to a molded body formed of a composite material. An attempt is being made. The graphite layer constituting the carbon nanotube is a substance having a regular, six-membered ring arrangement structure, and chemically, mechanically and thermally stable properties as well as its unique electrical properties. Therefore, for example, if such fine carbon fibers can be dispersed and blended in solid materials such as various resins, ceramics, metals, or liquid materials such as fuel oil and lubricant, the above-described physical properties can be utilized. It is expected that an excellent composite material can be provided.

Specifically, for example, Patent Documents 1 and 2 propose composite materials containing carbon nanotubes in a matrix. In Patent Document 3, when carbon nanotubes are blended in a resin composition, the carbon nanotubes are not simply blended as they are, but aggregates are formed from the carbon nanotubes or entangled with each other. It is also known to form and blend this.
Japanese Patent No. 2641712 JP 2003-12939 A Japanese Patent No. 3034027

  However, in the conventional composite materials represented by the above-mentioned documents, the excellent characteristics of the fine carbon fibers (carbon nanotubes) have not been fully utilized, and the fine carbon fibers themselves have been improved. There was room for.

  The present invention is an invention made in such a situation, and a main object is to provide a novel skeleton structure and a composite material that make the most of the unique properties of fine carbon fibers.

  In order to solve the above problems, as a result of intensive studies, the present inventors have found that carbon fibers that are as fine as possible are used in order to impart various properties such as conductivity and strength properties to the composite material. Structures that are firmly bonded to each other without being separated from each other, and each of the carbon fibers constituting the structure is bonded to each other in three dimensions using carbon. The present inventors have found that it is effective to use a skeleton structure, and to impregnate a void formed in the skeleton structure with a resin or the like.

  That is, this invention which solves the said subject is exhibiting the three-dimensional network shape comprised from the carbon fiber of 15-100 nm in outer diameter, and couple | bonds the said carbon fiber mutually in the aspect which the said carbon fiber extends in multiple numbers. A skeletal structure having a granular part, and the granular part is formed by joining a carbon fiber structure formed in the carbon fiber growth process in three dimensions with carbon Is the body.

  Further, the skeleton structure may contain boron.

  Moreover, 0.001-10 mass% may be sufficient as content of the said boron with respect to the said frame | skeleton structure.

  The carbon fiber structure may have an area-based circle equivalent average diameter of 50 to 500 μm.

The skeletal structure may have an I _D / I _G measured by Raman spectroscopy of 1.4 or less and an I _{G ′} / I _G of 1.5 or less.

The skeleton structure may have a bulk density of 0.2 to 2.3 g / cm ³ .

  The skeleton structure may have a combustion start temperature in air of 700 ° C. or higher.

  Moreover, the particle diameter of the said granular part may be larger than the outer diameter of the said carbon fiber in the coupling | bond part of the said carbon fiber.

  Moreover, the said carbon fiber structure may be produced | generated using the at least 2 or more carbon compound from which decomposition temperature differs as a carbon source.

  Moreover, this invention which solves the said subject is exhibiting the three-dimensional network shape comprised from carbon fiber with an outer diameter of 15-100 nm, and couple | bonds the said carbon fiber mutually in the aspect which the said carbon fiber extends in multiple numbers. And having a granular part, and the granular part has a skeletal structure formed by joining a carbon fiber structure formed in the carbon fiber growth process in three dimensions with carbon, A void formed in the skeleton structure is impregnated with a resin, rubber, metal, or carbon-based material.

  Further, the skeleton structure may contain boron.

  Moreover, 0.001-10 mass% may be sufficient as content of the said boron with respect to the said frame | skeleton structure.

  The carbon fiber structure may have an area-based circle equivalent average diameter of 50 to 500 μm.

The skeletal structure may have an I _D / I _G measured by Raman spectroscopy of 1.4 or less and an I _{G ′} / I _G of 1.5 or less.

The skeleton structure may have a bulk density of 0.2 to 2.3 g / cm ³ .

  The skeleton structure may have a combustion start temperature in air of 700 ° C. or higher.

  Moreover, the particle diameter of the said granular part may be larger than the outer diameter of the said carbon fiber in the coupling | bond part of the said carbon fiber.

  Moreover, the said carbon fiber structure may be produced | generated using the at least 2 or more carbon compound from which decomposition temperature differs as a carbon source.

  In the present invention, the fine structure carbon fibers arranged in a three-dimensional network as described above in the skeleton structure serving as the framework of the composite material are strongly bonded to each other by the granular portions formed in the carbon fiber growth process. The carbon fiber structure having a shape in which a plurality of the carbon fibers extend from the granular portion is three-dimensionally bonded with carbon, so that the carbon fiber structure itself has a three-dimensional structure. In addition to the wide spread, the carbon fiber structures are further three-dimensionally bonded to each other, so that a skeletal structure with an unprecedented spread can be obtained, and the electrical conductivity and mechanical properties of fine carbon fibers. In addition, the heat conduction characteristics can be sufficiently exhibited.

  In addition, since carbon fibers that originally have a three-dimensional network form are used as starting materials, it is different from conventional aggregates that have been forcibly made by applying external force, so that there is no defect in each carbon fiber. This is a feature of the invention, and it is possible to improve electrical conductivity, mechanical properties, and heat conduction properties.

  Furthermore, in the present invention, when boron is contained in the skeleton structure, high conductivity can be obtained even if the structure contains some defects.

  Hereinafter, the present invention will be described in detail based on preferred embodiments.

  The composite material of the present invention includes a skeleton structure composed of a carbon fiber structure, and a resin, rubber, metal, or carbon-based material impregnated in a void formed inside the skeleton structure. .

  First, a skeleton structure which is one of the features of the present invention will be described.

  The skeleton structure is formed by three-dimensionally bonding a carbon fiber structure with carbon.

  Here, the carbon fiber structure used in the present invention is, for example, a three-dimensional network composed of carbon fibers having an outer diameter of 15 to 100 nm as seen in the SEM photograph shown in FIG. 1 or the TEM photograph shown in FIG. The carbon fiber structure is characterized in that the carbon fiber structure has a granular portion that bonds the carbon fibers to each other in a form in which a plurality of the carbon fibers extend. Is the body.

  The outer diameter of the carbon fiber constituting the carbon fiber structure is in the range of 15 to 100 nm, when the outer diameter is less than 15 nm, the cross section of the carbon fiber is not polygonal as described later, On the other hand, the smaller the diameter due to the physical properties of the carbon fiber, the greater the number per unit amount and the longer the length of the carbon fiber in the axial direction, so that high conductivity can be obtained, and the outer diameter must exceed 100 nm. This is because it is not suitable as a carbon fiber structure to be disposed as a modifier or additive in a matrix such as a resin. The outer diameter of the carbon fiber is particularly preferably in the range of 20 to 70 nm. A cylindrical graphene sheet laminated in a direction perpendicular to the axis, that is, a multi-layered one in this outer diameter range is difficult to bend and is elastic, that is, has a property of returning to its original shape even after deformation. Because.

  When the annealing treatment is performed at 1800 ° C. or higher, the spacing between the stacked graphene sheets is narrowed and the true density is increased, and the carbon fiber has a polygonal axial cross section. Since it becomes dense and has few defects in both the surface directions of the cylindrical graphene sheet to be formed, the bending rigidity (EI) is improved.

  In addition, the fine carbon fiber desirably has an outer diameter that changes along the axial direction. As described above, when the outer diameter of the carbon fiber is not constant along the axial direction and changes, it is considered that a kind of anchor effect is produced in the carbon fiber when impregnated with a resin or the like. It is possible to prevent the resin or the like from moving.

  In the carbon fiber structure used in the present invention, fine carbon fibers having such a predetermined outer diameter are present in a three-dimensional network, and these carbon fibers are granular formed in the growth process of the carbon fibers. The carbon fibers are bonded to each other at the portion, and a plurality of the carbon fibers extend from the granular portion. In this way, the fine carbon fibers are not merely entangled with each other, but are firmly bonded to each other in the granular portion, so that a strong structure is formed when the skeleton structure is formed. Can do. Further, in the carbon fiber structure used in the present invention, since the carbon fibers are bonded to each other by the granular portion formed in the growth process of the carbon fiber, the electrical characteristics of the structure itself are also very high. For example, the electrical resistance value measured at a constant compression density is a simple entanglement of fine carbon fibers, or a junction between fine carbon fibers attached by a carbonaceous material or a carbide thereof after synthesis of the carbon fiber. Compared with the value of the structure or the like obtained, the value is very low, and a good conductive path can be formed when a composite material is used.

Since the granular part is formed in the growth process of the carbon fiber as described above, the carbon-carbon bond in the granular part is sufficiently developed, and although it is not exactly clear, sp ² bond and It seems to include a mixed state of sp ³ bonds. And after the generation (intermediate and first intermediate described later), the granular part and the fiber part are continuous with a structure in which patch-like sheet pieces made of carbon atoms are bonded together, and thereafter After the high temperature heat treatment, at least a part of the graphene layer constituting the granular part is continuous with the graphene layer constituting the fine carbon fiber extending from the granular part. In the carbon fiber structure used in the present invention, between the granular portion and the fine carbon fiber, it is a symbol that the graphene layer constituting the granular portion as described above is continuous with the graphene layer constituting the fine carbon fiber. As described above, the carbon crystal structural bonds are connected (at least a part thereof), thereby forming a strong bond between the granular portion and the fine carbon fiber. .

  In the present specification, the term “extending” of the carbon fiber from the granular part simply means that the granular part and the carbon fiber are apparently connected to each other by another binder (including carbonaceous material). It does not indicate such a state, but mainly means a state in which they are connected by carbon crystal structural bonds as described above.

  Further, as described above, the granular part is formed in the carbon fiber growth process. As a trace, at least one catalyst particle or the catalyst particle is volatilized and removed in the subsequent heat treatment process. And the resulting voids. These pores (or catalyst particles) are essentially independent from the hollow portions formed inside the fine carbon fibers extending from the granular portions (note that only a small part is accidental) In addition, it is also observed that it is continuous with the hollow part.)

  The number of catalyst particles or holes is not particularly limited, but is about 1 to 1000, more preferably about 3 to 500, per granular part. By forming the granular portion in the presence of such a number of catalyst particles, it is possible to obtain a granular portion having a desired size as described later.

  The size of each catalyst particle or hole present in the granular part is, for example, 1 to 100 nm, more preferably 2 to 40 nm, and further preferably 3 to 15 nm.

  Further, although not particularly limited, it is desirable that the particle size of the granular portion is larger than the outer diameter of the fine carbon fiber as shown in FIG. Specifically, for example, the outer diameter of the fine carbon fiber is 1.3 to 250 times, more preferably 1.5 to 100 times, and still more preferably 2.0 to 25 times. In addition, the said value is an average value. Thus, when the particle diameter of the granular part which is a bonding point between carbon fibers is sufficiently large as 1.3 times or more of the outer diameter of the fine carbon fiber, it is higher than the carbon fiber extending from the granular part. When a skeleton structure is formed using this to obtain a composite material of the present invention, a three-dimensional network structure is maintained even when a certain amount of elasticity is applied. Become. On the other hand, if the size of the granular portion is extremely large exceeding 250 times the outer diameter of the fine carbon fiber, the fibrous characteristics of the carbon fiber structure may be impaired, and the composite material of the present invention is formed. This is not desirable because it may not be suitable for constructing the skeleton structure. The “particle size of the granular part” in the present specification is a value measured by regarding the granular part, which is a bonding point between carbon fibers, as one particle.

  The specific particle size of the granular part depends on the size of the carbon fiber structure and the outer diameter of the fine carbon fiber in the carbon fiber structure, but for example, an average value of 20 to 5000 nm, more preferably It is about 25 to 2000 nm, more preferably about 30 to 500 nm.

  Furthermore, since this granular part is formed in the growth process of the carbon fiber as described above, it has a relatively spherical shape, and the circularity is 0.2 to <1 on average. , Preferably 0.5 to 0.99, more preferably about 0.7 to 0.98.

  In addition, the granular portion is formed in the carbon fiber growth process as described above, and, for example, the joining point between the fine carbon fibers is adhered by the carbonaceous material or the carbide after the carbon fiber synthesis. Compared with the structure, etc., the bonds between the carbon fibers in the granular part are very strong, and even under conditions where the carbon fiber breaks in the carbon fiber structure, the granular part (Coupling part) is held stably. Specifically, for example, as shown in the examples described later, the carbon fiber structure is dispersed in a liquid medium, and ultrasonic waves with a predetermined output and a predetermined frequency are applied to the carbon fiber structure so that the average length of the carbon fibers is almost halved. Even when the load condition is such that the change rate of the average particle diameter of the granular part is less than 10%, more preferably less than 5%, the granular part, that is, the bonded part of the fibers is stably held. It is what.

  The carbon fiber structure used in the present invention preferably has an area-based circle-equivalent mean diameter of about 50 to 500 μm. Here, the area-based circle-equivalent mean diameter is obtained by photographing the outer shape of the carbon fiber structure using an electron microscope or the like, and in this photographed image, the contour of each carbon fiber structure is represented by an appropriate image analysis software such as WinRoof. (Trade name, manufactured by Mitani Shoji Co., Ltd.) is used to determine the area within the contour, calculate the equivalent circle diameter of each fiber structure, and average it. When this circle-equivalent average diameter is 50 μm or less, the three-dimensional structure cannot sufficiently exhibit effects such as conductivity and strength. The carbon fiber structure used for the skeletal structure is preferably larger, but if it is too large, it becomes difficult to handle as a powder, and therefore it is preferably 500 μm or less.

  Further, as described above, the carbon fiber structure used in the present invention has a shape in which carbon fibers existing in a three-dimensional network are bonded to each other in the granular portion, and a plurality of the carbon fibers extend from the granular portion. However, in a single carbon fiber structure, when a plurality of granular portions that combine carbon fibers are present to form a three-dimensional network, the average distance between adjacent granular portions is, for example, 0.5 μm. ˜300 μm, more preferably 0.5 to 100 μm, and even more preferably about 1 to 50 μm. In addition, the distance between this adjacent granule part measures the distance from the center part of one granular material to the center part of the granule part adjacent to this. When the average distance between the granular materials is less than 0.5 μm, the carbon fiber does not sufficiently develop into a three-dimensional network. On the other hand, if the average distance exceeds 300 μm, the skeletal structure constituting the composite material becomes rough, and sufficient strength may not be obtained. Because there is.

In addition, since the carbon fiber structure used in the present invention is bonded to each other in the granular portion formed in the growth process, the carbon fibers existing in a three-dimensional network form are electrically connected as described above. For example, the powder resistance value measured at a constant compression density of 0.8 g / cm ³ is 0.02 Ω · cm or less, more preferably 0.001 to 0.00. It is preferably 010 Ω · cm. This is because when the powder resistance value exceeds 0.02 Ω · cm, it is difficult to form a good conductive path when a composite material is formed.

  Next, the skeleton structure formed using the carbon fiber structure described above will be described.

  The skeletal structure that forms the skeleton of the composite material of the present invention is configured by three-dimensionally joining the three-dimensional network-like carbon fiber structure with carbon. According to such a skeletal structure, as compared with the conventional skeleton structure formed by bonding carbon fibers alone, the carbon fiber which is the starting material itself has a three-dimensional network, so that the bond is strong. It is a skeletal structure with high power and high conductivity.

  In the skeleton structure used in the present invention, boron may be contained. By containing boron, each carbon fiber can be made into a highly crystalline carbon fiber. In the present invention, “boron is contained in the skeletal structure” means that boron is attached to the surface of the skeletal structure in addition to a state in which a part of carbon atoms constituting the skeletal structure is substituted by boron. The thing including the state which was done.

  The method for containing (doping) boron in the carbon fiber and the bonding carbon constituting the skeletal structure is not particularly limited. For example, the carbon fiber and the bonding carbon are still heat-treated at a low temperature (for example, 1500 ° C. or less), but still By mixing carbon fibers in an undeveloped state, carbon fibers in an unheated (as-grown) state, and boron (including boron compound), and then annealing at a high temperature, carbon fibers and Boron can be included in the bonding carbon. Although it is not impossible to incorporate boron into carbon fiber that has been graphitized at a temperature of 2000 ° C. or higher, and further 2300 ° C. or higher, it is not preferable in view of energy for doping boron. Since it also acts as a catalyst for promoting crystallization of carbon fibers, it is preferable to contain boron before the graphitization treatment.

Even if boron is contained in the skeletal structure, the present invention is not particularly limited. Here, “boron” in the present invention is a concept including not only elemental boron but also boron compounds. As described above, when boron is included in the skeletal structure, annealing is performed at a high temperature (for example, 1800 ° C. or higher), and therefore boron that is not evaporated by decomposition or the like before reaching at least 1800 ° C. is used. is required. Examples of boron that satisfies this condition include elemental boron, B ₂ O ₃ , H ₃ BO ₄ , B ₄ C, and BN.

  As content of boron, it is preferable that it is 0.001-10 mass% with respect to a skeleton structure, and it is especially preferable that it is 0.01-3.0 mass%. When the boron content is less than 0.001% by mass, it is difficult to improve the effect of boron content, that is, the crystallinity of the carbon fiber. On the other hand, if the content exceeds 10% by mass, not only the processing cost becomes high, but also at the stage of heat treatment, it is easy to be melt-sintered and hardened, or the fiber surface is coated with boron, conversely, the conductivity deteriorates. There is a case to let you.

Further, the size and shape of the skeletal structure constituting the composite material of the present invention are not particularly limited, and can be appropriately selected depending on the application field, required performance, and the like. density, specifically, 0.2~2.3g / cm ^3, and particularly preferably in the range 0.4~2.1cm ^3. This is because if the bulk density exceeds 2.3 g / cm ³ , it becomes difficult to impregnate the voids of the skeleton structure with a resin or the like.

In addition, the skeletal structure used in the present invention desirably has high strength and electrical conductivity, and preferably has few defects in the graphene sheet constituting the carbon fiber. Specifically, for example, Raman spectroscopy is used. It is desirable that the measured I _D / I _G ratio is 0.25 or less, more preferably 0.1 or less, and I _{G ′} / I _G is 0.6 to 1.5. Incidentally, in Raman spectroscopic analysis of up to 2000 cm ^-1, the peak around 1580 cm ^-1 in a large single crystal graphite (G-band) only appear. A peak (D band) appears in the vicinity of 1360 cm ⁻¹ due to the crystal having a finite minute size or lattice defects. Further, when the measurement range is expanded, a G ′ band appears in the vicinity of 2700 cm ⁻¹ . Therefore, the intensity ratio between the D band and the G band (R = I ₁₃₆₀ / I ₁₅₈₀ = I _D / I _G ) and the intensity ratio between the G ′ band and the G band (I ₂₇₀₀ / I ₁₅₈₀ = I _{G ′} / I _G ) This is because, as described above, it is recognized that the amount of defects in the graphene sheet is small within the predetermined range.

In addition, it is desirable to add boron to the graphene sheet when the purpose is to obtain high conductivity even if the structure contains some defects. Specifically, for example, Raman spectroscopy It is desirable that the I _D / I _G ratio measured in (1) is 0.2 to 1.4, and I _{G ′} / I _G is 0.2 to 0.8. The intensity ratio between the D band and the G band (R = I ₁₃₆₀ / I ₁₅₈₀ = I _D / I _G ) and the intensity ratio between the G ′ band and the G band (I ₂₇₀₀ / I ₁₅₈₀ = I _{G ′} / I _G ) This is because it is considered that boron is contained in the graphene sheet when the thickness is within the predetermined range. When boron is contained in the graphene sheet, the G band waveform in Raman spectroscopy becomes asymmetric, and a shoulder is recognized on the high wave number side.

  In addition, the skeletal structure used in the present invention desirably has a combustion start temperature in air of 700 ° C. or higher, more preferably 800 to 900 ° C. As described above, since the carbon fiber structure constituting the skeleton structure has few defects and the carbon fiber has an intended outer diameter, such a high thermal stability is obtained.

  The carbon fiber structure having the desired shape as described above is not particularly limited, but can be prepared, for example, as follows.

  Basically, an organic compound such as hydrocarbon is chemically pyrolyzed by CVD using transition metal ultrafine particles as a catalyst to obtain a fiber structure (hereinafter referred to as an intermediate). When the metal fiber contains boron, after separating hydrocarbons such as this stage or tar, boron or a boron compound is mixed. Further, a high temperature heat treatment is performed. Note that boron or a boron compound may be mixed in advance with an organic compound such as hydrocarbon (that is, boron is added before obtaining an intermediate), and further boron is mixed after high-temperature heat treatment. It is also possible.

  As the raw material organic compound, hydrocarbons such as benzene, toluene and xylene, alcohols such as carbon monoxide (CO) and ethanol can be used. Although not particularly limited, in obtaining the fiber structure used in the present invention, it is preferable to use at least two or more carbon compounds having different decomposition temperatures as the carbon source. The “at least two or more carbon compounds” described in the present specification does not necessarily mean that two or more kinds of raw material organic compounds are used, and one kind of raw material organic compound is used. However, in the process of synthesizing the fiber structure, for example, a reaction such as hydrodealkylation of toluene or xylene occurs, and in the subsequent thermal decomposition reaction system, two decomposition temperatures are different. The aspect which becomes the above carbon compound is also included.

  In addition, when two or more types of carbon compounds are present as carbon sources in the thermal decomposition reaction system, the decomposition temperature of each carbon compound is not limited to the type of the carbon compound, but the carbon compound in the raw material gas. Since it varies depending on the gas partial pressure or molar ratio, a relatively large number of combinations can be used as carbon compounds by adjusting the composition ratio of two or more carbon compounds in the raw material gas.

  For example, alkanes or cycloalkanes such as methane, ethane, propanes, butanes, pentanes, hexanes, heptanes, cyclopropane, cyclohexane, etc., particularly alkanes having about 1 to 7 carbon atoms; ethylene, propylene, butylenes, Alkenes or cycloolefins such as pentenes, heptenes and cyclopentenes, especially alkenes having about 1 to 7 carbon atoms; alkynes such as acetylene and propyne, especially alkynes having about 1 to 7 carbon atoms; benzene, toluene, styrene, xylene, naphthalene , Aromatic or heteroaromatic hydrocarbons such as methylnaphthalene, indene and phenanthrene, especially aromatic or heteroaromatic hydrocarbons having about 6 to 18 carbon atoms, alcohols such as methanol and ethanol, especially about 1 to 7 carbon atoms Of alcohol; its Combine two or more carbon compounds selected from carbon monoxide, ketones, ethers, etc., by adjusting the gas partial pressure so that different decomposition temperatures can be exhibited in the desired thermal decomposition reaction temperature range. It can be used by adjusting the residence time in a predetermined temperature range, and the carbon fiber structure used in the present invention can be efficiently produced by optimizing the mixing ratio.

  Among such combinations of two or more carbon compounds, for example, in the combination of methane and benzene, the molar ratio of methane / benzene is> 1 to 600, more preferably 1.1 to 200, still more preferably. It is desirable to set it as 3-100. This value is the gas composition ratio at the entrance of the reactor. For example, when toluene is used as one of the carbon sources, toluene is decomposed 100% in the reactor, and methane and benzene are 1 In consideration of the occurrence of: 1, a shortage of methane may be supplied separately. For example, when the methane / benzene molar ratio is 3, 2 moles of methane may be added to 1 mole of toluene. In addition, as methane added to such toluene, not only a method of preparing fresh methane separately, but also the unreacted methane contained in the exhaust gas discharged from the reactor is circulated and used. It is also possible to use it.

  By setting the composition ratio within such a range, it becomes possible to obtain a carbon fiber structure having a structure in which both the carbon fiber part and the granular part are sufficiently developed.

  Note that an inert gas such as argon, helium, or xenon, or hydrogen can be used as the atmospheric gas.

  As the catalyst, a transition metal such as iron, cobalt or molybdenum, or a mixture of a transition metal compound such as ferrocene or metal acetate and sulfur or a sulfur compound such as thiophene or iron sulfide is used.

  The synthesis of the intermediate is carried out by using a CVD method such as hydrocarbon which is usually performed, evaporating a mixed liquid of hydrocarbon and catalyst as raw materials, introducing hydrogen gas or the like into the reaction furnace as a carrier gas, Pyrolysis at a temperature of 1300 ° C. Thereby, from several centimeters in which a plurality of carbon fiber structures (intermediates) having a sparse three-dimensional structure in which fibers having an outer diameter of 15 to 100 nm are bonded together by granular materials grown using the catalyst particles as nuclei are collected. Synthesize an aggregate of several tens of centimeters.

  The thermal cracking reaction of the hydrocarbon as a raw material mainly occurs on the surface of the granular particles grown using the catalyst particles or the core, and the recrystallization of carbon generated by the decomposition proceeds in a certain direction from the catalytic particles or granular materials. Grows in a fibrous form. However, in obtaining the carbon fiber structure according to the present invention, the balance between the thermal decomposition rate and the growth rate is intentionally changed. For example, as described above, at least two carbon sources having different decomposition temperatures are used. By using the above carbon compound, the carbon material is grown three-dimensionally around the granular material without growing the carbon material only in a one-dimensional direction. Of course, the growth of such three-dimensional carbon fibers does not depend only on the balance between the thermal decomposition rate and the growth rate, but the crystal surface selectivity of the catalyst particles, the residence time in the reactor, and the furnace temperature. The balance between the pyrolysis reaction and the growth rate is influenced not only by the type of carbon source as described above but also by the reaction temperature and gas temperature, etc. When the growth rate is faster than the thermal decomposition rate, the carbon material grows in a fibrous form. On the other hand, when the thermal decomposition rate is faster than the growth rate, the carbon material grows in the circumferential direction of the catalyst particles. To do. Therefore, by intentionally changing the balance between the pyrolysis rate and the growth rate, the carbon material growth direction as described above is made to be a multi-direction under control without changing the growth direction to a constant direction, as in the present invention. A three-dimensional structure can be formed. In order to easily form the three-dimensional structure in which the fibers are bonded to each other by the granular material in the produced intermediate, the composition of the catalyst, the residence time in the reaction furnace, the reaction temperature, and the gas temperature Etc. are desirable.

  In addition, as a method for efficiently producing the carbon fiber structure used in the present invention, in addition to the approach of using two or more carbon compounds having different decomposition temperatures as described above at an optimum mixing ratio, the carbon fiber structure is supplied to the reactor. An approach for generating turbulent flow in the vicinity of the supply port of the raw material gas can be mentioned. The turbulent flow here is a flow that is turbulent and turbulent and flows in a spiral.

  In the reaction furnace, immediately after the raw material gas is introduced into the reaction furnace from the supply port, metal catalyst fine particles are formed by the decomposition of the transition metal compound as the catalyst in the raw material mixed gas. It is brought about through such a stage. That is, first, the transition metal compound is decomposed to become metal atoms, and then cluster generation occurs by collision of a plurality of, for example, about 100 atoms. At the stage of this generated cluster, it does not act as a catalyst for fine carbon fibers, and the generated clusters are further aggregated by collision and grow into crystalline particles of metal of about 3 nm to 10 nm to produce fine carbon fibers. It will be used as metal catalyst fine particles.

  In this catalyst formation process, if there is a vortex due to intense turbulence as described above, more intense collision is possible compared to collisions between metal atoms or clusters with only Brownian motion, and by increasing the number of collisions per unit time Metal catalyst fine particles can be obtained in a high yield in a short time, and metal catalyst fine particles having a uniform particle size can be obtained by equalizing the concentration, temperature, etc. by vortex. Furthermore, in the process of forming the metal catalyst fine particles, an aggregate of metal catalyst fine particles in which a large number of metal crystalline particles are gathered is formed by vigorous collision due to vortex. In this way, the metal catalyst fine particles are rapidly generated, so that the decomposition of the carbon compound is promoted and sufficient carbon material is supplied, and the metal catalyst fine particles of the aggregate are radially formed as nuclei. On the other hand, when the fine carbon fibers grow, and as described above, when the thermal decomposition rate of some of the carbon compounds is faster than the growth rate of the carbon material, the carbon material also grows in the circumferential direction of the catalyst particles, A granular part is formed around the body, and a carbon fiber structure having an intended three-dimensional structure is efficiently formed. The metal catalyst fine particle aggregate may include a part of catalyst fine particles that are less active than other catalyst fine particles or have been deactivated during the reaction. A non-fibrous or very short fibrous carbon material layer that has grown on the surface of such a catalyst fine particle before agglomeration or has grown into an aggregate after such a fine particle has become an aggregate. It seems that the granular part of the carbon fiber structure according to the present invention is formed by being present at the peripheral position of the body.

  The specific means for generating a turbulent flow in the raw material gas flow in the vicinity of the raw material gas supply port of the reaction furnace is not particularly limited. For example, the raw material gas introduced into the reaction furnace from the raw material gas supply port It is possible to adopt means such as providing some type of collision part at a position where it can interfere with the current flow. The shape of the collision part is not limited in any way, as long as a sufficient turbulent flow is formed in the reactor by the vortex generated from the collision part. It is possible to adopt a form in which one or a plurality of plates, paddles, taper tubes, umbrellas, etc. are arranged alone or in combination.

  Thus, the intermediate obtained by heating and producing the mixed gas of catalyst and hydrocarbon at a constant temperature in the range of 800 to 1300 ° C. is like a patch-like sheet piece made of carbon atoms ( It has an incomplete (burnt) structure and its Raman spectroscopic analysis reveals that the D band is very large and has many defects. Moreover, since the produced | generated intermediate body contains an unreacted raw material, a non-fibrous carbide, a tar content, and a catalyst metal, after removing volatile content, such as an unreacted raw material and a tar content, by heating at 800-1200 degreeC. It may be used for a skeletal structure. Further, after the high-temperature heat treatment (1800 ° C. or higher) is applied to the intermediate body, it may be used for the skeletal structure, but it is not preferable in terms of energy for doping boron as described above.

  In addition, before or after such high-temperature heat treatment, a carbon fiber structure having a desired circle-equivalent average diameter is obtained by performing a process of crushing and pulverizing the circle-equivalent average diameter of the carbon fiber structure to 50 to 500 μm. Get the body.

  The method for producing the skeleton structure having such characteristics is not particularly limited, but specific examples are as follows.

  First, the carbon fiber structure described above and an organic binder are mixed and kneaded using a double-arm kneader or a mixer-type kneader. Examples of the binder include a thermosetting resin or pitch. Thermosetting resins are in a liquid state at room temperature or in a solid form but become liquid at a heating temperature of about 50 to 90 ° C., but are crosslinked and polymerized by a curing process by heating at about 100 to 200 ° C. In addition, it has the property of becoming a polymer and solidifying, and in addition, any material that has the property of decomposing and carbonizing without being in a fluid state even when heated to a high temperature may be used. Good. There are various types of pitch, but any pitch such as isotropic pitch and mesophase pitch may be used.

  In addition, in the thermosetting resin using a solvent at the time of kneading, the solvent is dried at a temperature that does not cure the thermosetting resin after kneading.

  Subsequently, when the carbon fiber structure is mixed and kneaded with the thermosetting resin to form a lump, the carbon fiber structure is crushed and used for the next forming step.

  In the molding step, a method of pressing from above and below using a mold, a method of isotropic pressing using isostatic pressure using a rubber die, and the like are suitable.

The molding pressure during pressing is preferably about 1 to 2000 kg / cm ³ . The carbon fiber structures are bonded with thermosetting resin at the time of molding, but if the thermosetting resin is not cured, the bonding force is weak, and if the pressure is released, the carbon fiber structure has a restorability. Since the bonded ones come off, it is preferable that the thermosetting resin is cured by heating to a temperature of about 100 to 200 ° C. during pressing to increase the bonding force.

  Next, the thermosetting resin is carbonized by heating the molded body obtained by curing the thermosetting resin in a deoxygenated atmosphere or an inert gas atmosphere. The thermosetting resin is decomposed and carbonized in the range of 300 to 900 ° C., and further subjected to an annealing treatment at a high temperature, whereby the patch-like sheet pieces constituting the carbon fiber structure are bonded to each other to form a plurality of pieces. A graphene sheet-like layer is formed. In the annealing process, the carbonized portion of the thermosetting resin is also modified in the same manner as the carbon fiber structure and graphitized.

  When using a pitch for a binder, it infusibilizes in an oxidizing atmosphere at 150-400 degreeC after press molding, and carbonizes at 800-1500 degreeC after that.

  In the stage of performing the high-temperature heat treatment, boron can be included (doped) in the crystal of the carbon fiber by mixing the compact and boron. Here, in order to efficiently contain boron in the crystal of the carbon fiber structure, it is necessary to mix the carbon fiber structure and boron well so that they are in uniform contact. For this purpose, it is preferable to use boron (or boron compound) particles having a particle size as small as possible. If the particles are large, a high concentration region is partially generated, which may cause solidification. Specifically, the average particle size of boron is 100 μm or less, preferably 50 μm or less, and more preferably 20 μm or less. When boric acid or the like is used as the boron source, a method of adding water as an aqueous solution and evaporating water in advance or a method of evaporating water during the heating process can be used. If the aqueous solution is uniformly mixed, the boron compound can be uniformly attached to the fiber surface after moisture evaporation.

  It is preferable to apply pressure to the formed body until the binder is hardened or infusible by using either thermosetting resin or pitch to prevent contact and separation of the joint portion due to restoration of the carbon fiber structure. More preferably, pressure is also applied when the binder in the carbonization and graphitization steps is carbonized and the carbon fiber structure and the carbon derived from the binder are graphitized. When heat treatment is performed at a high temperature of 1800 ° C. or higher, the carbon fiber structure is heat-treated while being constrained, and the shape of the carbon fiber structure in the molded body can be fixed by annealing.

  Next, a resin, rubber, metal, or carbon-based material is impregnated into the void formed inside the skeleton structure in which the carbon fiber structure is bonded with carbon after the above carbonization and graphitization steps are completed. An impregnation step is performed.

  Examples of the resin to be impregnated in the impregnation step include polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyacetal, polyethylene terephthalate, polycarbonate, polyvinyl acetate, polyamide, polyamideimide, polyetherimide, polyether ether ketone, polyvinyl alcohol, polyphenylene ether, Various thermoplastic resins such as poly (meth) acrylate and liquid crystal polymer, epoxy resins, vinyl ester resins, phenol resins, unsaturated polyester resins, furan resins, imide resins, urethane resins, melamine resins, silicone resins and urea resins A thermosetting resin etc. can be mentioned. The rubber to be impregnated includes natural rubber, styrene / butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene / propylene rubber (EPDM), nitrile rubber (NBR), and chloroprene rubber (CR). Butyl rubber (IIR), urethane rubber, silicone rubber, fluorine rubber, acrylic rubber (ACM), epichlorohydrin rubber, ethylene acrylic rubber, norbornene rubber and the like. Examples of the metal to be impregnated include aluminum, magnesium, lead, copper, tungsten, titanium, niobium, hafnium, vanadium, and alloys and mixtures thereof. Further, examples of the carbon-based material to be impregnated include glassy carbon.

  As the impregnation method, either a pressure method or a suction method can be applied. When a pressure type impregnation apparatus is used, the aforementioned skeleton structure and impregnation material are inserted into a compression mold composed of a female mold and a male mold, and the impregnation material is placed inside the skeleton structure by pressure. The formed void is impregnated. The compression mold can be heated by a heater. When the impregnating material is a resin monomer that is cured by a curing agent, heating by the heater is not necessary. This pressure system is applicable to all of the above impregnated materials.

  On the other hand, when a suction type impregnation apparatus is used, it is not applicable when the impregnation material is a metal or a carbon-based material, but it is an effective method for a resin monomer to be cured by a curing agent.

  The volume% of the skeletal structure with respect to the entire composite material of the present invention depends on the porosity of the skeleton structure and the type of impregnating material, and cannot be generally specified, but is 10 to 99.9%. Is preferable, and 30 to 90% is particularly preferable. When the volume% of the skeleton structure is 10% or less, the strength of the skeleton structure is not sufficient. On the other hand, when the volume% of the skeletal structure is 99.9% or more, it is difficult to impregnate the voids with the material.

  Further, regarding the composite material according to the present invention, when specific examples are shown according to the function of the carbon fiber structure to be blended, the following are exemplified, but of course, it is not limited to these at all. .

1) What uses conductivity As a conductive resin and a conductive resin molding by impregnating a resin, for example, it is suitably used for packaging materials, gaskets, containers, resistors, electric wires, and the like. In addition to the composite material with the resin, the same effect can be expected for a composite material impregnated with an inorganic material, particularly a material such as ceramics or metal.

2) Using thermal conductivity The same usage as in the case of using the above-mentioned conductivity can be performed.

3) Utilizing electromagnetic wave shielding properties Impregnation with resin is suitable as an electromagnetic wave shielding material.

4) Utilizing physical properties Impregnating with resin or metal to improve slidability can be used for rolls, brake parts, tires, bearings, lubricants, gears, pantographs, etc.

  In addition, it will be possible to use it for electric wires, bodies of home appliances / vehicles / airplanes, and housings of machines by utilizing its light weight and tough characteristics. In addition, it can be used as an alternative to conventional carbon fibers and beads, and can be applied to, for example, battery pole materials, switches, and vibration-proof materials.

5) Utilization of filler characteristics The fine fibers of the carbon fiber structure have excellent strength, flexibility, and excellent filler characteristics that constitute a network structure. By utilizing this characteristic, it can contribute to the enhancement of the electrodes of energy devices such as lithium ion secondary batteries, lead storage batteries, capacitors, fuel cells, and improvement of cycle characteristics.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to the following Example at all.

  In addition, below, each physical-property value of the carbon fiber structure used for this invention was measured as follows.

<Area-based circle equivalent average diameter>
First, a photograph of the pulverized product is taken with an SEM. In the obtained SEM photograph, only the carbon fiber structure with a clear outline was targeted, and the carbon fiber structure with a broken outline was not targeted because the outline was unclear. All carbon fiber structures (about 60 to 80) that can be targeted in one field of view were used, and about 200 carbon fiber structures were targeted in three fields of view. Trace the contour of each carbon fiber structure targeted using image analysis software WinRoof (trade name, manufactured by Mitani Corp.), obtain the area within the contour, and calculate the equivalent circle diameter of each fiber structure This was averaged.

<Measurement of bulk density>
A transparent cylinder with an inner diameter of 70 mm is filled with 1 g of powder, and air with a pressure of 0.1 Mpa and a capacity of 1.3 liters is sent from the lower part of the dispersion plate to blow out the powder and let it settle naturally. At the time of blowing out 5 times, the height of the powder layer after settling is measured. At this time, the number of measurement points was six, and after calculating the average of the six points, the bulk density was calculated.

<Raman spectroscopy>
Using a LabRam800 manufactured by Horiba Jobin Yvon, measurement was performed using a wavelength of 514 nm of an argon laser.

<Conductivity>
The conductivity of the obtained plate specimen was measured using a four-point probe low resistivity meter (Made by Mitsubishi Chemical Co., Ltd., Loresta GP) and converted to volume resistance (Ω · cm) using the same resistance meter. The average value was calculated.

<TG combustion temperature>
Using TG-DTA manufactured by Mac Science, the temperature was increased at a rate of 10 ° C./min while circulating air at a flow rate of 0.1 liter / min, and the combustion behavior was measured. During combustion, TG indicates a decrease in weight and DTA indicates an exothermic peak. Therefore, the top position of the exothermic peak was defined as the combustion start temperature.

<Restorability>
1 g of CNT powder is weighed, filled and compressed in a resin die (inner dimensions 40 L, 10 W, 80 Hmm), and the displacement and load are read. When the density was measured to 0.9 g / cm ³ , the pressure was released and the density after restoration was measured.

<Average particle size of granular part, circularity, ratio with fine carbon fiber>
Similar to the measurement of the area-based circle-equivalent mean diameter, first, a photograph of the carbon fiber structure is taken with an SEM. In the obtained SEM photograph, only the carbon fiber structure with a clear outline was targeted, and the carbon fiber structure with a broken outline was not targeted because the outline was unclear. All carbon fiber structures (about 60 to 80) that can be targeted in one field of view were used, and about 200 carbon fiber structures were targeted in three fields of view.

  In each of the targeted carbon fiber structures, a granular portion that is a bonding point between carbon fibers is regarded as one particle, and its outline is defined by using image analysis software WinRoof (trade name, manufactured by Mitani Corporation). By tracing, the area in the contour was obtained, the equivalent circle diameter of each granular part was calculated, and this was averaged to obtain the average particle diameter of the granular part. Further, the circularity (R) is calculated based on the following equation from the area (A) in the contour measured using the image analysis software and the measured contour length (L) of each granular portion. Was averaged.

R = A * 4π / L ²
Furthermore, the outer diameter of fine carbon fibers in each targeted carbon fiber structure is obtained, and the size of the granular portion in each carbon fiber structure is determined from this and the equivalent circle diameter of the granular portion in each carbon fiber structure. It calculated | required as a ratio with a fine carbon fiber, and averaged this.

<Average distance between granular parts>
Similar to the measurement of the area-based circle-equivalent mean diameter, first, a photograph of the carbon fiber structure is taken with an SEM. In the obtained SEM photograph, only the carbon fiber structure with a clear outline was targeted, and the carbon fiber structure with a broken outline was not targeted because the outline was unclear. All carbon fiber structures (about 60 to 80) that can be targeted in one field of view were used, and about 200 carbon fiber structures were targeted in three fields of view.

  In each target carbon fiber structure, find all the places where the granular parts are connected by the fine carbon fibers, and the distance between adjacent granular parts connected by the fine carbon fibers in this way (the center of the granular material at one end) The length of the fine carbon fiber including the part to the central part of the granular material at the other end) was measured and averaged.

<Destructive test of carbon fiber structure>
A carbon fiber structure was added to 100 ml of toluene in a vial with a lid at a rate of 30 μg / ml to prepare a dispersion sample of the carbon fiber structure.

  The dispersion sample of the carbon fiber structure thus obtained was subjected to ultrasonic waves using an ultrasonic cleaner having a transmission frequency of 38 kHz and an output of 150 w (trade name: USK-3, manufactured by SND Co., Ltd.). Irradiation was performed, and changes in the carbon fiber structure in the dispersion liquid sample were observed over time.

First, ultrasonic waves are irradiated, and after 30 minutes, a predetermined amount of 2 ml of the dispersion liquid sample is extracted from the bottle, and a photograph of the carbon fiber structure in the dispersion liquid is taken with an SEM. 200 fine carbon fibers (fine carbon fibers having at least one end bonded to the granular part) in the carbon fiber structure of the obtained SEM photograph were randomly selected, and the length of each selected fine carbon fiber It was measured to obtain the D ₅₀ average, which was used as the initial average fiber length.

On the other hand, 200 granular parts which are the bonding points between carbon fibers in the carbon fiber structure of the obtained SEM photograph are selected at random, and each selected granular part is regarded as one particle, and its outline is defined. Then, the image analysis software WinRoof (trade name, manufactured by Mitani Corporation) was traced to determine the area within the contour, calculate the equivalent circle diameter of each granular portion, and determine the D ₅₀ average value. And the resulting D ₅₀ average value as the initial average diameter of the granular part.

Thereafter, a fixed amount of 2 ml of the dispersion liquid sample was taken out from the bottle at regular intervals in the same manner as described above, a photograph of the carbon fiber structure in the dispersion liquid was taken with an SEM, and the carbon fiber of the obtained SEM photograph the D ₅₀ average diameter of D ₅₀ average length and granular part of the carbon fibers in the structure in was determined in the same manner as above.

And the D ₅₀ average length of the calculated fine carbon fiber is about half of the initial average fiber length (in this example, after irradiating ultrasonic waves and 500 minutes have elapsed), the D of the granular portion _{The 50} average diameter was compared with the initial average diameter, and the variation ratio (%) was examined.

Example 1
i) Synthesis of carbon fiber structure A carbon fiber structure was synthesized by a CVD method using toluene as a raw material.

  A mixture of ferrocene and thiophene was used as a catalyst, and the reaction was performed in a hydrogen gas reducing atmosphere. Toluene and the catalyst were heated to 380 ° C. together with hydrogen gas, supplied to the production furnace, and pyrolyzed at 1250 ° C. to obtain a carbon fiber structure (first intermediate).

  1 and 2 show SEM and TEM photographs observed after the first intermediate is dispersed in toluene and a sample for an electron microscope is prepared.

  In addition, the schematic structure of the production | generation furnace used when manufacturing this carbon fiber structure (1st intermediate body) is shown in FIG. As shown in FIG. 4, the production furnace 1 has an introduction nozzle 2 for introducing a raw material mixed gas composed of toluene, a catalyst and hydrogen gas as described above into the production furnace 1 at the upper end portion thereof. Further, a cylindrical collision portion 3 is provided outside the introduction nozzle 2. The collision unit 3 is capable of interfering with the flow of the raw material gas introduced into the reaction furnace from the raw material gas supply port 4 located at the lower end of the introduction nozzle 2. In the production furnace 1 used in this embodiment, the inner diameter a of the introduction nozzle 2, the inner diameter b of the production furnace 1, the inner diameter c of the cylindrical collision portion 3, and the raw material mixed gas inlet 4 from the upper end of the production furnace 1 are used. Distance d, the distance e from the raw material mixed gas inlet 4 to the lower end of the collision part 3, and the distance from the raw material mixed gas inlet 4 to the lower end of the production furnace 1 are f, : B: c: d: e: f = 1.0: 3.6: 1.8: 3.2: 2.0: 21.0. The raw material gas introduction rate into the reactor was 1850 NL / min, and the pressure was 1.03 atm.

  The intermediate synthesized as described above was calcined at 900 ° C. in nitrogen to separate hydrocarbons such as tar to obtain a second intermediate. The R value of this second intermediate measured by Raman spectroscopy was 0.82.

  Further, an SEM photograph of the obtained carbon fiber structure as it is placed on an electron microscope sample holder and observed is shown in FIG. 3, and the particle size distribution is shown in Table 1.

Furthermore, the circle-equivalent mean diameter of the obtained carbon fibrous structures, 155 .mu.m, a bulk density of 0.0029 g / cm ^3, Raman _I D / _{I G} ratio, the density after decompression at 0.25 g / cm ³ there were.

  Further, the average particle size of the granular portion in the carbon fiber structure was 443 nm (SD 207 nm), which was 7.38 times the outer diameter of the fine carbon fiber in the carbon fiber structure. The circularity of the granular part was 0.67 (SD 0.14) on average.

Further, when the carbon fiber structure was subjected to the destructive test according to the procedure described above, the initial average fiber length (D ₅₀ ) after 30 minutes of application of the ultrasonic wave was 12.8 μm. The average fiber length (D ₅₀ ) was almost half of 6.7 μm, indicating that many cuts were generated in the fine carbon fibers in the carbon fiber structure. However, when the average diameter (D ₅₀ ) of the granular part 500 minutes after application of ultrasonic waves is compared with the initial average diameter (D ₅₀ ) 30 minutes after application of ultrasonic waves, the rate of change (decrease) is only 4. 8%, and taking into account measurement errors, etc., the cut granular part itself is functioning as a bonding point between the fibers without being destroyed even under a load condition in which many cuts are generated in the fine carbon fiber. Became clear.

  The various physical property values of the carbon fiber structure synthesized in Example 1 are summarized in Table 2.

ii) Formation of skeletal structure A skeletal structure was formed using the carbon fiber structure synthesized in i) above.

  Specifically, the carbon fiber structure synthesized in i) was added and mixed with a phenol resin (Gunei Chemical Industry Co., Ltd., Resitop) using methanol as a solvent. The binder was added in an amount of 25% by mass based on the carbon fiber structure, and kneading was performed using a mixer-type kneading machine (Shinky Awatori Rentaro Co., Ltd.). Next, the obtained kneaded material was dried on a hot plate at 70 ° C., and after drying, was molded by heating at 150 ° C. to cure the phenol resin. Next, the obtained molded body was heated to 2500 ° C. in an argon gas atmosphere to obtain a skeleton structure in which the binder component was carbonized and graphitized.

  Table 3 shows the physical property values of the skeletal structure in Example 1.

(Example 2)
In the same manner as in Example 1, the molded body obtained by curing the resin was impregnated with a solution obtained by dissolving B ₂ O ₃ in methanol and then dried, and the boron addition amount was 3.5% by mass with respect to the molded body. Repeated. In the same manner as in Example 1, the formed body supporting boron was heated to 2500 ° C. in an argon gas atmosphere to obtain a skeleton structure in which the binder component was carbonized and graphitized.

  Table 3 shows the physical property values of the skeleton structure in Example 2.

It is a SEM photograph of the intermediate body of the carbon fiber structure used for the frame structure of the present invention. It is a TEM photograph of the intermediate body of the carbon fiber structure used for the frame structure of the present invention. It is a SEM photograph of the carbon fiber structure used for the frame structure of the present invention. It is drawing which shows schematic structure of the production | generation furnace used for manufacture of the carbon fiber structure in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Generation furnace 2 Introduction nozzle 3 Collision part 4 Raw material gas supply port a Inner diameter of introduction nozzle b Inner diameter of production furnace c Inner diameter of collision part d Distance from upper end of production furnace to raw material mixed gas introduction port e From raw material mixed gas introduction port Distance to the lower end of the collision part f Distance from the raw material mixed gas inlet to the lower end of the generating furnace

Claims (18)

  It has a three-dimensional network configuration composed of carbon fibers having an outer diameter of 15 to 100 nm, has a granular portion that binds the carbon fibers to each other in a form in which a plurality of the carbon fibers extend, and the The granular part is formed by joining a carbon fiber structure formed in the carbon fiber growth process in three dimensions with carbon.   The skeletal structure according to claim 1, wherein boron is contained.   The skeleton structure according to claim 2, wherein the boron content is 0.001 to 10 mass% with respect to the skeleton structure.   The skeleton structure according to any one of claims 1 to 3, wherein the carbon fiber structure has an area-based circle-equivalent mean diameter of 50 to 500 µm. 2. The skeleton structure has an I _D / I _G measured by Raman spectroscopy of 1.4 or less and an I _{G ′} / I _G of 1.5 or less. The skeleton structure according to any one of -4. The skeleton structure according to any one of claims 1 to 5, wherein the skeleton structure has a bulk density of 0.2 to 2.3 g / cm ³ .   The skeleton structure according to any one of claims 1 to 6, wherein the skeleton structure has a combustion start temperature in air of 700 ° C or higher.   The skeletal structure according to any one of claims 1 to 7, wherein a particle size of the granular portion is larger than an outer diameter of the carbon fiber at a bonding portion of the carbon fibers.   The skeleton structure according to any one of claims 1 to 8, wherein the carbon fiber structure is formed using at least two or more carbon compounds having different decomposition temperatures as a carbon source. It has a three-dimensional network configuration composed of carbon fibers having an outer diameter of 15 to 100 nm, has a granular portion that binds the carbon fibers to each other in a form in which a plurality of the carbon fibers extend, and the The granular part has a skeletal structure formed by joining a carbon fiber structure formed in the carbon fiber growth process in three dimensions with carbon,
A composite material, wherein a void formed inside the skeleton structure is impregnated with resin, rubber, metal, or a carbon-based material.   The composite material according to claim 10, wherein the skeleton structure contains boron.   The composite material according to claim 11, wherein a content of the boron is 0.001 to 10 mass% with respect to the skeleton structure.   The composite material according to claim 10, wherein the carbon fiber structure has an area-based circle-equivalent mean diameter of 50 to 500 μm. 11. The skeleton structure has an I _D / I _G measured by Raman spectroscopy of 1.4 or less and an I _{G ′} / I _G of 1.5 or less. The composite material as described in any one of ˜13. The composite material according to claim 10, wherein the skeletal structure has a bulk density of 0.2 to 2.3 g / cm ³ .   The composite material according to any one of claims 10 to 15, wherein the skeletal structure has a combustion start temperature in air of 700 ° C or higher.   The composite material according to any one of claims 10 to 16, wherein a particle diameter of the granular portion is larger than an outer diameter of the carbon fiber at a bonding portion of the carbon fibers.   The composite material according to any one of claims 10 to 17, wherein the carbon fiber structure is formed using at least two or more carbon compounds having different decomposition temperatures as a carbon source.