JP5288441B2 - High thermal conductive composite material and its manufacturing method - Google Patents

Abstract

This invention provides a composite material that can effectively utilize the properties of a metal powder base material per se or further added ceramic, and ceramic base material per se, and excellent electric conductivity and thermal conductivity and strength properties possessed by a fibrous carbon material formed of graphene. To this end, a fibrous carbon material formed of graphene such as carbon nanotubes or vapor phase grown carbon fibers is incorporated, followed by discharge plasma sintering for integration to produce a metal sinter or a mixed sinter composed of a metal and ceramic or a ceramic sinter. The incorporation of the fibrous carbon material formed of graphene can improve various properties such as thermal conductivity and electric conductivity possessed by the metal material. Although the rollability of the sinter is lower than a fibrous carbon material-free material, the sinter can be rolled. When the selection of various conditions, for example, rolling conditions such as rolling direction and rolling reduction and number of times of rolling, and annealing after rolling is taken into consideration, Young's modulus and elongation, residual stress or other ductile properties and various other properties can be regulated without causing a change in tensile strength after rolling.

Description

  In addition to the characteristics inherent to metal materials and ceramic materials, the present invention provides a fibrous carbon material such as carbon nanotube (CNT) or vapor grown carbon fiber (VGCF) contained in the sintered body made of the powder. The present invention relates to a high thermal conductive composite material imparted with excellent electrical conductivity, thermal conductivity and strength characteristics, and a method for producing the same.

  Today, composite materials having various functions using carbon nanotubes have been proposed. For example, for the purpose of improving the thermal conductivity and tensile strength of an aluminum alloy material, at least one of Si, Mg, and Mn, which are components contained in the aluminum alloy material, is combined with carbon nanofibers, and the carbon nanofibers are combined with an aluminum matrix. An aluminum alloy material included in the material has been proposed. This is obtained by mixing carbon nanofibers in 0.1-5 vol% molten aluminum alloy material, kneading and forming a billet, and providing it as an extrusion mold material of an aluminum alloy material obtained by extruding the billet (Patent Document 1). )

Furthermore, for the purpose of a highly conductive material excellent in moldability that can be applied to a separator of a fuel cell and the like, a metal compound (boride: TiB ₂ , WB, MoB, (Patent Document 2) has been proposed (Patent Document 2) in which moldability and conductivity are compatible by blending appropriate amounts of CrB, AlB2, MgB, carbide: WC, nitride: TiN, and the like.

  As a field emitter containing carbon nanotubes, conductive material powders such as metal alloys of nanotube wettable elements such as indium, bismuth or lead, and relatively soft and ductile metal powders as in the case of Ag, Au or Sn After the body and carbon nanotubes are press-molded, cut and polished, the protruding nanotubes are formed on the surface, the surface is etched to form the nanotube tips, and then the metal surface is re-dissolved and aligned to align the protruding nanotubes. A method has been proposed (Patent Document 3).

JP 2002-363716 A JP 2003-34751 A JP 2000-223044 A

  The carbon nanotubes to be dispersed in the above-described resin or aluminum alloy are dispersed with the shortest possible length in consideration of obtaining manufacturability of the resulting composite material and obtaining the required moldability. It is not intended to effectively utilize the excellent electrical and thermal conductivity characteristics of the carbon nanotube itself.

  Further, in the invention that attempts to utilize the above-mentioned carbon nanotube itself, it can be specialized for a specific and specific use, for example, a field emitter, but cannot be easily applied to other uses. In the method of manufacturing ceramic composite nanostructures consisting of specific columnar bodies by selecting oxides of polyvalent metal elements for the purpose of function, it takes a lot of steps and trials to set the purpose and the probability of the element selection and manufacturing method It is unavoidable to make mistakes.

  Vapor-grown carbon fiber has been known as a fibrous carbon material other than carbon nanotubes, and this vapor-grown carbon fiber, which is thicker than carbon nanotubes, is combined with various base materials to make a composite material. There is a problem.

  The present invention provides a composite material that has corrosion resistance, heat resistance, purely uses the characteristics of a metal material having versatility, ductility, etc., and imparts or improves electrical conductivity and thermal conductivity. In addition to the characteristics of the metal powder base material itself or further added ceramics, and the ceramic powder base material itself, the fibrous carbon material itself has excellent electrical and thermal conductivity and strength characteristics. The purpose is to provide a highly heat-conductive composite material that effectively utilizes the material and its manufacturing method.

  The present inventors, based on a contract commissioned by the Japan Science and Technology Agency, incorporated into a composite material in which a fibrous carbon material such as a carbon nanotube is blended in a base material, the electrical conduction characteristics and thermal conduction characteristics of the fibrous carbon material. In addition, as a result of various studies on configurations that can effectively use strength characteristics, the following facts have been found.

1) Long-chain carbon nanotubes (including those in which only carbon nanotubes are previously subjected to discharge plasma treatment) are kneaded and dispersed in a fireable ceramic powder or metal powder such as aluminum powder with a ball mill or the like, and this is used for discharge plasma sintering. By integrating them, the carbon nanotubes can be made to circulate in the sintered body.

2) In an aluminum-based carbon fiber composite material, aluminum carbide is generated at the interface, the carbon fiber is damaged by this reaction, and the carbide is brittle and it cannot be said that excellent properties as a composite material can be obtained. However, by using spark plasma sintering, an aluminum-based carbon fiber composite material having excellent characteristics can be obtained without producing carbides.

3) Specifically, excellent thermal conductivity and plastic deformation without problems are obtained. Especially, plastic deformation is not so difficult as to be rolled or press-molded, and it is processed into various shapes by the plastic deformation. Further, for example, by selecting and considering various rolling conditions such as rolling direction, compression ratio, number of rolling, and annealing after rolling, the tensile strength after rolling does not change. It is possible to control ductility and various properties such as rate, elongation, and residual stress, and to impart new or improved properties such as thermal conductivity and electrical conductivity to metal materials, resulting in various uses. Application to is possible.

4) When a vapor-grown carbon fiber is used as the fibrous carbon material instead of the carbon nanotube, the composite material similarly has high thermal conductivity, and can be plastically deformed such as rolling. By the way, in the case of composite materials using carbon fibers that are thicker than carbon nanotubes and vapor-grown carbon fibers and have no regular crystal structure, they have low thermal conductivity and peel at the interface due to plastic deformation such as rolling. And the function as a composite material is lost.

The high thermal conductive composite material of the present invention has been completed on the basis of these findings, and is based on a metal powder, or a mixed powder of metal and ceramics, or a discharge plasma sintered body made of ceramic powder. A fibrous carbon material composed of an ultra-thin tubular structure composed of single-layer or multilayer graphene, particularly a sheet composed of vapor-grown carbon fiber, more specifically, a vapor-grown carbon fiber dispersion. It is a laminate in which a vapor-grown carbon fiber oriented sheet produced by solidification and oriented in the direction parallel to the sheet surface is formed in a plurality of layers in the substrate.

Graphene is a honeycomb-structured net consisting of six carbon atoms arranged two-dimensionally regularly, and is also called a carbon hexagonal mesh surface. Called. The single-layer or multi-layered and ultrafine tube-like structure made of this graphene is the fibrous carbon material referred to in the present invention , and includes both carbon nanotubes and vapor-grown carbon fibers.

  That is, the carbon nanotube is a seamless tube in which graphene is rounded into a cylindrical shape, and there are a single-walled tube and a multi-walled tube that is concentrically stacked. Single-walled ones are called single-walled nanotubes, and multiple-walled ones are called multi-walled nanotubes. In addition, the vapor grown carbon fiber has a single-layer or multiple-layer graphene tube in which graphene is rounded into a cylindrical shape, that is, a carbon nanotube in the core, and surrounds the core in multiple and polygonal shapes. Graphite is laminated in the radial direction of the graphene tube, and it is also called ultra-multi-walled carbon nanotube due to its structure. In other words, the single-layer or multi-layer carbon tube present at the center of the vapor-grown carbon fiber is a carbon nanotube.

  The manufacturing method in particular of a fibrous carbon material is not ask | required. Although any of an arc discharge method, a laser evaporation method, a thermal decomposition method, a chemical vapor deposition method, and the like may be used, the vapor grown carbon fiber is manufactured by a chemical vapor deposition method. VGCF, which stands for vapor growth carbon fiber, is an abbreviation for Vapor Growth Carbon Fiber.

The fibrous carbon material is formed into a sheet shape and alternately stacked with the powder layer to constitute a laminate.

The fibrous carbon material is also oriented in a direction parallel to the sheet surface . There are two types of orientation, one is a three-dimensional orientation in which the fibrous carbon material is oriented in a specific position direction, and the other is oriented in a direction parallel to a specific plane, and 2 random in that plane. Dimensional orientation. Non-orientation is a three-dimensional random form in which the fibrous carbon material is oriented in a three-dimensional and random direction. A sheet made of a fibrous carbon material can be easily oriented in a direction parallel to the surface, and can be easily oriented in the same direction. Due to the orientation of the fibrous carbon material, the thermal conductivity in the orientation direction can be improved in the carbon material-containing metal material.

  The spark plasma sintered body can be subjected to plastic working. Carbon nanotubes at the powder boundaries and grain boundaries are oriented by repetitive stress due to plastic working, for example, rolling, and self-organization also proceeds by dislocation accumulation. However, thermal conductivity may decrease due to plastic working.

Further, the method for producing a high thermal conductive composite material of the present invention includes a metal powder layer, or a mixed powder layer of metal powder and ceramic powder, or a ceramic powder layer, and a sheet composed of a fibrous carbon material , In particular, the method includes a step of alternately laminating vapor-grown carbon fiber oriented sheets and a step of spark plasma sintering of the obtained laminate.

In the method for producing a high thermal conductive composite material of the present invention, oriented sheets of vapor-grown carbon fibers are arranged at predetermined intervals in a discharge plasma sintered body of metal powder, mixed powder of metal and ceramics, or ceramic powder. A highly heat-conductive composite material having a laminated structure is produced.

In the production method of the high heat conduction composite material of the present invention, it causes orientation of the fibrous carbon material constituting the sheet in a direction parallel to the sheet surface. In this case, the fibrous carbon material may be oriented in the same direction as that in the case where the fibrous carbon material is random. As described above, the orientation of the fibrous carbon material improves the thermal conductivity in the orientation direction of the carbon material-containing metal material.

This orientation operation can be performed at the stage of producing a sheet of fibrous carbon material. As a method for orienting the fibrous carbon material in a predetermined direction, a method of preparing a dispersion of the fibrous carbon material and solidifying the dispersion in a magnetic field or an electric field is preferable because it is simple and has good orientation. In a planar fiber assembly in which extremely short fibrous carbon materials are gathered two-dimensionally in the radial direction, an oriented sheet can be produced by pushing down the fibrous carbon material in one direction.

  The metal powder used in the present invention is preferably one or more of aluminum, aluminum alloy, titanium, titanium alloy, copper, copper alloy, and stainless steel, and has excellent versatility and versatility. This makes it possible to produce industrial products with special characteristics.

  The average particle diameter of the metal powder is preferably 200 μm or less, and the average particle diameter of the ceramic powder is preferably 10 μm or less, respectively, and it is possible to easily obtain the desired characteristics with excellent sinterability and ductility.

  Ceramic powders include oxides such as alumina and zirconia, nitrides such as aluminum nitride, titanium nitride, and silicon nitride, carbides such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide, titanium boride, and boride. One or more borides such as zirconia and chromium boride are preferred. This ceramic powder can constitute a base material alone. In addition, mixing with metal powder improves grain boundary sliding during rolling, which makes it possible to produce industrial products having various characteristics with excellent versatility and versatility.

  The content of the fibrous carbon material is preferably 20 wt% or less by weight, and this makes it possible to easily obtain the desired characteristics with excellent sinterability and ductility. However, in the case where the carbon material-mixed metal material has a laminated structure of a powder layer and a sheet-like carbon material, a content of 50 wt% or less is allowed unless plastic processing is required.

  The ceramic content in the mixed powder of metal and ceramic is preferably 20 wt% or less in terms of weight ratio, so that the desired characteristics can be easily obtained with excellent sinterability and ductility.

  Examples of plastic working include rolling and press forming, and the rolling may be any of cold rolling, warm rolling, and hot rolling. Annealing can be performed after plastic working. Select the optimum rolling method according to the type of metal, ceramics to be mixed, type and amount of fibrous carbon material, etc., and further reduce the residual stress of the resulting metal material by annealing to further improve the rolling effect The desired characteristics can be easily obtained.

  The fibrous carbon material before blending into the substrate can be preliminarily subjected to a discharge plasma treatment, whereby the uniform dispersibility of the fibrous carbon material in the metal substrate can be remarkably improved.

  The fibrous carbon material is short. At present, the length of the carbon nanotube is several hundred μm, and even the vapor grown carbon fiber is at most 2 to 3 cm. These fibrous carbon materials usually have long chains formed by continuous fibers, and those in which they are entangled or further forming a lump-like lump, or only the fibrous carbon material is subjected to a discharge plasma treatment. These carbon nanotubes and vapor-grown carbon fibers have been developed to be relatively long and straight, and the shape is not particularly limited.

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  In the discharge plasma sintering process, a two-stage process in which low temperature plasma discharge is performed under low pressure and then low temperature discharge plasma sintering is performed under high pressure while ensuring the dispersibility of the long-chain fibrous carbon material. It is effective to obtain a good sintered body.

The high thermal conductive composite material of the present invention uses a sintered body of a metal powder or a ceramic powder of pure aluminum, aluminum alloy, titanium or the like excellent in corrosion resistance and heat dissipation as a base, so that the material itself is Taking advantage of the inherent corrosiveness and excellent durability under high temperature environment, the vapor-grown carbon fiber itself is formed by making the oriented sheet of vapor-grown carbon fiber form a plurality of layers in this substrate. In combination with the excellent electric conduction, heat conduction characteristics and strength of the material, the required characteristics can be enhanced, synergistic effects, or new functions can be exhibited.

  The highly heat-conductive composite material of the present invention can be processed into a required shape by press molding after obtaining a required shape material such as a plate material, a bar material or a block material of a metal powder sintered body containing a fibrous carbon material. . Moreover, the form according to the objective uses, such as a thin plate and a wire, can be obtained by rolling.

  The high thermal conductive composite material of the present invention can disperse, for example, ceramic powders such as alumina and zirconia which are excellent in corrosion resistance and heat resistance when obtaining the above-mentioned sintered body. For example, corrosion, electrodes and heating elements in high temperature environments, wiring materials, heat exchangers and heat sink materials with improved thermal conductivity, brake components, or fuel cell electrodes Or as a separator. Further, by dispersing fine particles such as silicon carbide and silicon nitride when obtaining the above-mentioned sintered body, grain boundary sliding during plastic deformation is improved and superplasticity can be expressed.

  In the present invention, pure aluminum, a known aluminum alloy, titanium, a titanium alloy, copper, a copper alloy, stainless steel, or the like can be used as the metal powder to be used. For example, a known functional metal that can perform sintering and plastic deformation and exhibits necessary functions such as corrosion resistance, thermal conductivity, and heat resistance may be employed.

  As the particle size of the metal powder, those having a particle size of about 100 μm or less, further 50 μm or less, having sinterability capable of forming a necessary sintered body and crushing ability at the time of kneading dispersion with a fibrous carbon material. Preferably, the particle size can be large or small, and a configuration in which the particle size is plural and the particle size is different can be adopted. In the case of a single powder, the particle size is preferably 10 μm or less. In addition to the spheres, the powders can be appropriately used in the form of fibers, irregular shapes, trees, and various forms. In addition, as for aluminum etc., 50 micrometers-150 micrometers are preferable.

  In the present invention, the ceramic powder used includes oxides such as alumina and zirconia, nitrides such as aluminum nitride, titanium nitride, and silicon nitride, carbides such as silicon carbide, titanium carbide, tantalum carbide, and tungsten carbide, Ceramics having various known mechanical functions such as borides such as titanium boride, zirconia boride, and chromium boride, and a function of improving grain boundary sliding at the time of plastic deformation can be employed. For example, a known functional ceramic that exhibits necessary functions such as corrosion resistance and heat resistance may be employed.

  As for the particle size of ceramic powder, considering the sinterability that can form the required sintered body, considering the crushing ability when kneading and dispersing with carbon nanotubes, and the grain boundary sliding ability during plastic deformation Although determined in consideration, it is preferably about 10 μm or less, for example, it can be a large or small particle size, a configuration in which a plurality of powder types and different particle sizes can be adopted, and in the case of a single powder, 5 μm or less Further, it is preferably 1 μm or less. In addition to spheres, powders, irregular shapes, and various forms can be used as appropriate.

  In the high thermal conductive composite material, the content of the fibrous carbon material is not particularly limited as long as a sintered body having a required shape and strength can be formed. By selecting, it is possible to contain 20 wt% or less by weight ratio, for example. In particular, when aiming at homogeneity of the metal material, for example, the content of the fibrous carbon material is reduced to 3 wt% or less, and to about 0.05 wt% if necessary, and kneading conditions such as selection of the particle size and kneading dispersion It is necessary to devise a method.

  In the high thermal conductive composite material, the ceramic content is preferably 20 wt% or less by weight.

As a premise of the present invention , there is a method for producing a carbon material-containing metal material in which a fibrous carbon material is dispersed in a metal powder, a mixed powder of metal and ceramics, or a discharge plasma sintered body of ceramic powder . This method
(P) a step of subjecting the long-chain fibrous carbon material to discharge plasma treatment,
(1) Kneading ceramic powder or metal powder or mixed powder of ceramic and metal with a long-chain fibrous carbon material by applying gravity without rotating the container in which the container is stored Dispersing step,
(2) A step of wet-dispersing the powder and the carbon nanotube using a dispersant, that is, a step of creating and solidifying a dispersion.
(3) a step of subjecting the kneaded dispersion to a discharge plasma treatment,
(4) It includes a step of spark plasma sintering of the dried kneaded dispersion material. (1) + (4), (P) + (1) + (4), (1) + (2) + ( 4), (P) + (1) + (2) + (4), (1) + (3) + (4), (P) + (1) + (3) + (4), (1) Each process of + (2) + (3) + (4) and (P) (1) + (2) + (3) + (4) is possible. Note that any of the steps (1) and (2) may be combined first, and a plurality of steps may be appropriately combined.

  In the kneading and dispersing step, it is important to loosen and crush the long-chain fibrous carbon material described above in ceramic powder, metal powder, or a mixed powder of ceramic and metal. For kneading and dispersing, various mills, crushers, and shaker devices for performing known crushing, crushing, and crushing can be appropriately employed, and the mechanisms thereof are also rotary impact type, rotary shear type, rotary impact shear type, medium stirring type Well-known mechanisms such as a stirring type, a stirring type without a stirring blade, and an airflow grinding type can be used as appropriate.

  In particular, the ball mill can be used in any structure as long as it is configured to pulverize and disintegrate using a medium such as a ball, such as a known horizontal type, planetary type, or stirring type mill. Further, the material and particle size of the media can be appropriately selected. When only the carbon nanotubes are previously subjected to the discharge plasma treatment, it is necessary to set conditions for improving the crushing ability by selecting the powder particle diameter and the ball particle diameter.

  In particular, the planetary mill is configured such that the storage container rotates and revolves at the same time and is usually pulverized and crushed using a medium such as a ball. Dispersion and adhesion of fibrous carbon material to ceramics and metal particles by appropriately selecting the amount to be stored, the particle size and amount of fibrous carbon material, ceramics, metal, etc. and the rotation speed of the container (applied gravity) Can be executed efficiently and reliably. That is, the gravitational force to be applied is appropriately selected along with the processing time according to the storage amount in the container capacity, the fibrous carbon material, ceramics, the particle size and amount of the metal, and the rotation speed of the container.

In the wet dispersion process, known nonionic dispersants and cationic anionic dispersants can be added and dispersed using the above-described various mills, crushers and shakers, including an ultrasonic dispersing device and a ball mill. The dry dispersion time can be shortened and the efficiency can be improved. In addition, as a method of drying the slurry after the wet dispersion, a known heat source or a spin method can be appropriately employed.

There are various kneading and dispersing process patterns, such as kneading and dispersing, and wet dispersing, in addition to dry kneading and dispersing, wet dispersing and then dry kneading and mixing with dry, wet, and dry. Can be adopted. Further, when kneading and dispersing in the same dry, for example, carbon nanotubes and ceramics can be kneaded and dispersed first, and then metal powder can be kneaded and dispersed, or kneading and dispersing can be repeated for each particle size of the powder. Furthermore, in the combination of wet and dry, for example, various kneading and dispersing process patterns are adopted such as wet kneading and dispersing the fibrous carbon material and ceramics first, and then dry kneading and dispersing the metal powder in the dried dispersion material. be able to.

The step of orienting the fibrous carbon material in the kneading and dispersing material uses, for example, the wet dispersion step described above. Specifically, a dispersion liquid of a mixed dispersion material in which a fibrous carbon material is mixed and dispersed in a metal powder, a mixed powder of metal and ceramics, or a ceramic powder is prepared. Gelatin or the like is blended in the dispersion as a binder for solidification. This dispersion is placed in a strong magnetic field such as 3000 gauss in a solution state (heated state) and solidified by cooling. A strong magnetic field such as 3000 gauss can be formed by a neodymium iron boron magnet or the like. This forms a mixed powder solid in which the fibrous carbon material is dispersed in the metal powder, the mixed powder of metal and ceramics or in the ceramic powder, and the fibrous carbon material is oriented in a specific direction. The Besides using a magnetic field, you can use an electric field.

When the fibrous carbon material is oriented in the sheet of the fibrous carbon material in the present invention, a method of applying a magnetic field or an electric field using the dispersion liquid can be used. Also, physical methods such as placing the dispersion in an injection machine such as a syringe and extruding several rows in one direction, flowing the dispersion on a standing plate, and slowly immersing the plate in the dispersion and pulling it up slowly A sheet in which the fibrous carbon material is oriented in a specific direction can also be formed by the method.

  In the present invention, the step of spark plasma sintering (treatment) is carried out by loading a dry kneaded dispersion powder or solid material between a carbon die and a punch, and applying a direct current pulse current while pressing with the upper and lower punches. This is a method in which Joule heat is generated in the die, punch, and material to be processed, and the kneaded dispersion material is sintered. Discharging between powder, powder, and fibrous carbon material by applying a pulse current Sintering proceeds smoothly by the action of plasma being generated and the impurities on the surface of the powder and the fibrous carbon material disappearing and being activated.

  The discharge plasma treatment conditions applied only to the fibrous carbon material are not particularly limited. For example, the temperature can be appropriately selected from the range of 200 to 1400 ° C., the time of about 1 to 2 hours, and the pressure of 0 to 10 MPa. .

  The step of further subjecting the kneaded dispersion material obtained by the dry method or wet method to the discharge plasma treatment is performed before the discharge plasma sintering step to further proceed the crushing of the kneaded dispersion material or to extend the carbon nanotubes. In addition, effects such as surface activation and powder diffusion occur, and the thermal conductivity and conductivity imparted to the sintered body are improved along with the smooth progress of subsequent discharge plasma sintering.

  The discharge plasma treatment conditions for the kneaded dispersion are not particularly limited, but considering the sintering temperature of the material to be treated, for example, the temperature is 200 to 1400 ° C., the time is about 1 to 15 minutes, and the pressure is 0 to 0. It can select suitably from the range of 10 MPa.

  In the present invention, the discharge plasma sintering is preferably performed at a temperature lower than the normal sintering temperature of the ceramic powder or metal powder used. In addition, it is preferable to set conditions so that a relatively low pressure and a low temperature treatment are required during sintering without requiring a particularly high pressure.

  Further, in the step of performing discharge plasma sintering of the above kneaded dispersion material, it is also preferable to perform two steps in which low temperature plasma discharge is first performed under low pressure and then low temperature discharge plasma sintering is performed under high pressure. It is also possible to use precipitation hardening after sintering and phase transformation by various heat treatments. Note that the pressure and temperature levels are relative between the two steps, and it is only necessary to set a difference in height between the two steps.

  The step of plastically deforming the obtained spark plasma sintered body, which is one of the features of the present invention, is any rolling method of cold rolling, warm rolling, and hot rolling in addition to known press forming. Also good. For example, an optimum rolling method is selected according to the metal species of the sintered metal, the ceramic species to be mixed, and the amount of fibrous carbon material. In addition, when performing multiple passes of rolling, for example, cold rolling and warm rolling can be combined.

  Cold rolling is a process in which the obtained block, plate, and linear sintered bodies are rolled as they are, and a plurality of passes are repeated from a single pass at a required reduction rate to obtain a plate, thin plate, or wire having a required thickness. Can be processed. The rolling reduction ratio, total rolling reduction ratio, rolling roll diameter, and the like are appropriately selected according to the metal species, the ceramic species to be mixed, and the amount of fibrous carbon material so that cracks do not occur in the rolling material.

  The hot or hot press forming or rolling can be appropriately selected according to the required form and material. For example, cold rolling is not easy or the rolling efficiency is improved depending on the properties of the sintered metal. Depending on the metal type of the sintered metal, the type of ceramics to be mixed and the amount of fibrous carbon material, it is possible to take into consideration the rolling reduction ratio, total rolling reduction ratio, number of passes, rolling roll diameter, etc. The heating temperature of the material is appropriately selected.

  The annealing process after press forming and rolling is performed as necessary.For example, as described above, the optimum rolling method, combination, and rolling conditions are selected according to the metal species, the ceramic species to be mixed, and the amount of carbon nanotubes. However, depending on the selected rolling method, combination, rolling conditions, etc., such as the purpose of further reducing the residual stress of the rolled metal material to further improve the rolling effect and easily obtaining the required characteristics, The temperature condition, the number of times, etc. are appropriately selected.

  The metal material of the present invention that has been subjected to plastic deformation or plastic deformation and annealing treatment can be further machined easily, can be processed into various shapes according to the intended use and form, and further, the processed metal materials can be different from each other. It is also possible to bond the material with a brazing material or the like.

In the present invention, a highly heat-conductive composite material having a laminated structure in which sheets of fibrous carbon material are arranged at predetermined intervals in a discharge plasma sintered body of metal powder or a mixed powder of metal and ceramics or ceramic powder. When manufacturing, the sheet | seat of a fibrous carbon material is produced first. For example, a sheet is prepared by unraveling a lump of fibers entangled to make a dispersion and solidifying it thinly. As described above, the fibers can be oriented by applying a magnetic field or an electric field to the dispersion. Also, physical methods such as placing the dispersion in an injection machine such as a syringe and extruding several rows in one direction, flowing the dispersion on a standing plate, and slowly immersing the plate in the dispersion and pulling it up slowly As described above, a sheet in which the fibrous carbon material is oriented in a specific direction can also be produced by the method.

  When a sheet of fibrous carbon material is produced, metal powder, a mixed powder of metal and ceramics, or ceramic powder is adhered to both surfaces or one surface of the sheet. A high thermal conductive composite material having a laminated structure is manufactured by applying pressure and sintering by discharge plasma. When using a sheet in which the fibrous carbon material is oriented in the same direction, it is important to align the orientation direction. The discharge plasma sintering process, the subsequent plastic process, and the prior discharge plasma process for the fibrous carbon material are as described in the production of the high thermal conductive composite material having a fiber dispersion structure.

Examples will be described below. Examples 1 to 7 are examples on which the present invention is based. Examples 8 and 9 are examples of the present invention, and Examples 10 to 13 are reference examples.
Example 1-1
In kneading and crushing an aluminum alloy (3003) powder having an average particle size of 30 μm and 0.5 wt% long-chain carbon nanotubes, only the carbon nanotubes were previously loaded in a die of a discharge plasma sintering apparatus. Prepare a plasma mill that does not perform the same treatment as a discharge plasma treatment at 5 ° C for 5 minutes. Each planetary mill uses a container made of alumina. The kneading dispersion was performed by combining the unit and the rotation speed of the container.

  The kneaded dispersion was loaded into a die of a discharge plasma sintering apparatus and subjected to discharge plasma sintering at 575 ° C. for 60 minutes. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied.

  As a result of measuring the thermal conductivity of the obtained composite material, it was about 200 W / mK (198 W / mK). The thermal conductivity of the solidified body obtained by spark plasma sintering of only the aluminum alloy powder under the above conditions was 157 W / mK, and the thermal conductivity of the composite material according to the present invention increased by about 21%. I understand.

  Example 1-2 In kneading and crushing of aluminum alloy (3003) powder having an average particle diameter of 30 μm and long-chain carbon nanotubes of 2.5 wt%, only the carbon nanotubes were previously stored in the die of the discharge plasma sintering apparatus. A non-dispersed sample that was charged with a discharge plasma at 800 ° C. for 5 minutes and was not subjected to the same treatment was used. Each planetary mill using an alumina container was used for 2 hours in a dry state without using dispersion media. The kneading dispersion was carried out by combining the following various time units and the number of rotations of the container.

  The kneaded dispersion was loaded into a die of a discharge plasma sintering apparatus and subjected to a discharge plasma treatment at 800 ° C. for 5 minutes. Thereafter, the kneaded dispersion was subjected to spark plasma sintering at 600 ° C. for 5 minutes in a spark plasma sintering apparatus. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied.

  As a result of measuring the thermal conductivity of the obtained composite material, it was 221 W / mK. In addition, the thermal conductivity of the solidified body obtained by performing discharge plasma sintering without performing each discharge plasma treatment on the carbon nanotubes and the kneading dispersion material under the above conditions was 94.1 W / mK.

  Example 1-3 In kneading and pulverization of aluminum powder having an average particle diameter of 30 μm and long-chain carbon nanotubes of 0.25 wt%, only carbon nanotubes were previously loaded in a die of a discharge plasma sintering apparatus, Dispersion plasma treatment at 800 ° C. for 5 minutes, a planetary mill using a stainless steel container, and kneading and dispersing in various dry time units of 2 hours or less and the rotational speed of the container without using a dispersion medium Went.

  The kneaded dispersion was loaded into a die of a discharge plasma sintering apparatus and subjected to discharge plasma treatment at 400 ° C. for 5 minutes. Thereafter, the kneaded dispersion was subjected to spark plasma sintering at 600 ° C. for 5 minutes in a spark plasma sintering apparatus.

  FIG. 5 shows an electron micrograph of the forced fracture surface of the obtained composite material. FIG. 5B shows an electron micrograph of a net-like carbon nanotube when FIG. 5A having a scale of the order of 100 μm is enlarged to the order of 5.0 μm.

  6A and 6B show electron micrographs of the aluminum particles before kneading and crushing. FIG. 7A shows an electron micrograph of the aluminum particles after kneading and pulverizing with a planetary high-speed mill, and FIG. 7B shows an enlarged electron micrograph of the concave portion shown in FIG. 7A on the order of 10 μm. Furthermore, enlarged electron micrographs of the order of 1 μm and 500 nm of the recesses shown in FIG. 7A are shown in FIGS. 8A and 8B. 9A, 9B, and 10 show enlarged electron micrographs of the smooth portion shown in FIG. 7A in the order of 10 μm, 1 μm, and 500 nm.

  From the electron micrographs of FIGS. 6 to 10, the carbon nanotubes uniformly adhere to the surface of the aluminum particles by kneading and crushing with a planetary high-speed mill. In particular, the carbon nanotubes are three-dimensional as is apparent from FIGS. It is clear that the particles adhere to the surface of the aluminum particles vertically and horizontally.

Example 2-1
In kneading and crushing aluminum powder with an average particle diameter of 30 μm and long-chain carbon nanotubes with addition amounts of 0.05 wt%, 0.25 wt%, and 0.5 wt%, only the carbon nanotubes are preliminarily spark plasma sintered. The sample was loaded into a die of the apparatus, subjected to discharge plasma treatment at 800 ° C. for 5 minutes, and kneaded and dispersed in a dry state for 2 hours or less in a planetary mill using a stainless steel container without using a dispersion medium. The obtained kneading and dispersing material is loaded into a die of a discharge plasma sintering apparatus and subjected to a discharge plasma treatment at 400 ° C. for 5 minutes, and then the kneading dispersion material is placed in a discharge plasma sintering apparatus at 600 ° C. for 5 minutes. Spark plasma sintering was performed.

  The obtained spark plasma sintered body was a short cylindrical body having a height of 10 mm and an outer diameter of 60 mm. This was cold-rolled for 2 passes until the thickness became 1 mm. FIG. 1A shows a state photograph after rolling of an aluminum sintered body containing 0.05 wt% of carbon nanotubes, and FIG. 1B shows an enlarged electron micrograph of 2 μm order of the structure after rolling. It is clear that the metal material of the example achieved good rolling.

Example 2-2
Although it manufactures with the manufacturing method similar to Example 2-1, it rolls by changing the rolling conditions (rolling direction) of a sintered compact, and the content of a carbon nanotube is 0.05 wt%, 0.5 wt%, 0.25 wt%. Four types of rolled metal materials of samples R2, R3, R4, and R5 that are%, 0.25 wt%, and 0.25 wt% were manufactured. As shown in FIG. 2, the test pieces were cut out from four types of samples R2, R3, R4, and R5 having different production conditions by aligning the test piece axes in the rolling direction and the width direction, and represented by T and L subscripts, respectively. .

  In order to confirm the rolling effect, when the stress-strain relationship for each sample was examined, as shown in FIG. 3, the stress-strain relationship in the rolling direction and the width direction was almost the same in all samples. That is, the development of anisotropy was not observed by rolling. Moreover, when the stress-strain relationship of the test piece of the rolling direction and the width direction was investigated, the difference of the stress-strain relationship by a manufacturing condition was hardly seen by the rolling direction and the board width direction. This is considered because the material was stabilized by rolling.

  Furthermore, when the Young's modulus obtained from the tensile test performed on the sintered body material before rolling and the above-mentioned test after rolling were compared with the tensile strength, the Young's modulus of the test piece after rolling was a carbon nanotube. It has been confirmed that the content decreases with increasing content, and that the tensile strength is not affected by the content of carbon nanotubes. Also, it was confirmed that the rolling effect was increased by increasing the Young's modulus and tensile strength by rolling. This is thought to be because the defects inside the sample were reduced by rolling.

Example 2-3
The four types of rolled metal materials of samples R2, R3, R4, and R5 manufactured in Example 2-2 were annealed at a temperature of 400 ° C. × 1 hour. When the stress-strain relationship for each sample after rolling and annealing was examined, as shown in FIG. 4, when compared with the stress-strain relationship of the test piece without annealing in FIG. It can be seen that decreases and the overall growth increases. This is thought to be because the residual stress and strain generated during rolling recovered by annealing.

  Compared with the stress-strain relationship after rolling a pure aluminum sintered material containing no carbon nanotubes, it can be seen that annealing reduces the tensile strength and increases the total elongation. The Young's modulus is changed by annealing. In particular, the sample R3 having a high content increases the Young's modulus by annealing. This is considered to be because the interface state of the carbon nanotube was improved by annealing, or the orientation direction of the carbon nanotube was changed.

  The total elongation of the sample R2 having a small carbon nanotube content is greatly increased by annealing. However, the sample R3 having a high content rate is not significantly different between before and after annealing. That is, it is considered that the smaller the content rate, the larger the rate at which the total elongation increases due to annealing.

Example 2-4
In producing the four types of rolled metal materials of Samples R2, R3, R4, and R5 in Example 2-2, warm rolling was performed by heating to a temperature of 380 ° C. instead of cold rolling. When the stress-strain relationship of all the specimens was examined, the stress-strain relationship was almost the same, and it was confirmed that the development of anisotropy was not observed by warm rolling.

  Compared with the results of R2 and R2A specimens with the same carbon nanotube content in cold rolling, the warm rolling between the stress strain relationship without annealing after cold rolling and the stress strain relationship with annealing after cold rolling It can be seen that the stress-strain relationship due to is located. Further, it was confirmed that the Young's modulus did not change so much by warm rolling, and the tensile strength became an intermediate value before and after the cold annealing.

Example 3-1
Use a dispersion medium in a planetary mill using pure titanium powder with an average particle diameter of 10 to 20 μm and 0.1 to 0.25 wt% long-chain carbon nanotubes (CNT) using a titanium container. In a dry state, kneading dispersion was performed by combining various time units of 2 hours or less and the rotation speed of the container.

  The obtained kneaded dispersion was loaded into a die of a discharge plasma sintering apparatus, and was subjected to discharge plasma sintering at 900 ° C. for 10 minutes. At that time, the temperature increase rate was 100 ° C./min, and a pressure of 60 MPa was continuously applied.

  FIG. 11 shows an electron micrograph of the forced fracture surface of the obtained composite material (CNT: 0.25 wt% added). FIG. 11B shows an electron micrograph of the net-like carbon nanotubes when FIG. 11A having a scale of the order of 10 μm is enlarged to the order of 1.0 μm.

  It was 18.4 W / mK as a result of measuring the heat conductivity of the obtained composite material. The thermal conductivity of the solidified body obtained by subjecting only pure titanium powder to spark plasma sintering under the above conditions is 13.8 W / mK, and the thermal conductivity of the composite material according to the present invention is increased by about 30%. I understand that.

Example 3-2
In kneading and crushing pure titanium powder having an average particle size of 10 to 20 μm and long-chain carbon nanotubes of 0.05 to 0.5 wt%, only the carbon nanotubes are previously loaded in the die of the discharge plasma sintering apparatus. Prepared for 5 minutes discharge plasma treatment at 575 ° C., which is not subjected to the same treatment, each planetary mill using a titanium container, various kinds of 60 minutes or less in a dry state without using dispersion media The kneading dispersion was performed by combining the minute unit and the rotation speed of the container.

  The kneaded and dispersed material was loaded into a die of a discharge plasma sintering apparatus, and was subjected to discharge plasma sintering at 900 ° C. for 10 minutes. At that time, the temperature increase rate was 100 ° C./min, and a pressure of 60 MPa was continuously applied. As a result of measuring the thermal conductivity of the obtained composite material, it was 17.2 W / mK when only the carbon nanotubes were previously subjected to the discharge plasma treatment.

  Electron micrographs of the titanium particles before kneading and crushing and the titanium particles after kneading and crushing with a planetary high speed mill are shown in FIGS. 12A and 12B. 13A and 13B show enlarged electron micrographs of the order of 1 μm and 500 nm on the surface of the titanium particles shown in FIG. 12B after kneading and pulverizing with a planetary high-speed mill. From the electron micrographs of FIGS. 12 to 13, it is clear that the carbon nanotubes are uniformly and three-dimensionally and vertically attached to the surface of the titanium particles by kneading and crushing with a planetary high-speed mill.

Example 3-3
The spark plasma titanium sintered body having a carbon nanotube content of 0.05 wt%, 0.25 wt%, and 0.5 wt% obtained in Example 3-2 is a short cylindrical body having a height of 10 mm and an outer diameter of 60 mm. Met. This was cold-rolled for 4 passes until the thickness became 8 mm. When the state of the titanium sintered body after rolling and the structure after rolling were observed with an electron microscope on the order of 1 to 5 μm, it was confirmed that the metal material of the example achieved good rolling.

Example 4-1
An oxygen-free copper powder (Mitsui Metal atomized powder) with an average particle size of 20 to 30 μm and a long-chain carbon nanotube of 0.5 wt% are used in a planetary mill using a stainless steel container and a dispersion medium is used. Without mixing, kneading dispersion was performed by combining various time units of 2 hours or less and the rotation speed of the container in a dry state.

  Next, the kneaded dispersion was loaded into a die of a discharge plasma sintering apparatus, and subjected to discharge plasma treatment at 575 ° C. for 5 minutes. Thereafter, the kneaded and dispersed material was subjected to discharge plasma sintering at 800 ° C. for 15 minutes in a discharge plasma sintering apparatus. At that time, the rate of temperature increase was 100 ° C./min, and a pressure of 60 MPa was continuously applied.

  An electron micrograph of the forced fracture surface of the obtained composite material is shown in FIG. FIG. 14B shows an electron micrograph of the net-like carbon nanotubes when FIG. 14A having a scale of the order of 50 μm is enlarged to the order of 1.0 μm.

As a result of measuring the electrical resistivity of the obtained composite material, the electrical resistivity of the solidified body obtained by subjecting only the oxygen-free copper powder to spark plasma sintering under the above conditions is about 5 × 10 ⁻³ Ωm, The electrical resistivity of the composite material according to the present invention was about 56% (conductivity increased about 1.7 times). Note that Siemens / m = (Ωm) ⁻¹ in terms of conductivity units.

  Electron micrographs of the copper particles before kneading and crushing and the copper particles after kneading and crushing with a planetary high-speed mill are shown in FIGS. 15A and 15B. 16A and 16B show enlarged electron micrographs of the order of 1 μm and 500 nm on the surface of the copper particles shown in FIG. 15B after kneading and pulverizing with a planetary high-speed mill. It is clear from the electron micrographs of FIGS. 15 to 16 that the carbon nanotubes are evenly and three-dimensionally attached to the surface of the copper particles by kneading and crushing with a planetary high-speed mill.

Example 4-2
The discharge plasma copper sintered body having a carbon nanotube content of 0.5 wt% obtained in Example 4-1 was a short cylindrical body having a height of 10 mm and an outer diameter of 60 mm. This was cold-rolled for 3 passes until the thickness reached 8 mm. When the state of the copper sintered body after rolling and the structure after rolling were observed with an electron microscope in the order of 1 to 5 μm, it was confirmed that the metal material of the example achieved good rolling.

Example 5-1
Stainless steel powder (SUS316L) with an average particle size of 20-30 μm and 0.5 wt% long-chain carbon nanotubes in a dry state without using dispersion media in a planetary mill using a stainless steel container And kneading and dispersing in which various time units of 2 hours or less and the rotation speed of the container were combined.

  Next, the kneaded dispersion was loaded into a die of a discharge plasma sintering apparatus, and subjected to discharge plasma treatment at 575 ° C. for 5 minutes. Thereafter, the kneaded dispersion material was subjected to discharge plasma sintering at 900 ° C. for 10 minutes in a discharge plasma sintering apparatus. At that time, the temperature increase rate was 100 ° C./min, and a pressure of 60 MPa was continuously applied.

  As a result of measuring the thermal conductivity of the obtained composite material, the composite material according to the present invention has an increase of about 18% with respect to the thermal conductivity of the solidified body obtained by spark plasma sintering of only the stainless steel powder under the above conditions. did.

  Moreover, as a result of measuring the electrical resistivity of the obtained composite material, the electrical resistance of the composite material according to the present invention was compared with the electrical resistivity of the solidified body obtained by spark plasma sintering of only the stainless steel powder under the above conditions. The rate was about 60% (conductivity increased to about 1.65 times).

Example 5-2
The discharge plasma SUS sintered body having a carbon nanotube content of 0.5 wt% obtained in Example 5-1 was a short cylindrical body having a height of 10 mm and an outer diameter of 60 mm. This was cold-rolled for 5 passes until the thickness became 8 mm. When the state of the SUS sintered body after rolling and the structure after rolling were observed with an electron microscope in the order of 1 to 5 μm, it was confirmed that the metal material of the example achieved good rolling.

Example 6-1
A mixed powder (95 wt%, aluminum powder: alumina powder = 95; 5) of pure aluminum powder having an average particle diameter of 100 μm and alumina powder having an average particle diameter of 0.6 μm, and long-chain carbon nanotubes (5 wt. %) Was dispersed in a planetary mill using an alumina container.

  First, carbon nanotubes were blended, a non-ionic surfactant (Triton X-100) was added as a dispersant to prepare a mixed dispersion material with alumina powder, and this was dried. Next, pure aluminum powders and their dry dispersions were kneaded and dispersed in a dry state in combination with various time units of 2 hours or less and the rotation speed of the container in a dry state without using a dispersion medium.

  The kneaded and dispersed material was loaded into a die of a discharge plasma sintering apparatus, and plasma solidified at 500 to 600 ° C. for 7 minutes. At that time, the heating rate was 100 ° C./min and 230 ° C./min, and a pressure of 14 to 40 MPa was continuously applied. When the thermal conductivity of the obtained composite material was measured, it was 300 to 450 W / mK.

Example 6-2
The discharge plasma metal composite sintered body having a carbon nanotube content of 0.5 wt% obtained by the same method as in Example 6-1 was a short cylindrical body having a height of 10 mm and an outer diameter of 60 mm. This was cold-rolled for 5 passes until the thickness became 8 mm. When the state of this sintered body after rolling and the structure after rolling were observed with an electron microscope in the order of 1 to 5 μm, it was confirmed that the metal material of the example achieved good rolling.

Example 7-1
A stainless steel container containing a mixed powder of oxygen-free copper powder (Mitsui Metal atomized powder) with an average particle size of 50 μm and alumina powder with an average particle size of 0.6 μm, and 10 wt% long-chain carbon nanotubes It was dispersed with a planetary mill using First, carbon nanotubes are blended, and a mixed powder of oxygen-free copper powder and alumina powder that has been sufficiently dispersed in advance is blended, and these powders are in a dry state without using a dispersion medium. The kneading dispersion was performed by combining various time units of 2 hours or less and the rotational speed of the container.

  The knead-dispersed material was loaded into a die of a discharge plasma sintering apparatus and subjected to discharge plasma sintering at 700 to 900 ° C. for 5 minutes. At that time, the rate of temperature increase was 250 ° C./min, and a pressure of 10 MPa was continuously applied. As a result of measuring the thermal conductivity of the obtained two types of composite materials, both were 500 to 800 W / mK.

Example 7-2
The discharge plasma metal composite sintered body having a carbon nanotube content of 0.5 wt% obtained by the same method as in Example 7-1 was a short cylindrical body having a height of 10 mm and an outer diameter of 60 mm. This was cold-rolled for 8 passes until the thickness became 8 mm. When the state of this sintered body after rolling and the structure after rolling were observed with an electron microscope in the order of 1 to 5 μm, it was confirmed that the metal material of the example achieved good rolling.

  The above is an example of manufacturing a composite material using carbon nanotubes as a fibrous carbon material, particularly a composite material having no fiber orientation. Next, an example of producing a composite material using vapor-grown carbon fibers as the fibrous carbon material will be described for the case of fiber orientation and non-orientation, and an example of producing a fiber oriented composite material using carbon nanotubes together. explain.

Example 8
An oriented sheet made of a fibrous carbon material having a length of about 2 to 3 mm and having a fiber orientation parallel to the surface and oriented in the same direction was prepared in the order of 100 μm. A large number of circular fiber sheets having a diameter of 10 mm were punched from the fiber oriented sheet. While attaching aluminum powder having an average particle diameter of 30 μm as metal powder to both surfaces of the circular fiber sheets, the circular sheets were laminated in the thickness direction to prepare a cylindrical laminate having a diameter of 10 mm × height of 20 mm.

  At this time, the content of the fibrous carbon material was variously changed within the range of 2.5 wt% or more and 30 wt% or less by adjusting the adhesion amount of the aluminum powder adhered to both surfaces of the circular sheet. That is, by increasing the adhesion amount of the aluminum powder, the content of the fibrous carbon material is reduced, and the number of laminated circular sheets in the cylindrical laminate is also reduced. On the contrary, by reducing the adhesion amount of the aluminum powder, the content of the fibrous carbon material is increased, and the number of laminated circular sheets in the cylindrical laminate is increased. As a result, the number of stacked circular sheets in the cylindrical laminate changed within the range of about 100 to 250. When stacking circular sheets, care was taken that the fiber orientation direction was the same.

  The produced various cylindrical laminates were loaded into a die of a discharge plasma sintering apparatus and pressurized in the height direction. Thereby, the cylindrical laminated body in the die was compressed to a height of about 15 mm. In this state, the cylindrical laminate in the die was subjected to discharge plasma sintering under the condition of 575 ° C. × 60 minutes. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied. As a result, a composite material of cylindrical aluminum and a fibrous carbon material in which carbon fiber layers perpendicular to the center line are laminated at predetermined intervals in the center line direction in a cylindrical aluminum powder sintered body is obtained. manufactured.

  The manufactured composite material had a diameter of 10 mm and a height of about 11 to 12 mm due to shrinkage during the pressure sintering process. The fibers in the carbon fiber layer are parallel to the layer surface (perpendicular to the center line of the composite material) and oriented in the same direction.

  In order to measure the thermal conductivity in the fiber orientation direction, a disk-shaped test piece was taken in the orthogonal direction from the composite material. The test piece has a diameter of 10 mm and a thickness of 2 to 3 mm. The center line of the test piece is perpendicular to the center line of the composite material and coincides with the fiber orientation direction in the fiber layer. That is, in each test piece, a fiber layer parallel to the center line is laminated at a predetermined interval in a direction perpendicular to the center line, and the fiber orientation direction in each fiber layer coincides with the center line direction of the test piece. It is.

  For the composite material having a fibrous carbon material content of 13 wt% and 15 wt%, an Al—Si alloy powder containing 1 wt% of silicon powder in aluminum powder was used as the metal powder.

  The thermal conductivity in the center line direction, that is, the fiber orientation direction was measured with a test piece taken from the produced composite material. The results are indicated by ◯ in FIG. The black circles use Al—Si alloy powder as metal powder. Although the thermal conductivity of pure aluminum is 244 W / mK, an aluminum alloy is usually used in an actual composite material-using device such as a heat exchanger, and the thermal conductivity is lowered. Considering this, the thermal conductivity of aluminum at a practical level is about 200 W / mK. The composite material produced in this example has vapor-grown carbon fibers oriented in one direction as a fibrous carbon material, surpassing the thermal conductivity of aluminum at a practical level at all fiber contents. As the fiber content increases, the thermal conductivity tends to increase, and a result exceeding 600 W / mK is obtained at the maximum.

  In Example 8 above, in order to measure the thermal conductivity in the fiber orientation direction, a composite material having a multilayer structure in which a large number of fiber sheets were laminated was manufactured. However, in an actual product, one or several fiber sheets were used. In many cases, a small number of sheets are laminated. A thin composite material with a few laminated fiber sheets is more versatile. Use value is also great. The same applies to the following embodiments.

Example 9
In order to investigate the effect of rolling, in Example 8, a composite material for rolling test having a diameter of 60 mm × height of 10 mm was manufactured for a composite material having a fibrous carbon material content of 2.5 wt%. . The manufacturing method is the same as in Example 8. In the manufactured composite material, carbon fiber layers perpendicular to the center line are laminated in a number of layers at predetermined intervals in the center line direction in a cylindrical aluminum powder sintered body. In addition, the fibers in the carbon fiber layer are oriented in the same direction.

  The produced cylindrical composite material having a height of 60 mm was rolled in the fiber orientation direction in the carbon fiber layer until the thickness became 1 mm. A 25 mm square sample in which two parallel sides are parallel to the rolling direction (fiber orientation direction) and the other two parallel sides are perpendicular to the rolling direction (fiber orientation direction) is taken from the 1 mm-thick plate after rolling. The thermal conductivity of the sample was measured in two directions, a direction perpendicular to the rolling direction (fiber orientation direction) and the rolling direction (fiber orientation direction).

  The thermal conductivity in the rolling direction (fiber orientation direction) was 237 W / mK, and the thermal conductivity in the direction perpendicular to the rolling direction (fiber orientation direction) was 212 W / mK. As can be seen from FIG. 17, the thermal conductivity in the fiber orientation direction before rolling is about 330 W / mK, which exceeds 300 W / mK. Despite being subjected to rolling with a reduction ratio of 1/60, the thermal conductivity after rolling exceeds the thermal conductivity of aluminum at a practical level, and the thermal conductivity in the direction perpendicular to the fiber orientation direction. Even the rate exceeds the thermal conductivity of aluminum at this practical level.

Example 10
Lumps of vapor-grown carbon fibers having a length of 2 to 3 mm that were entangled were loosened with a shaker mill and separated. Aluminum powder was mixed in the shaker mill, and both were kneaded. The mixing ratio of the two was adjusted so that the content of the vapor-grown carbon fiber varied in a range of 2.5 to 15 wt%.

  The obtained powdery kneading dispersion material was loaded into a die of a discharge plasma sintering apparatus and pressurized in the height direction in the same manner as in Example 8. In this state, the kneaded dispersion material in the die was subjected to discharge plasma sintering under the condition of 575 ° C. × 60 minutes. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied. As a result, a composite material of aluminum and a fibrous carbon material in which the fibrous carbon material was uniformly dispersed in a cylindrical aluminum powder sintered body having a diameter of 10 mm and a height of 11 to 12 mm was produced.

  The vapor grown carbon fiber in the kneaded and dispersed material falls sideways by compression in the height direction of the kneaded and dispersed material in the die of the discharge plasma sintering apparatus. There are various ways to fall. For this reason, the produced composite material tends to be oriented along a plane perpendicular to the center line, although the vapor-grown carbon fibers are not oriented. That is, the vapor-grown carbon fiber in the composite material does not have a high degree of orientation, but exhibits a two-dimensional orientation along a plane perpendicular to the center line.

  Thereafter, in the same manner as in Example 8, a disk-shaped test piece was collected from the composite material in the orthogonal direction. The diameter of the test piece is 10 mm, the thickness is 2 to 3 mm, and the center line of the test piece is perpendicular to the center line of the composite material. The thermal conductivity in the center line direction of the test piece was measured. The results are shown by x marks in FIG.

  Although it is weakly oriented, it is basically non-oriented, and thus its thermal conductivity is inferior compared to the fiber-oriented material indicated by ◯. However, in all fiber contents, it exceeds the thermal conductivity (200 W / mK) of aluminum at a practical level, and shows a thermal conductivity close to 400 W / mK at the maximum.

  In addition, (triangle | delta) mark in FIG. 17 represents the average value of the heat conductivity of the composite material produced for every content of fibrous carbon material.

Example 11
Examples 8 to 10 are production examples of fiber-oriented composite materials using vapor-grown carbon fibers as fibrous carbon materials. On the other hand, Examples 1-7 use a carbon nanotube as a fibrous carbon material, and all are production examples of a fiber non-oriented type composite material. Therefore, in this embodiment, an example of manufacturing a fiber-oriented composite material using carbon nanotubes as the fibrous carbon material is shown.

  As a fibrous carbon material, a carbon nanotube aggregate sheet having a thickness of several μm was prepared, in which very short linear carbon nanotubes having a length of several μm were two-dimensionally closely gathered in the radial direction. A number of carbon nanotubes in the carbon nanotube aggregate sheet were pushed down in one direction by a roller to produce a thin fiber sheet in which the carbon nanotubes were oriented in a specific direction parallel to the surface.

  Many circular fiber sheets having a diameter of 10 mm were punched from this fiber sheet. While attaching aluminum powder having an average particle diameter of 30 μm as metal powder to both surfaces of the circular fiber sheets, the circular sheets were laminated in the thickness direction to prepare a cylindrical laminate having a diameter of 10 mm × height of 20 mm. At this time, the content of carbon nanotubes was adjusted to 1.5 wt% by adjusting the amount of aluminum powder adhered to both surfaces of the circular sheet. When stacking circular sheets, care was taken that the fiber orientation direction was the same.

  The produced cylindrical laminate was loaded into a die of a discharge plasma sintering apparatus and pressurized in the height direction. Thereby, the cylindrical laminated body in the die was compressed to a height of about 15 mm. In this state, the cylindrical laminate in the die was subjected to discharge plasma sintering under the condition of 575 ° C. × 60 minutes. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied. As a result, a fiber-oriented composite of columnar aluminum and carbon nanotubes, in which carbon fiber layers perpendicular to the centerline are laminated at predetermined intervals in the centerline direction in a cylindrical aluminum powder sintered body The material was manufactured.

  The manufactured composite material had a diameter of 10 mm and a height of about 11 to 12 mm due to shrinkage during the pressure sintering process. The fibers in the carbon fiber layer are carbon nanotubes, and are oriented in the same direction as the direction parallel to the layer surface (perpendicular to the center line of the composite material).

  In order to measure the thermal conductivity in the fiber orientation direction, a disk-shaped test piece was taken in the orthogonal direction from the composite material. The test piece has a diameter of 10 mm and a thickness of 2 to 3 mm. The center line of the test piece is perpendicular to the center line of the composite material and coincides with the fiber orientation direction in the fiber layer. That is, in each test piece, a fiber layer parallel to the center line is laminated at a predetermined interval in a direction perpendicular to the center line, and the fiber orientation direction in each fiber layer coincides with the center line direction of the test piece. It is.

  The thermal conductivity of the test piece was measured in the center line direction, that is, the fiber orientation direction. The results are indicated by ◎ in FIG. This carbon nanotube-oriented composite material exhibited a thermal conductivity of 274 W / mK when the carbon nanotube content was 1.5 wt%. Compared with the case where the fibrous carbon material is vapor-grown carbon fiber, the performance is comparable. However, in the case of carbon nanotubes, high-quality linear carbon nanotubes are very expensive at present, and the use of vapor-grown carbon fibers is meaningful when evaluated comprehensively and industrially in consideration of cost performance. It is.

Example 12
In this example, a non-oriented type composite material using a linear high-quality carbon nanotube having a length of several μm as a fibrous carbon material was manufactured. More specifically, aluminum powder having an average particle diameter of 30 μm and linear carbon nanotubes having a length of several μm were kneaded by a shaker mill. The carbon nanotube content was 0.5 wt%.

  The obtained powdery kneading dispersion was loaded into a die of a discharge plasma sintering apparatus and pressurized in the height direction. In this state, the kneaded dispersion material in the die was subjected to discharge plasma sintering under the condition of 575 ° C. × 60 minutes. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied. Thereby, a disk-shaped composite material having a diameter of 10 mm and a height of 2 to 3 was produced.

  In this composite material, carbon nanotubes are uniformly dispersed in a disk-shaped aluminum powder sintered body. Since carbon nanotubes are very short, even if they are compressed in the direction of the center line, the orientation does not substantially occur. For this reason, a thin disk-shaped composite material (diameter 10 mm × thickness 2 to 3 mm) having a size for measuring thermal conductivity was directly manufactured. The thermal conductivity in the direction of the center line was 240 W / mK as shown by ◎ in FIG. This performance is good considering that the compounding amount of the carbon nanotube is 0.5 wt%.

Example 13
In the above embodiments, the substrate is a metal powder sintered body or a mixed powder sintered body of metal and ceramics. On the other hand, in the present Example, the composite material of the ceramic base material and the vapor growth fiber was manufactured.

  Specifically, in the same manner as in Example 10, a mass of vapor-grown carbon fibers having a length of 2 to 3 mm entangled was loosened with a shaker mill and separated. The shaker mill was mixed with alumina powder having an average particle size of 0.6 μm, and both were kneaded. The content of the vapor growth carbon fiber was 5 wt%.

  The obtained powdery kneading dispersion was loaded into a die of a discharge plasma sintering apparatus in the same manner as in Example 8 and Example 10, and pressurized in the height direction. In this state, the kneaded dispersion material in the die was subjected to spark plasma sintering under the conditions of 1400 ° C. × 3 minutes. At that time, the rate of temperature increase was 100 ° C./min, and a pressure of 30 MPa was continuously applied. As a result, a composite material of alumina and a fibrous carbon material in which vapor-grown carbon fibers were uniformly dispersed in a cylindrical alumina powder sintered body having a diameter of 10 mm and a height of 11 to 12 mm was produced.

  The vapor grown carbon fiber in the kneaded and dispersed material falls sideways by compression in the height direction of the kneaded and dispersed material in the die of the discharge plasma sintering apparatus. There are various ways to fall. For this reason, the produced composite material tends to be oriented along a plane perpendicular to the center line, although the vapor-grown carbon fibers are not oriented. That is, the vapor-grown carbon fiber in the composite material does not have a high degree of orientation, but exhibits a two-dimensional orientation along a plane perpendicular to the center line.

  Thereafter, in the same manner as in Example 8 and Example 10, a disk-shaped test piece was collected from the composite material in the orthogonal direction. The diameter of the test piece is 10 mm, the thickness is 2 to 3 mm, and the center line of the test piece is perpendicular to the center line of the composite material. It was 243 W / mK when the heat conductivity in the centerline direction of the test piece was measured. Since the thermal conductivity of the alumina powder sintered body itself is about 25 W / mK, the thermal conductivity has increased about 10 times due to the combination with the fibrous carbon material. The performance is not inferior even when compared.

Comparative Example For reference, a composite material using carbon fiber as a fibrous carbon material was produced. The manufacturing method was the same as in Example 10. That is, the tangled carbon fiber lump was loosened with a shaker mill and separated. Aluminum powder was mixed in the shaker mill, and both were kneaded. The carbon fiber content was 15 wt%.

  The obtained powdery kneading dispersion was loaded into a die of a discharge plasma sintering apparatus and pressed in the height direction in the same manner as in Examples 8 and 10. In this state, the kneaded dispersion material in the die was subjected to discharge plasma sintering under the condition of 575 ° C. × 60 minutes. At that time, the temperature rising rate was 100 ° C./min, and a pressure of 50 MPa was continuously applied. As a result, a composite material of aluminum and a fibrous carbon material in which carbon fibers are uniformly dispersed in a cylindrical aluminum powder sintered body having a diameter of 10 mm and a height of 11 to 12 mm was produced.

  The carbon fiber in the kneaded and dispersed material falls sideways by compression in the height direction of the kneaded and dispersed material in the die of the discharge plasma sintering apparatus. For this reason, the carbon fiber in the manufactured composite material does not have a high degree of orientation, but exhibits a two-dimensional orientation along a plane perpendicular to the center line.

  Thereafter, in the same manner as in Examples 8 and 10, a disk-shaped test piece was collected from the composite material in the orthogonal direction. The diameter of the test piece is 10 mm, the thickness is 2 to 3 mm, and the center line of the test piece is perpendicular to the center line of the composite material. The thermal conductivity in the center line direction of the test piece was measured. The results are indicated by ● marks in FIG.

  Since the carbon fiber content was as high as 15 wt%, the thermal conductivity was 208 W / mK. However, in Example 10, when the content of the vapor growth carbon fiber is 15 wt%, the thermal conductivity is about 350 W / mK. The fibrous carbon material used in the present invention is far superior to carbon fiber as a contained material in the composite material.

  The high thermal conductive composite material of the present invention can produce heat exchangers, heat sinks, fuel cell separators, etc. having excellent high thermal conductivity using metal powder such as aluminum alloy and stainless steel. An electrode material, a heating element, a wiring material, a heat exchanger, a fuel cell, and the like excellent in corrosion resistance and high temperature resistance characteristics can be manufactured using the body and ceramic powder.

FIG. 1A is a state photograph after rolling of an aluminum sintered body containing carbon nanotubes in a dispersed manner, and FIG. 1B is an enlarged electron micrograph of the 2 μm order of the structure after rolling. (A)-(d) is a state photograph figure which shows the test piece cutout location of four types of rolled metal materials of R2, R3, R4, and R5. (A)-(d) is a graph which shows the stress-strain relationship for every 4 types of rolling metal materials (no annealing) of R2, R3, R4, R5. (A)-(d) is a graph which shows the stress-strain relationship for every 4 types of rolling metal materials (with annealing) of R2, R3, R4, R5. Figure 5 A is an electron micrograph of a forced fracture surface of a carbon nanotube dispersed composite materials with a matrix of Al Miniumu, FIG. 5B is an enlarged electron micrograph of a forced fracture. FIG. 6 is an electron micrograph of aluminum particles before kneading and pulverization. FIG. 6A shows a scale on the order of 20 μm, and FIG. 6B shows an order of 10 μm. FIG. 7 is an electron micrograph of aluminum particles after kneading and pulverization, FIG. 7A is an enlarged electron micrograph of the order of 30 μm and FIG. 7B is an order of 10 μm of the recess shown in FIG. 7A. 8A is an enlarged electron micrograph of the order of 1 μm of the recess shown in FIG. 7A, and FIG. 8B is an enlarged electron micrograph of the order of 500 nm. 9A is an enlarged electron micrograph of the order of 10 μm of the smooth portion shown in FIG. 7A, and FIG. 9B is an enlarged electron micrograph of the order of 1 μm. FIG. 10 is an enlarged electron micrograph of the smooth portion shown in FIG. 7A on the order of 500 nm. FIG. 11A is an electron micrograph of a forced fracture surface of a carbon nanotube-dispersed composite material using titanium as a matrix, and FIG. 11B is an enlarged electron micrograph of the forced fracture surface. FIG. 12A is an electron micrograph of titanium particles before kneading and crushing, and FIG. 12B is an electron micrograph of titanium particles after kneading and crushing. 13A is an enlarged electron micrograph of the order of 1 μm on the surface of the titanium particles shown in FIG. 12B, and FIG. 13B is an enlarged electron micrograph of the order of 500 nm. 14A is an electron micrograph of a forced fracture surface of a carbon nanotube-dispersed composite material using copper as a matrix, and FIG. 14B is an enlarged electron micrograph of the forced fracture surface. FIG. 15 is an electron micrograph of copper particles before kneading and pulverization. FIG. 15A shows a scale on the order of 10 μm, and FIG. 15B shows an order of 50 μm. FIG. 16A is an enlarged electron micrograph of the order of 1 μm on the copper particle surface after kneading and pulverization, and FIG. 16B is an enlarged electron micrograph of the order of 500 nm. FIG. 17 is a graph showing the relationship between the carbon material content and the thermal conductivity in a composite material of aluminum and a carbon material in Examples and Reference Examples of the present invention .

Claims (12)

  A laminate in which a fibrous carbon material is present in a plurality of layers in a base material made of a metal powder, or a mixed powder of metal and ceramics, or a discharge plasma sintered body made of ceramic powder. Each layer of fibrous carbon material in the laminate has a single-layer or multiple-layer graphene tube with a graphene sheet rounded in a cylindrical shape, and the graphene sheet has a diameter of the graphene tube so as to surround the core in multiple layers. High-temperature heat-sensitive carbon fiber oriented sheet produced by solidifying a dispersion of vapor-grown carbon fibers laminated in a direction, and oriented in a direction parallel to the sheet surface. Conductive composite material.   The high heat transfer composite material according to claim 1, wherein the direction of the fibers in the vapor-grown carbon fiber oriented sheet is oriented in the same direction as the direction parallel to the sheet surface.   The highly heat-conductive composite material according to claim 1, wherein the base material is a processed material that has undergone plastic processing in the stacking direction together with the fibrous carbon material. The base material is a discharge plasma sintered body made of metal powder or a mixed powder of metal and ceramics , and the metal is one of aluminum, aluminum alloy, titanium, titanium alloy, copper, copper alloy, and stainless steel. The high thermal conductive composite material according to any one of claims 1 to 3, which is a seed or two or more kinds. The base material is a discharge plasma sintered body made of a mixed powder of metal and ceramic, or ceramic powder , and the ceramic is one or more of oxide, nitride, carbide, and boride. The high heat conductive composite material according to claim 1.   A step of alternately laminating a metal powder layer, or a mixed powder layer of metal powder and ceramic powder, or a ceramic powder layer, and a sheet made of a fibrous carbon material, and an obtained laminate The sheet is pressure-sintered in the stacking direction and sintered by discharge plasma. The sheet has a single-layered or multi-layered graphene tube in which the graphene sheet is rounded into a cylindrical shape, and surrounds the core in multiple layers. Is a sheet produced by solidifying a vapor-grown carbon fiber dispersion in which a graphene sheet is laminated in the radial direction of the graphene tube, and the fiber direction is oriented in a direction parallel to the sheet surface A method for producing a high thermal conductive composite material which is a grown carbon fiber oriented sheet.   The method for producing a high thermal conductive composite material according to claim 6, wherein the vapor-grown carbon fiber oriented sheet has a fiber direction parallel to the surface of the sheet and oriented in the same direction.   The manufacturing method of the high heat conductive composite material of Claim 6 or 7 including the process of plastically deforming the obtained discharge plasma sintered compact.   The method for producing a high thermal conductive composite material according to claim 8, wherein the plastic deformation is any one of cold rolling, warm rolling, and hot rolling.   The manufacturing method of the high heat conductive composite material of Claim 9 including the process of annealing after plastic deformation. In the step of alternately laminating the metal powder layer, or the mixed powder layer of the metal powder and the ceramic powder, or the ceramic powder layer and the sheet made of the fibrous carbon material, the metal powder layer, or A mixed powder layer of metal powder and ceramic powder and a sheet made of fibrous carbon material are alternately laminated, and the metal powder is pure aluminum, aluminum alloy, titanium, titanium alloy, copper, copper alloy. The method for producing a highly heat-conductive composite material according to any one of claims 6 to 10, which is one or more of stainless steels. In the process of alternately laminating the metal powder layer, or the mixed powder layer of the metal powder and the ceramic powder, or the ceramic powder layer and the sheet made of the fibrous carbon material, the metal powder and the ceramic powder The mixed powder layer of the body or the ceramic powder layer and the sheet composed of the fibrous carbon material are alternately laminated, and the ceramic powder is oxide, nitride, silicon carbide, titanium carbide, carbide, The method for producing a high thermal conductive composite material according to any one of claims 6 to 11, which is one or more of borides.