WO2005040067A1

WO2005040067A1 - Carbon nanotube-dispersed composite material, method for producing same and article same is applied to

Info

Publication number: WO2005040067A1
Application number: PCT/JP2004/016496
Authority: WO
Inventors: Kazuaki Katagiri; Atsushi Kakitsuji
Original assignee: Sumitomo Precision Products Co., Ltd.; Osaka Prefectural Government
Priority date: 2003-10-29
Filing date: 2004-10-29
Publication date: 2005-05-06
Also published as: JPWO2005040067A1; JP4593472B2

Abstract

Disclosed is a carbon nanotube-dispersed composite material which makes the best of excellent electrical conduction, thermal conduction and strength characteristics of a carbon nanotube while making good use of features of alumina which has corrosion resistance and heat resistance. Also disclosed is a method for producing such a carbon nanotube-dispersed composite material. Long-chain carbon nanotubes (including a carbon nanotube subjected to discharge plasma processing by itself in advance) and a sinterable alumina or aluminum powder are kneaded and dispersed using a ball mill, and then the resulting is compacted through discharge plasma sintering. Consequently, the carbon nanotubes spread inside the sintered body like a net, thereby enabling to make effective use of electrical conduction, thermal conduction and strength characteristics of the carbon nanotube together with the characteristics of the powder base.

Description

Specification

FIELD OF THE INVENTION

The present invention relates to a composite material that takes advantage of the characteristics of alumina ceramics having corrosion resistance and heat resistance, and has electrical conductivity, thermal conductivity, and excellent strength properties. TECHNICAL FIELD The present invention relates to a carbon nanotube-dispersed composite material dispersed in a sintered body of aluminum powder or aluminum alloy powder having high flexibility, a method for producing the composite material, and an applied product thereof. Background art

Today, composite materials having various functions using carbon nanotubes have been proposed. For example, carbon nanotubes with an average diameter of l to 45 nm and an average aspect ratio of 5 or more were produced using carbon fibers, metal-coated carbon fibers, and carbon fibers in order to produce molded articles that have excellent strength, moldability, and conductivity. It has been proposed that a carbon-containing resin composition in which a filler such as powder or glass fiber is kneaded and dispersed in a resin such as an epoxy resin or an unsaturated polyester resin is processed and molded (JP-A-2003-12939). I have.

In addition, in order to improve the thermal conductivity and tensile strength of the aluminum alloy material, at least one of Si, Mg, and Mn, which is a component of the aluminum alloy material, is combined with carbon nanofibers to form carbon nanofibers. An aluminum alloy material contained in an aluminum base material has been proposed. In this method, carbon nanofibers are mixed into a molten aluminum alloy material of 0.1 to 5 vol% and kneaded to form a billet, which is provided as an extruded material of an aluminum alloy material obtained by extruding the billet (Japanese Unexamined Patent Application Publication No. 363716). Furthermore, with the aim of providing highly conductive materials with excellent moldability that can be applied to separators for fuel cells, etc., metal compounds (borides: TiB ₂ , WB , MoB, CrB, A1B ₂ , MgB, carbide: WC, nitride: TiN, etc.) and a proper amount of carbon nanotubes to propose a resin molded product having both moldability and conductivity (Japanese Unexamined Patent Publication (Kokai) 2003-2003). 34751).

In addition, in order to improve electrical, thermal, and mechanical properties, carbon nanotubes are compounded in the matrix of organic polymers such as thermoplastic resins, curable resins, rubber, and thermoplastic elastomers. A composite molded article that is oriented in a magnetic field, aligned in a certain direction, and molded in a composite state has been proposed.To improve wettability and adhesion between carbon nanotubes and matrix materials, carbon It has been proposed that the surface of the nanotube be subjected to various treatments such as a degreasing treatment and a washing treatment in advance (Japanese Patent Application Laid-Open No. 2002-273741).

Field emitters containing carbon nanotubes include metal alloys of nanotube wetting elements such as indium, bismuth or lead, and relatively soft and ductile metal powders such as Ag, Au or Sn. Press-molding conductive material powder and carbon nanotubes, cutting and polishing, forming protruding nanotubes on the surface, etching the surface to form nanotube tips, then re-dissolving the metal surface and aligning the protruding nanotubes A method of manufacturing in a step of causing the same to be produced has been proposed (JP-A-2000-223004).

To realize various functions from multiple aspects and to optimize the functions, the ceramic composite nanostructure is to be composed of multiple polyvalent metal element oxides selected for a certain function. For example, it is proposed to select a manufacturing method in which different kinds of metal elements are bonded via oxygen, and to manufacture a columnar body having a short-axis cross section with a maximum diameter of 500 nm or less by various known methods (Japanese Patent Application Laid-Open 2003-238120).

The above-mentioned carbon nanotubes that are to be dispersed in a resin or an aluminum alloy are required in consideration of the manufacturability of the resulting composite material and the required formability. In addition, a material having a length as short as possible is used to improve dispersibility, and does not attempt to effectively utilize the excellent electrical and thermal conductivity characteristics of the carbon nanotube itself.

In addition, in the above-mentioned invention which utilizes the carbon nanotube itself, for example, it is possible to specialize in a specific and specific application like a field emitter, but it cannot be easily applied to other applications. On the other hand, in a method of manufacturing an oxide of a polyvalent metal element for a certain function and manufacturing a ceramic composite nanostructure composed of a specific columnar body, the purpose setting, selection of the element, and the probability of the manufacturing method are limited. It is inevitable that a lot of processes, trial and error are required. Disclosure of the invention

The present invention is a composite material which, for example, makes full use of the characteristics of alumina ceramics, which is insulative, but has corrosion resistance and heat resistance, or aluminum which is highly versatile, and which is provided with electrical conductivity and thermal conductivity. In addition to the properties of ceramics and metal powder substrates, carbon nanotubes themselves and carbon that make use of the excellent electrical and thermal conductivity and strength properties of their inherent long-chain or net-like structure The purpose is to provide a nanotube-dispersed composite material and a method for producing the same.

The present inventors, based on the development commission of the Japan Science and Technology Agency, have made effective use of the electric conductivity, heat conduction, and strength properties of carbon nanotubes in a composite material in which carbon nanotubes are dispersed in a base material. As a result of various studies on the available configurations, long-chain carbon nanotubes (including those obtained by treating only carbon nanotubes in advance with discharge plasma) were kneaded and dispersed in a ball mill with ceramics or metal powder that could be fired. By integrating by spark plasma sintering, the carbon nanotubes can be wrapped around the sintered body in a net-like manner. - That is, according to the present invention, long-chain carbon nanotubes are dispersed and integrated in a net-like manner in a discharge plasma sintered body composed of alumina powder or aluminum, which is an insulating ceramic, and its alloy powder. And a carbon nanotube-dispersed composite material having high thermal conductivity and high strength.

Further, the present invention provides a process for kneading and dispersing an alumina powder, an aluminum powder, or an aluminum alloy powder, and long-chain carbon nanotubes (including those in which only carbon nanotubes have been subjected to discharge plasma treatment) using a ball mill. Or further comprising a step of wet-dispersing the powder and the carbon nanotubes using a dispersant, and a step of subjecting the dried kneading and dispersing material to electric discharge plasma sintering. is there.

The composite material according to the present invention is characterized in that the base material is a sintered body of alumina powder having excellent corrosion resistance and heat resistance, or a sintered body of pure aluminum and aluminum alloy powder having excellent corrosion resistance and heat dissipation. The material itself is inherently corrosive and has excellent durability in high-temperature environments, and by dispersing long-chain carbon nanotubes uniformly, the excellent electrical properties of carbon nanotubes themselves The combination of conduction and heat conduction properties and strength can enhance required properties, synergistic effects, or exert new functions.

The composite material according to the present invention is a relatively simple manufacturing method in which alumina powder or aluminum powder or aluminum alloy powder and long-chain carbon nanotubes are kneaded and dispersed by a ball mill, and the dispersed material is spark plasma sintered. It can be manufactured and used as electrodes, heating elements, wiring materials, heat exchangers and heat sink materials with improved thermal conductivity, and brake parts under corrosion and high temperature environments. Brief Description of Drawings

Figure 1 is a graph showing the relationship between plasma sintering temperature and electrical conductivity. FIG. 2 is a graph showing the relationship between the sintering pressure and the electrical conductivity.

FIG. 3 is a schematic view of an electron micrograph of a carbon nanotube dispersed composite material using aluminum as a matrix according to the present invention.

FIG. 4 is a schematic view of an electron micrograph of a cocoon-shaped carbon nanotube according to the present invention.

FIG. 5 is a schematic diagram of an electron micrograph of a cocoon-shaped carbon nanotube according to the present invention.

FIG. 6 is a schematic diagram of an electron micrograph of the carbon nanotube dispersed composite material according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, alumina, which exhibits corrosion resistance and heat resistance, is employed, but the particle size of the powder may be determined in consideration of the sintering property capable of forming a required sintered body, or kneaded with carbon nanotubes. It is determined in consideration of the crushing ability at the time of dispersion, but it is preferably about ΙΟμπι or less, for example, it is possible to use several kinds of particle sizes, and it is preferably 5μπι or less, more preferably Ιμπι or less. In addition to the spheres, fibrous, amorphous and various types of powders can be used as appropriate.

In the present invention, pure aluminum, an aluminum alloy such as JIS, which exhibits the required functions such as corrosion resistance, thermal conductivity, heat resistance, etc., is employed. A particle size of about 200 μπι or less, more preferably 150 μπι or less, which has a sintering property capable of forming a carbon nanotube and a crushing ability at the time of kneading and dispersing with carbon nanotubes, is preferable. 150μπι is preferred. In addition to the spheres, fibrous, amorphous, tree-like or various forms of powder can be used as appropriate.

In the present invention, the long-chain carbon nanotubes used are literally carbon nanotubes connected to form a long chain, and these are not entangled. Those which form a lump like a cocoon, or those having a cocoon or net-like form obtained by discharge plasma treatment of only carbon nanotubes are used. In addition, the structure of the carbon nanotube itself can be either single-walled or multi-walled. In the composite material according to the present invention, the content of carbon nanotubes is not particularly limited as long as a sintered body having a required shape and strength can be formed. By selecting as appropriate, for example, by weight ratio

90 wt% or less can be contained. In particular, when aiming for the homogeneity of the composite material, it is necessary to devise a kneading and dispersing method by reducing the content of carbon nanotubes to, for example, 3 wt% or less and about 0.05 wt%.

The method for producing a carbon nanotube-dispersed composite material according to the present invention comprises:

(P) a step of subjecting the long-chain carbon nanotubes to discharge plasma treatment,

(1) a step of kneading and dispersing a ceramic powder or a metal powder or a mixed powder of a ceramic and a metal, and a long-chain carbon nanotube in a ball mill;

(2) a step of wet-dispersing the powder and carbon nanotubes using a dispersant,

(3) a process of subjecting the dried kneading and dispersing material to electric discharge plasma sintering, including (1) (3), (P) (l) (3), (1) (2) (3), There are steps (P), (1), (2) and (3).

In the step of kneading and dispersing with a ball mill, it is important to disintegrate and disintegrate the long-chain carbon nanotubes in alumina powder, aluminum powder or aluminum alloy powder. For kneading and dispersing, various known mills, crushers and shakers for pulverizing, crushing and disintegrating can be appropriately employed, and the mechanism is also a rotary shock type, a rotary shear type, a rotary shock shear type, and a medium stirring. A well-known mechanism such as a stirring type, a stirring type, a stirring type without a stirring blade, and an air-flow crushing type can be appropriately used. In particular, a ball mill, such as a known horizontal mill, planetary mill, or stirring mill, can be used even if it has a misaligned structure as long as it is configured to pulverize and break using media such as balls. Also, the material and particle size of the media can be appropriately selected. In the wet dispersing step, a known nonionic dispersant and a cationic anionic dispersant can be added and dispersed by using an ultrasonic wave or a ball mill, thereby shortening the dry dispersion time and increasing the efficiency. Can be achieved. 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.

In the process of spark plasma sintering (processing), a dry kneading and dispersing material is loaded between a die made of Rybon and a punch, and a DC pulse current is applied while pressurizing the upper and lower punches, so that the die, punch, And a method in which Joule heat is generated in the material to be processed and the kneading and dispersing material is sintered.Discharge plasma is generated between the powder and the powder or carbon nanotubes by passing a pulse current, Re-sintering proceeds smoothly due to actions such as activation of the nanotube surface due to disappearance of impurities. In the present invention, the spark plasma sintering is preferably performed at a temperature lower than the normal sintering temperature of the ceramic powder or metal powder to be used. In addition, it is preferable to set conditions so that a relatively low pressure and a low temperature treatment are not required during sintering without requiring a particularly high pressure. Further, in the step of spark plasma sintering of the kneading and dispersing material, it is also preferable to have two steps of first performing low-temperature plasma discharge under low pressure and then performing low-temperature discharge plasma sintering under high pressure.

The composite material according to the present invention can be manufactured by the above-described relatively simple manufacturing method, and is provided with electrodes, heating elements, wiring materials, heat exchangers and heat sink materials with improved thermal conductivity, and brakes under corrosion, high temperature environment. Although it can be applied as a part, it is possible to obtain a thermal conductivity of 600 W / mK or more, as shown in the examples. It can be easily fired into a shape and is ideal for heat exchanger applications. Example

Example 1

Alumina powder having an average particle diameter of 06 μπι and long-chain carbon nanotubes were dispersed in a ball mill using an alumina bowl and balls. First, 5 wt% of carbon nanotubes were blended, alumina powder which had been sufficiently dispersed in advance was blended, and these powders were kneaded and dispersed in a dry state for 96 hours.

Furthermore, a nonionic surfactant (Triton X-100, lwt%) was added as a dispersant, and the mixture was wet-dispersed by applying ultrasonic waves for 2 hours or more. The resulting slurry was filtered and dried.

The dried kneading and dispersing material is loaded into a die of a discharge plasma sintering apparatus,

Plasma solidification was performed at 1300 ° C to 1500 ° C for 5 minutes. At that time, the heating rate is

The temperature was set to 100 ° C / Min and 230 ° C / Min, and a pressure of 15 to 40 MPa was continuously applied. The electrical conductivity of the obtained composite material was measured, and the results shown in FIGS. 1 and 2 were obtained.

Example 2

In the kneading and disintegration of pure aluminum powder with an average particle diameter of 30μπι and 0.25 wt% of long-chain carbon nanotubes, only carbon nanotubes were previously loaded into the die of the discharge plasma sintering device. , A plasma mill for 5 minutes at 800 ° C, and a planetary mill using a stainless steel container.The rotation of the container and various time units of 3 hours or less in a dry state without using dispersing media. The combined kneading and dispersion was performed.

The kneading and dispersing material was loaded into a die of a discharge plasma sintering apparatus, and discharge plasma sintering was performed at 575 ° C for 60 minutes. At that time, the heating rate was 100 ° C / Min, and the pressure of 60 MPa was continuously applied.

Fig. 3 shows an electron micrograph of the forced fracture surface of the obtained composite material. Fig. 4 shows an electron micrograph of the reticulated carbon nanotube when the scale of Fig. 3 with the scale of the order of ΙΟΟμπι is enlarged to the order of 5.0μπι. As a result of measuring the thermal conductivity of the obtained composite material, it was 221 W / mK. The thermal conductivity of the solidified body obtained by spark plasma sintering of pure aluminum powder alone under the above conditions is 194 W / mK, and the thermal conductivity of the composite material according to the present invention is about 14% higher. You can see that it has risen.

Example 3

A pure aluminum powder with an average particle size of ΙΟΟμιη, or an aluminum alloy powder with an average particle size of ΙΟΟμπι (equivalent to a forging alloy), and a 10 wt% long-chain carbon nanotube are placed in a stainless steel bowl and chrome iron In a ball mill using a ball, a nonionic surfactant (Triton X-100, lwt%) was added as a dispersing agent, and the mixture was kneaded and dispersed for at least 100 hours in a wet state.

The kneading and dispersing material was loaded into a die of a discharge plasma sintering apparatus, and discharge plasma sintering was performed at 1400 ° C for 5 minutes. At that time, the heating rate was 250 ° C / Min, and the pressure of lOMPa was continuously applied. The thermal conductivity of the obtained composite material was measured to be 400 to 600 W / mK.

Example 4

Only carbon nanotubes were pre-loaded into the die of the discharge plasma sintering apparatus and were subjected to discharge plasma treatment at 1400 ° C for 5 minutes. Fig. 5 shows an electron micrograph of the obtained cocoon-shaped nanotube.

The alumina powder having an average particle size of 05 μιη and the carbon nanotubes were dispersed by a ball mill using an alumina bowl and balls. First, 5 wt% of carbon nanotubes were blended, and then sufficiently dispersed alumina powder was blended and kneaded and dispersed in a dry state for 96 hours. Further, the same ultrasonic wet dispersion as in Example 1 was performed. The resulting slurry was filtered and dried.

The dried kneading and dispersing material was loaded into a die of a discharge plasma sintering apparatus, and was plasma-solidified at 1400 ° C for 5 minutes. At that time, the heating rate was 200 ° C / Min, Then, a pressure of 30 MPa was applied. The electric conductivity of the obtained composite material was in the same range as in Example 1. FIG. 6 shows an electron micrograph of the obtained composite material.

Industrial applicability

The carbon nanotube-dispersed composite material according to the present invention can produce, for example, an electrode material, a heating element, a wiring material, a heat exchanger, and the like having excellent corrosion resistance and high temperature resistance using ceramic powder. . Further, a heat exchanger, a heat sink, and the like having excellent high thermal conductivity can be manufactured by using ceramic powder and aluminum alloy powder.

Claims

The scope of the claims

1. A carbon nanotube-dispersed composite material in which long-chain carbon nanotubes are dispersed and integrated in a net-like manner in a discharge plasma sintered body made of alumina powder.

2. Carbon nanotube-dispersed composite material that is integrated into a discharge plasma sintered compact made of aluminum powder or aluminum alloy powder in the form of a long chain force-bon nanotube force network.

3. The carbon nanotube-dispersed composite according to claim 1, wherein the average particle size of the alumina powder is ΙΟμια or less, or the average particle size of the aluminum powder or the aluminum alloy powder is 200μιη or less.

4. The carbon nanotube dispersed composite material according to claim 1 or 2, wherein the carbon nanotubes are contained in a weight ratio of 90 wt% or less.

5. A process for kneading and dispersing alumina powder, aluminum powder, or aluminum alloy powder, and long-chain carbon nanotubes of 10 wt% or less by a ball mill, and a process of discharge plasma sintering the dispersing material. A method for producing a tube-dispersed composite material.

6. A process of kneading and dispersing alumina powder, aluminum powder or aluminum alloy powder and 10 wt% or less of long-chain carbon nanotubes previously subjected to discharge plasma treatment in a ball mill, and a process of discharge plasma sintering the dispersing material. A method for producing a carbon nanotube-dispersed composite material comprising:

7. A step of kneading and dispersing alumina powder, aluminum powder or aluminum alloy powder and long-chain carbon nanotubes in a ball mill, and wet-dispersing the powder and carbon nanotubes using a dispersant. And subjecting the dried kneading and dispersing material to spark plasma sintering.

8. A step of kneading and dispersing alumina powder, aluminum powder or aluminum alloy powder, and long-chain carbon nanotubes previously subjected to discharge plasma treatment with a ball mill, and using a dispersant to disperse the powder and carbon nanotubes. And a step of subjecting the dried kneading / dispersing material to spark plasma sintering.

9. The step of spark plasma sintering of the kneading and dispersing material is a two-step process of performing low-temperature plasma discharge under low pressure and then performing low-temperature discharge plasma sintering under high pressure. Or a method for producing a carbon nanotube-dispersed composite material.

10. A heat exchanger formed of a carbon nanotube-dispersed composite material in which long-chain carbon nanotubes are dispersed and integrated in a net-like manner in a discharge plasma sintered body made of alumina powder.

11. A heat exchanger formed of a carbon nanotube dispersion composite material in which long-chain carbon nanotubes are dispersed and integrated in a net-like manner in a discharge plasma sintered body made of aluminum powder or aluminum alloy powder.