WO2008004386A1

WO2008004386A1 - Highly functional composite material and method for producing the same

Info

Publication number: WO2008004386A1
Application number: PCT/JP2007/060962
Authority: WO
Inventors: Mamoru Omori; Toshiyuki Hashida; Hisamichi Kimura; Akira Okubo; Akihisa Inoue
Original assignee: Tohoku University
Priority date: 2006-06-05
Filing date: 2007-05-30
Publication date: 2008-01-10
Also published as: JPWO2008004386A1; JP5366193B2

Abstract

Disclosed is a novel highly functional composite material which is excellent in mechanical performance, electrical conductivity and electromagnetic wave absorption. Also disclosed is a method for producing such a highly functional composite material. Specifically disclosed is a highly functional composite material comprising a ceramic polycrystalline body composed of a plurality of first alumina-magnesia ceramic crystals, and a nanocomposite body (1) having a structure wherein a plurality of carbon nanotubes (2) and a plurality of crystals of a second alumina-magnesia ceramic (3) are intertwined with each other. The nanocomposite body (1) is dispersed in the ceramic polycrystalline body. The total composition of the highly functional composite material containing the ceramic polycrystalline body and the nanocomposite body (1) is composed of 0.1-90 mass% of the carbon nanotubes and 99.9-10 mass% of the alumina-magnesia ceramics. The alumina-magnesia ceramics are composed of 99.8-0.5 mass% of alumina and 0.2-99.5 mass% of magnesia.

Description

Specification

High performance composite material and manufacturing method thereof

Technical field

[0001] The present invention is a composite material composed of alumina magnesia ceramics composed of alumina and magnesia, which are important as practical ceramics, and carbon nanotubes. By combining carbon nanotubes with ceramics, The present invention relates to a high-performance composite material that improves the performance of conventional ceramics and has a new function, and a method for producing the same.

Background art

[0002] Ceramics made from alumina magnesia are used in a wide range of industries because of their low price. These ceramics are superior in heat resistance and oxidation resistance compared to metals. In addition, since it is insulative and does not conduct electricity, it is dielectric, so that it can absorb electromagnetic waves with a small amount. Alumina magnesia and its compounds have excellent corrosion resistance. These ceramics lack reliability as materials with lower toughness than metals, and are easily destroyed by the application of stress. Therefore, if the toughness can be increased, the range of application will be greatly expanded, and if a composite material imparted with electrical conductivity such as metal or a composite material with excellent electromagnetic wave absorption performance is developed, conventional ceramics will be developed. Use beyond the scope of use of tus.

[0003] Carbon nanotubes are a material discovered in 1991 (see, for example, Non-Patent Document 1). This material is a nanofiber having a fine tube structure with a large aspect ratio. The chemical properties are almost similar to graphite materials. Carbon nanotubes have much higher strength and elastic modulus than other materials. Multi-walled carbon nanotubes have an elastic modulus of 18 OOGPa (see Non-Patent Document 2, for example), and single-walled carbon nanotubes have a strength of 45 GPa. It is reported that there is (for example, non-patent document 3)!

[0004] As one of the development of materials utilizing the mechanical strength characteristics of carbon nanotubes, development of composite materials using carbon nanotubes or materials obtained by solidifying them has been actively conducted. In these composite materials, the synthesis is at or near room temperature. When it is carried out at a high temperature, that is, when a carbon nanotube force composite material is synthesized using a polymer, no major problem occurs. However, when using metals or ceramics, the synthesis is performed at high temperatures, so the residual stress caused by the difference in thermal expansion between the two materials becomes a problem. Carbon nanotubes hardly expand even when the temperature is raised (see Non-Patent Document 4, for example). In contrast, the thermal expansion coefficient of the metal or ceramics carbon nanotubes and Ru is complexed is, 4x10- ^⁶ / K~20χ10- ⁶ / Κ and the carbon nanotube fairly large instrument other Me A between these materials A large residual stress is generated. Unless a material with a small residual stress is made, it cannot be applied to practical industrial materials. In addition, acicular carbon nanotubes are more difficult to disperse uniformly in the matrix than fine particles, especially when the proportion of carbon nanotubes increases, this uniform dispersion becomes difficult! Excellent composite material is manufactured! / ,!

[0005] The synthesis of a composite material of a carbon nanotube and an alumina-magnesia ceramic has been performed for an alumina single body and a magnesia single body. The main method is to mix carbon nanotubes and alumina powder and sinter them using them as raw materials. The particle size of the alumina powder used as the starting material in this method is 200 nanometers or more, and usually becomes larger than 1000 nanometers after sintering. Carbon nanotubes are dispersed within the alumina crystal grains or at the grain boundaries. Even in such a dispersed state, it has been reported that the toughness value of alumina-single-walled carbon nanotube composites increased by a factor of 3 compared to the single-walled carbon nanotube when 10 vol% of single-walled carbon nanotubes were added (for example, Non-patent document 5). In subsequent studies, it has been proved that this improvement in toughness is wrong, and the toughness of this alumina single-walled carbon nanotube composite is almost the same as that of alumina alone (for example, Non-Patent Document 6). reference). As an example of improved mechanical properties, the toughness value of a composite material obtained by mixing alumina fine powder and 10 vol% multi-walled carbon nanotubes is 24% higher than that of alumina alone. (For example, see Non-Patent Document 7).

[0006] With the same technique using alumina powder, there is a material development aimed at reducing the electrical resistance value of alumina (see, for example, Patent Document 1). Here, with the addition of 0 · 1νο1% carbon nanotubes, the electrical resistance decreases to the order of 10 ¹³ to 10 ⁶ (Ω 'cm). With alumina powder As a different raw material, butoxy aluminum (A1 (CH)) is used as the precursor of alumina,

4 9 3

This is dissolved in alcohol, mixed with multi-walled carbon nanotubes, water is added to hydrolyze butoxyaluminum, dried, and calcined at 1250 ° C in a non-oxidizing atmosphere. The mixed powder is made and sintered. The particle size of alumina in the obtained mixed powder has grown to 500 nanometers or more, and the particle size of alumina in the composite material obtained by sintering it has increased to 1000 nanometers or more. The carbon nanotubes are dispersed in the alumina grains and, at the same time, lump together and exist at the grain boundaries. The toughness of this composite material is maximized with the addition of 1.5 vol% carbon nanotubes, and is only 1.1 times greater than that of alumina alone (see Non-Patent Document 8, for example).

[0007] In the method described above, it is difficult to control the alumina crystals in the composite material having a large crystal diameter of the powder as the starting material to 500 nanometers or less. The production of single nanocomposites from alumina and magnesia has also been reported (see, for example, Patent Document 2). There, alumina and magnesia powder are used alone as raw materials. In order to manufacture a nanocomposite material without crystal growth by this method, it is necessary to strictly control the manufacturing conditions, and the increase in manufacturing cost is inevitable. There are references to aluminum hydroxide regarding the use of raw materials other than alumina powder. (For example, see Patent Document 3). However, it is difficult to manufacture high-performance composite materials because the crystal diameter of alumina grows larger than 20 micrometers and the strength is greatly reduced due to the composite materials obtained from pure aluminum hydroxide. It is.

[0008] thermal expansion coefficient of alumina is 8x10- ⁶ / K, the thermal expansion coefficient of the spinel (A1 0 .MgO) 11χ10_ ⁶

twenty three

/ K, the thermal expansion coefficient of the magnesia is 13x10- ⁶ / Κ. When the carbon nanotubes are present in the alumina magnesia ceramic polycrystal, which has a larger coefficient of thermal expansion than that of the carbon nanotubes, the alumina-magnesia ceramic shrinks during the cooling from the sintering temperature to room temperature, and the carbon Nanotubes do not shrink, generating large residual stresses, reducing the toughness and strength of the composite material, making it difficult to apply as a practical material. In addition, carbon nanotubes that exist at the grain boundaries of alumina magnesia ceramics have a small function to prevent the development of fracture cracks. As seen in the nanotube-alumina composite report, toughness and strength have not increased. The reason for this is that when ceramic powder and carbon nanotubes are mixed in a slurry state to produce a composite material, the carbon nanotubes condense and the ceramic powder raw material enters the carbon nanotube condensate. This is because carbon nanotubes are present in a lump in the resulting composite material.

Non-Patent Document 1: S. Iijima, "Helical Microtubules of Graphite Carbon", Nature, 1991, 3 54, p.56-58

Non-Patent Document 2: MMJ Treacy and TW Ebbesen, "Exceptionally High Young's Modulus Observed for Individual Carbon Nanobtubes, Nature, 1996, 381, p.678-680 Non-Patent Document 3: DA Walters, M. Ericso, J Casavant, J. Liu, DT Colbert,. A. Smith and RE Smalley, "Elastic Strain of Freely Suspended Single-Walled Arbon Nanotube Ropes", Appl. Phy. Lett., 1999, 74, 25, p.3803- 3805

Non-Patent Document 4: Y. Maniwa, R. Fujiwara, H. Kira, H. Tou, H. Kataura, S. Suzuki, Y. A chiba, E. Nishibori, M. Takata, M. Sakata, A. Fujiwara and H. Suematsu, Thermal Expansion of single-Walled Carbon Nanotube (SWNT) Bundles: X-ray Diffraction Studies ", Phys. Rev. B, 2001, 64, p.241402-1-3

Non-Patent Document 5: G. -D. Zhan, JD untz, J. Wan and A.. Mukherjee, "Single-Wall Carbon Nanotubes as Attractive Toughening Agents in Alumina-Based Nanocompo sites", Nature Mater., 2003, 2, p.38-42

Non-Patent Document 6: X. Wang, NP Padture and H. Tanaka, "Contact-Damage-Resistanc e Ceramic / Single-Wall Carbon Nanotubes and Ceramic / Graphite Composites, Nature Mater., 2004, 3, p.539-544

Non-Patent Document 7: RW Siegel, S.. Chang, BJ Ash, J. Stone, PM Ajayan, RW Doremus and LS Schadler, Mechanical Behavior of Polymer and Ceramics Matrix Nanocomposites ", Scripta Mater., 2001, 44, p.2061 -2064

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-244273

Non-Patent Document 8: CB Mo, SI Cha,. T. Kim,. Η. Lee and SH Hong, "Fabricat ion of Carbon Nanotube Reinforced Alumina Matrix Nanocomposite by Sol-Gel Proc ess ", Mater. Sci. Eng., 2005, A 395, p.124-128

Patent Document 2: Japanese Translation of Special Publication 2004 507434

Patent Document 3: Japanese Patent Publication No. 2004-256382

Disclosure of the invention

Problems to be solved by the invention

[0010] With the conventional techniques as described above, it is impossible to produce a high-performance composite material that exhibits excellent mechanical and electrical characteristics by adding carbon nanotubes to ceramics. There was a problem.

The present invention has been made paying attention to such problems, and provides a novel high-functional composite material excellent in mechanical performance, electrical conductivity and electromagnetic wave absorption, and a method for producing the same. It is aimed.

Means for solving the problem

[0012] In order to achieve the above object, a highly functional composite material according to the present invention includes a ceramic polycrystalline body composed of a plurality of first alumina-magnesia ceramic crystals, a plurality of carbon nanotubes, and a plurality of second nanotubes. A nanocomposite having a structure in which alumina magnesia-based ceramic crystals are intertwined, and the nanocomposite is dispersed inside the ceramic polycrystal.

[0013] The present inventors have intensively studied the effect of carbon nanotubes on the crystal growth of alumina magnesia ceramics and their dispersibility. As a result, they discovered a method by which carbon nanotubes can prevent the crystal nuclei of alumina-magnesia ceramics from growing into large crystals and greatly improve their dispersibility. In other words, when precursors (aluminum hydroxide and magnesium hydroxide) that produce alumina magnesia ceramic crystals are used as the starting material, dispersion in the composite material of carbon nanotubes is improved, and only carbon nanotubes exist as lumps. As a result, the crystal growth of the second alumina magnesia-based ceramics can be suppressed to a nano size of 200 nanometers or less. As a result, an intertwined nanocomposite structure is formed, in which a plurality of nanoalumina-magnesia ceramic crystals are bonded in a form that bridges carbon nanotubes.

Yes [0014] When the nanoceramic crystal in the nanocomposite shrinks, the carbon nanotubes that are intertwined with the crystal can be deformed, so that the residual stress generated in the composite material is reduced, and the toughness and strength of the entire composite material are reduced. It can be improved. On the other hand, in a composite material obtained from a single aluminum hydroxide and a single magnesium hydroxide, the ceramic crystal grows larger than 20 micrometers and the strength of the composite material is significantly reduced. Since the ceramic phase of the alumina-magnesia ceramic composite is not a single phase, the crystal phase of the ceramic phase is prevented by the influence of the mixed spinel phase, and does not grow larger than 20 micrometers. Even below a few micrometers. Therefore, the dispersibility is improved, and the addition of a small amount of carbon nanotubes has been found to improve mechanical properties, electrical conductivity, and electromagnetic wave absorption, and the present invention relating to a highly functional composite material and a method for producing the same is completed. It came to.

[0015] The high-functional composite material according to the present invention has a structure in which an alumina magnesia-based ceramic crystal is reinforced with a single bon nanotube. For this reason, a nanocomposite having a structure in which a plurality of carbon nanotubes and a plurality of second alumina magnesia-based ceramic crystals are intertwined forms a composite material having high toughness and strength. Since this nanocomposite force is dispersed inside a ceramic polycrystal composed of a plurality of first alumina-magnesia ceramic crystals, it has excellent mechanical performance with greater toughness and strength.

[0016] The highly functional composite material according to the present invention is excellent in wear resistance due to the characteristics of carbon nanotubes as graphite, and has a small coefficient of friction. In addition, because carbon nanotubes are formed by converting insulating alumina magnesia ceramics into conductive composite materials, the electrical resistance varies widely and is excellent in electrical conductivity and electromagnetic wave absorption. . High-performance composite materials according to the present invention, it is preferable coefficient of friction from 0.07 to 0.35, the electric resistance is ^{^{10 _ 2 ~10 7 Ω 'cm}} . Since inexpensive alumina magnesia ceramics is used as a raw material, it can be manufactured at low cost. Carbon nanotube is a general term for single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon nanotubes, and carbon nanorods.

[0017] The high-functional composite material according to the present invention, the second alumina magnesia-based ceramics The crystal preferably has a grain size that is an order of magnitude smaller than the drain size of the first alumina magnesia ceramic crystal. In particular, the second alumina-magnesia ceramic crystal preferably has a grain size smaller than 200 nm. Furthermore, it is preferable that the nanocomposite is larger than the grain size of the first alumina-magnesia ceramic crystal. The carbon nanotubes preferably have an average length longer than lOOOnm and an average thickness thinner than lOOnm.

In these cases, particularly excellent mechanical performance, electrical conductivity, and electromagnetic wave absorption are provided. In particular, when the grain size of the second alumina-magnesia ceramic crystal is smaller than 200 nm, a nanocomposite in which carbon nanotubes longer than lOOOnm are bonded in a form that bridges a plurality of second alumina-magnesia ceramic crystals is formed. The When the second alumina magnesia-based ceramic crystal in this nanocomposite is cooled and contracted, the entangled carbon nanotubes can be deformed, so that the residual stress generated is smaller compared to the case where the carbon nanotubes cannot be deformed. Toughness and strength can be improved.

[0019] The high-functional composite material according to the present invention preferably contains 4 to 85 mass% of carbon nanotubes, 0.2 to 95 mass% of alumina, and 1 to 27 mass% of magnesia. In this case, it has particularly excellent electrical conductivity and electromagnetic wave absorption.

[0020] In the high-functional composite material according to the present invention, the carbon nanotube is one or more of a single-walled carbon nanotube, a double-walled carbon nanotube, a multi-walled carbon nanotube, an amorphous carbon nanotube, and a carbon nanorod. It is preferable to consist of a mixture of In this case, even if one or a mixture of two or more of these is used, the effect on improving mechanical performance, electrical conductivity and electromagnetic wave absorption is not changed! /.

[0021] The high-functional composite material according to the present invention comprises a sintered body containing carbon nanotubes 0.1 to 90 mass% and alumina magnesia ceramics 99.9 to 10 mass%, and the alumina-magnesia ceramics is alumina 99.8 to 0.5 masss. % And magnesia 0.2 to 99.5 mass%, and the carbon nanotube and the alumina magnesia ceramic nanocrystals may be intertwined as a constituent element. Also in this case, it has particularly excellent mechanical performance, electrical conductivity, and electromagnetic wave absorption. [0022] The method for producing high-performance composite material according to the present invention, placed in a carbon nanotube 0. l~90ma _SS% and alumina magnesia-based ceramics 99.9～10Mass% solvent water or an alcohol, in the slurry 3 After mixing for ˜180 minutes and removing the solvent from this mixture, sintering is performed in a non-oxidizing atmosphere at a temperature range of 1050 ° C. to 1800 ° C. for 5 minutes to 5 hours. .

[0023] According to the method for producing a highly functional composite material according to the present invention, the highly functional composite material according to the present invention having excellent mechanical performance, electrical conductivity, and electromagnetic wave absorption can be produced. For mixing the slurry, it is preferable to use a rotation / revolution supermixer capable of uniform mixing without destroying the carbon nanotubes.

[0024] The method for producing a high-performance composite material according to the present invention comprises adding 0.3 to 70 ma _SS % of carbon nanotubes and 99.7 to 30 mass% of alumina magnesia ceramic in water or an alcohol solvent to form a slurry. After mixing for 5 minutes and removing the solvent from the mixture, the mixture may be sintered in a non-oxidizing atmosphere at a temperature range of 1050 ° C. to 1800 ° C. for 5 minutes to 5 hours. Further, in the method for producing a high-performance composite material according to the present invention, the alumina magnesia-based ceramics comprises 99.8 to 0.5 mass% aluminum hydroxide (Al (OH)) in terms of alumina and 0.2 to 0.2 in terms of magnesia. It preferably contains 99.5 mass% magnesium hydroxide (Mg (OH) 3). In these cases, a highly functional composite material having particularly excellent mechanical performance, electrical conductivity, and electromagnetic wave absorption can be produced.

[0025] In the method for producing a highly functional composite material according to the present invention, as a pretreatment for performing the sintering, the solvent is removed from the mixture and then in a non-oxidizing atmosphere at 300 ° C to 900 ° C. It is preferable to perform calcining for 5 to 60 minutes in the temperature range of C for dehydration. In this case, the temperature can be raised quickly during sintering, and moisture can be prevented from adhering to the sintering furnace.

[0026] In the method for producing a highly functional composite material according to the present invention, the sintering is preferably performed by a pressureless sintering method, a hot press method, or a discharge plasma sintering method. For sintering, the force S, which is basically possible with the pressureless sintering method, when the amount of carbon nanotubes is larger than the amount of alumina-magnesia ceramics, use a pressure sintering machine. Densification becomes easy. As a pressure sintering machine, a hot press (HP) or a spark plasma sintering machine (SP S) can be used. The invention's effect

[0027] According to the present invention, it is possible to provide a novel high-performance composite material excellent in mechanical performance, electrical conductivity, and electromagnetic wave absorption, and a method for producing the same.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the best mode for carrying out the present invention will be described in detail. The highly functional composite material according to the embodiment of the present invention is manufactured by the method for manufacturing a highly functional composite material according to the embodiment of the present invention.

Alumina is industrially produced by the buyer method. That is, when the raw material bauxite is heat-treated with a sodium hydroxide solution to form a sodium aluminate solution, which is diluted and then added with aluminum hydroxide seed crystals, aluminum hydroxide is precipitated. This aluminum hydroxide is calcined at 1200 ° C or higher to produce alumina powder. Thus, aluminum hydroxide is a precursor for alumina and is less expensive than alumina. This aluminum hydroxide begins to decompose at 276 ° C and ends at 375 ° C, producing nuclei of alumina crystals. This nucleus crystal growth becomes prominent above 1000 ° C.

[0029] Magnesium hydroxide used in the method for producing a highly functional composite material according to the embodiment of the present invention is the starting material for most of magnesia's industrial raw materials in Japan. By adding Ca (OH) to seawater, it can be obtained by precipitating magnesium hydroxide, and if the magnesium hydroxide is calcined at 900 ° C., magnesia can be generated. This magnesium hydroxide can decompose at about 490 ° C to generate nuclei of magnesia crystals.

[0030] The alumina-magnesia ceramics of the high-functional composite material and the manufacturing method thereof according to the embodiment of the present invention do not include alumina alone and magnesia alone. When a composite material is synthesized from aluminum hydroxide and carbon nanotubes, the alumina grows to a particle size of 20 micrometers or more during sintering. In the course of the grain growth, carbon nanotubes aggregate and aggregate to form a lump, resulting in poor dispersibility, and the mechanical and electrical performance of the resulting composite material is significantly reduced. The growth of this crystal grain is the same for magnesia alone, and in a composite material using magnesium hydroxide alone, magnesia crystals grow to 20 micrometers or more. [0031] Carbon nanotubes used in the high-performance composite material and the manufacturing method thereof according to the embodiment of the present invention are mainly made by an arc discharge method, a laser evaporation method, a plasma synthesis method, and a hydrocarbon catalyst decomposition method. . Carbon nanotubes produced by these methods include single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon nanotubes, and carbon nanotubes called carbon nanorods with small or little hollow portions. Exists. Because the synthesis is easier when metals such as Fe, Co, Ni, and Ce are used as catalysts, these metals coexist in many carbon nanotube products. However, since these metal catalysts can be removed by washing with an acid, there is no problem in use. In addition to these metal impurities, impurity carbon such as amorphous carbon and fullerene is often mixed. However, even if these impurities are mixed, if the ratio is 50% by weight or less, the performance of the composite material will not be significantly reduced even if it is used as a raw material compared to when pure carbon nanotubes are used. However, for the production of nanocomposites, it is advantageous that the proportion of carbon nanotubes is large. The mechanical properties of these five types of carbon nanotubes do not change even if they are used alone or in combination.

[0032] In the method for producing a highly functional composite material according to the embodiment of the present invention, aluminum hydroxide that is a precursor of alumina and magnesium hydroxide that is also a magnesia precursor are used. Aluminum hydroxide decomposes at 400 ° C or lower to produce alumina crystal nuclei, and grows as the heating temperature is increased, and becomes a powder that is commercially available as alumina powder by treatment at 1200 ° C or higher. Become. Magnesium hydroxide decomposes below 500 ° C to produce magnesia crystal nuclei and is fired at 900 ° C for use as magnesia. When composite materials are manufactured from these single bodies, the alumina and magnesia crystals of the composite materials grow to a size of 20 m or more. When carbon nanotubes, magnesia, and alumina coexist, growth of alumina, magnesia, and spinel crystal nuclei is suppressed, and even when heated above the sintering temperature of the composite material, alumina, spinel, and magnesia crystals It does not grow as large as 200 nanometers and remains in the nanocrystalline state. Since carbon nanotubes have a length of 1000 nanometers or more, they form a structure in an intertwined state by bridging multiple nano alumina crystals, nano magnesia crystals, and nano spinel crystals. like this The structure of nano-alumina magnesia-based ceramics and carbon nanotubes is a nanocomposite, and the present inventors have discovered it for the first time. If the carbon nanotubes are small relative to the amount of alumina-magnesia ceramics, the nanocomposite forms a structure dispersed in islands in a polycrystalline matrix of alumina-magnesia ceramics. Since the alumina-magnesia ceramic used as the matrix is not pure alumina or magnesia, it does not grow larger than 20 micrometers, but at most several micrometers.

[0033] The strength and toughness of the composite material depend on the magnitude of the residual stress. In general, as residual stress increases, strength and toughness decrease. The reason is that the residual stress can be relaxed by the occurrence of cracks. In general ceramic polycrystals, when the residual stress is relatively low, the grain boundary strength is weakened mainly, and the effect of improving toughness by deflection of cracks can be expected, and the possibility of improving strength and toughness is also possible. is there. The difference in thermal expansion between carbon nanotubes and alumina magnesia ceramics is large. When carbon nanotubes are uniformly dispersed, large compressive stress acts on the carbon nanotubes from the matrix alumina magnesia ceramics. Even if there is little, large residual stress is generated in the composite material. As a result, as the added amount of carbon nanotubes increases, cracks are likely to occur in the composite material, and when the amount of carbon nanotubes increases, the composite material cannot be manufactured due to the occurrence of cracks.

[0034] However, in the high-performance composite material according to the embodiment of the present invention, the nanocomposite is a structure in which the nanocomposite is dispersed in the alumina-magnesia ceramic, even when the proportion of the carbon nanotube is small, and the carbon nanotube is a matrix. It is not in a state of being uniformly dispersed. As shown in FIG. 1, the carbon nanotubes 2 in the nanocomposite 1 are not confined in the nanocrystals of the alumina magnesia ceramic 3, but are intertwined with the nanocrystals of the alumina magnesia ceramic 3. Yes. Nanoalumina-magnesia ceramics 3 particles are 200 nanometers or less, and are entangled with carbon nanotubes 2 that are much longer than their diameter. The possibility of a strong chemical bond between the two intertwined is linked by a weak force similar to the van der Waals force. In this nanocomposite 1, carbon nanotube 2 and alumina If the bonding strength with the magnesia-based ceramics 3 is strong, the residual stress due to the difference between these two thermal expansions cannot be relaxed, and as the amount of multi-walled carbon nanotubes 2 increases, the residual stress becomes complex. Until the material is destroyed. However, the fact that a composite material that is dense and does not crack indicates that the residual stress has been relaxed. That is, in the nanocomposite 1, the multi-walled carbon nanotube 2 is in a deformable state due to the weak binding. As the nanocrystals of the alumina-magnesia ceramics 3 shrink, the multi-walled carbon nanotubes 2 can bend in the length direction, thereby reducing the residual stress. Relieving the residual stress does not reduce the toughness and strength of the composite material. When cracks develop in the composite material, the carbon nanotubes 2 are pulled out in the nanocomposite 1, which leads to increased toughness and strength. When the proportion of carbon nanotubes 2 increases, the force that increases the proportion of nanocomposites 1 is generated. Residual stress is alleviated, so the strength of the composite material will never decrease!

[0035] In order to produce the high-performance composite material according to the embodiment of the present invention, fine and highly anisotropic carbon nanotubes, aluminum hydroxide and magnesium hydroxide, which are raw materials for alumina-magnesia ceramics, Must be mixed uniformly. As a mixing technique, these three raw materials cannot be made into a solution, so it is necessary to adopt a method of mixing powders. There are various powder mixing methods, but since carbon nanotubes tend to aggregate, uniform mixing in a dry state is difficult. In addition, in wet mixing using a solvent, if the amount of the solvent is large, separation occurs due to a difference in precipitation rate due to a difference in specific gravity, and it is difficult to achieve uniform mixing. In order to prevent this separation and precipitation, a method is generally used in which powder is put into water or alcohol to form a highly viscous slurry, which is rotated and mixed with a ball mill for a long time.

In this method, the carbon nanotube is broken by the ball. In the method for producing a high-performance composite material according to the embodiment of the present invention, the slurry is mixed using a rotation / revolution supermixer in order to prevent this destruction and to perform uniform mixing in a short time. This device rotates a container containing slurry and revolves the main body that supports it in the opposite direction to perform mixing. It is suitable for mixing highly viscous materials. In this way By rotating and revolving, a shearing stress is applied to the slurry to give a force to break up the agglomerated part. This method enables uniform mixing in a relatively short time. When making this slurry, adding a surfactant or dispersant to improve dispersion can shorten the time for uniform mixing.

[0037] The high-functional composite material according to the embodiment of the present invention can be basically sintered under no pressure. However, if the mixing ratio force of alumina magnesia ceramics becomes smaller than the amount of carbon nanotubes, the sintering performance will be inferior, so the pressureless sintering method can produce a dense and strong sintered body. It becomes difficult. If the sintering method under pressure is used, a dense composite material can be easily produced in the entire mixing range. High industrial use value! /, Pressure sintering method is hot press method (HP) and spark plasma sintering method (SPS)

[0038] In the hot press method, while pressurizing a graphite mold containing a sample, the temperature is raised to a sintering temperature by an external heating method, usually in a non-oxidizing atmosphere, and kept at that temperature for a certain period of time. It is a method of manufacturing a product. In this method, since the effect of promoting densification by pressurization can be expected, it is possible to easily densify high-functional composite materials whose alumina magnesia-based ceramics are 60 mass% or less and have poor sinterability. it can.

[0039] The spark plasma sintering machine (SPS) is called plasma activated sintering machine (PAS), discharge plasma system (SPS), pulsed current sintering machine, etc., and has been developed to sinter metals and ceramics. Device. The structure is characterized in that a sample is packed in a conductive mold and heated directly by passing a pulse direct current. As a result, a no-less electric field acts on the sample in the mold, the diffusion of the material is promoted, and plastic deformation is likely to occur. Furthermore, in powders with high electrical resistance, a slight current flows on the sample surface, which accelerates the movement of molecules on the crystal surface and promotes crystal growth. In the solid-phase reaction, since the movement of molecules is promoted, the reaction can be performed at a lower temperature than before. By using such SPS effects, it has become possible to produce sintered bodies consisting of WC, which was not possible before, and A1N! /, Sintered bodies consisting of SiC only.

[0040] The high-functional composite material of the embodiment of the present invention is composed of a sintered body containing carbon nanotubes 0.1 to 90 mass% and alumina magnesia-based ceramics 99.9 to 10 mass%, It has a nanocomposite in which carbon nanotubes and alumina magnesia ceramic nanocrystals are intertwined with each other. This nanocomposite itself is a composite material with high toughness and strength, and when it is dispersed in an alumina-magnesia ceramic, it produces a highly functional composite material with high toughness and strength. If the mixing ratio of carbon nanotubes is less than 0.1 mass%, the friction coefficient, which is part of the wear resistance, cannot be reduced compared to that of alumina. When the proportion of carbon nanotubes is increased to 90 mass% or more, the strength of the composite material remains the same as that obtained by solidifying only carbon nanotubes.

[0041] Further, the ceramic portion of the high-functional composite material according to the embodiment of the present invention is alumina 99.

This is an alumina magnesia-based ceramics consisting of 8 to 0.5 mass% and magnesia 0.2 to 99.5 mass%. When the raw material aluminum hydroxide and magnesium hydroxide each are mixed and sintered with carbon nanotubes, the resulting composite material crystal grows to a particle size of alumina and magnesia of 20 micrometers or more, toughness and strength Will drop and become unusable. This crystal growth can be prevented by using a mixed composition of alumina and magnesia. When the mixing power of magnesia is 0.2 mass% or more, the crystal growth of alumina is completely suppressed, and a highly functional composite material with high toughness and strength can be produced. Similarly, when 0.5 mass% or more of alumina is added to magnesia, magnesia grain growth is suppressed, and strength reduction and non-uniform dispersion of carbon nanotubes can be prevented.

[0042] Next, a method for producing a highly functional composite material according to an embodiment of the present invention will be described. Single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon nanotubes, and carbon nanorods can all be used for the production of high-performance composite materials. Furthermore, a mixture of two or more of these can also be used. On the other hand, as a raw material for alumina-magnesia ceramics, a mixed raw material of aluminum hydroxide, which is an alumina precursor, and magnesium hydroxide, which is a magnesia precursor, is used.

[0043] In mixing aluminum hydroxide, magnesium hydroxide, and carbon nanotubes, first, a prescribed amount of carbon nanotubes is weighed and placed in a container, and water or distilled water or alcohol such as methanol or ethanol is added. In addition, make a slurry. In slurry The mixing time can be shortened by adding a surfactant or a dispersing agent in order to improve the dispersion of the carbon nanotubes. This additive also plays a role in adjusting the viscosity of the slurry. There are many types of surfactants and dispersants. Among these, it is necessary to use those that do not contain alkali or alkaline earth elements. This is because if these elements are contained, they remain in the composite material. The standard of the amount to be added is 0.1 to 10 vol% with respect to the solvent. The effect of addition is small at 0.1 vol% or less, and there is no change in effect even when 10 vol% or more is added.

[0044] To this slurry, aluminum hydroxide and magnesium hydroxide powder are added and mixed for 3 to 180 minutes. For this mixing, the use of a rotating / revolving supermixer can achieve efficient uniform mixing. If the mixing time is 3 minutes or less, the mixing is not performed uniformly, and the mixing state does not change even if the mixing time is 180 minutes or more. Water is removed from the mixed slurry and further dried at 150 to 250 ° C. using a hot plate or a dryer. At the same time, the added surfactant or dispersant is decomposed to obtain a mixed raw material for sintering.

[0045] Even if this mixed raw material is used as it is, sintering for obtaining an aluminum magnesia-based ceramic composite material can be performed. However, in order to produce large-sized products or to increase the temperature quickly, it is better to remove the moisture by calcining the mixed raw materials aluminum hydroxide and magnesium hydroxide during the sintering process. The rate can be suppressed, the product can be prevented from cracking, and the atmosphere furnace used for sintering can be prevented from being contaminated with moisture. This calcination needs to be performed in a non-oxidizing atmosphere. In an oxidizing atmosphere, carbon nanotubes are oxidized and lost. The calcination temperature is suitably in the range of 300 ° C to 900 ° C. When the temperature is lower than 300 ° C, aluminum hydroxide or magnesium hydroxide is not sufficiently decomposed, and above 900 ° C, alumina crystals, spinel crystals, and magnesia crystals become large, forming a nanocomposite of carbon nanotubes. I can't do that. In addition, the calcination time is suitably 5 to 60 minutes. In other words, if the time is shorter than 5 minutes, the decomposition is not enough. Even if it decomposes for more than 60 minutes, the decomposition is already completed, so there is no effect.

[0046] In order to produce an alumina magnesia-based ceramic composite material by a pressureless sintering method, it is necessary to form it into a necessary shape prior to sintering. This molding involves injection molding, embossing. It can be carried out by using conventional techniques such as a molding method and a slip casting method. The pressureless sintering temperature ranges from 1300 ° C to 1800 ° C. At 1300 ° C or lower, sintering under no pressure does not proceed sufficiently, and even if the sintering temperature is increased to 1800 ° C or higher, sintering is completed, so the effect on sintering remains unchanged! / ,. The pressureless sintering time is suitably in the range of 0.2 to 5 hours. If the time is shorter than 0.2 hours, sintering is not sufficient. Sintering for 5 hours or more has almost no densification effect. This pressureless sintering can be performed even using an electromagnetic wave sintering machine. Graphite materials are used as dielectric electromagnetic wave absorbers mixed with polymers and concrete. Similarly, alumina magnesia ceramics are dielectric electromagnetic wave absorbers. After molding the mixed raw material for pressureless sintering, heat it to 1300 ° C ~ 1800 ° C by the heat generated by electromagnetic wave absorption using an electromagnetic sintering machine, and hold it at the final temperature for 0.1 ~ 3 hours Thus, by completing the sintering, it is possible to obtain the high-performance composite material according to the embodiment of the present invention. If the sintering time is 0.1 hour or less, the effect on sintering will not change even if the time is increased to 3 hours or longer, which is not sufficient.

The pressure sintering method is advantageous when the ratio of carbon nanotubes is high and mixed raw materials are used. As a pressure sintering machine, a dense sintered body can be obtained by using a hot press and SPS. In hot pressing, the mixed raw materials packed in the mold are heated by external heat and sintered under pressure. On the other hand, in SPS, a pulsed direct current is passed through a mold containing mixed raw materials, heated directly and sintered under pressure. The sintering temperature is in the range of 1050 ° C to 1600 ° C, the sintering time is 5 minutes to 2 hours, and the applied pressure is 2 to 200 MPa. The sintering temperature is related to the applied pressure, and it is necessary to increase the applied pressure to lower the sintering temperature. The pressure is determined by the pressure resistance of the mold. The dense graphite mold can be used up to a temperature of 2400 ° C up to 200MPa. If the sintering temperature is set to 1050 ° C or lower, the composite material cannot be sintered densely even if the applied pressure is increased to 200 MPa. Therefore, it is essential to set the sintering temperature to 1050 ° C or higher. . Even if the temperature is higher than 1600 ° C, it is already sintered at a lower temperature! /, So there is no effect on densification. If the sintering time is shorter than 5 minutes, the sintering has already been completed for 2 hours or more, which is not sufficient, so that no further densification effect can be expected. If the pressurizing force is increased to 200 MPa or more, even a dense graphite mold with excellent pressure resistance performance will break, so it is necessary to sinter the composite material below this pressurizing force. If the value is lowered, the effect of pressure sintering is lost.

[0048] Since carbon nanotubes are oxidized when calcination and sintering are performed in an oxidizing atmosphere, non-oxidizing vacuum, argon gas, nitrogen gas, helium gas and other non-oxidizing materials are used. A gas atmosphere is required.

Example 1

[0049] Using multi-walled carbon nanotubes (MWNT), aluminum hydroxide and magnesium hydroxide were weighed in the amounts corresponding to A10 and MgO shown in Table 1. These raw materials were mixed with water to form a slurry, to which Arabic glue was added to make about 5 vol% of water as a dispersing agent, and mixed for 1 hour using a rotation and revolution super mixer. After drying this mixed raw material, it is heated to about 200 ° C in air to decompose the dispersant, and further heated to 500 ° C in 1 hour while flowing nitrogen gas using an atmospheric furnace. The aluminum hydroxide and magnesium hydroxide as raw materials were decomposed by holding for a minute. The decomposed raw material was molded, heated to 1700 ° C over 2 hours in a nitrogen atmosphere using a graphite heating electric furnace, and held at that temperature for 3 hours to complete the sintering.

[0050] The force, bulk density, bending strength, toughness, coefficient of friction, electrical resistance, and heat generation due to electromagnetic wave absorption with respect to the mixing ratio of MWNT of the obtained high-performance composite material were measured, and the results are shown in Table 1. For comparison, a pure alumina sintered body to which MWNT was not added and an alumina sintered body to which lmass% MgO was added were synthesized by the same method. The results are also shown in Table 1.

[0051] [Table 1]

7): Alumina-magnesia ceramic composite material obtained by sintering

MWNT AI2O3 MgO Bulk Density Bending Strength m Property Abrasion '5¾ Resistance Electron Lever' i.mass%) (mass% (mass%) (g / cm ³ ) (MPa) (MPa m ¹ ' ² ) Coefficient ( Fever at Q'cm

0.3 98.8 0.7 3.81 410 3.5 0.63 3.7 X 10 ¹⁰ X

1 98.0 1.0 3.71 461 3.9 0.51 6.3 X 10 ⁸ X

2 97.0 1.0 3.67 515 4.2 0.46 4.1 X 10 '○

4 95.0 1.0 3.51 585 6.1 0.27 3.9 X 106 oo

10 88.5 1.5 3.11 541 5.9 0.21 1.1 X 103 oo

20 78.5 1.5 2.79 525 5.5 0.17 1.7 X 10

30 68.0 2.0 2.61 518 5.3 0.15 9.6 oo

40 58.0 2.0 2.42 457 4.9 0.11 8.1 oo

0 99.0 1.0 3.89 395 3.4 0.77 7.6 X 10 ^{1 1} X

0 100 0 3.94 190 3.3 0.80 1.2 X 10 ¹³ X [0052] As shown in Table 1, the toughness and strength of the alumina sintered body are small, and the friction coefficient and electrical resistance are considerably large. In particular, in the alumina sintered body to which MgO is not added, the strength is remarkably reduced due to the growth of alumina crystals. However, a slight addition of MWNT significantly reduces the friction coefficient and electrical resistance. To improve toughness and strength, the effect of adding carbon nanotubes of lmass% or less is not so great, but the effect of adding a few percent is significant. As the amount of MWNT added increases, the proportion of the nanocomposite increases and becomes a property of the nanocomposite rather than a composite material with alumina, and the friction coefficient and electrical resistance are greatly reduced. Toughness and strength are stronger than that of sintered alumina. Heat generation due to electromagnetic wave absorption (“Heat generation in microwave oven” in Table 1) is measured by examining the heat generation status due to electromagnetic wave absorption of the composite material using the microwave oven, and the X mark in Table 1 indicates that no heat is generated. The 〇 mark indicates a slight fever, and the 〇 mark indicates a considerable fever! The addition of lmass% MWNT did not generate heat! /, but the addition of 2 mass% produced a little heat, and the addition of more than that showed a large exothermic phenomenon.

Example 2

[0053] Using single-walled carbon nanotubes (SWNT), aluminum hydroxide and magnesium hydroxide were weighed so as to correspond to the amounts of A10 and MgO shown in Table 2. All this

twenty three

In this synthesis, spinel (MgAl 0) is produced from the mixing ratio of aluminum hydroxide and magnesium hydroxide. Mix these ingredients with water to make a slurry

twenty four

Then, triethanolamine was added as a dispersant to about 3 · 5νο1% as a dispersant, and the mixture was mixed for 1.2 hours using a rotation / revolution supermixer. After drying this mixed raw material, it is heated to 240 ° C in air to decompose the dispersant, and further heated to 600 ° C in 1.5 hours while flowing nitrogen gas using an atmospheric furnace, and the temperature is raised to that temperature for 30 minutes. The raw material aluminum hydroxide and magnesium hydroxide were decomposed. This decomposed and dehydrated raw material was molded, heated to 1700 ° C in a nitrogen atmosphere for 1.5 hours using an electric furnace with graphite heating, and held at that temperature for 2 hours to complete the sintering.

[0054] Bulk density, bending strength, toughness, coefficient of friction, electrical resistance, and heat generation due to electromagnetic wave absorption with respect to the mixing ratio of carbon nanotubes (SWNT) in the obtained high-performance composite material were measured, and the results are shown in Table 2. Shown in The high-performance composite materials in Table 2 consist of SWNT and spinel. For comparison, the results of a spinel sintered body synthesized under the same conditions without adding SWNT are also shown.

[0055] [Table 2]

Spinel composites obtained by pressureless sintering.

[0056] As shown in Table 2, strength and toughness can be increased by adding SWNT to spinel to form a nanocomposite. It can be seen that the coefficient of friction and electrical resistance drop sharply with the addition of a small amount of SWNT, and the effect of adding carbon nanotubes is significant. Heat generation due to electromagnetic wave absorption (“Heat generation in microwave oven” in Table 2) was measured by examining the heat generation status due to electromagnetic wave absorption in the composite material using the microwave oven, and the X mark in Table 2 did not generate heat. 〇 mark shows a little fever and 〇 mark shows a considerable amount of heat. The addition of SWNT to lmass% showed no exotherm. It was found that the addition of 3 mass% produced a little heat, and the addition of more than that caused a considerable exotherm.

Example 3

[0057] Using multi-walled carbon nanotubes (MWNT), aluminum hydroxide and magnesium hydroxide were weighed so as to correspond to A10 and MgO shown in Table 3. These raw materials

twenty three

Was mixed with ethanol to make a slurry, and butylhydroxytoluene was added as a dispersant to about 3 vol% of ethanol, and mixed for 1 hour using a rotation / revolution supermixer. After drying this mixed raw material, it is heated to 200 ° C in the air on a hot plate, further heated to 500 ° C in 2 hours while flowing nitrogen gas using an atmospheric furnace, and kept at that temperature for 30 minutes. Raw material aluminum hydroxide and magnesium hydroxide were decomposed. This raw material is packed in a graphite mold and is heated under a pressure of 20 MPa in argon gas using a hot press machine. Then, the temperature was raised to 1550 ° C in 1 hour, and this temperature was maintained for 1 hour to complete the sintering.

[0058] The force, bulk density, bending strength, toughness, coefficient of friction, electrical resistance, and heat generation due to electromagnetic wave absorption with respect to the mixing ratio of MWNT of the obtained high-performance composite material were measured. For comparison, a magnesia sintered body obtained by adding lmass% of alumina to magnesia and a single magnesia sintered body were synthesized under the same conditions, and the results are also shown in Table 3.

[0059] [Table 3]

Alumina-magnesia ceramic composites obtained by hot press sintering

[0060] As shown in Table 3, the strength of the single magnesia sintered body is small due to grain growth, and it can be seen that the strength increases when alumina is added thereto. When the amount of carbon nanotubes added exceeds S40ma _SS %, it becomes difficult to synthesize dense high-performance composite materials by sintering under no pressure, but it is shown in Table 3 by using a hot press. As described above, it is possible to produce a dense and highly functional composite material having large strength and toughness. This high-performance composite material has sufficient strength S, toughness, and strength that are almost composed of nanocomposites, and is a value that can be practically used as a product. Heat generation due to electromagnetic wave absorption (“Heat generation in microwave oven” in Table 3) is measured by examining the heat generation status due to electromagnetic wave absorption of the composite material using the microwave oven, and the X mark in Table 3 does not generate heat. 〇 mark shows a little fever and 〇 mark shows a considerable amount of heat. Due to the high carbon nanotube content in the high-performance composite material, a large exotherm was observed. The sintered body containing no carbon nanotubes did not generate heat. Example 4

[0061] Using multi-walled carbon nanotubes (MWNT), aluminum hydroxide and magnesium hydroxide were weighed so as to correspond to A10 and MgO shown in Table 4. These raw materials Was mixed with water to make a slurry, and propylene glycol was added to the slurry so that the volume of water was about 2 vol%, and the mixture was mixed for 1.5 hours using a rotation / revolution supermixer. After drying this mixed raw material, it is heated to 220 ° C in air, and further heated to 150 ° C over 1 hour while flowing nitrogen gas in an atmosphere furnace, and then raised to 700 ° C in 1.5 hours. The mixture was kept at that temperature for 5 minutes to decompose the aluminum hydroxide and magnesium hydroxide as raw materials. This decomposed raw material is packed in a graphite mold, set in a spark plasma sintering machine (SPS), heated to 1500 ° C in 1 hour under a pressure of 80 MPa in vacuum, and the temperature is reached. Hold for 20 minutes to complete the sintering.

[0062] The force, bulk density, bending strength, toughness, coefficient of friction, electrical resistance, and heat generation due to electromagnetic wave absorption were measured with respect to the MWNT mixing ratio of the obtained high-performance composite material, and the results are shown in Table 4. For comparison, a sintered body containing only MWNT was synthesized by the same method, and the results are also shown in Table 4.

[0063] [Table 4]

Alumina-magnesia ceramics obtained by spark plasma sintering

As shown in Table 4, even if 60 mass% or more of MWNT is added, it is possible to synthesize dense high-functional composite materials by using SPS. When the addition of MWNT reaches 85 mass%, the electrical resistance approaches that of carbon, and the friction coefficient decreases significantly. Heat generation due to electromagnetic wave absorption ("Heat generation in microwave oven" in Table 4) is measured by examining the heat generation status due to electromagnetic wave absorption of composite materials using a microwave oven, and X in Table 4 does not generate heat. 〇 mark shows a little fever and 〇 mark shows a considerable amount of heat. Since both samples contained a lot of MWNT, a fairly large exotherm was observed. Industrial applicability

[0065] As described above in detail, the highly functional composite material including the carbon nanotube of the present invention and the alumina-magnesia ceramic has improved the toughness of the conventional alumina-magnesia ceramics and has a high strength. Has also been improved. In addition, the friction coefficient shows a greatly improved wear resistance. The electrical resistance decreases with respect to the amount of carbon nanotubes added, and a high-functional composite material with a small amount of alumina-magnesia ceramics is close to a graphite material and has an electrical resistance!

[0066] The high-performance composite material according to the present invention can be used in fields where conventional alumina-magnesia ceramics are used !, and also in new fields utilizing the characteristics of carbon nanotubes. . Capacitor-type secondary batteries, members for electron beam drawing devices, IC manufacturing members, various cutting blades such as ferrules, knives, artificial bones, artificial joints, hip joint cups (inserts), and crusher device members (Balls, pulverizer parts, lining materials, etc.), molding machine parts (nozzles, cylinders, molds), processing machine parts (shafts, bearings, pumps, etc.), tool parts (cutting tools, snap gauges) , Bearings, surface plates, ball bearings, welding jigs, etc.), sliding parts (mechanical seals, tilting pads, rolls for wire drawing machines, pulleys, thread paths, fishing tools, porcelain head sliders, slip plates for paper machines), Chemical equipment components (bubbles, stoppers, flow meters, spray nozzles, agitators, shafts, etc.) and other general mechanical components such as shafts, nozzles, spray nozzles, bearings It is useful to mechanical seal.

[0067] The electronic material of the high-functional composite material according to the present invention reflects the function of a chiral type that is one of the structures of carbon nanotubes, and absorbs 300 MHz to 300 GHz band microwave and millimeter wave electromagnetic wave absorbers, It can be applied to electromagnetic wave reflectors, couplers, modulators, electromagnetic wave switches, antennas, micromechanical elements, microsensors, energy conversion elements, radar protection dome, noise absorbers, and electromagnetic wave absorption heating elements.

Brief Description of Drawings

FIG. 1 is a schematic diagram showing an alumina-magnesia nanocomposite of a high-functional composite material according to an embodiment of the present invention.

Explanation of symbols Nanocomposite Car Alumina

Claims

The scope of the claims

[1] a ceramic polycrystalline body comprising a plurality of first alumina-magnesia ceramic crystals;

A nanocomposite having a structure in which a plurality of carbon nanotubes and a plurality of second alumina magnesia-based ceramic crystals are intertwined,

The nanocomposite is dispersed in the ceramic polycrystalline body. A high-functional composite material, characterized in that:

[2] The high-functional composite material according to claim 1, wherein the second alumina-magnesia ceramic crystal has a grain size that is an order of magnitude or more smaller than the grain size of the first alumina-magnesia ceramic crystal. .

[3] The highly functional composite material according to claim 1 or 2, wherein the second alumina magnesia ceramic crystal has a grain size smaller than 200 nm.

[4] The highly functional composite material according to [1], [2] or [3], wherein the nanocomposite is larger than the grain size of the first alumina magnesia ceramic crystal.

5. The highly functional composite material according to claim 1, 2, 3 or 4, wherein the carbon nanotube has an average length longer than lOOOnm and an average thickness smaller than lOOnm.

[6] 4 to 85 mass% carbon nanotubes, 0.2 to 95 mass% alumina, magnesia;

The high-functional composite material according to claim 1, 2, 3, 4 or 5, characterized by containing 7% _SS %.

[7] The carbon nanotube is composed of one kind or a mixture of two or more kinds of single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, amorphous carbon nanotubes, and carbon nanotubes. , Characterized in claims 1, 2, 3,

4. High-performance composite material according to 4, 5 or 6.

[8] Carbon nanotubes 0.1-90 mass% and alumina magnesia ceramics 99.9-

It consists of a sintered body containing 10 mass%,

The alumina magnesia-based ceramic is 99.8-0.5 mass% alumina and magnesia 0.2

Including ~ 99.5mass%,

It has a nanocomposite in which the carbon nanotubes and the alumina magnesia ceramic nanocrystals are intertwined with each other as a constituent element. Characteristic high-performance composite material.

Carbon nanotubes 0.1 to 90 mass% and alumina magnesia ceramics 99.9 to 10 mass% are placed in a solvent of water or alcohol, mixed in a slurry for 3 to 180 minutes, and after removing the solvent from this mixture, A method for producing a high-performance composite material, characterized by sintering in a non-oxidizing atmosphere at a temperature range of 1050 ° C to 1800 ° C for 5 minutes to 5 hours.

Carbon nanotubes 0.3 to 70 mass% and alumina magnesia ceramics 99.7 to 30 mass% are placed in water or an alcohol solvent, mixed in a slurry for 3 to 180 minutes, and after removing the solvent from this mixture, non-oxidizing A method for producing a high-performance composite material characterized by sintering in an atmosphere at a temperature range of 1050 ° C to 1800 ° C for 5 minutes to 5 hours.

The alumina-magnesia ceramic is composed of 99.8 to 0.5 mass% aluminum hydroxide (Al (OH)) in terms of alumina and 0.2-99.5 mass% magnesium hydroxide (Mg (OH)) in terms of magnesia. The method for producing a high-performance composite material according to claim 9 or 10, characterized by comprising:

As a pretreatment for performing the sintering, after removing the solvent from the mixture, it is calcined in a non-oxidizing atmosphere at a temperature range of 300 ° C to 900 ° C for 5 to 60 minutes for decomposition and dehydration. The method for producing a high-performance composite material according to claim 9, 10 or 11, characterized in that:

13. The method for producing a high-functional composite material according to claim 9, 10, 11 or 12, wherein the sintering is performed by a pressureless sintering method, a hot press method, or a discharge plasma sintering method.