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Composite and method of manufacturing the sameRelated Patent Categories: Compositions, Electrically Conductive Or Emissive CompositionsComposite and method of manufacturing the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070145335, Composite and method of manufacturing the same. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION AND RELATED ART STATEMENT [0001] The present invention relates to a composite formed by combining a carbon nanotube structure and ceramics and a method of manufacturing the same. [0002] Carbon nanotubes (CNTs), with their unique shapes and characteristics, are being considered for various applications. A carbon nanotube has a tubular shape of one-dimensional nature which is obtained by rolling one or more graphene sheets composed of six-membered rings of carbon atoms into a tube. A carbon nanotube that is formed from one graphene sheet is called a single-wall nanotube (SWNT) while a carbon nanotube that is formed from graphene sheet layers is called a multi-wall nanotube (MWNT). Single-wall nanotubes are about 1 nm in diameter whereas multi-wall carbon nanotubes measure several tens nm in diameter, and both are far thinner than their predecessors, which are called carbon fibers. [0003] One of the characteristics of carbon nanotubes resides in that the aspect ratio of length to diameter is very large since the length of carbon nanotubes is on the order of micrometers. Carbon nanotubes are unique in their extremely rare nature of being both metallic and semiconductive because six-membered rings of carbon atoms in carbon nanotubes are arranged into a spiral. In addition, the electric conductivity of carbon nanotubes is very high and allows a current flow at a current density of 100 MA/cm.sup.2 or more. [0004] Carbon nanotubes excel not only in electrical characteristics but also in mechanical characteristics. That is, the carbon nanotubes are distinctively tough, as attested by their Young's moduli exceeding 1 TPa, which belies their extreme lightness resulting from being formed solely of carbon atoms. In addition, the carbon nanotubes have high elasticity and resiliency resulting from their cage structure. Having such various and excellent characteristics, carbon nanotubes are very appealing as industrial materials. [0005] Applied researches that exploit the excellent characteristics of carbon nanotubes have been made heretofore extensively. To give a few examples, a probe of a scanning probe microscope, minute electron source, hydrogen storage, and diodes and transistors as electronic materials and electronic devices have been prototyped. [0006] As described above, various applications for the carbon nanotubes are conceived. An example close to practical application includes an application of adding a carbon nanotube as a resin reinforcer or a conductive composite material. [0007] A ceramics-carbon nanotube composite is one such composite. The ceramics have advantages such as thermal resistance, abrasive resistance, and lightweight properties. By adding the carbon nanotubes to the ceramics, a mechanical strength or thermal conductivity of the ceramics increases, and further electric conductivity can be imparted to the ceramics. Such a ceramics-carbon nanotube composite is disclosed in JP 2001-288626 A. SUMMARY OF THE INVENTION [0008] In JP 2001-288626 A, a SiO.sub.2-carbon nanotube composite is obtained by mixing carbon nanotubes in an organopolysiloxane composition and calcining after application of the mixture. However, in the mixing process, organopolysiloxane adheres to a carbon nanotube surface, thus merely incidentally prompting contact between the carbon nanotubes surfaces and lowering the electric conductivity owing to a coarse electrical path. Further, the thermal conductivity is also lowered owing to a coarse network of the carbon nanotubes. [0009] Therefore, the present invention has been made in view of the above circumstances and provides a ceramics composite with an enhanced mechanical strength and enhanced thermal or electric conductivity by constituting the composite using a carbon nanotube structure. [0010] The above ceramics composite is achieved through the following present invention. [0011] That is, according to the present invention, there is provided a composite formed by combining a carbon nanotube structure and ceramics characterized in that the carbon nanotube structure is constituted by chemically bonding functional groups bonded to multiple carbon nanotubes to mutually cross-link to construct a network structure. [0012] The composite of the present invention has the carbon nanotubes mutually cross-linked, thus is different from a case of simple contact between the carbon nanotube surfaces, thereby providing a connection assuredly and stably. As a result, the thermal or electric conductivity between nanotubes is secured and the electric conductivity or the thermal conductivity which is a characteristic inherent in carbon nanotubes can be used. Therefore, the composite can be provided with satisfactory electric conductivity or thermal conductivity while retaining advantages of ceramics. In the composite of the present invention, the carbon nanotube structure preferably has multiple carbon nanotubes in a state of a network structure via multiple cross-linked sites. [0013] Examples of the ceramics used for the composite of the present invention include oxide-based ceramics, nitride-based ceramics, carbide-based ceramics, boride-based ceramics, and silicide-based ceramics, and oxide-based ceramics are preferably because of its ease of production. [0014] The carbon nanotube structure is preferably obtained by curing a liquid solution containing multiple carbon nanotubes to which functional groups are bonded to chemically bond the multiple functional groups bonded to the carbon nanotubes together for formation of a cross-linked site. [0015] Of those, a preferable first structure for the cross-linked site is a structure cross-linking the multiple functional groups together with a cross-linking agent in the liquid solution, and the cross-linking agent is more preferably not self-polymerizable. [0016] By forming the carbon nanotube structure through the above curing of the liquid solution, the cross-linked site where the carbon nanotubes are cross-linked together has a cross-linking structure, and the carbon nanotube structure can be networked. In the cross-linking structure, residues remaining after a cross-linking reaction of the functional groups are connected together using a connecting group which is a residue remaining after the cross-linking reaction of the cross-linking agent. [0017] Alkoxide or the like, disclosed in JP 2002-234000 A, for example, can be used as a cross-linking agent which cross-links the carbon nanotubes together. However, if the cross-linking agent has a property of polymerizing with other cross-linking agents (self-polymerizability) such as the alkoxide, the cross-linking agents per se polymerize multiply into a state of a connected construction. The carbon nanotubes may be in a state of being dispersed in the construction of the cross-linking agents. Therefore, an actual density of the carbon nanotubes in the carbon nanotube structure becomes low. [0018] On the other hand, if the cross-linking agent is not self-polymerizable, a gap between each of the carbon nanotubes can be controlled to a size of a cross-linking agent residue used. Therefore, a desired network structure of carbon nanotubes can be obtained with high duplicability. Further, reducing the size of the cross-linking agent residue can extremely narrow a gap between each of the carbon nanotubes both electrically and physically. In addition, carbon nanotubes in the structure can be densely structured. [0019] Therefore, if the cross-linking agent is not self-polymerizable, using the carbon nanotube structure of the present invention as a filler assuredly can provide a skeleton with nanotubes bonded together in a short range. As a result, the carbon nanotube structure becomes an electrical and thermal network path having a satisfactory mechanical strength, electric conductivity, or thermal conductivity. In the present invention, the term "self-polymerizable" refers to a property of which the cross-linking agents may prompt a polymerization reaction with each other in the presence of other components such as water or in the absence of other components. On the other hand, "not self-polymerizable" means that the cross-linking agent has no such a property. [0020] If a not self-polymerizable cross-linking agent is selected as the cross-linking agent, a cross-linked site, where carbon nanotubes are cross-linked to each other, in the composite of the present invention has primarily an identical cross-linking structure. Furthermore, the coupling group preferably employs a hydrocarbon as its skeleton, and the number of carbon atoms of the skeleton is preferably 2 to 10. Reducing the number of carbon atoms can shorten the length of a cross-linked site and sufficiently narrow a gap between carbon nanotubes as compared to the length of a carbon nanotube itself. As a result, a carbon nanotube structure of a network structure composed substantially only of carbon nanotubes can be obtained. Therefore, the composite of the present invention with excellent electric conductivity and thermal conductivity can be obtained. [0021] Examples of the functional group include --OH, --COOH, --COOR (where R represents a substituted or unsubstituted hydrocarbon group), --COX (where x represents a halogen atom), --NH.sub.2, and --NCO. A selection of at least one functional group from the group consisting of the above functional groups is preferable, and in such a case, a cross-linking agent, which may prompt a cross-linking reaction with the selected functional group, is selected as the cross-linking agent. [0022] Further, examples of the preferable cross-linking agent include polyol, polyamine, polycarboxylic acid, polycarboxylate, polycarboxylic acid halide, polycarbodiimide, and polyisocyanate. A selection of at least one cross-linking agent from the group consisting of the above functional groups is preferable, and in such a case, a functional group, which may prompt a cross-linking reaction with the selected cross-linking agent, is selected as the cross-linking agent. Continue reading about Composite and method of manufacturing the same... Full patent description for Composite and method of manufacturing the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Composite and method of manufacturing the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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