Carbon material

Abstract

Carbon material which contains carbon nanotubes, wherein: 90-100%, inclusive, of the carbon nanotubes by number have a diameter which is 0.9-2nm, inclusive; 90-100%, inclusive, of the carbon nanotubes by number have an armchair-type chirality; and the conductivity of the carbon material is at least 5×106Sm-1 in at least one direction.

Description

carbon materials

[0001] The present disclosure relates to a carbon material. This application claims priority to Japanese Patent Application No. 2023-037672, filed on March 10, 2023. The entire contents of the Japanese patent application are incorporated herein by reference.

[0002] Carbon nanotubes are materials in which graphene sheets formed from carbon are formed into a single-layer or multi-layer coaxial tube shape. Here, graphene is a sheet-like material in which sp2-bonded carbon atoms are covalently bonded to each other to form a hexagonal lattice structure. The thickness of the graphene is the thickness of one atom.

[0003] Carbon nanotubes are said to be the next generation carbon material or nanomaterial due to their thinness, lightness, and flexibility, and various applications are being developed.

[0004] For example, Japanese Patent Publication No. 2014-503448 (Patent Document 1) describes a carbon material containing carbon nanotubes, in which at least 70% of the carbon nanotubes have diameters in the range of 1 nm to 2.5 nm, and are at least 0.7 × 10 in at least one direction. ６ Sm －１ A carbon material characterized by having a conductivity of

[0005] Special table 2014-503448 publication

[0006] The carbon material according to the present disclosure is a carbon material containing carbon nanotubes, wherein 90% to 100% of the carbon nanotubes by number have a diameter of 0.9 nm to 2 nm, and 90% to 100% of the carbon nanotubes by number have armchair chirality, and the carbon material has a chirality of 5×10 in at least one direction. ６ Sm －１ It has a conductivity of at least 1000 .mu.m.

[0007] FIG. 1 is a schematic diagram showing a carbon nanotube manufacturing apparatus according to this embodiment.

[0008] [Problem to be Solved by the Present Disclosure] Carbon materials including carbon nanotubes are expected to be used as materials for electric wires because they are electrically conductive. However, their conductivity is lower than that of copper or aluminum, and there is room for improvement.

[0009] The present disclosure has been made in view of the above circumstances, and aims to provide a carbon material containing carbon nanotubes that has excellent electrical conductivity.

[0010] According to the present disclosure, it is possible to provide a carbon material containing carbon nanotubes with excellent electrical conductivity.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. [1] A carbon material according to the present disclosure is a carbon material containing carbon nanotubes, wherein 90% to 100% of the carbon nanotubes have a diameter of 0.9 nm to 2 nm, 90% to 100% of the carbon nanotubes have an armchair chirality, and the carbon material has a chirality of 5×10 in at least one direction. ６ Sm －１ It has a conductivity of at least 1000 .mu.m.

[0012] The carbon material is mainly composed of carbon nanotubes with armchair chirality. Therefore, the carbon material has improved electrical conductivity compared to conventional carbon materials. In other words, the present disclosure provides a carbon material containing carbon nanotubes with excellent electrical conductivity by incorporating the above-described configuration. Here, "armchair chirality" refers to a specific regular structure in which the chiral index is expressed as (a, a) in the winding manner of the graphene planes that make up the carbon nanotubes (a represents a natural number). "Conductivity" refers to the ease of electrical conduction in the carbon material.

[0013] [2] In the above [1], the content of the carbon nanotubes may be 80 mass % or more relative to the carbon material, thereby making it possible to provide a carbon material with even better electrical conductivity.

[0014] [3] In the above [1] or [2], the carbon material may be a fiber or a film. This makes it possible to provide a carbon material that has excellent conductivity and excellent continuum moldability. Here, "continuum" refers to a solid material in an undivided state, in which tensile stress applied to one point of the solid material propagates throughout the solid material (e.g., a material that is not a powder). "Continuum moldability" refers to the property of forming a solid material in the form of a thread or sheet, rather than a powder.

[0015] [4] In any one of the above [1] to [3], at least one dimension of the carbon material may exceed 1 m. This makes it possible to provide a carbon material that has excellent electrical conductivity and excellent continuum moldability.

[0016] [5] In any one of the above [1] to [4], the density of the carbon material is 0.5 g / cm ３ 2.0g / cm or more ３ In this way, it is possible to provide a carbon material that is excellent in continuum moldability in addition to excellent electrical conductivity.

[0017] [6] In any one of the above [1] to [5], the specific strength of the carbon material may be 0.2 GPa / SG or more in at least one direction. This makes it possible to provide a carbon material that has excellent electrical conductivity and excellent continuum formability.

[0018] [7] In any one of the above [1] to [6], the specific rigidity of the carbon material may be 10 GPa / SG or more. This makes it possible to provide a carbon material that has excellent electrical conductivity and excellent continuum formability.

[0019] [8] In any one of the above [1] to [7], the carbon material may further have catalyst particles dispersed therein, the catalyst particles containing tungsten as a constituent element, and the content of the catalyst particles may be 0.1% by mass or more and 20% by mass or less with respect to the carbon material. This makes it possible to provide a carbon material that has excellent electrical conductivity and excellent formability into a continuous body.

[0020] [9] In the above [8], the catalyst particles may further contain one or more metal elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth metal elements. By doing so, it is possible to provide a carbon material that has excellent electrical conductivity and excellent continuum formability.

[0021]

[10] In the above [8] or [9], 99% to 100% of the catalyst particles may have a diameter of 1 nm to 4 nm, thereby providing a carbon material that has excellent electrical conductivity and excellent formability into a continuous body.

[0022] [Details of the embodiment of the present disclosure] Hereinafter, one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described. However, the present embodiment is not limited to this. In this specification, the notation in the format "A to Z" means the upper and lower limits of a range (i.e., A or more and Z or less), and when no unit is described for A and only a unit is described for Z, the unit of A and the unit of Z are the same. Furthermore, in this specification, when a compound is expressed by a chemical formula in which the composition ratio of the constituent elements is not limited, such as "TiC", the chemical formula is considered to include all conventionally known composition ratios (element ratios). In this case, the above chemical formula is considered to include not only stoichiometric compositions but also non-stoichiometric compositions. For example, the chemical formula of "WFe" includes the stoichiometric composition "W １ Fe １ " as well as, for example, "W １ Fe １．１７ This also applies to the description of compounds other than "WFe."

[0023] <Carbon Material> The carbon material according to the present disclosure is a carbon material containing carbon nanotubes, wherein 90% to 100% of the carbon nanotubes by number have a diameter of 0.9 nm to 2 nm, and 90% to 100% of the carbon nanotubes by number have armchair chirality, and the carbon material has a chirality of 5×10 in at least one direction. ６ Sm －１ It has a conductivity of at least 1000 .mu.m.

[0024] The carbon material of this embodiment includes carbon nanotubes (hereinafter, sometimes referred to as "CNTs"). Here, "carbon nanotubes" refers to a substance in which graphene sheets formed from carbon are formed into a single-layer or multi-layer coaxial tube shape. "Graphene" refers to a sheet-like substance in which sp2-bonded carbon atoms are covalently bonded to each other to form a hexagonal lattice structure, and the layer thickness is the thickness of one atom.

[0025] <Carbon Nanotubes> In this embodiment, the shape of the carbon nanotube is not particularly limited, and examples thereof include those with closed ends and those with open ends. Furthermore, catalyst particles used in the synthesis of the carbon nanotube may be attached to one or both ends of the carbon nanotube. Furthermore, a cone made of conical graphene may be formed at one or both ends of the carbon nanotube.

[0026] In this embodiment, 90% to 100% of the carbon nanotubes have a diameter of 0.9 nm to 2 nm, or may have a diameter of 0.9 nm to 1.8 nm, or may have a diameter of 1 nm to 1.7 nm. The diameter of the CNTs can be calculated by examining the radial breathing mode (RBM) of each CNT using Raman spectroscopy. The specific procedure will be described later.

[0027] In this embodiment, 90% to 100% of the carbon nanotubes have armchair chirality. 95% to 100% of the carbon nanotubes may have armchair chirality. In one aspect of this embodiment, the phrase "90% to 100% of the carbon nanotubes have armchair chirality" can also be understood to mean that the probability of the existence of carbon nanotubes with armchair chirality is 90% to 100% based on the total number of carbon nanotubes. Carbon nanotubes with armchair chirality tend to be conductive. Therefore, the chirality of a target carbon nanotube can be evaluated based on the conductivity of the carbon nanotube. The conductivity of the carbon nanotube is determined using a Kataura plot of the optical absorption spectrum in a spectrofluorometer. Optical transitions in carbon nanotubes with armchair chirality (metallic carbon nanotubes) are observed at higher energy levels than optical transitions in semiconducting carbon nanotubes (e.g., chiral carbon nanotubes) with the same diameter, and this can be used as a criterion for determination.

[0028] (Conditions for measuring optical absorption spectra using a spectrofluorometer) Measuring device: spectrofluorometer, JASCO FP-8750 Measurement temperature: room temperature (25°C) Measurement wavelength: 300 nm to 1700 nm Reference armchair (metallic) CNT: CNT with a chiral index of (12,12), (10,10), (9,9), (8,8), (7,7) or (6,6) and having the same diameter as the CNT being measured Determination method: By comparing the obtained optical absorption spectra, if the optical transition in the CNT being measured is observed to be equal to or on the higher energy side than the optical transition in the reference armchair CNT, the CNT being measured is determined to have armchair chirality.

[0029] At least 90% by number of the carbon nanotubes may be armchair carbon nanotubes. At least 95%, 96%, 97%, 98% or 99% by number of the carbon nanotubes may be armchair carbon nanotubes.

[0030] The proportion of carbon nanotubes with armchair chirality (probability of existence) can be calculated by examining the radial breathing mode (RBM) of each CNT using Raman spectroscopy, which will be described later. Specifically, the chirality of the same carbon material is determined 20 times based on the RBM peak, and the probability of existence is calculated from the number of times it is determined to be armchair chiral, based on the following formula 1. Probability of existence of armchair CNT (%) = 100 × (number of times it is determined to be armchair based on the RBM peak) / 20 Formula 1

[0031] Carbon nanotubes may have aligned major axes. Usually, when the carbon material is a fiber, the axis of the fiber is treated as the major axis of the carbon nanotube. This is, of course, easily confirmed during TEM analysis. Here, the "major axis of the carbon nanotube" is the axis parallel to the longitudinal direction of the carbon nanotube.

[0032] Suitable armchair chiralities of the carbon nanotubes include the following parameters. The chiralities are listed together with the chiral indexes (n, m) and their diameters (Table 1). The notation of the chiral indexes (n, m) used in this application is well known to those skilled in the art. Here, n and m each represent a natural number.

[0033]

[0034] In this embodiment, the carbon nanotube content may be 80% by mass or more, 80% by mass to 100% by mass, or 90% by mass to 100% by mass, relative to the carbon material. The carbon nanotube content can be determined by measuring using thermogravimetric differential thermal analysis (TG-DTA) under the following conditions. (Measurement conditions for thermogravimetric differential thermal analysis) Air flow: 50 ml / min Measurement temperature: Measurement from room temperature (25°C) to 1000°C at a heating rate of 5°C / min Calculation method: The content is calculated from the ratio of the residue mass after measurement up to 1000°C to the initial mass (mass before measurement).

[0035] <Catalyst Particles> In the present embodiment, the carbon material may further include catalyst particles dispersed in the carbon material, the catalyst particles may contain tungsten as a constituent element, and the content of the catalyst particles may be 0.1 mass % or more and 20 mass % or less with respect to the carbon material.

[0036] The inclusion of the above-described catalyst particles in the carbon material indicates that the carbon material was produced by the production method described below.

[0037] The catalyst particles may further contain one or more metal elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth metal elements.

[0038] Specific examples of lanthanoid rare earth metals include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0039] In one aspect of this embodiment, the catalyst particles may be a substance having the following chemical composition:

[0040] Binary catalysts: WV, WFe １．１７ , WFe ２ , WFe, WCo １．１７ , WCo ３ , WCo, WNi, WNi ４ , WNi ５．６７ , WCu ０．６７ , WCu ５．２５ , WRe, WRe ３ , WRe ０．２５ , WRe １０．１１ , W １３ Re ７ , WOs ０．５ , WOs ２ , WI, WPt ２ , WRh ３ , WRh ４ , WRu ０．１８ , WRu １．５ , WEu ０．１８ , WC ３ , WPr ３ .

[0041] Ternary catalysts: WCoNi, WFeNi ５ , WMn ３ Fe, WPtNi １０ , WRu ２ Fe ５ , WRhCo, WCu ２ Fe １２ , WFeV ４ , WRe ０．１２５ Ni ０．１２５ , WRu ３ Cu １２ , WPtCu １０ ; WMn １．５ V ０．６３ , WLFe ３ .

[0042] Multielement catalysts: WFeCoNi, WFeCoMn, WFeCu ３ Ru, WMn ５ V ３ Cr, WRuPtAu, WFe ０．１ Au ０．２ Mn ０．１ , WFeRe ２ Mn, WOsCu ３ Mn ８ .

[0043] The composition of the catalyst particles dispersed in the carbon material can be quantitatively identified by combusting the obtained target carbon material (CNT) in a differential thermal analyzer (TG-DTA or the like) and then quantitatively identifying the metal oxides (ash content) of the catalyst particles using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX).

[0044] The content of the catalyst particles may be 0.1% by mass or more and 20% by mass or less, 0.1% by mass or more and 10% by mass or less, or 0.1% by mass or more and 5% by mass or less, relative to the carbon material. The content of the catalyst particles can be determined by measurement using a TG-DTA method under the following conditions. (Measurement conditions for thermogravimetric differential thermal analysis) Air flow: 50 ml / min Measurement temperature: Measurement is performed from room temperature (25°C) to 1000°C at a heating rate of 5°C / min Calculation method: The content is calculated from the ratio of the residue mass after measurement up to 1000°C to the initial mass (mass before measurement).

[0045] In this embodiment, 99% to 100% of the number of the catalyst particles may have a diameter of 1 nm to 4 nm, or may have a diameter of 1 nm to 3 nm, or may have a diameter of 1 nm to 2 nm. The diameter of the catalyst particles is obtained by directly observing the surface of the carbon material using a TEM, measuring the distance between the two most distant points on the periphery of the catalyst particles, and calculating the average value from the obtained values. The number of catalyst particles observed may be at least 20, or may be at least 40.

[0046] <Other Components> The carbon material according to this embodiment may contain amorphous carbon, graphene, and the like in addition to carbon nanotubes and catalyst particles, as long as the effects of the present disclosure are achieved.

[0047] <Characteristics of Carbon Material> (Conductivity) In this embodiment, the carbon material has a conductivity of 5×10 ６ Sm －１ and has a conductivity of 5×10 ６ Sm －１ 20 x 10 or more ６ Sm －１ It may have a conductivity of 10×10６ Sm －１ 15 x 10 or more ６ Sm －１ The carbon material may have the following electrical conductivity: The electrical conductivity of the carbon material can be determined by "resistance measurement by four-probe method" according to JIS K7194.

[0048] (Metallic Properties, Semiconductor Properties) The metallic properties and semiconductor properties of the carbon material according to this embodiment can be evaluated by using Raman spectroscopy.

[0049] One vibrational mode of carbon nanotubes is the radial breathing mode (RBM). This radial breathing mode can be investigated using Raman spectroscopy. For a given wavelength of incident light, only the RBM of a carbon nanotube with a certain diameter will resonate, and therefore, the radial breathing mode (RBM) peak will occur only within a certain range of carbon nanotube diameters in the Raman spectrum. Using the wavelength of a given RBM peak, the equation d = 239 / ω can be used. ＲＢＭ can be used to define the diameter of the carbon nanotube that gives rise to that peak, where d is the diameter of the nanotube in nm and ω ＲＢＭ is cm －１ is the wavenumber of the RBM peak in units of .

[0050] Once the diameter of carbon nanotubes that produce RBM peaks is determined, it is possible to determine whether these carbon nanotubes are metallic or semiconducting. This can be done, for example, using a plot called a Kataura plot. The diameter of the carbon nanotube is read off the x-axis, and the excitation energy used to produce the RBM peak of interest is read off the y-axis. For a given diameter and excitation energy, the plot indicates whether the carbon nanotube that produces the RBM peak has metallic or semiconducting properties.

[0051] For example, a typical method for investigating the metallic or semiconducting properties of carbon nanotubes in carbon materials involves the following steps: (i) collecting a first Raman spectrum using an incident wavelength of 633 nm; (ii) collecting a first Raman spectrum using an incident wavelength of 120 cm －１ From 350 cm －１ (iii) using a Lorentzian fit to determine each RBM peak position (ω ＲＢＭ (iv) determining the diameter of the nanotube associated with each RBM peak using the formula: d=239 / ω ＲＢＭ where d is the diameter of the carbon nanotube in nm and ω ＲＢＭ is cm －１ (v) comparing this diameter with the Cataura plot using an excitation energy of 1.96±0.1 eV (corresponding to incident light at 633 nm) to determine whether each RBM peak corresponds to metallic or semiconducting carbon nanotubes; (vi) acquiring a second Raman spectrum using an incident wavelength of 514 nm, corresponding to an excitation energy of 2.41±0.1 eV, and repeating steps (i) through (v) on this second Raman spectrum.

[0052] (Shape and properties of carbon material) The shape of the carbon material is not particularly limited, and may be a fiber, a film, or a powder. In one aspect of the present embodiment, the carbon material may be a fiber or a film.

[0053] In this embodiment, at least one dimension of the carbon material may exceed 1 m, may be 10 m or more, or may be 100 m or more. The upper limit of the at least one dimension of the carbon material is not particularly limited, but may be, for example, 20,000 m or less.

[0054] In this embodiment, the density of the carbon material is 0.5 g / cm ３ 2.0g / cm or more ３ or less, and３ 1.5g / cm or more ３ or less, and ３ 1.4g / cm or more ３ or less, and ３ 1.3g / cm or more ３ The density of the carbon material can be measured using a commonly used dry densitometer.

[0055] In this embodiment, the specific strength of the carbon material may be 0.2 GPa / SG or more, 0.3 GPa / SG or more, or 0.5 GPa / SG or more in at least one direction. The upper limit of the specific strength of the carbon material is not particularly limited, but may be, for example, 20.0 GPa / SG or less. The specific strength of the carbon material can be measured by a commonly used tensile test (for example, JIS R7606:2000 Carbon fiber - Test method for tensile properties of single fiber (ISO 11566)).

[0056] In this embodiment, the specific rigidity of the carbon material may be 10 GPa / SG or more, 40 GPa / SG or more, 45 GPa / SG or more, or 50 GPa / SG or more. The upper limit of the specific rigidity of the carbon material is not particularly limited, but may be, for example, 200.0 GPa / SG or less. The specific rigidity of the carbon material can be measured by a commonly used tensile test (for example, JIS R7606:2000 Test method for tensile properties of carbon fibers - single fibers (ISO 11566) and JIS R 7607:2000 Test method for diameter and cross-sectional area of ​​carbon fibers - single fibers).

[0057] <Method for producing carbon material> The method for producing a carbon material according to this embodiment includes: a step of preparing catalyst particles (hereinafter, sometimes simply referred to as "first step"); and a step of bringing the catalyst particles in a suspended state into contact with a carbon-containing gas to form carbon nanotubes (hereinafter, sometimes simply referred to as "second step"), wherein the catalyst particles contain tungsten as a constituent element.

[0058] <First Step: Step of Preparing Catalyst Particles> In the first step, catalyst particles are prepared. The catalyst particles contain tungsten as a constituent element.

[0059] The catalyst particles may further contain one or more metal elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth metal elements.

[0060] Specific examples of lanthanoid rare earth metals include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0061] In one aspect of this embodiment, the catalyst particles may be a substance having the following chemical composition:

[0062] Two-way catalyst: WV, WFe １．１７ , WFe ２ , WFe, WCo １．１７ , W.C.O. ３ , WCo, WNi, WNi ４ , WNi ５．６７ , W.C.u. ０．６７ , W.C.u. ５．２５ , WRe, WRe ３ , W.R.E. ０．２５ , W.R.E. １０．１１ , W １３ Re ７ , WOs ０．５ , WOs ２ , WIr, WPt ２ , WRh ３ , WRh ４ , W.R.u. ０．１８ , W.R.u. １．５ , W.E.u. ０．１８ , W.C.e. ３ , WPr ３ .

[0063] Three-way catalyst: WCoNi, WFeNi５ , W.M.n ３ Fe, WPtNi １０ , W.R.u. ２ Fe ５ , WRhCo, WCu ２ Fe １２ , WFeV ４ , W.R.E. ０．１２５ Ni ０．１２５ , W.R.u. ３ Cu １２ , WPtCu １０ ;WMn １．５ V ０．６３ , WLaFe ３ .

[0064] Multi-catalyst: WFeCoNi, WFeCoMn, WFeCu ３ Ru, W.M.n ５ V ３ Cr, WRuPtAu, WFe ０．１ Au ０．２ Mn ０．１ , WFeRe ２ Mn, WOsCu ３ Mn ８ .

[0065] In one aspect of this embodiment, the catalyst particles are WCo １．１７ (Co ７ W ６ ), and WFe １．１７ It may contain at least one selected from the group consisting of:

[0066] In this embodiment, 99% to 100% of the catalyst particles may have a diameter of 1 nm to 4 nm, 1 nm to 3 nm, or 1 nm to 2 nm. The diameter of the catalyst particles is obtained by directly observing the catalyst particles using a TEM, measuring the distance between the two most distant points on the periphery of the catalyst particles, and calculating the average value from the obtained values. The number of catalyst particles observed may be at least 20, or may be at least 40.

[0067] The catalyst particles can be produced, for example, by the following method. First, an aqueous solution containing tungsten (hereinafter sometimes referred to as a "tungsten aqueous solution" or "W aqueous solution") is prepared. If necessary, an aqueous solution containing another metal element, such as a cobalt aqueous solution (Co aqueous solution), may be added to the tungsten aqueous solution to prepare a mixed solution.

[0068] Next, the prepared tungsten aqueous solution or mixed solution (sometimes referred to as "raw aqueous solution") is electrostatically sprayed using an electrostatic sprayer to generate nanometer-sized droplets (sometimes referred to as "nanodroplets") (Figure 1). The generated nanodroplets are introduced into a dryer and dried in a nitrogen gas atmosphere to generate nanometer-sized particles (sometimes referred to as "nanoparticles") (Figure 1). An example of an apparatus for electrostatic spraying is the Electrospray 3480 Nanoparticle Generator manufactured by Tokyo Dylec Corporation.

[0069] Then, nanoparticles of the target size (e.g., 1 nm particle size) are collected using a particle classifier and introduced into a tubular furnace under a hydrogen gas atmosphere. The nanoparticles are subjected to a reduction treatment in the tubular furnace to obtain catalyst particles. The obtained catalyst particles are used directly in the second step.

[0070] Examples of tungsten-containing compounds used in preparing the tungsten aqueous solution include ammonium metatungstate ((NH ４ ) ６ [H ２ W １２ O ４０ ]), ammonium paratungstate, tungsten chloride, etc.

[0071] The concentration of tungsten in the aqueous tungsten solution may be 0.1 atomic % or more and 2 atomic % or less, or 0.5 atomic % or more and 1 atomic % or less.

[0072] Examples of compounds containing other metal elements that can be used to prepare the aqueous solution containing the other metal elements include cobalt nitrate hexahydrate (Co(NO ３ ) ２ ・6H ２O), cobalt chloride hexahydrate (CoCl ２ ・6H ２ O) and the like.

[0073] The concentration of the other metal element in the aqueous solution containing the other metal element may be 0.1 atomic % or more and 2 atomic % or less, or 0.5 atomic % or more and 1 atomic % or less.

[0074] Conventionally, ferrocene and the like have been used as catalysts. However, because ferrocene is water-insoluble, it has been difficult to precisely control the size of catalyst particles using electrostatic spraying as described above. The catalyst particles according to this embodiment are made from a water-soluble salt as a starting material, and therefore it is possible to precisely control the size of catalyst particles using electrostatic spraying as described above.

[0075] <Second Step: Forming Carbon Nanotubes> In the second step, the suspended catalyst particles are brought into contact with a carbon-containing gas to form carbon nanotubes. In this embodiment, the second step may be performed in a CNT synthesis furnace (FIG. 1).

[0076] The carbon-containing gas may be a reducing gas such as a hydrocarbon gas. Examples of such a carbon-containing gas include a mixed gas of methane and argon, a mixed gas of ethylene and argon, a mixed gas of methane and hydrogen, a mixed gas of ethylene and hydrogen, a mixed gas of ethanol and argon, and a mixed gas of ethanol and hydrogen. The carbon-containing gas may contain carbon disulfide (CS) as an auxiliary catalyst. ２ ) or thiophene (C ４ H ４ S).

[0077] The second step may be performed, for example, at a temperature of 800° C. to 1500° C. Under the temperature condition of 800° C. to 1500° C., the carbon-containing gas is thermally decomposed, and carbon crystals grow on the suspended catalyst particles, forming carbon nanotubes. By separating a plurality of closely-contacted catalyst particles in the flow of the carbon-containing gas, CNTs can also be grown between the plurality of catalyst particles.

[0078] When the temperature is 800°C or higher, the growth rate of the carbon crystals is high and production efficiency is improved. On the other hand, when the temperature is 1500°C or lower, the content of impurity carbon is reduced and the quality of the CNTs is improved. The temperature condition for the second step may be 900°C or higher and 1450°C or lower, or 1100°C or higher and 1400°C or lower.

[0079] The lower limit of the flow rate of the carbon-containing gas may be 0.05 cm / sec or more, 0.10 cm / sec or more, or 0.20 cm / sec or more. On the other hand, the upper limit of the flow rate of the carbon-containing gas may be 10.0 cm / sec or less. When the flow rate of the carbon-containing gas is 0.05 cm / sec or more, the carbon-containing gas supplied to the catalyst particles is sufficient, and the growth of carbon nanotubes synthesized between the catalyst particles is promoted. On the other hand, when the flow rate of the carbon-containing gas is 10.0 cm / sec or less, it is possible to prevent the carbon nanotubes from peeling off from the catalyst particles and stopping the growth of the carbon nanotubes. The flow rate of the carbon-containing gas may be 0.05 cm / sec or more and 10.0 cm / sec or less, 0.10 cm / sec or more and 10.0 cm / sec or less, or 0.20 cm / sec or more and 10.0 cm / sec or less. In this specification, the "flow rate of the carbon-containing gas" refers to the amount of gas supplied per unit time (cm ３ / sec) is the cross-sectional area of ​​the reaction tube (cm ２ ) is the value calculated by dividing the

[0080] The lower limit of the Reynolds number of the flow of the carbon-containing gas supplied from the carbon-containing gas supply port in the CNT synthesis furnace may be 0.01 or more, or 0.05 or more. On the other hand, the upper limit of the Reynolds number may be 1000 or less, 100 or less, or 10 or less. When the Reynolds number is 0.01 or more, the degree of freedom in designing the device is improved. When the Reynolds number is 1000 or less, it is possible to prevent the flow of the carbon-containing gas from being disturbed, thereby preventing the synthesis of carbon nanotubes between catalyst particles from being hindered.

[0081] In the manufacturing method according to this embodiment, in addition to the above-described steps, additional steps may be appropriately performed as long as the effects of this embodiment are achieved. Examples of the additional steps include a step of removing catalyst particles, a step of orienting and assembling the plurality of carbon nanotubes along the longitudinal direction of the carbon nanotubes to form a carbon nanotube assembled wire, a step of purifying the carbon nanotubes, and a step of twisting and winding the carbon nanotubes.

[0082] The step of removing the catalyst particles can be carried out by, for example, heat treating the collected carbon nanotubes with chlorine gas at 500°C.

[0083] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0084] <Preparation of Carbon Material> <Sample 1> The carbon material according to this example (carbon material of Sample 1) was prepared by the following steps. <First Step: Step of Preparing Catalyst Particles> First, aqueous solutions with the following concentrations were prepared. Co aqueous solution: cobalt nitrate hexahydrate Co(NO ３ ) ２ ・6H ２ O (Wako Pure Chemical Industries, Ltd.) (aqueous solution with a concentration of 1 mol%), W aqueous solution: ammonium metatungstate (NH ４ ) ６ [H ２ W １２ O ４０ ] (Nippon Inorganic Chemical Industry) (aqueous solution with a concentration of 1 mol%)

[0085] Both aqueous solutions were mixed at a predetermined ratio (Co ７ W ６ A raw material aqueous solution was prepared by mixing Co-W and Co-Al alloy. The prepared raw material aqueous solution (Co-W mixed aqueous solution) was electrostatically sprayed using a nanoparticle generator Electrospray 3480 (trade name) manufactured by Tokyo Dylec Corporation to generate nanodroplets. The nanoparticle generator was set at a voltage of 2 kV and a current of 500 nA. The generated nanodroplets were introduced into a tubular dryer at 500°C and dried in a nitrogen gas atmosphere to generate nanoparticles.

[0086] The generated nanoparticles were processed using a particle classification device platform DMA3082 (trade name) to collect nanoparticles with a particle size of 1 nm. The collected nanoparticles were introduced into a hydrogen atmosphere furnace (tubular furnace) at 800°C together with a carrier gas (hydrogen gas), and Co was reduced by hydrogen. ７ W ６ The resulting alloy was used to obtain catalyst particles, which were then directly supplied to a CNT synthesis furnace.

[0087] <Second Step: Step of Forming Carbon Nanotubes> Argon gas with an argon gas concentration of 100% by volume was supplied from the carbon-containing gas supply port into the CNT synthesis furnace at a flow rate of 1000 cc / min (flow rate 3.4 cm / sec) for 50 minutes, while the temperature inside the electric furnace (heating device) was raised to 1130° C. Next, the argon gas was stopped, and hydrogen gas was supplied at a flow rate of 7000 cc / min (flow rate 8.84 cm / sec), methane gas at a flow rate of 50 cc / min (flow rate 0.17 cm / sec), and carbon disulfide (CS ２ ) gas was supplied at a flow rate of 1 cc / min (flow rate 0.003 cm / sec) for 120 minutes. The total flow rate of the mixed gas (carbon-containing gas) containing argon gas, methane gas, and carbon disulfide was 9.0 cm / sec. CNTs grew when the methane gas came into contact with the catalyst particles supplied in advance.

[0088] <Step 3: Forming into Carbon Nanotube Wire> The obtained CNT was heat-treated in air at 420°C for 2 hours. The heat-treated CNT was then immersed in 12M hydrochloric acid at 80°C for 2 hours, washed with water, and vacuum-dried at 120°C for 12 hours. The dried CNT was then placed in an aqueous chlorosulfonic acid solution at a concentration of 0.2 mass%. The aqueous solution was then subjected to ultrasonic irradiation at 120°C for 72 hours to disperse the CNT in the aqueous solution. This dispersion was passed through a 0.5 mm diameter Teflon tube, and the CNT was formed into a wire. The formed wire was then washed with acetone to remove the chlorosulfonic acid, yielding a carbon nanotube wire (a carbon material containing carbon nanotubes).

[0089] Through the above steps, the carbon material of Sample 1 was obtained.

[0090] <Sample 2> A carbon material was obtained in the same manner as Sample 1, except that the prepared catalyst raw material liquid was atomized with a commercially available ultrasonic nebulizer without using Electrospray 3480, and then introduced into a tubular dryer.

[0091] <Sample 3> A carbon material was obtained in the same manner as in Sample 1, except that only a 1 mass % ferrocene solution dissolved in toluene was used as the catalyst raw material.

[0092] Carbon materials Samples 1 to 3 were prepared by the above steps.

[0093] <<Characteristic Evaluation of Carbon Materials>> Using the carbon material samples prepared as described above, the properties of the carbon materials were evaluated as follows. Here, the carbon material of Sample 1 corresponds to an example. The carbon materials of Samples 2 and 3 correspond to comparative examples. Furthermore, as reference examples, data on copper (Cu), aluminum (Al), and iron (Fe), which have traditionally been used as materials for electric wires, are shown in Table 2.

[0094] <Carbon Nanotube Diameter> The diameter of the CNTs was calculated by examining the radial breathing mode (RBM) of each CNT using Raman spectroscopy. Specifically, the following steps were performed: (i) collecting a first Raman spectrum of each CNT using an incident wavelength of 633 nm; (ii) collecting a first Raman spectrum of each CNT using an incident wavelength of 120 cm －１ From 350 cm －１ (iii) identifying each peak (RBM peak) falling in the range of ω ＲＢＭ (iv) determining the diameter of the nanotube associated with each RBM peak using the formula: d=239 / ω ＲＢＭ where d is the diameter of the carbon nanotube in nm and ω ＲＢＭ is cm －１ The results are shown in Table 2 (column "RBM equivalent diameter"). The numerical ranges shown in Table 2 indicate that 90% or more of the number of carbon nanotubes falls within the numerical range.

[0095] <Chirality of Carbon Nanotubes> The chirality of the carbon nanotubes contained in each sample was determined by the following procedure. First, an optical absorption spectrum was obtained for each sample using a spectrofluorophotometer. The measurement conditions were as follows: (Measurement conditions for optical absorption spectrum using spectrofluorophotometer) Measurement device: spectrofluorophotometer, JASCO FP-8750 Measurement temperature: room temperature (25°C) Measurement wavelength: 300 nm to 1700 nm Reference armchair (metallic) CNT: CNT with a chiral index of (6,6) and the same diameter as the CNT to be measured

[0096] The obtained optical absorption spectra were then compared, and if the optical transition in the CNT being measured was observed to be equal to or higher in energy than the optical transition in the reference armchair CNT, the CNT being measured was determined to have armchair chirality. The results are shown in Table 2 (column "Peak Chirality"). The chiral index shown in Table 2 indicates that 90% or more of the carbon nanotubes belong to that chiral index. "Random" indicates that the chiral index was not determined.

[0097] <Carbon Nanotube Content> The carbon nanotube content was determined by thermogravimetric differential thermal analysis (TG-DTA) under the following conditions. As a result, it was found that the carbon nanotube content in the carbon materials of Samples 1 to 3 was almost 100% by mass. (Measurement conditions for thermogravimetric differential thermal analysis) Air flow: 50 ml / min Measurement temperature: Measurement was performed from room temperature (25°C) to 1000°C at a heating rate of 5°C / min Calculation method: The content was calculated from the ratio of the residue mass after measurement up to 1000°C to the initial mass (mass before measurement).

[0098] <Proportion of carbon nanotubes with armchair chirality> The proportion of carbon nanotubes with armchair chirality (probability of existence) was calculated by examining the radial breathing mode (RBM) of each CNT using Raman spectroscopy. Specifically, the chirality was determined 20 times for the same carbon material based on the RBM peak, and the probability of existence was calculated based on the number of times it was determined to be armchair chirality using the above formula 1. As a result, it was found that the proportion of carbon nanotubes with armchair chirality in the carbon material of sample 1 was 90% or more. On the other hand, in samples 2 and 3, the proportion of carbon nanotubes with armchair chirality was 50% or less, and metallic chirality was not predominant.

[0099] <Catalyst Particle Components, Content, and Diameter> The catalyst particle composition was determined by combusting the carbon material contained in each sample using a differential thermal analyzer (e.g., TG-DTA) and quantitatively identifying the metal oxides (ash) of the catalyst particles using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). The catalyst particle content was determined using TG-DTA under the following conditions. As a result, it was found that the catalyst particle content in the carbon material of Samples 1 to 3 was nearly 0% by mass. (Thermogravimetric Differential Thermal Analysis Measurement Conditions) Air flow: 50 ml / min Measurement temperature: Measured from room temperature (25°C) to 1000°C at a heating rate of 5°C / min Calculation method: The content was calculated from the ratio of the residue mass after measurement up to 1000°C to the initial mass (mass before measurement).

[0100] <Conductivity of Carbon Material> The conductivity of the carbon material was determined by "resistance measurement by four-probe method" according to JIS K 7194. The results are shown in Table 2 (column "Conductivity").

[0101] <Density, specific strength, and specific rigidity of carbon material> The density of the carbon material was measured using a dry densitometer. The specific strength and specific rigidity of the carbon material were measured using a tensile test specified in JIS (JIS R7606:2000 Carbon fiber - Test method for tensile properties of single fiber (ISO 11566)). The results are shown in Table 2 (columns for "volume density," "specific strength," and "specific rigidity," respectively).

[0102]

[0103] Results From the results in Table 2, it was found that the carbon material of Sample 1 (Example) had a peak chirality of (6,6) and an armchair chirality. In addition, the carbon material of Sample 1 had a conductivity of 15.5 × 10 ６ S / m, indicating excellent conductivity. On the other hand, it was found that Samples 2 and 3 (Comparative Examples) did not have armchair chirality. The carbon materials of Samples 2 and 3 had a conductivity of 3.0×10 ６ It was less than S / m.

[0104] The above description includes the following additional features: (Additional Note 1) A carbon material containing carbon nanotubes, wherein 90% to 100% of the carbon nanotubes by number have a diameter of 0.9 nm to 2 nm, 90% to 100% of the carbon nanotubes by number have armchair chirality, and the carbon material has a chirality of 5×10 in at least one direction. ６ Sm －１ (Appendix 2) The carbon material according to Appendix 1, wherein the carbon nanotube content is 80 mass % or more relative to the carbon material. (Appendix 3) The carbon material according to Appendix 1 or Appendix 2, wherein the carbon material is a fiber or a film. (Appendix 4) The carbon material according to Appendix 1 or Appendix 2, wherein at least one dimension of the carbon material exceeds 1 m. (Appendix 5) The density of the carbon material is 0.5 g / cm ３ 2.0g / cm or more ３(Supplementary Note 6) The carbon material according to Supplementary Note 1 or Supplementary Note 2, wherein the specific strength of the carbon material is 0.2 GPa / SG or more in at least one direction. (Supplementary Note 7) The carbon material according to Supplementary Note 1 or Supplementary Note 2, wherein the specific rigidity of the carbon material is 10 GPa / SG or more. (Supplementary Note 8) The carbon material according to Supplementary Note 1 or Supplementary Note 2, further comprising catalyst particles dispersed in the carbon material, the catalyst particles containing tungsten as a constituent element, and a content of the catalyst particles of the carbon material of 0.1 mass % or more and 20 mass % or less. (Supplementary Note 9) The carbon material according to Supplementary Note 8, wherein the catalyst particles further contain one or more metal elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth metal elements. (Supplementary Note 10) The carbon material according to Supplementary Note 8, wherein 99% to 100% of the catalyst particles by number have a diameter of 1 nm to 4 nm.

[0105] Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined.

[0106] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

Claims

1. A carbon material containing carbon nanotubes, 90% to 100% by number of the carbon nanotubes have a diameter of 0.9 nm to 2 nm, 90% to 100% of the carbon nanotubes by number have armchair chirality; The carbon material has a particle size of 5×10 in at least one direction. ６ Sm －１ A carbon material having a conductivity of at least 1000 kJ / cm.

2. The carbon material according to claim 1 , wherein the carbon nanotubes are contained in an amount of 80 mass % or more relative to the carbon material.

3. The carbon material according to claim 1 or 2, which is a fiber or a film.

4. The carbon material according to claim 1 or claim 2, wherein at least one dimension of the carbon material exceeds 1 m.

5. The density of the carbon material is 0.5 g / cm ３ 2.0g / cm or more ３ The carbon material according to claim 1 or claim 2, wherein:

6. 3. The carbon material according to claim 1, wherein the specific strength of the carbon material is 0.2 GPa / SG or more in at least one direction.

7. The carbon material according to claim 1 or 2, wherein the specific rigidity of the carbon material is 10 GPa / SG or more.

8. further comprising catalyst particles dispersed in the carbon material; the catalyst particles contain tungsten as a constituent element, 3. The carbon material according to claim 1, wherein a content of the catalyst particles is 0.1% by mass or more and 20% by mass or less with respect to the carbon material.

9. 9. The carbon material according to claim 8, wherein the catalyst particles further contain one or more metal elements selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth metal elements.

10. 9. The carbon material of claim 8, wherein 99% to 100% of the catalyst particles by number have a diameter of 1 nm to 4 nm.