Carbon material

Abstract

A carbon material containing carbon nanotubes, in which 90% or more and 100% or less of the number of the carbon nanotubes have a diameter of 0.9 nm or more and 2 nm or less, 90% or more and 100% or less of the number of the carbon nanotubes have armchair-type chirality, and the carbon material has an electrical conductivity of 5 * 106 Sm <-1 > or more in at least one direction.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a carbon material. This application claims priority based on Japanese Patent Application, i.e., Japanese Patent Application No. 2023-037672, filed on March 10, 2023. All the descriptions described in the Japanese Patent Application are hereby incorporated by reference in the present specification. BACKGROUND

[0002] A carbon nanotube is a substance in which graphene sheets formed of carbon are formed into a single layer or multiple layers of coaxial tubular shape. Here, graphene is a sheet-shaped substance in which sp2-bonded carbon atoms are bonded to each other by a covalent bond to form a hexagonal lattice structure. The thickness of the graphene is the thickness of one atom.

[0003] A carbon nanotube is called a next-generation carbon material, a nanomaterial, or the like due to its fineness, lightness, and softness, and various uses are being developed.

[0004] For example, in Japanese Patent Application Publication No. 2014-503448 (Patent Literature 1), a carbon material including a carbon nanotube is disclosed, which is characterized in that at least 70% of the number of the carbon nanotube has a diameter in the range of 1 nm to 2.5 nm and has a conductivity of at least 0.7 x 10 6 Sm -1 .

[0005] PRIOR ART DOCUMENT

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2014-503448 SUMMARY

[0008] The carbon material according to the present disclosure includes a carbon nanotube in which,

[0009] at least 90% and less than 100% of the number of the carbon nanotube has a diameter of 0.9 nm or more and less than 2 nm,

[0010] at least 90% and less than 100% of the number of the carbon nanotube has armchair chirality,

[0011] the carbon material has a conductivity of at least 5 x 10 6 Sm -1 or more in at least one direction. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a schematic view showing a manufacturing apparatus of a carbon nanotube according to the present embodiment. DETAILED DESCRIPTION

[0013] [Problem to be Solved by the Invention]

[0014] Carbon materials containing carbon nanotubes have conductivity, and thus are expected as materials for electric wires, but have a low conductivity compared to copper or aluminum, and thus have room for improvement.

[0015] The present invention has been achieved in view of the above, and aims to provide a carbon material containing carbon nanotubes having excellent conductivity.

[0016] [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a carbon material containing carbon nanotubes having excellent conductivity.

[0018] [Explanation of Embodiments of the Invention]

[0019] First, an embodiment of the present invention will be explained.

[0020] [1] The carbon material according to the present invention contains carbon nanotubes, in which,

[0021] 90% or more and 100% or less of the number of the above carbon nanotubes have a diameter of 0.9 nm or more and 2 nm or less,

[0022] 90% or more and 100% or less of the number of the above carbon nanotubes have armchair-type chirality,

[0023] The above carbon material has a conductivity of 5 x 10 6 Sm -1 or more in at least one direction.

[0024] In the above carbon material, carbon nanotubes having armchair-type chirality are the main constituent elements. Thus, the conductivity of the above carbon material is improved compared to conventional carbon materials. That is, the present invention can provide a carbon material containing carbon nanotubes having excellent conductivity by having the above configuration. Here, "armchair-type chirality" refers to a specific regularity structure in which the chirality index is represented by (a, a) in the winding manner of the graphene plane constituting the carbon nanotube (a represents a natural number). "Conductivity" refers to the ease of conduction in the above carbon material.

[0025] [2] On the basis of the above [1], the content ratio of the above carbon nanotubes in the above carbon material can be 80% by mass or more. By doing so, it is possible to provide a carbon material having even more excellent conductivity.

[0026] [3] In the above [1] or [2], the carbon material can also be a fiber or a film. By so doing, a carbon material having excellent electrical conductivity and excellent continuity formability can be provided. Here, the "continuity" refers to a state in which a solid substance is not divided, and a substance in which a tensile stress applied to one point of the solid substance is propagated to the entire solid substance (for example, a substance that is not a powder). The "continuity formability" refers to a property of a solid substance that is formed in a linear or sheet shape without being formed as a powder.

[0027] [4] In any one of the above [1] to [3], the size of at least one of the carbon materials can be greater than 1 m. By so doing, a carbon material having excellent electrical conductivity and excellent continuity formability can be provided.

[0028] [5] In any one of the above [1] to [4], the density of the carbon material can be 0.5 g / cm 3 or more and 2.0 g / cm 3 or less. By so doing, a carbon material having excellent electrical conductivity and excellent continuity formability can be provided.

[0029] [6] In any one of the above [1] to [5], the specific strength of the carbon material can be 0.2 GPa / SG or more in at least one direction. By so doing, a carbon material having excellent electrical conductivity and excellent continuity formability can be provided.

[0030] [7] In any one of the above [1] to [6], the specific rigidity of the carbon material can be 10 GPa / SG or more. By so doing, a carbon material having excellent electrical conductivity and excellent continuity formability can be provided.

[0031] [8] In any one of the above [1] to [7], the carbon material can further have catalyst particles dispersed therein,

[0032] the catalyst particles contain tungsten as a constituent element,

[0033] the proportion of the catalyst particles contained with respect to the carbon material can be 0.1 mass% or more and 20 mass% or less. By so doing, a carbon material having excellent electrical conductivity and excellent continuity formability can be provided.

[0034] [9] On the basis of the above [8], the catalyst particles can also contain one or more metal elements selected from the group consisting of Group 4 elements of the periodic table, Group 5 elements of the periodic table, Group 6 elements of the periodic table, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth elements. By so doing, a carbon material having excellent electrical conductivity and excellent continuous body formability can be provided.

[0035]

[10] On the basis of the above [8] or [9], 99% or more and 100% or less of the number of the catalyst particles can have a diameter of 1 nm or more and 4 nm or less. By so doing, a carbon material having excellent electrical conductivity and excellent continuous body formability can be provided.

[0036] [Details of Embodiments of the Present Disclosure]

[0037] Hereinafter, one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described. However, the present embodiment is not limited thereto. In the present specification, the expression "A to Z" means the upper limit and the lower limit of the range (i.e., A or more and Z or less). In the case where the unit is not described in A but is described in Z, the unit of A is the same as that of Z. Furthermore, in the present specification, in the case where a compound is expressed by a chemical formula without limiting the composition ratio of the constituent elements, such as "TiC", the chemical formula includes all composition ratios (element ratios) known in the art. At this time, the above chemical formula includes not only the stoichiometric composition but also the non-stoichiometric composition. For example, in the chemical formula of "WFe", not only the stoichiometric composition "W1Fe1" but also the non-stoichiometric composition such as "W1Fe0.9" is included. The same applies to the description of compounds other than "WFe". 1.17

[0038] Carbon Material

[0039] The carbon material according to the present disclosure contains carbon nanotubes,

[0040] 90% or more and 100% or less of the number of the above carbon nanotubes have a diameter of 0.9 nm or more and 2 nm or less,

[0041] 90% or more and 100% or less of the number of the above carbon nanotubes have a chirality of armchair type,

[0042] The above carbon material has an electrical conductivity of 5 x 10 6 Sm -1 or more in at least one direction.

[0043] ​The carbon material of the present embodiment contains carbon nanotubes (hereinafter, sometimes referred to as "CNT"). Here, the "carbon nanotube" refers to a substance in which graphene sheets formed of carbon are formed into a single layer or multiple layers of coaxial tubular shape. The "graphene" refers to a sheet-shaped substance in which sp2-bonded carbon atoms are bonded to each other by a covalent bond to form a hexagonal lattice structure and the thickness of the layer is the thickness of one atom.

[0044] <Carbon nanotube>

[0045] In the present embodiment, the shape of the carbon nanotube is not particularly limited, and a shape in which the front end is closed or a shape in which the front end is open can be cited. In addition, a catalyst particle used at the time of synthesis of the carbon nanotube can be attached to one or both of the end portions of the carbon nanotube. In addition, a tapered portion composed of a conical graphene can be formed at one or both of the end portions of the carbon nanotube.

[0046] In the present embodiment, 90% or more and 100% or less of the number of the above-described carbon nanotubes have a diameter of 0.9 nm or more and 2 nm or less, can have a diameter of 0.9 nm or more and 1.8 nm or less, or can have a diameter of 1 nm or more and 1.7 nm or less. The diameter of the CNT can be calculated by detecting the radial breathing mode (RBM) in each CNT using Raman spectroscopy. The specific procedure is described later.

[0047] In the present embodiment, 90% or more and 100% or less of the number of the above-described carbon nanotubes have armchair chirality. 95% or more and 100% or less of the number of the above-described carbon nanotubes can also have armchair chirality. In one aspect of the present embodiment, "90% or more and 100% or less of the number of the carbon nanotubes have armchair chirality" can also be grasped as meaning that the existence probability of the carbon nanotubes having armchair chirality is 90% or more and 100% or less, based on the total number of the carbon nanotubes. The carbon nanotubes having armchair chirality tend to have electrical conductivity. Therefore, the chirality of the carbon nanotubes can be evaluated in accordance with the electrical conductivity of the carbon nanotubes. The electrical conductivity of the above-described carbon nanotubes is judged by Kataura plot of the optical absorption spectrum in a spectrophotometer. The optical transition in the carbon nanotubes having armchair chirality (metallic carbon nanotubes) is observed at a higher energy side than the optical transition in the carbon nanotubes having the same diameter and semiconductor type (for example, carbon nanotubes of chiral type), and thus can be judged based thereon.

[0048] (Measurement conditions of optical absorption spectrum in spectrophotometer)

[0049] Measurement device: Spectrophotometer, JASCO FP-8750, Japan

[0050] Measurement temperature: Room temperature (25°C)

[0051] Measurement wavelength: 300 nm to 1700 nm

[0052] Armchair-type CNT serving as a reference: CNT having 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 to be measured

[0053] Judging method: The obtained optical absorption spectrum is compared, and when the optical transition in the CNT to be measured is equal to the optical transition in the armchair-type CNT serving as a reference or is observed on the higher-energy side than the optical transition in the armchair-type CNT serving as a reference, it is judged that the CNT to be measured has an armchair-type chirality.

[0054] Also, at least 90% of the number of carbon nanotubes can be armchair-type carbon nanotubes. Also, at least 95%, 96%, 97%, 98%, or 99% of the number of carbon nanotubes can be armchair-type carbon nanotubes.

[0055] The proportion (existence probability) of the number of carbon nanotubes having an armchair-type chirality can be calculated by detecting a radial breathing mode (RBM) in each CNT using a Raman spectroscopy method described later. Specifically, for the same carbon material, 20 times of chirality judgment is performed based on the RBM peak, and the number of times judged to be armchair-type is calculated based on the following Formula 1.

[0056] Existence probability (%) of armchair-type CNT = 100 x (number of times judged to be armchair-type based on the RBM peak) / 20 Formula 1

[0057] The carbon nanotube can also have an alignment main axis. Generally, in the case where the carbon material is a fiber, the axis of the fiber is taken as the main axis of the carbon nanotube. Of course, this is easily confirmed at the time of TEM analysis. Here, the "main axis of the carbon nanotube" is an axis parallel to the long side direction of the carbon nanotube.

[0058] The preferred armchair-type chirality of the above-described carbon nanotube can be exemplified by the following parameters. The above-described chirality is disclosed together with the chiral index (n, m) and its diameter (Table 1). The expression of the chiral index (n, m) used in this application is an expression well known to those skilled in the art. Here, n and m each represent a natural number.

[0059] [Table 1]

[0060]

[0061] In the present embodiment, the above-described carbon nanotube can have a content ratio of 80% by mass or more, 80% by mass or more and 100% by mass or less, or 90% by mass or more and 100% by mass or less, with respect to the above-described carbon material. The content ratio of the carbon nanotube can be calculated by using a thermogravimetric differential thermal analysis method (TG-DTA method) under the following conditions.

[0062] (Measurement conditions of thermogravimetric differential thermal analysis)

[0063] Atmospheric flow: 50 ml / min

[0064] Measurement temperature: Measurement from room temperature (25°C) to 1000°C at a temperature increase rate of 5°C / min

[0065] Calculation method: The content ratio is calculated from the ratio of the residual mass after measurement to 1000°C to the initial mass (mass before measurement).

[0066] <Catalyst particles>

[0067] In the present embodiment, the above-described carbon material can further have catalyst particles dispersed in the above-described carbon material,

[0068] The above-described catalyst particles contain tungsten as a constituent element,

[0069] The above-described catalyst particles have a content ratio of 0.1% by mass or more and 20% by mass or less with respect to the above-described carbon material.

[0070] By the above-described catalyst particles being contained in the above-described carbon material, it can be seen that the carbon material is manufactured by the manufacturing method described later.

[0071] The above-described catalyst particles can further contain one or more metal elements selected from the group consisting of Group 4 elements of the periodic table, Group 5 elements of the periodic table, Group 6 elements of the periodic table, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid metal elements.

[0072] As the lanthanoid metal, specifically, 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) can be listed.

[0073] In one aspect of the present embodiment, the above-described catalyst particles can be substances having the following chemical compositions.

[0074] Binary catalysts: WV, WFe 1.17 , WFe2, WFe, WCo 1.17, WCo3, WCo, WNi, WNi4, WNi 5.67 , WCu 0.67 , WCu 5.25 , WRe, WRe3, WRe 0.25 , WRe 10.11 , W 13 Re7, WOs 0.5 , WOs2, WIr, WPt2, WRh3, WRh4, WRu 0.18 , WRu 1.5 , WEu 0.18 , WCe3, WPr3.

[0075] Ternary catalyst: WCoNi, WFeNi5, WMn3Fe, WPtNi 10 , WRu2Fe5, WRhCo, WCu2Fe 12 , WFeV4, WRe 0.125 Ni 0.125 , WRu3Cu 12 , WPtCu 10 ; WMn 1.5 V 0.63 , WLaFe3.

[0076] Multi-component catalyst: WFeCoNi, WFeCoMn, WFeCu3Ru, WMn5V3Cr, WRuPtAu, WFe 0.1 Au 0.2 Mn 0.1 , WFeRe2Mn, WOsCu3Mn8.

[0077] The composition of the catalyst particles dispersed in the above-described carbon material can be quantitatively identified using a scanning electron microscope-energy dispersive X-ray spectrometry (SEM-EDX) for the metal oxides (ash) of the catalyst particles, by combusting the resulting object carbon material (CNT) using a differential thermal analysis device (TG-DTA or the like).

[0078] The content ratio of the above-described catalyst particles with respect to the above-described carbon material can be 0.1 mass% or more and 20 mass% or less, can be 0.1 mass% or more and 10 mass% or less, and can be 0.1 mass% or more and 5 mass% or less. The content ratio of the catalyst particles can be obtained by measuring using a TG-DTA method under the following conditions.

[0079] (Measurement conditions of thermogravimetric differential thermal analysis)

[0080] Atmospheric flow: 50 ml / min

[0081] Measurement temperature: From room temperature (25°C) to 1000°C at a temperature increase rate of 5°C / min

[0082] Calculation method: The contained ratio is calculated from the ratio of the residue mass after measurement to 1000°C to the initial mass (mass before measurement).

[0083] In the present embodiment, 99% or more and 100% or less of the number of the above-described catalyst particles can have a diameter of 1 nm or more and 4 nm or less, can have a diameter of 1 nm or more and 3 nm or less, and can have a diameter of 1 nm or more and 2 nm or less. The diameter of the catalyst particles is obtained by directly observing the surface of the above-described carbon material using TEM, measuring the distance between the two points farthest apart on the outer circumference of the catalyst particles, and calculating the average value from the obtained value. The number of catalyst particles observed can be at least 20, and can be at least 40.

[0084] <Other components>

[0085] Within the range where the effects of the present disclosure are exerted, the carbon material according to the present embodiment can contain amorphous carbon, graphene, and the like in addition to the carbon nanotube and the catalyst particle.

[0086] <Properties of the carbon material>

[0087] (Electrical conductivity)

[0088] In the present embodiment, the above-described carbon material has an electrical conductivity of 5 x 10 6 Sm -1 or more and 20 x 10 6 Sm -1 or more. The above-described carbon material can have an electrical conductivity of 10 x 10 6 Sm -1 or more and 15 x 10 6 Sm -1 or more. The above-described carbon material can have an electrical conductivity of 10 x 10 6 Sm -1 or more. The electrical conductivity of the above-described carbon material can be obtained by "Resistance measurement based on four-probe method" of JIS K7194.

[0089] (Metal property, semiconductor property)

[0090] The carbon material according to the present embodiment can be evaluated for the metal property and the semiconductor property by using Raman spectroscopy.

[0091] One of the vibration modes of carbon nanotubes is a radial breathing mode (RBM). This radial breathing mode can be detected using Raman spectroscopy. The RBM resonance of only carbon nanotubes having a certain diameter with respect to a given wavelength of incident light, and thus, in a Raman spectrum, a radial breathing mode (RBM) peak is generated only in the range of a certain diameter of carbon nanotubes. Using the wavelength of a given RBM peak, the diameter of carbon nanotubes generating the peak can be determined using the formula d = 239 / ω RBM , where d is the diameter of the nanotube in nm units, and ω RBM is the wave number of the RBM peak in cm -1 units.

[0092] Once the diameter of carbon nanotubes generating the RBM peak is determined, it is possible to determine whether these carbon nanotubes are metallic or semiconducting. This is performed, for example, using a graph known as a Kataura plot. The diameter of the carbon nanotube is read on the x-axis, and the excitation energy for generating the target RBM peak is read on the y-axis. For a predetermined diameter and excitation energy, the above graph indicates whether the carbon nanotube generating the RBM peak has metallic properties or semiconducting properties.

[0093] For example, a typical method of detecting the metallic or semiconducting properties of carbon nanotubes in a carbon material has the following steps:

[0094] (i) a step of extracting a first Raman spectrum using an incident wavelength of 633 nm,

[0095] (ii) a step of identifying each peak (RBM peak) that decreases in the range from 120 cm -1 to 350 cm -1 ,

[0096] (iii) a step of determining the position (ω RBM ) of each RBM peak using a Rorentzian fit,

[0097] (iv) a step of determining the diameter of the nanotube associated with each RBM peak using the formula,

[0098] d = 239 / ω RBM

[0099] where d is the diameter of the carbon nanotube in nm units, and ω RBM is the wave number of the RBM peak in cm -1 units,

[0100] (v) a step of determining whether each RBM peak corresponds to a metallic or semiconducting carbon nanotube using the diameter at the Kataura plot with an excitation energy of 1.96 ± 0.1 eV (corresponding to an incident light of 633 nm),

[0101] (vi) a step of obtaining a second Raman spectrum using an incident wavelength of 514 nm corresponding to an excitation energy of 2.41 ± 0.1 eV, and repeating the steps (i) to (v) for the second Raman spectrum.

[0102] (Shape, physical properties of carbon material)

[0103] The shape of the carbon material is not particularly limited, and can be a fiber shape, a film shape, or a powder shape. In one aspect of the present embodiment, the carbon material can also be a fiber or a film.

[0104] In the present embodiment, the size of at least one of the carbon materials can be greater than 1 m, can be 10 m or more, or can be 100 m or more. The upper limit of the size of at least one of the carbon materials is not particularly limited, and for example, can be 20,000 m or less.

[0105] In the present embodiment, the density of the carbon material can be 0.5 g / cm 3 or more and 2.0 g / cm 3 or more. The density of the carbon material can also be 0.5 g / cm 3 or more and 1.5 g / cm 3 or more. The density of the carbon material can also be 0.5 g / cm 3 or more and 1.4 g / cm 3 or more. The density of the carbon material can also be 0.5 g / cm 3 or more and 1.3 g / cm 3 or more. The density of the carbon material can be measured using a dry densimeter commonly used.

[0106] In the present embodiment, the specific strength of the carbon material can be 0.2 GPa / SG or more, can be 0.3 GPa / SG or more, or can be 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, and for example, can be 20.0 GPa / SG or less. The specific strength of the carbon material can be measured by a tensile test commonly used (for example, JIS R7606: 2000 Carbon Fiber - Test Method for Tensile Properties of Single Fibers (ISO 11566)).

[0107] In the present embodiment, the specific rigidity of the carbon material described above can be 10 GPa / SG or greater, 40 GPa / SG or greater, 45 GPa / SG or greater, or 50 GPa / SG or greater. The upper limit of the specific rigidity of the carbon material described above is not particularly limited, and for example, 200.0 GPa / SG or less can be cited. The specific rigidity of the carbon material described above can be measured by a tensile test that is generally used (for example, JIS R7606:2000 Carbon fibers - Test method for tensile properties of single fibers (ISO 11566) and JIS R7607:2000 Carbon fibers - Test method for diameter and cross-sectional area of single fibers).

[0108] Method for manufacturing carbon material

[0109] The method for manufacturing a carbon material according to the present embodiment includes:

[0110] a step of preparing catalyst particles (hereinafter, sometimes referred to as "first step"); and

[0111] a step of forming carbon nanotubes by bringing the catalyst particles in a suspended state into contact with a carbon-containing gas (hereinafter, sometimes referred to as "second step"),

[0112] The catalyst particles contain tungsten as a constituent element.

[0113] <First step: step of preparing catalyst particles>

[0114] The catalyst particles are prepared in the first step. The catalyst particles described above contain tungsten as a constituent element.

[0115] The catalyst particles described above can further contain one or more metal elements selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and a lanthanoid metal element.

[0116] As the lanthanoid metal, specifically, 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) can be cited.

[0117] In one aspect of the present embodiment, the catalyst particles described above can cite a substance having the following chemical composition.

[0118] Binary catalysts: WV, WFe 1.17 , WFe2, WFe, WCo 1.17 , WCo3, WCo, WNi, WNi4, WNi5.67 , WCu 0.67 , WCu 5.25 , WRe, WRe3, WRe 0.25 , WRe 10.11 , W 13 Re7, WOs 0.5 , WOs2, WIr, WPt2, WRh3, WRh4, WRu 0.18 , WRu 1.5 , WEu 0.18 , WCe3, WPr3.

[0119] Ternary catalyst: WCoNi, WFeNi5, WMn3Fe, WPtNi 10 , WRu2Fe5, WRhCo, WCu2Fe 12 , WFeV4, WRe 0.125 Ni 0.125 , WRu3Cu 12 , WPtCu 10 ; WMn 1.5 V 0.63 , WLaFe3.

[0120] Multi-component catalyst: WFeCoNi, WFeCoMn, WFeCu3Ru, WMn5V3Cr, WRuPtAu, WFe 0.1 Au 0.2 Mn 0.1 , WFeRe2Mn, WOsCu3Mn8.

[0121] In one aspect of the embodiment, the above-described catalyst particles can also contain at least one selected from the group consisting of WCo 1.17 (Co7W6), and WFe 1.17 .

[0122] In the embodiment, 99% or more and 100% or less of the number of the above-described catalyst particles can have a diameter of 1 nm or more and 4 nm or less, can have a diameter of 1 nm or more and 3 nm or less, and can have a diameter of 1 nm or more and 2 nm or less. The diameter of the catalyst particles is obtained by directly observing the above-described catalyst particles using TEM, measuring the distance between the two points farthest apart on the outer circumference of the catalyst particles, and calculating the average value from the obtained value. The number of catalyst particles observed can be at least 20, and can be at least 40.

[0123] The above-described catalyst particles can be produced, for example, by the following method. First, an aqueous solution containing tungsten (hereinafter sometimes referred to as "tungsten aqueous solution" or "W aqueous solution") is prepared. At this time, an aqueous solution containing another metal element such as an aqueous solution of cobalt (Co aqueous solution) can be added to the above-described tungsten aqueous solution as necessary to prepare a mixed solution.

[0124] Next, the prepared tungsten aqueous solution or mixed solution (sometimes referred to as "raw material aqueous solution") is subjected to electrostatic spraying using an electrostatic sprayer to generate nanometer-sized droplets (hereinafter sometimes referred to as "nanometer droplets"). Figure 1 The generated nanometer droplets are introduced into a drier and dried under a nitrogen atmosphere to generate nanometer-sized particles (hereinafter sometimes referred to as "nanometer particles"). Figure 1 As the device for performing electrostatic spraying, for example, a nanometer particle generator Electrospray 3480 manufactured by Tokyo Dylec Corporation can be cited.

[0125] Subsequently, the nanometer particles of a target size (for example, 1 nm in particle diameter) among the obtained nanometer particles are recovered using a particle classifier and introduced into a tubular furnace under a hydrogen atmosphere. The above-described nanometer particles are subjected to reduction treatment in the above-described tubular furnace to obtain catalyst particles. The obtained catalyst particles are directly used in the second process.

[0126] As the compound containing tungsten used when the tungsten aqueous solution is prepared, for example, ammonium metatungstate ((NH4)6[H2W12O39]· 4H2O), ammonium paratungstate, tungsten chloride, and the like can be cited. 12 O 40 ]), ammonium paratungstate, tungsten chloride, and the like can be cited.

[0127] The concentration of tungsten in the tungsten aqueous solution can be 0.1 atomic% or more and 2 atomic% or less, or can be 0.5 atomic% or more and 1 atomic% or less.

[0128] As the compound containing another metal element used when the aqueous solution containing the above-described another metal element is prepared, for example, cobalt nitrate hexahydrate (Co(NO3)2· 6H2O), cobalt chloride hexahydrate (CoCl2· 6H2O), and the like can be cited.

[0129] The concentration of another metal element in the aqueous solution containing another metal element can be 0.1 atomic% or more and 2 atomic% or less, or can be 0.5 atomic% or more and 1 atomic% or less.

[0130] Conventionally, as a catalyst, ferrocene or the like is used. However, ferrocene is non-water-soluble, and thus it is difficult to precisely control the size of catalyst particles by electrostatic spraying as described above. The catalyst particles according to the present embodiment use a water-soluble salt as a starting material, and thus it is possible to precisely control the size of catalyst particles by electrostatic spraying as described above.

[0131] <Second step: Carbon nanotube forming step>

[0132] In the second step, the above catalyst particles in a suspended state are contacted with a carbon-containing gas to form carbon nanotubes. In the present embodiment, the second step can also be performed in the CNT synthesizing furnace. Figure 1

[0133] The carbon-containing gas uses a gas having a reducing property such as a hydrocarbon gas. As such a carbon-containing gas, for example, 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, a mixed gas of ethanol and hydrogen, or the like can be used. The carbon-containing gas can also contain carbon disulfide (CS2) or thiophene (C4H4S) as an auxiliary catalyst.

[0134] The second step can be performed, for example, under a temperature condition of 800°C or higher and 1500°C or lower. Under a temperature condition of 800°C or higher and 1500°C or lower, the carbon-containing gas thermally decomposes, and carbon crystals grow on the catalyst particles in a suspended state to form carbon nanotubes. By separating the multiple catalyst particles in a close contact state in the flow of the carbon-containing gas, CNTs can also grow between the multiple catalyst particles.

[0135] If the temperature is 800°C or higher, the growth speed of carbon crystals is fast, and the production efficiency improves. On the other hand, if the temperature is 1500°C or lower, the content of impurity carbon decreases, and the quality of CNTs improves. The temperature condition of the second step can be 900°C or higher and 1450°C or lower, or 1100°C or higher and 1400°C or lower.

[0136] The lower limit of the flow rate of the carbon-containing gas can be 0.05 cm / sec or higher, or 0.10 cm / sec or higher, or 0.20 cm / sec or higher. On the other hand, the upper limit of the flow rate of the carbon-containing gas can be 10.0 cm / sec or lower. In the case where the flow rate of the carbon-containing gas is 0.05 cm / sec or higher, 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, in the case where the flow rate of the carbon-containing gas is 10.0 cm / sec or lower, the growth of carbon nanotubes can be inhibited from stopping due to peeling of carbon nanotubes from the catalyst particles. The flow rate of the carbon-containing gas can be 0.05 cm / sec or higher and 10.0 cm / sec or lower, or 0.10 cm / sec or higher and 10.0 cm / sec or lower, or 0.20 cm / sec or higher and 10.0 cm / sec or lower. In the present specification, the "flow rate of the carbon-containing gas" refers to the amount of gas supplied per unit time (cm3 / sec) in the CNT synthesizing furnace. 3 ​(cm / sec) divided by the cross-sectional area of the reaction tube (cm 2 ) and calculated.

[0137] The lower limit of the Reynolds number of the flow of the carbon-containing gas in the CNT synthesizing furnace supplied from the carbon-containing gas supply port can be 0.01 or more, or 0.05 or more. On the other hand, the upper limit of the Reynolds number can be 1000 or less, or 100 or less, or 10 or less. If the Reynolds number is 0.01 or more, the degree of freedom of the design of the apparatus is increased. In the case where the Reynolds number is 1000 or less, the flow of the carbon-containing gas can be suppressed from becoming turbulent, and the synthesis of carbon nanotubes between catalyst particles can be hindered.

[0138] <Other Process>

[0139] In the manufacturing method according to the present embodiment, in addition to the above-described processes, an additional process can be appropriately added within a range where the effects of the present embodiment are exerted. As the above-described additional process, for example, a process of removing catalyst particles, a process of aligning and collecting a plurality of the above-described carbon nanotubes in the longitudinal direction of the carbon nanotubes to form a carbon nanotube collection wire, a process of performing purification of the above-described carbon nanotubes, and a process of performing twist winding of the above-described carbon nanotubes, and the like can be exemplified.

[0140] The process of removing catalyst particles can be performed, for example, by performing heat treatment of the recovered carbon nanotubes using chlorine gas at 500°C.

[0141] Example

[0142] Hereinafter, the present application will be described in detail by citing examples, but the present application is not limited to these examples.

[0143] <Manufacture of Carbon Material>

[0144] <Sample 1>

[0145] The carbon material according to the present embodiment (carbon material of Sample 1) was manufactured by the following processes.

[0146] <First Process: Process of Preparing Catalyst Particles>

[0147] First, the following aqueous solution in which the concentration was adjusted was prepared.

[0148] Co aqueous solution: cobalt nitrate hexahydrate Co(N03)2-6H20 (Wako Pure Chemical Industries) (aqueous solution having a concentration of 1 mol%)

[0149] W aqueous solution: ammonium metatungstate (NH4)6[H2W 12 O 40 ] (Japan Inorganic Chemical Industry) (aqueous solution having a concentration of 1 mol%)

[0150] Two kinds of aqueous solutions were mixed at a predetermined ratio (Co7W6 alloy) to prepare a raw material aqueous solution. The prepared raw material aqueous solution (Co-W mixed aqueous solution) was subjected to electrostatic spraying using a nanoparticle generator Electrospray 3480 (trade name) manufactured by Tokyo Dylec Corporation, to generate nanodroplets. At this time, the nanoparticle generator was set to a voltage of 2 kV and a current of 500 nA. The generated nanodroplets were introduced into a tubular drier at 500°C and dried under a nitrogen atmosphere to generate nanoparticles.

[0151] The generated nanoparticles were subjected to treatment using a particle sizing device bench DMA 3082 (trade name), whereby nanoparticles having a particle diameter of 1 nm were recovered. The recovered nanoparticles were introduced into a hydrogen atmosphere furnace (tubular furnace) at 800°C together with a carrier gas (hydrogen), and were formed into a Co7W6 alloy by hydrogen reduction to obtain catalyst particles. The obtained catalyst particles were directly supplied to a CNT synthesis furnace.

[0152] <Second process: process of forming carbon nanotubes>

[0153] Argon gas at 100 vol% was supplied at a flow rate of 1000 cc / min (flow velocity 3.4 cm / sec) from the carbon-containing gas supply port into the CNT synthesis furnace for 50 minutes while the temperature in the electric furnace (in the heating device) was raised to 1130°C. Subsequently, the argon gas was stopped, and hydrogen gas was supplied at a flow rate of 7000 cc / min (flow velocity 8.84 cm / sec), methane gas was supplied at a flow rate of 50 cc / min (flow velocity 0.17 cm / sec), and carbon disulfide (CS2) gas was supplied at a flow rate of 1 cc / min (flow velocity 0.003 cm / sec) for 120 minutes. The total flow velocity of the mixed gas (carbon-containing gas) containing argon gas, methane gas, and carbon disulfide was 9.0 cm / sec. CNTs were grown by the contact of the catalyst particles supplied in advance with the methane gas.

[0154] <Third process: process of shaping into carbon nanotube wire>

[0155] The obtained CNTs were heat-treated at 420°C for 2 hours in the atmosphere. Subsequently, after the heat-treated CNTs were immersed in 12M hydrochloric acid at 80°C for 2 hours, washing was performed, and vacuum drying was performed at 120°C for 12 hours. The dried CNTs were put into an aqueous solution of chlorosulfonic acid at a proportion of 0.2 mass% with respect to the aqueous solution of chlorosulfonic acid. Subsequently, the aqueous solution was subjected to ultrasonic irradiation at 120°C for 72 hours to disperse the CNTs in the aqueous solution.

[0156] The dispersion liquid was passed through a Teflon tube having a diameter of 0.5 mm to shape the CNTs into a wire. After that, the shaped wire was washed with acetone to remove the chlorosulfonic acid, thereby obtaining a carbon nanotube wire (carbon material containing carbon nanotubes).

[0157] Through the above procedure, the carbon material of Sample 1 was obtained.

[0158] <Sample 2>

[0159] Except that the prepared catalyst raw liquid was atomized by a commercially available ultrasonic atomizer instead of the Electrospray 3480 and introduced into a tubular drier, the carbon material was obtained by the same method as Sample 1.

[0160] <Sample 3>

[0161] Except that only a 1 mass% ferrocene liquid dissolved in toluene was used as the catalyst raw material, the carbon material was obtained by the same method as Sample 1.

[0162] Through the above procedure, the carbon materials of Samples 1 to 3 were prepared.

[0163] "Evaluation of Properties of Carbon Materials"

[0164] The carbon materials of the samples prepared as described above were used to evaluate each property of the carbon materials as described below. Here, the carbon material of Sample 1 corresponds to an example. The carbon materials of Sample 2 and Sample 3 correspond to comparative examples. In addition, as a reference example, each data of copper (Cu), aluminum (Al), and iron (Fe) that have been used as a material for electric wires is listed in Table 2.

[0165] "Diameter of Carbon Nanotubes"

[0166] The diameter of the CNTs was calculated by detecting the radial breathing mode (RBM) in each CNT using Raman spectroscopy. The following steps were specifically performed.

[0167] (i) a step of extracting the first Raman spectrum in each CNT using an incident wavelength of 633 nm,

[0168] (ii) a procedure of identifying each peak (RBM peak) that decreases in the range of 120 cm -1 to 350 cm -1 ,

[0169] (iii) a step of determining the position (ω RBM ) of each RBM peak using a Rorentzian fit,

[0170] (iv) a step of determining the diameter of the nanotube associated with each RBM peak using the following formula,

[0171] d = 239 / ω RBM

[0172] Here, d is the diameter of the carbon nanotube in nm, ω RBM is the wave number of the RBM peak in cm -1 unit. The results are shown in Table 2 (column "RBM converted diameter"). The numerical range shown in Table 2 indicates that 90% or more of the number of carbon nanotubes is included in the numerical range.

[0173] <Chirality of carbon nanotube>

[0174] The chirality of the carbon nanotube included in each sample was found by the following steps. First, for each sample, an optical absorption spectrum was obtained using a spectrophotofluorometer. The measurement conditions at this time are described below.

[0175] (Measurement conditions of optical absorption spectrum in spectrophotofluorometer)

[0176] Measurement device: Spectrophotofluorometer, JASCO FP-8750, Japan

[0177] Measurement temperature: Room temperature (25°C)

[0178] Measurement wavelength: 300 nm to 1700 nm

[0179] Armchair (metal) type CNT serving as a reference: CNT having a chirality index of (6, 6) and the same diameter as the CNT to be measured

[0180] After that, the obtained optical absorption spectrum was compared, and when the optical transition in the CNT to be measured was equal to the optical transition in the armchair type CNT serving as a reference, or was observed on the higher energy side than the optical transition in the armchair type CNT serving as a reference, it was judged that the CNT to be measured had armchair type chirality. The results are shown in Table 2 (column "Peak chirality"). The chirality index shown in Table 2 indicates that 90% or more of the number of carbon nanotubes belongs to its chirality index. In addition, "random" means that the chirality index is not determined.

[0181] <Proportion of carbon nanotube>

[0182] The proportion of the carbon nanotube was found by measuring under the following conditions using a thermogravimetric differential thermal analysis method (TG-DTA method). As a result, it was found that the proportion of the carbon nanotube in the carbon material of Sample 1 to Sample 3 was almost 100 mass%.

[0183] (Measurement conditions of thermogravimetric differential thermal analysis)

[0184] Atmospheric flow: 50 ml / min

[0185] Measurement temperature: From room temperature (25°C) to 1000°C at a temperature increase rate of 5°C / min

[0186] Calculation method: The contained proportion was calculated from the ratio of the residue mass after measurement to 1000°C to the initial mass (mass before measurement).

[0187] <Proportion of number of carbon nanotubes having armchair chirality>

[0188] The proportion of number of carbon nanotubes having armchair chirality (probability of presence) was calculated by detecting the radial breathing mode (RBM) in each CNT using Raman spectroscopy. Specifically, for the same carbon material, 20 times of chirality determination was performed based on the RBM peak, and the number of times determined as armchair was calculated based on the above-described Formula 1. As a result, in the carbon material of Sample 1, the proportion of number of carbon nanotubes having armchair chirality was 90% or more. On the other hand, in Sample 2 and Sample 3, the proportion of number of carbon nanotubes having armchair chirality was 50% or less, and was not a metal type advantage.

[0189] <Composition, contained proportion, and diameter of catalyst particles>

[0190] The composition of the catalyst particles was quantitatively identified by burning the carbon material contained in each sample using a differential thermal analysis device (TG-DTA or the like), and using scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) for the metal oxides (ash) of the catalyst particles. In addition, the contained proportion of the catalyst particles was found by measuring using the TG-DTA method under the following conditions. As a result, the contained proportion of the catalyst particles in the carbon materials of Sample 1 to Sample 3 was almost 0 mass%.

[0191] (Measurement conditions for thermogravimetric differential thermal analysis)

[0192] Atmospheric flow: 50 ml / min

[0193] Measurement temperature: From room temperature (25°C) to 1000°C at a temperature increase rate of 5°C / min

[0194] Calculation method: The contained proportion was calculated from the ratio of the residue mass after measurement to 1000°C to the initial mass (mass before measurement).

[0195] <Conductivity of carbon material>

[0196] The conductivity of the carbon material was found according to "Resistance measurement based on four-probe method" of JIS K7194. The results are shown in Table 2 (column of "conductivity").

[0197] Density, specific strength, specific rigidity of carbon material

[0198] The density of the carbon material was measured using a dry densimeter. The specific strength and the specific rigidity of the carbon material were measured by a tensile test prescribed by JIS (JIS R7606: 2000 Carbon Fiber - Test method for tensile properties of single fibers (ISO 11566)). The results are shown in Table 2 (in the columns of "bulk density", "specific strength", and "specific rigidity", respectively).

[0199] [Table 2]

[0200]

[0201] Results

[0202] From the results of Table 2, it was found that the carbon material of Sample 1 (Example) had a peak chirality of (6, 6), which is a hand-rail type chirality. In addition, the carbon material of Sample 1 had an electrical conductivity of 15.5 x 10 6 S / m, and had excellent electrical conductivity. On the other hand, it was found that Samples 2 and 3 (Comparative Examples) did not have a hand-rail type chirality. The carbon materials of Samples 2 and 3 had an electrical conductivity of 3.0 x 10 6 S / m or less.

[0203] The above description contains the following features.

[0204] (Feature 1)

[0205] A carbon material containing carbon nanotubes, wherein

[0206] 90% or more and 100% or less of the number of the carbon nanotubes have a diameter of 0.9 nm or more and 2 nm or less,

[0207] 90% or more and 100% or less of the number of the carbon nanotubes have a hand-rail type chirality,

[0208] the carbon material has an electrical conductivity of 5 x 10 6 S / m -1 or more in at least one direction.

[0209] (Feature 2)

[0210] The carbon material according to Feature 1, wherein the content ratio of the carbon nanotubes with respect to the carbon material is 80 mass% or more.

[0211] (Feature 3)

[0212] The carbon material according to Feature 1 or Feature 2, wherein the carbon material is a fiber or a film.

[0213] (Feature 4)

[0214] The carbon material according to the above-mentioned 1 or 2, wherein the size of at least one of the carbon materials is greater than 1 m.

[0215] (Paragraph 5)

[0216] The carbon material according to the above-mentioned 1 or 2, wherein the density of the carbon material is 0.5 g / cm 3 or more and 2.0 g / cm 3 or less.

[0217] (Paragraph 6)

[0218] The carbon material according to the above-mentioned 1 or 2, wherein the specific strength of the carbon material is 0.2 GPa / SG or more in at least one direction.

[0219] (Paragraph 7)

[0220] The carbon material according to the above-mentioned 1 or 2, wherein the specific rigidity of the carbon material is 10 GPa / SG or more.

[0221] (Paragraph 8)

[0222] The carbon material according to the above-mentioned 1 or 2, wherein,

[0223] The carbon material further has catalyst particles dispersed in the carbon material,

[0224] The catalyst particles contain tungsten as a constituent element,

[0225] The catalyst particles have a content ratio of 0.1 mass% or more and 20 mass% or less with respect to the carbon material.

[0226] (Paragraph 9)

[0227] The carbon material according to the above-mentioned 8, wherein the catalyst particles further contain one or more metal elements selected from the group consisting of Group 4 elements of the periodic table, Group 5 elements of the periodic table, Group 6 elements of the periodic table, manganese, iron, cobalt, nickel, copper, zinc, rhodium, ruthenium, palladium, platinum, gold, silver, osmium, iridium, and lanthanoid rare earth metal elements.

[0228] (Paragraph 10)

[0229] The carbon material according to the above-mentioned 8, wherein 99% or more and 100% or less of the number of the catalyst particles have a diameter of 1 nm or more and 4 nm or less.

[0230] As described above, the embodiments and examples of the present application have been described, but it is also intended from the outset to appropriately combine the configurations of the above-mentioned respective embodiments and respective examples.

[0231] It should be understood that the embodiments and examples disclosed herein are illustrative in all respects, rather than restrictive. The scope of the present application is not represented by the embodiments and examples, but by the claims, and is intended to include all changes within the meaning and range of equivalency of the claims.

Claims

1. A carbon material comprising carbon nanotubes, wherein: 90% or more and 100% or less of the carbon nanotubes have a diameter of 0.9 nm or more and 2 nm or less, 90% or more and 100% or less of the carbon nanotubes have armchair chirality, The carbon material has a 5×10 6 Sm -1 conductivity above .

2. The carbon material according to claim 1, wherein The content ratio of the carbon nanotubes relative to the carbon material is 80% by mass or more.

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

4. The carbon material according to any one of claims 1 to 3, wherein At least one of the carbon materials has a size greater than 1 m.

5. The carbon material according to any one of claims 1 to 4, wherein The density of the carbon material is 0.5 g / cm 3 Above and 2.0g / cm 3 the following.

6. The carbon material according to any one of claims 1 to 5, wherein The carbon material has a specific strength of 0.2 GPa / SG or more in at least one direction.

7. The carbon material according to any one of claims 1 to 6, wherein The carbon material has a specific rigidity of 10 GPa / SG or more.

8. The carbon material according to any one of claims 1 to 7, wherein The carbon material further has catalyst particles dispersed in the carbon material, The catalyst particles contain tungsten as a constituent element, The content ratio of the catalyst particles relative to the carbon material is 0.1 mass % or more and 20 mass % or less.

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 lanthanide rare earth metal elements.

10. The carbon material according to claim 8 or claim 9, wherein 99% or more and 100% or less of the catalyst particles have a diameter of 1 nm or more and 4 nm or less.

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