Carbon nanotube wire

Abstract

To provide a carbon nanotube wire having excellent electrical conductivity through reduction of voids in the carbon nanotube wire.SOLUTION: A carbon nanotube wire containing one or more carbon nanotube bundles composed of a plurality of carbon nanotubes, wherein a proportion (R1: unit %) of a first component (τ1), a proportion (R2: unit %) of a second component (τ2), and a proportion (R3: unit %) of a third component (τ3), which are obtained by performing the positron annihilation life measurement by irradiating the carbon nanotube bundle with positrons at a driving energy of 10 keV, and performing the three-component analysis using the nonlinear least-squares method, satisfy the following formula (1): R3 / (R1+R2+R3)≤0.1...(1) (In formula (1), R1+R2+R3=100).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon nanotube wire comprising one or more carbon nanotube bundles composed of multiple carbon nanotubes, and to a carbon nanotube wire having excellent conductivity. [Background technology]

[0002] Carbon nanotubes are materials with diverse properties and are expected to have applications in many fields. For example, carbon nanotubes are three-dimensional network structures composed of a single layer of tubular bodies with a hexagonal lattice network structure, or multiple layers arranged approximately coaxially. They are lightweight and possess excellent properties such as electrical conductivity, thermal conductivity, and mechanical strength. Therefore, the use of carbon nanotubes as a substitute for metals is being considered. When using carbon nanotubes as a substitute for metals, there is also a need to further improve the electrical conductivity of carbon nanotubes.

[0003] On the other hand, since carbon nanotube wires contain a carbon nanotube bundle structure formed by the aggregation of multiple carbon nanotubes, contact resistance can occur between the carbon nanotubes, leaving room for improvement in the conductivity of the carbon nanotube wire. Furthermore, because the carbon nanotubes constituting the carbon nanotube wire do not necessarily have uniform diameters, nano-sized voids (voids in the radial direction of the carbon nanotubes) can occur between the carbon nanotubes, which can reduce the density of the carbon nanotube wire and increase its resistance.

[0004] Therefore, in order to improve the density of carbon nanotube wires, it is being considered to form carbon nanotube wires by bundling multiple carbon nanotubes with small and uniform diameters in a manner that provides high orientation. Specifically, carbon nanotubes with small diameters and improved radial roundness are formed, and a hexagonal close-packed structure is formed using these carbon nanotubes with improved roundness to increase the packing density of the carbon nanotubes, thereby creating carbon nanotube wires. By using carbon nanotubes with improved roundness to increase the packing density of the carbon nanotubes, the generation of voids between carbon nanotubes is suppressed, thereby preventing an increase in the resistance value of the carbon nanotube wires.

[0005] Furthermore, carbon nanotube wires with improved conductivity have been proposed by doping them with iodine, a different element, and interposing iodine between the carbon nanotubes (Patent Document 1). Iodine is easy to uniformly dope into carbon nanotube wires and has excellent stability of its position within the carbon nanotube wire. In other words, iodine is used as a dopant for carbon nanotube wires because of its excellent handling properties.

[0006] However, even when increasing the packing density by using carbon nanotubes with improved roundness, voids still exist between the carbon nanotubes, so there was room for improvement in terms of improving the conductivity of the carbon nanotube wire.

[0007] Furthermore, even when iodine is doped into the carbon nanotube wire to reduce the contact resistance between the carbon nanotubes, voids still exist between the carbon nanotubes, indicating room for improvement in terms of improving the conductivity of the carbon nanotube wire. Additionally, iodine has a high molecular weight of 253.8, suggesting room for improvement in terms of reducing the weight of the carbon nanotube wire. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Special Publication No. 2009-535294 [Overview of the project] [Problems that the invention aims to solve]

[0009] In view of the above circumstances, the present invention aims to provide a carbon nanotube wire having excellent conductivity by reducing the voids in the carbon nanotube wire. [Means for solving the problem]

[0010] The gist of the present invention, which solves the above problems, is as follows. [1] A carbon nanotube wire comprising one or more carbon nanotube bundles composed of multiple carbon nanotubes, Positrons were fired into the carbon nanotube bundle and irradiated with an energy of 10 keV to measure the positron annihilation lifetime. The proportions of the first component (τ1) (R1: unit %), the second component (τ2) (R2: unit %), and the third component (τ3) (R3: unit %) obtained by 3-component analysis using the nonlinear least squares method are given by the following equation (1) R3 / (R1+R2+R3)≦0.1···(1) (In formula (1), R1+R2+R3=100) A carbon nanotube wire that satisfies the requirements. [2] The carbon nanotube wire according to [1], wherein the carbon nanotube bundle comprises nitrogen molecules and / or carbon dioxide molecules.

[0011] In the above embodiment, "positron annihilation lifetime measurement" refers to measuring the time (on the order of several hundred picoseconds to several tens of nanoseconds) from the time a positron is incident on a sample until it annihilates, and non-destructively evaluating information about the size of a void of about 0.1 to 10 nm based on that annihilation lifetime. [Effects of the Invention]

[0012] According to an aspect of the carbon nanotube wire of the present invention, positrons are implanted into a carbon nanotube bundle and irradiated at an energy of 10 keV to perform positron annihilation lifetime measurement, and the ratio (R1: unit %) of the first component (τ1), the ratio (R2: unit %) of the second component (τ2), and the ratio (R3: unit %) of the third component (τ3) obtained by three-component analysis using the non-linear least squares method satisfy the formula (1) R3 / (R1 + R2 + R3) ≤ 0.1 (in formula (1), R1 + R2 + R3 = 100). By satisfying this, the voids between the carbon nanotubes are reduced and the packing density of the carbon nanotube wire is improved, so that a carbon nanotube wire having excellent conductivity can be obtained.

[0013] According to an aspect of the carbon nanotube wire of the present invention, since the carbon nanotube bundle contains nitrogen molecules and / or carbon dioxide molecules, the voids between the carbon nanotubes are surely reduced and the packing density of the carbon nanotube wire is further improved, so that a carbon nanotube wire having further excellent conductivity can be obtained. Further, since the carbon nanotube bundle contains nitrogen molecules having a molecular weight of 28.0 and / or carbon dioxide molecules having a molecular weight of 44.0, a carbon nanotube wire having excellent conductivity while maintaining the light weight of the carbon nanotubes can be obtained.

Brief Description of Drawings

[0014] [Figure 1] It is an explanatory diagram showing an outline of a carbon nanotube wire according to an embodiment of the present invention. [Figure 2] It is an example of a positron lifetime spectrum obtained when a sample is irradiated with positrons to perform positron annihilation lifetime measurement. [Figure 3] It is an explanatory diagram of a method for introducing nitrogen molecules and / or carbon dioxide molecules into a carbon nanotube wire. [Figure 4] It is an image of a scanning transmission electron microscope in the radial cross section of the carbon nanotube wire of Example 1. [Figure 5] A graph showing the relationship between the positron annihilation lifetime (horizontal axis) and the count number (vertical axis) obtained by positron annihilation lifetime measurement in the examples and comparative examples.

Mode for Carrying Out the Invention

[0015] Hereinafter, the carbon nanotube wire according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an overview of the carbon nanotube wire according to an embodiment of the present invention. FIG. 2 is an example of a positron lifetime spectrum obtained when positron annihilation lifetime measurement is performed by irradiating a sample with positrons.

[0016] As shown in FIG. 1, a carbon nanotube wire (hereinafter sometimes referred to as "CNT wire") 12 according to an embodiment of the present invention is composed of a plurality of carbon nanotubes (hereinafter sometimes referred to as "CNT") 11a, 11a, 11a... having a single-layer or multi-layer structure of two or more layers. A carbon nanotube bundle (hereinafter sometimes referred to as "CNT bundle") 11 formed by bundling one or a plurality of CNT bundles 11, 11, 11... That is, the CNT wire 12 includes one or a plurality of CNT bundles 11 composed of a plurality of CNTs 11a, 11a, 11a... The outer diameter of the CNT wire 12 is, for example, 0.01 mm or more and 10 mm or less, preferably 0.01 mm or more and 1 mm or less. The CNT wire 12 means a wire in which the proportion of CNT 11a is 90% by mass or more. In calculating the proportion of CNT 11a in the CNT wire 12, plating and dopants are excluded. The "plating" referred to here is composed of metal, and refers to a structure in which they are arranged on the surfaces of the CNT wire 12 and the CNT bundle 11. Also, the "dopant" referred to here is composed of atoms other than carbon or molecules containing atoms other than carbon. Also, the "dopant" refers to those arranged on the surfaces of the CNT wire 12 and the CNT bundle 11, in the void S between CNT 11a - CNT 11a in the CNT bundle 11, and in the space at the center of one CNT 11a.

[0017] In the CNT bundle 11, multiple CNTs 11a, 11a, ... are arranged with their long axis directions almost aligned. The CNT bundle 11 is linear, and the longitudinal direction of the CNT bundle 11 forms the longitudinal direction of the CNT wire 12. The equivalent circular diameter of the CNT bundle 11 can be, for example, between 20 nm and 1000 nm.

[0018] Furthermore, the CNT wire 12 is a bundle of long CNTs 11a having one or more layers. The CNTs 11a constituting the CNT wire 12 are cylindrical bodies having a single-layer structure or a multi-layer structure, and are called SWNTs (single-walled nanotubes) and MWNTs (multi-walled nanotubes), respectively. In Figure 1, for the sake of explanation, only CNTs 11a having a two-layer structure are shown, but the CNT wire 12 may also include CNTs 11a having a three or more-layer structure or CNTs 11a having a single-layer structure. In addition, the CNT wire 12 may be formed from CNTs 11a having a three or more-layer structure or CNTs 11a having a single-layer structure.

[0019] In the CNT11a constituting the CNT wire 12, the CNT11a with a two-layer structure has a three-dimensional network structure in which two cylindrical bodies T1 and T2, each having a hexagonal lattice network structure, are arranged approximately coaxially, and is called a DWNT (Double-walled nanotube). The constituent unit, the hexagonal lattice, is a six-membered ring with carbon atoms at its vertices, and these are continuously bonded adjacent to other six-membered rings.

[0020] In the CNT wire 12, positrons are injected into the CNT bundle 11 and irradiated at an energy of 10 keV to measure the positron annihilation lifetime. The proportions of the first component (τ1) (R1: unit %), the second component (τ2) (R2: unit %), and the third component (τ3) (R3: unit %) obtained by 3-component analysis using the nonlinear least squares method are given by the following equation (1) R3 / (R1+R2+R3)≦0.1···(1) The equation (1) satisfies the condition R1 + R2 + R3 = 100.

[0021] Positron annihilation lifetime measurement is performed using positrons (e + This method measures the time from when a positron enters a sample (in this invention, the CNT bundle 11) until it annihilates, and non-destructively evaluates information about the size of voids between 0.1 and 10 nm based on the positron annihilation lifetime. The positron annihilation lifetime measurement method utilizes the fact that positrons are extremely small, making it possible to evaluate voids (free volume voids) with a diameter of approximately 0.1 nm to 10 nm, which are difficult to measure with other measurement methods. Therefore, by using the positron annihilation lifetime measurement method, it is possible to evaluate voids present in the CNT wire 12, such as the void S between CNTs 11a and the void inside the innermost layer of CNTs 11a (in Figure 1, the tubular body T1 of the two tubular bodies T1 and T2 of CNTs 11a). Note that the void S between CNTs 11a mainly refers to the void in the radial direction of CNTs 11a.

[0022] As shown in the example in Figure 2, positrons are fired into the CNT bundle 11 and irradiated with an energy of 10 keV to measure the positron annihilation lifetime. Using the nonlinear least-squares program POSITRONFIT (PALSfit3 program), the first component (τ1) originating from the positron lifetime of the positron on the surface of the CNT bundle 11 (lifetime less than 0.4 nanoseconds), the second component (τ2) originating from the positron lifetime of the positron in the atomic defect of CNT11a (lifetime between 0.4 nanoseconds and 1.4 nanoseconds), and the third component (τ3) originating from the positron lifetime of the void S between CNT11a and CNT11a present in the CNT bundle 11 (lifetime greater than 1.4 nanoseconds and less than or equal to 20 nanoseconds) are analyzed (i.e., 3-component analysis). By measuring the third component positron lifetime (τ3) from the positron lifetime spectrum obtained from the positron annihilation lifetime measurement, the size of the void S between CNT11a and CNT11a can be calculated. The positron is an electron (e) in the CNT wire 12. -It combines with ) to form orthopositronium (o-Ps). Orthopositronium is thought to be trapped and annihilated in the void S between CNT11a. Since orthopositronium emits gamma rays when it annihilates, its lifetime can be measured by detecting gamma rays. The long-lived third component (τ3) is the lifetime of orthopositronium in the void S between CNT11a, and the third component (τ3) provides information about the void S between CNT11a.

[0023] The third component (τ3), which originates from the lifetime of orthopositronium trapped in the void S between CNT11a, is expressed as a function of the radius R of the void S between CNT11a. The function is shown below. TIFF0007894002000001.tif21158

[0024] Positrons and electrons bond to each other via Coulomb force to form neutral positronium (Ps). Depending on whether the spins of the positrons and electrons are antiparallel or parallel, Ps can be classified as parapositronium (p-Ps) or orthopositronium (o-Ps). Parapositronium:orthopositronium is formed in a ratio of 1:3. The average lifetime of parapositronium is 125 picoseconds, and the average lifetime of orthopositronium is 140 nanoseconds. In condensed materials, the probability of orthopositronium overlapping with an electron other than the one it is bonded to (pick-off annihilation) increases, resulting in a reduction in the average lifetime of orthopositronium to a few nanoseconds. The annihilation of orthopositronium in the CNT wire 12 is due to the overlap of orthopositronium with electrons present in the void S between CNTs 11a and CNTs 11a; therefore, the smaller the void size, the faster the annihilation rate. From the above, the third component (τ3) derived from the lifetime of orthopositronium can be related to the size (diameter) of the void S between CNT11a atoms.

[0025] From the above, the percentage of the first component (τ1) count (R1: unit %), the percentage of the second component (τ2) count (R2: unit %), and the percentage of the third component (τ3) count (R3: unit %) can be calculated from the positron lifetime spectrum. The lower the percentage of the third component (τ3), expressed as R3 / (R1+R2+R3), the smaller the void S between the CNT11a particles, or the reduced void S due to the introduction of other materials into the void S between the CNT11a particles. Note that R1+R2+R3=100%, which corresponds to the total count.

[0026] In the CNT wire 12 according to the embodiment of the present invention, the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) is reduced to 0.1 or less. In the CNT wire 12, in addition to suppressing the generation of the void S between the CNTs 11a, the void S between the CNTs 11a is reduced by introducing other substances into the void S between the CNTs 11a. As a result, in the CNT wire 12, the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) is 0.1 or less. Therefore, since the voids in the CNT wire 12 are reduced, a CNT wire 12 with excellent conductivity can be obtained. The ratio of the third component (τ3), represented by R3 / (R1+R2+R3), is not particularly limited as long as it is 0.1 or less, and a lower value is preferable. However, a value of 0.05 or less is preferable, and a value of 0.01 or less is particularly preferable, as this further reduces the voids in the CNT wire 12 and further improves conductivity. On the other hand, the lower limit of the ratio of the third component (τ3), represented by R3 / (R1+R2+R3), is preferably 0, but for example, 0.001 is preferable from the viewpoint of improving the productivity of the CNT wire 12.

[0027] In the CNT wire 12 in which the proportion of the third component (τ3), represented by R3 / (R1+R2+R3), is reduced to 0.1 or less, the electrical resistivity is reduced to, for example, 10 μΩ·cm or more and 20 μΩ·cm.

[0028] As shown in Figure 1, in the CNT wire 12 according to the embodiment of the present invention, for example, the CNT bundle 11 contains nitrogen molecules and / or carbon dioxide molecules G as other substances, thereby reducing the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) to 0.1 or less. Specifically, nitrogen molecules and / or carbon dioxide molecules G are introduced into the void S between the CNTs 11a that constitute the CNT bundle 11 (i.e., the void S between the CNTs 11a and CNTs 11a is doped with nitrogen molecules and / or carbon dioxide molecules G), and the presence of nitrogen molecules and / or carbon dioxide molecules G reduces the void S between the CNTs 11a. As a result, the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) is reduced to 0.1 or less.

[0029] One embodiment in which nitrogen molecules and / or carbon dioxide molecules G are introduced into the void S between the CNT11a is, for example, an embodiment in which nitrogen molecules and / or carbon dioxide molecules G are filled into the void S between the CNT11a.

[0030] By including nitrogen molecules and / or carbon dioxide molecules G in the CNT bundle 11, the voids S between the CNTs 11a are reliably reduced, further improving the packing density of the CNT wire 12, thus enabling the production of a CNT wire 12 with even better conductivity. Furthermore, by including nitrogen molecules with a molecular weight of 28.0 and / or carbon dioxide molecules with a molecular weight of 44.0 in the CNT bundle 11, it is possible to obtain a CNT wire 12 that is lightweight compared to CNT wires doped with heavier heterogeneous elements such as iodine, while maintaining excellent conductivity.

[0031] Furthermore, the presence of hydrogen molecules and / or water molecules in the CNT bundle 11 also reduces the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) to 0.1 or less. Specifically, the introduction of hydrogen molecules and / or water molecules into the void S between the CNTs 11a constituting the CNT bundle 11 (i.e., the void S between the CNTs 11a and CNTs 11a is doped with hydrogen molecules and / or water molecules) reduces the void S between the CNTs 11a and CNTs 11a, and as a result, the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) is reduced to 0.1 or less.

[0032] One example of an embodiment in which hydrogen molecules and / or water molecules are introduced into the void S between the CNT11a is an embodiment in which hydrogen molecules and / or water molecules are filled into the void S between the CNT11a.

[0033] In the CNT wire 12 according to an embodiment of the present invention, the void S between the CNTs 11a is, for example, preferably 0.10 nm in the radial cross-section of the CNT wire 12. 2 More than 10nm 2 The following areas, more preferably 0.10 nm 2 More than 5.0nm 2 The following areas, particularly preferably 0.10 nm 2 More than 3.0nm 2 The following area is present. Nitrogen molecules and / or carbon dioxide molecules G are introduced into the void S between the CNT11a having the above area.

[0034] The diameter of the CNT11a constituting the CNT bundle 11 is not particularly limited, but is preferably 0.5 nm to 15 nm, and particularly preferably 0.5 nm to 10 nm, in order to reliably suppress the generation of the void S between the CNT11a.

[0035] The density of the CNT wire itself in which nitrogen molecules and / or carbon dioxide molecules G are introduced into the gap S between CNT11a and CNT11a is not particularly limited. However, from the viewpoint of surely suppressing the generation of the gap S itself between CNT11a and CNT11a and improving the longitudinal conductivity of the CNT wire itself, it is 0.30 g / cm 3 or more and 2.0 g / cm 3 or less, preferably 1.20 g / cm 3 or more and 1.9 g / cm 3 or less, more preferably 1.40 g / cm 3 or more and 1.9 g / cm 3 or less, even more preferably, particularly 1.8 g / cm 3 is preferred.

[0036] Next, an example of a method for manufacturing the CNT wire 12 according to an embodiment of the present invention will be described. FIG. 3 is an explanatory diagram of a method for introducing nitrogen molecules and / or carbon dioxide molecules into the CNT wire.

[0037] As an example of a method for manufacturing the CNT wire 12, first, CNT11a is manufactured, a CNT bundle 11 is manufactured from the obtained plurality of CNTs 11a, 11a, 11a ···, and a CNT wire 12' is manufactured from the CNT bundle 11. Here, nitrogen molecules and / or carbon dioxide molecules G are introduced into the gap S between CNT11a and CNT11a existing in the CNT bundle 11, and the CNT wire 12 according to an embodiment of the present invention can be manufactured by doping the gap S between CNT11a and CNT11a with nitrogen molecules and / or carbon dioxide molecules G. The doping of nitrogen molecules and / or carbon dioxide molecules G may be performed on the CNT bundle 11 as described above, or may be performed on the CNT wire 12'.

[0038] CNT11a can be produced by methods such as the floating catalyst method (Patent No. 5819888) and the substrate method (Patent No. 5590603). CNT wires 12' into which nitrogen molecules and / or carbon dioxide molecules G are introduced can be produced by methods such as dry spinning (Patent No. 5819888, Patent No. 5990202, Patent No. 5350635), wet spinning (Patent No. 5135620, Patent No. 513157, Patent No. 5288359), and liquid crystal spinning (Japanese Patent Publication No. 2014-530964).

[0039] One method for creating a CNT wire 12 according to the present invention by introducing nitrogen molecules and / or carbon dioxide molecules G into the void S between CNTs 11a present in the CNT bundle 11 is to use the following gas replacement device 30.

[0040] As shown in Figure 3, the gas replacement device 30 is provided with a container 20 having a container body 21 and a lid 22. The container 20 is connected to a supply unit 23 for supplying nitrogen molecules and / or carbon dioxide molecules G into the container body 21, and a discharge unit 24 for discharging nitrogen molecules and / or carbon dioxide molecules G from the container body 21. One end of the supply unit 23 is connected to the container 20, and the other end is connected to a storage unit (not shown) where nitrogen molecules and / or carbon dioxide molecules G are stored. The supply unit 23 is also provided with a supply on / off valve 25 for adjusting whether or not nitrogen molecules and / or carbon dioxide molecules G are supplied into the container body 21 and the amount supplied. The discharge unit 24 is provided with a discharge on / off valve 26 for adjusting whether or not nitrogen molecules and / or carbon dioxide molecules G are discharged from the container body 21 and the amount discharged.

[0041] First, the CNT wire 12' or CNT bundle 11 is placed inside the container body 21 of the container 20 provided in the gas replacement device 30, and the inside of the container body 21 is sealed with the lid 22, thereby sealing the CNT wire 12' or CNT bundle 11 inside the container 20. Next, the supply valve 25 and the discharge valve 26 are set to the "open" state. Then, nitrogen molecules and / or carbon dioxide molecules G in the gas phase are supplied from the supply unit 23 to the inside of the container body 21, thereby discharging the air inside the container body 21 and the nitrogen molecules and / or carbon dioxide molecules G supplied to the inside of the container body 21 from the inside of the container body 21 to the discharge unit 24. The supply of nitrogen molecules and / or carbon dioxide molecules G from the supply unit 23 to the inside of the container body 21 is continued until the gas component discharged from the inside of the container body 21 to the discharge unit 24 consists only of nitrogen molecules and / or carbon dioxide molecules G, thereby replacing the atmosphere inside the container body 21 with nitrogen molecules and / or carbon dioxide molecules G. After the replacement with nitrogen molecules and / or carbon dioxide molecules G is complete, the supply valve 25 and the discharge valve 26 are closed, and the CNT wire 12' or CNT bundle 11 contained in the container 20 is left for a predetermined time. By leaving the CNT wire 12' or CNT bundle 11 contained in the container 20 for a predetermined time, nitrogen molecules and / or carbon dioxide molecules G are introduced into the void S between the CNTs 11a present in the CNT bundle 11, thereby manufacturing the CNT wire 12 according to the embodiment of the present invention. In Figure 3, for the sake of explanation, the container body 21 of the container 20 provided in the gas replacement device 30 is shown to contain the CNT wire 12'.

[0042] Furthermore, when leaving the CNT wires 12' or CNT bundles 11 contained in the container 20 for a predetermined time, the inside of the container body 21 may be heated and pressurized as necessary in order to more smoothly introduce gaseous nitrogen molecules and / or carbon dioxide molecules G into the void S between the CNTs 11a.

[0043] Next, another embodiment of the CNT wire of the present invention will be described. In the above embodiment of the CNT wire 12, a CNT wire 12 consisting of a plurality of CNT bundles 11, each composed of a plurality of CNTs 11a having one or more layers, was used. However, instead, a CNT wire 12 consisting of a single CNT bundle 11 composed of a plurality of CNTs 11a may be used. [Examples]

[0044] Next, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments.

[0045] Example 1 Carbon nanotubes (CNTs) were prepared using the floating catalytic vapor deposition (CCVD) method, and CNT bundles were obtained by aggregating these CNTs. Next, the prepared CNT bundles were placed in a sealed container of a gas exchange apparatus, and nitrogen molecules and / or carbon dioxide molecules in the gas phase were filled into the sealed container to introduce nitrogen molecules and / or carbon dioxide molecules into the voids between the CNTs. After that, CNT wires were manufactured using these CNT bundles.

[0046] Comparative Example 1 CNT wires were manufactured in the same manner as in Example 1, except that nitrogen molecules and / or carbon dioxide molecules were not introduced into the voids between the CNTs. As described above, in the CNT wire of Comparative Example 1, nitrogen molecules and carbon dioxide molecules present in the atmosphere were simply physically adsorbed onto the outer surface of the CNTs.

[0047] Figure 4 is a scanning transmission electron microscope image of the radial cross-section of the CNT wire of Example 1. The triangles in Figure 4 indicate the main voids between CNTs into which nitrogen molecules and / or carbon dioxide molecules have been introduced.

[0048] The evaluation criteria are as follows:

[0049] Positron annihilation lifetime measurement The positron annihilation lifetimes of the CNT wires manufactured as described above, for both the example and comparative example, were measured under the following conditions. <Measuring device> Positron probe microanalyzer (National Institute of Advanced Industrial Science and Technology, Advanced Nano-Measurement Facility) Positron source: Electron accelerator pair production method Incidence direction: The direction perpendicular to the longitudinal direction of the CNT bundle. Detector: Gamma-ray detector <Measurement conditions> Incident energy: 10 keV Measurement temperature: room temperature (25℃) Measurement atmosphere: Vacuum <Analysis method> Program used for analysis: Nonlinear least squares program POSITRONFIT (PALSfit3 program) Model: 3-component analysis Total count: 30,000 counts

[0050] Based on the analysis program described above, the obtained data was analyzed for the first component (τ1), the second component (τ2), and the third component (τ3), and the proportions of the first component (τ1) (R1: unit %), the second component (τ2) (R2: unit %), and the third component (τ3) (R3: unit %) were calculated. Figure 5 is a graph showing the relationship between the positron annihilation lifetime (horizontal axis) and the count (vertical axis) obtained from the positron annihilation lifetime measurement in the example and comparative example. Furthermore, the calculation results for the proportions of the first component (τ1) (R1: unit %), the second component (τ2) (R2: unit %), and the third component (τ3) (R3: unit %) are shown in Table 1 below.

[0051] [Table 1]

[0052] Electrical resistance measurement Electrical resistance was measured using a 2450 SourceMeter (manufactured by Keithley Instruments) with the four-terminal method.

[0053] The measurement results for electrical resistivity are shown in Table 2 below.

[0054] [Table 2]

[0055] From Tables 1 and 2 above, in the CNT wire of Example 1, in which nitrogen molecules and / or carbon dioxide molecules were introduced into the voids between CNTs, the proportion of the third component (τ3) represented by R3 / (R1+R2+R3) was 0.1 or less (0 in Example 1), and the electrical resistivity was reduced to 14-20 μΩ·cm. Furthermore, as shown in Figure 5, in the CNT wire of Example 1, the third component (τ3) present in the CNT bundle, which originates from the lifetime of positrons in the voids between CNTs, was at a background level, and it was determined that no gamma rays were detected. Therefore, in the CNT wire of Example 1, the voids between CNTs were reduced, improving the packing density of the CNT wire and resulting in excellent conductivity.

[0056] On the other hand, in the CNT wire of Comparative Example 1, where nitrogen molecules and / or carbon dioxide molecules were not introduced into the voids between the CNTs, the ratio of the third component (τ3), represented by R3 / (R1+R2+R3), was 1.4, and the electrical resistivity was 30-40 μΩ·cm. Furthermore, as shown in Figure 5, in the CNT wire of Comparative Example 1, the gamma rays emitted when orthopositronium annihilated became background noise for the third component (τ3), and gamma rays were detected. Therefore, in Comparative Example 1, the packing density of the CNT wire was insufficient due to the voids between the CNTs, and excellent conductivity could not be obtained. [Industrial applicability]

[0057] The CNT wire of the present invention achieves further low resistance and improved conductivity by reducing the voids between CNTs, making it particularly valuable for applications such as electric wires. [Explanation of symbols]

[0058] 11 Carbon Nanotube Bundle 11a carbon nanotubes 12 Carbon nanotube wire G Nitrogen molecules and / or carbon dioxide molecules

Claims

1. A carbon nanotube wire containing one or more carbon nanotube bundles composed of multiple carbon nanotubes, Positrons were fired into the carbon nanotube bundle and irradiated with an energy of 10 keV to measure the positron annihilation lifetime. The proportions of the first component (τ1) (R1: unit %), the second component (τ2) (R2: unit %), and the third component (τ3) (R3: unit %) obtained by three-component analysis using the nonlinear least squares method are given by the following equation (1): R3 / (R1+R2+R3)≦0.1...(1) (In formula (1), R1+R2+R3=100) A carbon nanotube wire that satisfies the requirements.

2. The carbon nanotube wire according to claim 1, wherein the carbon nanotube bundle comprises nitrogen molecules and / or carbon dioxide molecules.

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