JP2017171545A - Method for producing carbon nanotube wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon nanotube wire that has excellent conductivity, reduced variations, high productivity, and capability of mass production.SOLUTION: A method for producing a CNT wire includes forming a CNT wire by twisting together a plurality of carbon nanotubes having a layered structure of one or more layer (step S12), refining the CNT wire (step S13), and doping the refined CNT wire with a dissimilar element (step S14).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for producing a carbon nanotube wire, and more particularly, to a method for producing a carbon nanotube wire composed of carbon nanotubes doped with different elements.

  Conventionally, as power lines and signal lines in various fields such as automobiles and industrial equipment, electric wires composed of a core wire made of one or a plurality of wires and an insulating coating covering the core wire have been used. As the material of the wire constituting the core wire, copper or a copper alloy is usually used from the viewpoint of electrical characteristics, but in recent years, aluminum or an aluminum alloy has been proposed from the viewpoint of weight reduction. For example, the specific gravity of aluminum is about 1/3 of the specific gravity of copper, and the electrical conductivity of aluminum is about 2/3 of the electrical conductivity of copper (pure aluminum is about 66% IACS when pure copper is used as the standard of 100% IACS). Yes, to allow the same current to flow through the aluminum wire as the copper wire, the cross-sectional area of the aluminum wire must be about 1.5 times the cross-sectional area of the copper wire. Even if a large aluminum wire is used, the mass of the aluminum wire is about half of the mass of the pure copper wire, so the use of the aluminum wire is advantageous from the viewpoint of weight reduction.

  Based on the above background, in recent years, higher performance and higher functionality of automobiles, industrial equipment, etc. are being promoted, and with this increase in the number of various electrical equipment, control equipment, etc. There is also a tendency for the number of wirings of electrical wiring bodies used in these devices to increase. On the other hand, in order to improve the fuel efficiency of moving bodies such as automobiles for environmental reasons, it is strongly desired to reduce the weight of wires.

  As one of new means for achieving such further weight reduction, a technique for utilizing carbon nanotubes as a wire has been newly proposed. The carbon nanotube is a single layer of a cylindrical body having a hexagonal lattice network structure, or a three-dimensional network structure composed of multiple layers arranged substantially coaxially, and is lightweight and has conductivity, current capacity, Because of its excellent properties such as elasticity and mechanical strength, it has attracted attention as a material that can replace metals used in power lines and signal lines.

The specific gravity of the carbon nanotube is about 1/5 of the specific gravity of copper (about 1/2 of aluminum), and the single carbon nanotube is higher than copper (resistivity 1.68 × 10 ⁻⁶ Ω · cm). Shows conductivity. Therefore, theoretically, if a carbon nanotube aggregate is formed by twisting a plurality of carbon nanotubes, further weight reduction and high electrical conductivity can be realized. However, when carbon nanotubes in units of nm are twisted to produce an aggregate of carbon nanotubes in the unit of μm to mm, contact resistance between carbon nanotubes and internal defect formation are factors, and the resistance value of the entire wire increases. Therefore, it is difficult to use the carbon nanotube as a wire as it is.

Therefore, as one method for improving the conductivity of the aggregate of carbon nanotubes, a method of doping the carbon nanotubes that are structural units has been proposed. For example, carbon nanotubes are heated with boron oxide (B ₂ O ₃ ) in an argon stream at 1000 ° C. for 4 hours, and boron oxides (B ₂ O ₃ , B ₂ O ₂ ) that have reached the carbon nanotubes by vaporization or surface diffusion. And the like) cause a chemical reaction, and boron is partially dissolved in the carbon nanotubes, whereby a method of generating carbon nanotubes containing boron is disclosed (Patent Document 1).

JP 2000-281323 A

  However, in the above patent document, carbon nanotubes alone and boron oxide are put in a graphite crucible, and the carbon nanotubes alone and boron oxide are heated in the graphite crucible, so the doping position of the carbon nanotubes cannot be controlled, There is a problem in that the doping position or doping amount tends to be biased, and when a plurality of generated carbon nanotubes are bundled to form a carbon nanotube bundle, the conductivity of the carbon nanotube bundle and thus the carbon nanotube wire varies. In addition, since the carbon nanotubes are heated in an inert gas in the above production method, the carbon nanotubes having defects remain without reacting with oxygen, and a carbon nanotube wire having good conductivity cannot be produced. In addition, in the manufacturing method in which carbon nanotubes are taken out from a graphite crucible after carbon nanotubes are doped and twisted to form a carbon nanotube wire, the productivity of the wire is low and it cannot be said that it is excellent in mass production.

  An object of the present invention is to provide a method for producing a carbon nanotube wire that has good conductivity, suppresses variation, has high productivity, and is excellent in mass production.

  In order to achieve the above object, a method for producing a carbon nanotube wire according to the present invention is a method for producing a carbon nanotube wire obtained by twisting a plurality of carbon nanotubes, and a plurality of carbons having a layer structure of one or more layers. A carbon nanotube forming step of twisting nanotubes to form a carbon nanotube wire, a purification step of purifying the carbon nanotube wire, and a doping step of doping the carbon nanotube wire after purification with a different element To do.

  The purification step oxidizes the carbon nanotube wire to remove impurities such as defective carbon nanotubes and amorphous carbon from the carbon nanotube wire.

  In the purification step, the carbon nanotube wire is preferably heated at 300 ° C to 700 ° C.

  The doping step preferably includes an immersion step of immersing the carbon nanotube wire in a liquid containing the different element and a heating step of heating the carbon nanotube wire after the immersion step.

  In the dipping step, the carbon nanotube wire is preferably dipped in a liquid containing at least one different element selected from the group consisting of nitrogen, boron and silicon.

  The liquid preferably includes any one of an aqueous solution, an organic solvent, an ionic liquid, and a supercritical fluid.

  In the heating step, the carbon nanotube wire is preferably fired at 1300 ° C to 1800 ° C.

  In the heating step, it is preferable that at least one carbon atom located at the apex of the hexagonal lattice which is a structural unit of the carbon nanotube is substituted with the heterogeneous element.

  The carbon nanotubes preferably have a two-layer or three-layer structure.

  According to the present invention, a carbon nanotube wire obtained by twisting a plurality of carbon nanotubes having a layer structure of one or more layers is purified, and then the carbon nanotube wire is doped with a different element. That is, carbon nanotubes having defects are removed from the carbon nanotube wire by a purification process performed before the doping process. If the carbon nanotube has a defect, a different element is preferentially bonded to the defect during the doping process, so that it is difficult to replace the carbon atom of the hexagonal lattice constituting the carbon nanotube. Since the carbon nanotubes having carbon atoms are removed before the doping process, preferential bonding between the different elements and defects does not occur in the subsequent doping process, and the carbon atoms of the hexagonal lattice constituting the carbon nanotubes can be reliably ensured by the different elements. It can be replaced. Therefore, it is possible to produce a carbon nanotube wire with good conductivity and suppressed variation in conductivity.

  In addition, since carbon nanotube wire can be formed, purified and doped in a series of flows, for example, carbon containing different elements from carbon material can be obtained by using a production method that can produce carbon nanotube wire from carbon material. Nanotube wire can be produced continuously, the productivity of the wire can be increased, and a production method excellent in mass production can be provided.

  Further, in the doping treatment, the carbon nanotube wire from which the defective carbon nanotubes are removed is immersed in a liquid containing a different element, and the carbon nanotube wire after the immersion treatment is heated, so that the liquid is uniformly in the carbon nanotube wire. More uniform conductivity can be realized by permeating into the substrate.

It is an expansion perspective view showing roughly the composition of the carbon nanotube bundle in the carbon nanotube manufactured with the manufacturing method of the carbon nanotube wire concerning the embodiment of the present invention. It is a figure which shows an example of arrangement | positioning of the dissimilar element doped by the carbon nanotube in FIG. 1, (a) is a top view, (b) is a front view. It is a figure which shows an example of arrangement | positioning of the different element doped by the carbon nanotube which has a single layer structure, (a) is a top view, (b) is a front view. It is a flowchart which shows the manufacturing method of the carbon nanotube wire which concerns on this embodiment. It is a flowchart which shows the detail of the doping process in the manufacturing method of FIG. It is a figure which shows an example of the manufacturing apparatus which manufactures a carbon nanotube by the floating catalyst vapor phase growth method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Configuration of carbon nanotube wire>
A carbon nanotube wire manufactured by the manufacturing method according to the present embodiment (hereinafter referred to as a CNT wire) is a bundle of a plurality of carbon nanotubes 11A, 11A,... Alternatively, a plurality of CNT bundles 11A are twisted together. The outer diameter of the CNT wire 1 is 0.01 to 1 mm.

  As shown in the enlarged perspective view of FIG. 1, the CNT bundle 11A is a bundle of a plurality of carbon nanotubes 11a, 11a,... (Hereinafter referred to as CNT). The axial direction is almost aligned. Further, a plurality of gaps 11B are formed along the longitudinal direction of the CNT bundle 11A between the outermost layers of the plurality of CNTs 11a, 11a,.

  The CNTs 11a constituting the CNT bundle 11A are cylindrical bodies having a single-layer structure or a multi-layer structure, and are called SWNT (single-walled nanotube) and MWNT (multi-walled nanotube), respectively. In FIG. 1, only CNTs having a two-layer structure are shown for convenience, but there are actually CNTs having a three-layer structure. CNTs having a single layer structure or a layer structure of four or more layers may be included in the bundle 11 of CNTs, but the amount is smaller than that of a CNT having a two-layer or three-layer structure.

  When the CNT 11a has a two-layer structure, the CNT 11a has a three-dimensional network structure in which two cylindrical bodies T1 and T2 having a hexagonal lattice network structure are arranged substantially coaxially, and is a DWNT (Double-walled nanotube). Called. The hexagonal lattice, which is a structural unit, is a six-membered ring in which a carbon atom is arranged at the apex, and these are continuously bonded adjacent to another six-membered ring. In addition, a plurality of CNTs 11a, 11a,... Are directly doped with a predetermined different element by a doping process described later.

  The property of the CNT 11a depends on the chirality of the cylindrical body as described above. Chirality is broadly divided into armchair type, zigzag type, and other chiral types. Armchair type is metallic, chiral type is semiconducting, and zigzag type shows intermediate behavior. Therefore, the conductivity of CNTs varies greatly depending on which chirality is present, and in order to improve the conductivity of CNT aggregates, it has been important to increase the proportion of armchair CNTs that exhibit metallic behavior. It was. On the other hand, it has been found that doping a chiral CNT having semiconducting properties with a substance (heterogeneous element) having an electron donating property or an electron accepting property exhibits a metallic behavior. In addition, in general metals, doping of different elements causes scattering of conduction electrons inside the metal, resulting in a decrease in conductivity. Similarly, when metallic CNTs are doped with different elements. , Causing a decrease in conductivity.

  Thus, since the doping effect on metallic CNT and semiconducting CNT can be said to have a trade-off relationship from the viewpoint of conductivity, theoretically, metallic CNT and semiconducting CNT are produced separately. In addition, it is desirable to combine these after performing doping treatment only on the semiconducting CNTs. However, it is difficult to selectively produce metallic CNT and semiconducting CNT selectively with the current manufacturing technique, and the metallic CNT and semiconducting CNT are produced in a mixed state. For this reason, in order to improve the electrical conductivity of the CNT wire made of a mixture of metallic CNT and semiconducting CNT, it is preferable to select a CNT structure in which the doping treatment with different elements / molecules is effective.

In the CNT bundle 11A configured by bundling a plurality of CNTs 11a, 11a,..., The ratio of the sum of the number of CNTs having a two-layer structure or a three-layer structure to the number of the plurality of CNTs 11a, 11a,. It is preferably 50% or more, and more preferably 75% or more. That is, the total number of all CNTs constituting one CNT aggregate is N _TOTAL , the sum of the number of CNTs (2) having a two-layer structure among all the CNTs is N _{CNT (2)} , and three layers among all the CNTs When the sum of the number of CNTs (3) having a structure is N _{CNT (3)} , it can be expressed by the following formula (1).
(N _{CNT (2)} + N _{CNT (3)} ) / N _TOTAL × 100 (%) ≧ 50 (%) (1)

  A CNT with a small number of layers such as a two-layer structure or a three-layer structure has a relatively higher conductivity than a CNT with a larger number of layers. In addition, the dopant is introduced into the innermost layer of the CNT or in a gap between the CNTs formed by a plurality of CNTs. The interlayer distance of CNT is equivalent to 0.335 nm which is the interlayer distance of graphite, and in the case of multilayer CNT, it is difficult in terms of size for the dopant to enter the interlayer. From this, the doping effect is manifested by introducing dopants inside and outside the CNT, but in the case of multi-walled CNT, the doping effect of the tube located inside the outermost layer and the innermost layer that is not in contact with the innermost layer becomes difficult to manifest. . For the reasons described above, when doping treatment is performed on CNTs having a multi-layer structure, the doping effect of CNTs having a two-layer structure or a three-layer structure is the highest. In addition, the dopant is often a highly reactive reagent that exhibits strong electrophilicity or nucleophilicity. CNTs having a single-layer structure are less rigid than multilayers and are inferior in chemical resistance. Therefore, when a doping process is performed, the structure of the CNT itself may be destroyed. Therefore, the present invention focuses on the number of CNTs having a two-layer structure or a three-layer structure included in the CNT aggregate. In addition, when the ratio of the sum of the number of CNTs having a two-layer structure or a three-layer structure is less than 50%, the ratio of CNTs having a single-layer structure or a multi-layer structure of four or more layers increases, and the CNT aggregate as a whole is doped. The effect is reduced and high conductivity is difficult to obtain. Therefore, the ratio of the sum of the number of CNTs having a two-layer or three-layer structure is set to a value within the above range.

  Moreover, it is preferable that the outer diameter of the outermost layer of CNT constituting the CNT bundle 11 is 5.0 nm or less. When the outer diameter of the outermost layer of the CNTs constituting the CNT aggregate 11 exceeds 5.0 nm, the porosity due to the gap between the CNTs and the innermost layer is increased, which is not preferable. .

  In the present embodiment, the CNT constituting the CNT bundle 11A preferably has no defects in the layer structure. The defect here is, for example, a lattice defect such as a five-membered ring or a seven-membered ring formed in a regular lattice arrangement consisting of six-membered rings, or a portion where a covalent bond between carbon atoms in the regular array is broken. Say. If the CNT 11a has a defect, when the CNT wire is doped with a different element, the different element is preferentially bonded to the defect, so that it is difficult to replace the carbon atoms of the hexagonal lattice constituting the carbon nanotube. Therefore, in this embodiment, it is preferable that the CNT constituting the CNT bundle 11A has no defect. Moreover, although defects may exist in the CNT, it is desirable that the defects be so few that they do not affect the substitution reaction with the carbon atoms of the hexagonal lattice in the doping process.

(Disposition of different elements in CNT)
2A and 2B are diagrams showing the arrangement of different elements doped in the CNT 11a in FIG. 1, wherein FIG. 2A is a top view and FIG. 2B is a front view.
As shown in FIGS. 2 (a) and 2 (b), the CNT 11a includes a CNT body 11a-1 having a multilayer structure composed of cylindrical bodies T1 and T2, and a configuration of an outermost layer constituting the cylindrical body T2. And a heterogeneous element 11a-2 located at the apex of a hexagonal lattice as a unit. This heterogeneous element 11a-2 is incorporated in the carbon skeleton of CNT, and is substituted with one of the six carbon atoms 13a located at the apex of the hexagonal lattice by a carbon substitution type doping treatment. . As described above, the dissimilar element 11a-2 is located in the carbon skeleton of the CNT 11a, so that many carriers can be generated in the CNT itself.

  In FIG. 2, the dissimilar element 11a-2 is replaced with one of the six carbon atoms 13a located at the apex of the hexagonal lattice. However, the present invention is not limited to this. It may be substituted with a plurality of carbon atoms 13a. Moreover, although the different element 11a-2 is incorporated in the outermost layer (tubular body T2) of the CNT 11a having a two-layer structure, the present invention is not limited thereto, and may be incorporated in the inner layer (tubular body T1). Further, a different element may be incorporated in the outermost layer of the CNT having a multilayer structure having a three-layer structure, or may be incorporated in at least one inner layer of the multilayer structure.

The different element 11a-2 is preferably at least one different element selected from the group consisting of nitrogen, boron and silicon. When an atom near carbon is used as a heterogeneous element in the periodic table, since the electron arrangement is close to that of carbon, a substitution reaction with the carbon atom can be easily performed during the doping treatment.
Further, the content of the different element 11a-2 in the CNT bundle 11a is preferably 0.1 atomic% to 50 atomic%, more preferably 10 atomic% or less, in terms of atomic composition percentage.

  In FIG. 2, the CNT 11a having the two-layer structure is doped with the different element 11a-2. However, as shown in FIGS. 3A and 3B, the CNT having the single-layer structure is doped with the different element. May be. Specifically, the CNT 21a includes a CNT body 21a-1 having a single-layer structure, and a heterogeneous element 21a-2 that constitutes a part of the apex of a hexagonal lattice that is a constituent unit of the CNT body 21a-1. May be. As described above, the dissimilar element 21a-2 is located on the carbon skeleton of the CNT 21a having a single-layer structure, so that a large number of carriers can be generated in the CNT itself as in the case of the multilayer structure.

<Method for producing carbon nanotube wire>
FIG. 4 is a flowchart showing a carbon nanotube wire manufacturing method according to the present embodiment, and FIG. 5 is a flowchart showing details of the doping process in the manufacturing method of FIG.
As shown in FIG. 4, first, a mixture containing a catalyst and a reaction accelerator is supplied to a carbon source by a floating catalyst vapor deposition (CCVD) method to generate a CNT wire in which a plurality of CNTs are twisted (step). S11). At this time, a saturated hydrocarbon having a six-membered ring can be used as the carbon source, a metal catalyst such as iron can be used as the catalyst, and a sulfur compound can be used as the reaction accelerator. For example, using the CNT manufacturing apparatus as shown in FIG. 6, inside the alumina tube 32 heated to about 1300 ° C. by the electric furnace 31, there is decahydronaphthalene as a carbon source, ferrocene as a catalyst, and a reaction accelerator. The raw material solution L containing thiophene is supplied by spraying. Further, hydrogen is supplied into the alumina tube 32 as the carrier gas G. The obtained CNTs are collected in a sheet form by the collection machine 33, and the CNT wires are produced by winding and twisting the sheets.

  At this time, a saturated hydrocarbon having a six-membered ring can be used as the carbon source, a metal catalyst such as iron can be used as the catalyst, and a sulfur compound can be used as the reaction accelerator. Further, in the present embodiment, in consideration of the fact that the ratio of SWNT decreases as the carrier gas flow rate increases, the ratio of CNTs having a two-layer or three-layer structure is increased by adjusting the raw material composition and spraying conditions. In addition, in order to adjust the size of iron as a catalyst so that the outer diameter of the outermost layer of CNT is 5.0 nm or less, the raw material is supplied to the reaction furnace by spraying so that the mist particle size is about 20 μm.

  Then, a plurality of carbon nanotubes having a layer structure of one or more layers obtained in step S11 are twisted to form a carbon nanotube wire (step S12).

  Thereafter, the CNT wire obtained in step S12 is purified (step S13). First, the remaining iron catalyst is removed by subjecting the CNT wire to an acid treatment. The CNT wire obtained by CCVD contains a large amount of catalyst, amorphous carbon, and the like, and the original characteristics of the CNT wire can be obtained by a purification process for removing these. In the present embodiment, the CNT wire obtained in the above step is heated at a predetermined temperature in the atmosphere, and the heated CNT wire is purified with a strong acid.

  Next, the highly purified CNT wire is subjected to a heat oxidation treatment to remove defective CNTs from the CNT wire. In the heat oxidation treatment, for example, the CNT wire is heated at 300 to 700 ° C. in the air, and the carbon of the defective CNT is oxidized to remove impurities such as CNT having the defect and amorphous carbon from the CNT wire. . As a result, a CNT wire composed only of CNTs without defects or a CNT wire with very few CNTs with defects can be obtained.

  Thereafter, the purified CNT wire is doped with a different element (step S14). Specifically, the purified CNT wire is immersed in a liquid containing a different element for a predetermined time (FIG. 4, step S21). The liquid preferably includes any one of an aqueous solution, an organic solvent, an ionic liquid, and a supercritical fluid. The content of different elements in the liquid is preferably 1 wt% to 50 wt%. The plurality of void portions of the CNT bundle in the CNT wire are distributed substantially evenly in the cross section, and are provided side by side along the longitudinal direction of the CNT bundle. Therefore, by immersing the CNT wire in the above liquid as it is for a predetermined time, the liquid containing the different element uniformly penetrates into the CNT wire through the gap or interface between the CNT and CNT, and the different element is introduced into the CNT wire. It can be distributed almost evenly.

Then, the CNT wire after the immersion treatment is heated to 1300 ° C. to 1800 ° C. in the atmosphere, preferably in an inert gas (step S22). By heating at a temperature within the above range, the different element enters the carbon skeleton and is replaced with one of the carbon atoms constituting the hexagonal lattice. At this time, the dissimilar elements are uniformly dispersed and arranged in the CNT wire by the immersion treatment, and the dissimilar elements are injected from the outer peripheral side of the CNT, so that the substitution reaction between the dissimilar elements and the carbon atoms is performed in the CNT wire. Is called.
At this time, when the CNT is a multilayer (MWNT), the layer located on the outer peripheral side is preferentially doped, and the inner layer is hardly doped. By setting the number ratio of CNTs having a two-layer or three-layer structure to 50% or more, the doping amount of the entire CNT aggregate can be increased, and an excellent doping effect can be obtained.

  As described above, according to the present embodiment, a CNT wire obtained by twisting a plurality of CNTs 11a having a layer structure of one or more layers is purified (step S13), and then the CNT wire is doped with a different element 11a-2. (Step S14). That is, since the defective CNT is removed from the CNT wire by the purification process performed before the doping process, preferential bonding between the different element 11a-2 and the defect does not occur in the subsequent doping process, and the CNT 11a is configured. It becomes possible to reliably replace carbon atoms in the square lattice with different elements. Therefore, the CNT wire 1 having good conductivity can be manufactured.

  In addition, since the formation, purification and doping of the CNT wire can be performed in a series of flows, for example, by using a production method capable of producing a carbon nanotube wire from a carbon raw material, the heterogeneous element 11a-2 is contained from the carbon raw material. The CNT wire 1 to be produced can be continuously produced, the productivity of the wire can be increased, and a production method excellent in mass production can be provided.

  Further, in the doping process, the CNT wire from which the defective CNT is removed is immersed in a liquid containing the different element 11a-2 (step S21), and the CNT wire after the immersion process is heated (step S22). More uniform conductivity can be realized by allowing the liquid to uniformly penetrate into the CNT wire.

  As mentioned above, although the manufacturing method of the CNT wire material concerning embodiment of this invention was described, this invention is not limited to description embodiment, Various deformation | transformation and change are possible based on the technical idea of this invention. is there.

  For example, you may comprise a CNT covering electric wire provided with the carbon nanotube wire formed by twisting the CNT bundle of the above-mentioned embodiment, and the coating layer which coats the perimeter of the carbon nanotube wire. In particular, the CNT wire of the present embodiment is suitable as a wire material for electric wires for transmitting electric power and signals, and is more suitable as a material for wire wires mounted on a moving body such as a four-wheeled vehicle. This is because it is lighter than metal wires and is expected to improve fuel efficiency.

  Moreover, you may comprise the wire harness which has at least one said carbon nanotube covering electric wire.

1 CNT wire 11A CNT bundle 11a CNT
11a-1 CNT body 11a-2 Heterogeneous element 13a Carbon atom 21a CNT
21a-1 CNT body 21a-2 Heterogeneous element 31 Electric furnace 32 Alumina tube 33 Recovery machine T1 Tubular body T2 Tubular body

Claims (9)

A method of manufacturing a carbon nanotube wire formed by twisting a plurality of carbon nanotubes,
A carbon nanotube forming step of forming a carbon nanotube wire by twisting a plurality of carbon nanotubes having a layer structure of one or more layers;
A purification step of refining the carbon nanotube wire,
A doping step of doping the carbon nanotube wire after purification with a different element;
A method for producing a carbon nanotube wire, characterized by comprising:   The method for producing a carbon nanotube wire according to claim 1, wherein in the purification step, the carbon nanotube wire is oxidized to remove carbon nanotubes having defects from the carbon nanotube wire.   The said refinement | purification process heats the said carbon nanotube wire at 300 to 700 degreeC, The manufacturing method of the carbon nanotube wire of Claim 2 characterized by the above-mentioned. The doping step includes
An immersion step of immersing the carbon nanotube wire in a liquid containing the different element;
A heating step of heating the carbon nanotube wire after the immersion step;
The method for producing a carbon nanotube wire according to claim 1, comprising:   5. The carbon nanotube wire according to claim 4, wherein in the dipping step, the carbon nanotube wire is dipped in a liquid containing at least one different element selected from the group consisting of nitrogen, boron, and silicon. Production method.   The method for producing a carbon nanotube wire according to claim 4 or 5, wherein the liquid includes any one of an aqueous solution, an organic solvent, an ionic liquid, and a supercritical fluid.   5. The method of manufacturing a carbon nanotube wire according to claim 4, wherein in the heating step, the carbon nanotube wire is fired at 1300 ° C. to 1800 ° C. 5.   5. The carbon nanotube wire according to claim 4, wherein in the heating step, at least one of carbon atoms positioned at the apex of a hexagonal lattice which is a structural unit of the carbon nanotube is replaced with the heterogeneous element. Production method.   The method for producing a carbon nanotube wire according to claim 1, wherein the carbon nanotube has a two-layer or three-layer structure.

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