JP2023152922A - Carbon nanotube wire material composite - Google Patents

Abstract

To provide a carbon nanotube wire material capable of further improving conductivity by achieving further reduction in resistance due to high density packing of carbon nanotube.SOLUTION: In a carbon nanotube wire material which is composed of one or more carbon nanotube assemblies each including a plurality of carbon nanotubes each having a layer structure of one or more layers, the circularity of the carbon nanotube constituting the carbon nanotube wire material is 0.80 or less in average.SELECTED DRAWING: Figure 2

Description

The present invention consists of one or more carbon nanotube aggregates each having a plurality of carbon nanotubes having a layer structure of one or more layers, and the carbon nanotube wire constituting the carbon nanotube wire has a distorted shape in the radial direction. Regarding carbon nanotube wire.

Carbon nanotubes are materials with various properties and are expected to be applied to many fields. For example, carbon nanotubes are three-dimensional network structures consisting of a single layer of cylindrical bodies or multiple layers arranged approximately coaxially with a hexagonal lattice network structure, and are not only lightweight but also conductive and It also has excellent properties such as thermal conductivity and mechanical strength.

Conventionally, conductive core wires made of one or more wire materials have been used as power lines and signal lines in various fields such as automobiles and industrial equipment. As the core wire, a metal wire such as copper or aluminum is generally used. However, with the increasing performance and functionality of automobiles, industrial equipment, etc., the number of installed various electrical devices and control devices has increased, and the number of wires and core wires of the electrical wiring bodies used in these devices has increased. fever is also on the rise. Furthermore, in order to reduce the environmental load, there is a demand for lighter wire rods.

Therefore, as mentioned above, carbon nanotube wires have excellent lightness, electrical conductivity, thermal conductivity, mechanical strength, etc., so carbon nanotube wires are being used as power lines and signal lines in various fields instead of metal wire core wires. The use of wire rods is required. On the other hand, with the further improvement in performance and functionality of automobiles, industrial equipment, etc., carbon nanotube wires are required to have further improved conductivity.

Since a carbon nanotube wire is a structure formed by aggregating a plurality of carbon nanotubes, contact resistance may occur between the carbon nanotubes, so there is room for improvement in the conductivity of the carbon nanotube wire. Furthermore, since the carbon nanotubes that make up the carbon nanotube wire are not necessarily uniform in diameter, nano-sized gaps may occur between the carbon nanotubes, reducing the density of the carbon nanotube wire and increasing the resistance value. Ta. Therefore, by doping the carbon nanotube wire with a different element and interposing the different element between the carbon nanotubes, the contact resistance between the carbon nanotubes is reduced and the conductivity is improved. is proposed.

In order to obtain a carbon nanotube wire with improved conductivity, iodine is sometimes used as a different element doped into the carbon nanotube wire (Patent Document 1). Iodine can be easily doped uniformly into a carbon nanotube wire and has excellent stability in its position in the carbon nanotube wire. That is, iodine is a different element that is used as a dopant for carbon nanotube wires because it has excellent handling properties.

In addition, in order to improve the conductivity of carbon nanotube wires, we have doped carbon nanotube wires with different elements and formed carbon nanotubes with a smaller diameter and improved radial roundness. Carbon nanotube wires with increased packing density of carbon nanotubes have also been produced by forming a hexagonal close-packed structure with carbon nanotubes with improved roundness. By increasing the packing density of carbon nanotubes by using carbon nanotubes with improved roundness, the generation of gaps between carbon nanotubes is suppressed, thereby preventing an increase in the resistance value of the carbon nanotube wire.

However, even if the packing density is increased by using carbon nanotubes with improved circularity, there are still gaps between the carbon nanotubes, so improvements must be made to improve the conductivity of carbon nanotube wires. There was room for.

Special Publication No. 2009-535294

In view of the above circumstances, the present invention provides carbon nanotubes that are aligned in the longitudinal direction of the carbon nanotube wire and whose cross section is originally a perfect circle due to agglomeration of carbon nanotubes, which are distorted and pulled off in the radial direction. The purpose of the present invention is to provide a carbon nanotube wire material that can realize further lower resistance and further improve conductivity by increasing the packing of carbon nanotubes in the wire material and increasing the density of the carbon nanotubes.

The gist of the configuration of the present invention for solving the above problems is as follows.
[1] A carbon nanotube wire consisting of one or more carbon nanotube aggregates consisting of a plurality of carbon nanotubes,
A carbon nanotube wire, wherein the carbon nanotubes constituting the carbon nanotube wire have an average roundness of 0.80 or less.
[2] The carbon nanotube wire according to [1], wherein the carbon nanotube having a roundness of 0.50 or less is contained in an amount of 10% or more by number.
[3] The carbon nanotube wire according to [1], wherein the carbon nanotube having a roundness of 0.50 or less is contained in an amount of 30% or more by number.
[4] A different element is introduced into the voids of the carbon nanotubes, and the different element is selected from the group consisting of iodine (I), tellurium (Te), antimony (Sb), tin (Sn), and indium (In). The carbon nanotube wire according to any one of [1] to [3], which contains at least one selected element.
[5] The carbon nanotube according to [4], wherein the content of the different element is 1.0 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the carbon nanotubes contained in the carbon nanotube wire. wire.
[6] The carbon nanotube wire according to [4] or [5], wherein the different elements form a continuum of different elements arranged along the longitudinal direction of the carbon nanotubes.
[7] The void portion of the carbon nanotube is a region inside the innermost layer of the carbon nanotube, between layers of a layered structure of the carbon nanotube, and/or a region surrounded by the outermost layer of the plurality of carbon nanotubes.[4] The carbon nanotube wire according to any one of [6].
[8] The carbon nanotube wire according to any one of [4] to [7], wherein the carbon nanotube has the different element introduced into two or more locations inside the innermost layer of the carbon nanotube.
[9] The carbon nanotube has a portion in which the innermost layer of the carbon nanotube has a circular equivalent diameter of 1.5 nm or more, and the opposing surfaces of the innermost layer of the carbon nanotube have a diameter of 0.400 nm or less [1] to The carbon nanotube wire according to any one of [8].
[10] Among all the carbon nanotubes constituting the carbon nanotube wire, the total of the carbon nanotubes having a two-layer structure and the carbon nanotubes having a three-layer structure is 75% or more by number [1] to [ 9]. The carbon nanotube wire according to any one of [9].
[11] Any one of [1] to [9], wherein of all the carbon nanotubes constituting the carbon nanotube wire, the carbon nanotubes having a layer structure of four or more layers account for 75% or more by number. Carbon nanotube wire material described in .
[12] The carbon nanotube wire according to any one of [1] to [11], wherein the carbon nanotubes constituting the carbon nanotube wire have an average circular equivalent diameter of 5.0 nm or more.
[13] The carbon nanotube wire according to any one of [1] to [12], wherein the degree of orientation of the carbon nanotubes in the longitudinal direction of the carbon nanotube wire is 1.0° or more and 10° or less.
[14] A state of an iodine bond in which the different element contains iodine (I), and three or more iodine (I) are arranged side by side along the longitudinal direction of the carbon nanotube. The carbon nanotube wire according to any one of [4] to [8].

The "roundness" in the above embodiment is determined and defined by the following procedure. A highly oriented carbon nanotube wire is sliced into rings using a focused ion beam, and thin specimens of several tens of nanometers or less that can be subjected to scanning transmission electron observation are further created. Find a place where the cross section of the carbon nanotube itself matches the crystal zone axis of the electron beam in the scanning transmission electron microscope, or tilt the holder, for the cross section of the thin sample of carbon nanotube wire in the radial direction (i.e., perpendicular to the longitudinal direction). A bright field image (BF-STEM image) obtained by adjusting the axis is obtained, and the outer circumference of the carbon nanotube is drawn by plotting the outer circumference of the carbon nanotube at a maximum of 100 points or more on the image, and the outer circumference of the carbon nanotube is drawn. The circumference and area of the circle are calculated using the formula: circularity=4π×(area)/(square of circumference). In this formula, when the roundness is 1, it is a perfect circle.

According to an aspect of the carbon nanotube wire of the present invention, the carbon nanotube wire is composed of one or more carbon nanotube aggregates composed of a plurality of carbon nanotubes, and the carbon nanotube wire is the carbon nanotube wire that constitutes the carbon nanotube wire. Because the circularity is less than 0.80 on average, the radial shape of many carbon nanotubes is not a perfect circle but a distorted shape. Compared to carbon nanotube wires that are close to a perfect circle, carbon nanotubes are packed at a higher density. Therefore, in the aspect of the carbon nanotube wire of the present invention, it is possible to realize further lower resistance and further improve conductivity.

According to the aspect of the carbon nanotube wire of the present invention, since the carbon nanotubes having a circularity of 0.50 or less are contained in a proportion of 10% or more by number, the carbon nanotubes are more reliably packed at a high density. Further lower resistance can be realized more reliably and conductivity can be further improved.

According to an aspect of the carbon nanotube wire of the present invention, a different element is introduced into the voids of the carbon nanotubes, and the different element includes iodine (I), tellurium (Te), antimony (Sb), and tin (Sn). By containing at least one element selected from the group consisting of and indium (In), the contact resistance between carbon nanotubes can be reduced, so even better conductivity can be obtained.

According to an aspect of the carbon nanotube wire of the present invention, the content of the different element is 1.0 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the carbon nanotubes contained in the carbon nanotube wire. As a result, the lattice vibration of carbon nanotubes due to temperature rise is suppressed by the action of different elements, and the different elements are introduced into the voids of carbon nanotubes, which improves conductivity while doping with different elements. It is possible to reliably prevent a decrease in the conductivity of the carbon nanotubes themselves due to scattering of electrons in the carbon nanotubes.

According to an aspect of the carbon nanotube wire of the present invention, the different elements form a continuum of different elements arranged along the longitudinal direction of the carbon nanotube, thereby further increasing carriers contributing to conductivity. This further improves the longitudinal conductivity of the carbon nanotubes, and further suppresses the lattice vibration of the carbon nanotubes, which is a cause of increased electrical resistance, resulting in even better conductivity.

According to an aspect of the carbon nanotube wire of the present invention, the void portion of the carbon nanotube is located inside the innermost layer of the carbon nanotube, between layers of the layered structure of the carbon nanotube, and/or in the outermost layer of the plurality of carbon nanotubes. Due to the enclosed region, the carrier density that contributes to conductivity is improved in the entire carbon nanotube wire, and even more excellent conductivity can be obtained.

According to an aspect of the carbon nanotube wire of the present invention, by including carbon nanotubes into which the different element is introduced at two or more locations inside the innermost layer of the carbon nanotube, the carbon nanotube wire as a whole , the carrier density, which contributes to conductivity, is improved.

According to an aspect of the carbon nanotube wire of the present invention, the carbon nanotube has a portion in which the innermost layer has a circular equivalent diameter of 1.5 nm or more, and the opposing surfaces of the innermost layer of the carbon nanotube have a diameter of 0.400 nm or less. By including carbon nanotubes, the conductivity within the carbon nanotubes is improved, so even better conductivity can be reliably obtained.

According to an aspect of the carbon nanotube wire of the present invention, among the plurality of carbon nanotubes constituting the carbon nanotube wire, the total of the carbon nanotubes having a two-layer structure and the carbon nanotubes having a three-layer structure is 75% by number. By doing so, the conductivity of the carbon nanotubes is improved, and even better conductivity can be reliably obtained.

According to an aspect of the carbon nanotube wire of the present invention, among the plurality of carbon nanotubes constituting the carbon nanotube wire, the carbon nanotubes having a layer structure of four or more layers account for 75% or more by number. Since the heat resistance of carbon nanotubes is improved, the heat resistance of carbon nanotube wires is improved.

According to an aspect of the carbon nanotube wire of the present invention, the degree of orientation of the carbon nanotubes in the longitudinal direction of the carbon nanotube wire is 1.0° or more and 10° or less, thereby increasing the contact area between the carbon nanotubes. , it is possible to reliably obtain even better conductivity, and the tensile strength of the carbon nanotube wire is improved.

1 is a diagram schematically showing the configuration of a carbon nanotube wire according to an embodiment of the present invention, (a) is a perspective view of the carbon nanotube wire, (b) is a perspective view of a carbon nanotube aggregate, and (c) ) is a perspective view of a carbon nanotube. FIG. 2 is an explanatory diagram schematically showing a configuration in an oblique direction of a carbon nanotube aggregate in which a different element is introduced into the voids between carbon nanotubes, the inside of the innermost layer of carbon nanotubes, and the voids between the layers. 1 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire according to an embodiment of the present invention. FIG. 2 is an explanatory view in the radial direction of a carbon nanotube wire, showing an example of a state in which a continuum of different elements is introduced into the voids between carbon nanotubes and into the layered structure of carbon nanotubes. 1 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire into which iodine is introduced as a different element, according to an embodiment of the present invention. 1 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire into which iodine is introduced as a different element, according to an embodiment of the present invention. 1 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire into which iodine is introduced as a different element, according to an embodiment of the present invention. 1 is an enlarged scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire according to an embodiment of the present invention. 1 is an overall image taken by a scanning transmission electron microscope of a radial cross section of a carbon nanotube wire according to an embodiment of the present invention. 1 is a scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire of Example 1. 2 is a scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire of Example 2. 1 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire of Comparative Example 1. 2 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire of Comparative Example 2.

Below, embodiments of the carbon nanotube wire of the present invention will be described in detail. FIG. 1 is a diagram schematically showing the configuration of a carbon nanotube wire according to an embodiment of the present invention, in which (a) is a perspective view of the carbon nanotube wire, and (b) is a perspective view of a carbon nanotube aggregate. Figures 1 and 2 (c) are perspective views of carbon nanotubes. FIG. 2 is an explanatory diagram schematically showing a diagonal configuration of a carbon nanotube aggregate in which a different element is introduced into the voids between carbon nanotubes, the innermost layer of carbon nanotubes, and the voids between the layers. FIG. 3 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire according to an embodiment of the present invention. FIG. 4 is an explanatory view in the radial direction of a carbon nanotube wire showing an example of a state in which a continuum of different elements is introduced into the voids between carbon nanotubes and into the layered structure of carbon nanotubes. FIG. 5 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire into which iodine is introduced as a different element, according to an embodiment of the present invention. FIG. 6 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire into which iodine is introduced as a different element, according to an embodiment of the present invention. FIG. 7 is a scanning transmission electron microscope image of a radial cross section of a carbon nanotube wire into which iodine is introduced as a different element, according to an embodiment of the present invention. FIG. 8 is an enlarged scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire according to the embodiment of the present invention. FIG. 9 is an overall image taken by a scanning transmission electron microscope of a radial cross section of a carbon nanotube wire according to an embodiment of the present invention.

As shown in FIG. 1(a), a carbon nanotube wire (hereinafter sometimes referred to as "CNT wire") 1 according to an embodiment of the present invention is a carbon nanotube (hereinafter referred to as "CNT wire") having a layer structure of one or more layers. It is constructed by bundling one or more carbon nanotube aggregates (hereinafter sometimes referred to as "CNT aggregates") 11. The outer diameter of the CNT wire 1 is, for example, 0.01 mm or more and 10 mm or less, preferably 0.01 mm or more and 1 mm or less.

In the CNT wire 1, it is preferable that the longitudinal direction of the CNT wire 1 and the longitudinal direction of the CNTs are aligned, and that the plurality of CNTs in the CNT wire 1 have a high degree of orientation. As for the degree of orientation of the plurality of CNTs in the longitudinal direction of the CNT wire 1, by increasing the contact area between the CNTs, even better conductivity can be reliably obtained, and the tensile strength of the carbon nanotube wire is improved. From this point of view, the angle is preferably 10° or less, particularly preferably 9.0° or less. C
The degree of orientation of CNTs in the longitudinal direction of the NT wire 1 can be calculated by analyzing (FFT analysis) an image obtained by fast Fourier transform of an image (SEM image) obtained by observation with a scanning electron microscope (SEM). can. For example, the CNT wire 1 is cut along the longitudinal direction using ion milling, the cut surface is observed with a scanning electron microscope (SEM), and the SEM image of the cut surface is processed by FFT (fast Fourier transform). By performing orientation analysis, the degree of orientation of CNTs in the longitudinal direction of the CNT wire 1 can be calculated. The degree of orientation of CNTs is preferably as low as possible, and its lower limit is, for example, 1.0°.

As shown in FIG. 1(b), the CNT aggregate 11 is a bundle of CNTs formed by bundling a plurality of CNTs 11a, 11a, . . . having a multilayer structure of one layer or two or more layers. . The CNT wire 1 is formed by twisting CNT aggregates 11, for example. Here, the CNT wire 1 means a CNT wire 1 in which the proportion of CNTs 11a is 90% by mass or more. Note that in calculating the proportion of CNT 11a in CNT wire 1, plating and dopant are excluded. In the CNT aggregate 11, the plurality of CNTs 11a, 11a, . . . are arranged with their long axes substantially aligned. Further, the CNT aggregate 11 is linear, and the longitudinal direction of the CNT aggregate 11 forms the longitudinal direction of the CNT wire 1. From the above, the longitudinal direction of the CNT 11a forms the longitudinal direction of the CNT wire 1. The equivalent circle diameter of the CNT aggregate 11 is, for example, 20 nm or more and 1000 nm or less.

The CNT 11a is a cylindrical body having a single-walled structure or a multi-walled structure, and is called a single-walled nanotube (SWNT) or a multi-walled nanotube (MWNT), respectively. In FIGS. 1(b) to 1(c), for convenience of explanation, only CNTs 11a having a two-layer structure are shown, but in reality, CNTs 11a have a one-layer structure, and CNTs 11a have a three-layer structure. There is also a CNT11a having the following.

As shown in FIGS. 2 and 3, many of the CNTs 11a constituting the CNT wire 1 have distorted shapes in the radial direction (that is, in the direction perpendicular to the longitudinal direction). Therefore, many CNTs 11a do not have a circular shape in the radial direction. In the CNT wire 1, the roundness of the CNTs 11a constituting the CNT wire 1 is 0.80 or less on average. Since the roundness of the CNTs 11a constituting the CNT wire 1 is less than 0.80 on average, the radial shape of many CNTs 11a is not a perfect circle but a distorted shape. Since the degree of distortion is also moderately large, the CNT wire 1 is packed with CNTs 11a at a high density compared to many CNT wires in which the radial shape of the CNTs is a perfect circle or close to a perfect circle. Therefore, in the CNT wire 1, it is possible to further reduce the resistance and further improve the conductivity.

The circularity of the CNTs 11a constituting the CNT wire 1 is not particularly limited as long as it is 0.80 or less on average, but even better conductivity can be obtained by filling the CNTs 11a with higher density. In view of this, an average of 0.70 or less is preferable, and an average of 0.65 or less is particularly preferable. The lower limit of the roundness of the CNTs 11a constituting the CNT wire 1 is not particularly limited, but from the viewpoint of reducing contact resistance due to high density, and even in a completely crushed state, both ends of the crushed CNTs 11a have a curvature. 0.15 is preferable, and 0.15 is preferable because maintaining the CNT 11a as a carrier ensures the high electron mobility inherent in the CNT 11a, and a foreign element enters that part, causing charge transfer and lowering the resistance of the CNT 11a itself. 20 is particularly preferred. In addition, in the CNT wire 1 of FIG. 3, the circularity of the CNTs 11a constituting the CNT wire 1 is 0.59.

In the CNT wire 1, the number ratio of CNTs 11a with a roundness of 0.50 or less is not particularly limited, but by ensuring that the CNTs 11a are packed with high density, further lowering of resistance is more reliably achieved and conductivity is achieved. In order to further improve the properties, it is preferable that the number ratio of CNTs 11a having a roundness of 0.50 or less is 10% or more of the total number of CNTs 11a constituting the CNT wire 1, It is more preferable that the content is 30% by number or more, and it is particularly preferable that the content is 40% by number or more. The upper limit of the number ratio of CNTs 11a with a roundness of 0.50 or less is not particularly limited, but from the point of view of appropriately lowering the average roundness and densely packing CNTs 11a, the CNT wire 1 is configured. It is preferably 70% by number, and particularly preferably 60% by number of the total number of CNTs 11a. In addition, in the CNT wire 1 of FIG. 3, the number ratio of CNTs 11a having a roundness of 0.50 or less is 52 number %.

In addition, in the CNT wire 1, in order to ensure that the CNTs 11a are packed with high density, the number ratio of CNTs 11a with a roundness of 0.50 or less is 10% of the total number of CNTs 11a constituting the CNT wire 1. It is preferable that the number ratio of CNTs 11a containing the above and having a circularity of 0.80 or more and 1.0 or less is 10% or more, and 20% or more of the total number of CNTs 11a that constitute the CNT wire 1. It is more preferable that it be included, and it is especially preferable that it be included in an amount of 30% or more by number. The upper limit of the number ratio of CNTs 11a with a roundness of 0.80 or more and 1.0 or less is 50% of the total number of CNTs 11a that constitute the CNT wire 1 in order to ensure high density packing of CNTs 11a. is preferable, and 40% by number is particularly preferable.

An example of a method for adjusting the average roundness is a method for adjusting the catalyst size in the manufacturing method of the CNT wire 1, which will be described later. Since the diameter size of CNT 11a depends on the catalyst size, CNT 11a with a large diameter is synthesized using metal catalyst particles with a diameter of 5.0 nm or more, and then CNT wire 1 is manufactured by a spinning method such as direct spinning. By twisting this, the CNT 11a having a high roundness can be crushed and the roundness of the CNT 11a can be adjusted. In addition, by spinning a combination of CNTs 11a having a plurality of diameters synthesized with different catalyst sizes to produce the CNT wire 1, some of the CNTs 11a are crushed and the CNT wire 1 having a desired roundness histogram is produced. can be manufactured.

As shown in FIGS. 2, 4, 5, and 6, the CNT wire 1 of the present invention has a structure in which the CNT aggregate 11 is doped with a plurality of different elements 12a, 12a, . . . as required. You may do so. Note that in FIGS. 5 and 6, the portions with high brightness are the portions doped with the different element 12a.

In the CNT wire 1, the different element 12a includes at least one element selected from the group consisting of iodine (I), tellurium (Te), antimony (Sb), tin (Sn), and indium (In). . Iodine (I) can be easily doped uniformly into the CNT wire 1 and has excellent stability in its position in the CNT wire 1. Tellurium (Te), antimony (Sb), tin (Sn), and indium (In) have high electrical conductivity as a single substance, so they contribute to improving the electrical conductivity of the CNT wire 1 as a whole. The different element 12a exists in the form of a simple substance, oxide, carbide, alloy, or the like.

When the different element 12a is iodine (I), the iodine (I) is in the state of an iodine bond in which three or more iodine (I) are arranged in a line along the longitudinal direction of the CNT 11a, that is, iodine may exist in the form of a trimer or more. Examples of the iodine bond include an iodine trimer in which three iodines (I) are arranged side by side along the longitudinal direction of the CNT 11a. Further, when the different element is tellurium (Te), it may exist in the form of a tellurium compound or the like. Among these, the different elements 12a include iodine (I), tellurium (Te), Antimony (Sb) is preferred. Note that "excellent positional stability" specifically refers to the fact that detachment of the different element 12a is difficult to occur even in a vacuum or an inert atmosphere at 500° C. or higher. In order to investigate the stability of the existing positions, the CNT wire 1 doped with the different element 12a is left in a vacuum or inert atmosphere at 500°C or higher for 24 hours or more, and then the resistance of the CNT wire 1 is measured and fluorescent X-ray analysis is carried out. and/or a method of investigating to what extent the foreign element 12a is desorbed by SEM-EDX measurement.

Furthermore, when tin (Sn) or indium (In) is doped as the dissimilar element 12a, it is possible to suppress the reduction in conductivity when connecting the CNT wire 1 to other members such as other wires, terminals, and substrates. It will be done. This is because when tin (Sn) and indium (In) are doped, they adhere to the CNT wire 1 as fine particles. Solder is generally used to connect the CNT wire 1 to other members such as other wires, terminals, and substrates.

As shown in FIGS. 2, 4, 5, and 6, in the CNT wire 1, a plurality of CNTs 11a, 11a, . . . are formed in a CNT aggregate 11 formed by bundling a plurality of CNTs 11a, 11a, . - It has a configuration in which a plurality of different elements 12a, 12a, . . . are introduced into the gap 11B between them. In the CNT wire 1, a plurality of voids 11B, 11B, . . . are formed between the outermost layers of the plurality of CNTs 11a, 11a, . . . , a plurality of different elements 12a, 12a, . . . are arranged. The void 11B is formed along the longitudinal direction of the CNT aggregate 11, and the plurality of different elements 12a, 12a, . . . arranged in the void 11B are also formed along the longitudinal direction of the CNT aggregate 11, that is, The CNTs 11a are arranged side by side along the longitudinal direction.

Furthermore, in the CNT wire 1 of the present invention, a plurality of different elements 12a, 12a, .・Has been introduced. The interior 11C of the innermost layer T1 of the CNTs 11a extends along the longitudinal direction of the CNT aggregate 11, and the plurality of different elements 12a, 12a, . . . arranged in the interior 11C of the innermost layer T1 of the CNTs 11a also , are arranged in line along the longitudinal direction of the CNT aggregate 11, that is, along the longitudinal direction of the CNTs 11a. In particular, in FIG. 6, a plurality of different elements 12a, 12a, . . . are introduced in a plate shape in the radial direction of the CNT 11a into the interior 11C of the innermost layer T1 of the highly distorted CNT 11a with low roundness.

In addition, as shown in FIGS. 2 and 4, in the CNT wire 1 of the present invention, an interlayer 11D of the layer structure of the CNT 11a, which is a void part (in the figure, an interlayer 11D between the innermost layer T1 and the outermost layer T2 of the CNT 11a, which has a two-layer structure) Furthermore, a plurality of different elements 12a, 12a, . . . are introduced into the region between them. The interlayer 11D extends along the longitudinal direction of the CNT aggregate 11, and the plurality of different elements 12a, 12a, . , are arranged in line along the longitudinal direction of the CNTs 11a.

The cavity 11B, which is the hollow part between the CNTs 11a, is an insulating part, and the dissimilar element 12a is placed in the cavity 11B, which is the insulator, to reduce the contact resistance between the CNTs 11a. Therefore, even better conductivity can be obtained. In particular, since the CNTs 11a have a linear structure with a large aspect ratio, and the voids 11B exist parallel to the longitudinal direction of the CNT wire 1, the different elements 12a are also arranged in the longitudinal direction. This can reduce contact resistance. Furthermore, the inside of the layer structure of the CNT 11a, especially the inside 11C of the innermost layer T1 of the CNT 11a, is also an insulating part, and the dissimilar element 12a is arranged in the inside 11C, which is the insulating part, thereby reducing the resistance inside the CNT 11a. be able to. Moreover, the interlayer 11D of the layer structure of the CNT 11a is also an insulating part, and by disposing the different element 12a in the interlayer 11D, which is the insulating part, it is possible to reduce the resistance inside the CNT 11a.

From the above, in the CNT wire 1, the innermost layer 11C of the innermost layer T1 of the CNT 11a, which is the void of the CNT 11a, the interlayer 11D of the layer structure of the CNT 11a, and/or the outermost layer of the plurality of CNTs 11a, 11a, etc. A different element 12a is introduced into the cavity 11B. Therefore, in the CNT wire 1, the carrier density contributing to conductivity is improved throughout the CNT wire 1.

Further, as shown in FIG. 7, the CNT wire 1 may include CNTs 11a into which different elements 12a are introduced at two or more locations in the interior 11C of the innermost layer T1 of one CNT 11a. In FIG. 7, a CNT 11a is shown in which a different element 12a is introduced in two places into the interior 11C of the innermost layer T1 of the CNT 11a, which has a very low circularity, that is, a very distorted radial shape. have. In other words, in FIG. 7, one CNT 11a has two internal regions 11C of the innermost layer T1 that are generated by approaching the innermost layer T1 to a value close to the interlayer distance of the CNT 11a. By having the CNT 11a in which the different element 12a is introduced into two or more locations in the interior 11C of the innermost layer T1 of the CNT 11a, the carrier density contributing to conductivity is improved in the entire CNT wire 1. Further, since conductive carriers are generated by having two innermost layer T1 internal parts 11C in one CNT 11a, it is advantageous in terms of conductivity. Note that in FIG. 7, the portion with high brightness is the portion doped with the different element 12a.

Next, the arrangement of the different elements 12a in the CNT wire 1 in the longitudinal direction of the CNTs 11a will be described.

As shown in FIGS. 2 and 4, a different element 12a is introduced into the void 11B formed by the outermost layer of the plurality of CNTs 11a, 11a, . . . , and the different element 12a extends in the longitudinal direction of the CNTs 11a. The elements are arranged side by side to form a first dissimilar element continuum 12. A plurality of different elements 12a, 12a, . . . are arranged in a substantially linear line over a length in a range of, for example, 2 nm or more and 100 nm or less, to form one first different element continuum 12. . The plurality of different elements 12a, 12a, . . . are continuously arranged in a substantially linear line to form one first different element continuum 12.

Further, as shown in FIGS. 5 to 7, the existence of the first dissimilar element continuum 12 can be confirmed from the brightness of the dissimilar elements in the voids formed by the outermost layer of a plurality of CNTs.

As shown in FIGS. 2 and 4, the CNT wire 1 is provided with one or more first dissimilar element continuum 12 along the circumferential direction of the CNTs 11a. Further, along the longitudinal direction of the CNT aggregate 11, one or more first dissimilar element continuums 12, 12, . . . are arranged side by side.

In the CNT wire 1, one or more first dissimilar element continuum 12, 12, . . . are arranged in one void 11B formed between the plurality of CNTs 11a, 11a, . arranged along the direction. Further, in the CNT wire 1, the plurality of first dissimilar element continuums 12, 12, . . . are arranged so as to substantially fill the void portion 11B. The number of the first dissimilar element continuum 12 arranged in one cavity 11B formed between the plurality of CNTs 11a, 11a, . . . can be determined as appropriate depending on the size and shape of one cavity 11B. It can be selected and is not particularly limited.

The number of first dissimilar element continuum 12 arranged varies depending on the size, shape, etc. of one cavity 11B. In the CNT wire 1 of the present invention, for example, the size of the cavity 11B can be set to 0.05 nm ² or more in order to arrange one or more first dissimilar element continuum 12, and two or more In order to arrange the first dissimilar element continuum 12, the size of the cavity 11B can be set to 0.1 nm2 ^or more, and in order to arrange the first dissimilar element continuum 12 of 25 or less. It is possible to set the size of the cavity 11B to be 10 nm ² or less. By selecting an appropriate size of the void 11B, the stability of the presence of the different element 12a is improved.

Further, as shown in FIGS. 2 and 4, a different element 12a is introduced into the layered structure of the CNT 11a, and the different element 12a is arranged in a line along the longitudinal direction of the CNT 11a. A continuum 22 of different elements is formed. More specifically, a different element 12a is introduced into the interior 11C of the innermost layer T1 of the CNT 11a. Further, the different element 12a is also introduced into the interlayer 11D of the CNT 11a (in the figure, the region between the innermost layer T1 and the outermost layer T2 of the CNT 11a having a two-layer structure). A plurality of different elements 12a, 12a, . . . are arranged in a substantially linear line over a length in a range of, for example, 2 nm or more and 100 nm or less, to form one second different element continuum 22. . The plurality of different elements 12a, 12a, . . . are continuously arranged in a substantially linear line to form one second different element continuum 22.

In addition, as shown in FIGS. 5 to 7, the presence of the different elements 12a, including the second different element continuum 22, means that in the transmission electron microscope image, the electrons transmitted from the sample are affected by the interaction with the sample. This can be determined from the contrast that occurs in the image obtained due to crystallinity and constituent elements. In an electron microscope image (HAADF-STEM), the intensity of brightness is proportional to the atomic number (Z). Although carbon constituting the CNT 11a is the 6th atom in the periodic table of elements, atoms with lower brightness are hydrogen to boron, and conversely, elements with higher brightness than carbon are atoms of nitrogen and higher. Since the different element 12a has a larger atomic number than carbon, its brightness becomes higher in the HAADF-STEM image. When checking the HAADF-STEM image based on this, a structure with high brightness is confirmed between and within the CNT 11a, and it can be concluded that this is necessarily the doped foreign element 12a. In FIG. 5, a different element with crystallinity is contained inside a distorted carbon nanotube, and functions as a conductive path inside the carbon nanotube. In addition, a structure composed of three or one atoms of different elements as a cross section in the gap between the carbon nanotubes in FIGS. 5 and 6 functions as a conductive path between the carbon nanotubes. The cross-sectional image in Figure 6 shows a plate-shaped structure composed of different elements contained in a carbon nanotube with low circularity, or the plate-shaped structure composed of different elements contained in the carbon nanotube with low circularity in Figure 7. The structure composed of different elements has both the function of a conductive path and the function of improving the conductivity of the carbon nanotube itself through carrier doping due to its adhesiveness.

As shown in FIGS. 2 and 4, in the CNT wire 1, one or more second dissimilar element continuums 22, 22, . . . are arranged side by side along the longitudinal direction of the CNT aggregate 11. There is. In addition, in FIG. 2, for convenience of explanation in the drawing, one second dissimilar element continuum 22 is formed in both the interior 11C of the innermost layer T1 of the CNT 11a and the interlayer 11D of the CNT 11a.

Inside the layer structure of the CNT 11a, a plurality of second dissimilar element continuum bodies 22, 22, . . . are arranged along the radial direction of the CNT 11a. In the CNT wire 1, a plurality of second dissimilar element continuum bodies 22, 22, .

When the space in the interior 11C of the innermost layer T1 of the layer structure of the CNT 11a has an inner diameter of 1.0 nm or more and 4.0 nm or less, as shown in FIG. * are arranged along the radial direction of the CNT 11a. Furthermore, when the space in the interior 11C of the innermost layer T1 of the layered structure of the CNTs 11a has an inner diameter of less than 1.0 nm, one or more second dissimilar element continuum 22 is arranged in the radial direction.

By forming the first dissimilar element continuum 12 and/or the second dissimilar element continuum 22, the number of carriers contributing to conductivity is further increased, and the conductivity in the longitudinal direction of the CNT 11a is further improved. Moreover, since the lattice vibration of the CNTs 11a, which is a cause of an increase in electrical resistance, can be further suppressed, the CNT wire 1 can obtain even better conductivity.

The content of the different element 12a is not particularly limited, but the lower limit is such that the lattice vibration of the CNT 11a due to temperature rise is suppressed by the action of the different element 12a, and the different element 12a is introduced into the voids of the CNT 11a. From the viewpoint of reliably improving conductivity, the amount is preferably 1.0 parts by mass, more preferably 2.0 parts by mass, and particularly preferably 3.0 parts by mass based on 100 parts by mass of CNTs contained in the CNT wire 1. . On the other hand, the upper limit of the content of the different element 12a is set in such a way that it is possible to reliably prevent a decrease in the conductivity of the CNT 11a itself caused by scattering of electrons of the CNT 11a due to doping with the different element 12a. It is preferably 20 parts by mass, more preferably 17 parts by mass, and particularly preferably 15 parts by mass, based on 100 parts by mass of CNTs.

Further, as shown in FIG. 8, which is an enlarged image of the radial cross section of the CNT wire 1, and FIG. 9, which is the entire image, in the CNT wire 1, the equivalent circle diameter of the innermost layer of the CNTs 11a is 1.5 nm or more, and the CNTs 11a The innermost layer of the CNT 11a may have a portion where opposing surfaces (double arrow portions in FIG. 8) have a thickness of 0.400 nm or less. In the above embodiment, the circularity of the CNTs 11a is very low, and the CNTs 11a are crushed and the opposing surfaces of the innermost layer of the CNTs 11a are close to each other, so that the CNTs 11a are packed even more densely, and the conductivity inside the CNTs 11a is improved, so that the CNT wire 1 can reliably obtain even better conductivity.

Next, the structure and characteristics of the CNT 11a will be explained. The two-layered CNTs 11a constituting the CNT aggregate 11 have a three-dimensional network structure in which two cylindrical bodies (innermost layer T1, outermost layer T2) having a hexagonal lattice network structure are arranged substantially coaxially. It is called DWNT (Double-walled nanotube). The hexagonal lattice, which is a constituent unit, is a six-membered ring with a carbon atom at its apex, and these six-membered rings are adjacent to and continuously bonded to other six-membered rings.

The properties of CNT 11a depend on the chirality of the cylindrical body. The chirality of the cylindrical body is roughly classified into armchair type, zigzag type, and other chiral types. The armchair type exhibits metallic behavior, the chiral type exhibits semiconducting behavior, and the zigzag type exhibits an intermediate behavior. The conductivity of CNTs 11a varies greatly depending on which chirality they have, and in order to improve the conductivity of CNT aggregates 11, it is important to increase the proportion of armchair-shaped CNTs 11a that exhibit metallic behavior. It has been. On the other hand, the chiral type CNTs 11a having semiconducting properties exhibit metallic behavior by being doped with a different element 12a having electron-donating or electron-accepting properties. In addition, when a general metal is doped with a different element 12a, conduction electrons are scattered inside the metal and its conductivity decreases. If doped, it causes a decrease in conductivity.

As described above, since the doping effect of the different element 12a on the metallic CNT 11a and the semiconducting CNT 11a is in a trade-off relationship from the viewpoint of conductivity, theoretically, the doping effect of the metallic CNT 11a and the semiconducting CNT 11a is It is desirable that the metallic CNTs 11a and the semiconducting CNTs 11a be combined after the CNTs 11a are fabricated separately and only the semiconducting CNTs 11a are doped. However, since it is very complicated to selectively produce metallic CNTCNTs 11a and semiconducting CNTs 11a, metallic CNTs 11a and semiconducting CNTs 11a are produced in a mixed state. Therefore, in order to improve the conductivity of the CNT wire 1 made of a mixture of metallic CNTs 11a and semiconducting CNTs 11a, it is preferable to select a structure of the CNTs 11a in which doping treatment with the different element 12a is effective.

In the CNT wire 1 consisting of a plurality of CNTs 11a, 11a, . . . , the CNT wire 1 is preferred because the CNT wire 1 can reliably obtain even better conductivity since the conductivity of the CNTs 11a is improved. It is preferable that the total of the CNTs 11a having a two-layer structure and the CNTs 11a having a three-layer structure be 75% or more by number among all the CNTs 11a forming the structure.

CNTs 11a with a small number of layers, such as a two-layer structure or a three-layer structure, have relatively higher conductivity than CNTs 11a with a multilayer structure of four or more layers. Further, the CNT 11a having a small number of layers tends to have a distorted radial shape with low roundness in the CNT wire 1.

Further, the different element 12a is introduced into the void 11B between the CNTs 11a formed by the plurality of CNTs 11a, 11a, . . . and into the interior 11C of the innermost layer T1 of the CNTs 11a. Furthermore, in the multilayered CNT 11a, the different element 12a may be introduced not only into the interior 11C of the innermost layer T1 but also into the interlayer 11D. In particular, in a CNT 11a having a small number of layers such as a two-layer structure or a three-layer structure, the voids between the layers 11D are relatively large, and the different element 12a is likely to be introduced into the voids between the layers 11D. In this way, the doping effect of the different element 12a is produced by introducing the different element 12a into the inside and outside of the CNT 11a. For the reasons mentioned above, when CNTs 11a with a multilayer structure are doped with a different element 12a, the CNTs 11a with a two-layer structure or a three-layer structure improve the conductivity in the interlayer 11D of the multilayer CNTs 11a. has the highest doping effect. Further, the single-layered CNT 11a may be oxidized and decomposed by a trace amount of oxygen remaining during the heat treatment in the doping process. Therefore, in the CNT wire 1 of the present invention, attention is paid to the number of CNTs 11a having a two-layer structure or a three-layer structure. Furthermore, if the ratio of the sum of the numbers of CNTs 11a having a two-layer structure or three-layer structure is less than 75%, the ratio of CNTs 11a having a single-layer structure or a multi-layer structure of four or more layers becomes high. The doping effect of the different element 12a is reduced for the aggregate 11 as a whole, making it difficult to obtain high electrical conductivity. Therefore, the ratio of the sum of the numbers of CNTs 11a having a two-layer structure or a three-layer structure is set to a value of 75 number % or more. In this way, by setting the ratio of the sum of the numbers of CNTs 11a with a two-layer structure or a three-layer structure to 75% or more, the conductivity of the CNT wire 1 itself is improved, and the inside of the layer structure of the CNTs 11a also has different types. Since the element 12a is easily introduced, even better conductivity can be obtained. In addition, from a manufacturing standpoint, the upper limit of the ratio of the sum of the numbers of CNTs 11a with a two-layer structure and CNTs 11a with a three-layer structure is preferably 99% by number, more preferably 95% by number, and even more preferably 90% by number. Particularly preferred is 85% by number.

On the other hand, when CNTs 11a having a layer structure of four or more layers account for 75% or more of all the CNTs 11a constituting the CNT wire 1, the heat resistance of the CNTs 11a is improved. Improves heat resistance. From the viewpoint of production, the upper limit of the ratio of CNTs 11a having a structure of four or more layers is preferably 99% by number, more preferably 95% by number, even more preferably 90% by number, and particularly preferably 85% by number.

The equivalent circle diameter of the CNTs 11a constituting the CNT wire 1 is not particularly limited, but the lower limit is the value obtained by obtaining a predetermined proportion of CNTs 11a that have a distorted radial shape with low roundness and constituting the CNT wire 1. The average circularity of the CNTs 11a is preferably 0.80 or less, preferably 5.0 nm, and particularly preferably 6.0 nm. On the other hand, the upper limit of the equivalent circle diameter of the CNTs 11a constituting the CNT wire 1 is preferably 12.0 nm, particularly preferably 10.0 nm, from the viewpoint of ensuring high density packing of the CNTs 11a. Note that the equivalent circle diameter in this specification is calculated by calculating the cross-sectional area of the CNT 11a at 100 or more points with respect to the cross-section of the CNT 11a, and assuming that the cross-sectional area = 2 × pi × the square of the radius of the CNT 11a. After calculating the radius, double the radius.

Next, a method for manufacturing a CNT wire according to the present invention will be explained. The CNT wire 1 according to the embodiment of the present invention can be manufactured, for example, by the following method. First, a mixture containing a catalyst and a reaction accelerator is supplied to a carbon source by a floating catalytic vapor deposition (CCVD) method, a substrate method, or the like to generate a plurality of CNTs 11a. At this time, a saturated hydrocarbon having a six-membered ring can be used as the carbon source, a metal catalyst containing iron or the like can be used as the catalyst, and a sulfur compound can be used as the reaction promoter. Furthermore, since the proportion of SWNT decreases as the carrier gas flow rate increases, the proportion of CNTs 11a having a two-layer structure or a three-layer structure can be increased by adjusting the raw material composition and spraying conditions.

Further, in order to adjust the diameter of the CNTs 11a (outer diameter of the outermost layer) to be equal to or greater than a predetermined value, for example, equal to or greater than 5.0 nm, the size of the metal catalyst is adjusted. For this reason, the raw material is supplied to the reactor by spraying so that the mist particle size becomes around 20 μm. Thereafter, the remaining metal catalyst is removed by subjecting the CNT aggregate 11, which is a bundle of a plurality of CNTs 11a, 11a, . . . , to acid treatment. Next, the plurality of CNT aggregates 11 are spun to produce the CNT wire 1. The CNT wire 1 can be produced by, for example, dry spinning (Patent No. 5819888, Patent No. 5990202, Patent No. 5350635), wet spinning (Patent No. 5135620, Patent No. 5131571, Patent No. 5288359), liquid crystal spinning (Japanese Patent No. 5131571, Patent No. 5288359), 2014-530964) and other spinning methods.

By adjusting the number of layers of the CNTs 11a, the diameter of the CNTs 11a, the spinning method, the spinning conditions, etc., the roundness of the CNTs 11a constituting the CNT wire 1 is made to be 0.80 or less on average.

When introducing a different element 12a into the CNT aggregate 11, the CNT aggregate 11 after acid treatment is doped with the different element 12a, and the void 11B of the CNT aggregate 11 and the interior 11C of the innermost layer T1 of the CNT 11a are doped. And/or a CNT aggregate 11 is produced in which the interlayer 11D of the layered structure of the CNTs 11a is doped with a different element 12a. Further, after producing the CNT wire 1, the CNT wire 1 may be subjected to doping treatment with the different element 12a. A method for doping the CNT aggregate 11 or CNT wire 1 with the different element 12a is to put the CNT aggregate 11 or CNT wire 1 and the different element 12a into a container that has been subjected to reduced pressure treatment, and then heat the container to evaporate the different element 12a. Examples include a gas phase method in which the element 12a is applied to the CNT aggregate 11 or the CNT wire 1, and a liquid phase method in which the CNT aggregate 11 or the CNT wire 1 is immersed in a solution in which the different element 12a is dissolved. Among these methods, the vapor phase method is preferable since the void 11B of the CNT aggregate 11 and the interior 11C of the innermost layer T1 of the CNTs 11a are reliably doped with the different element 12a.

The state of the different element 12a before doping is not limited and can be appropriately selected depending on the doping method. When using the gas phase method, for example, the different element 12a is prepared as a simple substance (metal) that is easily vaporized. When using the liquid phase method, the different element 12a is selected as a compound (eg, oxide, sulfate, etc.) that is easily soluble in the solvent used.

Note that an insulating coating layer (not shown) made of a thermosetting resin, a thermoplastic resin, or the like may be disposed around the outer periphery of the CNT wire 1 of the present invention. Examples of the thermosetting resin include polyimide and phenol resin. Examples of thermoplastic resins include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polyacetal, polystyrene, polycarbonate, polyamide, polyvinyl chloride, polyvinyl acetate, polyurethane, polymethyl methacrylate, acrylonitrile butadiene styrene resin, acrylic resin, etc. can be mentioned.

Next, other embodiments of the CNT wire of the present invention will be described. In the above embodiment of the CNT wire 1, the CNT wire 1 is made up of a plurality of CNT aggregates 11 made up of a plurality of CNTs 11a having a layer structure of one or more layers, but instead of this, it is made up of a plurality of CNTs 11a. A CNT wire 1 made of a single CNT aggregate 11 may be used. Furthermore, the CNT wire 1 contains an element other than at least one element selected from the group consisting of iodine (I), tellurium (Te), antimony (Sb), tin (Sn), and indium (In). You can also dope.

Next, examples of the present invention will be described. Note that the present invention is not limited to the following examples.

Example 1
A CNT wire made using floating catalytic vapor deposition (CCVD), with an average circularity of 0.59 and a CNT wire containing 52% by number of CNTs with a circularity of 0.50 or less. was prepared. Next, the prepared CNT wire was placed in the center of the quartz tube in the longitudinal direction, and iodine (I) particles as a different element were placed in one end of the quartz tube in the longitudinal direction, and the CNT wire was heated while degassing the inside of the quartz tube. , the quartz tube was sealed. A quartz tube was placed in a heating furnace so that the iodine (I) particles were directed downward in the direction of gravity, and the temperature was raised to 700°C at a rate of 100°C/hour and held at 700°C for 48 hours. Thereafter, the CNT wire was taken out from the quartz tube and washed with acid to obtain a CNT wire doped with iodine (I).

Comparative example 1
Comparative Example 1 was carried out in the same manner as in Example 1, except that a CNT wire in which the CNTs constituting the CNT wire had an average circularity of 0.99 was prepared by floating catalytic vapor deposition (CCVD). A CNT wire doped with iodine (I) was obtained.

Example 2
A CNT wire was obtained in the same manner as in Example 1, except that iodine (I) was not doped by floating catalytic vapor deposition (CCVD).

Comparative example 2
The iodine (I) A CNT wire rod not doped with was obtained.

Note that FIG. 10 is a scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire of Example 1. FIG. 11 is a scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire of Example 2. FIG. 12 is a scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire of Comparative Example 1. FIG. 13 is a scanning transmission electron microscope image of a radial cross section of the carbon nanotube wire of Comparative Example 2. Note that FIGS. 10 to 13 are all images at the same magnification.

The evaluation items of the examples are as follows.

(1) Resistivity change The resistivity of the CNT wire doped with iodine (I) and the CNT wire that was not subjected to the doping process was measured. After measuring the resistance using the four-terminal method, the diameter of the wire at the point where the resistance was measured was measured using a microscope. From the distance between the terminals and the diameter, the CNT wire doped with iodine (I) and the doping process were determined. The resistivity of the CNT wire that was not tested was calculated. The resistivity of the CNT wire doped with iodine (I) was calculated as a change in resistivity (%) with respect to the resistivity of the CNT wire that was not subjected to the doping process. Further, the resistivity change was evaluated based on the following criteria.
○: Resistivity change is -30% or less △: Resistivity change is greater than -30% but lower than -20% ×: Resistivity change is -20% or more

In Example 1, in which the CNTs constituting the CNT wire had an average roundness of 0.59 and were doped with iodine (I), the resistivity change was evaluated as ○, and the resistance was further reduced by doping with iodine (I). By achieving this, we were able to further improve conductivity. On the other hand, in Comparative Example 1, in which the CNTs constituting the CNT wire have an average circularity of 0.99, the resistivity change is rated as ×, and even with iodine (I) doping, further lower resistance was achieved. Therefore, it was not possible to further improve the conductivity.

The carbon nanotube wire of the present invention is filled with carbon nanotubes at a high density and can further reduce resistance and further improve conductivity. is high.

1 Carbon nanotube wire 11 Carbon nanotube aggregate 11a Carbon nanotube 12a Different element

Claims (14)

A carbon nanotube wire consisting of one or more carbon nanotube aggregates consisting of a plurality of carbon nanotubes,
A carbon nanotube wire, wherein the carbon nanotubes constituting the carbon nanotube wire have an average roundness of 0.80 or less. The carbon nanotube wire according to claim 1, wherein the carbon nanotubes having a roundness of 0.50 or less are contained in an amount of 10% or more by number. The carbon nanotube wire according to claim 1, wherein the carbon nanotubes having a roundness of 0.50 or less are contained in an amount of 30% or more by number. A different element is introduced into the voids of the carbon nanotubes, and the different element is selected from the group consisting of iodine (I), tellurium (Te), antimony (Sb), tin (Sn), and indium (In). The carbon nanotube wire according to any one of claims 1 to 3, containing at least one element. The carbon nanotube wire according to claim 4, wherein the content of the different element is 1.0 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the carbon nanotubes contained in the carbon nanotube wire. The carbon nanotube wire according to claim 4, wherein the different elements form a continuum of different elements arranged along the longitudinal direction of the carbon nanotube. 5. The void portion of the carbon nanotube is an area inside the innermost layer of the carbon nanotube, between layers of a layered structure of the carbon nanotube, and/or a region surrounded by the outermost layer of the plurality of carbon nanotubes. Carbon nanotube wire. 5. The carbon nanotube wire according to claim 4, wherein the carbon nanotube has the different element introduced into two or more locations inside the innermost layer of the carbon nanotube. Any one of claims 1 to 3, wherein the carbon nanotube has a portion in which the innermost layer of the carbon nanotube has a circular equivalent diameter of 1.5 nm or more, and the opposing surfaces of the innermost layer of the carbon nanotube have a diameter of 0.400 nm or less. The carbon nanotube wire according to item 1. Any one of claims 1 to 3, wherein of all the carbon nanotubes constituting the carbon nanotube wire, the total of the carbon nanotubes having a two-layer structure and the carbon nanotubes having a three-layer structure is 75% or more by number. The carbon nanotube wire according to item 1. The carbon according to any one of claims 1 to 3, wherein of all the carbon nanotubes constituting the carbon nanotube wire, the carbon nanotubes having a layer structure of four or more layers account for 75% or more by number. Nanotube wire. The carbon nanotube wire according to any one of claims 1 to 3, wherein the carbon nanotubes constituting the carbon nanotube wire have an average circular equivalent diameter of 5.0 nm or more. The carbon nanotube wire according to any one of claims 1 to 3, wherein the degree of orientation of the carbon nanotubes in the longitudinal direction of the carbon nanotube wire is 1.0° or more and 10° or less. A claim in which the different element contains iodine (I), and the iodine (I) is in the form of an iodine bond in which three or more iodine (I) are arranged in a line along the longitudinal direction of the carbon nanotube. Item 4. Carbon nanotube wire according to item 4.

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