JP2009274936A - Carbon wire, assembled wire material and method for manufacturing those - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon wire using carbon filaments having sufficiently low electric resistance, such as CNTs, and an assembled wire material using such carbon wires. <P>SOLUTION: The carbon wire 1 comprises an assembled part 3 and a graphite layer 4. The assembled part 3 is composed by bringing a plurality of carbon nanotubes 2 as carbon filaments into contact with each other. The graphite layer 4 is formed on an outer periphery of the assembled part 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to carbon wires, aggregate wires, and methods for producing them, and more specifically, to carbon wires using a plurality of carbon filaments, aggregate wires, and methods for producing them.

  Carbon nanotubes (CNT) as an example of carbon filaments are expected to have various industrial applications due to their excellent characteristics. For example, the electrical resistance value of CNT is almost as low as copper, and it can be considered to be used as a material for wire. Various methods have been proposed for producing such CNTs (for example, Japanese Patent Application Laid-Open No. 2007-112661: hereinafter referred to as Patent Document 1).

In Patent Document 1, gallium (Ga) is used as a catalyst metal, and a CNT having a desired size, shape and orientation is manufactured by applying a direct current to an amorphous carbon linear structure into which the catalyst metal is introduced. Has been proposed.
JP 2007-112661 A

  The conventional CNT manufacturing method as described above focuses on controlling the size and the like of a single CNT, but considering the industrial application of CNT, it is a long-sized collection of a plurality of such CNTs. The necessity to manufacture a wire (carbon wire) is considered. However, when the inventor examined, about the wire (carbon wire) formed by assembling (for example, twisting together) such a plurality of CNTs (for example, CNTs having a length of several tens to several hundreds μm), Despite the extremely low resistance of CNT alone, the electrical resistance value as a carbon wire is about three orders of magnitude higher than that of a wire made of copper.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to use a carbon wire using a carbon filament such as CNT having a sufficiently low electrical resistance value or the carbon wire. It is to realize the gathered wire rod.

  The carbon wire according to the present invention includes an aggregate portion and a graphite layer. The assembly portion is configured by contacting a plurality of carbon filaments. The graphite layer is formed on the outer periphery of the aggregate part.

  If it does in this way, an aggregate part can be held so that carbon filaments of an aggregate part may contact certainly by a graphite layer formed in the perimeter part in a carbon wire. Therefore, the contact area between the carbon filaments in the assembly part and the pressure at the contact part can be increased, so that the electrical resistance of the carbon wire caused by insufficient contact between the carbon filaments in the assembly part Increase in value can be suppressed. In addition, the graphite layer also acts as a conductive layer, whereby the electric resistance value of the carbon wire can be further reduced.

  In the carbon wire, the carbon filament may be a carbon nanotube. In this case, since the carbon nanotube exhibits good conductivity (low electric resistance value), the electric resistance value of the carbon wire can be further reduced.

  In the carbon wire, the graphite layer may be a carbon nanotube. In this case, the electrical resistance of the carbon wire can be more effectively reduced by the graphite layer also acting as a conductive layer.

  The assembly wire according to the present invention includes a plurality of the carbon wires. In this way, a sufficiently low resistance assembly wire can be realized. Further, by using a plurality of carbon wires, an aggregate wire having a large cross-sectional area can be realized, so that a current value that can be passed through the aggregate wire can be increased.

  In the carbon wire manufacturing method according to the present invention, a step of preparing an assembly part in which a plurality of carbon filaments are in contact is performed. Then, a step of forming a graphite layer on the surface of the aggregate portion is performed by bringing the surface of the aggregate portion into contact with liquid gallium.

  In this way, by bringing the portion of the carbon filament exposed on the surface of the aggregate portion into contact with liquid gallium, a graphite layer can be formed by the catalytic action of the liquid gallium. Therefore, it is possible to obtain the carbon wire according to the present invention by forming the graphite layer at a lower processing temperature than in the case where the graphite layer is directly grown on the surface of the aggregate part.

  In the carbon wire manufacturing method, compressive stress may be applied to the aggregate portion in the step of forming the graphite layer. In this case, since the graphite layer is formed in a state where compressive stress is applied to the aggregate portion, the area and contact pressure of the contact portions between the carbon filaments constituting the aggregate portion in the formed carbon wire are increased. can do. As a result, the electric resistance value of the carbon wire can be more reliably reduced.

  In the carbon wire manufacturing method, in the step of forming the graphite layer, compressive stress may be applied to the aggregate portion by pressurizing liquid gallium. In this case, the compressive stress is applied to the aggregate portion by applying pressure to the liquid gallium (for example, a method for increasing the pressure of the atmospheric gas in contact with the liquid gallium, or after encapsulating Ga and CNT in a container such as a capsule, ) And the like, and the like.

  In the carbon wire manufacturing method, in the step of forming the graphite layer, the liquid gallium may be pressurized by adjusting the pressure of the atmospheric gas in contact with the liquid gallium. In this case, it is possible to easily pressurize the liquid gallium. Further, by adjusting the pressure of the atmospheric gas, the value of the pressure applied to the liquid gallium can be easily adjusted.

  In the carbon wire manufacturing method, in the step of forming the graphite layer, the temperature of the liquid gallium is preferably 450 ° C. or higher and 750 ° C. or lower. In this case, the catalytic reaction of liquid gallium that forms the graphite layer from the outer peripheral portion of the aggregate portion can be caused more efficiently. Here, the lower limit of the temperature of the liquid gallium is set to 450 ° C. because the liquid gallium catalytic reaction becomes insufficient when the temperature of the liquid gallium is lower than the temperature. The upper limit of the temperature of the liquid gallium is set to 750 ° C. in order to avoid decomposition of the carbon filament constituting the aggregate portion.

  The carbon wire manufacturing method may include a step of forming an amorphous carbon layer as a surface layer of the aggregate portion before the step of forming the graphite layer. In this case, the graphite layer can be formed while maintaining the structure of the carbon filament in the aggregate portion by previously forming an amorphous carbon layer that is to be a graphite layer. For this reason, the freedom degree of design of the structure of a carbon wire can be enlarged.

  The carbon wire manufacturing method may further include a step of removing gallium adhering to the surface of the carbon wire after the step of forming the graphite layer. In this case, even if gallium solidified with liquid gallium adheres to the surface of the carbon wire in the step of forming the graphite layer, the solidified gallium can be removed from the surface of the carbon wire.

  In the manufacturing method of the aggregate wire according to the present invention, a step of forming a plurality of carbon wires using the above-described carbon wire manufacturing method is performed. And the process of twisting together a plurality of carbon wires and forming an aggregate wire is carried out. In this case, the aggregate wire can be formed using a low resistance carbon wire according to the present invention.

  According to the present invention, a low resistance carbon wire and an assembly wire can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  FIG. 1 is a schematic cross-sectional view showing an embodiment of a carbon wire according to the present invention. 2 is a schematic cross-sectional view taken along line II-II in FIG. With reference to FIG. 1 and FIG. 2, the carbon wire 1 by this invention is demonstrated. 1 shows a cross section in a direction perpendicular to the longitudinal direction of the carbon wire 1, and FIG. 2 shows a cross section in a direction along the longitudinal direction of the carbon wire 1.

  As shown in FIGS. 1 and 2, the carbon wire 1 includes an aggregate portion 3 and a graphite layer 4. The aggregate portion 3 is configured by contacting carbon nanotubes 2 as a plurality of carbon filaments. The graphite layer 4 is formed so as to surround the outer periphery of the aggregate portion 3. In FIG. 1 and FIG. 2, two carbon nanotubes 2 appear in the cross section of the carbon wire 1, but the carbon nanotubes (CNT) constituting the cross section of the aggregate portion 3 in the carbon wire 1. 2 may be 2 or more, for example, 3 or 4 or more. Further, as shown in FIGS. 1 and 2, the carbon nanotubes 2 constituting the aggregate portion 3 are in contact with each other. And, as shown in FIG. 2, the carbon nanotubes 2 are sequentially in contact with each other in the longitudinal direction of the carbon wire 1, so that the aggregate portion 3 extends along the longitudinal direction of the carbon wire 1. A conductive path through which a current can flow is constituted by the carbon nanotubes 2.

  In this way, the aggregate portion 3 can be held so that the carbon nanotubes 2 of the aggregate portion 3 are reliably in contact with each other by the graphite layer 4 formed on the outer peripheral portion of the carbon wire 1. Therefore, since the contact area between the carbon nanotubes 2 in the aggregate part 3 and the pressure at the contact part can be increased, the contact between the carbon nanotubes 2 in the aggregate part 3 becomes insufficient. An increase in the electric resistance value of the wire 1 can be suppressed. Further, the graphite layer 4 also acts as a conductive layer, whereby the electric resistance value of the carbon wire 1 can be further reduced.

  Moreover, in the said carbon wire 1, since the carbon filament which comprises the aggregate part 3 is the carbon nanotube 2 which shows a favorable electrical conductivity, the electrical resistance value of the carbon wire 1 can be reduced reliably.

  In the carbon wire 1, the graphite layer 4 is preferably a carbon nanotube. In this case, the electrical resistance of the carbon wire 1 can be further reduced by the graphite layer 4 also acting as a conductive layer.

  Moreover, it is preferable that the carbon nanotubes 2 constituting the aggregate portion 3 are pressed against each other by the graphite layer 4. In this way, the contact area and the contact pressure at the contact portions between the carbon nanotubes 2 in the aggregate portion 3 and between the graphite layer 4 and the carbon nanotubes 2 in the aggregate portion 3 can be increased. As a result, a low resistance carbon wire 1 can be realized.

  FIG. 3 is a schematic cross-sectional view showing an embodiment of an assembly wire according to the present invention. With reference to FIG. 3, the assembly wire 5 according to this invention is demonstrated. FIG. 3 shows a cross section in a direction perpendicular to the longitudinal direction of the assembly wire 5.

  With reference to FIG. 3, the assembly wire 5 is provided with a plurality of carbon wires 1 (seven in FIG. 3). In this way, a sufficiently low resistance aggregate wire 5 can be realized using the low resistance carbon wire 1 according to the present invention. In addition, by using a plurality of carbon wires 1, the aggregate wire 5 having a large cross-sectional area can be realized, so that the current value that can be passed through the aggregate wire 5 can be increased. Further, in the aggregate wire 5, a plurality of carbon wires 1 may be put together, or a plurality of fixing members that simply bundle a plurality of carbon wires 1 and bind the plurality of carbon wires 1 bundled together. You may arrange | position in the outer peripheral part of the carbon wire 1 of. As the fixing member, for example, an annular fixing tool made of an insulator (for example, resin) may be used.

  In addition, the number of the carbon wires 1 constituting the assembly wire 5 can be different from the number in the configuration shown in FIG. 3 (for example, an arbitrary number of 2 or more). Moreover, although the carbon wire 1 which comprises the assembly wire 5 is equipped with the same structure in the structure shown in FIG. 3, you may change the structure of the carbon wire 1 by the position in the cross section of the assembly wire 5. FIG. For example, in the central portion of the cross section of the aggregate wire 5, the number of carbon nanotubes 2 (see FIG. 1) constituting the carbon wire 1 (the number of carbon nanotubes 2 appearing in the cross section in the direction perpendicular to the extending direction of the carbon wire 1). On the other hand, in the outer peripheral portion of the cross section of the assembly wire 5, the number of carbon nanotubes 2 constituting the carbon wire 1 is determined by the number of carbon nanotubes 1 positioned in the central portion. A configuration in which the number is less than the number of integration (for example, the number of integration is less than 10, more specifically, 5 or less) may be adopted.

  In addition, similar to the step of forming the graphite layer 4 of the carbon wire 1 to be described later, the assembly wire 5 is subjected to a process of bringing liquid gallium (Ga catalyst) into contact with the assembly wire 5. You may form the graphite layer surrounding the outer periphery. Also, a plurality of aggregated wires 5 having a graphite layer formed on the outer periphery are prepared, and the aggregated wires 5 are bundled to prepare a wire having a larger cross-sectional area. And the process which makes liquid gallium contact also with respect to the wire in order to form the graphite layer surrounding outer periphery. Further, a plurality of wires having graphite layers formed on the outer periphery are bundled to form a wire having a larger cross-sectional area. In this way, the wires are bundled to form an aggregate wire, and after the aggregate wire is brought into contact with liquid gallium to form a graphite layer on the surface of the aggregate wire, a plurality of aggregate wires on which the graphite layer is formed are further bundled. By repeating the process, it is possible to produce a collective wire having a lower resistance and a larger diameter.

  FIG. 4 is a flowchart for explaining a method of manufacturing the aggregate wire shown in FIG. With reference to FIG. 4, the manufacturing method of the assembly | attachment wire shown in FIG. 3 is demonstrated.

  As shown in FIG. 4, in the manufacturing method of the assembly wire 5, a CNT production | generation process (S10) is first implemented. In this CNT (carbon nanotube) generation step (S10), short (for example, several μm long) carbon nanotubes are produced by a conventionally known method.

  For example, a base film is formed on the surface of a substrate for CNT generation, and a plurality of nanoparticles that act as a catalyst for forming carbon nanotubes are dispersed on the base film. Here, examples of the material constituting the base film include aluminum compounds such as alumina, silica, sodium aluminate, alum, and aluminum phosphate, calcium compounds such as calcium oxide, calcium carbonate, and calcium sulfate, magnesium oxide, and magnesium hydroxide. It is preferable to use a magnesium compound such as magnesium sulfate, or an apatite-based material such as calcium phosphate or magnesium phosphate. Moreover, an active metal can be used as a material which comprises a nanoparticle. Examples of the metal constituting such nanoparticles include vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc ( Zn) or the like can be used.

  The particle size of the nanoparticles is, for example, 100 nm or less, preferably 1.0 nm or more and 10 nm or less, more preferably 0.5 nm or more and 5 nm or less. In addition, as the thickness of the base film, for example, a value of 2.0 nm to 100 nm can be used.

  Then, the substrate is heated while supplying the raw material gas for forming the carbon nanotubes to the surface of the substrate on which the nanoparticles are formed. As a result, carbon nanotubes grow on the surfaces of the nanoparticles arranged on the surface of the substrate. The carbon nanotubes grown in this way are used to form an aggregate part composed of a plurality of carbon nanotubes as described below.

  Next, a CNT aggregate forming step (S20) is performed as shown in FIG. In this step (S20), a plurality of carbon nanotubes produced in the above step (S10) are twisted together by a conventionally known method to form an aggregate portion made of carbon nanotubes. In this step (S20), an aggregate portion of carbon nanotubes can be formed by a conventionally known method. For example, by growing carbon nanotubes (CNT) by adjoining the required number of nano-sized catalysts close to each other, the required number of CNTs can be joined, and the ends of multiple CNTs A method of forming a stranded wire by chucking and rotating can be used.

  Next, a Ga catalyst reaction step (S30) is performed. In this step (S30), the surface of the aggregate portion made of the carbon nanotubes formed in the above step (S20) is brought into contact with liquid gallium (Ga). As a result, the surface layer of the aggregate portion made of carbon nanotubes changes into a graphite layer surrounding the aggregate portion by the catalytic reaction of liquid gallium. As a result, as shown in FIGS. 1 and 2, the carbon wire 1 having a structure in which the aggregate portion 3 is surrounded by the graphite layer 4 can be obtained. That is, the said process (S10)-process (S30) respond | correspond to the manufacturing method of the carbon wire 1. FIG.

  At this time, the temperature of the liquid gallium is preferably 450 ° C. or higher and 750 ° C. or lower, more preferably 550 ° C. or higher and 700 ° C. or lower. In this case, the catalytic reaction of liquid gallium that forms the graphite layer from the outer peripheral portion of the aggregate portion 3 can be more efficiently caused.

  Moreover, it is preferable that compressive stress is applied to the aggregate portion 3 in the step (S30) as the step of forming the graphite layer. In this case, since the graphite layer 4 is formed in a state where compressive stress is applied to the aggregate portion 3, the area of the contact portion between the carbon nanotubes 2 constituting the aggregate portion 3 in the formed carbon wire 1. And the contact pressure can be increased. As a result, the electric resistance values of the carbon wire 1 and the assembly wire 5 obtained can be more reliably reduced.

Moreover, in the said process (S30), it is preferable that a compressive stress is applied with respect to the aggregate part 3 by pressurizing liquid gallium. More specifically, the liquid gallium may be pressurized by adjusting the pressure of the atmospheric gas in contact with the liquid gallium. For example, a method may be used in which a bathtub in which liquid gallium is held is held inside a holding container (chamber), and the pressure of atmospheric gas (atmospheric gas in contact with liquid gallium) inside the chamber is adjusted. . In this case, the compressive stress can be easily applied to the aggregate portion 3 by pressurizing the liquid gallium. Further, by adjusting the pressure of the atmospheric gas, the value of the pressure applied to the liquid gallium can be easily adjusted. Here, as the atmospheric gas, for example, an inert gas that does not easily react with carbon nanotubes or liquid gallium, such as argon gas or nitrogen gas, can be used. The pressure of the atmospheric gas can be, for example, not less than the vapor pressure of gallium (Ga) and not more than 10 MPa, more preferably not less than 1 × 10 ⁻⁵ torr and not more than 1 MPa.

  Next, an adhesion Ga removal step (S40) is performed. After the step of forming the graphite layer (S30), in the adhered Ga removing step (S40), which is a step of removing gallium adhering to the surface of the carbon wire 1, the surface of the formed carbon wire 1 (the surface of the graphite layer 4) ) Is removed. As a method for removing the gallium, any method can be used. For example, a chemical solution capable of dissolving gallium (for example, dilute hydrochloric acid or dilute nitric acid) may be sprayed on the carbon wire 1 or the carbon wire 1 may be immersed in a bath containing the chemical solution. In this case, even if liquid gallium solidified gallium adheres to the surface of the carbon wire 1 in the step (S30), the solidified gallium can be removed from the surface of the carbon wire 1. For this reason, when forming the assembly wire 5 in the post-process (S50), the possibility that the solidified gallium causes a problem can be reduced.

  Then, by performing the above steps (S10) to (S40) a plurality of times, or in step (S20), a plurality of aggregate parts made of carbon nanotubes are formed, and the process (for the plurality of aggregate parts ( A plurality of carbon beams are obtained by performing S30) and the step (S40) in parallel. Thus, the process of forming two or more carbon wires using the manufacturing method of the carbon beam shown by the said process (S10)-(S40) is implemented.

  Next, a processing step (S50) is performed. In this step (S50), the assembly wire 5 (see FIG. 3) is formed by twisting together a plurality of carbon wires 1 obtained by performing the above steps (S10) to (S40). In this step (S50), a plurality of carbon wires 1 can be twisted together using any conventionally known method. For example, by growing CNTs with the necessary number of nano-sized catalysts close to each other, the required number of CNTs can be joined, and the ends of multiple CNTs can be chucked. A method of forming a stranded wire by rotating it can be used. In this way, a low resistance aggregate wire 5 made of the carbon wire 1 shown in FIG. 3 can be obtained.

  In the method of manufacturing the carbon wire 1 or the assembly wire 5 described above, as described in the step (S30), the portion of the carbon nanotube exposed on the surface in the assembly section 3 is brought into contact with the liquid gallium, so that the liquid The graphite layer 4 (see FIGS. 1 and 2) can be formed by the catalytic action of gallium. For this reason, the graphite layer 4 can be formed at a lower processing temperature than when the graphite layer 4 is directly grown on the surface of the aggregate portion 3, and the carbon beam according to the present invention can be obtained.

  FIG. 5 is a flowchart for explaining another method of manufacturing the assembly wire according to the present invention. FIG. 6 is a schematic diagram for explaining the covering step shown in FIG. FIG. 7 is a schematic diagram for explaining the Ga catalyst reaction step shown in FIG. With reference to FIGS. 5-7, the other manufacturing method of the assembly wire according to this invention is demonstrated.

  The assembly wire manufacturing method shown in FIG. 5 basically includes the same steps as the assembly wire manufacturing method shown in FIG. 4, but before the Ga catalyst reaction step (S30), the surface of the assembly portion. The difference is that the covering step (S60), which is a step of forming an amorphous carbon layer as a layer, is performed.

That is, the assembly wire manufacturing method shown in FIG. 5 was obtained as shown in FIG. 6 after first performing step (S10) and step (S20) as in the manufacturing method shown in FIG. An amorphous carbon layer 11 which is a layer to be the graphite layer 4 (see FIG. 7) is formed on the surface of the aggregate portion 3. As a method for forming the amorphous carbon layer 11, any conventionally known method can be used. For example, the amorphous carbon layer 11 may be formed by thermally decomposing phenanthrene (C ₁₄ H ₁₀ ), pyrene, methaneacetylene, or the like, or a method of decomposing a hydrocarbon gas using an electron beam or an ion beam. It may be used. As a result, the structure shown in FIG. 6 is obtained.

  Next, as shown in FIG. 5, a Ga catalyst reaction step (S30) is performed. In this step (S30), a method similar to the step (S30) in the manufacturing method shown in FIG. 4 can be basically used. However, in the step (S30) shown in FIG. 5, the surface layer of the amorphous carbon layer 11 becomes the graphite layer 4 by the catalytic reaction of liquid gallium. As a result, the carbon wire 1 having the structure shown in FIG. 7 can be obtained.

  As described above, according to the manufacturing method shown in FIG. 5, the graphite layer 4 can be formed from the amorphous carbon layer 11 while maintaining the structure of the carbon nanotubes 2 in the aggregate portion 3. For this reason, the freedom degree of the design of the structure of the carbon wire 1 can be enlarged.

  Thereafter, the assembly wire similar to the assembly wire 5 shown in FIG. 3 can be obtained by carrying out the step (S40) and the step (S50) similarly to the manufacturing method shown in FIG. In the aggregate wire manufactured by the manufacturing method shown in FIG. 5, as can be seen from FIG. 7, in the carbon wire 1 constituting the aggregate wire, the carbon nanotube 2 and the graphite layer 4 constituting the aggregate portion 3 In this state, the amorphous carbon layer 11 is disposed.

Example 1
Sample preparation:
A 0.3 mm diameter CNT filament stranded wire was prepared as an aggregate portion made of unpurified single-walled carbon nanotubes (CNTs) produced by the arc method. The length of the stranded wire was 10 mm.

And the said strand wire was immersed in liquid gallium (Ga) heated at 600 degreeC for 1 hour. At this time, the atmosphere gas was Ar gas, and the pressure of the atmosphere gas was 1 × 10 ⁻⁵ Torr.

  Thereafter, Ga adhering to the surface of the stranded wire pulled up from the liquid Ga was removed with dilute hydrochloric acid. Thus, the carbon wire in which the gufalite layer was formed on the surface of the CNT filament strand was obtained. The thickness of the graphite layer was about 5 μm.

Measurement:
The electric resistance value of the carbon wire on which the graphite layer was formed was measured. As a measuring method, a four-terminal method was used.

result:
The electric resistance value of the carbon wire on which the graphite layer was formed was reduced to about 1/5 compared to the electric resistance value of the sample of Comparative Example 1 described later.

(Example 2)
Sample preparation:
A CNT filament strand having a diameter of 5 μm was prepared as an aggregate portion, which was composed of unpurified single-walled carbon nanotubes (CNT) produced by the arc method. The length of the stranded wire was 10 mm.

Then, the surface of the strand was phenanthrene (C _{14 H 10)} forming the amorphous carbon layer by thermal decomposition.

  Next, the stranded wire was immersed in liquid gallium (Ga) heated to 600 ° C. for 1 hour. At this time, the atmosphere gas was Ar gas, and the pressure of the atmosphere gas was 2 atm.

  Thereafter, Ga adhering to the surface of the stranded wire pulled up from the liquid Ga was removed with dilute hydrochloric acid. Thus, the carbon wire in which the gufalite layer was formed on the surface of the CNT filament strand was obtained. The thickness of the graphite layer was about 1 μm.

Measurement:
The electric resistance value of the carbon wire on which the graphite layer was formed was measured. As a measuring method, a four-terminal method was used.

result:
The electric resistance value of the carbon wire on which the graphite layer was formed was reduced to about 1/20 as compared with the comparative example of Example 1.

  From this result, it is considered that a plurality of carbon nanotubes are almost integrated inside the carbon wire.

(Example 3)
Sample preparation:
Carbon nanotubes (CNT) having a diameter of 10 nm and a length of 300 μm were prepared, and by superimposing these CNTs by 100 μm, a CNT filament bonding line as an aggregate portion was prepared. The length of the joining line was 50 mm, and the diameter of the joining line was 2 μm.

Then, the surface of the bonding wire, and phenanthrene (C _{14 H 10)} forming the amorphous carbon layer by thermal decomposition.

  Then, the bonding wire was immersed in liquid gallium (Ga) heated to 500 ° C. for 1 hour. At this time, the atmosphere gas was argon (Ar) gas, and the pressure of the atmosphere gas was 10 atm. This is because the carbon nanotubes inside the bonding line are brought into close contact with each other.

  Then, Ga adhering to the surface of the joining line pulled up from the liquid Ga was removed with dilute hydrochloric acid. In this way, a carbon wire having a gufalite layer formed on the surface of the CNT filament bonding line was obtained. The thickness of the graphite layer was about 0.2 μm. It was also found that the graphite layer was formed in a continuous ring shape so as to enclose the inner CNTs, and was converted to carbon nanotubes (CNT conversion).

Measurement:
The electric resistance value of the carbon wire on which the graphite layer was formed was measured. As a measuring method, a four-terminal method was used.

result:
The electric resistance value of the carbon wire on which the graphite layer was formed was an order of magnitude smaller than that of the comparative example. This is presumably because the carbon nanotubes are in close contact and integrated within the carbon wire.

Example 4
Sample preparation:
Using a catalytic CVD method, multi-wall carbon nanotubes (CNT) having a diameter of 30 nm and a length of 500 μm were prepared, and these CNTs were overlapped by 200 μm to prepare a CNT filament bonding line as an aggregate portion. The length of the joining line was 10 mm, and the diameter of the joining line was 0.6 μm.

  Then, the bonding wire was immersed in liquid gallium (Ga) heated to 550 ° C. for 1 hour. Specifically, liquid gallium and a bonding wire were sealed in a stainless capsule. The atmosphere gas around the capsule was argon (Ar) gas. By pressurizing the atmospheric gas, pressure was applied to the liquid gallium and the bonding line together with the capsule. The pressurizing pressure at this time was 100 atm. This is because the carbon nanotubes inside the bonding line are brought into close contact with each other.

  Then, Ga adhering to the surface of the joining line pulled up from the liquid Ga was removed with dilute hydrochloric acid. In this way, a carbon wire having a gufalite layer formed on the surface of the CNT filament bonding line was obtained. The thickness of the graphite layer was about 80 nm. It was also found that the graphite layer was formed in a continuous ring shape so as to enclose the inner CNTs, and was converted to carbon nanotubes (CNT conversion).

  Further, the carbon wire on which the graphite layer was formed was bundled into a stranded wire to produce a bonding wire having a diameter of 0.5 μm. Then, by immersing the bonding line in the liquid Ga in the same manner as described above, a plurality of carbon lines constituting the bonding line are bonded (the surface of the bundle is surrounded by graphite so as to surround the outer periphery of the bundle of the plurality of carbon lines). Forming the layer). In this way, a step of bundling a plurality of carbon wires, a step of joining a plurality of carbon wires by immersing the aggregated wires of the bundled carbon wires in liquid Ga, and an assembly line composed of a plurality of carbon wires joined together Further, a plurality of wires were prepared and the step of bundling the plurality of assembly wires was repeated to produce a wire rod having a larger diameter (specifically, a bonding wire having a diameter of 0.1 mm).

Measurement:
The electric resistance value of the carbon wire on which the graphite layer was formed was measured. As a measuring method, a four-terminal method was used.

result:
The electric resistance value of the carbon wire on which the graphite layer was formed was two digits or more smaller than that of the comparative example. This is presumably because the carbon nanotubes are in close contact and integrated within the carbon wire.

(Comparative Example 1)
Sample preparation:
A 0.3 mm diameter CNT filament stranded wire was prepared as an aggregate portion made of unpurified single-walled carbon nanotubes (CNTs) produced by the arc method. The length of the stranded wire was 10 mm.

Measurement:
The electrical resistance value was measured about the CNT filament strand. As a measuring method, a four-terminal method was used.

result:
The electrical resistance value of the CNT filament stranded wire as a comparative example was 7.8 × 10 ⁻³ Ω · cm. This value was 3 digits or more higher than copper.

(Comparative Example 2)
Sample preparation:
A 0.3 mm diameter CNT filament stranded wire was prepared as an aggregate portion made of unpurified single-walled carbon nanotubes (CNTs) produced by the arc method. The length of the stranded wire was 10 mm.

And the said strand wire was immersed in liquid gallium (Ga) heated at 800 degreeC for 1 hour. At this time, the atmosphere gas was Ar gas, and the pressure of the atmosphere gas was 1 × 10 ⁻⁵ Torr.

result:
As a result of immersing the stranded wire in the liquid Ga as described above, the stranded wire was decomposed in the liquid Ga and disappeared. For this reason, the heating temperature of the liquid gallium in which the stranded wire is immersed is preferably less than 800 ° C., more preferably 750 ° C. or less.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is particularly advantageously applied to a carbon wire configured by combining a plurality of short carbon nanotubes and an assembly wire using the carbon wire.

It is a cross-sectional schematic diagram which shows embodiment of the carbon wire according to this invention. It is a cross-sectional schematic diagram in line segment II-II of FIG. It is a cross-sectional schematic diagram which shows embodiment of the assembly wire according to this invention. It is a flowchart for demonstrating the manufacturing method of the assembly | attachment wire shown in FIG. It is a flowchart for demonstrating the other manufacturing method of the assembly | attachment wire according to this invention. It is a schematic diagram for demonstrating the covering | coating process shown in FIG. It is a schematic diagram for demonstrating the Ga catalyst reaction process shown in FIG.

Explanation of symbols

  1 carbon wire, 2 carbon nanotube, 3 aggregate part, 4 graphite layer, 5 aggregate wire, 11 amorphous carbon layer.

Claims (12)

An assembly portion in which a plurality of carbon filaments are in contact;
A carbon wire comprising a graphite layer formed on the outer periphery of the aggregate part.   The carbon wire according to claim 1, wherein the carbon filament is a carbon nanotube.   The carbon wire according to claim 1, wherein the graphite layer is a carbon nanotube.   An assembly wire comprising a plurality of the carbon wires according to claim 1. A step of preparing an assembly portion in which a plurality of carbon filaments are in contact;
Forming a graphite layer on the surface of the aggregate part by bringing the surface of the aggregate part into contact with liquid gallium.   The carbon wire manufacturing method according to claim 5, wherein in the step of forming the graphite layer, a compressive stress is applied to the aggregate portion.   The carbon wire manufacturing method according to claim 6, wherein in the step of forming the graphite layer, compressive stress is applied to the aggregate portion by pressurizing the liquid gallium.   The method for producing a carbon wire according to claim 7, wherein in the step of forming the graphite layer, the liquid gallium is pressurized by adjusting a pressure of an atmospheric gas in contact with the liquid gallium.   9. The method for producing a carbon wire according to claim 5, wherein in the step of forming the graphite layer, the temperature of the liquid gallium is 450 ° C. or higher and 750 ° C. or lower.   The method for producing a carbon beam according to any one of claims 5 to 9, further comprising a step of forming an amorphous carbon layer as a surface layer of the aggregate portion before the step of forming the graphite layer.   The method for producing a carbon beam according to any one of claims 5 to 10, further comprising a step of removing gallium adhering to the surface of the carbon beam after the step of forming the graphite layer. A step of forming a plurality of carbon wires using the carbon wire manufacturing method according to any one of claims 5 to 11,
And a step of forming the aggregate wire by twisting the plurality of carbon wires.

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