Laminated electric wire and manufacturing method thereof

Abstract

To provide a laminated wire that has an improved current capacity and also has a reduced weight.SOLUTION: A laminated wire 1 comprises a core wire 3 containing metal, and a carbon nanotube layer 2 covering an outer periphery of the core wire and having a current capacity of 3,000-10,000,000 A / cm2 at -269°C to -100°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated electric wire and a method for manufacturing the same. [Background technology]

[0002] Cited document 1 (International Publication No. 2006 / 121155) discloses a device in which carbon nanotubes are arranged on a metal substrate by electrochemical reaction, and discloses that the carbon nanotubes are mainly single-walled but may also be multi-walled (Claim 10,

[0041] ,

[0075] ,

[0145] ).

[0003] Cited document 2 (International Publication No. 2021 / 060097) discloses an electrode in which a carbon nanotube layer is formed by applying a solution in which carbon nanotubes are dispersed in carboxymethyl cellulose to a metal substrate, and that the electrode is used as a sensor for detecting uric acid (Claim 1, Examples, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2006 / 121155 [Patent Document 2] International Publication No. 2021 / 060097 Summary of the Invention [Problem to be solved by the invention]

[0005] Although cited document 1 discloses an invention related to a device, it does not sufficiently consider laminated electric wires. Furthermore, cited document 1 does not consider improving the current capacity or reducing the weight of laminated electric wires. cited document 2 merely discloses an electrode and a sensor in which a carbon nanotube layer is formed on a metal substrate, and does not consider improving the current capacity or reducing the weight of laminated electric wires.

[0006] The present invention has been made in view of the above circumstances, and aims to improve the current carrying capacity and reduce the weight of a laminated electric wire by providing a carbon nanotube layer that covers the outer periphery of a core wire containing metal. [Means for solving the problem]

[0007] The present invention has the following embodiments. [1] A core wire containing metal; The core wire is covered with a material having a current capacity of 3,000 to 10,000,000 A / cm at -269 to 100°C. 2 a carbon nanotube layer, A laminated electric wire having the above structure. [2] The laminated electric wire according to the above [1], wherein the ratio of the total number of single-walled carbon nanotubes, double-walled carbon nanotubes, and triple-walled carbon nanotubes to the total number of carbon nanotubes constituting the carbon nanotube layer, as represented by the following formula (1), is 70% or more. (Total number of single-walled, double-walled, and triple-walled carbon nanotubes) / (Total number of carbon nanotubes in the carbon nanotube layer) × 100 (1) [3] The laminated electric wire according to [1] above, wherein the ratio of the total number of carbon nanotubes having four or more walls to the total number of carbon nanotubes constituting the carbon nanotube layer, as represented by the following formula (2), is 70% or more. (Total number of carbon nanotubes with four or more walls) / (Total number of carbon nanotubes constituting the carbon nanotube layer) × 100 (2) [4] The laminated electric wire according to any one of [1] to [3] above, further comprising a coating layer as an outermost layer so as to cover the outer periphery of the carbon nanotube layer. [5] The laminated electric wire according to any one of [1] to [4] above, wherein the core wire contains a superconducting material as the metal. [6] A method for producing the laminated electric wire according to any one of [1] to [5] above, preparing the core wire; forming a carbon nanotube layer to cover the outer periphery of the core wire; The method for producing the laminated electric wire comprising the steps of: [Effects of the Invention]

[0008] It is possible to provide a laminated electric wire that has improved current carrying capacity and is lightweight. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a laminated electric wire according to one embodiment. [Figure 2] FIG. 2 is a diagram illustrating a laminated electric wire according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Laminated wire) The laminated electric wire of the present invention comprises a core wire containing a metal and a laminated electric wire covering the outer periphery of the core wire and having a current capacity of 3,000 to 10,000,000 A / cm at -269 to 100°C. 2 The laminated electric wire has a carbon nanotube layer (hereinafter, sometimes referred to as a "CNT layer") that is a conductive material. In a typical multilayer electric wire, the conductor (conductive route) is metal, but in the present invention, by providing a CNT layer on the core wire, which is the main conductive route, it is possible to increase the current capacity of the laminated electric wire and reduce its weight. Furthermore, when the laminated electric wire of the present invention is used as an electric wire for ultra-high current densities, it is possible to prevent breakage of the electric wire and achieve high strength. Furthermore, the CNT layer prevents oxidation of the metal that is the material of the core wire, thereby improving the environmental resistance of the laminated electric wire. Note that, because the cross-sectional area of ​​the core wire containing metal is larger than that of the CNT layer, the CNT layer becomes the main conductive route when current is passed through the laminated electric wire.

[0011] The cross-sectional shape perpendicular to the longitudinal direction of the laminated electric wire is not particularly limited, and various shapes such as circle, oval, square, rectangle, and polygon can be exemplified. Preferably, the cross-sectional shape perpendicular to the longitudinal direction of the laminated electric wire is rectangular. When the cross-sectional shape perpendicular to the longitudinal direction of the laminated electric wire is rectangular, the laminated electric wire becomes a flat electric wire. When the cross-sectional shape perpendicular to the longitudinal direction of the laminated electric wire is circular, the diameter of the cross-section is preferably 1 μm to 10 mm, and more preferably 1 μm to 1 mm. When the cross-sectional shape perpendicular to the longitudinal direction of the laminated electric wire is rectangular, the length of the short side of the rectangle (thickness of the laminated electric wire) is preferably 1 μm to 10 mm, and more preferably 1 to 100 μm, and the length of the long side of the rectangle (length in the width direction of the laminated electric wire) is preferably 100 μm to 30 mm, more preferably 100 μm to 15 mm, and even more preferably 100 μm to 5 mm. In the case of a flat laminated electric wire in which the core wire contains a superconducting material as the metal, the thickness of the laminated electric wire is preferably 10 to 1000 μm, and the length in the width direction of the laminated electric wire is preferably 1 to 30 mm. The laminated electric wire may further have one or more additional layers between the core wire and the CNT layer so as to cover the outer periphery of the core wire, as necessary. For example, when the core wire contains a superconducting material as the metal, the laminated electric wire has a protective layer between the core wire and the CNT layer. Furthermore, the laminated electric wire may further have one or more coating layers so as to cover the outer periphery of the CNT layer, as necessary. For example, the laminated electric wire has a coating layer made of an insulating material so as to cover the outer periphery of the CNT layer.

[0012] The metal constituting the core wire is not particularly limited, and examples thereof include a single metal or an alloy of multiple metals. More specifically, examples of metals include Ag, Cu, Al, Fe, Ni, Au, Pt, Ti, W, or alloys of these metals, and examples of alloys include SUS. The core wire can contain multiple types of metals. The core wire can also contain a superconducting material as the metal. Examples of superconducting materials include Nb-Ti, Nb3Sn, REBa2Cu3O 7-δ(RE is a rare earth element, Y, Gd, Eu, or Sm, and δ is 0 to 1), MgB2, etc. The core wire may be composed of one layer or two or more layers. The shape of the cross section perpendicular to the longitudinal direction of the core wire is not particularly limited, and various shapes such as circle, ellipse, square, rectangle, and polygon can be exemplified. Preferably, the cross section perpendicular to the longitudinal direction of the core wire is rectangular, and the laminated electric wire is a flat laminated electric wire. When the cross section perpendicular to the longitudinal direction of the core wire is circular, the diameter of the cross section is preferably 1 μm to 10 mm, and more preferably 1 to 1,000 μm. When the cross section perpendicular to the longitudinal direction of the core wire is rectangular, the length of the short side of the rectangle (thickness of the core wire) is preferably 1 μm to 10 mm, and more preferably 1 to 100 μm, and the length of the long side of the rectangle (length in the width direction of the laminated electric wire) is preferably 100 μm to 30 mm, and more preferably 100 μm to 15 mm.

[0013] At -269 to 100°C, the current capacity of the CNT layer is 3,000 to 10,000,000 A / cm 2 However, 10,000 to 10,000,000 A / cm 2 It is preferable that the resistance is 100,000 to 1,000,000 A / cm 2 It is more preferable that the current capacity of the CNT layer is within the above range. Even when the laminated electric wire of the present invention is used as an electric wire for ultra-high current densities in which the core wire contains a superconducting material, breakage of the electric wire can be prevented and high strength can be achieved. Furthermore, when the core wire contains a material other than a superconducting material, the current capacity of the CNT layer is 3000 to 10000 A / cm 2When the core wire contains a material other than a superconducting material, the temperature of the CNT layer during use of the laminated electric wire is approximately -10 to 100°C. When the core wire contains a superconducting material, the temperature of the CNT layer during use of the laminated electric wire is approximately -269 to -180°C. The thickness of the CNT layer is preferably 1 nm to 1 mm, more preferably 20 to 1,000 μm. The bending strength of the CNT layer is preferably 1 to 10,000 MPa, more preferably 10 to 10,000 MPa, and even more preferably 100 to 10,000 MPa. The bending strength of the CNT layer can be measured by a method such as the four-point bending method. For example, a sample is prepared by forming a CNT layer by a known method (e.g., a coating and drying method, a vapor phase deposition method, etc.) so as to cover the outer periphery of a metal-containing core wire, and the bending strength of the sample is measured according to the procedure of JIS H8504 (1999). When the bending strength of the CNT layer is within the above range, the laminated electric wire can be strengthened and can be used safely for a long period of time.

[0014] The CNT layer is formed from a single carbon nanotube aggregate (hereinafter may be referred to as "CNT aggregate") composed of a plurality of carbon nanotubes (hereinafter may be referred to as "CNT") having one or more layer structures, or by bundling a plurality of such aggregates. In one embodiment, the CNT layer is configured by bundling a plurality of CNT aggregates, and the longitudinal direction of the CNT aggregate forms the longitudinal direction of the CNT layer. In this case, the CNT aggregates are linear and arranged with their long axes aligned substantially in the same direction, and the plurality of CNT aggregates are aligned.

[0015] A CNT aggregate is a bundle of CNTs with one or more layer structures. The longitudinal direction of the CNTs forms the longitudinal direction of the CNT aggregate. The multiple CNTs in a CNT aggregate are arranged with their long axes aligned, and the multiple CNTs in a CNT aggregate are aligned. The CNTs that make up a CNT aggregate are cylindrical bodies with a single-layer structure or a double-layer structure, and are called SWNTs (single-walled nanotubes) and MWNTs (multi-walled nanotubes), respectively. The CNT layer may have CNTs with a single layer structure, or may have CNTs with a single layer structure, a double-layer structure, a triple-layer structure, or a four or more layer structure.

[0016] For example, a CNT with a two-layer structure has a three-dimensional network structure in which two cylindrical bodies T1 and T2, each with a hexagonal lattice network structure, are arranged approximately coaxially, and is called a DWNT (double-walled nanotube). The hexagonal lattice, which is the structural unit, is a six-membered ring with a carbon atom at its vertex, and these six-membered rings are adjacent to each other and continuously bonded. The properties of CNT depend on the chirality of the cylindrical bodies. Chirality is broadly classified into armchair, zigzag, and chiral types, with armchair types exhibiting metallic behavior, zigzag types exhibiting semiconducting and semimetallic behavior, and chiral types exhibiting semiconducting and semimetallic behavior.

[0017] In one embodiment of the laminated electric wire, it is preferable that the ratio of the total number of single-walled carbon nanotubes, double-walled carbon nanotubes, and triple-walled carbon nanotubes to the total number of carbon nanotubes constituting the carbon nanotube layer, as represented by the following formula (1), is 70% or more. (Total number of single-walled, double-walled, and triple-walled carbon nanotubes) / (Total number of carbon nanotubes in the carbon nanotube layer) × 100 (1) Since CNTs with single-, double-, and triple-walled structures have higher current carrying capacity than CNTs with four or more walled structures, by making the ratio of the total number of single-, double-, and triple-walled carbon nanotubes to the total number of carbon nanotubes constituting the carbon nanotube layer 70% or more, the thickness of the CNT layer can be made thin while maintaining a high current carrying capacity. Such a laminated electric wire can be suitably used, for example, in small and lightweight mobile motors.

[0018] In another embodiment of the laminated electric wire, the ratio of the total number of carbon nanotubes having four or more walls to the total number of carbon nanotubes constituting the carbon nanotube layers, as represented by the following formula (2), is preferably 70% or more. (Total number of carbon nanotubes with four or more walls) / (Total number of carbon nanotubes constituting the carbon nanotube layer) × 100 (2) Because CNTs with a four or more layer structure have high mechanical strength, a laminated electric wire having a CNT layer in which the ratio of the total number of carbon nanotubes with four or more layers to the total number of carbon nanotubes constituting the carbon nanotube layer is 70% or more can withstand high power and heat generation, and therefore such a laminated electric wire can be suitably used, for example, as a superconducting wire for a nuclear fusion reactor.

[0019] The proportion of CNTs in the CNT layer that have a layer structure of one, two, three, or more than four layers can be calculated by observing and analyzing a cross section of the CNT layer perpendicular to the longitudinal direction using a transmission electron microscope (TEM), selecting a predetermined number of CNTs in the range of 50 to 200, and measuring the number of layers of each CNT.

[0020] The laminated electric wire preferably further has a coating layer as the outermost layer so as to cover the outer periphery of the carbon nanotube layer. By having the coating layer, the interior of the laminated electric wire can be insulated from the external environment. Examples of materials for the coating layer include thermoplastic resins. Examples of thermoplastic resins include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polyacetal, polystyrene, polycarbonate, polyamide, polyvinyl chloride, polyvinyl acetate, polyurethane, polymethyl methacrylate, acrylonitrile butadiene styrene resin, and acrylic resin. These may be used alone or in an appropriate mixture of two or more types. The coating layer may be one layer or two or more layers.

[0021] (Laminated Wire Manufacturing Method) The method for manufacturing a laminated electric wire of the present invention includes the steps of preparing a core wire and forming a carbon nanotube layer to cover the core wire. In the core wire preparation step, the core wire is prepared by processing the core wire material into a predetermined shape. A commercially available core wire may be used. Next, in the step of forming a carbon nanotube layer to cover the core wire, a CNT layer is formed to cover the core wire. The method for forming the CNT layer is not particularly limited, but examples include coating, immersion, electrochemical, and vapor-phase methods. In the coating method, a dispersion liquid in which CNTs are dispersed in a dispersing medium such as water or an organic solvent is applied to the core wire, and the dispersion liquid is then dried to form the CNT layer. If necessary, the dispersion liquid may contain an acid of a type and concentration that does not adversely affect the core wire material. Furthermore, before forming the CNT layer, the surface of the core wire (metal) may be subjected to a hydrophilization treatment such as UV cleaning (ozone cleaner), ion sputtering, or application of a dedicated solution. In this case, by applying a dispersion liquid containing hydrophobic CNTs to a hydrophilically treated core wire (metal), the CNTs are uniformly dispersed on the surface of the core wire, forming a CNT layer of uniform thickness. In the immersion method, the core wire is immersed in a CNT dispersion liquid, then pulled out of the dispersion liquid, and the dispersion liquid attached to the outer periphery of the core wire is dried to form a CNT layer. In the gas-phase method, a CNT layer is formed on the outer periphery of the core wire using arc discharge, laser deposition (PLD), sputtering, etc.

[0022] Examples of laminated electric wires according to embodiments will be described in detail below with reference to the drawings. Note that the laminated electric wire of the present invention is not limited to the examples below. Furthermore, the respective components shown in the examples below include those that can be easily imagined by a person skilled in the art and those that are substantially the same.

[0023] Fig. 1A is a perspective view of the laminated electric wire, and Fig. 1B is a cross-sectional view taken along line XX perpendicular to the longitudinal direction of the laminated electric wire in Fig. 1A. As shown in Fig. 1, the laminated electric wire 1 has a flat core wire 3 (the cross-section perpendicular to the longitudinal direction is rectangular) and a CNT layer 2 provided so as to cover the outer periphery of the core wire 3.

[0024] FIG. 2 shows a laminated electric wire according to another embodiment, with FIG. 2A being a perspective view of the laminated electric wire and FIG. 2B being a cross-section of the laminated electric wire taken along the line XX perpendicular to the longitudinal direction of the laminated electric wire in FIG. 2A. As shown in FIG. 2, the laminated electric wire 1 has a flat core wire (having a rectangular cross section perpendicular to the longitudinal direction) and a CNT layer 2 provided so as to cover the outer periphery of the core wire. The core wire is composed of a substrate 6, an intermediate layer 5, and a superconducting layer 4. Methods for fabricating the superconducting layer 4 include laser deposition (PLD), metal-organic chemical vapor deposition (MOCVD), and metal-organic decomposition (MOD). Materials for the substrate 6 include Hastelloy, Ni, and A. The thickness of the substrate 6 is preferably 10 to 200 μm, more preferably 10 to 100 μm, and even more preferably 10 to 50 μm. The intermediate layer 5 is composed of one or more layers and functions to align the crystal orientation of the superconducting layer 4 and prevent diffusion of the substrate material from the substrate to the superconducting layer. Examples of materials for the intermediate layer 5 include MgO, YSZ, CeO2, and LaMnO3, and the thickness of the intermediate layer 5 is preferably 0.1 to 10 μm, more preferably 0.1 to 5 μm, and even more preferably 0.1 to 3 μm. Examples of materials for the superconducting layer 4 include Nb—Ti, Nb3Sn, and REBa2Cu3O. 7-δ(RE is a rare earth element, Y, Gd, Eu, or Sm, and δ is 0 to 1), MgB2, etc., and the thickness of the superconducting layer 4 can be preferably 1 to 30 μm, more preferably 1 to 20 μm, and even more preferably 1 to 10 μm. The protective layer 7 has the function of protecting the superconducting layer 4. Examples of materials for the protective layer 7 include Ag and Ag-Cu, with silver being preferred. The thickness of the protective layer 7 can be preferably 1 to 10 μm, more preferably 1 to 5 μm, and even more preferably 1 to 3 μm. Conventional superconducting wires use a stabilizing layer made of Cu to cover the outer periphery of the protective layer 7. However, the laminated electric wire of the present invention uses a CNT layer as a layer equivalent to this stabilizing layer. Therefore, the current capacity of the CNT layer can be increased, and the laminated electric wire 1 can be prevented from breaking and have high strength even when a high current is passed through it. Although not shown in FIG. 2, it is preferable to house the laminated electric wire 1 in a thermal insulation pipe and run a refrigerant such as liquid nitrogen through the thermal insulation pipe to keep the superconducting layer 4 at an extremely low temperature so that the superconducting layer 4 is stably in a superconducting state during use. [Example]

[0025] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0026] (Examples 1 and 2, Comparative Example 2) CNTs were produced by catalytic chemical vapor deposition (CCVD) with reference to Japanese Patent No. 5819888, and CNT layers with the thicknesses shown in Table 1 were produced with reference to wet methods (Japanese Patent Nos. 5135620, 5131571, and 5288359). The number of CNT layers was determined by changing the carbon source, catalyst diameter, etc. with reference to known techniques, to produce CNTs with the ratio of layer numbers shown in Table 1. (Examples 3 and 4) CNTs were produced by a substrate growth method with reference to Japanese Patent No. 5590603, and CNT layers with the thicknesses shown in Table 1 were produced with reference to dry methods (Japanese Patent Nos. 5819888, 5990202, and 5350635). The number of CNT layers was determined by changing the carbon source, catalyst diameter, etc. with reference to known techniques, to produce CNTs with the ratio of layer numbers shown in Table 1. (Comparative Example 3) CNTs were grown by catalytic chemical vapor deposition (CCVD) with reference to the aforementioned patent documents, and CNT layers with the thicknesses shown in Table 1 were created with reference to the aforementioned dry method. CNTs with the layer number ratios shown in Table 1 were created by changing the carbon source, catalyst diameter, etc. with reference to known techniques.

[0027] Furthermore, a TEM device was used to select a predetermined number of CNTs within the range of 50 to 200 from the CNTs constituting the CNT layer obtained in each example, and the number of layers of each CNT was measured to determine the proportion of CNTs with a layer structure of one to three layers among all CNTs (hereinafter, sometimes referred to as "proportion (1)") and the proportion of CNTs with a layer structure of four or more layers among all CNTs (hereinafter, sometimes referred to as "proportion (2)"). Next, a 2401 Source Meter (manufactured by Keithley) was used to measure the current value for a single CNT layer maintained at room temperature every 5 seconds, and the current capacity until the CNT layer broke and the breaking power at the time of CNT layer breakage were measured. The thickness of the CNT layer for each example and the above measurement results are shown in Table 1 below. Furthermore, additional tests showed that the current capacity of the CNT layers produced in Examples 1 to 4 was 3,000 to 10,000,000 A / cm in the temperature range of -269°C to 100°C specified in claim 1. 2 It was also confirmed that it falls within the range of

[0028] (Comparative Example 1) A copper plate measuring 100 mm in length, 15 mm in width, and 25 μm in thickness was prepared, and the current carrying capacity until the copper plate broke and the breaking power when the copper plate broke were measured in the same manner as in Example 1. The thickness of the copper plate and the measurement results are shown in Table 1 below. [Table 1] [Explanation of symbols]

[0029] 1. Laminated wire 2 CNT layer 3-core wire 4 Superconducting layer 5. Middle class 6 PCB 7 Protective layer

Claims

1. a core wire containing metal; The outer periphery of the core wire is covered, and the current capacity is 3,000 to 10,000,000 A / cm at -269 to 100°C. ２ a carbon nanotube layer, and the ratio of the total number of single-walled carbon nanotubes, double-walled carbon nanotubes, and triple-walled carbon nanotubes to the total number of carbon nanotubes constituting the carbon nanotube layer, as represented by the following formula (1), is 70% or more; The carbon nanotube layer includes at least one layer of carbon nanotubes. (Total number of single-walled carbon nanotubes, double-walled carbon nanotubes, and triple-walled carbon nanotubes) / (Total number of carbon nanotubes constituting the carbon nanotube layer) × 100 (1)

2. A core wire containing metal; a carbon nanotube layer covering the outer periphery of the core wire and having a current carrying capacity of 3,000 to 10,000,000 A / cm 2 at −269 to 100° C.; and A laminated electric wire, wherein the ratio of the total number of carbon nanotubes having four or more walls to the total number of carbon nanotubes constituting the carbon nanotube layer, as represented by the following formula (2), is 70% or more: (Total number of carbon nanotubes having four or more walls) / (Total number of carbon nanotubes constituting the carbon nanotube layer) × 100 (2)

3. The laminated electric wire according to claim 1 or 2, further comprising a coating layer as an outermost layer so as to cover the outer periphery of the carbon nanotube layer.

4. The laminated electric wire according to claim 1 , wherein the core wire contains a superconducting material as the metal.

5. The method for manufacturing the laminated electric wire according to any one of claims 1 to 4, preparing the core wire; forming a carbon nanotube layer to cover the outer periphery of the core wire; The method for producing the laminated electric wire comprising the steps of:

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