JP2007280731A - Manufacturing method for carbon nanotube wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a wire using a carbon nanotube that has a current density 10<SP>3</SP>as large as that of copper as a conductive material, is light in weight, and has superior weatherproofness. <P>SOLUTION: Fine metallic powder is stuck to a carbon fiber element wire. As the fine metallic powder is used as a catalysis, carbon ions generated by decomposing a hydrocarbon by various methods are caused to grow on the surface of the element wire in an electric field into the carbon nanotube. Then, a plurality of such element wires are twisted together. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of manufacturing wiring wires in all fields of the electrical industry.

  Carbon nanotubes themselves have been known to have very high electrical conductivity, but there is no carbon nanotube wire because there is no method for producing carbon nanotube wires. Accordingly, since copper wires and aluminum wires are used, large power transmission lines are reinforced with steel wires to withstand the weight. Also, motors, generators, etc. are very heavy because copper wires are used as windings. In particular, those loaded on a moving body are often heavy due to this copper winding and are inferior in energy efficiency, or often give up use.

In addition, it is very difficult to fabricate an electric wire by using only carbon nanotubes, and it is very difficult to knit it in a rope shape because it is a short material (see Patent Document 1 below). Even if possible, it is not possible to beat conventional electric wires because of productivity and cost.
JP 2005-48206 A

  The subject of this invention is manufacturing an electric wire using the carbon nanotube which attracts attention as an electroconductive material.

(Principle of the present invention)
The present invention uses the characteristic properties of carbon nanotubes described below to produce a practical electric wire.
(1) Current density: Copper is 10 ⁶ A / cm, while it is 10 ⁹ A / cm, which is 3 digits larger.
(2) Tensile strength: 1,200 tons with a diameter of 1 cm, several tens of times that of steel. Moreover, it is supple.
(3) Lightweight: Graphite has a specific gravity of 2.25, which is 1/4 that of copper (8.93).
(4) Chemical resistance: as good as graphite.
(5) Heat conductivity: better than diamond.
(6) Shape: 1 μm to 10 μm in length with respect to a diameter of 1 nm, which is several thousand times.

  Taking advantage of this light weight and large current density, the carbon fiber wire using carbon nanotubes will be finished.

  However, it is extremely difficult to convert a carbon nanotube having a length of 1 μm to 10 μm into a macroscopic fiber with respect to a diameter of 1 nm, and it is impossible to finish a short fiber into an electric wire as in the prior art. Fortunately, carbon nanotubes can be expected to have electrical conductivity through intermolecular conduction and hopping conduction by contact between fibers between concentric tubes (see FIG. 1).

On the other hand, amorphous carbon is contained in the carbon fiber as impurities, and it is considered that graphite having good conductivity is crushed and broken (see FIG. 2). For this reason, the electrical conductivity of carbon fiber cannot be expected so much.

  The present invention maintains the good electrical conductivity and high current density characteristics of these carbon nanotubes, and compensates for the disadvantages of microfibers that are difficult to handle by the method of implanting them on the surface of the carbon fiber. It is a manufacturing method.

  First, metal fine powder is attached to a carbon fiber strand, hydrocarbon is decomposed using the metal fine powder as a catalyst, and carbon nanotubes are grown on the surface of the strand.

  When the carbon nanotube is grown, the carbon fiber strand is used as a cathode, the decomposed carbon cation of the hydrocarbon is attracted by an electric field, and the carbon nanotube is oriented and grown in the direction perpendicular to the surface of the carbon fiber strand.

  Next, a large number of the carbon fiber strands covered with the carbon nanotubes are bundled, and an electric wire having a structure in which the basic structure is hierarchized using the structure formed in a rope shape as a basic structure is manufactured.

Furthermore, an electric wire having a structure in which a fiber made of optical fiber, steel or aluminum is twisted simultaneously with the electric wire is manufactured.

  Wires made of carbon nanotubes as the main conductive material according to the present invention have a current density about three orders of magnitude higher than copper, and are lightweight and have excellent weather resistance. It can be used as an electric wire.

In particular, the following three major areas are expected to be extremely effective:
(1) High-efficiency, high-power transmission line network (2) Motors for moving objects such as trains, electric vehicles, and traveling robots (3) Alternatives to copper wires for conductive use in all fields

  The present invention will be described below with reference to the drawings.

  A plurality of carbon fiber strands are placed in a low vacuum state or an atmosphere of argon and a mixed gas of hydrogen and made into a cathode. Metal fine powder as a catalyst is fixed on the surface by various methods such as evaporation, spraying or discharge.

  At this time, each carbon fiber is rotated in the same direction because it is necessary to make it adhere uniformly and to form a rope shape in a subsequent process. FIG. 3 is a schematic view of an apparatus that, as an example, irradiates a catalyst metal with laser light to evaporate the catalyst metal and adheres it to the carbon fiber surface.

  After that, the carbon fiber with the catalytic metal attached is heated by argon discharge method, laser evaporation method, method using heating furnace, etc. in the atmosphere where argon or hydrogen is mixed in this gas and hydrocarbon gasified from benzene etc. Decomposes and generates carbon cations.

  The carbon ions are attracted by an electric field, and synthesize and grow carbon nanotubes on the carbon fiber strands in the direction perpendicular to the surface. This is generated to the thickness required for conductivity. As a result, a strand in which carbon nanotubes are implanted is manufactured.

  FIG. 4 shows a schematic view of manufacturing this strand by a method using a heating furnace. In this step, argon, hydrogen and unreacted hydrocarbons are recovered, impurities are removed, introduced, and reused. In FIG. 5, the schematic diagram of the strand made by this process is shown.

In the next step, a large number of carbon fiber strands covered with the carbon nanotubes are bundled and formed into a rope-like structure. Based on this structure, as many layers as necessary for current capacity and tensile strength are layered and the wires To do. A schematic diagram of this manufacturing process is shown in FIG. FIG. 7 shows a basic structure of an electric wire composed of three strands as an example. FIG. A shows a cross section of this electric wire.

Wires made of carbon nanotubes as the main conductive material according to the present invention have a current density about three orders of magnitude higher than copper, and are lightweight and have excellent weather resistance. It can be used as an electric wire.

Schematic diagram of intertwined carbon nanotubes Carbon fiber microstructure Schematic diagram of an apparatus for fixing a metal catalyst to the surface of a carbon fiber Schematic diagram of an example of a reaction tank device for vegetating carbon nanotubes on the surface of carbon fibers Carbon fiber strand implanted with carbon nanotube Single wire manufacturing equipment for knitting carbon fiber strands with carbon nanotubes in a rope-like structure Basic structure of a wire made by twisting carbon fiber strands into a rope shape A sectional view of FIG.

Claims (6)

A method of manufacturing a wire comprising attaching a metal fine powder to a carbon fiber wire, and using the metal fine powder as a catalyst to grow carbon ions generated by decomposing hydrocarbons as carbon nanotubes on the surface of the wire. . The method for producing a bare wire according to claim 1, wherein the carbon nanotube is grown to a thickness necessary for conductivity. The method for producing a bare electric wire according to claim 1 or 2, wherein the hydrocarbon is decomposed by an arc discharge method, a laser evaporation method, or a method using a heating furnace. When growing the carbon nanotube, the carbon fiber strand is used as a cathode, the carbon cation of the decomposed hydrocarbon is attracted by an electric field, and the carbon nanotube is oriented and grown in a direction perpendicular to the surface of the carbon fiber strand. The manufacturing method of the bare wire in any one of Claim 1 to 3 characterized by the above-mentioned. 5. The structure according to claim 1, wherein the carbon fiber strands covered with the carbon nanotubes are bundled together, and a structure formed in a rope shape is used as a basic structure, and the basic structure is hierarchized. A method of manufacturing an electric wire bundled with elementary wires. 6. A method of manufacturing an electric wire, characterized in that an optical fiber wire, a wire made of steel or aluminum is made to be twisted simultaneously with the electric wire according to claim 5.

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