KR20180071925A - Complex material wire for transmission line and Manufacturing method thereof - Google Patents

Abstract

The present invention relates to a composite wire for a transmission line and to a manufacturing method thereof, and more specifically, to a composite wire for a transmission line, to a method for manufacturing the composite wire for the transmission line, and to a cable for the transmission line using the method, wherein the composite wire for the transmission line has mechanical strength and electrical characteristics to replace an existing iron core (steel core) which has low conductivity, high specific gravity and the like used in the transmission line.

Description

TECHNICAL FIELD [0001] The present invention relates to a composite wire for a transmission line and a manufacturing method thereof,

TECHNICAL FIELD The present invention relates to a composite wire for transmission lines having excellent mechanical properties and electrical characteristics, and a method of manufacturing the same.

Transmissive methods are widely used as a method for transmitting power generated by a power plant to a remote paper or primary substation. The process transmission method transfers power produced by a power plant to a sheet of paper through a processing power line supported by a ground tower.

As a typical transmission conductor, an aluminum conductor reinforced by a strong conductor, that is, aluminum conductor steel reinforced (ACSR) is mainly used. It is generally used that the stranded aluminum strand is formed by stranding multiple strands of aluminum alloy conductors on the outer periphery of the steel core made of a plurality of strands of galvanized high carbon steel wire.

Generally, in case of high-voltage transmission lines, as the distance between the transmission towers increases, the initial investment cost and the operating cost can be reduced. Therefore, a high tensile strength is required to maintain the long distance. Aluminum cables with currently used steel cores have been used as industry standards for half a century since 1960, but steel cores in bundles of aluminum transmission lines are necessary to reinforce weak aluminum, but require more high voltage transmission towers And the problem of corrosion and cracking due to the difference in deformation amount at the hetero-bonding interface between aluminum and steel occurs. In recent years, the high voltage direct current (HVDC) method is called for long-distance transmission. In the case of direct current (DC) conduction, since the entire cross-sectional area of the cable transmits current, Fall off. Therefore, it is required to develop a machined transmission line to which a center line having a high conductivity and a light weight is applied.

In order to solve these problems, researches for producing a composite material of a carbon material and aluminum excellent in tensile strength are active. However, there are some problems to be solved in manufacturing a composite of a carbon material and aluminum. For example, carbon materials such as carbon nanomaterials are difficult to disperse due to their interaction due to van der Waals forces between the materials, which makes it difficult to uniformly disperse them in aluminum. Further, there is a problem that the carbon material and aluminum do not mix well due to the difference in surface tension between the carbon material and aluminum.

Korea Registration No. 10-0755128 (Notification Date 2007.09.04)

In order to solve the problem of high specific gravity, low dead weight and cracking at the interface between the iron core and the aluminum of the existing iron core (steel core) transmission line, C composite wire, and a method for efficiently manufacturing the same. Further, the present invention provides a transmission line core, a transmission line including the same, and a separate core And it is an object of the present invention to provide a transmission line which is not provided.

In order to solve the above-described problems, the present invention relates to a composite wire for a transmission line including an aluminum matrix and a carbonaceous material, in which a carbon material in an aluminum matrix is dispersed.

In one preferred embodiment of the present invention, the carbon material of the composite wire component of the present invention is selected from the group consisting of fullerene, single wall carbon nanotubes (SWNTs), multiwall carbon nanotubes (MWNTs) and reduced graphene oxides Or more species.

In one preferred embodiment of the present invention, when the carbonaceous material of the composite wire component of the present invention includes fullerene, the composite wire rod may contain an aluminum matrix containing 0.5 to 5% by volume of fullerene and unavoidable impurities.

In one preferred embodiment of the present invention, when the carbon material of the composite wire rod component of the present invention comprises carbon nanotubes selected from single-walled carbon nanotubes and multi-walled carbon nanotubes, 0.5 to 4.5% by volume, and inevitable impurities.

In one preferred embodiment of the present invention, when the carbonaceous material of the composite wire rod component of the present invention includes reduced graphene oxide (rGO), an aluminum matrix containing 0.2 to 1.5% by volume of rGO and unavoidable impurities As a residual amount.

As a preferred embodiment of the present invention, the composite wire of the present invention may have alumina (Al ₂ O ₃ ) formed at an interface where the carbonaceous material and the aluminum matrix are in contact with each other.

As a preferred embodiment of the present invention, the composite wire of the present invention may be extruded extruded material or drawn wire.

As a preferred embodiment of the present invention, when the carbonaceous material among the composite wire components of the present invention includes fullerene, the composite wire according to the present invention has tensile strengths of 600 to 800 Mpa and an elastic modulus of 70 to 100 Gpa and has a coefficient of thermal expansion (CTE) of (14 to 24) x 10 < ^-6 > / DEG C measured according to a method of measuring a thermal expansion coefficient according to ASTM E831, The electrical conductivity may be 30 to 45% IACS when measured based on electrical conductivity measurements using eddy currents.

In a preferred embodiment of the present invention, when the carbon material of the composite wire rod component of the present invention comprises carbon nanotubes, the composite wire rod of the present invention has tensile strength at the time of measurement based on the tensile test method of the ASTM E8 standard 300 to 600 MPa and a rigidity of 60 to 90 Gpa and a thermal expansion coefficient (CTE) of (22 to 25) x 10 < ^-6 > / DEG C measured according to a thermal expansion coefficient measurement method of the ASTM E831 standard, , The electric conductivity may be 40 to 55% IACS when measured based on the electric conductivity measurement method using an eddy current according to the following formula.

In one preferred embodiment of the present invention, when the carbonaceous material among the composite wire components of the present invention includes rGO, the composite wire according to the present invention has tensile strength of 320 (20 to 26) x 10 < ^-6 > / DEG C, measured according to the ASTM E831 standard, measured according to ASTM E831, The electrical conductivity may be between 45 and 54% IACS when measured based on the electrical conductivity measurement method using an eddy current.

Another object of the present invention is to provide a composite wire for a transmission line described above, and a composite wire can be manufactured by the following method according to the type of carbon material.

In one preferred embodiment of the present invention, when the carbon material is fullerene, a first step of planetary ball milling a mixture of fullerene, aluminum (Al) powder and a lubricant is performed; Mixing the oil-milled mixed powder and the lubricant, and then performing attrition milling; A third step of removing the lubricant from the attrition milled mixed powder; A fourth step of performing a plastic working process on the mixed powder from which the lubricant has been removed to produce a wire rod; And a fifth step of heat-treating the wire rod, thereby manufacturing a composite wire rod.

In one preferred embodiment of the present invention, when the carbon material is a carbon nanotube, attrition milling of a mixture of a carbon nanotube, an aluminum (Al) powder and a lubricant is performed. A second step of removing the lubricant from the attrition milled mixed powder; A third step of performing a plastic working process on the mixed powder from which the lubricant has been removed to produce a wire rod; And a fourth step of heat treating the wire rod.

In one preferred embodiment of the present invention, when carbonaceous material is reduced graphene oxide, a mixture of aluminum (Al) powder and a lubricant is milled; Removing the lubricant from the milled mixed powder to produce an aluminum flake powder (AFP); A third step of preparing a polymer-coated AFP slurry by filtering and washing the AFP-polymer solution mixed with the aqueous polymer solution and the AFP; Adding a graphene oxide suspension to a polymer-coated AFP slurry and stirring to prepare a mixed solution; Filtering the mixed solution, filtering and drying the resulting product to produce a GO / Al composite powder; A sixth step of producing the rGO / Al composite powder by subjecting the GO / Al composite powder to a thermal reduction treatment under a vacuum or hydrogen atmosphere; rGO / Al composite powder and Al powder 1: 2.5 to 4 weight ratio; 7) planetary ball milling the mixture powder; Step 8 in which a mixed powder obtained by oil-milling and a lubricant are mixed, followed by attrition milling; 9) removing the lubricant from the attrition milled mixed powder; A step 10 of producing a wire rod by performing a plastic working process on the mixed powder from which the lubricant is removed; And a step 11 of heat treating the wire rod to produce a composite wire rod.

As one preferred embodiment of the present invention, in each of the three manufacturing methods, the plastic working step can be performed at a reduction rate of 10 to 14% per 460 to 550 캜.

In one preferred embodiment of the present invention, in each of the three manufacturing methods, the plastic working step is an extrusion step, and the extrusion step may be carried out at a temperature of 460 ° C to 600 ° C and a pressure of 250 to 290 bar.

In one preferred embodiment of the present invention, in each of the three manufacturing methods, the heat treatment is performed by applying heat of 400 ° C to 530 ° C for 2 to 30 hours in an atmospheric environment

In one preferred embodiment of the present invention, in each of the three manufacturing methods, the heat treatment may be performed by applying heat at 480 ° C to 600 ° C for 12 hours to 30 hours under a mixed gas of hydrogen and nitrogen.

Another object of the present invention is to provide a core for power transmission lines including the above-described various types of composite wire rods (see A in Fig. 1).

Further, the present invention provides a surface-treating agent comprising: a surface portion containing aluminum; And a core part embedded in the surface part, wherein the core part includes the composite wire as described above.

Another object of the present invention is to provide a transmission line of a single material that includes only the various types of composite wires described above and does not have a separate core (see FIG. 1B).

The composite wire of the present invention has high tensile strength and rigidity, low thermal expansion coefficient and excellent electrical conductivity, and is thus suitable for use as a transmission line. In addition, a dead weight due to low electrical conductivity is generated by using steel as a core material of a conventional transmission line. However, a dead weight problem of a transmission line employing the composite wire of the present invention is advantageous for a direct current transmission of a door, The problem of heterogeneous bonding between the steel core and the surface portion made of aluminum can be prevented. The composite wire according to the present invention can be applied to the fabrication of ultra-high voltage high-DC direct current (HVDC) cable cores and HVDC cables including ultra-light and high transmission efficiency HVDC cables applicable to the future smart grid / super grid.

1 (A) is a schematic view of a transmission line (cable) having a core portion and a surface portion to which the composite wire of the present invention is applied, and B is a schematic view of a transmission line (cable) formed only of the composite wire of the present invention.
Figs. 2 and 3 are HRTEM images of the composite wire of Example 1-1 fabricated in Experimental Example 1-1. Fig.
4 shows the results of Raman spectrum measurement of the composite wire of Example 1-1 performed in Experimental Example 1-1.
Fig. 5 shows the tensile strength and stiffness measurement results of the composite cord according to Experimental Example 1-2. Fig.
6 shows the results of measurement of thermal expansion coefficient and electric conductivity of the composite wire material in Experimental Example 1-2.
7 is a HRTEM photograph of the composite wire of Example 2-3 applied in Experimental Example 2-1.
Fig. 8 shows the tensile strength and stiffness measurement results of the composite cord according to Experimental Example 2-2.
9 shows the results of measurement of thermal expansion coefficient and electric conductivity of the composite wire rod in Experimental Example 2-2.
10 is a photograph of the HRTEM of the composite wire of Example 3-1 conducted in Experimental Example 3-1.
11 shows the results of Raman spectrum measurement of the composite wire of Example 3-1 conducted in Experimental Example 3-1.
Fig. 12 shows tensile strength and stiffness measurement results of the composite wire material in Experimental Example 3-2. Fig.
13 shows the results of measurement of thermal expansion coefficient and electric conductivity of the composite wire material in Experimental Example 3-2.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the method for producing a composite wire for transmission line of the present invention.

The present invention relates to a composite wire having carbon material dispersed in an aluminum matrix containing at least one selected from fullerene, single wall carbon nanotubes (SWNT), multiwall carbon nanotubes (MWNT) and reduced graphene oxides (rGO) , There is a slight difference in manufacturing method depending on the type of carbon material.

First, in the case of applying fullerene as a carbon material (Production Method 1), the composite wire of the present invention is produced by a method comprising: a first step of planetary ball milling a mixture of fullerene, aluminum (Al) powder and lubricant; Mixing the oil-milled mixed powder and the lubricant, and then performing attrition milling; A third step of removing the lubricant from the attrition milled mixed powder; A fourth step of performing a plastic working process on the mixed powder from which the lubricant has been removed to produce a wire rod; And a fifth step of heat-treating the wire rod, thereby manufacturing a composite wire rod.

In the first step of Production Process 1, the fullerene and the aluminum powder in the mixture components are suitable for adjusting the content of the titled fullerenes in the composite wire rod prepared from 1:20 to 150 parts by weight, preferably from 30 to 80 parts by weight .

The lubricants of the first and second stages are solid lubricants and / or liquid lubricants. The lubricants are used to prevent excessive aggregation between powders. Conventional lubricants used in the art can be used, but stearic acid more preferably at least one selected from the group consisting of stearic acid, graphite, and ethyl alcohol, at least one selected from the group consisting of acetic acid, graphite, ethyl alcohol, acetone, toluene and NMP (N-Methyl-2-pyrrolidone) The amount of the lubricant to be used is suitably 5 to 15 parts by weight, preferably 7 to 12 parts by weight, based on 100 parts by weight of the fullerene. If the amount of the lubricant used is less than 5 parts by weight, There may be a problem that it is difficult to prevent excessive aggregation, and when it is used in excess of 15 parts by weight, There is a problem that it may act as an impurity which interferes with the hot forming step.

In the first-stage oil milling, STS ball is added to the mixture at a weight ratio of 10 to 20 times the mixture, and the mixture is milled at a milling speed of 100 to 300 rpm, preferably 180 to 250 rpm for 10 to 20 minutes, And the cycle of stopping the milling for 60 minutes to 80 minutes is repeated 6 to 10 times, preferably 7 to 9 times. If the milling speed is less than 100 rpm during the planetary milling, there is a problem that the mechanical energy applied to the powder during milling is insufficient, so that the pulverization and mixing of the powder can not proceed sufficiently. If the milling speed exceeds 300 rpm, There may be a problem that the molecular structure of the carbon nanomaterial such as fullerene is destroyed.

In the method 1, the above-mentioned two-stage induction milling is intended to uniformly disperse carbon nanomaterials such as fullerene in aluminum powder and to miniaturize the grain size of aluminum. In 100 parts by weight of the oil-milled mixed powder prepared in the first step 0.5 to 5 parts by weight, preferably 1 to 2 parts by weight of a lubricant is mixed with argon (Ar) gas at 450 to 600 rpm, preferably 480 to 550 rpm for 6 to 30 hours . If the amount of the lubricant is less than 0.5 parts by weight, excessive aggregation of the powder may not be prevented. If the amount of the lubricant is more than 5 parts by weight, the powder may act as an impurity which may interfere with the hot forming process of the powder . If the milling speed of the abrasive is less than 450 rpm, there is a problem that the mechanical energy applied to the milling is insufficient during milling, so that the pulverization and mixing of the powder can not proceed sufficiently. If the attrition milling speed exceeds 600 rpm The molecular structure of the fullerene may be destroyed. Therefore, it is preferable to perform the milling at the above-mentioned speed.

In the first to third steps, the lubricant is removed from the mixed powder subjected to the attrition milling. The mixed milled powder is put into a vacuum oven and heated at 450 to 520 ° C in a vacuum atmosphere to 15 Min to 30 min to remove the lubricant.

In the first to fourth steps, the mixed powder obtained by removing the lubricant is subjected to a plastic working step to produce a wire rod. The plastic working step may be performed by a general method used in the art such as an extrusion step or a drawing step, In one embodiment, for example, the lubricant-free mixed powder is subjected to hot rolling at a temperature of 450 ° C to 550 ° C, preferably 460 ° C to 500 ° C, at a reduction rate of 10% to 14% Or rolling) processes to produce composite rods, such as rods and wires. In another preferred embodiment, the mixed powder from which the lubricant has been removed can be extruded at a temperature of 460 ° C to 600 ° C and a pressure of 250 to 290 bar, preferably 460 ° C to 570 ° C and a pressure of 260 to 285 bar Extrusion may be performed to produce composite rods such as rods and wires.

The heat treatments 1 to 5 are for improving the mechanical properties such as tensile strength and rigidity of the composite wire, and can be carried out under a mixed gas of hydrogen and nitrogen or under a vacuum atmosphere in an air atmosphere. Concretely, the heat treatment can be carried out by heating at 400 ° C. to 530 ° C. for 2 hours to 30 hours under an atmospheric atmosphere, and heating at 480 ° C. to 600 ° C. under a mixed gas of hydrogen and nitrogen, preferably at 480 ° C. to 560 ° C. For 12 hours to 30 hours. If the heat treatment temperature is less than 480 DEG C, there may be a problem that the removal of impurities and the reduction reaction of graphene oxide can not proceed sufficiently. If the heat treatment temperature is too high at 600 DEG C, graphene reacts with aluminum to generate aluminum carbide It is preferable to perform the heat treatment under the temperature within the above range.

As shown in the photograph of the high-resolution electron microscope (HRTEM) of FIG. 2, the composite wire according to the present invention thus prepared contains a residual amount of an aluminum matrix containing fullerene and unavoidable impurities as a composite wire in the form of fullerene dispersed in an aluminum matrix . The fullerene content is 0.5 to 5% by volume, preferably 1 to 4.5% by volume, more preferably 1.5 to 3.5% by volume based on the total volume% of the composite wire. When the fullerene content is less than 0.5% by volume, sufficient tensile strength And the stiffness can not be ensured. If the fullerene content exceeds 5 vol%, not only the electric conductivity decreases but also the tensile strength is lowered.

Alumina (Al ₂ O ₃ ) may be formed at the interface between the fullerene in the composite wire and the aluminum matrix.

The composite wire according to the present invention to which fullerene is applied as a carbon material has a tensile strength of 600 to 800 Mp, preferably a tensile strength of 680 To 800 Mpa, and more preferably from 700 to 780 Mpa.

When the composite wire has an average diameter of 1.3 mm, the elastic modulus is 70 to 100 MPa, preferably 75 to 98 MPa, and more preferably 80 to 100 MPa when measured according to the tensile test method of the ASTM E8 standard. 95 Mpa.

When the composite wire rod has an average diameter of 1.3 mm, the coefficient of thermal expansion (CTE) is (14 to 24) x 10 ^-6 / ° C, preferably (18 ~ 24) x 10 < ^-6 > / [deg.] C.

In addition, when the composite wire has an average diameter of 1.3 mm, the electric conductivity is 30 to 45% IACS, preferably 31 to 42% IACS when measured based on electric conductivity measurement using an eddy current according to ASTM E1004 .

Next, a method for producing a composite wire using carbon nanotubes (CNTs) as carbon materials will be described.

In the case where CNT is applied as a carbon material (Production Method 2), the composite wire of the present invention has a first step of attrition milling a mixture of CNT, aluminum (Al) powder and a lubricant; A second step of removing the lubricant from the attrition milled mixed powder; A third step of performing a plastic working process on the mixed powder from which the lubricant has been removed to produce a wire rod; And a fourth step of heat treating the wire rod.

In Step 1 of Production Process 2, the CNTs may be used either alone or in combination of two or more selected from single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs).

The mixture of the first step may contain CNT and Al powder at a weight ratio of 1: 30 to 160, preferably 1: 50 to 150, and the use of CNT within the above range is preferable in that the content of the titled fullerene in the composite wire .

More specifically, when the CNT is a single-walled carbon nanotube (SWNT), it is preferable to use the SWNT and the Al powder at a weight ratio of 60 to 160, preferably 65 to 150, and the weight ratio of the SWNT and the Al powder The composite wire rod manufactured using the composite wire may contain 0.5 to 2.5% by volume, preferably 0.8 to 2.3% by volume, of SWNT in the Al matrix.

When the CNT is a multi-walled carbon nanotube (MWNT), it is preferable to use the MWNT and Al powder at a weight ratio of 30 to 75, preferably 40 to 72, and the weight ratio of MWNT and Al powder A composite wire rod may contain 1.8 to 4.5% by volume, preferably 2.0 to 3.2% by volume of MWNT in the Al matrix.

The first-stage lubricant of Production Process 2 is a solid lubricant and / or a liquid lubricant. It serves to prevent excessive agglomeration between powders. Conventional lubricants used in the art can be used, but stearic acid (stearic acid ), At least one selected from graphite, ethyl alcohol, acetone, toluene and NMP (N-methyl-2-pyrrolidone), more preferably at least one selected from stearic acid, graphite and ethyl alcohol The amount of the lubricant to be used is suitably 0.5 to 3 parts by weight, preferably 0.7 to 2 parts by weight, based on 100 parts by weight of the CNT. If the amount of the lubricant used is less than 0.5 part by weight, There may be a problem that it is difficult to prevent the development, and if it is used in excess of 3 parts by weight, the hot- It is because there is a problem that can act as impurities that interfere with the process.

In the first stage of the abrasion milling, an STS ball is charged into the mixture at a weight ratio of 10 to 20 times of the mixture, and then, under argon gas, at a milling speed of 400 to 700 rpm, preferably 450 to 650 rpm Milling can be performed for about 4 hours to 12 hours. If the milling speed is less than 400 rpm, the mechanical energy applied to the milling process may be insufficient for the pulverization and mixing of the powders. If the milling speed exceeds 700 rpm It is preferable to perform the milling at the above-mentioned speed because there may be a problem that the molecular structure of the CNT is destroyed.

Processes 2 to 2 are the steps of removing the lubricant from the mixed powder subjected to the induction milling. The mixed milled powder is put into a vacuum oven and heated at 450 to 520 ° C in a vacuum to 15 Min to 30 min to remove the lubricant.

Processes 2 to 3 are processes for producing a mixed powder from which a lubricant has been removed from a wire, and can be carried out in the same manner as in the plastic working process mentioned in Step 4 of Production Method 1.

The heat treatment steps 2 to 4 can be carried out in the same manner as the heat treatment step mentioned in step 5 of Production Method 1.

As shown in the photograph of the high-resolution electron microscope (HRTEM) of FIG. 7, the thus-prepared CNT-containing composite wire of the present invention is a composite wire in which CNTs in an aluminum matrix are dispersed, and an aluminum matrix containing CNTs and unavoidable impurities . The CNT content may include 0.5 to 3.5% by volume of the total volume of the composite wire. When the CTN is SWNT, the SWNT is preferably 0.5 to 2.5% by volume, and more preferably 0.8 to 2.3% by volume. When the CNT is MWNT, the MWNT is preferably 1.8 to 4.5% by volume, and more preferably 2.0 to 3.2% by volume, in terms of mechanical properties and electric conductivity.

Alumina (Al ₂ O ₃ ) may be formed at the interface between the CNTs in the composite wire and the aluminum matrix.

The composite wire according to the present invention, to which CNT is applied as a carbon material, has a tensile strength of 300 to 480 Mpa when measured according to the tensile test method of ASTM E8 standard with an average diameter of 1.3 mm, May be 350 to 480 MPa, and more preferably 400 to 480 MPa.

When the composite wire has an average diameter of 1.3 mm, the elastic modulus is preferably 60 to 80 MPa, more preferably 62 to 78 MPa, more preferably 62 to 78 MPa when measured according to the ASTM E8 standard tensile test method. 70 to 78 MPa.

When the composite wire rod has an average diameter of 1.3 mm, the coefficient of thermal expansion (CTE) is (22-25) 占^10-6 / 占 폚, preferably (22.5 ~ 24) x 10 < ^-6 > / [deg.] C.

In addition, when the composite wire has an average diameter of 1.3 mm, the electrical conductivity may be 40 to 55% IACS, preferably 41 to 53% IACS when measured according to the electric conductivity measurement method using an eddy current according to ASTM E1004.

Next, a method of producing a composite wire using graphene oxide (GO) as a carbon material will be described.

In order to introduce reduced graphene oxide (rGO) as a carbon material (Production Method 2), the composite wire according to the present invention comprises a first step of milling a mixture of an aluminum (Al) powder and a lubricant; Removing the lubricant from the milled mixed powder to produce an aluminum flake powder (AFP); A third step of preparing a polymer-coated AFP slurry by filtering and washing the AFP-polymer solution mixed with the aqueous polymer solution and the AFP; Dropping the graphene oxide suspension into the AFP slurry and stirring to prepare a mixed solution; Filtering the mixed solution, filtering and drying the resulting product to produce a GO / Al composite powder; A sixth step of producing the rGO / Al composite powder by subjecting the GO / Al composite powder to a thermal reduction treatment under a vacuum or hydrogen atmosphere; rGO / Al composite powder and Al powder 1: 2.5 to 4 weight ratio; 7) planetary ball milling the mixture powder; Step 8 in which a mixed powder obtained by oil-milling and a lubricant are mixed, followed by attrition milling; 9) removing the lubricant from the attrition milled mixed powder; A step 10 of producing a wire rod by performing a plastic working process on the mixed powder from which the lubricant is removed; And a step 11 of heat treating the wire rod to produce a composite wire rod.

In the first step of Production Process 3, the mixture may be used in an amount of 0.5 to 2 parts by weight, preferably 0.5 to 1.5 parts by weight, based on 100 parts by weight of the Al powder. If the amount of the lubricant is less than 0.5 parts by weight, it may be difficult to prevent the powder from being excessively agglomerated. If the amount of the lubricant is more than 2 parts by weight, the powder may act as an impurity which may interfere with the hot- It can be. The lubricant is a solid lubricant and / or a liquid lubricant. It serves to prevent excessive aggregation between powders. The lubricant may be a conventional lubricant used in the art, but preferably includes stearic acid, graphite, At least one selected from ethyl alcohol, acetone, toluene and NMP (N-methyl-2-pyrrolidone), and more preferably at least one selected from stearic acid, graphite and ethyl alcohol.

The one-step milling can be performed using attrition milling, planetary milling, hand mixing, or speck milling, . ≪ / RTI > In one preferred embodiment of the present invention, 1 part by weight of the lubricant and 1,500 parts by weight of the STS ball are added to 100 parts by weight of the Al powder, and then subjected to attrition milling at 300 to 500 rpm for 2 to 4 hours .

The second step of Process 3 is a process for removing the lubricant from the milled Al powder. The milled mixed powder is put into a vacuum oven and heated at 450 to 520 ° C for 15 to 30 minutes under vacuum to remove the lubricant To produce an aluminum flake powder (AFP).

Step 3 of Production Process 3 is a step of preparing a polymer-coated aluminum flake powder (AFP) slurry. The AFP-polymer solution is prepared by mixing and stirring the AFP in an aqueous solution of a polymer, , Followed by filtration, followed by washing with distilled water, non-ionized water (DI water) or the like to prepare an AFP slurry. At this time, the polymer aqueous solution is obtained by dissolving a polymer containing at least one selected from polyvinyl alcohol, polyethylene oxide, polyacrylamide and glycerol in water. The AFP-polymer solution can be prepared by mixing and stirring an aqueous solution of a polymer in an amount of about 50 cc to about 200 cc on the basis of 10 g of AFP.

Step 4 of Production Process 3 is a step of dropping and stirring a graphene oxide (GO) suspension into a polymer-coated AFP slurry to prepare a mixed solution. At this time, the GO suspension can be prepared by mixing GO with water and then subjecting it to ultrasonic treatment, and the production method of the GO suspension is not particularly limited thereto.

Step 5 of Production Process 3 is a process for producing a GO / Al composite powder by drying a wet GO / Al composite powder as a filtrate of the mixed solution of Step 4, wherein drying is performed by a general method used in the art In one preferred embodiment, it is possible to apply hot air at 25 to 35 DEG C or to put it in an oven to perform drying.

Step 6 of the process 3 is a process for reducing the GO of the GO / Al composite powder. The GO / Al composite powder is heated in a vacuum or hydrogen atmosphere at a temperature of 450 to 600 ° C for about 40 minutes to 1 hour and 30 minutes, The rGO / Al composite powder can be produced by a thermal reduction treatment.

Step 7 of Process 3 is a process of mixing the mixed powder of the rGO / Al composite powder and Al powder prepared in Step 6 and the STS ball, followed by planetary ball milling.

At this time, it is preferable that the mixed powder contains 1: 2.5 ~ 4 weight ratio of rGO / Al composite powder and Al powder, preferably 1: 2.7 ~ 3.5 weight ratio. When the amount of the Al powder is less than 2.5 weight ratio The rGO content in the composite wire rod becomes too large and mechanical properties of the composite wire rod can be lowered. If the amount of the Al powder is more than 4.0 weight ratio, the rGO content may be too small to ensure sufficient mechanical properties.

The 7-step planetary milling is performed at a milling speed of 70 to 150 rpm, preferably 80 to 130 rpm for 20 to 40 minutes, followed by a cycle of stopping the milling for 60 to 90 minutes for 6 to 10 times, Preferably 7 to 9 times.

In the abrasion milling of the eight steps of Production Method 3, 0.5 to 3 parts by weight, preferably 0.5 to 2 parts by weight of a lubricant is mixed with 100 parts by weight of the oil-milled mixed powder prepared in Step 7, Under a gas at a milling speed of 450 to 600 rpm, preferably 520 to 580 rpm, for 4 to 10 hours. If the amount of the lubricant used is less than 0.5 parts by weight, it may be difficult to prevent excessive aggregation of the powder. If the amount of the lubricant is more than 3 parts by weight, the powder may act as an impurity which may interfere with the hot- It is because. If the milling speed of the abrasive is less than 450 rpm, there is a problem that the mechanical energy applied to the milling is insufficient during milling, so that the pulverization and mixing of the powder can not proceed sufficiently. If the attrition milling speed exceeds 600 rpm The molecular structure of the fullerene may be destroyed. Therefore, it is preferable to perform the milling at the above-mentioned speed.

Step 9 of the process 3 is a process for removing the lubricant from the mixed powder subjected to the attrition milling. The mixed milled powder is put into a vacuum oven and heated at 450 to 520 ° C in a vacuum atmosphere to 15 Min to 30 min to remove the lubricant.

In the processes 3 to 10, the mixed powder obtained by removing the lubricant is subjected to a plastic working process to produce a wire rod. The plastic working process may be performed by a general method used in the art such as an extrusion process or a drawing process, In one embodiment, the lubricant-free mixed powder is drawn (or dried) at a reduction rate of 10-14% per cycle using hot rolling at 450 ° C to 550 ° C, preferably 460 ° C to 500 ° C Rolling) process can be performed to produce composite rods such as rods and wires. In another preferred embodiment, the mixed powder from which the lubricant has been removed can be extruded at a temperature of 460 ° C to 600 ° C and a pressure of 250 to 290 bar, preferably 460 ° C to 570 ° C and a pressure of 260 to 285 bar Extrusion may be performed to produce composite rods such as rods and wires.

The heat treatments of Processes 3 to 11 are for improving the mechanical properties such as tensile strength and rigidity of the composite wire, and can be carried out under a mixed gas of hydrogen and nitrogen or under a vacuum atmosphere in an air atmosphere. Concretely, the heat treatment can be carried out by heating at 400 ° C. to 530 ° C. for 2 hours to 30 hours under an atmospheric atmosphere, and heating at 480 ° C. to 600 ° C. under a mixed gas of hydrogen and nitrogen, preferably at 480 ° C. to 560 ° C. For 12 hours to 30 hours. If the heat treatment temperature is less than 480 DEG C, there may be a problem that the removal of impurities and the reduction reaction of graphene oxide can not proceed sufficiently. If the heat treatment temperature is too high at 600 DEG C, graphene reacts with aluminum to generate aluminum carbide It is preferable to perform the heat treatment under the temperature within the above range.

Alumina (Al ₂ O ₃ ) may be formed at the interface between the rGO and the aluminum matrix in the composite wire (see FIG. 10).

The composite wire of the present invention containing rGO as the carbon material has a tensile strength of 320 to 400 MPa when measured according to the tensile test method of the ASTM E8 standard when the average diameter is 1.3 mm, The strength may be from 340 to 400 MPa, more preferably from 350 to 400 MPa.

Further, when the composite wire has an average diameter of 1.3 mm, the rigidity may be 70 to 90 MPa, preferably 72 to 87 MPa when measured according to the tensile test method of the ASTM E8 standard.

When the composite wire rod has an average diameter of 1.3 mm, the thermal expansion coefficient (CTE) is (20-26) 占^10-6 / 占 폚, preferably (22 ~ 26) x 10 < ^-6 > / [deg.] C.

In addition, when the composite wire has an average diameter of 1.3 mm, the electrical conductivity may be 45 to 54% IACS, preferably 48 to 54% IACS when measured according to the electrical conductivity measurement method using an eddy current according to ASTM E1004.

Hereinafter, the present invention will be described more specifically based on examples. However, the following examples are provided to aid understanding of the present invention and should not be construed as limiting the scope of the present invention by examples.

[ Example ]

Example 1-1: Preparation of fullerene-containing composite wire rod

1 g of fullerene, 80 g of aluminum powder and 0.1 g of stearic acid were mixed and stirred to prepare a mixture. Next, STS powder having a mass of 15 times the mass of the mixture was mixed with the mixture, followed by oil milling at a speed of 200 rpm for 15 minutes, and the milling was stopped for 75 minutes (1 cycle). This oil milling was repeated eight times to prepare oil milled mixed powders.

Subsequently, 1 part by weight of stearic acid was mixed with 100 parts by weight of the oil-milled mixed powder, and then subjected to induction milling at a speed of 500 rpm under argon gas for 24 hours.

Next, the mixed powder subjected to the induction milling was put into a vacuum oven, and then the lubricant was removed by heating at 500 ° C for 20 minutes in a vacuum atmosphere.

Next, the acid-removed mixed powder was subjected to a drawing process at a reduction rate of 12% per one time by hot rolling at 480 캜 to produce a wire having an average diameter of about 1.3 mm.

Next, the wire rod was heat-treated at 500 ° C for 12 hours in a vacuum atmosphere to prepare a final composite wire rod containing fullerene (2 vol%).

Example 1-2 to Example 1-6 and Comparative Examples 1-1 to 1-6: Article of the fullerene-containing composite wire

Composite wire materials having the same conditions and composition as those in Table 1 below were prepared in the same manner as in Example 1-1 to prepare fullerene-containing composite wire materials, and Examples 1-2 to 1-6 and Comparative Examples 1-1 to 1- 6 respectively.

division In Al matrix
Fullerene volume% Heat treatment time Comparative Example 1-1 2 volume% X Example 1-1 2 volume% 12 hours Examples 1-2 2 volume% 24 hours Comparative Example 1-2 3 volume% X Example 1-3 3 volume% 12 hours Examples 1-4 3 volume% 24 hours Comparative Example 1-3 5 vol% X Examples 1-5 5 vol% 12 hours Examples 1-6 5 vol% 24 hours Comparative Example 1-4 0 X Comparative Example 1-5 0 12 hours Comparative Example 1-6 0 24 hours

Experimental Example  1-1: Fullerene  contain Composite wire HRTEM  Measurement and Raman Spectrum  Measure

The results of HRTEM (high-resolution transmission electron microscopy) measurement of the wire rod prepared in Example 1-1 are shown in FIG. 2 and FIG. 2, it can be confirmed that fullerene is uniformly dispersed in the Al matrix.

In addition, the Raman spectrum measurement data of the wire rod prepared in Example 1-1 is shown in Fig. 4, and it can be confirmed that fullerene in the wire rod is present without serious breakage.

Experimental Example  1-2: Fullerene  contain Composite wire  Measurement of mechanical and electrical properties

The tensile strength, the elastic modulus, the coefficient of thermal expansion (CTE), and the electrical conductivity of the wire rod prepared in Examples 1-2 to 1-6 and Comparative Examples 1-1 to 1-6 (Electrical conductivity), and the results are shown in Table 2, FIG. 5, and FIG. 6, respectively.

The tensile strength and the stiffness were measured in accordance with the tensile test method according to the ASTM E8 standard, and the thermal expansion coefficient was measured according to the thermal expansion coefficient measurement method according to the ASTM E831 standard. The electric conductivity was measured according to ASTM E1004 Eddy current was measured according to the electric conductivity measurement method.

division The tensile strength
(Mpa) Stiffness
(Mpa) Coefficient of thermal expansion
(10 ^-6 / ° C) Electrical conductivity
(% IACS) Comparative Example 1-1 574 71 19.7 40.2 Example 1-1 728 88 23.8 40.1 Examples 1-2 686 93 21.2 40.3 Comparative Example 1-2 577 75 21.2 37.2 Example 1-3 733 87 19.9 37.0 Examples 1-4 783 89 22.1 36.9 Comparative Example 1-3 582 80 19.5 31.5 Examples 1-5 725 85 17.2 31.2 Examples 1-6 925 89 15.0 31.3 Comparative Example 1-4 396 77 23.7 48.1 Comparative Example 1-5 415 77 14.5 51.0 Comparative Example 1-6 398 78 15.9 51.6

The experimental results of Table 2 and Figs. 5 to 6 were compared with those of the wire materials subjected to the heat treatment than the wire materials without heat treatment (Comparative Example 1-1, Comparative Example 1-2, Comparative Example 1-3, and Comparative Example 1-4) Overall, it showed excellent tensile strength and rigidity. However, the heat treatment did not significantly affect the electrical conductivity.

It was confirmed that the fullerene content and the heat treatment time had an influence on the mechanical properties and the electrical properties of the wire. When the fullerene was 2 vol%, the heat treatment time was 12 hours (Example 1-1) The tensile strength was higher than that in the case where the heat treatment time was 24 hours (Example 1-3), but the rigidity tended to be somewhat lowered. When the fullerene content was 3 vol.%, The tensile strength and rigidity tended to be somewhat higher than in the case of heat treatment for 24 hours (Example 1-4) than in the case of heat treatment time of 12 hours (Example 1-3).

However, when the fullerene content was 5 vol% (Examples 1-5 and Examples 1-6), the mechanical properties were not improved, but the results were lower than those of the case where the fullerene content was 3 vol%.

And, as the fullerene content increased, the thermal expansion coefficient tended to decrease.

Example  2-1: CNT  contain Composite wire  Produce

0.68 g of single-walled carbon nanotubes (SWNT), 99.32 g of aluminum powder and 1 g of stearic acid were mixed and stirred to prepare a mixture. Next, STS powder having a mass of 15 times the mass of the mixture was mixed with the mixture, and then subjected to induction milling at a speed of 500 rpm under argon gas for 6 hours.

Next, the mixed milled powders were put into a vacuum oven and heated at 500 ° C. for 20 minutes in a vacuum atmosphere to remove the lubricant.

Next, the acid-removed mixed powder was drawn at a reduction rate of 12% per one time by hot rolling at 480 캜 to produce a rolled material having an average diameter of about 1.3 mm.

Next, the wire material was heat-treated at 500 ° C for 12 hours in a vacuum atmosphere to prepare a composite wire rod (wire rod) containing final SWNT (1 volume%).

Example  2-2 ~ Example  2-3 and Comparative Example  2-1: CNT  contain Composite wire  Produce

A CNT-containing wire rod was prepared in the same manner as in Example 2-1, and CNT-containing wire rod materials having the compositions shown in Table 3 were prepared.

Here, CNT was not used in Comparative Example 2-1, and MWNT was used instead of SWNT in Example 2-3.

Example  2-4: CNT  contain Of composite wire (extruded material)  Produce

0.68 g of single-walled carbon nanotubes (SWNT), 99.32 g of aluminum powder and 1 g of stearic acid were mixed and stirred to prepare a mixture. Next, STS powder having a mass of 15 times the mass of the mixture was mixed with the mixture, and then subjected to induction milling at a speed of 500 rpm under argon gas for 6 hours.

Next, the mixed milled powders were put into a vacuum oven and heated at 500 ° C. for 20 minutes in a vacuum atmosphere to remove the lubricant.

Next, the acid-removed mixed powder was extruded at 500 DEG C and 275 bar using an extruder to produce an extruded material having an average diameter of about 1.3 mm.

division In Al matrix
CNT volume% CNT type Composite wire processing Comparative Example 2-1 - - Drawing process Example 2-1 1 volume% Single wall CNT Drawing process Example 2-2 2 volume% Single wall CNT Drawing process Example 2-3 3 volume% Multi-wall CNT Drawing process Examples 2-4 3 volume% Multi-wall CNT Extrusion process

Experimental Example  2-1: CNT  contain Composite wire HRTEM  Measure

The results of HRTEM (high-resolution transmission electron microscopy) measurement of the wire rod prepared in Example 2-3 are shown in FIG. Referring to FIG. 7, it can be seen that the multi-walled carbon nanotube is uniformly dispersed in the Al matrix.

Experimental Example  2-2: CNT  contain Composite wire  Measurement of mechanical and electrical properties

The tensile strength, the elastic modulus, the coefficient of thermal expansion (CTE) and the electrical conductivity of the wire rod prepared in Examples 2-1 to 2-4 and Comparative Example 2-1 were measured, And the results are shown in Table 4, FIG. 8, and FIG. 9, respectively.

The tensile strength, the stiffness, the thermal expansion coefficient and the electric conductivity were measured in the same manner as in Experimental Example 1-2.

division The tensile strength
(Mpa) Stiffness
(Mpa) Thermal expansion
(10 ^-6 / ° C) Electrical conductivity
(% IACS) Comparative Example 2-1 105 65 21.7 60.1 Example 2-1 323 76 22.5 49.8 Example 2-2 461 70 22.8 41.2 Example 2-3 356 66 22.8 51.3 Examples 2-4 305 70 18.1 48.2

8 and 9, CNT-free wire rod and Comparative Example 2-1) have excellent electrical conductivity, but have a tensile strength significantly lower than those of Examples 2-1 to 2-4. It looked.

In addition, the result of Example 2-3 (drawing process) showed a relatively higher tensile strength, stiffness and electrical conductivity than that of Example 2-4 (extrusion process).

In addition, in the rolled material, the wire material containing 2 vol% of SWNT (Example 2-2) showed better mechanical properties than the wire material containing 3 vol% of MWNT (Example 2-3).

Example 2-2 had better mechanical properties than Example 2-1, but showed excellent electrical conductivity in Example 2-1.

Example  3-1: rGO  contain Composite wire  Produce

100 g of aluminum powder, 1 g of stearic acid and 1500 g of STS balls were mixed and subjected to induction milling under argon gas at a milling speed of 400 rpm for 3 hours.

Next, the powder subjected to attrition milling was placed in a vacuum oven and heated at 500 DEG C under a vacuum atmosphere for 20 minutes to remove the lubricant, thereby preparing an aluminum flake powder (AFP).

Next, 1 g of polyvinyl alcohol (PVA) was mixed with DI water (150 ml) and ultrasonicated to prepare a PVA aqueous solution. 10 g of the AFP was added to the PVA aqueous solution and stirred for 1 hour to prepare an AFP-polymer solution.

Next, the AFP-polymer solution was filtered through a filter paper, and the filtrate was rinsed three times with DI water to prepare a polymer (PVA) -coated AFP slurry.

Next, the GO suspension was dropped and stirred in a polymer-coated AFP slurry using a buret, and agitation was performed until a transparent aqueous solution layer was formed. Here, the GO suspension was prepared by adding 0.152 g of graphene oxide (GO) to 200 ml of DI water and ultrasonication for 1 hour.

Next, the solution having the transparent aqueous solution layer was filtered to obtain the GO / Al composite powder as a filtrate, which was then slowly dried in an oven at 30 ° C.

Next, the dried GO / Al composite powder was put into an oven, and then subjected to a thermal reduction treatment in an atmosphere of H ₂ and N ₂ mixed gas and 500 ° C. for 1 hour to obtain a reduced grapheme oxide / .

Next, 20 g of the rGO / Al composite powder, 60 g of the Al powder, and 1200 g of the STS powder were mixed, followed by oil milling for 5 minutes at a speed of 100 rpm, and the milling was stopped for 90 minutes (1 cycle). This oil milling was repeated eight times to prepare oil milled mixed powders.

Subsequently, 1 part by weight of stearic acid was mixed with 100 parts by weight of the oil-milled mixed powder, and then subjected to induction milling at a rate of 550 rpm under argon gas for 6 hours.

Next, the milled mixed powder was put into a vacuum oven, and the lubricant was removed by heating at 500 ° C. for 20 minutes in a vacuum atmosphere.

Next, the acid-removed mixed powder was subjected to a drawing process at a reduction rate of 12% per one time by hot rolling at 480 캜 to produce a wire having an average diameter of about 1.3 mm.

Next, the wire was subjected to heat treatment at 500 ° C for 12 hours in a vacuum atmosphere to prepare a wire rod (composite wire rod) containing final rGO (0.2% by volume).

Example  3-2 ~ Example  3-8 and Comparative Example  3-1: rGO  contain Composite wire  Produce

RGO-containing wires were prepared in the same manner as in Example 3-1, and rGO-containing wires having the compositions shown in Table 5 were prepared.

Here, rGO was not used in Comparative Example 3-1.

Examples 3-6 to 3-8 were obtained by performing a thermal reduction treatment for 1 hour under a vacuum atmosphere and a temperature of 500 占 폚 in the atmosphere of H ₂ and N ₂ mixed gas during thermal reduction.

division In Al matrix
rGO volume% Reduction condition Composite wire processing Comparative Example 3-1 - - Drawing process Example 3-1 0.2 vol% H ₂ / N ₂ mixed gas Drawing process Example 3-2 0.4 volume% Drawing process Example 3-3 0.6 vol% Drawing process Example 3-4 0.8 volume% Drawing process Example 3-5 1.0 volume% Drawing process Examples 3-6 0.2 vol% vacuum Drawing process Examples 3-7 0.4 volume% Drawing process Examples 3-8 0.6 vol% Drawing process

Experimental Example  3-1: rGO  contain Composite wire HRTEM  Measurement and Raman Spectrum  Measure

The results of HRTEM (high-resolution transmission electron microscopy) measurement of the rolled material prepared in Example 3-1 are shown in FIG. Referring to FIG. 10, it is confirmed that alumina exists between the interface of rGO and aluminum existing in the Al matrix.

In addition, the Raman spectrum measurement data of the wire rod prepared in Example 3-1 is shown in FIG. 11, and it can be confirmed that the graphene in the wire rod is present without serious breakage.

Experimental Example  3-2: rGO  contain Composite wire  Measurement of mechanical and electrical properties

The tensile strength, the elastic modulus, the coefficient of thermal expansion (CTE), and the electrical conductivity of the wire rod prepared in Examples 3-1 to 3-7 and Comparative Example 3-1 were measured. And the results are shown in Table 6, FIG. 12, and FIG. 13, respectively.

The tensile strength, the stiffness, the thermal expansion coefficient and the electric conductivity were measured in the same manner as in Experimental Example 1-2.

division The tensile strength
(Mpa) Stiffness
(Mpa) Thermal expansion
(10 ^-6 / ° C) Electrical conductivity
(% IACS) Comparative Example 3-1 317 63.8 23.2 51.3 Example 3-1 345 72.7 21.1 51.0 Example 3-2 397 81.4 23.7 48.8 Example 3-3 367 83.8 22.9 50.6 Example 3-4 364 79.3 26.2 50.9 Example 3-5 372 83.7 24.4 48.7 Examples 3-6 374 77.4 23.1 50.8 Examples 3-7 370 79.2 22.7 52.5 Examples 3-8 378 75.3 24.5 52.1

Referring to Table 6 and FIG. 12 to FIG. 13, the comparison of Comparative Example 3-1 with Examples 3-1 to 3-8 reveals that there is no significant difference in the electric conductivity change depending on the rGO content. However, it was confirmed that the wire rods containing rGO had better overall tensile strength and rigidity than those wire rogs containing no rGO. In comparison between Examples 3-1 to 3-3 and Examples 3-6 to 3-8, the same ratios of rGO and rGO were obtained in a vacuum state rather than under a mixed gas of H ₂ and N ₂ It was confirmed that the improvement of the tensile strength of the wire rod was somewhat advantageous.

It can be seen from the above Examples and Experimental Examples that a composite wire for transmission line having excellent mechanical properties and electrical characteristics can be provided. By applying the composite wire for transmission line according to the present invention to a transmission line core, And a core portion that is core-embedded in the surface portion, and that a transmission cable can be provided. Further, it can be confirmed that the composite wire of the present invention has excellent mechanical properties and can be applied as a transmission line of a single material having no separate core. It is expected that the composite wire of the present invention can be applied to the manufacture of ultra-high voltage direct current (HVDC) cable cores and HVDC cables including ultra-light and high transmission efficiency HVDC cables applicable to the future smart grid / super grid.

Claims (10)

Wherein the interface between the dispersed carbon material and the aluminum matrix comprises alumina (Al ₂ O ₃ )
0.5 to 2.5% by volume of single-walled carbon nanotubes or 1.8 to 4.5% by volume of multi-walled carbon nanotubes; And an aluminum matrix containing unavoidable impurities,
Characterized in that the wire is a drawn wire. 5. The method according to claim 4, wherein tensile strength is from 300 to 600 MPa, rigidity is from 60 to 90 MPa,
Wherein the thermal expansion coefficient (CTE) is (22 to 25) x 10 < ^-6 > / DEG C and the electrical conductivity is 40 to 55% IACS. A step of attrition milling a mixture of a carbon nanotube, an aluminum (Al) powder and a lubricant;
A second step of removing the lubricant from the attrition milled mixed powder;
A third step of performing a plastic working process on the mixed powder from which the lubricant has been removed to produce a wire rod; And
A fourth step of heat treating the wire rod;
Wherein the step of forming the composite wire comprises the steps of: 4. The method according to claim 3, wherein the lubricant in the first step includes at least one selected from the group consisting of stearic acid, graphite, ethyl alcohol, acetone, toluene and NMP (N-methyl-2-pyrrolidone) Wherein said method comprises the steps of: 4. The method according to claim 3, wherein 0.5 to 3 parts by weight of the lubricant is mixed with 100 parts by weight of the carbon nanotubes. 4. The method according to claim 3, wherein the first stage of the induction milling is a step of milling the mixture at a milling speed of 400 to 700 rpm for 4 hours under an argon (Ar) gas, Wherein the milling is performed for about 12 hours to about 12 hours. 4. The method according to claim 3, wherein the heat treatment is performed by applying heat at 400 to 530 DEG C for 2 to 30 hours in a vacuum atmosphere, or
Characterized in that the heat treatment is carried out by applying heat of 480 캜 to 600 캜, preferably 480 캜 to 560 캜, for 12 hours to 30 hours under a mixed gas of hydrogen and nitrogen. The method according to claim 3, wherein the plastic working step includes a drawing step performed at a reduction rate of 10 to 14% per one time at 460 ° C to 550 ° C. A core for a transmission line comprising the composite wire of any one of claims 1 or 2. 4. A transmission line comprising the composite wire of claim 1 or claim 2 and not having a separate core.

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