High-conductivity graphene aluminum alloy wire and cold rolling preparation method

Abstract

The present invention relates to the technical field of conductive wire preparation, and particularly relates to a high-conductivity graphene aluminum alloy wire and a cold rolling preparation method. For the problem of poor conductivity of rare earth graphene aluminum alloy conductive wires prepared by means of existing methods, the present invention provides a high-conductivity graphene aluminum alloy wire and a cold rolling preparation method. High-purity graphene powder and a carbon nanotube slurry are used and prepared into a dispersion liquid, and the dispersion liquid is atomized and then sprayed onto a substrate to prepare a high-conductivity graphene aluminum alloy wire, such that the dispersion effect of the graphene and the carbon nanotubes in the aluminum alloy is improved, the conductivity of the graphene aluminum alloy is significantly increased, and the conductivity can be increased to 67% IACS. The present invention can be widely applied to the fields such as data centers and aerospace.

Description

Highly conductive graphene aluminum alloy wire and cold-rolled preparation method Technical Field

[0001] The present invention belongs to the technical field of conductive wire preparation, and specifically relates to a highly conductive graphene aluminum alloy wire and a cold rolling preparation method. Background Art

[0002] Conductive wire is the main raw material for the preparation of cables, wires, enameled wires, conductor profiles, connection and conversion terminals, etc. With the rapid development of the power industry, infrastructure construction, and household appliances in recent years, the demand and application of conductive wire has become more and more extensive, the demand for conductive wire has increased, and higher requirements have been put forward.

[0003] Currently, most conductive wires in the industry are made of copper, with a few using ordinary aluminum alloys or pure aluminum. The scarcity of copper resources has limited the industrial development of copper-based conductive wires, necessitating the development of alternative materials for conductive wire. However, the conductivity of currently developed ordinary aluminum alloys and pure aluminum wires is inferior to that of copper. Graphene-based aluminum alloys are prone to agglomeration, which can affect the effective conductivity of graphene.

[0004] Patent CN103943281A discloses a method for preparing wires and cables with a copper-graphene composite conductive core. This method involves electroplating and then stretching the wire into a wire. It uses a large number of chemical reagents, such as sulfuric acid and hydrochloric acid, and has numerous processing steps and a small production volume, making it difficult to achieve industrial production.

[0005] Patent CN106636776A discloses a rare earth graphene aluminum alloy conductive wire and its preparation method. This method uses low-temperature ball milling powder metallurgy to prepare rare earth graphene aluminum alloy. Although it can achieve uniform dispersion of graphene in aluminum and improve the graphene / aluminum interface bonding, this method is complex and costly, making it unsuitable for large-scale engineering applications in low-value-added fields (such as electrical appliances, cables, etc.). Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the conductive performance of rare earth graphene aluminum alloy conductive wires prepared by existing methods is not high.

[0007] The present invention solves the above technical problems by providing a method for cold-rolling a highly conductive graphene aluminum alloy wire. The method comprises the following steps:

[0008] a. Preparation of graphene carbon nanotube dispersion

[0009] Graphene powder and carbon nanotube conductive paste are mixed in a weight ratio of 1:8-10, dispersed in alcohol, and ultrasonically stirred to obtain a graphene carbon nanotube dispersion.

[0010] b. Graphene aluminum alloy mother ingot

[0011] The pure aluminum powder and the graphene carbon nanotube dispersion obtained in step a are mixed in a weight ratio of 3 to 5:1, atomized in a fluorine-containing inert gas atmosphere, sprayed on a substrate at 100 to 200° C., and after spraying a layer evenly, compacted with a roller at 20 to 80° C., and the fluorine- and alcohol-containing gases are recovered; the spraying is repeated, and the graphene aluminum alloy mother ingot is deposited layer by layer;

[0012] c. Aluminum rod extrusion and post-processing

[0013] The graphene aluminum alloy mother ingot is extruded to obtain an aluminum rod, and then stress relief annealing is performed at an annealing temperature of 210 to 350° C. for 4 to 6 hours to obtain a highly conductive graphene aluminum alloy wire.

[0014] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the graphene described in step a is graphene with a carbon content of 98-99wt%.

[0015] Furthermore, the graphene is one of single-layer graphene, double-layer graphene or multi-layer graphene.

[0016] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the carbon nanotube slurry described in step a is a carbon nanotube slurry with a carbon content of ≥5%, an impurity content of 0.2-1%, and an alcohol solvent.

[0017] Furthermore, the carbon nanotubes have a specific surface area of ​​160 to 230 m 2 / g, tube diameter 10~25nm, tube length 10~30μm, density 0.1~0.2g / cm 3 .

[0018] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the weight ratio of the total amount of graphene and carbon nanotube slurry described in step a to alcohol is 1:8-10.

[0019] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the speed of ultrasonic stirring described in step a is 25-50 r / min, and the ultrasonic stirring time is 30-60 min.

[0020] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the substrate described in step b is an aluminum alloy substrate.

[0021] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the iron content in the final aluminum alloy ingot is 0.05-0.5wt%, the carbon content is 0.1-0.5wt%, the copper content is 0.02-0.25wt%, the silicon content is 0.005-0.25wt%, and the balance is aluminum.

[0022] Among them, in the above-mentioned cold-rolling preparation method of high-conductivity graphene aluminum alloy wire, the fluorine-containing inert gas described in step b refers to fluorine-containing nitrogen gas.

[0023] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the aluminum rod described in step c is an aluminum rod with a diameter of 9 to 10 mm.

[0024] Wherein, in the above-mentioned cold-rolled preparation method of highly conductive graphene aluminum alloy wire, the temperature of the aluminum rod obtained by extrusion molding in step c is 400-600°C.

[0025] Among them, in the above-mentioned cold-rolled preparation method of high-conductivity graphene aluminum alloy wire, the heating rate during the stress relief annealing in step c is 10-15°C / min.

[0026] The present invention also provides a highly conductive graphene aluminum alloy wire prepared by the above method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a cold-rolled preparation method for highly conductive graphene aluminum alloy wires. The method uses high-purity graphene powder and carbon nanotube slurry, prepares the two into a dispersion liquid, and then atomizes and sprays the liquid onto a substrate. This method improves the dispersion effect of graphene and carbon nanotubes in the aluminum alloy, significantly improves the conductivity of the graphene aluminum alloy, and can increase the conductivity to 67% IACS. The method can be widely used in data centers, aerospace and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 shows a TEM image of a graphene aluminum alloy conductive wire prepared by the method of the present invention;

[0030] FIG2 shows a TEM image of a graphene aluminum alloy conductive wire produced by the existing melt addition method. DETAILED DESCRIPTION

[0031] The present invention uses high-purity graphene and carbon nanotubes. The carbon content of the graphene is 98-99%, and the carbon content of the carbon nanotube slurry is ≥5%. Both contain less impurity elements, which improves the conductivity of the material.

[0032] At the same time, the present invention adopts a method of adding alcohol for dispersion when dispersing graphene powder and carbon nanotube slurry. The alcohol can volatilize in subsequent processing steps. The volatilized alcohol forms a physical barrier, which can reduce the risk of oxidation.

[0033] At the same time, the present invention adopts a method of atomizing aluminum powder and a dispersion of graphene and carbon nanotubes in a fluorine-containing atmosphere and spraying the atomized aluminum powder and a dispersion of graphene and carbon nanotubes on a substrate to prepare a graphene aluminum alloy conductive wire. By spraying and compacting the graphene and carbon nanotubes layer by layer, the graphene and carbon nanotubes are prepared into a slurry, which is less likely to agglomerate than powders and can be dispersed more evenly, thereby further improving the conductivity of the graphene aluminum alloy conductive wire.

[0034] The present invention adopts a fluorine-containing nitrogen atmosphere, which can generate nano-fluoride AlF3 and nitride AIN with component elements, thereby improving the fatigue performance and wear resistance of the graphene aluminum alloy conductive wire.

[0035] The electrical conductivity of the graphene aluminum alloy conductive wire obtained by the present invention reaches 67% IACS, which is 6% IACS higher than that of electrical aluminum.

[0036] Traditional graphene-aluminum alloys are prepared by melting, where graphene comes into direct contact with the high-temperature aluminum alloy melt, potentially causing burnout. Furthermore, due to its low specific gravity, graphene can only be dispersed within the alloy grains, pinning dislocations and subgrain boundaries. Therefore, traditional graphene addition methods primarily enhance alloy hardness, with limited research on enhancing conductivity. Furthermore, in traditional methods, graphene is dispersed, which can act as electron scattering particles, reducing the alloy's conductivity to a certain extent.

[0037] The present invention uses a special addition method, limits the appropriate ratio of graphene powder, carbon nanotube slurry and aluminum powder, and promotes the formation of an amorphous bonding surface through high-temperature sintering. Graphene + carbon nanotubes overlap inside the alloy to form a second conductive phase. Ultimately, the alloy's conductivity not only exceeds the 61% IACS of pure aluminum, but also increases by 6%, achieving a very significant improvement.

[0038] The specific embodiments of the present invention will be further explained below with reference to the examples, but the protection scope of the present invention is not limited to the scope described in the examples.

[0039] The graphene used in the embodiment has a composition of 98.3% carbon content, 1.5% sulfur content, and 0.2% other impurities.

[0040] The carbon nanotubes used in the examples have the following composition: C content ≥ 99.5%, Co ≤ 650 ppm, Fe ≤ 100 ppm, Cr ≤ 20 ppm, Zn ≤ 20 ppm, Ni ≤ 10 ppm, and Cu ≤ 10 ppm.

[0041] Example 1 Preparation of high-conductivity graphene aluminum alloy wire using the method of the present invention

[0042] The specific experimental steps are as follows:

[0043] a. Preparation of graphene carbon nanotube dispersion

[0044] Weigh 4 g of graphene and 40 g of carbon nanotube slurry, mix them, add them to 750 ml of alcohol, and stir them ultrasonically at 50 rpm for 30 min to obtain a graphene-carbon nanotube dispersion.

[0045] b. Graphene aluminum alloy mother ingot

[0046] 3000g of pure aluminum powder was weighed, mixed with a graphene carbon nanotube dispersion, atomized in a fluorine-containing inert gas atmosphere, and sprayed onto an 80°C substrate. After spraying a uniform layer, a 20°C roller was used to compact the mixture, and the fluorine- and alcohol-containing gases were recovered. The spraying was repeated to form a graphene aluminum alloy mother ingot through layer-by-layer deposition.

[0047] c. Aluminum rod extrusion and post-processing

[0048] The graphene aluminum alloy mother ingot was extruded into an aluminum rod with a diameter of 9.5 mm at 400° C. and subjected to stress relief annealing at a temperature of 230° C. for 6 h to obtain a graphene aluminum alloy conductive wire.

[0049] Example 2 Preparation of Highly Conductive Graphene Aluminum Alloy Wire Using the Method of the Present Invention

[0050] The specific experimental steps are as follows:

[0051] a. Preparation of graphene carbon nanotube dispersion

[0052] Weigh 6 g of graphene and 40 g of carbon nanotube slurry, mix them, add them to 750 ml of alcohol, and stir them ultrasonically at 50 r / min for 30 min to obtain a graphene carbon nanotube dispersion;

[0053] b. Graphene aluminum alloy mother ingot

[0054] 3000g of pure aluminum powder was weighed, mixed with a graphene carbon nanotube dispersion, atomized in an atmosphere of F-containing inert gas, and sprayed onto a substrate at 100°C. After a uniform layer was sprayed, it was compacted with a 20°C roller and the F- and alcohol-containing gases were recovered. The spraying was repeated to form a graphene aluminum alloy mother ingot through layer-by-layer deposition.

[0055] c. Aluminum rod extrusion and post-processing

[0056] The graphene aluminum alloy mother ingot was extruded into an aluminum rod with a diameter of 9.5 mm at 400° C. and subjected to stress relief annealing at a temperature of 270° C. for 5 h to obtain a graphene aluminum alloy conductive wire.

[0057] Example 3 Preparation of Highly Conductive Graphene Aluminum Alloy Wire Using the Method of the Present Invention

[0058] The specific experimental steps are as follows:

[0059] a. Preparation of graphene carbon nanotube dispersion

[0060] Weigh 8 g of graphene and 0 g of carbon nanotube slurry, add them to 790 ml of alcohol, and stir them ultrasonically at 40 r / min for 30 min to obtain a graphene carbon nanotube dispersion;

[0061] b. Graphene aluminum alloy mother ingot

[0062] 3000g of pure aluminum powder was weighed, mixed with a graphene carbon nanotube dispersion, atomized in a fluorine-containing inert gas atmosphere, and sprayed onto a substrate at 100°C. After spraying a uniform layer, a 60°C roller was used to compact the mixture, and the fluorine- and alcohol-containing gases were recovered. The spraying was repeated to form a graphene aluminum alloy mother ingot through layer-by-layer deposition.

[0063] c. Aluminum rod extrusion and post-processing

[0064] The graphene aluminum alloy mother ingot was extruded into an aluminum rod with a diameter of 9.5 mm at 500° C. and subjected to stress relief annealing at a temperature of 270° C. for 4 h to obtain a graphene aluminum alloy conductive wire.

[0065] The TEM image of the graphene aluminum alloy conductive wire prepared in this embodiment is shown in Figure 1. As can be seen from Figure 1, graphene can be observed in the prepared graphene aluminum alloy.

[0066] Comparative Example 1: Graphene aluminum alloy wire is not prepared using the method of the present invention

[0067] The difference from Example 3 is:

[0068] The graphene powder and carbon nanotube slurry are not of high purity. The graphene powder is graphene with a carbon content of 80% and an impurity content of 15%, and the carbon nanotube slurry is a carbon content of 4% and an impurity content of 2%.

[0069] Comparative Example 2: Graphene aluminum alloy wire is not prepared using the method of the present invention

[0070] The difference from Example 3 is that in step a, 40 g of graphene and 10 g of carbon nanotube slurry are used, and in step b, 1950 g of pure aluminum powder is used, and the ratio of graphene to aluminum powder exceeds 2%.

[0071] Comparative Example 3: Graphene aluminum alloy wire is not prepared using the method of the present invention

[0072] The difference from Example 3 is that the atomization and spraying methods are not adopted, and the melt addition method is adopted.

[0073] The specific operation steps are as follows: 1950g of melt is blown into the aluminum alloy melt using nitrogen under inert gas protection. The melt is then electromagnetically stirred for 30 minutes and cast into an aluminum ingot. After cooling to 400°C, the ingot is extruded into an aluminum alloy wire with a diameter of 9-10mm.

[0074] The TEM image of the graphene aluminum alloy conductive wire prepared in this embodiment is shown in Figure 2. As can be seen from Figure 2, no graphene is observed in the prepared graphene aluminum alloy.

[0075] Comparative Example 4: Graphene aluminum alloy wire is not prepared using the method of the present invention

[0076] The difference from Example 3 is that no fluorine-containing inert gas is added.

[0077] The conductivity, elongation, and fatigue limit tests of the graphene aluminum alloy conductive wires obtained in the examples and comparative examples were performed. The test methods adopted were the methods in GB / T351-2019, GB / T 10120-2013, and GB / T 15248-2008, respectively. The results are shown in Table 1 below.

[0078] Table 1 Properties of graphene aluminum alloy conductive wires prepared by different methods Conductivity (% IACS) Elongation (%) Fatigue limit (MPa) Example 1 67.0 25.8 86 Example 2 66.8 26.3 85 Example 3 64 3090 Comparative Example 1 50 2079 Comparative Example 2 60.7 3078 Comparative Example 3 59 4292 Comparative Example 4 62.8 2762

[0079] It can be seen from the examples and comparative examples that the method of the present invention can overlap with each other to form a second conductive phase, thereby improving the conductivity of the alloy. The graphene aluminum alloy conductive wire prepared by the present invention reaches 67% IACS, which greatly broadens the application range of the graphene aluminum alloy conductive wire and has good application prospects.

Claims

1. A method for preparing a highly conductive graphene aluminum alloy wire by cold rolling, characterized in that: The following steps are involved: a. Preparation of graphene carbon nanotube dispersion The graphene powder and the carbon nanotube conductive slurry are mixed in a weight ratio of 1:8-10, dispersed in alcohol, and ultrasonically stirred to obtain a graphene carbon nanotube dispersion; The graphene described in step a is graphene with a carbon content of 98-99wt%; The carbon nanotube slurry described in step a is a carbon nanotube slurry with a carbon content of ≥5%, an impurity content of 0.2-1%, and an alcohol solvent; b. Graphene aluminum alloy master ingot The pure aluminum powder and the graphene carbon nanotube dispersion obtained in step a are mixed in a weight ratio of 3 to 5:1, atomized in a fluorine-containing inert gas atmosphere, sprayed on a substrate at 100 to 200° C., and after spraying a layer evenly, compacted with a 20 to 80° C. roller, and the fluorine- and alcohol-containing gases are recovered; the spraying is repeated, and the graphene aluminum alloy mother ingot is deposited layer by layer; c. Aluminum rod extrusion and post-processing The graphene aluminum alloy mother ingot is extruded at 400-600° C. to obtain an aluminum rod, and stress relief annealing is performed at a temperature of 210-350° C. for 4-6 hours to obtain a highly conductive graphene aluminum alloy wire.

2. The method for preparing a highly conductive graphene aluminum alloy wire by cold rolling according to claim 1, characterized in that: The graphene is one of single-layer graphene, double-layer graphene or multi-layer graphene.

3. The cold-rolling method for preparing a highly conductive graphene aluminum alloy wire according to claim 1, characterized in that: The specific surface area of ​​the carbon nanotubes is 160 to 230 m 2 / g, tube diameter 10~25nm, tube length 10~30μm, density 0.1~0.2g / cm 3 .

4. The method for preparing a highly conductive graphene aluminum alloy wire by cold rolling according to claim 1, characterized in that: The weight ratio of the total amount of graphene and carbon nanotube slurry to alcohol described in step a is 1:8-10.

5. The method for preparing a highly conductive graphene aluminum alloy wire by cold rolling according to claim 1, characterized in that: The speed of the ultrasonic stirring in step a is 25 to 50 r / min, and the ultrasonic stirring time is 30 to 60 min.

6. The method for preparing a highly conductive graphene aluminum alloy wire by cold rolling according to claim 1, characterized in that: The heating rate during the stress relief annealing in step c is 10-15°C / min.

7. A highly conductive graphene aluminum alloy wire prepared by the cold-rolling preparation method of a highly conductive graphene aluminum alloy wire according to any one of claims 1 to 6.

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