A copper graphene composite material and a preparation method thereof

Abstract

The present application relates to the field of composite materials, and particularly relates to a copper graphene composite material and a preparation method thereof.The present application provides a preparation method of the copper graphene composite material, which comprises the following steps: S1, expanding and deforming a copper pipe into a tapered pipe; S2, applying a graphene slurry to the inner and outer surfaces of the tapered pipe, and drying to obtain a tapered pipe with a graphene coating; S3, taking a plurality of the tapered pipes with the graphene coating obtained in step S2, stacking the pipes, and then rotating and rubbing the pipes to weld the pipes; and S4, extruding the welded pipes in step S3 into a block material, and then stirring and rotating the block material to obtain the copper graphene composite material.The method can simultaneously achieve the effects of high content and high dispersity of graphene.

Description

Technical Field

[0001] This invention relates to the field of composite materials, and in particular to a copper-graphene composite material and its preparation method. Background Technology

[0002] Numerous studies have shown that the addition of graphene improves the electrical, thermal, and tribological properties of copper. Currently reported copper-graphene composites are prepared by CVD graphene on copper foil or by hot-pressing and solidifying copper foil coated with graphene. The amount of graphene added is significantly affected by the thickness of the copper foil. Graphene, being a single-layer or few-layer carbon atom structure, has a nanometer-scale thickness far lower than the micrometer-scale thickness of copper foil. Therefore, the actual graphene content in the materials obtained by this process is relatively low. Furthermore, the temperature used in the hot-pressing process is far below the melting point of copper, while graphene maintains chemical stability at high temperatures. The hot-pressing temperature cannot destroy the graphene structure to generate a large number of free carbon atoms. Moreover, in the solid state, carbon atoms in the copper lattice undergo only a very small amount of interstitial solid solution, resulting in high lattice distortion energy. At this temperature, solid solution, diffusion, precipitation, and growth are greatly hindered, and the graphene structure is stably locked in the interlayer positions of the copper foil. These material and process properties severely restrict further improvements in the dispersion and content of graphene in the composite material. Therefore, due to the limitations of current industry-standard processes, the graphene content in graphene-copper composite materials is low and the dispersion is poor, which restricts their further application.

[0003] Stirring and swirl extrusion is a process that mixes materials through rotation and frictional heat. It has been used in the preparation of low-melting-point materials such as aluminum-based composites. The rotating and pushing action of the stirring head promotes the homogenization of additives in aluminum and the densification of the composite material. The temperature range of this process is near the melting point of the base metal. It is typically applied in the semi-solid region of aluminum alloys, and the stirring head, die cavity, and other process equipment are made of hot-work die steel or high-temperature alloys. Copper does not have a semi-solid region and exhibits high fluidity near its melting point, making it unable to effectively shear, peel, break up, and disperse graphene agglomerates. Furthermore, copper's melting point is much higher than that of aluminum and aluminum alloys. The temperature generated by prolonged stirring and swirl extrusion exceeds the thermal creep temperature of hot-work die steel and high-temperature alloys, causing deformation, cracking, and failure, thus failing to effectively ensure the material preparation process.

[0004] In addition, if the copper-based graphene composite material is prepared by friction stir processing, the following problems exist: (1) The graphene dispersion is very poor when the copper-based graphene composite material is prepared by single-pass friction stir processing. Therefore, a multi-pass processing process is required to improve it. However, the multi-pass process will destroy the structure of graphene, which limits the improvement of graphene performance of the process; (2) The plate itself will produce flash and burrs after friction stir processing. The processing area is firstly related to the geometric size of the stirring head. Therefore, the processed plate needs to be turned twice to make a working blank for subsequent processing; (3) Due to the characteristics of the process itself, the stirring head cannot directly touch the bottom of the pad supporting the plate to be processed. This results in a certain processing vacuum area below the processing weld nugget area. The stirring process is asymmetrical, which makes the graphene in the final composite material have obvious regional uneven distribution. Summary of the Invention

[0005] In view of this, the present invention provides a graphene-copper composite material and a method for preparing the same. The method for preparing the graphene-copper composite material provided by the present invention can simultaneously achieve high graphene content and high dispersibility.

[0006] This invention provides a method for preparing a copper-graphene composite material, comprising the following steps:

[0007] S1. Expand and deform the copper tube into a tapered tube;

[0008] S2. Apply graphene slurry to the inner and outer surfaces of the conical tube and dry it to obtain a conical tube with a graphene coating.

[0009] S3. Take several tapered tubes with graphene coating obtained in step S2, stack them together, and then perform rotational friction to weld the tapered tubes together.

[0010] S4. The conical tube welded in step S3 is extruded into a block material, and then stirred and spun to obtain a copper-graphene composite material.

[0011] Preferably, in step S1:

[0012] The taper of the tapered tube is 0.3° to 10°;

[0013] The wall thickness of the copper tube is 0.5~2mm.

[0014] Preferably, in step S3, the number of tapered tubes with graphene coating is 5 to 10.

[0015] The selected tapered tubes with graphene coating have the same taper; the selected tapered tubes with graphene coating have the same wall thickness.

[0016] Preferably, in step S3, the rotational speed of the rotary friction is 400~1200 r / min; the rotary friction is stopped when the temperature of the outermost conical tube reaches 1120±10℃.

[0017] Preferably, in step S4, the stirring head of the stirring swirl extruder rotates at a speed of 500~1000 r / min; the feeding speed of the stirring swirl extruder is 13~28 g / min.

[0018] Preferably, in step S2, the graphene slurry comprises graphene and a dispersion medium; wherein the dispersion medium is an organic solvent; and the concentration of the graphene slurry is 0.01~0.1 g / mol.

[0019] Preferably, in step S2, the drying temperature is 60~100℃ and the time is 15~45min; the drying is vacuum drying.

[0020] Preferably, in step S3, the rotational friction includes: nesting the innermost conical tube on the rotating shaft, clamping and fixing the outermost conical tube, and rotating the rotating shaft;

[0021] In step S4, the stirring and spun extrusion includes: feeding the block material into the stirring and spun extrusion die cavity, and turning on the stirring head to rotate and push out the copper graphene composite material.

[0022] Preferably, in step S2, the graphene slurry is applied to the inner and outer surfaces of the conical tube by immersing the conical tube in the graphene slurry, thereby attaching the graphene slurry to the inner and outer surfaces of the conical tube.

[0023] In step S2, before applying the graphene slurry, the oxide scale and inclusions on the inner and outer surfaces of the conical tube are removed.

[0024] The present invention also provides a copper-graphene composite material, which is prepared by the preparation method described in the above technical solution;

[0025] The graphene content in the copper-graphene composite material is ≥0.1wt%.

[0026] The method for preparing copper-graphene composite material provided by this invention is a graphene dispersion and material composite forming process based on a two-stage rotational friction method, in order to improve the amount of graphene added and the dispersion uniformity. Initially, copper tubes are expanded into copper cone tubes, and then several copper cone tubes are stacked to obtain a composite material to be processed. This composite material is then subjected to two-stage rotary friction. Specifically, firstly, low-speed rotary friction is applied to the stacked copper cones. At low speed, the solid outer copper cone inner surface and the inner copper cone outer surface continuously grind the graphene coating between the layers, causing interlayer separation, intralayer breakage, and macroscopic dispersion of its molecules. When the heat accumulation generated by the rotary friction causes the copper substrate to reach its melting point, the interface between the inner and outer copper cones achieves large-area welding, and a transition in graphene distribution concentration appears from the center of the interface to both sides. Then, the copper-graphene composite material obtained from the low-speed rotary friction is fed into a mixing and rotary extrusion equipment as raw material. At high rotation speed, the material is further mixed by rotation. A relatively short rotation time allows for the uniform dispersion of a large amount of graphene in the copper and the output as copper-graphene rods. Furthermore, the temperature rise from the short-term friction accumulation is insufficient to cause the mixing head and mold cavity to reach the material's thermal creep temperature, effectively ensuring equipment lifespan and production continuity. Therefore, the method of the present invention can realize the preparation of copper graphene materials, which has the advantages of high graphene content, good dispersion uniformity, fast preparation speed and low process cost. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0028] Figure 1 This is a process flow diagram of the present invention;

[0029] Figure 2 Metallographic test images of the products obtained in Example 1 and Comparative Example 1; wherein, Figure 2 (a) is a metallographic image of the graphene-copper composite material obtained by the stirring spin extrusion method in Comparative Example 1. Figure 2 (b) is a metallographic image of the graphene-copper composite material obtained by the two-stage rotational friction method in Example 1;

[0030] Figure 3 The image shows the Raman spectrum of the product obtained in Example 1. Detailed Implementation

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0032] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0033] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0034] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0035] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 0.5~2mm means that the units for the left endpoint "0.5" and the right endpoint "2" are both mm.

[0036] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0037] This invention provides a method for preparing a copper-graphene composite material, comprising the following steps:

[0038] S1. Expand and deform the copper tube into a tapered tube;

[0039] S2. Apply graphene slurry to the inner and outer surfaces of the conical tube and dry it to obtain a conical tube with a graphene coating.

[0040] S3. Take several tapered tubes with graphene coating obtained in step S2, stack them together, and then perform rotational friction to weld the tapered tubes together.

[0041] S4. The conical tube welded in step S3 is extruded into a block material, and then stirred and spun to obtain a copper-graphene composite material.

[0042] See Figure 1 , Figure 1 This is a process flow diagram of the present invention. The present invention is a process combination method for preparing high graphene content copper composite materials based on a two-stage rotary friction method, particularly employing a conical tube approach and a further implementation of a nested rotary friction method utilizing the characteristics of the conical tube. This achieves both initial dispersion of graphene and welding consolidation of the material. Subsequent stirring and spin extrusion, through the two-stage rotary friction method, enables the preparation of high graphene content copper composite materials. Furthermore, the process boasts advantages in cost and manufacturing efficiency, and possesses industrial-scale application potential.

[0043] Regarding step S1 :

[0044] S1. Expand and deform the copper tube into a tapered tube.

[0045] In this invention, the wall thickness of the copper tube is preferably 0.5~2mm, specifically 0.5mm, 1mm, 1.5mm, 2mm, etc.

[0046] In this invention, the preferred method of expansion and extrusion is to use a hard mandrel with a tapered angle to expand and deform the copper tube into a tapered tube. The hard mandrel can be a high-strength cemented carbide mandrel.

[0047] In this invention, the taper of the tapered tube obtained after expansion and extrusion is preferably 0.3°~10°, specifically 0.3°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, etc. In subsequent stages, the shear stress of the downward tip force of the rotating shaft is used as the welding friction pressure. If the taper is too small, it cannot provide shear stress; if the taper is too large, it will lead to excessive shear stress and excessive heat input, which will cause the graphene in the material to break down and mix prematurely, which is not conducive to the final performance of the material. This invention controls the taper within the above range, which can achieve effective metallurgical bonding and welding between the expanded and extruded copper tubes, and will not cause the graphene in the material to break down and mix prematurely, thereby improving the final performance of the material.

[0048] Regarding step S2 :

[0049] S2. Apply graphene slurry to the inner and outer surfaces of the conical tube and dry it to obtain a conical tube with a graphene coating.

[0050] In this invention, preferably, the inner and outer surfaces of the conical tube are cleaned before applying the graphene slurry; specifically, oxide scale and inclusions are removed from the inner and outer surfaces of the conical tube. The preferred cleaning method is to degrease the conical tube with a weakly alkaline solution, then remove the oxide scale with a weakly acidic solution, followed by ultrasonic cleaning in water. There are no special limitations on the acid or alkaline solutions used for degreasing and oxide scale removal; any conventional cleaning agents in the art are acceptable. The water is preferably deionized water.

[0051] In this invention, preferably, the graphene slurry comprises graphene and a dispersion medium. The dispersion medium is preferably an organic solvent, more preferably ethanol. In this invention, the concentration of the graphene slurry is preferably 0.01~0.1 g / mol, specifically 0.01 g / mol, 0.02 g / mol, 0.03 g / mol, 0.04 g / mol, 0.05 g / mol, 0.06 g / mol, 0.07 g / mol, 0.08 g / mol, 0.09 g / mol, 0.1 g / mol, etc., more preferably 0.05 g / mol.

[0052] In this invention, the preferred method for applying graphene slurry to the inner and outer surfaces of the conical tube is to immerse the conical tube in the graphene slurry, thereby adhering the graphene slurry to the inner and outer surfaces of the conical tube. The preferred immersion time of the conical tube in the graphene slurry is 60-120 minutes, specifically 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes, etc. Afterwards, the conical tube is removed and dried.

[0053] In this invention, the drying temperature is preferably 60~100℃, specifically 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, etc., more preferably 80℃. The drying time is preferably 15~45min, specifically 15min, 20min, 25min, 30min, 35min, 40min, 45min, etc., more preferably 30min. In this invention, the drying is preferably vacuum drying, that is, maintaining a vacuum during the heating and drying process. In this invention, the drying can be carried out in a tube vacuum furnace. Through drying, the dispersion medium in the slurry decomposes and volatilizes upon heating, and the graphene powder particles adhere to the surface of the conical tube, resulting in a conical tube with a graphene coating.

[0054] Regarding step S3 :

[0055] S3. Take several tapered tubes with graphene coating obtained in step S2, stack them together, and then perform rotational friction to weld the tapered tubes together.

[0056] In this invention, the preferred number of graphene-coated conical tubes is 5 to 10, specifically 5, 6, 7, 8, 9, or 10. Preferably, the taper of the selected graphene-coated conical tubes is the same. Preferably, the wall thickness of the selected graphene-coated conical tubes is the same. Other dimensions, such as length, are not strictly required.

[0057] In this invention, after taking several conical tubes with graphene coating obtained in step S2, the conical tubes are stacked together, that is, the conical tubes are stacked together in the same direction. Specifically, the conical corners are stacked together in sequence so that the inner and outer surfaces of the conical tubes are sequentially attached.

[0058] In this invention, after the aforementioned nesting, rotational friction is performed. The rotational friction includes: nesting the innermost conical tube onto a rotating shaft, clamping and fixing the outermost conical tube, and rotating the rotating shaft. In this invention, graphene is dispersed and diffused through rotational friction, and the accumulated frictional heat welds the inner and outer conical tubes together. Specifically, during the rotational friction process, at a certain rotational speed, the inner conical tube rotates relative to the outer conical tube, causing continuous friction between the tube walls of the graphene, resulting in interlayer delamination, intralayer breakage, and macroscopic dispersion. The friction continuously generates heat, welding the inner and outer conical tubes together. In this invention, the rotational speed of the rotational friction is preferably 400~1200 r / min, specifically 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, 1100 r / min, 1200 r / min, etc., more preferably 800 r / min.

[0059] In this invention, preferably, the rotational friction is stopped when the temperature of the outermost conical tube reaches 1120±10℃; the specific temperature can be 1110℃, 1115℃, 1120℃, 1125℃, 1130℃, etc. After stopping the rotational friction, the part is removed to obtain the welded conical tube.

[0060] Regarding step S4 :

[0061] S4. The conical tube welded in step S3 is extruded into a block material, and then stirred and spun to obtain a copper-graphene composite material.

[0062] In this invention, the extrusion method is preferably a plastic deformation method such as roll forming. The tapered tube welded in step S3 is deformed into a block material by extrusion.

[0063] In this invention, after the above-mentioned extrusion, a stirring and spinning process is performed, that is, the bulk material is used as the ingot for stirring and spinning. In this invention, the stirring and spinning process includes: feeding the bulk material into the stirring and spinning die cavity, and starting the stirring head to rotate, pushing out the copper-graphene composite material. In this invention, the stirring head rotation speed is preferably 500~1000 r / min, specifically 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, etc., more preferably 700 r / min. In this invention, the feed rate of the stirring and spinning extrusion is preferably 13~28 g / min, more preferably 13.6~27.2 g / min, specifically 13.6 g / min, 14 g / min, 15 g / min, 16 g / min, 17 g / min, 18 g / min, 19 g / min, 20 g / min, 21 g / min, 22 g / min, 23 g / min, 24 g / min, 25 g / min, 26 g / min, 27 g / min, etc., and more preferably 20 g / min. Through stirring and spinning, the uniformity of graphene dispersion is further improved by mixing at high speed, and compacted graphene copper rods are extruded, thus obtaining a copper-graphene composite material.

[0064] Secondly, this invention also provides a copper-graphene composite material, prepared by the method described in the above technical solution. In this invention, the graphene content of the copper-graphene composite material is ≥0.1wt%, which can be ≥0.2wt%, ≥0.3wt%, ≥0.4wt%, ≥0.5wt%, and more specifically 0.1wt%~0.6wt%, achieving a high graphene content and good graphene dispersion uniformity. That is, this invention simultaneously achieves high graphene content and high dispersion characteristics. In the copper-graphene composite material obtained by this invention, the graphene sheet structure is more complete, with fewer layers and more uniform sheets. Therefore, compared with the prior art, the different method of this invention increases the graphene content in the obtained copper-graphene composite material, and the microscopic distribution of graphene is also different from the prior art, resulting in a different composition and microstructure of the composite material. The high-graphene-content copper composite material obtained by this invention can be formed into various desired shapes through various plastic processing methods without significantly changing its achieved high graphene content and high dispersion characteristics.

[0065] The method for preparing copper-graphene composite material provided by this invention is a graphene dispersion and material composite forming process based on a two-stage rotational friction method, in order to improve the amount of graphene added and the uniformity of dispersion. Initially, copper tubes are expanded into copper cone tubes, and then several copper cone tubes are stacked to obtain a composite material to be processed. This composite material is then subjected to two-stage rotary friction. Specifically, firstly, low-speed rotary friction is applied to the stacked copper cones. At low speed, the solid outer copper cone inner surface and the inner copper cone outer surface continuously grind the graphene coating between the layers, causing interlayer separation, intralayer breakage, and macroscopic dispersion of its molecules. When the heat accumulation generated by the rotary friction causes the copper substrate to reach its melting point, the interface between the inner and outer copper cones achieves large-area welding, and a transition in graphene distribution concentration appears from the center of the interface to both sides. Then, the copper-graphene composite material obtained from the low-speed rotary friction is fed into a mixing and rotary extrusion equipment as raw material. At high rotation speed, the material is further mixed by rotation. A relatively short rotation time allows for the uniform dispersion of a large amount of graphene in the copper and the output as copper-graphene rods. Furthermore, the temperature rise from the short-term friction accumulation is insufficient to cause the mixing head and mold cavity to reach the material's thermal creep temperature, effectively ensuring equipment lifespan and production continuity. Therefore, the method of this invention can realize the preparation of copper graphene materials, possessing the advantages of high graphene content, good dispersion uniformity, fast preparation speed, and low process cost. In the prior art, the preparation of copper-based graphene composite materials using friction stirring requires multiple processes, while this invention only requires two stages of rotational friction to achieve uniform graphene dispersion. In the prior art, the processed plates require secondary turning to add working blanks for subsequent processing; however, the material produced by this invention can significantly reduce process costs. Furthermore, the graphene in the composite materials obtained in the prior art exhibits obvious regional uneven distribution, while this invention greatly improves the dispersion uniformity of graphene.

[0066] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0067] Example 1

[0068] S1. A hard mandrel with a tapered angle is used to expand and deform a copper tube (1mm wall thickness) into a tapered tube (5° taper).

[0069] S2. The conical tube is degreased with a weakly alkaline solution, then descaled with a weakly acidic solution, followed by ultrasonic cleaning in deionized water. Next, the cleaned conical tube is immersed in a graphene slurry (a mixture of graphene and ethanol, concentration 0.05 g / mol) for 60 minutes, allowing the graphene slurry to adhere to both the inner and outer surfaces of the tube. Then, the conical tube is removed and placed in a tube vacuum furnace, dried at 80°C for 30 minutes while maintaining a vacuum, thus obtaining a conical tube with a graphene coating.

[0070] S3. Take five graphene-coated conical tubes (with the same taper and wall thickness) obtained in step S2 and stack them together. Then, nest the innermost conical tube on the rotating shaft, clamp and fix the outermost conical tube, and perform rotational friction at a speed of 800 r / min. When the temperature of the outermost conical tube reaches 1120℃, stop the rotational friction to obtain a welded conical tube.

[0071] S4. The conical tube welded in step S3 is deformed into a block material by roller pressing. The block material is fed into the mixing and spun die cavity, and the mixing head is turned on to rotate at a speed of 700 r / min and a feeding speed of 20 g / min, thereby extruding a compacted graphene copper rod.

[0072] Comparative Example 1

[0073] The stirring spin extrusion method was adopted: pure copper rods were prepared, and graphene slurry was pre-added after blind holes were made in the rods. The rods were heated in a tube vacuum furnace, and a vacuum was maintained throughout the heating process. The ethanol in the slurry was decomposed by heat and evaporated. Then, the graphene copper rods were extruded through the stirring spin extrusion process. The copper rod material, graphene slurry, heating and drying conditions, and stirring spin extrusion conditions were all the same as in Example 1.

[0074] Product Testing :

[0075] (1) Metallographic testing:

[0076] Metallographic tests were performed on the products obtained in Example 1 and Comparative Example 1, respectively, and the results are as follows: Figure 2 As shown, where, Figure 2 (a) is a metallographic image of the graphene-copper composite material obtained by the stirring spin extrusion method in Comparative Example 1. Figure 2 (b) is a metallographic image of the graphene-copper composite material obtained by the two-stage rotational friction method in Example 1. Figure 2 (a) It can be seen that the composite material prepared by the direct stirring spin extrusion process contains a large number of complete, sheet-like black contrast regions. This indicates that the effect of achieving interlayer exfoliation and uniform dispersion of graphene within the pure copper matrix through the simple stirring spin extrusion process is not ideal, and there is a significant tendency for graphene agglomeration. Figure 2(b) In the two-stage spin extrusion friction material, the problem of uneven distribution and excessive size of this black precipitate region has been significantly improved, proving that the method of the present invention greatly improves the dispersion uniformity of graphene.

[0077] (2) Raman test:

[0078] Raman spectroscopy was performed on the graphene-copper composite material obtained in Example 1, and the results are as follows: Figure 3 As shown in the Raman spectroscopy, three main characteristic peaks were observed for graphite and graphene-like materials: the D peak, the G peak, and the 2D peak. The D peak, located at approximately 1350 cm⁻¹, is a characteristic peak of multilayer graphene. -1 The 2D peak is associated with defects in graphene, including vacancies, substituents, or impurities in carbon atoms. The presence of these defects disrupts the periodic structure of graphene, leading to reduced conductivity. In Raman spectroscopy, the intensity of the 2D peak is typically used to assess the uniformity of multilayer graphene, while a higher 2D peak indicates fewer graphene layers. Graphene I in Example 1... 2D / I G Approximately 0.45, while I D / I G The value is approximately 0.24, indicating that the graphene structure in the material obtained by this invention is relatively complete with fewer layers, which is beneficial for graphene to serve as a complete and good reinforcement for composite materials.

[0079] (3) Graphene content test:

[0080] The amount of graphene added was determined by carbon element analysis of the composite materials obtained in Example 1 and Comparative Example 1 using a carbon-sulfur analyzer. The carbon content of both Example 1 and Comparative Example 1 was 0.2~0.4 wt%.

[0081] (4) Conductivity test:

[0082] Conductivity tests were conducted on the composite materials obtained in Example 1 and Comparative Example 1, respectively. The results showed that the conductivity of the composite material obtained in Example 1 was 105% IACS, while the conductivity of the composite material obtained in Comparative Example 1 was only 95% IACS. This demonstrates that the composite material obtained in this invention has improved conductivity compared to Comparative Example 1.

[0083] Example 2

[0084] S1. A copper tube (wall thickness 0.5mm) is expanded and deformed into a tapered tube (taper 0.3°) using a hard core mold with a tapered angle.

[0085] S2. The conical tube is degreased with a weakly alkaline solution, then descaled with a weakly acidic solution, followed by ultrasonic cleaning in deionized water. Next, the cleaned conical tube is immersed in a graphene slurry (a mixture of graphene and ethanol, concentration 0.01 g / mol) for 60 minutes, allowing the graphene slurry to adhere to both the inner and outer surfaces of the tube. Then, the conical tube is removed and placed in a tube vacuum furnace, dried at 60°C for 45 minutes while maintaining a vacuum, thus obtaining a conical tube with a graphene coating.

[0086] S3. Take seven tapered tubes with graphene coating obtained in step S2 (with the same taper and wall thickness) and stack them together. Then, nest the innermost tapered tube on the rotating shaft, clamp and fix the outermost tapered tube, and perform rotational friction at a speed of 400 r / min. When the temperature of the outermost tapered tube reaches 1110℃, stop the rotational friction to obtain the welded tapered tube.

[0087] S4. The conical tube welded in step S3 is deformed into a block material by roller pressing. The block material is fed into the mixing and spun die cavity, and the mixing head is turned on to rotate at a speed of 500 r / min and a feeding speed of 14 g / min, thereby extruding a compacted graphene copper rod.

[0088] The graphene-copper composite material obtained in Example 2 was tested according to the aforementioned testing method, and the results are as follows: Metallographic results show that the problems of uneven distribution and excessively large size of the black precipitate area have been improved, proving that the method of the present invention improves the dispersion uniformity of graphene. Raman test results show I D / I G Approximately 0.2, while I 2D / I G The value is approximately 0.7, indicating that the graphene structure in the material obtained by this invention is relatively complete with fewer layers, which is beneficial for graphene as a complete and good reinforcement in composite materials. The graphene content result shows 0.26 wt%, proving that this invention achieves a high graphene content. The conductivity result shows 102% IACS, proving that the method of this invention improves conductivity.

[0089] Example 3

[0090] S1. A hard mandrel with a tapered angle is used to expand and deform the copper tube (wall thickness 2mm) into a tapered tube (taper 10°).

[0091] S2. The conical tube is degreased with a weak alkaline solution, then descaled with a weak acidic solution, followed by ultrasonic cleaning in deionized water. Next, the cleaned conical tube is immersed in a graphene slurry (a mixture of graphene and ethanol, concentration 0.1 g / mol) for 60 minutes, allowing the graphene slurry to adhere to both the inner and outer surfaces of the tube. Then, the conical tube is removed and placed in a tube vacuum furnace, dried at 100°C for 15 minutes while maintaining a vacuum, thus obtaining a conical tube with a graphene coating.

[0092] S3. Take 10 tapered tubes with graphene coating obtained in step S2 (with the same taper and wall thickness) and stack them together. Then, nest the innermost tapered tube on the rotating shaft, clamp and fix the outermost tapered tube, and perform rotational friction at a speed of 1200 r / min. When the temperature of the outermost tapered tube reaches 1120℃, stop the rotational friction to obtain the welded tapered tube.

[0093] S4. The conical tube welded in step S3 is deformed into a block material by roller pressing. The block material is fed into the mixing and spun die cavity, and the mixing head is turned on to rotate at a speed of 1000 r / min and a feeding speed of 28 g / min, thereby extruding a compacted graphene copper rod.

[0094] The graphene-copper composite material obtained in Example 3 was tested according to the aforementioned testing method, and the results are as follows: Metallographic results show that the problems of uneven distribution and excessively large size of the black precipitate area have been improved, proving that the method of the present invention improves the dispersion uniformity of graphene. Raman test results show I D / I G Approximately 0.32, while I 2D / I G The value is approximately 0.65, indicating that the graphene structure in the material obtained by this invention is relatively complete with fewer layers, which is beneficial for graphene as a complete and good reinforcement in composite materials. The graphene content result shows 0.45 wt%, proving that this invention achieves a high graphene content. The conductivity result shows 100% IACS, proving that the method of this invention improves conductivity.

[0095] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing a copper-graphene composite material, characterized in that, Includes the following steps: S1. Expand and deform the copper tube into a tapered tube; S2. Apply graphene slurry to the inner and outer surfaces of the conical tube and dry it to obtain a conical tube with a graphene coating. S3. Take several tapered tubes with graphene coating obtained in step S2, stack them together, and then perform rotational friction to weld the tapered tubes together. S4. The conical tube welded in step S3 is extruded into a block material, and then stirred and spun to obtain a copper-graphene composite material.

2. The preparation method according to claim 1, characterized in that, In step S1: The taper of the tapered tube is 0.3° to 10°; The wall thickness of the copper tube is 0.5~2mm.

3. The preparation method according to claim 1, characterized in that, In step S3, the number of tapered tubes with graphene coating taken is 5 to 10; The selected tapered tubes with graphene coating have the same taper; the selected tapered tubes with graphene coating have the same wall thickness.

4. The preparation method according to claim 1, characterized in that, In step S3, the rotational speed of the rotary friction is 400~1200 r / min; when the temperature of the outermost conical tube reaches 1120±10℃, the rotary friction is stopped.

5. The preparation method according to claim 1, characterized in that, In step S4, the stirring head of the stirring swirl extruder rotates at a speed of 500~1000 r / min; the feeding speed of the stirring swirl extruder is 13~28 g / min.

6. The preparation method according to claim 1, characterized in that, In step S2, the graphene slurry comprises graphene and a dispersion medium; wherein the dispersion medium is an organic solvent; and the concentration of the graphene slurry is 0.01~0.1 g / mol.

7. The preparation method according to claim 1, characterized in that, In step S2, the drying temperature is 60~100℃ and the time is 15~45min; the drying is vacuum drying.

8. The preparation method according to claim 1, characterized in that, In step S3, the rotational friction includes: nesting the innermost conical tube on the rotating shaft, clamping and fixing the outermost conical tube, and rotating the rotating shaft; In step S4, the stirring and spun extrusion includes: feeding the block material into the stirring and spun extrusion die cavity, and turning on the stirring head to rotate and push out the copper graphene composite material.

9. The preparation method according to claim 1, characterized in that, In step S2, the graphene slurry is applied to the inner and outer surfaces of the conical tube by immersing the conical tube in the graphene slurry, thereby attaching the graphene slurry to the inner and outer surfaces of the conical tube. In step S2, before applying the graphene slurry, the oxide scale and inclusions on the inner and outer surfaces of the conical tube are removed.

10. A copper-graphene composite material, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9; The graphene content in the copper-graphene composite material is ≥0.1wt%.

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