A graphene fiber bundle and a method for preparing the same

Abstract

This invention provides graphene fibers, graphene fiber bundles, and a method for preparing the same. The graphene fiber bundle has a core-sheath structure, with a polyacrylonitrile fiber as the inner core and a graphene layer as the sheath layer. The graphene fiber bundle is assembled from the graphene fibers. The method for preparing the graphene fiber bundle includes the following steps: electrospinning using a polyacrylonitrile solution as the spinning solution and a graphene oxide solution as the collecting bath to obtain graphene oxide composite fibers; and sequentially subjecting the graphene oxide composite fibers to pre-oxidation, carbonization, and graphitization treatments to obtain the graphene fiber bundle. The graphene fiber bundle of this invention is a graphene fiber bundle with a highly oriented and well-stacked nanofiber bundle structure, and possesses excellent electrical conductivity and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of high-strength graphene fiber bundle technology, specifically to a graphene fiber bundle and its preparation method, particularly to a graphene fiber bundle with a core-sheath structure, and a method for preparing graphene fiber bundles by water bath electrospinning. Background Technology

[0002] Graphene fiber bundles, as a novel type of carbon fiber, are one-dimensional continuous assembly materials composed of single graphene sheets arranged in a tightly ordered manner along the axial direction. Unlike traditional carbon fibers, graphene fiber bundles are directly and orderly assembled from large-sized graphene sheets. Benefiting from the excellent physical and chemical properties of graphene itself, its mechanical strength, electrical conductivity, and thermal conductivity are expected to break through the performance limits of traditional carbon fibers, making it a new generation of structural and functional integrated fibers.

[0003] The main method for preparing graphene fiber bundles currently involves using graphene oxide as a precursor material and drawing upon traditional fiber preparation methods, such as wet spinning, dry spinning, and dry-jet wet spinning, followed by a reduction process to obtain graphene fiber bundles. Alternatively, one-dimensional graphene fiber bundles can be obtained by twisting two-dimensional graphene films and performing topological transformations. While the mainstream wet spinning method is simple to operate and easy to mass-produce, it faces challenges in achieving a regular arrangement and high density of graphene sheets. These challenges include difficulty in controlling the alignment and orientation of graphene sheets within the fiber during wet spinning, voids and defects introduced by the double diffusion process during solidification, and chaotic wrinkles caused by significant volume shrinkage during drying. This severely hinders the transfer of the superior microscopic properties of graphene to macroscopic fiber materials, greatly impacting the application of graphene fiber bundles and their composites.

[0004] Currently, optimizing the microstructure of graphene and regulating the regular arrangement of graphene sheets to improve their orientation and density has become the main technical bottleneck in the preparation of graphene fiber bundles.

[0005] CN107475793A discloses a graphene oxide-encapsulated polyacrylonitrile composite nanofiber. The steps are as follows: (1) preparing an N,N-dimethylformamide dispersion of graphene oxide; (2) adding polyacrylonitrile precursor fibers to the solution in step (1) to obtain an electrospinning solution; (3) performing electrospinning using the electrospinning solution obtained in step (2), and drying the collected nanofibers to obtain graphene oxide-encapsulated polyacrylonitrile composite nanofiber. In this method, graphene oxide and polyacrylonitrile are directly mixed to prepare the spinning solution. This method can only encapsulate graphene oxide inside the fiber, but cannot attach a graphene layer to the surface of the polyacrylonitrile fiber to form a graphene layer.

[0006] CN108335917A discloses a method for preparing carbon nanofiber-supported ordered reduced graphene oxide (RGO) electrode materials. This method uses flake graphite as raw material, prepares graphene oxide using the Hummer method, and then surface-modifies the graphene oxide with an ionic liquid to obtain ionic liquid-modified graphene oxide. This modified graphene oxide is then added to a solvent along with a polymer and vigorously stirred under ultrasonic conditions to form an electrospinning solution. The electrospinning solution is then electrospun, and the resulting graphene oxide-polymer electrospun fibers on the electrospinning receiver are heat-treated to obtain a composite material with RGO embedded vertically ordered on the surface of carbon nanofibers. Similar to the aforementioned patent, this method also directly mixes the polymer and graphene oxide to obtain a spinning solution, followed by electrospinning. This method only allows the graphene oxide to be encapsulated inside the fiber, but it cannot adhere to the surface of the polyacrylonitrile fiber to form a graphene layer. Furthermore, its heat treatment temperature is low, lacking graphitization treatment, thus reducing the mechanical strength, toughness, and conductivity of the prepared fibers.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] One of the objectives of this invention is to provide a graphene fiber having a core-sheath structure, wherein the inner core of the core-sheath structure is a polyacrylonitrile fiber and the sheath layer is a graphene layer.

[0009] A second objective of this invention is to provide a graphene fiber bundle, which is formed by assembling the aforementioned graphene fibers. This structure allows the graphene to construct highly efficient conductive channels on the fiber surface, resulting in excellent conductivity. Furthermore, the graphene sheets do not disrupt the original polyacrylonitrile fiber's intact structure and regular arrangement due to steric hindrance, thus maintaining its mechanical strength.

[0010] A third objective of this invention is to provide a method for preparing graphene fiber bundles, particularly a method for preparing graphene fiber bundles by water bath electrospinning. The method includes: using a polyacrylonitrile solution as the spinning solution and a graphene oxide solution as the collecting bath, performing electrospinning to obtain graphene oxide composite fibers; and sequentially subjecting the graphene oxide composite fibers to pre-oxidation, carbonization, and graphitization treatments to obtain the graphene fiber bundles. This invention utilizes the high density of yarns obtained by water bath electrospinning to overcome the shortcomings of loose and low-strength graphene fiber bundles obtained after the reduction of single graphene oxide fiber bundles, resulting in a tightly packed graphene fiber bundle with high mechanical strength.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0012] In a first aspect, the present invention provides a graphene fiber having a core-sheath structure, wherein the inner core of the core-sheath structure is a polyacrylonitrile fiber and the sheath layer is a graphene layer.

[0013] Preferably, the diameter of the polyacrylonitrile fiber is 180-250 nm, for example, it can be 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, etc.

[0014] Preferably, the thickness of the graphene layer is 45-65 nm, for example, it can be 45 nm, 46 nm, 48 nm, 50 nm, 52 nm, 54 nm, 56 nm, 58 nm, 60 nm, 62 nm, 65 nm, etc.

[0015] In a second aspect, the present invention provides a graphene fiber bundle, the graphene fiber bundle being assembled from graphene fibers as described in the first aspect.

[0016] In this invention, the graphene fiber bundle is assembled from multiple graphene fibers with a core of polyacrylonitrile fibers and a sheath of graphene, exhibiting a yarn-like structure and high density. Furthermore, by using polyacrylonitrile fibers as the core and graphene as the sheath, it overcomes the shortcomings of graphene fiber bundles obtained by reducing single-oxide graphene fiber bundles, which are loose and have low strength, resulting in a tightly packed graphene fiber bundle with high mechanical strength. In addition, the "core-sheath" structure formed by the graphene sheets assembled on the surface of the nanofibers allows the graphene to construct highly efficient conductive channels on the fiber surface, giving it excellent conductivity. On the other hand, the graphene sheets do not disrupt the original polyacrylonitrile fiber's complete structure and regular arrangement due to steric hindrance, thus not affecting its mechanical strength.

[0017] Preferably, the number of graphene fibers is 3,000 or more, for example, 3,000, 3,500, 4,000, 4,500, 5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, 10,000, etc., and more preferably 5,000 to 7,000.

[0018] Preferably, the graphene fiber bundle has a flat structure.

[0019] Preferably, the radial cross-sectional area of ​​the graphene fiber bundle is 200–700 μm. 2 For example, it could be 200μm 2 250μm 2 300μm 2 350μm 2 400μm 2410μm 2 420μm 2 430μm 2 440μm 2 450μm 2 460μm 2 470μm 2 480μm 2 490μm 2 500μm 2 550μm 2 600μm 2 650μm 2 700μm 2 wait.

[0020] Preferably, the width of the radial cross-section of the graphene fiber bundle is 5 to 10 μm, for example, it can be 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.2 μm, 7.5 μm, 7.8 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, etc.

[0021] Preferably, the length of the radial cross-section of the graphene fiber bundle is 50-70 μm, for example, it can be 50 μm, 52 μm, 54 μm, 56 μm, 58 μm, 60 μm, 62 μm, 64 μm, 66 μm, 68 μm, 70 μm, etc.

[0022] Preferably, the electrical conductivity of the graphene fiber bundle is 500 S·cm. -1 The above, for example, could be 500 S·cm -1 520S·cm -1 540S·cm -1 560S·cm -1 580S·cm -1 600S·cm -1 620S·cm -1 640S·cm -1 660S·cm -1 680S·cm -1 700S·cm -1 720S·cm -1 740S·cm -1 760S·cm -1 780S·cm -1 800S·cm -1 825S·cm -1 850S·cm -1 wait.

[0023] Preferably, the tensile strength of the graphene fiber bundle is above 200 MPa, for example, it can be 200 MPa, 220 MPa, 240 MPa, 260 MPa, 280 MPa, 300 MPa, 320 MPa, 340 MPa, 360 MPa, 380 MPa, 400 MPa, 420 MPa, 440 MPa, 460 MPa, 480 MPa, 500 MPa, 520 MPa, 540 MPa, 560 MPa, 580 MPa, 600 MPa, 625 MPa, 650 MPa, etc.

[0024] Thirdly, the present invention provides a method for preparing graphene fiber bundles as described in the second aspect, the method comprising the following:

[0025] Electrospinning was performed using a polyacrylonitrile solution as the spinning solution and a graphene oxide solution as the collecting bath to obtain graphene oxide composite fibers.

[0026] The graphene oxide composite fibers were subjected to pre-oxidation, carbonization, and graphitization treatments in sequence to obtain the graphene fiber bundles.

[0027] This invention provides a method for preparing graphene fiber bundles via water bath electrospinning. This method utilizes water bath electrospinning, followed by pre-oxidation, carbonization, and graphitization treatments. The resulting graphene fiber bundle yarns exhibit high density, high mechanical strength, good toughness, and good electrical conductivity. Furthermore, the preparation method is simple, easy to operate, and can be continuously produced. The obtained graphene fiber bundles possess high strength, good toughness, and good electrical conductivity, showing promising application prospects.

[0028] Preferably, the polyacrylonitrile solution contains 13 to 20 wt% polyacrylonitrile, for example, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, etc.

[0029] Preferably, the solvent in the polyacrylonitrile solution is selected from any one or a combination of at least two of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), or N-methylpyrrolidone (NMP).

[0030] Preferably, the molecular weight of the polyacrylonitrile is 50,000 to 150,000 g / mol, for example, it can be 50,000 g / mol, 60,000 g / mol, 70,000 g / mol, 80,000 g / mol, 90,000 g / mol, 100,000 g / mol, 110,000 g / mol, 120,000 g / mol, 130,000 g / mol, 140,000 g / mol, 150,000 g / mol, etc.

[0031] Preferably, the spinning solution is prepared by mixing polyacrylonitrile with a solvent, heating and stirring to obtain the spinning solution.

[0032] Preferably, the mixing method involves adding polyacrylonitrile to a solvent.

[0033] Preferably, the heating and stirring temperature is 70-90℃, for example, 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, etc.; the heating and stirring time is 1-4h, for example, 1h, 1.2h, 1.5h, 1.8h, 2h, 2.2h, 2.5h, 2.8h, 3h, 3.2h, 3.5h, 3.8h, 4h, etc.

[0034] Preferably, the graphene oxide solution contains 0.02 to 0.5 wt% graphene oxide by mass, for example, 0.02 wt%, 0.04 wt%, 0.06 wt%, 0.08 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, 0.5 wt%, etc.

[0035] Preferably, the solvent for the graphene oxide solution is water.

[0036] Preferably, the graphene oxide solution also includes a surfactant.

[0037] Preferably, the surfactant is selected from any one or a combination of at least two of polyethylene glycol laurate, polyethylene glycol octylphenyl ether, or sodium dodecylbenzenesulfonate.

[0038] In this invention, the above-mentioned surfactant is added to the collection bath. On the one hand, as a surfactant, it reduces the surface tension of the collection bath, allowing the electrospun polyacrylonitrile nanofiber web to be better immersed in the collection bath. On the other hand, it modifies the graphene oxide to a certain extent, enhancing the interaction force between the graphene oxide and polyacrylonitrile molecules, so that the graphene oxide sheets can be more tightly and more fully assembled on the surface of the polyacrylonitrile nanofibers, thereby improving the mechanical properties and electrical conductivity of the graphene fiber bundle.

[0039] Preferably, the surfactant content in the graphene oxide solution is 0.5-5 wt%, for example, it can be 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.2 wt%, 2.5 wt%, 2.8 wt%, 3 wt%, 3.2 wt%, 3.5 wt%, 3.8 wt%, 4 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, 5 wt%, etc.

[0040] Preferably, the collection bath is prepared by dispersing graphene oxide in water and then mixing it with a surfactant to obtain the collection bath.

[0041] Preferably, the mixing method involves adding a surfactant to an aqueous solution of graphene oxide.

[0042] Preferably, the mixing temperature is 10 to 40°C, for example, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.; the mixing time is 10 to 24 hours, for example, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0043] Preferably, the spinning voltage during the electrospinning process is 10-20kV, for example, it can be 10kV, 11kV, 12kV, 13kV, 14kV, 15kV, 16kV, 17kV, 18kV, 19kV, 20kV, etc.

[0044] Preferably, the propulsion speed of the spinning solution during the electrospinning process is 0.8 to 2.5 mL / h, for example, it can be 0.8 mL / h, 1 mL / h, 1.2 mL / h, 1.4 mL / h, 1.6 mL / h, 1.8 mL / h, 2 mL / h, 2.2 mL / h, 2.4 mL / h, 2.5 mL / h, etc.

[0045] Preferably, the distance between the needle and the collecting bath during the electrospinning process is 10-25cm, for example, it can be 10cm, 12cm, 14cm, 16cm, 18cm, 20cm, 22cm, 24cm, 25cm, etc.

[0046] Preferably, the winding speed of the winding machine during the electrospinning process is 0.2 to 1 m / min, for example, it can be 0.2 m / min, 0.3 m / min, 0.4 m / min, 0.5 m / min, 0.6 m / min, 0.7 m / min, 0.8 m / min, 0.9 m / min, 1 m / min, etc.

[0047] Preferably, the temperature of the heating table during the electrospinning process is 70-120℃, for example, it can be 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, etc.

[0048] Preferably, the specific operation process of the electrospinning is as follows: electrospinning of polyacrylonitrile solution, and using graphene oxide solution as the wire mesh receiving device; the wire mesh is pulled by the end winding machine, passes through the wire guide, is dried on the heating table, and is finally collected on the winding machine to obtain graphene oxide composite fiber.

[0049] Preferably, the temperature of the pre-oxidation treatment is 240 to 290°C, for example, it can be 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, etc.

[0050] Preferably, the heating rate of the pre-oxidation treatment is 1 to 5 °C / min, for example, it can be 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.

[0051] Preferably, the pre-oxidation treatment time is 2 to 4 hours, for example, it can be 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, etc.

[0052] Preferably, the carbonization temperature is 800–1500°C, for example, it can be 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, etc.

[0053] Preferably, the heating rate of the carbonization treatment is 1 to 5 °C / min, for example, it can be 1 °C / min, 1.5 °C / min, 2 °C / min, 2.5 °C / min, 3 °C / min, 3.5 °C / min, 4 °C / min, 4.5 °C / min, 5 °C / min, etc.

[0054] Preferably, the carbonization treatment time is 2 to 4 hours, for example, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, etc.

[0055] Preferably, the graphitization treatment temperature is 2500-2800℃, for example, 2500℃, 2550℃, 2600℃, 2650℃, 2700℃, 2750℃, 2800℃, etc.

[0056] Preferably, the heating rate of the graphitization treatment is 5 to 10 °C / min, for example, it can be 5 °C / min, 5.5 °C / min, 6 °C / min, 6.5 °C / min, 7 °C / min, 7.5 °C / min, 8 °C / min, 8.5 °C / min, 9 °C / min, 9.5 °C / min, 10 °C / min, etc.

[0057] Preferably, the graphitization treatment time is 2 to 4 hours, for example, it can be 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, etc.

[0058] As a preferred embodiment of the present invention, the method for preparing graphene fiber bundles by water bath electrospinning specifically includes the following steps:

[0059] S1, Preparation of spinning solution and collecting bath:

[0060] Polyacrylonitrile is mixed with a solvent and heated and stirred at 70-90°C for 1-4 hours to obtain a polyacrylonitrile solution, which is then used as a spinning solution.

[0061] Graphene oxide is dispersed in water (or a prepared aqueous solution of graphene oxide is diluted), and then mixed with a surfactant to obtain a graphene oxide solution; this solution is then used as a collection bath.

[0062] S2, electrospinning:

[0063] Polyacrylonitrile solution is electrospun, and graphene oxide solution is used as the wire mesh receiving device. The wire mesh is pulled by the end winding machine, passes through the wire guide, is dried on the heating table, and is finally collected on the winding machine to obtain graphene oxide composite fiber.

[0064] The spinning voltage is 10–20 kV; the spinning solution propulsion speed is 0.8–2.5 mL / h; the distance between the needle and the collection bath is controlled at 10–25 cm; the winding speed of the winding machine is 0.2–1 m / min; and the heating table temperature is 70–120 °C.

[0065] S3, High-temperature treatment:

[0066] The graphene oxide composite fibers were subjected to pre-oxidation, carbonization, and graphitization treatments in sequence to obtain the graphene fiber bundles.

[0067] The pre-oxidation temperature is 240℃~290℃; the carbonization temperature is 800℃~1500℃; and the graphitization temperature is 2500℃~2800℃.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) In this invention, graphene sheets are assembled on the surface of nanofibers to form a "core-sheath" structure, with graphene as the "sheath" and polyacrylonitrile fiber as the "core". This structure enables graphene to build highly efficient conductive channels on the fiber surface, giving it excellent conductivity. On the other hand, the graphene sheets will not disrupt the original complete structure and regular arrangement of the polyacrylonitrile fiber due to its steric hindrance, thus affecting its mechanical strength;

[0070] (2) The present invention utilizes the high density of the yarn obtained by water bath electrospinning to obtain graphene oxide-polyacrylonitrile composite fiber, which overcomes the shortcomings of loose and low strength of graphene fiber bundles obtained after reduction of single graphene oxide fiber bundles, and obtains a graphene fiber bundle with tight arrangement and high mechanical strength.

[0071] (3) In this invention, the addition of surfactant to the collection bath serves two purposes. First, as a surfactant, it reduces the surface tension of the collection bath, allowing the electrospun polyacrylonitrile nanofiber web to be better immersed in the collection bath. Second, it modifies graphene oxide to a certain extent, enhancing the interaction force between graphene oxide and polyacrylonitrile molecules, enabling graphene oxide sheets to be more tightly and extensively assembled on the surface of polyacrylonitrile nanofibers, thereby improving the mechanical properties and electrical conductivity of the graphene fiber bundles.

[0072] (4) This invention provides a high-performance graphene fiber bundle and its preparation method; the preparation method is simple, easy to operate, and can be continuously produced. The obtained graphene fiber bundle has high strength, good toughness and conductivity, and has good application prospects. Attached Figure Description

[0073] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0074] Figure 1 This is a scanning electron microscope image of the surface of the graphene fiber bundle provided in Example 1.

[0075] Figure 2The image shows a scanning electron microscope (SEM) image of the cross-section of the graphene fiber bundle provided in Example 1.

[0076] Figure 3 Scanning electron microscope image of polyacrylonitrile carbon nanofiber bundles provided for Comparative Example 1. Detailed Implementation

[0077] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0078] It should be noted that specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many ways other than those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0079] Example 1

[0080] This embodiment provides a graphene fiber bundle, which is prepared by the following method:

[0081] S1, Preparation of spinning solution and collecting bath:

[0082] Add 3.4g of polyacrylonitrile to 16.6g of DMF and stir in an 80℃ water bath for 2 hours to completely dissolve it, thus obtaining the spinning solution.

[0083] Take 26.6g of a 1.5wt% graphene oxide solution and add deionized water to prepare 400g of a 0.1wt% graphene oxide aqueous solution; then add 4g of polyethylene glycol octylphenyl ether and stir at room temperature for 12h to obtain a collection bath.

[0084] S2, electrospinning:

[0085] The above spinning solution was transferred to a syringe for electrospinning. The spinning voltage was 15kV and the spinning solution propulsion speed was 1.5mL / h. The above collection bath was used as the wire mesh receiving device. The distance between the needle and the collection bath was 10cm. The wire mesh was guided by the end winding machine, passed through the guide, and dried on the heating table at a temperature of 90℃. Finally, it was collected on the winding machine at a winding speed of 0.35m / min to obtain graphene oxide composite fibers.

[0086] S3, High-temperature treatment:

[0087] The obtained graphene oxide composite fibers were subjected to pre-oxidation, carbonization and graphitization treatments in sequence to obtain graphene fiber bundles.

[0088] The pre-oxidation process involved heating the material at 2℃ / min to 270℃ and holding it at that temperature for 2 hours; the carbonization process involved heating the material at 3℃ / min to 1200℃ and holding it at that temperature for 2 hours; and the graphitization process involved heating the material at 10℃ / min to 2700℃ and holding it at that temperature for 2 hours.

[0089] Figure 1 and Figure 2 These are scanning electron microscope (SEM) images of the surface and cross-section of the graphene fiber bundle in this embodiment; from Figure 1 As can be seen, tiny axial wrinkles appear on the surface of the nanofibers, and the graphene sheets are uniformly distributed axially on the surface of the nanofibers. From... Figure 2 As can be seen, the graphene fiber bundle prepared by water bath electrospinning is a nanofiber bundle structure. Graphene sheets are coated on the surface of each nanofiber. The resulting graphene fiber bundle is tightly arranged and well stacked, thus possessing excellent electrical conductivity and mechanical properties.

[0090] Example 2

[0091] This embodiment provides a graphene fiber bundle, which is prepared by the following method:

[0092] S1, Preparation of spinning solution and collecting bath:

[0093] Add 3.4g of polyacrylonitrile to 16.6g of DMF and stir in an 80℃ water bath for 2 hours to completely dissolve it, thus obtaining the spinning solution.

[0094] Take 5.3g of 1.5wt% graphene oxide solution and add deionized water to prepare 400g of 0.02wt% graphene oxide aqueous solution; add 4g of polyethylene glycol laurate and stir at room temperature for 12h to obtain a collection bath.

[0095] S2, electrospinning:

[0096] The above spinning solution was transferred to a syringe for electrospinning. The spinning voltage was 15kV and the spinning solution propulsion speed was 1.5mL / h. The above collection bath was used as the wire mesh receiving device. The distance between the needle and the collection bath was 10cm. The wire mesh was guided by the end winding machine, passed through the guide, and dried on the heating table at a temperature of 90℃. Finally, it was collected on the winding machine at a winding speed of 0.35m / min to obtain graphene oxide composite fibers.

[0097] S3, High-temperature treatment:

[0098] The obtained graphene oxide composite fibers were subjected to pre-oxidation, carbonization and graphitization treatments in sequence to obtain graphene fiber bundles.

[0099] The pre-oxidation process involved heating the material at 2℃ / min to 270℃ and holding it at that temperature for 2 hours; the carbonization process involved heating the material at 3℃ / min to 1200℃ and holding it at that temperature for 2 hours; and the graphitization process involved heating the material at 10℃ / min to 2700℃ and holding it at that temperature for 2 hours.

[0100] Example 3

[0101] This embodiment provides a graphene fiber bundle, which is prepared by the following method:

[0102] S1, Preparation of spinning solution and collecting bath:

[0103] Add 3.4g of polyacrylonitrile to 16.6g of DMF and stir in an 80℃ water bath for 2 hours to completely dissolve it, thus obtaining the spinning solution.

[0104] Take 26.6g of a 1.5wt% graphene oxide solution and add deionized water to prepare 400g of a 0.1wt% graphene oxide aqueous solution; then add 10g of polyethylene glycol octylphenyl ether and stir at room temperature for 12h to obtain a collection bath.

[0105] S2, electrospinning:

[0106] The above spinning solution was transferred to a syringe for electrospinning. The spinning voltage was 15kV and the spinning solution propulsion speed was 1.5mL / h. The above collection bath was used as the wire mesh receiving device. The distance between the needle and the collection bath was 10cm. The wire mesh was guided by the end winding machine, passed through the guide, and dried on the heating table at a temperature of 90℃. Finally, it was collected on the winding machine at a winding speed of 0.35m / min to obtain graphene oxide composite fibers.

[0107] S3, High-temperature treatment:

[0108] The obtained graphene oxide composite fibers were subjected to pre-oxidation, carbonization and graphitization treatments in sequence to obtain graphene fiber bundles.

[0109] The pre-oxidation process involved heating the material at 2℃ / min to 270℃ and holding it at that temperature for 2 hours; the carbonization process involved heating the material at 3℃ / min to 1200℃ and holding it at that temperature for 2 hours; and the graphitization process involved heating the material at 10℃ / min to 2700℃ and holding it at that temperature for 2 hours.

[0110] Example 4

[0111] This embodiment provides a graphene fiber bundle, which differs from Example 1 only in that, in the process of preparing the collection bath in S1, polyethylene glycol octylphenyl ether is replaced with an equal mass of sodium dodecylbenzenesulfonate. The other steps are completely consistent with Example 1.

[0112] Example 5

[0113] This embodiment provides a graphene fiber bundle, which differs from Embodiment 1 only in that the spinning voltage during the electrospinning process is 10kV; the spinning solution propulsion speed is 2.5mL / h; the distance between the needle and the collection bath is controlled at 25cm; the winding speed of the winding machine is 1m / min; and the heating table temperature is 70℃. All other steps are completely consistent with Embodiment 1.

[0114] Example 6

[0115] This embodiment provides a graphene fiber bundle, which differs from Embodiment 1 only in that the spinning voltage during the electrospinning process is 20kV; the spinning solution propulsion speed is 0.8mL / h; the distance between the needle and the collection bath is controlled at 10cm; the winding speed of the winding machine is 0.2m / min; and the heating table temperature is 120℃. All other steps are completely consistent with Embodiment 1.

[0116] Example 7

[0117] This embodiment provides a graphene fiber bundle, which differs from Embodiment 1 only in that the pre-oxidation is carried out by heating to 240°C at 1°C / min and holding for 4 hours; the carbonization is carried out by heating to 800°C at 1°C / min and holding for 4 hours; and the graphitization is carried out by heating to 2500°C at 5°C / min and holding for 4 hours. The other steps are completely consistent with Embodiment 1.

[0118] Example 8

[0119] This embodiment provides a graphene fiber bundle, which differs from Embodiment 1 only in that the pre-oxidation is carried out by heating to 290°C at 5°C / min and holding for 2 hours; the carbonization is carried out by heating to 1500°C at 5°C / min and holding for 2 hours; and the graphitization is carried out by heating to 2800°C at 10°C / min and holding for 2 hours. The other steps are completely consistent with Embodiment 1.

[0120] Comparative Example 1

[0121] This comparative example provides a polyacrylonitrile fiber, which is prepared by the following method:

[0122] S1, Preparation of spinning solution and collecting bath:

[0123] Add 3.4g of polyacrylonitrile to 16.6g of DMF and stir in an 80℃ water bath for 2 hours to completely dissolve it, thus obtaining the spinning solution; take 400g of deionized water as the collection bath.

[0124] S2, electrospinning:

[0125] The above spinning solution was transferred to a syringe for electrospinning. The spinning voltage was 15kV and the spinning solution feed rate was 1.5mL / h. The above collection bath was used as the wire mesh receiving device. The distance between the needle and the collection bath was 10cm. The wire mesh was guided by the end winding machine, passed through the guide, and dried on the heating table at a temperature of 90℃. Finally, it was collected on the winding machine at a winding speed of 0.35m / min to obtain polyacrylonitrile fibers.

[0126] S3, High-temperature treatment:

[0127] The polyacrylonitrile fibers obtained above were subjected to pre-oxidation, carbonization and graphitization treatments in sequence to obtain high-temperature treated polyacrylonitrile fibers.

[0128] The pre-oxidation process involved heating the material at 2℃ / min to 270℃ and holding it at that temperature for 2 hours; the carbonization process involved heating the material at 3℃ / min to 1200℃ and holding it at that temperature for 2 hours; and the graphitization process involved heating the material at 10℃ / min to 2700℃ and holding it at that temperature for 2 hours.

[0129] Figure 3 Here is a scanning electron microscope image of the polyacrylonitrile carbon nanofiber bundles in this comparative example, as shown. Figure 3 As shown, the surface of the nanofiber is smooth and flat.

[0130] Comparative Example 2

[0131] This comparative example provides a graphene fiber bundle, which is prepared by the following method:

[0132] S1. Preparation of spinning solution:

[0133] 3.4g of polyacrylonitrile, 0.05g of graphene oxide powder, and 0.1g of polyethylene glycol octylphenyl ether were added to 16.5g of DMF and stirred in an 80℃ water bath for 2 hours to completely dissolve the polyacrylonitrile / graphene oxide mixture, which was used as the spinning solution. 400g of deionized water was used as the collection bath.

[0134] S2, electrospinning:

[0135] The spinning solution was allowed to stand to remove air bubbles, and then electrospinning was performed in the constructed electrospinning device. The electrospinning parameters were set as follows: spinning voltage of 15kV, spinning solution feed speed of 1.5mL / h, receiving distance of 10cm, heating table temperature of 90℃, and winding speed of the winding machine of 0.35m / min. Subsequently, after high-temperature treatment as in Example 1, graphene fiber bundles (graphene as the inner core and polypropylene as the sheath) were obtained.

[0136] Comparative Example 3

[0137] This comparative example provides a graphene fiber bundle, which differs from Example 1 only in that it does not undergo graphitization treatment; all other steps are completely consistent with Example 1.

[0138] Comparative Example 4

[0139] This comparative example provides a graphene fiber bundle, which differs from Example 1 only in that it does not undergo carbonization treatment; all other steps are completely consistent with Example 1.

[0140] Test case

[0141] Test samples: Fibers provided in Examples 1-8 and Comparative Examples 1-4;

[0142] Test method:

[0143] Tensile strength was tested according to GB / T1040-2006, electrical conductivity was tested according to GB / T 40007-2021, and fiber cross-sectional area was measured according to GB / T 20307-2006;

[0144] The test results are shown in Table 1 below:

[0145] Table 1

[0146] sample <![CDATA[Conductivity / S·cm -1 > Tensile strength / MPa <![CDATA[Cross-sectional area / μm 2 > Example 1 633 452 450 Example 2 525 225 352 Example 3 774 579 431 Example 4 440 172 421 Example 5 587 237 271 Example 6 453 252 678 Example 7 567 196 432 Example 8 684 348 471 Comparative Example 1 65 10 254 Comparative Example 2 66 15 378 Comparative Example 3 290 200 464 Comparative Example 4 632 370 478

[0147] As shown in Table 1, the graphene fiber bundles obtained by this invention exhibit high electrical conductivity and tensile strength, indicating that they possess excellent electrical conductivity and mechanical properties. Combined with the data from Examples 1-3, it is evident that the higher the content of surfactant and graphene oxide in the collection bath, the better the performance. This demonstrates that the surfactant does indeed modify graphene oxide, enhancing the interaction between graphene oxide and polyacrylonitrile molecules, thereby improving material properties. Furthermore, the comparative data shows that using a pure water bath to prepare single polyacrylonitrile carbon nanofiber bundles results in carbon fibers with low conductivity and extremely poor mechanical properties. However, if the water bath is replaced with an aqueous solution of graphene oxide, the electrical conductivity and mechanical strength of the resulting graphene fiber bundles far exceed those of the carbon fiber bundles.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A graphene fiber bundle, characterized by, The graphene fiber bundle is assembled by graphene fibers; wherein the graphene fibers have a core-sheath structure, the inner core of the core-sheath structure is polyacrylonitrile fiber, and the sheath layer is graphene layer; The number of the graphene fibers is 3000 or more; the conductivity of the graphene fiber bundle is 500 S•cm -1 The tensile strength of the graphene fiber bundle is 200 MPa or more; The graphene fiber bundle is prepared by the following steps: electrospinning is performed by taking polyacrylonitrile solution as spinning solution and taking graphene oxide solution as collection bath to obtain graphene oxide composite fiber; The graphene fiber bundle is obtained by sequentially performing pre-oxidation treatment, carbonization treatment and graphitization treatment on the graphene oxide composite fiber. The temperature of the pre-oxidation treatment is 240-290°C, and the time of the pre-oxidation treatment is 2-4 h; the temperature of the carbonization treatment is 800-1500°C, and the time of the carbonization treatment is 2-4 h; the temperature of the graphitization treatment is 2500-2800°C, and the time of the graphitization treatment is 2-4 h.

2. The graphene fiber bundle of claim 1, wherein, The diameter of the polyacrylonitrile fiber is 180-250 nm; and the thickness of the graphene layer is 45-65 nm.

3. The graphene fiber of claim 1, wherein, The number of the graphene fibers is 5000-7000.

4. The graphene fiber of claim 1, wherein, The graphene fiber bundle has a flat structure.

5. The graphene fiber of claim 1, wherein, The area of the radial cross section of the graphene fiber bundle is 200-700 μm 2 .

6. The graphene fiber of claim 1, wherein, The width of the radial cross section of the graphene fiber bundle is 5-10 μm.

7. The graphene fiber of claim 1, wherein, The length of the radial cross section of the graphene fiber bundle is 50-70 μm.

8. A method of producing the graphene fiber bundle according to any one of claims 1 to 7, characterized by, The preparation method of the graphene fiber bundle comprises the following: electrospinning is performed by taking polyacrylonitrile solution as spinning solution and taking graphene oxide solution as collection bath to obtain graphene oxide composite fiber; The graphene fiber bundle is obtained by sequentially performing pre-oxidation treatment, carbonization treatment and graphitization treatment on the graphene oxide composite fiber. The temperature of the pre-oxidation treatment is 240-290°C, and the time of the pre-oxidation treatment is 2-4 h; the temperature of the carbonization treatment is 800-1500°C, and the time of the carbonization treatment is 2-4 h; the temperature of the graphitization treatment is 2500-2800°C, and the time of the graphitization treatment is 2-4 h.

9. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The mass percentage of polyacrylonitrile in the polyacrylonitrile solution is 13-20 wt%.

10. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The solvent in the polyacrylonitrile solution is selected from N,N - dimethylformamide, N,N - dimethylacetamide or N - methylpyrrolidone, or a combination of at least two of any of the foregoing. ​ 11. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The molecular weight of the polyacrylonitrile is 50000-150000 g / mol.

12. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The spinning solution is prepared by the following method: mixing polyacrylonitrile with solvent, heating and stirring to obtain the spinning solution. ​ 13. The method of claim 12, wherein the graphene fiber bundle is prepared by a process comprising: The mixing method is to add polyacrylonitrile into solvent.

14. The method of claim 12, wherein the graphene fiber bundle is prepared by the steps of: The heating and stirring temperature is 70-90°C; and the heating and stirring time is 1-4 h. ​ 15. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The mass percentage of graphene oxide in the graphene oxide solution is 0.02-0.5 wt%. ​ 16. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The solvent of the graphene oxide solution is water. ​ 17. The method of claim 8, wherein the graphene fiber bundle is prepared by a process comprising: The graphene oxide solution further comprises surfactant. ​ 18. The method of claim 17, wherein the graphene fiber bundle is prepared by a process comprising: The surfactant is selected from any one or a combination of at least two of polyethylene glycol laurate, polyethylene glycol octylphenyl ether or sodium dodecyl benzene sulfonate. ​ 19. The method of claim 17, wherein the graphene fiber bundle is prepared by a process comprising: The mass percentage of surfactant in the graphene oxide solution is 0.5-5 wt%.

20. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The collection bath is prepared by the following method: dispersing graphene oxide in water, and then mixing with surfactant to obtain the collection bath. ​ 21. The method of claim 20, wherein the graphene fiber bundle is prepared by a process comprising: The mixing method is to add the surfactant into the aqueous solution of graphene oxide.

22. The method of claim 20, wherein the graphene fiber bundle is prepared by the steps of: The mixing temperature is 10-40 DEG C, and the mixing time is 10-24 h.

23. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: In the electrospinning process, the spinning voltage is 10-20 kV; the spinning solution propelling speed is 0.8-2.5 mL / h; the distance between the needle and the collecting bath is 10-25 cm; the winding speed of the winding machine is 0.2-1 m / min; and the temperature of the heating table is 70-120 DEG C. ​ 24. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The specific operation process of the electrospinning is as follows: polyacrylonitrile solution is electrospun, and the graphene oxide solution is used as a silk screen receiving device; the silk screen is pulled by the end winding machine, passes through a guide, is dried on a heating table, and is finally collected on the winding machine to obtain graphene oxide composite fibers. ​ 25. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The heating rate of the pre-oxidation treatment is 1-5 DEG C / min. ​ 26. The method of claim 8, wherein the graphene fiber bundle is prepared by the steps of: The heating rate of the carbonization treatment is 1-5 DEG C / min. ​ 27. The method of claim 8, wherein the graphene fiber bundle is prepared by a process comprising: The heating rate of the graphitization treatment is 5-10 DEG C / min. ​

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