Preparation method of a high-performance graphene-based carbon fiber

Abstract

The present invention discloses a preparation method of high-performance graphene-based carbon fibers, which comprises the following steps: (1) dispersing graphene oxide powder in an organic solvent to form a uniform dispersion liquid, adding an ammonia source to the dispersion liquid to form a corresponding mixed liquid, and obtaining amino-functionalized graphene powder; (2) dissolving the amino-functionalized graphene powder in an organic solvent to form a dispersion liquid, fully immersing polyacrylonitrile fibers in the formed dispersion liquid, and obtaining polyacrylonitrile fibers infiltrated with amino-functionalized graphene; (3) performing pre-oxidation treatment on the polyacrylonitrile fibers infiltrated with amino-functionalized graphene to form a nitrided composite fiber; (4) continuously subjecting the nitrided composite fiber to crosslinking carbonization at a high temperature of 1000-1300 °C to form a composite carbon fiber material, and then further raising the temperature to 1400-1800 °C for graphitization treatment to form high-crystallinity graphene-based carbon fibers. The graphene-based carbon fiber preparation scheme provided by the present invention can prepare high-performance graphene-based carbon fibers, which have high strength and strong electrical conductivity.

Description

Technical Field

[0001] The present invention relates to the field of composite carbon fiber materials, and particularly to a preparation method of a carbon fiber material based on graphene as a base material. Background Art

[0002] Graphene has ultra-high mechanical properties, with a modulus of 1100 GPa and a strength of 130 GPa; and has ultra-high thermal conductivity, reaching 5300 W / (m·K); ultra-high electrical conductivity, reaching 108 S / m, and ultra-high current load capacity.

[0003] Carbon fiber material is an inorganic polymer fiber with a carbon content higher than 90%, which combines high mechanical strength, high modulus, low specific gravity, high temperature resistance, chemical corrosion resistance and excellent electrical and physical mechanical properties. Its excellent properties and unique functions have opened up broad application prospects in the fields of aerospace, military products, automobile manufacturing, photovoltaic industry, energy storage components, etc.

[0004] If the two can be further compounded, the superior properties of the two can be combined to obtain a composite material with the common superior properties of the two. Some compounding schemes are also given in the existing technology for this.

[0005] The Chinese patent application with publication number CN113136640 A discloses a method for preparing graphene-based carbon fiber at room temperature, which prepares macroscopic graphene-based carbon fiber using graphene oxide raw material as an assembly unit. For the graphene carbon fiber prepared by this method, its raw material is graphene, and the graphene sheets are not connected by chemical bonds, so the internal continuity of the finally prepared fiber is not strong and the strength is insufficient.

[0006] The Chinese patent application with publication number CN 109423702 A discloses a preparation scheme in which a spinning solution obtained by mixing an aqueous solution of graphene oxide and a polymer solution is spun by solution spinning to obtain an initial graphene oxide-based fiber, and then the initial fiber is carbonized to obtain carbon fiber. The preparation process of this method uses graphene oxide spinning technology, and the problem of weak connection strength between graphene sheets also exists in the case of nitrile carbonization.

[0007] The Chinese patent application with publication number CN110747537 A discloses a preparation scheme in which a graphene dispersion liquid and a purified lignin solution are mixed and stirred in a certain proportion to obtain a spinning solution, and then a polyelectrolyte complex spinning method is used to ion-complex with a chitosan solution to obtain a lignin / graphene oxide composite fiber, and the composite fiber is placed in a tube furnace and carbonized at high temperature in a nitrogen atmosphere to obtain a lignin / graphene-based carbon fiber. During the carbonization process of lignin, holes and cracks will be formed inside the fiber, which has a great impact on the strength and conductivity of the fiber.

[0008] The Chinese patent application with the publication number CN102534870A discloses a preparation scheme for preparing graphene-modified polyacrylonitrile-based carbon fibers. In this scheme, a graphene suspension is uniformly dispersed into a polyacrylonitrile solution by a blending method to obtain a graphene-modified polyacrylonitrile solution. Using this solution as a spinning dope, fiber filaments are prepared through a wet spinning or dry-jet wet spinning process. Finally, pre-oxidation and carbonization treatments are carried out to obtain graphene-modified polyacrylonitrile-based carbon fibers. In this method, the connection between graphene and carbon fibers is a physical connection, with insufficient connection ability, and there may be problems such as ash shedding in the later stage.

[0009] The Chinese patent application with the publication number CN 103320901 A discloses a preparation scheme for preparing carbon fibers with high strength, high modulus, and excellent conductivity. In this scheme, a solvated mesophase pitch is prepared, the mesophase pitch and graphene oxide are mixed in liquid phase, and after recovering the solvent, the temperature is raised to obtain a mesomorphic liquid of the asphalt mixture. The original filaments are prepared by melt spinning, and then pre-oxidation and carbonization are carried out. This method is similar to the method using lignin. During the carbonization process of the asphalt, structural collapse and loss will occur, and defects will be generated inside the fibers.

[0010] The Chinese patent application with the publication number CN116285007A discloses a preparation method for an amino-functionalized graphene powder that can be directly and efficiently dispersed in an organic system. In this method, various amine monomer substances are added to a graphene oxide solution, and polymerization reactions are specifically carried out based on the surface functional groups of graphene oxide. The product of the reaction is essentially a co-insertion polymer of graphene and a nitrogen-containing polymer, which belongs to a polymer polymerization reaction and is not a single amino-functionalized graphene. Moreover, due to the large volume of this polymer, it is easy to entangle and agglomerate with fibers during the composite process with fibers and be discarded. Furthermore, the in-situ polymerization reaction process has many steps, each link requires precise control, and the separation of reaction by-products and the treatment cost of waste materials in the later stage are high, and the process is complex.

[0011] The Chinese patent application with the publication number CN104862828A discloses a high-thermal-conductivity carbon fiber and its preparation method. It proposes to prepare high-thermal-conductivity polyacrylonitrile fibers by adding a graphene concentrate through an in-situ polymerization method or a dissolution method, and then pre-oxidizing, carbonizing, and graphitizing the high-thermal-conductivity polyacrylonitrile fibers to obtain high-thermal-conductivity carbon fibers. In this scheme, an ultra-fine graphene concentrate is used, which has no surface functional groups. During the polymerization process of acrylonitrile monomers, a wrapping effect will be formed on the graphene. Although it is a composite process through a chemical reaction, the final product formed is a physical composite of graphene and polyacrylonitrile fibers, and no strong chemical bond is formed between the two, that is, the connection between graphene and acrylonitrile is not tight, and there are easy agglomeration and powder shedding situations.

[0012] In summary, the existing carbon fiber and graphene composite schemes mainly have the following problems:

[0013] (1) Most of the existing solutions are process solutions for the composite of carbon fiber and graphene based on different resins. In all of them, graphene is added during the fiber composite process, and finally carbonization treatment is performed together to form composite carbon fiber. The advantage of this solution of adding graphene during the process is that it can realize the combination between graphene and carbon fiber, but the connection is a physical connection or a mixed method, the process is complicated and the structure formed is prone to defects during the back-end process, resulting in insufficient conductivity and mechanical strength.

[0014] (2) The existing scheme uses graphene as a unit for combined carbonization and graphene spinning. Since the amount of graphene added in the scheme is relatively large, the production cost is high, and the consistency and uniformity of the finished product in the process are difficult to control. The batch consistency of the product is difficult to control during large-scale industrialization. Summary of the invention

[0015] In view of the problems existing in the existing graphene-based carbon fiber preparation scheme, the purpose of the present invention is to provide a scheme for preparing carbon fiber materials with graphene as the basic material, which can overcome the difficult chemical combination and grafting problems on the carbon fiber surface, combine graphene and carbon fiber into a whole, improve the strength and conductivity of the composite, and thus prepare high-performance graphene-based carbon fiber.

[0016] In order to achieve the above object, the present invention provides a method for preparing high-performance graphene-based carbon fiber, which mainly comprises the following steps:

[0017] (1) dispersing graphene oxide powder in an organic solvent in a certain proportion to form a uniform dispersion, adding a certain proportion of nitrogen-containing small molecules as an ammonia source to the dispersion to form a corresponding mixed solution, subjecting the mixed solution to a hydrothermal reaction, and then freeze-drying the mixed solution to obtain amination graphene powder;

[0018] (2) dissolving the aminated graphene powder obtained in step (1) in an organic solvent in a certain proportion to form a dispersion, fully immersing the polyacrylonitrile fiber in the formed dispersion to form a mixed solution of aminated graphene and polyacrylonitrile fiber, and then taking out the mixed solution, drying it to remove the organic solvent, and obtaining the polyacrylonitrile fiber impregnated with aminated graphene;

[0019] (3) performing a pre-oxidation treatment on the polyacrylonitrile fiber impregnated with amino graphene obtained in step (2) to chemically bond the N element in the amino graphene with the N element in the polyacrylonitrile to form a nitride composite fiber;

[0020] (4) Continuously crosslink and carbonize the nitrided composite fibers generated in step (3) at a high temperature of 1000 - 1300 °C to remove nitrogen-containing chemical bonds, leaving only C elements and carbon-containing chemical bonds to form a composite carbon fiber material, and then further raise the temperature to 1400 - 1800 °C for graphitization treatment to transform the original carbon structure to form more sp 2 hybridized π=π conjugated structure carbon to form highly crystalline graphene-based carbon fibers.

[0021] In some examples of the present invention, the graphene oxide in step (1) serves as a precursor for nitrogen-doped graphene, and the size of the graphene oxide is 10 - 20 μm and the oxygen content is 30 - 36 wt%.

[0022] In some examples of the present invention, the ammonia source material is one or more of melamine, ethylenediamine, hexamethylenediamine, triethylenetetramine, ammonium hydroxide, etc.

[0023] In some examples of the present invention, the addition amount of the ammonia source in the graphene oxide dispersion solution is 3 - 4 wt%.

[0024] In some examples of the present invention, the nitrogen content of the amino-functionalized graphene is 20 - 30 wt.% and the sheet size is 10 - 20 μm.

[0025] In some examples of the present invention, the diameter of the polyacrylonitrile fiber is 15 - 20 μm.

[0026] In some examples of the present invention, the organic solvent is one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMAC).

[0027] In some examples of the present invention, the temperature of the pre-oxidation treatment of the composite fiber in step (3) is 200 - 400 °C and the time is 2 - 4 h;

[0028] In some examples of the present invention, the temperature of the crosslinking carbonization treatment in step (4) is 1000 - 1300 °C and the time is 4 - 6 h.

[0029] In some examples of the present invention, the temperature of the graphitization treatment in step (4) is 1400 - 1800 °C and the time is 10 - 12 h.

[0030] The graphene-based carbon fiber preparation scheme provided by the present invention can prepare high-performance graphene-based carbon fibers with high strength and strong electrical conductivity.

[0031] Furthermore, the graphene-based carbon fiber preparation scheme provided by the present invention has the following technical characteristics compared with the prior art:

[0032] (1) In the solution of the present invention, aminated graphene is more likely to crosslink with polyacrylonitrile, thereby increasing the bonding firmness between graphene and carbon fiber filaments.

[0033] (2) In the solution of the present invention, through multiple temperature-raising processes, the chemical bonds inside the composite fiber gradually transform from bonding, debonding and impurity removal, and finally the C-C and C═C structures into π═π double bonds, so that the structure and performance of the final carbon fiber have been greatly improved.

[0034] (3) When the solution of the present invention is finally formed, the graphene composite carbon fiber structure contains a large number of conjugated carbon structures, greatly improving the strength and electrical conductivity of the carbon fiber.

[0035] (4) The solution of the present invention effectively combines the performance advantages of graphene and carbon fiber, overcomes the major problem that it is difficult to graft other carbon materials on the surface of carbon fiber in this field, and thus further improves the performance and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0037] Figure 1 It is a synthesis reaction diagram of the preparation process of graphene-based composite carbon fiber in the example of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific drawings.

[0039] Through full research on the performance of graphene and carbon fiber materials, aiming at the technical problem that it is difficult to chemically bond other materials on the surface of carbon fiber in the prior art, the solution of the present invention innovatively adopts the idea of combining graphene amino-functionalization and polyacrylonitrile fiber to realize the chemical bond connection between graphene and carbon fiber, so that the two are connected to form a real whole, and a composite fiber with chemical bond connection between graphene and carbon fiber is prepared, with significantly improved electrical conductivity and strength.

[0040] In this solution, an innovative hydrothermal polymerization amination method is used to form aminated graphene powder. Compared with the existing solution, in this solution, the replacement of oxygen-containing functional groups in the original graphene oxide is realized by adding amino-containing small molecules (that is, a separate functional group replacement reaction), and it is only necessary to connect amino groups on the graphene sheets, without the need for a macromolecular polymerization process. The material utilization rate is 100%, there are no by-products, the production cost is low, the process is simple, there is no pollution, and it is suitable for fiber composite.

[0041] On this basis, in this solution, based on the formed amino-functionalized graphene powder, a high-performance graphene-based carbon fiber is further prepared through an amino-bonding and carbonization process, which can effectively overcome the problems existing in the prior art.

[0042] Based on the above mechanism, the present invention provides a solution for preparing a high-performance graphene-based carbon fiber. This solution is based on graphene oxide powder and polyacrylonitrile fiber, and realizes the preparation of the high-performance graphene-based carbon fiber through the following steps in cooperation.

[0043] Specifically, in step (1), the graphene oxide powder is dispersed in an organic solvent at a ratio of 5-10 wt.% to form a homogeneous dispersion liquid. A certain proportion of nitrogen-containing small molecules is added as an ammonia source in the dispersion liquid to form a corresponding mixed liquid. After the mixed liquid is subjected to a hydrothermal reaction, it is then freeze-dried to obtain amino-functionalized graphene powder; in this step, the grafting of amino functional groups is realized by means of a hydrothermal reaction. Compared with other existing solutions, the reaction process is mild, the cost is low, and the obtained substance is relatively pure and free of impurities.

[0044] (2) The amino-functionalized graphene powder obtained in step (1) is dissolved in an organic solvent at a ratio of 10 wt.% to form a dispersion liquid. The polyacrylonitrile fiber is fully immersed in the formed dispersion liquid to form a mixed liquid of amino-functionalized graphene and polyacrylonitrile fiber. Then the mixed liquid is taken out and dried to remove the organic solvent, and the polyacrylonitrile fiber infiltrated with amino-functionalized graphene is obtained;

[0045] (3) The polyacrylonitrile fiber infiltrated with amino-functionalized graphene obtained in step (2) is subjected to a pre-oxidation treatment to bond the N element in the amino-functionalized graphene with the N element in the polyacrylonitrile to form a nitrided composite fiber. Here, the composite fiber is a graphene and polyacrylonitrile composite fiber containing -N=N- or -NH-NH- chemical bonds in the middle. The nitrogen element in the graphene in the composite fiber is at the edge of the graphene, and the nitrogen element in the polyacrylonitrile is distributed on the surface of the fiber. After the two are combined, a bonding relationship of -N=N- or -NH-NH- can be formed between the two nitrogens, thereby connecting the two together;

[0046] (4) The nitrided composite fiber generated in step (3) is continuously cross-linked and carbonized at a high temperature of 1000-1300 °C to remove the nitrogen-containing chemical bonds, and only C elements and carbon-containing chemical bonds are retained. Finally, the C-C and C=C structures are converted into π=π double bonds to form a composite carbon fiber material. Then, the temperature is further raised to 1400-1800 °C for graphitization treatment to convert the original carbon structure to form more sp2-hybridized π=π conjugated structure carbon, forming a high-crystallinity graphene-based carbon fiber.

[0047] In some embodiments of the present invention, in this preparation scheme, graphene oxide is used as the precursor of amino-functionalized graphene. Preferably, the size of the graphene oxide is 10-20 μm and the oxygen content is 30-36 wt%, so as to form a stable structure in adaptation with polyacrylonitrile fibers.

[0048] Furthermore, in this preparation scheme, the nitrogen content of the obtained amino-functionalized graphene (i.e., nitrogen-doped graphene) is 20-30 wt%, and the graphene sheets are 10-20 μm. They can correspond to each other when subsequently compounded with polyacrylonitrile fibers. Based on the doped nitrogen functional groups, stable connections can be formed with polyacrylonitrile fibers.

[0049] In some embodiments of the present invention, the organic solvents used in step 1 of this preparation scheme include one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), etc. Using nitrogen-containing organic solvents is beneficial to the dispersion of nitrogen-containing graphene and polyacrylonitrile fibers.

[0050] Furthermore, in this preparation scheme, the proportion of graphene oxide powder used in step 1 is preferably such that the concentration of graphene oxide powder in the dispersion is 5-10 w%. This can ensure the stability of the subsequent combination with carbon fibers. If the addition amount is too small, the effect of improving the combination of the two cannot be achieved. If too much is added, too much graphene cannot combine with carbon fibers, resulting in graphene powder falling off the formed fibers.

[0051] In some embodiments of the present invention, the ammonia source substances used in step (1) of this preparation scheme are preferably one or several of melamine, ethylenediamine, hexamethylenediamine, triethylenetetramine, ammonium hydroxide, etc.; at the same time, the addition amount of the ammonia source in the graphene oxide solution is 3-4 wt%. Such nitrogen sources are small-molecule nitrogen-containing compounds, which are easily soluble in organic solvents, and the chemical binding energy with graphene is relatively low, making the reaction easy. Moreover, with an addition amount of 3-4 wt% of the ammonia source, the degree of amino-functionalization of graphene can be maximally ensured, approaching 100% amino-functional group substitution, thereby ensuring the maximum subsequent combination with polyacrylonitrile fibers.

[0052] In some embodiments of the present invention, when preparing amino-functionalized graphene powder from the mixed solution in step (1) of this preparation scheme, it is preferably to place the mixed solution in a hydrothermal reaction kettle at 200 °C for hydrothermal reaction, and then perform freeze-drying treatment for 12 h to obtain amino-functionalized graphene powder. In this way, a corresponding high-temperature and high-pressure reaction environment is formed to meet the optimal conditions for amino substitution of epoxy functional groups. If the temperature is too high, the risk of the reaction increases, and at the same time, unnecessary side reactions are also increased, resulting in the decomposition of the newly formed amino-functionalized graphene. When the temperature is too low, the substitution reaction cannot proceed.

[0053] In some embodiments of the present invention, the organic solvents used in step (2) of this preparation scheme also include one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), etc.

[0054] Furthermore, in step (2) of this preparation scheme, the polyacrylonitrile fiber preferably uses a polyacrylonitrile fiber with a diameter of 15 - 20 μm. Such polyacrylonitrile fiber can be similar to the sheet size of the graphene used. During the bonding process, it can effectively bond the graphene without being wrapped by the graphene on its surface. This ensures that the connection of the graphene is on the fiber surface, forming a fiber-graphene-fiber connection form between the fibers, which can further enhance the overall structural strength.

[0055] Furthermore, in step (2) of this preparation scheme, when infiltrating the polyacrylonitrile fiber, the pre-prepared polyacrylonitrile fiber is immersed in a dispersion formed by the amino-functionalized graphene powder to make it fully infiltrated. The infiltration vessel is a square or circular groove, and the polypropylene fiber is arranged along the groove or wound circularly therein, ensuring that the fiber is infiltrated in the solution for 2 h to form a mixture of amino-functionalized graphene and polyacrylonitrile fiber. In this way, it can ensure that the amino-functionalized graphene and the polyacrylonitrile fiber are fully combined and react.

[0056] Furthermore, in step (2) of this preparation scheme, it is preferably dried at 120 °C to remove the solvent, so that the liquid part in the mixture can be completely volatilized.

[0057] In some embodiments of the present invention, in step (3) of this preparation scheme, the temperature for the pre-oxidation treatment of the composite fiber is preferably 200 - 400 °C, and the time is 2 - 4 h. In this way, it can ensure that the nitrogen-containing groups of the two materials react with each other to form effective -N=N- and -NH-NH- chemical bonds.

[0058] In some embodiments of the present invention, when performing the cross-linking carbonization treatment in step (4), in a vacuum environment, the temperature is 1000 - 1300 °C, and the time is 4 - 6 h. In this way, carbonization can achieve the connection of pure carbon-carbon chemical bonds and remove other elements; at the same time, when performing graphitization treatment, in a vacuum environment, the temperature is 1400 - 1800 °C, and the time is 10 - 12 h.

[0059] The scheme of the high-performance graphene-based carbon fiber given by the present invention creatively uses amino-functionalized graphene as a raw material, which is easier to bond with the N element in polyacrylonitrile, combined Figure 1As shown, in the reaction of aminating graphene oxide, the hydrothermal reaction method is adopted in the solution of the present invention, rather than high-temperature heating, which is more conducive to energy conservation and environmental protection, and the process is relatively safe; then in the pre-oxidation process, the reaction occurring at a relatively low heating temperature is the bonding and curing process of N-N, N-O. During the process, due to the change of the chemical bond of the N element, the polyacrylonitrile structure is transformed; then the cross-linking carbonization process is carried out. Specifically, this process is the process of breaking the functional groups containing N and O, volatilizing small molecules of N and O elements, and re-bonding and rearranging C elements to form a fully carbon cross-linked structure; finally, a higher-temperature graphitization process is carried out. Specifically, this process is the process of converting sp 3 carbon to sp 2 carbon structure transformation, increasing the hexagonal conjugate structure of carbon and having higher crystallinity.

[0060] The following provides a corresponding application example for the solution of the present invention to further illustrate its implementation process and corresponding technical features.

[0061] Example 1:

[0062] Based on the solution of the present invention, this example specifically prepares high-performance graphene-based carbon fibers through the following steps:

[0063] (1) Graphene oxide is used as the precursor of nitrogen-doped graphene. The size of graphene oxide is 10 μm and the oxygen content is 36 wt%. Graphene oxide is dispersed in N,N-dimethylformamide (DMF) according to a ratio, and the dispersion concentration is 8 wt%. After being fully mixed to form a viscous solution, melamine powder is added to the graphene oxide dispersion liquid according to an addition ratio of 4 wt%. It is fully stirred and mixed in a shear stirrer to obtain a uniformly dispersed slurry, where the stirring time is 30 min and the rotation speed is 500 rpm.

[0064] (2) The uniformly dispersed graphene oxide and melamine dispersion slurry are placed in a hydrothermal reaction kettle and reacted at 200 °C for 12 h, so that the nitrogen-containing groups in melamine are fully replaced by the oxygen-containing groups of graphene oxide. After taking out, it is placed in a freeze dryer for drying treatment to obtain aminated graphene powder with a nitrogen content of 30 wt% and a size of 10 μm.

[0065] (3) The aminated graphene powder obtained in step 2 is dispersed in dimethyl sulfoxide (DMSO) to form a slurry with a concentration of 10%. Polyacrylonitrile fibers with a diameter of 15 μm are immersed in the dimethyl sulfoxide solution of aminated graphene and fully mixed. Then the fibers are placed in an oven at 120 °C for drying treatment to obtain an infiltrated body of aminated graphene and polyacrylonitrile.

[0066] (4) The impregnated body in step 3 is placed in a tubular furnace at 400° C. for pre-oxidation treatment for 2 h to obtain NN cross-linked graphene and carbon fiber nitride composite fibers, and the protective atmosphere is nitrogen.

[0067] (5) The nitride composite fiber in step 4 is placed in a high-temperature furnace at 1200°C for cross-linking carbonization treatment for 4 hours to remove the NN bond, completely remove elements such as N and O, retain the cross-linked composite carbon fiber structure, and the protective atmosphere is argon; then the carbonized composite carbon fiber is further heated to 1800°C and treated for 12 hours to obtain highly graphitized graphene-based carbon fiber filaments.

[0068] The strength, modulus, electrical conductivity and thermal conductivity of the highly graphitized graphene-based carbon fiber prepared in this example were tested. The strength and modulus were tested using a universal testing machine, the electrical conductivity was tested using a conductivity tester, and the thermal conductivity was tested using a thermal conductivity coefficient tester.

[0069] The test results show that the graphene-based carbon fiber composite material prepared in this example has a strength of up to 6 GPa, a modulus of 260 GPa, and a conductivity of 3×10 4 S / m, thermal conductivity 600W / m K, the overall performance is improved by 1.3 times compared with pure carbon fiber filaments.

[0070] Embodiment 2:

[0071] This example is based on the scheme of the present invention, and specifically prepares high-performance graphene-based carbon fibers through the following steps:

[0072] (1) Graphene oxide is used as a precursor of nitrogen-doped graphene, wherein the graphene oxide has a size of 20 μm and an oxygen content of 36 wt %; the graphene oxide is dispersed in dimethylformamide (DMAC) at a dispersion concentration of 5 wt %, and is fully mixed to form a viscous solution; melamine powder is added to the graphene oxide dispersion at an addition ratio of 3 wt %, and the mixture is fully stirred and mixed in a shear mixer to obtain a uniformly dispersed slurry, wherein the stirring time is 30 min and the rotation speed is 500 rpm.

[0073] (2) placing the evenly dispersed graphene oxide and ethylenediamine dispersion slurry in a hydrothermal reactor and reacting at 200° C. for 12 hours to allow the nitrogen-containing groups in ethylenediamine to be fully replaced with the oxygen-containing groups in graphene oxide, taking out and placing in a freeze dryer for drying to obtain amino graphene powder with a nitrogen content of 20 wt% and a size of 20 μm.

[0074] (3) The aminated graphene powder in step 2 is dispersed in N,N-dimethylformamide (DMF) to obtain a slurry with a concentration of 10%, and polyacrylonitrile fiber with a diameter of 20 μm is immersed in the N,N-dimethylformamide (DMF) solution of aminated graphene, mixed thoroughly, and then the fiber is placed in an oven at 120°C for drying to obtain an aminated graphene and polyacrylonitrile impregnation body.

[0075] (4) The impregnated body in step 3 is placed in a tubular furnace at 200° C. for pre-oxidation treatment for 4 h to obtain NN-crosslinked graphene and carbon fiber nitride composite fibers, with the protective atmosphere being nitrogen.

[0076] (5) The nitride composite fiber in step 4 is placed in a high-temperature furnace at 1000°C for cross-linking carbonization treatment for 6 hours to remove the NN bond, completely remove elements such as N and O, retain the cross-linked composite carbon fiber structure, and the protective atmosphere is argon; then the carbonized composite carbon fiber is further heated to 1400°C and treated for 10 hours to obtain highly graphitized graphene-based carbon fiber filaments.

[0077] The strength, modulus, electrical conductivity and thermal conductivity of the highly graphitized graphene-based carbon fiber prepared in this example were tested. The strength and modulus were tested using a universal testing machine, the electrical conductivity was tested using a conductivity tester, and the thermal conductivity was tested using a thermal conductivity coefficient tester.

[0078] The test results show that the graphene-based carbon fiber composite material prepared in this example has a strength of up to 5.5 GPa, a modulus of 258 GPa, and a conductivity of 3.1×10 4 S / m, thermal conductivity 550W / m K, the overall performance is doubled compared with pure carbon fiber.

[0079] Embodiment 3:

[0080] This example is based on the scheme of the present invention, and specifically prepares high-performance graphene-based carbon fibers through the following steps:

[0081] (1) Graphene oxide is used as a precursor of nitrogen-doped graphene, wherein the graphene oxide has a size of 16 μm and an oxygen content of 33 wt%; the graphene oxide is dispersed in dimethyl sulfoxide (DMSO) at a dispersion concentration of 6 wt%, and is fully mixed to form a viscous solution, melamine powder is added to the graphene oxide dispersion at an addition ratio of 3.5 wt%, and the mixture is fully stirred and mixed in a shear mixer to obtain a uniformly dispersed slurry, wherein the stirring time is 30 min and the rotation speed is 500 rpm.

[0082] (2) The evenly dispersed graphene oxide and ethylenediamine dispersion slurry are placed in a hydrothermal reactor and reacted at 200 °C for 12 h to fully replace the oxygen-containing groups of graphene oxide with nitrogen-containing groups in ethylenediamine. After taking out, it is placed in a freeze dryer for drying treatment to obtain amino-functionalized graphene powder with a nitrogen content of 26 wt% and a size of 15 μm.

[0083] (3) The amino-functionalized graphene powder in step (2) is dispersed in N,N-dimethylformamide (DMF) to form a slurry with a concentration of 10%. Polyacrylonitrile fibers with a diameter of 18 μm are immersed in the N,N-dimethylformamide (DMF) solution of amino-functionalized graphene and mixed thoroughly. Then, the fibers are placed in an oven at 120 °C for drying treatment to obtain an infiltrated body of amino-functionalized graphene and polyacrylonitrile.

[0084] (4) The infiltrated body in step (3) is placed in a tube furnace at 200 °C for pre-oxidation treatment for 4 h to obtain a nitride composite fiber of N-N cross-linked graphene and carbon fiber, and the protective atmosphere is nitrogen.

[0085] (5) The nitride composite fiber in step (4) is placed in a high-temperature furnace at 1300 °C for cross-linking carbonization treatment for 5 h to remove the N-N bond and completely remove elements such as N and O, retaining the cross-linked composite carbon fiber structure, and the protective atmosphere is argon; then, the carbonized composite carbon fiber is continuously heated to a high-temperature environment of 1600 °C and treated for 11 h to obtain highly graphitized graphene-based carbon fiber filaments.

[0086] The strength, modulus, conductivity, and thermal conductivity of the highly graphitized graphene-based carbon fiber filaments prepared in this example are tested. Among them, the strength and modulus are tested using a universal testing machine, the conductivity is tested using a conductivity tester, and the thermal conductivity is tested using a thermal conductivity tester.

[0087] After testing, it is determined that the strength of the graphene-based carbon fiber composite material prepared in this example is as high as 5.8 GPa, the modulus is 259 GPa, the conductivity is 3.3×10 4 S / m, and the thermal conductivity is 620 W / m K, and the overall performance is improved by 1.2 times compared with pure carbon fiber filaments.

[0088] Comparative Example 1:

[0089] This example prepares graphene-based carbon fiber through the following steps:

[0090] (1) Disperse graphene oxide powder in dimethyl sulfoxide (DMSO) to form a slurry with a concentration of 10%. Immerse polyacrylonitrile fibers with a diameter of 15 μm in the dimethyl sulfoxide solution of graphene oxide, mix well, and then place the fibers in an oven at 120 °C for drying to obtain a graphene and polyacrylonitrile infiltrated body.

[0091] (2) Place the infiltrated body in step 1 in a tube furnace at 400 °C for pre-oxidation treatment for 2 h to obtain a nitride composite fiber of N-N cross-linked graphene and carbon fiber, with a protective atmosphere of nitrogen.

[0092] (3) Place the nitride composite fiber in step 2 in a high-temperature furnace at 1200 °C for cross-linking carbonization treatment to remove the N-N bond and completely remove elements such as N and O, retaining the cross-linked composite carbon fiber structure, with a protective atmosphere of argon; then continue to heat the carbonized composite carbon fiber to a high-temperature environment of 1800 °C and process it for 12 h to obtain graphene-based carbon fiber filaments.

[0093] Perform tests on the strength, modulus, conductivity, and thermal conductivity of the graphene-based carbon fiber filaments prepared in this example. Among them, the strength and modulus are tested using a universal testing machine, the conductivity is tested using a conductivity tester, and the thermal conductivity is tested using a thermal conductivity tester.

[0094] After testing, it is determined that the strength of the prepared graphene-based carbon fiber composite is 3.5 GPa, the conductivity is 2×10 4 S / m, and the thermal conductivity is 150 W / m K. Compared with existing market carbon fibers, the performance has not been effectively improved because the binding force between graphene oxide and polyacrylonitrile is not strong enough to achieve effective connection.

[0095] Comparative Example 2:

[0096] This example prepares graphene-based carbon fibers through the following steps:

[0097] (1) Place polyacrylonitrile fibers with a diameter of 15 μm in a tube furnace at 400 °C for pre-oxidation treatment for 2 h to obtain carbon fiber pre-oxidized filaments, with a protective atmosphere of nitrogen.

[0098] (2) Place the pre-oxidized filaments in step 1 in a high-temperature furnace at 1200 °C for cross-linking carbonization treatment to completely remove elements such as N and O, retaining the cross-linked carbon fiber structure, with a protective atmosphere of argon; then continue to heat the carbonized carbon fiber to a high-temperature environment of 1800 °C and process it for 12 h to obtain carbon fiber filaments.

[0099] The strength, modulus, electrical conductivity, and thermal conductivity of the graphene-based carbon fiber filaments prepared in this example were tested. Among them, the strength and modulus were tested using a universal testing machine, the electrical conductivity was tested using a conductivity tester, and the thermal conductivity was tested using a thermal conductivity tester.

[0100] After testing, it was determined that the strength of the graphene-based carbon fiber composite prepared in this example was 2.8 GPa, the electrical conductivity was 2×10 4 S / m, and the thermal conductivity was 100 W / m K. For comparison with the composite carbon fiber after adding graphene, in this comparative example, the original fiber diameter of polyacrylonitrile was processed into carbon fiber filaments.

[0101] Comparative Example 3:

[0102] In this example, the strength, modulus, electrical conductivity, and thermal conductivity of pure carbon fiber were tested. Among them, the strength and modulus were tested using a universal testing machine, the electrical conductivity was tested using a conductivity tester, and the thermal conductivity was tested using a thermal conductivity tester.

[0103] After testing, it was determined that the strength of the pure carbon fiber reached 4.8 GPa, the modulus was 200 GPa, the electrical conductivity was 2.3×10 4 S / m, and the thermal conductivity was 100 W / m K.

[0104] The specific experimental data of the above three groups of examples based on this solution and three groups of comparative examples are compared as follows:

[0105] Serial number Strength Modulus Electrical conductivity Thermal conductivity Example 1 6 GPa 260 GPa <![CDATA[3×10 4 S / m]]> 600 W / m K Example 2 5.5 GPa 258 GPa <![CDATA[3.1×10 4 S / m]]> 550 W / m K Example 3 5.8 GPa 259 GPa <![CDATA[3.3×10 4 S / m]]> 620 W / m K Comparative example 1 3.5 GPa / <![CDATA[2×10 4 S / m]]> 150 W / m K Comparative example 2 2.8 GPa / <![CDATA[2×10 4 S / m]]> 100 W / m K Pure carbon fiber 4.8 GPa 200 GPa <![CDATA[2.3×10 4 S / m]]> 100 W / m K

[0106] Through the comparison of the above examples, it can be seen that the graphene-based carbon fibers prepared by the graphene-based carbon fiber preparation scheme provided by the present invention have been greatly improved synchronously in terms of strength, modulus, electrical conductivity, and thermal conductivity compared with the graphene-based carbon fibers or pure carbon fibers prepared by the conventional scheme, effectively overcoming the major problem that it is difficult to graft other carbon materials on the surface of carbon fibers in this field, thereby further improving the performance and purity.

[0107] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. Preparation method of high-performance graphene-based carbon fiber, characterized in that, The preparation method mainly includes the following steps: (1) Dispersing graphene oxide powder in an organic solvent according to a certain proportion to form a uniform dispersion liquid, adding a certain proportion of nitrogen-containing small molecules as an ammonia source in the dispersion liquid to form a corresponding mixed liquid, subjecting the mixed liquid to hydrothermal reaction, and then performing freeze-drying treatment to obtain amino-functionalized graphene powder; the addition amount of the ammonia source in the graphene oxide dispersion solution is 3-4 wt%; the nitrogen content of the amino-functionalized graphene is 20-30 wt. %, and the sheet size is 10-20 μm; (2) Dissolving the amino-functionalized graphene powder obtained in step (1) in an organic solvent according to a certain proportion to form a dispersion liquid, fully immersing polyacrylonitrile fibers in the formed dispersion liquid to form a mixed liquid of amino-functionalized graphene and polyacrylonitrile fibers, and then taking out the mixed liquid and drying it to remove the organic solvent to obtain polyacrylonitrile fibers infiltrated with amino-functionalized graphene; (3) Performing pre-oxidation treatment on the polyacrylonitrile fibers infiltrated with amino-functionalized graphene obtained in step (2) to bond the N element in the amino-functionalized graphene with the N element in the polyacrylonitrile to form a nitride composite fiber; (4)Continuously crosslink and carbonize the nitrided composite fibers generated in step (3) at a high temperature of 1000 - 1300 °C to remove nitrogen-containing chemical bonds, leaving only C elements and carbon-containing chemical bonds to form a composite carbon fiber material, and then further raise the temperature to 1400 - 1800 °C for graphitization treatment to transform the original carbon structure to form more sp 2 hybridized π=π conjugated structure carbon to form highly crystalline graphene-based carbon fibers.

2. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, wherein, The graphene oxide in step (1) serves as a precursor of the amino-functionalized graphene, and the size of the graphene oxide is 10-20 μm and the oxygen content is 30-36 wt%.

3. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, wherein, The ammonia source substance is one or more of melamine, ethylenediamine, hexamethylenediamine, triethylenetetramine, ammonium hydroxide, etc.

4. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, characterized in that The diameter of the polyacrylonitrile fiber is 15-20 μm.

5. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, characterized in that, The organic solvent is one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylacetamide (DMAC).

6. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, characterized in that, The pre-oxidation treatment temperature of the composite fiber is 200-400 °C, and the time is 2-4 h.

7. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, characterized in that, The time for crosslinking carbonization treatment in step (4) is 4-6 h.

8. The preparation method of the high-performance graphene-based carbon fiber according to claim 1, wherein, The time for graphitization treatment in step (4) is 10-12 h.

Images