Preparation method for high-performance graphene-based carbon fiber

Abstract

A preparation method for a high-performance graphene-based carbon fiber, comprising the following steps: (1) dispersing graphene oxide powder in an organic solvent to form a uniform dispersion liquid, adding an ammonia source into the dispersion liquid to form a corresponding mixed solution, and obtaining aminated graphene powder; (2) dissolving the aminated graphene powder in an organic solvent to form a dispersion liquid, and fully soaking a polyacrylonitrile fiber in the formed dispersion liquid to obtain the polyacrylonitrile fiber infiltrated with aminated graphene; (3) performing pre-oxidation treatment on the polyacrylonitrile fiber infiltrated with aminated graphene, so as to form a nitride composite fiber; and (4) continuously performing cross-linking carbonization on the nitride composite fiber at a high temperature of 1000-1300°C to form a composite carbon fiber material, and then heating to 1400-1800°C to perform graphitization treatment to form the graphene-based carbon fiber having high crystallinity. The graphene-based carbon fiber prepared by the preparation method has high strength and high conductivity.

Description

A method for preparing high-performance graphene-based carbon fiber Technical Field

[0001] The present invention relates to the field of composite carbon fiber materials, in particular to a method for preparing a carbon fiber material composited with graphene as a base material. Background Art

[0002] Graphene has super high mechanical properties, with a modulus of 1100GPa and a strength of 130GPa; it also has super high thermal conductivity, up to 5300W / (m·K); super high electrical conductivity, up to 10 8 S / m, and ultra-high current carrying capacity.

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

[0004] If the two can be further combined, the advantages of the two can be combined to obtain a composite material with the common advantages of the two. The existing technology also provides some composite solutions for this.

[0005] Chinese patent application publication number CN113136640 A discloses a method for producing graphene-based carbon fibers at room temperature, using graphene oxide as the assembly unit to produce macroscopic graphene-based carbon fibers. The graphene carbon fibers produced by this method are made from graphene, but the graphene sheets are not chemically bonded together, resulting in a weak internal continuity and insufficient strength of the fibers.

[0006] Chinese patent application publication number CN 109423702 A discloses a method for preparing carbon fibers by using a solution spinning method to spin a mixture of an aqueous solution of graphene oxide and a polymer solution into graphene oxide-based initial fibers, which are then carbonized to form carbon fibers. This method utilizes graphene oxide spinning technology, but carbonization also suffers from the problem of weak interlayer connectivity between graphene sheets.

[0007] Chinese patent application publication number CN110747537 A discloses a method for preparing lignin / graphene-based carbon fibers by mixing a graphene dispersion with a purified lignin solution in a specific ratio. This solution is then ion-complexed with a chitosan solution using a polyelectrolyte complex spinning method to produce lignin / graphene oxide composite fibers. The composite fibers are then carbonized at high temperature in a tubular furnace under a nitrogen atmosphere to produce lignin / graphene-based carbon fibers. The carbonization of the lignin creates pores and cracks within the fibers, significantly impacting their strength and conductivity.

[0008] Chinese patent application publication number CN102534870A discloses a method for preparing graphene-modified polyacrylonitrile carbon fibers by uniformly dispersing a graphene suspension into a polyacrylonitrile solution using a blending method; using this solution as a spinning solution to prepare fiber precursors via a wet spinning or dry-jet wet spinning process; and finally, pre-oxidation and carbonization treatment to obtain graphene-modified polyacrylonitrile-based carbon fibers. This method involves a physical connection between the graphene and carbon fibers, which is insufficient and may cause dust loss later.

[0009] Chinese patent application publication number CN 103320901 A discloses a method for preparing a solvated mesophase pitch, mixing the mesophase pitch with graphene oxide in a liquid phase, recovering the solvent, and heating the mixture to produce a melt-induced liquid crystal. This mixture is melt-spun to produce precursor fibers, which are then pre-oxidized and carbonized to produce high-strength, high-modulus, and highly conductive carbon fibers. This method, similar to the lignin-based method, involves structural collapse and loss during the carbonization of the pitch, resulting in defects within the fibers.

[0010] Chinese patent application publication number CN116285007A discloses a method for preparing aminated graphene powder that can be directly and efficiently dispersed in an organic system. The method involves adding multiple amine monomers to a graphene oxide solution, and specifically conducting a polymerization reaction based on the surface functional groups of the graphene oxide. The reaction product is essentially a co-embedded polymer of graphene and a nitrogen-containing polymer, which is a high-molecular polymerization reaction, not a separate aminated graphene. However, due to its large volume, this high-molecular polymer easily entangles with the fiber during the fiber composite process and is discarded. Furthermore, the in-situ polymerization process has many steps, and each link requires precise control. The separation of reaction byproducts and waste treatment in the later stage is costly and involves multiple processes.

[0011] Chinese patent application publication number CN104862828A discloses a high thermal conductivity carbon fiber and a preparation method thereof. It proposes preparing high thermal conductivity polyacrylonitrile fiber by adding graphene concentrate through in-situ polymerization or dissolution method, and then pre-oxidizing, carbonizing and graphitizing the high thermal conductivity polyacrylonitrile fiber to obtain high thermal conductivity carbon fiber. Ultrafine graphene concentrate is used in this solution, and there is no functional group on the surface. During the polymerization of acrylonitrile monomer, the graphene will be wrapped. Although the composite process is carried out through chemical reaction, the final product is a physical composite of graphene and polyacrylonitrile fiber, and no strong chemical bond is formed between the two. That is, the connection between graphene and acrylonitrile is not tight, and it is easy to agglomerate and lose powder.

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

[0013] (1) Most existing solutions are process solutions for the composite of carbon fiber and graphene based on different resins. Graphene is added during the fiber composite process and then carbonized together to form composite carbon fiber. The advantage of this solution of adding graphene during the process is that it can achieve the combination of graphene and carbon fiber. However, the connection is physical or mixed, which is complex and the resulting structure is prone to defects during the back-end processing, resulting in insufficient conductivity and mechanical strength.

[0014] (2) In the existing scheme, graphene is used 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. In the process of large-scale industrialization, the batch consistency of the product is difficult to control.

[0015] Summary of the Invention

[0016] In response to 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 problems of difficult combination and grafting 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.

[0017] In order to achieve the above object, the present invention provides a method for preparing high-performance graphene-based carbon fibers, which mainly comprises the following steps:

[0018] (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 to obtain amino-treated graphene powder;

[0019] (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 the aminated graphene and the polyacrylonitrile fiber, and then taking out the mixed solution, drying it to remove the organic solvent, and obtaining the polyacrylonitrile fiber impregnated with the aminated graphene;

[0020] (3) performing a pre-oxidation treatment on the polyacrylonitrile fiber impregnated with the amino-treated graphene obtained in step (2) to chemically bond the nitrogen element in the amino-treated graphene with the nitrogen element in the polyacrylonitrile to form a nitride composite fiber;

[0021] (4) The nitride 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 retain only the C element and the carbon-containing chemical bonds to form a composite carbon fiber material. The temperature is then further increased to 1400-1800°C for graphitization treatment to transform the original carbon structure into more sp 2 Hybridized π=π conjugated structure carbon forms highly crystalline graphene-based carbon fibers.

[0022] In some embodiments of the present invention, the graphene oxide in step (1) is used as a precursor of nitrogen-doped graphene, and the graphene oxide has a size of 10-20 μm and an oxygen content of 30-36 wt.%.

[0023] In some examples of the present invention, the ammonia source is one or more of melamine, ethylenediamine, hexamethylenediamine, triethylenetetramine, ammonium hydroxide, and the like.

[0024] In some examples of the present invention, the amount of the ammonia source added to the graphene oxide dispersion solution is 3-4 wt.%.

[0025] In some examples of the present invention, the nitrogen content of the amino-treated graphene is 20-30 wt.%, and the sheet size is 10-20 μm.

[0026] In some examples of the present invention, the polyacrylonitrile fiber has a diameter of 15-20 μm.

[0027] In some embodiments of the present invention, the organic solvent is one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and dimethylformamide (DMAC).

[0028] In some embodiments of the present invention, the temperature of the composite fiber pre-oxidation treatment in step (3) is 200-400° C. and the time is 2-4 hours;

[0029] In some embodiments of the present invention, the cross-linking carbonization treatment in step (4) is performed at a temperature of 1000-1300° C. for 4-6 hours.

[0030] In some embodiments of the present invention, the graphitization treatment temperature in step (4) is 1400-1800° C. and the time is 10-12 hours.

[0031] The graphene-based carbon fiber preparation scheme provided by the present invention can produce high-performance graphene-based carbon fibers with high strength and strong electrical conductivity.

[0032] Furthermore, the graphene-based carbon fiber preparation solution provided by the present invention has the following technical features compared to the prior art:

[0033] (1) The amino-treated graphene in the present invention is more easily cross-linked with polyacrylonitrile, thereby increasing the bonding strength between the graphene and the carbon fiber;

[0034] (2) In the scheme of the present invention, after multiple heating processes, the chemical bonds inside the composite fiber are gradually transformed from bonding, debonding and impurity removal, and finally C-C and C=C structures into π=π double bonds, so that the final carbon fiber has greatly improved both structure and performance;

[0035] (3) When the present invention is finally formed, the graphene composite carbon fiber structure contains a large amount of conjugated carbon structures, which greatly improves the strength and conductivity of the carbon fiber;

[0036] (4) The present invention effectively combines the performance advantages of graphene and carbon fiber, overcoming the major problem in the field of carbon fiber that is difficult to graft other carbon materials onto the surface, thereby further improving the performance and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0038] FIG1 is a synthetic reaction diagram of the preparation process of graphene-based composite carbon fibers in an example of the present invention. DETAILED DESCRIPTION

[0039] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific illustrations.

[0040] Through a thorough study of the properties of graphene and carbon fiber materials, and in response to the technical difficulty in chemically bonding other materials to the surface of carbon fiber in the prior art, the present invention innovatively adopts the idea of ​​combining graphene amino functionalization with polyacrylonitrile fiber to achieve chemical bonding between graphene and carbon fiber, so that the two are connected to form a true whole, thereby preparing a composite fiber of chemically bonded graphene and carbon fiber, with significantly improved conductivity and strength.

[0041] This scheme adopts an innovative hydrothermal polymerization amination method to form amination graphene powder. Compared with the existing scheme, this scheme replaces the oxygen-containing functional groups in the original graphene oxide by adding amino-containing small molecules (i.e., a separate functional group replacement reaction is performed), thereby connecting amino groups to the graphene sheets. No macromolecular polymerization process is required, the material utilization rate is 100%, there are no by-products, the production cost is low, the process is simple, and there is no pollution, making it suitable for fiber composites.

[0042] On this basis, the present invention further prepares high-performance graphene-based carbon fibers based on the formed amino-treated graphene powder through amino bonding and carbonization processes, which can effectively overcome the problems existing in the existing technology.

[0043] Based on the above mechanism, the present invention provides a solution for preparing high-performance graphene-based carbon fibers. The solution is based on graphene oxide powder and polyacrylonitrile fiber, and is prepared by combining the following steps.

[0044] Specifically, in step (1), graphene oxide powder is dispersed in an organic solvent at a ratio of 5-10 wt.% to form a uniform dispersion, a certain ratio of nitrogen-containing small molecules is added to the dispersion as an ammonia source to form a corresponding mixed solution, the mixed solution is subjected to a hydrothermal reaction, and then freeze-dried to obtain amination graphene powder. In this step, amino functional group grafting is achieved by a hydrothermal reaction. Compared with other existing schemes, the reaction process is mild, the cost is low, and the obtained material is relatively pure and free of impurities.

[0045] (2) dissolving the aminated graphene powder obtained in step (1) in an organic solvent at a ratio of 10 wt.% to form a dispersion, fully immersing the polyacrylonitrile fiber in the dispersion to form a mixture of the aminated graphene and the polyacrylonitrile fiber, and then taking out the mixture and drying it to remove the organic solvent, thereby obtaining the polyacrylonitrile fiber impregnated with the aminated graphene;

[0046] (3) Pre-oxidation treatment is performed on the polyacrylonitrile fiber impregnated with amino graphene obtained in step (2), so that the N element in the amino graphene is chemically bonded with the N element in the polyacrylonitrile to form a nitride composite fiber. The composite fiber here is a graphene and polyacrylonitrile composite fiber containing a -N=N- or -NH-NH- chemical bond in the middle. In the composite fiber, the nitrogen element in the graphene is at the edge of the graphene, and the nitrogen element in the polyacrylonitrile is distributed on the fiber surface. After the two are combined, a bonding relationship of -N=N- or -NH-NH- can be formed between the nitrogen of the two, thereby connecting the two together;

[0047] (4) The nitride 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, leaving only the C element and the carbon-containing chemical bonds. The final CC and C=C structures are converted into π=π double bonds to form a composite carbon fiber material, and then further increased to 1400-1800 ° C for graphitization treatment to transform the original carbon structure into more sp 2 Hybridized π=π conjugated structure carbon forms highly crystalline graphene-based carbon fibers.

[0048] In some embodiments of the present invention, in this preparation scheme, graphene oxide is used as a precursor of amination graphene, and the graphene oxide preferably has a size of 10-20 μm and an oxygen content of 30-36 wt % so as to adapt to polyacrylonitrile fiber to form a stable structure.

[0049] Furthermore, in this preparation scheme, the obtained amino graphene (i.e., nitrogen-doped graphene) has a nitrogen content of 20-30wt% and a graphene sheet of 10-20μm, which can correspond to each other when subsequently composited with polyacrylonitrile fiber, and can form a stable connection with the polyacrylonitrile fiber based on the doped nitrogen functional group.

[0050] In some embodiments of the present invention, the organic solvent used in step 1 of this preparation scheme includes one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylformamide (DMAC), etc. The use of nitrogen-containing organic solvents is conducive to dispersing nitrogen-containing graphene and polyacrylonitrile fibers.

[0051] Furthermore, in the preparation scheme, the proportion of graphene oxide powder in step 1 is preferably such that the concentration of graphene oxide powder in the dispersion is 5-10 wt.%. This ensures the stability of subsequent bonding with carbon fibers. If the addition amount is too small, the bonding between the two will not be improved. If too much is added, the excess graphene cannot bond with the carbon fibers, resulting in graphene powder falling off the formed fibers.

[0052] In some embodiments of the present invention, the ammonia source used in step (1) of the preparation scheme is preferably one or more of melamine, ethylenediamine, hexamethylenediamine, triethylenetetramine, ammonium hydroxide, and the like; and the amount of the ammonia source added to the graphene oxide solution is 3-4 wt.%. Such a nitrogen-like source is a small molecule nitrogen-containing compound that is easily soluble in an organic solvent and has a relatively low chemical binding energy with graphene, making it easy to react. Furthermore, the addition of the ammonia source in an amount of 3-4 wt.% can maximize the degree of amination of the graphene, approaching 100% amino functionalization substitution, thereby ensuring maximum subsequent bonding with the polyacrylonitrile fiber.

[0053] In some embodiments of the present invention, in step (1) of this preparation scheme, when preparing the aminated graphene powder from the mixed solution, the mixed solution is preferably placed in a hydrothermal reactor at 200° C. for hydrothermal reaction, and then freeze-dried for 12 hours to obtain the aminated graphene powder. In this way, a corresponding high-temperature and high-pressure reaction environment is formed to meet the optimal conditions for amino groups to replace epoxy functional groups. If the temperature is too high, the risk of the reaction is increased, and unnecessary side reactions are also increased, resulting in the decomposition of the newly formed aminated graphene. If the temperature is too low, the substitution reaction cannot proceed.

[0054] In some embodiments of the present invention, the organic solvent used in step (2) of the preparation scheme also includes one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylformamide (DMAC), etc.

[0055] 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 close to the size of the graphene sheet used, and can effectively bond with the graphene during the bonding process without causing the graphene to wrap around the surface. This ensures that the connection of the graphene is on the fiber surface, forming a fiber-graphene-fiber connection between the fibers, and can further enhance the overall structural strength.

[0056] Furthermore, in the preparation scheme, when soaking the polyacrylonitrile fiber in step (2), the pre-prepared polyacrylonitrile fiber is immersed in a dispersion formed by the amino graphene powder to completely soak it. The soaking vessel is a square or circular groove, and the polypropylene fiber is arranged along the groove or placed in a ring shape, ensuring that the fiber is soaked in the solution for 2 hours to form a mixed solution of the amino graphene and the polyacrylonitrile fiber, so as to ensure that the amino graphene and the polyacrylonitrile fiber are fully combined and reacted.

[0057] Furthermore, in step (2) of this preparation scheme, the solvent is preferably removed by drying at 120° C., so that the liquid portion of the mixed solution can be completely volatilized.

[0058] In some embodiments of the present invention, the temperature for pre-oxidation treatment of the composite fiber in step (3) of the present preparation scheme is preferably 200-400°C and the time is 2-4 hours, so as to ensure that the nitrogen-containing groups of the two materials react with each other to form effective -N=N- and -NH-NH- chemical bonds.

[0059] In some embodiments of the present invention, when the cross-linking carbonization treatment is performed in step (4) of the preparation scheme, the temperature is 1000-1300°C and the time is 4-6 hours in a vacuum environment, so that the carbonization can achieve the connection of pure carbon-carbon chemical bonds and remove other elements; at the same time, when the graphitization treatment is performed, the temperature is 1400-1800°C and the time is 10-12 hours in a vacuum environment.

[0060] The high-performance graphene-based carbon fiber solution provided by the present invention creatively uses amino graphene as a raw material, which makes it easier to bond with the N element in polyacrylonitrile. As shown in Figure 1, the solution of the present invention adopts a hydrothermal reaction method in the amination reaction of graphene oxide, rather than high-temperature heating, which is more conducive to energy saving and environmental protection, and the process is also relatively safe; then, in the pre-oxidation process, a relatively low heating temperature is used to cause the reaction to be a NN, NO bonding and curing process. During the process, the chemical bond of the N element is changed, thereby transforming the polyacrylonitrile structure; then a cross-linking carbonization process is carried out, which specifically involves the rupture of N, O-containing functional groups, the volatilization of small molecules of the N, O elements, and the rebonding and rearrangement of the C element to form a full carbon cross-linked structure; finally, a higher-temperature graphitization process is carried out, which specifically involves the sp 3 Carbon to sp 2 During the process of carbon structure transformation, the hexagonal conjugated structure of carbon increases and the crystallinity is higher.

[0061] The following further illustrates the implementation process and corresponding technical features of the solution provided by the present invention through corresponding application examples.

[0062] Example 1:

[0063] This example is based on the solution of the present invention and specifically prepares high-performance graphene-based carbon fibers through the following steps:

[0064] (1) Graphene oxide was used as a precursor of nitrogen-doped graphene, with a graphene oxide size of 10 μm and an oxygen content of 36 wt.%. The graphene oxide was dispersed in N,N-dimethylformamide (DMF) in proportion to a dispersion concentration of 8 wt.%, and the mixture was fully mixed to form a viscous solution. Melamine powder was added to the graphene oxide dispersion at a ratio of 4 wt.%, and the mixture was fully stirred and mixed in a shear mixer to obtain a uniformly dispersed slurry. The stirring time was 30 min and the rotation speed was 500 rpm.

[0065] (2) The uniformly dispersed graphene oxide and melamine dispersion slurry was placed in a hydrothermal reactor and reacted at 200°C for 12 hours to fully replace the nitrogen-containing groups in melamine with the oxygen-containing groups in graphene oxide. After being taken out, it was placed in a freeze dryer for drying to obtain amino-modified graphene powder with a nitrogen content of 30 wt.% and a size of 10 μm.

[0066] (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 fiber with a diameter of 15 μm is immersed in the dimethyl sulfoxide solution of aminated graphene and mixed thoroughly. The fiber is then placed in an oven at 120°C for drying to obtain an aminated graphene and polyacrylonitrile impregnation body.

[0067] (4) The impregnated body in step 3 is placed in a tube 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.

[0068] (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 N-N 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.

[0069] The highly graphitized graphene-based carbon fiber filaments prepared in this example were tested for strength, modulus, electrical conductivity, and thermal conductivity. Strength and modulus were tested using a universal testing machine, electrical conductivity was tested using a conductivity tester, and thermal conductivity was tested using a thermal conductivity coefficient tester.

[0070] 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, and overall performance improvement of 1.3 times compared with pure carbon fiber filaments.

[0071] Example 2:

[0072] This example is based on the solution of the present invention and specifically prepares high-performance graphene-based carbon fibers through the following steps:

[0073] (1) Graphene oxide was used as a precursor of nitrogen-doped graphene, with a size of 20 μm and an oxygen content of 36 wt.%. The graphene oxide was dispersed in dimethylformamide (DMAC) at a dispersion concentration of 5 wt.%, and fully mixed to form a viscous solution. Melamine powder was added to the graphene oxide dispersion at a ratio of 3 wt.%, and the mixture was fully stirred and mixed in a shear mixer to obtain a uniformly dispersed slurry. The stirring time was 30 min and the rotation speed was 500 rpm.

[0074] (2) The uniformly dispersed graphene oxide and ethylenediamine dispersion slurry is placed in a hydrothermal reactor and reacted at 200°C for 12 hours to fully replace the nitrogen-containing groups in ethylenediamine with the oxygen-containing groups in graphene oxide. After being taken out, it is placed in a freeze dryer for drying to obtain amino-modified graphene powder with a nitrogen content of 20wt% and a size of 20μm.

[0075] (3) The aminated graphene powder in step 2 is dispersed in N,N-dimethylformamide (DMF) to obtain a slurry with a concentration of 10%. Polyacrylonitrile fiber with a diameter of 20 μm is immersed in the N,N-dimethylformamide (DMF) solution of aminated graphene and mixed thoroughly. The fiber is then placed in an oven at 120°C for drying to obtain an aminated graphene and polyacrylonitrile impregnation body.

[0076] (4) The impregnated body in step 3 is placed in a tube furnace at 200° C. for pre-oxidation treatment for 4 h to obtain NN cross-linked graphene and carbon fiber nitride composite fibers, with the protective atmosphere being nitrogen.

[0077] (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 N-N 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 a high-temperature environment of 1400°C and treated for 10 hours to obtain highly graphitized graphene-based carbon fiber filaments.

[0078] The highly graphitized graphene-based carbon fiber filaments prepared in this example were tested for strength, modulus, electrical conductivity, and thermal conductivity. Strength and modulus were tested using a universal testing machine, electrical conductivity was tested using a conductivity tester, and thermal conductivity was tested using a thermal conductivity coefficient tester.

[0079] 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.

[0080] Example 3:

[0081] This example is based on the solution of the present invention and specifically prepares high-performance graphene-based carbon fibers through the following steps:

[0082] (1) Graphene oxide was used as a precursor of nitrogen-doped graphene, with a size of 16 μm and an oxygen content of 33 wt.%. The graphene oxide was dispersed in dimethyl sulfoxide (DMSO) at a dispersion concentration of 6 wt.%, and fully mixed to form a viscous solution. Melamine powder was added to the graphene oxide dispersion at a ratio of 3.5 wt.%, and the mixture was fully stirred and mixed in a shear mixer to obtain a uniformly dispersed slurry. The stirring time was 30 min and the rotation speed was 500 rpm.

[0083] (2) The uniformly dispersed graphene oxide and ethylenediamine dispersion slurry was placed in a hydrothermal reactor and reacted at 200°C for 12 hours to fully replace the nitrogen-containing groups in ethylenediamine with the oxygen-containing groups in graphene oxide. After being taken out, it was placed in a freeze dryer for drying to obtain amino-modified graphene powder with a nitrogen content of 26 wt.% and a size of 15 μm.

[0084] (3) The aminated graphene powder in step 2 is dispersed in N,N-dimethylformamide (DMF) to obtain a slurry with a concentration of 10%. Polyacrylonitrile fiber with a diameter of 18 μm is immersed in the N,N-dimethylformamide (DMF) solution of aminated graphene and mixed thoroughly. The fiber is then placed in an oven at 120°C for drying to obtain an aminated graphene and polyacrylonitrile impregnation body.

[0085] (4) The impregnated body in step 3 is placed in a tube furnace at 200° C. for pre-oxidation treatment for 4 h to obtain NN cross-linked graphene and carbon fiber nitride composite fibers, with the protective atmosphere being nitrogen.

[0086] (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 hours to remove the N-N 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 a high-temperature environment of 1600°C and treated for 11 hours to obtain highly graphitized graphene-based carbon fiber filaments.

[0087] The highly graphitized graphene-based carbon fiber filaments prepared in this example were tested for strength, modulus, electrical conductivity, and thermal conductivity. Strength and modulus were tested using a universal testing machine, electrical conductivity was tested using a conductivity tester, and thermal conductivity was tested using a thermal conductivity coefficient tester.

[0088] The test results show that the graphene-based carbon fiber composite material prepared in this example has a strength of up to 5.8 GPa, a modulus of 259 GPa, and a conductivity of 3.3×10 4 S / m, thermal conductivity 620W / m K, the overall performance is improved by 1.2 times compared with pure carbon fiber filaments.

[0089] Comparative Example 1:

[0090] In this example, graphene-based carbon fibers are prepared by the following steps:

[0091] (1) Graphene oxide powder was dispersed in dimethyl sulfoxide (DMSO) to form a slurry with a concentration of 10%. Polyacrylonitrile fiber with a diameter of 15 μm was immersed in the graphene oxide dimethyl sulfoxide solution and mixed thoroughly. The fiber was then placed in an oven at 120°C for drying to obtain a graphene and polyacrylonitrile impregnation body.

[0092] (2) The impregnated body in step 1 is placed in a tube furnace at 400° C. for pre-oxidation treatment for 2 h to obtain NN cross-linked graphene and carbon fiber nitride composite fibers, with the protective atmosphere being nitrogen.

[0093] (3) The nitride composite fiber in step 2 is placed in a high-temperature furnace at 1200°C for cross-linking carbonization treatment to remove the N-N 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 graphene-based carbon fiber filaments.

[0094] The graphene-based carbon fiber filaments prepared in this example were tested for strength, modulus, electrical conductivity, and thermal conductivity. Strength and modulus were tested using a universal testing machine, electrical conductivity was tested using a conductivity tester, and thermal conductivity was tested using a thermal conductivity coefficient tester.

[0095] The test results show that the strength of the graphene-based carbon fiber composite material prepared is 3.5GPa and the conductivity is 2×10 4 S / m, thermal conductivity 150W / m K. Compared with the existing carbon fibers on the market, the performance has not been effectively improved because the bonding force between graphene oxide and polyacrylonitrile is not strong enough to achieve effective connection.

[0096] Comparative Example 2:

[0097] In this example, graphene-based carbon fibers are prepared by the following steps:

[0098] (1) Polyacrylonitrile fiber with a diameter of 15 μm was placed in a tube furnace at 400 °C for pre-oxidation treatment for 2 h to obtain carbon fiber pre-oxidation yarn. The protective atmosphere was nitrogen.

[0099] (2) The pre-oxidized fiber in step 1 is placed in a high-temperature furnace at 1200°C for cross-linking and carbonization treatment to completely remove elements such as N and O, retaining the cross-linked carbon fiber structure, and the protective atmosphere is argon; then the carbonized carbon fiber is further heated to 1800°C and treated for 12 hours to obtain carbon fiber fiber.

[0100] The graphene-based carbon fiber filaments prepared in this example were tested for strength, modulus, electrical conductivity, and thermal conductivity. Strength and modulus were tested using a universal testing machine, electrical conductivity was tested using a conductivity tester, and thermal conductivity was tested using a thermal conductivity coefficient tester.

[0101] The test results show that the strength of the graphene-based carbon fiber composite material prepared in this example is 2.8 GPa and the conductivity is 2×10 4 S / m, thermal conductivity 100W / m K, used for comparison with the composite carbon fiber after adding graphene. In this comparative example, the diameter of the polyacrylonitrile raw fiber is processed into carbon fiber fiber.

[0102] Comparative Example 3:

[0103] This example tests the strength, modulus, electrical conductivity, and thermal conductivity of pure carbon fiber. Strength and modulus are tested using a universal testing machine, electrical conductivity is tested using a conductivity tester, and thermal conductivity is tested using a thermal conductivity coefficient tester.

[0104] The test results show that the strength of pure carbon fiber is 4.8GPa, the modulus is 200GPa, and the conductivity is 2.3×10 4 S / m, thermal conductivity 100W / m K.

[0105] The specific experimental data comparison of the above three groups of embodiments based on this solution and three groups of comparative examples are as follows:

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

[0107] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-performance graphene-based carbon fibers, characterized in that: The preparation method mainly comprises the following steps: (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; (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 the aminated graphene and the polyacrylonitrile fiber, and then taking out the mixed solution and drying it to remove the organic solvent, thereby obtaining the polyacrylonitrile fiber impregnated with the aminated graphene; (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; (4) The nitride 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, leaving only the C element and the carbon-containing chemical bonds to form a composite carbon fiber material, and then further raised to 1400-1800°C for graphitization treatment to transform the original carbon structure into more sp 2 Hybridized π=π conjugated structure carbon forms highly crystalline graphene-based carbon fibers.

2. The method for preparing high-performance graphene-based carbon fiber according to claim 1, characterized in that: The graphene oxide in step (1) is used as a precursor of amination graphene, and the graphene oxide has a size of 10-20 μm and an oxygen content of 30-36 wt.%.

3. The method for preparing high-performance graphene-based carbon fiber according to claim 1, characterized in that: The ammonia source material is one or more of melamine, ethylenediamine, hexamethylenediamine, triethylenetetramine, ammonium hydroxide and the like.

4. The method for preparing high-performance graphene-based carbon fiber according to claim 3, characterized in that: The amount of the ammonia source added to the graphene oxide dispersion solution is 3-4 wt.%.

5. The method for preparing high-performance graphene-based carbon fiber according to claim 1, characterized in that: The nitrogen-doped graphene material has a nitrogen content of 20-30 wt.% and a sheet size of 10-20 μm.

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

7. The method for preparing 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 dimethylformamide (DMAC).

8. The method for preparing high-performance graphene-based carbon fiber according to claim 1, characterized in that: The composite fiber pre-oxidation treatment temperature is 200-400°C and the time is 2-4h; 9. The method for preparing high-performance graphene-based carbon fiber according to claim 1, characterized in that: The cross-linking carbonization treatment in step (4) is carried out at a temperature of 1000-1300° C. and for a time of 4-6 hours.

10. The method for preparing high-performance graphene-based carbon fiber according to claim 1, characterized in that: The graphitization treatment temperature in step (4) is 1400-1800° C. and the time is 10-12 hours.

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