Carbon nanotube / graphene composite fiber and preparation method thereof

Abstract

The invention discloses a carbon nanotube / graphene composite fiber and a preparation method thereof, and the preparation method comprises the following steps: mixing graphene powder with chlorosulfonic acid to obtain a graphene / chlorosulfonic acid dispersion liquid; immersing a carbon nanotube into the graphene / chlorosulfonic acid dispersion liquid, and drafting the carbon nanotube fiber; and taking out the carbon nanotube fiber, and carrying out heat treatment under a protective atmosphere to obtain the carbon nanotube / graphene composite fiber silk yarn. According to the invention, chlorosulfonic acid is used for generating protonation on carbon nanotube fibers, so that the carbon nanotube fibers are swelled, combination between tube bundles is removed, and conditions are provided for recombination and re-orientation of an internal structure; the graphene two-dimensional sheet structure is axially inserted into gaps of the carbon nanotubes in the drafting process to cooperatively construct an orderly arranged three-dimensional network structure, so that the orientation degree is improved, the pore structure is compressed, the defect density is reduced, the interface bonding force and the load transmission efficiency are enhanced, and the mechanical properties of the fiber under quasi-static state and high strain rate are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite fibers, and particularly relates to a carbon nanotube / graphene composite fiber and a preparation method thereof. Background Art

[0002] Due to its unique structure and excellent physical and chemical properties, such as high strength, high modulus, excellent electrical and thermal conductivity, and ultra-light mass, carbon nanotubes have been widely studied and applied in the field of high-performance fibers. However, since the excellent properties of single carbon nanotubes are difficult to be directly reflected on the macroscopic scale, the development of macroscopic assemblies of carbon nanotubes, such as carbon nanotube fibers, has become the focus of current research.

[0003] Traditional preparation methods of carbon nanotube fibers mainly include floating catalyst chemical vapor deposition method, array stretching method, wet spinning method, etc. Although these methods can successfully prepare carbon nanotube fibers, due to the low orientation degree of carbon nanotubes inside the fibers and the weak binding force between tube bundles, the mechanical properties of the prepared carbon nanotube fibers are far lower than the theoretical limit of single carbon nanotubes. In addition, in a high strain rate environment, mechanical stability is crucial for the application of fiber materials in protective clothing, composite armor, and spacecraft structures, and there is still a large room for improvement in the impact resistance of carbon nanotube fibers.

[0004] In recent years, in order to improve the mechanical properties of carbon nanotube fibers, researchers have proposed various enhancement strategies, including increasing the orientation degree of carbon nanotubes, increasing the densification degree of fibers, optimizing the interfacial interaction force of fibers, etc. Existing research has attempted to use chlorosulfonic acid solvent to disperse and reconstruct carbon nanotubes, and at the same time introduce graphene as an interfacial reinforcement material to improve the binding force between tube bundles. However, existing methods mainly focus on solution spinning and chemical compounding, and there are still obvious deficiencies in the reorientation of carbon nanotubes, the densification of the structure, and the improvement of the interfacial strength.

[0005] Therefore, it is of great significance to research and develop a carbon nanotube-based composite fiber with high orientation degree, dense structure, and strong interfacial binding force to improve its mechanical properties. Summary of the Invention

[0006] The present invention aims at the deficiencies in the prior art and provides a carbon nanotube / graphene composite fiber and a preparation method thereof. Chlorosulfonic acid is used as a strong acid to protonate the carbon nanotube (CNT) fiber, so that the CNT fiber swells and releases the bonding between the tube bundles, thereby providing conditions for the reorganization and reorientation of the internal structure. The graphene is stably dispersed in the chlorosulfonic acid, and its two-dimensional sheet structure is inserted into the gaps of the carbon nanotubes along the axial direction during the drawing process to collaboratively construct an orderly arranged three-dimensional network structure. The orientation degree of the carbon nanotubes and the graphene in the axial direction of the fiber is significantly improved through auxiliary drawing, the pore structure is effectively compressed, the defect density is reduced, the interface bonding force and the load transfer efficiency are enhanced, and the mechanical properties of the fiber under quasi-static conditions and high strain rates are significantly improved.

[0007] In order to solve the above technical problems, the first aspect of the present invention provides a method for preparing carbon nanotube / graphene composite fibers, comprising the following steps:

[0008] S1, mixing graphene powder with chlorosulfonic acid to obtain a graphene / chlorosulfonic acid dispersion;

[0009] S2, immersing the carbon nanotubes in a graphene / chlorosulfonic acid dispersion and drawing the carbon nanotube fibers;

[0010] Among them, the stretching time is 30-300s, and the stretching elongation is 30%-70%;

[0011] S3, taking out the carbon nanotube fiber, and subjecting it to heat treatment under a protective atmosphere to obtain the carbon nanotube / graphene composite fiber thread.

[0012] The present invention places carbon nanotube fibers in a graphene / chlorosulfonic acid dispersion. In a chlorosulfonic acid environment, carbon nanotubes are protonated, the binding force between tube bundles is significantly reduced, and the carbon nanotube fibers are swollen and reconfigurable. At the same time, the two-dimensional structure of graphene nanosheets uniformly dispersed in chlorosulfonic acid is inserted into the gaps between carbon nanotubes and arranged in an orderly manner along the axial direction under the driving force of carbon nanotube drawing, forming a synergistically enhanced composite network. Importantly, the carbon nanotube drawing process can not only induce the carbon nanotubes and graphene to be highly oriented in the axial direction, but also promote the densification and defect reconstruction of the structure, significantly enhance the interface coupling and load transfer efficiency of the composite fiber, and thus improve the mechanical properties of the fiber under quasi-static and high strain rates.

[0013] The present invention not only achieves the complete removal of residual solvent and moisture in the fiber through the heat treatment process under a protective atmosphere, but also promotes the removal of impurities, functional groups and part of amorphous carbon adsorbed on the surface of carbon nanomaterials, thereby improving the purity, structural stability and comprehensive performance of the composite fiber.

[0014] Further, between S2 and S3, it also includes: soaking the carbon nanotube fiber in acetone for 0.5 - 5 min. As a polar solvent, acetone can neutralize the residual chlorosulfonic acid in the carbon nanotube fiber while effectively improving the densification degree of the carbon nanotube fiber.

[0015] Further, after being soaked in acetone, the carbon nanotube fiber is placed in pure water for cleaning.

[0016] Further, in S1, the concentration of graphene in the graphene / chlorosulfonic acid dispersion is 0.01 wt% - 0.04 wt%.

[0017] Further, in S1, the particle size of the graphene is 0.3 - 20 μm.

[0018] Further, in S3, the temperature of the heat treatment is 350 - 450 °C, and the time is 1 - 2 h.

[0019] Further, in S3, the protective atmosphere for the heat treatment is argon.

[0020] Further, after S3, it also includes: twisting and plying the carbon nanotube / graphene composite fiber filaments to obtain a carbon nanotube / graphene composite fiber strand. Through the twisting and plying processes, its impact resistance and energy absorption capacity are significantly enhanced, providing important technical support and theoretical basis for the practical application of high-performance fiber materials in the fields of lightweight and high-strength, impact-resistant fabrics, etc.

[0021] Further, the twist of the twisting is 10 - 200 Tt, and the twist direction is Z twist and / or S twist.

[0022] Further, the plying is as follows:

[0023] Two twist yarns with a twist direction of Z twist are combined and twisted, the twist direction is S twist, and the twist is 20 - 80 Tt;

[0024] Or, a twist yarn with a twist direction of Z twist and a twist yarn with a twist direction of S twist are combined and twisted, the twist direction is S twist, and the twist is 20 - 80 Tt.

[0025] The second aspect of the present invention provides a carbon nanotube / graphene composite fiber prepared by the preparation method described in the first aspect.

[0026] Advantages of the present invention:

[0027] In the present invention, in an environment of chlorosulfonic acid, the carbon nanotubes in the carbon nanotube fiber are protonated, the binding force between the bundles is significantly reduced, and the carbon nanotube fiber shows a swollen and reconfigurable state. At the same time, the two-dimensional structure of the graphene nanosheets uniformly dispersed in the chlorosulfonic acid is inserted into the gaps between the carbon nanotubes and arranged axially in an orderly manner under the driving of the carbon nanotube stretching, forming a synergistically enhanced composite network.

[0028] Through the drawing process of carbon nanotubes, the present invention can not only induce the highly oriented carbon nanotubes and graphene in the axial direction, but also promote the densification of the structure and the reconstruction of defects, significantly enhancing the interfacial coupling and load transfer efficiency of the composite fiber, and thus improving the mechanical properties of the fiber under quasi-static and high strain rate conditions.

[0029] Through the heat treatment process under a protective atmosphere, the present invention not only realizes the complete removal of residual solvents and moisture in the fiber, but also promotes the removal of adsorbed impurities, functional groups and some amorphous carbon on the surface of the carbon nanomaterials, thereby improving the purity, structural stability and comprehensive performance of the composite fiber.

[0030] Through the twisting and ply yarn processes, the present invention significantly enhances its impact resistance and energy absorption capacity, providing important technical support and theoretical basis for the practical application of high-performance fiber materials in the fields of lightweight and high-strength, impact-resistant fabrics, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 is a schematic diagram of the fiber drawing device of the present invention;

[0033] Figure 2 is the SEM image of the composite fiber obtained in Example 3 of the present invention, where a-c are the internal morphology diagrams of the fiber after being torn along the axial direction, and d-f are the surface morphology diagrams of the fiber;

[0034] Figure 3 a-f in are respectively the SEM images of the composite fiber ply yarns in Examples 6-11;

[0035] Figure 4 a-f in are respectively the SEM images of the dynamic tensile fracture surfaces of the composite fiber ply yarns in Examples 6-11. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] This embodiment provides a method for preparing a carbon nanotube / graphene composite fiber, including the following steps:

[0038] S1. Mix graphene powder with chlorosulfonic acid to obtain a graphene / chlorosulfonic acid dispersion;

[0039] Among them, the concentration of graphene in the graphene / chlorosulfonic acid dispersion is 0.01 wt% - 0.04 wt%, and the particle size of the graphene is 0.3 - 20 μm.

[0040] S2. Immerse carbon nanotube fibers in the graphene / chlorosulfonic acid dispersion and draw the carbon nanotube fibers;

[0041] Among them, the drawing time is 30 - 300 s, and the elongation of drawing is 30% - 70%;

[0042] S3. Take out the carbon nanotube fibers and perform heat treatment in an argon atmosphere to obtain the carbon nanotube / graphene composite fiber filaments;

[0043] Among them, the temperature of the heat treatment is 350 - 450 °C, and the time is 1 - 2 h.

[0044] In this embodiment, the carbon nanotube fibers are placed in the graphene / chlorosulfonic acid dispersion. In the chlorosulfonic acid environment, the carbon nanotubes are protonated, the binding force between the tube bundles is significantly reduced, and the carbon nanotube fibers show a swollen and reconfigurable state. At the same time, the two-dimensional structure of the graphene nanosheets uniformly dispersed in the chlorosulfonic acid is inserted into the gaps between the carbon nanotubes and arranged orderly along the axial direction under the drive of the carbon nanotube drawing, forming a synergistically enhanced composite network. Importantly, the carbon nanotube drawing process can not only induce the highly oriented carbon nanotubes and graphene in the axial direction, but also promote the densification of the structure and defect reconstruction, significantly enhancing the interfacial coupling and load transfer efficiency of the composite fiber, and further improving the mechanical properties of the fiber under quasi-static and high strain rate conditions; through the heat treatment process under a protective atmosphere, not only the complete removal of the residual solvent and moisture in the fiber is achieved, but also the removal of the adsorbed impurities, functional groups and part of the amorphous carbon on the surface of the carbon nanomaterials is promoted, thereby improving the purity, structural stability and comprehensive performance of the composite fiber.

[0045] As a preferred embodiment, between S2 and S3, it further includes: soaking the carbon nanotube fibers in acetone for 0.5 - 5 min. Acetone, as a polar solvent, can neutralize the residual chlorosulfonic acid in the carbon nanotube fibers while effectively improving the densification degree of the carbon nanotube fibers. The carbon nanotube fibers are soaked in acetone and then washed in pure water.

[0046] As a preferred embodiment, after S3, it further includes: twisting and plying the carbon nanotube / graphene composite fiber silk thread to obtain a carbon nanotube / graphene composite fiber strand. The impact resistance and energy absorption capacity are significantly enhanced through the twisting and plying processes, providing important technical support and theoretical basis for the practical application of high-performance fiber materials in the fields of lightweight and high-strength, impact-resistant fabrics, etc. The twist of the twisting is 10-200 Tt, and the twist direction is Z twist and / or S twist; the plying is: combining and twisting two twisted threads with a twist direction of Z twist, the twist direction is S twist, and the twist is 20-80 Tt; or, combining and twisting a twisted thread with a twist direction of Z twist and a twisted thread with a twist direction of S twist, the twist direction is S twist, and the twist is 20-80 Tt.

[0047] Another embodiment provides a carbon nanotube / graphene composite fiber obtained by the preparation method described in the above embodiment.

[0048] Example 1

[0049] This example provides a preparation method of a carbon nanotube / graphene composite fiber, including the following steps:

[0050] (1) Add chlorosulfonic acid to a beaker, then add graphene powder with a particle size of 0.5-5 μm to the beaker. Subsequently, use a magnetic stirrer to stir at a speed of 400 r / min for 30 minutes to prepare a graphene / chlorosulfonic acid dispersion with a graphene concentration of 0.02 wt%.

[0051] (2) Cut the carbon nanotube fiber into several small sections with a length of 8 cm, and perform drawing through the Figure 1 device shown. Specifically: fix the carbon nanotube fiber on a pair of polytetrafluoroethylene clamps in the clamping part as a group of samples to be processed; then assemble the sample clamping part and the threaded drive drawing part together and put them into the graphene / chlorosulfonic acid dispersion, ensuring that the liquid surface completely covers the surface of the fiber sample;

[0052] (3) Use an electric screwdriver as the drive power device to draw the fiber. The drawing time is 60 s, and the elongation of the drawing is 30%, that is, 30% of the original length of the fiber;

[0053] (4) After the drawing is completed, soak the fiber in an acetone solution for 1 min, and then soak the fiber in ultrapure water for 1 min to wash away the residual liquid in the pretreatment step

[0054] (5) Put the fiber into a tube furnace and treat it under the conditions of 400 °C and an argon atmosphere for 1.5 h to prepare a carbon nanotube / graphene composite fiber G60-30.

[0055] Example 2

[0056] The difference between this example and Example 1 is that the elongation of drawing is 70%, and other steps and parameters remain unchanged, to prepare composite fiber G60-70.

[0057] Example 3

[0058] The difference between this example and Example 1 is that the elongation of drawing is 50%, and other steps and parameters remain unchanged, to prepare composite fiber G60-50.

[0059] Figure 2 In a-c are SEM micrographs of the interior of the fiber after G60-50 is torn axially, where Figure 2 b in is an enlarged view of the framed area in a, Figure 2 c in is an enlarged view of the framed area in b. It can be clearly seen that graphene with small particle size is successfully introduced into the interior of the fiber and is evenly distributed between the carbon nanotube bundles. Graphene can form π-π interaction forces stronger than van der Waals forces with carbon nanotubes, improving the load transfer efficiency between carbon nanotubes; the introduction of graphene can also further improve the densification degree inside the fiber, effectively preventing crack propagation by increasing the interfacial shear strength. Figure 2 In d-f are SEM micrographs of the surface of G60-50, where Figure 2 f in is an enlarged view of the framed part in e. It can be seen that the surface of the composite fiber is smooth, the internal pores and pore sizes are small, the structure is tight, and the densification degree is high.

[0060] Example 4

[0061] The difference between this example and Example 3 is that the drawing time is 30 s, and other steps and parameters remain unchanged, to prepare composite fiber G30-50.

[0062] Example 5

[0063] The difference between this example and Example 3 is that the drawing time is 300 s, and other steps and parameters remain unchanged, to prepare composite fiber G300-50.

[0064] The composite fibers obtained in Examples 1-5 were subjected to mechanical property tests, and the results are shown in Table 1.

[0065] Table 1

[0066]

[0067] As can be seen from Table 1, the composite fibers under the drawing conditions of Examples 1-5 all have excellent mechanical properties. Among them, in Example 3, when the drawing time is 60 s and the drawing length is 50%, the prepared composite fiber has the optimal mechanical properties. This is because moderate drawing is a necessary condition for obtaining high-strength carbon nanotube fibers. During the drawing process, the originally disordered carbon nanotube bundles in the carbon nanotube fibers gradually change from disorder to order, and the degree of orientation continuously increases. At this time, the strength of the fiber will also continuously increase with the increase of the drawing ratio. When the drawing length reaches 50%, most of the carbon nanotube bundles inside the fiber are reoriented, and the originally bent carbon nanotube bundles are completely straightened. However, if the drawing is excessive, it may cause some carbon nanotube bundles to break. Therefore, the drawing length is limited to 30-70%. When the drawing length is fixed at 50%, when the time is about 60 s, the degree of protonation inside the carbon nanotube fiber is optimal, and graphene is completely immersed in the fiber, thus having the optimal performance. However, if the time is too long, it may cause excessive swelling of the fiber, and even permanently damage the internal structure of the fiber, making the fiber structure looser, thereby reducing the overall strength of the fiber. Therefore, the time is limited to 30-300 s.

[0068] Example 6

[0069] The difference between this example and Example 3 is that after the composite fiber G60-50 is prepared in step (5), the following steps are further included:

[0070] (6) Twist the carbon nanotube / graphene composite fiber with a yarn twister, the twist is 50 Tt, and the twist direction is Z twist for both, to prepare a carbon nanotube / graphene composite fiber twisted yarn;

[0071] (7) Ply the twisted yarn with a yarn twister, combine and twist two twisted yarns with Z twist, the twist direction is S twist, and the twist is 20 Tt, to prepare a carbon nanotube / graphene composite fiber ply yarn (50Z + 50Z) / 20S.

[0072] Example 7

[0073] The difference between this example and Example 6 is that in step (7), the twist is 50 Tt, to prepare a carbon nanotube / graphene composite fiber ply yarn (50Z + 50Z) / 50S.

[0074] Example 8

[0075] The difference between this example and Example 6 is that in step (7), the twist is 80 Tt, to prepare a carbon nanotube / graphene composite fiber ply yarn (50Z + 50Z) / 80S.

[0076] Example 9

[0077] The difference between this example and Example 6 is that:

[0078] (6) Twist the carbon nanotube / graphene composite fiber with a yarn twist meter, with a twist of 50 Tt, twist directions of Z twist and S twist, and each with a quantity of half, to prepare carbon nanotube / graphene composite fiber twisted yarns;

[0079] (7) Ply the twisted yarns using a yarn twist meter, combine and twist a Z-twisted yarn and an S-twisted yarn, with a twist direction of S twist and a twist of 20 Tt, to prepare carbon nanotube / graphene composite fiber ply yarns (50Z + 50S) / 20S.

[0080] Example 10

[0081] The difference between this example and Example 9 is that: in step (7), the twist is 50 Tt, and carbon nanotube / graphene composite fiber ply yarns (50Z + 50S) / 50S are prepared.

[0082] Example 11

[0083] The difference between this example and Example 9 is that: in step (7), the twist is 80 Tt, and carbon nanotube / graphene composite fiber ply yarns (50Z + 50S) / 80S are prepared.

[0084] Figure 3 In a-f are SEM images of the composite fiber ply yarns of Examples 6-11. It can be seen that the fiber surface is smooth and uniformly composite. Figure 4 In a-f are SEM images of the dynamic tensile fracture surfaces of the composite fiber ply yarns of Examples 6-11. It can be seen that the fracture surfaces of the ply yarns obtained in the examples are relatively neat. Among them, the fracture surface of the twisted yarn in Example 7 has the best neatness, and the carbon nanotube bundles at the fracture surface are tightly combined. However, when the twist is too large, the off-axis weakening effect and the compressive-shear competition effect between the carbon nanotube bundles are enhanced, and splitting phenomena occur between large carbon nanotube bundles. Therefore, the twist is limited to 20 - 80 Tt.

[0085] Perform mechanical property tests on the composite fibers obtained in Examples 6-9 and compare them with Example 3. The results are shown in Table 2.

[0086] Table 2

[0087]

[0088] As can be seen from Table 2, after the fibers in Examples 6-11 are plied, compared with the fibers before plying in Example 3, the mechanical properties show a certain degree of decline. This is because stress concentration areas are easily formed at the contact points and joints between the fibers, resulting in local stress being significantly higher than other parts, thereby causing fiber fracture or damage. In addition, the friction and relative slip between the fibers will weaken their synergistic effect, making the external force unable to be evenly transmitted. The increase in the number of plies and excessive twist also lead to a decrease in the fiber orientation degree, and the uneven arrangement of the fibers will also cause uneven stress distribution, thereby reducing the overall strength and modulus of the material. The fiber damage during the processing and the negative impact of environmental factors (such as temperature and humidity) on the fiber properties will also weaken the mechanical properties of the plied fibers to a certain extent. Therefore, the decline in the mechanical properties after fiber plying is the result of the combined action of the interaction between the fibers, the structural characteristics of the yarn, and external factors.

[0089] Among them, the mechanical properties of the plied fibers in Example 7 are the best, with a quasi-static tensile strength of 2.50 GPa and an energy absorption value of 70.2 MJ / m 3 , which is close to the quasi-static mechanical properties of the single-fiber twist, indicating that the ply yarn obtained in this way has the optimal mechanical properties and is not reduced compared with the single-fiber twist. Although the ply yarns obtained by plying two twist yarns with opposite twist directions in Examples 9-11 have excellent mechanical properties, they show a certain degree of decline compared with Example 7. For the dynamic tensile properties, the tensile strength and energy absorption value of the ply yarns obtained by plying the twist yarns with the same twist direction reach the maximum values at a ply twist of 50 Tt, which are 2.44 GPa and 101.9 MJ / m3 respectively; the strength of the ply yarns obtained by plying and twisting the twist yarns with opposite twist directions also reaches the maximum value at a ply twist of 50 Tt, with a maximum strength of 2.0 GPa and a maximum energy absorption value of 75.0 MJ / m3, showing a certain degree of decline. It can be seen that the properties of the composite fibers obtained with the ply parameters in Example 7 are the best. In addition, compared with the quasi-static tensile properties of the ply yarns, the tensile strength of the ply yarns at a strain rate of 1670 s -1 is lower than the quasi-static tensile strength, indicating that there is no obvious strain rate enhancement effect on the tensile strength of the ply yarns.

[0090] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A preparation method of a carbon nanotube / graphene composite fiber, characterized in that, It includes the following steps: S1. Mix graphene powder with chlorosulfonic acid to obtain a graphene / chlorosulfonic acid dispersion; S2. Immerse carbon nanotubes in the graphene / chlorosulfonic acid dispersion and draw the carbon nanotube fibers; Among them, the drawing time is 30 - 300 s, and the elongation of drawing is 30% - 70%; S3. Take out the carbon nanotube fibers and perform heat treatment under a protective atmosphere to obtain carbon nanotube / graphene composite fiber filaments.

2. The preparation method of the carbon nanotube / graphene composite fiber according to claim 1, characterized in that, Between S2 and S3, it also includes: soaking the carbon nanotube fibers in acetone for 0.5 - 5 min.

3. The preparation method of the carbon nanotube / graphene composite fiber according to claim 2, characterized in that, The carbon nanotube fibers are soaked in acetone and then washed in pure water.

4. The preparation method of the carbon nanotube / graphene composite fiber according to claim 1, wherein, In S1, the concentration of graphene in the graphene / chlorosulfonic acid dispersion is 0.01 wt% - 0.04 wt%.

5. The preparation method of the carbon nanotube / graphene composite fiber according to claim 1, characterized in that, In S1, the particle size of the graphene is 0.3 - 20 μm.

6. The preparation method of the carbon nanotube / graphene composite fiber according to claim 1, characterized in that, In S3, the temperature of the heat treatment is 350 - 450 °C, and the time is 1 - 2 h.

7. The preparation method of the carbon nanotube / graphene composite fiber according to claim 1, wherein, After S3, it also includes: twisting and plying the carbon nanotube / graphene composite fiber filaments to obtain carbon nanotube / graphene composite fiber strands.

8. The preparation method of the carbon nanotube / graphene composite fiber according to claim 7, characterized in that, The twist of the twisting is 10 - 200 Tt, and the twist direction is Z twist and / or S twist.

9. The preparation method of the carbon nanotube / graphene composite fiber according to claim 8, characterized in that, The plying is as follows: Merge and twist two twisted yarns with a Z twist direction, the twist direction is S twist, and the twist is 20 - 80 Tt; Or, merge and twist a twisted yarn with a Z twist direction and a twisted yarn with an S twist direction, the twist direction is S twist, and the twist is 20 - 80 Tt.

10. A carbon nanotube / graphene composite fiber prepared by the preparation method according to any one of claims 1 - 9.

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