Carbon nanotube composite fiber with gradient structure, preparation method and application

Abstract

The invention discloses a carbon nano tube composite fiber with a gradient structure, a preparation method and application, and belongs to the technical field of fiber materials, the appearance of the carbon nano tube composite fiber with the gradient structure is in a black filament shape, the surface is loose and porous, and the pore diameter is gradually reduced from the surface to a core layer; according to the carbon nano tube composite fiber with the gradient structure, due to the fact that the gradient pore diameter structure which is gradually reduced from outside to inside is arranged, when the carbon nano tube composite fiber makes contact with liquid, the liquid is rapidly diffused inwards, transmitted in the axial direction of the fiber and interacts with the carbon nano tube, and potential difference is formed at the two ends of the fiber; therefore, continuous green power generation can be achieved through interaction of fluid and the fiber, the fiber has wide application prospects in the field of power supply for small electronic equipment, and meanwhile the fiber has good flexibility and weaving performance and has potential value in the technical field of wearable self-power-supply material preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber materials, and in particular relates to a carbon nanotube composite fiber with a gradient structure, a preparation method and an application thereof. Background Art

[0002] Common fiber preparation methods include melt spinning, solution spinning, dry spinning, wet spinning, etc. Different spinning methods can be selected according to the properties of the raw materials and the characteristics of the fibers to be obtained. However, the fibers prepared by the traditional spinning process have the problems of simple composition and single structure, and it is difficult to expand the application of fibers in more fields. Carbon nanotubes have potential in the field of energy conversion devices. As early as 2003, scientists discovered that when liquid flows on a single-walled carbon nanotube bundle, a voltage can be induced along the flow direction (Science 299, 1042-1044 (2003).). Carbon nanomaterials, due to their inherent conductivity and adjustable surface properties, will form a double electric layer at the solid-liquid interface when in contact with a flowing liquid, and the channel only allows ions with opposite charges to pass through, thereby generating considerable electricity. At present, many studies have focused on the precise regulation of the surface of carbon nanomaterials and the careful design of the carbon-water interface, ignoring the strengthening effect of other components on the system and practical applicability.

[0003] Natural materials such as chitin, chitosan, and plant cellulose are green, environmentally friendly, easy to produce, and low-cost. They have been widely used in various industries and have become the basis for various composite materials.

[0004] Chinese patent CN 115961375 A discloses a spinning solution for aramid and carbon nanotube composite fibers and a method for preparing aramid and carbon nanotube composite fibers using the spinning solution. In the patent, aramid, carbon nanotubes and superacid are mixed to prepare the spinning solution, and the aramid and carbon nanotube composite fibers are prepared by a wet spinning method. The fiber prepared by this method has a single structure and performance. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a carbon nanotube composite fiber with a gradient structure, which is a composite material of carbon nanotubes and fibers, with a black filamentous appearance, a loose and porous surface, and a gradually decreasing pore size from the surface to the core layer. Due to the gradient pore size structure that gradually decreases from the outside to the inside, when it comes into contact with liquid, the liquid quickly diffuses inward, is transmitted along the fiber axis, interacts with the carbon nanotubes, and forms a potential difference at both ends of the fiber. Therefore, continuous green power generation can be achieved by utilizing the interaction between the fluid and the fiber, and can power small electronic devices. At the same time, the fiber provided by the present invention has good flexibility and weavability, and has potential value in the field of preparing wearable self-powered material technology.

[0006] The present invention also provides a method for preparing a carbon nanotube composite fiber with a gradient structure. The carbon nanotube composite fiber with a gradient structure is prepared based on microfluidic chip technology. The fluid can be transmitted in a direction in the fiber. The hydrophilic cellulose component is conducive to a strong interaction between the carbon surface and water molecules. The fluid drives the movement of charges to form an electric current. The accumulation of positive and negative ions at both ends of the fiber forms an electric potential difference, which can realize green power generation.

[0007] The present invention also provides an application of a carbon nanotube composite fiber with a gradient structure as a fluid power generation material. The carbon nanotube composite fiber can generate electricity in a fluid with ionization properties and can provide power for small electronic devices.

[0008] The present invention also provides an application of a carbon nanotube composite fiber with a gradient structure as a textile material, which can be prepared into a wearable self-powered woven material.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] A carbon nanotube composite fiber with a gradient structure is a composite material of carbon nanotubes and fibers, has a black filamentous appearance, a loose and porous surface, and a pore size that gradually decreases from the surface to the core layer.

[0011] The diameter of the carbon nanotube composite fiber is 100 μm to 300 μm.

[0012] The carbon nanotube composite fiber has a strength of 7 to 15 MPa.

[0013] The carbon nanotube composite fiber has an axial fluid transmission rate of 150 to 200 μm / s, and a radial fluid transmission rate of 200 to 400 μm / s.

[0014] The carbon nanotube composite fiber can generate electricity in a fluid having an ionizing property.

[0015] The fluid with ionization properties is any one or more of sea water, lake water, human sweat, and salt solution.

[0016] The present invention also provides a method for preparing the carbon nanotube composite fiber with a gradient structure, the method comprising the following steps:

[0017] (1) preparing a mixed aqueous solution I, wherein the mixed aqueous solution I is a mixed aqueous solution of an inorganic base and urea;

[0018] (2) dispersing carbon nanotubes in a mixed aqueous solution I, adding fiber raw materials thereto, and stirring and mixing at -65 to -75°C for 2 to 5 hours to obtain a black carbon nanotube / cellulose mixed suspension;

[0019] (3) adding a crosslinking agent to the carbon nanotube / cellulose mixed suspension, stirring at -10 to 0°C for 1 to 2 hours, and centrifuging to degas, thereby obtaining a solution B;

[0020] (4) pumping solution B and mixed aqueous solution I into the core channel and sheath channel of the microfluidic chip respectively, and then collecting the outflow material in a hydrochloric acid solution, centrifuging, washing, and drying to obtain the carbon nanotube composite fiber with a gradient structure;

[0021] In step (4), the pumping speed of solution B is lower than the pumping speed of mixed aqueous solution I.

[0022] In step (1), the inorganic base is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide; the mass percentage concentrations of the inorganic base and urea in the mixed aqueous solution I are 7-15% and 3-30%, respectively, preferably 8% and 15%, respectively.

[0023] In step (2), the amount of carbon nanotubes added is 20-100% of the weight of the fiber raw material; the mass percentage concentration of the fiber raw material in the carbon nanotube / cellulose mixed suspension is 5-7%.

[0024] In step (2), the fiber raw material is at least one of cellulose, chitin, chitosan, and cotton linters.

[0025] In step (3), the ratio of the carbon nanotube / cellulose mixed suspension to the cross-linking agent is 200 g: (1.0-4.0) mL; the cross-linking agent is epichlorohydrin.

[0026] In step (3), the conditions for centrifugal degassing are: centrifugal speed of 4000-8000 rad / min, time of 3-5 min, and temperature of -5-0°C.

[0027] In step (4), the pumping speed of the solution B is 200-300 μL / min, and the pumping speed of the mixed aqueous solution I is 300-500 μL / min. If the pumping speed of solution B is too fast, the outer layer of solution B in the liquid channel of the chip will not be diluted by the mixed aqueous solution I in time. At this time, the mixed aqueous solution I only has a shearing effect on solution B, and the carbon nanotube composite fiber with a relatively loose surface cannot be obtained; on the contrary, if the propulsion speed of solution B is too slow, the dilution effect of the mixed aqueous solution I on solution B penetrates all positions of solution B, and the fiber structure formed is loose and irregular.

[0028] In step (4), the mass percentage concentration of the hydrochloric acid solution is 20-30%.

[0029] In step S6, the microfluidic chip includes a core channel 100, a sheath channel 200 and a mixing channel 300; the core channel 100 and the mixing channel 300 are on the same vertical line and are interconnected, and the sheath channel 200 is on a horizontal line and is arranged in a cross pattern with the core channel 100 and the mixing channel 300. Figure 4 shown.

[0030] The present invention also provides the use of the carbon nanotube composite fiber with a gradient structure as a fluid power generation material or a fabric material.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The carbon nanotube composite fiber with a gradient structure provided by the present invention is in the form of porous filaments, which are relatively dense in the center and relatively loose at the edge, and have a gradient pore size structure that gradually decreases from the outside to the inside. Therefore, when it comes into contact with liquid, the liquid quickly diffuses radially inward and then quickly transmits along the axial direction of the fiber, and has a fast water transmission characteristic.

[0033] The carbon nanotube composite fiber with a gradient structure provided by the present invention has carbon nanotubes uniformly oriented and distributed on the fiber. When water flows along the axial direction of the fiber, it interacts with the carbon nanotubes. The narrow channels form a double electric layer, which only allows ions with opposite charges to pass through, thereby forming an electric potential difference at both ends of the fiber. The continuous water flow carries the ions to form a continuous current, so it can power small electronic devices.

[0034] In the preparation method of the carbon nanotube composite fiber with gradient structure provided by the present invention, microfluidic technology is used for preparation. Figure 4 In the microfluidic chip shown, solution B is pumped into the core channel 100, and the mixed aqueous solution I is pumped into the sheath channel 200, and then the two are mixed in the mixing channel 300, and then flow out to the hydrochloric acid solution for solidification, and after centrifugation, washing, and drying, a carbon nanotube composite fiber with a gradient structure is obtained. Since the core channel and the sheath channel are interconnected, coupled with the dynamic diffusion effect, the systems in the two channels will contact each other during the spinning process, and solution B is wrapped and squeezed by the mixed aqueous solution I, so that the fiber chains and carbon nanotubes in the fiber solution are oriented and arranged along the shear direction, and the fiber chains are sheared from both sides to make the fiber solution thinner to form fibers.

[0035] The carbon nanotube composite fiber with a gradient structure provided by the present invention has a novel structure. By immersing it in a fluid with ionizing properties, it can achieve green power generation and power small electronic devices. It is expected to play an important role in portable wearable self-powered systems.

[0036] The preparation method of the carbon nanotube composite fiber provided by the invention is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a SEM image of the carbon nanotube composite fiber with a gradient structure obtained in Example 1;

[0038] Figure 2 This is a SEM image of the carbon nanotube composite fiber with a gradient structure obtained in Example 1;

[0039] Figure 3 This is a SEM image of the carbon nanotube composite fiber with a gradient structure obtained in Example 1;

[0040] Figure 4 The schematic diagram of the structure of the microfluidic chip used in the present invention, in which 100 is a core channel; 200 is a sheath channel; 300 is a mixing channel;

[0041] Figure 5 This is a SEM image of the carbon nanotube composite fiber with a gradient structure obtained in Example 2;

[0042] Figure 6 This is a SEM image of the carbon nanotube composite fiber with a gradient structure obtained in Example 3;

[0043] Figure 7 This is a SEM image of the regenerated carbon nanotube composite fiber obtained in Comparative Example 1;

[0044] Figure 8 This is a graph showing the test results of the water transmission rate of the carbon nanotube composite fiber with a gradient structure obtained in Example 1;

[0045] Fig. 9 The electrical test results of the carbon nanotube composite fibers in various embodiments and comparative examples are shown;

[0046] Fig.10 The strength test results of the carbon nanotube composite fibers in various embodiments and comparative examples are shown;

[0047] Fig.11 This is the weaving result of the carbon nanotube composite fiber with gradient structure in the application example. DETAILED DESCRIPTION

[0048] The present invention is described in detail below with reference to the embodiments.

[0049] Example 1

[0050] A method for preparing a carbon nanotube composite fiber with a gradient structure, comprising the following steps:

[0051] S1. Weigh 80 g of lithium hydroxide and 150 g of urea, add 770 mL of ultrapure water, stir and dissolve to obtain a mixed aqueous solution I;

[0052] S2. Prepare a 26% aqueous solution of hydrochloric acid to obtain a solution II;

[0053] S3. 60 g of the mixed aqueous solution I and 40 g of a 10% mass concentration CNT aqueous solution were mixed to obtain a solution III;

[0054] S4. The cooled solution III in step S3 was mixed with 4 g of cotton linters at a stirring speed of 1500 rad / min for 5 min to obtain a black carbon nanotube / cellulose mixed suspension;

[0055] S5. Centrifuge the carbon nanotube / cellulose mixed suspension obtained in step S4 to obtain solution A, wherein the centrifugal speed is 8000 rad / min, the time is 30 min, and the temperature is 0°C;

[0056] S6. Add the crosslinking agent epichlorohydrin to solution A at a ratio of 1.0 mL crosslinking agent / 100 g solution A, and stir on a cold well at -5°C at a speed of 300 rad / min for 2 h;

[0057] S7. The mixed system obtained by centrifugation step S6 is degassed to obtain solution B, wherein the centrifugation speed is 6000 rad / min, the time is 5 min, the temperature is 0°C, and then solution B is refrigerated at 5°C;

[0058] S8. Figure 4 In the chip shown, the cooled solution B is pumped into the core channel 100 at a speed of 250 μL / min, and 500 g of the mixed aqueous solution I is pumped into the sheath channel 200 at a speed of 400 μL / min, and they are ejected together from the outlet of the mixing channel 300 to solidify in the solution II; the solidified material is collected by a roller, and the rotation speed of the roller is 20 rpm;

[0059] S9. The cured material in step S8 is washed in ultrapure water until the residual acid solution is removed;

[0060] S10. Freeze the cleaned material in liquid nitrogen and dry it for 3 hours using freeze drying to obtain carbon nanotube composite fibers with a gradient structure.

[0061] The SEM image of the carbon nanotube composite fiber with gradient structure obtained in this example is as follows: Figures 1 to 3 As shown; the schematic diagram of the chip structure used is as shown Figure 4 shown.

[0062] Example 2

[0063] This embodiment prepares a carbon nanotube composite fiber with a gradient structure. The specific process is different from that of embodiment 1 as follows:

[0064] (1) In step S6, the addition ratio of the cross-linking agent epichlorohydrin is 1.0 mL of the cross-linking agent / 200 g of solution A;

[0065] (2) In step S6, the stirring time is 1.5 h;

[0066] (3) In step S8, the advancing speed of the cooled solution B is 200 μL / min; the advancing speed of the mixed aqueous solution I is 500 μL / min.

[0067] The SEM image of the carbon nanotube composite fiber with gradient structure obtained in this example is as follows: Figure 5 shown.

[0068] Example 3

[0069] This embodiment prepares a carbon nanotube composite fiber with a gradient structure. The specific process is different from that of embodiment 2 as follows:

[0070] (1) In step S3, 88 g of mixed aqueous solution II (solvent) and 12 g of 10% CNT aqueous solution were mixed to obtain solution III;

[0071] (2) In step S8, the propulsion speed of the cooled solution B is 250 μL / min; the propulsion speed of the mixed aqueous solution I is 350 μL / min.

[0072] The SEM image of the carbon nanotube composite fiber with gradient structure obtained in this example is as follows: Figure 6 shown.

[0073] Comparative Example 1

[0074] This comparative example prepares a carbon nanotube composite fiber, which differs from Example 1 in that:

[0075] (1) In step S8, the cooled solution B is sprayed out from the discharge port 300 along the core layer channel 100 at a propulsion speed of 250 μL / min until it solidifies in the solution II; no solution is injected into the sheath layer channel 200.

[0076] The SEM image of the carbon nanotube composite fiber obtained in this comparative example is as follows Figure 7 shown.

[0077] Test example

[0078] This test example tests the morphology, fluid power generation performance, water transmission rate, and fiber strength of the carbon nanotube composite fibers obtained in Examples 1 to 3 and Comparative Example 1.

[0079] The morphology test is carried out with the aid of a scanning electron microscope; particle distribution software is used to calculate the diameter of the fiber on the acquired scanning electron microscope image.

[0080] Test of power generation performance: The electrical performance data was obtained using a Keithley 2400 ammeter. One end of the dried carbon nanotube composite fiber was immersed in a 0.5 mol / L NaCl solution, and the other end was exposed to the air. Both ends were contacted with a test electric pen coated with ink (eliminating redox reaction).

[0081] Test of water transmission rate in fiber: Use an upright fluorescence microscope to observe and photograph, drop a water solution containing fluorescent particles on the fiber, and record the process and speed of the solution transmission along the axial and radial directions of the fiber;

[0082] The test method for fiber strength is: at a temperature of 25°C and a relative humidity of 65%, a fiber mechanical property tester is used with a test rate of 1 mm / min to perform a tensile test on carbon nanotube composite fibers and regenerated fibers with a clamping length of 10 mm.

[0083] The morphology test results are as follows:

[0084] The morphology of the carbon nanotube composite fiber with gradient structure obtained in Example 1 is as follows Figures 1 to 3 As shown, the morphology of the carbon nanotube composite fiber with gradient structure obtained in Example 2 is as follows Figure 5 The morphology of the carbon nanotube composite fiber with gradient structure obtained in Example 3 is as shown Figure 6 The morphology of the carbon nanotube composite fiber obtained in Comparative Example 1 is as shown Figure 7 shown.

[0085] from Figure 1 It can be seen that the surface of the carbon nanotube composite fiber prepared in Example 1 is loose and porous, presenting a porous network; and the average pore size of the central part of its cross section is smaller than the average pore size of the edge part, such as Figure 2 As shown, Figure 2 ), it can be seen that the carbon nanotube composite fiber prepared in Example 1 has a relatively loose outer layer and a relatively dense core layer. Therefore, when it comes into contact with liquid, the liquid quickly diffuses inward along the diameter direction, and then quickly transmits along the fiber axis, and has a fast water transmission characteristic.

[0086] In Example 2, compared with Example 1, the propulsion speed of the sheath channel is much greater than that of the core channel. The dilution effect of the sheath injection mixed aqueous solution I on solution B penetrates all positions of solution B, and the fiber structure formed is loose and irregular, such as Figure 5 shown.

[0087] Example 3 Compared with Example 1, the amount of carbon nanotubes used is less. When the amount of carbon nanotubes used is 20wt% of cellulose, the content of carbon nanotubes in the solution is low and it is easier to be diluted by the sheath injection agent. The pore size of the formed fiber becomes larger and the color becomes lighter. Figure 6 shown.

[0088] The carbon nanotube composite fiber prepared in Comparative Example 1 has a relatively large diameter of 350 μm, and the pore size distribution of the generated material is uniform. Figure 7 As shown, such a morphology will reduce the diffusion rate of the liquid on the fiber, limiting the electrical properties of the carbon nanotube composite fiber.

[0089] The diameter test results of the carbon nanotube composite fibers with gradient structures obtained in Examples 1 to 3 and the carbon nanotube composite fibers obtained in Comparative Example 1 are shown in Table 1.

[0090] Table 1. Fiber diameters.

[0091]

[0092] Electrical test results:

[0093] The electrical test results of the carbon nanotube composite fibers obtained in Examples 1 to 3 and Comparative Example 1 are as follows: Fig. 9 As shown in the figure, it can be seen that the carbon nanotube composite fibers with gradient structures obtained in Examples 1 to 3 have good hydrovoltaic power generation capabilities, which are 0.51, 0.47, and 0.46V, respectively. This is because they have a gradient pore structure that gradually decreases from the outside to the inside. Therefore, when they come into contact with liquid, the liquid quickly diffuses inward, transmits along the fiber axis, interacts with the carbon nanotubes, and forms a stable potential difference at both ends of the fiber. The carbon nanotube composite fiber obtained in Comparative Example 1 does not have a gradient pore structure, and the voltage is only 0.37V.

[0094] Fiber strength test results:

[0095] The strength test results of the carbon nanotube composite fibers obtained in Examples 1 to 3 and Comparative Example 1 are shown in the figure below: Fig.10 As shown, the strength range of the carbon nanotube composite fiber with a gradient structure is 6.09 to 10.59 MPa. It can be seen from the figure that the carbon nanotube composite fiber with a gradient structure is superior to the carbon nanotube composite fiber obtained in Example 1 in terms of stress and strain. It can be seen that the gradient structure effectively enhances the stress and strain of the fiber.

[0096] Test results of water transmission rate in fiber:

[0097] The test results of water transmission rate of carbon nanotube composite fibers obtained in Examples 1 to 3 and Comparative Example 1 are shown in Table 2.

[0098] Table 2 Water transmission rate in fibers

[0099] Example 1 Example 2 Example 3 Comparative Example 1 Axial transmission rate (μm / s) 120 182 185 60 Radial transmission rate (μm / s) 355 320 358 58

[0100] The water transmission rate test results of the carbon nanotube composite fiber with gradient structure obtained in Example 1 are as follows: Figure 8 shown.

[0101] Application Examples

[0102] Application of carbon nanotube composite fibers with gradient structure as textile materials

[0103] The carbon nanotube composite fiber with a gradient structure (black part) prepared in Example 1 was inserted and woven in one direction into a cloth woven in the warp and weft directions by cotton thread (white part), and the following was obtained: Fig.11 Fabric shown.

[0104] It can be seen from the figure that the carbon nanotube composite fiber with gradient structure has good flexibility and can be used as a weaving material for fabrics. It has potential value in the field of preparing wearable self-powered material technology.

[0105] The above data show that the carbon nanotube composite fiber with a gradient structure provided by the present invention has a moderate diameter, directional rapid water transmission and excellent fluid power generation performance. At the same time, its good flexibility and strength can be used for fabric manufacturing. It has excellent application prospects in the field of powering small electronic devices and has potential value in the field of preparing wearable self-powered material technology.

[0106] The above-mentioned reference embodiments provide a detailed description of a carbon nanotube composite fiber, a carbon nanotube composite fiber with a gradient structure, a carbon nanotube composite fiber with a gradient structure, a preparation method and an application. This is illustrative rather than restrictive, and several embodiments can be listed within the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A carbon nanotube composite fiber with a gradient structure, characterized in that: The carbon nanotube composite fiber with gradient structure is a composite material of carbon nanotubes and fibers, and has a black filamentous appearance, a loose and porous surface, and a pore size that gradually decreases from the surface to the core.

2. The carbon nanotube composite fiber according to claim 1, characterized in that: The diameter of the carbon nanotube composite fiber is 100 μm to 300 μm.

3. The carbon nanotube composite fiber according to claim 1, characterized in that: The carbon nanotube composite fiber has an axial fluid transmission rate of 150 to 200 μm / s, and a radial fluid transmission rate of 200 to 400 μm / s.

4. The carbon nanotube composite fiber according to claim 1, characterized in that: The carbon nanotube composite fiber can generate electricity in a fluid having an ionizing property.

5. The method for preparing a carbon nanotube composite fiber having a gradient structure according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) preparing a mixed aqueous solution I, wherein the mixed aqueous solution I is a mixed aqueous solution of an inorganic base and urea; (2) dispersing carbon nanotubes in a mixed aqueous solution I, adding fiber raw materials thereto, and stirring and mixing at -65 to -75°C for 2 to 5 hours to obtain a black carbon nanotube / cellulose mixed suspension; (3) adding a crosslinking agent to the carbon nanotube / cellulose mixed suspension, stirring at -10 to 0°C for 1 to 2 hours, and centrifuging to degas, thereby obtaining a solution B; (4) pumping solution B and mixed aqueous solution I into the core channel and sheath channel of the microfluidic chip respectively, and then collecting the outflow material in a hydrochloric acid solution, centrifuging, washing, and drying to obtain the carbon nanotube composite fiber with a gradient structure; In step (4), the pumping speed of solution B is lower than the pumping speed of mixed aqueous solution I.

6. The preparation method according to claim 5, characterized in that: In step (1), the inorganic base is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide; the mass percentage concentrations of the inorganic base and urea in the mixed aqueous solution I are 7-15% and 3-30%, respectively.

7. The preparation method according to claim 5, characterized in that: In step (2), the amount of carbon nanotubes added is 20-100% of the weight of the fiber raw material; the mass percentage concentration of the fiber raw material in the carbon nanotube / cellulose mixed suspension is 5-7%; the fiber raw material is at least one of cellulose, chitin, chitosan, and cotton linters.

8. The preparation method according to claim 5, characterized in that: In step (3), the ratio of the carbon nanotube / cellulose mixed suspension to the cross-linking agent is 200 g: (1.0-4.0) mL; the cross-linking agent is epichlorohydrin.

9. The preparation method according to claim 5, characterized in that: In step (4), the pumping speed of the solution B is 200-300 μL / min, and the pumping speed of the mixed aqueous solution I is 300-500 μL / min.

10. Use of the carbon nanotube composite fiber with gradient structure as claimed in any one of claims 1 to 4 as a fluid power generation material or a textile material.

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