A carbon nanotube composite fiber with a gradient structure, its preparation method and application

Abstract

This invention discloses a carbon nanotube composite fiber with a gradient structure, its preparation method, and its applications, belonging to the field of fiber material technology. The carbon nanotube composite fiber with a gradient structure appears as a black filament with a loose and porous surface, and the pore size gradually decreases from the surface to the core layer. Because of the gradient pore size structure provided by this invention, when the carbon nanotube composite fiber with a gradient structure is contacted with a liquid, the liquid rapidly diffuses inward and travels along the fiber axis, interacting with the carbon nanotubes and forming a potential difference at both ends of the fiber. Therefore, the interaction between the fluid and the fiber can be used to achieve continuous green power generation, which has broad application prospects in the field of powering small electronic devices. At the same time, the fiber provided by this invention has good flexibility and weaving properties, and has potential value in the field of preparing wearable self-powered materials.

Description

Technical Field

[0001] This invention belongs to the field of fiber materials technology, specifically relating to a carbon nanotube composite fiber with a gradient structure, its preparation method, and its application. Background Technology

[0002] Common fiber preparation methods include melt spinning, solution spinning, dry spinning, and wet spinning. Different spinning methods can be selected based on the properties of the raw materials and the desired fiber characteristics. However, fibers prepared by traditional spinning processes suffer from simple composition and uniform structure, hindering their application in more fields. Carbon nanotubes hold promise in energy conversion devices. As early as 2003, scientists discovered that a voltage could be induced along the flow direction when liquid flows over a bundle of single-walled carbon nanotubes (Science 299, 1042-1044 (2003)). Due to their inherent conductivity and tunable surface properties, carbon nanomaterials form an electric double layer at the solid-liquid interface when in contact with flowing liquids. The channels only allow ions with opposite charges to pass through, generating considerable electricity. Currently, much research focuses on the precise control of carbon nanomaterial surfaces and the careful design of carbon-water interfaces, neglecting the reinforcing effects of other components and their practical applicability.

[0003] Natural materials such as chitin, chitosan, and plant cellulose are characterized by being green and environmentally friendly, easy to produce, and low in cost. They have been widely used in various industries and have become the base 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 same solution. In this patent, aramid, carbon nanotubes and superacid are mixed to prepare the spinning solution, and a wet spinning method is used to prepare aramid and carbon nanotube composite fibers. The fiber structure and properties prepared by this method are simple. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a carbon nanotube composite fiber with a gradient structure. This fiber is a composite material of carbon nanotubes and fibers, appearing as black filaments with a loose, porous surface and gradually decreasing pore size from the surface to the core. Due to its gradient pore size structure, upon contact with a liquid, the liquid rapidly diffuses inward, travels along the fiber axis, and interacts with the carbon nanotubes, creating a potential difference at the fiber's ends. Therefore, the interaction between the fluid and the fiber enables continuous green power generation, potentially powering small electronic devices. Furthermore, the fiber provided by this invention possesses excellent flexibility and weaving properties, showing potential value in the field of wearable self-powered materials.

[0006] This invention also provides a method for preparing carbon nanotube composite fibers with a gradient structure. Based on microfluidic chip technology, carbon nanotube composite fibers with a gradient structure are prepared. Fluid can be directionally transported in the fiber. The hydrophilic cellulose component facilitates 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 a potential difference that can realize green power generation.

[0007] The present invention also provides an application of carbon nanotube composite fibers with a gradient structure as a fluid power generation material, wherein the carbon nanotube composite fibers are capable of generating electricity in fluids with ionization properties and can power small electronic devices.

[0008] This invention also provides an application of carbon nanotube composite fibers with a gradient structure as a fabric material, which can be prepared into wearable self-powered woven materials.

[0009] To achieve the above objectives, 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. It appears as black filaments with a loose and porous surface, and the pore size gradually decreases from the surface to the core layer.

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

[0012] The strength of the carbon nanotube composite fiber is 7–15 MPa.

[0013] The axial fluid transport rate of the carbon nanotube composite fiber is 150–200 μm / s, and the radial fluid transport rate is 200–400 μm / s.

[0014] The carbon nanotube composite fibers can generate electricity in fluids with ionizing properties.

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

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

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

[0018] (2) Disperse carbon nanotubes in mixed aqueous solution I, add fiber raw materials to it, stir and mix at -65 to -75℃ for 2 to 5 hours to obtain a black carbon nanotube / cellulose mixed suspension;

[0019] (3) Add crosslinking agent to carbon nanotube / cellulose mixed suspension, stir at -10 to 0℃ for 1 to 2 hours, centrifuge and degas to obtain solution B;

[0020] (4) Pump solution B and mixed aqueous solution I into the core layer channel and sheath layer channel of the microfluidic chip respectively, and then collect the effluent in hydrochloric acid solution. After centrifugation, washing and drying, the carbon nanotube composite fiber with gradient structure is obtained.

[0021] In step (4), the pumping rate of solution B is less than the pumping rate 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 crosslinking agent is 200g:(1.0~4.0)mL; the crosslinking agent is epichlorohydrin.

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

[0027] In step (4), the pumping rate of solution B is 200–300 μL / min, and the pumping rate of the mixed aqueous solution I is 300–500 μL / min. If the pumping rate of solution B is too fast, the outer layer of solution B in the liquid channel of the chip will not have enough time to be diluted by the mixed aqueous solution I. In this case, the mixed aqueous solution I only has a shearing effect on solution B, and a relatively loose carbon nanotube composite fiber cannot be obtained. Conversely, if the pumping rate of solution B is too slow, the dilution effect of the mixed aqueous solution I on solution B will penetrate to all positions of solution B, and the resulting fiber structure will be 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 layer channel 100, a sheath layer channel 200, and a mixing channel 300; the core layer channel 100 and the mixing channel 300 are on the same vertical line and interconnected, while the sheath layer channel 200 is on a horizontal line and arranged in a cross shape with the core layer channel 100 and the mixing channel 300. Figure 4 As shown.

[0030] The present invention also provides the application of the carbon nanotube composite fiber with the 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 this invention is porous filamentous, with a relatively dense central part and a relatively loose edge part. It has 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 is rapidly transported along the fiber axis, exhibiting rapid water transport characteristics.

[0033] The present invention provides a carbon nanotube composite fiber with a gradient structure. The carbon nanotubes are uniformly oriented and distributed on the fiber. When water flows along the fiber axis, it interacts with the carbon nanotubes. The narrow channel forms an electric double layer, which only allows ions with opposite charges to pass through. This creates a potential difference at both ends of the fiber. The continuous water flow carries ions to form a continuous current, which can thus power small electronic devices.

[0034] The method for preparing carbon nanotube composite fibers with a gradient structure provided by this invention employs microfluidic technology. Figure 4 In the microfluidic chip shown, solution B is pumped into the core channel 100, and mixed aqueous solution I is pumped into the sheath channel 200. The two are then mixed in the mixing channel 300 and flow out into a hydrochloric acid solution for solidification. After centrifugation, washing, and drying, carbon nanotube composite fibers with a gradient structure are obtained. Because the core and sheath channels are interconnected, and due to dynamic diffusion, the systems within the two channels come into contact during spinning. Solution B is encapsulated and compressed by mixed aqueous solution I, causing the fiber chains and carbon nanotubes in the fiber solution to align along the shear direction. Simultaneously, the fiber chains are sheared from both sides inwards, making the fiber solution thinner and forming fibers.

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

[0036] The method for preparing carbon nanotube composite fibers provided by this invention is simple. Attached Figure Description

[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 This is a schematic diagram of the microfluidic chip used in this invention. In the diagram, 100 - core layer channel; 200 - sheath layer channel; 300 - 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 SEM image of the regenerated carbon nanotube composite fiber obtained in Comparative Example 1.

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

[0045] Figure 9 The figures show the electrical test results of the carbon nanotube composite fibers in each embodiment and comparative example.

[0046] Figure 10 The strength test results of the carbon nanotube composite fibers in each embodiment and comparative example are shown.

[0047] Figure 11 The image shows the weaving result of carbon nanotube composite fibers with a gradient structure in an application example. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the embodiments.

[0049] Example 1

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

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

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

[0053] S3. Mix 60g of mixed aqueous solution I and 40g of 10% CNT aqueous solution to obtain solution III;

[0054] S4. Mix and stir the cooled solution III from step S3 with 4g of cotton linters at a stirring speed of 1500 rad / min for 5min 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 centrifugation speed is 8000 rad / min, the time is 30 min, and the temperature is 0℃;

[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 mixture obtained in 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℃, and then solution B is placed in a refrigerator at 5℃.

[0058] S8. In Figure 4 In the chip shown, cooled solution B is pumped into core layer channel 100 at a rate of 250 μL / min, and 500 g of mixed aqueous solution I is pumped into sheath layer channel 200 at a rate of 400 μL / min. Both are sprayed out from the outlet of mixing channel 300 into solution II for solidification. The solidified material is collected by a roller with a rotation speed of 20 rpm.

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

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

[0061] The SEM image of the carbon nanotube composite fiber with a gradient structure obtained in this embodiment is shown below. Figures 1-3 As shown; the structural diagram of the chip used is as follows. Figure 4 As shown.

[0062] Example 2

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

[0064] (1) In step S6, the crosslinking agent epichlorohydrin is added at a ratio of 1.0 mL crosslinking agent / 200 g solution A;

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

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

[0067] The SEM image of the carbon nanotube composite fiber with a gradient structure obtained in this embodiment is shown below. Figure 5 As shown.

[0068] Example 3

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

[0070] (1) In step S3, 88g of mixed aqueous solution II (solvent) and 12g of 10% CNT aqueous solution are 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 a gradient structure obtained in this embodiment is shown below. Figure 6 As shown.

[0073] Comparative Example 1

[0074] This comparative example prepared 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 outlet 300 along the core layer channel 100 at a propulsion speed of 250 μL / min and solidified in 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 shown below. Figure 7 As shown.

[0077] Test case

[0078] This experiment tested the morphology, hydrodynamic performance, water transport rate, and fiber strength of the carbon nanotube composite fibers obtained in Examples 1-3 and Comparative Example 1. Among them:

[0079] Morphology testing was performed using a scanning electron microscope; the diameter of the fibers was statistically analyzed using particle distribution software on the acquired scanning electron microscope images.

[0080] Power generation performance testing: Electrical performance data were obtained using a Keithley 2400 meter. One end of the dried carbon nanotube composite fiber was immersed in a 0.5 mol / L NaCl solution, while the other end was exposed to air. Both ends were then in contact with a test pen coated with ink (to eliminate redox reactions).

[0081] Water transport rate test in fibers: Observe and photograph using an upright fluorescence microscope, drop an aqueous solution containing fluorescent particles onto the fiber, and record the process and speed of the solution transport along the axial and radial directions of the fiber;

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

[0083] The morphological 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 1-3 As shown, the morphology of the carbon nanotube composite fiber with a gradient structure obtained in Example 2 is as follows. Figure 5 As shown; the morphology of the carbon nanotube composite fiber with a gradient structure obtained in Example 3 is as follows. Figure 6 As shown; the morphology of the carbon nanotube composite fibers obtained in Comparative Example 1 is as follows. Figure 7 As shown.

[0085] from Figure 1 As can be seen, the carbon nanotube composite fibers prepared in Example 1 have a loose and porous surface, forming a porous network; and the average pore size of the central portion of its cross-section is smaller than that of the edge portion, such as... Figure 2 As shown, Figure 2 As can be seen, 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 is rapidly transported along the fiber axis, exhibiting rapid water transport characteristics.

[0086] In Example 2, compared to Example 1, the propagation speed of the sheath channel was much greater than that of the core channel. The dilution effect of the sheath injection solution I on solution B penetrated to all locations in solution B, resulting in a loose and irregular fibrous structure, such as... Figure 5 As shown.

[0087] In Example 3, compared to Example 1, the amount of carbon nanotubes used was less. When the amount of carbon nanotubes was 20 wt% of cellulose, the content of carbon nanotubes in the solution was low, making them easier to dilute with the sheathing agent. This resulted in fibers with larger pore sizes and lighter colors. Figure 6 As shown.

[0088] The carbon nanotube composite fibers prepared in Comparative Example 1 have a larger diameter of 350 μm, and the resulting material has a uniform pore size distribution, such as... Figure 7 As shown, this morphology reduces the diffusion rate of 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 1-3 and the carbon nanotube composite fibers obtained in Comparative Example 1 are shown in Table 1.

[0090] Table 1. Fiber diameter.

[0091]

[0092] Electrical test results:

[0093] The electrical test results of the carbon nanotube composite fibers obtained in Examples 1-3 and Comparative Example 1 are as follows: Figure 9 As shown in the figure, the carbon nanotube composite fibers with gradient structures obtained in Examples 1-3 exhibit good hydrovoltaic power generation capabilities, at 0.51, 0.47, and 0.46 V respectively. This is due to the gradient pore size structure that gradually decreases from the outside to the inside. Therefore, when in contact with liquid, the liquid rapidly diffuses inward, travels along the fiber axis, and interacts with the carbon nanotubes, forming a stable potential difference at both ends of the fiber. In contrast, the carbon nanotube composite fiber obtained in Comparative Example 1 does not possess a gradient pore structure, and its voltage is only 0.37 V.

[0094] Fiber strength test results:

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

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

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

[0098] Table 2 Water transport 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 transport velocity test results of the carbon nanotube composite fiber with gradient structure obtained in Example 1 are as follows: Figure 8 As shown.

[0101] Application examples

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

[0103] The carbon nanotube composite fiber (black part) with a gradient structure prepared in Example 1 was inserted into a fabric woven from cotton yarn (white part) in both warp and weft directions along one direction, resulting in the following: Figure 11 The fabric shown.

[0104] As can be seen from the figure, carbon nanotube composite fibers with gradient structures have good flexibility and can be used as weaving materials for fabrics, which has potential value in the field of wearable self-powered materials technology.

[0105] The above data shows that the carbon nanotube composite fiber with a gradient structure provided by the present invention has a moderate diameter, directional rapid water transport and excellent hydrodynamic power generation performance. At the same time, its good flexibility and strength can be used for fabrication. 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 materials.

[0106] The above-described detailed description of a carbon nanotube composite fiber with a gradient structure, its preparation method, and its application, with reference to the embodiments, is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing carbon nanotube composite fibers with a gradient structure, characterized in that, The preparation method includes the following steps: (1) Prepare a mixed aqueous solution I, wherein the mixed aqueous solution I is a mixed aqueous solution of inorganic alkali and urea; (2) Disperse carbon nanotubes in mixed aqueous solution I, add fiber raw materials to it, stir and mix at -65~-75 ℃ for 2~5 h to obtain a black carbon nanotube / cellulose mixed suspension; (3) Add a crosslinking agent to the carbon nanotube / cellulose mixed suspension, stir at -10~0 ℃ for 1~2 h, centrifuge and degas to obtain solution B; (4) Pump solution B and mixed aqueous solution I into the core layer channel and sheath layer channel of the microfluidic chip respectively, and then collect the effluent in hydrochloric acid solution. After centrifugation, washing and drying, the carbon nanotube composite fiber with gradient structure is obtained. In step (4), the pumping rate of solution B is less than the pumping rate of mixed aqueous solution I; In step (4), the pumping rate of solution B is 250~300 μL / min, and the pumping rate of mixed aqueous solution I is 300~400 μL / min; The carbon nanotube composite fiber with a gradient structure is a composite material of carbon nanotubes and fibers. It appears as black filaments with a loose and porous surface, and the pore size gradually decreases from the surface to the core.

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

3. The preparation method according to claim 1, characterized in that, The axial fluid transport rate of the carbon nanotube composite fiber is 150~200 μm / s, and the radial fluid transport rate is 200~400 μm / s.

4. The preparation method according to claim 1, characterized in that, The carbon nanotube composite fibers can generate electricity in fluids with ionizing properties.

5. The preparation method according to claim 1, 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.

6. The preparation method according to claim 1, 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 and cotton linters.

7. The preparation method according to claim 1, characterized in that, In step (3), the ratio of the carbon nanotube / cellulose mixed suspension to the crosslinking agent is 200g: (1.0~4.0)mL; the crosslinking agent is epichlorohydrin.

8. The carbon nanotube composite fiber with a gradient structure prepared by the preparation method according to any one of claims 1-4.

9. The application of the carbon nanotube composite fiber with a gradient structure as described in claim 8 as a fluid power generation material or a fabric material.

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