A carbon nanotube thin film and its preparation method and apparatus

Abstract

The present invention discloses a carbon nanotube film and a preparation method and device thereof. The specific method comprises the following steps: pressing a spinning solution into a micron-sized pipe whose inner diameter gradually decreases along the flow direction of the solution, wherein the spinning solution contains magnetic metal-filled carbon nanotubes; orienting the carbon nanotubes in the spinning solution in the micron-sized pipe by an induced magnetic field; spraying the oriented spinning solution onto the surface of a collecting device for attachment to obtain a carbon nanotube film. The present invention orients the magnetic metal-filled carbon nanotubes in the spinning solution by an induced magnetic field. At the same time, the flow velocity difference and the gradient inner diameter in the micron-sized pipe cause the carbon nanotubes to gradually converge radially along the center. Through the combined effect of the induced magnetic field and the capillary effect of the micron-sized pipe, the orientation degree of the carbon nanotube film is high. The device has a simple structure, is easy to operate, and has high production efficiency. The size of the induced magnetic field can be adjusted according to actual needs.

Description

Technical Field

[0001] The invention relates to the technical field of film material preparation, and in particular to a carbon nanotube film and a preparation method and device thereof. Background Art

[0002] At present, the methods for orienting carbon nanotubes include chemical vapor deposition (CVD), external electric field, external magnetic field, mechanical stretching, electrostatic spinning, etc., and the methods for preparing carbon nanotube films include chemical vapor deposition, layer-by-layer self-assembly film formation, electrophoresis, printing, spinning, etc. However, these methods have complex process, strict requirements on experimental instruments, etc., and the product quality is easily affected by external environmental factors. In the preparation process, it is impossible to effectively control the orientation degree of carbon nanotubes and the thickness and density of the oriented carbon nanotube film; in addition, the prepared carbon nanotube film has poor self-support, poor electromagnetic and mechanical properties, which greatly limits its application range.

[0003] The technology of improving the conductivity of fibers or films by changing the arrangement of carbon nanotubes has attracted increasing attention. Patent CN105565295 A discloses a method for preparing an oriented carbon nanotube film, firstly polymer-modifying carboxylated multi-walled carbon nanotubes, then uniformly loading magnetic particles by chemical coprecipitation, then pouring the configured solution into a vacuum filtration device, applying a magnetic field and changing the direction of the magnetic field to obtain an in-plane vertically oriented film or an in-plane parallel oriented film, and finally using liquid nitrogen to remove the base film to obtain an oriented carbon nanotube film. This patent uses a magnetic field to induce the orientation of carbon nanotubes, but because the distribution of magnetic particles loaded on carbon nanotubes is not necessarily uniform, it is not possible to ensure that all carbon nanotubes have an ideal orientation degree under the action of a fixed magnetic field force, and the operating steps of the method are relatively complicated, and it is not possible to achieve continuous and efficient preparation of carbon nanotube films. Patent CN106497048 A discloses a method for preparing an anisotropic conductive polymer composite film, wherein a carbon nanotube / ferroferric oxide-polyaniline solution or a carbon nanotube / ferroferric oxide-polyaniline-polyurethane solution is dripped onto a glass sheet and cast into a film, and the obtained film is placed in a magnetic field for magnetic orientation, and dried at high temperature to prepare an anisotropic conductive polymer composite film. The orientation method of this patent cannot guarantee the complete orientation of the carbon nanotubes, and the limitations of the equipment operation are very large, and the output efficiency of the film is very low. Patent CN108625040 A discloses a method for preparing a carbon nanotube-enhanced anion exchange membrane by coaxial electrospinning, wherein the functionalized carbon nanotubes are fixed inside the nanofibers and oriented along the axial direction of the nanofibers by coaxial electrospinning, and the addition of imidazole functional groups on the surface promotes the aggregation of ion clusters in the membrane, thereby effectively enhancing the compatibility of organic / inorganic components, and improving ionic conductivity and mechanical strength. This patent also faces the problem of carbon nanotubes clustered inside the fiber and unsatisfactory orientation, which affects the ion conductivity. At the same time, due to the limited spinning distance of electrospinning, the solvent evaporation is relatively incomplete, which is not conducive to better crystallization of the fiber and forming a stronger structure. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a carbon nanotube film and a preparation method and device thereof. A spinning solution containing magnetic metal-filled carbon nanotubes is used, which is oriented under the combined action of an induced magnetic field and a micron-level channel capillary effect, and then sprayed onto a collecting device to prepare a highly oriented carbon nanotube film, thereby overcoming the problems of low orientation degree and unsatisfactory electrical conductivity of the carbon nanotube film in the prior art, as well as bulky equipment, complicated operation and inability to produce on a large scale in the preparation process.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing a carbon nanotube film, comprising the following steps:

[0007] (1) pressing a spinning solution into a micrometer-sized pipe whose inner diameter gradually decreases along a flow direction of the solution, wherein the spinning solution contains magnetic metal-filled carbon nanotubes;

[0008] (2) orienting the carbon nanotubes in the spinning solution in the micron-sized tube by inducing a magnetic field;

[0009] (3) The oriented spinning solution is sprayed onto the surface of a collecting device and attached to the surface to obtain a carbon nanotube film.

[0010] The present invention adopts magnetic metal filled carbon nanotubes to magnetize carbon nanotubes, so that it can be more captured by the induced magnetic field, and its magnetic moment is stronger and its conductivity is stronger than that of the magnetization mode of loaded metal particles. When the spinning solution passes through the induced magnetic field with uniform intensity, the carbon nanotubes filled with magnetic metals are more evenly stressed than the carbon nanotubes loaded with magnetic particles, and are more likely to be arranged and oriented in the direction parallel to the magnetic field lines, while increasing the flow rate of the spinning solution in the micron-sized pipe. At the same time, the flow velocity at the center of the micron-sized pipe is higher than the flow velocity at the pipe wall, and due to the flow velocity difference and the gradually reduced gradient inner diameter inside the micron-sized pipe, the carbon nanotubes are gradually radially gathered in the center. Only when arranged along the streamline direction, the torque received is equal to zero. According to the right-hand screw rule, the direction of the magnetic field force received by the filled carbon nanotubes is consistent with the center streamline direction. After the spinning solution is subjected to the combined action of the induced magnetic field and the capillary effect of the micron-scale channel, a high degree of orientation of the carbon nanotubes is achieved, and a highly oriented anisotropic carbon nanotube film is obtained by spraying it on the surface of the collecting device. The conductivity of the film is strong along the orientation direction of the carbon nanotubes, and the conductivity of the film is relatively weak perpendicular to the orientation direction of the carbon nanotubes.

[0011] Furthermore, the carbon nanotubes can be magnetized by filling the carbon nanotubes with magnetic metals, wherein the magnetic metals can be iron, nickel, etc.

[0012] Furthermore, the magnetic metal is iron, and the magnetic metal-filled carbon nanotubes are specifically iron nanowire-filled carbon nanotubes.

[0013] Furthermore, the spinning solution contains a polyisobutylene-polyaniline composite material, which includes two polymer materials, polyisobutylene and polyaniline. The molecular weight of the polyisobutylene is 5000-10000, and the molecular weight of the polyaniline is 5000-7000. The content of polyisobutylene in the polyisobutylene-polyaniline composite material is 5wt%-18wt%, preferably 7wt%. Polyisobutylene is a thermoplastic elastomer with good weather resistance, chemical corrosion resistance and tensile resistance; while polyaniline is a conductive polymer with excellent electrical properties and stability. The polyisobutylene-polyaniline composite material has both mechanical strength and electrical properties. Good mechanical strength can improve the strength of the film, and good high conductivity can increase the speed of the spinning solution in the induced magnetic field and the auxiliary electric field.

[0014] Furthermore, the method for preparing the spinning solution of magnetic metal-filled carbon nanotubes is as follows: add the polyisobutylene-polyaniline composite material and polyacrylonitrile to an organic solvent, stir until completely dissolved, add the magnetic metal-filled carbon nanotubes, and ultrasonically disperse to obtain a spinning solution. Preferably, the addition amount of the polyisobutylene-polyaniline composite material is 15%-30% of the dry weight of the polyacrylonitrile, preferably 25%.

[0015] Furthermore, the organic solvent may be N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone or other organic solvents.

[0016] Furthermore, the length of the magnetic metal-filled carbon nanotubes is 10 μm-30 μm, and the mass fraction of the magnetic metal-filled carbon nanotubes in the spinning solution is 0.5 wt%-1 wt%.

[0017] Furthermore, the spinning solution is pressurized by a liquid storage pressurizing device, and the spinning solution is pressed into a micrometer-sized pipe.

[0018] Furthermore, the inner diameter of the micron-sized pipe is 200 μm-300 μm, which gradually decreases along the flow direction of the solution, so that the carbon nanotubes gradually converge radially along the center. Preferably, the inner diameter of the micron-sized pipe is 200 μm-250 μm.

[0019] Furthermore, the induced magnetic field is generated by a solenoid wound on a micron-sized pipe, and the voltage across the solenoid is 8-12KV. The carbon nanotubes filled with magnetic metal are oriented in the induced magnetic field, and the magnitude of the induced magnetic field is controlled by adjusting the magnitude of the voltage across the solenoid, which is specifically adjusted according to the spinning requirements.

[0020] Furthermore, in step (3), the spinning solution is mixed with the high-pressure gas at the tail end of the micrometer-sized pipe and then sprayed out through the spinneret to adhere to the surface of the collecting device. The introduction of the high-pressure gas drives the spinning solution to be sprayed.

[0021] Furthermore, the high-pressure gas is argon or nitrogen, and the gas flow pressure is 0.3-1.5Mpa.

[0022] Furthermore, an aluminum film is attached to the surface of the collecting device, and the collecting device can be optionally a roller collecting device, the diameter of the roller collecting device is 7 cm, and the linear speed of rotation is 5m / s-45m / s.

[0023] Furthermore, an auxiliary electric field is set between the spinneret and the collecting device, and the spinning solution passes through the auxiliary electric field when being sprayed. The voltage at both ends of the auxiliary electric field is 8-12KV, preferably 10KV, which is used to increase the spraying speed, thereby increasing the receiving distance of the collecting device to a certain extent, accelerating the evaporation of the solvent, and enhancing the traction and stretching effect of the high-speed airflow on the spinning solution jet, thereby enhancing the strength of the film.

[0024] The second aspect of the present invention provides a carbon nanotube film prepared by the preparation method of the first aspect.

[0025] The third aspect of the present invention provides a device for preparing the carbon nanotube film of the second aspect, the device comprising:

[0026] Liquid storage booster device;

[0027] A micron-sized pipe, one end of which is connected to the liquid storage and pressurizing device, and the other end is connected to the spinneret, and a high-pressure gas inlet is arranged near the spinneret, and the inner diameter of the micron-sized pipe gradually decreases along the flow direction of the solution;

[0028] An induced magnetic field generating device, the induced magnetic field generating device is composed of a hollow metal tube, a solenoid wound on the hollow metal tube, and a first high-voltage power supply connected to the solenoid, wherein the hollow metal tube is sleeved on the micron-sized pipe;

[0029] A collecting device is arranged opposite to the spinneret, and the spinneret and the collecting device are respectively connected to a second high voltage power supply.

[0030] In the present invention, the liquid storage booster device boosts the spinning solution and presses the spinning solution into a micron-sized pipe. Along the flow direction of the solution, the inner diameter of the micron-sized pipe gradually decreases. Through the flow velocity difference and the gradient inner diameter, the carbon nanotubes gradually converge radially along the center. At the same time, the first high-voltage power supply is energized for the solenoid, and the solenoid sleeved outside the micron-sized pipe generates an induced magnetic field, and the magnetic metal-filled carbon nanotubes flowing through are oriented under the action of the magnetic field. After the spinning solution is acted upon by the induced magnetic field and the micron-sized pipe, a high degree of orientation of the carbon nanotubes is achieved, and the spinning solution is sprayed on the surface of the collecting device. The second high-voltage power supply is connected to the spinneret and the collecting device, and the collecting device is grounded, and an auxiliary electric field is generated between the spinneret and the collecting device, and the auxiliary electric field speeds up the spraying of the spinning solution and speeds up the film strength.

[0031] Furthermore, the micron-scale pipe is a PDMS (polydimethylsiloxane) pipe.

[0032] Furthermore, the hollow metal tube is made of an iron-nickel alloy and is sleeved on a micron-sized pipe to concentrate magnetic flux lines, enhance the induced magnetic field, and assist in heat dissipation, thereby making the carbon nanotubes in the spinning solution more evenly distributed.

[0033] Furthermore, the solenoid is composed of thin copper wires with uniform thickness. The thin copper wires are tightly wound around the hollow metal tube in a clockwise direction along the flow direction of the spinning solution in multiple layers. The number of winding turns is 200-300 turns, and the number of layers is 2-4. The multi-layered, high-density wound thin copper wires will generate an induced magnetic field sufficient to orient the carbon nanotubes. At the same time, after the iron-nickel alloy hollow metal tube is magnetized, the magnetic lines of force will be further concentrated, thereby enhancing the magnitude of the magnetic force on the filled carbon nanotubes.

[0034] Furthermore, the outer diameter of the micron-scale pipe is 3 mm and the length is 70 cm; the inner diameter of the hollow metal tube is 3.5 mm and the length is 35 cm.

[0035] Furthermore, it also includes a high-pressure gas source, which is connected to the high-pressure gas inlet at the tail end of the micron-sized pipe through a pipeline, and is used to introduce high-pressure gas into the micron-sized pipe and drive the spinning solution to spray.

[0036] Furthermore, the spinneret is preferably a steel spinneret with a structure of a 27G syringe needle specification and an inner diameter of 200 μm.

[0037] Furthermore, the distance between the spinneret and the collecting device is 40-80 cm.

[0038] Beneficial effects of the present invention:

[0039] The present invention uses the induced magnetic field generated by connecting a solenoid to a high-voltage power supply to orient the magnetic metal-filled carbon nanotubes uniformly distributed in the spinning solution; the flow velocity difference and the gradient inner diameter in the micron-sized pipe cause the carbon nanotubes to gradually contract radially along the center; the carbon nanotubes have a high degree of orientation through the combined effect of the induced magnetic field and the capillary effect of the micron-sized pipe;

[0040] The iron-nickel alloy hollow metal tube can concentrate the magnetic flux lines and enhance the induced magnetic field, thereby making the carbon nanotubes in the spinning solution more evenly distributed and assisting in heat dissipation;

[0041] The jet speed of the spinning solution is increased under the action of the auxiliary electric field, thereby increasing the jet distance and improving the evaporation path of the solvent in the air, thereby improving the film strength;

[0042] The device adopted by the present invention has a simple structure, is easy to operate, has high production efficiency, and the size of the induced magnetic field is adjustable, so that the size of the induced magnetic field can be adjusted according to actual needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the structure of the device for preparing carbon nanotube film of the present invention;

[0044] Figure 2 It is a schematic diagram of the positional relationship of the solenoid, the hollow metal tube and the micron-sized pipeline of the present invention;

[0045] Figure 3 It is a schematic diagram of the internal structure of the micron-scale pipeline of the present invention;

[0046] Figure 4 It is a schematic diagram of the orientation of the carbon nanotubes of the present invention in a micron-sized pipe with a gradient inner diameter;

[0047] Figure 5 This is a scanning electron microscope image of the carbon nanotube film prepared in Example 3 of the present invention.

[0048] Explanation of the numbers in the figure: 1. liquid storage and boosting device, 2. micron-sized pipeline, 3. spinneret, 4. hollow metal tube, 5. solenoid, 6. first high-voltage power supply, 7. collecting device, 8. second high-voltage power supply, 9. carbon nanotube, 10-high-pressure gas source. DETAILED DESCRIPTION

[0049] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0050] Reference Figure 1As shown, an embodiment of the present invention provides a device for preparing a carbon nanotube film, the device comprising: a liquid storage and pressurizing device 1, a micron-sized pipe 2, one end of the micron-sized pipe 2 is connected to the liquid storage and pressurizing device 1, and the other end is connected to a spinneret 3, and a high-pressure gas inlet is arranged near the spinneret of the micron-sized pipe 2, and the inner diameter of the micron-sized pipe 2 gradually decreases along the flow direction of the solution; an induction magnetic field generating device, the induction magnetic field generating device is composed of a hollow metal tube 4, a solenoid 5 wound on the hollow metal tube 4 and a first high-voltage power supply 6 connected to the solenoid 5, the hollow metal tube 4 is sleeved on the micron-sized pipe 2, as shown in FIG. Figure 2 As shown; a collecting device 7, wherein the collecting device 7 is arranged opposite to the spinneret 3, and the spinneret 3 and the collecting device 7 are respectively connected to a second high-voltage power supply 8.

[0051] In this embodiment, the working principle of the device for preparing carbon nanotube film is as follows: the liquid storage pressurizing device 1 is started to pressurize the spinning solution placed therein, and the spinning solution is pressed into the micron-sized pipe 2. High-pressure gas is introduced into the tail of the micron-sized pipe 2, and at the same time, the first high-voltage power supply 6 is turned on to generate an induced magnetic field through the spiral tube 5 to orient the spinning solution flowing through the micron-sized pipe 2 surrounded by the spiral tube 5. Figure 3 As shown, along the direction of the spinning solution flowing, the inner diameter of the micron-sized pipe 2 gradually decreases, and the carbon nanotubes 9 gradually gather and orient radially along the center in the gradient inner diameter. The orientation diagram is shown in FIG. Figure 4 As shown, under the combined effect of the induced magnetic field and the capillary effect of the micron-sized pipe 2, the carbon nanotubes 9 in the spinning solution are rapidly oriented in a direction parallel to the central axis of the micron-sized pipe 2, and finally ejected from the spinneret 3 and attached to the surface of the collecting device 7, thereby obtaining a highly oriented carbon nanotube film.

[0052] Preferably, the micron-sized pipe 2 is a PDMS pipe, the outer diameter of the micron-sized pipe 2 is 3 mm, and the length is 70 cm. The hollow metal pipe 4 is made of an iron-nickel alloy, and is sleeved on the micron-sized pipe 2 to concentrate magnetic flux lines, enhance the induced magnetic field, and assist in heat dissipation, so that the carbon nanotubes in the spinning solution are more evenly distributed. The inner diameter of the hollow metal pipe 4 is 3.5 mm, and the length is 35 cm.

[0053] Preferably, the solenoid 5 is composed of thin copper wires of uniform thickness, which are tightly wound around the hollow metal tube 4 in a clockwise direction along the flow direction of the spinning solution in multiple layers, with 200-300 turns and 2-4 layers. The multi-layered, high-density wound thin copper wires will generate an induced magnetic field sufficient to orient the carbon nanotubes.

[0054] Preferably, it also includes a high-pressure gas source 10, which is connected to the high-pressure gas inlet at the tail end of the micron-sized pipe 2 through a pipeline, and is used to introduce high-pressure gas into the micron-sized pipe 2 and drive the spinning solution to be sprayed.

[0055] Preferably, the spinneret 3 is a steel spinneret with a structure of a 27G syringe needle specification and an inner diameter of 200 μm. The distance between the spinneret 3 and the collecting device 7 is 40-80 cm.

[0056] The following is an example of a method for preparing a carbon nanotube film of the present invention.

[0057] Example 1

[0058] This embodiment relates to a method for preparing a carbon nanotube film, using Figure 1 The device for preparing the carbon nanotube film specifically comprises the following steps:

[0059] (1) A polyacrylonitrile / N,N-dimethylformamide solution with a concentration of 10% is prepared, and then polyisobutylene-polyaniline composite solid particles are added to the above solution at a mass ratio of 25% relative to the mass of the polyacrylonitrile, and magnetically stirred at a speed of 400 r / min for 40 minutes to completely dissolve the solid particles to obtain a polyisobutylene-polyaniline solution with a concentration of 20%, and then iron-filled carbon nanotubes are added, ultrasonically dispersed at a power of 100 W for 20 minutes, and then magnetically stirred at a speed of 400 r / min for 40 minutes to obtain a uniformly dispersed and stable magnetic iron-filled carbon nanotube spinning solution, wherein the length of the iron-filled carbon nanotubes in the spinning solution is 10 μm-30 μm, and the mass percentage is 0.5 wt%.

[0060] (2) The spinning solution prepared in step (1) is injected into the liquid storage and pressurizing device 1, and the liquid storage and pressurizing device 1 is started to press the spinning solution into the PDMS pipe, wherein the inner diameter of the PDMS pipe gradually decreases from 250 μm at the starting end to 200 μm.

[0061] (3) The voltage value of the first high-voltage power supply 6 is adjusted to 8 kV, and the solenoid 5 is energized to generate an induced magnetic field. The iron-filled carbon nanotubes in the spinning solution are oriented when flowing through the solenoid 5.

[0062] (4) The spinning solution is mixed with the high-pressure gas at the tail end of the PDMS pipe, and is ejected through the spinneret 3, passes through the auxiliary electric field generated by the second high-voltage power supply 8, and adheres to the surface of the rotating drum collecting device 7 to prepare a highly oriented carbon nanotube film. The diameter of the spinneret 3 is 200 μm, the spinning solution flow rate is 3 mL / h, the pressure value of the second high-voltage power supply 8 is 10 KV, the distance between the spinneret 3 and the collecting device 7 is 50 cm, and the rotating linear speed of the collecting device 7 is 45 m / s.

[0063] Example 2

[0064] This embodiment relates to a method for preparing a carbon nanotube film, using Figure 1The device for preparing the carbon nanotube film specifically comprises the following steps:

[0065] (1) A polyacrylonitrile / N,N-dimethylformamide solution with a concentration of 10% is prepared, and then polyisobutylene-polyaniline composite solid particles are added to the above solution at a mass ratio of 25% relative to the mass of the polyacrylonitrile, and magnetically stirred at a speed of 400 r / min for 40 minutes to completely dissolve the solid particles to obtain a polyisobutylene-polyaniline solution with a concentration of 20%, and then iron-filled carbon nanotubes are added, ultrasonically dispersed at a power of 100 W for 20 minutes, and then magnetically stirred at a speed of 400 r / min for 40 minutes to obtain a uniformly dispersed and stable magnetic iron-filled carbon nanotube spinning solution, wherein the length of the iron-filled carbon nanotubes in the spinning solution is 10 μm-30 μm, and the mass percentage is 0.8 wt%.

[0066] (2) The spinning solution prepared in step (1) is injected into the liquid storage and pressurizing device 1, and the liquid storage and pressurizing device 1 is started to press the spinning solution into the PDMS pipe, wherein the inner diameter of the PDMS pipe gradually decreases from 250 μm at the starting end to 200 μm.

[0067] (3) The voltage value of the first high-voltage power supply 6 is adjusted to 10 kV, and the solenoid 5 is energized to generate an induced magnetic field. The iron-filled carbon nanotubes in the spinning solution are oriented when flowing through the solenoid 5.

[0068] (4) The spinning solution is mixed with the high-pressure gas at the tail end of the PDMS pipe, and is ejected through the spinneret 3, passes through the auxiliary electric field generated by the second high-voltage power supply 8, and adheres to the surface of the rotating drum collecting device 7 to prepare a highly oriented carbon nanotube film. The diameter of the spinneret 3 is 200 μm, the spinning solution flow rate is 3 mL / h, the pressure value of the second high-voltage power supply 8 is 10 KV, the distance between the spinneret 3 and the collecting device 7 is 50 cm, and the rotating linear speed of the collecting device 7 is 45 m / s.

[0069] Example 3

[0070] This embodiment relates to a method for preparing a carbon nanotube film, using Figure 1 The device for preparing the carbon nanotube film specifically comprises the following steps:

[0071] (1) A polyacrylonitrile / N,N-dimethylformamide solution with a concentration of 10% is prepared, and then polyisobutylene-polyaniline composite solid particles are added to the above solution at a mass ratio of 25% relative to the mass of the polyacrylonitrile, and magnetically stirred at a speed of 400 r / min for 40 minutes to completely dissolve the solid particles to obtain a polyisobutylene-polyaniline solution with a concentration of 20%, and then iron-filled carbon nanotubes are added, ultrasonically dispersed at a power of 100 W for 20 minutes, and then magnetically stirred at a speed of 400 r / min for 40 minutes to obtain a uniformly dispersed and stable magnetic iron-filled carbon nanotube spinning solution, wherein the length of the iron-filled carbon nanotubes in the spinning solution is 10 μm-30 μm, and the mass percentage is 1 wt%.

[0072] (2) The spinning solution prepared in step (1) is injected into the liquid storage and pressurizing device 1, and the liquid storage and pressurizing device 1 is started to press the spinning solution into the PDMS pipe, wherein the inner diameter of the PDMS pipe gradually decreases from 250 μm at the starting end to 200 μm.

[0073] (3) The voltage value of the first high-voltage power supply 6 is adjusted to 12 kV, and the solenoid 5 is energized to generate an induced magnetic field. The iron-filled carbon nanotubes in the spinning solution are oriented when flowing through the solenoid 5.

[0074] (4) The spinning solution is mixed with the high-pressure gas at the tail end of the PDMS pipe and ejected through the spinneret 3, passing through the auxiliary electric field generated by the second high-voltage power supply 8, and adhering to the surface of the rotating drum collecting device 7 to prepare a highly oriented carbon nanotube film. The diameter of the spinneret 3 is 200 μm, the spinning solution flow rate is 3 mL / h, the pressure value of the second high-voltage power supply 8 is 10 KV, the distance between the spinneret 3 and the collecting device 7 is 50 cm, and the linear speed of the collecting device 7 is 45 m / s. The scanning electron microscope photo of the highly oriented carbon nanotube film prepared in this embodiment is shown in FIG. Figure 5 ,Depend on Figure 5 It can be seen that the carbon nanotubes in the film are uniform in thickness, arranged in an orderly manner, and have a high degree of orientation.

[0075] Comparative Example 1

[0076] The only difference between Comparative Example 1 and Example 1 is that the mass percentage of iron-filled carbon nanotubes in the spinning solution is 2 wt %, and the remaining steps are the same.

[0077] Comparative Example 2

[0078] The only difference between Comparative Example 2 and Example 1 is that the voltage of the first high-voltage power supply 6 is 5 kV, and the remaining steps are the same.

[0079] Comparative Example 3

[0080] The only difference between Comparative Example 3 and Example 1 is that the inner diameter of the PDMS pipe is a fixed value of 250 μm, and the other steps are the same.

[0081] Comparative Example 4

[0082] The difference between Comparative Example 4 and Example 1 is that the first high-voltage power supply 6 is turned off and the induction magnetic field generating device is not enabled, and the remaining steps are the same.

[0083] Performance Study

[0084] The electrical conductivity of the materials prepared in Examples 1-3 and Comparative Examples 1-4 was tested, and the test results are shown in Table 1:

[0085] Table 1 Sheet resistance and conductivity of examples and comparative examples

[0086]

[0087] As shown in Table 1, the materials prepared in Examples 1-3 have lower surface resistance and higher conductivity than Comparative Examples 2-4, and have excellent conductivity, wherein the lowest surface resistance is 244Ω / sq, and the highest conductivity is 381S / cm. Comparative Example 1 cannot smoothly eject the spinning solution from the spinneret due to the excessively high carbon nanotube content. In Comparative Example 2, the voltage of the first high-voltage power supply used to control the induced magnetic field is too small, and the spinning solution stagnates when flowing in the micron-sized pipe, causing the film to be not uniform enough and affecting the overall conductivity. In addition, since the induced magnetic field is too small, it is not enough to fully orient the carbon nanotubes in the solution, thereby affecting the conductivity of the entire material. In Comparative Example 3, the pore size inside the PDMS pipe remains unchanged, so the orientation of the carbon nanotubes that lose the gradient capillary effect is significantly reduced, resulting in a significant decrease in the conductivity of the film. In Comparative Example 4, there is no orientation and driving effect of the induced magnetic field, and the overall orientation of the carbon nanotubes is greatly reduced. At the same time, the driving effect of the induced magnetic field is lost, and the spinning solution gathers at the mouth of the PDMS pipe, and stagnates when flowing, which seriously affects the overall uniformity and conductivity of the film.

[0088] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A method for preparing a carbon nanotube film, characterized in that: The steps include: (1) Pressing a spinning solution into a micrometer-sized pipe whose inner diameter gradually decreases along the flow direction of the solution, wherein the spinning solution contains magnetic metal-filled carbon nanotubes, and the mass fraction of the magnetic metal-filled carbon nanotubes in the spinning solution is 0.5wt%-1wt%; (2) Orienting carbon nanotubes in the spinning solution in a micrometer-sized tube by inducing a magnetic field; (3) The oriented spinning solution is sprayed onto the surface of a collecting device and attached to the surface to obtain a carbon nanotube film.

2. The method for preparing a carbon nanotube film according to claim 1, characterized in that: The magnetic metal is iron.

3. The method for preparing a carbon nanotube film according to claim 1, characterized in that: The spinning solution contains a polyisobutylene-polyaniline composite material, the molecular weight of the polyisobutylene is 5000-10000, and the molecular weight of the polyaniline is 5000-7000.

4. The method for preparing a carbon nanotube film according to claim 1, characterized in that: The length of the magnetic metal-filled carbon nanotubes is 10 μm-30 μm.

5. The method for preparing a carbon nanotube film according to claim 1, characterized in that: The inner diameter of the micron-scale pipe is 200 μm-300 μm.

6. The method for preparing a carbon nanotube film according to claim 1, characterized in that: The induced magnetic field is generated by a solenoid wound on a micron-sized pipe, and the voltage across the solenoid is 8-12KV.

7. The method for preparing a carbon nanotube film according to claim 1, characterized in that: In step (3), the spinning solution is mixed with the high-pressure gas at the tail end of the micrometer-sized pipe and then ejected through the spinneret to adhere to the surface of the collecting device.

8. The method for preparing a carbon nanotube film according to claim 1, characterized in that: The spinning solution passes through an auxiliary electric field when being sprayed, and the voltage across the auxiliary electric field is 8-12KV.

9. A carbon nanotube film prepared by the preparation method according to any one of claims 1 to 8.

10. A device for preparing the carbon nanotube film according to claim 9, characterized in that: The device comprises: Liquid storage booster device; A micron-sized pipe, one end of which is connected to the liquid storage and pressurizing device, and the other end of which is connected to the spinneret, and a high-pressure gas inlet is arranged near the spinneret, and the inner diameter of the micron-sized pipe gradually decreases along the flow direction of the solution; An induced magnetic field generating device, the induced magnetic field generating device is composed of a hollow metal tube, a solenoid wound on the hollow metal tube, and a first high-voltage power supply connected to the solenoid, wherein the hollow metal tube is sleeved on the micron-sized pipe; A collecting device is arranged opposite to the spinneret, and the spinneret and the collecting device are respectively connected to a second high voltage power supply.

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