A method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning

Abstract

The present invention relates to the field of high-performance carbon nanotube fiber preparation, specifically a dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density, and high conductivity. Using high-quality, large-aspect-ratio double-walled carbon nanotubes as raw materials, a protonation technique is employed to disperse the double-walled carbon nanotube liquid crystal spinning solution with low loss. During the wet spinning process for preparing carbon nanotube fibers, an air segment is introduced, and the double-walled carbon nanotube liquid crystal spinning solution is injected through a syringe through a length of air before entering a coagulation bath. The height of the air segment is controlled to regulate the gravity-induced orientation and close packing of the carbon nanotubes in the liquid crystal solution. The difference between the extrusion rate and the reel collection rate is regulated, and the extrusion rate and reel collection pulling are combined to achieve high orientation and densification of the double-walled carbon nanotubes, thereby achieving the preparation of high-orientation, high-density double-walled carbon nanotube fibers with an electrical conductivity of up to 11.2×10 6 S / m.

Description

Technical Field

[0001] The present invention relates to the field of preparation of high-performance carbon nanotube fibers, in particular to a method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning. Background Art

[0002] Carbon nanotubes (CNTs) possess high current carrying capacity, high strength, and high electrical conductivity, as well as excellent chemical stability, corrosion resistance, and oxidation resistance. Therefore, CNTs are an ideal material for constructing lightweight, highly conductive fibers. In 2000, Vigolo et al. reported fibers and ribbons composed of aligned CNTs (Reference 1: Vigolo B, Penicaud A, Coulon C, Sauder C., Pailler R., Journet C, Bernier B, Poulin B. Science. 2000, 290(5495), 1331-1334). Over the past two decades, numerous research groups have devoted themselves to the preparation and performance research of carbon nanotube fibers. Three main preparation methods have been developed: solution spinning, array spinning, and floating chemical vapor deposition aerosol spinning (Reference 2: Ericson LM, Fan H, Peng H. Science, 2004, 305(5689):1447-1450; Reference 3: Jiang K, Li Q, Fan S. Nature. 2002, 419(6909), 801; Reference 4: Wang JN, Luo XG, Wu T, Chen Y. Nat Commun, 2014, 5:3848). Of these three methods, solution spinning draws on the established polymer wet spinning technology. The carbon nanotube fibers produced by solution spinning have advantages such as high density, high conductivity, and ease of large-scale production. Therefore, it is considered the most promising technology for large-scale assembly of nanoscale carbon nanotube monomers into macroscale fibers.

[0003] Although the conductivity of carbon nanotube fibers produced by wet spinning is much higher than that of fibers spun by the other two methods, its performance is still far lower than the intrinsic performance of a single carbon nanotube (Reference 5: Kim SG, Choi GM, Jeong HD, et al. Carbon, 2022, (196-): 196), which limits the practical application of carbon nanotube fibers. The fundamental reason is that key scientific and technological issues in the process of assembling macroscale fibers from nanoscale carbon nanotube monomers still need to be overcome, mainly including: 1) The pulling force during wet spinning is insufficient to stretch the carbon nanotubes, resulting in low orientation of the carbon nanotubes, thereby introducing more contact resistance and reducing the conductivity of the carbon nanotube fibers. 2) During wet spinning, the coagulation bath solution diffuses from the fiber surface to the fiber core first, resulting in a difference in the coagulation rate of the core and surface, forming a skin-core structure, which reduces the conductivity of the carbon nanotube fibers. 3) The density between carbon nanotubes is not high, and there are pores. The presence of pores affects the electron transition between carbon nanotubes, thereby reducing the conductivity of carbon nanotube fibers. 4) During the preparation of carbon nanotube spinning solution, defects are inevitably introduced into the tube wall, reducing the conductivity of carbon nanotubes.

[0004] In summary, the key to preparing high-performance carbon nanotube fibers is: how to reduce the introduction of structural defects during the dispersion process to maximize the ballistic transport of electrons in the carbon nanotubes, and how to obtain skin-core-free, highly oriented, and highly dense carbon nanotube fibers to reduce interfacial contact resistance. Summary of the Invention

[0005] The present invention aims to provide a method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning. The method uses double-walled carbon nanotubes with a large aspect ratio as raw materials, adopts protonation dispersion technology to prepare liquid crystal spinning solution, introduces air segments into the wet spinning technology to increase the gravity traction directionality of the double-walled carbon nanotube spinning stream, and changes the difference between the extrusion rate and the reel collection rate to control the magnitude of the tensile force applied to the double-walled carbon nanotube fibers, thereby obtaining double-walled carbon nanotube fibers with high orientation, high density and high conductivity, and having an electrical conductivity of up to 6.0 to 11.2×10 6 S / m.

[0006] The technical solution of the present invention is:

[0007] A method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning, which uses high-quality double-walled carbon nanotubes with a large aspect ratio as raw materials and adopts protonation technology to prepare double-walled carbon nanotube liquid crystal spinning solution with low loss dispersion; an air segment is introduced during the wet spinning process for preparing carbon nanotube fibers, and the double-walled carbon nanotube liquid crystal spinning solution is injected through a length of air via a syringe and then enters a coagulation bath; the orientation and close packing of the gravity-induced carbon nanotubes in the liquid crystal solution are controlled by regulating the height of the air segment; the difference between the extrusion rate and the reel collection rate is regulated, and the extrusion rate and the reel collection pulling are combined to make the double-walled carbon nanotubes highly oriented and densified, thereby realizing the preparation of double-walled carbon nanotube fibers with high orientation and high density.

[0008] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity comprises injecting the double-walled carbon nanotube liquid crystal spinning solution vertically into an air segment through a needle with a pore size of 140 to 220 μm, and then injecting the solution from the air segment into an acetone or N-methylpyrrolidone coagulation bath.

[0009] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density, and high conductivity introduces an air segment during the wet spinning process, so that the double-walled carbon nanotubes are highly oriented under the action of gravity, effectively alleviating the skin-core structure caused by the difference in coagulation time between the core and the surface layer after the fibers enter the coagulation bath, reducing the contact resistance caused by the skin-core structure, and improving the conductivity of the double-walled carbon nanotube fibers; by adjusting the height of the air segment, the gravity action time of the double-walled carbon nanotube liquid crystal solution is controlled, and the air segment height is 20 to 300 mm.

[0010] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density, and high conductivity achieves control of the magnitude of the tensile force applied to the double-walled carbon nanotube liquid crystal solution by changing the difference between the extrusion rate and the reel collection rate, thereby further improving the alignment of the double-walled carbon nanotube fibers. The extrusion rate is 0.07 to 0.30 ml / min, and the reel collection rate is 70 to 300 mm / s.

[0011] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity is described. The carbon nanotubes used are high-quality double-walled carbon nanotubes with a large aspect ratio. The inner diameter of the double-walled carbon nanotubes is distributed in the range of 0.8 to 2.2 nm, the outer diameter is distributed in the range of 1.5 to 3.0 nm, the aspect ratio is 25,000 to 100,000, the oxidation resistance temperature is greater than 820°C, the residual catalyst content is less than 6.0 wt%, and the Raman spectrum I G / I D The ratio is greater than 80.

[0012] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity comprises placing high-quality double-walled carbon nanotubes with a large aspect ratio in a 30wt% aqueous hydrogen peroxide solution and magnetically stirring them for 6 to 12 days to protonate them. The mass-to-volume ratio of the double-walled carbon nanotubes to the aqueous hydrogen peroxide solution is 1mg:1-1.5mL.

[0013] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity comprises adding protonated double-walled carbon nanotubes to a chlorosulfonic acid solution for protonation and low-loss dispersion. The mass fraction of the double-walled carbon nanotubes in the obtained double-walled carbon nanotube liquid crystal spinning solution is 1.0 to 4.0 wt%.

[0014] The dry-jet wet spinning method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity is described. The spun double-walled carbon nanotube fibers have high orientation and high density, and the electrical conductivity of the double-walled carbon nanotube fibers is 6.0 to 11.2×10 6 S / m.

[0015] The design concept of the present invention is:

[0016] The present invention uses high-quality, high-purity, high-aspect-ratio double-walled carbon nanotubes as raw materials. During the preparation of a carbon nanotube liquid crystal spinning solution, the outer walls of the double-walled carbon nanotubes are selectively functionalized without affecting electron transport within the inner walls of the double-walled carbon nanotubes, thus avoiding the incompatibility between functionalizing single-walled carbon nanotubes and achieving ballistic transport. Furthermore, an adjustable air segment is introduced during the wet spinning process to prepare carbon nanotube fibers. By regulating the air segment height in conjunction with the spinning solution concentration, gravity is utilized to orient the spinning liquid crystal stream. The oriented spinning stream enters a coagulation bath and begins to coagulate, further enhancing the fiber's orientation and density through a pulling effect, ultimately yielding high-performance double-walled carbon nanotube fibers.

[0017] The advantages and beneficial effects of the present invention are:

[0018] 1. The present invention uses high-quality, high-purity, and large aspect ratio double-walled carbon nanotubes as raw materials to prepare double-walled carbon nanotube fibers, which not only improves the solubility of double-walled carbon nanotubes in chlorosulfonic acid but also does not affect the ballistic transport of electrons inside the double-walled carbon nanotubes; at the same time, the large aspect ratio reduces the contact resistance in the fiber, thereby improving the electrical conductivity of the double-walled carbon nanotube fibers.

[0019] 2. The dry-jet wet spinning technology developed by the present invention successfully improves the skin-core structure of the spun fiber by introducing an air segment with adjustable length, thereby greatly improving the directionality and density of the spun fiber.

[0020] 3. The electrical conductivity of the double-walled carbon nanotube fibers prepared by the present invention is as high as 6.0 to 11.2×106 S / m, and the fiber diameter is 15±5μm, reaching the highest level of conductivity in this field with stable performance.

[0021] 4. The method of the present invention is simple and easy to prepare on a large scale and quickly, and is expected to meet the needs of high-performance cables, flexible sensors, national defense and military industries, and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the apparatus for preparing highly oriented, dense, and conductive double-walled carbon nanotube fibers. In the diagram, 1 is the syringe; 2 is the air section; 3 is the coagulation bath; and 4 is the filament winding and collection device.

[0023] Figure 2 (a) TEM image of a double-walled carbon nanotube with a high aspect ratio; (b) Thermogravimetric curve of a double-walled carbon nanotube, where the horizontal axis Temperature represents temperature (°C), the vertical axis TG represents weight loss (%), and the vertical axis DTA represents the potential difference of the thermocouple caused by each milligram of sample at a certain temperature (μV / mg); (c) Laser Raman spectrum of a double-walled carbon nanotube, where the horizontal axis Raman Shift represents the Raman shift (cm -1 ), the vertical axis Intensity represents the Raman peak intensity (au), and the laser wavelength is 532nm.

[0024] Figure 3 (a) Optical photograph of the prepared double-walled carbon nanotube fiber wound on a bobbin; (b) Low-magnification SEM photograph of the double-walled carbon nanotube fiber; (c) High-magnification SEM photograph of the double-walled carbon nanotube fiber; (d) Laser Raman spectrum of the double-walled carbon nanotube fiber, the horizontal axis Raman Shift represents the Raman shift (cm -1 ), the vertical axis Intensity represents the Raman peak intensity (au), and the laser wavelength is 532nm.

[0025] Figure 4 . Relationship between conductivity of prepared carbon nanotube fibers and carbon tube wall number. In the figure, the horizontal axis represents Examples 1-3 and Comparative Examples 1-3, and the vertical axis Conductivity represents conductivity (×10 6 S / m). DETAILED DESCRIPTION

[0026] like Figure 1As shown, the dry-wet spray method apparatus for preparing double-walled carbon nanotube fibers with high orientation, high density, and high conductivity of the present invention mainly includes an extruder 1, an air section 2, a coagulation bath 3, and a winding and collection device 4. The specific operation is as follows: the extruder 1 is placed vertically to ensure that the internal bubbles are on the upper surface of the spinning solution, and the speed of the extruder 1 can be adjusted. By adjusting the extrusion speed, the expanded spinning stream is injected vertically into the air section 2. By adjusting the height of the air section 2, the time for gravity to act on the spinning stream is controlled, forming a highly oriented, continuous double-walled carbon nanotube spinning stream. The spinning stream is injected into a coagulation bath 3 filled with acetone, where the spinning stream undergoes double diffusion behavior: the acetone in the coagulation bath diffuses into the spinning stream, and the chlorosulfonic acid in the spinning stream diffuses into the coagulation bath. By adjusting the difference between the speed of the extruder 1 and the speed of the winding and collection device 4, the preparation of double-walled carbon nanotube fibers with high orientation, high density, and high conductivity is achieved. Among them, the high orientation degree is 0.9-0.98, and the high density is 1.6-1.98g / cm 3 , the conductivity is 6.0~11.2×10 6 The present invention uses high-quality, high-aspect-ratio double-walled carbon nanotubes as raw materials. The double-walled carbon nanotubes have a concentrated anti-oxidation temperature greater than 820°C, an inner diameter distribution of 0.8 to 2.2 nm, an outer diameter distribution of 1.5 to 3.0 nm, an aspect ratio of 25,000 to 100,000, and a residual catalyst content of 3.0 to 6.0 wt%.

[0027] Below, the present invention is further described in detail by examples.

[0028] Example 1

[0029] In this embodiment, the method for preparing highly oriented and highly conductive double-walled carbon nanotube fibers comprises the following steps:

[0030] (1) 200 mg of high-quality, high-aspect-ratio double-walled carbon nanotubes (DWCNTs) were placed in 300 mL of a 30 wt% H₂O₂ aqueous solution and magnetically stirred for protonation (at a speed of 500 rpm). 100 mg of the dried DWCNTs were added to 3.13 g of a 97 wt% chlorosulfonic acid solution for protonation and low-loss dispersion to prepare a DWCNT liquid crystal spinning solution with a mass fraction of 3.2 wt%.

[0031] (2) A double-walled carbon nanotube liquid crystal solution was vertically injected into an air segment at an extrusion rate of 0.10 ml / min. The air segment height was 15 cm. The spun liquid crystal stream then entered a coagulation bath containing acetone, was stretched and collected by a winding device, and the reel collection rate was 150 mm / s. The collected fibers were soaked in ethanol for 20 minutes to remove residual chlorosulfonic acid and acetone on the surface, and then dried in a vacuum drying oven at 120°C for 3 hours. The length of the double-walled carbon nanotube fibers was unlimited, and the diameter of the double-walled carbon nanotube fibers was 15 μm.

[0032] The double-walled carbon nanotubes treated in step (1) were structurally characterized. Figure 2 As shown in (a), a typical transmission electron microscope photo of a double-walled carbon nanotube sample shows that the double-walled carbon nanotube wall is intact and has no obvious damage. The inner and outer diameter distribution of 200 double-walled carbon nanotubes was statistically analyzed under a transmission electron microscope. The outer diameter distribution ranged from 1.8 to 2.7 nm, and the inner diameter distribution ranged from 1.0 to 2.1 nm. Based on the carbon nanotube length estimated under a scanning electron microscope (>100 μm), the aspect ratio of the double-walled carbon nanotube was calculated to be >50,000. Figure 2 As shown in (b), the thermogravimetric curve of double-walled carbon nanotubes shows that its central anti-oxidation temperature is greater than 820°C and the catalyst content is 5.6 wt%. Figure 2 As shown in (c), the Raman spectra of the samples before and after hydrogen peroxide treatment show that the initial treatment has an impact on the I G / I D The above structural characterizations all prove that double-walled carbon nanotubes have the characteristics of high quality, high crystallinity and large aspect ratio.

[0033] The double-walled carbon nanotube fibers prepared in step (2) were structurally characterized. Figure 3 (a) is an optical photograph of the prepared double-walled carbon nanotube fiber. Figure 3 (b) and (c) are typical scanning electron microscope images of double-walled carbon nanotube fibers. It can be seen that the fiber diameter is uniform, and the double-walled carbon nanotubes inside the fiber are clearly oriented and dense, with an orientation degree of 0.97 and a density of 1.93 g / cm 3 .like Figure 3 (d) shows a typical Raman spectrum of double-walled carbon nanotube fibers. G / I D The ratio (46) is 42.5% lower than that of double-walled carbon nanotubes (82), indicating that the protonation dispersion process does introduce structural defects on the outer wall of double-walled carbon nanotubes. The resistance of double-walled carbon nanotube fibers was tested using the four-wire method, and the electrical conductivity of the fibers was calculated to be 11.2×10 6 S / m.

[0034] Example 2

[0035] In this embodiment, step (1) is the same as step (1) in Example 1. The double-walled carbon nanotube sample is 45 mg, the chlorosulfonic acid concentration is 97 wt %, and the dosage is 3.00 g, and finally a double-walled carbon nanotube liquid crystal spinning solution with a mass fraction of 1.5 wt % is obtained.

[0036] Step (2) was the same as step (2) in Example 1. The needle aperture was 160 μm, the extrusion rate was 0.07 ml / min, the air segment length was 10 cm, and the reel collection rate was 100 mm / s.

[0037] The diameter of the double-walled carbon nanotube fiber is 18 μm. Scanning electron microscopy images show that the fiber diameter is uniform, the double-walled carbon nanotubes inside the fiber are clearly oriented and densely arranged, and the electrical conductivity of the double-walled carbon nanotube fiber is 6.2×10 6 S / m, orientation degree is 0.92, density is 1.76g / cm 3 .

[0038] Example 3

[0039] In this embodiment, step (1) is the same as step (1) in Example 1. The double-walled carbon nanotube sample is 70 mg, the chlorosulfonic acid concentration is 97 wt%, and the dosage is 3.00 g, and finally a double-walled carbon nanotube liquid crystal spinning solution with a mass fraction of 2.3 wt% is obtained.

[0040] Step (2) was the same as step (2) in Example 1. The needle aperture was 200 μm, the extrusion rate was 0.14 ml / min, the air segment length was 5 cm, and the reel collection rate was 170 mm / s.

[0041] The diameter of the double-walled carbon nanotube fiber is 17 μm. Scanning electron microscopy images show that the fiber diameter is uniform, the double-walled carbon nanotubes inside the fiber are clearly oriented and densely arranged, and the electrical conductivity of the double-walled carbon nanotube fiber is 7.8×10 6 S / m, orientation degree is 0.95, density is 1.81g / cm 3 .

[0042] Comparative Example 1

[0043] In this comparative example, step (1) is the same as step (1) in Example 1. However, multi-walled carbon nanotubes were selected as the raw material, the multi-walled carbon nanotube sample was 145 mg, the chlorosulfonic acid concentration was 97 wt %, and the dosage was 3.00 g. Finally, a multi-walled carbon nanotube liquid crystal spinning solution with a mass fraction of 4.8 wt % was obtained.

[0044] Step (2) was the same as step (2) in Example 1. The needle aperture was 220 μm, the extrusion rate was 0.10 ml / min, the air segment length was 5 cm, and the reel collection rate was 160 mm / s.

[0045] The diameter of the multi-walled carbon nanotube fiber is 22 μm. Scanning electron microscopy shows that the fiber diameter is uniform, the multi-walled carbon nanotubes inside the fiber are oriented along the fiber axis, and the fiber conductivity is 8.4×10 5 S / m, orientation degree is 0.85, density is 2.11g / cm 3 .

[0046] Comparative Example 2

[0047] In this comparative example, step (1) is identical to step (1) of Example 1. Step (2) is identical to step (2) of Example 1, except that high-purity, high-aspect-ratio single-walled carbon nanotubes are used as raw materials to prepare single-walled carbon nanotube fibers.

[0048] The diameter of the single-walled carbon nanotube fiber is 15 μm. Scanning electron microscopy images show that the diameter of the single-walled carbon nanotube fiber is uniform, and the single-walled carbon nanotubes inside the fiber are oriented along the fiber axis. The fiber conductivity is 3.4×10 6 S / m, orientation degree is 0.74, density is 1.34g / cm 3 .

[0049] Comparative Example 3

[0050] In this comparative example, step (1) is identical to step (1) of Example 1. Step (2) is identical to step (2) of Example 1. Double-walled carbon nanotube fibers are obtained by injecting the double-walled carbon nanotube liquid crystal directly into a coagulation bath containing acetone without passing through an air section.

[0051] The diameter of the double-walled carbon nanotube fiber is 25 μm. Scanning electron microscope photos show that the diameter of the double-walled carbon nanotube fiber is uniform, and the double-walled carbon nanotubes inside the fiber are oriented along the fiber axis. The fiber conductivity is 4.2×10 6 S / m, orientation degree is 0.80, density is 1.42g / cm 3 .

[0052] like Figure 4 As shown in the graph showing the relationship between the conductivity of the prepared carbon nanotube fibers and the number of carbon tube walls, it can be seen that the conductivity of fibers prepared from double-walled carbon nanotubes is higher than that of single-walled and multi-walled carbon nanotubes. This is because the walls of single-walled carbon nanotubes are damaged during the dispersion and spinning process, affecting the transmission of electrons through the tube walls. In contrast, even if the outer wall of double-walled carbon nanotubes is damaged, the inner wall can still bear the load. Existing multi-walled carbon nanotubes have poor quality due to production issues, resulting in poor conductivity.

[0053] The results of the examples and comparative examples show that the present invention uses high-purity, high-quality, and high-aspect-ratio double-walled carbon nanotubes as raw materials. By adding an air segment during the wet spinning process to apply gravity traction to the spinning stream to adjust the orientation, and by combining the difference between the extrusion rate and the reel collection rate to further control the orientation and densification induced by applying a tensile force to the double-walled carbon nanotube liquid crystal solution, the controlled preparation of high-orientation, high-density, and high-conductivity double-walled carbon nanotube fibers is achieved. The electrical conductivity of the double-walled carbon nanotube fibers can reach 6.0 to 11.2×10 6 S / m( Figure 4 This highly conductive, lightweight double-walled carbon nanotube fiber is at the forefront of current international research and is expected to meet the needs of rapidly developing applications in the military, defense, aerospace, and other fields. Although the present invention has been described in detail above using general instructions and specific embodiments, it will be apparent to those skilled in the art that modifications or improvements can be made based on the present invention. Therefore, such modifications or improvements made without departing from the spirit of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning, characterized in that: Using high-quality, high-aspect-ratio double-walled carbon nanotubes as raw materials, a protonation technique is used to disperse the double-walled carbon nanotube liquid crystal spinning solution with low loss. An air segment is introduced during the wet spinning process to prepare carbon nanotube fibers. The double-walled carbon nanotube liquid crystal spinning solution is injected through a syringe through a length of air before entering a coagulation bath. The height of the air segment is controlled to regulate the gravity-induced orientation and close packing of the carbon nanotubes in the liquid crystal solution. The difference between the extrusion rate and the reel collection rate is regulated. The extrusion rate and reel collection pulling are combined to achieve high orientation and densification of the double-walled carbon nanotubes, thereby achieving the preparation of high-orientation, high-density double-walled carbon nanotube fibers. The carbon nanotubes used are high-quality, large aspect ratio double-walled carbon nanotubes, with an inner diameter distribution of 0.8 to 2.2 nm, an outer diameter distribution of 1.5 to 3.0 nm, an aspect ratio of 25,000 to 100,000, an oxidation resistance temperature greater than 820°C, a residual catalyst content of less than 6.0 wt%, and a Raman spectrum of I G / I D The ratio is greater than 80; The spun double-walled carbon nanotube fibers have high orientation and density, with an orientation degree of 0.9 to 0.98 and a density of 1.6 to 1.98 g / cm 3 The electrical conductivity of double-walled carbon nanotube fibers is 6.0-11.2×10 6 S / m.

2. The method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning according to claim 1, characterized in that: The double-walled carbon nanotube liquid crystal spinning solution is vertically injected into the air segment through a needle with a pore size of 140 to 220 μm, and then enters the acetone or N-methylpyrrolidone coagulation bath from the air segment.

3. The method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning according to claim 1, characterized in that: Introducing an air segment during the wet spinning process allows the double-walled carbon nanotubes to be highly oriented under the action of gravity, effectively alleviating the skin-core structure caused by the difference in coagulation time between the core and surface layers after the fiber enters the coagulation bath, reducing the contact resistance caused by the skin-core structure, and improving the electrical conductivity of the double-walled carbon nanotube fiber; by adjusting the height of the air segment, the gravity action time of the double-walled carbon nanotube liquid crystal solution can be controlled, and the air segment height is 20 to 300 mm.

4. The method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning according to claim 1, wherein: By changing the difference between the extrusion rate and the reel collection rate, the magnitude of the tensile force applied to the double-walled carbon nanotube liquid crystal solution can be controlled, further improving the alignment of the double-walled carbon nanotube fibers. The extrusion rate is 0.07-0.30 ml / min, and the reel collection rate is 70-300 mm / s.

5. The method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning according to claim 1, wherein: High-quality, high-aspect-ratio double-walled carbon nanotubes are placed in a 30wt% aqueous hydrogen peroxide solution and magnetically stirred for 6 to 12 days to protonate them. The mass-to-volume ratio of the double-walled carbon nanotubes to the aqueous hydrogen peroxide solution is 1 mg: 1 to 1.5 mL.

6. The method for preparing double-walled carbon nanotube fibers with high orientation, high density and high conductivity by dry-jet wet spinning according to claim 1 or 5, characterized in that: The protonated double-walled carbon nanotubes are added into a chlorosulfonic acid solution for protonation and low-loss dispersion. In the obtained double-walled carbon nanotube liquid crystal spinning solution, the mass fraction of the double-walled carbon nanotubes is 1.0-4.0 wt%.

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