Method for preparing high-conductivity and high-toughness carbon nanotube fiber by vacuum sealing, two-phase region atmospheric pressure ferric chloride non-destructive doping

Abstract

The present application relates to the field of high-performance carbon nanotube fiber preparation, in particular to a method for preparing high-conductivity and high-toughness carbon nanotube fiber by vacuum sealing and two-phase zone normal pressure ferric trichloride nondestructive doping. The method uses carbon nanotube fiber as raw material and adopts normal pressure two-phase zone heating method to realize controllable doping of ferric trichloride molecules between carbon nanotubes and in the lumen of the carbon nanotubes without destroying the intrinsic structure of the carbon nanotubes. Through surface charge transfer between ferric trichloride molecules and carbon nanotubes and the interaction between ferric trichloride molecules and carbon nanotube walls, the electrical and mechanical properties of the carbon nanotube fiber are greatly improved. The present application realizes stable and controllable doping of ferric trichloride while maintaining the integrity of the carbon nanotube structure, improves the electrical and mechanical properties of the carbon nanotube fiber, and is expected to be applied in the fields of wearable electronic devices, aerospace and the like.

Description

Technical Field

[0001] This invention relates to the field of high-performance carbon nanotube fiber preparation, specifically a method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride at ambient pressure in a two-phase region. Background Technology

[0002] Single carbon nanotubes possess a one-dimensional tubular structure, exhibiting ballistic transport characteristics and excellent mechanical properties; their electrical conductivity can reach ~10. 8 With a strength of S / m and a mechanical strength reaching 120 GPa, carbon nanotubes are considered an ideal material for constructing next-generation high-strength, high-conductivity fibers, with promising applications in military defense, aerospace, and power electronics. However, the low intrinsic carrier concentration of carbon nanotubes and the presence of microscopic pore defects during fabrication result in a significant decrease in the performance of macroscopic carbon nanotube fibers compared to single carbon nanotubes, limiting their practical applications.

[0003] Currently, besides improving the spinning process (Reference 1: Hao-Zike Wang, et al. Adv. Funct. Mater. 2024, 2404538.) and enhancing the quality of carbon nanotube raw materials (Reference 2: Dmitri E. Tsentalovich, et al. ACS Appl. Mater. Interfaces. 2017, 9, 41.), phosphorus doping of carbon nanotubes is one of the effective methods to improve the conductivity of macroscopic bulk fibers. The principle is that electrons on the surface of carbon nanotubes are transferred to the dopant, thereby increasing the carrier concentration of the carbon nanotubes and thus improving the conductivity of the carbon nanotube fibers (Reference 3: Lin Qiu, et al. Appl. Therm. Eng. 2018, 141, 913-920.). Currently, the p-type dopants used to achieve doping in carbon nanotube fibers include iodine (Reference 4: Yao Zhao, et al. Sci. Rep. 2011, 1, 83.), potassium tetrabromoaurate (Reference 5: Karen J. Soule, et al. ACS Appl. Nano Mater. 2019, 2, 11.), and bromine (Reference 6: Cristina Madrona, et al. Carbon, 2023, 204, 211-218.). Iodine doping simultaneously improves the electrical conductivity and strength of carbon nanotube fibers (Sci. Rep. 2011, 1, 83.). However, iodine-doped fibers form unstable CI bonds, which can affect the crystallinity of carbon nanotubes. Furthermore, dedoping leads to a decrease in the electrical and mechanical properties of the fibers, limiting the practical applications of doped carbon nanotube fibers. Meanwhile, commonly used gas-phase doping is negative pressure two-phase region doping, which, due to weak doping driving force, results in low doping amounts and insufficient improvement in the electrical conductivity of carbon nanotube fibers.

[0004] In summary, there is an urgent need to explore a stable new type of P-type dopant and doping method to simultaneously and significantly improve the electrical and mechanical properties of carbon nanotube fibers, thereby promoting the practical application of carbon nanotube fibers in military defense, aerospace, power electronics and other fields. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride in a two-phase region under ambient pressure. High-quality carbon nanotube fiber raw materials and anhydrous ferric chloride dopant are sealed inside a vacuum quartz tube. A near-ambient pressure doping atmosphere is obtained by utilizing the low volatilization temperature and high saturated vapor pressure characteristics of ferric chloride. A two-phase region heating method is used to ensure that the ferric chloride dopant penetrates into the interior of the carbon nanotube fibers rather than depositing on the surface. The doping amount is controlled by adjusting the doping temperature, the temperature difference in the two-phase region, and the doping time. For the first time, stable and controllable doping of a high doping amount of ferric chloride (5.0 wt%) within carbon nanotube fibers has been achieved. Due to the electron transfer and inter-tube anchoring effect of ferric chloride, the conductivity and toughness of the fibers are increased by 4 times and 9 times, respectively, ultimately achieving the controllable preparation of high-conductivity and high-toughness carbon nanotube fibers.

[0006] The technical solution of this invention is:

[0007] A method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride in a two-phase region under ambient pressure is disclosed. Using carbon nanotube fibers as raw materials, the method employs ambient pressure two-phase region heating to achieve controllable doping of ferric chloride molecules between and within the carbon nanotubes without destroying the intrinsic structure of the carbon nanotubes. Through surface charge transfer between ferric chloride molecules and carbon nanotubes, as well as the interaction between ferric chloride molecules and the carbon nanotube walls, the electrical and mechanical properties of the carbon nanotube fibers are significantly improved.

[0008] The method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in a two-phase region at atmospheric pressure involves vacuum sealing carbon nanotube fibers and ferric chloride in a mass ratio of 1:1 to 1:70 inside a quartz tube, placing the carbon nanotubes in a high-temperature region and the ferric chloride in a low-temperature region, and adjusting the saturated vapor pressure of ferric chloride molecules by adjusting the temperature of the two-phase region, thereby achieving near-atmospheric pressure doping of ferric chloride molecules.

[0009] The method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride in the two-phase region at ambient pressure, wherein the carbon nanotube fibers are high-quality carbon nanotube fibers prepared by wet spinning, and the G / D ratio of the Raman spectrum of the carbon nanotube fibers is greater than 50.

[0010] The method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region at atmospheric pressure uses strictly anhydrous ferric chloride with a purity >98wt.%.

[0011] The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride in the two-phase region at atmospheric pressure ensures that the gas pressure inside the quartz tube is 0.8 × 10⁻⁶ after heating by adjusting the ferric chloride content and temperature. 5Pa ~ 1.4 × 10 5 Pa enhances the driving force for ferric chloride to enter carbon nanotube fibers.

[0012] The method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region under normal pressure involves placing a vacuum-sealed quartz tube containing ferric chloride and carbon nanotube fibers into a tube furnace. By utilizing the temperature gradient of the tube furnace and adjusting the distance between ferric chloride and carbon nanotube fibers, a temperature difference of 20℃ to 100℃ is achieved between the low-temperature and high-temperature regions. This controls the diffusion direction and speed of gaseous ferric chloride molecules, allowing ferric chloride molecules to be doped into the carbon nanotube fibers.

[0013] The method for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region at atmospheric pressure involves heating to 310℃~330℃ in the low-temperature region to ensure that the saturated vapor pressure of ferric chloride reaches near atmospheric pressure; and heating to 330℃~410℃ in the high-temperature region to ensure that the temperature at the ends of the carbon nanotube fibers is high without damaging the intrinsic structure of the carbon nanotubes.

[0014] The method described above for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region at ambient pressure utilizes the near-ambient pressure driving force of ferric chloride gas molecules to allow ferric chloride molecules to diffuse directionally into the cavity of carbon nanotubes and the pores between carbon nanotubes, thereby achieving surface charge transfer and inter-tube anchoring between ferric chloride and carbon nanotubes, while improving the conductivity and toughness of carbon nanotube fibers.

[0015] The method described above for preparing high-conductivity and high-toughness carbon nanotube fibers using vacuum sealing and non-destructive doping with ferric chloride in the two-phase region under ambient pressure produces high-performance carbon nanotube fibers with a Raman spectrum G / D ratio greater than 50, controllable doping amount within 5.0 wt%, and a maximum conductivity reaching 2.0 × 10⁻⁶. 7 S / m, with a maximum toughness of 300 MJ / m 3 .

[0016] The design concept of this invention is:

[0017] This invention selects ferric chloride, known for its stability and low boiling point, as a P-type dopant. It is vacuum-sealed with high-quality carbon nanotubes within a two-phase heating quartz tube. Utilizing the low boiling point of ferric chloride, the gas pressure inside the quartz tube is controlled to near atmospheric pressure by regulating the temperature at the ferric chloride end. This drives the gas-phase diffusion of ferric chloride molecules into the high-temperature carbon nanotube fibers and the pores between the tubes. Surface charge transfer increases the carrier concentration in the carbon nanotubes, and inter-tube bonding enhances the inter-tube interactions, ultimately significantly improving the electrical and mechanical properties of the carbon nanotube fibers. This invention achieves stable and controllable ferric chloride doping while maintaining the structural integrity of the carbon nanotubes, improving the electrical and mechanical properties of the carbon nanotube fibers, and holds promise for applications in wearable electronic devices, aerospace, and other fields.

[0018] The advantages and beneficial effects of this invention are:

[0019] 1. This invention develops vacuum sealing and two-phase atmospheric pressure doping technology, which realizes the controllable doping of high concentration of ferric chloride while maintaining the intrinsic structure of carbon nanotube fibers.

[0020] 2. The ferric chloride P-type dopant of this invention enters the hollow cavity of carbon nanotubes and fills the inter-tube pores at the same time; this increases the carrier concentration of carbon nanotubes and enhances the inter-tube interaction, thereby simultaneously improving the electrical and mechanical properties of carbon nanotube fibers.

[0021] 3. This invention achieves stable and controllable doping of ferric chloride in carbon nanotube fibers, with the doping amount controllable within 5.0 wt%.

[0022] 4. This invention improves the electrical and mechanical properties of carbon nanotube fibers by 4 times and 9 times, respectively, with the prepared carbon nanotube fibers achieving a conductivity of up to ~2.0×10⁻⁶. 7 S / m, toughness up to ~300MJ / m 3 It achieves the highest conductivity level in the field and has stable performance, and is expected to meet the needs of high-performance cables, flexible sensors, defense and military industries. Attached Figure Description

[0023] Figure 1 A schematic diagram of a fabrication apparatus for preparing high-conductivity, high-toughness carbon nanotube fibers using vacuum sealing and non-destructive doping under ambient pressure in the two-phase region. In the diagram, 1 represents the temperature control system for the low-temperature region; 2 represents the low-temperature region; 3 represents the temperature control system for the high-temperature region; 4 represents the high-temperature region; and 5 represents the quartz tube.

[0024] Figure 2 Laser Raman spectroscopy. (a) shows the original carbon nanotube fiber, and (b) shows the ferric chloride-doped fiber. The abscissa Raman shift represents the Raman shift (cm). -1The vertical axis Intensity represents the Raman peak intensity (au), and the laser wavelength is 532nm.

[0025] Figure 3 TEM images of fiber cross-sections. Among them, (a) original carbon nanotube fiber; (b) ferric chloride-doped fiber.

[0026] Figure 4 Ferric chloride-doped fiber under ambient pressure: (a) Scanning electron microscope (SEM) image; (b) Energy dispersive spectroscopy (EDS) map of iron distribution; (c) EDS map of chloride distribution.

[0027] Figure 5 X-ray photoelectron spectroscopy (XPS) spectra of ferric chloride-doped fibers. (a) Fine spectrum of iron 2p, (b) Fine spectrum of chlorine 2p. The horizontal axis represents binding energy (eV), and the vertical axis represents intensity (au).

[0028] Figure 6 Stability test curves for ferric chloride doping. In the figure, the horizontal axis Time represents time (Month), and the left vertical axis Conductivity represents conductivity (×10). 7 S / m), with the right vertical axis representing toughness (MJ / m). 3 ). Detailed Implementation

[0029] like Figure 1 As shown, the apparatus for preparing high-conductivity and high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping in a two-phase region under ambient pressure according to the present invention mainly includes a low-temperature zone temperature control system 1, a low-temperature zone 2, a high-temperature zone temperature control system 3, a high-temperature zone 4, and a quartz tube 5. The specific structure is as follows: The reactor contains a low-temperature zone 2 and a high-temperature zone 4. The quartz tube 5 is a dumbbell-shaped tubular structure with thicker ends and a thinner middle section, connected as one piece. The two thicker sections of the quartz tube 5 are located in the low-temperature zone 2 and the high-temperature zone 4, respectively. The low-temperature zone temperature control system 1 is installed in the low-temperature zone 2, and the high-temperature zone temperature control system 3 is installed in the high-temperature zone 4. In use, high-quality carbon nanotube fibers are used as raw materials. The carbon nanotubes are placed in the high-temperature zone, and ferric chloride is placed in the low-temperature zone. A vacuum sealing and two-phase region ambient pressure heating method is adopted. By controlling the doping temperature, doping pressure, temperature difference between ferric chloride and the fiber, and doping time, the doping state of ferric chloride inside the fiber is regulated. The surface charge transfer between ferric chloride molecules and carbon nanotubes and their interaction with the tube wall are utilized to significantly improve the electrical and mechanical properties of the carbon nanotube fibers.

[0030] In its specific implementation, this invention establishes a vacuum-sealed, two-phase region atmospheric pressure non-destructive doping technology for ferric chloride (the apparatus used is described in [reference needed]). Figure 1The specific operating steps are as follows: Anhydrous ferric chloride and carbon nanotube fibers are placed in the low-temperature zone 2 and high-temperature zone 4 of quartz tube 5, respectively, and then vacuum sealed; quartz tube 5 is placed in a reactor, and the temperature and temperature difference of low-temperature zone 2 and high-temperature zone 4 are adjusted by controlling the low-temperature zone temperature control system 1 and the high-temperature zone temperature control system 3, respectively, to ensure that ferric chloride diffuses to high-temperature zone 4 in gaseous form, and the gas pressure and doping time of ferric chloride are adjusted to achieve controllable doping of ferric chloride molecules in carbon nanotube fibers.

[0031] The present invention will now be further described in detail through examples.

[0032] Example 1

[0033] In this embodiment, the method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive ferric chloride doping in the two-phase region under ambient pressure includes the following steps:

[0034] (1) Place 10 mg of high-quality carbon nanotube fiber prepared by wet spinning into one end of a quartz tube, and at the same time weigh 0.7 g of anhydrous ferric chloride with a purity of 99 wt.% into the other end of the quartz tube, and seal both ends of the quartz tube.

[0035] (2) Place the quartz tube in the reactor, the carbon nanotube in the high-temperature zone, and the ferric chloride in the low-temperature zone. The temperature of the low-temperature zone is set to 320℃, the temperature of the high-temperature zone is set to 360℃, and the heating time is 8 hours. During heating, the gas pressure of ferric chloride inside the quartz tube is 1.1×10⁻⁶. 5 Pa; After heating, remove the carbon nanotube fibers, clean the surface of residual ferric chloride with ethanol, and dry them in an 80℃ vacuum drying oven for 3 hours.

[0036] (3) Raman and transmission electron microscopy were used to characterize the carbon nanotube fibers before and after doping treatment. For example... Figure 2 The Raman spectra of the fibers before and after doping are shown in (a) and (b). The Raman D peak is almost invisible. The Raman G / D ratios of the fibers before and after doping are 72.4 and 70.2, respectively. This indicates both the high crystallinity of the fibers and the good preservation of the intrinsic structure of the carbon nanotubes during doping. Figure 3 Transmission electron microscopy (TEM) images of the fiber cross-sections before and after doping, shown in (a) and (b), reveal that the carbon nanotubes before doping are few-walled carbon nanotubes with intact walls and no obvious damage, and the carbon nanotubes are highly oriented. After doping, the structure of the carbon nanotubes does not change significantly, but nanoparticles can be observed in the carbon nanotube lumen and between tubes. Figure 4 The iron and chloride distributions in the EDS energy spectra of carbon nanotube fibers shown in (b) and (c) are compared with those in... Figure 4 The morphology of the fibers in (a) is completely identical, indicating that ferric chloride has been successfully and uniformly doped into the carbon nanotube fibers. XPS characterization shows that the ferric chloride doping content within the fibers is 5.0 wt.%. Figure 5 The XPS fine spectra of iron and chlorine shown in (a) and (b) reveal that both iron and chlorine enter the carbon nanotube fibers as ferric chloride molecules and do not form bonds with carbon. This indicates that the carbon nanotubes only undergo surface charge transfer with ferric chloride without disrupting their intrinsic structure, thus increasing the carrier concentration in the carbon nanotube fibers. The resistivity was measured using the four-wire method, and the fiber conductivity before and after doping was calculated to be 0.4 × 10⁻⁶. 7 S / m and 2.0×10 7 S / m; After fiber tensile testing, the calculated toughness of the fibers before and after doping was 28.9 MJ / m. 3 and 300MJ / m 3 Three months after fiber doping, its conductivity and toughness were measured respectively. Figure 6 The results showed no change in the values, indicating good stability of the doping.

[0037] Example 2

[0038] In this embodiment, the method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive ferric chloride doping in the two-phase region under ambient pressure includes the following steps:

[0039] (1) In this embodiment, step (1) is the same as step (1) in Example 1, except that it is changed to 20mg of high-quality carbon nanotube fiber prepared by wet spinning.

[0040] (2) Step (2) is the same as step (2) in Example 1, except that the temperature of the high temperature zone is changed to 380°C and the doping time is changed to 18h.

[0041] (3) The Raman spectral G / D ratio of the doped carbon nanotube fiber was 69.2, indicating that the doping preserved the intrinsic structure of the carbon nanotube. Transmission electron microscopy revealed nanoparticles in the lumen and between tubes of the carbon nanotube. EDS and XPS results showed that ferric chloride was successfully and uniformly doped into the carbon nanotube fiber, with a doping amount of 3.6 wt.%. The electrical conductivity of the doped fiber was 1.1 × 10⁻⁶. 7 S / m, toughness is 155.6 MJ / m 3 Three months after fiber doping, its conductivity and toughness were measured, and the values ​​showed no change, indicating that the doping was stable.

[0042] Example 3

[0043] In this embodiment, the method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive ferric chloride doping in the two-phase region under ambient pressure includes the following steps:

[0044] (1) In this embodiment, step (1) is the same as step (1) in Example 1, except that the content of ferric chloride is changed to 0.4g.

[0045] (2) Step (2) is the same as step (2) in Example 1. The pressure of ferric chloride inside the quartz tube during heating is 0.8 × 10⁻⁶. 5 Pa, the temperature in the low-temperature zone is changed to 310℃.

[0046] (3) The Raman spectrum G / D ratio of the doped carbon nanotube fibers was 70.8, indicating that the doping preserved the intrinsic structure of the carbon nanotubes. Transmission electron microscopy revealed the presence of nanoparticles in the lumens and between tubes of the carbon nanotubes. EDS and XPS results showed that ferric chloride was successfully and uniformly doped into the carbon nanotube fibers at a doping amount of 1.6 wt.%. The electrical conductivity of the doped fibers was 1.0 × 10⁻⁶. 7 S / m, toughness 97.6 MJ / m 3 Three months after fiber doping, its conductivity and toughness were measured, and the values ​​showed no change, indicating that the doping was stable.

[0047] Comparative Example 1:

[0048] In this comparative example, the method for preparing carbon nanotube fibers using negative pressure ferric chloride doping includes the following steps:

[0049] (1) Step (1) is the same as step (1) in Example 1, except that the content of ferric chloride is changed to 0.1g.

[0050] (2) Step (2) is the same as step (2) in Example 1. The pressure of ferric chloride inside the quartz tube during heating is 0.2 × 10⁻⁶. 5 Pa.

[0051] (3) Scanning electron microscopy (SEM) images of the doped carbon nanotube fibers showed obvious residual ferric chloride particles on the fiber surface. Transmission electron microscopy (TEM) observation revealed no nanoparticles in the carbon nanotube lumen or between tubes, indicating that ferric chloride was deposited only on the surface of the carbon nanotube fibers and did not penetrate into the interior of the fibers. EDS and XPS results showed that the ferric chloride content in the carbon nanotube fibers was 0.2 wt.%, and the conductivity of the doped fibers was 0.4 × 10⁻⁶. 7 S / m, toughness is 28.9 MJ / m 3 .

[0052] Comparative Example 2:

[0053] In this comparative example, the method for preparing carbon nanotube fibers using non-vacuum sealing and atmospheric pressure doping includes the following steps:

[0054] (1) Step (1) is the same as step (1) in Example 1, except that the quartz tube is not sealed.

[0055] (2) Step (2) is the same as step (2) in Example 1.

[0056] (3) Scanning electron microscopy (SEM) images of the doped carbon nanotube fibers showed obvious residual ferric chloride particles on the fiber surface. Transmission electron microscopy (TEM) observation revealed no nanoparticles in the carbon nanotube lumen or between tubes, indicating that ferric chloride was deposited only on the surface of the carbon nanotube fibers and did not penetrate into the interior of the fibers. EDS and XPS results showed that the ferric chloride content in the carbon nanotube fibers was 0.1 wt.%, and the conductivity of the doped fibers was 0.3 × 10⁻⁶. 7 S / m, toughness is 25.7 MJ / m 3 .

[0057] Comparative Example 3:

[0058] In this comparative example, the method for preparing carbon nanotube fibers using iodine doping includes the following steps:

[0059] (1) Step (1) is the same as step (1) in Example 1, except that the dopant is replaced with iodine.

[0060] (2) Step (2) is the same as step (2) in Example 1, except that the temperature of the low temperature zone is changed to 200°C and the temperature of the high temperature zone is changed to 240°C.

[0061] (3) EDS results of the doped carbon nanotube fibers showed that iodine successfully entered the carbon nanotube fibers, but the G / D ratio of the Raman spectrum was only 20, indicating that iodine would destroy the intrinsic structure of the carbon nanotubes; the doping amount of the carbon nanotube fibers was 0.8 wt.%, and the conductivity was 0.7 × 10⁻⁶. 7 S / m, toughness is 46.4 MJ / m 3 Three months after fiber doping, its electrical conductivity and toughness were measured, and the values ​​were found to have decreased to 0.5 × 10⁻⁶. 7 S / m and 39.7MJ / m 3 This indicates that the doping is unstable.

[0062] Comparative Example 4:

[0063] In this comparative example, the method for preparing carbon nanotube fibers using single-phase region doping includes the following steps:

[0064] (1) Step (1) is the same as step (1) in Example 1.

[0065] (2) Step (2) is the same as step (2) in Example 1, except that the low temperature zone and the high temperature zone are combined and the temperature is changed to 320°C.

[0066] (3) Scanning electron microscopy (SEM) images of the doped carbon nanotube fibers showed obvious residual ferric chloride particles on the fiber surface. Transmission electron microscopy (TEM) observation revealed no nanoparticles in the carbon nanotube lumen or between tubes, indicating that ferric chloride was deposited only on the surface of the carbon nanotube fibers and did not penetrate into the interior of the fibers. The ferric chloride content inside the carbon nanotube fibers was 0.5 wt.%, and the conductivity was 0.5 × 10⁻⁶. 7 S / m, toughness is 34.7 MJ / m 3 .

[0067] The results of the examples and comparative examples show that this invention uses high-quality carbon nanotube fibers as raw materials and anhydrous ferric chloride as a dopant. By employing a vacuum-sealed, atmospheric-pressure heating method in the two-phase region, the driving force for ferric chloride molecules to enter the carbon nanotube fibers is increased by changing the volatilization rate of ferric chloride. Furthermore, the doping amount is controlled by altering the temperature difference and doping time in the two-phase region. This achieves non-destructive and controllable doping of high-doped ferric chloride into carbon nanotube fibers. After doping, the conductivity and toughness of the carbon nanotube fibers are increased by up to 4 times and 9 times, respectively, with stable performance. The prepared high-performance carbon nanotube fibers exhibit a Raman spectrum G / D ratio greater than 50 and reaching 70.8. The ferric chloride doping amount is controllable between 1.6 wt.% and ~5.0 wt%. The conductivity of the doped carbon nanotube fibers can reach 1.0 × 10⁻⁶. 7 S / m or higher and reaching a maximum of ~2.0×10 7 S / m, toughness can reach 97.6MJ / m 3 The above, and the highest reaches ~300MJ / m 3 The electrical and mechanical properties of doped carbon nanotube fibers are at the forefront of international standards, and they are expected to meet the application needs of rapidly developing fields such as military defense, aerospace and other related industries.

[0068] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all 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 high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride in the two-phase region under ambient pressure, characterized in that... Using carbon nanotube fibers as raw materials, a method of atmospheric pressure two-phase region heating is employed to achieve controllable doping of ferric chloride molecules between and within carbon nanotubes without damaging their intrinsic structure. Through surface charge transfer between ferric chloride molecules and carbon nanotubes, as well as the interaction between ferric chloride molecules and the carbon nanotube walls, the electrical and mechanical properties of carbon nanotube fibers are significantly improved. Carbon nanotube fibers and ferric chloride are vacuum-sealed within a quartz tube, with the carbon nanotubes placed in a high-temperature region and the ferric chloride in a low-temperature region. By adjusting the temperature of the two-phase region, the saturated vapor pressure of ferric chloride molecules is adjusted, thereby achieving near-atmospheric pressure doping of ferric chloride molecules.

2. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride at atmospheric pressure in the two-phase region according to claim 1, characterized in that, The mass ratio of carbon nanotube fibers to ferric chloride is 1:1 to 1:

70.

3. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region under ambient pressure according to claim 1 or 2, characterized in that... The carbon nanotube fibers are high-quality carbon nanotube fibers prepared by wet spinning, and the G / D ratio of the Raman spectrum of the carbon nanotube fibers is greater than 50.

4. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region under ambient pressure according to claim 1 or 2, characterized in that, The ferric chloride used was strictly anhydrous ferric chloride with a purity >98 wt.%.

5. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride at ambient pressure in the two-phase region according to claim 2, characterized in that... By adjusting the ferric chloride content and temperature, the gas pressure inside the quartz tube was ensured to be 0.8 × 10⁻⁶ after heating. 5 Pa ~1.4×10 5 Pa enhances the driving force for ferric chloride to enter carbon nanotube fibers.

6. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride in the two-phase region under ambient pressure according to claim 2 or 5, characterized in that... A vacuum-sealed quartz tube containing ferric chloride and carbon nanotube fibers is placed in a tube furnace. By utilizing the temperature gradient of the tube furnace and adjusting the distance between the ferric chloride and carbon nanotube fibers, a temperature difference of 20 ℃ to 100 ℃ is achieved between the low-temperature and high-temperature zones. This controls the diffusion direction and speed of ferric chloride gaseous molecules, allowing ferric chloride molecules to be incorporated into the carbon nanotube fibers.

7. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping with ferric chloride at ambient pressure in the two-phase region according to claim 6, characterized in that... The low-temperature zone is heated to 310 ℃~330 ℃ to ensure that the saturated vapor pressure of ferric chloride reaches near atmospheric pressure; the high-temperature zone is heated to 330 ℃~410 ℃ to ensure that the temperature of the carbon nanotube fiber ends is high and that the intrinsic structure of carbon nanotubes is not damaged.

8. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region under ambient pressure according to claim 1 or 2, characterized in that, By utilizing the near-ambient pressure driving force of ferric chloride gas molecules, ferric chloride molecules are directionally diffused into the lumen of carbon nanotubes and the pores between carbon nanotubes, achieving surface charge transfer and inter-tube anchoring between ferric chloride and carbon nanotubes, while improving the electrical conductivity and toughness of carbon nanotube fibers.

9. The method for preparing high-conductivity, high-toughness carbon nanotube fibers by vacuum sealing and non-destructive doping of ferric chloride in the two-phase region under ambient pressure according to claim 1 or 2, characterized in that, The prepared high-performance carbon nanotube fibers exhibit a Raman spectrum G / D ratio greater than 50, with controllable doping levels within 5.0 wt%, and a maximum electrical conductivity reaching 2.0 × 10⁻⁶. 7 S / m, with a maximum toughness of 300 MJ / m 3 .

Images