A method for preparing a high-conductivity single-walled carbon nanotube fiber

Abstract

The application belongs to the technical field of single-walled carbon nanotube fiber preparation, and particularly relates to a preparation method of high-conductivity single-walled carbon nanotube fiber, single-walled carbon nanotube crude products are prepared by chemical vapor deposition, and the single-walled carbon nanotubes are obtained by acid washing and high-temperature oxidation purification; the single-walled carbon nanotubes are added into a poly[2,5-dihydroxy-1,4-benzene pyridine diimidazole] aqueous solution, and after dispersion, the upper clear liquid is collected to obtain a single-walled carbon nanotube purification liquid; under an argon atmosphere, chlorosulfonic acid is added into the single-walled carbon nanotube purification liquid to obtain a single-walled carbon nanotube spinning liquid; under the argon atmosphere, the single-walled carbon nanotube spinning liquid is injected into a coagulation bath to prepare single-walled carbon nanotube fiber. In the application, poly[2,5-dihydroxy-1,4-benzene pyridine diimidazole] is used for selective dispersion of metallic single-walled carbon nanotubes, the purity of the metallic single-walled carbon nanotubes in the single-walled carbon nanotube fiber is high, and the conductivity can be improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of single-walled carbon nanotube fiber preparation, and particularly relates to a preparation method of high-conductivity single-walled carbon nanotube fiber. BACKGROUND

[0002] Single-walled carbon nanotube fiber is a macro-scale one-dimensional material assembled by single-walled carbon nanotubes along the axial direction, and is a high-performance fiber product. Due to the excellent intrinsic physical and chemical properties of single-walled carbon nanotubes, single-walled carbon nanotube fiber exhibits high conductivity, high thermal conductivity, high strength, corrosion resistance, light weight, high flexibility and other characteristics, and is expected to become the next generation of light, high-strength and high-conductivity material.

[0003] The preparation method of single-walled carbon nanotube fiber includes dry spinning, wet spinning and floating catalytic CVD spinning. Compared with wet spinning, dry spinning process needs to be carried out in a semi-closed environment above 1000℃ and requires high-concentration hydrogen, which has high energy consumption and needs safety protection. Floating catalytic CVD spinning has high catalyst content, low purity of prepared carbon nanotube fiber and poor consistency, which is not conducive to industrialization. Wet spinning generally prepares single-walled carbon nanotube into a spinning solution, which is then injected into a certain component coagulation bath through a spinning hole. The spinning solution undergoes component double diffusion in the coagulation bath and solidifies into a fiber. After the fiber leaves the coagulation bath, the coagulation bath component remaining on the surface of the fiber volatilizes, forming a dry single-walled carbon nanotube fiber.

[0004] Single-walled carbon nanotubes include metallic single-walled carbon nanotubes (m-SWCNT) and semiconductive single-walled carbon nanotubes (s-SWCNT), wherein the metallic single-walled carbon nanotubes have better conductivity.

[0005] However, the single-walled carbon nanotubes obtained by the existing preparation method of single-walled carbon nanotubes are not pure and contain various carbon family byproducts. It is difficult to separate and purify the metallic single-walled carbon nanotubes and the semiconductive single-walled carbon nanotubes. Therefore, the single-walled carbon nanotube fiber contains both metallic single-walled carbon nanotubes and semiconductive single-walled carbon nanotubes, and the conductivity of the single-walled carbon nanotube fiber needs to be further improved. SUMMARY

[0006] The present application aims to provide a preparation method of high-conductivity single-walled carbon nanotube fiber to solve the above technical problems.

[0007] To achieve the above technical purpose, the technical scheme of the present application is as follows:

[0008] A preparation method of high-conductivity single-walled carbon nanotube fiber, comprising the following steps:

[0009] S1, preparing a single-walled carbon nanotube crude product by chemical vapor deposition method;

[0010] S2. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes.

[0011] S3. Add single-walled carbon nanotubes to an aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole], disperse by ultrasonication at 10-12℃ for 20-24h, then centrifuge at 20000r / min for 2h, and collect the supernatant to obtain the purified single-walled carbon nanotube solution.

[0012] S4. Under an argon atmosphere, add chlorosulfonic acid to the single-walled carbon nanotube purification solution, seal and stir at 3000 r / min for 5 min to obtain the single-walled carbon nanotube spinning solution.

[0013] S5. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes is injected into the coagulation bath using a syringe to prepare single-walled carbon nanotube fibers, which are then wound up and dried.

[0014] As a further improvement, in step S1, the preparation of crude single-walled carbon nanotubes by chemical vapor deposition is specifically as follows: a homogeneous colloidal solution of ferric hydroxide is loaded onto an a-plane-Al2O3 substrate as a catalyst, annealed at 1000℃ for 10-15 min, then the substrate loaded with the catalyst is placed in the center of a tube furnace and reduced at 800℃ for 20-23 min, then the substrate is moved to 540℃, a mixed gas of ethanol and hydrogen is introduced, and the substrate is grown for 35-60 min to obtain crude single-walled carbon nanotubes.

[0015] As a further improvement, the preparation method of the homogeneous colloidal solution of ferric hydroxide is as follows: ferric chloride powder is dissolved in water, and added dropwise to boiling water to hydrolyze and obtain ferric hydroxide colloidal solution. Then, ethanol is added to dilute it to a concentration of ferric hydroxide of 0.05 mmol / L, and the solution is ultrasonicated for 10 min to obtain the final product.

[0016] As a further improvement, the a-plane-Al2O3 substrate is cleaned before use. The specific method is as follows: the substrate is cleaned sequentially with water, acetone, ethanol and water, and ultrasonically cleaned for 35-40 minutes in each cleaning process. Then it is dried with nitrogen gas, placed in a crucible, annealed at 1100℃ for 10 hours, then cooled to 300℃ within 6 hours, and finally cooled to room temperature.

[0017] As a further improvement, in step S2, the acid washing purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 400~450℃ for 2~2.5h.

[0018] As a further improvement, in step S3, the mass fraction of poly[2,5-dihydroxy-1,4-phenylenepyridinidazole] in the aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinidazole] is 1%.

[0019] As a further improvement, the poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] is obtained by polymerization of 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers.

[0020] As a further improvement, in step S3, the solid-liquid ratio of the single-walled carbon nanotubes and the aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] is 1 g: 1 L.

[0021] As a further improvement, in step S4, the volume ratio of the single-walled carbon nanotube purification solution to the chlorosulfonic acid is 28~28.3:1.

[0022] As a further improvement, in step S5, the coagulation bath is polyvinyl alcohol, the syringe needle tip has an inner diameter of 180 μm, a length of 14~50 mm, and an extrusion rate of 0.07 mL / min.

[0023] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0024] This invention provides a method for preparing highly conductive single-walled carbon nanotube fibers. The method involves selectively dispersing metallic single-walled carbon nanotubes with poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole]. The prepared single-walled carbon nanotube fibers have high purity of metallic single-walled carbon nanotubes, which can improve the conductivity of the single-walled carbon nanotube fibers.

[0025] Poly[2,5-dihydroxy-1,4-phenylenepyridinidazole] is used to purify single-walled carbon nanotubes. The polymer backbone is electron-deficient, which selectively disperses metallic single-walled carbon nanotubes. Furthermore, the imidazole ring conjugated system in the polymer generates π-π interactions with the metallic single-walled carbon nanotubes, allowing the polymer molecules to be tightly and uniformly adsorbed on the surface of single-walled carbon nanotubes, breaking up the metallic single-walled carbon nanotube bundles and selectively dispersing the metallic single-walled carbon nanotubes.

[0026] In this invention, ferric hydroxide colloid is used as a catalyst loaded onto an a-plane-Al2O3 substrate to prepare single-walled carbon nanotubes at 540°C. The growth temperature is low, and the crude single-walled carbon nanotubes obtained have a high content of metallic single-walled carbon nanotubes.

[0027] In this invention, the polymer interacts with the metallic single-walled carbon nanotubes, resulting in electron transfer and the polymer stealing electrons from the single-walled carbon nanotubes to form holes inside the single-walled carbon nanotubes, thereby increasing the electrical conductivity of the single-walled carbon nanotube fibers.

[0028] In the process of preparing single-walled carbon nanotube fibers, polymers fill the gaps between the single-walled carbon nanotubes, reducing the contact resistance between the single-walled carbon nanotubes and improving the conductivity of the single-walled carbon nanotube fibers. Furthermore, the polymers accept electrons from the single-walled carbon nanotubes and generate negatively charged electrons as charge carriers, realizing continuous conductivity between the single-walled carbon nanotubes in the fiber, which further improves the conductivity of the single-walled carbon nanotube fibers. Attached Figure Description

[0029] Figure 1 The image shows the Raman spectrum of the crude single-walled carbon nanotubes prepared in Example 1, where a is the total RBM peak measured at four laser wavelengths, and b is an enlarged view of the RBM peak in a. Detailed Implementation

[0030] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] Example 1: A method for preparing highly conductive single-walled carbon nanotube fibers, comprising the following steps:

[0032] S1. Dissolve 0.3244 g (2 mmol) of ferric chloride powder in 20 mL of water and stir until the solid is completely dissolved. Use a pipette to add 5 mL of ferric chloride aqueous solution dropwise to 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to reddish-orange. Ferric chloride hydrolyzes to form ferric hydroxide colloid. Continue to boil gently for 2 hours, then cool to room temperature to obtain ferric hydroxide colloidal solution. Then add ethanol to dilute to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and sonicate for 10 min to obtain a homogeneous ferric hydroxide colloidal solution catalyst.

[0033] S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned sequentially with water, acetone, ethanol and water. Each cleaning process was ultrasonically cleaned for 40 min. The cleaned substrate was then dried with nitrogen and placed face up in a crucible. It was annealed in a muffle furnace at 1100℃ for 10 h. Then it was cooled to 300℃ within 6 h and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites.

[0034] S3. Preparation of crude single-walled carbon nanotubes by CVD: A homogeneous colloidal solution of ferric hydroxide was loaded onto a cleaned a-plane-Al2O3 substrate as a catalyst and annealed at 1000℃ for 10 min to allow the catalyst to be incorporated into the substrate. The substrate loaded with the catalyst was then placed in the center of a tube furnace and reduced at 800℃ for 20 min. The substrate was then moved to 540℃ and a mixed gas of ethanol and hydrogen (volume ratio of ethanol to hydrogen of 50:300) was introduced. The substrate was grown for 35 min to obtain crude single-walled carbon nanotubes.

[0035] S4. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes. The acid washing and purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 450℃ for 2 hours. The specific method is the existing technology.

[0036] S5. Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimide] is prepared by polymerization using 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers. The specific preparation method is the prior art.

[0037] S6. Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] was dissolved in water to prepare a 1% (w / w) aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole].

[0038] 1 g of single-walled carbon nanotubes were added to 1 L of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] aqueous solution and ultrasonically dispersed at 10 °C for 24 h. Then, the mixture was centrifuged at 20,000 r / min for 2 h and the supernatant was collected to obtain the purified single-walled carbon nanotube solution.

[0039] S7. Under an argon atmosphere, add chlorosulfonic acid to the single-walled carbon nanotube purification solution. The volume ratio of the single-walled carbon nanotube purification solution to chlorosulfonic acid is 28:1. After sealing, stir at 3000 r / min for 5 min to obtain the single-walled carbon nanotube spinning solution.

[0040] S8. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The syringe needle tip had an inner diameter of 180 μm and a length of 14 mm. The extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110 °C after winding.

[0041] The crude single-walled carbon nanotubes prepared above were subjected to Raman mapping tests at 488 nm, 532 nm, 633 nm, and 785 nm. The test results are as follows: Figure 1As shown in the figure, a represents the total RBM peak under four laser wavelengths, and b is a magnified view of the RBM peak in a. It is clear from the figure that most of the radial breathing peaks of single-walled carbon nanotubes are concentrated in the figure. and Statistical analysis of the RBM peaks appearing at four laser wavelengths under two wavelengths revealed that the number of peaks concentrated at these two wavelengths was close to 89%. According to the Kataura plot, the chiral (9,6) and (13,1) single-walled carbon nanotubes corresponding to the RBM peaks at these two wavelengths are both metallic single-walled carbon nanotubes. Therefore, the crude single-walled carbon nanotubes prepared in this embodiment have a high content of metallic single-walled carbon nanotubes.

[0042] Example 2: A method for preparing highly conductive single-walled carbon nanotube fibers, comprising the following steps:

[0043] S1. Dissolve 0.3244 g (2 mmol) of ferric chloride powder in 20 mL of water and stir until the solid is completely dissolved. Use a pipette to add 5 mL of ferric chloride aqueous solution dropwise to 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to reddish-orange. Ferric chloride hydrolyzes to form ferric hydroxide colloid. Continue to boil gently for 2 hours, then cool to room temperature to obtain ferric hydroxide colloidal solution. Then add ethanol to dilute to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and sonicate for 10 min to obtain a homogeneous ferric hydroxide colloidal solution catalyst.

[0044] S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned sequentially with water, acetone, ethanol and water. Each cleaning process was ultrasonically cleaned for 35 minutes. The cleaned substrate was then dried with nitrogen and placed face up in a crucible. It was annealed in a muffle furnace at 1100℃ for 10 hours. Then it was cooled to 300℃ within 6 hours and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites.

[0045] S3. Preparation of crude single-walled carbon nanotubes by CVD: A homogeneous colloidal solution of ferric hydroxide was loaded onto a cleaned a-plane-Al2O3 substrate as a catalyst. The substrate was annealed at 1000℃ for 15 min to allow the catalyst to be incorporated into the substrate. The substrate loaded with the catalyst was then placed in the center of a tube furnace and reduced at 800℃ for 23 min. The substrate was then moved to 540℃ and a mixed gas of ethanol and hydrogen (volume ratio of ethanol to hydrogen of 50:300) was introduced. The substrate was grown for 60 min to obtain crude single-walled carbon nanotubes.

[0046] S4. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes. The acid washing and purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 400℃ for 2.5h. The specific method is the existing technology.

[0047] S5. Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimide] is prepared by polymerization using 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers. The specific preparation method is the prior art.

[0048] S6. Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] was dissolved in water to prepare a 1% (w / w) aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole].

[0049] 1 g of single-walled carbon nanotubes were added to 1 L of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] aqueous solution and ultrasonically dispersed at 12 °C for 20 h. Then, the mixture was centrifuged at 20000 r / min for 2 h and the supernatant was collected to obtain the purified single-walled carbon nanotube solution.

[0050] S7. Under an argon atmosphere, chlorosulfonic acid was added to the single-walled carbon nanotube purification solution. The volume ratio of the single-walled carbon nanotube purification solution to chlorosulfonic acid was 28.3:1. After sealing, the solution was stirred at 3000 r / min for 5 min to obtain the single-walled carbon nanotube spinning solution.

[0051] S8. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The syringe needle tip had an inner diameter of 180 μm and a length of 50 mm. The extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110 °C after winding.

[0052] Example 3: A method for preparing highly conductive single-walled carbon nanotube fibers, comprising the following steps:

[0053] S1. Dissolve 0.3244 g (2 mmol) of ferric chloride powder in 20 mL of water and stir until the solid is completely dissolved. Use a pipette to add 5 mL of ferric chloride aqueous solution dropwise to 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to reddish-orange. Ferric chloride hydrolyzes to form ferric hydroxide colloid. Continue to boil gently for 2 hours, then cool to room temperature to obtain ferric hydroxide colloidal solution. Then add ethanol to dilute to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and sonicate for 10 min to obtain a homogeneous ferric hydroxide colloidal solution catalyst.

[0054] S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned sequentially with water, acetone, ethanol and water. Each cleaning process was ultrasonically cleaned for 38 min. The cleaned substrate was then dried with nitrogen and placed face up in a crucible. It was annealed in a muffle furnace at 1100℃ for 10 h. Then it was cooled to 300℃ within 6 h and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites.

[0055] S3. Preparation of crude single-walled carbon nanotubes by CVD: A homogeneous colloidal solution of ferric hydroxide was loaded onto a cleaned a-plane-Al2O3 substrate as a catalyst. The substrate was annealed at 1000℃ for 13 min to allow the catalyst to be incorporated into the substrate. The substrate loaded with the catalyst was then placed in the center of a tube furnace and reduced at 800℃ for 21 min. The substrate was then moved to 540℃ and a mixed gas of ethanol and hydrogen (volume ratio of ethanol to hydrogen of 50:300) was introduced. The substrate was grown for 45 min to obtain crude single-walled carbon nanotubes.

[0056] S4. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes. The acid washing and purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 430℃ for 2.3h. The specific method is the existing technology.

[0057] S5. Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimide] is prepared by polymerization using 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers. The specific preparation method is the prior art.

[0058] S6. Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] was dissolved in water to prepare a 1% (w / w) aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole].

[0059] 1 g of single-walled carbon nanotubes were added to 1 L of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] aqueous solution and ultrasonically dispersed at 11 °C for 22 h. Then, the mixture was centrifuged at 20000 r / min for 2 h and the supernatant was collected to obtain the purified single-walled carbon nanotube solution.

[0060] S7. Under an argon atmosphere, chlorosulfonic acid was added to the single-walled carbon nanotube purification solution. The volume ratio of the single-walled carbon nanotube purification solution to chlorosulfonic acid was 28.2:1. After sealing, the solution was stirred at 3000 r / min for 5 min to obtain the single-walled carbon nanotube spinning solution.

[0061] S8. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The syringe tip had an inner diameter of 180 μm and a length of 35 mm. The extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110 °C after winding.

[0062] Comparative Example 1 This comparative example provides a method for preparing single-walled carbon nanotube fibers. The specific steps are the same as in Example 1. The difference is that single-walled carbon nanotubes are directly used for wet spinning to prepare single-walled carbon nanotube fibers. It was found that single-walled carbon nanotubes cannot be well dispersed in water, and single-walled carbon nanotube fibers cannot be prepared.

[0063] Comparative Example 2: This comparative example provides a method for preparing single-walled carbon nanotube fibers. The specific steps are the same as in Example 1, except that single-walled carbon nanotubes are directly used for wet spinning. However, a surfactant is added to the single-walled carbon nanotube spinning solution to disperse the single-walled carbon nanotubes during the preparation process. The specific steps are as follows:

[0064] S1. Dissolve 0.3244 g (2 mmol) of ferric chloride powder in 20 mL of water and stir until the solid is completely dissolved. Use a pipette to add 5 mL of ferric chloride aqueous solution dropwise to 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to reddish-orange. Ferric chloride hydrolyzes to form ferric hydroxide colloid. Continue to boil gently for 2 hours, then cool to room temperature to obtain ferric hydroxide colloidal solution. Then add ethanol to dilute to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and sonicate for 10 min to obtain a homogeneous ferric hydroxide colloidal solution catalyst.

[0065] S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned sequentially with water, acetone, ethanol and water. Each cleaning process was ultrasonically cleaned for 40 min. The cleaned substrate was then dried with nitrogen and placed face up in a crucible. It was annealed in a muffle furnace at 1100℃ for 10 h. Then it was cooled to 300℃ within 6 h and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites.

[0066] S3. Preparation of crude single-walled carbon nanotubes by CVD: A homogeneous colloidal solution of ferric hydroxide was loaded onto a cleaned a-plane-Al2O3 substrate as a catalyst and annealed at 1000℃ for 10 min to allow the catalyst to be incorporated into the substrate. The substrate loaded with the catalyst was then placed in the center of a tube furnace and reduced at 800℃ for 20 min. The substrate was then moved to 540℃ and a mixed gas of ethanol and hydrogen (volume ratio of ethanol to hydrogen of 50:300) was introduced. The substrate was grown for 35 min to obtain crude single-walled carbon nanotubes.

[0067] S4. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes. The acid washing and purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 450℃ for 2 hours. The specific method is the existing technology.

[0068] S5. Add sodium dodecyl sulfate to 1L of water, mix well, then add 1g of single-walled carbon nanotubes, disperse by ultrasonication, add chlorosulfonic acid, seal and stir to obtain single-walled carbon nanotube spinning solution.

[0069] S6. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The syringe needle tip had an inner diameter of 180 μm and a length of 14 mm. The extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110 °C after winding.

[0070] Comparative Example 3: A method for preparing highly conductive single-walled carbon nanotube fibers. The specific method is the same as in Example 1, except that in this comparative example, the single-walled carbon nanotubes are purified using an imidazole-based ionic liquid after high-temperature oxidation purification, as detailed below:

[0071] S1. Dissolve 0.3244 g (2 mmol) of ferric chloride powder in 20 mL of water and stir until the solid is completely dissolved. Use a pipette to add 5 mL of ferric chloride aqueous solution dropwise to 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to reddish-orange. Ferric chloride hydrolyzes to form ferric hydroxide colloid. Continue to boil gently for 2 hours, then cool to room temperature to obtain ferric hydroxide colloidal solution. Then add ethanol to dilute to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and sonicate for 10 min to obtain a homogeneous ferric hydroxide colloidal solution catalyst.

[0072] S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned sequentially with water, acetone, ethanol and water. Each cleaning process was ultrasonically cleaned for 40 min. The cleaned substrate was then dried with nitrogen and placed face up in a crucible. It was annealed in a muffle furnace at 1100℃ for 10 h. Then it was cooled to 300℃ within 6 h and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites.

[0073] S3. Preparation of crude single-walled carbon nanotubes by CVD: A homogeneous colloidal solution of ferric hydroxide was loaded onto a cleaned a-plane-Al2O3 substrate as a catalyst and annealed at 1000℃ for 10 min to allow the catalyst to be incorporated into the substrate. The substrate loaded with the catalyst was then placed in the center of a tube furnace and reduced at 800℃ for 20 min. The substrate was then moved to 540℃ and a mixed gas of ethanol and hydrogen (volume ratio of ethanol to hydrogen of 50:300) was introduced. The substrate was grown for 35 min to obtain crude single-walled carbon nanotubes.

[0074] S4. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes. The acid washing and purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 450℃ for 2 hours. The specific method is the existing technology.

[0075] S5. Take 16 mL (0.2 mol) of 1-methylimidazole and 0.2 mol of bromoethane and stir to mix. Heat the mixture in an oil bath at 70 °C for 4 h. After stopping the reaction, quickly remove the upper liquid layer. Wash the lower solidified product three times with ethyl acetate to remove impurities. Then add anhydrous acetonitrile and heat to obtain a solid substance. After crystallization, wash with ethyl acetate to obtain a colorless and transparent intermediate. Finally, dry the intermediate at 80 °C for 24 h.

[0076] The dried intermediate was dissolved in 4 times its mass of methanol, and then sodium tetrafluoroborate was added and mixed. The molar amounts of sodium tetrafluoroborate and intermediate were equal. The mixture was magnetically stirred at room temperature for 24 h, and after standing for 0.5 h, a colorless solid precipitated. The supernatant was collected by filtration under normal pressure, and methanol in the supernatant was removed by rotary evaporation. Then, chloroform was added to precipitate a solid, and the solid was obtained by vacuum filtration. The filtrate was then removed by vacuum distillation to remove chloroform, and the product was dried to constant weight to obtain an imidazole ionic liquid.

[0077] S6. Imidazole ionic liquid is dissolved in water to prepare an aqueous solution of 1% by mass of imidazole ionic liquid;

[0078] 1 g of single-walled carbon nanotubes were added to 1 L of imidazole ionic liquid aqueous solution and ultrasonically dispersed at 10 °C for 24 h. Then, the mixture was centrifuged at 20000 r / min for 2 h, and the supernatant was collected to obtain the purified single-walled carbon nanotube solution.

[0079] S7. Under an argon atmosphere, add chlorosulfonic acid to the single-walled carbon nanotube purification solution. The volume ratio of the single-walled carbon nanotube purification solution to chlorosulfonic acid is 28:1. After sealing, stir at 3000 r / min for 5 min to obtain the single-walled carbon nanotube spinning solution.

[0080] S8. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The syringe needle tip had an inner diameter of 180 μm and a length of 14 mm. The extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110 °C after winding.

[0081] The electrical conductivity of the single-walled carbon nanotube fibers prepared in Example 1, Comparative Example 2, and Comparative Example 3 was tested respectively. First, the resistance of the fibers was measured by the four-wire method using a Keithley 2400 source meter. The conductivity of the single-walled carbon nanotube fibers was then tested, and the results are shown in Table 1.

[0082] Table 1. Conductivity results of single-walled carbon nanotube fibers in Example 1 and Comparative Examples 2 and 3

[0083]

[0084] As shown in Table 1, the single-walled carbon nanotube fibers prepared in Example 1 have the highest electrical conductivity. The electrical conductivity of the single-walled carbon nanotube fibers in Comparative Example 3 is higher than that in Comparative Example 2. This is because the single-walled carbon nanotubes in Comparative Example 3 are further purified using imidazole-based ionic liquids, which can selectively disperse metallic single-walled carbon nanotubes, thereby improving the electrical conductivity of the single-walled carbon nanotube fibers. However, the electrical conductivity of the single-walled carbon nanotubes in Comparative Example 3 is still not as high as that in Example 1. This is because in Example 1, the polymer fills the gaps between the single-walled carbon nanotubes, reduces the contact resistance between the single-walled carbon nanotubes, improves the conductivity of the single-walled carbon nanotube fibers, and the polymer receives electrons from the single-walled carbon nanotubes, generating negatively charged electrons as charge carriers, realizing continuous conduction between the single-walled carbon nanotubes in the fiber, further improving the electrical conductivity of the single-walled carbon nanotube fibers.

[0085] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing highly conductive single-walled carbon nanotube fibers, characterized in that, Includes the following steps: S1. Preparation of crude single-walled carbon nanotubes by chemical vapor deposition; S2. After acid washing and purification of crude single-walled carbon nanotubes, high-temperature oxidation purification is carried out to obtain single-walled carbon nanotubes. S3. Add single-walled carbon nanotubes to an aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole], disperse by ultrasonication at 10-12℃ for 20-24h, then centrifuge at 20000r / min for 2h, and collect the supernatant to obtain the purified single-walled carbon nanotube solution. S4. Under an argon atmosphere, add chlorosulfonic acid to the single-walled carbon nanotube purification solution, seal and stir at 3000 r / min for 5 min to obtain the single-walled carbon nanotube spinning solution. S5. Under an argon atmosphere, the spinning solution of single-walled carbon nanotubes is injected into the coagulation bath using a syringe to prepare single-walled carbon nanotube fibers, which are then wound up and dried.

2. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, characterized in that, In step S1, the preparation of crude single-walled carbon nanotubes by chemical vapor deposition is as follows: a homogeneous colloidal solution of ferric hydroxide is loaded onto an a-plane-Al2O3 substrate as a catalyst and annealed at 1000℃ for 10-15 min. Then, the substrate loaded with the catalyst is placed in the center of a tube furnace and reduced at 800℃ for 20-23 min. The substrate is then moved to 540℃, and a mixed gas of ethanol and hydrogen is introduced for growth for 35-60 min to obtain crude single-walled carbon nanotubes.

3. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 2, characterized in that, The preparation method of the homogeneous colloidal solution of ferric hydroxide is as follows: ferric chloride powder is dissolved in water, and added dropwise to boiling water to hydrolyze and obtain ferric hydroxide colloidal solution. Then, ethanol is added to dilute it to a concentration of ferric hydroxide of 0.05 mmol / L, and the solution is ultrasonicated for 10 min to obtain the final solution.

4. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 2, characterized in that, The a-plane-Al2O3 substrate is cleaned before use. The specific method is as follows: the substrate is cleaned sequentially with water, acetone, ethanol and water. Each cleaning process is ultrasonically cleaned for 35-40 minutes. Then it is dried with nitrogen gas, placed in a crucible, and annealed at 1100℃ for 10 hours. Then it is cooled to 300℃ within 6 hours and finally cooled to room temperature.

5. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, characterized in that, In step S2, the acid washing purification uses dilute nitric acid, and the high-temperature oxidation purification uses high-temperature calcination at 400~450℃ for 2~2.5h.

6. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, characterized in that, In step S3, the mass fraction of poly[2,5-dihydroxy-1,4-phenylenepyridinidazole] in the aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinidazole] is 1%.

7. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 6, characterized in that, The poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] is obtained by polymerization of 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers.

8. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, characterized in that, In step S3, the solid-liquid ratio of the single-walled carbon nanotubes and the aqueous solution of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] is 1 g: 1 L.

9. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, characterized in that, In step S4, the volume ratio of the single-walled carbon nanotube purification solution to the chlorosulfonic acid is 28~28.3:

1.

10. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, characterized in that, In step S5, the coagulation bath is polyvinyl alcohol, the syringe needle tip has an inner diameter of 180 μm, a length of 14~50 mm, and an extrusion rate of 0.07 mL / min.

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