Preparation method of high-conductivity single-walled carbon nanotube fiber

Abstract

The invention belongs to the technical field of preparation of single-walled carbon nanotube fibers, and particularly relates to a preparation method of high-conductivity single-walled carbon nanotube fibers, which comprises the following steps: preparing a single-walled carbon nanotube crude product by a chemical vapor deposition method, pickling and purifying, and oxidizing and purifying at high temperature to obtain a single-walled carbon nanotube; the preparation method comprises the following steps: adding a single-walled carbon nanotube into a poly [2, 5-dihydroxy-1, 4-phenylene pyridine diimidazole] aqueous solution, dispersing, and collecting supernatant liquid to obtain a single-walled carbon nanotube purified liquid; adding chlorosulfonic acid into the single-walled carbon nanotube purified solution in an argon atmosphere to obtain a single-walled carbon nanotube spinning solution; and injecting the single-walled carbon nanotube spinning solution into a coagulating bath in an argon atmosphere to prepare the single-walled carbon nanotube fiber. According to the invention, the poly [2, 5-dihydroxy-1, 4-phenylenediimidazole] is adopted to selectively disperse the metallic single-walled carbon nanotubes, and the gold single-walled carbon nanotubes in the single-walled carbon nanotube fibers are high in purity, so that the conductivity can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of single-wall carbon nanotube fiber preparation, and in particular relates to a method for preparing highly conductive single-wall carbon nanotube fibers. Background Art

[0002] Single-walled carbon nanotube fiber is a macroscopic, one-dimensional material composed of axially aligned single-walled carbon nanotubes. It is a high-performance fiber product. Due to the excellent intrinsic physical and chemical properties of single-walled carbon nanotubes, single-walled carbon nanotube fibers exhibit high electrical and thermal conductivity, high strength, corrosion resistance, lightweight, and high flexibility, making them promising candidates for the next generation of lightweight, high-strength, and highly conductive materials.

[0003] The preparation methods of single-walled carbon nanotube fibers include dry spinning, wet spinning, and floating catalytic CVD spinning. Compared with the wet method, the dry direct spinning process needs to be carried out in a semi-enclosed environment above 1000°C and requires high concentrations of hydrogen, which has high energy consumption and requires safety protection. Floating catalytic CVD spinning has a high catalyst content, and the purity and consistency of the prepared carbon nanotube fibers are low, which is not conducive to industrialization. Wet spinning generally prepares single-walled carbon nanotubes into a spinning solution, which is then injected into a coagulation bath of a certain component through a spinneret. The spinning solution undergoes component double diffusion in the coagulation bath and solidifies into fibers. After the fibers leave the coagulation bath, the coagulation bath components remaining on the fiber surface evaporate to form dry single-walled carbon nanotube fibers.

[0004] Single-walled carbon nanotubes include metallic single-walled carbon nanotubes (m-SWCNTs) and semiconducting single-walled carbon nanotubes (s-SWCNTs). Among them, metallic single-walled carbon nanotubes have better conductivity.

[0005] However, the single-walled carbon nanotubes obtained by existing single-walled carbon nanotube preparation methods are impure and contain various carbon family byproducts. In addition, the separation and purification of metallic single-walled carbon nanotubes and semiconducting single-walled carbon nanotubes are difficult. The single-walled carbon nanotube fibers prepared contain both metallic single-walled carbon nanotubes and semiconducting single-walled carbon nanotubes. Therefore, the conductive properties of single-walled carbon nanotube fibers need to be further improved. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing highly conductive single-walled carbon nanotube fibers to solve the above technical problems.

[0007] In order to achieve the above technical objectives, the technical solution of the present invention is: A method for preparing highly conductive single-walled carbon nanotube fibers comprises the following steps: S1. Preparation of crude single-walled carbon nanotubes by chemical vapor deposition; S2, acid-washing and purifying the crude single-walled carbon nanotubes, and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes; S3, adding single-walled carbon nanotubes to a poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution, ultrasonically dispersing the solution at 10-12° C. for 20-24 hours, and then ultracentrifuging the solution at 20,000 rpm for 2 hours, collecting the supernatant to obtain a purified single-walled carbon nanotube solution; S4. Under an argon atmosphere, chlorosulfonic acid was added to the purified single-walled carbon nanotube solution, and the mixture was sealed and stirred at a speed of 3000 r / min for 5 minutes to obtain a single-walled carbon nanotube spinning solution; S5. In an argon atmosphere, injecting the single-walled carbon nanotube spinning solution into the coagulation bath with a syringe to prepare the single-walled carbon nanotube fibers, which are rolled up and then dried.

[0008] As a further improvement, in step S1, the chemical vapor deposition method is used to prepare crude single-walled carbon nanotubes as follows: a uniform colloidal solution of ferric hydroxide is loaded as a catalyst onto an a-plane-Al2O3 substrate, annealed at 1000°C for 10 to 15 minutes, and then the substrate loaded with the catalyst is placed in the center of a tubular furnace, reduced at 800°C for 20 to 23 minutes, and then the substrate is moved to 540°C, a mixed gas of ethanol and hydrogen is introduced, and grown for 35 to 60 minutes to obtain crude single-walled carbon nanotubes.

[0009] As a further improvement, the preparation method of the uniform ferric hydroxide colloidal solution is as follows: dissolving ferric chloride powder in water, adding it dropwise into boiling water for hydrolysis to obtain a ferric hydroxide colloidal solution, then adding ethanol to dilute it to a ferric hydroxide concentration of 0.05 mmol / L, and ultrasonicating for 10 minutes to obtain the solution.

[0010] As a further improvement, the a-plane-Al2O3 substrate is cleaned before use. The specific method is: the substrate is cleaned with water, acetone, ethanol, and water in sequence, and each cleaning process is ultrasonically cleaned for 35 to 40 minutes, then blown dry with nitrogen, and then placed in a crucible, annealed at 1100°C for 10 hours, then cooled to 300°C within 6 hours, and finally cooled to room temperature.

[0011] As a further improvement, in step S2, the acid washing purification adopts dilute nitric acid, and the high-temperature oxidation purification adopts high-temperature calcination at 400-450° C. for 2-2.5 hours.

[0012] As a further improvement, in step S3, the mass fraction of poly[2,5-dihydroxy-1,4-phenylenepyridobiimidazole] in the poly[2,5-dihydroxy-1,4-phenylenepyridobiimidazole] aqueous solution is 1%.

[0013] As a further improvement, the poly[2,5-dihydroxy-1,4-phenylenepyridinodiimidazole] is obtained by polymerizing 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers.

[0014] As a further improvement, in step S3, the solid-to-liquid ratio of the single-walled carbon nanotubes and the poly[2,5-dihydroxy-1,4-phenylenepyridobiimidazole] aqueous solution is 1 g:1 L.

[0015] As a further improvement, in step S4, the volume ratio of the single-walled carbon nanotube purified solution to the chlorosulfonic acid is 28-28.3:1.

[0016] As a further improvement, in step S5, the coagulation bath is polyvinyl alcohol, the inner diameter of the needle tip of the syringe is 180 μm, the length is 14-50 mm, and the extrusion rate is 0.07 mL / min.

[0017] Due to the adoption of the above technical solution, the present invention has the following beneficial effects: The present invention provides a method for preparing highly conductive single-walled carbon nanotube fibers, which selectively disperses metallic single-walled carbon nanotubes using poly[2,5-dihydroxy-1,4-phenylenepyridiniumdiimidazole]. The prepared single-walled carbon nanotube fibers have high purity of metallic single-walled carbon nanotubes and can improve the conductive properties of the single-walled carbon nanotube fibers.

[0018] Poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] is used to purify single-walled carbon nanotubes. The polymer backbone lacks electrons, which selectively disperses metallic single-walled carbon nanotubes. The conjugated imidazole ring system in the polymer produces π-π interactions with metallic single-walled carbon nanotubes. The polymer molecules can be tightly and evenly adsorbed on the surface of the single-walled carbon nanotubes, breaking up the metallic single-walled carbon nanotube bundles and selectively dispersing the metallic single-walled carbon nanotubes.

[0019] In the present 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 content of metallic single-walled carbon nanotubes in the obtained crude single-walled carbon nanotubes is high.

[0020] In the present invention, the polymer interacts with the metallic single-walled carbon nanotube to generate electron transfer, which captures the electrons of the single-walled carbon nanotube, forms holes inside the single-walled carbon nanotube, and improves the conductivity of the single-walled carbon nanotube fiber.

[0021] In the process of preparing single-walled carbon nanotube fibers, the polymer fills the gaps between the single-walled carbon nanotubes, reduces the contact resistance between the single-walled carbon nanotubes, and improves the conductive properties of the single-walled carbon nanotube fibers. In addition, the polymer accepts electrons from the single-walled carbon nanotubes and generates negatively charged electrons as carriers, thereby achieving continuous conductivity between the single-walled carbon nanotubes in the fiber, further improving the conductive properties of the single-walled carbon nanotube fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 3 is the Raman spectrum of the crude single-walled carbon nanotube prepared in Example 1, wherein a is the total RBM peak under four laser wavelength tests, and b is an enlarged view of the RBM peak in a. DETAILED DESCRIPTION

[0023] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0024] Example 1 A method for preparing highly conductive single-walled carbon nanotube fibers comprises the following steps: 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 draw 5 mL of ferric chloride aqueous solution and add it dropwise into 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to orange-red. The ferric chloride is hydrolyzed to form ferric hydroxide colloid. Continue to boil slightly for 2 hours, then cool to room temperature to obtain a ferric hydroxide colloidal solution. Then add ethanol to dilute it to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and ultrasonicate for 10 minutes to obtain a uniform ferric hydroxide colloidal solution catalyst. S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned with water, acetone, ethanol, and water in sequence, with each cleaning process ultrasonically cleaning for 40 minutes. The cleaned substrate was then blown dry with nitrogen, placed face up in a crucible, and annealed at 1100°C in a muffle furnace for 10 hours. The substrate was then cooled to 300°C within 6 hours and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites. S3. Preparation of crude single-walled carbon nanotubes by CVD: A uniform colloidal solution of ferric hydroxide was loaded as a catalyst onto a cleaned a-plane-Al2O3 substrate, and annealed at 1000°C for 10 minutes to allow the catalyst to integrate into the substrate. The catalyst-loaded substrate was then placed in the center of a tube furnace and reduced at 800°C for 20 minutes. The substrate was then moved to 540°C and a mixed gas of ethanol and hydrogen (the volume ratio of ethanol and hydrogen in the mixed gas was 50:300) was introduced. The mixture was grown for 35 minutes to obtain crude single-walled carbon nanotubes. S4. Purifying the crude single-walled carbon nanotubes by acid washing and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes, wherein the acid washing and purification are performed using dilute nitric acid, and the high-temperature oxidation purification is performed by calcining at 450° C. for 2 h, and the specific method is the existing technology; S5. Poly[2,5-dihydroxy-1,4-phenylenepyridinodiimidazole] is prepared by polymerization using 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers, and the specific preparation method is the existing technology; S6, poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] is dissolved in water to prepare a poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution with a mass fraction of 1%; 1 g of single-walled carbon nanotubes was added to 1 L of poly[2,5-dihydroxy-1,4-phenylenepyridinium diimidazole] aqueous solution, ultrasonically dispersed at 10°C for 24 h, and then ultracentrifuged at 20,000 r / min for 2 h. The supernatant was collected to obtain a purified single-walled carbon nanotube solution; S7. Under an argon atmosphere, chlorosulfonic acid was added to the purified single-walled carbon nanotube solution, with the volume ratio of the purified single-walled carbon nanotube solution to chlorosulfonic acid being 28:1. After sealing, the solution was stirred at a speed of 3000 rpm for 5 minutes to obtain a single-walled carbon nanotube spinning solution. S8. Under an argon atmosphere, the single-walled carbon nanotube spinning solution was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The inner diameter of the syringe needle tip was 180 μm, the length was 14 mm, and the extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110°C after winding.

[0025] The crude single-walled carbon nanotubes prepared above were subjected to Raman mapping tests at 488nm, 532nm, 633nm and 785nm. The test results are as follows: Figure 1 As shown, a is the total RBM peak under four laser wavelength tests, and b is the magnified view of the RBM peak in a. It is obvious from the figure that most of the radial breathing peaks of single-walled carbon nanotubes are concentrated in and At two wavelengths, statistics on the RBM peaks appearing at four laser wavelengths found that the number of peaks concentrated at these two wavelengths was close to 89%. According to Kataura plot comparison, 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.

[0026] Example 2 A method for preparing highly conductive single-walled carbon nanotube fibers comprises the following steps: 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 draw 5 mL of ferric chloride aqueous solution and add it dropwise into 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to orange-red. The ferric chloride is hydrolyzed to form ferric hydroxide colloid. Continue to boil slightly for 2 hours, then cool to room temperature to obtain a ferric hydroxide colloidal solution. Then add ethanol to dilute it to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and ultrasonicate for 10 minutes to obtain a uniform ferric hydroxide colloidal solution catalyst. S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned with water, acetone, ethanol, and water in sequence. Each cleaning process was ultrasonically cleaned for 35 minutes. The cleaned substrate was then blown dry with nitrogen and placed face up in a crucible. It was annealed at 1100°C in a muffle furnace for 10 hours, then cooled to 300°C within 6 hours and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites. S3. Preparation of crude single-walled carbon nanotubes by CVD: A uniform colloidal solution of ferric hydroxide was loaded as a catalyst onto a cleaned a-plane-Al2O3 substrate, and annealed at 1000°C for 15 minutes to allow the catalyst to integrate into the substrate. The catalyst-loaded substrate was then placed in the center of a tube furnace and reduced at 800°C for 23 minutes. The substrate was then moved to 540°C and a mixed gas of ethanol and hydrogen (the volume ratio of ethanol and hydrogen in the mixed gas was 50:300) was introduced. The mixture was grown for 60 minutes to obtain crude single-walled carbon nanotubes. S4, acid-washing and purifying the crude single-walled carbon nanotubes, and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes, the acid-washing and purification using dilute nitric acid, and the high-temperature oxidation purification using high-temperature calcination at 400° C. for 2.5 hours, the specific method is the existing technology; S5. Poly[2,5-dihydroxy-1,4-phenylenepyridinodiimidazole] is prepared by polymerization using 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers, and the specific preparation method is the existing technology; S6, poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] is dissolved in water to prepare a poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution with a mass fraction of 1%; 1 g of single-walled carbon nanotubes was added to 1 L of poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution, and ultrasonically dispersed at 12°C for 20 h, and then ultracentrifuged at 20,000 r / min for 2 h, and the supernatant was collected to obtain a purified single-walled carbon nanotube solution; S7. Under an argon atmosphere, chlorosulfonic acid was added to the purified single-walled carbon nanotube solution, with the volume ratio of the purified single-walled carbon nanotube solution to chlorosulfonic acid being 28.3:1. After sealing, the solution was stirred at a speed of 3000 rpm for 5 minutes to obtain a single-walled carbon nanotube spinning solution. S8. Under an argon atmosphere, the single-walled carbon nanotube spinning solution was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The inner diameter of the syringe needle tip was 180 μm, the length was 50 mm, and the extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110°C after winding.

[0027] Example 3 A method for preparing highly conductive single-walled carbon nanotube fibers comprises the following steps: 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 draw 5 mL of ferric chloride aqueous solution and add it dropwise into 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to orange-red. The ferric chloride is hydrolyzed to form ferric hydroxide colloid. Continue to boil slightly for 2 hours, then cool to room temperature to obtain a ferric hydroxide colloidal solution. Then add ethanol to dilute it to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and ultrasonicate for 10 minutes to obtain a uniform ferric hydroxide colloidal solution catalyst. S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned with water, acetone, ethanol, and water in sequence, with each cleaning process ultrasonically cleaning for 38 minutes. The cleaned substrate was then blown dry with nitrogen, placed face up in a crucible, and annealed at 1100°C in a muffle furnace for 10 hours. The substrate was then cooled to 300°C within 6 hours and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites. S3. Preparation of crude single-walled carbon nanotubes by CVD: A uniform colloidal solution of ferric hydroxide was loaded as a catalyst onto a cleaned a-plane-Al2O3 substrate, and annealed at 1000°C for 13 minutes to allow the catalyst to integrate into the substrate. The catalyst-loaded substrate was then placed in the center of a tube furnace and reduced at 800°C for 21 minutes. The substrate was then moved to 540°C and a mixed gas of ethanol and hydrogen (the volume ratio of ethanol and hydrogen in the mixed gas was 50:300) was introduced. The mixture was grown for 45 minutes to obtain crude single-walled carbon nanotubes. S4, acid-washing and purifying the crude single-walled carbon nanotubes, and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes, the acid-washing and purification using dilute nitric acid, and the high-temperature oxidation purification using high-temperature calcination at 430° C. for 2.3 hours, the specific method being the existing technology; S5. Poly[2,5-dihydroxy-1,4-phenylenepyridinodiimidazole] is prepared by polymerization using 2,3,5,6-tetraaminopyridine hydrochloride and 2,5-dihydroxyterephthalic acid as monomers, and the specific preparation method is the existing technology; S6, poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] is dissolved in water to prepare a poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution with a mass fraction of 1%; 1 g of single-walled carbon nanotubes was added to 1 L of poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution, and ultrasonically dispersed at 11°C for 22 h, and then ultracentrifuged at 20,000 r / min for 2 h. The supernatant was collected to obtain a purified single-walled carbon nanotube solution; S7. Under an argon atmosphere, chlorosulfonic acid was added to the purified single-walled carbon nanotube solution, with the volume ratio of the purified single-walled carbon nanotube solution to chlorosulfonic acid being 28.2:1. After sealing, the solution was stirred at a speed of 3000 rpm for 5 minutes to obtain a single-walled carbon nanotube spinning solution. S8. Under an argon atmosphere, the single-walled carbon nanotube spinning solution was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The inner diameter of the syringe needle tip was 180 μm, the length was 35 mm, and the extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110°C after winding.

[0028] Comparative Example 1 This comparative example provides a method for preparing single-walled carbon nanotube fibers. The specific steps are the same as those in Example 1, except that single-walled carbon nanotubes are directly used for wet spinning to prepare single-walled carbon nanotube fibers. It is found that single-walled carbon nanotubes cannot be well dispersed in water, and single-walled carbon nanotube fibers cannot be prepared.

[0029] Comparative Example 2 This comparative example provides a method for preparing single-walled carbon nanotube fibers. The specific steps are the same as those in Example 1, except that single-walled carbon nanotubes are directly used for wet spinning. However, during the preparation of the single-walled carbon nanotube spinning solution, a surfactant is added thereto to disperse the single-walled carbon nanotubes. The specific steps are as follows: 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 draw 5 mL of ferric chloride aqueous solution and add it dropwise into 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to orange-red. The ferric chloride is hydrolyzed to form ferric hydroxide colloid. Continue to boil slightly for 2 hours, then cool to room temperature to obtain a ferric hydroxide colloidal solution. Then add ethanol to dilute it to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and ultrasonicate for 10 minutes to obtain a uniform ferric hydroxide colloidal solution catalyst. S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned with water, acetone, ethanol, and water in sequence, with each cleaning process ultrasonically cleaning for 40 minutes. The cleaned substrate was then blown dry with nitrogen, placed face up in a crucible, and annealed at 1100°C in a muffle furnace for 10 hours. The substrate was then cooled to 300°C within 6 hours and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites. S3. Preparation of crude single-walled carbon nanotubes by CVD: A uniform colloidal solution of ferric hydroxide was loaded as a catalyst onto a cleaned a-plane-Al2O3 substrate, and annealed at 1000°C for 10 minutes to allow the catalyst to integrate into the substrate. The catalyst-loaded substrate was then placed in the center of a tube furnace and reduced at 800°C for 20 minutes. The substrate was then moved to 540°C and a mixed gas of ethanol and hydrogen (the volume ratio of ethanol and hydrogen in the mixed gas was 50:300) was introduced. The mixture was grown for 35 minutes to obtain crude single-walled carbon nanotubes. S4. Purifying the crude single-walled carbon nanotubes by acid washing and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes, wherein the acid washing and purification are performed using dilute nitric acid, and the high-temperature oxidation purification is performed by calcining at 450° C. for 2 h, and the specific method is the existing technology; S5. Sodium lauryl sulfate was added to 1 L of water, and after mixing, 1 g of single-walled carbon nanotubes was added thereto. After ultrasonic dispersion, chlorosulfonic acid was added thereto. The mixture was sealed and stirred to obtain a single-walled carbon nanotube spinning solution. S6. Under an argon atmosphere, the single-walled carbon nanotube spinning solution was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The inner diameter of the syringe needle tip was 180 μm, the length was 14 mm, and the extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110°C after winding.

[0030] Comparative Example 3 A method for preparing highly conductive single-walled carbon nanotube fibers is the same as that 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 follows: 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 draw 5 mL of ferric chloride aqueous solution and add it dropwise into 175 mL of boiling water for hydrolysis. The solution slowly changes from orange to orange-red. The ferric chloride is hydrolyzed to form ferric hydroxide colloid. Continue to boil slightly for 2 hours, then cool to room temperature to obtain a ferric hydroxide colloidal solution. Then add ethanol to dilute it to a ferric hydroxide concentration of 0.05 mmol / L. Finally, place it in an ultrasonic cleaner and ultrasonicate for 10 minutes to obtain a uniform ferric hydroxide colloidal solution catalyst. S2. Cleaning of the growth substrate a-plane-Al2O3: The substrate was cleaned with water, acetone, ethanol, and water in sequence, with each cleaning process ultrasonically cleaning for 40 minutes. The cleaned substrate was then blown dry with nitrogen, placed face up in a crucible, and annealed at 1100°C in a muffle furnace for 10 hours. The substrate was then cooled to 300°C within 6 hours and finally cooled to room temperature to reconstruct the substrate surface and generate more active sites. S3. Preparation of crude single-walled carbon nanotubes by CVD: A uniform colloidal solution of ferric hydroxide was loaded as a catalyst onto a cleaned a-plane-Al2O3 substrate, and annealed at 1000°C for 10 minutes to allow the catalyst to integrate into the substrate. The catalyst-loaded substrate was then placed in the center of a tube furnace and reduced at 800°C for 20 minutes. The substrate was then moved to 540°C and a mixed gas of ethanol and hydrogen (the volume ratio of ethanol and hydrogen in the mixed gas was 50:300) was introduced. The mixture was grown for 35 minutes to obtain crude single-walled carbon nanotubes. S4. Purifying the crude single-walled carbon nanotubes by acid washing and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes, wherein the acid washing and purification are performed using dilute nitric acid, and the high-temperature oxidation purification is performed by calcining at 450° C. for 2 h, and the specific method is the existing technology; S5. Take 16 mL (0.2 mol) of 1-methylimidazole and 0.2 mol of ethyl bromide, stir and mix, heat in an oil bath at 70°C for 4 h, stop the reaction, quickly remove the upper liquid, wash the lower solidified product with ethyl acetate three times to remove impurities, then add anhydrous acetonitrile and heat to obtain a solid substance, wash with ethyl acetate after crystallization to obtain a colorless and transparent intermediate, and finally dry the intermediate at 80°C for 24 h; The dried intermediate was dissolved in 4 times the mass of methanol, and then sodium tetrafluoroborate was added thereto, the molar amounts of sodium tetrafluoroborate and the intermediate were equal, and magnetic stirring was carried out at room temperature for 24 hours. After standing for 0.5 hours, a colorless solid was precipitated, and the supernatant was filtered under normal pressure. The methanol in the supernatant was removed by rotary evaporation, and then chloroform was added to precipitate the solid. The filtrate was filtered under reduced pressure to obtain a filtrate, and the filtrate was distilled under reduced pressure to remove chloroform. The product was dried to constant weight to obtain an imidazolyl ionic liquid; S6, dissolving the imidazolyl ionic liquid in water to prepare an imidazolyl ionic liquid aqueous solution with a mass fraction of 1%; 1 g of single-walled carbon nanotubes was added to 1 L of an imidazole-based ionic liquid aqueous solution, ultrasonically dispersed at 10°C for 24 h, and then ultracentrifuged at 20,000 rpm for 2 h. The supernatant was collected to obtain a purified single-walled carbon nanotube solution. S7. Under an argon atmosphere, chlorosulfonic acid was added to the purified single-walled carbon nanotube solution, with the volume ratio of the purified single-walled carbon nanotube solution to chlorosulfonic acid being 28:1. After sealing, the solution was stirred at a speed of 3000 rpm for 5 minutes to obtain a single-walled carbon nanotube spinning solution. S8. Under an argon atmosphere, the single-walled carbon nanotube spinning solution was transferred to a stainless steel syringe and injected into a polyvinyl alcohol coagulation bath. The inner diameter of the syringe needle tip was 180 μm, the length was 14 mm, and the extrusion rate was 0.07 mL / min. Single-walled carbon nanotube fibers were prepared and dried at 110°C after winding.

[0031] The conductive properties of the single-walled carbon nanotube fibers prepared in Example 1, Comparative Example 2, and Comparative Example 3 were tested respectively. First, the resistance of the fibers was measured using a four-wire method using a Keithley 2400 source meter. The electrical conductivity of the single-walled carbon nanotube fibers was tested, and the results are shown in Table 1.

[0032] Table 1 Electrical conductivity results of single-walled carbon nanotube fibers of Example 1, Comparative Examples 2 and 3

[0033] As can be seen from Table 1, the single-walled carbon nanotube fiber prepared in Example 1 has the highest conductivity, while the single-walled carbon nanotube fiber in Comparative Example 3 has a higher conductivity than that in Comparative Example 2. This is because in Comparative Example 3, imidazole-based ionic liquid is used to further purify the single-walled carbon nanotubes, which can selectively disperse the metallic single-walled carbon nanotubes, thereby improving the conductivity of the single-walled carbon nanotube fiber. However, the conductivity of the single-walled carbon nanotubes in Comparative Example 3 is still lower than 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, and improves the conductive properties of the single-walled carbon nanotube fiber. In addition, the polymer accepts electrons from the single-walled carbon nanotubes, generates negatively charged electrons as carriers, realizes continuous conductivity between the single-walled carbon nanotubes in the fiber, and further improves the conductivity of the single-walled carbon nanotube fiber.

[0034] The specific embodiments of the present invention described above do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in 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: The following steps are involved: S1. Preparation of crude single-walled carbon nanotubes by chemical vapor deposition; S2, acid-washing and purifying the crude single-walled carbon nanotubes, and then performing high-temperature oxidation purification to obtain single-walled carbon nanotubes; S3, adding single-walled carbon nanotubes to a poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution, ultrasonically dispersing the solution at 10-12° C. for 20-24 hours, and then ultracentrifuging the solution at 20,000 rpm for 2 hours, collecting the supernatant to obtain a purified single-walled carbon nanotube solution; S4. Under an argon atmosphere, chlorosulfonic acid was added to the purified single-walled carbon nanotube solution, and the mixture was sealed and stirred at a speed of 3000 r / min for 5 minutes to obtain a single-walled carbon nanotube spinning solution; S5. In an argon atmosphere, injecting the single-walled carbon nanotube spinning solution into the coagulation bath with a syringe to prepare the single-walled carbon nanotube fibers, which are rolled up and then dried.

2. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, wherein: In step S1, the chemical vapor deposition method is used to prepare crude single-walled carbon nanotubes. Specifically, a uniform colloidal solution of ferric hydroxide is loaded as a catalyst onto an a-plane-Al2O3 substrate, annealed at 1000°C for 10 to 15 minutes, and then the substrate loaded with the catalyst is placed in the center of a tubular furnace, reduced at 800°C for 20 to 23 minutes, and then the substrate is moved to 540°C, a mixed gas of ethanol and hydrogen is introduced, and grown for 35 to 60 minutes to obtain crude single-walled carbon nanotubes.

3. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 2, wherein: The preparation method of the uniform ferric hydroxide colloidal solution is as follows: dissolving ferric chloride powder in water, adding the solution dropwise to boiling water for hydrolysis to obtain a ferric hydroxide colloidal solution, then adding ethanol to dilute the solution to a ferric hydroxide concentration of 0.05 mmol / L, and performing ultrasonic treatment for 10 minutes to obtain the solution.

4. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 2, wherein: The a-plane-Al2O3 substrate was cleaned before use. The specific method was as follows: the substrate was cleaned with water, acetone, ethanol, and water in sequence, with each cleaning process ultrasonically cleaning for 35 to 40 minutes, then blown dry with nitrogen, and then placed in a crucible, annealed at 1100°C for 10 hours, then cooled to 300°C 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, wherein: In step S2, the acid washing purification adopts dilute nitric acid, and the high-temperature oxidation purification adopts high-temperature calcination at 400-450° C. for 2-2.5 hours.

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

7. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 6, wherein: The poly[2,5-dihydroxy-1,4-phenylene pyridinium diimidazole] is obtained by polymerizing 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, wherein: In step S3, the solid-to-liquid ratio of the single-walled carbon nanotubes and the poly[2,5-dihydroxy-1,4-phenylenepyridodiimidazole] aqueous solution is 1 g:1 L.

9. The method for preparing highly conductive single-walled carbon nanotube fibers according to claim 1, wherein: In step S4, the volume ratio of the single-walled carbon nanotube purified 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, wherein: In step S5, the coagulation bath is polyvinyl alcohol, the inner diameter of the needle tip of the syringe is 180 μm, the length is 14-50 mm, and the extrusion rate is 0.07 mL / min.

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