Double-walled carbon nanotube and preparation method thereof

Abstract

The invention discloses a double-walled carbon nanotube and a preparation method thereof, and the method comprises the following steps: (1) preparing a reaction liquid: adding thiophene and a catalyst into absolute ethyl alcohol, and ultrasonically dispersing uniformly to obtain the reaction liquid for later use; (2) air replacement: argon is introduced into the quartz tube reactor for air replacement; (3) after replacement is completed, raising the temperature and introducing carrier gas, and after the temperature is raised to the reaction temperature, injecting the preheated reaction liquid into the quartz tube reactor to start reaction; and (4) after the reaction is finished, stopping injecting the reaction liquid, maintaining the reaction temperature, reacting for a period of time, finally cooling to room temperature, and taking out the reactant, thereby obtaining the double-walled carbon nanotube product. The prepared carbon nano tube is high in purity and few in defect, and comprehensive utilization of the carbon nano tube is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon nanotube preparation, and particularly relates to a double-walled carbon nanotube and a preparation method thereof. Background Art

[0002] Nanocarbon materials are a new type of nanomaterials, mainly including carbon nanotubes, carbon nanofibers, and nanocarbon spheres. Among them, since carbon nanotubes were discovered in 1991, due to their unique structure and excellent mechanical, electrical, and chemical properties, they have shown broad application prospects, attracting great attention from many scientists in the fields of materials, physics, electronics, chemistry, etc., and becoming the research forefront and hotspot in the international new materials field.

[0003] Currently, the preparation of carbon nanotubes mainly includes three methods: arc discharge method, laser ablation method, and chemical vapor deposition method. The arc discharge method uses graphite rods as the anode and cathode, and the anode graphite rod is loaded with catalyst particles. In a vacuum reaction chamber filled with a certain inert gas, hydrogen, or other gases, the high-temperature arc between the two electrodes evaporates the solid graphite carbon source of the anode, causing carbon atoms to precipitate into tubular, granular, etc. on the cathode; the carbon nanotubes prepared by the arc discharge method have a high degree of graphitization and fewer defects, but this method requires high equipment requirements, high growth temperature, and low yield. The laser ablation method, also known as the laser evaporation method, is a method of preparing carbon nanotubes by bombarding a graphite target doped with transition metals with a laser under the protection of an inert gas at a temperature of about 1200 °C, forming gaseous carbon atoms under the action of a catalyst; the carbon nanotubes prepared by the laser ablation method have a high purity and controllable conditions, but the equipment used is expensive and the production cost is high. The chemical vapor deposition method is to crack the carbon source under the action of a catalyst at a relatively low temperature, and carbon atoms dissolve on the catalyst particles and then precipitate in the form of tubes to form carbon nanotubes; among them, because the chemical vapor deposition method has mild reaction conditions and high yield, it is considered to be one of the most promising methods.

[0004] The floating catalyst chemical vapor deposition method is an improved method of the chemical vapor deposition method. It is a process of volatilizing carbon sources and catalysts into gaseous state and cracking out various elements, and then forming carbon nanotubes under the catalytic action of the catalyst. It has the advantages of simple process, in-situ preparation of catalysts, and easy realization of continuous production. In the prior art, the patent document CN117285033A discloses a floating catalyst preparation method of highly graphitized single-walled carbon nanotubes based on an iron salt catalyst. The prepared single-walled carbon nanotube product has a high degree of graphitization and a low amorphous carbon content. The purity of the purified carbon nanotubes is about 70% approximately, and the purity of the carbon nanotubes needs to be further improved. Optimizing the reaction conditions to improve the preparation purity of carbon nanotubes is of great significance for the application of carbon nanotubes.

[0005] Compared with single-walled carbon nanotubes, double-walled carbon nanotubes exhibit better performance in terms of structural stability, electrochemical stability, etc. Therefore, it is very necessary to provide a preparation method for efficiently preparing carbon nanotubes.

[0006] Based on the above considerations, the present invention is proposed. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a double-walled carbon nanotube and a preparation method thereof. The prepared double-walled carbon nanotubes have high purity and few defects, which is beneficial to the comprehensive utilization of carbon nanotubes.

[0008] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method for double-walled carbon nanotubes, including the following steps:

[0010] (1) Prepare the reaction solution: After adding thiophene and a catalyst to absolute ethanol, ultrasonically disperse them evenly to obtain the reaction solution for standby;

[0011] (2) Air replacement: Pass argon into the quartz tube reactor for air replacement;

[0012] (3) After the replacement is completed, heat up and pass in the carrier gas. When the temperature rises to the reaction temperature, inject the preheated reaction solution into the quartz tube reactor to start the reaction;

[0013] (4) After the reaction ends, stop injecting the reaction solution, maintain the reaction temperature for a period of time, and finally cool to room temperature, take out the reactants, and obtain the double-walled carbon nanotube product.

[0014] As a further preference of the technical solution of the present invention, in step (1), the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.2 to 0.35.

[0015] As a further preference of the technical solution of the present invention, in step (1), the mass ratio of thiophene, catalyst, and absolute ethanol is 0.3 to 0.5:2 to 5:100.

[0016] As a further preference of the technical solution of the present invention, in step (2), the flow rate of argon is 200 to 300 mL / min.

[0017] As a further preference of the technical solution of the present invention, in step (3), the heating rate is 5 to 50 °C / min, the carrier gas is a mixed gas of hydrogen and argon, the flow rate of hydrogen is 500 to 650 mL / min, and the flow rate of argon is 300 to 450 mL / min.

[0018] As a further preference of the technical solution of the present invention, in step (3), the preheating temperature of the reaction solution is 350 - 450 °C.

[0019] As a further preference of the technical solution of the present invention, in step (4), the reaction temperature is 1080 - 1150 °C, the reaction time is 0.5 - 5 h, and the injection rate of the reaction solution is 0.05 - 0.2 mL / min.

[0020] As a further preference of the technical solution of the present invention, in step (4), the time for maintaining the reaction temperature is 10 - 60 min.

[0021] As a further preference of the technical solution of the present invention, in step (4), the cooling process is: first stop the introduction of hydrogen and keep introducing argon until it cools to room temperature.

[0022] In the second aspect, the present invention also aims to protect the double-walled carbon nanotube products prepared by the above method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Focusing on the goal of improving the purity of double-walled carbon nanotube products, the present invention optimizes the use of catalysts and synthesis process parameters, so that the purity of double-walled carbon nanotubes exceeds 80%. And based on the advantage of easy continuous production of the floating catalyst chemical vapor deposition method, the carbon nanotube products in the present invention can be continuously and large-scale produced, with good application prospects.

[0025] (2) During the synthesis process of double-walled carbon nanotubes, the present invention selects a composite system of ferrocene and vanadocene as the catalyst. The combination of the two is creatively proposed by the applicant and has achieved very good catalytic effects.

[0026] (3) The present invention preheats the reaction solution before injection, which is beneficial to further improving the yield of double-walled carbon nanotube products.

[0027] (4) The carbon source in the present invention is ethanol, and thiophene is a production promoter, and the raw materials are common.

[0028] (5) The preparation method of double-walled carbon nanotubes provided by the present invention repeatedly optimizes process parameters such as synthesis temperature and catalyst type, and obtains the best production process conditions. Description of the Drawings

[0029] Figure 1 It is an electron microscope image of the double-walled carbon nanotube product prepared in Example 1. Detailed Embodiments

[0030] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Unless otherwise specified, all products in the present invention are purchased through market channels.

[0032] A preparation method of double-walled carbon nanotubes includes the following steps:

[0033] (1) Prepare the reaction solution: After adding thiophene and a catalyst into absolute ethanol, ultrasonically disperse them evenly to obtain the reaction solution for standby;

[0034] (2) Air replacement: Introduce argon into the quartz tube reactor for air replacement;

[0035] (3) After the replacement is completed, heat up and introduce the carrier gas. When the temperature rises to the reaction temperature, inject the preheated reaction solution into the quartz tube reactor to start the reaction;

[0036] (4) After the reaction ends, stop injecting the reaction solution, maintain the reaction temperature for a period of time, and finally cool it to room temperature, then take out the reactants to obtain the double-walled carbon nanotube product.

[0037] In the above technical solution, the preparation of double-walled carbon nanotubes is based on the floating catalyst chemical vapor deposition method, which has the advantages of simple process, in-situ preparation of the catalyst, and easy realization of continuous production. In order to improve the purity of double-walled carbon nanotubes, the applicant creatively improved the synthesis process. Specifically, during the synthesis process, the type of catalyst used was changed, and a small amount of vanadocene was introduced and used in combination with the traditional ferrocene, which achieved a very good catalytic effect. Ethanol is used as the carbon source and thiophene is used as the growth promoter during the synthesis process, and the raw materials are common.

[0038] In the above technical solution, the quartz tube reactor is a common instrument and equipment in the laboratory, and there have been many uses and reports in the floating catalyst chemical vapor deposition method. The specific structure of it is not described in the present invention. The peristaltic pump involved in the injection of the reaction solution is also a conventional device on the market, and its model and structure are not specifically required in the present invention.

[0039] In step (1) of the above process for preparing double-walled carbon nanotubes, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.2 to 0.35. Obviously, different from the common metal components such as iron, cobalt, nickel, etc. commonly used in the prior art, the use of vanadium is introduced in the present invention, which can greatly improve the purity of double-walled carbon nanotubes and improve the catalytic effect. For the compounding ratio of the two, obviously, the amount of iron used is relatively large, and the amount of vanadium used is relatively small. Further, the molar ratio of iron and vanadium atoms is 1:0.2 to 0.35. For example, 1:0.2, 1:0.25, 1:0.3, 1:0.35 are all acceptable. After repeated optimization, the optimal usage ratio of the two is 1:0.25.

[0040] Furthermore, in the above step (1), the mass ratio of thiophene, catalyst, and absolute ethanol is 0.3 to 0.5:2 to 5:100, and the amounts of each substance within this range can be flexibly adjusted. More preferably, the mass ratio of thiophene, catalyst, and absolute ethanol is 0.35 to 0.45:3 to 4.5:100; most preferably, the mass ratio of thiophene, catalyst, and absolute ethanol is 0.4:4:100.

[0041] In step (2) of the above process for preparing double-walled carbon nanotubes, the flow rate of the replaced argon gas introduced can be flexibly adjusted, and the preferred range is 200 to 300 mL / min; more preferably, it is 220 mL / min.

[0042] In step (3) of the above process for preparing double-walled carbon nanotubes, the heating rate is 5 to 50 °C / min. It can be understood that the heating rate can be a certain value among 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, 25 °C / min, 30 °C / min, 35 °C / min, 40 °C / min, 45 °C / min, 50 °C / min or any value within the above range. The carrier gas is a mixed gas of hydrogen and argon. The amount of hydrogen is larger than that of argon. The flow rate of hydrogen is 500 to 650 mL / min, and the flow rate of argon is 300 to 450 mL / min. It can be understood that the flow rate of hydrogen can be a certain value among 500 mL / min, 510 mL / min, 520 mL / min, 530 mL / min, 540 mL / min, 550 mL / min, 560 mL / min, 570 mL / min, 580 mL / min, 590 mL / min, 600 mL / min, 610 mL / min, 620 mL / min, 630 mL / min, 640 mL / min, 650 mL / min or any value within the above range; the flow rate of argon can be a certain value among 300 mL / min, 310 mL / min, 320 mL / min, 330 mL / min, 340 mL / min, 350 mL / min, 360 mL / min, 370 mL / min, 380 mL / min, 390 mL / min, 400 mL / min, 410 mL / min, 420 mL / min, 430 mL / min, 440 mL / min, 450 mL / min or any value within the above range. More preferably, the flow rate of hydrogen is 550 mL / min, and the flow rate of argon is 350 mL / min.

[0043] In step (3) of the above process for preparing double-walled carbon nanotubes, the preheating temperature of the reaction solution is 350 to 450 °C. Preheating the reaction solution can cause the reaction solution to be pre-decomposed into atoms, which is beneficial to improving the synthesis efficiency and the quality of the synthesized product. It can be understood that different preheating temperatures have different effects on the synthesis. Those skilled in the art can select a suitable preheating temperature according to the combination of process parameters, such as a certain value among 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C, 370 °C, 380 °C, 390 °C, 400 °C, 410 °C, 420 °C, 430 °C, 440 °C, 450 °C or any value within the above range; more preferably, the preheating temperature in the present invention is preferably 360 °C, and the synthesis effect is the best at this temperature.

[0044] In step (4) of the above process for preparing double-walled carbon nanotubes, the reaction temperature is also important. In this preparation process, the optimized range of the reaction temperature is 1080 - 1150 °C, and the reaction time is 0.5 - 5 h. Of course, more preferably, the reaction temperature is 1090 °C; the preferred reaction time is about 40 min. During the reaction process, the pumping rate of the reaction solution is 0.05 - 0.2 mL / min. It can be understood that the pumping rate can be a certain value among 0.05 mL / min, 0.06 mL / min, 0.07 mL / min, 0.08 mL / min, 0.09 mL / min, 0.1 mL / min, 0.11 mL / min, 0.12 mL / min, 0.13 mL / min, 0.14 mL / min, 0.15 mL / min, 0.16 mL / min, 0.17 mL / min, 0.18 mL / min, 0.19 mL / min, 0.2 mL / min or any value within the above range; more preferably, the pumping rate is 0.18 mL / min.

[0045] In step (4) of the above process for preparing double-walled carbon nanotubes, after the reaction ends, the reaction is maintained for a period of time, which is beneficial to the full reaction of the system. Specifically, the time for maintaining the reaction temperature is 10 - 60 min. It can be understood that the above time can be a certain value among 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min or any value within the above range; more preferably, it is 20 min.

[0046] In step (4) of the above process for preparing double-walled carbon nanotubes, during cooling, the introduction of hydrogen is stopped first, and then the introduction of argon is maintained until it is cooled to room temperature.

[0047] To more specifically present the technical concept and effect of the present invention, the following embodiments are provided by the present invention for further description.

[0048] Example 1

[0049] A method for preparing double-walled carbon nanotubes, comprising the following steps:

[0050] (1) Prepare the reaction solution: According to the mass ratio of 0.4:4:100, add thiophene and the catalyst to absolute ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0051] (2) Air replacement: Pass argon with a flow rate of 220 mL / min into the quartz tube reactor for air replacement;

[0052] (3) After the replacement is completed, heat up at a heating rate of 10 °C / min and introduce a mixed gas of hydrogen and argon with flow rates of 550 mL / min and 350 mL / min respectively. When the temperature rises to 1090 °C, inject the reaction solution preheated to 360 °C into the quartz tube reactor at a rate of 0.18 mL / min and react for 40 min;

[0053] (4) After the reaction is completed, stop injecting the reaction solution, maintain the reaction temperature for 20 min, and finally cool to room temperature. Take out the reactant to obtain the double-walled carbon nanotube product.

[0054] Among them, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.25.

[0055] Example 2

[0056] A method for preparing double-walled carbon nanotubes includes the following steps:

[0057] (1) Prepare the reaction solution: According to the mass ratio of 0.35:4.2:100, add thiophene and the catalyst to anhydrous ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0058] (2) Air replacement: Introduce argon with a flow rate of 210 mL / min into the quartz tube reactor for air replacement;

[0059] (3) After the replacement is completed, heat up at a heating rate of 10 °C / min and introduce a mixed gas of hydrogen and argon with flow rates of 560 mL / min and 340 mL / min respectively. When the temperature rises to 1100 °C, inject the reaction solution preheated to 370 °C into the quartz tube reactor at a rate of 0.19 mL / min and react for 35 min;

[0060] (4) After the reaction is completed, stop injecting the reaction solution, maintain the reaction temperature for 25 min, and finally cool to room temperature. Take out the reactant to obtain the double-walled carbon nanotube product.

[0061] Among them, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.25.

[0062] Example 3

[0063] A method for preparing double-walled carbon nanotubes includes the following steps:

[0064] (1) Prepare the reaction solution: According to the mass ratio of 0.32:3.9:100, add thiophene and the catalyst to anhydrous ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0065] (2) Air displacement: Argon with a flow rate of 230 ml / min was introduced into the quartz tube reactor to displace the air.

[0066] (3) After the displacement was completed, the temperature was increased at a rate of 8 °C / min and a mixed gas of hydrogen and argon with flow rates of 540 mL / min and 360 mL / min respectively was introduced. When the temperature reached 1110 °C, the reaction solution preheated to 365 °C was injected into the quartz tube reactor at a rate of 0.19 mL / min and reacted for 30 min.

[0067] (4) After the reaction ended, the injection of the reaction solution was stopped, and the reaction temperature was maintained for 30 min. Finally, it was cooled to room temperature, and the reactant was taken out to obtain the double-walled carbon nanotube product.

[0068] Among them, the catalyst was a mixture of ferrocene and vanadocene with a molar ratio of 1:0.3.

[0069] Comparative Example 1

[0070] Compared with Example 1, only ferrocene was used as the catalyst in Comparative Example 1, and the rest were the same. Specifically, a method for preparing carbon nanotubes includes the following steps:

[0071] A method for preparing carbon nanotubes includes the following steps:

[0072] (1) Preparation of the reaction solution: Thiophene and the catalyst were added to anhydrous ethanol according to a mass ratio of 0.4:4:100, and then ultrasonically dispersed evenly to obtain the reaction solution for standby.

[0073] (2) Air displacement: Argon with a flow rate of 220 mL / min was introduced into the quartz tube reactor to displace the air.

[0074] (3) After the displacement was completed, the temperature was increased at a rate of 10 °C / min and a mixed gas of hydrogen and argon with flow rates of 550 mL / min and 350 mL / min respectively was introduced. When the temperature reached 1090 °C, the reaction solution preheated to 360 °C was injected into the quartz tube reactor at a rate of 0.18 mL / min and reacted for 40 min.

[0075] (4) After the reaction ended, the injection of the reaction solution was stopped, and the reaction temperature was maintained for 20 min. Finally, it was cooled to room temperature, and the reactant was taken out to obtain the carbon nanotube product.

[0076] Among them, the catalyst was ferrocene.

[0077] Comparative Example 2

[0078] Compared with Example 1, in Comparative Example 2, the dosage ratio of the catalyst was changed while the rest remained the same. Specifically, a method for preparing carbon nanotubes includes the following steps:

[0079] A method for preparing carbon nanotubes includes the following steps:

[0080] (1) Prepare the reaction solution: According to a mass ratio of 0.4:4:100, add thiophene and the catalyst to absolute ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0081] (2) Air displacement: Pass argon with a flow rate of 220 mL / min into the quartz tube reactor for air displacement;

[0082] (3) After the displacement is completed, heat up at a heating rate of 10 °C / min and pass a mixed gas of hydrogen and argon with flow rates of 550 mL / min and 350 mL / min respectively. When the temperature rises to 1090 °C, inject the reaction solution preheated to 360 °C into the quartz tube reactor at a rate of 0.18 mL / min and react for 40 min;

[0083] (4) After the reaction ends, stop injecting the reaction solution, maintain the reaction temperature for 20 min, and finally cool to room temperature, then take out the reactant to obtain the carbon nanotube product.

[0084] Among them, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.4.

[0085] Comparative Example 3

[0086] Compared with Example 1, in Comparative Example 3, the dosage ratio of the catalyst was changed while the rest remained the same. Specifically, a method for preparing carbon nanotubes includes the following steps:

[0087] A method for preparing carbon nanotubes includes the following steps:

[0088] (1) Prepare the reaction solution: According to a mass ratio of 0.4:4:100, add thiophene and the catalyst to absolute ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0089] (2) Air displacement: Pass argon with a flow rate of 220 mL / min into the quartz tube reactor for air displacement;

[0090] (3) After the displacement is completed, heat up at a heating rate of 10 °C / min and pass a mixed gas of hydrogen and argon with flow rates of 550 mL / min and 350 mL / min respectively. When the temperature rises to 1090 °C, inject the reaction solution preheated to 360 °C into the quartz tube reactor at a rate of 0.18 mL / min and react for 40 min;

[0091] (4) After the reaction is completed, stop injecting the reaction solution, maintain the reaction temperature for 20 min, and finally cool to room temperature. Take out the reactants to obtain the carbon nanotube product.

[0092] Among them, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.15.

[0093] Comparative Example 4

[0094] Compared with Example 1, in Comparative Example 4, the reaction solution is not preheated, and the rest are the same. Specifically, a method for preparing carbon nanotubes includes the following steps:

[0095] (1) Prepare the reaction solution: According to the mass ratio of 0.4:4:100, add thiophene and the catalyst to anhydrous ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0096] (2) Air replacement: Pass argon with a flow rate of 220 mL / min into the quartz tube reactor for air replacement;

[0097] (3) After the replacement is completed, heat up at a heating rate of 10 °C / min and pass a mixed gas of hydrogen and argon with flow rates of 550 mL / min and 350 mL / min respectively. When the temperature rises to 1090 °C, inject the reaction solution into the quartz tube reactor at a rate of 0.18 mL / min and react for 40 min;

[0098] (4) After the reaction is completed, stop injecting the reaction solution, maintain the reaction temperature for 20 min, and finally cool to room temperature. Take out the reactants to obtain the carbon nanotube product.

[0099] Among them, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.25.

[0100] Comparative Example 5

[0101] Compared with Example 1, in Comparative Example 5, the reaction temperature is adjusted to 1250 °C, and the rest are the same. Specifically, a method for preparing carbon nanotubes includes the following steps:

[0102] (1) Prepare the reaction solution: According to the mass ratio of 0.4:4:100, add thiophene and the catalyst to anhydrous ethanol, and then ultrasonically disperse evenly to obtain the reaction solution for standby;

[0103] (2) Air replacement: Pass argon with a flow rate of 220 mL / min into the quartz tube reactor for air replacement;

[0104] (3) After the replacement is completed, heat up at a heating rate of 10 °C / min and introduce a mixed gas of hydrogen and argon with flow rates of 550 mL / min and 350 mL / min respectively. When the temperature rises to 1250 °C, inject the reaction solution preheated to 360 °C into the quartz tube reactor at a rate of 0.18 mL / min and react for 40 min;

[0105] (4) After the reaction is completed, stop injecting the reaction solution, maintain the reaction temperature for 20 min, and finally cool to room temperature. Take out the reactant to obtain the carbon nanotube product.

[0106] Among them, the catalyst is a mixture of ferrocene and vanadocene with a molar ratio of 1:0.25.

[0107] Next, perform performance tests on the carbon nanotube products prepared in Example 1 and Comparative Examples 1-5, as follows:

[0108] First, wash the obtained carbon nanotube product with 6 mol / L hydrochloric acid, dry it, then heat and reflux it with concentrated nitric acid for 2.5 h. Finally, after filtration, washing, and drying, the purification of the carbon nanotubes is completed. Test the purity of the obtained carbon nanotubes and perform Raman analysis to calculate the I G / I D value.

[0109]

[0110]

[0111] As can be seen from Table 1, the carbon nanotubes prepared in this application have high purity, good structure, and few defects, which is beneficial to the comprehensive utilization of carbon nanotubes.

[0112] The present invention uses the above embodiments to illustrate the technical concept of the present invention, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of individual raw materials of the products of the present invention, the addition of auxiliary components, and the selection of specific methods all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing double-walled carbon nanotubes, characterized in that: The steps include: (1) preparing a reaction solution: adding thiophene and a catalyst to anhydrous ethanol, and uniformly dispersing by ultrasonication to obtain a reaction solution for later use; (2) Air replacement: introducing argon gas into the quartz tube reactor to replace the air; (3) After the replacement is completed, the temperature is raised and a carrier gas is introduced. When the temperature reaches the reaction temperature, the preheated reaction solution is injected into the quartz tube reactor to start the reaction; (4) After the reaction is completed, stop injecting the reaction liquid, maintain the reaction temperature for a period of time, and finally cool to room temperature, take out the reactant, and obtain the double-walled carbon nanotube product.

2. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (1), the catalyst is a mixture of ferrocene and vanadium cyclopentadienyl in a molar ratio of 1:0.2-0.

35.

3. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (1), the mass ratio of thiophene, catalyst and anhydrous ethanol is 0.3-0.5:2-5:

100.

4. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (2), the flow rate of argon gas is 200-300 mL / min.

5. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (3), the heating rate is 5-50°C / min, the carrier gas is a mixture of hydrogen and argon, the flow rate of hydrogen is 500-650mL / min, and the flow rate of argon is 300-450mL / min.

6. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (3), the preheating temperature of the reaction solution is 350-450°C.

7. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (4), the reaction temperature is 1080-1150° C., the reaction time is 0.5-5 h, and the injection rate of the reaction solution is 0.05-0.2 mL / min.

8. The method for preparing carbon nanotubes according to claim 1, characterized in that: In step (4), the reaction temperature is maintained for a reaction time of 10 to 60 minutes.

9. The method for preparing double-walled carbon nanotubes according to claim 1, characterized in that: In step (4), the cooling process is as follows: first stop the introduction of hydrogen and continue to introduce argon until cooling to room temperature.

10. A double-walled carbon nanotube prepared by the method according to any one of claims 1 to 9.

Images