Single-walled carbon nanotube and preparation method and device thereof

Abstract

The invention discloses a single-walled carbon nanotube and a preparation method and device thereof, and belongs to the technical field of nano materials. The device comprises an inert gas cylinder, a carrier gas injection pipeline, a gas flow controller, a cavity, a positive electrode bar, a negative electrode bar, two graphite felt electrodes woven with carbon fibers, a stainless steel screen, a filter membrane, a graphite table and a tubular furnace. When the electrode starts to discharge and the temperature of the high-temperature plasma gasification area reaches the gasification temperature of the solid carbon source and the solid catalyst, the solid carbon source and the catalyst start to be gasified, gasified reactants enter the sample growth area along with the inert gas flow to grow, and the grown single-walled carbon nanotubes reach the sample deposition area along with the gas flow. The device disclosed by the invention can generate uniform, stable and high-capacity ultrahigh-temperature plasma under normal pressure and relatively low voltage and current, and the simple and practical plasma technology is low in energy consumption, green and environment-friendly, can be used for macro preparation and is beneficial to overcoming the challenge of high-temperature synthesis.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and in particular relates to a single-walled carbon nanotube and a preparation method and device thereof. Background Art

[0002] Since single-walled carbon nanotubes (SWNTs) were discovered in 1993, they have a unique structure with high aspect ratio, high Young's modulus, high conductivity and excellent semiconductor properties. They have broad potential application prospects in the fields of nanoelectronic components, hydrogen storage, field emission and composite materials, and have set off a global research boom in the field of carbon materials. Although the synthesis method of single-walled carbon nanotubes is gradually becoming mature, facing the huge application market, designing an economical, efficient and environmentally friendly method for the large-scale synthesis of single-walled carbon nanotubes is still a daunting challenge.

[0003] So far, there are three main methods for preparing single-walled carbon nanotubes: chemical vapor deposition, arc method and laser ablation.

[0004] In recent years, based on chemical vapor deposition technology, different quantitative production equipment can be developed according to the principle of chemical vapor deposition, which are mainly divided into two categories: floating catalysis and fluidized bed growth system. Among them, the floating catalysis method is generally used to provide carbon nanotube film samples. Its products contain various impurities such as amorphous carbon and metal catalysts. Therefore, before using carbon nanotube materials, the crude carbon nanotube products must be purified and separated as necessary. The team of Academician Cheng Huiming of the Institute of Metal Research, Chinese Academy of Sciences, reported the difference in chemical stability between metallic and semiconducting single-walled carbon nanotubes, and proposed an oxygen-assisted floating catalyst chemical vapor deposition method to grow semiconducting single-walled carbon nanotubes, directly preparing a large sample with a semiconducting carbon nanotube content of 90%. (Yu B, Liu C, Hou PX, Tian Y, Li SS, Liu BL, Li F, Esko I. Kauppinen, and Cheng HM. Bulk Synthesis of Large Diameter Semiconducting Single-Walled Carbon Nanotubes by Oxygen-Assisted Floating Catalyst Chemical Vapor Deposition. Journal of the American Chemical Society, 2011, 133, (14): 5232-5235). Fluidized bed method is more commonly used in the current commercialization of carbon nanotubes, and it is easier to achieve the amplification of carbon nanotube production. The production of carbon nanotubes has also developed from the original several grams to the current kilogram level. Professor Wei Fei's team at Tsinghua University reported the use of vermiculite and layered double metal hydroxide templates as carriers, loading metal iron particles in the interlayer gaps, and using fluidized bed technology to prepare single-walled carbon nanotubes. (Literature Zhao MQ, Zhang Q, Huang JQ, Nie JQ, Wei F, Layered double hydroxides as catalysts for the efficient growth of high quality single-walled carbon nanotubes in afluidizedbed reactor, Carbon 48 (2010) 3260-3270).

[0005] When the arc discharge method uses a solid carbon source, due to the requirement for electrode conductivity, a binder or carbon powder needs to be mixed with coal to form an electrode, and the prepared product has a complex composition, containing many products such as carbon balls with a high degree of graphitization, multi-walled carbon nanotubes or onion carbon.

[0006] The laser ablation process does not require conductivity, and the laser is used to evaporate the carbon source and catalyst, but the equipment is complex, expensive, and has high energy consumption, and does not have the advantage of scalability.

[0007] In summary, the similarities among different preparation methods are that single-walled carbon nanotubes are mainly transformed by the interaction between carbon precursors and catalysts. The catalyst provides a direct template for the growth of carbon nanotubes. Therefore, the morphology of the catalyst and the distribution of the surface atomic structure determine the edge structure of the carbon nanotubes and the final chiral structure. It can be seen that the catalyst plays an important role in the growth of single-walled carbon nanotubes. At present, it is a problem to be optimized and solved to make the catalyst continuously change from solid to atomic state. The catalyst used in the chemical vapor deposition method generally needs to be treated in advance, rather than directly using solid iron, cobalt and nickel as catalysts. The laser ablation method uses the energy of the laser to atomize the solid catalyst, which has high energy consumption and high cost, and is not conducive to mass production. The arc discharge method is a small area plasma generated by the arc from point to point or point to surface, which has high energy but is unstable. We innovated a plasma preparation device proposed by Professor Hu Liangbing to provide the atomic catalyst required in the preparation process of single-walled carbon nanotubes.

[0008] In 2023, Professor Hu Liangbing and others first proposed the atmospheric-pressure ultrahigh temperature stable plasma technology (USP) in Nature (Hu LB, Xie H, Zhang QA stable atmospheric-pressure plasma for extreme-temperature synthesis. Nature, 2023, 10, 1038). Using graphite felt as an electrode, brushing out some long fibers to trigger plasma, and short fibers to stabilize and expand plasma, multi-walled carbon nanotubes were prepared in situ with carbon black under catalyst-free conditions. During the experiment, we found that the long and short fiber graphite felt prepared by this method could not ensure the repeatability and success of the experiment by adjusting the appropriate resistance. Therefore, we improved the original graphite felt by weaving carbon fibers on the graphite felt. The improved carbon fiber reinforced electrode can adjust the resistance by trimming the length of the carbon fiber, and the resistance is used to judge whether plasma can be generated. Our method uses carbon fiber reinforced electrodes for the first time, and can successfully generate single-walled carbon nanotubes in ultrahigh temperature plasma by selecting appropriate transition metal catalysts and using solid carbon sources such as bituminous coal. Summary of the invention

[0009] In view of the problems of high energy consumption and high cost in the current preparation methods of single-walled carbon nanotubes, the present invention provides a single-walled carbon nanotube and a preparation method and device thereof.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] A device for preparing single-walled carbon nanotubes, the device comprising a plasma gasification zone, a sample growth zone, and a sample deposition zone;

[0012] The plasma gasification zone is used to gasify the solid carbon source and the catalyst, and the gasified catalyst atoms collide with each other and aggregate to form catalyst nanoparticles;

[0013] The sample growth zone is used to make the gasified carbon atoms grow in a gas phase on the surface of the catalyst nanoparticles to form single-walled carbon nanotubes;

[0014] The sample deposition area is used to collect the generated single-walled carbon nanotubes by condensation at room temperature;

[0015] The plasma gasification zone is connected to one end of the sample growth zone, and the other end of the sample growth zone is connected to the sample deposition zone;

[0016] The plasma gasification zone adopts two graphite felts woven with carbon fibers which are opposite to each other up and down as electrodes, and the solid carbon source and the catalyst are dispersed between the two electrodes.

[0017] Further, the plasma gasification zone includes: an inert gas cylinder, a carrier gas injection pipeline, a gas flow controller, a cavity, a positive electrode rod, a negative electrode rod, two graphite felt electrodes woven with carbon fibers, a stainless steel screen, a filter membrane, and a graphite table; the sample growth zone includes a tubular furnace;

[0018] Furthermore, the inert gas cylinder is connected to the carrier gas injection pipeline, and the carrier gas flow rate is controlled by a gas flow controller arranged on the carrier gas injection pipeline; the cavity is a quartz tube, and both ends are sealed with flanges and sealing rings; the constant voltage power supply is connected to one end of the positive electrode rod and the negative electrode rod through a wire, and the other end of the positive electrode rod and the negative electrode rod enter the cavity through the air inlet of the flange at the head end of the cavity, and the positive electrode rod and the negative electrode rod are insulated and supported by boron nitride material; two graphite felt electrodes woven with carbon fibers up and down are arranged in the cavity, and the two graphite felt electrodes woven with carbon fibers up and down are respectively connected to the other end of the positive electrode rod and the negative electrode rod; a filter membrane is arranged at the end of the cavity, and a stainless steel screen is installed between the filter membrane and the end flange to support the filter membrane to prevent the filter membrane from being broken during vacuuming; the other end of the carrier gas injection pipeline passes through the air inlet on the flange at the head end of the cavity to correspond to the gap between the two graphite felt electrodes woven with carbon fibers up and down; a graphite table is composed of two graphite felt electrodes woven with carbon fibers up and down; a tubular furnace is arranged at the end of the graphite table ();

[0019] The end flange of the chamber is connected to the sample deposition area through a pipeline.

[0020] Furthermore, the carrier gas injection pipeline is made of a stainless steel tube, the positive electrode rod and the negative electrode rod are both metal rods used for conducting electricity and connecting the graphite table; the sealing ring is a polytetrafluoroethylene sealing ring;

[0021] Furthermore, the constant voltage power supply is a device for setting the discharge voltage and current. The voltage is set to 0-220V and the current is set to 0-100A according to the requirements.

[0022] Furthermore, the graphite felt electrode woven with carbon fibers is woven with carbon fiber bundles with an interval of 5 mm, each bundle contains 6000 to 24000 carbon fibers, and the diameter of each carbon fiber is 4 to 10 μm.

[0023] Furthermore, the graphite felt electrode woven with carbon fiber is a rectangular graphite felt with a length of 10 to 200 mm and a width of 10 to 200 mm, or a cylindrical graphite felt or a circular graphite felt with a diameter of 10 to 100 mm or other shapes can be set according to the needs; the carbon fiber can be selected according to the needs. 500 、T 600 、T 700 、T 800 Etc. The carbon fiber T 800 Tensile strength: 5880Mpa, tensile modulus: 294Gpa, elongation: 2.0%, density: 1.80g / cm 3 , diameter: 7μm, tow: 6K. Different types of carbon fiber can be selected according to needs, and the length of the carbon fiber woven on the graphite felt can be trimmed according to the resistance.

[0024] Furthermore, the center line of the electrode rod is perpendicular to the center line of the horizontally arranged carbon fiber reinforced graphite felt electrode.

[0025] A method for preparing single-walled carbon nanotubes using the above device comprises the following steps:

[0026] Step 1, a solid carbon source and a catalyst are mixed in proportion to obtain reactant particles, and the reactant particles are added to the graphite felt hooked with carbon fibers, and the graphite felt loaded with reactants is loaded into the graphite table electrode, and the electrode loaded with reactants is inserted into the quartz tube from one end of the quartz tube and fixed with a flange; the filter membrane is placed on the stainless steel screen and the flange is fixed; the quartz tube is placed, the furnace of the tube furnace is closed, the power supply is connected, and the vacuum pump is started to evacuate the tube;

[0027] Step 2, adjust the resistance to the resistance value required for the reaction, start the tube furnace to heat up, and start discharging after reaching a suitable temperature; adjust the gas flow rate to a suitable gas flow rate through the gas flow controller, and adjust the pressure gauge to a suitable negative pressure;

[0028] Step 3, set appropriate discharge voltage, current, discharge time, discharge times and interval time; start plasma discharge reaction, and after discharge is completed, stop data recording in time and save the data;

[0029] Step 4, take out the reaction product after cooling down: turn off the switch of the constant voltage power supply, wait for the temperature of the tube furnace to drop to room temperature, turn off the vacuum pump to let the air pressure return to normal pressure, open the flange, take out the filter membrane with the deposited product and the reaction product of the carbon felt in situ for storage and subsequent testing.

[0030] Furthermore, the mass ratio of the solid carbon source to the catalyst is 100:0 to 100:10; the reactant particles are 0.15 g to 5 g;

[0031] Furthermore, the temperature for heating in step 2 is 800°C to 1000°C.

[0032] Furthermore, in step 2, the gas flow rate is 600-2000 sccm.

[0033] Furthermore, in step 2, the negative pressure is -0.03 to 0 MPa.

[0034] Furthermore, the resistance value in S2) is 1 to 2 ohms.

[0035] Furthermore, in step 3, the discharge voltage is 10-220V, the current is 10-100A, each discharge time is 30-60 seconds, the number of discharges is 1-10 times, and the interval time is 0.1-1S.

[0036] Further, the catalyst is one or two of iron powder, cobalt powder, and nickel powder, or a solid catalyst using one or two of iron wire, cobalt wire, and nickel wire and other metal compounds;

[0037] Furthermore, the carbon source is at least one of a solid carbon source such as bituminous coal, anthracite, graphite, carbon black, a gaseous carbon source such as ethanol, methanol, and a gaseous carbon source such as methane, ethane, etc.

[0038] Furthermore, the gas in step 2 is one of argon, helium and nitrogen.

[0039] In order to ensure the complete gasification of the solid carbon source and the catalyst, the carbon source powder cannot be directly used for heating, because the solid carbon source is light and can be easily carried to the deposition area by the argon gas flow, resulting in incomplete gasification of the reactants. The reactants need to be pretreated, and the catalyst is mixed into the ball-milled micron carbon source powder in a certain proportion and mixed evenly. The mixed powder is placed in a tablet press for tableting. A mold with an inner diameter of 15 mm is used, and the mixed powder is pressed at 20 MPa for 30 minutes with a tablet press. Usually, a target with a height of 8 mm can be obtained with 2 grams of sample. The target is annealed in Ar at 1173K for 1 hour to remove volatile components. The annealed target is broken into millet-sized particles with a small hammer for use as a reactant, ensuring the complete gasification of the reactant.

[0040] The preparation of graphite felt in the plasma gasification zone plays a key role in the operation of the reaction. Cut graphite felt with a length of 26mm, a width of 20mm and a height of 8mm; evenly mark 15 points of 3*5 on the cut graphite felt, and hook a cluster of carbon fiber on each point. A cluster consists of 12,000 carbon fibers. Carbon fiber is the key to initiating plasma. When using graphite felt without carbon fiber for experiments, it was found that there was no way to generate plasma for a long time and it was impossible to continuously provide carbon atoms and catalyst atoms.

[0041] Compared with the prior art, the present invention has the following advantages:

[0042] By adopting the device of the present invention, ultra-high temperature, large volume, uniform and stable plasma can be instantly generated under normal pressure, relatively low voltage and current, and stable operation can be performed for a long time under high temperature state, and solid carbon source and catalyst can be continuously evaporated to provide carbon atoms and catalyst atoms to the growth zone, and finally high-quality single-walled carbon nanotubes can be obtained in the deposition zone after growth in the growth zone. This is particularly important for low-energy consumption, green, rapid and large-scale preparation of high-quality single-walled carbon nanotubes.

[0043] The device of the present invention can not only effectively reduce the power of the plasma generator for preparing carbon sources and catalyst nanoparticles, save energy and reduce consumption, but also provide ultra-high temperature, large volume, uniform and stable plasma in a short time, which can be used for large-scale preparation of various high-temperature materials and has great commercial value. At the same time, it has similar effects on other similar reactors and has certain versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1It is an overall schematic diagram of the device of the present invention;

[0046] Figure 2 It is a schematic diagram of the arrangement structure of the plasma gasification zone;

[0047] Figure 3 is a schematic diagram of the sample growth area layout structure;

[0048] Figure 4 is a schematic diagram of the sample collection area layout structure;

[0049] Figure 5 is a scanning electron microscope image of the single-walled carbon nanotube prepared in Example 1 of the present invention;

[0050] Figure 6 is a transmission electron microscope image of the single-walled carbon nanotube prepared in Example 1 of the present invention;

[0051] Figure 7 This is the Raman spectrum of the single-walled carbon nanotubes prepared in Example 1 of the present invention.

[0052] Figure numerals: 1. inert gas cylinder; 2. constant voltage power supply; 3. gas flow controller; 4. carrier gas injection pipeline; 5. cavity; 6. positive electrode rod; 7. negative electrode rod; 8. graphite felt electrode woven with carbon fiber; 9. stainless steel screen; 10. filter membrane; 11. graphite table; 12. flange; 13. sealing ring; 14. tubular furnace; 15. inert gas; 16. boron nitride support; 17. plasma gasification zone; 18. sample growth zone; 19. sample deposition zone. DETAILED DESCRIPTION

[0053] In order to gain a deeper understanding of the present invention, we will provide a comprehensive and detailed description of the present invention. However, the present invention has multiple implementations and is not limited to the specific examples listed herein. The presentation of these examples is intended to deepen the comprehensive understanding of the disclosure of the present invention.

[0054] A device for preparing single-walled carbon nanotubes, such as Figure 1 As shown, the device includes a plasma gasification area, a sample growth area, and a sample deposition area;

[0055] The plasma gasification zone is used to gasify the solid carbon source and the catalyst, and the gasified catalyst atoms collide with each other and aggregate to form catalyst nanoparticles;

[0056] The sample growth zone is used to make the gasified carbon atoms grow in a gas phase on the surface of the catalyst nanoparticles to form single-walled carbon nanotubes;

[0057] The sample deposition area is used to collect the generated single-walled carbon nanotubes by condensation at room temperature;

[0058] The plasma gasification zone is connected to one end of the sample growth zone, and the other end of the sample growth zone is connected to the sample deposition zone;

[0059] The plasma gasification zone adopts two graphite felts woven with carbon fibers which are opposite to each other up and down as electrodes, and the solid carbon source and the catalyst are dispersed between the two electrodes.

[0060] The plasma gasification zone includes: an inert gas cylinder 1, a carrier gas injection pipeline 4, a gas flow controller 3, a cavity 5, a positive electrode rod 6, a negative electrode rod 7, two graphite felt electrodes woven with carbon fibers 8, a stainless steel screen 9, a filter membrane 10, and a graphite table 11; the sample growth zone includes a tubular furnace 14; Figure 2 As shown;

[0061] The inert gas cylinder 1 is connected to the carrier gas injection pipeline 4, and the carrier gas flow rate is controlled by the gas flow controller 3 arranged on the carrier gas injection pipeline 4; the cavity 5 is a quartz tube, and the two ends are sealed with flanges 12 and sealing rings 13; the constant voltage power supply 2 is connected to one end of the positive electrode rod 6 and the negative electrode rod 7 through a wire, and the other end of the positive electrode rod 6 and the negative electrode rod 7 enters the cavity 5 through the air inlet of the flange at the head end of the cavity 5, and the positive electrode rod 6 and the negative electrode rod 7 are insulated and supported by a boron nitride support; two graphite felt electrodes 8 woven with carbon fibers on the upper and lower sides are arranged in the cavity 5, and the two graphite felt electrodes woven with carbon fibers on the upper and lower sides are provided. 8 are connected to the other ends of the positive electrode rod 6 and the negative electrode rod 7 respectively; a filter membrane 10 is provided at the end of the cavity 5, and a stainless steel screen 9 is installed between the filter membrane 10 and the flange 12 at the end to support the filter membrane 10 to prevent the filter membrane from being broken during vacuuming; the other end of the carrier gas injection pipeline 4 passes through the air inlet on the flange 12 at the head end of the cavity 5 to correspond to the gap between the two graphite felt electrodes 8 woven with carbon fibers on the top and bottom; a graphite table 11 is composed of two graphite felt electrodes woven with carbon fibers on the top and bottom; a tubular furnace 14 is arranged at the end of the graphite table 11; the flange 12 at the end of the cavity 5 is connected to the sample deposition area through a pipeline.

[0062] The carrier gas injection pipeline 4 is made of a stainless steel pipe. The positive electrode rod 6 and the negative electrode rod 7 are both metal rods used for conducting electricity and connecting the graphite stage 11 .

[0063] The constant voltage power supply 2 is a device for setting the discharge voltage and current. The voltage is set to 0-220V and the current is set to 0-100A according to the requirements.

[0064] The graphite felt electrode woven with carbon fibers is woven with carbon fiber bundles with an interval of 5 mm, each bundle contains 6000 to 24000 carbon fibers, and the diameter of each carbon fiber is 4 to 10 μm.

[0065] The graphite felt electrode woven with carbon fiber is a rectangular graphite felt with a length of 10 to 200 mm and a width of 10 to 200 mm, or can be a roller-shaped or circular graphite felt with a diameter of 10 to 100 mm or other shapes of graphite felt according to requirements.

[0066] A method for preparing single-walled carbon nanotubes using the above device comprises the following steps:

[0067] Step 1, a solid carbon source and a catalyst are mixed in proportion to obtain reactant particles, and the reactant particles are added to the graphite felt hooked with carbon fibers, and the graphite felt loaded with reactants is loaded into the graphite table electrode, and the electrode loaded with reactants is inserted into the quartz tube from one end of the quartz tube and fixed with a flange; the filter membrane is placed on the stainless steel screen and the flange is fixed; the quartz tube is placed, the furnace of the tube furnace is closed, the power supply is connected, and the vacuum pump is started to evacuate the tube;

[0068] Step 2, adjust the resistance to the resistance value required for the reaction, start the tube furnace to heat up, and start discharging after reaching a suitable temperature; adjust the gas flow rate to a suitable gas flow rate through the gas flow controller, and adjust the pressure gauge to a suitable negative pressure;

[0069] Step 3, set appropriate discharge voltage, current, discharge time, discharge times and interval time; start plasma discharge reaction, and after discharge is completed, stop data recording in time and save the data;

[0070] Step 4, take out the reaction product after cooling down: turn off the switch of the constant voltage power supply, wait for the temperature of the tube furnace to drop to room temperature, turn off the vacuum pump to let the air pressure return to normal pressure, open the flange, take out the filter membrane with the deposited product and the reaction product of the carbon felt in situ for storage and subsequent testing.

[0071] The mass ratio of the solid carbon source to the catalyst is 100:0 to 100:10; the reactant particles are 0.15 g to 5 g;

[0072] The temperature for heating in step 2 is 800°C to 1000°C; the gas flow rate in step 2 is 600 to 2000sccm; the negative pressure in step 2 is -0.03 to 0MPa; the discharge voltage in step 3 is 10 to 220V, the current is 10 to 100A, each discharge time is 30 to 60 seconds, the number of discharges is 1 to 10 times, and the interval time is 0.1 to 1S.

[0073] The catalyst is one or two of iron powder, cobalt powder, and nickel powder; the carbon source is a solid carbon source of bituminous coal, anthracite, graphite, or carbon black, or a gaseous carbon source of methane, ethanol, ethane, or methanol; and the gas in step 2 is one of argon, helium, and nitrogen.

[0074] Embodiment 1:

[0075] Weigh 0.15g of the treated reactant particles and add them to the graphite felt hooked with carbon fiber, and then put the graphite felt containing the reactants into the graphite table electrode; use a multimeter to measure the resistance and adjust the electrode resistance to 1-2Ω; install a stainless steel screen in front of the end flange, and then put in the filter membrane required for sample deposition.

[0076] Turn on the vacuum pump to exhaust the air in the reaction device to keep the device in a vacuum state. The temperature of the growth zone where the tubular furnace is located is programmed to 950°C. When the set temperature is reached, open the gas cylinder to introduce high-purity argon gas, adjust the fine-tuning valve to control the flow rate to around 1700sccm, and at the same time adjust the rear-end gas unloading valve to keep the pressure of the entire device stable at around -0.03Mpa.

[0077] Adjust the voltage of the electric box (36V, 83A) to the maximum 36V, turn on the power switch, and continuously discharge in the plasma gasification zone to generate plasma. The generation of products can be clearly observed in the deposition area. At the same time, it can be observed that the reading of the electric box gradually stabilizes, generally maintaining around 25V, 80A. Use a mobile phone to record the video and the experiment duration, which is generally controlled between 30S-6min.

[0078] Embodiment 2:

[0079] Weigh 0.15g of the treated reactant particles and add them to the graphite felt hooked with carbon fiber. Put the graphite felt containing the reactants into the graphite table electrode. Use a multimeter to measure the resistance between the two electrodes and control it at 1-2 ohms. Insert the electrode containing the reactants into the quartz tube from one end and fix it with a flange. Install a stainless steel screen in front of the end flange and then put in the filter membrane required for sample deposition.

[0080] Turn on the vacuum pump to exhaust the air in the reaction device to keep the device in a vacuum state. The temperature of the growth zone where the tubular furnace is located is programmed to 950°C. When the set temperature is reached, open the gas cylinder to introduce high-purity argon gas, adjust the fine-tuning valve to control the flow rate to around 1700sccm, and at the same time adjust the rear-end gas unloading valve to keep the pressure of the entire device stable at around -0.03Mpa.

[0081] Adjust the voltage of the electric box (36V, 83A) to the maximum 36V, turn on the power switch, and continuously discharge in the plasma gasification zone to generate plasma. The generation of products can be clearly observed in the deposition area. At the same time, it can be observed that the reading of the electric box gradually stabilizes, generally maintaining around 25V, 80A. Use a mobile phone to record the video and the experiment duration, which is generally controlled between 30S-6min.

[0082] Embodiment 3:

[0083] The same process as in Example 1 is adopted except that the stainless steel tube required for the carrier gas inlet is removed and the carrier gas is introduced directly from the flange; the small tubular furnace (heating zone 20 cm) is replaced with a large tubular furnace (heating zone 40 cm) to increase the length of the original quartz tube; other operating techniques remain unchanged and are the same as in Example 1.

[0084] Furthermore, the carbon fiber reinforced graphite felt electrode is a rectangular graphite felt of 20 mm*26 mm, on which 3*5 carbon fiber bundles are woven, a total of 15 bundles, each bundle containing 12,000 carbon fibers, and each carbon fiber having a diameter of 4 to 5 μm.

[0085] Furthermore, the center lines of the two electrode rods are perpendicular to the center line of the horizontally arranged graphite felt electrode woven with carbon fibers.

[0086] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. Although the illustrative specific embodiments of the present invention are described above to facilitate the understanding of the present invention by the technical personnel in the field, it should be clear that the present invention is not limited to the scope of the specific embodiments. For the ordinary technical personnel in the field, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A device for preparing single-walled carbon nanotubes, characterized in that: The device includes a plasma gasification area, a sample growth area, and a sample deposition area; The plasma gasification zone is used to gasify the solid carbon source and the catalyst, and the gasified catalyst atoms collide with each other and aggregate to form catalyst nanoparticles; The sample growth zone is used to make the gasified carbon atoms grow in a gas phase on the surface of the catalyst nanoparticles to form single-walled carbon nanotubes; The sample deposition area is used to collect the generated single-walled carbon nanotubes by condensation at room temperature; The plasma gasification zone is connected to one end of the sample growth zone, and the other end of the sample growth zone is connected to the sample deposition zone; The plasma gasification zone adopts two graphite felts woven with carbon fibers which are opposite to each other up and down as electrodes, and the solid carbon source and the catalyst are dispersed between the two electrodes.

2. The device for preparing single-walled carbon nanotubes according to claim 1, characterized in that: The plasma gasification zone comprises: an inert gas cylinder (1), a carrier gas injection pipeline (4), a gas flow controller (3), a cavity (5), a positive electrode rod (6), a negative electrode rod (7), two graphite felt electrodes woven with carbon fibers (8), a stainless steel screen (9, a filter membrane (10), and a graphite table (11); the sample growth zone comprises a tubular furnace (14); The inert gas cylinder (1) is connected to a carrier gas injection pipeline (4), and the carrier gas flow rate is controlled by a gas flow controller (3) arranged on the carrier gas injection pipeline (4); the cavity (5) is a quartz tube, and the two ends are sealed by flanges (12) and sealing rings (13); the constant voltage power supply (2) is connected to one end of a positive electrode rod (6) and a negative electrode rod (7) through a wire, and the other ends of the positive electrode rod (6) and the negative electrode rod (7) pass through the air inlet of the flange at the head end of the cavity (5) and enter the cavity (5), and a boron nitride support is used to insulate and support the positive electrode rod (6) and the negative electrode rod (7); two graphite felt electrodes (8) woven with carbon fibers on the top and bottom are arranged in the cavity (5), and the two graphite felt electrodes (8) woven with carbon fibers on the top and bottom are 8) are respectively connected to the other ends of the positive electrode rod (6) and the negative electrode rod (7); a filter membrane (10) is provided at the end of the cavity (5), and a stainless steel screen (9) is installed between the filter membrane (10) and the flange (12) at the end to support the filter membrane (10) and prevent the filter membrane from being broken during vacuuming; the other end of the carrier gas injection pipeline (4) passes through the air inlet on the flange (12) at the head end of the cavity (5) and corresponds to the gap between the two graphite felt electrodes (8) woven with carbon fibers on the top and bottom; a graphite table (11) is composed of the two graphite felt electrodes (8) woven with carbon fibers on the top and bottom; a tubular furnace (14) is arranged at the end of the graphite table (11); and the flange (12) at the end of the cavity (5) is connected to the sample deposition area through a pipeline.

3. The device for preparing single-walled carbon nanotubes according to claim 1, characterized in that: The carrier gas injection pipeline (4) is made of a stainless steel tube, and the positive electrode rod (6) and the negative electrode rod (7) are both metal rods used for conducting electricity and connecting to the graphite stage (11).

4. The device for preparing single-walled carbon nanotubes according to claim 1, characterized in that: The constant voltage power supply (2) is a device for setting the discharge voltage and current. The voltage is set to 0-220V and the current is set to 0-100A according to the requirements.

5. The device for preparing single-walled carbon nanotubes according to claim 1, characterized in that: The graphite felt electrode woven with carbon fibers is woven with carbon fiber bundles with an interval of 5 mm, each bundle contains 6000 to 24000 carbon fibers, and the diameter of each carbon fiber is 4 to 10 μm; the graphite felt electrode woven with carbon fibers is a rectangular graphite felt with a length of 10 to 200 mm and a width of 10 to 200 mm, or can be set as a roller-shaped or circular graphite felt with a diameter of 10 to 100 mm or other shapes of graphite felt according to needs.

6. A method for preparing single-walled carbon nanotubes using the device according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1, a solid carbon source and a catalyst are mixed in proportion to obtain reactant particles, and the reactant particles are added to the graphite felt hooked with carbon fibers, and the graphite felt loaded with reactants is loaded into the graphite table electrode, and the electrode loaded with reactants is inserted into the quartz tube from one end of the quartz tube and fixed with a flange; the filter membrane is placed on the stainless steel screen and the flange is fixed; the quartz tube is placed, the furnace of the tube furnace is closed, the power supply is connected, and the vacuum pump is started to evacuate the tube; Step 2, adjust the resistance to the resistance value required for the reaction, start the tube furnace to heat up, and start discharging after reaching a suitable temperature; adjust the gas flow rate to a suitable gas flow rate through the gas flow controller, and adjust the pressure gauge to a suitable negative pressure; Step 3, set appropriate discharge voltage, current, discharge time, discharge times and interval time; start plasma discharge reaction, and after discharge is completed, stop data recording in time and save the data; Step 4, take out the reaction product after cooling down: turn off the switch of the constant voltage power supply, wait for the temperature of the tube furnace to drop to room temperature, turn off the vacuum pump to let the air pressure return to normal pressure, open the flange, take out the filter membrane with the deposited product and the reaction product of the carbon felt in situ for storage and subsequent testing.

7. The method for preparing single-walled carbon nanotubes according to claim 6, characterized in that: The mass ratio of the solid carbon source to the catalyst is 100:0 to 100:10; the reactant particles are 0.15 g to 5 g; 8. The method for preparing single-walled carbon nanotubes according to claim 6, characterized in that: The temperature for heating in step 2 is 800°C to 1000°C; the gas flow rate in step 2 is 600 to 2000sccm; the negative pressure in step 2 is -0.03 to 0MPa; the discharge voltage in step 3 is 10 to 220V, the current is 10 to 100A, each discharge time is 30 to 60 seconds, the number of discharges is 1 to 10 times, and the interval time is 0.1 to 1S.

9. The method for preparing single-walled carbon nanotubes according to claim 6, characterized in that: The catalyst is one or two of iron powder, cobalt powder, and nickel powder; the carbon source is a solid carbon source of bituminous coal, anthracite, graphite, or carbon black, or a gaseous carbon source of methane, ethanol, ethane, or methanol; and the gas in step 2 is one of argon, helium, and nitrogen.

10. Single-walled carbon nanotubes prepared by the method according to claim 6.

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