Apparatus and method for preparing single-walled carbon nanotubes by thermal plasma CVD

Abstract

The application discloses a device and a method for preparing single-wall carbon nanotubes by using thermal plasma CVD method, and relates to the technical field of nanometer carbon material preparation. The structure of the device comprises a thermal plasma arc furnace, a CVD growth chamber, a cooling chamber and a collecting tank which are connected in sequence. The structure of the thermal plasma arc furnace comprises a hollow graphite serving as a cathode, a graphite crucible serving as an anode and a furnace body. The graphite crucible is located at the lower part of the thermal plasma arc furnace, and the hollow graphite is located at the upper part of the thermal plasma arc furnace and above the graphite crucible. The device and the method adopt a two-step continuous growth process, and the yield and quality of the single-wall carbon nanotubes are significantly improved. Meanwhile, the shallow crucible and the bottom gas inlet mode can effectively avoid the common problems in the process of preparing single-wall carbon nanotubes by using a conventional plasma arc method, such as catalyst excess, coking short circuit and arc breaking, so that the reaction continuity and stability and the yield are greatly improved. The device and the method are effective routes for large-scale preparation and have important commercial value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanocarbon material preparation, and particularly provides a device and method for preparing single-walled carbon nanotubes by thermal plasma CVD. BACKGROUND

[0002] Single-walled carbon nanotubes are tubular nanomaterials formed by rolling a single layer of graphene, and have excellent mechanical, electrical and thermal properties, showing great application potential in the fields of electronic devices, energy storage and composite materials. The development of its preparation method has experienced a process from laboratory exploration to industrialization promotion. The current mainstream technologies mainly include arc discharge method, laser ablation method, chemical vapor deposition method (CVD) and its derivative processes, and different methods have their own characteristics in yield, purity, cost and structure controllability. The core challenge of SWCNTs preparation technology is how to balance large-scale production and structure precise control, and giving consideration to efficiency and quality is still a key problem for large-scale preparation and application of single-walled carbon nanotubes, and developing new efficient preparation equipment and method is still a hot spot of current research.

[0003] Chinese patent CN 201910533219.0 is a preparation method of single-walled carbon nanotubes, which uses plasma arc evaporation of catalyst metal to prepare catalyst, and simultaneously introduces carbon source gas, so that high-temperature plasma simultaneously realizes high-temperature evaporation of metal to prepare catalyst and cracking of organic carbon source, and directly prepares single-walled carbon nanotubes.

[0004] Chinese patent 202210608795.9 utilizes the high-temperature zone formed by the arc limited in the deep graphite crucible to obtain higher reaction temperature and longer reaction residence time, and simultaneously utilizes the activation effect of arc plasma to prepare single-walled carbon nanotubes with high crystallinity. SUMMARY

[0005] However, the biggest disadvantage of the above method is that the catalyst is excessively evaporated, and the catalyst particle size cannot be effectively screened. In addition, the catalyst condensation and carbon nanotube product coking formed between the electrodes will cause short circuit of the cathode and anode, thereby causing arc breakage, resulting in sharp decrease of arc stability, and it is difficult to realize stable and continuous preparation. Therefore, controlling the evaporation amount of catalyst and avoiding electrode coking are the core points for ensuring continuous preparation of high-quality products.

[0006] The present application provides the following technical solutions in view of the above problems.

[0007] In one aspect, the present application provides a device for preparing single-walled carbon nanotubes by thermal plasma CVD, and the structure of the device comprises a thermal plasma arc furnace, a CVD growth chamber, a cooling chamber and a collection tank connected in series.

[0008] The structure of the hot plasma arc furnace comprises hollow graphite as cathode, graphite crucible as anode and furnace body;

[0009] The graphite crucible is located at the lower part of the hot plasma arc furnace, the hollow graphite is located at the upper part of the hot plasma arc furnace, above the graphite crucible;

[0010] The hollow graphite enters the furnace body at a certain angle with the vertical direction of the graphite crucible, and the inclination angle is 30-80°.

[0011] The graphite crucible is a shallow crucible with a through hole at the edge, and the inner wall of the crucible is arc-shaped, with a depth of 1-5 cm.

[0012] Further, the device further comprises a gas supplementing port and a gas inlet port, wherein the gas supplementing port is located between the hot plasma arc furnace and the CVD growth chamber, and the gas inlet port is located at the left end of the hot plasma arc furnace.

[0013] Further, the structure of the collection tank comprises a screen, a pulse back-blowing port, an exhaust port and a discharge port, wherein the pulse back-blowing port and the exhaust port are located at the upper end of the collection tank, the screen is located at the lower part of the pulse back-blowing port and the exhaust port, and the discharge port is located at the lower end of the collection tank.

[0014] The collection tank is filtered and enriched by using a metal screen, and the product enriched on the screen is blown to the bottom discharge port through the pulse back-blowing port, so as to collect the finished product, and the excess gaseous material is discharged from the exhaust port.

[0015] The plasma power source has a power of 100-1000 kW, a current of 100-10000 A and a voltage of 10-500 V.

[0016] In another aspect of the present application, a method for preparing single-walled carbon nanotubes by hot plasma CVD is provided, which comprises the following steps: generating an arc between the cathode and the anode of a plasma arc furnace, raising the temperature of the furnace, sending the catalyst from the hollow cathode to the position of the graphite crucible, rapidly evaporating to form catalyst clusters, discharging the excess catalyst through the discharge port of the arc furnace, introducing the carbon source mixed gas into the plasma arc furnace through the through hole at the edge of the anode graphite crucible, combining with the catalyst clusters after cracking, growing into single-walled carbon nanotubes in the CVD growth chamber, and obtaining the final product under the carrying of the carrier gas.

[0017] Further, the method specifically comprises the following steps:

[0018] S1) introducing plasma gas, turning on the plasma power source, generating an arc between the anode and the cathode, raising the temperature of the furnace to a specified temperature, and turning on the CVD growth chamber to heat and raise the temperature to the growth temperature;

[0019] S2) The catalyst is sent to the crucible position by the hollow electrode channel, rapidly evaporated to form catalyst clusters, and the excess unevaporated catalyst particles are blown by the carrier gas blown out of the gas inlet 3 to the electric arc furnace discharge port;

[0020] S3) The carbon source gas and the carrier gas are mixed and then enter the plasma electric arc furnace through the through hole at the edge of the graphite crucible, and after high-temperature cracking, they enter the CVD growth chamber together with the catalyst;

[0021] S4) The carbon source gas and the carrier gas are further supplemented through the gas supplementing port in the CVD growth chamber to achieve sufficient growth of single-walled carbon nanotubes;

[0022] S5) The product is cooled by the carrier gas and then enters the collection tank, and the product accumulated on the screen is blown off to the discharge port through the pulse back blowing port to collect the final product.

[0023] Further, the plasma gas in step S1) is any one of argon, nitrogen, helium, hydrogen, water vapor, or a mixture of two or more of them in any mixing ratio, with a flow rate of 10-500 L / min;

[0024] The furnace designated temperature is 1200-2000℃, and the CVD chamber growth temperature is 900-1400℃.

[0025] Further, the catalyst in step S2) is a mixture of 50-95% metal powder and 5-50% catalyst promoter, wherein:

[0026] The metal powder is iron, cobalt, or nickel metal or a mixture thereof;

[0027] Or an alloy or mixture of iron, cobalt, or nickel and refractory metals, wherein the refractory metal elements are molybdenum, tungsten, tantalum, niobium, hafnium, or zirconium, and the refractory metal element content is 20-60% by weight, and the particle size is 50-350 mesh;

[0028] The catalyst promoter is any one of sulfur powder, selenium powder, iron sulfide, ferrous sulfide, nickel sulfide, or cobalt sulfide, or a mixture thereof, with a particle size of 100-500 mesh;

[0029] The catalyst feeding rate is 0.1 g / min-100 g / min.

[0030] Further, the carbon source gas in step S3) is any one of methane, ethylene, acetylene, propylene, or propane; and the carrier gas is a mixture of nitrogen, argon, or helium inert gas and hydrogen, wherein the volume of the carbon source gas is 10-80%, the volume of hydrogen is 0-35%, and the rest is nitrogen, argon, or helium inert gas, with a total flow rate of 10-200 L / min.

[0031] Furthermore, in step S4), the total flow rate of carbon source gas and carrier gas in the CVD growth chamber is further supplemented to 10-200 L / min.

[0032] Furthermore, in step S5), the aperture of the screen 10 is 0.5-50 mm, the backflushing gas is nitrogen, argon or helium, and the pulse backflushing frequency is 5-300 seconds / time.

[0033] Compared with existing technologies, the apparatus and method for preparing single-walled carbon nanotubes by thermal plasma CVD of the present invention have the following outstanding advantages:

[0034] The apparatus and method of this invention employ a two-step continuous growth process, which significantly improves the yield and quality of single-walled carbon nanotubes. At the same time, the shallow crucible and bottom gas inlet effectively avoid common problems such as catalyst overload, coking short circuit, and arc interruption in the conventional plasma arc method for preparing single-walled carbon nanotubes. This greatly improves the continuous stability and yield of the reaction, making it an effective route for large-scale preparation and of significant commercial value. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the preparation device of the present invention;

[0036] Figure 2 This is a schematic diagram of the graphite citrus structure of the present invention;

[0037] Figure 3 This is a scanning electron microscope image of the prepared carbon nanotube product;

[0038] Figure 4 This is the Raman spectrum of the prepared carbon nanotube product. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0040] like Figure 1 As shown, an apparatus for preparing single-walled carbon nanotubes by thermal plasma CVD is described. The apparatus comprises a thermal plasma arc furnace 4, a CVD growth chamber 7, a cooling chamber 8, and a collection tank 9 connected in series.

[0041] The structure of the thermal plasma arc furnace 4 includes a hollow graphite 5 as the cathode, a graphite crucible 2 as the anode, and a furnace body.

[0042] The graphite crucible 2 is located at the lower part of the thermal plasma arc furnace 4, and the hollow graphite 5 is located at the upper part of the thermal plasma arc furnace 4, above the graphite crucible 2.

[0043] The hollow graphite 5 and the graphite crucible 2 enter the furnace body at a certain angle to the vertical direction, with an inclination angle of 30 to 80°.

[0044] like Figure 2 As shown, the graphite crucible 2 is a shallow crucible with a through hole 1 on the edge, and the inner wall of the crucible is arc-shaped with a depth of 1-5cm.

[0045] The device also includes a gas supply port 6 and an air inlet 3, wherein the gas supply port 6 is located between the thermal plasma arc furnace 4 and the CVD growth chamber 7; and the air inlet 3 is located at the left end of the thermal plasma arc furnace 4.

[0046] The structure of the collection tank 9 includes a screen 10, a pulse backflush port 11, an exhaust port 12, and a discharge port 13. The pulse backflush port 11 and the exhaust port 12 are located at the upper end of the collection tank 9, the screen 10 is located at the lower part of the pulse backflush port 11 and the exhaust port 12, and the discharge port 13 is located at the lower end of the collection tank 9.

[0047] The collection tank 9 uses a metal screen 10 for filtration and enrichment. Combined with the pulse backflush port 11, the product enriched on the screen 10 is blown down to the bottom discharge port 13, thereby collecting the finished product. Excess gaseous substances are discharged from the air outlet 12.

[0048] Example 1

[0049] Adopting such Figure 1 The apparatus shown is for preparing single-walled carbon nanotubes using thermal plasma CVD. This equipment consists of a thermal plasma arc furnace, a CVD growth chamber, a cooling chamber, and a collection tank connected in series. The thermal plasma arc furnace comprises a hollow graphite cathode, a graphite crucible anode, a furnace body, and auxiliary systems. The hollow graphite cathode and the graphite crucible anode enter the furnace body at a 60° angle. The graphite crucible anode is a shallow crucible with through-holes at the edges (e.g., [example of a shallow crucible]). Figure 2 The crucible has an arc-shaped inner wall with a depth of 2cm; the plasma power supply has a power of 150kW, a current of 1000A, and a voltage of 150V.

[0050] Preparation process of single-walled carbon nanotubes:

[0051] S1) Introduce argon plasma gas at a flow rate of 50 L / min, turn on the plasma power supply, generate a plasma arc between the anode and cathode, raise the furnace temperature to 1500℃, and simultaneously turn on the CVD growth chamber heating to raise the temperature to the growth temperature of 1200℃.

[0052] S2) The catalyst (Fe80%-FeS20% mixed powder, particle size 200 mesh) is fed to the crucible position through the hollow electrode channel at a feeding rate of 5g / min. It evaporates rapidly to form catalyst clusters, and excess unevaporated catalyst particles are blown to the discharge port of the electric arc furnace.

[0053] S3) The carbon source gas and the carrier gas are mixed and then enter the plasma arc furnace through the channel outside the graphite crucible. After high-temperature cracking, the mixture enters the CVD growth chamber together with the catalyst. The volume fraction of the mixed gas is 20% methane, 40% hydrogen, and the remainder is argon. The flow rate is 50 L / min.

[0054] S4) Further replenish carbon source gas and carrier gas in the CVD growth chamber to achieve full growth of single-walled carbon nanotubes. The volume fraction of the replenished carbon source gas mixture is 40% methane, 20% hydrogen, and the remainder is argon, with a flow rate of 50 L / min.

[0055] S5) After being cooled by the carrier gas in the cooling section, the product enters the collection tank. The product enriched in the 2mm pore size filter is blown off to the discharge port by nitrogen pulse backflushing (backflushing frequency 15 seconds / time) to obtain the final product.

[0056] The reaction proceeded steadily and continuously. After 72 hours, the product was collected and weighed, and the yield of single-walled carbon nanotubes was calculated to be approximately 1250 g / h. The product was calcined in a muffle furnace at 900℃ for 2 hours, and the ash content was weighed, yielding a calculated purity of 86.3%. The morphology of the product was observed using a scanning electron microscope as follows: Figure 4 As shown, the crystallinity is evaluated using the ratio of the peak intensities of the G and D peaks in the Raman spectrum. Figure 3 As shown, the G / D ratio is ~68.4.

[0057] Example 2

[0058] Adopting such Figure 1 The apparatus shown is for preparing single-walled carbon nanotubes using thermal plasma CVD. This equipment consists of a thermal plasma arc furnace, a CVD growth chamber, a cooling chamber, and a collection tank connected in series. The thermal plasma arc furnace comprises a hollow graphite cathode, a graphite crucible anode, a furnace body, and auxiliary systems. The hollow graphite cathode and the graphite crucible anode enter the furnace body at a 30° angle. The graphite crucible anode is a shallow crucible with through-holes at the edges (e.g., [missing information - likely a reference to a specific type of crucible]). Figure 2 The crucible has an arc-shaped inner wall with a depth of 2cm; the plasma power supply has a power of 300kW, a current of 1500A, and a voltage of 200V.

[0059] Preparation process of single-walled carbon nanotubes:

[0060] S1) Introduce argon plasma gas at a flow rate of 100 L / min, turn on the plasma power supply, generate a plasma arc between the anode and cathode, raise the furnace temperature to 1700℃, and simultaneously turn on the CVD growth chamber heating to raise the temperature to the growth temperature of 1100℃.

[0061] S2) The catalyst (Fe72%-Mo18%-S10% mixed powder, particle size 200 mesh) is fed to the crucible position through the hollow electrode channel at a feeding rate of 10g / min. It evaporates rapidly to form catalyst clusters, and excess unevaporated catalyst particles are blown to the discharge port of the electric arc furnace.

[0062] S3) The carbon source gas and the carrier gas are mixed and then enter the plasma arc furnace through the channel outside the graphite crucible. After high-temperature cracking, the mixture enters the CVD growth chamber together with the catalyst. The volume fraction of the mixed gas is 20% ethylene, 40% hydrogen, and the remainder is argon. The flow rate is 80 L / min.

[0063] S4) Further replenish carbon source gas and carrier gas in the CVD growth chamber to achieve full growth of single-walled carbon nanotubes. The volume fraction of the replenished carbon source gas mixture is 40% ethylene, 20% hydrogen, and the remainder is argon, with a flow rate of 100 L / min.

[0064] S5) After being cooled by the carrier gas in the cooling section, the product enters the collection tank. The product enriched in the 2mm pore size filter is blown off to the discharge port by nitrogen pulse backflushing (backflushing frequency 15 seconds / time) to obtain the final product.

[0065] The reaction proceeded steadily and continuously. After 72 hours, the product was collected and weighed, and the yield of single-walled carbon nanotubes was calculated to be approximately 1750 g / h. The product was calcined in a muffle furnace at 900℃ for 2 hours, and the ash content was weighed, yielding a calculated purity of 87.5%. The morphology of the product was observed using a scanning electron microscope as follows... Figure 4 As shown, the crystallinity is evaluated using the ratio of the peak intensities of the G and D peaks in the Raman spectrum. Figure 3 As shown, the G / D ratio is ~65.4.

[0066] Example 3

[0067] Adopting such Figure 1 The apparatus shown is for preparing single-walled carbon nanotubes using thermal plasma CVD. This equipment consists of a thermal plasma arc furnace, a CVD growth chamber, a cooling chamber, and a collection tank connected in series. The thermal plasma arc furnace comprises a hollow graphite cathode, a graphite crucible anode, a furnace body, and auxiliary systems. The hollow graphite cathode and the graphite crucible anode enter the furnace body at a 60° angle. The graphite crucible anode is a shallow crucible with through-holes at the edges (e.g., [example of a shallow crucible]). Figure 2 The crucible has an arc-shaped inner wall with a depth of 2cm; the plasma power supply has a power of 150kW, a current of 1000A, and a voltage of 150V.

[0068] Preparation process of single-walled carbon nanotubes:

[0069] S1) Introduce argon plasma gas at a flow rate of 50 L / min, turn on the plasma power supply, generate a plasma arc between the anode and cathode, raise the furnace temperature to 1500℃, and simultaneously turn on the CVD growth chamber heating to raise the temperature to the growth temperature of 1400℃.

[0070] S2) The catalyst (Co48%-Mo32%-S20% mixed powder, particle size 200 mesh) is fed to the crucible position through the hollow electrode channel at a feeding rate of 5g / min. It is rapidly evaporated to form catalyst clusters, and excess unevaporated catalyst particles are blown to the discharge port of the electric arc furnace.

[0071] S3) The carbon source gas and the carrier gas are mixed and then enter the plasma arc furnace through the channel outside the graphite crucible. After high-temperature pyrolysis, the mixture enters the CVD growth chamber together with the catalyst. The volume fraction of the mixed gas is 20% propylene, 40% hydrogen, and the remainder is argon. The flow rate is 50 L / min.

[0072] S4) Further replenish carbon source gas and carrier gas in the CVD growth chamber to achieve full growth of single-walled carbon nanotubes. The volume fraction of the replenished carbon source gas mixture is 60% propylene, 10% hydrogen, and the remainder is argon, with a flow rate of 100 L / min.

[0073] S5) After being cooled by the carrier gas in the cooling section, the product enters the collection tank. The product enriched in the 2mm pore size filter is blown off to the discharge port by nitrogen pulse backflushing (backflushing frequency 15 seconds / time) to obtain the final product.

[0074] The reaction proceeded steadily and continuously. After 72 hours, the product was collected and weighed, and the yield of single-walled carbon nanotubes was calculated to be approximately 1550 g / h. The product was calcined in a muffle furnace at 900°C for 2 hours, and the ash content was weighed, yielding a calculated purity of 85.8%. The morphology of the product was observed using a scanning electron microscope as follows... Figure 4 As shown, the crystallinity is evaluated using the ratio of the peak intensities of the G and D peaks in the Raman spectrum. Figure 3 As shown, the G / D ratio is ~78.2.

[0075] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solutions of the present invention should be included within the protection scope of the present invention.

Claims

1. An apparatus for preparing single-walled carbon nanotubes by thermal plasma CVD, characterized in that, The structure of the device includes a thermal plasma arc furnace (4), a CVD growth chamber (7), a cooling chamber (8), and a collection tank (9) connected in series, wherein: The structure of the thermal plasma arc furnace (4) includes a hollow graphite (5) as the cathode, a graphite crucible (2) as the anode, and a furnace body; The graphite crucible (2) is located at the lower part of the thermal plasma arc furnace (4), and the hollow graphite (5) is located at the upper part of the thermal plasma arc furnace (4), above the graphite crucible (2). The hollow graphite (5) enters the furnace body at a certain angle to the vertical direction of the graphite crucible (2); The graphite crucible (2) is a shallow crucible with a through hole (1) on the edge; After the carbon source gas and the carrier gas are mixed, they enter the plasma arc furnace (4) through the through hole (1) at the edge of the graphite crucible (2). After high-temperature pyrolysis, they enter the CVD growth chamber (7) together with the catalyst. The device also includes a gas supply port (6) and an air inlet (3), wherein the gas supply port (6) is located between the thermal plasma arc furnace (4) and the CVD growth chamber (7); the air inlet (3) is located at the left end of the thermal plasma arc furnace (4); The structure of the collection tank (9) includes a screen (10), a pulse backflush port (11), an exhaust port (12), and a discharge port (13). The pulse backflush port (11) and the exhaust port (12) are located at the upper end of the collection tank (9), the screen (10) is located at the lower part of the pulse backflush port (11) and the exhaust port (12), and the discharge port (13) is located at the lower end of the collection tank (9).

2. A method for preparing single-walled carbon nanotubes by thermal plasma CVD, characterized in that, The method uses the apparatus described in claim 1. By igniting an arc between the cathode and anode of the plasma arc furnace (4), the furnace temperature is raised. Then, the catalyst is sent from the hollow graphite (5) to the position of the graphite crucible (2) and rapidly evaporates to form catalyst clusters. Excess catalyst is discharged through the discharge port (14) of the arc furnace. At the same time, the carbon source mixture enters the plasma arc furnace (4) through the through hole (1) on the edge of the anode graphite crucible (2). After cracking, it combines with the catalyst clusters and enters the CVD growth chamber (7) to grow into single-walled carbon nanotubes. The final product is obtained by carrying the carrier gas into the collection tank (9).

3. The method for preparing single-walled carbon nanotubes by thermal plasma CVD according to claim 2, characterized in that, The method specifically includes the following steps: S1) Introduce plasma gas, turn on the plasma power supply, generate a plasma arc between the anode and cathode, raise the furnace temperature to the specified temperature, and at the same time turn on the CVD growth chamber (7) to heat up to the growth temperature. S2) The catalyst is sent to the crucible (2) position through the hollow graphite (5) channel, and evaporates rapidly to form catalyst clusters. Excess unevaporated catalyst particles are blown to the electric arc furnace discharge port (14) by the carrier gas blown out from the air inlet (3). S3) The carbon source gas and the carrier gas are mixed at the same time and then enter the plasma arc furnace (4) through the through hole (1) on the edge of the graphite crucible (2). After high-temperature pyrolysis, they enter the CVD growth chamber (7) together with the catalyst. S4) In the CVD growth chamber (7), carbon source gas and carrier gas are further supplemented through the gas inlet (6) to achieve full growth of single-walled carbon nanotubes; S5) The product is cooled in the cooling chamber (8) under the drive of the carrier gas and then enters the collection tank (9). The product enriched on the screen (10) is blown off to the discharge port (13) through the pulse backflush port (11) to obtain the final product.

4. The method for preparing single-walled carbon nanotubes by thermal plasma CVD according to claim 3, characterized in that, In step S1), the plasma gas is any one, two or more of argon, nitrogen, helium, hydrogen, and water vapor in any proportion, with a flow rate of 10-500 L / min. The specified temperature of the furnace is 1200-2000℃; the growth temperature of the CVD chamber is 900-1400℃.

5. The method for preparing single-walled carbon nanotubes by thermal plasma CVD according to claim 3, characterized in that, In step S2), the catalyst is a mixture of 50-95% metal powder and 5-50% co-catalyst, wherein: The metal powder is iron, cobalt, or nickel metal or a mixture thereof; Or an alloy or mixture of iron, cobalt or nickel with a refractory metal, wherein the refractory metal element is molybdenum, tungsten, tantalum, niobium, hafnium or zirconium, the weight ratio of the refractory metal element is 20-60%, and the particle size is 50-350 mesh; The co-catalyst is any one or a mixture of sulfur powder, selenium powder, iron sulfide, ferrous sulfide, nickel sulfide or cobalt sulfide, with a particle size of 100-500 mesh; The catalyst feed rate is 0.1 g / min to 100 g / min.

6. The method for preparing single-walled carbon nanotubes by thermal plasma CVD according to claim 3, characterized in that, In step S3), the carbon source gas is any one of methane, ethylene, acetylene, propylene, or propane; the carrier gas is a mixture of nitrogen, argon, or helium inert gas and hydrogen, wherein the volume of the carbon source gas is 10-80%, the volume of hydrogen is 0-35%, and the remainder is nitrogen, argon, or helium inert gas, with a total flow rate of 10-200 L / min.

7. The method for preparing single-walled carbon nanotubes by thermal plasma CVD according to claim 3, characterized in that, In step S4), the total flow rate of carbon source gas and carrier gas in the CVD growth chamber (7) is further supplemented to 10-200 L / min.

8. The method for preparing single-walled carbon nanotubes by thermal plasma CVD according to claim 3, characterized in that, In step S5), the aperture of the sieve (10) is 0.5-50 mm, the backflushing gas is nitrogen, argon or helium, and the pulse backflushing frequency is 5-300 seconds / time.

Images