Device and method for preparing carbon nano tube at low temperature in different temperature zones by Venturi tube method

Abstract

The invention provides a device and a method for preparing a carbon nano tube in different temperature zones at low temperature by a Venturi tube method. The device adopted by the method consists of a horizontal tube furnace, sealing boxes at two ends, a carbon source gas inlet system and an exhaust system, the horizontal tube furnace comprises a Venturi furnace tube, and the Venturi furnace tube is divided into a high-temperature section furnace tube and a low-temperature section furnace tube by a throat tube section in the middle of the Venturi furnace tube; in the production process, a catalyst is located in a low-temperature section furnace tube, carbon source gas is subjected to thermal cracking through a high-temperature section furnace tube to generate activated carbon species, and the activated carbon species are carried into the low-temperature section furnace tube by carrier gas so as to realize growth of carbon nanotubes on the surface of the catalyst; and the carbon source gas inlet system and the exhaust system are respectively used for inputting carbon source gas and exhausting tail gas in the production process. The device and the method have the beneficial effects that low-temperature and high-quality growth of carbon nano-tubes on a heat-sensitive substrate is realized by adopting a temperature zone dividing system for separating a carbon source gas cracking process and a carbon nano-tube growth process in space by adopting a Venturi tube method.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and more specifically, to an apparatus and method for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones. Background Technology

[0002] Nanomaterials refer to materials in which the size of the dispersed phase is at least one dimension less than 100 nm. Currently reported carbon nanomaterials include carbon nanofibers, graphene, carbon nanospheres, etc., while carbon nanotubes are recognized as the finest fibers in the world. These materials play an important role in renewable energy conversion technologies such as electrochemical catalysis and energy storage due to their good electrical conductivity, high mechanical properties and high specific surface area.

[0003] Currently, the main method for large-scale preparation of carbon nanotubes is chemical vapor deposition (CVD), which utilizes a catalyst to crack hydrocarbons, using active metal atoms as catalyst nuclei, and carbon atoms depositing on these nuclei to form carbon nanotubes. However, traditional single-temperature CVD technology has an inherent contradiction: the carbon source gas requires a high temperature, typically above 700 degrees Celsius, to effectively crack and generate active carbon species; and many potential substrates for applications, such as aluminum foil for electrodes and flexible polymers for electronic devices, cannot withstand such high temperatures, as they will melt, deform, or undergo harmful interfacial reactions at high temperatures.

[0004] Existing technologies attempt to lower the growth temperature by introducing plasma or using special catalysts, but these methods often suffer from problems such as complex equipment, high cost, or poor carbon nanotube quality. Therefore, it is crucial to develop a simple method for efficiently growing high-quality carbon nanotubes on low-temperature substrates.

[0005] To address the aforementioned technical problems, this invention discloses a method and apparatus for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones.

[0006] To achieve the above objectives, this invention discloses an apparatus and method for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones. This method effectively separates the high-temperature pyrolysis process of the carbon source gas from the low-temperature growth process of the carbon nanotubes on the substrate, thereby enabling the preparation of high-quality, uniformly distributed carbon nanotubes on a thermosensitive substrate at a lower temperature. Summary of the Invention

[0007] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art. For example, one objective of this invention is to provide an apparatus and method for low-temperature preparation of carbon nanotubes using a venturi tube method. This apparatus is a venturi tube system that separates the carbon source gas pyrolysis process from the carbon nanotube growth process in space using a venturi tube throat, thereby achieving low-temperature, high-quality growth of carbon nanotubes on a thermosensitive substrate.

[0008] To achieve the above objectives, this invention discloses a method for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones. The apparatus used in this method consists of a horizontal tube furnace, sealed boxes at both ends, a carbon source gas inlet system, and an exhaust system. The horizontal tubular furnace includes a Venturi tube, which is divided into a high-temperature section and a low-temperature section by a throat section in its middle. During the production process, the catalyst is located in the low-temperature section of the furnace tube, and the carbon source gas undergoes thermal decomposition through the high-temperature section of the furnace tube to generate active carbon species. The active carbon species are carried by the carrier gas to the low-temperature section of the furnace tube to achieve the growth of carbon nanotubes on the catalyst surface. The carbon source gas intake system and exhaust system are used to input carbon source gas and discharge exhaust gas, respectively, during the production process.

[0009] In a preferred embodiment of this solution, the apparatus used in the method further includes a catalyst piston injection device system and a catalyst feeding system; The catalyst piston injection device system includes a piston injection device, and the catalyst feeding system includes a catalyst feeding pipe located above the right side of the low-temperature section furnace tube for feeding catalyst into the piston injection device. The piston injection device is located inside the low-temperature section furnace tube and can reciprocate within the low-temperature section furnace tube under the traction of the winch and the winch tube. The inner cavity of the winch tube is connected to the inner cavity of the piston injection device. Carrier gas is introduced into the piston injection device through the winch tube, and forms a gas-solid phase with the catalyst inside. The gas is injected into the low-temperature section furnace tube through the catalyst injection hole, thereby realizing catalyst injection. The movement of the piston injection device can scrape and collect the carbon nanotubes grown and deposited in the low-temperature section of the Venturi tube into the collection box.

[0010] In a preferred embodiment of this scheme, a method for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones includes the following steps: 1) Substrate preparation and catalyst loading; 2) Device preparation and base placement The carbon nanotube low-temperature catalyst is added to the piston injection device through a feeding tube; 3) Catalyst activation The high-temperature section furnace tube and the low-temperature section furnace tube are heated simultaneously, and the low-temperature section furnace tube is heated to the catalyst activation temperature T2. 4) Temperature-differentiated growth Keep the temperature of the furnace tube in the low-temperature section constant at T2, raise the temperature of the furnace tube in the high-temperature section to the high-temperature pyrolysis temperature T1, where T1 > T2, introduce carbon source gas, and simultaneously introduce argon carrier gas to carry it, and maintain the growth time t. 5) Cooling and Sampling After growth is complete, the power supply to the carbon source gas and the heaters of the high-temperature section furnace tube and the low-temperature section furnace tube is turned off. The system is allowed to cool naturally to room temperature under an inert atmosphere, and the substrate with grown carbon nanotubes is removed.

[0011] In a preferred embodiment of this scheme, in step 1), the substrate is selected as aluminum foil or aluminum powder with a thickness of 10-100 micrometers supporting sodium-based catalyst, or SiO2 / Si substrate with a Co-Mo content of 3-10%.

[0012] In a preferred embodiment of this scheme, the activation temperature T2 of the catalyst is 400-600℃; and / or the high-temperature pyrolysis temperature T1 of the high-temperature section furnace tube is 700-900℃; In a preferred embodiment of this solution, in step 4), the carbon nanotube growth time t is 5-60 minutes.

[0013] On the other hand, the present invention also provides an apparatus for low-temperature preparation of carbon nanotubes by the Venturi tube method with temperature zones, which can be used in the above-mentioned method, and includes a horizontal tube furnace, a left sealed box, and a right sealed box. The horizontal tubular furnace includes a Venturi tube, the two ends of which are respectively sealed to a left sealing box and a right sealing box to form a reaction chamber; The Venturi tube is divided into a high-temperature section and a low-temperature section by a throat section in its middle. The high-temperature section furnace tube is equipped with a carbon source gas inlet, and the low-temperature section furnace tube is equipped with a tail gas outlet on the right side.

[0014] In a preferred embodiment of this solution, the device further includes a piston injection device; the piston injection device is slidably and sealably installed inside the low-temperature section furnace tube; The piston injection device is connected to a winch rope on the left and a winch rope tube on the right. The piston injection device can reciprocate and stop through the winch rope and the winch rope tube, so as to realize the piston injection device stopping at the three key positions S1, S2 and S3 in the low temperature section furnace tube. The piston injection device is provided with a catalyst injection hole on the right side. Carrier gas is introduced into the piston injection device through the winch tube, and forms a gas-solid phase with the catalyst inside. The gas is then injected into the low-temperature section of the Venturi furnace tube from the catalyst injection hole to the right.

[0015] In a preferred embodiment of this solution, the materials used to prepare the Venturi furnace tube include, but are not limited to, quartz, graphite, carbon-carbon composite materials and various metals; and / or the diameter of the diffuser section of the Venturi furnace tube is 100-1000 mm, the diameter of the throat section is 10-150 mm, and the diffusion angle is 5-15°. In a preferred embodiment of this solution, the piston injection device is provided with a connecting threaded hole at each end, and the rope and the rope tube are fixed to the piston injection device through the corresponding connecting threaded holes. The piston injection device has a catalyst injection hole on one end face, the hollow inner cavity of the piston injection device is used as a catalyst loading chamber, and the top is provided with a piston injection device receiving port.

[0016] In a preferred embodiment of this solution, the catalyst injection orifice includes multiple large injection orifices and multiple small injection orifices, the diameter of the large injection orifices is 5~50mm, and the diameter of the small injection orifices is 1~30mm; the multiple large injection orifices and the multiple small injection orifices are evenly distributed along the circumference, and the multiple large injection orifices are located outside the multiple small injection orifices.

[0017] In a preferred embodiment of this solution, a catalyst feeding device is provided on the top of the right sealing box. When the right sealing box is located below the catalyst feeding device (at position S3), the catalyst feeding pipe of the catalyst feeding device is aligned with the piston injection device receiving port on the top of the piston injection device.

[0018] In a preferred embodiment of this solution, the catalyst feeding pipe is located at the bottom of the catalyst feeding device, and the lower part of the catalyst feeding pipe extends into the right sealing box. When the piston injection device is located below the catalyst feeding device, the catalyst feeding pipe port of the catalyst feeding pipe can be aligned with the piston injection device receiving port at the top of the piston injection device. The catalyst feeding device also includes a catalyst silo located at the top of the catalyst feeding pipe, a catalyst feeding valve installed in the middle of the catalyst feeding pipe, and a catalyst feeding port located at the top of the catalyst silo.

[0019] In a preferred embodiment of this solution, the rope tube is a high-temperature resistant, flexible hollow tube. The flexibility ensures it can be wound along the winch; the hollow structure allows for the introduction of nitrogen gas.

[0020] In a preferred embodiment of this solution, the material used to prepare the rope tube is selected from one of the following: metal, carbon fiber, carbon fiber composite material, and inorganic fiber.

[0021] In a preferred embodiment of this solution, the inorganic fiber is a blend of ceramic fiber, high-silica fiber, or basalt fiber and at least one of ceramic fiber and high-silica fiber.

[0022] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) This invention proposes an apparatus and method for preparing carbon nanotubes at low temperatures in a divided temperature zone using the Venturi tube method. The throat of the Venturi tube divides the furnace tube into a high-temperature zone and a low-temperature zone. The throat of the Venturi tube can effectively eliminate the influence of thermal expansion radiation from the high-temperature zone to the high-temperature zone, thus achieving true low-temperature growth. At the same time, the carbon source gas is decomposed into carbon atoms and hydrogen gas in the diffusion section and accelerated by the throat tube to form a uniform spray, which is conducive to uniform contact with the catalyst in the low-temperature zone, thus achieving uniform growth of carbon nanotubes and obtaining carbon nanotubes with uniform diameter. The substrate is always in the lower second temperature zone, i.e., the low-temperature zone, which effectively avoids damage to the heat-sensitive substrate and greatly expands the application scenarios of carbon nanotubes, such as flexible electronics. (2) Ensure the quality of carbon source supply for growth: The high temperature of the first temperature zone ensures that the carbon source is fully and uniformly decomposed, providing sufficient and high-quality "building materials" for growth in the low temperature zone, thus overcoming the defect of insufficient carbon source decomposition in a single low temperature zone; (3) Achieving both growth and quality: This method can still produce high-quality carbon nanotubes with high crystallinity, few defects, and uniform distribution while reducing the growth temperature. (4) High process flexibility: By adjusting parameters such as T1, T2, gas flow rate, and catalyst type, the morphology, density, tube diameter and number of layers of the grown carbon nanotubes can be precisely controlled; (5) The device is simple and easy to promote: Compared with complex equipment such as plasma CVD, this device only adds an independent temperature zone on the basis of traditional CVD. The modification is small and the cost is low, making it very suitable for industrial promotion and laboratory research. Attached Figure Description

[0023] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 The diagram shows the structural schematic of Example 1 of the apparatus and method for low-temperature preparation of carbon nanotubes using the Venturi tube method in temperature zones according to the present invention.

[0024] Figure 2 The diagram shows a schematic of the piston injection device structure of Example 1 of the apparatus and method for low-temperature preparation of carbon nanotubes by the Venturi tube method.

[0025] Figure 3 The image shows an electron microscope scan of carbon nanotubes prepared in Example 2 of the apparatus and method for low-temperature preparation of carbon nanotubes using the Venturi tube method according to the present invention.

[0026] Figure 4 The image shows an electron microscope scan of carbon nanotubes prepared in Example 3 of the present invention, which is a device and method for preparing carbon nanotubes at low temperatures in a temperature-divided zone using the Venturi tube method.

[0027] Key reference numerals in the attached drawings: 1. Winch 1; 2. Left sealing box; 3. Winch rope; 4. Venturi tube; 5. Tube contraction section; 6. Large injection hole; 7. Small injection hole; 8. Piston injection device inlet; 9. Connecting threaded hole; 10. Throat section; 11. Diffusion section; 12. Piston injection device; 13. Winch rope tube; 14. Horizontal tube furnace; 15. Catalyst charging port; 16. Catalyst silo; 17. Catalyst charging pipe; 18. Catalyst charging valve; 19. Winch 2; 20. Right sealing box. Detailed Implementation

[0028] In the following description, an apparatus and method for low-temperature preparation of carbon nanotubes using the Venturi tube method with temperature zones will be explained in detail with reference to exemplary embodiments.

[0029] It should be noted that terms such as "up," "down," "front," "back," "left," "right," "inner," and "outer" are used only to facilitate the description and formation of relative orientations or positional relationships, and do not indicate or imply that the component referred to must have that specific orientation or position.

[0030] Example 1 refer to Figure 1 , Figure 2 As shown, an apparatus for the low-temperature preparation of carbon nanotubes using the Venturi tube method includes a horizontal tubular furnace 14, a left sealed box 2, and a right sealed box 20. The horizontal tubular furnace 14 includes a Venturi tube 4, the two ends of which are sealed to the left sealed box 2 and the right sealed box 20, respectively. The horizontal tubular furnace consists of a high-temperature zone (high-temperature section furnace tube) and a low-temperature zone (low-temperature section furnace tube). The high-temperature section furnace tube and the low-temperature section furnace tube are connected by a Venturi tube structure formed by a furnace tube contraction section 5, a throat section 10, and a diffusion section 11. The high-temperature section furnace tube and the low-temperature section furnace tube can be individually temperature-controlled. The left wall of the high-temperature section furnace tube has a carbon source gas inlet connected to a carbon source gas intake system, and the right wall of the low-temperature section furnace tube has a tail gas outlet connected to an exhaust system.

[0031] In this embodiment, an apparatus for low-temperature preparation of carbon nanotubes by the Venturi tube method in temperature zones further includes a catalyst piston injection device system and a catalyst feeding system. The catalyst piston injection device system includes a piston injection device 12. The piston injection device 12 is slidably and sealably installed inside the low-temperature furnace tube. The piston injection device 12 is connected to a winch 3 on the left side and a winch tube 13 on the right side. The piston injection device 12 can achieve reciprocating motion and stop through the winch 3 and the winch tube 13.

[0032] refer to Figure 2As shown, the catalyst injection orifice in the piston injection device 12 consists of a large injection orifice 6 and a small injection orifice 7 (the diameter of the large injection orifice 6 is 5~50mm, and the diameter of the small injection orifice 7 is 1~30mm). The piston injection device moves within the Venturi tube 4, and the control points S1, S2, and S3 are all in the low-temperature section. Carrier gas is introduced into the piston injection device 12 through the winch tube 13, forming a gas-solid phase with the catalyst inside. The gas is then injected into the low-temperature section of the furnace tube through the catalyst injection orifice, thereby achieving catalyst injection. When the piston injection device 12 moves to the right, the carbon nanotubes grown and deposited in the low-temperature section of the Venturi tube can be scraped and collected into the receiving box, i.e., the right sealed box 20.

[0033] In this embodiment, the left sealing box 2 is provided with a winch 1 and the right sealing box 20 is provided with a winch 2 19. The left end of the winch rope 3 and the right end of the winch tube 13 are respectively wound around the winch 1 and the winch 2 19 to drive the piston injection device 12 to reciprocate and stop.

[0034] Furthermore, in this scheme, a catalyst feeding system is provided at the top of the right sealing box 20. The catalyst feeding system includes a catalyst feeding device, a catalyst feeding pipe 17 is located at the bottom of the catalyst feeding device, and the lower part of the catalyst feeding pipe 17 extends into the right sealing box 20. When the piston injection device 12 is located below the catalyst feeding device, the catalyst feeding port of the catalyst feeding pipe 17 can be aligned with the piston injection device receiving port 8 at the top of the piston injection device 12. The catalyst feeding device also includes a catalyst silo 16 located at the top of the catalyst feeding pipe 17, a catalyst feeding valve 18 installed in the middle of the catalyst feeding pipe 17, and a catalyst feeding port 15 located at the top of the catalyst silo 16.

[0035] In this embodiment, the rope tube 13 has a flexible hollow tube structure. The flexibility ensures that it can be wound along the winch; the hollow structure allows nitrogen gas to be introduced.

[0036] Optionally, the material used to prepare the rope tube is selected from one of the following: metal, carbon fiber, carbon fiber composite material, and inorganic fiber; wherein the inorganic fiber is ceramic fiber, high silica fiber, or a mixture of basalt fiber and at least one of ceramic fiber and high silica fiber.

[0037] Optionally, in this embodiment, the method for setting positions S1, S2, and S3 includes, but is not limited to, position switches, position sensor detection, and positioning methods obtained by setting displacement, time, and winch rotation speed variables (positioning methods are common in the mechanical field and will not be elaborated in detail in this embodiment).

[0038] In this embodiment, a connecting threaded hole 9 is provided on each side of the piston injection device 12 to facilitate the connection of the rope 3 and the rope tube 13.

[0039] In this embodiment, the diameter of the diffuser section 11 of the Venturi tube 4 is 100-1000 mm, the diameter of the throat section 10 is 10-150 mm, and the diffusion angle is 5-15°. Example 2 This embodiment describes a method for preparing carbon nanotubes by piston-injection catalytic cracking of hydrocarbons based on the apparatus described in Example 1, including the following steps: Take 140g of catalyst with a Co-Mo loading of 6% on a SiO2 / Si substrate. The piston injection device 12 (large injection hole 6 with a diameter of 15mm and small injection hole 7 with a diameter of 5mm) reaches position S3, aligning the piston injection device inlet 8 with the catalyst feeding pipe 17. The catalyst feeding valve 18 is opened, and the catalyst is added into the inner cavity of the piston injection device 12. After the feeding time T2 is reached, the catalyst feeding valve 18 is closed. The nitrogen inlet valve is opened, and oxygen from the nitrogen replacement device is introduced. Once the system oxygen content is less than 1%, the nitrogen is shut off. The horizontal furnace is heated to 750℃ in the high-temperature zone and to 450℃ in the low-temperature zone. The carbon source gas valve is opened, and methane is introduced, with the methane flow rate controlled at 2.5m³. 3 / h, open the regulating exhaust valve to ensure the system pressure difference is about +250Pa, start winch 1 to rotate forward and winch 2 19 to rotate in reverse, the winch rope 3 pulls the piston injection device 12 from position S3 to the left. When it reaches position S2, the nitrogen in the winch rope tube 13 is opened, and the catalyst in the piston injection device 12 is injected through the catalyst injection hole and added into the Venturi furnace tube 4 (diffuser section 11 diameter 500mm, throat section 10 diameter 100mm, diffusion angle 10°); when it reaches position S1, the nitrogen in the winch rope tube 13 is closed, and the catalyst injection stops; winch 1 and winch 2 19 stop. The growth time T1 is approximately 0.5 hours. At 790℃, the carbon-hydrogen bonds of methane gas are broken down into active carbon atoms and hydrogen. The hydrogen flows from high-temperature zone A through the Venturi tube section into the low-temperature zone, reducing molybdenum oxide and cobalt oxide in the catalyst of the low-temperature zone into elemental molybdenum and elemental cobalt. Using these elemental metals as nuclei, it catalyzes the breaking down of more hydrocarbon carbon-hydrogen bonds. The active carbon atoms broken down in the high-temperature zone flow through the Venturi tube section into the low-temperature zone, where they deposit using the elemental metals as nuclei, forming carbon nanotubes. Specifically, within the Venturi furnace tube 4, the carbon-hydrogen bonds in the high-temperature zone continuously break down into active carbon atoms and hydrogen. These active carbon atoms continuously and uniformly pass through the Venturi tube section into the low-temperature zone, where they grow and deposit on the surface of the cobalt-based catalyst, forming carbon nanotubes. Simultaneously, part of the generated hydrogen is used as a carrier gas in the Venturi furnace tube 4, and the rest is discharged through the exhaust pipe. After reaching growth time T1, winch 11 reverses and winch 219 rotates forward. The winch tube 13 pulls the piston injection device 12 to the right, pushing and scraping the carbon nanotubes grown and deposited in the Venturi furnace tube 4 into the right sealed box 20.

[0040] After the above reaction is complete, stop heating the horizontal furnace, close the carbon source gas valve, open the nitrogen valve, and introduce nitrogen to purge the waste gas and cool the furnace. After 30 minutes of nitrogen purging, close the nitrogen valve. Once the horizontal tubular furnace has cooled to room temperature, remove the material to obtain hollow fibrous carbon nanotubes, such as... Figure 3 As shown, the carbon nanotubes have good morphology and relatively uniform diameter, with the diameter mainly distributed between 30 and 50 nm.

[0041] Example 3 This embodiment describes a method for preparing carbon nanotubes by piston-injection catalytic cracking of hydrocarbons based on the apparatus described in Example 1, including the following steps: After grinding 70 grams of Fe / Na composite catalyst with an aluminum foil loading of 6%, the piston injection device 12 (large injection hole 6 with a diameter of 15 mm and small injection hole 7 with a diameter of 5 mm) reaches position S3. The inlet 8 of the piston injection device is aligned with the inlet of the catalyst feeding pipe 17, and the catalyst feeding valve 18 is opened, adding the catalyst into the inner cavity of the piston injection device 12. After the feeding time T2 is reached, the catalyst feeding valve 18 is closed. The nitrogen inlet valve is opened, and oxygen in the nitrogen replacement device is introduced. After the oxygen content in the system is less than 1%, the nitrogen is turned off. The horizontal furnace is heated to 800℃ in the high-temperature zone and 550℃ in the low-temperature zone. The carbon source gas valve is opened, and acetylene is introduced, with the acetylene flow rate controlled at 1.5 m³ / min. 3 / h, open the regulating exhaust valve to ensure the system pressure difference is about +250Pa, start winch 1 to rotate forward and winch 2 19 to rotate in reverse, the winch rope 3 pulls the piston injection device 12 from position S3 to the left. When it reaches position S2, the nitrogen in the winch rope tube 13 is opened, and the catalyst in the piston injection device 12 is injected through the catalyst injection hole and added into the Venturi furnace tube 4 (diffuser section 11 diameter 500mm, throat section 10 diameter 100mm, diffusion angle 10°); when it reaches position S1, the nitrogen in the winch rope tube 13 is closed, and the catalyst injection stops; winch 1 and winch 2 19 stop. The growth time T1 is approximately 20 minutes. At 800℃, the carbon-hydrogen bonds of acetylene gas are broken down into active carbon atoms and hydrogen. The hydrogen flows from high-temperature zone A through the Venturi tube section into the low-temperature zone, reducing the iron oxide in the catalyst of the low-temperature zone to elemental iron and elemental sodium. Using these elemental metals as nuclei, it catalyzes the breaking down of more hydrocarbon carbon-hydrogen bonds. The active carbon atoms broken down in the high-temperature zone flow through the Venturi tube section into the low-temperature zone, where they deposit using the elemental metals as nuclei, forming carbon nanotubes. Specifically, within the Venturi furnace tube 4, the carbon-hydrogen bonds in the high-temperature zone continuously break down into active carbon atoms and hydrogen. These active carbon atoms continuously and uniformly pass through the Venturi tube section into the low-temperature zone, where they grow and deposit on the surface of the cobalt-based catalyst, forming carbon nanotubes. Simultaneously, part of the generated hydrogen serves as the carrier gas in the Venturi furnace tube 4, while the rest is discharged through the exhaust pipe. After reaching growth time T1, winch 11 reverses and winch 219 rotates forward. The winch tube 13 pulls the piston injection device 12 to the right, pushing and scraping the carbon nanotubes grown and deposited in the Venturi furnace tube 4 into the right sealed box 20.

[0042] After the above reaction is complete, stop heating the horizontal furnace, close the carbon source gas valve, open the nitrogen valve, and introduce nitrogen to purge the waste gas and cool the furnace. After 30 minutes of nitrogen purging, close the nitrogen valve. Once the horizontal tubular furnace has cooled to room temperature, remove the material to obtain hollow fibrous carbon nanotubes, such as... Figure 4 As shown, the carbon nanotubes have good morphology and relatively uniform diameter, with the diameter mainly distributed between 10 and 20 nm.

[0043] In summary, the preparation method of the present invention is relatively simple to operate, and different carbon nanotubes can be prepared using all hydrocarbons as carbon source gases and different catalysts.

[0044] In summary, this invention successfully resolves the technical challenge of achieving high-quality carbon nanotubes at low temperatures through an ingenious "temperature zone" design for a Venturi furnace tube, providing a technical foundation for the widespread application of carbon nanotubes in flexible electronics, aerospace, and energy storage.

[0045] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones, characterized in that, The apparatus used in the method consists of a horizontal tubular furnace and sealed boxes at both ends, a carbon source gas inlet system, and an exhaust system. The horizontal tubular furnace includes a Venturi tube, which is divided into a high-temperature section and a low-temperature section by a throat section in its middle. During the production process, the catalyst is located in the low-temperature section of the furnace tube, and the carbon source gas undergoes thermal decomposition through the high-temperature section of the furnace tube to generate active carbon species. The active carbon species are carried by the carrier gas to the low-temperature section of the furnace tube to achieve the growth of carbon nanotubes on the catalyst surface. The carbon source gas intake system and exhaust system are used to input carbon source gas and discharge exhaust gas, respectively, during the production process.

2. The method for low-temperature preparation of carbon nanotubes using the Venturi tube method according to claim 1, characterized in that, The apparatus used in the method also includes a catalyst piston injection system and a catalyst feeding system; The catalyst piston injection device system includes a piston injection device; the catalyst feeding system includes a catalyst feeding pipe located above the right side of the low-temperature section furnace tube for feeding catalyst into the piston injection device. The piston injection device is located inside the low-temperature section furnace tube and can reciprocate within the low-temperature section furnace tube under the traction of the winch and the winch tube. The inner cavity of the winch tube is connected to the inner cavity of the piston injection device. Carrier gas is introduced into the piston injection device through the winch tube, and forms a gas-solid phase with the catalyst inside. The gas is injected into the low-temperature section furnace tube through the catalyst injection hole, thereby realizing catalyst injection. The movement of the piston injection device can scrape and collect the carbon nanotubes grown and deposited in the low-temperature section of the Venturi tube into the collection box.

3. The method for preparing carbon nanotubes at low temperatures in temperature zones using the Venturi tube method according to claim 1, characterized in that, Includes the following steps: 1) Substrate preparation and catalyst loading; 2) Device preparation and base placement The carbon nanotube low-temperature catalyst is added to the piston injection device through the catalyst feeding tube; 3) Catalyst activation The high-temperature section furnace tube and the low-temperature section furnace tube are heated simultaneously, and the low-temperature section furnace tube is heated to the catalyst activation temperature T2. 4) Temperature-differentiated growth Keep the temperature T2 inside the low-temperature section furnace tube constant, raise the temperature of the high-temperature section furnace tube to the high-temperature pyrolysis temperature T1, T1>T2, introduce carbon source gas, and simultaneously introduce carrier gas to carry it, and maintain the growth time t. 5) Cooling and Sampling After growth is complete, the power supply to the carbon source gas and the heaters of the high-temperature section furnace tube and the low-temperature section furnace tube is turned off. The system is allowed to cool naturally to room temperature under an inert atmosphere, and the substrate with grown carbon nanotubes is removed.

4. The method for low-temperature preparation of carbon nanotubes using the Venturi tube method according to claim 3, characterized in that, In step 1), the substrate is selected as aluminum foil or aluminum powder with a thickness of 10-100 micrometers supporting sodium-based catalyst, or SiO2 / Si substrate with a Co-Mo content of 3-10%.

5. The method for low-temperature preparation of carbon nanotubes using the Venturi tube method with temperature zones according to claim 3, characterized in that, In step 3), the activation temperature T2 of the catalyst is 400-600℃.

6. The method for low-temperature preparation of carbon nanotubes using the Venturi tube method with temperature zones according to claim 3, characterized in that, In step 4), the growth time t of the carbon nanotubes is 5-60 minutes; and / or In step 4), the high-temperature pyrolysis temperature T1 of the high-temperature section furnace tube is 700-900℃.

7. An apparatus for low-temperature preparation of carbon nanotubes using a venturi tube method with temperature zones, characterized in that, It can be used in the method according to any one of claims 1 to 6, which includes a horizontal tubular furnace, a left sealed box, and a right sealed box; The horizontal tubular furnace includes a Venturi tube, the two ends of which are respectively sealed to a left sealing box and a right sealing box to form a reaction chamber; the throat section in the middle divides it into a high-temperature section furnace tube and a low-temperature section furnace tube. The high-temperature section furnace tube is equipped with a carbon source gas inlet, and the low-temperature section furnace tube is equipped with a tail gas outlet on the right side.

8. The apparatus for low-temperature preparation of carbon nanotubes using the Venturi tube method with temperature zones according to claim 7, characterized in that: The device also includes a piston injection device; The piston injection device can be sealed and slidably installed inside the low-temperature section furnace tube; The piston injection device is connected to a winch rope on the left and a winch rope tube on the right. The piston injection device can reciprocate and stop through the winch rope and the winch rope tube, so as to realize the piston injection device stopping at the three key positions S1, S2 and S3 in the low temperature section furnace tube. The piston injection device is provided with a catalyst injection hole on the right side. Carrier gas is introduced into the piston injection device through the winch tube, and forms a gas-solid phase with the catalyst inside. The gas is then injected into the low-temperature section of the Venturi furnace tube from the catalyst injection hole to the right.

9. The apparatus for low-temperature preparation of carbon nanotubes using the Venturi tube method with temperature zones according to claim 7, characterized in that: The materials used to prepare the Venturi furnace tubes include, but are not limited to, quartz, graphite, carbon-carbon composite materials, and various metals; and / or The diameter of the diffuser section of the Venturi tube is 100-1000 mm, and the diameter of the throat section is 10-150 mm. Diffusion angle 5-15°.

10. The apparatus for low-temperature preparation of carbon nanotubes using the Venturi tube method with temperature zones according to claim 7, characterized in that: The piston injection device is provided with a connecting threaded hole at each end, and the rope and rope tube are fixed to the piston injection device through the corresponding connecting threaded holes. One end face of the piston injection device is provided with a catalyst injection hole, the hollow inner cavity of the piston injection device is used as a catalyst loading chamber, and the top is provided with a piston injection device receiving port. The catalyst injection orifice includes multiple large injection orifices and multiple small injection orifices. The diameter of the large injection orifices is 5~50mm and the diameter of the small injection orifices is 1~30mm. The multiple large injection orifices and multiple small injection orifices are evenly distributed along the circumference, and the multiple large injection orifices are located outside the multiple small injection orifices.

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