Single chiral carbon nanotube synthesis device and its usage method

Abstract

The present invention belongs to the technical field of carbon nanotube synthesis, and specifically discloses a single-chirality carbon nanotube synthesis device and its usage method. The synthesis device includes a source chamber and a reaction chamber. Inside the reaction chamber, there is a sample stage, on which a substrate and a catalyst are provided. Inside the source chamber, there is a dielectric tube, around which a spiral wire is wound, and ring electrodes are provided at both ends of the dielectric tube. One end of the dielectric tube is connected to an external working gas. A magnetic coil is provided outside the source chamber, and the reaction chamber is externally connected to a chemical vapor deposition system, and the source chamber is externally connected to a high-voltage pulse generating component. By using the above single-chirality carbon nanotube synthesis device and its usage method, the synthesis device is convenient to operate and suitable for mass preparation. By precisely controlling the reaction conditions, single-chirality carbon nanotubes can be efficiently synthesized with a purity of over 95%. By adjusting the reaction parameters, selective synthesis of different chirality carbon nanotubes can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanotube synthesis, and more particularly to a single-chirality carbon nanotube synthesis device and its usage method. Background Art

[0002] Carbon nanotubes are a kind of nanoscale tubular structure materials, which are curled by single-layer or multi-layer graphite sheets. They have extremely high carrier mobility and a tunable bandgap, and have important application values in the fields of composite material reinforcement, nano-devices, field emission, and high-performance electronic devices. Moreover, due to their unique hollow structure, good electrical conductivity, large specific surface area, and intertwined network structure, they are considered to be ideal electrode materials for high-performance lithium-ion batteries and supercapacitors, and are also the best hydrogen storage materials that can be used in hydrogen fuel cell vehicles, and have received extensive attention in new energy storage in recent years.

[0003] Freely grown carbon nanotubes usually mix different structures and chiralities, and are prone to agglomeration and entanglement, which severely limits their application as conductive agents. Single-chirality carbon nanotubes are spiral nanostructures formed by curling single-layer carbon atoms, with a unified chiral structure and unique electronic, optical, and mechanical properties. Research shows that even tiny structural differences (such as different chiral angles) between different carbon nanotubes will lead to huge differences in their optical and electrical properties, and there will also be a photo-electric coupling effect between carbon nanotubes with different structures. The mixture of carbon nanotubes with different structures existing in the growth preparation seriously hinders the research on their characteristics and device applications. Therefore, the large-scale preparation of single-chirality carbon nanotubes is the prerequisite and key for constructing high-speed and low-power carbon-based electronics and optoelectronic devices. However, so far, the large-scale high-purity preparation and precise manipulation of single-chirality carbon nanotubes still face many challenges, and have become a hot issue in recent research.

[0004] Although the plasma-enhanced chemical vapor deposition method has been widely used in the preparation of carbon nanotube materials, there is a lack of a regulation mechanism that can stably induce the chiral growth of carbon nanotubes. Recently, a low-temperature plasma with a spiral morphology propagation was formed by pulse modulation electromagnetic drive in a low-pressure dielectric tube, and its spiral chiral direction changes with the electromagnetic parameters. The present invention provides a carbon nanotube synthesis device, which realizes the controllable synthesis of single-chirality carbon nanotubes through specific device design and process combination. Summary of the Invention

[0005] The purpose of the present invention is to provide a single-chirality carbon nanotube synthesis device and its usage method. The synthesis device is convenient to operate and suitable for macroscale preparation. By precisely controlling the reaction conditions, it can efficiently synthesize single-chirality carbon nanotubes with a purity of more than 95%. By adjusting the reaction parameters, the selective synthesis of different chiral carbon nanotubes can be achieved.

[0006] To achieve the above object, the present invention provides a single chiral carbon nanotube synthesis device, which includes a source chamber and a reaction chamber. Inside the reaction chamber, there is a sample stage. On the sample stage, there are a substrate and a catalyst. Inside the source chamber, there is a dielectric tube. A spiral is wound around the outside of the dielectric tube, and ring electrodes are provided at both ends of the dielectric tube. One end of the dielectric tube is connected to the external working gas. A magnetic coil is provided outside the source chamber. The reaction chamber is externally connected to a chemical vapor deposition system, and the source chamber is externally connected to a high-voltage pulse generating assembly.

[0007] Preferably, the substrate material is single-crystalline silicon, and the catalyst is one or more of iron, cobalt, nickel, aluminum oxide, and magnesium oxide.

[0008] Preferably, the dielectric tube is a quartz dielectric tube, with a length of 1 m, an inner diameter of 6 mm, and an outer diameter of 9 mm.

[0009] Preferably, for the ring electrodes at both ends, one is connected to the high-voltage pulse generating assembly, and the other is connected to the ground.

[0010] Preferably, the working gas is argon.

[0011] Preferably, the chemical vapor deposition system includes a gas source, a gas delivery pipe, and a nozzle. A flow control valve is provided on the gas delivery pipe. The gas source includes a carbon source gas and an auxiliary gas. The carbon source gas is one of methane and acetylene, and the auxiliary gas is one of argon and hydrogen.

[0012] The usage method of the single chiral carbon nanotube synthesis device is realized through the synthesis device, and includes the following steps:

[0013] S1. Uniformly place the catalyst on the substrate of the reaction chamber sample stage, and seal the reaction chamber;

[0014] S2. Turn on the chemical vapor deposition system, adjust the flow rate of the gas source through the flow control valve of the gas delivery pipe, so that the carbon source gas and the auxiliary gas are mixed in a volume ratio of 4:1 and sprayed into the reaction chamber through the nozzle. At the same time, evacuate the dielectric tube in the source chamber and introduce the working gas into the dielectric tube to make the air pressure in the dielectric tube reach 4000 Pa, and control the pressure in the reaction chamber;

[0015] S3. Start the magnetic coil, and adjust the magnetic field strength by applying a voltage according to the requirements of the target chiral carbon nanotubes;

[0016] S4. Trigger the high-voltage pulse generating assembly, apply a high-voltage pulse to the reaction chamber, set the pulse frequency, amplitude, and pulse width. Under the synergistic action of chemical vapor deposition, magnetic field, and high-voltage pulse, the growth reaction of carbon nanotubes occurs on the surface of the catalyst;

[0017] S5. After the reaction ends, cool the reaction chamber and collect the prepared single chiral carbon nanotubes.

[0018] Preferably, in step S2, the flow rate of the carbon source gas is 105 - 145 ml / min, the flow rate of the auxiliary gas is 25 - 35 ml / min, and the pressure in the reaction chamber is controlled at 3500 - 4500 Pa.

[0019] Preferably, in step S3, the magnetic field strength is 80 - 200 mT, and the applied voltage is 3.5 - 3.9 kV.

[0020] Preferably, in step S4, the pulse frequency is 650 - 750 Hz, the amplitude is 5.5 - 7 kV, and the pulse width is 2 - 4 μs.

[0021] The advantages and beneficial effects of the present invention adopting the above-mentioned single - chirality carbon nanotube synthesis device and its usage method are as follows:

[0022] 1. By precisely controlling the reaction conditions and magnetic field, the present invention can efficiently synthesize single - chirality carbon nanotubes with a purity of over 95%.

[0023] 2. By adjusting the reaction parameters and magnetic field strength, the present invention can achieve the selective synthesis of different - chirality carbon nanotubes.

[0024] 3. The synthesis device of the present invention is easy to operate and suitable for large - scale preparation.

[0025] 4. The magnetic field generated by the magnetic coil of the present invention can further control the growth direction and chirality of carbon nanotubes, improving the synthesis efficiency and purity.

[0026] The technical solution of the present invention will be further described in detail below through the drawings and examples. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the single - chirality carbon nanotube synthesis device of the present invention;

[0028] Figure 2 is a flowchart of the usage of the single - chirality carbon nanotube synthesis device of the present invention.

[0029] Reference Signs

[0030] 1. High - voltage pulse generating assembly; 2. Magnetic coil; 3. Helix; 4. Dielectric tube; 5. Ring electrode; 6. Substrate; 7. Sample stage; 8. Gas delivery tube; 9. Carbon source gas; 10. Auxiliary gas; 11. Working gas; 12. Reaction chamber; 13. Source chamber. Detailed Embodiments

[0031] The technical solution of the present invention will be further described below through the drawings and examples.

[0032] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings as understood by those of ordinary skill in the field to which the present invention pertains. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0033] As Figure 1 shown, a single chiral carbon nanotube synthesis device includes a source chamber 13 and a reaction chamber 12. Inside the reaction chamber 12, there is a sample stage 7. On the sample stage 7, there is a substrate 6 and a catalyst (not shown in the figure). The material of the substrate 6 is single-crystalline silicon, and the catalyst is one or more of iron, cobalt, nickel, alumina, and magnesia. The source chamber 13 and the reaction chamber 12 are in communication.

[0034] Inside the source chamber 13, there is a dielectric tube 4. The dielectric tube 4 is a quartz dielectric tube with a length of 1 m, an inner diameter of 6 mm, and an outer diameter of 9 mm.

[0035] A helix 3 is wound around the outside of the dielectric tube 4. The presence of the helix 3 can effectively modulate the morphology of the helix and other three-dimensional shapes. Both ends of the dielectric tube 4 are provided with ring electrodes 5. One end of the dielectric tube 4 is connected to the external working gas 11, and the working gas 11 is argon. A magnetic coil 2 is provided outside the source chamber 13. The reaction chamber 12 is externally connected to a chemical vapor deposition system, and the source chamber 13 is externally connected to a high-voltage pulse generating assembly 1. One of the two end ring electrodes 5 is connected to the high-voltage pulse generating assembly 1, and the other is grounded.

[0036] The chemical vapor deposition system includes a gas source, a gas delivery pipe 8, and a nozzle (not shown in the figure). A flow control valve is provided on the gas delivery pipe 8. The gas source includes a carbon source gas 9 and an auxiliary gas 10. The carbon source gas 9 is one of methane and acetylene, and the auxiliary gas 10 is one of argon and hydrogen. The chemical vapor deposition system and the high-voltage pulse generating assembly 1 are prior arts.

[0037] The usage method of the single chiral carbon nanotube synthesis device, as Figure 2 shown, includes the following steps:

[0038] S1. Place the catalyst evenly on the substrate 6 of the sample stage 7 in the reaction chamber 12, and seal the reaction chamber 12.

[0039] S2. Turn on the chemical vapor deposition system, adjust the flow rate of the gas source through the flow control valve of the gas delivery pipe 8, so that the carbon source gas 9 and the auxiliary gas 10 are mixed in a volume ratio of 4:1 and sprayed into the reaction chamber 12 through the nozzle. While evacuating the medium tube 4 in the source chamber 13, introduce the working gas 11 into the medium tube 4 to make the air pressure in the medium tube 4 reach 4000 Pa, and control the pressure in the reaction chamber 12; the flow rate of the carbon source gas 9 is 105 - 145 ml / min, the flow rate of the auxiliary gas 10 is 25 - 35 ml / min, and the pressure in the reaction chamber is controlled at 3500 - 4500 Pa.

[0040] S3. Start the magnetic coil 2, and adjust the magnetic field strength by applying a voltage according to the requirements of the target chiral carbon nanotubes; the magnetic field strength is 80 - 200 mT, the applied voltage is 3.5 - 3.9 kV, and adjust the magnetic field strength and direction according to the number of turns and current intensity of different magnetic coils 2. The magnetic field strength and direction have a crucial impact on the chirality of carbon nanotubes.

[0041] S4. Trigger the high - voltage pulse generating component 1, apply a high - voltage pulse to the reaction chamber, set the pulse frequency at 650 - 750 Hz, the amplitude at 5.5 - 7 kV, and the pulse width at 2 - 4 μs. Under the combined action of chemical vapor deposition, magnetic field and high - voltage pulse, the growth reaction of carbon nanotubes occurs on the catalyst surface.

[0042] S5. After the reaction is completed, cool the reaction chamber and collect the prepared single - chirality carbon nanotubes.

[0043] Example 1

[0044] The usage method of the single - chirality carbon nanotube synthesis device includes the following steps:

[0045] S1. Evenly place the catalyst iron on the single - crystal silicon substrate 6 of the sample stage 7 in the reaction chamber 12 and seal the reaction chamber 12.

[0046] S2. Turn on the chemical vapor deposition system, adjust the flow rate of the gas source through the flow control valve of the gas delivery pipe 8, so that methane and hydrogen are mixed in a volume ratio of 4:1 and sprayed into the reaction chamber 12 through the nozzle. While evacuating the quartz medium tube in the source chamber 13, introduce argon into the quartz medium tube to make the air pressure in the medium tube 4 reach 4000 Pa, and control the pressure in the reaction chamber 12 at 3800 Pa; the flow rate of methane is 145 ml / min, and the flow rate of hydrogen is 30 ml / min.

[0047] S3. Start the magnetic coil 2, and adjust the magnetic field strength by applying a voltage according to the requirements of the target chiral carbon nanotubes; the magnetic field strength is 160 mT, and the applied voltage is 3.9 kV. Adjust the magnetic field strength and direction according to the number of turns and current intensity of different magnetic coils 2. The magnetic field strength and direction have a crucial impact on the chirality of carbon nanotubes.

[0048] S4. Trigger the high-voltage pulse generating component 1 to apply a high-voltage pulse to the reaction chamber. Set the pulse frequency to 700 Hz, the amplitude to 7 kV, and the pulse width to 3 μs. Under the combined action of chemical vapor deposition, magnetic field, and high-voltage pulse, the growth reaction of carbon nanotubes occurs on the catalyst surface.

[0049] S5. After the reaction is completed, cool the reaction chamber and collect the prepared single-chirality carbon nanotubes with a purity of 97%.

[0050] Example 2

[0051] The usage method of the single-chirality carbon nanotube synthesis device includes the following steps:

[0052] S1. Uniformly place the catalyst cobalt on the single-crystalline silicon substrate 6 of the sample stage 7 in the reaction chamber 12 and seal the reaction chamber 12.

[0053] S2. Turn on the chemical vapor deposition system. Adjust the flow rate of the gas source through the flow control valve of the gas delivery pipe 8 so that methane and argon are mixed in a volume ratio of 4:1 and sprayed into the reaction chamber 12 through the nozzle. Vacuum the quartz dielectric tube in the source chamber 13 and introduce argon into the quartz dielectric tube at the same time to make the air pressure in the dielectric tube 4 reach 4000 Pa, and control the pressure in the reaction chamber 12 to be 4000 Pa; the flow rate of methane is 105 ml / min, and the flow rate of argon is 30 ml / min.

[0054] S3. Start the magnetic coil 2 and adjust the magnetic field strength by applying a voltage according to the requirements of the target single-chirality carbon nanotubes; the magnetic field strength is 80 mT, and the applied voltage is 3.5 kV. Adjust the magnetic field strength and direction according to the number of turns and current intensity of different magnetic coils 2. The magnetic field strength and direction have a crucial impact on the chirality of carbon nanotubes.

[0055] S4. Trigger the high-voltage pulse generating component 1 to apply a high-voltage pulse to the reaction chamber. Set the pulse frequency to 700 Hz, the amplitude to 6 kV, and the pulse width to 3 μs. Under the combined action of chemical vapor deposition, magnetic field, and high-voltage pulse, the growth reaction of carbon nanotubes occurs on the catalyst surface.

[0056] S5. After the reaction is completed, cool the reaction chamber and collect the prepared single-chirality carbon nanotubes with a purity of 95%.

[0057] The magnetic field strength and direction have a crucial impact on the chirality of carbon nanotubes. When the magnetic field strength is in a lower range, such as less than 80 mT, the growth of carbon nanotubes is mainly dominated by chemical vapor deposition and other factors, and the chirality distribution is relatively random; as the magnetic field strength gradually increases to the range of 80 - 200 mT, the nucleation rate of carbon nanotubes with specific chirality will gradually increase. This is because the magnetic field will change the electron cloud distribution and atomic magnetic moment in the reaction system, thereby affecting the adsorption and decomposition processes of carbon source molecules on the catalyst surface, and promoting the formation of carbon nanotube precursors with specific chiral structures. For the magnetic field direction, the magnetic field along the axis of the reaction chamber 12 and the magnetic field perpendicular to the axis will induce the growth of carbon nanotubes with different chiralities. For example, when the magnetic field is along the axis, it is beneficial to form carbon nanotubes with a chiral angle of 0 - 30 degrees; when the magnetic field is perpendicular to the axis, it is more likely to generate carbon nanotubes with a chiral angle of 20 - 30 degrees. By precisely controlling the current magnitude and direction of the magnetic coil 2, a magnetic field with appropriate strength and direction can be generated.

[0058] In the low-pressure dielectric tube 4, a low-temperature plasma propagating in a helical form is formed by pulsed modulation electromagnetic drive, and its helical chirality direction changes with the electromagnetic parameters. Under given parameters, the plasma discharge mode is a helical wave discharge mode. Under a given CH4 flow rate, the electron energy distribution in the plasma is sufficient to dissociate methane molecules and form carbon-containing active radicals. By adjusting the CH4 flow rate, the preparation of different carbon-based thin films is achieved.

[0059] Therefore, the present invention adopts the above-mentioned single-chirality carbon nanotube synthesis device and its usage method. The synthesis device is convenient to operate and suitable for large-scale preparation. By precisely controlling the reaction conditions, single-chirality carbon nanotubes can be efficiently synthesized with a purity of over 95%. By adjusting the reaction parameters, the selective synthesis of carbon nanotubes with different chiralities can be achieved.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements do not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for synthesizing single chiral carbon nanotubes, characterized in that: The invention comprises a single chiral carbon nanotube synthesis device, which comprises a source chamber and a reaction chamber. A sample stage is arranged inside the reaction chamber, a substrate and a catalyst are arranged on the sample stage, a dielectric tube is arranged inside the source chamber, a spiral wire is wound around the outside of the dielectric tube, and ring electrodes are arranged at both ends of the dielectric tube, one end of the dielectric tube is connected to an external working gas, a magnetic coil is arranged outside the source chamber, a vapor deposition system is connected to the reaction chamber, and a high-voltage pulse generating component is connected to the source chamber; A method for synthesizing single chiral carbon nanotubes comprises the following steps: S1. Place the catalyst evenly on the base of the reaction chamber sample stage and seal the reaction chamber; S2. Turn on the vapor deposition system, adjust the flow rate of the gas source through the flow control valve of the gas delivery pipe, so that the carbon source gas and the auxiliary gas are mixed in a volume ratio of 4:1 and then sprayed into the reaction chamber through the nozzle, evacuate the medium pipe in the source chamber and introduce the working gas into the medium pipe at the same time, so that the gas pressure in the medium pipe reaches 4000Pa, and control the pressure in the reaction chamber; S3. Start the magnetic coil and adjust the magnetic field strength by applying voltage according to the requirements of the target chiral carbon nanotubes, the magnetic field strength is 80-200mT; S4. Triggering the high-voltage pulse generating assembly to apply a high-voltage pulse to the reaction chamber, setting the pulse frequency to 650-750 Hz, the amplitude to 5.5-7 kV, and the pulse width to 2-4 μs, and performing a growth reaction of carbon nanotubes on the catalyst surface under the synergistic effect of vapor deposition, magnetic field and high-voltage pulse; S5. After the reaction is completed, the reaction chamber is cooled and the prepared single chiral carbon nanotubes are collected.

2. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: The substrate material is single crystal silicon, and the catalyst is one or more of iron, cobalt, nickel, aluminum oxide, and magnesium oxide.

3. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: The medium tube is a quartz medium tube with a length of 1 m, an inner diameter of 6 mm, and an outer diameter of 9 mm.

4. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: One of the ring electrodes at both ends is connected to the high voltage pulse generating component, and the other is grounded.

5. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: The working gas is argon.

6. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: The vapor deposition system includes a gas source, a gas delivery pipe, and a nozzle. The gas delivery pipe is provided with a flow control valve. The gas source includes a carbon source gas and an auxiliary gas. The carbon source gas is one of methane and acetylene, and the auxiliary gas is one of argon and hydrogen.

7. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: In step S2, the pressure in the reaction chamber is controlled at 3500-4500Pa.

8. The method for synthesizing single chiral carbon nanotubes according to claim 1, characterized in that: In step S3, a voltage of 3.5-3.9 kV is applied.

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