Electrode for preparing single-walled carbon nanotube by plasma arc method and application

Abstract

The invention provides an electrode for preparing a single-walled carbon nanotube by a plasma arc method and application, and relates to the technical field of carbon nanotubes. Specifically, the electrode comprises a graphite cathode rod, the graphite cathode rod is provided with a conveying channel in the length direction of the graphite cathode rod, and the two ends of the graphite cathode rod are provided with an air inlet and an air outlet which are communicated with the conveying channel respectively; a plurality of shunting ports are formed in positions, close to the air outlet, of the side surface of the graphite cathode rod; and the shunting ports are communicated with the conveying channel through shunting channels. According to the graphite cathode based on the specific structure, the material winding phenomenon in the preparation process of the carbon nanotubes can be avoided under the conditions that external force is not applied and plasma discharge is not affected, the single-walled carbon nanotubes with high content and high yield are obtained, the IG / ID value of the single-walled carbon nanotubes is about 60, and the graphite cathode has good application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanotubes, and in particular to an electrode for preparing single-walled carbon nanotubes by a plasma arc method and its application. Background Art

[0002] Single-walled carbon nanotubes (SWCNTs) are tubular nanomaterials composed of single-layer graphene sheets. Due to their excellent mechanical, electrical and thermal properties, they have shown application advantages in many fields. Specifically, single-walled carbon nanotubes have ultra-high strength and modulus, light weight, excellent electrical and thermal conductivity, good chemical stability, and a large specific surface area; these advantages make single-walled carbon nanotubes have great potential in the preparation of high-performance composite materials, improvement of battery electrodes, manufacture of high-performance sensors and actuators, and as drug delivery systems. In addition, carbon nanotubes also show unique application value in energy storage, catalyst carriers, environmental protection technology, etc.

[0003] The main traditional methods for preparing single-walled carbon nanotubes include arc discharge, floating catalytic chemical deposition, laser ablation, etc., but they have disadvantages such as low yield and low purity. In comparison, the plasma arc method for preparing single-walled carbon nanotubes can not only obtain single-walled carbon nanotubes in large quantities with high quality; however, there are still other defects in the process of plasma preparation of single-walled carbon nanotubes, such as material collection problems and catalyst addition methods.

[0004] When plasma is used to prepare single-walled carbon nanotubes, a strong voltage is applied between the positive and negative electrodes, so that a small amount of charged particles in the plasma gas in the generation chamber are accelerated in the electric field to gain energy, collide with gas atoms to exchange energy, and thus ionize the gas to form a conductive fluid; this process converts electrical energy into heat energy and light energy, and dissociates and recombine the carbon source gas to form carbon nanotubes. In this process, cathode and anode discharges are required, and in a large number of preparation practices, it is found that the cathode graphite rod is often accompanied by single-walled carbon nanotube entanglements, which cannot flow out of the reaction chamber in time with the airflow.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide an electrode for preparing single-walled carbon nanotubes by a plasma arc method, so as to avoid the material entanglement phenomenon at the bottom of the cathode during the carbon nanotube growth reaction without applying external force and affecting plasma discharge.

[0007] The second object of the present invention is to provide a device for preparing single-walled carbon nanotubes by a plasma arc method.

[0008] The third object of the present invention is to provide a method for preparing single-walled carbon nanotubes by a plasma arc method.

[0009] The present invention detects the entanglement material attached to the graphite electrode and finds that it is not tightly wrapped around the electrode. If a force in the opposite direction can be applied to it, even if the force is relatively light, combined with the relatively light weight of the single-walled carbon nanotubes themselves, the electrode entanglement phenomenon can be avoided. However, conventional external force methods such as stirring may touch the electrode and affect the discharge process. If the structure of the graphite electrode itself can be modified and adjusted, the cathode entanglement phenomenon will be avoided without affecting the normal progress of the plasma preparation process.

[0010] Therefore, in order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] An electrode for preparing single-walled carbon nanotubes by a plasma arc method, comprising a graphite cathode rod, wherein the graphite cathode rod is provided with a conveying channel along its length direction, and both ends of the graphite cathode rod are respectively provided with an air inlet and an air outlet connected to the conveying channel;

[0012] A plurality of diversion openings are arranged on the side surface of the graphite cathode rod at a position close to the gas outlet, and the diversion openings are connected with the conveying channel through a diversion channel.

[0013] A device for preparing single-walled carbon nanotubes by a plasma arc method, comprising the electrode for preparing single-walled carbon nanotubes by a plasma arc method;

[0014] The device comprises a solid-phase feeding unit, a gas-phase feeding unit, a plasma arc furnace and a collecting unit. The electrode is arranged in the plasma arc furnace. The gas-phase feeding unit, the solid-phase feeding unit and the graphite cathode rod are connected in sequence.

[0015] A method for preparing single-walled carbon nanotubes by a plasma arc method, the method adopts the electrode for preparing single-walled carbon nanotubes by a plasma arc method, or the device for preparing single-walled carbon nanotubes by a plasma arc method; the method comprises the following steps:

[0016] The plasma arc furnace is evacuated to a vacuum, and then plasma gas is input, the arc power supply is turned on and a plasma arc atmosphere is obtained;

[0017] Inputting growth gas, solid raw material and carrier gas into the plasma arc furnace to carry out a growth reaction of single-walled carbon nanotubes;

[0018] Single-walled carbon nanotubes are obtained by collecting the reaction tail gas.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention provides an electrode for preparing single-walled carbon nanotubes by a plasma arc method. By improving the graphite cathode and adding a diversion port and a diversion channel on the basis of the conventional structure, part of the airflow is diverted from the side wall of the cathode graphite rod, forming a force in the opposite direction to the material attachment direction at the bottom of the cathode, thereby effectively preventing the generated carbon nanotube material from winding around the electrode.

[0021] (2) Based on the electrode, the present invention also provides a corresponding device and method for preparing single-walled carbon nanotubes by a plasma arc method. By increasing the gas phase flow rate at the electrode feed end, it is possible to achieve continuous production of single-walled carbon nanotubes without affecting plasma discharge, and obtain single-walled carbon nanotubes with high content, high yield and high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic structural diagram of a graphite cathode for preparing single-walled carbon nanotubes by a plasma arc method in the present invention is provided;

[0024] Figure 2 A schematic structural diagram of a device for preparing single-walled carbon nanotubes by a plasma arc method in the present invention is provided;

[0025] Figure 3 A line graph of the Raman spectrum of Example 1 is provided;

[0026] Figure 4 A Raman spectrum of a comparative example is provided.

[0027] Reference numerals:

[0028] 10-graphite cathode rod; 11-transport channel;

[0029] 12-air inlet; 13-air outlet;

[0030] 14-diversion channel; 15-diversion port;

[0031] 20-gas phase feeding unit; 30-solid phase feeding unit;

[0032] 40 - plasma arc furnace; 50 - collection unit. DETAILED DESCRIPTION

[0033] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0034] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0035] A first aspect of the present invention is to provide an electrode for preparing single-walled carbon nanotubes by a plasma arc method.

[0036] The electrode comprises a graphite cathode rod 10, such as Figure 1 As shown, Figure 1 A schematic diagram of the structure of a feasible graphite cathode rod of the present invention is provided. The graphite cathode rod 10 is provided with a conveying channel 11 along its length direction, and the two ends of the graphite cathode rod 10 are respectively provided with an air inlet 12 and an air outlet 13 connected to the conveying channel 11; the side of the graphite cathode rod 10 is provided with a plurality of diversion ports 15 at a position close to the air outlet 13, and the diversion ports 15 are connected to the conveying channel 11 through a diversion channel 14.

[0037] It should be emphasized that the graphite cathode rod 10 forms a "hollow" tubular structure based on the conveying channel 11, which can also be regarded as a through hole structure starting from the gas inlet 12 and ending at the gas outlet 13 in the graphite cathode rod 10. The conveying channel 11 can transmit plasma gases such as argon and hydrogen for discharge on the one hand, and solid-phase powder materials such as catalysts and co-catalysts can be brought into the arc furnace body (the molten pool) through the carrier gas on the other hand; and the above two functions can be performed simultaneously without affecting each other.

[0038] That is, the delivery channel 11, the air inlet 12 and the air outlet 13 in the present invention are used to input plasma gas, carrier gas, solid raw materials and other materials necessary for the plasma arc method into the plasma arc furnace. On this basis, the present invention further designs a plurality of diversion ports 15 and diversion channels 14 on the side wall of the graphite cathode rod 10 to solve the technical problem that the electrode (especially at the gas outlet end) is prone to material entanglement; the diversion channel 14 of the present invention can divert part of the gas as the purge gas of the electrode graphite rod, and by controlling the number and aperture of the diversion ports 15 and the diversion channel 14, a certain proportion of gas can be diverted to purge the material entangled on the graphite cathode rod 10, so that it can be carried out of the reaction chamber by the airflow, while ensuring that the required discharge effect is not affected after the diversion of part of the gas.

[0039] Regarding the position of each pair of the diverter ports 15, since the electrode material wrapping phenomenon mostly occurs at the electrode outlet 13 end, and the electrode graphite rod will be lost in a high temperature environment, the present invention provides the diverter ports 15 set at "a position close to the outlet"; further, as a preferred embodiment, in terms of the length direction of the graphite cathode rod 10, the distance between the diverter ports 15 and the outlet 13 is 1 / 20 to 1 / 2 of the length of the graphite cathode. For example, when a hollow graphite rod with a length of 100 cm is used as the cathode, a hole is punched in the interval of 5 cm to 50 cm from the outlet end and used as the diverter channel 14.

[0040] As a more preferred embodiment, in the length direction of the graphite cathode rod 10, the distance between the diverter port 15 closest to the gas outlet 13 and the gas outlet 13 is 1 / 20 to 1 / 12 of the length of the graphite cathode rod 10. It is worth noting that the distance between at least one diverter port 15 (or a pair of symmetrically arranged diverter ports 15) and the gas outlet 13 is 1 / 20 to 1 / 12 of the length of the graphite cathode rod 10, so as to ensure that the graphite cathode rod 10 is free of entangled materials near the gas outlet 13.

[0041] As a preferred embodiment, the length of the graphite cathode rod 10 is 50 cm to 80 cm, and the diversion ports 15 are distributed at 2.5 cm to 40 cm from the gas outlet 13. By setting the position of the diversion ports 15, it is possible not to affect the electrode discharge effect, and at the same time, it is possible to avoid the inevitable loss of the graphite cathode rod 10 during each reaction process, which leads to the disappearance of the holes, thereby ensuring that the effect of discharge and purging the material wrapped on the graphite rod is not affected.

[0042] As a preferred embodiment, the pore size of the diversion channel 14 is 1.5 mm to 3 mm, including but not limited to any one of 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 (mm) or a numerical range consisting of any two of them.

[0043] As a preferred embodiment, the plurality of diversion ports 15 are evenly distributed around the side surface of the graphite cathode rod 10 .

[0044] As a more preferred embodiment, the diversion openings 15 (and / or the diversion channels 14) are symmetrically arranged, and the aperture of each group of the symmetrically arranged diversion openings 15 should be consistent. However, the aperture size of the asymmetrically arranged diversion openings 15 can be independently selected within the above-mentioned preferred range, without having to ensure that the apertures of all the diversion openings 15 are the same.

[0045] As a further preferred embodiment, the diversion ports 15 (and / or the diversion channels 14) are symmetrically arranged in groups of two.

[0046] As a preferred embodiment, the number of the diversion openings 15 is 20 to 40; as a more preferred embodiment, the diversion openings 15 are 10 to 20 pairs symmetrically arranged. As a more preferred embodiment, the distance between adjacent diversion openings 15 is 3 cm to 10 cm.

[0047] As a preferred embodiment, the diversion channel 14 extends from the delivery channel 11 to the diversion port 15 in a direction away from the air outlet 13 .

[0048] As a more preferred embodiment, the angle between the extension direction of the diversion channel 14 and the extension direction of the delivery channel 11 is α, and α is 45° to 75°.

[0049] In the present invention, in order to make the diverted gas passing through the diverter port 15 have a better material entanglement and purging effect, the channel angle of the diverter channel 14 is designed; it is worth noting that the angle of each pair of mutually symmetrical diverter channels 14 should be the same to ensure the symmetry of the flow field.

[0050] As a preferred embodiment, the two ends of the graphite cathode rod 10 respectively include at least one air inlet 12 and at least one air outlet 13, and there is at least one conveying channel 11 in the graphite cathode rod 10, and the number of the air inlet 12, the air outlet 13 and the conveying channel 11 should be consistent.

[0051] As a preferred embodiment, the electrode also includes an anode; the material of the anode includes graphite, and optional additives such as metal catalysts and growth promoters; the overall structure of the anode includes but is not limited to a cylinder, a cube, or has special surface structures such as drilled holes and grooves; in the present invention, there is no restriction on the anode, and any anode that can be matched with the graphite cathode rod 10 of the present invention and generate single-walled carbon nanotubes can be used as an embodiment of the present invention.

[0052] The second aspect of the present invention is to provide a device for preparing single-walled carbon nanotubes by a plasma arc method, comprising the electrode for preparing single-walled carbon nanotubes by a plasma arc method as described in the first aspect.

[0053] The device at least comprises a solid-phase feeding unit 30, a gas-phase feeding unit 20, a plasma arc furnace 40 and a collecting unit 50, wherein the electrode is arranged in the plasma arc furnace 40, and the gas-phase feeding unit 20, the solid-phase feeding unit 30 and the graphite cathode rod 10 are connected in sequence. Figure 2 The figure shows a feasible schematic diagram of the connection relationship of the device.

[0054] The solid-phase feeding unit 30 is used to fully mix the solid-phase raw materials (such as raw materials, catalysts, etc.) as a functional unit for storing materials and conveying the solid-phase raw materials to the plasma arc furnace 40. The gas-phase feeding unit 20 is used to provide plasma gas to the plasma arc furnace 40, and is also used to provide carrier gas for transporting the solid-phase raw materials to the solid-phase feeding unit 30. The plasma arc furnace 40 is the main synthesis site for preparing single-walled carbon nanotubes by the plasma arc method. The electrodes in the furnace body discharge in a plasma gas environment to form a high-temperature plasma, and the carbon source raw materials are pyrolyzed and reorganized to obtain single-walled carbon nanotubes. The collecting unit 50 is used to collect the single-walled carbon nanotubes generated in the plasma arc furnace 40.

[0055] As a preferred embodiment, the device further comprises a second gas phase feeding unit connected to the plasma arc furnace 40 for directly providing growth gas to the interior of the plasma arc furnace 40, wherein the growth gas serves as another carbon source for the single-walled carbon nanotubes.

[0056] In some optional embodiments, the device also includes conventional or unconventional functional units such as a cooling unit, a temperature or flow monitoring unit, an airflow control unit, a product detection unit, etc. Under the premise of ensuring that the electrodes and the generation of single-walled carbon nanotubes are included, the present invention does not impose any restrictions on the additional functional units of the device.

[0057] The third aspect of the present invention is to provide a method for preparing single-walled carbon nanotubes by plasma arc method, comprising the electrode for preparing single-walled carbon nanotubes by plasma arc method as described in the first aspect.

[0058] The method comprises the following steps: 1) evacuating a plasma arc furnace 40 to a vacuum, and then inputting plasma gas, turning on an arc power supply and obtaining a plasma arc atmosphere; 2) inputting a growth gas, a solid raw material and a carrier gas into the plasma arc furnace 40 to carry out a growth reaction of single-walled carbon nanotubes; and 3) obtaining single-walled carbon nanotubes by collecting reaction tail gas.

[0059] As a preferred embodiment, in the growth reaction stage, the ratio of the gas flow through the diversion port 15 to the gas flow through the gas outlet 13 is 1 / 3 to 1 / 2; it should be noted that this embodiment refers to the ratio of the sum of the gas flow through all the diversion ports 15 to the gas flow through the gas outlet 13.

[0060] In the present invention, by comprehensively designing the number and aperture of the diversion ports 15 on the graphite cathode rod 10 and the total gas flow at the gas inlet 12, the above-mentioned specific gas diversion ratio can be controlled and achieved, thereby avoiding the occurrence of material entanglement while ensuring the normal growth reaction.

[0061] As a preferred implementation, the gas flow rate of the air inlet 12 is 300 L / min to 800 L / min.

[0062] As a preferred embodiment, the gas flow rate of the gas outlet 13 is 200L / min to 500L / min, and the total gas flow rate of the diversion port 15 is 100L / min to 300L / min.

[0063] As a preferred embodiment, the raw materials input through the gas inlet 12 of the graphite cathode rod 10 include: the plasma gas, the solid raw material and the carrier gas; and the growth gas is directly transported to the plasma arc furnace 40 through other gas paths.

[0064] As a preferred embodiment, the plasma gas includes hydrogen and a first inert gas; wherein the first inert gas includes at least one of nitrogen, argon or helium.

[0065] As a preferred embodiment, the carrier gas includes at least one of nitrogen, argon and helium.

[0066] As a preferred embodiment, the growth gas includes a carbon source gas, a reducing gas and a second inert gas; wherein the carbon source gas includes at least one of carbon monoxide, methane, benzene, ethylene or acetylene, the reducing gas includes at least one of hydrogen, carbon monoxide or hydrogen sulfide, and the second inert gas includes at least one of nitrogen, argon or helium.

[0067] In some optional embodiments, in the growth gas, the volume proportion of the carbon source gas is 2% to 15%, the volume proportion of the reducing gas is 2% to 30%, and the remaining volume is the second inert gas.

[0068] In some optional embodiments, during the growth reaction stage, the volume ratio of the growth gas to the carrier gas is 0.01 to 0.1.

[0069] It should be noted that the method of the present invention should also include parameters such as the type of solid raw material, the feed amount of solid raw material, and the specifications of the arc power supply. Those skilled in the art can adjust them adaptively, and the parameters are not strictly limited in the present invention.

[0070] Example 1

[0071] The graphite cathode used in this embodiment has a length of 70 cm and a diameter of 15 cm. A delivery channel with an aperture of 10 cm is set at the center of the graphite cathode. A pair of symmetrically positioned inclined holes are set on the rod wall 4 cm away from the bottom of the graphite cathode as diversion channels. The aperture of the inclined holes is 2.5 mm, and the angle between the diversion channel direction and the length direction of the graphite cathode is 60°.

[0072] This example uses the following method to prepare single-walled carbon nanotubes:

[0073] S1: Weigh iron powder and sulfur powder in a weight ratio of 9:1, grind and mix them thoroughly, and load them into the powder feeding device.

[0074] S2: Evacuate the plasma arc furnace and then switch to argon arc gas with a flow rate of 400L / min. After the pressure stabilizes, turn on the arc power supply with a current of 1300A and a voltage of 80V to generate a plasma arc. The vortex formed will increase the furnace temperature to more than 900℃; turn on the cooling auxiliary unit.

[0075] S3: A carrier gas is introduced into the plasma arc furnace through the conveying channel of the graphite cathode, wherein the carrier gas will pass through the powder feeding device, carrying iron powder and sulfur powder together through the arc cathode into the graphite crucible in the arc furnace for reaction; the feeding rate of the powder feeder is 100g / h, and the carrier gas flow rate is 500L / min.

[0076] At the same time, growth gas is introduced through the gas inlet point on the wall of the reaction chamber in the plasma arc furnace, wherein the growth gas is methane, hydrogen and argon (volume ratio is 5:10:80), and the total flow rate of the growth gas is 80L / min.

[0077] S4: The single-walled carbon nanotubes enter the collection device together with the reaction tail gas to obtain the product of this embodiment.

[0078] The peaks at 1450 and 1590 of the Raman spectrum of the product of this example correspond to the D peak and G peak of the carbon material, and the peak intensity ratio G / D is 60.9.

[0079] Example 2

[0080] It is basically the same as Example 1, except that two pairs of symmetrically positioned inclined holes are set on the rod wall 5 cm away from the bottom of the graphite cathode, the distances between the four inclined holes are the same, and the diameter of the inclined holes is 1.5 mm.

[0081] Example 3

[0082] It is basically the same as Example 1, except that a pair of symmetrically positioned inclined holes are provided on the rod wall at a position 3.5 cm away from the bottom of the graphite cathode, and the diameter of the inclined holes is 3 mm.

[0083] Example 4

[0084] It is basically the same as Example 1, with the only difference being that: a pair of symmetrically positioned inclined holes with a diameter of 1.5 mm is set on the rod wall at a distance of 4 cm from the bottom of the graphite cathode; another pair of symmetrically positioned inclined holes with a diameter of 1.5 mm is set on the rod wall at a distance of 10 cm from the bottom of the graphite cathode; the two pairs of inclined holes have the same circumferential position on the graphite cathode.

[0085] Example 5

[0086] It is basically the same as Example 1, except that the angle between the direction of the shunt channel and the length direction of the graphite cathode is 75°.

[0087] Example 6

[0088] It is basically the same as Example 1, except that the angle between the direction of the shunt channel and the length direction of the graphite cathode is 45°.

[0089] Example 7

[0090] It is basically the same as Example 1, except that the methane gas is replaced by carbon monoxide gas.

[0091] Comparative Example

[0092] It is basically the same as Example 1, except that there is no inclined hole on the graphite cathode.

[0093] Test example

[0094] The single-walled carbon nanotubes prepared in each embodiment and comparative example were tested by Raman spectrometer, and the peaks at 1450 and 1590 of the Raman spectrum were recorded as the D peak and G peak of the carbon material, and the peak intensity ratio G / D ratio was calculated. The purity and yield of the single-walled carbon nanotubes prepared in each embodiment and comparative example were calculated. The results of this test example are recorded in the following Table 1.

[0095] In addition, if Figure 3 , Figure 4 As shown, the Raman spectra of Example 1 and the comparative example are provided respectively.

[0096] Table 1

[0097] purity(%) Productivity (g / h) G / D Example 1 80 100 60.9 Example 2 78 96 59.0 Example 3 73 94 57.5 Example 4 80 102 67.2 Example 5 50 70 43.7 Example 6 82 103 65.0 Example 7 60 88 51.0 Comparative Example 25 40 7.5

[0098] Among them, the G peak of the single-walled carbon nanotube in the Raman spectrum mainly comes from the stretching vibration of the sp2 hybridized carbon atom and the π electron, and the D peak mainly comes from the stretching vibration of the CC bond and the C=C double bond. When the G / D ratio is higher, it means that the carbon nanotube has better crystallinity and can show better electrical conductivity and mechanical properties. It can be seen from Table 1 that by using the special graphite cathode of the present invention, compared with the conventional graphite cathode, the embodiment of the present invention has better yield and product performance.

[0099] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. An electrode for preparing single-walled carbon nanotubes by plasma arc method, characterized in that: The electrode comprises a graphite cathode rod, the graphite cathode rod is provided with a conveying channel along its length direction, and both ends of the graphite cathode rod are respectively provided with an air inlet and an air outlet connected to the conveying channel; A plurality of diversion openings are arranged on the side surface of the graphite cathode rod at a position close to the gas outlet, and the diversion openings are connected with the conveying channel through a diversion channel.

2. The electrode according to claim 1, characterized in that The plurality of diversion ports are evenly distributed around the side surface of the graphite cathode rod; and / or, along the length direction of the graphite cathode rod, the distance between the diversion port and the gas outlet is 1 / 20 to 1 / 2 of the length of the graphite cathode rod; And / or, along the length direction of the graphite cathode rod, the distance between the diversion port and the gas outlet is 2.5 cm to 40 cm.

3. The electrode according to claim 1, characterized in that The aperture of the diversion channel is the same as that of the diversion port, and the aperture is 1.5 mm to 3 mm; And / or, the plurality of diversion openings are arranged in groups of two and are symmetrically arranged, and the apertures of the two symmetrically arranged diversion openings in each group are the same.

4. The electrode according to claim 1, characterized in that The included angle α between the extension direction of the diversion channel and the extension direction of the delivery channel is 45° to 75°; And / or, from the delivery channel to the diversion port, the diversion channel extends in a direction away from the air outlet.

5. The electrode according to claim 1, characterized in that The diversion port is configured such that a ratio of a gas flow rate passing through the diversion port to a gas flow rate of the gas outlet is 1 / 3 to 1 / 2.

6. A device for preparing single-walled carbon nanotubes by a plasma arc method, characterized in that: An electrode for preparing single-walled carbon nanotubes by plasma arc method as claimed in any one of claims 1 to 5; The device comprises a solid-phase feeding unit, a gas-phase feeding unit, a plasma arc furnace and a collecting unit. The electrode is arranged in the plasma arc furnace. The gas-phase feeding unit, the solid-phase feeding unit and the graphite cathode rod are connected in sequence.

7. A method for preparing single-walled carbon nanotubes by a plasma arc method, characterized in that: The method uses the electrode for preparing single-walled carbon nanotubes by plasma arc method as claimed in any one of claims 1 to 5 or the device for preparing single-walled carbon nanotubes by plasma arc method as claimed in claim 6; the method comprises the following steps: The plasma arc furnace is evacuated to a vacuum, and then plasma gas is input, the arc power supply is turned on and a plasma arc atmosphere is obtained; Inputting growth gas, solid raw material and carrier gas into the plasma arc furnace to carry out a growth reaction of single-walled carbon nanotubes; Single-walled carbon nanotubes are obtained by collecting the reaction tail gas.

8. The method according to claim 7, characterized in that The raw materials input through the gas inlet of the graphite cathode rod include: the plasma gas, the solid-phase raw material and the carrier gas.

9. The method according to claim 7, characterized in that: The plasma gas includes hydrogen and a first inert gas; wherein the first inert gas includes at least one of nitrogen, argon or helium; And / or, the carrier gas includes at least one of nitrogen, argon and helium.

10. The method according to claim 7, characterized in that The growth gas includes a carbon source gas, a reducing gas and a second inert gas; Wherein, the carbon source gas includes at least one of carbon monoxide, methane, benzene, ethylene or acetylene, the reducing gas includes at least one of hydrogen, carbon monoxide or hydrogen sulfide, and the second inert gas includes at least one of nitrogen, argon or helium.

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