Carbon nanotube and growth unit, growth method, continuous preparation method and system thereof

Abstract

The invention discloses a carbon nanotube and a growth unit, a growth method, a continuous preparation method and a system thereof. The carbon nanotube continuous preparation system comprises a carbon nanotube growth unit and a product collection unit, the carbon nanotube growth unit comprises a reaction container, an anode, a cathode and an arc stabilizer solution supply mechanism, the arc starting end of the anode and the arc starting end of the cathode are arranged at an interval and are opposite to each other, the arc stabilizer solution supply mechanism is used for injecting an arc stabilizer solution into the reaction container, and when the carbon nanotube growth unit works, the arc stabilizer solution is fed into the reaction container; and the arcing ends of the anode and the cathode are both infiltrated in the arc stabilizer solution. And the product collecting unit is communicated with the reaction container and is used for collecting the carbon nanotubes generated in the reaction container. The controllable continuous preparation of the high-performance carbon tube can be realized, and the prepared product has the advantages of low length-diameter ratio, high conductivity, high crystallinity, high purity and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterial preparation, and in particular to a carbon nanotube and a growth unit, a growth method, a continuous preparation method and a continuous preparation system thereof. Background Art

[0002] Single-walled carbon nanotubes (SWCNTs) are widely used in lithium-ion battery silicon anodes due to their exceptionally high electrical and thermal conductivity, high strength, high flexibility, and high aspect ratio, as well as their ability to form a robust network within the material even at low dosages. They also play an indispensable role in emerging battery technologies, such as dry cell electrode coating processes and solid-state batteries.

[0003] Currently, the main methods for preparing SWCNTs include arc discharge, chemical vapor deposition, and laser ablation. Arc discharge involves the evaporation of the catalyst and carbon source, making the particle size and distribution of the resulting catalyst difficult to control and resulting in numerous purity defects. Many byproducts (such as multi-walled carbon nanotubes, carbon spheres, and metallic impurities) account for up to 30% of the product, requiring complex post-processing. These byproducts are difficult to separate and purify, affecting the purity and uniformity of the product and limiting its application. Furthermore, traditional arc discharge methods produce onion carbon, C60, and other fullerenes, as well as insoluble metallic impurities (such as tungsten, tantalum, and silicon), further complicating purification.

[0004] To overcome the above problems, researchers have attempted to synthesize SWCNTs using arc discharge technology at low current density. However, this method cannot produce nanocatalysts with high volume concentrations, and the yield is often below the gram level, resulting in a final yield of only 3-5 g / h, which is difficult to meet market demand. In addition, the existing arc method is mostly intermittent, which is difficult to meet industrial-grade needs. Single-walled and double-walled carbon nanotubes prepared by traditional arc and chemical vapor deposition methods are relatively long, with aspect ratios generally greater than 3000-50000. The industry consensus is that high aspect ratios are difficult to disperse, which brings great difficulties and costs to subsequent processing. There is an urgent need for a single-walled and double-walled carbon nanotube with high crystallinity, high conductivity and an aspect ratio of less than 2000 that is easy to disperse for actual production. How to achieve continuous preparation of low aspect ratios while ensuring high crystallinity and high yield of single-walled and double-walled carbon nanotubes is a problem that needs to be solved in this field. Summary of the Invention

[0005] The main purpose of the present invention is to provide a carbon nanotube and a growth unit, a growth method, a continuous preparation method and a continuous preparation system thereof, thereby overcoming the deficiencies in the prior art.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include: A first aspect of the present invention provides a carbon nanotube growth unit, comprising a reaction vessel, an anode, and a cathode, wherein the arc starting end of the anode and the arc starting end of the cathode are spaced apart and opposite to each other, and further comprising: The arc stabilizer solution supply mechanism is used to inject the arc stabilizer solution into the reaction container, and when the carbon nanotube growth unit is working, the arc starting ends of the anode and the cathode are immersed in the arc stabilizer solution.

[0007] In some more specific embodiments, the arc-starting end of the anode and the arc-starting end of the cathode are respectively provided with a first nozzle and a second nozzle, the first nozzle being at least used to output a catalyst to the carbon nanotube growth zone between the anode and the cathode, and the second nozzle being at least used to output an arc-starting gas or a carbon source to the carbon nanotube growth zone. Specifically, the anode and the cathode both have a hollow tubular structure; the distance between the arc-starting end of the anode and the arc-starting end of the cathode is 10-350 mm; the anode and the cathode are coaxially arranged, and when the carbon nanotube growth unit is operating, the distance between the axes of the anode and the cathode and the liquid surface of the arc stabilizer solution is 100-1200 mm; when the carbon nanotube growth unit is operating, the diffusion angle of the plasma arc formed between the anode and the cathode is within 15°; the diameter of the anode is 5-600 mm, and the diameter of the cathode is 15-200 mm.

[0008] In some more specific schemes, the arc stabilizer content in the arc stabilizer solution is 5-30wt%, the conductivity of the arc stabilizer solution is 1-30 S / cm; the injection flow rate of the arc stabilizer solution is 15-260 L / min; the arc stabilizer in the arc stabilizer solution includes one or more combinations of potassium chloride, potassium carbonate, sodium carbonate, barium nitrate, sodium chloride or calcium-potassium mixed salt.

[0009] In some specific embodiments, the carbon nanotube growth unit further includes a liquid level meter for monitoring the liquid level of the arc stabilizer solution in the reaction vessel. The arc stabilizer solution supply mechanism includes a storage tank and a conveying assembly for transferring the arc stabilizer solution in the storage tank into the reaction vessel.

[0010] In some more specific schemes, a sedimentation filtration component is provided at the bottom of the reaction container, and the sedimentation filtration component includes a first valve, a second valve and a sedimentation chamber located between the first valve and the second valve; the first valve transports the precipitate-containing arc stabilizer solution in the reaction container to the sedimentation chamber through an open / close operation, and the second valve transports the precipitate-containing arc stabilizer solution in the sedimentation chamber to the filtration chamber through an open / close operation; a filter screen and a filter pump are provided in the filtration chamber for collecting precipitates generated during the growth of carbon nanotubes.

[0011] A second aspect of the present invention provides a carbon nanotube growth method, comprising: A voltage is applied between the anode and the cathode to generate an arc, and an arc-starting gas is input into the carbon nanotube growth zone between the anode and the cathode, and at least the arc-starting end of the anode and the arc-starting end of the cathode are immersed in an arc stabilizer solution, thereby forming a spatially compressed plasma arc at least in the carbon nanotube growth zone, and then a catalyst and a carbon source are input into the carbon nanotube growth zone to grow carbon nanotubes.

[0012] In some more specific solutions, the arc-starting gas is an inert gas, the input flow rate of the arc-starting gas is 5-350 L / min, and the arc-starting gas is argon.

[0013] In some more specific solutions, the arc length of the plasma arc is 30-350 mm, the temperature of the plasma arc is 5000-50000 K, and the energy density of the plasma arc is 10 5 -10 6 W / cm², and the arc flame velocity of the plasma arc is 300-1000 m / s.

[0014] In some more specific schemes, the catalyst includes a metal component and an anticoagulant, the metal component includes one or more of iron, cobalt, and nickel, the anticoagulant is a compound containing sulfur, and the molar ratio of the metal element in the metal component to the sulfur element in the anticoagulant is 1:5-80:1.

[0015] In some more specific embodiments, the carbon source includes one or more of methane, ethane, ethylene, acetylene, propylene, propane, ethanol, methanol or natural gas, and the flow rate of the carbon source is 3-90 m / s.

[0016] The third aspect of the present invention provides a carbon nanotube grown by a carbon nanotube growth method, wherein the carbon nanotube comprises a single-walled or double-walled carbon nanotube, has a G / D ratio exceeding 50, and an electrical conductivity greater than 1.1×10 7 S / m, aspect ratio less than 2000, diameter of 0.9-3nm, specific surface area of ​​300-1300 m 2 / g.

[0017] A fourth aspect of the present invention provides a continuous carbon nanotube production system, comprising a carbon nanotube growth unit and a product collection unit; the product collection unit is connected to the reaction vessel and is used to collect the carbon nanotubes generated in the reaction vessel. The product collection unit includes a filtration assembly, a liquid-solid separation assembly, and a collection tank; the filtration assembly is used to extract the arc stabilizer solution containing carbon nanotubes from the upper layer of the reaction vessel, the liquid-solid separation assembly is used to separate the carbon nanotubes from the arc stabilizer solution, and the separated carbon nanotubes are stored in the collection tank; the collection tank is provided with an outlet for exhausting waste gas.

[0018] A fifth aspect of the present invention provides a method for continuously preparing carbon nanotubes, comprising: A voltage is applied between the anode and the cathode to generate an arc, and an arc-starting gas is input into the carbon nanotube growth zone between the anode and the cathode, and at least the arc-starting end of the anode and the arc-starting end of the cathode are immersed in an arc stabilizer solution, thereby forming a spatially compressed plasma arc at least in the carbon nanotube growth zone, and then a catalyst and a carbon source are input into the carbon nanotube growth zone to grow carbon nanotubes, and finally a product collection unit collects the carbon nanotubes generated in the reaction vessel.

[0019] Compared with the prior art, the advantages of the present invention include at least: First, the present invention provides a carbon nanotube growth method that achieves efficient regulation of the plasma arc through the arc deflection compression ability of the arc stabilizer solution and the conductivity constraint effect of the liquid medium: the arc stabilizer solution can effectively compress the plasma arc deflection and limit its diffusion angle to within 15°, thereby obtaining an ultra-high temperature, high energy density plasma arc; at the same time, the conductivity constraint effect of the liquid medium will compress the arc diameter (reduced to 1 / 3-1 / 5 of that of traditional gas-phase discharge), ultimately making the prepared carbon nanotubes have a lower aspect ratio and better dispersion.

[0020] Secondly, the present invention provides a continuous preparation method for carbon nanotubes, which relies on the synergistic effect of arc discharge in the arc stabilizer solution and the rapid cooling-compression effect of the liquid to achieve high-yield catalyst and carbon nanotube preparation: the rapid cooling effect of the liquid and the arc compression effect work together to maintain the arc ultra-high temperature (5000-50000K) and high energy density (10 5 -10 7 W / cm²), and can generate a large number of highly catalytically active nanocatalyst particles through instant cooling, significantly improving the reaction efficiency of the catalyst and the carbon source; this mechanism supports a single-machine yield of 10-200g / min, a daily output of >20kg, and can continuously produce kilogram-level high-quality carbon nanotubes.

[0021] Third, the present invention provides a continuous preparation method for carbon nanotubes. By optimizing the arc stabilizer solution and modularizing the continuous production design, the controllable continuous preparation of high-performance carbon nanotubes is achieved. By optimizing the formula of the arc stabilizer solution and modularizing the production process, the stability and controllability of the arc in the liquid can be effectively guaranteed. Finally, carbon nanotubes with low aspect ratio (<2000) and high conductivity (>1.1×10 7 S / m), high crystallinity (G / D ratio>50) and high purity carbon nanotubes to meet the needs of continuous production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of a continuous carbon nanotube preparation system provided by an embodiment of the present invention; Figure 2 Schematic diagram of the plasma arc diffusion angle provided by an embodiment of the present invention; Figure 3 is a scanning electron microscope image of the single / double-walled carbon nanotubes provided in Example 1 of the present invention; Figure 4 is a Raman spectrum of single-walled / double-walled carbon nanotubes provided in Example 3 of the present invention; Figure 5 is a transmission electron microscope image of the single-walled carbon nanotube provided in Example 3 of the present invention; Figure 6 is a transmission electron microscope image of double-walled carbon nanotubes provided in Example 3 of the present invention; Figure 7 This is a graph of the specific surface area of ​​single-walled and double-walled carbon nanotubes provided in Example 3 of the present invention.

[0023] Reference numerals: 100 - carbon nanotube continuous preparation system; 110 - reaction vessel; 120 - composite anode; 130 - composite cathode; 140 - liquid level gauge; 150 - sedimentation chamber, 151 - first valve; 153 - second valve; 155 - filter screen; 157 - filter pump; 159 - filter chamber; 160 - storage tank; 170 - delivery pump; 190 - liquid level controller; 210 - collection tank; 220 - suction filter; 230 - transition chamber; 240 - gas outlet. DETAILED DESCRIPTION

[0024] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The following will further explain this technical solution, its implementation process and principles.

[0025] Please refer to Figure 1One embodiment of the present invention provides a continuous carbon nanotube production system 100, comprising a carbon nanotube growth unit and a product collection unit. The carbon nanotube growth unit includes a reaction vessel 110, a composite anode 120, a composite cathode 130, a storage tank 160, and a delivery pump 170. The product collection unit includes a collection tank 210, a filter 220, and a transition chamber 230.

[0026] In this embodiment, an injection port for the arc stabilizer solution is designed at the top of the reaction vessel 110 for easy addition. A finished product output port is also provided on the side wall of the reaction vessel 110 to facilitate the collection of the generated carbon nanotubes. The arc stabilizer solution is stored in the reserve tank 160, and the reserve tank 160 is connected to the injection port at the top of the reaction vessel 110 through a pipeline. In order to ensure that the arc stabilizer solution can be stably and continuously delivered to the reaction vessel 110, a delivery pump 170 is provided on the pipeline. The delivery pump 170 effectively and quantitatively delivers the arc stabilizer solution in the reserve tank 160 to the reaction vessel 110 to maintain the continuity and stability of the reaction.

[0027] In this embodiment, the arc-starting ends of the composite anode 120 and the composite cathode 130 are immersed in the arc stabilizer solution, spaced apart and facing each other. Under the action of appropriate voltage, the arc-starting ends of the composite anode 120 and the composite cathode 130 can be excited to generate a plasma arc within the space. The generation of a plasma arc is the key to carbon nanotube synthesis. Please refer to Figure 2 In order to ensure the stability of the plasma arc and control its diffusion angle, the arc stabilizer solution is used to compress the diffusion angle of the plasma arc so that it does not exceed 15°. Specifically, the composite anode 120 and the composite cathode 130 are coaxially arranged and both remain parallel to the surface of the arc stabilizer solution. The distance between the axis of the composite anode 120 and the composite cathode 130 and the liquid surface of the arc stabilizer solution is 100-1200 mm. In addition, the diameter of the composite anode 120 is 5-600 mm, and the diameter of the composite cathode 130 is 15-200 mm. The distance between the arc starting end of the composite anode 120 and the arc starting end of the composite cathode 130 is 10-350 mm.

[0028] More specifically, the composite anode 120 has a hollow tubular structure with a hollow iron rod at the front end. A first nozzle is provided at the arc-starting end of the composite anode 120. This first nozzle is used to deliver catalyst to at least the carbon nanotube growth zone between the composite anode 120 and the composite cathode 130 within the reaction vessel 110. Similarly, the composite cathode 130 has a hollow tubular structure with a hollow graphite at the front end. A second nozzle is provided at the arc-starting end of the composite cathode 130. This second nozzle is used to deliver at least an arc-starting gas or carbon source to the carbon nanotube growth zone. During catalyst injection, the arc stabilizer solution may partially overflow from the composite anode 120. To address this issue, a certain amount of gas is introduced simultaneously with the arc stabilizer solution injection. This effectively prevents overflow of the arc stabilizer solution. Furthermore, a one-way valve can be added at the front end. This one-way valve prevents backflow of gas and liquid. Preferably, the one-way valve is L-shaped. This design ensures that the arc stabilizer solution level always remains below the uppermost end of the L-shaped one-way valve. The above settings can be used individually or in combination according to actual conditions to achieve the best effect.

[0029] A sedimentation filtration assembly is installed at the bottom of reaction vessel 110 to promptly isolate amorphous carbon precipitates produced during carbon nanotube growth, preventing them from affecting the conductivity stability of the arc stabilizer solution. Specifically, the precipitate produced during carbon nanotube growth is primarily composed of amorphous carbon. When mixed with the arc stabilizer solution, this material alters the solution's conductivity, causing conductivity fluctuations and impacting the stability of the reaction system. Therefore, it is necessary to isolate this precipitate as soon as possible.

[0030] Specifically, the precipitation filtration component includes a first valve 151, a second valve 153 and a precipitation chamber 150 located therebetween; the reaction vessel 110 is further provided with a filtration chamber 159, in which a filter screen 155 and a filtration pump 157 are provided, wherein the filtration pump 157 is used to extract the arc stabilizer solution containing the precipitate, and collect the precipitate after filtering through the filter screen 155.

[0031] The specific operation process is as follows: at the beginning of the reaction, the first valve 151 is in the open state and the second valve 153 is in the closed state. At this time, the arc stabilizer solution containing amorphous carbon precipitates in the reaction vessel 110 can flow into the precipitation chamber 150 through the first valve 151; after the reaction is carried out for 1-5 hours, the first valve 151 is closed to block the connection between the reaction vessel 110 and the precipitation chamber 150, and the second valve 153 is opened simultaneously to connect the precipitation chamber 150 with the filtration chamber, and then the filter pump 157 is started to pump the precipitate solution in the precipitation chamber 150 into the filtration chamber, and the amorphous carbon precipitates are intercepted by the filter mesh 155 and collected; by repeating the above-mentioned "open the first valve-close the first valve and open the second valve-start the filter pump" operation process, the continuous growth of carbon nanotubes and the dynamic isolation of the precipitates can be achieved, and the conductivity stability of the arc stabilizer solution can be effectively maintained.

[0032] A liquid level gauge 140 is provided on the side wall of the reaction vessel 110 for real-time monitoring of the height of the arc stabilizer solution in the reaction vessel 110 to ensure the stability of the reaction process.

[0033] When the carbon nanotubes are prepared and float on the surface of the arc stabilizer solution, the finished product output port on the side wall will be connected to the pipe of the collection tank 210. The collection tank 210 is directly connected to the reaction vessel 110, the transition chamber 230 is connected to the collection tank 210, and the filter 220 is connected to the transition chamber 230. Through the action of the filter 220, the upper arc stabilizer solution in the reaction vessel 110 is input into the collection tank 210. The transition chamber 230 is used to separate the carbon nanotubes in the arc stabilizer solution. The separated carbon nanotubes will be stored in the collection tank 210, and the remaining arc stabilizer solution can be stored in the transition chamber 230 and discharged. The collection tank 210 is provided with an air outlet 240, which is used to discharge the waste gas generated during the preparation process, avoid excessive pressure in the reaction vessel 110, and ensure preparation safety.

[0034] In this embodiment, the content of arc stabilizer in the arc stabilizer solution is 5-30wt%, and the conductivity of the arc stabilizer solution is 1-30 S / cm. The arc stabilizer includes one or more combinations of potassium chloride, potassium carbonate, sodium carbonate, barium nitrate, sodium chloride or calcium-potassium mixed salts. Potassium-containing compounds such as potassium carbonate serve as core arc stabilizers, and utilize the high ionization characteristics of potassium to enhance the conductivity of the arc channel and maintain the stability of the discharge. Sodium salts (such as sodium carbonate) and barium salts (such as barium nitrate) reduce arc impedance and increase arc energy density by releasing metal ions. Calcium-potassium mixed salts (such as perovskite-type complexes) enhance the arc compression effect through synergistic ionization effect, thereby increasing the current density by 2-3 times. Its mechanism of action is ionization enhancement: containing 、 The compounds are preferentially ionized, providing a continuous conductive path for the arc and preventing the discharge from being interrupted. However, too much and Ions hinder the flight of carbon ions from the anode to the central cathode. This can result in short single- and double-walled carbon nanotubes (SWCNTs) with low aspect ratios and easy dispersion. Arc discharge in an arc stabilizer solution offers a simple and cost-effective method for synthesizing CNTs. The arc consistently produces high-quality SWCNTs in an arc stabilizer solution. These CNTs are easily dispersed in electrochemical power sources, elastomers, composites, plastics, paints, and coatings, reducing processing costs.

[0035] One embodiment of the present application further provides a method for continuously preparing carbon nanotubes, the method being implemented by a carbon nanotube continuous preparation system, and the method comprising: S1) applying a voltage to the composite anode 120 and the composite cathode 130 to generate an arc, supplying an arc-starting gas into the carbon nanotube growth region between the composite anode 120 and the composite cathode 130, and immersing at least the arc-starting end of the composite anode 120 and the arc-starting end of the composite cathode 130 in an arc stabilizer solution, thereby forming a spatially compressed plasma arc at least within the carbon nanotube growth region. The details are as follows: First, the power supply to the composite anode 120 and composite cathode 130 is turned on. Argon gas is then delivered into the reaction vessel 110 through the second nozzle of the composite cathode 130. Next, an arc stabilizer solution is injected into the reaction vessel 110 via the delivery pump 170 until the arc stabilizer solution completely submerges the electrode ends of the composite anode 120 and composite cathode 130. Within the carbon nanotube growth zone between the composite anode 120 and composite cathode 130, the arc-starting ends of the composite anode 120 and composite cathode 130 are excited, generating a plasma arc.

[0036] At this point, the arc stabilizer solution effectively compresses the plasma arc, ensuring that the diffusion angle of the plasma arc does not exceed 15°, thereby obtaining a plasma arc with ultra-high temperature and high energy density. The arc stabilizer solution itself has the ability to compress arc deflection, which helps to increase energy density. In the liquid medium space, due to the confinement effect of conductivity, the arc will be compressed by the medium pressure, resulting in a significant reduction in its diameter, to 1 / 3 to 1 / 5 of the diameter of traditional gas-phase discharge. This convergence effect is very obvious. However, if the arc deflection angle exceeds 15 degrees, the discharge stroke will be increased, thereby reducing the energy density. In this case, it is not conducive to the formation of high-quality carbon nanotubes. Specifically, the G / D ratio of the carbon nanotubes will be greater than 50, indicating that the quality of the carbon nanotubes is not ideal. In addition, an excessively large deflection angle can easily cause arc breaking, making it impossible to conduct the experiment continuously, affecting the uniformity of the product, and leading to inconsistent experimental results.

[0037] In this embodiment, the arc length of the plasma arc is 30-350 mm, the temperature of the plasma arc is 5000-50000 K, and the energy density of the plasma arc is 105 -10 6 W / cm², and the arc velocity of the plasma arc is 300-1000 m / s. The argon flow rate is 5-350 L / min. To achieve a specific power, current and voltage are typically adjusted. In practice, the desired effect is often achieved through the synergistic effects of mechanical compression, thermal compression, and electromagnetic compression. Mechanical compression is the foundation and prerequisite for the entire process, providing the initial constraints for subsequent compression. However, the compression effect of mechanical compression is relatively limited. Therefore, the compression effect is enhanced by the combined effects of a cooling medium and the current magnetic field. Specifically, thermal compression further reduces the effective conductive area of ​​the arc, significantly increasing the energy density. Electromagnetic compression, on the other hand, further enhances the arc's constriction effect through electromagnetic forces under high current conditions. These three compression methods work together to transform a conventional arc into a plasma arc with high temperature and high energy density. The principle of the thermal compression effect can be explained as follows: by introducing a cooling medium, such as gas or water, a low-temperature gas film is formed near the inner wall of the nozzle. The presence of this gas film significantly reduces the degree of ionization at the arc's periphery, forcing the current to concentrate toward the arc's high-temperature center. This concentration further shrinks the arc, thereby increasing energy density. This multi-layered compression and synergistic effect ultimately achieves efficient control and utilization of the arc.

[0038] Under the same power conditions, the longer the arc length, the greater the energy density, the higher the arc temperature, and the higher the G / D ratio of the corresponding product; but if the arc length is the same, a 15° deflection is more likely to affect the effective arc stroke than a 5° deflection, resulting in a decrease in energy density and temperature; and under the same deflection angle conditions, the longer the arc length and the longer the arc stroke, the more significant the impact on temperature, temperature range and energy density, and ultimately it is more difficult to form a product with a G / D ratio greater than 50.

[0039] The introduction of argon can prevent a portion of the arc stabilizer solution from entering the reaction vessel 110. In addition, the purpose of introducing argon is to reduce the difficulty of arc starting, ensure the smooth start of discharge, suppress interference, maintain the uniformity of discharge, and optimize the growth environment of carbon tubes. Specifically, in the gas phase medium, the presence of high ionization energy components such as oxygen and nitrogen will make arc starting difficult or delayed. In the initial stage of arc discharge, it is necessary to ionize the gas between the electrodes to form a conductive channel, that is, to start the arc. As an inert gas, argon has a low ionization energy and is more easily ionized to form plasma under a high voltage electric field, thereby reducing the voltage threshold required for arc starting. In addition, in a liquid arc environment, although the arc stabilizer solution can constrain the arc shape, the gas phase region between the electrodes, such as the through hole of the composite cathode 130, still needs to be protected by an inert gas. Argon can effectively exclude active components such as oxygen and water vapor in the gas phase region, preventing oxygen from reacting with the electrode material after ionization, resulting in uneven erosion of the electrode surface, causing arc position offset or intensity fluctuation. At the same time, it is possible to prevent the hydrogen and oxygen free radicals generated by the decomposition of water vapor from participating in the carbon source reaction and generating oxygen-containing compounds or amorphous carbon, thereby reducing the purity of the product. By filling the gas phase area with argon gas, the stability of the arc discharge can be maintained, ensuring the diffusion angle (A≤15°), temperature (5000-50000 K) and energy density (10 5 -10 6 W / cm²) meets the growth requirements of single / double-walled carbon nanotubes.

[0040] S2) Subsequently, a catalyst and a carbon source are introduced into the carbon nanotube growth zone to grow carbon nanotubes. Specifically, the catalyst is introduced into the reaction vessel 110 through the first nozzle of the composite anode 120, and the carbon source is introduced into the reaction vessel 110 through the second nozzle of the composite cathode 130 to grow carbon nanotubes.

[0041] In this embodiment, the catalyst comprises a metal component and an anticoagulant. The metal component can be one or a combination of iron, cobalt, and nickel. The anticoagulant is a sulfur-containing compound that inhibits excessive growth of catalyst particles, thereby controlling the diameter and quality of the carbon nanotubes. In this embodiment, the molar ratio of the metal component to the sulfur in the anticoagulant is 1:5-80:1, ensuring catalyst activity and selectivity, thereby improving the yield and quality of the carbon nanotubes.

[0042] In this embodiment, the carbon source includes a combination of one or more of methane, ethane, ethylene, acetylene, propylene, propane, ethanol, methanol, or natural gas. These carbon sources are activated by a catalyst within reaction vessel 110 to generate carbon nanotubes through a chemical reaction. To ensure the growth rate and quality of the carbon nanotubes, the flow rate of the carbon source is controlled at 3-90 m / s, which can effectively prevent excessive growth or defects in the carbon nanotubes.

[0043] The catalyst is introduced into the plasma arc through the composite anode 120 to form high-concentration, high-efficiency catalyst nanoparticles. These nanoparticles are highly active in the high-temperature environment of the plasma arc and can effectively promote the growth of single-walled or double-walled carbon nanotubes.

[0044] S3) Finally, the product collecting unit collects the carbon nanotubes generated in the reaction container 110 .

[0045] In this embodiment, the generated carbon nanotubes will gradually float to the surface of the arc stabilizer solution. Subsequently, by controlling the liquid level meter 140, the products floating on the solution surface flow into the collection tank 210 along with the arc stabilizer solution.

[0046] To achieve continuous reaction and stable collection of carbon nanotubes, this solution sets graded liquid level thresholds and combines them with a dynamic liquid level control mechanism. The specific technical solution is as follows: First, based on the reaction requirement that the axes of the anode and cathode must maintain an effective distance of 100-1200mm from the liquid surface of the arc stabilizer solution, the following key liquid level parameters are defined: minimum liquid level H1: 250mm from the axes of the anode and cathode, maximum liquid level H2: 1050mm from the axes of the anode and cathode, standard working liquid level H3: range is 250-1050mm.

[0047] The current liquid level H0 of the arc stabilizer solution in the reaction vessel 110 is collected in real time by the liquid level meter 140, and the hierarchical control logic is triggered based on the relative relationship between H0 and H1, H2, and H3: When H0 < H1 is detected, the liquid level gauge 140 sends a low liquid level signal to the liquid level controller 190, which immediately activates the delivery pump 170 to replenish the arc stabilizer solution from the storage tank 160 to the reaction vessel 110 until the liquid level returns to the standard operating liquid level H3. This operation ensures that the distance between the electrode and the liquid surface returns to the effective reaction range, avoiding reaction interruptions caused by insufficient solution.

[0048] If H0 is within the standard working liquid level H3 range (250mm≤H0≤1050mm), the liquid level meter 140 determines that the current liquid level meets the reaction requirements and does not send a signal to the liquid level controller 190, maintaining a stable state of "no replenishment, no extraction", maintaining the optimal reaction conditions of the distance between the electrode and the liquid surface, and ensuring the continuous growth of carbon nanotubes.

[0049] When it is detected that H0>H2, the liquid level meter 140 sends a high liquid level signal to the liquid level controller 190. The liquid level controller 190 starts the filter 220 to extract the upper layer of arc stabilizer solution containing carbon nanotubes in the reaction vessel (the collection of carbon nanotubes is completed simultaneously) until the liquid level drops back to the standard working liquid level H3. This not only avoids the risk of solution overflow, but also realizes the continuous collection of carbon nanotubes through filtration, ensuring the dynamic balance of the reaction system.

[0050] Through the above-mentioned closed-loop control logic of "low liquid level replenishment-normal liquid level maintenance-high liquid level filtration", the liquid level of the arc stabilizer solution in the reaction vessel 110 can be dynamically maintained stable, so that the electrode and the liquid surface are always in an effective reaction distance, and ultimately the continuous growth and efficient collection of carbon nanotubes are achieved.

[0051] During the collection process, the filter 220 is used to continuously perform liquid-solid separation operations to ensure that the carbon nanotubes can be effectively separated from the solution. At the same time, the waste gas generated is discharged through the gas outlet 240, thereby efficiently obtaining pure carbon nanotubes.

[0052] The carbon nanotubes obtained in this application include single-walled or double-walled carbon nanotubes, with a G / D ratio exceeding 50 and an electrical conductivity greater than 1.1×10 7 S / m, aspect ratio less than 2000, diameter of 0.9-3nm, specific surface area of ​​300-1300 m 2 The single- and double-walled carbon nanotubes prepared by this method not only have high crystallinity, high electrical conductivity, and a low aspect ratio, but are also easily dispersed in electrochemical power sources, elastomers, composite materials, plastics, paints, and coatings. They can be widely used in new energy batteries and high-end composite materials, possessing significant commercial value and broad application prospects, and can also meet the needs of continuous production.

[0053] In this application, the axial growth of carbon nanotubes in a liquid environment is limited by thermal-fluid coupling, which is specifically achieved through the following mechanism: First, the high heat capacity and thermal conductivity of the liquid medium induce rapid cooling in the arc region, forming a steep axial temperature gradient (high temperature at the arc center and low temperature at the periphery). This inhibits the prolonged deposition of carbon sources (such as decomposed carbon atoms) at the tube ends, thereby shortening the tube length. Simultaneously, shear stress generated by liquid flow (either convection induced by the arc heat or external forced flow) acts on the growing carbon tube surface, disrupting the directional deposition of carbon atoms along the axial direction and promoting radial (diameter) growth while also damaging the fragile ends of the newly formed carbon tubes, preventing their continued extension. Furthermore, the cooling and flow of the liquid phase reduce the mobility of the active sites of metal catalysts (such as iron and cobalt) dispersed in the liquid, restricting the carbon tubes to nucleation and short-range growth within a limited region of the catalyst surface, rather than continuous axial extension. Ultimately, the "microscale turbulence" generated by the thermal-fluid coupling and the interaction with the catalyst interface lead to an unstable carbon tube growth environment, preferentially forming short, thick structures (aspect ratio <2000).

[0054] Finally, the prepared carbon nanotubes, due to their light density and hydrophobicity, will slowly float on the surface of the arc stabilizer solution, while dense impurities will slowly settle in the precipitation and filtration chamber 150 below. This natural physical separation process can initially separate the product from the impurities, thereby simplifying subsequent purification steps, improving the efficiency of the entire preparation process and improving the purity of the product.

[0055] During the liquid arc method for preparing carbon nanotubes, the distance L1 between the arc-starting end of the composite anode 120 and the arc-starting end of the composite cathode 130 significantly affects the carbon nanotube growth characteristics through three core pathways: electricity, thermodynamics, and fluid mechanics. The specific mechanisms are as follows: First, the electrical path is directly related to arc stability: when L1 increases, the resistance of the liquid medium increases, and a higher arc voltage is required to maintain discharge, which can easily cause arc fluctuations or even breakage (for example, when the vacuum arc spacing increases from 100mm to 200mm, the voltage increases significantly and the shape becomes unstable). A smaller L1 can enhance the liquid's constraint on the arc, causing the medium pressure to compress the arc diameter to 1 / 3-1 / 5 of that of traditional gas phase discharge, thereby increasing the current density to 10 7 A / m² level, high current density generates high temperature of several thousand K, promoting efficient cracking of carbon sources.

[0056] In the thermodynamic control of carbon nanotubes prepared by liquid arc method, the liquid medium plays a key role through a dual mechanism: on the one hand, the liquid medium absorbs heat by vaporization to achieve a steep drop in the temperature gradient in the arc zone (greater than 10 4K / s), forming an instantaneous quenching effect on high-temperature synthesized nanomaterials (such as catalyst particles and carbon nanotubes), thereby inhibiting excessive grain growth and maintaining their nanoscale characteristics; on the other hand, although the liquid medium reduces the arc core temperature by about 15%-20%, it increases the local energy density by 3 to 5 times through the compression effect, ultimately forming a gradient temperature field, providing suitable thermodynamic conditions for different reaction stages.

[0057] Secondly, thermodynamics and fluid mechanics paths synergistically regulate the carbon tube morphology: under small L1, the arc energy is more concentrated, but the high thermal conductivity of the liquid will form a steep axial temperature gradient, limiting the long-distance diffusion and deposition of carbon atoms and inhibiting the axial extension of the carbon tube; at the same time, the violent convection of the liquid caused by the arc generates turbulent shear force, mechanically destroying the fragile ends of the newly formed carbon tubes, causing the carbon tubes to thicken radially rather than grow axially; in addition, the spatial limitations of the narrow discharge area further constrain the growth morphology of the carbon tubes (for example, the aspect ratio of the carbon tube can be reduced to less than 2000 by coaxially setting the composite electrode).

[0058] In summary, the electrode spacing achieves effective control of the carbon tube growth characteristics through the synergistic effect of three mechanisms: "electrical path (reduced spacing → reduced resistance → increased current density), thermodynamic path (reduced spacing → increased energy density → increased temperature gradient → inhibition of axial growth), and fluid path (reduced spacing → increased turbulent shear force → dominated by radial growth of carbon tubes)."

[0059] In general, under the spatial confinement effect of the liquid medium, the arc will be compressed by the medium pressure, resulting in a significant reduction in its diameter, down to 1 / 3 to 1 / 5 of the diameter of the traditional gas phase discharge. This compression effect greatly increases the local current density, which can reach 10 7 The enhanced discharge stability and liquid phase resistance characteristics cause the arc to automatically adjust its channel impedance, enabling more precise control. Through precise control of the liquid's compression structure, the liquid phase environment utilizes thermal-fluid coupling to effectively restrict the axial growth of carbon nanotubes, enabling the production of double-walled carbon nanotubes with a low aspect ratio (less than 2000) and high crystallinity.

[0060] The arc stabilizer solution not only has a certain electrical conductivity and can stabilize the arc, but also has a strong cooling capacity, which is significantly higher than deionized water, but lower than liquid nitrogen. However, arc discharge in liquid nitrogen is unstable due to its electrical insulation. The superior cooling capacity of the arc stabilizer solution is conducive to the synthesis of single / double-walled carbon nanotubes during the arc discharge process, and the flow of the solution during the arc discharge process will also hinder the further growth of single / double-walled carbon nanotubes, thereby forming high-quality single / double-walled carbon nanotubes with a low aspect ratio. In traditional preparation techniques, such as arc discharge and chemical vapor deposition, the single-walled or double-walled carbon nanotubes produced usually have a high aspect ratio, generally between 3000 and 50000. However, the aspect ratio of the carbon nanotubes obtained in the present application is less than 2000, which greatly improves the dispersibility of the carbon nanotubes. When the aspect ratio is relatively low, carbon nanotubes can be more evenly dispersed in various matrix materials, such as electrochemical power sources, elastomers, composite materials, etc., which helps to reduce the agglomeration of carbon nanotubes, allowing them to more fully exert their excellent physical and chemical properties, reduce costs in the material processing process, and improve production efficiency.

[0061] The Raman spectroscopy, thermogravimetric characterization, scanning electron microscopy and energy dispersive X-ray spectroscopy, transmission electron microscopy, UV-visible-near-infrared absorption spectroscopy, and gas absorption method for the determination of solid specific surface area of ​​single-walled carbon nanotube samples are described in accordance with GB / T 32871-2016, ISO / TS 11308:2011 (E) Nanotechnology, ISO / TS 10798:2011 (E) Nanotechnology, ISO / TS 10797:2012 (E) Nanotechnology, GB_T 39114-2020, and ISO / TS9277:2010 (E). The test protocols described in Table 1 are as follows.

[0062] Table 1 Test plan ; The following is a detailed explanation based on experimental data.

[0063] Example 1 The method for continuously preparing carbon nanotubes provided in this embodiment is based on Figure 1 The carbon nanotube continuous preparation system shown is implemented.

[0064] In this carbon nanotube continuous preparation system, the composite anode 120 is made of 316L stainless steel and pure iron, and the composite cathode 130 is made of 316L stainless steel and graphite. The diameter of the anode is 600 mm, the diameter of the cathode is 200 mm, the distance between the arc starting ends is 250 mm, the arc stabilizer solution is potassium chloride with a concentration of 30 wt%, and the conductivity of the arc stabilizer solution is 30 S / cm.

[0065] The continuous preparation method of carbon nanotubes specifically comprises the following steps: S1) Start the power supply, introduce argon gas into the composite cathode 130 through the middle hole, and control the arc length to 350, the arc temperature to 6000K, and the energy density to 1.2×10 5 W / cm 2 The plasma arc flame flow rate is 300 m / s. Then, through the liquid level meter 140, the pump 170 slowly injects the arc stabilizer solution in the arc stabilizer storage tank 160 into the reactor 110 at a flow rate of 100 L / min until the distance between the electrode axis and the liquid surface is 1200 mm, thereby forming a spatially compressed plasma arc between the composite cathode 130 and the composite anode 120. The diffusion angle of the plasma arc formed between the anode and cathode is within 14 degrees. S2) A catalyst mixture is then injected from the composite anode 120, and a carbon source gas is injected at a predetermined flow rate from the composite cathode 130 to initiate product generation. The catalyst mixture comprises iron powder and thiophene, with a molar ratio of 2:1 between the metal element in the metal component and the sulfur element in the inhibitor. The carbon source gas is methane at a flow rate of 80 m / s.

[0066] S3) The product slowly floats to the surface of the arc stabilizing agent, and then the floating product is allowed to flow into the collection tank 210 along with the arc stabilizing liquid by controlling the liquid level meter 140. The product is continuously separated into liquid and solid by the suction filter 220, and the waste gas is discharged through the gas outlet 240 and continuously collected through the transition chamber 230 to obtain the initial product.

[0067] The final product obtained in this example is single-walled / double-walled carbon nanotubes, with a yield of 20.3 kg / d and a conductivity of 1.15×10 7 s / m, diameter of 1.8-3.0 nm, aspect ratio of 1950, and specific surface area of ​​357 m 2 / g, and its Raman spectrum (excitation wavelength: 532 nm) is at 1570 cm -1 、1350 cm -1 and 200cm -1 The amplitude of the product shows a sharp graphite peak (G band), an unusually small disorder peak (D band) and a highly obvious radial breathing mode characteristic peak RBM, indicating that the product contains single-walled / double-walled carbon nanotubes. The ratio of the peak intensity of the G band to the peak intensity of the D band (G / D ratio) is 52, indicating that it has a high degree of crystallinity. Please refer to Figure 3 Scanning electron microscopy characterization of the single / double-walled carbon nanotubes prepared in Example 1 shows that the initial product has relatively few impurities and good product uniformity.

[0068] Example 2 The method for continuously preparing carbon nanotubes provided in this embodiment is based on Figure 1 The carbon nanotube continuous preparation system shown is implemented.

[0069] In the carbon nanotube continuous preparation system, the composite anode 120 is made of 304 stainless steel and pure iron, and the composite cathode 130 is made of 304 stainless steel and graphite. The specific dimensions are: the diameter of the composite anode is 5 mm, the diameter of the composite cathode is 15 mm, and the distance between the arc starting ends of the two is 10 mm. The specific composition of the arc stabilizer solution is potassium carbonate, the concentration is 5 wt%, and the conductivity of the arc stabilizer solution is 5 S / cm.

[0070] The continuous preparation method of carbon nanotubes specifically comprises the following steps: S1) Start the power supply, introduce argon gas into the composite cathode 130 through the middle hole, and control the arc length to 30 mm, the arc temperature to 35000 K, and the energy density to 1.0×10 6 W / cm 2 The plasma arc flame velocity is 1000 m / s. Then, through the liquid level meter 140, the delivery pump 170 slowly injects the arc stabilizer solution from the arc stabilizer storage tank 160 into the reactor 110 at a flow rate of 90 L / min until the distance between the electrode axis and the liquid surface is 100 mm, thereby forming a spatially compressed plasma arc between the composite cathode 130 and the composite anode 120. The diffusion angle of the plasma arc formed between the anode and cathode is within 12°. S2) A catalyst mixture is then injected from the composite anode 120, and a carbon source gas is injected at a predetermined flow rate from the composite cathode 130 to initiate product generation. The catalyst mixture comprises cobalt powder and sulfur powder, with a molar ratio of 10:1 between the metal element in the metal component and the sulfur element in the anticoagulant. The molar ratio of 60:1 between the metal element in the metal component and the sulfur element in the anticoagulant is achieved. The carbon source gas is ethylene at a flow rate of 3 m / s.

[0071] S3) The product slowly floats to the surface of the arc stabilizing agent, and then the floating product is allowed to flow into the collection tank 210 along with the arc stabilizing liquid by controlling the liquid level meter 140. The product is continuously separated into liquid and solid by the suction filter 220, and the waste gas is discharged through the gas outlet 240 and continuously collected through the transition chamber 230 to obtain the initial product.

[0072] The final product of this example is single-walled / double-walled carbon nanotubes, with a yield of 23.5 kg / d and a conductivity of 2.23×10 7 s / m, diameter is 1.5-2.3nm, aspect ratio is 1823, specific surface area is 551 m 2 / g, and the ratio of the G band peak intensity to the D band peak intensity (G / D ratio) is 58, indicating that it has high crystallinity.

[0073] Example 3 The method for continuously preparing carbon nanotubes provided in this embodiment is based on Figure 1 The carbon nanotube continuous preparation system shown is implemented.

[0074] In this carbon nanotube continuous preparation system, the composite anode 120 is made of 310s and pure iron, and the composite cathode 130 is made of 310s and isostatic graphite. The diameter of the composite anode is 400 mm, the diameter of the composite cathode is 120 mm, the distance between the arc starting ends of the two is 60 mm, the specific composition of the arc stabilizer solution is a mixture of potassium chloride and sodium chloride with a concentration of 18 wt%, and the conductivity of the arc stabilizer solution is 23 S / cm.

[0075] The continuous preparation method of carbon nanotubes specifically comprises the following steps: S1) Start the power supply, introduce argon gas into the composite cathode 130 through the middle hole, and control the arc length to 135 mm, the arc temperature to 27000 K, and the energy density to 1.6×10 6 W / cm 2 The plasma arc flame velocity is 50 m / s. Then, the delivery pump 170 slowly injects the arc stabilizer solution from the arc stabilizer storage tank 160 into the reactor 110 at a flow rate of 46 L / min through the liquid level meter 140 until the distance between the electrode axis and the liquid surface is 280 mm, thereby forming a spatially compressed plasma arc between the composite cathode 130 and the composite anode 120. The diffusion angle of the plasma arc formed between the anode and cathode is within 8°. S2) A catalyst mixture is then injected from the composite anode 120, and a carbon source gas is injected at a predetermined flow rate from the composite cathode 130 to initiate product generation. The catalyst mixture comprises pure iron powder and hydrogen sulfide, with a molar ratio of 20:1 between the metal component and the sulfur element in the inhibitor. The carbon source gas is methane at a flow rate of 68 m / s.

[0076] S3) The product slowly floats to the surface of the arc stabilizing agent, and then the floating product is allowed to flow into the collection tank 210 along with the arc stabilizing liquid by controlling the liquid level meter 140. The product is continuously separated into liquid and solid by the suction filter 220, and the waste gas is discharged through the gas outlet 240 and continuously collected through the transition chamber 230 to obtain the initial product.

[0077] The final product of this embodiment is single / double-walled carbon nanotubes. Please refer to Figure 4 The Raman spectrum of the sample prepared in Example 3 (excitation wavelength: 532 nm) was found at 150 cm -1The product exhibits distinct and sharp RBM characteristic absorption peaks, indicating that the product is high-quality single-walled / double-walled carbon nanotubes. The RBM characteristic peaks are relatively concentrated, and the G / D ratio is 147, indicating high crystallinity. The output is 26.2 kg / d, which can achieve a daily output of 20 kg of primary product and an annual production capacity of tons, paving the way for its industrialization. The conductivity is 4.53×10 7 s / m, please refer to Figure 5 The product prepared in Example 3 contains single-walled carbon nanotubes with a diameter of 1.15 nm. Figure 6 The product prepared in Example 5 contains double-walled carbon nanotubes with a diameter of 2.1 nm. Figure 7 It can be seen that the single / double-walled carbon nanotubes have a larger specific surface area of ​​1268.74 m 2 / g.

[0078] Comparative Example 1 The system and method for continuous preparation of carbon nanotubes provided in this comparative example are basically the same as those in Example 1, except that no arc stabilizer solution is injected into the reaction vessel during the growth of carbon nanotubes. The single / double-walled carbon nanotubes have an output of 1.77 kg / d, a diameter of 1.0-2.8 nm, and an aspect ratio of 32850, which is much longer than that in Example 1, and a specific surface area reduced to 316 m 2 / g, the ratio of the peak intensity of the G band to the peak intensity of the D band (G / D ratio) is 32, the crystallinity is also deteriorated, and the electrical conductivity is significantly reduced by 3.1×10 6 s / m.

[0079] Comparative Example 2 The continuous preparation system and method of carbon nanotubes provided in this comparative example are basically the same as those in Example 2, except that: during the growth of carbon nanotubes, the distance between the axis of the cathode and the anode and the liquid surface of the arc stabilizer solution is 500 mm, the output of single / double-walled carbon nanotubes is 21.5 kg / d, and the conductivity is 2.12×10 7 s / m, diameter is 1.2-2.6nm, aspect ratio is 16:17, specific surface area is 780 m 2 / g, and the G / D ratio is 51.

[0080] Comparative Example 3 The carbon nanotube continuous preparation system and method provided in this comparative example are basically the same as those in Example 1, except that: during the growth of carbon nanotubes, the arc flame velocity of the plasma arc is 600 m / s, the output of single / double-walled carbon nanotubes is 21.7 kg / d, and the electrical conductivity is 1.19×10 7 s / m, diameter is 0.9-2.7nm, aspect ratio is 1489, specific surface area is 913m 2 / g, and the G / D ratio is 57.

[0081] Comparative Example 4 The continuous preparation system and method of carbon nanotubes provided in this comparative example are basically the same as those in Example 3, except that when the concentration of the arc stabilizer solution is too high (40 wt%) during the growth of carbon nanotubes, the arc is severely constrained, the energy density is high, and the arc is short, resulting in some products being damaged by high temperature, making it difficult to form highly conductive, high-quality single-walled / double-walled carbon nanotubes. The output is 3.8 kg / d, and the conductivity is 5.31×10 6 s / m, diameter is 1.4-2.8nm, aspect ratio is 5326, specific surface area is 913 m 2 / g, G / D ratio is 17.

[0082] Comparative Example 5 The continuous preparation system and method of carbon nanotubes provided in this comparative example are basically the same as those in Example 3, except that: when growing carbon nanotubes, the concentration of the arc stabilizer solution is too low. When the concentration is 2 wt%, the arc confinement angle is difficult to control within 15°, and the plasma energy density will drop sharply, which cannot provide sufficient energy for growth, making it difficult to produce high-quality, high-yield, and highly conductive single-walled / double-walled carbon nanotubes. The yield is 2.2 kg / d, and the conductivity is 2.11×10 6 s / m, diameter is 1.8-5.3nm, aspect ratio is 2856, specific surface area is 438 m 2 / g, and the G / D ratio is 13.

[0083] Comparative Example 6 The system and method for continuous preparation of carbon nanotubes provided in this comparative example are basically the same as those in Example 3, except that the arc length of the plasma arc is 400 mm during the growth of carbon nanotubes. The longer the arc length, the lower the arc temperature and the lower the arc energy density. The conductivity and quality of the single / double-walled carbon nanotubes formed are not very good, and the tube diameter is uncontrollable. The output is 1.1 kg / d, and the conductivity is 3.15×10 6 s / m, diameter is 0.9-5.6nm, aspect ratio is 4589, specific surface area is 325 m 2 / g, G / D ratio is 23.

[0084] Comparative Example 7 The continuous production system and method of carbon nanotubes provided in this comparative example are basically the same as those in Example 3, except that the arc length of the plasma arc is 20 mm during the growth of carbon nanotubes. The energy density of the arc is increased, and high-quality carbon nanotubes can be formed, but some of the yield is lost. The yield of single-walled / double-walled carbon nanotubes is 0.3 kg / d, and the conductivity is 1.19×10 7s / m, diameter of 0.6-1.6nm, aspect ratio of 860, and specific surface area of ​​487 m 2 / g, G / D ratio is 176.

[0085] Table 2 Product indicators in the examples ; As can be seen from Table 2 above, Example 3 is the most optimized solution. Its crystallinity reaches the highest level, while the aspect ratio of carbon nanotubes is relatively low. More importantly, its yield also reaches the highest.

[0086] In contrast, Comparative Example 2 and Example 2 exhibit basically similar characteristics overall, but there are still subtle differences between the two: during the growth of carbon nanotubes, the distance between the axes of the cathode and anode of Comparative Example 2 and the liquid surface of the arc stabilizer solution is set to 500 mm, and the adjustment of this parameter makes Example 2 perform better in terms of crystallinity and yield, with higher crystallinity and more considerable yield.

[0087] Similarly, Comparative Example 3 is consistent with Example 1 in most aspects, but the key difference is that when growing carbon nanotubes, the arc flame flow rate of the plasma arc used in Comparative Example 3 is set to 600 m / s. By comparison, it can be found that Comparative Example 3 has improved in terms of crystallinity and output, showing higher crystallinity and higher output. The average G / D ratio of Comparative Example 1 is relatively low, reflecting its low crystallinity and low output, which fails to achieve the desired effect. Further analysis of the data of Comparative Examples 4, 5, and 6 shows that the average G / D ratios of these three comparative examples are also low, indicating that the crystallinity is at a low level and the expected crystallization effect is not achieved. Although Comparative Example 7 has a relatively high G / D, it performs poorly in terms of output, with a low output, is not suitable for large-scale production, and limits its practical application value.

[0088] It should be understood that the above embodiments are merely illustrative of the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent variations or modifications made in accordance with the spirit and substance of the present invention are intended to be encompassed within the scope of protection of the present invention.

Claims

1. A method for growing carbon nanotubes, characterized in that: include: A voltage is applied between the anode and the cathode to generate an arc, and an arc-starting gas is input into the carbon nanotube growth zone between the anode and the cathode, and at least the arc-starting end of the anode and the arc-starting end of the cathode are immersed in an arc stabilizer solution, thereby forming a spatially compressed plasma arc at least in the carbon nanotube growth zone, and then a catalyst and a carbon source are input into the carbon nanotube growth zone to grow carbon nanotubes.

2. The carbon nanotube growth method according to claim 1, wherein: The arc-starting gas is an inert gas, and the input flow rate of the arc-starting gas is 5-350 L / min. and / or, the arc striking gas comprises argon; and / or, the arc length of the plasma arc is 30-350 mm, and / or, the temperature of the plasma arc is 5000-50000 K, the energy density of the plasma arc is 10 5 -10 6 W / cm², the arc flame velocity of the plasma arc is 300-1000 m / s; And / or, the catalyst comprises a metal component and an anticoagulant, the metal component comprises one or more of iron, cobalt, and nickel, the anticoagulant is a compound containing sulfur, and the molar ratio of the metal element in the metal component to the sulfur element in the anticoagulant is 1:5-80:1; And / or, the carbon source includes one or a combination of methane, ethane, ethylene, acetylene, propylene, propane, ethanol, methanol or natural gas, and the flow rate of the carbon source is 3-90 m / s.

3. A carbon nanotube growth unit for implementing the carbon nanotube growth method according to claims 1-2, comprising a reaction vessel, an anode and a cathode, wherein the arc starting end of the anode and the arc starting end of the cathode are spaced apart and opposite to each other, characterized in that: Also includes: The arc stabilizer solution supply mechanism is used to inject the arc stabilizer solution into the reaction container, and when the carbon nanotube growth unit is working, the arc starting ends of the anode and the cathode are immersed in the arc stabilizer solution.

4. The carbon nanotube growth unit according to claim 3, characterized in that: The arc starting end of the anode and the arc starting end of the cathode are respectively provided with a first nozzle and a second nozzle, the first nozzle is at least used to output a catalyst to the carbon nanotube growth zone between the anode and the cathode, and the second nozzle is at least used to output an arc starting gas or a carbon source to the carbon nanotube growth zone; and / or, the anode and cathode both have a hollow tubular structure; And / or, the distance between the arc starting end of the anode and the arc starting end of the cathode is 10-350 mm; And / or, the anode and cathode are coaxially arranged, and when the carbon nanotube growth unit is in operation, the distance between the axis of the anode and cathode and the liquid surface of the arc stabilizer solution is 100-1200 mm; and / or, when the carbon nanotube growth unit is in operation, a diffusion angle of a plasma arc formed between the anode and the cathode is within 15°; And / or, the diameter of the anode is 5-600 mm, and the diameter of the cathode is 15-200 mm.

5. The carbon nanotube growth unit according to claim 3, characterized in that: The arc stabilizer solution contains an arc stabilizer having a content of 5-30 wt % and an electrical conductivity of 1-30 S / cm; and / or, the injection flow rate of the arc stabilizer solution is 15-260 L / min; And / or, the arc stabilizer in the arc stabilizer solution includes one or a combination of potassium chloride, potassium carbonate, sodium carbonate, barium nitrate, sodium chloride or calcium-potassium mixed salt.

6. The carbon nanotube growth unit according to claim 3, characterized in that: The carbon nanotube growth unit further includes a liquid level meter for monitoring the liquid level of the arc stabilizer solution in the reaction container.

7. The carbon nanotube growth unit according to claim 3, characterized in that: The arc stabilizer solution supply mechanism includes a storage tank and a conveying assembly, and the conveying assembly is used to input the arc stabilizer solution in the storage tank into the reaction container; And / or, a sedimentation filtration component is provided at the bottom of the reaction container, and the sedimentation filtration component includes a first valve, a second valve and a sedimentation chamber located between the first valve and the second valve; the first valve transports the precipitate-containing arc stabilizer solution in the reaction container to the sedimentation chamber through an open / close operation, and the second valve transports the precipitate-containing arc stabilizer solution in the sedimentation chamber to the filtration chamber through an open / close operation; a filter screen and a filter pump are provided in the filtration chamber for collecting precipitates generated during the growth of carbon nanotubes.

8. A continuous production system for carbon nanotubes, characterized in that: comprising a carbon nanotube growth unit and a product collection unit according to any one of claims 3 to 7; the product collection unit being in communication with the reaction vessel and configured to collect the carbon nanotubes generated in the reaction vessel; The product collection unit includes a filtration component, a liquid-solid separation component, and a collection tank; the reaction vessel is connected to the collection tank, and the collection tank, the liquid-solid separation component, and the filtration component are connected in sequence; the filtration component is used to extract the arc stabilizer solution containing carbon nanotubes in the upper layer of the reaction vessel and input it into the collection tank, the liquid-solid separation component is used to filter the carbon nanotubes in the arc stabilizer solution, and store the filtered carbon nanotubes in the collection tank, and the arc stabilizer solution flows into the interior of the liquid-solid separation component; the collection tank is provided with an air outlet for discharging exhaust gas.

9. A method for continuously preparing carbon nanotubes, characterized in that: The method is implemented based on the carbon nanotube continuous preparation system according to claim 8, and the method comprises: synthesizing carbon nanotubes in a carbon nanotube growth unit and outputting a reaction mixture containing the carbon nanotubes; The carbon nanotubes in the reaction mixture are separated and collected by a product collection unit.

10. A carbon nanotube, characterized in that: Grown by the carbon nanotube growth method according to any one of claims 1-2, The carbon nanotubes include single-walled or double-walled carbon nanotubes, with a G / D ratio exceeding 50 and an electrical conductivity greater than 1.1×10 7 S / m, aspect ratio less than 2000, diameter of 0.9-3nm, specific surface area of ​​300-1300 m 2 / g.

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