A method for growing single-walled carbon nanotubes based on a freeze-drying method

Abstract

This invention discloses a method for growing single-walled carbon nanotubes using a catalyst prepared by freeze-drying. The method includes the following steps: dissolving an active component, a support component, and a complexing agent in deionized water to obtain a mixed solution; placing the mixed solution in liquid nitrogen for incubation and then performing vacuum freeze-drying to obtain a solid catalyst; transporting the solid catalyst to the plasma region of a plasma device via a carrier gas to form catalytically active plasma; then transporting the plasma to the growth region of the plasma device and introducing a carbon source gas into the growth region to cause the carbon source gas to decompose and grow, forming single-walled carbon nanotubes. This invention uses freeze-drying to prepare easily decomposable solid catalysts, combined with the heating, etching, and decomposition effects of plasma, to prepare single-walled carbon nanotubes with a single-wall ratio greater than 90% and a graphitization degree (G / D) greater than 100, at a cost lower than 5000 yuan / kg.

Description

Technical Field

[0001] This invention belongs to the field of carbon materials technology, specifically relating to a method for growing single-walled carbon nanotubes based on a catalyst prepared by freeze-drying. Background Technology

[0002] Carbon nanotubes are a novel type of carbon nanomaterial with excellent mechanical, thermal, electrical, and optical properties. Multi-walled carbon nanotubes have been mass-produced and applied in various industries. Single-walled carbon nanotubes possess superior mechanical, thermal, and electrical properties. Among them, the Young's modulus of single-walled carbon nanotubes (SWCNTs) can reach 1.8 TPa, and the tensile strength can reach 1 TPa (Nanoscale, 2011, 3(2): 503-518). The thermal conductivity of single-walled carbon nanotubes is greater than 6000 W / (m·K) (Phys. Rev. Lett., 2000, 84: 4613-6). In addition, single-walled carbon nanotubes have a larger aspect ratio and a higher degree of graphitization (I G / I D >10), with superior conductivity and flexibility, when used as a conductive agent in secondary batteries, it can form a well-developed conductive network inside the positive and negative electrode materials with low addition amount (as low as 0.05%), thereby significantly extending the cycle life and rate performance of lithium batteries.

[0003] The main methods for growing SWCNTs include laser ablation (Science, 1996, 273:483-7), arc discharge (Nature, 1997, 388:756-8), and chemical vapor deposition (CVD). Among these, CVD is considered the most promising method for the controllable preparation of SWCNTs due to its simple operation and good controllability. CVD methods can be further divided into: substrate-supported catalyst CVD (SCCVD, Chem. Phys. Lett., 1998, 292: 567-74), fluidized bed CVD (FBCVD, Scientia. Sinica. Chimica., 2013, 43: 641-66), high-pressure carbon monoxide (HiPco, Chem. Phys. Lett., 1999, 313: 91-7) and floating catalyst CVD (FCCVD, Appl. Phys. Lett., 1998, 72: 3282-4), etc. Significant progress has been made in the controllable preparation of CNTs using the SCCVD method, particularly in terms of orientation alignment (Acc. Chem. Res., 2014, 47: 2273-81), density (Nat. Commun., 2015, 6: 6099), diameter (Small, 2013, 9: 3584-92), electrical conductivity (Adv. Matter., 2017, 29: 1605719), and even chirality (Nature, 2017, 543: 234-8). However, the problem with this method is its low yield, which cannot meet the needs of practical applications. Besides SCCVD, other methods mentioned above can also achieve large-scale preparation of SWCNTs, but each has its own advantages and disadvantages. For example, FBCVD has high yield but low graphitization; HiPco requires high pressure and harsh conditions; and other methods such as FCCVD still have high production costs. Summary of the Invention

[0004] This invention addresses the technical problems of low single-wall carbon nanotube ratio (less than 70%), low graphitization degree (G / D less than 100), and high production cost (greater than 10,000 yuan / kg) of current single-wall carbon nanotube products on the market. It proposes a method for growing single-wall carbon nanotubes based on a catalyst prepared by freeze-drying. This method uses freeze-drying to prepare an easily decomposable solid catalyst, and combines this with the heating, etching, and decomposition effects of plasma. This allows for the preparation of single-wall carbon nanotubes with a single-wall ratio greater than 90% and a graphitization degree (G / D) greater than 100, at a cost less than 5,000 yuan / kg.

[0005] To address the aforementioned technical problems, a first aspect of the present invention provides a method for growing single-walled carbon nanotubes, comprising the following steps:

[0006] (1) Dissolve the active component, carrier component and complexing agent in deionized water to obtain a mixed solution;

[0007] (2) After the mixed solution is kept warm in liquid nitrogen, it is freeze-dried under vacuum to obtain a solid catalyst;

[0008] (3) The solid catalyst is transported to the plasma region of the plasma device by a carrier gas to form a catalytically active plasma; then the plasma is transported to the growth region of the plasma device, and a carbon source gas is introduced into the growth region to cause the carbon source gas to decompose and grow, forming the single-walled carbon nanotube.

[0009] Specifically, this invention first prepares a solid catalyst using freeze-drying, which has a loose structure and a low decomposition temperature. Then, through the heating, etching, and decomposition effects of plasma, the catalyst is transformed into a catalytically active plasma. Simultaneously, the catalyst with its low decomposition temperature readily decomposes in the high-temperature atmosphere of the plasma, generating gas. This gas breaks down the catalyst and accelerates its decomposition. This positive feedback allows for the faster formation of a more uniform plasma containing catalytic activity, resulting in a uniform distribution, small diameter (nanoscale), and low aggregation of the active components within the plasma. These characteristics are crucial for growing small-diameter and uniformly distributed single-walled carbon nanotubes, facilitating the production of carbon nanotube powders with a high proportion of single-walled components. Furthermore, the plasma itself has a high temperature, providing the energy required for the cracking of the carbon source gas. Only heat preservation is needed in the growth zone for carbon nanotube growth, eliminating the need for additional heat and significantly reducing production costs.

[0010] Preferably, the active component includes a nitrate, chloride, or sulfate whose cation is at least one of Fe, Co, Ni, W, Mn, La, or Y.

[0011] Preferably, the carrier component includes a nitrate, chloride, or sulfate whose cation is at least one of Mo, Al, or Mg.

[0012] Preferably, the complexing agent includes at least one of citric acid, glucose, and hydroxyethyl ethylenediamine. The complexing agent can bond with metal ions in the active component and the carrier component, increasing the solubility of the active component and the carrier component, while simultaneously separating the metals and preventing metal aggregation.

[0013] Preferably, the particle size of the active component, carrier component and complexing agent is at least sieve size of 400 mesh.

[0014] Preferably, the molar ratio of the active component to the carrier component is (10-40):1.

[0015] Preferably, the molar ratio of the total amount of the active component and the carrier component to the complexing agent is (0.4-1.3):1;

[0016] Preferably, the amount of deionized water used is calculated according to formula (1):

[0017]

[0018] In formula (1), For the quality of deionized water, m is the relative molecular mass of deionized water. i M represents the mass of the active component. i m is the relative molecular mass of the active component. j For the mass of the carrier component, M j m is the relative molecular mass of the carrier component. k For the quality of the complexing agent, M k The relative molecular mass of the complexing agent is denoted as . The value of the numerical coefficient is 1.1-4.2.

[0019] Preferably, in step (2), after the vacuum freeze-drying, a grinding step is also included, and after grinding, the particle size of the solid catalyst is at least passing through a 400-mesh sieve.

[0020] Preferably, the solid catalyst has a specific surface area greater than 100 m². 2 / g.

[0021] Preferably, in step (2), the heat preservation time is 0.5-1.5 hours; the vacuum freeze-drying temperature is -90℃ to -10℃, and the vacuum freeze-drying time is 24-48 hours.

[0022] Preferably, in step (3), the carrier gas is an inert gas, including nitrogen, argon or helium.

[0023] Preferably, the flow rate of the carrier gas is 10-40 L / min.

[0024] Preferably, in step (3), the temperature of the plasma region is greater than 2500℃; more preferably, the temperature of the plasma region is 2800-3200℃.

[0025] Preferably, in step (3), argon and hydrogen are supplied in the plasma zone, with the argon flow rate being 1000-2000 L / min and the hydrogen flow rate being 10-20 L / min.

[0026] Preferably, in step (3), the carbon source gas includes at least one of methane, ethylene, and propylene.

[0027] Preferably, in step (3), the flow rate of the carbon source gas is 5-20 L / min.

[0028] Preferably, in step (3), the growth zone also contains hydrogen gas, and the flow rate of the hydrogen gas is 10-40 L / min.

[0029] A second aspect of the present invention provides a single-walled carbon nanotube, which is prepared by the above-described method for growing single-walled carbon nanotubes; wherein the single-wall ratio of the single-walled carbon nanotube is greater than 90%.

[0030] Preferably, the graphitization degree (G / D) of the single-walled carbon nanotubes is greater than 100.

[0031] A third aspect of the present invention provides the application of the above-described single-walled carbon nanotubes in batteries, catalyst supports, heat dissipation materials, reinforced composite materials, or electronic devices.

[0032] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages:

[0033] (1) This invention uses freeze-drying to prepare a solid catalyst with a fluffy structure. This catalyst has a low decomposition temperature (below 500℃) and is easily decomposed in the high-temperature atmosphere of plasma (above 2500℃) to generate gas. The generated gas breaks down the catalyst and accelerates its decomposition. This positive feedback can quickly form a uniform plasma containing catalytic activity, making the active components in the plasma uniformly distributed, small in diameter (nanoscale), and not prone to aggregation. This lays the foundation for the growth of single-walled carbon nanotubes with small diameter and uniform distribution, thereby obtaining carbon nanotube powder with a high proportion of single walls. At the same time, the high temperature of the plasma itself provides the energy required for the cracking of the carbon source gas. Only heat preservation is needed in the growth zone for the growth of carbon nanotubes, thereby greatly reducing production costs.

[0034] (2) In the single-walled carbon nanotubes prepared by the present invention, the proportion of single walls is greater than 90%, the degree of graphitization G / D is greater than 100, and the production cost can be reduced to 4,000 yuan / kg. Attached Figure Description

[0035] Figure 1 TEM image of the single-walled carbon nanotubes prepared in Example 1;

[0036] Figure 2 TEM image of the single-walled carbon nanotubes prepared for Comparative Example 1. Detailed Implementation

[0037] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or growth methods not mentioned in detail are process steps or growth methods known to those skilled in the art.

[0038] Example 1

[0039] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0040] (1) Weigh 30.7 kg of glucose and add it to 168.6 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 4.36 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0041] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0042] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 25 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 100 KW, the flow rate of argon gas entering the plasma zone is 1000 L / min, the flow rate of hydrogen gas entering the plasma zone is 10 L / min, and the temperature of the plasma zone is 3000 °C). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane entering the growth zone is 20 L / min, and the flow rate of hydrogen gas entering the growth zone is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this embodiment.

[0043] Figure 1 This is a TEM image of the single-walled carbon nanotubes prepared in Example 1. Figure 1 It can be seen that the diameter of the single-walled carbon nanotube is 1.8±0.3nm.

[0044] Example 2

[0045] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0046] (1) Weigh 30.7 kg of glucose and add it to 275.7 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 25.3 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0047] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0048] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 25 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 100 KW, the flow rate of argon gas entering the plasma zone is 1000 L / min, the flow rate of hydrogen gas entering the plasma zone is 10 L / min, and the temperature of the plasma zone is 3000 °C). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane entering the growth zone is 20 L / min, and the flow rate of hydrogen gas entering the growth zone is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this embodiment.

[0049] Example 3

[0050] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0051] (1) Weigh 30.7 kg of glucose and add it to 168.9 kg of deionized water. Stir for 30 minutes, then add 9.75 kg of ferric nitrate, 4.37 kg of cobalt nitrate, 13.13 kg of sodium tungstate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0052] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0053] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 25 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 100 KW, the flow rate of argon gas entering the plasma zone is 1000 L / min, the flow rate of hydrogen gas entering the plasma zone is 10 L / min, and the temperature of the plasma zone is 3000 °C). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane entering the growth zone is 20 L / min, and the flow rate of hydrogen gas entering the growth zone is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this embodiment.

[0054] Comparative Example 1

[0055] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0056] (1) Weigh 30.7 kg of glucose and add it to 353.0 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 40.5 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0057] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0058] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 25 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 100 KW, the flow rate of argon gas entering the plasma zone is 1000 L / min, the flow rate of hydrogen gas entering the plasma zone is 10 L / min, and the temperature of the plasma zone is 3000 °C). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane entering the growth zone is 20 L / min, and the flow rate of hydrogen gas entering the growth zone is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this comparative example.

[0059] Figure 2 The image shows a TEM image of the single-walled carbon nanotubes prepared in Comparative Example 1. Figure 2 It can be seen that the diameter of the single-walled carbon nanotube is 2.6±0.5nm.

[0060] Comparative Example 2

[0061] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0062] (1) Weigh 30.7 kg of glucose and add it to 161.7 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 4.36 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0063] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0064] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 25 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 70 KW, the flow rate of argon gas entering the plasma zone is 1000 L / min, the flow rate of hydrogen gas entering the plasma zone is 10 L / min, and the temperature of the plasma zone is 2000℃). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane entering the growth zone is 20 L / min, and the flow rate of hydrogen gas entering the growth zone is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this comparative example.

[0065] Comparative Example 3

[0066] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0067] (1) Weigh 30.7 kg of glucose and add it to 161.7 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 4.36 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0068] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0069] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 2 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 70 KW, the flow rate of argon gas input to the plasma zone is 1000 L / min, the flow rate of hydrogen gas input is 10 L / min, and the temperature of the plasma zone is 3000℃). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane input to the growth zone is 20 L / min, and the flow rate of hydrogen gas input is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this comparative example.

[0070] Comparative Example 4

[0071] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0072] (1) Weigh 30.7 kg of glucose and add it to 337.2 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 4.36 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0073] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0074] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 25 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 100 KW, the flow rate of argon gas entering the plasma zone is 1000 L / min, the flow rate of hydrogen gas entering the plasma zone is 10 L / min, and the temperature of the plasma zone is 3000 °C). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane entering the growth zone is 20 L / min, and the flow rate of hydrogen gas entering the growth zone is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this comparative example.

[0075] Comparative Example 5

[0076] A method for growing single-walled carbon nanotubes, specifically including the following steps:

[0077] (1) Weigh 30.7 kg of glucose and add it to 28.1 kg of deionized water. Stir for 30 minutes, then add 25.7 kg of ferric nitrate, 4.36 kg of cobalt nitrate, 0.71 kg of magnesium nitrate and 0.47 kg of aluminum nitrate in sequence. Stir at 40°C for 2 hours to obtain a clear and transparent mixed solution.

[0078] (2) Pour the mixed solution obtained in step (1) into a 0.5L aluminum boat, then immerse half of the aluminum boat in liquid nitrogen for 1 hour, and then put it into a freeze dryer at -60℃ for 48 hours. After grinding and passing through a 400-mesh sieve, solid catalyst powder is obtained.

[0079] (3) The solid catalyst powder prepared in step (2) is transported to the plasma zone of the plasma device at a rate of 2 g / min through a nitrogen flow rate of 10 L / min (wherein: the power of the plasma zone is 70 KW, the flow rate of argon gas input to the plasma zone is 1000 L / min, the flow rate of hydrogen gas input is 10 L / min, and the temperature of the plasma zone is 3000℃). The solid catalyst decomposes in the plasma zone to form catalytically active plasma. Then it enters the growth zone of the plasma device (wherein: the flow rate of methane input to the growth zone is 20 L / min, and the flow rate of hydrogen gas input is 40 L / min). Finally, the product is collected at the tail of the growth zone, which is the single-walled carbon nanotube powder of this comparative example.

[0080] Performance testing

[0081] The outer diameter, single-wall ratio, graphitization degree (G / D), and film resistance of the carbon nanotube samples prepared in Examples 1-3 and Comparative Examples 1-5 were tested, and the yield of carbon nanotubes was calculated.

[0082] The G / D ratio was characterized using Raman spectroscopy, where the test sample was within the range of 1450-1590 cm⁻¹. -1 The peak intensity is IG within the range of 1250-1300 cm⁻¹. -1 The peak intensity within the range is ID, and the G / D ratio is IG / ID; the tube diameter is tested by TEM; the membrane resistance of carbon nanotubes is tested according to standard GB / T 37152-2018.

[0083] The test results are shown in Table 1.

[0084] Table 1: Comparison of performance indicators of carbon nanotube samples prepared in Examples 1-3 and Comparative Examples 1-5

[0085] sample Outer diameter (nm) Single-wall percentage (%) G / D ratio Yield (g / h) Membrane resistance (mΩ·cm) Example 1 1.8±0.3 95 150-200 400 4 Example 2 1.9±0.4 92 100-180 500 5 Example 3 2.0±0.2 98 150-190 390 5 Comparative Example 1 2.6±0.5 69 100-150 300 8 Comparative Example 2 2.4±0.4 78 70-150 290 7 Comparative Example 3 20.2±6.1 1 0-20 200 10 Comparative Example 4 1.7±0.5 92 140-200 350 6 Comparative Example 5 2.2±0.5 90 90-180 300 11

[0086] As shown in Table 1, the carbon nanotubes prepared in Examples 1-3 have excellent performance, including: uniform outer diameter ranging from 1.8±0.3nm to 2.0±0.2nm; a single-wall ratio as high as 92-98%; graphitization degree (G / D) greater than 100; a maximum yield of 500g / h; and a film resistance as low as 4mΩ·cm.

[0087] In Example 2, compared to Example 1, the production of carbon nanotubes increased due to the increase in the active component cobalt nitrate. The active particles formed in the plasma region were slightly larger, resulting in an increase in the average tube diameter, a decrease in the single-wall ratio, a decrease in the G / D ratio, and a slightly worse carbon nanotube quality.

[0088] Example 3 adds sodium tungstate to Example 1, which increases the active component, increases the tube diameter, and increases the single-wall ratio, but decreases the G / D ratio and slightly reduces the yield.

[0089] Compared to Example 1, Comparative Example 1 had an excessive proportion of cobalt nitrate as the active component, resulting in a reduced single-wall ratio of 69% and an increased average tube diameter of 2.6 nm. Simultaneously, the G / D ratio decreased, leading to increased membrane resistance. This is because the increased proportion of the active component in Comparative Example 1 resulted in an excessive amount of active component in the aggregates formed in the plasma region, leading to an increased outer diameter of the carbon nanotubes, a decreased single-wall ratio, a reduced G / D ratio, poorer carbon nanotube quality, and a lower yield.

[0090] Compared to Example 1, Comparative Example 2 reduced the temperature of the plasma zone to 2000°C, resulting in a larger average diameter of carbon nanotubes, a smaller single-wall ratio, and increased membrane resistance. Due to insufficient heat, the production of carbon nanotubes also decreased.

[0091] In Comparative Example 3, a solid catalyst was prepared by sintering. The majority of the grown products were multi-walled carbon nanotubes. This is because the sintered catalyst has a high melting point and decomposition temperature (>1000℃). When it enters the plasma region, it cannot form a plasma with uniform active components relatively quickly, resulting in aggregates of active particles. This leads to an increase in the diameter and number of walls of the grown carbon nanotubes.

[0092] Compared to Example 1, Comparative Example 4 contained excessive deionized water in the aqueous solution before freeze-drying. The value is 6, indicating incomplete freeze-drying, reduced yield, and increased carbon nanotube membrane resistance.

[0093] Compared to Example 1, Comparative Example 5 had too little deionized water in its aqueous solution before freeze-drying. The value is 0.5, and the pores after freeze-drying are not abundant enough, which leads to a longer decomposition time of the catalyst in the plasma region, affecting the reaction and ultimately increasing the carbon nanotube membrane resistance.

[0094] For those skilled in the art, several simple deductions or substitutions can be made without departing from the inventive concept, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A method for growing single-walled carbon nanotubes, characterized in that, Includes the following steps: (1) Dissolve the active component, carrier component and complexing agent in deionized water to obtain a mixed solution; The active component includes nitrates, chlorides, or sulfates whose cations are at least one of Fe, Co, Ni, W, Mn, La, and Y. The carrier component includes nitrates, chlorides, or sulfates whose cations are at least one of Mo, Al, and Mg. The complexing agent includes at least one of citric acid, glucose, and hydroxyethyl ethylenediamine; The molar ratio of the active component to the carrier component is (10-40):1; The molar ratio of the total amount of the active component and the carrier component to the complexing agent is (0.4-1.3):1; The amount of deionized water used is calculated according to formula (1): Official (1) In formula (1), For the quality of deionized water, This represents the relative molecular mass of deionized water. For the mass of the active component, This represents the relative molecular mass of the active component. For the mass of the carrier component, The relative molecular mass of the carrier component. For the quality of the complexing agent, The relative molecular mass of the complexing agent is denoted as . These are numerical coefficients, and the range of values ​​for these numerical coefficients is 1.1-4.2; (2) After the mixed solution is kept warm in liquid nitrogen, it is then freeze-dried under vacuum to obtain a solid catalyst; (3) The solid catalyst is transported to the plasma region of the plasma device by a carrier gas to form a plasma with catalytic activity; then the plasma is transported to the growth region of the plasma device, and a carbon source gas is introduced into the growth region to cause the carbon source gas to decompose and grow, forming the single-walled carbon nanotubes. The temperature of the plasma region is greater than 2500℃.

2. The method for growing single-walled carbon nanotubes according to claim 1, characterized in that, The solid catalyst has a specific surface area greater than 100 m². 2 / g.

3. The method for growing single-walled carbon nanotubes according to claim 1, characterized in that, In step (2), the heat preservation time is 0.5-1.5 hours; the vacuum freeze-drying temperature is -90℃ to -10℃, and the vacuum freeze-drying time is 24-48 hours.

4. The method for growing single-walled carbon nanotubes according to claim 1, characterized in that, In step (3), the carrier gas is an inert gas; and / or the flow rate of the carrier gas is 10-40 L / min.

5. The method for growing single-walled carbon nanotubes according to claim 1, characterized in that, In step (3), argon and hydrogen are transported in the plasma zone, with the argon flow rate being 1000-2000 L / min and the hydrogen flow rate being 10-20 L / min.

6. The method for growing single-walled carbon nanotubes according to claim 1, characterized in that, In step (3), the carbon source gas includes at least one of methane, ethylene, and propylene; and / or, the flow rate of the carbon source gas is 5-20 L / min; and / or, hydrogen is also supplied to the growth zone, and the flow rate of the hydrogen is 10-40 L / min.

7. A single-walled carbon nanotube, characterized in that, The single-walled carbon nanotubes are prepared by the growth method according to any one of claims 1 to 6; wherein the single-walled carbon nanotubes have a single-wall ratio greater than 90%; and the graphitization degree (G / D) of the single-walled carbon nanotubes is greater than 100.

8. The application of the single-walled carbon nanotubes according to claim 7 in batteries, catalyst supports, heat dissipation materials, reinforced composite materials or electronic devices.

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