Preparation method of high-purity single-walled carbon nanotube

Abstract

The invention discloses a preparation method of a high-purity single-walled carbon nanotube, which comprises the following operation steps: S1, continuously introducing inert gas into a closed gasification chamber, firstly starting a plasma gun to generate high-temperature flame, and then introducing a catalyst into the plasma high-temperature flame for gasification; s2, the gasified mixed product is screened through a screening unit, catalyst particles with the particle size not meeting the requirement are screened out for use, and the catalyst particles with the particle size meeting the requirement and the catalyst in the molten state are rapidly fed into a closed floating growth chamber and mixed with a carbon source introduced into the growth chamber for reaction; and S3, controlling the temperature in the growth chamber to be in a proper constant-temperature state, and reacting for a period of time to prepare the high-purity single-walled carbon nanotube. According to the preparation method of the high-purity single-walled carbon nanotube provided by the invention, the content of the single-walled carbon nanotube in the product can be ensured to be relatively high, the preparation efficiency is relatively high, and the cost of rear-end purification treatment is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterial preparation, in particular to a preparation method of high-purity single-wall carbon nanotubes. BACKGROUND

[0002] Single-wall carbon nanotubes have excellent electronic, mechanical and mechanical properties, and have ultra-high mobility for both electrons and holes. Therefore, single-wall carbon nanotubes are determined as the most likely new device material to be applied in the future. Continuous production of high-quality single-wall carbon nanotubes is the basis and key to the application of single-wall carbon nanotubes. The existing research on single-wall carbon nanotubes is basically in the laboratory research stage, and there is no report on industrial large-scale production in China. Although there are many reports on the preparation of carbon nanotubes in the existing public patent documents and papers, the products obtained are mainly single-wall and multi-wall carbon nanotubes and various structural carbon composites, and the content of single-wall carbon nanotubes is relatively low. Since the performance of single-wall carbon nanotubes is much better than that of multi-wall carbon nanotubes and various carbon composites, how to improve the purity of single-wall carbon nanotubes is a technical problem to be solved by those skilled in the art. SUMMARY

[0003] To solve the above technical problems, the present application provides a preparation method of high-purity single-wall carbon nanotubes, which can ensure that the content of single-wall carbon nanotubes in the product is high and reduce the cost of subsequent purification treatment.

[0004] The technical scheme provided by the present application is as follows: A preparation method of high-purity single-wall carbon nanotubes, comprising the following operation steps: S1, continuously introducing inert gas into a closed gasification chamber to replace the atmosphere in the furnace, and then continuously introducing active gas, starting the plasma gun to generate high-temperature flame, and then continuously introducing catalyst into the plasma high-temperature flame for gasification; S2, screening the mixed product after gasification through a screening unit, and the catalyst particles with particle size not meeting the requirements are screened out and not used, and the catalyst particles with particle size meeting the requirements and the catalyst in the molten state are quickly sent into a closed floating growth chamber and mixed with the carbon source introduced into the growth chamber for reaction; S3, controlling the temperature in the growth chamber to be in a suitable constant temperature state, and obtaining high-purity single-wall carbon nanotubes after a period of reaction.

[0005] Preferably, the active gas introduced in step S1 forms a vortex gas field.

[0006] Preferably, the screening unit in step S2 is a filter plate, and the filter plate is arranged at the connection between the gasification chamber and the growth chamber and is in the vortex gas field to form a gravity screening effect.

[0007] Preferably, the step S2 is provided with a high-temperature molten pool at the bottom of the gasification chamber, and the catalyst particles with particle size not meeting the requirements are settled into the molten pool.

[0008] Preferably, the step S2 is provided with a high-temperature molten pool at the bottom of the gasification chamber, and the catalyst particles with particle size not meeting the requirements are settled into the molten pool.

[0009] Preferably, the step S1 is provided with a catalyst conveying channel in the plasma gun, and the catalyst is continuously fed from the conveying channel.

[0010] Preferably, the step S2 is provided with a high-temperature molten pool at the bottom of the gasification chamber, and the catalyst particles with particle size not meeting the requirements are settled into the molten pool.

[0011] Preferably, the step S3 is provided with a temperature of 1000-2000℃ in the growth chamber.

[0012] Preferably, the step S1 is provided with a high-temperature molten pool at the bottom of the gasification chamber, and the catalyst particles with particle size not meeting the requirements are settled into the molten pool.

[0013] Preferably, the step S2 is provided with a high-temperature molten pool at the bottom of the gasification chamber, and the catalyst particles with particle size not meeting the requirements are settled into the molten pool.

[0014] The present application has the following advantages over the prior art: The preparation method of the high-purity single-walled carbon nanotube of the present application first selects the catalyst particles before mixing the catalyst with the carbon source for reaction, and only uses the catalyst with particle size meeting the requirements to mix with the carbon source, thereby controlling the quality of the catalyst from the source, and blocking the influence of a large amount of disordered high-temperature turbulent flow generated by the plasma gun on the thermal field and flow field of the rear-end growth chamber, so as to effectively reduce the generation of by-products (such as multi-walled carbon nanotubes, carbon spheres, free carbon, mixed carbon, etc.), and make the content of the single-walled carbon nanotube in the obtained product higher, and the purity higher than 90%. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 SEM image of the product prepared in the embodiments of the present application; Figure 2SEM images of the product prepared in the embodiments of the present application in greater multiples. DETAILED DESCRIPTION

[0017] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0018] The embodiment of the present application provides a preparation method of high-purity single-walled carbon nanotubes, comprising the following operation steps: S1, continuously introducing inert gas into a closed gasification chamber to replace the atmosphere in the furnace, and then continuously introducing active gas, starting the plasma gun to generate high-temperature flame, and then continuously introducing catalyst into the plasma high-temperature flame for gasification; S2, screening the mixed product after gasification through a screening unit, and the catalyst particles with particle size not meeting the requirements are screened out and not used, and the catalyst particles with particle size meeting the requirements and the catalyst in a molten state are quickly sent into a closed floating growth chamber and mixed with the carbon source introduced into the growth chamber for reaction; S3, controlling the temperature in the growth chamber to be in a suitable constant temperature state, and preparing high-purity single-walled carbon nanotubes after a period of reaction.

[0019] In the embodiment, the active gas introduced at a rate of 500 L / min in step S1 is adjusted to a certain angle by the blowing head of the jet assembly to form a vortex gas field, and the gasified catalyst particles are in vortex motion in the gasification chamber under the vortex gas flow, which is beneficial to the screening of the catalyst particles by the screening unit during the motion.

[0020] In the example, the catalyst in step S1 can be a metal compound commonly used in the preparation of existing carbon nanotubes; and the carbon source in step S2 is methane, ethane, propane, propyne, acetylene or acetone, etc.

[0021] In the embodiment, the screening unit in step S2 is a filter plate, which is arranged at the connection between the gasification chamber and the growth chamber and is in the vortex gas field to form a gravity screening effect, relying on the cooperation of gravity and a plurality of filter holes on the filter plate (the particles with smaller particle size are lifted to the filter holes of the filter plate in the gasification chamber under the high-temperature gas flow, pass through the filter holes and enter the growth chamber, and the particles with larger particle size sink downward due to gravity), which can realize the screening of the catalyst.

[0022] In this embodiment, a high-temperature molten pool is provided at the bottom of the gasification chamber in step S2. Catalyst particles whose particle size does not meet the requirements settle into the molten pool to participate in the next gasification process. The high-temperature molten pool receives excess catalyst and absorbs excess plasma flame temperature. The high-temperature molten pool can release a large amount of heat and also act as a temperature stabilizer for the gasification chamber.

[0023] In this embodiment, the particle size of the catalyst particles that meet the size requirements in step S2 is no greater than 100 nm, ensuring that the particle size of the catalyst entering the growth chamber to react with the carbon source is small and the probability of impurities in the product is low.

[0024] In this embodiment, the plasma gun in step S1 is provided with a catalyst delivery channel, and the catalyst is continuously fed in through the delivery channel, which can ensure the continuity of the catalyst entering the gasification chamber and enable continuous operation.

[0025] In this embodiment, the outlet of the carbon source in the growth chamber in step S2 is arranged in a ring shape to form a vortex gas field, which is conducive to the mixing of carbon source and catalyst, and can also effectively prevent catalyst particles from agglomerating into large particles again in the growth chamber.

[0026] In this embodiment, the temperature in the growth chamber in step S3 is 1000-2000℃, and the growth environment of single-walled carbon nanotubes is stable and controllable.

[0027] In this embodiment, the gasification chamber in step S1 and the growth chamber in step S2 are independently arranged in the same direction. That is, if the gasification chamber and the growth chamber form a horizontal or vertical structure, the growth chamber is located on one side of the gasification chamber. When the gasification chamber and the growth chamber form a vertical structure, the growth chamber is located above the gasification chamber. When the gasification chamber and the growth chamber form a horizontal structure, the growth chamber is located on the right or left side of the gasification chamber. The gasification chamber and the growth chamber are sealed together. The screening unit is located at the inlet port of the growth chamber and is sealed together with the growth chamber. This arrangement of the screening unit can shorten the movement path of the catalyst, which is convenient for the continuous production of single-walled carbon nanotubes, and also serve as a barrier, which is convenient for the segmented control of the gasification chamber and the growth chamber.

[0028] In this embodiment, the growth chamber in step S2 is composed of a single-segment structure or a multi-segment structure connected in series, which can be reasonably selected according to actual needs. The discharge end of the growth chamber is provided with a cooling transition discharge section, which not only ensures that the environment inside the growth chamber is not changed during the discharge process, but also prevents the product from being etched away by water when it enters the collection system due to excessively high product temperature during discharge.

[0029] Using the above-described method for preparing high-purity single-walled carbon nanotubes, samples were taken at the outlet of the cooling transition section at regular intervals for purity testing. The test results are shown in the table below: Table 1 Purity test results

[0030] As can be seen from Table 1, the purity of the single-walled carbon nanotubes obtained by the preparation method of the present invention is almost all over 90%, and the batch stability is very good.

[0031] The product was subjected to SEM analysis, and the results are attached. Figure 1 , 2 As shown in the figure, the single-walled carbon nanotubes prepared by the method of this application have a diameter of 1 to 1.5 nm, a length of 150 μm to 260 μm, an aspect ratio of over 100,000, and the raw product has almost no impurities.

[0032] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high-purity single-walled carbon nanotubes, characterized in that, The following steps are included: S1. Inert gas is continuously introduced into the sealed gasification chamber to replace the atmosphere in the furnace, and then active gas is continuously introduced. First, the plasma gun is started to generate a high-temperature flame, and then the catalyst is continuously introduced into the high-temperature plasma flame for gasification. S2. The gasified mixture is screened by a screening unit. Catalyst particles that do not meet the size requirements are screened out and not used. Catalyst particles that meet the size requirements and the catalyst in the molten state are quickly fed into a closed floating growth chamber and mixed with the carbon source introduced into the growth chamber for reaction. S3. Control the temperature in the growth chamber to a suitable constant temperature state, and after reacting for a period of time, high-purity single-walled carbon nanotubes are obtained.

2. The method for preparing high-purity single-walled carbon nanotubes according to claim 1, characterized in that, The active gas introduced in step S1 forms a vortex gas field.

3. The method for preparing high-purity single-walled carbon nanotubes according to claim 2, characterized in that, The screening unit in step S2 is a filter plate, which is set at the connection between the gasification chamber and the growth chamber. The filter plate is located in the vortex gas field to form a gravity screening effect.

4. The method for preparing high-purity single-walled carbon nanotubes according to claim 3, characterized in that, In step S2, a high-temperature molten pool is set at the bottom of the gasification chamber, and catalyst particles whose particle size does not meet the requirements settle into the molten pool.

5. The method for preparing high-purity single-walled carbon nanotubes according to claim 3, characterized in that, In step S2, the particle size of the catalyst particles that meet the requirements is no greater than 100 nm.

6. The method for preparing high-purity single-walled carbon nanotubes according to any one of claims 1-5, characterized in that, In step S1, the plasma gun is equipped with a catalyst delivery channel, through which the catalyst is continuously fed.

7. The method for preparing high-purity single-walled carbon nanotubes according to any one of claims 1-5, characterized in that, In step S2, the carbon source is a gaseous or gas-liquid mixture carbon source, and the outlet of the carbon source in the growth chamber is distributed in a ring shape to form a vortex gas field.

8. The method for preparing high-purity single-walled carbon nanotubes according to any one of claims 1-5, characterized in that, The temperature in the growth chamber during step S3 is 1000–2000℃.

9. The method for preparing high-purity single-walled carbon nanotubes according to any one of claims 1-5, characterized in that, The gasification chamber in step S1 and the growth chamber in step S2 are independently set in the same direction. The growth chamber is located on one side of the gasification chamber and is sealed to the gasification chamber. The screening unit is set at the inlet port of the growth chamber and is sealed to the growth chamber.

10. The method for preparing high-purity single-walled carbon nanotubes according to any one of claims 1-5, characterized in that, In step S2, the growth chamber is composed of a single-segment structure or multiple segments connected in series, and the discharge end of the growth chamber is provided with a cooling transition discharge section.

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