A method for preparing ultra-high yield of ultra-long carbon nanotubes

Abstract

The present application discloses a method for preparing ultra-long carbon nanotubes with an ultra-high yield. The method includes setting a substrate in a reactor, introducing a mixed gas 1 into the reactor to displace the air in the reactor with the mixed gas 1, and raising the temperature in the reactor until the reaction temperature is reached. The mixed gas 1 includes hydrogen and an inert atmosphere gas; continuously introducing a mixed gas 2 and a catalyst solution into the reactor to react to obtain ultra-long carbon nanotubes; the mixed gas 2 includes a carbon source gas, hydrogen, the inert atmosphere gas, and water vapor; the catalyst solution includes a catalyst precursor, a promoter, and a solvent. This method for preparing ultra-long carbon nanotubes with an ultra-high yield is called the substrate interception and orientation strategy. This method uses the substrate placed in the tubular furnace to intercept and orient the floating short tubes generated by chemical vapor deposition, which can significantly extend the growth time of the carbon nanotubes and finally grow them into ultra-long carbon nanotubes.

Description

Technical Field

[0001] This document relates to, but is not limited to, the field of nanomaterials and their preparation technologies, and particularly relates to, but is not limited to, a method for preparing ultra-long carbon nanotubes with ultra-high yield. Background Art

[0002] As a one-dimensional Dirac nanomaterial, carbon nanotubes have excellent mechanical, electrical, optical, and thermal properties, and thus have broad application prospects in high-end fields such as transparent conductive films, super-strong fibers, and carbon-based integrated circuits. However, structural elements such as the length, degree of orientation, defect concentration, crystallinity, and chirality of carbon nanotubes have a very significant impact on their properties, and any shortcoming in any aspect may cause a significant decline in the performance of carbon nanotubes. Among these structural elements, the length of carbon nanotubes has a strong correlation with basic physical properties such as the tensile strength, elongation at break, electrical conductivity, and thermal conductivity of macroscopic fibers and films. Therefore, in the preparation of carbon nanotubes, their length should be increased as much as possible to ensure their intrinsic excellent properties.

[0003] According to the differences in the length, degree of orientation, and morphology of carbon nanotubes, they can be divided into agglomerated carbon nanotubes, vertical array carbon nanotubes, and horizontal array carbon nanotubes. Among them, the lengths of agglomerated carbon nanotubes and vertical array carbon nanotubes are usually very short (within 1 mm) and contain many defects, so their various properties are much lower than the theoretically predicted values. In contrast, since horizontal array carbon nanotubes grow on a flat substrate and the interaction between tubes is small, carbon nanotubes can grow relatively independently. Therefore, horizontal array carbon nanotubes usually have fewer defects, fewer tube walls, and excellent properties. Horizontal array carbon nanotubes can be further divided into two subcategories: bottom growth and tip growth, according to different growth mechanisms. Among them, bottom-grown horizontal array carbon nanotubes usually use materials such as single-crystal quartz or sapphire as the substrate, and the carbon nanotubes follow a crawling growth mode on the substrate. Due to the crawling growth process, the carbon nanotubes are always restricted by the van der Waals force from the substrate, and the mass transfer process at the wall surface is also relatively restricted. Therefore, bottom-grown horizontal array carbon nanotubes have problems such as short length (usually within 1 mm) and slow growth rate. In contrast, tip-grown carbon nanotubes follow a growth mode similar to that of a kite: the catalyst nanoparticles are located at the tip of the carbon nanotube, and the catalyst and the tip of the carbon nanotube float in the gas flow together. This growth mode allows the carbon nanotubes to grow freely and quickly, and the final length can reach centimeters or even decimeters. Therefore, this tip-grown horizontal array carbon nanotube is also called ultra-long carbon nanotube.

[0004] Although ultra-long carbon nanotubes have significant advantages over other types of carbon nanotubes in terms of length, structural perfection, and various properties, it is still difficult to realize their practical application at present. The fundamental reason lies in the low yield of ultra-long carbon nanotubes. First of all, the main reason for the low yield of ultra-long carbon nanotubes is the low utilization rate of the catalyst. The tip growth mode similar to that of a kite puts relatively harsh requirements on the growth conditions of ultra-long carbon nanotubes. Moreover, under relatively optimal growth conditions, only a small fraction of carbon nanotubes can float up and grow into ultra-long carbon nanotubes. Such a low catalyst utilization rate makes the array density of ultra-long carbon nanotubes usually about three orders of magnitude lower than that of the horizontally array grown at the bottom. Secondly, the aggregation of catalyst particles further reduces the number of catalyst particles suitable for the growth of ultra-long carbon nanotubes, thereby further reducing the yield of ultra-long carbon nanotubes. In addition, the entanglement of carbon nanotubes with each other and the situation where the tips of carbon nanotubes fall on the substrate during the growth process will also lead to a decrease in the yield of ultra-long carbon nanotubes. Therefore, there is an urgent need to develop a new method that can be compatible with the tip growth mode of ultra-long carbon nanotubes and at the same time improve the catalyst utilization rate to achieve the purpose of increasing the yield of ultra-long carbon nanotubes. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail in this document. This overview is not intended to limit the scope of protection of this application.

[0006] This application proposes a new method for preparing ultra-long carbon nanotubes from a methodological level, namely the substrate interception and guiding strategy, which can achieve the batch preparation of ultra-long carbon nanotubes with ultra-high yield. In the process of chemical vapor deposition, this method introduces a substrate for intercepting and guiding floating short tubes to achieve the purpose of extending the growth time of carbon nanotubes. With the help of the substrate interception and guiding strategy, the growth time of carbon nanotubes can be extended by about three orders of magnitude, and then they can grow efficiently into ultra-long carbon nanotubes. In the traditional method for growing ultra-long carbon nanotubes, only a very small number of carbon nanotubes can float up under the combined action of forces such as drag force, thermal buoyancy force, and van der Waals force and grow into ultra-long carbon nanotubes; the remaining carbon nanotubes can only be randomly distributed in the catalyst area and cannot continue to grow into ultra-long carbon nanotubes. In contrast, this method can effectively utilize the intrinsic floating state of carbon nanotubes, enabling most carbon nanotubes to meet the conditions for floating growth, and successfully overcoming problems such as low catalyst utilization rate and easy aggregation of catalyst particles in the traditional method for growing ultra-long carbon nanotubes.

[0007] This application provides a method for preparing ultra-long carbon nanotubes with ultra-high yield, including:

[0008] Setting a substrate in the reactor, introducing a mixed gas 1 into the reactor to replace the air in the reactor with the mixed gas 1, and raising the temperature in the reactor until the reaction temperature is reached. The mixed gas 1 includes hydrogen and a first atmosphere gas;

[0009] Continuously introduce mixed gas 2 and a catalyst solution into the reactor to obtain ultra-long carbon nanotubes; the mixed gas 2 includes a carbon source gas, hydrogen, a second inert atmosphere gas, and water vapor.

[0010] The catalyst solution includes a catalyst precursor, a promoter, and a solvent.

[0011] In an embodiment provided by the present application, the substrate is a substrate that can withstand 300°C to 2000°C, and during the growth process of the ultra-long carbon nanotubes, one end of the carbon nanotubes is fixed by the substrate.

[0012] In an embodiment provided by the present application, the material of the substrate is selected from any one or more of silicon, quartz, ceramics, and metals.

[0013] In an embodiment provided by the present application, place the substrate in the center of the tubular furnace reactor before growth.

[0014] In an embodiment provided by the present application, the extending direction of the substrate is parallel to the gas flow direction; or, the extending direction of the substrate is perpendicular to the gas flow direction and the substrate has through holes, and the through holes allow the unfixed end of the carbon nanotubes to grow through the through holes.

[0015] In the description of the present application, "the extending direction of the substrate is parallel to the gas flow direction" means that the included angle between the extending direction of the substrate and the gas flow direction is within the range of -10° to 10°.

[0016] "The extending direction of the substrate is perpendicular to the gas flow direction" means that the included angle between the extending direction of the substrate and the gas flow direction is within the range of 80° to 100°.

[0017] In an embodiment provided by the present application, the substrate is a perforated frame substrate or a non-perforated block substrate.

[0018] In an embodiment provided by the present application, the porosity of the perforated frame substrate is 0.001 to 0.999.

[0019] In an embodiment provided by the present application, the height of the non-perforated block substrate accounts for 0.1% to 90% of the inner diameter of the reactor.

[0020] In the embodiment provided by the present application, the reaction temperature is 300°C to 2000°C, and the reaction time of the reaction is 1 min to 2000 min; in an embodiment provided by the present application, the reaction time of the reaction is 3 min to 600 min.

[0021] In an embodiment provided by the present application, the total flow rate of the mixed gas 1 is from 0.01 sccm to 100000 sccm; in an embodiment provided by the present application, the total flow rate of the mixed gas 1 is from 1 sccm to 10000 sccm.

[0022] In an embodiment provided by the present application, the concentration of hydrogen in the mixed gas 1 is from 0.001 vol.% to 99 vol.%; in an embodiment provided by the present application, the concentration of hydrogen in the mixed gas 1 is from 1 vol.% to 99 vol.%.

[0023] In an embodiment provided by the present application, the total flow rate of the mixed gas 2 is from 0.01 sccm to 100000 sccm; in an embodiment provided by the present application, the total flow rate of the mixed gas 2 is from 1 sccm to 10000 sccm.

[0024] In an embodiment provided by the present application, the flow rate of the catalyst solution is from 0.001 μL / min to 10000 μL / min; in an embodiment provided by the present application, the flow rate of the catalyst solution is from 0.01 μL / min to 100 μL / min.

[0025] In an embodiment provided by the present application, the carbon source gas is selected from any one or more of methane, ethane, ethylene, acetylene, methanol vapor, ethanol vapor, isopropanol vapor, acetone vapor, and carbon monoxide.

[0026] In an embodiment provided by the present application, the concentration of the carbon source gas in the mixed gas 2 is from 0.00001 vol.% to 99 vol.%; in an embodiment provided by the present application, the concentration of the carbon source gas in the mixed gas 2 is from 0.01 vol.% to 80 vol.%.

[0027] In an embodiment provided by the present application, the concentration of hydrogen in the mixed gas 2 is from 0.001 vol.% to 99 vol.%; in an embodiment provided by the present application, the concentration of hydrogen in the mixed gas 2 is from 1 vol.% to 99 vol.%.

[0028] In an embodiment provided by the present application, the concentration of water vapor in the mixed gas 2 is from 0.0001 vol.% to 99 vol.%.

[0029] In an embodiment provided by the present application, the concentration of the catalyst precursor in the catalyst solution is 0.0001 wt.% to 99 wt.%; in an embodiment provided by the present application, the concentration of the catalyst precursor in the catalyst solution is 0.01 wt.% to 20 wt.%.

[0030] In an embodiment provided by the present application, the concentration of the cocatalyst in the catalyst solution is 0.0001 wt.% to 99 wt.%; in an embodiment provided by the present application, the concentration of the cocatalyst in the catalyst solution is 0.01 wt.% to 60 wt.%.

[0031] In an embodiment provided by the present application, the catalyst precursor is a metallocene compound and the cocatalyst is thiophene.

[0032] In an embodiment provided by the present application, the metallocene compound is selected from any one or more of metallocene compounds of Group VIII elements and metallocene compounds of Group IVB metals.

[0033] In an embodiment provided by the present application, the metallocene compound is selected from any one or more of ferrocene, cobaltocene, nickelocene, and titanocene dichloride.

[0034] In an embodiment provided by the present application, the solvent is selected from any one or more of methanol, ethanol, isopropanol, acetone, benzene, toluene, ethylbenzene, xylene, n-hexane, and cyclohexane.

[0035] In an embodiment provided by the present application, preparing the catalyst solution includes: dissolving the catalyst precursor and the cocatalyst thiophene in a solvent and obtaining a clear solution by ultrasonic treatment. After sucking the prepared solution with a syringe, it is installed on an injection pump, and the syringe is connected to a reactor.

[0036] In an embodiment provided by the present application, the method for ultra-high yield preparation of the ultra-long carbon nanotubes further includes: cooling under the protection of the mixed gas 1 after the growth of the ultra-long carbon nanotubes ends.

[0037] In an embodiment provided by the present application, the first inert gas and the second inert gas are each independently selected from any one or more of nitrogen, argon, and helium.

[0038] On the other hand, the present application provides ultra-long carbon nanotubes prepared by the above-mentioned method for ultra-high yield preparation of ultra-long carbon nanotubes;

[0039] In an embodiment provided by the present application, the length of the ultra-long carbon nanotubes is 1 cm to 100 cm.

[0040] On the other hand, the present application provides the use of the above-mentioned ultra-long carbon nanotubes in carbon-based chips, carbon nanotube fibers, and composite cables.

[0041] During the reactor heating process, a mixed gas of hydrogen and carrier gas is introduced into the reactor, and at the same time, the temperature of the tubular furnace is slowly increased.

[0042] The method described in the present application can prepare ultra-long carbon nanotubes with ultra-high yield. The obtained ultra-long carbon nanotubes can reach a length of centimeters to meters, and the growth rate of a single carbon nanotube can reach 2.37 mm / min (calculated from the horizontal array length at different growth times). The ultra-long carbon nanotubes prepared by this method also have the characteristics of perfect structure, fewer wall numbers (the number of tube walls is one to three walls), and excellent electrical properties.

[0043] In the method described in the present application, various substrates can be used for interception and guidance. For example, when using flat substrates such as single-crystal silicon wafers and single-crystal quartz wafers, a high-density horizontal array or film of ultra-long carbon nanotubes can be obtained; when using a mesh substrate with sieve holes, fibers composed of ultra-long carbon nanotubes can be obtained.

[0044] The ultra-long carbon nanotubes described in the present application have excellent electrical properties, and the purity of semiconductor-type carbon nanotubes can reach 95.7% (statistically obtained from Raman spectroscopy data).

[0045] Compared with the prior art, the method provided by the present application adopts a substrate interception and guidance strategy, which greatly improves the utilization rate of the catalyst and significantly inhibits the agglomeration of catalyst particles, thereby realizing the controllable preparation of ultra-long carbon nanotubes with high yield. Using the substrate interception and guidance strategy, not only can a horizontal array with an array density of 10 3 roots / mm to 10 5 roots / mm be formed on a planar substrate (2-4 orders of magnitude higher than the traditional method), but also interception substrates with different shapes and sizes (such as perforated frames, metal meshes, etc.) can be used to realize the batch preparation of ultra-long carbon nanotubes with different morphologies and different aggregation modes (such as films, fibers, etc.) to meet the needs of various application scenarios.

[0046] The ultra-long carbon nanotubes prepared by this method have a length of centimeters to meters, high degree of orientation, low defect concentration, and excellent mechanical, thermal, and electrical properties for a single carbon nanotube. The ultra-long carbon nanotube aggregates prepared by the substrate interception and guidance strategy can give full play to the excellent intrinsic properties of carbon nanotubes and can be used in fields such as super-strong fibers, transparent conductive films, and carbon-based chips. This method also has the advantages of being simple and easy to operate, having a wide operation window, and having low requirements for the substrate material, shape, and size.

[0047] Other features and advantages of the present application will be described in the following specification, and in part will be apparent from the specification, or can be understood by implementing the present application. Other advantages of the present application can be achieved and obtained through the solutions described in the specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings are used to provide an understanding of the technical solutions of the present application, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solutions of the present application, and do not constitute a limitation to the technical solutions of the present application.

[0049] Figure 1A Schematic diagram of the device for preparing a horizontal array of ultra-long carbon nanotubes with ultra-high productivity. Figure 1B Schematic diagram of the growth process for preparing a horizontal array of ultra-long carbon nanotubes with ultra-high productivity.

[0050] Figure 2A Schematic diagram of the device for preparing ultra-long carbon nanotube fibers with ultra-high productivity. Figure 2B Schematic diagram of the growth process for preparing ultra-long carbon nanotube fibers with ultra-high productivity.

[0051] Figure 3 Schematic diagram of the preparation process for an ultra-long carbon nanotube film.

[0052] Figure 4 Optical visualization assisted by water vapor of the horizontal array of ultra-long carbon nanotubes prepared in Example 3.

[0053] Figure 5 Scanning electron microscope image of the horizontal array of ultra-long carbon nanotubes prepared in Example 2.

[0054] Figure 6 Scanning electron microscope image of the ultra-long carbon nanotube film prepared in Example 5.

[0055] Figure 7 Scanning electron microscope image of the ultra-long carbon nanotube fibers prepared in Example 1.

[0056] Figure 8 Transmission electron microscope image and Raman spectrum of multiple monomers of ultra-long carbon nanotubes prepared in Example 2.

[0057] Figure 9 Graph showing the variation of the length of the ultra-long carbon nanotubes in Example 3 with the growth time.

[0058] Figure 10 Transfer characteristic curve of the ultra-long carbon nanotubes prepared in Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] To make the objectives, technical solutions, and advantages of this application clearer and more understandable, the embodiments of this application will be described in detail below. It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be arbitrarily combined with each other.

[0060] The definition of the ultra-long carbon nanotubes is: carbon nanotubes with a length of more than 1 cm.

[0061] The definition of the ultra-high yield is: based on the supply amount of the carbon source, the proportion of carbon atoms therein converted into ultra-long carbon nanotubes exceeds 1%.

[0062] Different from the traditional chemical vapor deposition process, this method uses a substrate placed in the reactor to achieve the functions of dividing the flow field, intercepting carbon nanotubes, and guiding them; the catalyst nanoparticles formed by the cracking and reduction of the catalyst precursor grow short carbon nanotubes in a floating state in the mixed gas 2. The formed floating short tubes continuously flow through the reactor with the gas flow. A part of the floating short tubes is intercepted by the substrate placed in the center of the reactor, one end of which is fixed by the substrate, and the other end is guided by the drag force of the gas flow. After a period of growth, ultra-long carbon nanotubes are obtained with an ultra-high yield.

[0063] In the embodiments of this application, on the premise that the volume of the reactor permits, the shape and size of the substrate are not limited (for example, it can be plate-shaped or sheet-shaped); the placement method of the substrate (such as position, orientation, etc.) is not limited; the reactor used can be a tubular reactor, the inner diameter of the reactor can be 5 mm to 1000 mm, and the length of the reactor can be 20 cm to 10000 cm.

[0064] In the embodiments of this application, the catalyst solution is filled in a syringe and connected to the reactor by an injection pump.

[0065] Example 1

[0066] Prepare a benzene solution of 6 wt.% cobaltocene and 2 wt.% thiophene as the catalyst solution, and then clarify it by ultrasonic treatment. After extracting the prepared solution with a syringe, install it on the injection pump, and connect the syringe to the reactor. Before growth, place a quartz sheet processed with sieve holes (porosity is 0.6) vertically in the center of the tubular furnace reactor (that is, the extension direction of the quartz sheet with sieve holes is perpendicular to the gas flow direction, such as Figure 2A and Figure 2BAs shown). Subsequently, start to introduce mixed gas 1 (500 sccm of hydrogen and 50 sccm of argon, the volume fraction of hydrogen is (500 / 550 = 90.91 vol.%), and the volume fraction of argon is (50 / 550 = 9.09 vol.%) into the reactor, and at the same time slowly raise the temperature of the tube furnace to 1400 °C. After the temperature stabilizes, introduce mixed gas 2 (20 sccm of ethanol vapor, 100 sccm of hydrogen, 3000 sccm of helium, and 26.21 sccm of water vapor, the volume fraction of ethanol vapor is (20 / 3146.21 = 0.64 vol.%), the volume fraction of hydrogen is (100 / 3146.21 = 3.18 vol.%), the volume fraction of helium is (3000 / 3146.21 = 95.35 vol.%), and the volume fraction of water vapor is 26.21 / 3146.21 = 0.83 vol.%). At the same time, turn on the syringe pump and introduce the catalyst solution at a flow rate of 0.5 μL / min. After growing for 80 minutes, the reactor is cooled under the protection of mixed gas 1. After the reactor is cooled to room temperature, take out the quartz wafer therein, so as to obtain ultra-long carbon nanotube fibers grown on the quartz wafer with sieve holes. After weighing the fibers and calculating, the yield is 5.2%.

[0067] From Figure 2A and Figure 2B It can be seen that when using a vertically placed mesh substrate for interception, one end of the intercepted carbon nanotubes passes through the mesh holes and continues to grow into ultra-long carbon nanotubes according to the gas flow direction. After the reaction is completed, the ultra-long carbon nanotube fibers can be collected from the mesh substrate.

[0068] From Figure 7 It can be seen that the carbon nanotube monomers in the ultra-long carbon nanotube fibers prepared in this example are arranged regularly and have a high degree of orientation.

[0069] Example 2:

[0070] Prepare a cyclohexane solution of 2 wt.% titanium dichloride bis(cyclopentadienyl) and 8 wt.% thiophene, and then clarify it by ultrasonic treatment. After extracting the prepared solution with a syringe, install it on the syringe pump, and connect the syringe to the reactor. Before growth, place a single-crystal quartz wafer (with a thickness of 3.0% of the inner diameter of the reactor) in the center of the tube furnace reactor, and make the extension direction of the single-crystal quartz wafer parallel to the gas flow direction (as Figure 1A and Figure 1BAs shown in the figure). Subsequently, the mixed gas 1 (300 sccm of hydrogen and 500 sccm of nitrogen, the volume fraction of hydrogen is (300 / 800 = 37.5 vol.%), and the volume fraction of nitrogen is (500 / 800 = 62.5 vol.%)) was introduced into the reactor, and at the same time, the temperature of the tube furnace was slowly raised to 800 °C. After the temperature stabilized, the mixed gas 2 (10 sccm of ethanol vapor, 500 sccm of hydrogen, 2000 sccm of helium, and 0.30 sccm of water vapor, the volume fraction of ethanol vapor is (10 / 2510.3 = 0.4 vol.%), the volume fraction of hydrogen is (500 / 2510.3 = 19.92 vol.%), the volume fraction of helium is (2000 / 2510.3 = 79.67 vol.%), and the volume fraction of water vapor is 0.3 / 2510.3 = 0.01 vol.%)) was introduced. At the same time, the injection pump was turned on, and the catalyst solution was introduced at a flow rate of 10 μL / min. After growing for 80 minutes, the reactor was cooled under the protection of the mixed gas 1. After the reactor was cooled to room temperature, the quartz wafer inside was taken out, and thus a horizontal array of ultra-long carbon nanotubes grown on the single-crystal quartz wafer was obtained. Calculated from the array density and the carbon nanotube diameter, the yield was 1.3% (the yield is the ratio of the mass of the carbon nanotubes to the mass of the carbon in the introduced reaction raw material carbon source).

[0071] From Figure 1A and Figure 1B it can be seen that when using a planar substrate for interception, the floating short tubes grow into ultra-long carbon nanotubes under the action of the gas flow guidance and finally land on the substrate to form a highly oriented horizontal array.

[0072] From Figure 5 it can be seen that the array density of the ultra-long carbon nanotubes prepared in this example is much higher than that of the traditional method and has a good degree of orientation.

[0073] From Figure 8 the transmission electron micrograph and Raman spectrum, it can be seen that the ultra-long carbon nanotubes prepared in this example have a nearly perfect structure, a clean surface, a small number of tube walls (mostly 1 to 3 walls), and a high purity of semiconductor-type carbon nanotubes (the purity can reach 95.7% when the array length is 40 mm).

[0074] Example 3:

[0075] Prepare a toluene solution of 3 wt.% ferrocene and 0.45 wt.% thiophene, and then clarify it by ultrasonic treatment. After extracting the prepared solution with a syringe, it was installed on an injection pump, and the syringe was connected to the reactor. Before growth, a single-crystal silicon wafer (with a thickness of 1.1% of the inner diameter of the reactor) was placed in the center of the tube furnace reactor (as Figure 1A and Figure 1BAs shown, subsequently, the mixed gas 1 (100 sccm of hydrogen and 100 sccm of argon, the volume fraction of hydrogen is (100 / 200 = 50 vol.%), and the volume fraction of argon is (100 / 200 = 50 vol.%)) was introduced into the reactor, and at the same time, the temperature of the tube furnace was slowly raised to 1050 °C. After the temperature stabilized, the mixed gas 2 (4 sccm of ethylene, 330 sccm of hydrogen, 1390 sccm of argon, and 8.28 sccm of water vapor, the volume fraction of ethylene is (4 / 1732.28 = 0.23 vol.%), the volume fraction of hydrogen is (330 / 1732.28 = 19.05 vol.%), the volume fraction of argon is (3000 / 1732.28 = 80.24 vol.%), and the volume fraction of water vapor is 8.28 / 1732.28 = 0.48 vol.%)) was introduced. At the same time, the injection pump was turned on, and the catalyst solution was introduced at a flow rate of 1.8 μL / min. After growing for 60 minutes, the reactor was cooled under the protection of the mixed gas 1. After the reactor was cooled to room temperature, the substrate therein was taken out, thereby obtaining a high-density ultra-long carbon nanotube horizontal array grown on a single-crystalline silicon wafer. Calculated from the array density and the carbon nanotube diameter, the yield was 2.2%.

[0076] As can be seen from Figure 1A and Figure 1B when using a planar substrate for interception, the floating short tubes grow into ultra-long carbon nanotubes under the action of the gas flow guiding, and finally land on the substrate to form a highly oriented horizontal array.

[0077] As Figure 4 shown, the bright lines in the figure are the positions of the ultra-long carbon nanotubes. As can be seen from the figure, the ultra-long carbon nanotube horizontal array prepared by this method can uniformly cover a silicon wafer substrate about 10 cm long and has a very high array density. A considerable part of the ultra-long carbon nanotubes can grow to 10 cm, indicating that the catalyst has high activity, long life, and slow attenuation of the array density. Theoretically, when the constant temperature zone of the tube furnace is long enough, the carbon nanotubes can continue to grow under constant conditions, so as to reach the length of meters.

[0078] As can be seen from Figure 9 the ultra-long carbon nanotubes prepared in this example have a growth rate as high as 2.37 mm / min.

[0079] As can be seen from Figure 10 the ultra-long carbon nanotubes prepared in this example can be used to prepare field effect transistor devices and exhibit excellent switching performance.

[0080] Example 4

[0081] Prepare a hexane solution containing 8 wt.% nickelocene, 2 wt.% cobaltocene, and 0.32 wt.% thiophene, and then clarify it by ultrasonic treatment. After extracting the prepared solution with a syringe, install it on an injection pump, and connect the syringe to the reactor. Before growth, vertically place a stainless steel mesh (porosity 0.9) in the center of the tubular furnace reactor (as Figure 2A and Figure 2B shown). Subsequently, start introducing mixed gas 1 (100 sccm of hydrogen and 100 sccm of argon, the volume fraction of hydrogen is (100 / 200 = 50 vol.%), and the volume fraction of argon is (100 / 200 = 50 vol.%) into the reactor, and at the same time slowly raise the temperature of the tubular furnace to 950 °C. After the temperature stabilizes, introduce mixed gas 2 (50 sccm of carbon monoxide, 600 sccm of hydrogen, 300 sccm of argon, and 9.12 sccm of water vapor, the volume fraction of carbon monoxide is (50 / 959.12 = 5.21 vol.%), the volume fraction of hydrogen is (600 / 959.12 = 62.56 vol.%), the volume fraction of argon is (300 / 959.12 = 31.28 vol.%), and the volume fraction of water vapor is 9.12 / 959.12 = 0.95 vol.%). At the same time, turn on the injection pump and introduce the catalyst solution at a flow rate of 26 μL / min. After growing for 180 minutes, the reactor is cooled under the protection of mixed gas 1. After the reactor is cooled to room temperature, take out the stainless steel mesh inside to obtain ultra-long carbon nanotube fibers grown on the stainless steel mesh. After weighing the fibers and calculating, the yield is 6.5%.

[0082] From Figure 2A and Figure 2B it can be seen that when using a vertically placed mesh substrate for interception, one end of the intercepted carbon nanotubes passes through the mesh holes and continues to grow into ultra-long carbon nanotubes according to the gas flow direction. After the reaction, the ultra-long carbon nanotube fibers can be collected from the mesh substrate.

[0083] Example 5:

[0084] Prepare a methanol solution containing 3 wt.% ferrocene, 3 wt.% cobaltocene, 6 wt.% nickelocene, and 9.5 wt.% thiophene, and then clarify it by ultrasonic treatment. After extracting the prepared solution with a syringe, install it on an injection pump and connect the syringe to the reactor. Before growth, place an alumina ceramic sheet (with a thickness of 5% of the inner diameter of the reactor) in the center of the tubular furnace reactor. Subsequently, start introducing mixed gas 1 (1000 sccm of hydrogen and 1000 sccm of nitrogen, the volume fraction of hydrogen is (1000 / 2000 = 50 vol.%), and the volume fraction of nitrogen is (1000 / 2000 = 50 vol.%)) into the reactor, and at the same time slowly raise the temperature of the tubular furnace to 1200 °C. After the temperature stabilizes, introduce mixed gas 2 (15 sccm of acetylene, 800 sccm of hydrogen, 300 sccm of nitrogen, and 15.61 sccm of water vapor, the volume fraction of acetylene is (15 / 1130.61 = 1.33 vol.%), the volume fraction of hydrogen is (800 / 1130.61 = 70.76 vol.%), the volume fraction of nitrogen is (300 / 1130.61 = 26.53 vol.%), and the volume fraction of water vapor is 15.61 / 1130.61 = 1.38 vol.%). At the same time, turn on the injection pump and introduce the catalyst solution at a flow rate of 14 μL / min. After growing for 80 minutes, the reactor is cooled under the protection of mixed gas 1. After the reactor is cooled to room temperature, take out the alumina ceramic sheet, rotate it 68° in the horizontal plane, and then put it back into the reactor. Repeat the growth step, and when taking it out again, an ultra-long carbon nanotube film grown on the alumina ceramic sheet is obtained. After conversion based on the array density and the carbon nanotube diameter, the yield is 1.9%.

[0085] It can be seen from Figure 3 that if the orientations of the ultra-long carbon nanotubes in two growths are different but are respectively consistent with the gas flow directions, an ultra-long carbon nanotube film with a certain crossing angle can be obtained after superposition. The preparation of the ultra-long carbon nanotube film follows the device and method for preparing a horizontal array. After completing the growth of a horizontal array once, take out the substrate and rotate it by a certain angle horizontally, and a film composed of staggered ultra-long carbon nanotubes can be obtained.

[0086] It can be seen from Figure 6 that the ultra-long carbon nanotube film prepared in this example is composed of two horizontal arrays with different orientations, and the array orientation is controlled by the gas flow direction.

[0087] Comparative Example 1:

[0088] As described in Reference 1, in the method for preparing carbon nanotubes, a catalyst precursor (an iron salt solution such as iron chloride) is coated on the edge of the substrate before growing the carbon nanotubes, and no additional catalyst precursor is introduced during the growth process. The yield of carbon nanotubes in Reference 1 is low, and the array density is usually less than 10 tubes / mm. The yield and array density of the carbon nanotubes prepared by the method provided in this application are 2 to 4 orders of magnitude higher than those of the carbon nanotubes prepared by the prior art 1.

[0089] Reference 1: Zhang R, Zhang Y, Wei F. Controlled synthesis of ultralong carbon nanotubes with perfect structures and extraordinary properties[J]. Accounts of chemical research, 2017, 50(2): 179-189.

[0090] The preparation method provided in this application requires continuous introduction of a catalyst precursor during the growth process, so that the prepared carbon nanotubes have the effect of ultra-long and ultra-high yield. The length of the obtained ultra-long carbon nanotubes can reach centimeters to meters, and the growth rate of a single carbon nanotube can reach 2.37 mm / min. The ultra-long carbon nanotubes prepared by this method also have characteristics such as perfect structure, fewer wall numbers (the number of tube walls is one to three walls), and excellent electrical properties.

Claims

1. A method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes, characterized in that, Comprising: A substrate that divides the flow field, intercepts floating short carbon nanotubes, and guides the gas flow is arranged in the reactor. A mixed gas 1 is introduced into the reactor to replace the air in the reactor with the mixed gas 1, and the temperature in the reactor is raised until the reaction temperature is reached. The extending direction of the substrate is parallel to the gas flow direction. The mixed gas 1 includes hydrogen and a first inert atmosphere gas; A mixed gas 2 and a catalyst solution are continuously introduced into the reactor. By using the flow field division, interception, and gas flow guiding effects of the substrate, an ultra-long carbon nanotube horizontal array is continuously grown. The mixed gas 2 includes a carbon source gas, hydrogen, a second inert atmosphere gas, and water vapor; The catalyst solution includes a catalyst precursor, a promoter, and a solvent, The length of the ultra-long carbon nanotube horizontal array is 1 cm to 100 cm, The substrate is a non-porous block substrate, and an array density of 10 is formed on a planar substrate by using a substrate interception and guidance strategy. 3 Root / mm to 10 5 Horizontal array of roots / mm.

2. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 1, wherein The material of the substrate is selected from any one or more of silicon, quartz, ceramics, and metals.

3. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 1 or 2, characterized in that, The reaction temperature is 300 °C to 2000 °C, and the reaction time of the reaction is 1 min to 2000 min; The total flow rate of the mixed gas 2 is 0.01 sccm to 100000 sccm; The flow rate of the catalyst solution is 0.001 μL / min to 10000 μL / min; The carbon source gas is selected from any one or more of methane, ethane, ethylene, acetylene, methanol vapor, ethanol vapor, isopropanol vapor, acetone vapor, and carbon monoxide; The concentration of the carbon source gas in the mixed gas 2 is 0.00001 vol.% to 99 vol.%; The concentration of hydrogen in the mixed gas 2 is 0.001 vol.% to 99 vol.%; The concentration of water vapor in the mixed gas 2 is 0.0001 vol.% to 99 vol.%.

4. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 3, characterized in that, The reaction time of the reaction is 3 min to 600 min.

5. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 3, characterized in that, The total flow rate of the mixed gas 2 is 1 sccm to 10000 sccm.

6. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 3, characterized in that, The flow rate of the catalyst solution is 0.01 μL / min to 100 μL / min.

7. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 3, characterized in that, The concentration of the carbon source gas in the mixed gas 2 is 0.01 vol.% to 80 vol.%; 8. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 3, characterized in that, The concentration of hydrogen in the mixed gas 2 is 1 vol.% to 99 vol.%; 9. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 1 or 2, characterized in that, The concentration of the catalyst precursor in the catalyst solution is 0.0001 wt.% to 99 wt.%; The concentration of the promoter in the catalyst solution is 0.0001 wt.% to 99 wt.%.

10. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 9, characterized in that, The concentration of the catalyst precursor in the catalyst solution is 0.01 wt.% to 20 wt.%.

11. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 9, characterized in that, The concentration of the promoter in the catalyst solution is 0.01 wt.% to 60 wt.%.

12. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 1, wherein The catalyst precursor is a metallocene compound, and the promoter is thiophene; The metallocene compound is selected from any one or more of metallocene compounds of Group VIII elements and metallocene compounds of Group IVB metals; The solvent is selected from any one or more of methanol, ethanol, isopropanol, acetone, benzene, toluene, ethylbenzene, xylene, n-hexane, and cyclohexane.

13. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 12, characterized in that, The metallocene compound is selected from any one or more of ferrocene, cobaltocene, nickelocene, and dichlorodicyclopentadienyl titanium.

14. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 1, wherein, It further includes: After the growth of the ultra-long carbon nanotube horizontal array is completed, it is cooled under the protection of the mixed gas 1.

15. The ultra-high yield preparation method of the horizontal array of ultra-long carbon nanotubes according to claim 1, characterized in that, The first inert atmosphere gas and the second inert gas are each independently selected from any one or more of nitrogen, argon, and helium.

16. The method for preparing an ultra-high yield of a horizontal array of ultra-long carbon nanotubes according to claim 1, characterized in that, The height of the non-porous block substrate accounts for 0.1% to 90% of the inner diameter of the reactor.

17. An ultra-long carbon nanotube horizontal array prepared by the method for preparing an ultra-high yield of an ultra-long carbon nanotube horizontal array according to any one of claims 1 to 16.

18. The application of the ultra-long carbon nanotube horizontal array according to claim 17 in carbon-based chips, carbon nanotube fibers, and composite cables.

Images