Method for efficiently growing density-controllable single-walled carbon nanotube parallel array
By using growth controllers to regulate catalyst activity during the growth process of single-wall carbon nanotubes, efficient preparation of parallel arrays of single-wall carbon nanotubes with adjustable density in large ranges is achieved, and the density uncontrollable and poor uniformity in the prior art is solved. The problem has improved the accuracy of preparation efficiency and density regulation, and is suitable for a variety of substrates and catalysts.
Patent Information
- Application Number
- CN202411240333.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-05
- Publication Date
- 2025-01-10
AI Technical Summary
The prior art is difficult to efficiently grow a parallel array of single-wall carbon nanotubes with controllable and uniform density, which has problems such as uncontrollable density, poor density uniformity, and low preparation efficiency, making it difficult to meet the application needs in the fields of electronic information and aerospace.
By regulating catalyst activity with different concentrations of growth controllers on single crystal oxide substrates, efficient preparation of parallel arrays of single-wall carbon nanotubes with adjustable density ranges, using transition metal catalyst nanoparticles to form and single-wall carbon nanotubes The annealing conditions during the growth stage are regulated, the transition metal layer and annealing conditions are prepared to prepare a parallel array of single-wall carbon nanotubes with a density uniform in the range of 0 to 250 roots/micron.
Achieve the preparation of single-wall carbon nanotube parallel arrays with adjustable density, high uniformity and high efficiency, avoid impurities and defects introduced by post-processing, simplify the process, improve the accuracy and flexibility of density regulation, and is suitable for multiple These substrates and catalysts reduce costs.
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Figure CN119287338A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of controllable preparation of single-walled carbon nanotube horizontal arrays, in particular to a method for efficiently growing a single-walled carbon nanotube parallel array with controllable density. Background Art
[0002] Single-walled carbon nanotubes have excellent mechanical, thermal and electrical properties and have broad application prospects in many fields. However, to realize their application in the fields of electronic information, aerospace, etc., it also depends on the regulation of the structure and arrangement of carbon nanotubes. Directed single-walled carbon nanotubes are mainly divided into two types, namely parallel arrays and vertical arrays. Among them, the parallel array is a special type of integration in which a single carbon nanotube is arranged in parallel on the surface of a flat substrate. It has attracted much attention due to its directional arrangement and excellent mechanical, electrical and thermal properties. However, the single-walled carbon nanotube parallel arrays prepared at present still have problems such as uncontrollable density, poor density uniformity, and low preparation efficiency, which makes it difficult to meet application requirements. Therefore, it is of great significance to develop a method for efficiently preparing single-walled carbon nanotube parallel arrays with adjustable and uniform density.
[0003] Although researchers have developed a variety of methods to control the density and uniformity of single-walled carbon nanotube parallel arrays, there are still many problems that need to be solved, such as poor density controllability, low preparation efficiency, and small size. The methods for preparing single-walled carbon nanotube parallel arrays are mainly divided into post-processing methods and direct growth methods. The former has the disadvantages of poor orientation, serious stacking, many impurities, and complicated and time-consuming procedures, so the research focus has gradually shifted to the direct growth method. At present, the highest density of single-walled carbon nanotube parallel arrays prepared by the direct growth method is 160 roots / micron, and there are shortcomings such as uneven density of single-walled carbon nanotubes, narrow density control range, and low preparation efficiency. For ultra-sparse single-walled carbon nanotube parallel arrays that are widely used in functional nanodevices, it is difficult to accurately control their density and distribution due to the lack of effective control strategies. Therefore, it is still very difficult to achieve the preparation of single-walled carbon nanotube parallel arrays with adjustable density, high uniformity, and high orientation. Among them, the representative works are as follows: (1) Using a size-restricted self-alignment procedure to achieve the preparation of parallel arrays of semiconducting single-walled carbon nanotubes with a density of 100 to 200 roots / micron (Literature 1: Lijun Liu; Jie Han. et al. Science, 2020, 368, 6493); (2) Using Trojan catalysts to prepare parallel arrays of single-walled carbon nanotubes with a maximum density of 130 roots / micron (Literature 2: Yue Hu, Lixing Kang. et al. Nature Communications, 2015, 6, 6099); (3) Using ethanol / methane chemical vapor deposition to prepare parallel arrays of semiconducting single-walled carbon nanotubes with a density higher than 100 roots / micron (Literature 3: Lixing Kang, Shuchen Zhang. et al. JACS. 2016, 138, 21); (4) Using density amplification method to achieve the preparation of parallel arrays of semiconducting single-walled carbon nanotubes with a density of 60 to 80 roots / micron (Literature 4: Jia Si, Donglai Zhong. et al. ACS Nano, 2018, 12, 1); (5) Preparation of parallel arrays of single-walled carbon nanotubes with 20 to 40 nanotubes per micron by multiple growth (Reference 5: Weiwei Zhou, Lei Ding. et al. ACS Nano, 2011, 5, 5).
[0004] At present, there are still many problems in the efficient preparation of single-walled carbon nanotube parallel arrays with uniform and adjustable density: (1) The single-walled carbon nanotube parallel arrays prepared by post-treatment methods are often of poor quality, high impurity content, and serious stacking phenomenon; (2) The conventional direct growth method for preparing single-walled carbon nanotube parallel arrays is time-consuming, has a narrow density control range, and is cumbersome. It also has disadvantages such as uneven density distribution; (3) The preparation of single-walled carbon nanotube parallel arrays is largely limited by the choice of catalysts and substrates, and the controllability and repeatability need to be improved.
[0005] Therefore, if a method for efficiently growing single-walled carbon nanotube parallel arrays with controllable density can be developed, it will be of great significance and value, as it can not only avoid problems such as the introduction of impurities and defects by post-processing, but also ensure the high controllability of the density of the single-walled carbon nanotube parallel arrays. Summary of the invention
[0006] The purpose of the present invention is to provide a method for efficiently growing a single-walled carbon nanotube parallel array with controllable density, utilizing the influence of a growth control agent on catalyst activity and carbon nanotube growth efficiency to achieve efficient preparation of a single-walled carbon nanotube parallel array with adjustable density over a wide range and uniformity.
[0007] The technical solution of the present invention:
[0008] A method for efficiently growing a single-walled carbon nanotube parallel array with controllable density comprises the following steps: annealing a single crystal oxide substrate containing a transition metal on its surface in a mixed atmosphere containing a growth control agent; the annealing process comprises a transition metal catalyst nanoparticle formation stage and a single-walled carbon nanotube growth stage; different stages correspond to mixed atmospheres of different components and concentrations; the annealing temperature is 600-1000°C; the transition metal catalyst nanoparticle formation time is 1-10 minutes; and the single-walled carbon nanotube growth time is 2-12 minutes. By regulating the transition metal layer and the annealing conditions, a single-walled carbon nanotube parallel array with adjustable density in a wide range can be efficiently prepared.
[0009] In the method for efficiently growing a density-controllable single-walled carbon nanotube parallel array, transition metals are distributed on the surface or inside of a single crystal oxide substrate in the form of thin films, particles or precursors, and the thickness of the transition metal layer is adjustable within the range of 0.1 to 0.5 nanometers.
[0010] In the method for efficiently growing a density-controllable single-walled carbon nanotube parallel array, the transition metal is iron, cobalt or nickel.
[0011] In the method for efficiently growing a density-controllable single-walled carbon nanotube parallel array, the single crystal oxide substrate is suitable for ST-cut quartz, α-plane aluminum oxide, γ-plane aluminum oxide or (110)-plane magnesium oxide.
[0012] In the method for efficiently growing a density-controllable single-walled carbon nanotube parallel array, the growth control agent in the mixed atmosphere is water vapor, sulfur vapor or thiophene vapor of different concentrations and flow rates.
[0013] The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array is preferably such that in the annealing atmosphere during the transition metal catalyst nanoparticle formation stage, the inert atmosphere flow rate is 200-350 sccm, the hydrogen flow rate is 2-30 sccm, the growth control agent flow rate is 3-20 sccm, the annealing temperature range is 700-800°C, and the annealing time range is 2-4 minutes.
[0014] The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array is preferably such that in the annealing atmosphere during the single-walled carbon nanotube growth stage, the inert atmosphere flow rate is 200-350 sccm, the hydrogen flow rate is 2-30 sccm, the ethylene flow rate is 1-5 sccm, the growth control agent flow rate is 3-20 sccm, the annealing temperature range is 700-800°C, and the annealing time range is 4-5 minutes.
[0015] The method for efficiently growing a density-controllable single-walled carbon nanotube parallel array has an adjustable density of 0 to 250 tubes / micron and uniform distribution of the single-walled carbon nanotubes.
[0016] The design idea of the present invention is:
[0017] The present invention introduces growth control agents of different concentrations, uses the growth control agents to regulate the catalyst to change its catalytic activity, and realizes efficient growth of single-walled carbon nanotube parallel arrays with controllable density from ultra-sparse to ultra-high on a single crystal oxide substrate. This method not only avoids the damage and pollution of the carbon nanotube structure caused by the introduction of impurities and defects in post-processing, but also can prepare single-walled carbon nanotube parallel arrays of the required density more efficiently and simply than general methods. By optimizing the catalyst pretreatment and carbon nanotube growth process, single-walled carbon nanotube parallel arrays with a density of 0 to 250 tubes / micrometer and uniform and adjustable can be quickly prepared.
[0018] The advantages and beneficial effects of the present invention are:
[0019] 1. The present invention proposes a method for regulating the density of parallel arrays of single-walled carbon nanotubes by using a growth control agent, which can not only ensure the purity and quality of single-walled carbon nanotubes, but also avoid the problem of carbon nanotube stacking caused by post-processing methods, solve the problem of narrow density control range in conventional direct growth methods, and make the control of the density of parallel arrays of carbon nanotubes more precise and flexible.
[0020] 2. The present invention utilizes growth control agents to regulate the activity of catalyst nanoparticles to change the density of carbon nanotubes, thereby greatly improving the growth efficiency and density uniformity of single-walled carbon nanotube parallel arrays, and has the advantages of simple method, low cost and good controllability.
[0021] 3. The present invention proposes a method for preparing a parallel array of single-walled carbon nanotubes with uniform and adjustable density induced by an efficient growth controller. This method has a certain universality and a wider range of choices for substrates and catalyst types, providing a new idea for material selection in the electronic information, catalysis and other industries.
[0022] 4. The single-walled carbon nanotube parallel array of the present invention is not limited by specific substrates and catalyst types, and can achieve rapid and uniform preparation of single-walled carbon nanotube parallel arrays with adjustable density in a wide range.
[0023] In summary, the present invention takes the use of growth controllers to regulate catalyst activity and carbon nanotube growth efficiency as a starting point, and adopts a method of introducing growth controllers of different types and concentrations during the preparation process of single-walled carbon nanotubes. On the premise of ensuring the quality, purity and density uniformity of single-walled carbon nanotubes, the density can be adjusted over a wide range, providing a new way to achieve controllable preparation of single-walled carbon nanotubes. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Atomic force microscopy and scanning electron microscopy images of single-walled carbon nanotube parallel arrays at different water vapor concentrations (0 ppm H2O, 327 ppm H2O, 654 ppm H2O, 981 ppm H2O) and growth times. (a) Growth for 4 minutes, (b) Growth for 12 minutes.
[0025] Figure 2 .Scanning electron microscope image of ultra-sparse single-walled carbon nanotube parallel arrays grown in a water atmosphere with a concentration of 1308 ppm.
[0026] Figure 3 .Density statistics of carbon nanotube parallel arrays with different water vapor concentrations and growth times.
[0027] Figure 4 .Scanning electron microscopy (a), atomic force microscopy (inset in a) and Raman spectroscopy characterization (b) of the single-walled carbon nanotube parallel array grown on ST-cut quartz substrate. Among them, the Raman spectrum compares the signal difference between the introduction of growth control agent water and the introduction of no growth control agent, and * is the characteristic peak of the quartz substrate.
[0028] Figure 5 Transmission electron microscopy characterization of parallel arrays of single-walled carbon nanotubes grown on ST-cut quartz substrates. Figure a shows a high-density array sample transferred to a copper mesh microgrid after single-walled carbon nanotubes were grown, and figure b shows a cross-sectional sample cut by an ion beam after HfO2 protective layer was evaporated on the substrate on which single-walled carbon nanotubes were grown. DETAILED DESCRIPTION
[0029] In the specific implementation process, the present invention introduces a growth control agent to change the catalyst activity and the carbon nanotube nucleation rate, and a density-adjustable and uniform single-walled carbon nanotube parallel array can be obtained by a short growth period. The specific process is as follows:
[0030] The present invention achieves efficient preparation of single-walled carbon nanotube parallel arrays of various densities by introducing a growth control agent during the preparation process of single-walled carbon nanotube parallel arrays. In order to effectively control the density of carbon nanotubes, a transition metal with high growth efficiency is selected as a catalyst. In addition, in order to ensure the directional arrangement of the single-walled carbon nanotube parallel array, a single crystal oxide with lattice orientation or step orientation is selected as a substrate. During the annealing process, a substrate with a low transition metal content on the surface or inside is selected as much as possible to ensure that the catalyst nanoparticles will not sinter quickly at high temperatures. Finally, the interaction between the growth control agent and the transition metal catalyst is utilized to achieve efficient preparation of single-walled carbon nanotube parallel arrays with a wide range of adjustable and uniform density.
[0031] The preferred method is: the voltage and current of the argon ion beam coating instrument are adjusted to 1-5 keV and 10-50 μA respectively, and the transition metal film is plated on the surface of the single crystal oxide substrate for 5-50 seconds, and a transition metal film with a thickness of 0.1-0.5 nanometers is obtained on the surface of the substrate. In the preparation process of the single-walled carbon nanotube parallel array, the process parameters involved mainly include annealing temperature, time, atmosphere type and content. The annealing temperature range is 600°C to 1000°C (preferably 700-800°C), the time of the catalyst formation stage is 1-10 minutes (preferably 2-4 minutes), the time of the carbon nanotube growth stage is 2-12 minutes (preferably 4-5 minutes), the atmosphere is an inert atmosphere, 0-100% hydrogen, 0-100% ethylene and 0-100% growth control agent, to achieve efficient preparation of single-walled carbon nanotube parallel arrays with adjustable density in a wide range and uniformity. In the preferred annealing atmosphere, the argon flow rate is 200-350 sccm, the hydrogen flow rate is 2-30 sccm, the ethylene flow rate is 1-5 sccm, and the growth control agent flow rate is 3-20 sccm. Among them, the argon gas acts as a carrier gas, the hydrogen gas acts to reduce the nanoparticles and promote their precipitation and agglomeration, the ethylene acts as a carbon source, and the growth control agent acts to regulate the density of the carbon nanotubes.
[0032] Below, the present invention is further described in detail by examples.
[0033] Example 1.
[0034] In this embodiment, the preparation and characterization of uniform single-walled carbon nanotube parallel arrays with different densities on ST-cut quartz substrates are as follows:
[0035] The voltage and current of the argon ion beam coating instrument were adjusted to 2.5 eV and 22 μA, respectively, and a Fe film with a thickness of about 100 μm was deposited on the cleaned ST-cut quartz substrate for 5 seconds. After the coated sample was taken out, it was placed in the quartz tube of the tube furnace. The quartz tube of the tube furnace was first cleaned with 1000sccm argon for 2 minutes, and then 250sccm argon, 25sccm hydrogen and 6sccm argon flowing through 30℃ deionized water (water vapor concentration is 654ppm) were introduced. At the same time, the sample was quickly heated to 780℃ and annealed for 3 minutes to form catalyst iron nanoparticles. After cleaning the quartz tube of the tube furnace with 1000sccm argon for 1 minute, 350sccm argon, 2.5sccm hydrogen, 3sccm ethylene and 0-12sccm argon flowing through 30℃ deionized water were introduced to grow parallel arrays of single-walled carbon nanotubes. The growth time was 4 minutes and 12 minutes. Finally, the sample was cooled to room temperature, taken out and characterized for its structure.
[0036] Characterize the density and arrangement of single-walled carbon nanotube parallel arrays: Use atomic force microscopy to count the density and arrangement of carbon nanotubes.
[0037] like Figure 1 a and Figure 3 As shown, the atomic force microscopy characterization results show that when the sample grows for 4 minutes, without the introduction of growth control agent water, the arrangement of carbon nanotubes is relatively disordered and the density is low, with an average density of less than 10 roots / micron. As the water vapor concentration increases, the arrangement of carbon nanotubes becomes neater and the density increases. When the water vapor concentration is 327ppm (3sccm of argon flowing through 30°C deionized water is introduced into the mixed atmosphere), the density of the parallel array of carbon nanotubes is 17 roots / micron. When the water vapor concentration is 654ppm (6sccm of argon flowing through 30°C deionized water is introduced into the mixed atmosphere), the density of carbon nanotubes is the highest, with an average density of more than 120 roots / micron. As the water vapor concentration continues to increase, the density of the carbon nanotube array decreases sharply. When the water vapor concentration is 981ppm (9sccm of argon flowing through 30°C deionized water is introduced into the mixed atmosphere), the density of the parallel array of carbon nanotubes is less than 5 roots / micron. Figure 2 It can be seen that when the concentration of water vapor is 1308 ppm (12 sccm of argon flowing through 30° C. deionized water is introduced into the mixed atmosphere), the density of the carbon nanotube parallel array is less than 10 tubes / mm.
[0038] In addition, Figure 1 b and Figure 3In the results of atomic force microscopy characterization, it is shown that the density of the carbon nanotube parallel array grown for 12 minutes without water is increased compared with the sample grown for 4 minutes, but the density is only about 20 / micron, and the density of the carbon nanotube parallel array after water is introduced only increases slightly. Therefore, by regulating the concentration of the growth control agent, the preparation of a single-walled carbon nanotube parallel array with a large adjustable density and uniformity can be achieved within 4 minutes. The preparation method of the single-walled carbon nanotube parallel array with adjustable density and uniformity in this embodiment is simple, low-cost, and fast, the growth control agent is rich in variety and easy to obtain, and the single-walled carbon nanotube growth only takes 4 minutes, which is at least twice as fast as the general method.
[0039] Example 2.
[0040] In this embodiment, the preparation and characterization of the ultra-high density uniform single-walled carbon nanotube parallel array on the ST-cut quartz substrate are as follows:
[0041] The voltage and current of the argon ion beam coating instrument were adjusted to 2.5 eV and 22 μA, respectively, and a Fe film with a thickness of about 100 μm was deposited on the cleaned ST-cut quartz substrate for 5 seconds. After the coated sample was taken out, it was placed in the quartz tube of the tube furnace. The quartz tube of the tube furnace was first cleaned with 1000sccm argon for 2 minutes, and then 250sccm argon, 25sccm hydrogen and 6.5sccm argon flowing through 30℃ deionized water were introduced. At the same time, the sample was quickly heated to 780℃ and annealed for 3 minutes to form catalyst iron nanoparticles. Then, after the quartz tube of the tube furnace was cleaned with 1000sccm argon for 1 minute, 350sccm argon, 2.5sccm hydrogen, 3sccm ethylene and 6.5sccm argon flowing through 30℃ deionized water were introduced to grow parallel arrays of single-walled carbon nanotubes for 4 minutes. Finally, the sample was cooled to room temperature, taken out and its structure was characterized.
[0042] Characterize the density and arrangement of single-walled carbon nanotube parallel arrays: Use scanning electron microscopy, transmission electron microscopy and atomic force microscopy to count the density and arrangement of carbon nanotube arrays, and Raman spectroscopy to characterize the density of carbon nanotubes.
[0043] like Figure 4 As shown in a, the atomic force microscope characterizes the high-density parallel array of carbon nanotubes, that is, single and tightly oriented carbon nanotubes are distributed throughout the field of view. We compared the scanning electron microscope photos of a large area and found that the high-density parallel array of carbon nanotubes is evenly distributed, with no obvious density distribution differences. Figure 4As shown in Fig. 2, the Raman spectrum also shows that, relative to the sample without the growth control agent in Example 1, when the water vapor concentration is 709 ppm (6.5 sccm of argon gas flowing through 30°C deionized water is introduced into the mixed atmosphere), the G mode and breathing mode signals of the carbon nanotubes increase significantly, while the I G / I D There is no obvious change, indicating that the appropriate amount of growth control agent will lead to an increase in the density of carbon nanotubes but its crystallinity (quality) will not decrease. Figure 5 a and Figure 5 As shown in Fig. 2, for both the transferred sample and the ion beam cut sample, the density of the single-walled carbon nanotubes can reach more than 200 / micron, and the highest density can even reach 250 / micron. Therefore, the introduction of an appropriate amount of growth control agent can greatly improve the density of the single-walled carbon nanotube parallel array, while ensuring its quality and density uniformity.
[0044] Comparative Example 1: Effect of the Type and Concentration of Growth Control Agent on the Preparation of Single-Walled Carbon Nanotube Parallel Arrays
[0045] After the reduction treatment, the Fe-coated sample in Example 1 was introduced with 350 sccm argon, 2.5 sccm hydrogen, 3 sccm ethylene and 0-15 sccm argon flowing through 30°C deionized water, sulfur powder, and thiophene, and annealed for 4 minutes respectively. The other treatment conditions were the same as in Example 1. The effects of the type and concentration of growth controllers on the preparation of parallel arrays of single-walled carbon nanotubes were studied. The results show that all three growth controllers have an effect on the density of parallel arrays of carbon nanotubes. With the increase of the concentration of the growth controller, the density of the parallel arrays of single-walled carbon nanotubes showed a trend of first increasing and then decreasing. This confirms that the method of preparing parallel arrays of single-walled carbon nanotubes with a wide range of adjustable and uniform density by regulating the concentration of the growth controller in Example 1 is universal for the selection of growth controllers.
[0046] Comparative Example 2: Effects of substrate and catalyst types on the preparation of single-walled carbon nanotube parallel arrays
[0047] The cleaned ST-cut quartz, α-alumina, γ-alumina, and (110)-face magnesium oxide substrates were selected, and the voltage and current of the argon ion beam coating instrument were adjusted to 2.5 eV and 22 μA, respectively. The above substrates were coated with Fe film, Co film, and Ni film for 5 seconds, respectively, and then annealed. The other processing conditions were the same as those in Example 1. The results show that regardless of the single crystal oxide substrate and transition metal catalyst, after adjusting the flow rate and concentration of the growth control agent, a single-walled carbon nanotube parallel array with a wide range of adjustable density can be prepared. Among them, Ni may have a lower atomic mobility and nucleation kinetic barrier, so its regulation effect is slightly worse than that of Fe and Co.
[0048] Comparison of the atomic force microscopy images of the single-walled carbon nanotube parallel array obtained in the above comparative example with those of Example 1 shows that the selection of appropriate substrate and catalyst type is crucial for regulating the density of the single-walled carbon nanotube parallel array, which also confirms that the selection of substrate and catalyst in Example 1 has a certain universality.
[0049] Comparative Example 3: Effect of Catalyst Distribution and Content on the Preparation of Single-Walled Carbon Nanotube Parallel Arrays
[0050] The samples of Fe film coating, spin-coated iron hydroxide colloid and substrate containing Fe ions in Example 1 were respectively grown into parallel arrays of single-walled carbon nanotubes, while changing the Fe film thickness, iron hydroxide colloid concentration and the concentration of Fe ions in the substrate, and other treatment conditions were the same as in Example 1. The results show that the three catalyst distribution forms can form nanoparticles on the surface of the quartz substrate during the catalyst formation stage, and can grow parallel arrays of single-walled carbon nanotubes with adjustable density over a wide range. As the catalyst content increases, the diameter and density of the catalyst nanoparticles will also increase. We found using transmission electron microscopy that the proportion of double-walled and multi-walled carbon nanotubes in carbon nanotubes grown by large-diameter catalysts will be significantly increased.
[0051] Comparing the carbon nanotube parallel array obtained in the above comparative example with the transmission electron microscope image in Example 2, it is found that high catalyst content leads to an increase in the proportion of double-walled and multi-walled carbon nanotubes, but the distribution of the catalyst has little effect on the growth of single-walled carbon nanotube parallel arrays. This confirms that the catalyst with appropriate content and distribution in Example 1 is conducive to the preparation of density-adjustable single-walled carbon nanotube parallel arrays.
[0052] Comparative Example 4: Effect of annealing temperature on the preparation of single-walled carbon nanotube parallel arrays
[0053] The Fe-film-coated samples in Example 1 were annealed at 600, 700, 800, 900 and 1000°C, respectively, and the other treatment conditions were the same as in Example 1, to study the effect of annealing temperature on the preparation of parallel arrays of carbon nanotubes. The results show that with the increase of annealing temperature, the growth rate of carbon nanotubes gradually increases, but the number of walls also increases significantly, which may be due to faster atomic mobility and Ostwald ripening at high temperatures. In addition, it is difficult to efficiently prepare ultra-sparse and ultra-high density parallel arrays of carbon nanotubes at too high or too low temperatures, that is, it is not conducive to the regulation of the density of parallel arrays of carbon nanotubes. This further confirms that the appropriate annealing temperature in Example 1 is conducive to the preparation of parallel arrays of single-walled carbon nanotubes with adjustable density.
[0054] The results of the embodiments and comparative examples show that the present invention uses a variety of single crystal oxide substrates and catalysts, and at a relatively low catalyst content and an appropriate annealing temperature, a simple method of introducing a growth control agent during the growth of a single-walled carbon nanotube parallel array is used to achieve the efficient preparation of a single-walled carbon nanotube parallel array with a large adjustable density and uniformity. The present invention quickly prepares a single-walled carbon nanotube parallel array with adjustable density and uniformity without introducing impurities and destroying the crystallinity of the carbon nanotubes. It has the characteristics of being stable, controllable, and easy to enlarge. The preparation process is simple, easy to operate, and low in cost, and the efficient preparation of a uniform single-walled carbon nanotube parallel array with multiple densities is achieved. This method improves the control range and precision of single-walled carbon nanotubes, and lays a material foundation for promoting the practical application of single-walled carbon nanotube parallel arrays in the fields of electronic information, catalysis, and micro-nano manufacturing.
[0055] The present invention is not limited to the above-mentioned embodiments and comparative examples, and all modifications and improvements made to the present solution by engineers and technicians in this field under the concept of the present invention should be protected by the claims of the present invention.
Claims
1. A method for efficiently growing a density-controlled single-walled carbon nanotube parallel array, characterized in that: A single crystal oxide substrate containing transition metals on its surface is annealed in a mixed atmosphere containing a growth control agent. The annealing process includes a transition metal catalyst nanoparticle formation stage and a single-walled carbon nanotube growth stage. Different stages correspond to mixed atmospheres of different components and concentrations. The annealing temperature is 600-1000°C, the transition metal catalyst nanoparticle formation time is 1-10 minutes, and the single-walled carbon nanotube growth time is 2-12 minutes. By regulating the transition metal layer and annealing conditions, a single-walled carbon nanotube parallel array with a wide range of adjustable density can be efficiently prepared.
2. The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array according to claim 1, characterized in that: The transition metal is distributed on the surface or inside of the single crystal oxide substrate in the form of a thin film, particles or precursor, and the thickness of the transition metal layer can be adjusted within the range of 0.1 to 0.5 nanometers.
3. The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array according to claim 1 or 2, characterized in that: The transition metal is iron, cobalt or nickel.
4. The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array according to claim 1, characterized in that: Single crystal oxide substrates are suitable for ST-cut quartz, α-alumina, γ-alumina or (110)-face magnesium oxide.
5. The method for efficiently growing a density-controllable single-walled carbon nanotube parallel array according to claim 1, characterized in that: The growth control agent in the mixed atmosphere is water vapor, sulfur vapor or thiophene vapor with different concentrations and flow rates.
6. The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array according to claim 1 or 5, characterized in that: Preferably, in the annealing atmosphere during the transition metal catalyst nanoparticle formation stage, the inert atmosphere flow rate is 200-350 sccm, the hydrogen flow rate is 2-30 sccm, the growth control agent flow rate is 3-20 sccm, the annealing temperature range is 700-800°C, and the annealing time range is 2-4 minutes.
7. The method for efficiently growing a density-controlled single-walled carbon nanotube parallel array according to claim 1 or 5, characterized in that: Preferably, in the annealing atmosphere during the single-walled carbon nanotube growth stage, the inert atmosphere flow rate is 200-350 sccm, the hydrogen flow rate is 2-30 sccm, the ethylene flow rate is 1-5 sccm, the growth control agent flow rate is 3-20 sccm, the annealing temperature range is 700-800°C, and the annealing time range is 4-5 minutes.
8. The method for efficiently growing a density-controllable single-walled carbon nanotube parallel array according to claim 1, characterized in that: The density of the single-walled carbon nanotube parallel array is adjustable within the range of 0 to 250 tubes / micron, and the single-walled carbon nanotubes are evenly distributed.