A method for preparing an oxide-coated single-walled carbon nanotube composite film

Abstract

The present application relates to controllable preparation of nanocarbon composite material, and particularly to a method for preparing oxide-coated single-walled carbon nanotube composite film. A film composed of surface-activated single-walled carbon nanotubes is used as a substrate, an organic compound containing oxygen and silicon / titanium / zirconium / aluminum is used as a precursor, and the precursor is carried by an inert atmosphere to form a ceramic compound such as silicon oxide / aluminum oxide / zirconium oxide / titanium oxide on the surface of the single-walled carbon nanotube through chemical vapor deposition. The method can control the thickness and crystallinity of the grown ceramic oxide coating layer by adjusting the surface activation state of the single-walled carbon nanotube and the chemical vapor deposition process conditions. The composite structure prepared by the method has good interface bonding, simple process and strong controllability. The ceramic oxide coating layer can improve the high-temperature oxidation resistance, plasma etching resistance and mechanical strength of the single-walled carbon nanotube film, and has potential application value in extreme service environments such as strong radiation and high temperature containing oxygen.

Description

Technical Field

[0001] This invention relates to the field of controllable preparation of composite carbon nanomaterials, specifically a method for preparing oxide-coated single-walled carbon nanotube composite films. Background Technology

[0002] Carbon nanotubes can be viewed as one-dimensional hollow tubular structures formed by rolling up graphene, with covalently linked sp... 2 Hybridized carbon atoms endow them with properties such as high thermal conductivity, high electrical conductivity, high modulus, and high strength. Macroscopic structures such as films, fibers, and foams constructed from carbon nanotubes inherit these excellent intrinsic properties, and their lightweight nature makes them promising for applications in structural and functional enhancement. However, the inherent poor high-temperature oxidation resistance and intolerance to highly reactive plasma etching of carbon materials limit their application in extreme service environments.

[0003] To improve the high-temperature oxidation resistance of carbon nanotubes, coating with high-temperature resistant inorganic materials is a common method. Researchers have developed various methods for coating carbon nanotubes with ceramic oxides. Zhu et al. used ZrCl4 as a precursor to hydrolyze and generate Zr(OH)4 sol, and obtained carbon nanotube powder coated with sol. After heat treatment in nitrogen, they obtained carbon nanotubes coated with ZrO2 particles. (Composites Part B: Engineering, 2008, 39(7–8): 1136-1141.) Yang et al. first modified carbon nanotubes with polymers, and then coated them with Al2O3 generated by the decomposition of Al(NO3)3 at 500℃ to form a shell. (Ceramics International, 2009, 35(3): 1305-13) T. Seeger et al. dissolved carbon nanotubes in an acidic solution, added tetraethyl orthosilicate, and obtained carbon nanotubes coated with silica after gelation, aging, drying, grinding, and high-temperature calcination in an inert atmosphere. (Chemical Communications, 2002, 1(1):34) These methods have achieved uniform coating of ceramic oxides on powdered multi-walled carbon nanotubes. However, coating of ceramic oxides on single-walled carbon nanotubes, especially macroscopic single-walled carbon nanotubes, has not yet been achieved. This is mainly due to:

[0004] (1) Most carbon nanotube macrostructures are composed of single / few-walled carbon nanotubes with small diameters. It is difficult for oxides in the liquid phase to be deposited on the surface of carbon nanotubes with small diameters and large curvatures.

[0005] (2) Liquid-phase synthesis often involves the dispersion of carbon nanotubes, and the degree of dispersion determines the uniformity of the coating structure. However, the dispersion of carbon nanotubes is a difficult problem in the current research field.

[0006] (3) The controllability of oxide deposition in the liquid phase is poor. The coating layer is formed by the accumulation of oxide nanoparticles, and the coating layer thickness is not uniform. Summary of the Invention

[0007] The purpose of this invention is to provide a method for efficiently and controllably preparing oxide-coated single-walled carbon nanotube composite films. By treating the surface to activate the surface, nucleation sites are controllably introduced on the wall of the single-walled carbon nanotubes. Then, an oxide layer is controllably deposited and grown on the tube wall by chemical vapor deposition. This solves the problems of dispersion and uneven coating layer formation required by existing liquid phase technology, and enables the direct growth of low-dimensional heterogeneous nanomaterial composite films with clean interfaces. Furthermore, the microstructure of the composite film can be controlled by changing the surface activation method and chemical vapor deposition conditions.

[0008] The technical solution of this invention is:

[0009] A method for preparing oxide-coated single-walled carbon nanotube composite films uses a film composed of a surface-activated single-walled carbon nanotube network as a substrate and an organic material containing oxygen and silicon, titanium, zirconium, or aluminum as a ceramic oxide precursor. The crystallinity and thickness of the ceramic oxide coating layer are controlled by adjusting the surface state of the single-walled carbon nanotubes and the chemical vapor deposition conditions. The specific steps are as follows:

[0010] Single-walled carbon nanotube (SUV) films are transferred onto a suspended substrate. The surface of the SUVs is activated by heat treatment in a weakly etchable gas or by plasma treatment to obtain active sites for depositing ceramic oxides. The ceramic oxide precursors in a water bath at 0–30 °C are carried by an inert atmosphere and chemical vapor deposition is performed at 400–1000 °C to obtain macroscopic composite films of oxide-coated SUVs with adjustable crystallinity and thickness.

[0011] The method for preparing oxide-coated single-walled carbon nanotube composite films uses a film composed of a surface-activated single-walled carbon nanotube network as a substrate. The surface activation of the single-walled carbon nanotubes is achieved by heat treatment or plasma treatment in a weakly etchable gas, such as air, ammonia, carbon dioxide, or water vapor.

[0012] The method for preparing oxide-coated single-walled carbon nanotube composite films utilizes the surface activation state of the single-walled carbon nanotube network to determine whether the ceramic oxide can completely coat the film. Heat treatment in an etchable atmosphere controls the surface activation degree of the single-walled carbon nanotubes. During heat treatment in an etchable atmosphere, the reactivity of the gas with the carbon nanotubes, as well as the heat treatment temperature and time, are controlled. Stronger chemical reactivity requires a lower reaction temperature and a shorter reaction time. Heat treatment temperatures in air are 200–500℃ for 1–30 min; in ammonia, the temperature is 200–400℃ for 5–20 min; in carbon dioxide, the temperature is 300–600℃ for 10–60 min; and in steam, the temperature is 400–700℃ for 10–30 min.

[0013] The crystallinity and thickness of the ceramic oxide are determined by the chemical vapor deposition process in the method for preparing oxide-coated single-walled carbon nanotube composite films. The crystallinity and thickness of the coated ceramic oxide are controlled by adjusting the volatilization temperature of the precursor source, the carrier gas flow rate, the growth temperature, and the growth time during the chemical vapor deposition process.

[0014] The method for preparing oxide-coated single-walled carbon nanotube composite films has a precursor evaporation rate of 0.2–1.0 mg / min, a deposition temperature of 400–1000 °C, and the thickness of the ceramic oxide coating is adjustable in the range of 1–50 nm.

[0015] The method for preparing oxide-coated single-walled carbon nanotube composite films involves growing ceramic oxides on single-walled carbon nanotube films using chemical vapor deposition. The method uses a high-purity inert atmosphere as the carrier gas, which may be nitrogen, argon, or helium. The precursor may be trimethoxysilane, tetraoxoethylsilane, ethyl titanate, tetrabutyl zirconate, or triethoxyaluminum, and the precursor volatilization temperature range is 0–50°C.

[0016] In the method for preparing oxide-coated single-walled carbon nanotube composite films, the ceramic oxide is silicon oxide, aluminum oxide, zirconium oxide, or titanium oxide.

[0017] The method for preparing oxide-coated single-walled carbon nanotube composite films described above produces oxide-coated single-walled carbon nanotube composite films with high-temperature oxidation resistance and plasma etching resistance.

[0018] The design concept of this invention:

[0019] This invention provides a method for efficiently and controllably preparing oxide-coated single-walled carbon nanotube composite films. The method involves activating the surface of single-walled carbon nanotubes through functionalization, and then using a carrier gas to carry a volatile precursor containing ceramic oxides. This precursor decomposes at high temperature and nucleates and grows on the surface of the single-walled carbon nanotubes, forming a dense oxide layer. By changing the composition of the precursor, its volatilization rate, and the temperature and carrier gas flow rate of the chemical vapor deposition, the chemical composition, phase, and thickness of the oxide can be controlled, achieving a highly efficient and controllable oxide coating layer and obtaining a flexible, self-supporting composite film.

[0020] This invention uses a self-supporting single-walled carbon nanotube network as a template, and obtains a surface-activated single-walled carbon nanotube network through plasma treatment or etching gas thermal treatment. The volatile ceramic oxide precursor is decomposed by chemical vapor deposition, and an oxide coating layer is formed and nucleated on the surface of the functionalized carbon nanotubes. Its advantages are:

[0021] (1) The method of the present invention designs and prepares a macroscopic body of oxide-coated single-walled carbon nanotube composite film. The method uses an activated carbon nanotube network as a template and directly grows a composite structure with good interfacial bonding through chemical vapor deposition, so that the carbon nanotube film has higher chemical stability and thermal stability.

[0022] (2) The preparation method of the present invention can regulate the composition of the oxide on the surface of carbon nanotubes by changing the precursor, and regulate the thickness and crystallinity of the oxide by changing the volatilization temperature and chemical vapor deposition conditions, so as to obtain single-walled carbon nanotube composite films coated with ceramic oxides of different structures. This method has good universality and controllability.

[0023] (3) The preparation method of the present invention can regulate the thickness and crystallinity of the grown ceramic oxide coating by adjusting the surface activation state of single-walled carbon nanotubes and the chemical vapor deposition process conditions.

[0024] (4) The composite structure prepared by the method of the present invention has good interfacial bonding, and the process is simple and highly controllable. The ceramic oxide coating layer can improve the high-temperature oxidation resistance, plasma etching resistance and mechanical strength of the single-walled carbon nanotube film, and has potential application value in extreme service environments such as strong radiation and high temperature oxygen content. Attached Figure Description

[0025] Figure 1 Transmission electron microscope image of a single-walled carbon nanotube network obtained by plasma surface activation.

[0026] Figure 2 Scanning electron microscope image of oxide-coated single-walled carbon nanotube composite films obtained by plasma surface activation.

[0027] Figure 3Transmission electron microscope image of oxide-coated single-walled carbon nanotube composite structures obtained by plasma surface activation.

[0028] Figure 4 Raman spectrum of oxide-coated single-walled carbon nanotube composite structure obtained by plasma surface activation (laser wavelength 633 nm).

[0029] Figure 5 1s X-ray photoelectron spectroscopy (C-s) spectrum of oxide-coated single-walled carbon nanotube composite structures obtained by plasma surface activation.

[0030] Figure 6 1s X-ray photoelectron spectroscopy (XPS) spectrum of oxide-coated single-walled carbon nanotube composite structures obtained by plasma surface activation.

[0031] Figure 7 X-ray photoelectron spectroscopy (XPS) of Si in oxide-coated single-walled carbon nanotube composite structures obtained by plasma surface activation.

[0032] Figure 8 Transmission electron microscope image of oxide-coated single-walled carbon nanotube composite structures prepared by direct growth without surface activation treatment. Detailed Implementation

[0033] In its specific implementation, this invention proposes a method for efficiently and controllably preparing oxide-coated single-walled carbon nanotube composite films, comprising: surface activation treatment of single-walled carbon nanotubes using plasma treatment or weak etching gas thermal treatment; using the film composed of surface-activated single-walled carbon nanotube mesh as a substrate, and an organic material containing oxygen and corresponding inorganic elements such as silicon, titanium, zirconium or aluminum as a precursor, and using an inert atmosphere to carry the precursor to nucleate and grow ceramic oxides such as silicon oxide, titanium oxide, zirconium oxide or aluminum oxide on the surface of single-walled carbon nanotubes through chemical vapor deposition to form a composite film of single-walled carbon nanotubes.

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention is described in detail below with reference to embodiments and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0035] Example 1.

[0036] In this embodiment, the process of controllably preparing oxide-coated single-walled carbon nanotube composite films is as follows:

[0037] (1) Preparation and transfer of single-walled carbon nanotube films.

[0038] Single-walled carbon nanotubes were prepared by chemical vapor deposition. The carbon nanotube films were collected onto a filter membrane using a designed thin film collection device and then transferred to form a suspended self-supporting macroscopic film.

[0039] (2) Activation of single-walled carbon nanotube films.

[0040] Plasma cleaning equipment was used, with a plasma power of 40W and a vacuum pressure of 3×10⁻⁶ ppm H₂. -4 Single-walled carbon nanotube films were treated for 120 s under Pa conditions; such as Figure 1 As shown, the microstructure of the single-walled carbon nanotubes obtained after treatment shows that impurities such as amorphous carbon on the surface of the carbon nanotubes are reduced, and a large number of defects are introduced on the surface of the carbon nanotubes to activate them.

[0041] (3) An oxide coating layer is deposited on the surface of a single-walled carbon nanotube network.

[0042] The activated single-walled carbon nanotube film from step (2) was placed in the isothermal zone of a tube furnace. 30 mg of trimethoxysilane precursor was placed in a Mannlich wash flask in an ice-water bath (0°C), and 15 sccm of Ar was introduced into the flask as a carrier gas to carry the trimethoxysilane, which had a volatilization rate of 0.2 mg / min, to participate in the reaction. Simultaneously, 300 sccm of Ar was introduced to carry the volatilized trimethoxysilane into the isothermal zone, and growth was carried out at 650°C for 20 min. Figure 2 , Figure 3 As shown in the figure, the microstructure of the prepared material shows that silicon oxide is uniformly coated on the surface of carbon nanotubes. The silicon oxide is amorphous, uniform in thickness, and well coated. The thickness of the silicon oxide coating layer is 1–20 nm.

[0043] Raman spectroscopy was performed on the oxide-coated single-walled carbon nanotube composite film sample prepared in step (3) above. Figure 4 It can be observed that it is located at 1350cm. -1 The D peak of carbon nanotubes is located at 1590 cm⁻¹. -1 The G peak of carbon nanotubes, and located at 566 cm⁻¹ -1 The silica peak.

[0044] like Figures 5-7 As shown, the chemical composition of the composite structure was analyzed using X-ray photoelectron spectroscopy. Figure 5 The peak at 284.6 eV in the middle confirms that the C element in the structure mainly exists in the form of C-C bonds; Figure 6 The peak located at 532.57 eV and Figure 7 The peak at 103.9 eV proves the presence of Si-O bonds in the structure.

[0045] This embodiment illustrates that plasma treatment can activate the surface of single-walled carbon nanotubes, and a uniform and dense amorphous silica coating layer can be successfully grown on the surface of carbon nanotubes during subsequent chemical vapor deposition, ultimately resulting in a composite film of single-walled carbon nanotubes coated with amorphous silica.

[0046] Example 2.

[0047] In this embodiment, the process of controllably preparing oxide-coated single-walled carbon nanotube composite films is as follows:

[0048] (1) Preparation and transfer of single-walled carbon nanotube films.

[0049] The same as step (1) in Example 1.

[0050] (2) Activation of single-walled carbon nanotube films.

[0051] Single-walled carbon nanotube films were heat-treated at 500°C for 5 minutes under normal pressure and air atmosphere. Air heat treatment can remove amorphous carbon and other impurities adsorbed on the surface of carbon nanotubes and introduce defects on the surface of carbon nanotubes to activate them.

[0052] (3) Deposition and growth of oxide coating on the surface of single-walled carbon nanotubes.

[0053] The activated single-walled carbon nanotube film from step (2) was placed in the constant temperature zone of a tube furnace. 30 mg of ethyl titanate precursor was placed in a warm water bath (30 °C) in a Mann-Bauer wash flask, and 20 sccm of Ar was introduced as a carrier gas to carry ethyl titanate with a volatilization rate of 0.5 mg / min to participate in the reaction. 300 sccm of Ar was introduced to carry the volatilized ethyl titanate into the constant temperature zone, and the film was grown at 450 °C for 10 min to obtain a titanium oxide-coated single-walled carbon nanotube composite film with a coating thickness of 10–25 nm.

[0054] Example 3.

[0055] In the embodiments, the process of controllably preparing zirconium oxide-coated single-walled carbon nanotube composite films is as follows:

[0056] (1) Preparation and transfer of single-walled carbon nanotube films.

[0057] The same as step (1) in Example 1.

[0058] (2) Activation of single-walled carbon nanotube films.

[0059] Single-walled carbon nanotube films were heat-treated at 400°C for 10 minutes under normal pressure and an ammonia atmosphere. Ammonia heat treatment can reduce the amorphous carbon and other impurities adsorbed on the surface of carbon nanotubes and introduce defects on the surface of carbon nanotubes to activate them.

[0060] (3) Growth and deposition of oxide coating on the surface of single-walled carbon nanotubes.

[0061] The activated single-walled carbon nanotube film from step (2) was placed in the constant temperature zone of a tube furnace. 30 mg of tetrabutyl zirconate precursor was placed in a Mann-Wall wash flask in a room temperature water bath (20 °C), and 30 sccm of Ar was introduced as a carrier gas to carry the tetrabutyl zirconate with a volatilization rate of 0.8 mg / min to participate in the reaction. 300 sccm of Ar was introduced to carry the volatilized tetrabutyl zirconate into the constant temperature zone. The film was grown at 800 °C for 30 min to obtain a zirconia-coated single-walled carbon nanotube composite film with a thickness of 20–40 nm.

[0062] Example 4.

[0063] In this embodiment, the process of controllably preparing an alumina-coated single-walled carbon nanotube composite film is as follows:

[0064] (1) Preparation and transfer of single-walled carbon nanotube films.

[0065] The same as step (1) in Example 1.

[0066] (2) Activation of single-walled carbon nanotube films.

[0067] Carbon nanotube films were heat-treated at 600°C for 20 minutes under normal pressure and a steam atmosphere. Steam heat treatment significantly reduced the amorphous carbon and other impurities adsorbed on the surface of carbon nanotubes and introduced defects on the surface of carbon nanotubes, thereby activating them.

[0068] (3) The oxide coating layer is grown and deposited on the surface of single-walled carbon nanotubes.

[0069] The activated single-walled carbon nanotube film from step (2) was placed in the constant temperature zone of a tube furnace. 30 mg of aluminum triethoxy precursor was placed at the gas inlet of the tube furnace at a stable temperature of 50 °C. 300 sccm of Ar was introduced to carry the aluminum triethoxy at a volatilization rate of 1.0 mg / min to participate in the reaction. The volatilized aluminum triethoxy was carried into the constant temperature zone by introducing 300 sccm of Ar. The film was grown at 1000 °C for 5 min to obtain an alumina-coated single-walled carbon nanotube composite film with a coating thickness of 35–50 nm.

[0070] Comparative example.

[0071] In this comparative example, the process for preparing amorphous silica-coated single-walled carbon nanotube composite films without surface activation treatment is as follows:

[0072] (1) Preparation and transfer of single-walled carbon nanotube films.

[0073] The same as step (1) in Example 1.

[0074] (2) The oxide coating layer is deposited and grown on the surface of single-walled carbon nanotubes.

[0075] Silicon oxide was grown by chemical vapor deposition using the single-walled carbon nanotube film prepared in step (1), specifically the same as step (3) in Example 1. Figure 8 The image shows the microstructure of the prepared silica-coated single-walled carbon nanotube composite film. Silica growth on the surface of the single-walled carbon nanotubes is uneven, with most carbon nanotubes having bare surfaces without silica growth, and silica agglomerates at the junctions of the carbon nanotube network.

[0076] Comparative examples and comparative results demonstrate that the present invention can control the preparation of oxide-coated single-walled carbon nanotube composite films by changing the surface treatment method and chemical vapor deposition conditions. Specifically, an air plasma / weakly etchable gas thermal treatment method is used to create defects on the surface of the single-walled carbon nanotubes, thereby depositing and growing a uniformly thick, well-coated oxide film. Compared with the original film, the single-walled carbon nanotube@ceramic oxide composite film still exhibits excellent flexibility and impact resistance. This composite film possesses excellent high-temperature oxidation resistance, plasma etching resistance, and acid and alkali resistance, showing great application potential in extreme service environments such as strong radiation and oxygen-containing high temperatures.

[0077] The design concept and implementation scheme of this invention have been described in detail above. However, some modifications and improvements can still be made based on this invention. All such modifications or improvements made without departing from the spirit of this invention fall within the scope of protection claimed by this invention.

Claims

1. A method for preparing oxide-coated single-walled carbon nanotube composite films, characterized in that, A thin film composed of a surface-activated single-walled carbon nanotube network was used as the substrate, and organic materials containing oxygen and silicon, titanium, zirconium, or aluminum were used as ceramic oxide precursors. The crystallinity and thickness of the ceramic oxide coating were controlled by adjusting the surface state of the single-walled carbon nanotubes and the chemical vapor deposition conditions. The specific steps are as follows: Single-walled carbon nanotube films are transferred onto a suspended substrate, and the surface of the single-walled carbon nanotubes is activated by heat treatment or plasma treatment in a weakly etchable gas, such as air, ammonia, carbon dioxide or water vapor, to obtain active sites for deposited ceramic oxides. By using an inert atmosphere to carry ceramic oxide precursors in a water bath at 0–30 °C, chemical vapor deposition is performed at 400–1000 °C to obtain macroscopic oxide-coated single-walled carbon nanotube composite films with adjustable crystallinity and thickness.

2. The method for preparing oxide-coated single-walled carbon nanotube composite films according to claim 1, characterized in that, The surface activation state of the single-walled carbon nanotube network determines whether the ceramic oxide can be completely coated. Heat treatment in an etchable atmosphere controls the surface activation degree of the single-walled carbon nanotubes. When heat treatment is performed in an etchable atmosphere, the reactivity of the gas with the carbon nanotubes and the heat treatment temperature and time are controlled. The stronger the chemical reactivity, the lower the reaction temperature and the shorter the reaction time; the heat treatment temperature in air is 200~500 ℃, and the time is 1~30 min; the heat treatment temperature in ammonia is 200~400 ℃, and the time is 5~20 min; the heat treatment temperature in carbon dioxide is 300~600 ℃, and the time is 10~60 min; the heat treatment temperature in water vapor is 400~700 ℃, and the time is 10~30 min.

3. The method for preparing oxide-coated single-walled carbon nanotube composite films according to claim 2, characterized in that, The crystallinity and thickness of ceramic oxides are determined by the chemical vapor deposition process. The crystallinity and thickness of the coated ceramic oxides can be controlled by adjusting the volatilization temperature of the precursor source, the carrier gas flow rate, the growth temperature, and the growth time during the chemical vapor deposition process.

4. The method for preparing oxide-coated single-walled carbon nanotube composite films according to claim 3, characterized in that, The precursor volatilization rate is 0.2~1.0 mg / min, the deposition temperature is 400~1000 ℃, and the thickness of the ceramic oxide coating is adjustable in the range of 1~50 nm.

5. The method for preparing oxide-coated single-walled carbon nanotube composite films according to claim 1, characterized in that, Ceramic oxides were grown on single-walled carbon nanotube films using chemical vapor deposition. The method used a high-purity inert atmosphere as the carrier gas, which could be nitrogen, argon, or helium. The precursors were trimethoxysilane, tetraoxoethylsilane, ethyl titanate, tetrabutyl zirconate, or triethoxyaluminum, and the precursor volatilization temperature range was 0–50 °C.

6. The method for preparing oxide-coated single-walled carbon nanotube composite films according to claim 1, characterized in that, The ceramic oxide is silicon oxide, aluminum oxide, zirconium oxide, or titanium oxide.

7. The method for preparing oxide-coated single-walled carbon nanotube composite films according to claim 1, characterized in that, The resulting oxide-coated single-walled carbon nanotube composite film exhibits high-temperature oxidation resistance and plasma etching resistance.

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