Carbon nanotube growing on nanofiber in situ as well as preparation method and application of carbon nanotube

Abstract

The invention relates to a carbon nanotube growing on nanofibers in situ and a preparation method and application thereof, and the preparation method comprises the following steps: uniformly mixing a matrix material, a dispersing aid and a transition metal catalyst with a continuous phase to prepare an electrostatic spinning solution; based on 100% of the mass of the electrostatic spinning solution, the content of the base material is 8%-15%, the content of the dispersing aid is 0.05%-1%, and the content of the transition metal catalyst is 1%-10%; filling an injector of electrostatic spinning equipment with the electrostatic spinning solution, and carrying out electrostatic spinning to obtain a nanofiber catalytic precursor; raising the temperature of the nanofiber catalytic precursor to 380-450 DEG C in a protective gas atmosphere; then introducing a reducing gas to reduce the transition metal catalyst; and heating to 650-750 DEG C, and introducing a carbon source gas to prepare the carbon nanotube growing on the nanofiber in situ. The method for preparing the carbon nanotube through in-situ growth is efficient and rapid, the substrate adaptability is high, and the binding force with the substrate is high.

Description

Technical Field

[0001] This application relates to the field of nanomaterials technology, and in particular to a carbon nanotube grown in situ from nanofibers, its preparation method, and its application. Background Technology

[0002] Carbon nanotubes, as one-dimensional nanomaterials, are coaxial cylindrical tubes composed of several to dozens of layers of hexagonally arranged carbon atoms. They are lightweight and have a perfectly connected structure. Their mechanical properties are outstanding, with a tensile strength of 50-200 GPa, 100 times that of steel, while their density is only 1 / 6 that of steel. Their elastic modulus is approximately 1 TPa, comparable to diamond and about 5 times that of steel. They also possess good flexibility, able to spring back to its original shape after being flattened under high pressure. Their aspect ratio is generally above 1000:1, making them ideal high-strength fiber materials. Electrically, due to the sp² hybridization and unique structure of carbon atoms, they exhibit excellent conductivity. Chemically, they are chemically inert and have minimal impact on most chemical substances. Based on these properties, carbon nanotubes have become a cutting-edge research subject in fields such as electromagnetics, mechanics, materials science, and electronics.

[0003] In the field of microwave absorbing materials, carbon nanotubes, due to their extremely high specific surface area and aspect ratio, can effectively absorb and scatter electromagnetic waves, reducing reflectivity; high-density carbon nanotubes can even form "black bodies." However, the application of carbon nanotubes in microwave absorbing materials currently faces bottlenecks. Because carbon nanotubes are prone to agglomeration, finished carbon nanotubes are often used as fillers in composite materials. To fully utilize the structural advantages and physicochemical properties of carbon nanotubes, in-situ growth of carbon nanotubes on target substrates has become a solution. However, carbon nanotube growth has high requirements for the substrate and catalyst, the related technologies are relatively complex and costly, the substrate applicability is low, and the bonding strength between carbon nanotubes and the substrate surface is low, posing a risk of detachment.

[0004] Therefore, it is necessary to design an efficient, rapid, substrate-adaptable, and substrate-bonding in-situ carbon nanotube growth process. Summary of the Invention

[0005] The main objective of this application is to provide a method for preparing carbon nanotubes grown in situ on nanofibers, and its application. The technical problem to be solved is to provide a method for preparing carbon nanotubes in situ with high efficiency and speed, high substrate adaptability, and strong bonding with the substrate, which is more suitable for practical use.

[0006] The objective of this application and the technical problem it solves are achieved through the following technical solution. A method for preparing carbon nanotubes grown in situ on nanofibers according to this application includes the following steps: The matrix material, dispersant, and transition metal catalyst are mixed uniformly with the continuous phase to prepare an electrospinning solution; based on the mass of the aforementioned electrospinning solution as 100%, the content of the aforementioned matrix material is 8%~15%, the content of the aforementioned dispersant is 0.05%~1%, and the content of the aforementioned transition metal catalyst is 1%~10%. The aforementioned electrospinning solution was loaded into the syringe of the electrospinning equipment and electrospinned to obtain a nanofiber catalytic precursor. The aforementioned nanofiber catalytic precursor was heated to 380-450°C under a protective gas atmosphere; then a reducing gas was introduced to reduce the aforementioned transition metal catalyst; then the temperature was raised to 650-750°C, and then a carbon source gas was introduced to obtain carbon nanotubes grown in situ on nanofibers.

[0007] The purpose of this application and the technical problems to be solved can also be further achieved by the following technical measures.

[0008] Preferably, in the aforementioned method for preparing carbon nanotubes grown in situ on nanofibers, the electrospinning parameters are set as follows: voltage of 20~50kV, feed rate of 0.1~2mL / h, distance between needle tip and collector of 12~20cm, and spinning time of 4~8h.

[0009] Preferably, in the aforementioned method for preparing carbon nanotubes grown in situ on nanofibers, the temperature is increased to 380-450°C at a rate of 15-30°C / min, the aforementioned reducing gas is introduced, and the temperature is maintained for 15-30 min to reduce the aforementioned transition metal catalyst. The temperature was increased to 650-750℃ at a rate of 15-30℃ / min, and the aforementioned carbon source gas was introduced. The temperature was maintained for 1-15 minutes to obtain the aforementioned carbon nanotubes grown in situ on nanofibers.

[0010] Preferably, in the aforementioned method for preparing carbon nanotubes grown in situ on nanofibers, the matrix material is one or more selected from polyacrylonitrile, polyaniline, polyvinyl alcohol, polytetrafluoroethylene, and polypropylene; and / or, The aforementioned dispersing agent is one or more selected from sodium dodecyl sulfate, dodecylbenzene sulfonic acid, ethyl butyrate, and triethyl phosphate; and / or, The aforementioned transition metal catalysts are one or more of the following: nickel acetylacetonate, iron acetylacetonate, cobalt acetate, ferrocene, nano-ferric oxide, nano-ferric oxide, nano-copper oxide, and nano-cobalt oxide; and / or, The aforementioned continuous phase is one or more of dimethylformamide, tetrahydrofuran, acetone, chloroform, dichloromethane, and water.

[0011] Preferably, in the aforementioned method for preparing carbon nanotubes grown in situ on nanofibers, the temperature is raised to 380~450°C, and then the aforementioned reducing gas is introduced, wherein the flow rate of the aforementioned protective gas is 6~8:2~3 of the flow rate of the aforementioned reducing gas.

[0012] Preferably, in the aforementioned method for preparing carbon nanotubes grown in situ on nanofibers, the temperature is raised to 650~750℃, and then the aforementioned carbon source gas is introduced, wherein the flow rate of the aforementioned protective gas: the flow rate of the aforementioned reducing gas: the flow rate of the aforementioned carbon source gas = 6~8: 2~3: 1~2.

[0013] Preferably, in the aforementioned method for preparing carbon nanotubes grown in situ on nanofibers, the carbon source gas is one or more of methane, ethylene, and acetylene.

[0014] The purpose of this application and the solution to its technical problem are also achieved by the following technical solution. A carbon nanotube grown in situ on nanofibers according to this application is prepared by any of the aforementioned preparation methods.

[0015] The purpose of this application and the solution to its technical problems are also achieved by the following technical solution. This application proposes the application of the aforementioned in-situ grown carbon nanotubes on nanofibers in the field of microwave absorbing materials.

[0016] By employing the above technical solution, the carbon nanotubes grown in situ on nanofibers, their preparation method, and their applications, as described in this application, have at least the following advantages: This application involves adding a transition metal catalyst to the electrospinning solution and reducing the catalyst to transition metal monomers using a reducing gas at 380–450°C. Then, a carbon source gas is introduced at 650–750°C. Under the catalysis of the transition metal monomers, the reducing gas further reduces the carbon source gas to carbon monomers. Using these transition metal monomers as a substrate, carbon nanotubes are grown on the surface of nanofibers. Because the transition metal monomers and nanofibers are integrated, the carbon nanotubes are tightly bonded to the nanofibers. The in-situ growth method for preparing carbon nanotubes provided in this application is highly efficient and rapid, exhibits high substrate adaptability, and demonstrates strong adhesion to the substrate.

[0017] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the carbon nanotubes grown in situ on nanofibers in Example 1. Detailed Implementation

[0019] To further illustrate the technical means and effects adopted by this application to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, provides a detailed description of the specific implementation methods, structures, features, and effects of carbon nanotubes grown in situ on nanofibers according to this application, their preparation methods, and applications. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0020] This application discloses a method for preparing carbon nanotubes grown in situ from nanofibers, the steps of which include: The matrix material, dispersant, and transition metal catalyst are mixed uniformly with the continuous phase to prepare an electrospinning solution; based on the mass of the aforementioned electrospinning solution as 100%, the content of the aforementioned matrix material is 8%~15%, the content of the aforementioned dispersant is 0.05%~1%, and the content of the aforementioned transition metal catalyst is 1%~10%. The aforementioned electrospinning solution was loaded into the syringe of the electrospinning equipment and electrospinned to obtain a nanofiber catalytic precursor. The aforementioned nanofiber catalytic precursor was heated to 380-450°C under a protective gas atmosphere; then a reducing gas was introduced to reduce the aforementioned transition metal catalyst; then the temperature was raised to 650-750°C, and then a carbon source gas was introduced to obtain carbon nanotubes grown in situ on nanofibers.

[0021] Specifically, the matrix material is the main substance forming nanofibers. During electrospinning, it solidifies along with the volatilization of the continuous phase, providing basic physical structure and morphological support for the nanofibers and determining their initial morphology, such as diameter, length, and surface roughness. Preferably, the matrix material is one or more of polyacrylonitrile, polyaniline, polyvinyl alcohol, polytetrafluoroethylene, and polypropylene. Based on 100% by mass of the electrospinning solution, the matrix material content is 8%–15%. When the content is below 8%, the viscosity of the electrospinning solution is insufficient, making it difficult to form a stable jet and causing spinning difficulties. When the content is above 15%, the viscosity of the electrospinning solution is too high, making it difficult for the continuous phase to volatilize, leading to adhesion between nanofibers.

[0022] The main function of dispersants is to improve the dispersibility of various components (especially transition metal catalysts) in the system composed of the matrix material and the continuous phase. Transition metal catalysts exist in particulate form and are prone to agglomeration. Dispersants reduce the surface tension between particles, allowing the catalyst particles to be more uniformly dispersed in the electrospinning solution, avoiding excessively high or low local concentrations. This ensures a uniform distribution of the transition metal catalyst in the final nanofibers, thereby guaranteeing the uniform growth of carbon nanotubes on the nanofiber surface. Preferably, the dispersant is one or more of sodium dodecyl sulfate, dodecylbenzene sulfonic acid, ethyl butyrate, and triethyl phosphate. Based on 100% by mass of the electrospinning solution, the content of the dispersant is 0.05% to 1%. Too low a content results in poor dispersion; too high a content may form excessive micelles in the electrospinning solution, affecting the flowability and conductivity of the solution, and consequently impacting the stability of the electrospinning process.

[0023] The transition metal catalyst is subsequently reduced from metal oxide to metal monomers. Under the catalytic action of the metal monomers, the carbon source gas is reduced to carbon monomers. These carbon monomers, using the metal monomers as "seeds," begin to grow on the surface of nanofibers, gradually forming carbon nanotubes. For example, transition metal catalysts such as nickel and iron can lower the activation energy of carbon source gas decomposition, promote the formation of carbon-carbon bonds, and thus guide the orderly growth of carbon nanotubes. Preferably, the transition metal catalyst is one or more of nickel acetylacetone, iron acetylacetone, cobalt acetate, ferrocene, nano-ferric oxide, nano-ferric oxide, nano-copper oxide, and nano-cobalt oxide. Based on the mass of the electrospinning solution as 100%, the content of the transition metal catalyst is 1% to 10%. When the content is less than 1%, the transition metal catalyst content is too low, providing few catalytic active sites on the nanofiber surface. The carbon source gas cannot be fully decomposed and grown, resulting in a small number of carbon nanotubes, a slow growth rate, and even the inability to form a continuous and complete carbon nanotube structure. When the content is greater than 10%, the transition metal catalyst is prone to agglomeration in the electrospinning solution.

[0024] The continuous phase forms a stable dispersion system with the matrix material, dispersing agent, and transition metal catalyst. During electrospinning, the continuous phase carries other components and is ejected from the spinneret, forming a jet under the action of an electric field. As the continuous phase volatilizes, the matrix material and other components solidify to form nanofibers. The properties of the continuous phase (such as volatility, polarity, viscosity, etc.) have a significant impact on the stability of the electrospinning process and the morphology and structure of the nanofibers. Preferably, the continuous phase is one or more of dimethylformamide, tetrahydrofuran, acetone, chloroform, dichloromethane, and water.

[0025] The electrospinning solution was loaded into the syringe of the electrospinning equipment. The electrospinning parameters were set as follows: voltage 20~50kV, feed rate 0.1~2mL / h, distance between needle tip and collector 12~20cm, and spinning time 4~8h. Electrospinning was then performed to obtain nanofiber catalytic precursors.

[0026] The nanofiber catalytic precursor was heated to 380–450 °C at a rate of 15–30 °C / min under a protective gas atmosphere, with a flow rate of 1200–1600 sccm. A reducing gas was then introduced at a flow rate of 400–600 sccm, and the temperature was maintained for 15–30 min to reduce the transition metal catalyst from metal oxide to metal monomer. The temperature was then increased to 650–750 °C at a rate of 15–30 °C / min, followed by the introduction of a carbon source gas (one or more of methane, ethylene, and acetylene) at a flow rate of 200–400 sccm, and the temperature was maintained for 1–15 min. During this process, under the catalytic action of the metal monomer, the reducing gas reduced the carbon source gas to carbon monomer, resulting in the growth of carbon nanotubes on the nanofiber surface. The introduction of both the reducing and carbon source gases was stopped, and the mixture was cooled to room temperature under a protective gas atmosphere to obtain in-situ grown carbon nanotubes on the nanofiber. During the heating and cooling processes, the flow rate of the protective gas is adjusted to maintain the pressure at 65-85 kPa. The protective gas can be nitrogen or argon, etc. The reducing gas can be hydrogen or carbon monoxide, etc.

[0027] The reduction temperature of transition metal catalysts is 380–450 °C, with a holding time of 15–30 min. Below 380 °C, the reduction reaction of transition metal catalysts is difficult to occur; above 450 °C, metal particle agglomeration and sintering are easily initiated. If the holding time is too short, the reaction will be incomplete; if the holding time is too long, it will not be able to further improve the catalytic activity and may lead to coarsening of the catalyst particles.

[0028] The growth temperature of carbon nanotubes is 650~750℃, with a holding time of 1~15 min. The growth temperature of carbon nanotubes needs to ensure sufficient decomposition of the carbon source gas. Above 650℃, the decomposition rate of hydrocarbons increases significantly. If the temperature is too low, the mobility and diffusion of carbon atoms on the catalyst particle surface are poor, potentially forming amorphous carbon. However, excessively high reaction temperatures can induce side reactions and may cause catalyst coarsening or even deactivation. The holding time is controlled within 1~15 min. This application grows carbon nanotubes on the fiber surface while the catalyst is integrated into the substrate, resulting in good catalytic activity. Therefore, a relatively short activation time is sufficient to grow carbon nanotubes. Furthermore, since the fiber itself is a relatively fragile substrate, it should not be exposed to high temperatures for extended periods, otherwise structural damage may occur.

[0029] This application involves adding a transition metal catalyst to the electrospinning solution and reducing the catalyst to transition metal monomers using a reducing gas at 380–450°C. Then, a carbon source gas is introduced at 650–750°C. Under the catalysis of the transition metal monomers, the reducing gas further reduces the carbon source gas to carbon monomers. Using these transition metal monomers as a substrate, carbon nanotubes are grown on the surface of nanofibers. Because the transition metal monomers and nanofibers are integrated, the carbon nanotubes are tightly bonded to the nanofibers. The in-situ growth method for preparing carbon nanotubes provided in this application is highly efficient and rapid, exhibits high substrate adaptability, and demonstrates strong adhesion to the substrate.

[0030] The carbon nanotubes in situ grown on nanofibers proposed in this application are prepared by any of the aforementioned preparation methods.

[0031] This application proposes the application of the aforementioned in-situ grown carbon nanotubes from nanofibers in the field of microwave absorbing materials.

[0032] The present application will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are still within the scope of protection of the present application.

[0033] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains.

[0034] Example 1 (1) Dissolve 20g of polyacrylonitrile, 0.5g of dodecylbenzenesulfonic acid and 5g of nickel acetylacetonate in 174.5g of dimethylformamide and stir magnetically for 12h to obtain a homogeneous solution, which is the electrospinning solution.

[0035] (2) Fill the electrospinning solution into the syringe of the electrospinning equipment, adjust the voltage to 25kV, the distance between the needle tip and the collector to 15cm, the feed rate to 0.8mL / h, and spin for 6h to obtain the nanofiber catalytic precursor.

[0036] (3) The nanofiber catalytic precursor was removed from the collector and placed into the quartz tube of a high-temperature tube furnace. It was heated to 400°C at a rate of 20°C / min in a N2 atmosphere, and 300 sccm of H2 was introduced. The temperature was maintained for 20 min. Then, without shutting off the H2 gas path, the temperature was increased to 700°C at a rate of 20°C / min, and 200 sccm of CH4 was introduced. After 5 min, the H2 and CH4 gas paths were shut off, allowing the quartz tube to cool to room temperature in the N2 atmosphere, thus obtaining carbon nanotubes grown in situ on the nanofibers. The flow rate of N2 was adjusted during each heating and cooling stage to maintain the pressure inside the quartz tube at 75 kPa.

[0037] Figure 1 This is a scanning electron microscope image of carbon nanotubes grown in situ on nanofibers obtained in Example 1.

[0038] Example 2 (1) Dissolve 30g of polyacrylonitrile, 1g of dodecylbenzenesulfonic acid and 10g of nickel acetylacetonate in 159g of dimethylformamide and stir magnetically for 12h to obtain a homogeneous solution, which is the electrospinning solution.

[0039] (2) Fill the electrospinning solution into the syringe of the electrospinning equipment, adjust the voltage to 30kV, the distance between the needle tip and the collector to 18cm, the feed rate to 0.5mL / h, and spin for 6h to obtain the nanofiber catalytic precursor.

[0040] (3) The nanofiber catalytic precursor was removed from the collector and placed into the quartz tube of a high-temperature tube furnace. It was heated to 400°C at a rate of 20°C / min in a N2 atmosphere, and 300 sccm of H2 was introduced. The temperature was maintained for 20 min. Then, without shutting off the H2 gas path, the temperature was increased to 700°C at a rate of 20°C / min, and 200 sccm of CH4 was introduced. After 5 min, the H2 and CH4 gas paths were shut off, allowing the quartz tube to cool to room temperature in the N2 atmosphere, thus obtaining carbon nanotubes grown in situ on the nanofibers. The flow rate of N2 was adjusted during each heating and cooling stage to maintain the pressure inside the quartz tube at 75 kPa.

[0041] Example 3 (1) Dissolve 16g of polyvinyl alcohol, 0.5g of sodium dodecyl sulfate and 5g of nickel acetylacetonate in 178.5g of water and stir magnetically for 12h to obtain a homogeneous solution, which is the electrospinning solution.

[0042] (2) Fill the electrospinning solution into the syringe of the electrospinning equipment, adjust the voltage to 25kV, the distance between the needle tip and the collector to 17cm, the feed rate to 0.25mL / h, and spin for 6h to obtain the nanofiber catalytic precursor.

[0043] (3) The nanofiber catalytic precursor was removed from the collector and placed into the quartz tube of a high-temperature tube furnace. It was heated to 400°C at a rate of 20°C / min in a N2 atmosphere, and 300 sccm of H2 was introduced. The temperature was maintained for 20 min. Then, without shutting off the H2 gas path, the temperature was increased to 700°C at a rate of 20°C / min, and 200 sccm of CH4 was introduced. After 5 min, the H2 and CH4 gas paths were shut off, allowing the quartz tube to cool to room temperature in the N2 atmosphere, thus obtaining carbon nanotubes grown in situ on the nanofibers. The flow rate of N2 was adjusted during each heating and cooling stage to maintain the pressure inside the quartz tube at 75 kPa.

[0044] Example 4 (1) Dissolve 2g sodium dodecyl sulfate in 175g water and stir magnetically for 1h; then add 5g nano ferric oxide (8nm) to the solution and disperse it for 20min by a high-power ultrasonic homogenizer; finally add 18g polyvinyl alcohol and stir magnetically for 12h to form a homogenized solution.

[0045] (2) Fill the electrospinning solution into the syringe of the electrospinning equipment, adjust the voltage to 20kV, the distance between the needle tip and the collector to 17cm, the feed rate to 0.3mL / h, and spin for 6h to obtain the nanofiber catalytic precursor.

[0046] (3) The nanofiber catalytic precursor was removed from the collector and placed into the quartz tube of a high-temperature tube furnace. It was heated to 400°C at a rate of 20°C / min in a N2 atmosphere, and 300 sccm of H2 was introduced. The temperature was maintained for 20 min. Then, without shutting off the H2 gas path, the temperature was increased to 700°C at a rate of 20°C / min, and 200 sccm of CH4 was introduced. After 5 min, the H2 and CH4 gas paths were shut off, allowing the quartz tube to cool to room temperature in the N2 atmosphere, thus obtaining carbon nanotubes grown in situ on the nanofibers. The flow rate of N2 was adjusted during each heating and cooling stage to maintain the pressure inside the quartz tube at 75 kPa.

[0047] The properties of the carbon nanotubes in situ grown on nanofibers obtained in Examples 1-4 were tested, and the results are shown in Table 1. The material density was tested using the water displacement method; the specific gravity of the carbon nanotubes was tested using thermogravimetric analysis; and the optimal microwave absorption efficiency was tested using vector network analysis.

[0048] Table 1. Properties of carbon nanotubes grown in situ from nanofibers in Examples 1-4 The embodiments of this application have now been described in detail. To avoid obscuring the concept of this application, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0049] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this application. In particular, as long as there is no logical conflict, the various technical features mentioned in the embodiments can be combined in any way.

Claims

1. A method for preparing carbon nanotubes grown in situ on nanofibers, characterized in that, The steps include: A matrix material, a dispersing agent, and a transition metal catalyst are uniformly mixed with a continuous phase to prepare an electrospinning solution. Based on the mass of the electrospinning solution (100%), the matrix material content is 8%–15%, the dispersing agent content is 0.05%–1%, and the transition metal catalyst content is 1%–10%. The electrospinning solution is loaded into the syringe of the electrospinning equipment and electrospinning is performed to obtain nanofiber catalytic precursor. The nanofiber catalytic precursor was heated to 380-450°C under a protective gas atmosphere; then a reducing gas was introduced to reduce the transition metal catalyst; then the temperature was raised to 650-750°C, and then a carbon source gas was introduced to obtain carbon nanotubes grown in situ on nanofibers.

2. The preparation method according to claim 1, characterized in that, The electrospinning parameters were set as follows: voltage 20~50kV, feed rate 0.1~2mL / h, distance between needle tip and collector 12~20cm, and spinning time 4~8h.

3. The preparation method according to claim 1, characterized in that, The temperature is increased to 380-450℃ at a rate of 15-30℃ / min, the reducing gas is introduced, and the temperature is maintained for 15-30min to reduce the transition metal catalyst. The temperature is increased to 650-750℃ at a rate of 15-30℃ / min, the carbon source gas is introduced, and the temperature is maintained for 1-15 minutes to obtain carbon nanotubes grown in situ on nanofibers.

4. The preparation method according to claim 1, characterized in that, The matrix material is one or more selected from polyacrylonitrile, polyaniline, polyvinyl alcohol, polytetrafluoroethylene, and polypropylene; and / or, The dispersing agent is one or more selected from sodium dodecyl sulfate, dodecylbenzene sulfonic acid, ethyl butyrate, and triethyl phosphate; and / or, The transition metal catalyst is one or more of nickel acetylacetone, iron acetylacetone, cobalt acetate, ferrocene, nano-ferric oxide, nano-ferric oxide, nano-copper oxide, and nano-cobalt oxide; and / or, The continuous phase is one or more of dimethylformamide, tetrahydrofuran, acetone, chloroform, dichloromethane, and water.

5. The preparation method according to claim 1, characterized in that, The temperature is raised to 380~450℃, and then the reducing gas is introduced. The flow rate of the protective gas is 6~8:2~3 of the flow rate of the reducing gas.

6. The preparation method according to claim 1, characterized in that, The temperature is raised to 650~750℃, and then the carbon source gas is introduced. The flow rate of the protective gas: the flow rate of the reducing gas: the flow rate of the carbon source gas = 6~8: 2~3: 1~2.

7. The preparation method according to claim 1, characterized in that, During the heating and cooling process, the flow rate of the protective gas is adjusted to maintain the pressure at 65~85 kPa.

8. The preparation method according to claim 1, characterized in that, The carbon source gas is one or more of methane, ethylene, and acetylene.

9. A carbon nanotube grown in situ on nanofibers, prepared by any one of the preparation methods described in claims 1-8.

10. The application of the carbon nanotubes grown in situ on nanofibers as described in claim 9 in the field of microwave absorbing materials.

Images