A kind of CNTs@HsGDY@PDA nanofiber-derived microwave absorber and its preparation method

Abstract

The present invention provides a CNTs@HsGDY@PDA nanofiber derivative. The carbon nanotubes are used as templates. The Glaser coupling reaction of 1,3,5-triacetylbenzene and the oxidative self-polymerization reaction of dopamine (DA) in a weakly alkaline solution are utilized to sequentially coat the surface of the carbon nanotubes with graphene hydrogenation and polydopamine. After high-temperature carbonization, a CNTs@HsGDY@PDA nanofiber derivative containing graphene hydrogenation and a core-shell structure, namely CNTs@HsGDY@NC nanofiber, is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of absorbing materials, and in particular relates to a CNTs@HsGDY@PDA nanofiber-derived absorbing agent and a preparation method thereof. Background Art

[0002] Carbon materials have attracted extensive attention in the field of electromagnetic wave absorption due to their excellent dielectric properties, good composite characteristics, and special microstructure (Chinese patents CN216600681U and CN110950320B).

[0003] Carbon nanotubes (CNTs) resemble one-dimensional tubular structures formed by curling graphene sheets. This unique structure endows CNTs with high surface area, high porosity, anisotropy, and long-range dielectric loss, leading to their extensive research as microwave absorbers. However, for pure CNTs, further applications are limited by their limited composition, lack of multiple electromagnetic wave loss mechanisms, and excessively high dielectric constants that reduce impedance matching.

[0004] At present, research on the improvement and performance enhancement of CNTs absorbing materials mainly focuses on three aspects:

[0005] 1. Compounding it with other functional components, including Chinese patent CN111205819B provides a carbon nanotube-aluminum nitride absorber and its preparation method, carbon nanotube-aluminum nitride composite absorber and its application, including carbon nanotubes and aluminum nitride; Chinese patent CN113249819B provides a carbon nanotube-nano Fe3O4-polyimide composite fiber and its preparation method;

[0006] 2. In-situ growth of CNTs on the surface of other materials. For example, Chinese patent CN109880591B provides a porous carbon@carbon nanotube absorbing material and its preparation method, and Chinese patent application CN111944482A provides a preparation method for sea urchin-shaped carbon nanotube-coated Co particle composite absorbing material.

[0007] 3. Filling other components inside CNTs, for example: Chinese patent CN104945759B provides a cerium-doped nickel-zinc ferrite-filled carbon nanotube composite absorbing material and its preparation, and Chinese patent CN102627834B provides a preparation method of a chitosan-modified barium ferrite-filled multi-walled carbon nanotube / poly-3-methylthiophene composite absorbing material.

[0008] Although the above-mentioned composite absorbing materials have improved in performance, they have problems such as complex preparation process and even difficulty in controlling the uniform distribution of metal particles. At the same time, it is difficult to find a balance between light weight, broadband absorption and high absorption intensity.

[0009] Based on the current research and development background, the present invention intends to provide a new composite absorbing material. Summary of the Invention

[0010] The research team of the present invention previously applied for an invention patent entitled "A novel one-dimensional tubular carbon-based absorber and its preparation method", with application number 202310809505.1. The invention uses carbon nanotubes as templates and coats hydrogenated graphene (HsGDY) on its surface, forming a double-layer core-shell tubular structure. Although the absorbing performance of this product as an absorber is better than that of existing composite absorbing materials, in order to improve its loss capacity, improve impedance matching performance, and reduce the amount of filler, the applicant team of the present invention further optimized the technology and provided a CNTs@HsGDY@PDA nanofiber-derived absorber and its preparation method, namely, a core-shell structured one-dimensional lightweight carbon-based absorber containing hydrogenated graphene interlayers and its preparation method.

[0011] The concept of the present invention:

[0012] In response to the problems existing in existing composite absorbing materials, the research team of the present invention has previously optimized the composition and designed the structure to regulate the dielectric parameters and optimize the absorption performance. They still chose the highly-regarded carbon nanotubes as templates and introduced hydrogenated graphene into them for optimization, designing a new one-dimensional absorber. Here, the new application of hydrogenated graphene discovered by the research and development team is fully utilized - it can be used to prepare absorbers. It forms a perfect π-type conjugated system (a conjugated body constructed by four types of carbon-carbon bonds) by introducing hydrogen atoms into the benzene ring for molecular modification. It has a high specific surface area, wide interplanar spacing, high crystallinity, uniformly dispersed pore configuration, adjustable electronic structure and semiconductor properties, good conductivity and a large number of active sites. It not only contains a large number of acetylenic bonds, but also has a unique hierarchical porous structure, which can provide a path for electron transmission, effectively enhancing the dielectric loss of the material, and is a functional component. To further optimize the research and development results, the present invention proposes to adhere to the design principles of "light weight, thin thickness, wide bandwidth, and strong absorption" by coating the outermost layer with a layer of polydopamine, introducing multiple heterogeneous interfaces, enhancing interfacial polarization, and improving loss capacity. At the same time, due to the combined effects of hydrogen bonding and π-π stacking, the polydopamine forms a dense film with significant stability. The presence of this dense film helps to improve the stability of the material. After high-temperature carbonization, the polydopamine is converted into a nitrogen-doped carbon layer. This nitrogen-doped carbon layer has a rich pore structure, significantly increasing the specific surface area of the material and achieving better microwave absorption than a pure carbon layer. Moreover, the nitrogen-doped carbon layer converted from carbonized polydopamine contains a large number of defects, which further induce dipole polarization, facilitating microwave dissipation and significantly contributing to the improvement of the material's microwave absorption performance. Therefore, the present invention proposes to use hydrogenated graphene combined with carbon nanotubes and nitrogen-doped carbon to prepare a new type of microwave absorber.

[0013] Based on the above invention concept, in order to achieve the above purpose, the technical solution provided by the present invention is:

[0014] A CNTs@HsGDY@PDA nanofiber derivative is unique in that it exhibits a three-layer core-shell structure, consisting of carbon nanotubes (CNTs), hydrogenated graphene (HsGDY) layers, and a nitrogen-doped carbon (NC) layer. The inner diameter and length of the CNTs are the same as those of the selected CNTs, the hydrogenated graphene layer is 8-20 nm thick, and the nitrogen-doped carbon layer is 15-25 nm thick.

[0015] The carbon nanotubes are single-walled or multi-walled carbon nanotubes containing carboxyl groups or hydroxyl groups on the surface; wherein the carboxyl group content is less than 2.5 wt % and the hydroxyl group content is less than 3 wt %.

[0016] The preparation method of the CNTs@HsGDY@PDA nanofiber derivative is special in that it comprises the following steps:

[0017] 1) mixing carbon nanotubes with solvent I and solvent II, and uniformly dispersing them by ultrasonication to obtain a suspension A;

[0018] The carbon nanotubes are single-walled or multi-walled carbon nanotubes containing carboxyl groups or hydroxyl groups on the surface; wherein the carboxyl group content is less than 2.5 wt% and the hydroxyl group content is less than 3 wt%;

[0019] The solvent I is tetrahydrofuran or pyridine;

[0020] The solvent II is trimethylamine or triethylamine;

[0021] 2) Under inert gas protection, 1,3,5-triethynylbenzene, catalyst I and catalyst II were added to the suspension A obtained in step 1), and the mixture was stirred and reacted at room temperature. After the reaction was completed, the mixture was centrifuged, washed with ethanol, and vacuum dried to obtain CNTs@HsGDY nanotubes;

[0022] The catalyst I is a palladium catalyst in the form of a complex;

[0023] The catalyst II is a cuprous halide catalyst;

[0024] 3) Ultrasonic uniformly dispersing the CNTs@HsGDY nanotubes obtained in step 2) in a buffer solution with a pH of 8.3 to 8.7 to obtain a suspension B;

[0025] 4) Under magnetic stirring, a buffer solution containing dopamine hydrochloride at pH 8.3 to 8.7 was added to the suspension B obtained in step 3), and the mixture was reacted at room temperature. After the reaction was completed, the suspension was centrifuged and washed with ethanol and water in sequence, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers;

[0026] 5) The CNTs@HsGDY@PDA nanofibers obtained in step 4) are vacuum carbonized to obtain the product CNTs@HsGDY@PDA nanofiber derivative - CNTs@HsGDY@NC nanofibers.

[0027] Furthermore, in step 1), the volume ratio of solvent I to solvent II is 1:1-3;

[0028] In the suspension A, the mass concentration of carbon nanotubes is 0.2-0.7 mg / mL.

[0029] Furthermore, in step 2), the catalyst I is bistriphenylphosphine palladium dichloride or tetrakis(triphenylphosphine)palladium;

[0030] The catalyst II is cuprous iodide, cuprous bromide or cuprous chloride;

[0031] The molar ratio of 1,3,5-triethynylbenzene, catalyst I and catalyst II is 3:1:1;

[0032] The mass ratio of 1,3,5-triethynylbenzene to carbon nanotubes is 1:2-8;

[0033] The reaction was carried out at room temperature under magnetic stirring for 48-72 hours.

[0034] Furthermore, in step 3), the buffer solution is a Tris hydrochloric acid buffer solution with a pH of 8.3 to 8.7;

[0035] In suspension B, the mass concentration of CNTs@HsGDY nanotubes is 0.5-1 mg / mL.

[0036] Furthermore, the buffer used in step 4) is a Tris hydrochloric acid buffer solution with a pH of 8.3 to 8.7; the mass concentration of dopamine hydrochloride is 1 to 3 mg / mL, and the mass ratio of CNTs@HsGDY nanotubes to dopamine hydrochloride is 1:1 to 5;

[0037] The reaction time is 18-24h.

[0038] Furthermore, step 5) is specifically as follows:

[0039] The CNTs@HsGDY@PDA nanofibers obtained in step 4) are vacuum carbonized in a tubular furnace at 600-900°C for 1-3 h, with a heating rate of 1-5°C / min (a heating rate that is too fast will destroy the product structure, form defects, and affect performance, while a heating rate that is too slow will affect production efficiency) to obtain a product CNTs@HsGDY@PDA nanofiber derivative - CNTs@HsGDY@NC nanofiber.

[0040] At the same time, the present invention also provides the use of the above-mentioned CNTs@HsGDY@PDA nanofiber derivative CNTs@HsGDY@NC as a wave absorbing agent.

[0041] And, a device with radar stealth function, which is special in that it uses the above-mentioned CNTs@HsGDY@PDA nanofiber derivative CNTs@HsGDY@NC as an absorber for filling.

[0042] Advantages of the present invention:

[0043] 1. In the present invention, carbon nanotubes (CNTs) are used as templates. Graphene hydrogenation (GDY) and polydopamine (PDA) are sequentially coated on the surface of CNTs via the Glaser coupling reaction of 1,3,5-triethynylbenzene and the oxidative self-polymerization reaction of dopamine (DA) in a weakly alkaline solution. After high-temperature carbonization, CNTs@HsGDY@NC nanofibers, a core-shell structured CNTs@HsGDY@PDA nanofiber derivative, are prepared. Among them, the selected carbon nanotubes have a certain amount of functional groups (carboxyl content is less than 2.5wt%, hydroxyl content is less than 3wt%), have moderate solvent compatibility and surface coating induction effect, the good conductivity of hydrogenated graphene is conducive to enhancing the conductive loss of the material, the polarization relaxation caused by multiple heterogeneous interfaces is conducive to enhancing the interface polarization, and the N doping in the carbon material promotes the generation of dipole polarization, which can effectively improve the overall impedance matching, attenuation characteristics, density of the material, broaden the narrow effective absorption bandwidth of the single component material, obtain significant electromagnetic wave absorption, and realize the controllable preparation of a new one-dimensional absorbing material with the characteristics of "light, thin, wide and strong".

[0044] 2. The preparation method of the target product of the present invention is simple, and there is a situation where the metal particles are unevenly distributed. Its morphology and absorbing properties can be effectively controlled by changing the amount of 1,3,5-triacetylbenzene, the amount of dopamine hydrochloride, and the coating time (to ensure reasonable conductivity of the material and high absorbing properties, the thickness of the hydrogenated graphene layer is 8-20nm, and the thickness of the nitrogen-doped carbon layer is 15-25nm). The absorber prepared by this method has the advantages of a hollow three-layer core-shell structure, a multi-component composite, and a one-dimensional material. It is a porous (can be formed when polydopamine is carbonized, and the hollow effect of carbon nanotubes is superimposed) and a one-dimensional structure with a large aspect ratio. It is lightweight, has a high specific surface area, high porosity, rich heterogeneous interfaces and nitrogen atom doping, has relatively excellent absorbing properties, and has potential application value in the field of absorbing waves, which can be extended to the fields of national defense, military, medicine, and electronics. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the preparation process of CNTs@HsGDY@PDA nanofiber-derived absorber;

[0046] Figure 2 This is a transmission electron microscope image of CNTs@HsGDY@CN nanofibers;

[0047] Figure 3 This is the loss curve of the CNTs@HsGDY@CN one-dimensional absorber. DETAILED DESCRIPTION

[0048] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments:

[0049] like Figure 1 As shown, the preparation method of the CNTs@HsGDY@PDA nanofiber-derived absorber comprises the following steps:

[0050] 1) Weigh carbon nanotubes into a single-necked bottle, add solvent I and solvent II, and disperse them uniformly under ultrasonication to obtain suspension A;

[0051] Wherein, the carbon nanotubes are single-walled or multi-walled carbon nanotubes containing carboxyl groups or hydroxyl groups on the surface; wherein the carboxyl group content is less than 2.5 wt% and the hydroxyl group content is less than 3 wt%;

[0052] Solvent I is tetrahydrofuran or pyridine;

[0053] Solvent II is trimethylamine or triethylamine;

[0054] The volume ratio of solvent I to solvent II is 1:1-3, and the mass concentration of carbon nanotubes is 0.2-0.7 mg / mL;

[0055] 2) Under inert gas protection, 1,3,5-triethynylbenzene, catalyst I and catalyst II were added to suspension A, and the mixture was reacted at room temperature for 48-72 hours under magnetic stirring. The mixture was centrifuged, washed with ethanol, and vacuum dried to obtain CNTs@HsGDY nanotubes;

[0056] Catalyst I is bistriphenylphosphine palladium dichloride or tetrakis(triphenylphosphine)palladium;

[0057] Catalyst II is cuprous iodide, cuprous bromide or cuprous chloride;

[0058] The molar ratio of 1,3,5-triethynylbenzene, catalyst I and catalyst II is 3:1:1;

[0059] The mass ratio of 1,3,5-triethynylbenzene to carbon nanotubes is 1:2-8;

[0060] 3) Weigh CNTs@HsGDY nanotubes and uniformly disperse them in a Tris-HCl buffer solution with a pH of 8.3 to 8.7 by ultrasonication to obtain a suspension B;

[0061] Among them, the mass concentration of CNTs@HsGDY nanotubes is 0.5-1 mg / mL;

[0062] 4) Under magnetic stirring, a Tris-HCl buffer solution containing dopamine hydrochloride at pH 8.3-8.7 was added to suspension B, and the mixture was reacted at room temperature for 18-24 hours. The mixture was then centrifuged and washed with ethanol and water, respectively, and vacuum-dried to obtain CNTs@HsGDY@PDA nanofibers.

[0063] The mass concentration of dopamine hydrochloride is 1-3 mg / mL, and the mass ratio of CNTs@HsGDY nanotubes to dopamine hydrochloride is 1:1-5;

[0064] 5) The CNTs@HsGDY@PDA nanofibers obtained in step 4) were subjected to vacuum carbonization treatment in a tubular furnace at 600-900° C. for 1-3 h, with the heating rate controlled at 1-5° C. / min to obtain the target product.

[0065] The inert gas may be argon or nitrogen.

[0066] The following are specific embodiments:

[0067] Example 1:

[0068] 20 mg of carbon nanotubes (surface carboxyl content less than 2.5 wt% and hydroxyl content less than 3 wt%) were weighed into a 100 mL single-necked bottle. 20 mL of ultra-dry tetrahydrofuran and 20 mL of ultra-dry trimethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 25.7 mg of tetrakis(triphenylphosphine)palladium, 4.2 mg of cuprous iodide, and 10 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 60 h. The solid product was washed with ethanol and vacuum-dried to obtain CNTs@HsGDY nanotubes. 80 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 160 mL of Tris-HCl buffer (pH 8.7). 240 mg of dopamine hydrochloride dissolved in 120 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 24 h. The resulting product was washed with ethanol and water, respectively, and vacuum-dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum-carbonized in a tube furnace at 800°C for 3 h at a heating rate of 5°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0069] from Figure 2 It can be seen that the whole presents a three-layer core-shell structure, which consists of carbon nanotubes, hydrogenated graphene layers and nitrogen-doped carbon layers from the inside to the outside. The inner diameter and length of these layers are the same as those of the selected carbon nanotubes. They are interwoven to form a three-dimensional network structure.

[0070] Example 2:

[0071] 20 mg of carbon nanotubes (surface carboxyl content less than 2.5 wt% and hydroxyl content less than 3 wt%) were weighed into a 100 mL single-necked flask. 20 mL of pyridine and 20 mL of ultra-dry triethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 12.5 mg of bistriphenylphosphine palladium dichloride, 2.6 mg of cuprous bromide, and 8 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 72 hours. The solid product was washed with ethanol and vacuum-dried to obtain CNTs@HsGDY nanotubes. 120 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 180 mL of Tris-HCl buffer (pH 8.5). 240 mg of dopamine hydrochloride dissolved in 200 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 18 hours. The resulting product was washed with ethanol and water, respectively, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum carbonized in a tube furnace at 600°C for 2 h at a heating rate of 5°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0072] Example 3:

[0073] 40 mg of carbon nanotubes (surface carboxyl content less than 2.5 wt% and hydroxyl content less than 3 wt%) were weighed into a 200 mL single-necked bottle. 40 mL of ultra-dry tetrahydrofuran and 80 mL of ultra-dry trimethylamine were added and dispersed homogeneously by sonication to obtain a suspension. Under argon, 20.5 mg of tetrakis(triphenylphosphine)palladium, 1.8 mg of cuprous chloride, and 8 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 72 hours. The solid product was washed with ethanol and dried under vacuum to obtain CNTs@HsGDY nanotubes. 80 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 160 mL of Tris-HCl buffer (pH 8.7). 240 mg of dopamine hydrochloride dissolved in 160 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 24 hours. The resulting product was washed with ethanol and water, respectively, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum carbonized in a tube furnace at 800°C for 3 h at a heating rate of 4°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0074] Example 4:

[0075] 40 mg of carbon nanotubes (with a surface carboxyl content of less than 2.5 wt% and a hydroxyl content of less than 3 wt%) were weighed into a 200 mL single-necked bottle. 40 mL of pyridine and 80 mL of ultra-dry trimethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 30.8 mg of tetrakis(triphenylphosphine)palladium, 3.8 mg of cuprous bromide, and 12 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 48 hours. The solid product was washed with ethanol and dried under vacuum to obtain CNTs@HsGDY nanotubes. 200 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 200 mL of Tris-HCl buffer (pH 8.5). 300 mg of dopamine hydrochloride dissolved in 300 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 24 hours. The resulting product was washed with ethanol and water, respectively, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum carbonized in a tube furnace at 900°C for 3 h at a heating rate of 5°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0076] Example 5:

[0077] 40 mg of carbon nanotubes (with a surface carboxyl content of less than 2.5 wt% and a hydroxyl content of less than 3 wt%) were weighed into a 200 mL single-necked bottle. 40 mL of ultra-dry tetrahydrofuran and 80 mL of ultra-dry trimethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 25.7 mg of tetrakis(triphenylphosphine)palladium, 2.2 mg of cuprous chloride, and 10 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 68 h. The solid product was washed with ethanol and dried under vacuum to obtain CNTs@HsGDY nanotubes. 100 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 200 mL of Tris-HCl buffer (pH 8.3). 400 mg of dopamine hydrochloride dissolved in 300 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 20 h. The resulting product was washed with ethanol and water, respectively, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum carbonized in a tube furnace at 700°C for 1 h at a heating rate of 5°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0078] Example 6:

[0079] 30 mg of carbon nanotubes (surface carboxyl content less than 2.5 wt% and hydroxyl content less than 3 wt%) were weighed into a 150 mL single-necked flask. 20 mL of pyridine and 60 mL of ultra-dry triethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 14 mg of bistriphenylphosphine palladium dichloride, 3.8 mg of cuprous iodide, and 9 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 48 hours. The solid product was washed with ethanol and dried under vacuum to obtain CNTs@HsGDY nanofibers. 200 mg of CNTs@HsGDY nanofibers were weighed and ultrasonically dispersed in 200 mL of Tris-HCl buffer (pH 8.7). 300 mg of dopamine hydrochloride dissolved in 240 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 24 hours. The resulting product was washed with ethanol and water, respectively, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum carbonized in a tube furnace at 700°C for 2 h at a heating rate of 4°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0080] Example 7:

[0081] 30 mg of carbon nanotubes (surface carboxyl content less than 2.5 wt% and hydroxyl content less than 3 wt%) were weighed into a 150 mL single-necked flask. 20 mL of pyridine and 60 mL of ultra-dry triethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 18.7 mg of bistriphenylphosphine palladium dichloride, 2.6 mg of cuprous chloride, and 12 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 72 hours. The solid product was washed with ethanol and vacuum-dried to obtain CNTs@HsGDY nanotubes. 150 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 200 mL of Tris-HCl buffer (pH 8.4). 260 mg of dopamine hydrochloride dissolved in 200 mL of Tris-HCl buffer was added to the mixture and the reaction was carried out under magnetic stirring for 24 hours. The resulting product was washed with ethanol and water, respectively, and vacuum-dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum-carbonized in a tube furnace at 800°C for 3 h at a heating rate of 5°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0082] Example 8:

[0083] 30 mg of carbon nanotubes (surface carboxyl content less than 2.5 wt% and hydroxyl content less than 3 wt%) were weighed into a 150 mL single-necked bottle. 30 mL of ultra-dry tetrahydrofuran and 20 mL of ultra-dry trimethylamine were added and ultrasonically dispersed to obtain a suspension. Under argon, 46.3 mg of tetrakis(triphenylphosphine)palladium, 7.6 mg of cuprous iodide, and 18 mg of 1,3,5-triethynylbenzene were added to the suspension. The mixture was reacted at room temperature under magnetic stirring for 60 h. The solid product was washed with ethanol and dried under vacuum to obtain CNTs@HsGDY nanotubes. 120 mg of CNTs@HsGDY nanotubes were weighed and ultrasonically dispersed in 180 mL of Tris-HCl buffer (pH 8.6). 120 mg of dopamine hydrochloride dissolved in 100 mL of Tris-HCl buffer was added to the mixture and the mixture was reacted under magnetic stirring for 24 h. The resulting product was washed with ethanol and water, respectively, and vacuum dried to obtain CNTs@HsGDY@PDA nanofibers. The CNTs@HsGDY@PDA nanofibers were then vacuum carbonized in a tube furnace at 700°C for 1 h at a heating rate of 3°C / min to obtain CNTs@HsGDY@NC nanofibers.

[0084] In addition, the present invention also tests the wave absorbing properties of the target product, such as Figure 3 The loss curve shows that the target product has a minimum reflection loss of -50.66dB, an effective absorption bandwidth of 5.9GHz, and a filler content of 7%. Compared with the previous solution (minimum reflection loss of -47.14dB, effective absorption bandwidth of 5.9GHz, and filler content of 9%), its loss capacity is not only improved, but the filler content is also significantly reduced. This shows that the present invention adds a layer of nitrogen-doped carbon to the outermost layer of the previous solution. The resulting CNTs@HsGDY@PDA nanofiber derivative CNTs@HsGDY@NC achieves simultaneous optimization of filler content and impedance matching compared to CNTs@HsGDY. At the same time, it also enriches the variety of absorbers and has great application prospects. It can be used as an absorbing filler to prepare devices with radar stealth capabilities.

[0085] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present invention, and these modifications or replacements should all be included in the scope of protection of the present invention.

Claims

1. A CNTs@HsGDY@PDA nanofiber derivative, characterized by: The overall structure is a three-layer core-shell structure, consisting of carbon nanotubes, hydrogenated graphene layers, and nitrogen-doped carbon layers. The inner diameter and length of the CNTs@HsGDY@PDA nanofiber derivatives are the same as those of the selected carbon nanotubes. The hydrogenated graphene layer is 8-20 nm thick, and the nitrogen-doped carbon layer is 15-25 nm thick. The carbon nanotubes are single-walled or multi-walled carbon nanotubes containing carboxyl groups or hydroxyl groups on the surface; wherein the carboxyl group content is less than 2.5 wt % and the hydroxyl group content is less than 3 wt %.

2. The method for preparing the CNTs@HsGDY@PDA nanofiber derivative according to claim 1, characterized in that: The following steps are involved: 1) mixing carbon nanotubes with solvent I and solvent II and uniformly dispersing them to obtain a suspension A; The carbon nanotubes are single-walled or multi-walled carbon nanotubes containing carboxyl groups or hydroxyl groups on the surface; wherein the carboxyl group content is less than 2.5 wt% and the hydroxyl group content is less than 3 wt%; The solvent I is tetrahydrofuran or pyridine; The solvent II is trimethylamine or triethylamine; 2) Under inert gas protection, 1,3,5-triethynylbenzene, catalyst I and catalyst II were added to the suspension A obtained in step 1), and the mixture was stirred and reacted at room temperature. After the reaction was completed, the mixture was centrifuged, washed, and vacuum-dried to obtain CNTs@HsGDY nanotubes; The catalyst I is a palladium catalyst in the form of a complex; The catalyst II is a cuprous halide catalyst; 3) dispersing the CNTs@HsGDY nanotubes obtained in step 2) in a buffer solution with a pH of 8.3 to 8.7 to obtain a suspension B; 4) adding a dopamine hydrochloride-dissolved buffer solution at pH 8.3 to 8.7 to the suspension B obtained in step 3) under stirring, reacting at room temperature, and centrifuging, washing, and vacuum drying after the reaction to obtain CNTs@HsGDY@PDA nanofibers; 5) vacuum carbonizing the CNTs@HsGDY@PDA nanofibers obtained in step 4) to obtain CNTs@HsGDY@PDA nanofiber derivatives CNTs@HsGDY@NC.

3. The method for preparing the CNTs@HsGDY@PDA nanofiber derivative according to claim 2, characterized in that: In step 1), the volume ratio of solvent I to solvent II is 1:1-3; In the suspension A, the mass concentration of carbon nanotubes is 0.2-0.7 mg / mL.

4. The method for preparing the CNTs@HsGDY@PDA nanofiber derivative according to claim 2 or 3, characterized in that: In step 2), the catalyst I is bistriphenylphosphine palladium dichloride or tetrakistriphenylphosphine palladium; The catalyst II is cuprous iodide, cuprous bromide or cuprous chloride; The molar ratio of 1,3,5-triethynylbenzene, catalyst I and catalyst II is 3:1:1; The mass ratio of 1,3,5-triethynylbenzene to carbon nanotubes is 1:2-8; The reaction was carried out at room temperature under magnetic stirring for 48-72 hours.

5. The method for preparing the CNTs@HsGDY@PDA nanofiber derivative according to claim 4, characterized in that: In step 3), the buffer solution is a Tris hydrochloric acid buffer solution with a pH of 8.3 to 8.7; In suspension B, the mass concentration of CNTs@HsGDY nanotubes is 0.5-1 mg / mL.

6. The method for preparing the CNTs@HsGDY@PDA nanofiber derivative according to claim 5, characterized in that: The buffer used in step 4) is a Tris hydrochloric acid buffer solution with a pH of 8.3 to 8.7; the mass concentration of dopamine hydrochloride is 1 to 3 mg / mL; The mass ratio of CNTs@HsGDY nanotubes to dopamine hydrochloride is 1:1 to 5; The reaction time is 18-24h.

7. The method for preparing the CNTs@HsGDY@PDA nanofiber derivative according to claim 6, characterized in that: Step 5) is specifically as follows: The CNTs@HsGDY@PDA nanofibers obtained in step 4) are vacuum carbonized in a tube furnace at 600-900° C. for 1-3 h, with a heating rate of 1-5° C. / min to obtain the product CNTs@HsGDY@NC nanofibers.

8. Use of the CNTs@HsGDY@PDA nanofiber derivative CNTs@HsGDY@NC according to claim 1 as a wave absorber.

9. A device with radar stealth function, characterized in that: It uses the CNTs@HsGDY@PDA nanofiber derivative CNTs@HsGDY@NC described in claim 1 as a wave absorbing agent for filling.

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