Zinc oxide coated carbon core-shell fiber as well as preparation method and application thereof

Abstract

The invention discloses a zinc oxide coated carbon core-shell fiber as well as a preparation method and application thereof, and relates to the technical field of electromagnetic wave absorbing materials. The preparation method comprises the following steps: mixing a zinc salt and a surfactant, carrying out electrostatic spinning to obtain zinc-based fibers, calcining the zinc-based fibers in air, adding pyridine, and carbonizing to obtain the zinc oxide coated carbon core-shell fibers. The zinc oxide and the nitrogen-doped carbon are compounded at a core-shell interface to generate interface polarization loss, so that impedance matching can be optimized, and multiple loss and scattering are increased. In addition, by controlling the carbonization temperature in the preparation process, it is guaranteed that the excellent impedance matching characteristic is kept while high conductivity loss is obtained, and therefore the material has the excellent wave absorbing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorption materials, and particularly to a zinc oxide-coated carbon core-shell fiber and a preparation method and application thereof. Background Art

[0002] Electromagnetic wave absorption materials can introduce incident electromagnetic waves on the material surface into the material interior and dissipate them as heat, effectively reducing the reflection and transmission of electromagnetic waves. Absorbing materials are widely used in the form of absorbing coatings inside precision electronic devices such as mobile phones and computers. While avoiding mutual interference of internal electronic components, they effectively reduce the electromagnetic wave dissipation of the device into the external space. With the aggravation of electromagnetic pollution of electronic communication devices, the preparation of new and efficient electromagnetic wave absorption materials has attracted more and more attention.

[0003] Zinc oxide (ZnO) is a typical dielectric loss material and an n-type wide-bandgap semiconductor. It is widely used for electromagnetic wave absorption due to its easy availability, light weight, low toxicity, and high stability. Although different morphologies of ZnO have been reported in the prior art as absorbing materials, for example, porous nanosheets, flower-like structures, and radial nanostructures, due to the non-magnetic and low-loss properties of ZnO, it is difficult for ZnO with any structure to achieve superior electromagnetic wave absorption performance alone. Therefore, how to introduce appropriate components into ZnO to prepare a composite material and optimize the structure of the composite material, so as to generate magnetic loss while optimizing the impedance matching characteristics, thereby further improving the electromagnetic wave absorption performance of the material is the current research hotspot.

[0004] In the prior art, CN114540985A discloses a hollow core-shell fiber material prepared by using zinc salt, iron salt, and surfactant as raw materials through electrospinning, calcination, and carbonization. The hollow core-shell fiber material mainly consists of zinc oxide, iron tetroxide, and nitrogen-doped carbon. However, in the preparation process of the above patent, in order to improve the graphitization degree and enhance the conductivity-type dielectric loss, the carbonization temperature is set at 500 - 700 °C. This carbonization temperature range will weaken the polarization loss, resulting in impedance mismatch of the material. Therefore, in order to compensate for the reduced electromagnetic wave absorption performance caused by the high carbonization temperature in the above patent, iron tetroxide that can improve the magnetic permeability of the material and enhance the magnetic loss is doped in zinc oxide. This method leads to complex components and preparation processes of the composite material, which is not convenient for industrial promotion and application.

[0005] Therefore, it is necessary to use zinc oxide as the base material, optimize the condition parameters in the preparation process, and ensure that the prepared material has excellent electromagnetic wave absorption performance while simplifying the components and preparation process of the composite material. Summary of the Invention

[0006] In view of the above-mentioned prior art, the object of the present invention is to provide a zinc oxide-coated carbon core-shell fiber, a preparation method thereof and an application. After mixing a zinc salt and a surfactant and subjecting them to electrospinning, a zinc-based fiber is obtained. After calcination in air, pyridine is added and then carbonization is carried out to obtain the zinc oxide-coated carbon core-shell fiber. The combination of zinc oxide and nitrogen-doped carbon generates interfacial polarization loss at the core-shell interface, and the synergistic effect of the two can optimize impedance matching, increase multiple losses and scattering. At the same time, the present invention also controls the carbonization temperature during the preparation process to ensure excellent impedance matching characteristics while obtaining a high conductivity loss, so that the material has excellent microwave absorption performance.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect of the present invention, a preparation method of a zinc oxide-coated carbon core-shell fiber is provided, comprising the following steps:

[0009] (1) Mix a zinc salt and a surfactant and disperse them in a solvent, and carry out electrospinning to obtain a zinc-based fiber;

[0010] (2) Heat and calcine the zinc-based fiber to obtain a precursor; mix the precursor and pyridine, and carry out carbonization at 400-450 °C for 1-4 h to obtain the zinc oxide-coated carbon core-shell fiber.

[0011] Preferably, in step (1), the zinc salt is one of zinc nitrate hexahydrate, zinc chloride, and zinc acetate dihydrate.

[0012] Preferably, in step (1), the surfactant is polyvinylpyrrolidone or polyacrylonitrile.

[0013] Preferably, in step (1), the solvent is N,N-dimethylformamide.

[0014] Preferably, in step (1), the addition ratio of the zinc salt, the surfactant and the solvent is (0.1-1.5) g: (0.1-1.5) g: (3-10) mL.

[0015] Further, the addition ratio of the zinc salt, the surfactant and the solvent is (0.5-1.5) g: (0.5-1.5) g: (4-8) mL.

[0016] Preferably, in step (1), during the electrospinning process, the voltage is 8-15 kV and the feeding rate is 0.1-0.8 mL / h.

[0017] Further, during the electrospinning process, the voltage is 10-13 kV and the feeding rate is 0.1-0.5 mL / h.

[0018] Further, during the electrospinning process, the voltage is 12 kV and the feeding rate is 0.24 mL / h.

[0019] Preferably, in step (2), during the heating and calcination process, the temperature is 300 - 600 °C, the heating rate is 1 - 5 °C / min, the time is 1 - 3 h, and the heating and calcination atmosphere is an air atmosphere.

[0020] Further, during the heating and calcination process, the temperature is 400 - 500 °C, the heating rate is 1 - 3 °C / min, and the reaction time is 2 - 3 h.

[0021] Preferably, in step (2), the ratio of the addition amounts of the precursor and pyridine is (0.1 - 1) g : (0.1 - 0.5) mL.

[0022] Further, the ratio of the addition amounts of the precursor and pyridine is 0.1 g : 0.25 mL.

[0023] Preferably, in step (2), during the carbonization process, the heating rate is 1 - 3 °C / min.

[0024] Further, during the carbonization process, the heating rate is 1 - 2 °C

[0025] In the second aspect of the present invention, there is provided a zinc oxide-coated carbon core-shell fiber prepared by the above preparation method.

[0026] In the third aspect of the present invention, there is provided the use of the above zinc oxide-coated carbon core-shell fiber in the preparation of an electromagnetic wave absorbing material.

[0027] Preferably, the electromagnetic wave absorbing material is prepared by the following method:

[0028] The zinc oxide-coated carbon core-shell fiber and paraffin are mixed and stirred evenly according to a mass ratio of (0.020 - 0.030) : 0.075 to obtain the electromagnetic wave absorbing material.

[0029] Preferably, the stirring temperature is 30 - 60 °C.

[0030] The zinc oxide-coated carbon core-shell fiber and paraffin are stirred at a temperature of 30 - 60 °C. Mixing is carried out at this stirring temperature, which can enhance the fluidity of paraffin and contribute to the uniform mixing of paraffin and the zinc oxide-coated carbon core-shell fiber.

[0031] Advantages of the present invention:

[0032] 1. In the zinc oxide-coated carbon core-shell fiber prepared by the present invention, zinc oxide, as a low-loss wave-absorbing material, allows electromagnetic waves to smoothly enter the material interior without reflection. After carbon coating on zinc oxide, it still maintains a three-dimensional network structure to promote conductance loss and multiple scattering. At the same time, the combination of zinc oxide and carbon generates interfacial polarization loss at the core-shell interface, and the synergistic effect of the two can optimize impedance matching, increase multiple losses and scattering.

[0033] 2. In the present invention, the carbonization temperature is controlled at 400 - 450 °C to ensure the wave-absorbing performance of the material by controlling the carbonization temperature. Specifically, the carbon in the present invention exists in two forms: graphitized carbon and amorphous carbon. As the carbonization temperature increases, the arrangement of carbon atoms becomes more orderly, the proportion of graphitized carbon increases, and the improvement of graphitization degree is beneficial to increasing the conductivity of the composite material, which is conducive to enhancing the conductance loss of the wave-absorbing material. However, when the conductivity is too high, it is easy to cause impedance mismatch of the composite material, which is not conducive to the entry of electromagnetic waves into the wave-absorbing material interior, resulting in a significant decrease in the attenuation ability. Therefore, the graphitization degree should be maintained within a reasonable range according to the dielectric properties of the composite material, which requires the carbonization temperature to be controlled within a small adjustment range to maintain excellent impedance matching characteristics while obtaining high conductance loss and excellent wave-absorbing performance.

[0034] 3. By controlling the carbonization temperature during the preparation process, the material prepared by the present invention is composed only of zinc oxide and nitrogen-doped carbon, simplifying the components of the material while ensuring that the material has excellent wave-absorbing performance. Specifically, the zinc oxide-coated carbon core-shell fiber prepared by the present invention is compounded with paraffin to obtain a wave-absorbing material, and the reflection loss of electromagnetic waves at high frequency (11.8 GHz) reaches -71.1 dB, and the matching thickness is 2.2 mm. The zinc oxide-coated carbon core-shell fiber material has high wave-absorbing performance and has wide application value. Description of the Drawings

[0035] Figure 1 : XRD pattern of the zinc oxide-coated carbon core-shell fiber prepared in Example 1;

[0036] Figure 2 : SEM images of the zinc oxide-coated carbon core-shell fiber prepared in Example 1 and its corresponding precursor; among them, (a) is the SEM image of the precursor of the zinc oxide-coated carbon core-shell fiber; (b) is the SEM image of the zinc oxide-coated carbon core-shell fiber;

[0037] Figure 3 : TEM image of the zinc oxide-coated carbon core-shell fiber prepared in Example 1;

[0038] Figure 4: Dielectric loss diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Example 1; wherein, (a) is the real part diagram of the dielectric constant; (b) is the imaginary part diagram of the dielectric constant; (c) is the dielectric loss tangent diagram;

[0039] Figure 5 : Impedance matching characteristic diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Example 1;

[0040] Figure 6 : Reflection loss diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Example 1, wherein, (a) is the three-dimensional reflection loss diagram; (b) is the two-dimensional reflection loss diagram;

[0041] Figure 7 : SEM diagram of the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 1;

[0042] Figure 8 : Dielectric loss diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 1; wherein, (a) is the real part diagram of the dielectric constant; (b) is the imaginary part diagram of the dielectric constant; (c) is the dielectric loss tangent diagram;

[0043] Figure 9 : Impedance matching characteristic diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 1;

[0044] Figure 10 : Reflection loss diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 1, wherein, (a) is the three-dimensional reflection loss diagram; (b) is the two-dimensional reflection loss diagram;

[0045] Figure 11 : SEM diagram of the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 2;

[0046] Figure 12 : Dielectric loss diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 2; wherein, (a) is the real part diagram of the dielectric constant; (b) is the imaginary part diagram of the dielectric constant; (c) is the dielectric loss tangent diagram;

[0047] Figure 13 : Impedance matching characteristic diagram of the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 2;

[0048] Figure 14 : Reflection loss diagram of the composite microwave absorption material corresponding to the zinc oxide-coated carbon core-shell fiber prepared in Comparative Example 2, wherein, (a) is the three-dimensional reflection loss diagram; (b) is the two-dimensional reflection loss diagram. Detailed implementation manners

[0049] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0050] In the prior art, although zinc oxide of different morphologies is widely used for electromagnetic wave absorption, due to its non-magnetic nature and low loss, it is difficult to use zinc oxide of any structure alone to achieve excellent wave absorption performance. Therefore, it is particularly necessary to introduce appropriate components into zinc oxide as a basic material to obtain a material with good wave absorption performance.

[0051] The present invention firstly disperses zinc salt and surfactant in a solvent, electrospins to obtain zinc-based fibers, and then heats and calcines the zinc-based fibers, adds pyridine and carbonizes them to obtain zinc oxide-coated carbon core-shell fibers. Zinc ions and surfactants self-assemble to form a fiber structure through coordination bonds, and the surfactant can bond and stabilize the morphology. After calcination, the surfactant containing only carbon, hydrogen and oxygen elements can be removed, and the zinc salt can be oxidized to obtain zinc oxide; and then high-temperature carbonization is performed. During this process, pyridine molecules are heated and vaporized, and are polymerized on the surface of the zinc-based oxide fiber precursor under the drive of molecular thermal motion. As the temperature cools, a carbon shell with a certain thickness is formed, and finally a hollow core-shell fiber material of zinc oxide-coated carbon is obtained.

[0052] From the perspective of composition, zinc oxide is a low-loss absorbing material that allows electromagnetic waves to enter the material smoothly without reflection; after carbon coating, the three-dimensional fiber network structure is still maintained to promote conductivity loss and multiple scattering. The two can work together to optimize impedance matching and increase multiple losses and scattering. From a structural perspective, the core-shell structure can increase interface polarization at the heterogeneous interface, the one-dimensional nanofiber has a large aspect ratio that can promote the transmission of electrons to promote conductivity loss, and the three-dimensional network of overlapping and interlaced fibers is conducive to multiple scattering and attenuation of electromagnetic waves.

[0053] The zinc oxide coated carbon hollow core-shell fiber material and paraffin are mixed and stirred at a temperature of 30-60° C. to obtain a wave absorbing material. Mixing at this stirring temperature can enhance the fluidity of the paraffin and help the paraffin and the zinc oxide coated carbon core-shell fiber to mix evenly.

[0054] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0055] The experimental materials used in the embodiments of the present invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0056] Embodiment 1:

[0057] (1) Zinc acetate dihydrate and polyvinylpyrrolidone are mixed and dispersed in N,N-dimethylformamide. After stirring for 60 min, a spinning solution is obtained. The spinning solution is transferred into a syringe for electrospinning and then dried at 50 °C for 6 h to obtain zinc-based fibers;

[0058] Among them, the addition ratio of zinc acetate dihydrate, polyvinylpyrrolidone and N,N-dimethylformamide is 1.1 g: 1.4 g: 10 mL; during the electrospinning process, the voltage at the needle tip is set to 12 kV, the receiving distance is 25 cm, and the supply rate of the spinning solution is 0.24 mL / h;

[0059] (2) The zinc-based fibers are placed in an air atmosphere and heated to 500 °C at a heating rate of 2 °C / min, and calcined at this temperature for 2 h, and then naturally cooled to room temperature to obtain a precursor;

[0060] The precursor and pyridine are mixed according to a feed liquid ratio of 0.1 g: 0.25 mL and carbonized at 425 °C for 3 h. After cooling to room temperature, zinc oxide-coated carbon core-shell fibers are obtained.

[0061] The structure of the zinc oxide-coated carbon core-shell fibers prepared in this example is characterized, and the results are as Figures 1 - 3 shown.

[0062] Figure 1 XRD pattern of the zinc oxide-coated nitrogen-doped carbon core-shell fibers prepared in Example 1, and it is determined that what is prepared is zinc oxide and carbon. Figure 2 (a) is the electron microscope image of the precursor prepared in this example. From Figure 2 (a), it can be seen that the diameter of the precursor is 110 - 120 nm. Figure 2 (b) is the SEM image of the zinc oxide-coated carbon core-shell fibers prepared in this example. From Figure 2 (b), it can be seen that the diameter of the zinc oxide-coated carbon core-shell fibers is 120 - 130 nm, and the fibers are well maintained without breakage. Figure 3 is the TEM image prepared in this example. From Figure 3 it can be seen that the prepared fibers have a core-shell structure, and among them, the thickness of the shell layer is about 5 - 10 nm.

[0063] Example 2:

[0064] (1) Zinc chloride and polyacrylonitrile are mixed and dispersed in N,N-dimethylformamide. After stirring for 60 min, a spinning solution is obtained. The spinning solution is transferred into a syringe for electrospinning and then dried at 50 °C for 6 h to obtain zinc-based fibers;

[0065] Among them, the addition amounts of zinc acetate dihydrate, polyvinylpyrrolidone, and N,N-dimethylformamide are in a ratio of 0.5 g: 1.5 g: 5 mL; during the electrospinning process, the voltage at the needle tip is set to 8 kV, the receiving distance is 20 cm, and the supply rate of the spinning solution is 0.1 mL / h;

[0066] (2) Place the zinc-based fiber in an air atmosphere, heat it to 300 °C at a heating rate of 1 °C / min, calcine it at this temperature for 1 h, and then naturally cool it to room temperature to obtain the precursor;

[0067] Mix the precursor and pyridine according to a material-liquid ratio of 0.1 g: 0.5 mL, and carbonize them at 400 °C for 4 h. After cooling to room temperature, zinc oxide-coated carbon core-shell fibers are obtained.

[0068] Example 3:

[0069] (1) Mix zinc acetate dihydrate and polyvinylpyrrolidone and disperse them in N,N-dimethylformamide. After stirring for 60 min, a spinning solution is obtained. Transfer the spinning solution into a syringe for electrospinning, and then dry it at 50 °C for 6 h to obtain zinc-based fibers;

[0070] Among them, the addition amounts of zinc acetate dihydrate, polyvinylpyrrolidone, and N,N-dimethylformamide are in a ratio of 0.1 g: 0.1 g: 3 mL; during the electrospinning process, the voltage at the needle tip is set to 15 kV, the receiving distance is 25 cm, and the supply rate of the spinning solution is 0.8 mL / h;

[0071] (2) Place the zinc-based fiber in an air atmosphere, heat it to 600 °C at a heating rate of 5 °C / min, calcine it at this temperature for 3 h, and then naturally cool it to room temperature to obtain the precursor;

[0072] Mix the precursor and pyridine according to a material-liquid ratio of 1 g: 0.1 mL, and carbonize them at 450 °C for 1 h. After cooling to room temperature, zinc oxide-coated carbon core-shell fibers are obtained.

[0073] Comparative Example 1:

[0074] The difference between this comparative example and Example 1 is that in step (3), the carbonization temperature is 380 °C.

[0075] The specific steps are as follows:

[0076] Place the zinc-based fiber in an air atmosphere, heat it to 500 °C at a heating rate of 2 °C / min, calcine it at this temperature for 2 h, and then naturally cool it to room temperature to obtain the precursor; mix the precursor and pyridine according to a material-liquid ratio of 0.1 g: 0.25 mL, and carbonize them at 380 °C for 3 h. After cooling to room temperature, zinc oxide-coated carbon core-shell fibers are obtained, where the preparation method of the zinc-based fiber is the same as that in Example 1.

[0077] The zinc oxide-coated carbon core-shell fibers prepared in this comparative example were subjected to structural characterization, and the results are as Figure 7 shown. From Figure 7 it can be seen that the prepared zinc oxide-coated carbon core-shell fibers were well maintained without damage.

[0078] Comparative Example 2:

[0079] The difference between this comparative example and Example 1 is that in step (3), the carbonization temperature was 470 °C.

[0080] The specific preparation method is as follows:

[0081] The zinc-based fibers were placed in an air atmosphere and heated to 500 °C at a heating rate of 2 °C / min, and calcined at this temperature for 2 h, and then naturally cooled to room temperature to obtain the precursor; the precursor and pyridine were mixed at a material-liquid ratio of 0.1 g:0.25 mL, and then carbonized at 470 °C for 3 h. After cooling to room temperature, zinc oxide-coated carbon core-shell fibers were obtained, wherein the preparation method of the zinc-based fibers was the same as that in Example 1.

[0082] The zinc oxide-coated carbon core-shell fibers prepared in this comparative example were subjected to structural characterization, and the results are as Figure 11 shown. Through Figure 11 it can be seen that the prepared zinc oxide-coated carbon core-shell fibers were well maintained without damage.

[0083] Test Example 1:

[0084] The dielectric loss performance, wave absorption performance, and impedance matching performance of the zinc oxide-coated carbon core-shell fibers prepared in Example 1 and Comparative Examples 1-2 were detected. The specific steps were as follows:

[0085] The zinc oxide-coated carbon core-shell fibers prepared in Example 1 and Comparative Examples 1-2 were respectively mixed with paraffin at a mass ratio of 0.025 g:0.075 g, and stirred at 60 °C to make them evenly mixed to obtain a composite wave-absorbing material. An Agilent Technologies E8363A electromagnetic wave vector network analyzer was used for electromagnetic parameter testing, and the wave absorption performance of the material was calculated based on the electromagnetic parameters.

[0086] Regarding dielectric loss: The real part of the dielectric constant represents the ability of the material to store electromagnetic waves, and the imaginary part represents the ability to dissipate electromagnetic waves. The tangent of dielectric loss is calculated from the ratio of the imaginary part of the dielectric constant to the real part of the dielectric constant, indicating the dielectric loss characteristics of the material. From Figure 4 , Figure 8 and Figure 12It can be seen that in the range of 2 - 18 GHz, the dielectric loss tangents of Example 1 and Comparative Examples 1 and 2 are all between 0.3 and 0.6, indicating that the dielectric loss capabilities of the materials themselves are similar. Whether the electromagnetic wave can be attenuated ultimately depends on whether the electromagnetic wave can enter the material interior, that is, the impedance matching characteristic.

[0087] Regarding impedance matching: The impedance matching characteristic of the wave - absorbing material represents the ratio of the impedance coefficient of the material to the impedance coefficient of the external free air. When the ratio is closer to 1, it indicates that the consistency of the impedance coefficients of the material and air is higher, which is conducive to the electromagnetic wave propagating in air entering the material interior for attenuation loss. The worse the impedance matching characteristic, the less conducive it is for the electromagnetic wave to enter the material interior, and most of them are reflected on the material surface. Figure 5 、 Figure 9 and Figure 13 It can be seen that the composite material prepared by the present invention has good impedance matching characteristics in the range of 2 - 18 GHz, while the materials prepared in Comparative Examples 1 - 2 have poor matching characteristics in the range of 2 - 18 GHz, resulting in poor wave - absorbing performance. Thus, it can be seen that the composite material prepared by the present invention by controlling the carbonization temperature has good impedance matching performance.

[0088] Regarding the electromagnetic wave absorption performance: Figure 6 It can be seen that the reflection loss of the composite wave - absorbing material prepared by the present invention to the electromagnetic wave is - 71.1 dB at 4.9 GHz, and the matching thickness is 2.2 mm. Figure 10 It can be seen that the reflection loss of the material prepared in Comparative Example 1 to the electromagnetic wave is - 24.8 dB at 9.3 GHz, and the matching thickness is 1.4 mm. Figure 12 It can be seen that the reflection loss of the material prepared in Comparative Example 2 to the electromagnetic wave is - 31.1 dB at 5.0 GHz, and the matching thickness is 1.8 mm. Thus, it can be seen that the composite wave - absorbing material prepared by the present invention has excellent electromagnetic wave absorption performance.

[0089] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for preparing zinc oxide coated carbon core-shell fiber, characterized in that: The following steps are involved: (1) mixing a zinc salt and a surfactant, dispersing the mixture into a solvent, and performing electrostatic spinning to obtain zinc-based fibers; (2) heating and calcining the zinc-based fiber to obtain a precursor; mixing the precursor with pyridine, and carbonizing the mixture at 400-450° C. for 1-4 hours to obtain zinc oxide-coated carbon core-shell fiber.

2. The method for preparing zinc oxide coated carbon core-shell fiber according to claim 1, characterized in that: In step (1), the zinc salt is one of zinc nitrate hexahydrate, zinc chloride, and zinc acetate dihydrate; the surfactant is polyvinyl pyrrolidone or polyacrylonitrile; and the solvent is N,N-dimethylformamide.

3. The method for preparing zinc oxide coated carbon core-shell fiber according to claim 1, characterized in that: In step (1), the ratio of the added amounts of zinc salt, surfactant and solvent is (0.1-1.5) g:(0.1-1.5) g:(3-10) mL.

4. The method for preparing zinc oxide coated carbon core-shell fiber according to claim 1, characterized in that: During the electrospinning process, the voltage was 8-15 kV and the feed rate was 0.1-0.8 mL / h.

5. The method for preparing zinc oxide coated carbon core-shell fiber according to claim 1, characterized in that: In step (2), during the heating and calcining process, the temperature is 300-600°C, the heating rate is 1-5°C / min, the time is 1-3h, and the heating and calcining atmosphere is air atmosphere.

6. The method for preparing zinc oxide coated carbon core-shell fiber according to claim 1, characterized in that: The ratio of the added amount of the precursor and pyridine is (0.1-1) g: (0.1-0.5) mL; during the carbonization process, the heating rate is 1-3°C / min.

7. The zinc oxide-coated carbon core-shell fiber prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the zinc oxide-coated carbon core-shell fiber according to claim 7 in the preparation of materials for absorbing electromagnetic waves.

9. The use according to claim 8, characterized in that The electromagnetic wave absorbing material is prepared by the following method: The zinc oxide coated carbon core-shell fiber and paraffin wax according to claim 7 are mixed in a mass ratio of (0.020-0.030):0.075 and stirred evenly at 30-60° C. to obtain an electromagnetic wave absorbing material.

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