CN108753251B - ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material and preparation method thereof - Google Patents
ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material and a preparation method thereof, relating to the technical field of electromagnetic wave absorbing materials. The method comprises the following steps: 1) dissolving a cobalt source and a zinc source in DMF, continuously adding PVP, and reacting after stirring to obtain a uniform viscous solution; 2) spinning the viscous solution obtained in the step 1) by adopting a high-voltage electrostatic spinning method to obtain organic nano fibers, and calcining the organic fibers after drying and pre-oxidation treatment; 3) and (3) placing the calcined product obtained in the step 2) in a reducing atmosphere for reduction treatment to obtain the catalyst. The ZnO/Co composite hollow nanofiber material prepared by combining the high-voltage electrostatic spinning method with calcination reduction has the characteristics of high saturation magnetic susceptibility, high coercive force, light weight, strong oxidation resistance and excellent electromagnetic wave absorption performance, and meanwhile, the preparation method is simple and easy to implement and low in cost.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave absorbing materials, in particular to a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material and a preparation method thereof.
Background
In recent years, the rapid development of remote sensing technology, computer technology and electronic communication technology inevitably brings problems of electromagnetic interference, electromagnetic radiation and the like, and meanwhile, the increasing electromagnetic energy density causes electromagnetic pollution and damages to the health of human bodies. In addition, electromagnetic wave absorbing materials have important applications in the military technology field. Therefore, the electromagnetic wave absorbing material has received more and more attention, especially for the absorption of electromagnetic wave in GHz frequency range, and is a hot spot of research. Considering the loss mechanism of the electromagnetic wave absorbing material, the material can be mainly divided into two categories, namely a magnetic wave absorbing material and a dielectric wave absorbing material. The traditional magnetic wave-absorbing material comprises ferrite and soft magnetic metal, and domain wall resonance, natural resonance and exchange resonance are main loss mechanisms of the magnetic wave-absorbing material.
Typical dielectric wave-absorbing materials include carbon materials, conductive polymers and metal oxides or sulfides, and the main loss mechanisms are interface polarization, dipole polarization, electron polarization and the like. It is known from the impedance matching condition in the electromagnetic wave absorption theory that it is difficult to satisfy the impedance matching condition by only one material, and it is also difficult to obtain an excellent electromagnetic wave absorption performance. Although the wave-absorbing property of zinc oxide is studied more deeply, zinc oxide as a non-magnetic material cannot provide proper magnetic loss, so that a good matching effect cannot be obtained, which limits the further development and application of the zinc oxide. To improve this deficiency, some researchers have combined zinc oxide with magnetic materials to achieve better electromagnetic wave absorption. For example, the document Nanoscale, 2014, 6(12) prepares ZnO/Fe3O4The composite porous ball reaches the maximum absorption when the matching thickness is 5mm, the maximum reflection loss reaches-40.0 dB, and a larger rising space exists.
In addition, most of the existing methods for preparing electromagnetic wave absorbing materials are hydrothermal or solvothermal methods, and for experimental research, the methods are simple to operate, but cannot be used for large-scale and industrial preparation of materials, so that the methods are not beneficial to practical application and industrial production. In addition, methods such as liquid phase exchange methods are expensive and cumbersome to operate, and are only suitable for laboratory studies. Therefore, there is a need to develop a zinc oxide electromagnetic wave absorbing material and a preparation method thereof, which are beneficial to practical application and industrial production and have good performance.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material and a preparation method thereof. The ZnO/Co composite hollow nanofiber material prepared by combining the high-voltage electrostatic spinning method with calcination reduction has the characteristics of high saturation magnetic susceptibility, high coercive force, light weight, strong oxidation resistance and excellent electromagnetic wave absorption performance, and meanwhile, the preparation method is simple and easy to implement, low in cost and extremely wide in industrial application prospect.
The first purpose of the invention is to provide a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material.
The second purpose of the invention is to provide a ZnO/Co composite nano hollow fiber electromagnetic wave absorber.
The third purpose of the invention is to provide a preparation method of the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material.
The fourth purpose of the invention is to provide the application of the high-voltage electrostatic spinning method in the preparation of the hollow fiber electromagnetic wave absorbing material.
The fifth purpose of the invention is to provide the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material, the preparation method thereof and the application of the ZnO/Co composite nano hollow fiber electromagnetic wave absorber.
In order to achieve the above purpose, the invention specifically discloses the following technical scheme:
the invention discloses a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material, which is a three-dimensional network structure formed by stacking one-dimensional hollow nano fibers, wherein the hollow nano fibers consist of ZnO and Co.
Preferably, in the electromagnetic wave absorbing material, the molar ratio of ZnO to Co is 1: 1; co is in a face-centered cubic structure, and ZnO is in a close-packed hexagonal structure.
Preferably, in the electromagnetic wave absorbing material, the outer diameter of the hollow nano-fiber is 200-300 nm.
Preferably, in the electromagnetic wave absorbing material, the wall thickness of the hollow nanofibers is 20-40 nm.
Preferably, the electromagnetic wave absorbing material has a saturation magnetic susceptibility of 31.15 emu/g.
Preferably, the coercive force H of the electromagnetic wave absorbing materialcIs 480.5 Oe.
The invention further discloses a ZnO/Co composite nano hollow fiber electromagnetic wave absorber which is prepared by mixing the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material prepared by the invention and paraffin.
Preferably, the mass ratio of the electromagnetic wave absorbing material to the paraffin is 1: 1.
Preferably, the absorber has a matching thickness of 3.0mm, a maximum absorption intensity at a frequency of 11.4GHz, and a reflection loss of-68.4 dB.
Preferably, the absorber is under single matching thickness, and when matching thickness was 2.6mm, the effective absorption bandwidth was 5.9GHz, the effective absorption bandwidth indicates: the electromagnetic wave absorption RL < -10dB, namely 90% of the electromagnetic wave is absorbed.
The invention further discloses a preparation method of the ZnO/Co composite nano hollow fiber electromagnetic wave absorption material, which comprises the following steps:
(1) with cobalt (II) acetylacetonate (C)10H14O4Co) or cobalt nitrate (Co (NO)3)2·9H2O) and zinc acetate dihydrate C4H6O4Zn·2H2Using polyvinylpyrrolidone (PVP) to provide the viscosity of the electrospinning solution, and using N, N-Dimethylformamide (DMF) as a solvent; dissolving cobalt acetylacetonate or cobalt nitrate and zinc acetate in DMF, continuously adding PVP, stirring and reacting to obtain a uniform viscous solution;
(2) spinning the viscous solution in the step (1) by adopting a high-voltage electrostatic spinning method to obtain organic nano-fibers, and calcining the organic nano-fibers after drying and pre-oxidation treatment;
(3) and (3) placing the calcined product in the step (2) in a reducing atmosphere for reduction treatment to obtain the catalyst.
In the step (1), the adding proportion of cobalt acetylacetonate or cobalt nitrate, zinc acetate dihydrate, DMF and PVP is 1 mmol: 1-3 mmol: 10 ml: 1-1.5g, preferably 1 mmol: 1 mmol: 10 ml: 1.5 g.
In the step (1), the reaction temperature is 500-600 ℃, and the reaction time is 3-5 h.
In the step (2), the voltage of the high-voltage electrostatic spinning method is 10-15 kV.
In the step (2), the drying temperature and time are as follows: 30-80 ℃ and 12-24 h.
In the step (2), the pre-oxidation treatment comprises the following steps: keeping the temperature at 150 ℃ and 300 ℃ for 1-4 h.
In the step (2), the calcination temperature is 400-700 ℃, and the time is 3-5 h.
In the step (3), the reducing atmosphere is hydrogen.
In the step (3), the heat preservation temperature is 200-400 ℃, and the time is 1-3 h.
In the step (3), the reduction treatment is performed in a closed tube furnace.
Finally, the invention also discloses a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material and a preparation method thereof, and application of the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing body in radio communication systems, high-frequency and microwave heating prevention equipment, microwave darkroom construction and stealth technologies.
It should be noted that, the metal cobalt has higher saturation magnetic susceptibility and Snoek limit, and is favorable for obtaining better chemical stability and saturation magnetic susceptibility performance after being compounded with the zinc oxide; in addition, in addition to the consideration of the intrinsic matching characteristics and loss properties of the material, the microstructure, the particle size, the morphology and the like of the material also have an important influence on the electromagnetic wave absorption performance of the material, and the hollow structure can provide a larger specific surface area and better dispersibility, improve the direct contact area of the electromagnetic wave and the absorption material, and is more beneficial to the absorption of the electromagnetic wave. Meanwhile, the hollow structure can effectively introduce air, reduce the relative dielectric constant of the material and be beneficial to improving the impedance matching performance of the material;
the high-voltage electrostatic spinning equipment is relatively simple, the operation is simple and convenient, the controllability is strong, and the high-voltage electrostatic spinning equipment is already used for actual industrial production, so that the solid nano-fibers with one-dimensional microstructures are prepared by utilizing the high-voltage electrostatic spinning, a three-dimensional network is constructed by the solid nano-fibers, the solid nano-fibers can be converted into hollow nano-fibers by combining a subsequent heat treatment mode, and the microstructures can provide larger specific surface area and long-range conductivity loss, are favorable for multiple reflection and multiple scattering of electromagnetic waves, and are favorable for further improving the absorption performance of the electromagnetic waves.
The principle of the invention is as follows: firstly, in the electrostatic spinning process, when the electric field force applied to the liquid solution is greater than the surface tension of the solution, the solution is pulled out from the positive electrode under the action of the electric field force and flies to the negative electrode; the PVP increases the viscosity of the solution, so that the solution cannot be broken into small droplets in the stretching process and is adhered to form filaments, the volatile solvent DMF is volatilized in the flying process of the nanowires, and finally the obtained solid nanofibers are received by the negative electrode. Thus obtaining the organic nano-fiber compounded by cobalt acetylacetonate or cobalt nitrate, zinc acetate and PVP.
Secondly, the formation of hollow structures, which benefit from the atomic diffusion process driven by the kirkendall effect: in the calcination process of the organic nano-fiber, because the diffusion speed of oxygen in the fiber is less than that of metal ions (cobalt and zinc), the metal ions diffuse to the outer layer of the fiber and are combined with the oxygen to form metal oxide, and at the same time, PVP is continuously oxidized and decomposed, so that the organic nano-fiber is finally converted into oxide (zinc oxide and cobaltosic oxide) nano hollow fiber.
And finally, in the reduction process, hydrogen is used as a reducing agent to reduce cobaltosic oxide into metallic cobalt, but zinc oxide cannot be reduced, and finally the ZnO/Co composite hollow nano-fiber is obtained.
Compared with the prior art, the invention has the beneficial effects that:
(1) the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material prepared by the invention has excellent impedance matching performance and unique micro-morphology, can keep suitable magnetic conductivity in a high-frequency range, and has very excellent electromagnetic wave absorbing performance.
(2) The hollow structure has the characteristic of light weight, so the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material prepared by the invention can be used for preparing a light electromagnetic wave absorber with thin thickness.
(3) The preparation method has the advantages of simple preparation process, no need of complex hardware equipment, no pollution to the environment, low manufacturing cost and suitability for industrial production.
(4) The ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material prepared by the invention has uniform fiber size and strong oxidation resistance and corrosion resistance.
(5) The ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material prepared by the invention has the saturation susceptibility of 31.15emu/g and the coercive force HcCan reach 480.5 Oe; when the mass ratio of the ZnO/Co composite hollow nano-fiber to the paraffin in the prepared absorber is 1:1, the prepared absorber reaches the maximum absorption strength when the matching thickness is 3.0mm and the frequency is 11.4GHz, and the reflection loss is-68.4 dB; under single matching thickness, when the matching thickness is 2.6mm, the effective absorption frequency bandwidth can reach 5.9 GHz.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 shows the ZnO/Co ratios obtained after calcination in example 13O4An XRD diffraction pattern of the composite hollow nanofiber material and an XRD diffraction pattern of the ZnO/Co composite hollow nanofiber electromagnetic wave absorption material.
Fig. 2 is an SEM image of the organic nanofibers prepared in example 1.
Fig. 3 is an SEM image of the ZnO/Co composite hollow nanofiber electromagnetic wave absorbing material prepared in example 1.
FIG. 4 is a TEM image of the ZnO/Co composite hollow nanofiber electromagnetic wave-absorbing material prepared in example 1.
FIG. 5 is a magnetic property test curve of the ZnO/Co composite hollow nanofiber electromagnetic wave absorbing material prepared in example 1.
FIG. 6 is an electromagnetic wave absorption curve of the ZnO/Co composite hollow nanofiber electromagnetic wave absorption material prepared in example 1.
Fig. 7 is an electromagnetic wave absorption curve of the ZnO hollow nanofiber electromagnetic wave absorption material prepared in comparative example 1.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As introduced in the background art, most of the existing methods for preparing electromagnetic wave absorbing materials are hydrothermal or solvothermal methods, and for experimental research, the method is simple and convenient to operate, but cannot be used for large-scale and industrial preparation of materials, so that the method is not beneficial to practical application and industrial production, and methods such as a liquid phase exchange method are expensive in price, complicated to operate, and only suitable for laboratory research, so that the invention provides a method for preparing a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material by using an electrostatic spinning process, and the invention is further described with reference to the accompanying drawings and specific embodiments.
In the examples of the present invention, cobalt (II) (C) acetylacetonate is used10H14O4Co) or cobalt nitrate (Co (NO)3)2·9H2O), zinc acetate dihydrate (C)4H6O4Zn·2H2O) is a cobalt source and a zinc source respectively, the viscosity of the electrospinning solution is provided by polyvinylpyrrolidone (PVP), and N, N-Dimethylformamide (DMF) is taken as a solvent.
Example 1
A preparation method of a ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material comprises the following steps:
(1) dissolving 1mmol of cobalt acetylacetonate and 1mmol of zinc acetate dihydrate in 10ml of DMF, fully dissolving, adding 1.5g of PVP, stirring, and reacting at 600 ℃ for 3 hours to obtain a uniform viscous solution;
(2) spinning the viscous solution in the step (1) by using a high-voltage electrostatic spinning process under the condition of 12kV high-voltage static electricity to obtain organic fibers, drying the organic fibers at 50 ℃ for 20 hours, carrying out pre-oxidation treatment at 200 ℃ for 3 hours, placing the organic fibers in a muffle furnace in an air atmosphere, and calcining the organic fibers at 600 ℃ for 3 hours;
(3) and (3) placing the calcined product in the step (2) in a closed tubular furnace, and carrying out reduction treatment at 400 ℃ for 1h in a hydrogen atmosphere to obtain the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material.
Comparative example 1
The difference from example 1 is that: cobalt (II) acetylacetonate as a cobalt source was not added.
Example 2
The difference from example 1 is that: in step (1), cobalt nitrate (Co (NO) is used3)2·9H2O) instead of cobalt (II) acetylacetonate (C)10H14O4Co). In the step (2), the drying time and temperature are as follows: 30 ℃ for 24 hours; the time and temperature of the pre-oxidation treatment were: pre-oxidation treatment is carried out for 1h at 300 ℃.
Example 3
The difference from example 1 is that: in the step (1), the addition amount of PVP is 1.0 g. In the step (2), the drying time and temperature are as follows: 80 ℃ for 12 h; the time and temperature of the pre-oxidation treatment were: pre-oxidation treatment at 150 ℃ for 4 h.
Example 4
The difference from example 1 is that: in the step (1), the addition amount of the zinc acetate dihydrate is 2 mmol. In the step (2), the drying time and temperature are as follows: at 70 ℃ for 20 h; the time and temperature of the pre-oxidation treatment were: pre-oxidation treatment is carried out for 2h at 250 ℃.
Example 5
The difference from example 1 is that: in the step (1), the reaction temperature is 500 ℃, and the reaction time is 5 hours. In the step (2), the voltage of the high-voltage electrostatic spinning method is 10kV, the calcining temperature is 700 ℃, and the time is 3 h. In the step (3), the heat preservation temperature is 200 ℃ and the time is 3 h.
Example 6
The difference from example 1 is that: in the step (1), the addition amount of the zinc acetate dihydrate is 3mmol, the reaction temperature is 550 ℃, and the reaction time is 4 h. In the step (2), the voltage of the high-voltage electrostatic spinning method is 15kV, the calcining temperature is 400 ℃, and the time is 5 h. In the step (3), the heat preservation temperature is 300 ℃ and the time is 2 hours.
And (3) performance testing:
XRD test of the ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material prepared in example 1 shows that the ZnO/Co composite hollow nano fiber contains metal cobalt with a body-centered cubic structure and zinc oxide with a hexagonal structure, and the comparison with standard diffraction data (JCPDS-150806) and (JCPDS-361451) shows that the purity of the synthesized iron is very high, as shown in figure 1.
When the organic nanofibers prepared in example 1 are observed under SEM, the results are shown in fig. 2, and it can be seen that: the organic nanofibers had a diameter of about 450nm and were solid fibers.
When the ZnO/Co composite hollow nanofiber electromagnetic wave absorbing material prepared in example 1 is observed under SEM and TEM, the results are shown in fig. 3 and 4, and it can be seen that: the nano-fiber after hydrogen reduction is a hollow structure, the wall thickness is between 20 and 40nm, and the outer diameter is between 200 and 300 nm.
The magnetic performance of the ZnO/Co composite hollow nanofiber electromagnetic wave absorbing material prepared in example 1 was tested with a VSM magnetometer, and the results are shown in fig. 5, where it can be seen that: saturation magnetic susceptibility of 31.15emu/g and coercive force HcUp to 480.5 Oe.
The ZnO/Co composite hollow nanofiber electromagnetic wave absorbing material prepared in example 1 and paraffin were mixed in a mass ratio of 1:1 and pressed into an annular absorber sample (D)Outer cover×dInner partXh ═ 7 × 3.04 × 2.0mm), the relevant parameter epsilonrAnd murBy AgileThe reflection loss is measured by an electromagnetic wave vector network analyzer of nt Technologies E8363Ar、μrThe absorption frequency and the thickness of the sample, and the electromagnetic wave absorption curve of the absorber is shown in FIG. 6, where it can be seen that εr' the range is 2-18GHz, which is a value between 5.4 and 9.2. Epsilonr"three resonance peaks at 10.0GHz, 14.0GHz and 15.2GHz respectively. Mu.sr' and murThe variation ranges are respectively 0.91-1.14 and 0-0.21, the minimum value of the absorption peak is-68.4 dB, and the bandwidth with the absorption rate of less than-10 dB under a single thickness is 5.9 GHz.
The ZnO hollow nanofiber electromagnetic wave absorbing material prepared in comparative example 1 and paraffin were mixed in a mass ratio of 1:1 and pressed into an annular absorber sample (D)Outer cover×dInner partXh ═ 7 × 3.04 × 2.0mm), the off-parameter ∈rAnd murReflection loss measured by Agilent technologies E8363A electromagnetic wave vector network analyzer isr、μrThe absorption frequency and the thickness of the sample, and the electromagnetic wave absorption curve of the absorber is shown in fig. 7, it can be seen that the electromagnetic wave absorption performance is deteriorated and the effective band is narrowed. In addition, XRD results show that the prepared ZnO/Co composite hollow nanofiber electromagnetic wave absorbing material is zinc oxide with a hexagonal structure, and because the material does not contain a magnetic substance, the impedance matching performance of the material is poor, the electromagnetic wave absorbing performance is poor, the effective frequency band is narrowed, and the absorption of electromagnetic waves is not facilitated.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (18)
1. A preparation method of a ZnO/Co composite nano hollow fiber electromagnetic wave absorption material is characterized by comprising the following steps: the method comprises the following steps:
(1) cobalt II acetylacetonate or cobalt nitrate and zinc acetate dihydrate are used as raw materials, polyvinylpyrrolidone is used for providing the viscosity of an electrospinning solution, and N, N-dimethylformamide is used as a solvent; dissolving cobalt acetylacetonate or cobalt nitrate and zinc acetate in DMF, continuously adding PVP, stirring and reacting to obtain a uniform viscous solution;
(2) spinning the viscous solution in the step (1) by adopting a high-voltage electrostatic spinning method to obtain organic nano-fibers, and calcining the organic nano-fibers after drying and pre-oxidation treatment;
(3) and (3) placing the calcined product obtained in the step (2) in a reducing atmosphere for heat preservation and reduction treatment to obtain the catalyst.
2. The method of claim 1, wherein: in the step (1), the adding proportion of cobalt acetylacetonate or cobalt nitrate, zinc acetate dihydrate, DMF and PVP is 1 mmol: 1-3 mmol: 10 ml: 1-1.5 g.
3. The method of claim 1, wherein: in the step (1), the adding proportion of cobalt acetylacetonate or cobalt nitrate, zinc acetate dihydrate, DMF and PVP is 1 mmol: 1 mmol: 10 ml: 1.5 g.
4. The method of claim 1, wherein: in the step (1), the reaction temperature is 500-600 ℃, and the reaction time is 3-5 h.
5. The method of claim 1, wherein: in the step (2), the drying temperature and time are as follows: 30-80 ℃ and 12-24 h.
6. The method of claim 1, wherein: in the step (2), the pre-oxidation treatment comprises the following steps: keeping the temperature at 150 ℃ and 300 ℃ for 1-4 h.
7. The method of claim 1, wherein: in the step (2), the voltage of the high-voltage electrostatic spinning method is 10-15 kV.
8. The method of claim 1, wherein: in the step (2), the calcination temperature is 400-700 ℃, and the time is 3-5 h.
9. The method of claim 1, wherein: in the step (3), the reducing atmosphere is hydrogen.
10. The method of claim 1, wherein: in the step (3), the heat preservation temperature is 200-400 ℃, and the time is 1-3 h.
11. The method of claim 1, wherein: in the step (3), the reduction treatment is performed in a closed tube furnace.
12. A ZnO/Co composite nano hollow fiber electromagnetic wave absorbing material is characterized in that: the electromagnetic wave absorbing material is a three-dimensional network structure formed by stacking one-dimensional hollow nanofibers, and the hollow nanofibers are composed of ZnO and Co, wherein Co is a body-centered cubic structure, and ZnO is a close-packed hexagonal structure;
the outer diameter of the hollow nanofiber is 200-300nm, the wall thickness of the hollow nanofiber is 20-40nm, and the molar ratio of ZnO to Co in the electromagnetic wave absorbing material is 1: 1.
13. An electromagnetic wave absorbing material as set forth in claim 12, wherein: the saturation magnetic susceptibility of the electromagnetic wave absorption material is 31.15emu/g, and the coercive force HcIs 480.5 Oe.
14. A ZnO/Co composite nano hollow fiber electromagnetic wave absorber is prepared by mixing an electromagnetic wave absorbing material and paraffin, and is characterized in that: the electromagnetic wave absorbing material is an electromagnetic wave absorbing material prepared by the method of any one of claims 1 to 11 and/or an electromagnetic wave absorbing material of claim 12 or 13.
15. The electromagnetic wave absorber of claim 14, wherein: the mass ratio of the electromagnetic wave absorbing material to the paraffin is 1: 1.
16. The electromagnetic wave absorber of claim 14, wherein: the absorber has a matching thickness of 3.0mm, reaches the maximum absorption intensity at a frequency of 11.4GHz, and has a reflection loss of-68.4 dB.
17. The electromagnetic wave absorber of claim 14, wherein: the absorber is under single matching thickness, and when matching thickness was 2.6mm, effective absorption bandwidth was 5.9 GHz.
18. Use of the method according to any one of claims 1 to 11 and/or the electromagnetic wave absorbing material according to claim 12 or 13 and/or the absorber according to any one of claims 14 to 17 in telecommunications systems, high frequency protection, microwave heating equipment, construction of microwave darkrooms, stealth technology.
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