Wave-absorbing material and preparation method thereof

Abstract

The invention relates to the technical field of composite materials, in particular to a wave-absorbing material and a preparation method thereof. According to the wave-absorbing material, pretreated polylactic acid melt-blown fibers serve as a template, the surfaces of the polylactic acid melt-blown fibers are coated with graphene oxide nanosheets loaded with magnetic particles through vacuum impregnation and ultrasonic treatment, and the wave-absorbing material is prepared after the template is removed. The wave-absorbing material is a micron-sized hollow tubular magnetic graphene wave-absorbing material, and the problem that magnetic nanoparticles are prone to agglomeration is solved while light weight and wave absorption are achieved. The graphene oxide sheet layers loaded with the magnetic particles are stacked into the carbon micron tube, so that the dielectric property of the composite material can be regulated and controlled by utilizing heteroatoms on the graphene oxide sheet layers, and stronger absorption can be realized by utilizing the dielectric confinement effect and interface polarization loss of the graphene oxide sheet layers; and effective absorption of wider frequency can be realized by utilizing the synergistic effect of dielectric loss and magnetic loss. Experiments show that the wave-absorbing material provided by the invention is light in weight, wide in frequency and strong in absorption.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a wave absorbing material and a preparation method thereof. Background Art

[0002] With the rapid development of electronic information technology, electromagnetic waves have become widely used. However, the accompanying problem of electromagnetic wave pollution is also becoming increasingly serious. In daily life, electromagnetic waves permeating space pose a potential threat to human health. In the information technology field, the leakage of electromagnetic waves raises information security issues. In the military, radar electromagnetic waves pose a significant threat to certain weapons and equipment. To more effectively utilize electromagnetic waves and reduce the occurrence of adverse factors, the development of electromagnetic shielding materials that primarily absorb electromagnetic waves is particularly important.

[0003] An ideal absorbing material should be lightweight, broadband, and offer strong absorption at a relatively thin thickness. Traditional absorbing materials, such as ferrites, magnetic alloys, and ceramics, suffer from common drawbacks such as high density, poor impedance matching, narrow effective absorption bandwidth, and low corrosion resistance. Pure carbon materials, due to their excellent electrical conductivity, exhibit an impedance mismatch with incident electromagnetic waves. Furthermore, traditional carbon materials, such as carbon black and carbon nanotubes, have limited structural designability, making them unsuitable as absorbing materials. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide an absorbing material and a preparation method thereof. The absorbing material provided by the present invention is lightweight, broadband, and has strong absorption.

[0005] The invention provides a wave absorbing material, which is prepared by using pretreated polylactic acid melt-blown fibers as a template, coating graphene oxide nanosheets loaded with magnetic particles on the surface of the polylactic acid melt-blown fibers through vacuum impregnation and ultrasonic treatment, and then removing the template.

[0006] Preferably, the absorbing material is prepared by mixing pretreated polylactic acid meltblown fibers and a graphene oxide solution loaded with magnetic particles, vacuum impregnation and ultrasonic treatment, and then heat treatment under inert gas conditions.

[0007] Preferably, the polylactic acid meltblown fiber is polyethylene glycol plasticized polylactic acid meltblown fiber, which is prepared by mixing polyethylene glycol and polylactic acid masterbatch.

[0008] Preferably, the pretreated polylactic acid meltblown fiber is a low-temperature pretreated polylactic acid meltblown fiber; the pretreated polylactic acid meltblown fiber is prepared according to the following method:

[0009] Polyethylene glycol and polylactic acid masterbatch are mixed and granulated, and then spun to obtain polylactic acid melt-blown fiber, which is then subjected to low-temperature treatment to obtain pretreated polylactic acid melt-blown fiber.

[0010] Preferably, the theoretical relative molecular mass of the polyethylene glycol is 500 to 2000;

[0011] The diameter of the polylactic acid meltblown fiber is 3 to 5 μm;

[0012] The temperature of the low temperature treatment is 60-80°C.

[0013] Preferably, the method for preparing the graphene oxide solution loaded with magnetic particles comprises the following steps:

[0014] The graphene oxide solution is mixed with magnetic particles, and then mixed with ammonia water for precipitation, and then heated to volatilize the ammonia water to obtain the graphene oxide solution loaded with magnetic particles.

[0015] Preferably, the concentration of the graphene oxide solution is 0.5 to 2.5 g / L;

[0016] The magnetic particles are selected from at least one of an iron-containing compound, a cobalt-containing compound, and a nickel-containing compound;

[0017] The mass ratio of the magnetic particles to the graphene oxide is 1:5-10;

[0018] The temperature for heating to volatilize the ammonia solution is 50-70°C.

[0019] Preferably, the vacuum degree of the vacuum impregnation is below 20 Pa, and the time is 10 to 60 minutes;

[0020] The power of the ultrasonic treatment is 240-300W, and the time is 10-60s.

[0021] Preferably, the inert gas is selected from argon or nitrogen;

[0022] The heat treatment temperature is 500-800° C. and the time is 2-4 hours.

[0023] The present invention also provides a method for preparing the above-mentioned absorbing material, comprising the following steps:

[0024] The pretreated polylactic acid melt-blown fibers and the graphene oxide solution loaded with magnetic particles are mixed, vacuum impregnated and ultrasonically treated, and then heat-treated under inert gas conditions to prepare the absorbing material.

[0025] The present invention provides an absorbing material. Using pretreated polylactic acid meltblown fibers as a template, magnetic particle-loaded graphene oxide nanosheets are coated on the surface of the polylactic acid meltblown fibers via vacuum impregnation and ultrasonic treatment, and the template is removed to produce the material. The absorbing material provided by the present invention is a micron-sized hollow tubular magnetic graphene absorbing material. The hollow tubular structure of the present invention can address the problem of high bulk density of magnetic materials, achieving lightweight and wave-absorbing properties while also addressing the problem of easy agglomeration of magnetic nanoparticles. Stacking magnetic particle-loaded graphene oxide sheets into carbon microtubes allows, firstly, the dielectric properties of the composite material to be modulated by utilizing heteroatoms on the graphene oxide sheets; secondly, the dielectric confinement effect and interfacial polarization loss of the graphene oxide sheets can be exploited to achieve enhanced absorption; and thirdly, the synergistic effect of dielectric loss and magnetic loss can be utilized to achieve effective absorption over a wider frequency band. Experimental results demonstrate that the absorbing material provided by the present invention is lightweight, broadband (effectively absorbing electromagnetic waves over a wider frequency band), and highly absorbing (excellent electromagnetic wave absorption). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a SEM image of the micron-sized hollow tubular magnetic graphene absorbing material prepared in Example 1 of the present invention at a voltage of 10 kV;

[0027] Figure 2 This is a SEM image of the micron-sized hollow tubular magnetic graphene absorbing material prepared in Example 1 of the present invention at a low voltage of 5 kV;

[0028] Figure 3 These are the reflection loss curves of the absorbing materials prepared in Examples 1 to 3 of the present invention for electromagnetic waves in the frequency band of 2 to 18 GHz, and the effective absorption bandwidth at a thickness of 2.35 mm. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] The invention provides a wave absorbing material, which is prepared by using pretreated polylactic acid melt-blown fibers as templates, coating graphene oxide (GO) nanosheets loaded with magnetic particles on the surface of the polylactic acid melt-blown fibers through vacuum impregnation and ultrasonic treatment, and then removing the template.

[0031] Specifically, the absorbing material is prepared by mixing pretreated polylactic acid meltblown fibers and a graphene oxide (GO) solution loaded with magnetic particles, vacuum impregnation and ultrasonic treatment, and then heat treatment under inert gas conditions.

[0032] The present invention has no special restriction on the usage ratio of the pretreated polylactic acid meltblown fiber and the graphene oxide (GO) solution loaded with magnetic particles, as long as the pretreated polylactic acid meltblown fiber can be completely immersed in the graphene oxide (GO) solution loaded with magnetic particles.

[0033] In some embodiments of the present invention, the polylactic acid meltblown fibers are polyethylene glycol (PEG)-plasticized polylactic acid meltblown fibers that do not self-bond to form a meltblown fabric. Specifically, the polylactic acid meltblown fibers are made by mixing polyethylene glycol (PEG) and polylactic acid (PLA) masterbatch. The mass ratio of the polyethylene glycol to the polylactic acid masterbatch is 3:100. The polylactic acid meltblown fibers have a diameter of 3 to 5 μm.

[0034] In some embodiments of the present invention, the pretreated polylactic acid meltblown fiber is a low-temperature pretreated polylactic acid meltblown fiber. Specifically, the pretreated polylactic acid meltblown fiber is prepared according to the following method:

[0035] Polyethylene glycol and polylactic acid masterbatch are mixed and granulated, and then spun to obtain polylactic acid melt-blown fiber, which is then subjected to low-temperature treatment to obtain pretreated polylactic acid melt-blown fiber.

[0036] The mixing and granulation are carried out in a twin-screw granulator. The spinning is carried out using a melt-blowing machine.

[0037] The polyethylene glycol is used as a plasticizer, and its theoretical relative molecular weight is 500 to 2000, for example, 500. The diameter of the polylactic acid meltblown fiber is 3 to 5 μm.

[0038] The temperature of the low-temperature treatment is 60-80° C., such as 60° C., 70° C., and 80° C.; and the time is 8-24 hours, such as 8 hours, 16 hours, and 24 hours.

[0039] In some embodiments of the present invention, the method for preparing the graphene oxide (GO) solution loaded with magnetic particles comprises the following steps:

[0040] After the graphene oxide solution and the magnetic particles are mixed evenly, the obtained liquid is mixed with ammonia water for precipitation, and then heated to volatilize the ammonia water to obtain a graphene oxide (GO) solution loaded with magnetic particles.

[0041] The concentration of the graphene oxide solution is 0.5 to 2.5 g / L, for example 0.5 g / L. The graphene oxide flakes used to prepare the graphene oxide solution have a diameter of 5 to 15 μm. The present invention has no particular limitation on the method for preparing the graphene oxide solution, and any method known to those skilled in the art can be used.

[0042] The magnetic particles are selected from at least one of an iron-containing compound, a cobalt-containing compound, and a nickel-containing compound; specifically, at least one of ferric chloride, ferric nitrate, cobalt chloride, cobalt nitrate, nickel chloride, and nickel nitrate; for example, the molar ratio of ferric chloride to cobalt chloride is 2:1. The mass ratio of the magnetic particles to the graphene oxide is 1:5 to 10, for example, 1:5.

[0043] The pH value of the obtained liquid after mixing with ammonia water is 8.5 to 9.5, for example 9.

[0044] The temperature for heating the ammonia solution to volatilize is 50-70° C., for example, 50° C. The ammonia solution is heated to completely volatilize.

[0045] In some embodiments of the present invention, the vacuum impregnation is performed at a vacuum level of less than 20 Pa for a duration of 10 to 60 minutes, such as 10 minutes. The ultrasonic treatment is performed at a power of 295 to 305 W, such as 300 W, for a duration of 10 to 60 seconds, such as 10 seconds. The ultrasonic treatment can intensify the Brownian motion of the GO sheets, increasing the probability of collision with the fibers, while also utilizing the cavitation effect of the ultrasound to achieve coating of the GO sheets with the PLA fibers.

[0046] In some embodiments of the present invention, after the ultrasonic treatment, the process further includes draining excess water and drying. The drying is performed by forced air drying at a temperature of 40°C to 60°C, for example, 40°C, and for a time of 24 to 48 hours, for example, 24 hours.

[0047] In some embodiments of the present invention, the inert gas is selected from argon or nitrogen.

[0048] In some embodiments of the present invention, the heat treatment is performed at a temperature of 500-800° C., such as 500° C., and for a time of 2-4 hours, such as 2 hours.

[0049] In the present invention, the absorbing material is a micron-sized hollow tubular magnetic graphene absorbing material, and the diameter of the absorbing material is 3 to 5 μm.

[0050] The present invention also provides a method for preparing the above-mentioned absorbing material, comprising the following steps:

[0051] The pretreated polylactic acid melt-blown fibers and the graphene oxide solution loaded with magnetic particles are mixed, vacuum impregnated and ultrasonically treated, and then heat-treated under inert gas conditions to prepare the absorbing material.

[0052] The raw material components, proportions and steps involved in the preparation method are the same as above and will not be repeated here.

[0053] The present invention uses PLA melt-blown fibers, which are easy to mass produce, low-cost, and have uniform diameters, as templates. The designed hollow tubular microstructure helps solve the problem of difficult dispersion of nanomaterials. The magnetic material is coated between the GO sheets, making it difficult to fall off, and can achieve stable wave absorption performance. The preparation method of hollow tubular magnetic graphene is low-cost and easy to prepare on a large scale.

[0054] The present invention has no particular limitation on the sources of the raw materials used above, and they can be generally commercially available.

[0055] In order to further illustrate the present invention, a wave absorbing material and a preparation method thereof provided by the present invention are described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] 1) PEG with a theoretical relative molecular mass of 500 is used as a plasticizer, and is blended and granulated with PLA masterbatch in a twin-screw granulator, wherein the mass ratio of the PEG to the PLA masterbatch is 3:100. The fibers are then spun through a melt-blown machine to prepare PLA melt-blown fibers with a fiber diameter of 3 to 5 μm, and then treated at 60° C. for 8 h to obtain pretreated PLA melt-blown fibers.

[0058] 2) Prepare 0.5 g / L GO solution;

[0059] 0.5 g GO powder was weighed, dissolved in 1000 mL of aqueous solution, and dispersed by ultrasonication for 30 min to prepare a 0.5 g / L GO solution.

[0060] 0.1 g of a mixture of ferric chloride and cobalt chloride (the molar ratio of ferric chloride to cobalt chloride is 2:1) was added to the GO solution and mixed evenly. Ammonia water was then added to the resulting solution to adjust the pH to 9 to precipitate the iron and cobalt magnetic ions. The solution was heated at 50° C. to completely evaporate the ammonia water, thereby obtaining a GO solution loaded with magnetic particles.

[0061] 3) The PLA melt-blown fiber obtained in step 1) was completely immersed in the GO solution loaded with magnetic particles obtained in step 2), and the mixture was first evacuated to a vacuum degree below 20 Pa and immersed for 10 minutes, then ultrasonically treated (power of 300 W) for 10 seconds, excess water was drained, and the mixture was dried at 40°C for 24 hours. Finally, the mixture was treated at 500°C for 2 hours under a nitrogen atmosphere to obtain a micron-sized hollow tubular magnetic graphene absorber.

[0062] Figure 1 This is a SEM image of the micron-sized hollow tubular magnetic graphene absorbing material prepared in Example 1 of the present invention at a voltage of 10KV. Figure 1The diameter of the micron-sized hollow tubular magnetic graphene absorber is 3 to 5 μm. Magnetic particles are supported on the graphene sheets. The bright spots on the micron-sized hollow tubular graphene are nanomagnetic particles. This indicates that the nanomagnetic particles have been grown in situ on the graphene sheets through co-precipitation and high-temperature annealing. The micron-sized hollow tubular magnetic graphene was ultimately prepared by combining graphene with magnetic materials.

[0063] Figure 2 This is a SEM image of the micron-sized hollow tubular magnetic graphene absorbing material prepared in Example 1 of the present invention at a low voltage of 5KV. Figure 1 and Figure 2 It can be seen that the line diameter of the micron-sized hollow tubular magnetic graphene absorbing material is relatively uniform.

[0064] The micron-sized hollow tubular magnetic graphene absorbing material was blended with paraffin wax. The mass fraction of the absorbing material in the blended material was 3%. A small coaxial device with an outer diameter of 7 mm and an inner diameter of 3.04 mm was prepared. The electromagnetic parameters were measured, and the reflection loss (RL) value was calculated according to formulas (1) to (4).

[0065]

[0066]

[0067] ε r =ε′-jε" (3);

[0068] μ r =μ′-jμ" (4);

[0069] Among them, Z in is the input impedance of the absorbing material, in Ω; Z0 is the input impedance of free space, in Ω; ε r is the complex dielectric constant; μ r is the complex magnetic permeability; ε′ is the real part of the complex dielectric constant; ε″ is the imaginary part of the complex dielectric constant; μ′ is the real part of the complex magnetic permeability; μ″ is the imaginary part of the complex magnetic permeability; f is the frequency of the electromagnetic wave, in Hz; d is the thickness of the absorbing layer, in m; c is the speed of light in vacuum, in m / s.

[0070] Figure 3 The reflection loss curves of the absorbing materials prepared in Examples 1 to 3 of the present invention for electromagnetic waves in the frequency range of 2 to 18 GHz, as well as the effective absorption bandwidth at a thickness of 2.35 mm. Figure 3 It can be seen that the minimum reflection loss (RL min) value is -18.58dB, and the effective absorption bandwidth for electromagnetic waves in the 2-18GHz frequency band is 4.52GHz (13.48-18.00GHz) at a thickness of 2.35mm.

[0071] Example 2

[0072] 1) PEG with a theoretical relative molecular mass of 1200 is used as a plasticizer, and is blended and granulated with PLA masterbatch in a twin-screw granulator, wherein the mass ratio of PEG to PLA masterbatch is 3:100. The fibers are then spun through a melt-blown machine to prepare PLA melt-blown fibers with a fiber diameter of 3 to 5 μm, and then treated at 70° C. for 16 h to obtain pretreated PLA melt-blown fibers.

[0073] 2) Prepare 1.5 g / L GO solution;

[0074] 1.5 g GO powder was weighed, dissolved in 1000 mL of aqueous solution, and dispersed by ultrasonication for 30 min to prepare a 1.5 g / L GO solution.

[0075] 0.2 g of a mixture of ferric chloride and cobalt chloride (the molar ratio of ferric chloride to cobalt chloride is 2:1) was added to the GO solution and mixed evenly. Ammonia water was then added to the resulting solution to adjust the pH to 9 to precipitate the iron and cobalt magnetic ions. The solution was heated at 60° C. to completely evaporate the ammonia water, thereby obtaining a GO solution loaded with magnetic particles.

[0076] 3) The PLA melt-blown fiber obtained in step 1) was completely immersed in the GO solution loaded with magnetic particles obtained in step 2), and the mixture was first evacuated to a vacuum degree of less than 20 Pa and immersed for 30 minutes, then ultrasonically treated (power of 300 W) for 30 seconds, excess water was drained, and the mixture was dried at 50°C for 36 hours. Finally, the mixture was treated at 650°C under a nitrogen atmosphere for 3 hours to obtain a micron-sized hollow tubular magnetic graphene absorber.

[0077] The micron-sized hollow tubular magnetic graphene absorbing material was blended with paraffin wax. The mass fraction of the absorbing material in the blended material was 3%. A small coaxial material with an outer diameter of 7 mm and an inner diameter of 3.04 mm was prepared. The electromagnetic parameters were measured and the RL value was calculated according to the method of Example 1. Figure 3 As shown. Figure 3 It can be seen that the RL of the micron-sized hollow tubular magnetic graphene absorbing material prepared in Example 2 is min The value is -23.83dB, and the effective absorption bandwidth for electromagnetic waves in the 2-18GHz frequency band is 6.35GHz (11.65-18.00GHz) at a thickness of 2.35mm.

[0078] Example 3

[0079] 1) PEG with a theoretical relative molecular mass of 2000 is used as a plasticizer, and is blended and granulated with PLA masterbatch in a twin-screw granulator, wherein the mass ratio of the PEG to the PLA masterbatch is 3:100. The fibers are then spun through a melt-blown machine to prepare PLA melt-blown fibers with a fiber diameter of 3 to 5 μm, and then treated at 80° C. for 24 h to obtain pretreated PLA melt-blown fibers.

[0080] 2) Prepare a 2.5 g / L GO solution;

[0081] 2.5 g of GO powder was weighed, dissolved in 1000 mL of aqueous solution, and dispersed by ultrasonication for 30 min to prepare a 2.5 g / L GO solution.

[0082] 0.25 g of a mixture of ferric chloride and cobalt chloride (the molar ratio of ferric chloride to cobalt chloride is 2:1) was added to the GO solution and mixed evenly. Ammonia water was then added to the resulting solution to adjust the pH to 9 to precipitate the iron and cobalt magnetic ions. The solution was heated at 70° C. to completely evaporate the ammonia water, thereby obtaining a GO solution loaded with magnetic particles.

[0083] 3) The PLA melt-blown fiber obtained in step 1) was completely immersed in the GO solution loaded with magnetic particles obtained in step 2), and the mixture was first evacuated to a vacuum degree of less than 20 Pa and immersed for 60 minutes, then ultrasonically treated (power of 300 W) for 60 seconds, excess water was drained, and the mixture was dried at 60°C for 48 hours. Finally, the mixture was treated at 800°C for 4 hours under a nitrogen atmosphere to obtain a micron-sized hollow tubular magnetic graphene absorber.

[0084] The micron-sized hollow tubular magnetic graphene absorbing material was blended with paraffin wax. The mass fraction of the absorbing material in the blended material was 3%. A small coaxial material with an outer diameter of 7 mm and an inner diameter of 3.04 mm was prepared. The electromagnetic parameters were measured and the RL value was calculated according to the method of Example 1. Figure 3 As shown. Figure 3 It can be seen that the RL of the micron-sized hollow tubular magnetic graphene absorbing material prepared in Example 3 is min The value is -17.71dB, and the effective absorption bandwidth for electromagnetic waves in the 2-18GHz frequency band is 6.01GHz (10.57-16.58GHz) at a thickness of 2.35mm.

[0085] Comparative Example 1

[0086] The difference from Example 3 is:

[0087] Replace PLA masterbatch with polypropylene (PP) masterbatch;

[0088] The remaining steps and parameters are the same as those in Example 3. The test results show that in step 3) of Example 3, carbon black is generated when PP is treated at 800°C and cannot be completely removed. At the same time, the hydrophilicity is poor and a hollow tubular structure cannot be obtained.

[0089] Comparative Example 2

[0090] The difference from Example 3 is:

[0091] Replace PLA masterbatch with polyethylene terephthalate (PET) masterbatch;

[0092] The remaining steps and parameters are the same as those in Example 3. The test results show that in step 3) of Example 3, carbon black is generated when PET is treated at 800°C and cannot be completely removed. At the same time, the hydrophilicity is poor and a hollow tubular structure cannot be obtained.

[0093] Comparative Example 3

[0094] The difference from Example 3 is that: the PLA meltblown fibers are not pretreated;

[0095] Specifically, step 1) is:

[0096] PEG with a weight-average molecular weight of 2000 was used as a plasticizer and blended and granulated with PLA masterbatch in a twin-screw granulator. The mass ratio of PEG to PLA masterbatch was 3:100. PLA melt-blown fibers with a fiber diameter of 3 to 5 μm were then spun through a melt-blown machine.

[0097] Step 3) uses the PLA melt-blown fiber obtained in step 1). Due to the lack of pretreatment, the hydrophilicity is poor, and the GO sheet coating effect on the fiber is poor, making it difficult to form a hollow tubular structure.

[0098] Comparative Example 4

[0099] The difference from Example 3 is that: in step 3), ultrasonic treatment is not performed;

[0100] Specifically, step 3) is:

[0101] The PLA meltblown fibers obtained in step 1) of Example 3 were completely immersed in the magnetic particle-loaded GO solution obtained in step 2). The fibers were first evacuated to a vacuum level below 20 Pa for 61 minutes. Excess water was then drained, and the fibers were dried at 60°C for 48 hours. Finally, the fibers were treated at 800°C under a nitrogen atmosphere for 4 hours. Due to the lack of ultrasonic treatment, the fiber coating was poor, making it difficult to form a hollow tubular structure.

[0102] The above embodiments are intended only to facilitate understanding of the methods and core concepts of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is intended to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A wave absorbing material is prepared by using pretreated polylactic acid meltblown fiber as a template, coating graphene oxide nanosheets loaded with magnetic particles on the surface of the polylactic acid meltblown fiber through vacuum impregnation and ultrasonic treatment, and then removing the template.

2. The absorbing material according to claim 1, characterized in that The wave-absorbing material is prepared by mixing pretreated polylactic acid melt-blown fibers and a graphene oxide solution loaded with magnetic particles, vacuum impregnation and ultrasonic treatment, and then heat treatment under inert gas conditions.

3. The absorbing material according to claim 2, characterized in that The polylactic acid melt-blown fiber is polyethylene glycol plasticized polylactic acid melt-blown fiber, which is prepared by mixing polyethylene glycol and polylactic acid masterbatch.

4. The absorbing material according to claim 2, characterized in that The pretreated polylactic acid melt-blown fiber is a low-temperature pretreated polylactic acid melt-blown fiber; the pretreated polylactic acid melt-blown fiber is prepared according to the following method: Polyethylene glycol and polylactic acid masterbatch are mixed and granulated, and then spun to obtain polylactic acid melt-blown fiber, which is then subjected to low-temperature treatment to obtain pretreated polylactic acid melt-blown fiber.

5. The absorbing material according to claim 4, characterized in that: The theoretical relative molecular mass of the polyethylene glycol is 500 to 2000; The diameter of the polylactic acid meltblown fiber is 3 to 5 μm; The temperature of the low temperature treatment is 60-80°C.

6. The absorbing material according to claim 2, characterized in that: The method for preparing the graphene oxide solution loaded with magnetic particles comprises the following steps: The graphene oxide solution is mixed with magnetic particles, and then mixed with ammonia water for precipitation, and then heated to volatilize the ammonia water to obtain the graphene oxide solution loaded with magnetic particles.

7. The absorbing material according to claim 6, characterized in that: The concentration of the graphene oxide solution is 0.5 to 2.5 g / L; The magnetic particles are selected from at least one of an iron-containing compound, a cobalt-containing compound, and a nickel-containing compound; The mass ratio of the magnetic particles to the graphene oxide is 1:5-10; The temperature for heating to volatilize the ammonia solution is 50-70°C.

8. The absorbing material according to claim 2, characterized in that The vacuum degree of the vacuum impregnation is below 20 Pa, and the time is 10 to 60 minutes; The power of the ultrasonic treatment is 240-300W, and the time is 10-60s.

9. The absorbing material according to claim 2, characterized in that: The inert gas is selected from argon or nitrogen; The heat treatment temperature is 500-800° C. and the time is 2-4 hours.

10. A method for preparing the absorbing material according to any one of claims 1 to 9, comprising the following steps: The pretreated polylactic acid melt-blown fibers and the graphene oxide solution loaded with magnetic particles are mixed, vacuum impregnated and ultrasonically treated, and then heat-treated under inert gas conditions to prepare the absorbing material.

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