Tunable wave-absorbing metamaterial and preparation method and application thereof

Abstract

The application discloses a tunable wave-absorbing metamaterial and a preparation method and application thereof, and belongs to the technical field of wave-absorbing materials. The method comprises the following steps: (1) preparing slurry containing a polymer polymerization base, a wave-absorbing agent and magnetic particles, and magnetizing the slurry to obtain magnetic slurry; (2) designing a porous target metamaterial structure to be printed, and magnetically programming the target metamaterial, so that the porous structure of the target metamaterial can be transformed under the action of a magnetic field; and (3) placing the magnetic slurry in a slurry direct-writing 3D printing device, printing according to the designed mode, and performing heat curing after printing to obtain the tunable wave-absorbing metamaterial, wherein the porous structure of the tunable wave-absorbing metamaterial can be transformed under the action of a magnetic field. The method is simple and efficient, overcomes the deficiency of the existing wave-absorbing materials in terms of electromagnetic wave absorption performance regulation, and has a wide application prospect in the fields of aerospace and communication equipment.

Description

A tunable microwave absorbing metamaterial, its preparation method and application Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, specifically to a tunable microwave absorbing metamaterial, its preparation method, and its application. Background Technology

[0002] The efficient absorption and precise control of electromagnetic waves play a crucial role in various fields such as communications, electromagnetic compatibility, and national defense. With the increasing prevalence of electronic devices and the growing complexity and variability of the electromagnetic environment, electromagnetic interference and radiation from some high-power electromagnetic radiation sources can affect the normal operation of equipment and human health. Electromagnetic wave absorbing materials can convert electromagnetic energy into other forms of energy to attenuate electromagnetic waves, thus creating an increasingly urgent need for high-performance electromagnetic wave absorbing materials and control methods.

[0003] Existing methods for preparing electromagnetic wave absorbing materials often suffer from several problems. For example, some methods use materials with a single composition, resulting in a limited absorption frequency band and failing to meet the requirements for broadband absorption; others involve complex processes requiring multiple steps and expensive equipment, increasing production and time costs. Furthermore, existing techniques for controlling electromagnetic wave absorption performance are often inflexible, making real-time, dynamic adjustment difficult.

[0004] Chinese patent document CN117335167A discloses a dual-band tunable broadband absorbing structure based on a periodic resistive film structure. This invention uses a metal substrate and three absorbing structural layers disposed thereon to form an absorbing structural unit, and arranges multiple absorbing structural units periodically. The absorbing structural layer includes a dielectric layer, a substrate, and a resonant layer disposed on the surface of the substrate near the dielectric layer. The resonant layer includes an annular polygonal resistive film. From bottom to top, the width and the length of the longest diagonal of the annular polygonal resistive film in each resonant layer decrease sequentially, while the surface resistance increases sequentially. This absorbing structure can achieve high-performance absorbing in a dual-band ultra-wideband, and the broadband absorption frequency is precisely controllable.

[0005] Chinese patent document CN116769300A discloses a tunable composite microwave absorbing material based on a honeycomb ordered structure and its preparation method. The invention crosslinks magnetic absorbing particles and a resin matrix to form a gel-like composite microwave absorbing material; fabricates a honeycomb ordered structure cavity; injects the gel-like composite microwave absorbing material into the honeycomb ordered structure cavity; uses an encapsulation process to combine the honeycomb ordered structure with the gel-like composite microwave absorbing material to obtain a tunable composite microwave absorbing material based on a honeycomb ordered structure; applies an excitation magnetic field to the tunable composite microwave absorbing material based on the honeycomb ordered structure, and by controlling the magnetization state, forms an absorbing superstructure.

[0006] The aforementioned absorbing materials / structures can exhibit good electromagnetic wave absorption performance in specific frequency bands, or ensure a certain degree of material stability during the fabrication process. However, some problems also exist. First, the selection of raw materials and the formulation of composite materials limit the range of absorption bands, making them unsuitable for various electromagnetic environments. Second, the complex fabrication process is not only inefficient but also makes it difficult to precisely control the microstructure and properties of the material. Furthermore, in terms of electromagnetic wave absorption modulation, there is a lack of flexibility and real-time capability, preventing rapid changes in absorption characteristics according to actual needs. Summary of the Invention

[0007] This invention provides a method for preparing tunable microwave absorbing metamaterials. The process steps are simple and efficient. By combining the process and raw materials, this method effectively overcomes the shortcomings of existing technologies in the control of electromagnetic wave absorption performance of microwave absorbing materials. It has broad application prospects and practical value in the fields of electromagnetic interference, aerospace, or communication equipment.

[0008] The specific technical solution adopted is as follows:

[0009] A method for preparing a tunable microwave absorbing metamaterial includes the following steps:

[0010] (1) Prepare a slurry containing a polymer matrix, a microwave absorber and magnetic particles, wherein the mass ratio of the polymer matrix, the microwave absorber and the magnetic particles in the slurry is 20-30:1:20-40; magnetize the slurry to obtain a magnetic slurry.

[0011] (2) Design the porous target metamaterial structure to be printed, and perform magnetic programming design on the target metamaterial so that the pore structure of the target metamaterial can be adjusted under the action of a magnetic field;

[0012] (3) Place the magnetic slurry from step (1) into a slurry direct writing 3D printing device and print it according to the method designed in step (2). After printing, perform thermal curing to prepare a tunable absorbing supermaterial whose pore structure can be changed under magnetic field drive.

[0013] The ability of the pore structure to change under magnetic field drive specifically means that when the tunable absorbing metamaterial is placed under a magnetic field (permanent magnet, coil, electromagnet), the internal pore structure of the absorbing metamaterial changes with the adjustment of the magnitude and direction of the magnetic field, thereby achieving stepless control over the absorption of different frequency bands.

[0014] Based on high-performance magnetic paste, this invention ensures the accuracy and controllability of target metamaterial preparation through precise design of the target metamaterial structure and accurate programming of the printing path. Furthermore, by utilizing advanced 3D direct-write printing technology, it is possible to easily construct complex metamaterial structures, further enhancing the absorption and control of electromagnetic waves.

[0015] The polymer matrix includes, but is not limited to, materials such as silicone rubber, polydimethylsiloxane (PDMS), polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polycarbonate, polyamide (such as nylon), and polyester (such as polyethylene terephthalate).

[0016] Preferably, when the polymer matrix is ​​silicone rubber or PDMS, the mass ratio of the polymer matrix, the microwave absorbing agent, and the magnetic particles is 20-25:1:20-30; when the polymer matrix is ​​polyurethane or polyethylene, the mass ratio of the polymer matrix, the microwave absorbing agent, and the magnetic particles is 25-30:1:25-40. Under these preferred conditions, the slurry exhibits better rheological properties, which is beneficial to the microwave absorption performance of the microwave-absorbing metamaterial.

[0017] The microwave absorbing agent is selected from at least one of the following: reduced graphene oxide, carbon nanotubes, carbonyl iron powder, manganese zinc ferrite, nickel zinc ferrite, silver nanoparticles, gold nanoparticles, polyaniline, polypyrrole, silicon carbide, titanium dioxide, and hexagonal boron nitride. In the slurry, the microwave absorbing agent not only functions as a microwave absorbing material but also as a thickener to improve the slurry's rheological properties.

[0018] The magnetic particles are selected as hard magnetic particles, including at least one of neodymium iron boron powder, samarium cobalt alloy powder, barium ferrite powder, strontium ferrite powder, and aluminum nickel cobalt alloy powder; furthermore, the average particle size of the hard magnetic particles is ≤30 μm.

[0019] Furthermore, the slurry also includes a curing co-catalyst based on a polymer matrix, wherein the mass ratio of the polymer matrix to the co-catalyst is 1-3:1.

[0020] Preferably, the slurry is magnetized to saturation under a pulsed magnetic field or a permanent magnet, with a magnetization intensity of generally 2-4 T, which can be magnetized to saturation instantaneously to obtain a magnetic slurry.

[0021] Specifically, the slurry direct-write 3D printing equipment includes a nozzle, a magnetic shielding sleeve around the nozzle, and electromagnets symmetrically arranged on the magnetic shielding sleeve around the nozzle. By changing the direction of the current in the electromagnets, the direction of the magnetic field at the nozzle is changed, thereby enabling the extruded slurry to be printed in a magnetically programmed manner.

[0022] In the printing process, different nozzle specifications and printing speeds can be selected according to different precision requirements. Preferably, the nozzle diameter is 210-620 μm and the printing speed is set to 3-15 mm / s. The thermosetting conditions depend on the polymer matrix. Generally speaking, the thermosetting conditions are 20-250℃ and the time is 30min-10h.

[0023] The present invention also provides a method for preparing the tunable absorbing metamaterial described above, and the tunable absorbing metamaterial obtained therefrom.

[0024] The tunable absorbing metamaterial exhibits varying degrees of pore structure contraction with changes in magnetic field strength, resulting in flexible and variable absorption performance. Both the absorption frequency and absorptivity can be precisely controlled using a magnetic field to suit different scenarios. It offers a high degree of design freedom, allowing for customized structures. The size, shape, and arrangement of periodic units can be flexibly set, and materials can be selected and combined to match the absorption wavelength range.

[0025] In the wave absorption control step, the precision of the magnetic field strength and direction can be further improved to achieve more refined electromagnetic wave absorption control.

[0026] This invention also provides the application of the aforementioned tunable absorbing metamaterial in the fields of aerospace or communication equipment.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] (1) By preparing high-performance magnetic paste and designing a specific preparation process, this invention effectively overcomes the shortcomings of existing technologies in electromagnetic wave absorption control. The tunable absorbing metamaterial in this invention can achieve flexible, precise and stepless control of electromagnetic wave absorption. Moreover, the preparation process is simple and efficient, with relatively low cost, and has broad application prospects and practical value.

[0029] (2) The method of the present invention can realize high-precision and efficient molding of complex metamaterial structures, avoiding the drawbacks of traditional processes. The absorption agent material can accurately determine the absorption range and the composite use can broaden the frequency band. The magnetic deformation characteristics of the tunable absorbing metamaterial can quickly and accurately adjust the absorption frequency band under the action of a magnetic field, which is far superior to the fixed structure absorbing material. Moreover, the pore structure design of the tunable absorbing metamaterial makes its deformation sensitivity extremely high. Small deformation can significantly change the absorption performance. Combined with high-quality magnetic materials, it can respond quickly to the magnetic field and dynamically adapt to complex electromagnetic environments. Attached Figure Description

[0030] Figure 1 is a design diagram of the rectangular cell structure in Example 1.

[0031] Figure 2 is a magnetic domain distribution diagram of the rectangular cell structure in Example 1.

[0032] Figure 3 shows the microstructure of the filament during the printing process of Example 1.

[0033] Figure 4 shows the sensitivity of the storage modulus and loss modulus of the magnetic slurry in Example 1 to changes in the magnetic field.

[0034] Figure 5 shows the deformation sensitivity characteristic curve of the tunable absorbing metamaterial in Example 1 under the action of a 1Hz frequency pulsed electromagnetic field.

[0035] Figure 6 shows the microwave absorption effect of the tunable absorbing metamaterial in Example 1.

[0036] Figure 7 shows the microwave absorption effect of the tunable absorbing metamaterial in Example 2. Detailed Implementation

[0037] The present invention will be further illustrated below with reference to the embodiments and accompanying drawings. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art.

[0038] In the printing process of the following embodiments, a slurry direct-write 3D printing device is used for 3D direct-write printing. The slurry direct-write 3D printing device includes a nozzle, a magnetic shielding sleeve is installed around the nozzle, and electromagnets are symmetrically arranged on the magnetic shielding sleeve around the nozzle. By changing the current direction of the electromagnets, the magnetic field direction at the nozzle is changed, so that the extruded slurry is printed in a magnetic programming manner. After printing, a thermosetting process is performed to achieve the curing and molding of the product's microwave absorbing metamaterial.

[0039] Example 1

[0040] (1) First, neodymium iron boron powder (average particle size not greater than 5 μm) was placed in anhydrous ethanol and ball-milled continuously at 200 rpm for 7 hours. Then, it was transferred to a drying oven at 60°C and dried for 24 hours. It was then carefully ground in a mortar and pestle and passed through a 200-mesh sieve to obtain non-agglomerated neodymium iron boron powder.

[0041] (2) The platinum silica matrix and platinum catalyst (Ecoflex 00-30 Part B and Ecoflex 00-30 Part A, respectively) were mixed in a 1:1 mass ratio and dispersed at 1500 rpm for 60 seconds using a planetary stirrer. Then, reduced graphene oxide was added and dispersed at 2000 rpm for 120 seconds using a planetary stirrer. Then, the neodymium iron boron powder obtained in step (1) was added and dispersed at 1500 rpm for 120 seconds using a planetary stirrer to prepare an unmagnetized printing slurry. The mass ratio of platinum silica matrix, reduced graphene oxide and neodymium iron boron powder in the slurry was 20:1:29.

[0042] (3) Place the paste from step (2) inside the permanent magnet for saturation magnetization (about 3 T) to obtain the magnetic paste to be printed;

[0043] (4) Using 3D modeling software, the rectangular cell structure of the target absorbing metamaterial is designed as shown in Figure 1, and the distribution and orientation of magnetic domains in the structure shown in Figure 2 are planned and converted into a format that can be recognized by the direct-write 3D printing equipment. In subsequent steps, the material is printed in the manner designed above.

[0044] (5) The material tube containing the magnetic slurry from step (3) is accurately installed on the direct-write 3D printing equipment. A 20 mT ring-shaped permanent magnet is fitted onto the printing nozzle to arrange the magnetic domains during the printing process. A 410 μm nozzle is used during the printing process, the printing speed is set to 6 mm / s, the single layer thickness is 0.35 mm, and the printing height is 1.8 mm. The printing is carried out according to the method designed in step (4). The microstructure of the printed filament is shown in Figure 3. Due to the weak extrusion expansion effect of the printing slurry, the magnetic domains are well arranged. The material obtained by the direct-write 3D printing equipment is placed in a drying oven at 210℃ for 1 hour for thermal curing. Finally, a tunable microwave absorbing metamaterial with a pore structure that can be changed under magnetic field drive is prepared.

[0045] Based on the magnetic domain arrangement of the porous structure, this invention successfully printed the superstructure shown in Figure 1. This superstructure exhibits excellent negative expansion characteristics; its pores can respond rapidly to the action of a magnetic field, producing varying degrees of contraction.

[0046] In this embodiment, the magnetic slurry is subjected to varying oscillating stress. Figure 4 shows the sensitivity of the storage modulus G' and loss modulus G'' to changes in the magnetic field under the given conditions. The G',G''-shear stress curves better reflect the printability of the slurry. When G' (storage modulus) > G'' (loss modulus), it indicates that the slurry is in a solid state, and G',G'' decreases with increasing shear stress. When the shear stress is approximately 82 Pa, G' (storage modulus) < G'' (loss modulus), at which point the slurry transitions to a liquid state, fully demonstrating that this slurry possesses shear-thinning characteristics. This indicates that when printing with this slurry, as the pressure inside the barrel increases, once a specific pressure value is exceeded, the slurry can be extruded from the nozzle. After the slurry is extruded from the nozzle, the shear pressure disappears instantly, the elastic modulus returns to G' > G'', the slurry returns to a solid state, and it can maintain the filament shape after extrusion.

[0047] Figure 5 shows the deformation sensitivity characteristic curve of the tunable absorbing metamaterial under the action of a 1 Hz frequency pulsed electromagnetic field. It was observed that due to its own inertial effect, the deformation rate of the absorbing metamaterial exceeded the dynamic magnetic field change rate, indicating that the control sensitivity can reach the second level.

[0048] The absorption effect of the tunable absorbing metamaterial without deformation obtained in this embodiment is shown in Figure 6. It can be found that the absorption efficiency reaches -32.11 dB in a specific frequency band, and the absorption frequency can be adjusted around the device.

[0049] The statistical results of the absorption performance of the tunable absorbing metamaterial under different magnetic fields are shown in Table 1. It can be seen that the absorption performance of the tunable absorbing metamaterial is flexible and variable, and the absorption frequency and absorption rate can be precisely controlled by the magnetic field according to actual needs.

[0050] Table 1. Statistical results of the absorption performance of tunable absorbing metamaterials under different magnetic fields.

[0051]

[0052] Example 2

[0053] (1) First, neodymium iron boron powder (average particle size not greater than 5 μm) was placed in anhydrous ethanol and ball milled continuously at 250 rpm for 6 h. Then, it was transferred to a drying oven and dried at 70°C for 22 h. It was then ground in a mortar and pestle and passed through a 250-mesh sieve to obtain non-agglomerated neodymium iron boron powder.

[0054] (2) The platinum silica matrix and platinum catalyst (Ecoflex 00-30 Part B and Ecoflex 00-30 Part A, respectively) were mixed at a mass ratio of 1:1 and dispersed at 1600 rpm for 50 s using a planetary stirrer. Then, reduced graphene oxide was added and dispersed at 2100 rpm for 110 s using a planetary stirrer. The neodymium iron boron powder obtained in step (1) was added and dispersed at 1600 rpm for 110 s using a planetary stirrer to prepare an unmagnetized printing slurry. The mass ratio of platinum silica matrix, reduced graphene oxide and neodymium iron boron powder in the slurry was 20:1:26.

[0055] (3) Place the paste from step (2) inside the permanent magnet for saturation magnetization (approximately 2.7 T) to obtain the magnetic paste to be printed;

[0056] (4) Use 3D modeling software to design the triangular cell structure of the target absorbing metamaterial, and plan the distribution and orientation of magnetic domains in the triangular cell structure. Convert it into a format that can be recognized by the direct-write 3D printing equipment, and print it in the following steps according to the above-designed method.

[0057] (5) Accurately install the material tube containing the magnetic slurry from step (3) onto the direct-write 3D printing equipment. The 25 mT ring-shaped permanent magnet fitted onto the printing nozzle is used to arrange the magnetic domains during printing. A 400 μm nozzle is used during the printing process, the printing speed is 7 mm / s, the single layer thickness is 0.25 mm, and the height is 2.5 mm. Printing is carried out according to the method designed in step (4). The material obtained by the direct-write 3D printing equipment is placed in a drying oven at 220℃ for 0.8 hours for thermosetting, and finally a tunable microwave absorbing metamaterial with a pore structure that can be changed under magnetic field drive is prepared.

[0058] The absorption effect of the tunable absorbing metamaterial without deformation obtained in this embodiment is shown in Figure 7. It can be found that the absorption efficiency reaches -22.79 dB in a specific frequency band, and the absorption frequency can be adjusted around the device.

[0059] Example 3

[0060] (1) The aluminum nickel cobalt alloy powder (average particle size not greater than 6 μm) was placed in anhydrous ethanol and ball-milled at 230 rpm for 7.5 hours. Then it was transferred to a drying oven and dried at 62°C for 25 hours. After grinding in a mortar, it was passed through a 230-mesh sieve to obtain non-agglomerated aluminum nickel cobalt alloy powder.

[0061] (2) The polycarbonate matrix and the co-catalyst (benzoyl peroxide) were mixed at a mass ratio of 3:1 and dispersed for 180 seconds using a planetary ball mill (200 rpm revolution, 300 rpm rotation). Then, manganese-zinc ferrite was added and dispersed for another 140 seconds. Next, the treated AlNiCo alloy powder was added and dispersed again for 140 seconds to prepare an unmagnetized printing slurry. The mass ratio of polycarbonate matrix, manganese-zinc ferrite and AlNiCo alloy powder in the slurry was 28:1:36.

[0062] (3) Place the paste from step (2) inside the permanent magnet for saturation magnetization (approximately 2.9 T) to obtain the magnetic paste to be printed;

[0063] (4) Use 3D modeling software to carry out the structural design of pentagonal cells for the target absorbing metamaterial, and plan the distribution and orientation of magnetic domains in the pentagonal cell structure. Convert it into a format that can be recognized by the direct writing 3D printing equipment, and print it in the following steps according to the above-designed method.

[0064] (5) Accurately install the material tube containing the magnetic slurry from step (3) onto the direct-write 3D printing equipment. The 20 mT ring-shaped permanent magnet fitted onto the printing nozzle is used to arrange the magnetic domains during printing. During the printing process, a 350 μm nozzle is used, the printing speed is 7 mm / s, the single layer thickness is 0.32 mm, and the height is 1.9 mm. Printing is carried out according to the method designed in step (4). The material obtained by the direct-write 3D printing equipment is placed in a drying oven at 160℃ for 1.1 hours for thermosetting, and finally a tunable microwave absorbing metamaterial with a pore structure that can be changed under magnetic field drive is prepared.

[0065] Example 4

[0066] (1) Take samarium cobalt alloy powder (average particle size not greater than 7 μm) and put it into anhydrous ethanol. Use a ball mill to ball mill at 210 rpm for 6.8 hours. Then transfer it to a drying oven and dry it at 58°C for 24.5 hours. After grinding in a mortar, pass it through a 210-mesh sieve to obtain non-agglomerated samarium cobalt alloy powder.

[0067] (2) The polypropylene matrix and the co-catalyst (benzoyl peroxide) were mixed at a mass percentage of 2.5:1 and dispersed at 1400 rpm for 68 seconds using a high-speed emulsifier. Then, nickel-zinc ferrite was added and dispersed at 1700 rpm for 135 seconds using a high-speed emulsifier. Finally, the treated samarium cobalt alloy powder was added and dispersed at 1400 rpm for 135 seconds using a high-speed emulsifier to prepare an unmagnetized printing paste. The mass ratio of polypropylene matrix, nickel-zinc ferrite and samarium cobalt alloy powder in the paste was 25:1:30.

[0068] (3) Place the paste from step (2) inside the permanent magnet for saturation magnetization (about 3 T) to obtain the magnetic paste to be printed;

[0069] (4) Use 3D modeling software to design the circular cell structure of the target absorbing metamaterial, and plan the distribution and orientation of magnetic domains in the circular cell structure. Convert it into a format that can be recognized by the direct writing 3D printing equipment, and print it in the following steps according to the above design.

[0070] (5) Accurately install the material tube containing the magnetic slurry from step (3) onto the direct-write 3D printing equipment. The 23 mT ring-shaped permanent magnet fitted onto the printing nozzle is used to arrange the magnetic domains during printing. During the printing process, a 450 μm nozzle is used, the printing speed is 6.5 mm / s, the single layer thickness is 0.27 mm, and the printing height is 2.1 mm. Printing is carried out according to the method designed in step (4). The material obtained by the direct-write 3D printing equipment is placed in a drying oven at 170℃ for 1 hour for thermosetting, and finally a tunable microwave absorbing metamaterial with a pore structure that can be changed under magnetic field drive is prepared.

[0071] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a tunable microwave absorbing metamaterial, characterized in that, The process includes the following steps: (1) preparing a slurry containing a polymer matrix, a microwave absorber, and magnetic particles, wherein the mass ratio of the polymer matrix, microwave absorber, and magnetic particles in the slurry is 20-30:1:20-40; magnetizing the slurry to obtain a magnetic slurry; (2) designing the porous target metamaterial structure to be printed, and performing magnetic programming design on the target metamaterial so that the pore structure of the target metamaterial can be adjusted under the action of a magnetic field; (3) placing the magnetic slurry from step (1) in a slurry direct-write 3D printing device, and printing according to the steps. (2) Printing is performed in a well-designed manner. After printing, thermal curing is performed to prepare a tunable absorbing metamaterial whose pore structure can be changed under magnetic field drive. The slurry direct writing 3D printing equipment includes a nozzle, a magnetic shielding sleeve is installed around the nozzle, and electromagnets for arranging magnetic domains are symmetrically arranged on the magnetic shielding sleeve around the nozzle. The direction of the magnetic field at the nozzle is changed by changing the current direction of the electromagnet, so that the extruded slurry is printed in a magnetic programming manner. The thermal curing conditions are 160-250℃ and the time is 30min-10h.

2. The method for preparing the tunable absorbing metamaterial according to claim 1, characterized in that, The polymer matrix includes silicone rubber, polydimethylsiloxane, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polycarbonate, polyamide, or polyester.

3. The method for preparing the tunable absorbing metamaterial according to claim 1, characterized in that, The microwave absorbing agent is selected from at least one of the following: reduced graphene oxide, carbon nanotubes, carbonyl iron powder, manganese zinc ferrite, nickel zinc ferrite, silver nanoparticles, gold nanoparticles, polyaniline, polypyrrole, silicon carbide, titanium dioxide, and hexagonal boron nitride.

4. The method for preparing the tunable absorbing metamaterial according to claim 1, characterized in that, The magnetic particles are selected as hard magnetic particles, including at least one of neodymium iron boron powder, samarium cobalt alloy powder, barium ferrite powder, strontium ferrite powder, and aluminum nickel cobalt alloy powder; the particle size of the hard magnetic particles is ≤30 μm.

5. The method for preparing the tunable absorbing metamaterial according to claim 1, characterized in that, The slurry is magnetized to saturation under a pulsed magnetic field or a permanent magnet to obtain a magnetic slurry.

6. The method for preparing the tunable absorbing metamaterial according to claim 2, characterized in that, During printing, the nozzle diameter is 210-620 μm, and the printing speed is set to 3-15 mm / s.

7. The tunable absorbing metamaterial prepared by the method according to any one of claims 1-6.

8. The tunable absorbing metamaterial according to claim 7, characterized in that, The tunable absorbing metamaterial exhibits different degrees of shrinkage in its pore structure as the magnetic field strength changes.

9. The application of the tunable absorbing metamaterial according to claim 8 in the fields of aerospace or communication equipment.

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