SiBOC ceramic-based wave-absorbing metamaterial and preparation method thereof

Abstract

The application discloses a SiBOC ceramic-based wave-absorbing metamaterial and a preparation method thereof. The SiBOC ceramic-based wave-absorbing metamaterial is composed of a plurality of unit structures arranged in parallel, the unit structure is a hollow spherical polyhedron with vertical holes on the upper and lower surfaces, and the preparation method comprises the following steps: drawing a model of the SiBOC ceramic-based wave-absorbing metamaterial, preparing a SiBOC ceramic-based wave-absorbing metamaterial blank through 3D printing, and then high-temperature cracking after solidification. The application uses a photosensitive ceramic precursor as a raw material, realizes high-precision preparation of the SiBOC ceramic-based wave-absorbing metamaterial with a full-dense complex structure through a DLP 3D printing process, has the advantages of rapidness, high efficiency and low cost, and the prepared wave-absorbing metamaterial has obvious wide-frequency wave-absorbing performance in a microwave band, the wave-absorbing performance is insensitive to polarization, and stable wave absorption can be realized within a wide range of incident angles, and the wave-absorbing performance has high stability.

Description

Technical Field

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

[0002] With breakthroughs in wireless communication technology and rapid development in radar detection technology, a large number of electronic devices and equipment have been applied in fields such as the Internet of Things, 5G communication, artificial intelligence, wearable electronic devices, microwave sensors, and high-performance radar. These devices have brought revolutionary changes to social development and national defense security, paving the way for the full-scale development of the intelligent era. However, the widespread use of electronic devices has filled modern working and living environments with electromagnetic radiation of various wavelengths, inevitably leading to increasingly serious electromagnetic pollution. The hazards of electromagnetic pollution mainly include two aspects: 1) Negative impacts on human health: Long-term exposure to radio frequency fields can have serious effects on health, especially on the nervous, immune, and reproductive systems. 2) Interference with electronic devices: Electromagnetic pollution can seriously interfere with the safe operation of communication systems and electronic devices, posing a serious threat to information security. Currently, electromagnetic pollution is widely recognized as the fourth largest source of pollution after air, water, and noise pollution. Therefore, it is necessary to find long-term and effective solutions to avoid electromagnetic interference to protect human health and ensure the safe and stable operation of electronic devices. Electromagnetic wave absorbing materials (wave-absorbing materials) are widely recognized as an effective way to solve the above problems and have been widely used in many fields of civilian and national defense.

[0003] With increasingly complex operating environments and ever-increasing performance requirements, the search for fabrication methods for microwave absorbing materials with wide absorption bandwidth, strong absorption performance, lightweight, and high stability has become a research hotspot and focus. Microwave absorbing metamaterials possess numerous advantages, including highly designable absorption performance and lightweight properties. Ceramic materials offer superior strength, hardness, creep resistance, low coefficient of thermal expansion, ablation resistance, chemical corrosion resistance, and high-temperature resistance. Combining microwave absorbing metamaterials with ceramic materials can greatly expand the design freedom of electromagnetic and service performance of microwave absorbing materials. However, ceramic materials are hard and brittle, making it difficult to accurately fabricate complex ceramic structures using convenient processing techniques. 3D printing technology can effectively solve the problem of forming complex structures, providing important support for the development of ceramic microwave absorbing metamaterials. Currently, ceramic 3D printing mainly involves the molding of ceramic powder mixed with photocurable polymer slurries. The powder is formed through resin curing, followed by sintering and debinding to obtain the ceramic product. However, high-viscosity slurries make it difficult to achieve rapid and high-precision printing, and the debinding process can also create defects such as pores and cracks, hindering the accurate fabrication of complex ceramic structures. A ceramic-based microwave absorbing material that can be designed and precisely fabricated based on 3D printing technology to achieve high-performance microwave absorbing metamaterials with complex structures is urgently needed. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a SiBOC ceramic-based microwave absorbing metamaterial and its preparation method, thereby solving the problem that the design concepts and processing techniques of existing traditional ceramic-based microwave absorbing materials are limited, making it difficult to achieve high-precision processing and microwave absorption performance control of complex ceramic material structures.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] A SiBOC ceramic-based microwave absorbing metamaterial is composed of several parallel-arranged unit structures. Each unit structure is a hollow spherical polyhedron with vertical openings at the top and bottom. The radius of the hollow spherical polyhedron is 1.95-3.9 mm, the wall thickness is 0.2-0.4 mm, and the radius of the vertical openings is 0.3-1 mm.

[0007] The beneficial effects of this invention are as follows: The basic theoretical basis for the design of the SiBOC ceramic-based absorbing metamaterial is the Effective Media Theory (EMT). The core of this theory lies in approximating the periodic structure as a homogeneous dielectric layer for calculation. This theoretical basis originates from the interaction between a grating structure smaller than the wavelength and light waves in diffraction optics. The significance of the EMT theory is that when the unit size of the periodic structure array is smaller than the incident wavelength, the metamaterial array can be approximated as a homogeneous dielectric material, and the dielectric constant of the dielectric material can be calculated through the metamaterial's geometry and its bulk electromagnetic properties.

[0008] Numerical analysis of electromagnetic fields essentially transforms the discretized Maxwell's equations into a process for numerical solution by computer programs. CST Studio Suite simulation software, based on the finite integral method, was used for numerical simulation of the electromagnetic response characteristics of metamaterials, as well as structural design and parameter optimization. In the electromagnetic simulation settings, the periodic element method was selected, simulating only one unit structure that makes up the metamaterial. This method greatly simplifies the calculation process and shortens the computation time. Periodic boundary conditions (PBC) were used to simulate an infinitely large absorbing metamaterial array structure. The frequency domain finite element method was selected for the calculation, with unit cell boundary conditions and Floquet port excitation. Since the actual testing and calculation of the RC process were based on a metal backplate model, the Z... min The boundary conditions are set as electric boundary to simulate a metal layer, at Z max An excitation port is set on the upper surface. Under this condition, the simulation results only need to focus on S. 11 parameter.

[0009] The simulation calculation model established in CST software according to this invention is shown in the figure below. Figure 1As shown in Figure a, Figure a illustrates the boundary conditions and defined characteristic dimensions of the unit structure. Figure b shows the metamaterial array composed of unit structures under periodic boundary conditions. The unit structure is a 98-sided polyhedron with vertically opening holes in a spherical shape. By combining polyhedral, hollow, and gradient structures, the SiBOC ceramic-based absorbing metamaterial prepared in this invention possesses excellent microwave absorption performance. Furthermore, the effective absorption bandwidth of the prepared SiBOC ceramic-based absorbing metamaterial can be adjusted by modifying three parameters of the unit structure: the circumscribed circle radius r, the wall thickness w, and the opening radius q.

[0010] Furthermore, the unit structure is an octahedron with a radius of 3.9 mm, a wall thickness of 0.4 mm, and a radius of 1 mm for the vertical openings at the top and bottom; or a radius of 2.55 mm, a wall thickness of 0.2 mm, and a radius of 0.5 mm for the vertical openings at the top and bottom; or a radius of 1.95 mm, a wall thickness of 0.2 mm, and a radius of 0.3 mm for the vertical openings at the top and bottom.

[0011] The beneficial effects of adopting the above-mentioned further technical solution are as follows: This invention calculates the three parameters of the unit structure by using an optimization algorithm, and the simulation calculation results are as follows: Figure 2 As shown. To ensure that the effective absorption bandwidth covers as much of the test band's frequency range as possible, this invention selects combinations where the unit size is an integer multiple of the sample size for the corresponding test band, thus guaranteeing the integrity of the prepared sample unit structure. Based on the above principles of parameter selection and Figure 2 Based on the simulation results, this invention obtained the following unit structure parameters for the SiBOC ceramic-based absorbing metamaterial in the C-band (5.4–8.2 GHz): r = 3.9 mm, w = 0.4 mm, q = 1 mm; for the X-band (8.2–12.4 GHz): r = 2.55 mm, w = 0.2 mm, q = 0.5 mm; and for the Ku-band (12.4–18.0 GHz): r = 1.95 mm, w = 0.2 mm, q = 0.3 mm. The SiBOC ceramic-based absorbing metamaterial with these three parameter combinations can achieve full-band absorption from 5.4 to 18 GHz in the corresponding test bands.

[0012] Furthermore, the unit cell structure is SiBOC ceramic.

[0013] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The SiBOC ceramic material used in this invention is an excellent dielectric loss absorbing material, possessing both absorbing performance and excellent high-temperature resistance. Based on this material, and combining DLP 3D printing technology and the design concept of absorbing metamaterials, this invention fabricates SiBOC ceramic into an all-dielectric absorbing metamaterial, effectively improving the absorbing performance of the material and significantly broadening its effective absorbing bandwidth. Simultaneously, the hollow structural design can significantly reduce the material's mass.

[0014] The above-mentioned method for preparing SiBOC ceramic-based microwave absorbing metamaterials includes the following steps:

[0015] Models of microwave absorbing metamaterials were drawn, and SiBOC ceramic-based microwave absorbing metamaterial preforms were fabricated by 3D printing. The preforms were then cured and then subjected to high-temperature pyrolysis to obtain the final product.

[0016] The beneficial effects of this invention are as follows: This invention uses SiBOC ceramic precursor as raw material and achieves the preparation of SiBOC ceramic-based microwave absorbing metamaterials with fully dense and complex structures through DLP 3D printing technology, which has the characteristics of being fast, efficient, and low-cost. When drawing the model of the SiBOC ceramic-based microwave absorbing metamaterial, the fixed shrinkage rate of SiBOC ceramic at 1100℃ is used as a template to enlarge the model, obtaining the SiBOC ceramic-based microwave absorbing metamaterial model. After DLP 3D printing, curing, and high-temperature pyrolysis, the preform structure linearly shrinks to obtain the SiBOC ceramic-based microwave absorbing metamaterial of the preset size. Through multiple preparation tests, the fixed shrinkage rate calculation of this invention is accurate, and the final product structure fully meets expectations.

[0017] Furthermore, the parameters for 3D printing are: irradiation intensity 10-20 mW·cm². -2 Single-layer exposure time: 5-7 seconds; first-layer exposure time: 7-9 seconds; scraper speed: 40-60 mm / s. -1 .

[0018] Furthermore, the parameters for 3D printing are: irradiation intensity 15 mW·cm². -2 Single-layer exposure time: 6 seconds; first-layer exposure time: 8 seconds; scraper speed: 50 mm / s. -1 .

[0019] Furthermore, the curing temperature is 40-50℃, and the irradiation intensity is 90-110 mW·cm. -2 The time is 20-40 minutes.

[0020] Furthermore, the curing temperature was 45℃, and the irradiation intensity was 100mW·cm. -2 The time is 30 minutes.

[0021] Furthermore, the parameters for high-temperature pyrolysis are as follows: under an inert atmosphere, first at 1-3℃·min -1 The temperature was increased to 140-160℃ at a heating rate and held for 0.5-1.5 hours; then increased at a rate of 1-3℃·min. -1 Heat to 200-300℃ at a heating rate and hold for 1-3 hours; then heat at a rate of 1-2℃·min -1 Heating rate increased to 450-550℃, held for 1-3 hours; then increased at 1-2℃ / min. -1 Heat to 650-750℃ at a heating rate and hold for 1-3 hours; then heat at a rate of 1-2℃·min -1 The temperature is increased to 1000-1200℃ at a heating rate and held for 2-4 hours; finally, the temperature is increased at 1-3℃·min. -1 The temperature is reduced to 450-550℃ at a cooling rate, and then naturally cooled to room temperature.

[0022] Furthermore, the parameters for high-temperature pyrolysis are as follows: under Ar atmosphere protection, first at 2℃·min -1 The temperature was increased to 150℃ at a heating rate and held for 1 hour; then heated at a rate of 2℃·min -1 The temperature was increased to 250℃ at a heating rate and held for 2 hours; then increased at a rate of 1℃·min -1 The temperature was increased to 500℃ at a heating rate and held for 2 hours; then the temperature was increased at a rate of 1℃·min. -1 The temperature was increased to 700℃ at a heating rate of 1℃·min, and held for 2 hours; then the temperature was increased to 700℃ at a heating rate of 1℃·min. -1 The temperature was increased to 1100℃ at a heating rate and held for 3 hours; finally, the temperature was increased at a rate of 2℃·min. -1 The temperature is reduced to 500℃ at a cooling rate, and then naturally cooled to room temperature.

[0023] The present invention has the following beneficial effects:

[0024] (1) This invention uses photosensitive ceramic precursors as raw materials and achieves high-precision preparation of SiBOC ceramic-based microwave absorbing metamaterials with fully dense and complex structures through DLP 3D printing process. It has the advantages of being fast, efficient and low cost.

[0025] (2) The SiBOC ceramic used in this invention is an excellent dielectric loss type microwave absorbing material, which not only has microwave absorption performance but also excellent high temperature resistance. This invention effectively improves the microwave absorption performance of this material and expands its effective microwave absorption bandwidth through DLP 3D printing technology and the design concept of microwave absorbing metamaterials.

[0026] (3) The SiBOC ceramic-based absorbing metamaterial prepared by this invention exhibits significant broadband absorption performance in the microwave band. The computer simulation results also show that the structure can achieve 100% effective absorption across the entire frequency band from 5.4 to 18 GHz by simply adjusting the characteristic parameters.

[0027] (4) The SiBOC ceramic-based absorbing metamaterial unit structure prepared by the present invention is a highly symmetrical spherical structure with polarization insensitivity. It can achieve stable absorption within a wide range of incident angles and has high absorption performance stability. Attached Figure Description

[0028] Figure 1 The simulation calculation model of this invention established in CST software is shown in the figure below. Figure 1 As shown, Figure a shows the boundary conditions and defined feature dimensions of the unit structure, and Figure b shows a metamaterial array composed of unit structures under periodic boundary conditions.

[0029] Figure 2 The results of simulation calculation and parameter optimization of the reflection coefficient of the SiBOC ceramic-based absorbing metamaterial prepared in this invention are shown below.

[0030] Figure 3 The model and unit feature dimensions of the C-band SiBOC ceramic-based microwave absorbing metamaterial prepared in Example 1;

[0031] Figure 4 The C-band SiBOC ceramic-based microwave absorbing metamaterial and its preform were prepared in Example 1, wherein the upper black material is the C-band SiBOC ceramic-based microwave absorbing metamaterial and the lower white material is the preform.

[0032] Figure 5 The model and unit feature dimensions of the X-band SiBOC ceramic-based absorbing metamaterial prepared in Example 2;

[0033] Figure 6 The X-band SiBOC ceramic-based absorbing metamaterial and its preform were prepared in Example 2, wherein the upper black material is the X-band SiBOC ceramic-based absorbing metamaterial and the lower white material is the preform.

[0034] Figure 7 The model and unit feature dimensions of the Ku-band SiBOC ceramic-based absorbing metamaterial prepared in Example 3;

[0035] Figure 8 The image shows the Ku-band SiBOC ceramic-based microwave absorbing metamaterial and its preform prepared in Example 3. The upper black material is the Ku-band SiBOC ceramic-based microwave absorbing metamaterial, and the lower white material is the preform.

[0036] Figure 9 This is a comparison chart of the simulated and measured absorption performance of the C-band SiBOC ceramic-based absorbing metamaterial prepared in Example 1.

[0037] Figure 10This is a comparison chart of the simulated and measured absorption performance of the X-band SiBOC ceramic-based absorbing metamaterial prepared in Example 2.

[0038] Figure 11 This is a comparison chart of the simulated and measured absorption performance of the Ku-band SiBOC ceramic-based absorbing metamaterial prepared in Example 3.

[0039] Figure 12 The high-temperature absorption performance test results of the X-band SiBOC ceramic-based absorbing metamaterial prepared in Example 2 are shown in Figure a, where ε′ is the real part of the equivalent electrical constant, ε″ is the imaginary part, ε″ is the loss tangent, and ε is the high-temperature absorption performance. Detailed Implementation

[0040] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0041] Example 1:

[0042] A method for preparing a C-band SiBOC ceramic-based microwave absorbing metamaterial includes the following steps:

[0043] (1) The unit structure parameters of the SiBOC ceramic-based absorbing metamaterial corresponding to the C-band (5.4~8.2GHz) are: circumscribed sphere radius r=3.9mm, wall thickness w=0.4mm, and aperture radius q=1mm. The unit structure is enlarged according to the linear shrinkage rate of pyrolysis at 1100℃. The corresponding unit structure is drawn using Solidworks and arranged in a 2×5 array structure.

[0044] (2) Using SiBOC ceramic precursor material as raw material, the working parameters of the 3D printer were set as follows: irradiation intensity 15mW·cm -2 Single-layer exposure time: 6 seconds; first-layer exposure time: 8 seconds; scraper speed: 50 mm / s. -1 Using the array structure drawn in step (1) as a template, 3D printing is performed to obtain the microwave absorbing metamaterial blank.

[0045] (3) The microwave absorbing metamaterial preform obtained in step (2) is cured at a temperature of 45°C and an irradiation intensity of 100 mW·cm. -2 Duration: 30 minutes.

[0046] (4) Transfer the solidified preform from step (3) to a tube furnace for high-temperature pyrolysis under an Ar atmosphere. The heating program is as follows: first at 2℃·min -1The temperature was increased to 150℃ at a heating rate and held for 1 hour; then increased at a rate of 2℃·min -1 The temperature was increased to 250℃ at a heating rate of 1℃·min, and held for 2 hours; -1 The temperature was increased to 500℃ at a heating rate and held for 2 hours; then the temperature was increased at a rate of 1℃·min. -1 The temperature was increased to 700℃ at a heating rate of 1℃·min, and held for 2 hours; -1 The temperature was increased to 1100℃ at a heating rate and held for 3 hours; finally, the temperature was increased at a rate of 2℃·min. -1 The temperature was lowered to 500℃ by a cooling rate and then naturally cooled to room temperature to obtain SiBOC ceramic-based microwave absorbing metamaterial.

[0047] The SiBOC ceramic-based absorbing metamaterial model and its element feature dimensions obtained in this embodiment are shown in the figure below. Figure 3 As shown, the preform obtained in step (2) and the SiBOC ceramic-based microwave absorbing metamaterial obtained in step (4) are as follows: Figure 4 As shown.

[0048] Example 2:

[0049] A method for preparing an X-band SiBOC ceramic-based microwave absorbing metamaterial includes the following steps:

[0050] (1) The unit structure parameters of the SiBOC ceramic-based absorbing metamaterial corresponding to the C-band (8.2~12.4GHz) are: circumscribed sphere radius r=2.55mm, wall thickness w=0.2mm, and aperture radius q=0.5mm. The unit structure is enlarged according to the linear shrinkage rate of pyrolysis at 1100℃. The corresponding unit structure is drawn using Solidworks and arranged in a 2×5 array structure.

[0051] (2) Using SiBOC ceramic precursor material as raw material, the working parameters of the 3D printer were set as follows: irradiation intensity 15mW·cm -2 Single-layer exposure time: 6 seconds; first-layer exposure time: 8 seconds; scraper speed: 50 mm / s. -1 Using the array structure drawn in step (1) as a template, 3D printing is performed to obtain the microwave absorbing metamaterial blank.

[0052] (3) The microwave absorbing metamaterial preform obtained in step (2) is cured at a temperature of 45°C and an irradiation intensity of 100 mW·cm. -2 Duration: 30 minutes.

[0053] (4) Transfer the solidified preform from step (3) to a tube furnace for high-temperature pyrolysis under an Ar atmosphere. The heating program is as follows: first at 2℃·min -1 The temperature was increased to 150℃ at a heating rate and held for 1 hour; then increased at a rate of 2℃·min -1The temperature was increased to 250℃ at a heating rate of 1℃·min, and held for 2 hours; -1 The temperature was increased to 500℃ at a heating rate and held for 2 hours; then the temperature was increased at a rate of 1℃·min. -1 The temperature was increased to 700℃ at a heating rate of 1℃·min, and held for 2 hours; -1 The temperature was increased to 1100℃ at a heating rate and held for 3 hours; finally, the temperature was increased at a rate of 2℃·min. -1 The temperature was lowered to 500℃ by a cooling rate and then naturally cooled to room temperature to obtain SiBOC ceramic-based microwave absorbing metamaterial.

[0054] The SiBOC ceramic-based absorbing metamaterial model and its element feature dimensions obtained in this embodiment are shown in the figure below. Figure 5 As shown, the preform obtained in step (2) and the SiBOC ceramic-based microwave absorbing metamaterial obtained in step (4) are as follows: Figure 6 As shown.

[0055] Example 3:

[0056] A method for preparing a Ku-band SiBOC ceramic-based microwave absorbing metamaterial includes the following steps:

[0057] (1) The unit structure parameters of the SiBOC ceramic-based microwave absorbing metamaterial corresponding to the C-band (12.4~18.0GHz) are: circumscribed sphere radius r=1.95mm, wall thickness w=0.2mm, and aperture radius q=0.3mm. The unit structure is enlarged according to the linear shrinkage rate of pyrolysis at 1100℃. The corresponding unit structure is drawn using Solidworks and arranged in a 2×4 array structure.

[0058] (2) Using SiBOC ceramic precursor material as raw material, the working parameters of the 3D printer were set as follows: irradiation intensity 15mW·cm -2 Single-layer exposure time: 6 seconds; first-layer exposure time: 8 seconds; scraper speed: 50 mm / s. -1 Using the array structure drawn in step (1) as a template, 3D printing is performed to obtain the microwave absorbing metamaterial blank.

[0059] (3) The microwave absorbing metamaterial preform obtained in step (2) is cured at a temperature of 45°C and an irradiation intensity of 100 mW·cm. -2 Duration: 30 minutes.

[0060] (4) Transfer the solidified preform from step (3) to a tube furnace for high-temperature pyrolysis under an Ar atmosphere. The heating program is as follows: first at 2℃·min -1 The temperature was increased to 150℃ at a heating rate and held for 1 hour; then increased at a rate of 2℃·min -1 The temperature was increased to 250℃ at a heating rate of 1℃·min, and held for 2 hours; -1The temperature was increased to 500℃ at a heating rate and held for 2 hours; then the temperature was increased at a rate of 1℃·min. -1 The temperature was increased to 700℃ at a heating rate of 1℃·min, and held for 2 hours; -1 The temperature was increased to 1100℃ at a heating rate and held for 3 hours; finally, the temperature was increased at a rate of 2℃·min. -1 The temperature was lowered to 500℃ by a cooling rate and then naturally cooled to room temperature to obtain SiBOC ceramic-based microwave absorbing metamaterial.

[0061] The SiBOC ceramic-based absorbing metamaterial model and its element feature dimensions obtained in this embodiment are shown in the figure below. Figure 7 As shown, the preform obtained in step (2) and the SiBOC ceramic-based microwave absorbing metamaterial obtained in step (4) are as follows: Figure 8 As shown.

[0062] Experimental Example 1: Wave Absorption Performance Test

[0063] The microwave absorption performance of SiBOC ceramic-based absorbing metamaterials in the C, X, and Ku bands prepared in Examples 1-3 was tested. The waveguide method was used with a vector network analyzer (VNA) (MS4644A, Anritsu, Japan). The test results are as follows: Figure 9-11 As shown.

[0064] The test results of the SiBOC ceramic-based microwave absorbing metamaterial prepared in Example 1 are as follows: Figure 9 As shown, in the C-band, the minimum reflection coefficient RC of the SiBOC ceramic-based absorbing metamaterial is... min = -18.83dB, with an effective absorption bandwidth of EAB = 2.45GHz (5.54~7.99GHz), covering 87.5% of the entire band.

[0065] The test results of the SiBOC ceramic-based microwave absorbing metamaterial prepared in Example 2 are as follows: Figure 10 As shown, in the X-band, the minimum reflection coefficient RC of the SiBOC ceramic-based absorbing metamaterial is... min = -27.97dB, with an effective absorption bandwidth of EAB = 4.01GHz (8.35~12.36GHz), covering 95.48% of the entire band.

[0066] The test results of the SiBOC ceramic-based microwave absorbing metamaterial prepared in Example 3 are as follows: Figure 11 As shown, in the Ku band, the minimum reflection coefficient RC of the SiBOC ceramic-based absorbing metamaterial is... min = -26.40dB, with an effective absorption bandwidth of EAB = 5.60GHz (8.2~12.4GHz), covering 100% of the entire band.

[0067] The measured absorption performance and the simulation results show a high degree of consistency, indicating the correctness of the simulation method of this invention and the effectiveness of the optimized design structure.

[0068] Test Example 2: High-Temperature Wave Absorption Performance Test

[0069] The SiBOC ceramic-based absorbing metamaterial prepared in Example 2 was subjected to high-temperature absorption performance testing using a waveguide method with a vector network analyzer (VNA) (MS4644A, Anritsu, Japan) and a matched high-temperature waveguide assembly and heating cavity to simulate a high-temperature environment. The test results are as follows: Figure 12 As shown.

[0070] Figure 12 Figure a shows the change in the equivalent dielectric constant of the absorbing metamaterial as the temperature increases. With increasing test temperature, both the real and imaginary parts of the metamaterial's equivalent dielectric constant begin to increase. Since the rate of increase of the imaginary part is greater than that of the real part, the loss tangent increases slightly with increasing temperature. Figure 12 (Figure b) This indicates that SiBOC ceramics exhibit enhanced electromagnetic wave loss performance at high temperatures. Figure 12 (See Figure c in the diagram). The increase in the real part of the dielectric constant is due to the increased number of electrons activated from the valence band to the conduction band in the nanocrystalline domains during the heating process, which reduces the relaxation time τ(T). According to Debye theory, the relaxation time is negatively correlated with the real part of the dielectric constant; therefore, the decrease in relaxation time leads to an increase in the real part of the dielectric constant. The increase in the imaginary part of the dielectric constant is mainly due to the increase in conductivity caused by the increase in temperature. Based on the complex dielectric constant, the minimum reflection coefficient RC of the SiBOC ceramic metamaterial at high temperatures of 100–600℃ can be obtained. min The effective absorption bandwidths (EAB) are as follows: -35.92dB, 3.78GHz; -28.34dB, 3.55GHz; -25.12dB, 3.44GHz; -21.48dB, 3.32GHz; -16.13dB, 2.98GHz. Figure 12 As shown in Figure d.

[0071] As can be seen from the above results, the SiBOC ceramic-based absorbing metamaterial prepared by this invention exhibits excellent high-temperature stability, strong electron wave loss capability, and strong controllability of the designed superstructure over the absorption performance from room temperature to 600℃.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A SiBOC ceramic-based microwave absorbing metamaterial, characterized in that, It consists of several parallel unit structures, each unit structure being a hollow spherical 98-sided polyhedron with vertical openings at the top and bottom. The radius of the hollow spherical 98-sided polyhedron is 1.95-3.9 mm, the wall thickness is 0.2-0.4 mm, and the radius of the vertical openings is 0.3-1 mm. The unit structure is SiBOC ceramic.

2. The SiBOC ceramic-based microwave absorbing metamaterial according to claim 1, characterized in that, The unit structure is a 98-sided polyhedron; the radius of the 98-sided polyhedron is 3.9 mm, the wall thickness is 0.4 mm, and the radius of the vertical opening at the top and bottom is 1 mm; or the radius is 2.55 mm, the wall thickness is 0.2 mm, and the radius of the vertical opening at the top and bottom is 0.5 mm; or the radius is 1.95 mm, the wall thickness is 0.2 mm, and the radius of the vertical opening at the top and bottom is 0.3 mm.

3. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 1 or 2, characterized in that, Includes the following steps: Models of microwave absorbing metamaterials were drawn, and SiBOC ceramic-based microwave absorbing metamaterial preforms were fabricated by 3D printing. The preforms were then cured and then subjected to high-temperature pyrolysis to obtain the final product.

4. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 3, characterized in that, The parameters for the 3D printing are: irradiation intensity 10-20 mW·cm. -2 Single-layer exposure time: 5-7 s; first-layer exposure time: 7-9 s; scraper speed: 40-60 mm / s. -1 .

5. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 4, characterized in that, The parameters for the 3D printing are: irradiation intensity 15 mW·cm. -2 Single-layer exposure time: 6 s; first-layer exposure time: 8 s; scraper speed: 50 mm / s. -1 .

6. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 3, characterized in that, The curing temperature is 40-50℃, and the irradiation intensity is 90-110 mW·cm. -2 The time is 20-40 minutes.

7. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 6, characterized in that, The curing temperature was 45 °C, and the irradiation intensity was 100 mW·cm. -2 The time is 30 minutes.

8. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 3, characterized in that, The parameters for the high-temperature pyrolysis are as follows: under an inert atmosphere, first at 1-3 °C·min -1 The temperature was increased to 140-160 °C at a heating rate and held for 0.5-1.5 h; then increased at a rate of 1-3 °C / min. -1 The temperature is increased to 200-300 ℃ at a heating rate and held for 1-3 h; then increased at a rate of 1-2 ℃·min. -1 The temperature was increased to 450-550 ℃ at a heating rate and held for 1-3 h; then increased at a rate of 1-2 ℃·min. -1 The temperature was increased to 650-750 ℃ ​​at a heating rate and held for 1-3 h; then increased at a rate of 1-2 ℃·min. -1 The temperature was increased to 1000-1200 ℃ at a heating rate and held for 2-4 h; finally, the temperature was increased at 1-3 ℃·min. -1 The temperature is reduced to 450-550 ℃ at a cooling rate, and then naturally cooled to room temperature.

9. The method for preparing the SiBOC ceramic-based microwave absorbing metamaterial according to claim 8, characterized in that, The parameters for the high-temperature pyrolysis are as follows: under Ar atmosphere protection, first at 2 °C·min -1 The temperature was increased to 150 °C at a heating rate and held for 1 h; then heated at 2 °C·min. -1 The temperature was increased to 250 °C at a heating rate of 1 °C / min and held for 2 h; then the temperature was increased to 250 °C and held for 2 h at a heating rate of 1 °C / min. -1 The temperature was increased to 500℃ at a heating rate and held for 2 hours; then heated at 1℃·min⁻¹. -1 The temperature was increased to 700 °C at a heating rate of 1 °C / min and held for 2 h; then the temperature was increased to 700 °C / min at a heating rate of 1 °C / min. -1 The temperature was increased to 1100 °C at a heating rate and held for 3 h; finally, the temperature was increased at 2 °C·min. -1 The temperature was reduced to 500 ℃ at a cooling rate, and then allowed to cool naturally to room temperature.

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