A broadband bionic wave-absorbing material with heat insulation and high temperature resistance and a preparation method thereof

Abstract

This invention relates to the field of electromagnetic wave absorbing materials technology, and discloses a broadband biomimetic absorbing material with both heat insulation and high-temperature resistance, as well as its preparation method. The material comprises several electromagnetic wave absorbing element structures arranged in a periodic array, with zero-space splicing between any adjacent electromagnetic wave absorbing element structures. The main body of the electromagnetic wave absorbing element structure is a wave-absorbing rubber block, and an inverted pyramid-shaped groove is formed inward on the upper surface of the wave-absorbing rubber block to form a concave pyramid-shaped biomimetic structure. Inspired by the microstructure of butterfly wings, the concave pyramid-shaped biomimetic electromagnetic wave absorbing element structure is adopted, and the composition design of the absorbing material is coordinated with the structural design to achieve efficient absorption of electromagnetic waves in the range of 75GHz~110GHz and 0.2THz~1.2THz, with an average reflection loss of -38.79dB. The biomimetic absorbing material exhibits excellent bending performance stability.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic wave absorbing materials technology, and in particular to a broadband biomimetic absorbing material that combines heat insulation and high temperature resistance, and its preparation method. Background Technology

[0002] In the fields of aerospace, electronic communications, and defense technology, electromagnetic wave absorbing materials are core functional materials for achieving target stealth and electromagnetic compatibility. However, existing absorbing materials still have many limitations in complex environments: First, their operating frequency band is narrow, limited by the contradiction between the Snoek limit of magnetic metals and impedance matching, making it difficult to cover the millimeter-wave to terahertz band; second, materials are prone to oxidation and instability in high-temperature environments (>300℃), leading to a sharp decline in absorption performance; third, thermal protection and electromagnetic stealth functions are incompatible, with an inherent contradiction between the requirement for low thermal conductivity and the construction of conductive networks. Taking hypersonic vehicles as an example, their surfaces need to simultaneously cope with aerodynamic heating exceeding 400℃ and broadband electromagnetic stealth, and existing material systems are unable to meet the requirements of multi-physics coupling.

[0003] Currently, biomimetic structures offer new insights into overcoming these bottlenecks. Researchers have achieved broadband absorption in the microwave band by reconstructing biological micro- and nano-structures such as moth eyes and butterfly wings. However, traditional biomimetic strategies still face the technical bottleneck of synergistically optimizing broadband electromagnetic loss and thermal management characteristics, and exhibit significant polarization angle sensitivity.

[0004] Therefore, there is a need for improvements to broadband biomimetic absorbing materials in the existing technology. Summary of the Invention

[0005] In view of this, the purpose of this invention is to propose a broadband biomimetic absorbing material and its preparation method that combines heat insulation and high temperature resistance, so as to optimize the composition and structural characteristics of the biomimetic absorbing material, so as to achieve ultra-wideband high-efficiency absorbing characteristics, while also having flexibility, heat insulation and high temperature resistance.

[0006] Based on the above objectives, embodiments of the present invention provide a broadband biomimetic absorbing material that combines heat insulation and high temperature resistance, comprising a plurality of electromagnetic wave absorbing element structures arranged in a periodic array, wherein any adjacent electromagnetic wave absorbing element structures are spliced ​​together with zero spacing. The main body of the electromagnetic wave absorbing element structure is a wave-absorbing rubber block. The upper surface of the wave-absorbing rubber block has an inverted pyramid-shaped groove to form a concave pyramid-shaped biomimetic structure.

[0007] In some embodiments, the upper surface of the absorbing rubber block and the top surface of the inverted pyramid-shaped groove are both square and have the same size, and the height of the inverted pyramid-shaped groove is less than the height of the absorbing rubber block.

[0008] In some implementations, each electromagnetic wave absorbing element structure arranged in a periodic array has a width of 2-4 mm, a height of 3-5 mm, and a bottom support thickness of 0.2-0.5 mm.

[0009] In some embodiments, the microwave-absorbing rubber mass includes room-temperature vulcanized silicone rubber, carbonyl iron microspheres, MXene nanosheets, and a crosslinking system.

[0010] In some embodiments, the carbonyl iron microspheres have a particle size of 2-5 μm, and the MXene nanosheets have a thickness of 10-40 nm; In the microwave absorbing slurry, the mass ratio of room temperature vulcanized silicone rubber, carbonyl iron microspheres and MXene nanosheets is (23~26):10:1; The crosslinking system consists of tetraethyl orthosilicate and dibutyltin dilaurate. The amount of tetraethyl orthosilicate used is 2% to 4% of the mass of the room temperature vulcanizing silicone rubber, and the amount of dibutyltin dilaurate used is 1% to 2% of the mass of the room temperature vulcanizing silicone rubber.

[0011] In some implementations, the average reflection loss of the absorbing material is ≤-30dB in the frequency ranges of 75GHz to 110GHz and 0.2THz to 1.2THz.

[0012] Another aspect of the present invention provides a method for preparing a broadband biomimetic absorbing material that combines heat insulation and high temperature resistance, comprising the following steps: S1 mixes room temperature vulcanized silicone rubber, carbonyl iron microspheres and MXene nanosheets, and after vacuum degassing, adds it to the crosslinking system and stirs it evenly to obtain a microwave absorbing slurry; S2 injects the microwave-absorbing paste into a 3D-printed mold with a structure that complements the electromagnetic wave absorbing element structure; S3 heats and solidifies the mold into which the slurry is injected, and after demolding, a broadband biomimetic absorbing material is obtained.

[0013] In some implementations, in S1, the specific steps include: Take room temperature vulcanized silicone rubber and perform the first mechanical stirring; Carbonyl iron microspheres and MXene nanosheets were added, and a second mechanical stirring was performed; Place the mixture in a vacuum dryer and remove air bubbles by vacuuming. Tetraethyl orthosilicate and dibutyltin dilaurate were added, and the mixture was mechanically stirred for the third time to obtain the microwave absorbing slurry.

[0014] In some embodiments, the first mechanical stirring time is 10 min to 20 min, and the stirring rate is 150 r / min to 300 r / min; the second mechanical stirring time is 30 min to 50 min, and the stirring rate is 500 r / min to 800 r / min; the third mechanical stirring time is 3 min to 5 min, and the stirring rate is 200 r / min to 400 r / min.

[0015] In some embodiments, in S3, the heating and curing temperature is 50°C to 60°C, and the curing time is 2 hours; after curing, the material is allowed to cool naturally for 30 minutes to 60 minutes before demolding.

[0016] The present invention has at least the following beneficial technical effects: 1) This invention provides a broadband biomimetic absorbing material. Inspired by the microstructure of butterfly wings, it adopts a concave pyramid-shaped biomimetic electromagnetic wave absorbing element structure. Based on the structural design, the component design of the absorbing material is coordinated to achieve efficient absorption of electromagnetic waves in the range of 75GHz~110GHz and 0.2THz~1.2THz, with an average reflection loss of -38.79dB. Furthermore, by adjusting the periodic size and height size of the absorbing element structure, the absorption peak frequency band and loss performance of the biomimetic absorbing material can be controlled. At the same time, the biomimetic absorbing material has excellent bending performance stability.

[0017] 2) This invention significantly extends the heat conduction path through the biomimetic design of the electromagnetic wave absorbing element structure, giving the biomimetic absorbing material excellent thermal stability, thereby achieving excellent heat insulation performance and infrared stealth characteristics.

[0018] 3) The biomimetic absorbing material provided by this invention has excellent high temperature resistance and can maintain its electromagnetic absorbing performance in high temperature environments.

[0019] 4) This invention also provides a method for preparing broadband biomimetic absorbing materials, which is simple in process, low in cost, and conducive to the industrial production and application of biomimetic absorbing materials. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the broadband biomimetic absorbing material that combines heat insulation and high temperature resistance in this invention. Figure 2This is a flowchart illustrating the preparation process of the broadband biomimetic absorbing material that combines heat insulation and high temperature resistance in this invention. Figure 3 This is a SEM image of a broadband biomimetic absorbing material that combines heat insulation and high temperature resistance in an embodiment of the present invention. Figure 4 This is a comparison of the reflection loss curves of the broadband biomimetic absorbing material in the 75 GHz ~ 110 GHz range with respect to the period P in the embodiments of the present invention. Figure 5 This is a comparison of the reflection loss curves of the broadband biomimetic absorbing material in the range of 0.2 THz to 1.2 THz with respect to the period P in the embodiments of the present invention. Figure 6 This is a comparison graph of the reflection loss curves of the broadband biomimetic absorbing material in the range of 75 GHz to 110 GHz with respect to height H in the embodiments of the present invention; Figure 7 This is a comparison graph of the reflection loss curves of the broadband biomimetic absorbing material in the range of 0.2 THz to 1.2 THz with respect to height H in the embodiments of the present invention; Figure 8 This is a comparison of the reflection loss curves of the broadband biomimetic absorbing material in the range of 75 GHz to 110 GHz with respect to the bending angle θ in the embodiments of the present invention. Figure 9 This is a comparison graph showing the reflection loss curves of the broadband biomimetic absorbing material in the range of 0.2 THz to 1.2 THz with respect to the bending angle θ in the embodiments of the present invention. Figure 10 This is a thermogravimetric curve of the broadband biomimetic absorbing material in the embodiment of the present invention at 50℃~600℃; Figure 11 This is a graph showing the surface temperature change of the broadband biomimetic absorbing material on a 100°C heating stage in an embodiment of the present invention. Figure 12 This is a comparison graph of the reflection loss curves of the broadband biomimetic absorbing material in the range of 75 GHz to 110 GHz with respect to ambient temperature in an embodiment of the present invention. Figure 13 This is a comparison graph showing the reflection loss curves of the broadband biomimetic absorbing material in the range of 0.2 THz to 1.2 THz with respect to ambient temperature in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0023] The terms "comprising" and "having," and any variations thereof, used in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion; the terms "first," "second," etc., used in the specification, claims, and accompanying drawings are used to distinguish different objects, not to describe a particular order. "A plurality of" means two or more, unless otherwise explicitly specified.

[0024] Furthermore, the reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] like Figure 1 The image shows a broadband biomimetic absorbing material inspired by the microstructure of butterfly wings, which combines heat insulation and high temperature resistance. It includes several electromagnetic wave absorbing elements arranged in a periodic array, with zero-pitch splicing between any adjacent electromagnetic wave absorbing elements. The main body of the electromagnetic wave absorbing element structure is a wave-absorbing rubber block. The upper surface of the wave-absorbing rubber block has an inverted pyramid-shaped groove to form a concave pyramid-shaped biomimetic structure.

[0026] Furthermore, the upper surface of the absorbing rubber block and the top surface of the inverted pyramid-shaped groove are both square and have the same size, and the height of the inverted pyramid-shaped groove is less than the height of the absorbing rubber block.

[0027] Furthermore, each electromagnetic wave absorbing element in the periodic array has a width of 2-4 mm, a height of 3-5 mm, and a bottom support thickness of 0.2-0.5 mm. The bottom support thickness h refers to the distance between the bottom of the inverted pyramid-shaped groove and the lower surface of the absorbing rubber block. The height H minus the bottom support thickness h is the height of the inverted pyramid-shaped groove.

[0028] Furthermore, the microwave-absorbing rubber block comprises room temperature vulcanized silicone rubber, carbonyl iron microspheres, MXene nanosheets, and a crosslinking system.

[0029] Furthermore, the carbonyl iron microspheres have a particle size of 2-5 μm, and the MXene nanosheets have a thickness of 10-40 nm; In the microwave absorbing slurry, the mass ratio of room temperature vulcanized silicone rubber, carbonyl iron microspheres and MXene nanosheets is (23~26):10:1; preferably 25:10:1.

[0030] The crosslinking system consists of tetraethyl orthosilicate and dibutyltin dilaurate. The amount of tetraethyl orthosilicate used is 2% to 4% of the mass of the room temperature vulcanizing silicone rubber, and the amount of dibutyltin dilaurate used is 1% to 2% of the mass of the room temperature vulcanizing silicone rubber.

[0031] This material achieves excellent absorption performance with a reflection loss of less than -30dB in the 75GHz~110GHz range and a reflection loss of less than -40dB in the 0.2THz~1.2THz range, while also possessing good thermal insulation performance and high temperature resistance exceeding 400℃.

[0032] Based on this, the structured absorbing rubber exhibits superior electromagnetic wave absorption performance, and its absorption performance is adjustable with changes in structural dimensions. Furthermore, the broadband biomimetic absorbing material possesses excellent tensile strength and flexibility, making it easy to bend and capable of bending over 150° without damage. The interface co-assembly of the broadband biomimetic absorbing material establishes a rich non-uniform interface as a polarization center. This interface polarization promotes efficient energy conversion, transforming electromagnetic wave energy into other forms. Simultaneously, the concave pyramid of the macroscopic biomimetic structure achieves wider impedance matching, allowing more electromagnetic waves to enter the biomimetic absorbing material. After a large number of electromagnetic waves enter, they undergo multiple reflections and scatterings on the structural walls and are absorbed or attenuated by the material within the structure. In addition, the small amount of attenuated electromagnetic waves transmitted by the material undergoes backscattering within the structure, extending the residence time of electromagnetic waves in the absorbing material and effectively prolonging the electromagnetic wave propagation path.

[0033] Furthermore, the present invention also provides a method for preparing the above-mentioned broadband biomimetic absorbing material, such as... Figure 2 As shown, the specific steps include: S1 mixes room temperature vulcanized silicone rubber, carbonyl iron microspheres and MXene nanosheets, and after vacuum degassing, adds it to the crosslinking system and stirs it evenly to obtain a microwave absorbing slurry; S2 injects the microwave-absorbing paste into a 3D-printed mold with a structure that complements the electromagnetic wave absorbing element structure; S3 heats and solidifies the mold into which the slurry is injected, and after demolding, a broadband biomimetic absorbing material is obtained.

[0034] In S1, the specific steps include: Take room temperature vulcanized silicone rubber and perform the first mechanical stirring; Carbonyl iron microspheres and MXene nanosheets were added, and a second mechanical stirring was performed; Place the mixture in a vacuum dryer and remove air bubbles by vacuuming. Tetraethyl orthosilicate and dibutyltin dilaurate were added, and the mixture was mechanically stirred for the third time to obtain the microwave absorbing slurry.

[0035] Furthermore, the first mechanical stirring time is 10 min to 20 min, and the stirring rate is 150 r / min to 300 r / min; the second mechanical stirring time is 30 min to 50 min, and the stirring rate is 500 r / min to 800 r / min; the third mechanical stirring time is 3 min to 5 min, and the stirring rate is 200 r / min to 400 r / min.

[0036] Furthermore, in S3, the heating and curing temperature is 50℃~60℃, and the curing time is 2h; after curing, it is naturally cooled for 30min~60min before demolding.

[0037] In some preferred embodiments, 20g of room temperature vulcanizing silicone rubber (RTV) was weighed and added to a beaker, and mechanically stirred for 10-20 minutes at a stirring speed of 150-300 rpm. Then, carbonyl iron microspheres (SCI) and monolayer MXene nanosheets (Ti3C2Tx) were weighed and added to the RTV, and mixed at a mass ratio of RTV:SCI:MXene = 25:10:1. The mixture was then mechanically stirred at a speed of 500-800 rpm for 30-50 minutes. The beaker was then placed in a vacuum dryer and evacuated for 20 minutes to remove air bubbles. Finally, 0.4-0.8g of tetraethyl orthosilicate and 0.1-0.2g of dibutyltin dilaurate were added, and the mixture was mechanically stirred at a speed of 200 rpm for 3 minutes to obtain the microwave absorbing slurry.

[0038] like Figure 3 The image shows a SEM image of the fabricated broadband biomimetic absorbing material (MCRC). As can be seen from the image, the inner wall of the structure has fewer defects and a smooth surface, which can better match the air impedance. This ensures that electromagnetic waves can enter the interior of the MCRC structure without significant reflection, thus achieving strong electromagnetic wave absorption.

[0039] To better illustrate the beneficial effects of the present invention, a detailed explanation is provided below in conjunction with the working principle and test results.

[0040] For absorbing materials, achieving broadband strong absorption generally requires simultaneously satisfying good impedance matching characteristics and strong intrinsic loss. First, to achieve minimal direct surface reflection, it is necessary to ensure that electromagnetic waves can enter the interior of the absorbing material as much as possible. Based on the principle of electromagnetic wave propagation, the input impedance of the material surface can be derived. The relationship between the direct reflection coefficient R and the expression is:

[0041] in, For free space impedance, ; The permeability of free space, ; The vacuum permittivity, Therefore, in order to minimize electromagnetic wave reflection, the input impedance of the material surface must be guaranteed. With free space impedance To achieve maximum matching; for electromagnetic waves incident perpendicularly to the surface of the absorbing material, their reflection loss can be calculated using transmission line theory. for:

[0042]

[0043] in, The relative permeability of the material, The relative permittivity of the material is . Represents the imaginary unit. The incident frequency of the electromagnetic wave. d The thickness of the absorbing material, Let be the speed of light in a vacuum. As can be seen from the formula, the reflection of electromagnetic waves at the surface of a material is closely related to the impedance of the material surface. At the same time, the reflection loss is also affected by the dielectric constant and permeability of the material. Therefore, by matching the impedance of the absorbing material with that of the air through structural design, and combining the material's loss on electromagnetic waves, efficient absorption of broadband electromagnetic waves can be achieved.

[0044] Furthermore, this invention introduces the average reflection loss (ARL) to evaluate the broadband electromagnetic absorption performance of the absorbing material. A larger ARL value means that the electromagnetic wave absorbing material achieves strong absorption across the entire measurement frequency range. The average reflection loss (ARL) is specifically expressed as follows:

[0045] in, For frequency points, This represents the RL value at the i-th frequency point.

[0046] Based on this, this embodiment tests broadband biomimetic absorbing materials with periods P of 2mm, 3mm, and 4mm, and their reflection loss in the 75GHz~110GHz range is as follows: Figure 4 As shown, the reflection loss in the range of 0.2THz to 1.2THz is as follows: Figure 5As shown, the height H of the electromagnetic wave absorbing element structure of this broadband biomimetic absorbing material is 4 mm, and the thickness h of the bottom support is 0.5 mm. As can be seen from the figure, two resonance peaks are generated in the 75 GHz to 110 GHz frequency band. Furthermore, changing the structural period can effectively control the resonance absorption range and reflection loss value. With the increase of the period, the frequency of the absorption peak shifts to lower frequencies; the shift range of the low-frequency resonance peak can decrease from 89.35 GHz to 83.37 GHz, while the shift range of the high-frequency resonance peak can decrease from 103.38 GHz to 93.51 GHz, exhibiting good frequency selectivity. The average reflection loss ARL of the biomimetic absorbing material in the 0.2 THz to 1.2 THz range is -34.67 dB, -38.79 dB, and -38.26 dB, respectively.

[0047] Furthermore, this embodiment tests broadband biomimetic absorbing materials with heights H of 3mm, 4mm, and 5mm, and their reflection loss in the 75GHz~110GHz range is as follows: Figure 6 As shown, the reflection loss in the range of 0.2THz to 1.2THz is as follows: Figure 7 As shown, the period P of the electromagnetic wave absorbing element structure of the broadband biomimetic absorbing material is 3 mm, and the thickness h of the bottom support is 0.5 mm. As can be seen from the figure, the reflection loss of the biomimetic absorbing material in the range of 75 GHz to 110 GHz gradually decreases with the increase of thickness, that is, the absorption performance is enhanced. After satisfying that the period size is greater than the wavelength of the electromagnetic wave, the multiple reflections generated inside the biomimetic structure increase with the increase of its thickness. The average reflection loss ARL of the biomimetic absorbing material in the range of 0.2 THz to 1.2 THz reaches -30.21 dB, -38.79 dB and -44.63 dB, respectively.

[0048] Meanwhile, the biomimetic absorbing material provided in this embodiment, through the design of a mass ratio of vulcanized silicone rubber, carbonyl iron microspheres, and MXene nanosheets of 25:10:1, possesses both flexible and bendable properties, enabling it to be attached to structural components with varying curvatures to meet a wider range of application needs. This embodiment tested the biomimetic absorbing material by attaching it to the surface of structural components with different bending angles θ (when θ = 0°, it is in a flat state). Its reflection loss in the 75GHz~110GHz range is as follows: Figure 8 As shown, the reflection loss in the range of 0.2THz to 1.2THz is as follows: Figure 9As shown in the figure, as the bending angle changes, the reflection loss performance of the biomimetic absorbing material is less than -20dB in the range of 75GHz to 110GHz and less than -40dB in the range of 0.2THz to 1.2THz. To more intuitively demonstrate the performance of the biomimetic absorbing material at different bending angles and analyze its average reflection loss, even when θ reaches 90°, the biomimetic absorbing material still provides excellent loss capability. The average reflection loss of the biomimetic absorbing material is below -30dB, which is equivalent to effectively absorbing more than 99.9% of electromagnetic waves. Furthermore, the minimum RL of the biomimetic absorbing material reaches -50.66dB (78.15GHz) in the 75GHz~110GHz range, corresponding to θ=30°, and the minimum RL reaches -78.71dB (0.76THz) in the 0.2THz~1.2THz range, corresponding to θ=60°. Therefore, the biomimetic absorbing material provided in this embodiment has excellent bending performance stability, which makes it more widely applicable in portable electronic devices and large electromagnetic compatibility devices.

[0049] Furthermore, thermogravimetric analysis (TGA) is crucial for characterizing the thermal stability of materials. The temperature at which a material experiences a 10% mass loss can be defined as the decomposition temperature, denoted as T. d Traditional microwave absorbing materials are generally unsuitable for high-temperature environments. To investigate the high-temperature resistance of the biomimetic microwave absorbing material provided in this embodiment, the thermal stability of pure RTV and MCRC samples in atmospheric temperatures ranging from 50°C to 600°C was tested using TGA. The test results are as follows: Figure 10 As shown in the figure, when the temperature is below 200℃, all samples exhibit slight mass loss due to the desorption of surface water; when the temperature rises from 200℃ to 600℃, a second stage of mass loss occurs. For the pure RTV sample, its decomposition temperature T0 is [missing value]. d The decomposition temperature was approximately 351.4℃. As the temperature continued to increase, its mass decreased rapidly due to the oxidative decomposition of polymeric amorphous carbon. The decomposition temperature of the MCRC sample reached 413.4℃, which is attributed to the excellent thermal stability of the filler and the fact that the biomimetic structure can effectively suppress the heat conduction path, giving the MCRC sample excellent high-temperature resistance. Furthermore, after reaching the decomposition temperature, MXene was oxidized into titanium dioxide and carbon dioxide, and the overall residual mass ratio increased to 40.17%, indicating that it has excellent thermal stability.

[0050] To meet the increasing demands of applications in complex environments, excellent thermal insulation capabilities enable microwave absorbing materials to effectively protect electronic devices and prevent damage from overheating. In this embodiment, an MCRC sample was placed on a heating stage with an initial temperature of 100°C, and its temperature change was measured using an infrared thermal imager. The results are as follows... Figure 11As shown in the figure, the initial temperature of the sample was 22.8℃; after 10s, the temperature at the top of the sample rose to 24.2℃; after 120s, the temperature at the top of the sample only rose to 38.6℃; after 600s, the temperature at the top of the sample almost stabilized at 51.4℃, with a temperature difference of 48.6℃ from the heating stage, indicating that the MCRC sample has good thermal insulation performance; furthermore, the excellent thermal insulation capability of the MCRC sample enables it to shield infrared detection. In the biomimetic absorbing material provided in this embodiment, the rubber material itself has inherent thermal insulation properties and low radiative heat transfer capability, and the concave aperture biomimetic structure effectively increases the collisions between air molecules and between air molecules and the structural walls, significantly extending the heat conduction path, thereby reducing the heat conduction capability.

[0051] Finally, this embodiment tests the biomimetic absorbing material before and after high-temperature (400℃) heating, and its reflection loss in the 75GHz~110GHz range is as follows: Figure 12 As shown, the reflection loss in the range of 0.2THz to 1.2THz is as follows: Figure 13 As shown in the figure, the overall absorption performance of the biomimetic absorbing material changes little before and after heating, with the average reflection loss changing from -38.79dB to -35.92dB, indicating that the electromagnetic absorption performance of the biomimetic absorbing material has strong thermal stability after high-temperature treatment.

[0052] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0053] It should be understood that, as used herein, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" means any and all possible combinations of one or more of the associated listed items.

[0054] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0055] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A broadband biomimetic microwave absorbing material that combines heat insulation and high-temperature resistance, characterized in that, It includes several electromagnetic wave absorbing element structures arranged in a periodic array, with zero-pitch splicing between any adjacent electromagnetic wave absorbing element structures; The main body of the electromagnetic wave absorbing element structure is a wave-absorbing rubber block. The upper surface of the wave-absorbing rubber block has an inverted pyramid-shaped groove to form a concave pyramid-shaped biomimetic structure.

2. The broadband biomimetic absorbing material with both heat insulation and high-temperature resistance according to claim 1, characterized in that, The upper surface of the microwave-absorbing rubber block and the top surface of the inverted pyramid-shaped groove are both square and have the same size. The height of the inverted pyramid-shaped groove is less than the height of the microwave-absorbing rubber block.

3. The broadband biomimetic absorbing material with both heat insulation and high-temperature resistance according to claim 1, characterized in that, Each of the electromagnetic wave absorbing elements arranged in the periodic array has a width of 2-4 mm, a height of 3-5 mm, and a bottom support thickness of 0.2-0.5 mm.

4. The broadband biomimetic absorbing material with both heat insulation and high-temperature resistance according to claim 1, characterized in that, The microwave-absorbing rubber block comprises room temperature vulcanized silicone rubber, carbonyl iron microspheres, MXene nanosheets, and a crosslinking system.

5. The broadband biomimetic absorbing material with both heat insulation and high-temperature resistance according to claim 4, characterized in that, The carbonyl iron microspheres have a particle size of 2~5μm, and the MXene nanosheets have a thickness of 10~40nm; In the microwave absorbing slurry, the mass ratio of room temperature vulcanized silicone rubber, carbonyl iron microspheres and MXene nanosheets is (23~26):10:1; The crosslinking system is tetraethyl orthosilicate and dibutyltin dilaurate. The amount of tetraethyl orthosilicate is 2% to 4% of the mass of the room temperature vulcanizing silicone rubber, and the amount of dibutyltin dilaurate is 1% to 2% of the mass of the room temperature vulcanizing silicone rubber.

6. The broadband biomimetic absorbing material with both heat insulation and high-temperature resistance according to claim 1, characterized in that, The absorbing material has an average reflection loss of ≤-30dB in the frequency ranges of 75GHz~110GHz and 0.2THz~1.2THz.

7. A method for preparing a broadband biomimetic absorbing material with both heat insulation and high-temperature resistance as described in any one of claims 1-6, characterized in that, include: S1 mixes room temperature vulcanized silicone rubber, carbonyl iron microspheres and MXene nanosheets, and after vacuum degassing, adds it to the crosslinking system and stirs it evenly to obtain a microwave absorbing slurry; S2 injects the microwave absorbing paste into a 3D printed mold having a structure complementary to the electromagnetic wave absorbing element structure; S3 heats and solidifies the mold into which the slurry is injected, and after demolding, the broadband biomimetic absorbing material is obtained.

8. The method for preparing the broadband biomimetic absorbing material with both heat insulation and high temperature resistance according to claim 7, characterized in that, In S1, the specific steps include: Take room temperature vulcanized silicone rubber and perform the first mechanical stirring; Carbonyl iron microspheres and MXene nanosheets were added, and a second mechanical stirring was performed; Place the mixture in a vacuum dryer and remove air bubbles by vacuuming. Tetraethyl orthosilicate and dibutyltin dilaurate were added, and the mixture was mechanically stirred for the third time to obtain the microwave absorbing slurry.

9. The method for preparing the broadband biomimetic absorbing material with both heat insulation and high temperature resistance according to claim 8, characterized in that, The first mechanical stirring time is 10 min to 20 min, and the stirring rate is 150 r / min to 300 r / min; the second mechanical stirring time is 30 min to 50 min, and the stirring rate is 500 r / min to 800 r / min; the third mechanical stirring time is 3 min to 5 min, and the stirring rate is 200 r / min to 400 r / min.

10. The method for preparing the broadband biomimetic absorbing material with both heat insulation and high temperature resistance according to claim 7, characterized in that, In S3, the heating and curing temperature is 50℃~60℃, and the curing time is 2h; after curing, it is naturally cooled for 30min~60min before demolding.

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