Electromagnetic protection / wave-absorbing material with energy selective surface and preparation method of electromagnetic protection / wave-absorbing material

Abstract

The invention provides an electromagnetic protection / wave-absorbing material with an energy selective surface and a preparation method, the electromagnetic protection / wave-absorbing material is composed of a layer of adaptive conversion material and a wave-absorbing material, and the electromagnetic protection / wave-absorbing material has electromagnetic protection capability under strong electromagnetic pulse and excellent wave-absorbing performance. Different wave-absorbing materials are selected according to different wave-absorbing frequency bands and application occasions, a layer of self-adaptive conversion material is introduced into the surface layer, and electrical property collaborative design is carried out. And the self-adaptive conversion material film on the surface layer can realize medium state / conductor state self-adaptive mutual conversion according to the intensity of an electromagnetic field in the surrounding environment, so that the intelligent self-adaptive electromagnetic protection / wave-absorbing capability is obtained, and the situation that the wave-absorbing material absorbs electromagnetic waves under strong electromagnetic pulses and the temperature rises sharply and is damaged is avoided.

Description

Technical Field

[0001] This invention relates to an electromagnetic shielding / absorbing material with an energy selective surface and its preparation method, belonging to the field of functional materials technology. Background Technology

[0002] With the advent of high-power weapons such as electromagnetic pulse weapons, significant damage can be caused to the electronic components of weaponry, as well as to the electromagnetic radiation absorbing materials. Because absorbing materials are highly effective at absorbing electromagnetic waves and converting them into heat, if weaponry equipped with such materials is attacked by an electromagnetic pulse weapon, it will absorb a large amount of electromagnetic waves in a short period, causing the absorbing material's temperature to rise rapidly, leading to its failure and even damage to the weaponry.

[0003] Traditional electromagnetic shielding materials, including metal mesh, highly conductive metal foil, and continuous carbon fiber composites, all possess excellent electromagnetic shielding capabilities. While these materials shield external electromagnetic waves, they also restrict the transmission of electromagnetic waves between the internal and external systems, blocking electromagnetic information exchange; or the shielded electromagnetic waves may be easily detected by enemy radar, making them easier to identify. Therefore, for stealth weapons and equipment, surface materials must also utilize radar-absorbing materials to achieve stealth. However, radar-absorbing materials are more susceptible to electromagnetic pulse (EMP) weapons, thus requiring protection against EMP attacks while maintaining their radar-absorbing capabilities after the EMP attack subsides.

[0004] Currently, to prevent attacks from high-power pulse weapons, a new approach of energy selective surfaces has been proposed. These are electromagnetic protection methods designed using field-induced conductive materials or voltage-controlled conductive structures, possessing electromagnetic environment adaptive characteristics. Essentially, they are spatial field strength limiters, achieving low-pass characteristics for electromagnetic energy. The applications of these energy selective surfaces are all for protecting electromagnetic components from damage and do not involve the field of electromagnetic absorption and stealth. Patent CN116284898A discloses a recyclable and remodelable transparent intelligent electromagnetic absorbing material, its preparation method, and its applications, belonging to the field of novel electromagnetic protection materials. Nano-vanadium dioxide is added to a polymer matrix, utilizing the phase transition properties of vanadium dioxide to achieve electromagnetic absorption at high temperatures; the role of vanadium dioxide is to transform into conductive particles at high temperatures, acting as an absorber to absorb electromagnetic waves. This patent does not involve the electromagnetic protection function of materials under strong electromagnetic pulses. Patent CN115322442A discloses an electromagnetic shielding composite material with temperature response characteristics, its preparation method, and its applications, belonging to the field of electromagnetic shielding material technology. This patent uses vanadium dioxide as a functional material, combining it with a matrix material to prepare a vanadium dioxide / nanocellulose film. Upon heating to a certain temperature, vanadium dioxide transforms from an insulating state to a metallic state, dramatically improving the electromagnetic shielding effectiveness of the composite material. Both patents utilize the property of vanadium dioxide transitioning from an insulating to a metallic state at high temperatures. When the prepared composite material is heated above its phase transition temperature under an external temperature field, it acquires new functional properties, such as the ability to absorb or shield electromagnetic waves, but it cannot self-regulate or intelligently switch according to the external environment. Furthermore, neither patent mentions the mutual conversion between wave absorption and shielding in the composite material, making it unsuitable for electromagnetic pulse attack protection using wave-absorbing materials.

[0005] Introducing energy selective surfaces into microwave absorbing materials requires consideration of issues such as electrical performance and structural design, ensuring microwave absorption while achieving electromagnetic protection capabilities under strong electromagnetic pulses. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a material and preparation method that have both electromagnetic protection capability under strong electromagnetic pulses and excellent wave absorption performance.

[0007] This invention introduces an adaptively convertible material onto the surface of a microwave absorbing material. This material has two states: a dielectric state, which allows wave transmission without affecting the material's ability to absorb electromagnetic waves; and a conductor state, which rapidly transforms from a dielectric to a conductor state under external field excitation, providing strong electromagnetic shielding and protecting the absorbing material. When the external excitation field disappears, it quickly transforms back into a dielectric state. By introducing a dielectric / conductor conversion material onto the surface of the absorbing material, the overall structure exhibits intelligent adaptive electromagnetic protection / stealth capabilities.

[0008] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0009] An electromagnetic shielding / absorbing material with an energy selective surface includes an absorbing material and an adaptive conversion material located on the surface of the absorbing material.

[0010] Furthermore, at low intensity (E a In an electromagnetic detection environment, the material adaptively switches to a dielectric state, and the overall structure exhibits excellent electromagnetic absorption performance (t0). When the external electromagnetic environment intensifies rapidly to a certain threshold (E... b When external stimuli such as temperature rise (due to energy absorption by the absorbing material) or strong electromagnetic field are generated, the adaptive conversion material rapidly transitions from a dielectric state to a conductor state, forming a shielding layer and achieving electromagnetic protection (t1~t2). When the external electromagnetic field weakens to below the threshold, the adaptive conversion material returns from the conductor state to the dielectric state, and the overall structure returns to the electromagnetic absorption state (t3).

[0011] Furthermore, the adaptive conversion material is VO2, La 0.67 Ca 0.33 MnO3, Cu / SiO2 and other thin films in metal / non-metal two-phase nanoparticle systems can undergo a dielectric / conductor phase transition under strong electromagnetic or temperature fields, with thicknesses ranging from 0.1 mm to 2 mm.

[0012] Furthermore, the absorbing material includes absorbing patches, absorbing foam, and absorbing sponge, etc. The absorbing material contains an absorbent, with an absorbent content (mass fraction) of 1% to 60%, and the absorbing frequency band includes 0.5 GHz to 40 GHz. Different types, thicknesses, and electrical properties of absorbing materials can be selected for different absorbing frequency bands and applications.

[0013] A method for preparing an electromagnetic shielding / absorbing material with an energy-selective surface includes the following steps:

[0014] Preparation of thin films of adaptive conversion materials;

[0015] By transferring a thin film of adaptive conversion material onto the surface of a microwave absorbing material, an electromagnetic protection / absorbing material with an energy-selective surface is obtained.

[0016] Furthermore, the adaptive conversion material thin film is obtained by magnetron sputtering, chemical vapor deposition, or physical vapor deposition. First, the adaptive conversion material thin film is deposited on a substrate, and then the adaptive conversion material thin film on the substrate is transferred to the surface of the absorbing material. The adaptive conversion material thin film and the absorbing material can be fixed together by adhesive bonding. The thin film preparation method is a known technology, and the specific process parameters are determined according to actual production needs.

[0017] Furthermore, the preparation methods of the microwave absorbing materials are mostly well-known technologies. The microwave absorbing patches are prepared by dense rolling and calendering, the microwave absorbing foam is prepared by foaming, and the microwave absorbing sponge is prepared by impregnation. The specific process parameters are determined according to the actual production needs.

[0018] Furthermore, electrical performance design is carried out for the absorption frequency band and absorption performance, and the type and thickness of adaptive conversion material, as well as the type and content of absorber in the absorption material, are determined.

[0019] Furthermore, the absorbent is one or more of the following: carbonyl iron powder, ferrite, iron-silicon-aluminum, carbon fiber, carbon black, carbon nanotubes, organic conductive fibers, etc.

[0020] The beneficial effects of this invention compared to the prior art are as follows:

[0021] (1) The present invention introduces a thin film that can be adaptively switched on the surface of the absorbing material. According to the external electromagnetic environment, the material as a whole can adaptively switch between absorbing and shielding electromagnetic waves, giving the absorbing material electromagnetic protection capability under strong electromagnetic pulses, and avoiding damage caused by the rapid increase in temperature of the absorbing material under strong electromagnetic pulses.

[0022] (2) Existing energy selective surfaces are only used as electromagnetic protection measures to protect electronic components from damage by strong electromagnetic pulses. This invention combines energy selective surfaces with microwave absorbing materials to achieve synergistic design of electrical performance, while simultaneously providing electromagnetic protection / wave absorption functions, thus expanding the application of energy selective surface technology to the field of microwave absorbing stealth.

[0023] (3) The thin film on the surface of the present invention can realize adaptive conversion between dielectric state and conductor state, and can intelligently switch according to the intensity of electromagnetic field in the surrounding environment, thus obtaining intelligent adaptive electromagnetic protection / wave absorption capability. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing the electromagnetic intensity at different times in the electromagnetic detection environment of the electromagnetic protection / absorbing material of the present invention.

[0025] Figure 2 This is a schematic diagram of the electromagnetic protection / absorbing material of the present invention and its electromagnetic protection process under strong electromagnetic pulses. Detailed Implementation

[0026] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings.

[0027] This invention provides an electromagnetic shielding / absorbing material with an energy-selective surface, comprising an adaptive conversion material and an absorbing material, wherein the electromagnetic intensity of the electromagnetic detection environment at different times is as follows: Figure 1As shown, the process by which it achieves its wave absorption function and electromagnetic protection capability under strong electromagnetic pulses is as follows: Figure 2 As shown. At low intensity (E a In an electromagnetic detection environment, the adaptive conversion material is in a dielectric state, and the overall structure exhibits excellent electromagnetic absorption performance (t0). When the external electromagnetic environment intensifies rapidly to a certain threshold (E... b When external stimuli such as temperature or strong electromagnetic fields are generated, the adaptive conversion material rapidly transforms from a dielectric state to a conductor state, forming a shielding layer and realizing electromagnetic protection (t1~t2). When the external electromagnetic field weakens to below the threshold, the intelligent conversion material returns from the conductor state to the dielectric state, and the overall structure returns to the electromagnetic absorption state (t3).

[0028] Example 1

[0029] In this embodiment, the absorbing material targets the absorption frequency band of 0.5GHz to 8GHz. The selected absorbents are flake-shaped iron-silicon-aluminum and carbonyl iron powder. The absorbing material is an absorbing patch with a thickness of 2mm and an absorbent content of 85wt%. The adaptive conversion material is a VO2 thin film with a thickness of 1mm. The absorbent is mixed with rubber, and after intensive kneading and calendering, a 2mm thick absorbing patch is obtained. A VO2 thin film is prepared by magnetron sputtering and transferred to the surface of the absorbing patch to obtain an electromagnetic shielding / absorbing material with an energy selective surface.

[0030] The microwave absorption performance was tested, and the reflectivity was ≤-8dB in the 0.5–1GHz range, ≤-10dB in the 1–2GHz range, and ≤-15dB in the 2–8GHz range. The absorbing material exhibits excellent absorption performance within the required electromagnetic wave frequency band (0.5–8GHz). After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the material's appearance. Upon cutting the material open and observing its internal structure, no change was found. Repeated microwave absorption performance tests showed no change in absorption performance.

[0031] Example 2

[0032] In this embodiment, the absorbing material targets the absorbing frequency band of 1GHz to 18GHz. The selected absorbents are chopped carbon fibers and carbonyl iron powder. The absorbing material is absorbing foam with a thickness of 20mm and an absorbent content of 20wt%. The adaptive conversion material is a VO2 film with a thickness of 0.5mm. The absorbent and foaming material are mixed and foamed to obtain a 20mm thick absorbing polyurethane foam. A VO2 film is prepared by magnetron sputtering and transferred to the surface of the absorbing foam to obtain an electromagnetic shielding / absorbing material with an energy selective surface.

[0033] The microwave absorption performance was tested, and the reflectivity was ≤-8dB in the 1–2 GHz range, ≤-15dB in the 2–8 GHz range, and ≤-20dB in the 8–18 GHz range. The absorbing material exhibits excellent absorption performance within the required electromagnetic wave frequency band (1–18 GHz). After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the appearance of the foam material. Cutting open the foam material to observe the interior also revealed no change. Repeated microwave absorption performance tests showed no change in absorption performance.

[0034] Example 3

[0035] In this embodiment, the absorbing material targets the absorption frequency band of 2GHz to 40GHz. The selected absorber is carbon black, the absorbing material is absorbing sponge with a thickness of 30mm and an absorber content of 6wt%, and the adaptive conversion material is a VO2 film with a thickness of 0.1mm. The absorber is mixed with an adhesive to prepare an absorbing slurry; a 30mm thick absorbing polyurethane sponge is obtained by impregnating the polyurethane sponge; a VO2 film is prepared by magnetron sputtering and transferred to the surface of the absorbing sponge to obtain an electromagnetic shielding / absorbing material with an energy selective surface.

[0036] The microwave absorption performance was tested, and the reflectivity was ≤-15dB in the 2–8GHz range, ≤-20dB in the 8–18GHz range, and ≤-25dB in the 26.5–40GHz range. The absorbing material exhibits excellent absorption performance within the required electromagnetic wave frequency band (2–40GHz). After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the appearance of the absorbing sponge material. Cutting open the sponge material to observe the interior also revealed no change. Repeated microwave absorption performance tests showed no change in absorption performance.

[0037] Example 4

[0038] In this embodiment, the adaptive conversion material is La. 0.67 Ca 0.33 A MnO3 thin film was prepared, with the remainder identical to that in Example 1, to obtain an electromagnetic shielding / absorbing material with an energy-selective surface. Its absorption performance was tested, and the reflectivity was ≤-6dB in the 0.5–1 GHz range, ≤-12dB in the 1–2 GHz range, and ≤-17dB in the 2–8 GHz range. The absorbing material exhibits excellent absorption performance within the desired electromagnetic wave frequency band (0.5–8 GHz). After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the material's appearance. Upon cutting the material and observing its internal structure, no change was observed. Repeated absorption performance tests showed no change in absorption performance.

[0039] Example 5

[0040] In this embodiment, the adaptive conversion material is a Cu / SiO2 thin film, a two-phase nanoparticle system of metal / non-metal, and the rest is the same as in Example 1, resulting in an electromagnetic shielding / absorbing material with an energy-selective surface. Its absorption performance was tested, and the reflectivity was ≤-10dB in the 0.5–1GHz range, ≤-14dB in the 1–2GHz range, and ≤-18dB in the 2–8GHz range. The absorbing material exhibits excellent absorption performance within the required electromagnetic wave frequency band (0.5–8GHz). After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the material's appearance. Cutting the material open to observe its internal structure also revealed no change. Repeated absorption performance tests showed no change in absorption performance.

[0041] Comparative Example 1

[0042] The surface film is a copper film, and the rest is the same as in Example 1, thus obtaining an absorbing patch material. Its absorption performance was tested, and no absorption performance was observed. After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the material's appearance; the material was cut open to observe the interior, and no change was found. The absorption performance was tested again, and no absorption performance was observed.

[0043] Comparative Example 2

[0044] Without an adaptive conversion VO2 film, and otherwise identical to Example 2, a microwave absorbing foam material was obtained. Its microwave absorption performance was tested, and the reflectivity was ≤-8dB in the 1–2 GHz range, ≤-18dB in the 2–8 GHz range, and ≤-23dB in the 8–18 GHz range. The microwave absorbing material exhibits excellent absorption performance within the required electromagnetic wave frequency band (1–18 GHz). After irradiating the microwave absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, no change was observed in the appearance of the foam material. However, upon cutting open the foam material and observing its interior, burning and carbonization were observed. Further microwave absorption performance testing revealed severe degradation: reflectivity ≤-2dB in the 1–2 GHz range, ≤-5dB in the 2–8 GHz range, and ≤-8dB in the 8–18 GHz range.

[0045] Comparative Example 3

[0046] Without an adaptive conversion VO2 film, the process remained the same as in Example 3, resulting in a microwave-absorbing sponge material. Its microwave absorption performance was tested: reflectivity ≤ -15dB in the 2–8 GHz range, ≤ -22dB in the 8–18 GHz range, and ≤ -28dB in the 26.5–40 GHz range. The absorbing material exhibited excellent microwave absorption within the desired electromagnetic wave frequency band (2–40 GHz). After irradiating the absorbing material with a high-power antenna (emitting electromagnetic waves) for 10 minutes, burning was observed. Upon cutting open the sponge material, significant carbonization was observed inside. A second microwave absorption performance test revealed no absorption performance.

[0047] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0048] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. An electromagnetic shielding / absorbing material with an energy-selective surface, characterized in that, It includes a microwave absorbing material and an adaptive conversion material located on the surface of the microwave absorbing material.

2. The electromagnetic shielding / absorbing material with an energy-selective surface according to claim 1, characterized in that, The adaptive conversion material is a material that can undergo a dielectric / conductor phase transition under a strong electromagnetic field or temperature field.

3. The electromagnetic shielding / absorbing material with an energy-selective surface according to claim 1, characterized in that, In low-intensity electromagnetic detection environments, the adaptive conversion material is in a dielectric state, and the overall material exhibits electromagnetic absorption properties. When the external electromagnetic field strengthens to a certain threshold, the adaptive conversion material undergoes an adaptive conversion from a dielectric state to a conductor state, forming a shielding layer to achieve electromagnetic protection. When the external electromagnetic field weakens to below the threshold, the adaptive conversion material returns from a conductor state to a dielectric state, returning to the electromagnetic absorption state.

4. The electromagnetic shielding / absorbing material with an energy selective surface according to claim 1, characterized in that, The adaptive conversion material is VO2 or La. 0.67 Ca 0.33 MnO3, or a metal / non-metal two-phase nanoparticle system thin film.

5. The electromagnetic shielding / absorbing material with an energy-selective surface according to claim 1, characterized in that, The thickness of the adaptive conversion material is 0.1 mm to 2 mm.

6. The electromagnetic shielding / absorbing material with an energy-selective surface according to claim 1, characterized in that, The absorbing material is an absorbing patch, absorbing foam, or absorbing sponge.

7. The electromagnetic shielding / absorbing material with an energy-selective surface according to claim 1, characterized in that, The microwave absorbing material contains an absorber with a mass fraction of 1% to 60%, and the microwave absorbing frequency band includes 0.5 GHz to 40 GHz.

8. The electromagnetic shielding / absorbing material with an energy-selective surface according to claim 7, characterized in that, The absorbent is at least one of carbonyl iron powder, ferrite, iron-silicon-aluminum, carbon fiber, carbon black, carbon nanotubes, and organic conductive fibers.

9. A method for preparing an electromagnetic shielding / absorbing material with an energy-selective surface, characterized in that, Includes the following steps: Preparation of thin films of adaptive conversion materials; By transferring a thin film of adaptive conversion material onto the surface of a microwave absorbing material, an electromagnetic protection / absorbing material with an energy-selective surface is obtained.

10. The method according to claim 9, characterized in that, The thin film of the adaptive conversion material is obtained by magnetron sputtering, chemical vapor deposition or physical vapor deposition. First, the thin film of the adaptive conversion material is deposited on the substrate, and then the thin film on the substrate is transferred to the surface of the microwave absorbing material.

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