Space environment-resistant electromagnetic wave absorbent and preparation method thereof

Abstract

The invention provides a space environment-resistant electromagnetic wave absorbent. The electromagnetic wave absorbent at least comprises iron particles and a coupling agent, wherein the iron particles are iron powder which is of a sheet-shaped structure and is prepared through cold machining treatment, and the surface of the iron powder of the sheet-shaped structure is sequentially subjected to oxidation treatment and coupling agent surface modification treatment, so that a dual-coating structure composed of a ferroferric oxide (Fe3O4) layer and a Si-O-Fe layer is formed. According to the prepared electromagnetic wave absorbent, the wrapping layer is the magnetic Fe3O4 formed on the surface of the iron particles, and the silane hydrophobic thin layer, so that the electromagnetic wave absorbent is high in adhesive force, good in temperature impact resistance, high in radiation resistance, free of gas escape substances, excellent in space environment resistance and good in wave absorbing performance, and can be well combined with macromolecular resin; wide application prospects are realized in the military field and the civil field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inorganic chemistry and high polymer materials, in particular to a space environment resistant electromagnetic wave absorber and a preparation method thereof. BACKGROUND

[0002] With the wide application of radio technology, the pollution of electromagnetic wave is also increasing. In order to reduce unnecessary electromagnetic energy, it is necessary to absorb the useless electromagnetic wave, and thus the electromagnetic wave absorbing material emerges as the times require. It is a material that can convert the incident electromagnetic wave energy into other forms of energy and is rarely reflected back, also known as "wave absorbing material".

[0003] According to the absorption mechanism, it can be divided into absorption type, interference type, resonance type and plasmonic type electromagnetic wave absorbing material; according to the material form, it can be divided into coating, patch and structural material. It is mainly used as stealth material in military to reduce the radar cross section of aircraft, warships, tanks and missiles. In civil field, it is widely used in electromagnetic shielding, anti-electromagnetic interference, personnel electromagnetic protection and environmental protection.

[0004] The main component of the wave absorbing material is the electromagnetic wave absorber, which ultimately determines the absorption performance of the wave absorbing material to the electromagnetic wave. There are many types of absorbers, among which the commonly used ones are electric loss and magnetic loss. The electric loss type mainly shows resistive loss, that is, the greater the conductivity, the greater the macroscopic current caused by the carrier, which is conducive to the conversion of electromagnetic energy into heat. However, the large macroscopic current leads to the increase of electromagnetic energy reflection on the surface of the material, which makes it difficult for electromagnetic energy to enter the coating, thereby affecting the wave absorption performance.

[0005] The absorption mechanism of the magnetic loss type is related to the magnetic permeability of the material, mainly showing the magnetic domain magnetic hysteresis loss. The commonly used magnetic loss absorber also has resistive loss, so there are many related electromagnetic parameter control means, which can overcome some shortcomings of electric loss, and thus become the mainstream absorber. However, the related electromagnetic parameters of the material need to be carefully controlled to match the impedance of the incident electromagnetic wave in space as much as possible, mainly the square root of the ratio of dielectric constant and magnetic permeability should be as close to 1 as possible. The dielectric constant of most magnetic absorbers is significantly greater than the magnetic permeability, so the performance of the absorber is generally improved by appropriately reducing the dielectric constant and increasing the magnetic permeability.

[0006] With the continuous expansion of the application of radio technology in outer space and marine environment, the wave absorbing material also goes to the same space, and new requirements for the space environment resistance of the absorber are put forward. In order to improve the environmental resistance of the absorber, inorganic or high polymer materials are often used to wrap it. They are basically insulating and have no magnetism, mainly relying on chemical or physical adsorption on the surface of the material.

[0007] For example, a Chinese patent with publication number CN1923413A discloses a magnetic micro powder and a preparation method, the wrapper is KH550, or a silicon dioxide, phosphating film, polystyrene film, etc., all of which are insulating and have no magnetism, and mainly rely on chemical or physical adsorption on the material surface, and have poor adhesion. Although the dielectric constant is reduced, the magnetic permeability is also reduced. For another example, a Chinese patent with publication number CN113692213A discloses a preparation method of a corrosion-resistant irregular-shaped magnetic wave-absorbing agent powder coated with a resin in situ, and the irregular-shaped magnetic wave-absorbing agent powder is coated by combining a resin in situ and a post-curing polymerization technology on the surface of the wave-absorbing agent powder. A Chinese patent with publication number CN112029480A discloses an organic-inorganic composite coated metal wave-absorbing filler and a preparation method thereof, and a silicon dioxide is generated in situ by using tetraethoxysilane to wrap. Although these wrapping materials can provide good environmental resistance, most of the wrapping materials do not have wave-absorbing performance, and after the iron particles are coated, the dielectric constant is reduced, but the magnetic permeability is also reduced, resulting in a decrease in wave-absorbing performance. Moreover, the adhesion to temperature shock of space environment of ±200 ℃ is not considered, and the space irradiation performance, outgassing performance, etc. are also required.

[0008] Therefore, there is a need for a high-performance absorber that can meet the requirements of space environment. SUMMARY

[0009] The present application aims at the deficiencies of the prior art, and provides a sheet-shaped inorganic and organic double-wrapped electromagnetic wave absorber and a preparation method thereof, which can be used in space environment. The wrapping layers are a magnetic Fe3O4 layer and a silane hydrophobic thin layer formed on the surface of the iron particles, have high adhesion, good temperature shock resistance, strong anti-irradiation ability, no outgassing material, excellent space environment resistance, good wave-absorbing performance, and can be well combined with high molecular resin, and have a wide application prospect in the military and civilian fields.

[0010] According to a first aspect of the present application, a space environment-resistant electromagnetic wave absorber is provided, and components of the electromagnetic wave absorber at least include an iron-based substrate and a coupling agent; wherein the iron-based substrate is a sheet-shaped iron powder prepared by cold processing, and the surface of the sheet-shaped iron powder is sequentially subjected to oxidation treatment and coupling agent surface modification treatment, to form a double-coating structure composed of a ferriferrous oxide (Fe3O4) layer and a Si-O-Fe layer.

[0011] As an optional implementation, the thickness of the ferriferrous oxide layer is 0.1 μm~0.2 μm.

[0012] As an optional implementation, the thickness of the Si-O-Fe layer is 30 nm~50 nm.

[0013] As an optional embodiment, the flaky structure iron powder has a flake thickness of 1-3 μm and a thickness-diameter ratio of 5-10.

[0014] As an optional embodiment, the coupling agent is a silane coupling agent that forms a silicon-hydrogen bond with iron and ferroferric oxide, and includes at least one of 1,2-bis(triethoxysilyl)ethane (BTSE), 1,2-bistrimethoxysilyl ethane (BTMSE), vinyltriethoxysilane and propyltrimethoxysilane.

[0015] As an optional embodiment, the ferruginous matrix is a ferruginous material with a surface oxidation rate of ≥90%, and includes at least one of pure iron, carbonyl iron, silicon iron and alloy steel.

[0016] According to a second aspect of the object of the present application, a method for preparing the aforementioned electromagnetic wave absorber resistant to space environment is provided, and includes the following steps: adding ferruginous particles into a ball mill to ball mill the ferruginous particles into a flaky structure, to obtain flaky structure iron powder; cleaning the surface of the flaky structure iron powder by oil removal, rinsing, pickling and other procedures, and then forming an oxide film on the surface by oxidation treatment, to obtain surface-oxidized flaky structure iron powder; adding the surface-oxidized flaky structure iron powder into a silane coupling agent solution, and dispersing the flaky structure iron powder to form a double-coating structure composed of a ferroferric oxide layer and a Si-O-Fe layer on the surface of the flaky structure iron powder.

[0017] As an optional embodiment, the thickness of the oxide film is 0.05-0.2 μm.

[0018] As an optional embodiment, the mass content of the coupling agent is 0.5%-1% based on the mass of the flaky structure iron powder.

[0019] As an optional embodiment, the oxidation treatment method includes a high-temperature water vapor method, a strong oxidant method or a hot air method.

[0020] As can be seen from the technical solutions of the application, the space environment-resistant electromagnetic wave absorber provided by the application widens the wave absorption frequency band and improves the magnetic permeability by processing the iron particles into a sheet structure, and realizes the function through double coating. The inner dense Fe3O4 film ensures high magnetic permeability due to the ferromagnetic property, and the semiconductor property improves the surface resistance to reduce electromagnetic wave reflection, and the film has strong adhesion, temperature impact resistance of ±200 DEG C, space radiation resistance, no gas leakage, and alkali and salt mist corrosion resistance. The outer Si-O-Fe thin layer seals the micropores of the Fe3O4 film to enhance corrosion resistance and improve insulation and hydrophobicity, and at the same time, the bonding strength with the polymer resin is improved. The square root of the dielectric constant and the magnetic permeability ratio of the absorber approaches 1 to match the incident electromagnetic wave, and the electromagnetic wave energy is converted into heat energy through magnetic domain hysteresis loss and dielectric loss to realize absorption. In the harsh environment of space and ocean, the L, S, C, X, Ku multi-frequency band electromagnetic wave absorption is realized, and the space environment-resistant electromagnetic wave absorber has good compounding with the polymer resin, and is suitable for subsequent wave absorption coating, patch and other film forming applications. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a preparation flowchart of the space environment-resistant electromagnetic wave absorber of the application. DETAILED DESCRIPTION

[0022] In order to better understand the technical content of the application, specific embodiments are described below with reference to the accompanying drawings.

[0023] Aspects of the present application are described in the disclosure by reference to the accompanying drawings, which show many illustrative embodiments. The embodiments of the disclosure are not necessarily intended to include all aspects of the application. It should be understood that the various concepts and embodiments introduced above, and those described in more detail below, can be implemented in any of a variety of ways.

[0024] In one exemplary embodiment of the application, a space environment-resistant electromagnetic wave absorber is provided, and the components of the electromagnetic wave absorber at least include an iron base and a coupling agent.

[0025] In the optional example, the iron base is selected from a high-microwave magnetic permeability ferromagnetic material, including carbonyl iron, silicon steel, pure iron, and alloy steel containing cobalt, nickel and other components. The surface of the iron base has an iron area that can be oxidized, which is required to be greater than or equal to 90% so as to form a dense magnetite film.

[0026] In order to widen the wave absorption frequency band and improve the magnetic permeability, sheeting treatment is required to obtain sheet structure iron powder. In the optional example, the sheeting size is 1 μm~3 μm in thickness, and the thickness-diameter ratio is between 5~10. Therefore, the initial iron particle diameter needs to be about 5 μm~15 μm (D50), which can be processed into sheeting particles by mechanical processing and cold processing methods such as ball milling.

[0027] The processed flaky particles have high surface activity and are very easy to be corroded, and need to be treated for corrosion prevention. The prior art generally adopts surface phosphating or wrapping with inorganic or organic substances to improve the corrosion prevention performance of the iron; these materials are generally insulators and also do not have magnetic permeability, although the corrosion prevention performance is solved, the dielectric constant and magnetic permeability are also reduced, resulting in a decrease in wave absorption performance.

[0028] In one example, a very dense Fe3O4 film is generated on the surface of the processed flaky iron particles in a strong oxidation manner, and the preferred film thickness is between 0.1 μm and 0.2 μm.

[0029] Fe3O4 is a ferromagnetic substance and has high magnetic permeability, and after wrapping, the magnetic permeability of the raw material is not reduced; at the same time, Fe3O4 is a semiconductor and has high surface resistance, which can reduce the reflection caused by macroscopic current and also does not reduce the dielectric loss too much. Since the oxidation layer is very thin, the magnetic hysteresis loss is also almost not affected.

[0030] Since the oxidation film is formed on the surface of the flaky iron particles itself, it has very high adhesion and insulation performance, and therefore has good resistance to high and low temperature impact. The Fe3O4 oxidation film is very stable to space irradiation and has no gas to be released, and is very dense itself, and has good corrosion resistance to alkaline and salt mist, and therefore is suitable for space and marine environments.

[0031] In order to further improve the corrosion resistance and facilitate the combination with high molecular film-forming substances in the later stage, a small amount of silane coupling agent is used for further treatment of the surface.

[0032] The coupling agent of the present application can select a silane coupling agent that forms a silicon-hydrogen bond with iron and ferroferric oxide, but cannot select a coupling agent containing an amino group, a chloro group and a mercapto group, which will produce polycondensation reaction with iron, reducing the corrosion resistance. For example In an optional example, non-functional 1,2-bis(triethoxysilyl)ethane (BTSE) and 1,2-bistrimethoxysilyl ethane (BTMSE) are selected to form a 30 nm to 50 nm thin layer of Si-O-Fe covalent bond grafting on the flaky iron particles, which not only seals the micropore defects of the oxidation film, but also improves the bonding strength with organic substances.

[0033] In another optional example, a common vinyl silane or epoxy silane coupling agent can be selected.

[0034] In this way, a double-coating structure composed of a ferroferric oxide (Fe3O4) layer and a Si-O-Fe layer is formed on the surface of the flaky iron powder.

[0035] In combination with the above-mentioned flaky iron particles, the present application also provides a flaky iron particle composite material. Figure 1As shown, in another exemplary embodiment of the present application, a method for preparing the aforementioned space environment-resistant electromagnetic wave absorber is provided, comprising the following steps: adding the iron particles into a ball mill to ball mill the iron particles to more than 90% of the iron particles being flaked to obtain flaky iron powder; cleaning the surface of the flaky iron powder by oil removal, rinsing, pickling and the like, and then forming an oxide film on the surface by oxidation treatment to obtain flaky iron powder with an oxidized surface; adding the flaky iron powder with an oxidized surface into a silane coupling agent solution, and dispersing the flaky iron powder to form a double-coating structure on the surface of the flaky iron powder, which is composed of a magnetite layer and a Si-O-Fe layer.

[0036] In an optional example, the thickness of the oxide film is 0.05 μm~0.2 μm.

[0037] In an optional example, the mass content of the coupling agent, based on the mass of the flaky iron powder, is 0.5%~1%.

[0038] In an optional example, the oxidation treatment method comprises a high-temperature water vapor method, a strong oxidant method or a hot air method.

[0039] In the following, a specific example is used to further illustrate the preparation process of the space environment-resistant electromagnetic wave absorber, which is as follows:

[0040] (1) Iron particles with a medium diameter (D50) of 5 μm~15 μm are weighed and then added into a ball mill, and 2% of tri-fatty acid glyceride and about 10% of propylene glycol solvent and the like are added as lubricants to prevent "cold welding" of the iron powder.

[0041] (2) Stainless steel grinding balls with diameters of 16 mm and 5 mm are used, and are configured in a ratio of 3:7, with a ball-to-material ratio of 8:1, and are ball milled at a speed of 300 revolutions per minute for 12 h~24 h. Pure iron and carbonyl iron with low hardness are ball milled for a short time, and alloys require a longer ball milling time, until more than 90% of the iron particles are flaked, with a flake thickness of 1 μm~3 μm and a thickness-to-diameter ratio of 5~10, to obtain flaky iron powder.

[0042] (3) The obtained flaky iron powder is cleaned by oil removal, rinsing, pickling and the like to ensure the surface cleanliness, and at the same time, the iron powder with a small particle size can also be rinsed away.

[0043] (4) The cleaned flaky iron powder is added into a steam oxidation box, and 450℃ superheated water vapor is passed through the box for 30 minutes, and the thickness of the oxide film is between 0.05 μm~0.2 μm, and is particularly preferably between 0.1 μm~0.2 μm.

[0044] (5) Silane coupling agent is prepared into a water-alcohol solution, and the water-alcohol ratio is 5:95. In order to better hydrolysis and prevent polymerization, acetic acid is further added to adjust PH=4, and hydrolysis is carried out for 1 hour; the coupling agent content is 0.5~1% according to the weight of the flaky structure iron powder, and the content in the water-alcohol solution is 10%.

[0045] (6) The flaky structure iron powder obtained in step (4) is cooled to below 100℃, and is added into the silane coupling agent prepared into a 95% ethanol solution in step (5). A dispersing machine is used to disperse at a speed of 200~500 revolutions / minute for 5 minutes, and after suction filtration and drying, a 80-mesh screen is used to screen to obtain the required electromagnetic wave absorber.

[0046] The electromagnetic wave absorber of the application realizes high-efficiency electromagnetic wave absorption in L, S, C, X, Ku multi-frequency bands under harsh environments such as space and ocean, has good composite adaptability with high polymer resin, and takes into account environmental stability and wave absorption performance.

[0047] (I) Wave absorption principle

[0048] 1. Optimization of magnetic properties of flaky structure: iron particles are processed into flaky structure with a thickness of 1 μm~3 μm and a thickness-diameter ratio of 5~10 by ball milling, which widens the wave absorption frequency band and improves the magnetic permeability, providing a structural basis for electromagnetic wave absorption.

[0049] 2. Double coating for regulating electromagnetic parameter matching: the inner layer Fe3O4 is a ferromagnetic material, which ensures high magnetic permeability without reducing the magnetic properties of the raw material, and its semiconductor properties increase the surface resistance, reduce electromagnetic wave reflection caused by macroscopic current, and balance dielectric loss and magnetic hysteresis loss; the outer layer Si-O-Fe thin layer further adjusts the dielectric constant, so that the square root of the dielectric constant and magnetic permeability ratio of the absorber approaches 1, realizing impedance matching with incident electromagnetic waves and improving absorption efficiency.

[0050] 3. Synergistic effect of loss mechanism: through magnetic hysteresis loss (ferromagnetic property of Fe3O4) and dielectric loss (semiconductor property of Fe3O4 and covalent bond effect of Si-O-Fe), the incident electromagnetic wave energy is converted into heat energy to avoid reflection.

[0051] (II) Space environment resistance principle

[0052] 1. Protective effect of Fe3O4 oxidation film: a dense Fe3O4 film with a thickness of 0.05 μm~0.2 μm is generated in situ on the surface of the flaky iron powder, which has strong adhesion and can withstand temperature shock of ±200℃; it is stable to space radiation, has no outgassing material, and can resist alkaline environment and salt spray corrosion.

[0053] 2. Reinforced protection of Si-O-Fe thin layer: a 30 nm-50 nm Si-O-Fe covalent bond thin layer seals the micropore defects of the Fe3O4 film, improves the insulation and hydrophobicity, and further enhances the corrosion resistance; at the same time, it improves the bonding strength of the absorbent and the polymer resin, and adapts to subsequent film forming applications.

[0054] (III) Composite adaptation principle

[0055] The Si-O-Fe layer is grafted on the surface of the Fe3O4 film through covalent bond, which does not destroy the magnetic and wave-absorbing properties of the absorbent, and can form stable combination with the polymer film forming material, solves the problem of poor compatibility of traditional coating materials with resin, expands the application scenarios in wave-absorbing coatings, patches and other products, and provides more choices for wave-absorbing materials applied in space and marine environment.

[0056] In order to better understand, the following will be further described in combination with several specific examples, but the preparation process is not limited thereto, and the content of the application is not limited thereto. As long as the method of generating Fe3O4 film on the surface of iron particles by oxidation method, and coating the magnetic material with silane coupling agent on the outer layer is similar, it is within the scope of the present application.

[0057] Unless otherwise specified, the materials in the examples are prepared according to the existing method, or directly purchased from the market.

[0058] In the following examples, the ball milling process parameters are as follows: stainless steel grinding balls with diameters of 16 mm and 5 mm are used, the proportion is 3:7, and the ball-to-material ratio is 8:1. Example 1

[0059] 1) Take 10 kg of commercially available carbonyl iron particles with a D50 particle size of 5 μm-15 μm and add them to a ball mill, and mill at a speed of 300 revolutions per minute for 12 hours, so that more than 90% of the above iron particles are flaked, with a flake thickness of 1 μm-3 μm and a thickness-to-diameter ratio of 5-10, to obtain flaky iron powder.

[0060] 2) The flaky iron powder obtained in step 1) is washed with a commercially available oil removal cleaning agent for 30 minutes, and then rinsed with clean water for 15 minutes; then a 10% hydrochloric acid aqueous solution is prepared, and the acid is washed for 5 seconds, and then rinsed with clean water for 15 minutes to ensure the surface is clean.

[0061] 3) The clean flaky iron powder is added to a blue oxidation box, and 450℃ superheated steam is passed through, and oxidized for 30 minutes, with an oxidation film thickness of 0.1 μm-0.2 μm, and then taken out and dried for standby.

[0062] 4) 1,2-bis(trimethoxysilyl)ethane (BTMSE) 200 g was dissolved in 2 liters of 95% ethanol solution, and then an appropriate amount of acetic acid was added to adjust the pH of the solution to about 4, and hydrolyzed for about 1 hour.

[0063] 5) The surface-oxidized flaky structure iron powder was added to the prepared solution, and dispersed for 5 minutes at a speed of about 400 rpm using a disperser. After drying by suction filtration, the final product was obtained by sieving through an 80-mesh sieve.

[0064] The flaky carbonyl iron powder before and after the 85% paraffin wrapping treatment was tested for comparison, and the test frequency was 2 GHz. The results are shown in Table 1.

[0065] Table 1: Measurement data table of electromagnetic parameters of flaky carbonyl iron powder Example 2

[0066] 1) 10 kg of commercially available silicon-iron particles with a silicon content of 3% and a D50 particle size of 5 μm~15 μm were added to a ball mill and ball milled at a speed of 300 rpm for 12 h. More than 90% of the above iron particles were flaky, with a flake thickness of 1 μm~3 μm and a thickness-diameter ratio of 5~10, to obtain flaky structure iron powder.

[0067] 2) The flaky structure iron powder obtained in step 1) was washed with a commercially available oil removal detergent for 30 minutes, and then rinsed with clean water for 15 minutes. Then, a 10% hydrochloric acid aqueous solution was prepared, and the acid was washed for 5 seconds, and then rinsed with clean water for 15 minutes to ensure the surface was clean.

[0068] 3) The clean flaky structure iron powder was added to a blue-oxidation box, and passed through 450℃ superheated steam for 30 minutes. The oxidation film thickness was between 0.1 μm~0.2 μm, and then dried for standby.

[0069] 4) 1,2-bis(trimethoxysilyl)ethane (BTMSE) 200 g was dissolved in 2 liters of 95% ethanol solution, and then an appropriate amount of acetic acid was added to adjust the pH of the solution to about 4, and hydrolyzed for about 1 hour.

[0070] 5) The surface-oxidized flaky structure iron powder was added to the prepared solution, and dispersed for 5 minutes at a speed of about 400 rpm using a disperser. After drying by suction filtration, the final product was obtained by sieving through an 80-mesh sieve.

[0071] The flaky silicon-iron powder before and after the 85% paraffin wrapping treatment was tested for comparison, and the test frequency was 2 GHz. The results are shown in Table 2.

[0072] Table 2: Measurement data table of electromagnetic parameters of flaky silicon-iron powder

[0073] From the data of Table 1 and Table 2, it can be seen that: From the dielectric constant, the real part and the imaginary part of the dielectric constant of the two kinds of iron powder after treatment are significantly reduced; the real part of the carbonyl iron powder is reduced from 17.35 to 15.54, and the imaginary part is reduced from 0.72 to 0.46, the real part of the silicon iron powder is reduced from 12.21 to 10.45, and the imaginary part is reduced from 0.43 to 0.28. This is because the outer Si-O-Fe thin layer and the inner Fe3O4 film (semiconductor properties) together play an insulating role, reducing the macroscopic current on the surface of the flaky iron powder, reducing the ability of the material to store electric field energy (the real part decreases), and reducing the invalid loss of electric field energy (the imaginary part decreases), ultimately driving the square root of the ratio of the dielectric constant and the magnetic permeability of the absorber to approach 1, achieving impedance matching with the incident electromagnetic wave, and solving the problem of high dielectric constant of traditional magnetic absorber, which is not conducive to the energy entering the material inside.

[0074] From the magnetic permeability, the real part and the imaginary part of the magnetic permeability of the two kinds of iron powder after treatment are basically stable; the real part of the carbonyl iron powder is increased from 3.53 to 3.62, and the imaginary part is decreased from 1.96 to 1.94, the real part of the silicon iron powder is increased from 1.64 to 1.65, and the imaginary part is decreased from 1.32 to 1.29. This is because the inner coated Fe3O4 is a ferromagnetic material itself, and its magnetic properties are compatible with the base iron powder (carbonyl iron, silicon iron), avoiding the defect of traditional insulating coating (such as silicon dioxide, resin) that causes a significant decrease in magnetic permeability due to the lack of magnetism, ensuring that the absorber always has sufficient magnetic domain hysteresis loss capacity, providing core support for the conversion of electromagnetic wave energy into heat energy.

[0075] From the resistance, the surface / body resistance of the two kinds of iron powder after treatment is greatly improved: the surface resistance of the carbonyl iron powder is increased from 78 Ω / sq to 1150 Ω / sq, and the bulk resistance of the silicon iron powder is increased from 267 Ω / sq to 1430 Ω / sq. This is because the dense structure of the Fe3O4 film and the sealing effect of the Si-O-Fe thin layer together enhance the insulation of the material, reduce the reflection of electromagnetic waves on the surface of the absorber, and enable more incident energy to enter the material inside to be absorbed, while also improving the corrosion resistance of the absorber (avoiding electrochemical corrosion caused by current), adapting to the needs of space and marine environment.

[0076] In summary, the two sets of data prove that the double coating treatment of the present application can achieve the synergistic optimization of wave absorption performance and environmental resistance by adjusting the dielectric parameters and enhancing the insulation without damaging the core of the magnetic properties, and this effect is stable on different types of iron-based substrates (carbonyl iron, silicon iron), verifying the universality of the method.

[0077] While the application has been described by way of example with reference to preferred embodiments, it is to be understood that this application is not limited to the embodiments disclosed, but is intended to cover modifications and variations within the spirit and scope of the application. Therefore, the scope of the application is defined not by the detailed description of the application but by the following claims, wherein reference to an alternative embodiment includes reference to all features describing that embodiment.

Claims

1. A space environment electromagnetic wave absorber, characterized in that, The electromagnetic wave absorber comprises at least an iron matrix and a coupling agent; wherein the iron matrix is ​​a sheet-like iron powder that has been cold-processed, and the surface of the sheet-like iron powder is successively subjected to oxidation treatment and surface modification treatment with coupling agent to form a double-coated structure consisting of a Fe3O4 layer and a Si-O-Fe layer.

2. The electromagnetic wave absorber resistant to space environment according to claim 1, characterized in that, The thickness of the iron oxide layer is 0.1 μm to 0.2 μm.

3. The electromagnetic wave absorber resistant to space environment according to claim 1, characterized in that, The thickness of the Si-O-Fe layer is 30 nm to 50 nm.

4. The electromagnetic wave absorber resistant to space environment according to claim 1, characterized in that, The sheet-like iron powder has a sheet thickness of 1 μm to 3 μm and a thickness-to-diameter ratio of 5 to 10.

5. The electromagnetic wave absorber resistant to space environment according to claim 1, characterized in that, The coupling agent is a silane coupling agent that forms a silicon-hydrogen bond with iron and iron(III) oxide, including at least one of 1,2-bis(triethoxysilyl)ethane (BTSE), 1,2-bistrimethoxysilylethane (BTMSE), vinyltriethoxysilane, and propyltrimethoxysilane.

6. The electromagnetic wave absorber resistant to space environment according to claim 1, characterized in that, The iron matrix is ​​an iron material with a surface oxidation rate of ≥90%, including at least one of pure iron, carbonyl iron, ferrosilicon and alloy steel.

7. A method for preparing an electromagnetic wave absorber resistant to space environment as described in any one of claims 1-6, characterized in that, Includes the following steps: Iron particles are added to a ball mill and ball-milled until more than 90% of the iron particles are in the form of flakes, thus obtaining iron powder with a flake structure. The sheet-like iron powder is cleaned by degreasing, rinsing, and pickling to ensure surface cleanliness; then, an oxide film is formed on the surface through oxidation treatment to obtain surface-oxidized sheet-like iron powder. The surface-oxidized sheet-like iron powder is added to a silane coupling agent solution and dispersed to form a double-coated structure on the surface of the sheet-like iron powder consisting of a magnetite layer and a Si-O-Fe layer.

8. The electromagnetic wave absorber resistant to space environment according to claim 7, characterized in that, The thickness of the oxide film is 0.05 μm to 0.2 μm.

9. The electromagnetic wave absorber resistant to space environment according to claim 7, characterized in that, The mass content of the coupling agent, based on the mass of the sheet-like iron powder, is 0.5% to 1%.

10. The electromagnetic wave absorber resistant to space environment according to claim 7, characterized in that, The oxidation treatment methods include high-temperature steam method, strong oxidant method, or hot air method.

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