Carbonyl iron / graphene oxide composite wave-absorbing material and preparation thereof

Abstract

The invention discloses a carbonyl iron / silane modified graphene oxide composite wave-absorbing material and preparation thereof, and belongs to the technical field of wave-absorbing materials. Silane modified graphene oxide and carbonyl iron powder are compounded to prepare the wave-absorbing material with the core-shell structure, and the wave-absorbing material comprises carbonyl iron and silane modified graphene oxide compounded on the surface of the carbonyl iron. Silane is used for carrying out surface modification on graphene oxide, and the dielectric constant of the composite wave-absorbing material is better matched with the wave impedance of a free space by regulating and controlling the dosage of silane and graphene oxide in the silane modification process and adjusting the ratio of silane modified graphene oxide to carbonyl iron when the composite material is prepared; the ratio of the magnetic conductivity to the dielectric constant is optimized, and the overall wave-absorbing strength of the composite material is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of absorbing materials, and in particular relates to a carbonyl iron / graphene oxide composite absorbing material, and discloses a preparation method of the composite absorbing material. Background Art

[0002] With the rapid development of modern electronic devices and wireless communication technologies, electromagnetic radiation pollution is becoming increasingly serious, posing a potential threat to device performance and human health. Therefore, the research and development of high-performance electromagnetic wave absorbing materials not only helps meet the needs of modern communication technology, but also has important implications for reducing electromagnetic interference, improving the performance and stability of communication equipment, protecting the human body from the harmful effects of electromagnetic radiation, promoting scientific and technological progress, and achieving environmental protection and sustainable development.

[0003] As a new two-dimensional nanomaterial, graphene oxide (GO) exhibits enormous potential for application in microwave-absorbing materials due to its unique electrical, mechanical, and thermal properties. However, its absorbing properties are affected by factors such as its mass fraction, dispersion state, and composite structure with other materials. In particular, its poor dispersibility in organic solvents has limited its application in microwave-absorbing materials. To overcome these limitations, modifying GO and composite it with other electromagnetic absorbing materials has become an effective strategy.

[0004] Carbonyl iron, as a traditional electromagnetic absorption material, has good magnetic loss performance and temperature stability, and is widely used in the field of absorbing materials. However, carbonyl iron powder also has shortcomings such as narrow absorption bandwidth and high density, which limit its scope of application. By compounding graphene oxide with carbonyl iron and giving full play to the synergistic effect of the two, it is expected to prepare an absorbing material with excellent performance. Chinese patent CN201811526716.X discloses a core-shell structured graphene oxide / carbonyl iron composite material, including carbonyl iron and a graphene oxide layer compounded on the surface of the carbonyl iron, combining the advantages of the two materials, so that the graphene oxide / carbonyl iron composite absorbing material has excellent electromagnetic absorption performance. However, this solution has obvious shortcomings, which are specifically manifested as follows: the coating effect of the material is not obvious, and the coating layer structure composed simply of graphene oxide has low strength. In complex application environments, the core structure (carbonyl iron) will be corroded after its surface coating layer is damaged. In addition, the graphene oxide suspension is unstable, the dielectric constant is high, and the impedance matching cannot be reasonably regulated.

[0005] To address the poor dispersion of graphene oxide and the resulting instability of its suspension, Shen Kaiyan proposed a solution in her paper, "Preparation of Silane-Modified Graphene Oxide Nanocomposites." This approach involves modifying graphene oxide with silane. This treatment increases the interlayer spacing of the graphene oxide, allowing for more stable dispersion in organic solvents. However, this proposal does not disclose the use of silane-modified graphene oxide to prepare composite absorbers, and the effectiveness of this preparation remains uncertain. To achieve composite materials with excellent absorbent properties, in addition to improving GO dispersion, it is also necessary to further enhance the bonding between graphene oxide and carbonyl iron, leverage the synergistic effects of carbonyl iron's magnetic properties and graphene oxide's dielectric properties, and optimize the impedance matching of the composite material. These are all key to preparing high-performance absorbers. Solving these issues is closely related to the composite material's preparation process and the selection of appropriate parameters. Further exploration of the appropriate preparation conditions is needed to achieve high-performance absorbers. Summary of the Invention

[0006] To address the above-mentioned problems, the present invention aims to provide a high-performance absorbing material prepared by combining silane-modified graphene oxide with carbonyl iron, and a preparation method thereof. Surface modification of graphene oxide with silane not only improves the dispersibility of graphene oxide, but also forms a dense silane layer on the surface of graphene oxide, introducing hydrophobic groups to improve the corrosion resistance of the composite material. In addition, by controlling the proportion of the composite raw materials, the dielectric constant of the entire core-shell structure material can be better matched with the wave impedance of free space, optimizing the ratio of magnetic permeability to dielectric constant, and ultimately effectively improving the overall absorption strength of the composite material.

[0007] The technical solution of the present invention is: a carbonyl iron / silane-modified graphene oxide composite absorbing material, which uses carbonyl iron powder as the core and forms a core-shell structure by surface-compounding silane-modified graphene oxide, wherein the silane-modified graphene oxide is uniformly coated on the surface of the carbonyl iron particles to constitute an absorbing functional unit.

[0008] Furthermore, the median particle size D50 of the composite absorbing material is 2 to 10 μm, preferably D50 is 3 to 5 μm.

[0009] Furthermore, the reflection loss of the composite absorbing material at 2-5 GHz is -10 to -50 dB.

[0010] Furthermore, the mass ratio of carbonyl iron to silane-modified graphene oxide is 100:3-15, preferably 100:8-12.

[0011] The preparation method of the carbonyl iron / silane-modified graphene oxide composite absorbing material is as follows:

[0012] 1) performing ultrasonic pretreatment on graphene oxide;

[0013] 2) after modifying the graphene oxide with silane, dispersing the modified product in an organic solvent to form a silane-modified graphene oxide dispersion;

[0014] 3) preparing flaky carbonyl iron powder by ball milling, wherein the median particle size D50 of the flaky carbonyl iron powder is 3 to 10 μm, preferably 4 to 6 μm;

[0015] 4) Dispersing the flaky carbonyl iron powder in an organic solvent under stirring, adding a coupling agent and water, and fully mixing, adding a silane-modified graphene oxide dispersion, heating, filtering, and drying to obtain a composite absorbing material.

[0016] Furthermore, in step 2), the specific process of modifying graphene oxide with silane is as follows: under the protection of inert gas, the graphene oxide is mixed with an organic solvent, and the reaction is carried out at 50-80 ° C for 50-150 min, preferably at 55-80 ° C for 70-120 min, more preferably at 55-75 ° C for 80-100 min, and after the reaction is completed, a benzene reagent, a silane reagent and distilled water are added, and the reaction is carried out at room temperature for 12-72 h, an alcohol reagent is added, and the silane-modified graphene oxide product is obtained after washing and standing.

[0017] The inert gas is nitrogen or argon, preferably nitrogen;

[0018] The organic solvent is one or both of n-butylamine and isobutylamine, preferably n-butylamine;

[0019] The benzene reagent is one or both of toluene and ethylbenzene, preferably toluene;

[0020] The silane reagent is any one or more of dichlorodimethylsilane, diphenyldimethoxysilane, and diisobutyldimethoxysilane, and can be two or three. Dichlorodimethylsilane is preferred.

[0021] Further, in step 2), the mass volume ratio of graphene oxide to silane is 1-3g:2-10mL, preferably 1.2-2.8g:3-8mL; specifically, 1.2g:3mL, 1.2g:3.5mL, 1.2g:4mL, 1.2g:5mL, 1.25g:3mL, 1.25g:3.5mL, 1.25g:4mL, 1.25g:5mL, 1.3g :3mL, 1.3g:3.5mL, 1.3g:4mL, 1.3g:5mL, 1.35g:3mL, 1.35g:3.5mL, 1.35g:4mL, 1.35g: 5mL, 1.4g:3mL, 1.4g:3.5mL, 1.4g:4mL, 1.4g:5mL, 1.45g:3mL, 1.45g:3.5mL, 1.45g:4mL , 1.45g:5mL, 1.5g:3mL, 1.5g:3.5mL, 1.5g:4mL, 1.5g:5mL, 1.55g:3mL, 1.55g:3.5mL, 1 .55g:4mL, 1.55g:5mL, 1.6g:3mL, 1.6g:3.5mL, 1.6g:4mL, 1.6g:5mL, 1.65g:3mL, 1.65g :3.5mL, 1.65g:4mL, 1.65g:5mL, 1.7g:3mL, 1.7g:3.5mL, 1.7g:4mL, 1.7g:5mL, 1.75g:3 mL, 1.75g:3.5mL, 1.75g:4mL, 1.75g:5mL, 1.8g:3mL, 1.8g:3.5mL, 1.8g:4mL, 1.8g:5mL.

[0022] The median particle size D50 of the silane-modified graphene oxide product is 2 to 8 μm, preferably 3 to 5 μm.

[0023] Furthermore, the solid content of the silane-modified graphene oxide dispersion obtained in step 2) is 5% to 25%, specifically 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%.

[0024] Furthermore, in step 4), the organic solvent is an alcohol solvent, preferably one or both of anhydrous ethanol and ethylene glycol, more preferably anhydrous ethanol; the coupling agent used is one or both of silane coupling agents KH-550 and KH560, preferably KH-550; the mass ratio of flaky carbonyl iron powder to silane-modified graphene oxide is 0.5 to 5:100, preferably 1 to 2:100, and the heating temperature is 60 to 100°C, preferably 60 to 90°C, more preferably 70 to 80°C.

[0025] Furthermore, the grinding balls used for ball milling are one or both of zirconium balls and steel balls, preferably zirconium balls; the particle size of the grinding balls is 0.5-6 mm, preferably 1-5 mm, and more preferably 1-3 mm; the ball milling speed is 600-1200 rpm, preferably 800-1000 rpm; the ball milling time is 12-72 h, preferably 12-64 h, and more preferably 12-48 h; and the flaky carbonyl iron powder is obtained by drying after ball milling, the drying temperature is 50-90 ° C, preferably 65-75 ° C; the drying time is 1-8 h, preferably 1-6 h, and more preferably 1-4 h.

[0026] The beneficial effects of the present invention are:

[0027] 1. This application uses silane to modify graphene oxide. The hydrophobic groups in the silane molecules cover the surface of graphene oxide, which can reduce its surface polarity and effectively improve the dispersibility of graphene oxide in non-polar or weakly polar solvents.

[0028] 2. This application uses silane to modify graphene oxide, forming a dense silane layer on the graphene oxide surface and simultaneously introducing hydrophobic groups. The silane layer can increase the diffusion path of the corrosive medium and enhance the barrier effect. The hydrophobic groups can reduce the surface energy, reduce the adsorption of water molecules and corrosive media, slow down the corrosion rate, and effectively improve the corrosion resistance of the composite material, making the prepared composite absorbing material suitable for complex application environments.

[0029] 3. The modification of graphene oxide with silane not only increases the active sites on the graphene oxide surface, but also introduces new polarization units, which can dissipate electromagnetic energy into heat and other forms through the polarization relaxation process, thereby enhancing the absorption strength of the composite material.

[0030] 4. Silane-modified graphene oxide has unique dielectric properties. By adjusting the ratio of silane to graphene oxide, the surface properties and structure of graphene oxide can be changed, and the dielectric constant of the material can be adjusted. When it is compounded with carbonyl iron in a suitable ratio and coated on the surface of carbonyl iron powder, on the one hand, the magnetic carbonyl iron powder and the dielectric modified graphene oxide are tightly combined. Through synergistic effect, the composite material absorbs electromagnetic waves over a wider frequency range, achieving the complementarity of magnetic loss and dielectric loss, thereby improving the overall wave absorption strength of the composite material. On the other hand, the dielectric constant of the entire core-shell structure material can be better matched with the wave impedance of free space. The appropriate dielectric constant can reduce the reflection of electromagnetic waves on the surface of the material, allowing more electromagnetic waves to enter the material and be absorbed, thereby improving the wave absorption performance.

[0031] 5. For absorbing materials, the ratio of magnetic permeability and dielectric constant is crucial to impedance matching. After silane-modified graphene oxide is coated with carbonyl iron powder, the ratio of magnetic permeability and dielectric constant can be optimized by adjusting the content and interaction of the two, so that the material can achieve good impedance matching in a wider frequency range, thereby improving the absorbing efficiency and widening the absorbing bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Sub-figures a and b are scanning electron microscope (SEM) images of the composite absorbing material prepared in Example 1 at different magnifications;

[0033] Figure 2 Sub-figures a and b are transmission electron microscope images of the composite absorbing material prepared in Example 1 at different magnifications;

[0034] Figure 3A is the real part curve of the complex magnetic permeability of the composite absorbing material prepared in Example 1;

[0035] Figure 3B is the imaginary part curve of the complex magnetic permeability of the composite absorbing material prepared in Example 1;

[0036] Figure 4A is the real part curve of the complex dielectric constant of the composite absorbing material prepared in Example 1;

[0037] Figure 4B is the imaginary part curve of the complex dielectric constant of the composite absorbing material prepared in Example 1;

[0038] Figure 5 1 is the reflection loss curve of the composite absorbing material prepared in Example 1 (coating thickness 0.5 to 5 mm);

[0039] Figure 6 This is the reflection loss curve of flake carbonyl iron powder (coating thickness 0.5 to 5 mm);

[0040] Figure 7 The surface morphologies of the two materials after 1000 hours of salt spray testing are compared. Sub-Figure a shows the appearance of the composite absorbing material prepared in Example 1 under a salt spray environment, while Sub-Figure b shows the appearance of the pure flaky carbonyl iron material without composite treatment under a salt spray environment.

[0041] Figure 8 Sub-figures a and b are scanning electron microscope (SEM) images of the composite absorbing material prepared in Example 2 at different magnifications;

[0042] Figure 9 Sub-figures a and b are transmission electron microscope images of the composite absorbing material prepared in Example 2 at different magnifications;

[0043] Figure 10A is the real part curve of the complex magnetic permeability of the composite absorbing material prepared in Example 2;

[0044] Figure 10B is the imaginary part curve of the complex magnetic permeability of the composite absorbing material prepared in Example 2;

[0045] Figure 11A is the real part curve of the complex dielectric constant of the composite absorbing material prepared in Example 2;

[0046] Figure 11B is the imaginary part curve of the complex dielectric constant of the composite absorbing material prepared in Example 2;

[0047] Figure 12 This is the reflection loss curve of the composite absorbing material prepared in Example 2 (coating thickness 0.5-5 mm). DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0049] Example 1

[0050] This embodiment discloses a method for preparing a corrosion-resistant composite wave-absorbing material

[0051] 1) Graphene Pretreatment: 5 g of industrial-grade graphene oxide powder (about 20 μm in flake diameter) was weighed and dispersed in 500 mL of pure water. Ultrasonic dispersion was performed for 2 h to obtain a graphene oxide dispersion. Ultrasonic dispersion was used to reduce the flake size and median particle size of the graphene oxide. The dispersion was allowed to stand, the supernatant was poured out, and the dispersion was dried in a vacuum drying oven to obtain graphene oxide powder.

[0052] 2) Silane Modification of Graphene Oxide: Under nitrogen, 1.5 g of graphene oxide powder was added to a polymerization flask, followed by 20 mL of n-butylamine. After reacting at 65°C for 70 minutes, 50 mL of toluene, 4 mL of dichlorodimethylsilane, and 4 mL of distilled water were added sequentially to the flask containing graphene oxide and n-butylamine. The reaction was allowed to proceed at room temperature for 24 hours, followed by the addition of 100 mL of methanol. The precipitate, after standing, was washed sequentially with anhydrous toluene, n-hexane, ethanol, acetone, a mixed solution of ethanol and water, and acetone to obtain the final product. The product was dispersed in anhydrous ethanol to obtain a silane-modified graphene oxide dispersion (solids content 15%).

[0053] 3) Preparation of flaky carbonyl iron powder: 10 g of carbonyl iron powder was weighed and placed in a planetary ball mill. 500 mL of anhydrous ethanol was added as a process control agent. 1000 g of zirconia balls with a diameter of 6 mm were added as grinding balls (i.e., a ball-to-material ratio of 100:1). After ball milling at 800 rpm for 24 h, the iron powder was removed, placed in a forced air drying oven, and dried at 60°C for 2 h to obtain flaky carbonyl iron powder with a diameter-to-thickness ratio of approximately 10:1.

[0054] 4) Preparation of composite absorbing material: 100 g of flaky carbonyl iron powder was dispersed in 200 mL of anhydrous ethanol using a blender at 500 rpm and stirred for 30 min to obtain a CIP dispersion; 0.1 g of silane coupling agent KH-550 and 1 g of distilled water were added dropwise to the CIP dispersion, and the mixture was stirred at 800 rpm for 1 h; 60 g of the silane-modified graphene oxide dispersion prepared in step 2) was then added and stirred in an oil bath at 70°C for 3 h; the mixed dispersion was filtered, and the composite was placed in a vacuum drying oven and vacuum-dried at 60°C for 4 h; the composite material was passed through a 50-mesh sieve and then vacuum-sealed for storage.

[0055] The median particle size D50 of the obtained composite absorbing material is about 5 μm.

[0056] This embodiment uses silane to modify graphene oxide. Silane molecules typically contain reactive groups (such as amino and epoxy groups) that can chemically react with oxygen-containing functional groups (such as hydroxyl and carboxyl groups) on the graphene oxide surface. Upon hydrolysis, the silane molecules form reactive Si-OH groups, which react with reactive groups such as hydroxyl (-OH) and carboxyl (-COOH) on the graphene oxide surface to form covalent bonds (such as Si-OC bonds). The formation of covalent bonds can enhance the interfacial bonding between graphene oxide and the matrix material (such as a polymer or resin), thereby improving the overall strength of the resulting composite material.

[0057] In addition, the oxygen-containing functional groups on the surface of graphene oxide give it a high polarity, making it very easy to agglomerate in polar solvents (such as water). After it is modified with silane, the hydrophobic groups (such as alkyl chains) in the silane molecules will cover the surface of graphene oxide, reducing its surface polarity. After the surface polarity of graphene oxide is reduced, the dispersibility of graphene oxide in non-polar or weakly polar solvents can be significantly improved.

[0058] Carbonyl iron powder is a soft magnetic particle that is easily magnetized under the action of an external magnetic field. The magnetized particles are prone to self-agglomeration. Therefore, the dispersion uniformity of pure carbonyl iron powder in the dispersion medium is poor. The carbonyl iron powder particles are initially modified by the silane coupling agent KH-550. One end of the coupling agent is hydrolyzed to form a Si-O bond and stably combined with the carbonyl iron powder particles, and the other end contains a large amount of -NH2.

[0059] Since graphene oxide carries a large number of silane groups on its surface after modification with silane, the carbonyl iron particles initially modified with a silane coupling agent will theoretically interact with the modified graphene oxide, which also carries a large number of silane groups on its surface, forming more chemical bonds. This will then form a low-dielectric graphene oxide coating on the carbonyl iron surface, rather than simply combining the graphene oxide and carbonyl iron materials. This can further improve the corrosion resistance and environmental weathering resistance of the carbonyl iron. These related properties were further verified through subsequent testing.

[0060] First, the microstructure of the experimental samples was characterized by scanning electron microscopy. Figure 1 As shown in the a and b pictures, it can be seen that the powder particles are relatively dispersed and the morphology is a certain regular flake structure. Combined with the low-magnification transmission electron microscope image of the sample ( Figure 2 Further observation (a and b in the middle) shows that the silane-modified graphene oxide material is completely coated on the surface of the carbonyl iron powder, indicating that the composite with the modified graphene oxide will indeed change the particle distribution state of the carbonyl iron, which may significantly affect the absorbing performance of the absorbing material, and at the same time help to improve the corrosion resistance of the material.

[0061] The complex magnetic permeability and complex dielectric constant (μ′, μ″, ε′, ε″) of the composite absorbing material sample obtained in Example 1 were measured in the frequency range of 1 to 18 GHz, as shown in FIG. Figure 3A 、 3B , 4A, and 4B.

[0062] from Figure 3A It can be seen that the real part of the complex magnetic permeability of the composite absorbing material obtained in Example 1 (i.e., the silane-modified graphene oxide-coated flaky carbonyl iron powder marked in the figure) generally shows a downward trend with increasing frequency, and the higher the frequency, the more gradual the downward trend becomes, which is similar to the trend of the real part of the complex magnetic permeability of the flaky carbonyl iron powder. Figure 3B It can be seen from the graph that the imaginary part of the complex magnetic permeability of the composite absorbing material obtained in Example 1 shows an overall trend of first increasing and then decreasing, and a more obvious magnetic loss peak appears at the frequency point of 3.8 GHz. Compared with the change of the imaginary part of the complex magnetic permeability of the flaky carbonyl iron powder, the magnetic permeability of the composite absorbing material prepared in this example changes less. Figure 3A and Figure 3BAccording to the data analysis, wrapping the carbonyl iron with silane-modified graphene oxide has little effect on the complex magnetic permeability of the carbonyl iron powder. This is mainly attributed to the fact that the modified graphene oxide forms a complete coating layer on the surface of the carbonyl iron.

[0063] from Figure 4A It can be seen that due to the dispersion phenomenon in the frequency range of 1 to 18 GHz, the real part of the complex dielectric constant of the composite absorbing material obtained in Example 1 generally shows a decreasing trend with increasing frequency, and the decreasing process is relatively gentle. Figure 4B It can be seen that within the frequency range of 1 to 18 GHz, the imaginary part of the complex dielectric constant of the composite absorbing material obtained in Example 1 decreases with increasing frequency, and the curve shows a multi-mode resonance within the frequency range. Figure 4A and Figure 4B From the perspective of dielectric constant, the composite absorbing material has lower real and imaginary parts of the complex dielectric constant than the sheet carbonyl iron, which is suitable for achieving better impedance matching.

[0064] Figure 5 and Figure 6 The reflection loss curves of the composite absorbing material and the flake carbonyl iron powder are obtained by designing the material thicknesses of 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, and 5 mm respectively using the electromagnetic field transmission line theory formula. Figure 5 It can be clearly seen that when the coating thickness is d = 3mm, the maximum reflection loss of the composite absorbing material can reach -35dB at the frequency of 3GHz; compared with the simple flaky carbonyl iron powder without composite treatment (when the coating thickness is d = 3mm, the maximum reflection loss of the flaky carbonyl iron is about -31.7dB at the frequency of 3.8GHz), the absorbing performance of the composite absorbing material is effectively improved.

[0065] The reason why coating silane-modified graphene oxide on the outside of carbonyl iron sheets can improve the overall absorption performance of the material may be mainly based on the following reasons:

[0066] 1) Increased polarization loss: Graphene oxide itself is rich in oxygen-containing functional groups, which can produce strong polarization losses. After silane modification, on the one hand, silane molecules can react with functional groups on the graphene oxide surface, further increasing its surface active sites and making the polarization mechanism more complex and diverse. On the other hand, adjusting the ratio of graphene oxide to silane during the silane modification process can introduce an appropriate proportion of organic groups on the graphene oxide surface, and thus introduce a certain proportion of new polarization units, such as dipole polarization. When electromagnetic waves are incident, these polarization units respond rapidly to changes in the electric field, converting electromagnetic energy into heat and other forms of energy through polarization relaxation, thereby enhancing the absorption strength.

[0067] 2) Synergistic Enhancement of Magnetic and Dielectric Properties: Carbonyl iron powder possesses excellent magnetic properties and absorbs electromagnetic waves primarily through magnetic loss. Graphene oxide, modified with silane and coated on the carbonyl iron, forms a core-shell structure that tightly bonds the magnetic carbonyl iron powder with the dielectric graphene oxide. The synergistic effect of magnetic and dielectric properties enables the material to absorb electromagnetic waves over a wider frequency range, achieving complementary magnetic and dielectric losses, thereby enhancing overall absorption.

[0068] The composite absorbing material prepared in this embodiment was subjected to a 1000h salt spray test. Figure 7 The carbonyl iron sheet composited with modified graphene oxide showed no obvious oxidative corrosion after 1000h of salt spray test ( Figure 7 Neutron image a). However, the pure carbonyl iron flake material without composite treatment will undergo obvious oxidation and corrosion after 1000 hours of salt spray test ( Figure 7 Neutron image b). This shows that carbonyl iron material coated with silane-modified graphene oxide has good corrosion resistance. The main reasons may be: 1) Silane modification introduces hydrophobic groups (such as alkyl chains) on the surface of graphene oxide, which reduces the surface energy and reduces the adsorption of water molecules and corrosive media. The enhanced hydrophobicity can effectively block moisture and corrosive ions (such as Cl-, SO4 2- etc.), slowing down the corrosion rate; 2) after silane modification, a dense silane layer is formed on the surface of graphene oxide, which increases the diffusion path of the corrosive medium. The dense silane layer can effectively block the penetration of oxygen, moisture and corrosive ions, thereby enhancing the barrier effect; 3) the Si-O bond in the silane molecule has high chemical stability and can form a stable protective layer on the surface of graphene oxide. The protective layer enhances the stability of the material in corrosive environments such as acid and alkali; 4) Silane modification enhances the interfacial bonding between graphene oxide and the matrix material through chemical bonding (such as Si-OC bond). The stronger interfacial bonding reduces the penetration path of the corrosive medium and delays corrosion.

[0069] Example 2

[0070] The difference between this embodiment and embodiment 1 is that the amounts of modified graphene oxide and flaky carbonyl iron powder used in preparing the composite absorbing material in step 4) are adjusted, thereby further optimizing the ratio of magnetic permeability to dielectric constant.

[0071] 1) Same as step 1) in Example 1;

[0072] 2) Same as step 2) in Example 1;

[0073] 3) Same as step 3) in Example 1;

[0074] 4) Preparation of composite absorbing material: 100 g of flaky carbonyl iron powder was dispersed in 500 mL of anhydrous ethanol solution using a blender at 500 rpm and stirred for 30 min to obtain a CIP dispersion; 0.1 g of silane coupling agent KH-550 and 1 g of distilled water were added dropwise to the CIP dispersion, and the mixture was stirred at 800 rpm for 1 h; 80 g of silane-modified graphene oxide dispersion (prepared by dispersing the modified graphene prepared in step 2) in ethylene glycol, 15% solid content) was then added, and stirred in an oil bath at 70°C for 3 h; the mixed dispersion was filtered, and the composite was placed in a vacuum drying oven at 60°C and vacuum dried for 4 h; the composite material was passed through a 50-mesh sieve and then vacuum-sealed for storage.

[0075] From the microstructural characterization results of the materials, it can be seen that ( Figure 8-9 ), the composite absorbing material prepared in this embodiment exhibits the following characteristics: Scanning electron microscope image ( Figure 8 ) showed that the powder particles were well dispersed and had regular flake morphology; transmission electron microscopy analysis ( Figure 9 ) further confirmed that silane-modified graphene oxide formed a continuous coating layer that evenly covered the surface of carbonyl iron powder. This core-shell structure provided the material with ideal interface bonding properties.

[0076] The complex magnetic permeability and complex dielectric constant (μ′, μ″, ε′, ε″) of the composite absorbing material sample obtained in Example 2 were measured in the frequency range of 1 to 18 GHz, as shown in FIG. Figure 10A 、 10B , 11A, and 11B.

[0077] The complex magnetic permeability (real part μ′ and imaginary part μ″) of the composite absorbing material prepared in this example shows a highly consistent trend with that of the material prepared in Example 1, indicating that the coating of the carbonyl iron powder with silane-modified graphene oxide did not significantly alter its intrinsic magnetic properties.

[0078] FIG11 shows that in the range of 1-18 GHz, the real part of the complex dielectric constant ( Figure 11A ) shows a gentle downward trend with increasing frequency, and the imaginary part ( Figure 11B ) exhibits a decreasing curve with multimode resonance characteristics. Compared to pure flake carbonyl iron, this composite material has lower real and imaginary dielectric constant values, which is beneficial for improving the material's impedance matching performance.

[0079] Figure 12 The reflection loss characteristics of composite absorbing materials with different thicknesses (0.5-5mm) were demonstrated. Among them, the 3mm thick sample showed the best absorbing performance at 2.6GHz, with the reflection loss peak reaching about -47dB, indicating that the material achieved the best electromagnetic wave absorption effect at this thickness.

[0080] Example 3

[0081] The difference between this embodiment and embodiment 1 is that the amounts of silane and graphene oxide used in preparing the silane-modified graphene oxide in step 2) are adjusted, thereby adjusting the dielectric constant of the silane-modified graphene oxide, thereby further optimizing the impedance matching.

[0082] 1) Same as step 1) in Example 1;

[0083] 2) Silane Modification of Graphene Oxide: Under nitrogen, 2 g of graphene oxide powder was added to a polymerization flask, along with 20 mL of n-butylamine. After reacting at 65°C for 70 minutes, 50 mL of toluene, 6 mL of diphenyldimethoxysilane, and 4 mL of distilled water were added sequentially to the flask containing graphene oxide and n-butylamine. The reaction was continued at room temperature for 24 hours, followed by the addition of methanol. The precipitate, after standing, was washed sequentially with anhydrous toluene, n-hexane, ethanol, acetone, a mixed solution of ethanol and water, and acetone to obtain the final product. The product was dispersed in anhydrous ethanol to obtain a silane-modified graphene oxide dispersion (solids content 15%).

[0084] 3) Same as step 3) in Example 1;

[0085] 4) Same as step 4) in Example 1.

[0086] Experiments have shown that by adjusting the ratio of silane to graphene oxide (GO) during the silane modification process, the dielectric constant of the silane-modified graphene can be precisely tuned, thereby improving the material's impedance matching properties. Further optimizing the ratio of silane-modified GO to carbonyl iron powder in the composite system can synergistically control the ratio of magnetic permeability to dielectric constant, enabling the material to achieve good impedance matching over a wider frequency range, improving absorption efficiency and broadening the absorption bandwidth.

[0087] The above shows and describes the basic principles, main features, and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any person skilled in the art without departing from the technical solution of the present invention should be included in the patent scope of the present invention.

Claims

1. A carbonyl iron / silane-modified graphene oxide composite absorbing material, characterized in that: Carbonyl iron powder is used as the core, and a core-shell structure is formed by surface composite silane-modified graphene oxide, wherein the silane-modified graphene oxide is evenly coated on the surface of the carbonyl iron particles to form a wave-absorbing functional unit.

2. The carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 1, wherein: The median particle size D50 of the composite absorbing material is 2 to 10 μm, preferably 3 to 5 μm.

3. The carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 1, wherein: The reflection loss of the composite absorbing material in the range of 2-5 GHz is -10 to -50 dB.

4. The carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 1, wherein: The mass ratio of carbonyl iron to silane-modified graphene oxide is 100:3-15.

5. The method for preparing the carbonyl iron / silane-modified graphene oxide composite absorbing material according to any one of claims 1 to 4, characterized in that: The steps include: 1) performing ultrasonic pretreatment on graphene oxide; 2) after modifying the graphene oxide with silane, dispersing the modified product in an organic solvent to form a silane-modified graphene oxide dispersion; 3) preparing flaky carbonyl iron powder by ball milling; 4) Dispersing the flaky carbonyl iron powder in an organic solvent under stirring, adding a coupling agent and water, and fully mixing, adding a silane-modified graphene oxide dispersion, heating, filtering, and drying to obtain a composite absorbing material.

6. The method for preparing the carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 5, wherein: In step 2), the specific process of modifying graphene oxide with silane is as follows: under the protection of inert gas, the graphene oxide is mixed with an organic solvent, reacted at 50-80 ° C for 50-150 min, a benzene reagent, a silane reagent and distilled water are added, and the reaction is carried out at room temperature for 12-72 h, an alcohol reagent is added, and the silane-modified graphene oxide product is obtained after washing and standing.

7. The method for preparing the carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 5, wherein: In step 2), the mass volume ratio of graphene oxide to silane is 1-3 g:2-10 mL; The median particle size D50 of the silane-modified graphene oxide product is 2 to 8 μm.

8. The method for preparing the carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 6, wherein: The inert gas is nitrogen or argon, the organic solvent is one or both of n-butylamine and isobutylamine; the benzene reagent is one or both of toluene and ethylbenzene; and the silane reagent is any one or more of dichlorodimethylsilane, diphenyldimethoxysilane, and diisobutyldimethoxysilane.

9. The method for preparing the carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 5, wherein: The solid content of the silane-modified graphene oxide dispersion obtained in step 2) is 5% to 25%.

10. The method for preparing a carbonyl iron / silane-modified graphene oxide composite absorbing material according to claim 5, wherein in step 4), the organic solvent is one or both of anhydrous ethanol and ethylene glycol; the coupling agent used is one or both of silane coupling agents KH-550 and KH560; and the mass ratio of the flaky carbonyl iron powder to the silane-modified graphene oxide is 100:3-15.

Images