Nanosheet electromagnetic wave absorbing material, preparation method and application
By growing two-dimensional nanosheet structures of cobalt-nickel hydroxide and tungsten source on a multi-channel carbon fiber matrix, the problems of poor conductivity and low dielectric loss of existing nanosheet electromagnetic wave absorbing materials are solved, realizing a wide-bandwidth, strong absorption and impedance-matched electromagnetic wave absorbing material with significant improvements in reflection loss and effective bandwidth.
Patent Information
- Application Number
- CN202511449237.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-11
- Publication Date
- 2025-12-19
AI Technical Summary
Existing nanosheet electromagnetic wave absorbing materials suffer from problems such as poor conductivity, low dielectric loss, poor broadband absorption performance, poor impedance matching, and uneven electromagnetic performance caused by the agglomeration of magnetic nanoparticles.
Two-dimensional nanosheet structures were formed by growing cobalt-nickel hydroxide and tungsten source on a multi-channel carbon fiber matrix. The morphology and composition ratio of the material were controlled by a modifier. Combined with electrospinning, hydrothermal and nitriding processes, a nanosheet electromagnetic wave absorbing material with excellent dielectric and magnetic loss properties was prepared.
The material's specific surface area, density, and effective absorption bandwidth were significantly improved, achieving a lightweight, wide-bandwidth, strong absorption, and weather-resistant electromagnetic wave absorption effect. The reflection loss was reduced from -33dB to -44.5dB, and the effective bandwidth was broadened to 7.5GHz.
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Abstract
Description
Technical Field
[0001] This application relates to the field of electromagnetic wave absorbing materials technology, and in particular to a nanosheet electromagnetic wave absorbing material, its preparation method and application. Background Technology
[0002] With the widespread use of modern electronic devices and the rapid iteration of wireless communication technology, electromagnetic radiation has permeated every corner of production and daily life. From the low-frequency radiation generated by everyday smartphones and smart home devices to the high-frequency electromagnetic waves released by base stations and radar systems, electromagnetic radiation not only interferes with the normal operation of precision instruments and affects the signal stability of electronic devices, but may also pose potential harm to the human body. Currently, electromagnetic wave absorbing materials that have been extensively studied and applied include carbon-based materials, magnetic materials, conductive polymers, and metal oxides / sulfides. Among them, some carbon-based nanosheets can effectively dissipate electromagnetic wave energy due to their high conductivity; magnetic nanosheets rely on magnetic loss mechanisms to function. However, existing nanosheet electromagnetic wave absorbing materials still have many significant drawbacks. On the one hand, some materials have poor conductivity, such as certain metal oxide / sulfide nanosheets, which have weak conductivity, resulting in low dielectric loss and difficulty in efficiently absorbing electromagnetic waves, greatly limiting their application in the field of electromagnetic wave absorption. On the other hand, some nanosheets with excellent conductivity, such as nitrogen-doped carbon (NC) nanosheets, cause a large amount of incident electromagnetic waves to be reflected at the material interface due to their excessive conductivity, preventing them from fully penetrating the material and being absorbed. Furthermore, existing materials also struggle to achieve ideal performance in terms of broadband absorption, thinness, and good impedance matching.
[0003] In recent years, one-dimensional fibers have become an ideal carrier for microwave absorbing materials due to their unique advantages. Their ultra-high specific surface area can construct rich electromagnetic wave transmission and loss channels, their excellent mechanical flexibility makes them easy to process into diverse forms such as thin films and fabrics, and their good designability can optimize the microwave absorption performance by adjusting parameters such as fiber diameter and pore structure. However, one-dimensional fibers with single components (such as pure carbon fiber and polymer fiber) have obvious shortcomings. Pure carbon fiber has too high conductivity, which can easily lead to an increase in electromagnetic wave reflectivity and make it difficult to achieve strong absorption. Polymer fiber has weak dielectric loss capacity, narrow absorption frequency band and is prone to aging. Therefore, it is necessary to improve their performance through surface modification or composite modification.
[0004] When magnetic metal nanoparticles are introduced into fibers, they tend to agglomerate in the polymer, making it difficult to ensure uniform dispersion. Once agglomeration occurs, the electromagnetic parameters of different regions of the material will vary greatly due to excessive particle aggregation in local areas, which will destroy the uniformity and stability of electromagnetic properties. This will cause the absorption and reflection of electromagnetic waves in different parts of the material to be inconsistent, ultimately affecting the stable performance of the overall electromagnetic properties. Summary of the Invention
[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by this application is to improve the specific surface area, density and effective absorption bandwidth of electromagnetic wave absorbing materials, thereby improving the electromagnetic wave absorption width and intensity.
[0006] To achieve the above objectives, in a first aspect, this application provides a nanosheet electromagnetic wave absorbing material, which is implemented using the following technical solution: A nanosheet electromagnetic wave absorbing material comprises a multichannel carbon fiber matrix, a cobalt-nickel hydroxide and a tungsten source grown on the surface of the multichannel carbon fiber matrix; the cobalt-nickel hydroxide includes a cobalt source, a nickel source, and a modifier; the modifier is a mixture containing fluorine atoms and capable of hydrolysis reaction and guiding the cobalt source and nickel source to grow into cobalt-nickel hydroxide; the mass ratio of the cobalt-nickel hydroxide to the tungsten source is 1:(4-6); the nanosheet electromagnetic wave absorbing material exhibits a two-dimensional sheet structure.
[0007] By employing the above technical solutions, the two-dimensional sheet-like structure of cobalt-nickel hydroxide provides abundant heterogeneous interfaces, which can enhance dielectric loss through interface polarization. The introduction of a tungsten source can regulate the conductivity of the material, avoiding excessively high conductivity and thus optimizing impedance matching. The tungsten source can form a tungsten-based phase with a high dielectric constant on the carbon fiber surface, significantly enhancing interface polarization and multiple scattering effects, providing a powerful attenuation channel for electromagnetic waves. The multi-channel carbon fiber matrix not only serves as a conductive framework to construct a three-dimensional conductive network, promoting electron transport to enhance conductivity loss, but its multi-channel structure can also extend the electromagnetic wave propagation path and increase the probability of energy attenuation. Uniform coating of two-dimensional nanosheets ensures uniform distribution of electromagnetic parameters, further improving absorption stability and efficiency. At the same time, the magnetic component provided by cobalt-nickel hydroxide introduces a magnetic loss mechanism, which works synergistically with dielectric loss to further enhance the overall absorption capacity. The cobalt and nickel sources, as bimetallic components, can adjust the electronic structure and magnetism of the material by controlling the ratio of cobalt to nickel. The modulator, by changing the solution chemical environment, induces the formation of a two-dimensional sheet-like morphology and introduces abundant defects and interfaces, significantly enhancing dielectric loss and generating cobalt-nickel hydroxide. These three factors give the material excellent dielectric and magnetic loss characteristics as well as good impedance matching, thereby improving its electromagnetic wave absorption performance.
[0008] Preferably, the tungsten source is a soluble tungsten source.
[0009] By employing the above technical solution and selecting a soluble tungsten source to prepare electromagnetic wave absorbing materials, the materials can dissociate into tungstate ions in aqueous solution, achieving uniform molecular-level dispersion and ensuring that tungsten, cobalt, nickel, and other components form a continuous dielectric network. Furthermore, its solubility characteristics allow for mild and controllable reaction conditions, facilitating stable regulation of the nanosheet morphology and electromagnetic parameters.
[0010] Preferably, the tungsten source is any one of ammonium paratungstate, phosphotungstic acid, and ammonium metatungstate.
[0011] By adopting the above technical solution, ammonium paratungstate, phosphotungstic acid, and ammonium metatungstate are selected as tungsten sources. Due to their good water solubility, they can be uniformly dispersed in the reaction system, realizing atomic-level composite of tungsten with components such as cobalt and nickel, suppressing phase separation and agglomeration, and optimizing impedance matching. Moreover, the process is simple and has good repeatability, which is conducive to the preparation of high-performance electromagnetic wave absorbing materials.
[0012] More preferably, the tungsten source is ammonium metatungstate.
[0013] By adopting the above technical solution, ammonium metatungstate exhibits ultra-high solubility in aqueous solution, and can be expressed as [H₂W] 12 O 40 ] 6- Molecular-level dispersion in the form of polyacid anions ensures that the tungsten-based component forms a uniform interface with other absorbing phases in subsequent reactions, providing a key loss channel for electromagnetic wave absorption. Simultaneously, it can be gradually converted into high-purity WO3 at 200-600℃, and the crystal phase and grain size of WO3 can be precisely controlled by adjusting the temperature. WO3 with specific crystal phases can further enhance dielectric loss due to lattice polarization effects, while the porous structure formed by nanoscale grains optimizes the material's impedance matching, reduces electromagnetic wave reflection, and thus improves overall absorption performance.
[0014] Preferably, the particle size of the tungsten source is 100-500 nm.
[0015] By adopting the above technical solution, tungsten sources with a particle size of 100-500nm are selected. This size matches the nanosheet structure, which is conducive to the formation of multi-level interfaces and enhances the interface polarization loss. It also facilitates precise control of the absorption frequency band through fine-tuning of the particle size.
[0016] Preferably, the specific surface area of the tungsten source is 10-50 m². 2 / g.
[0017] By adopting the above technical solution, a specific surface area of 10-50 m² is selected. 2 A tungsten source of / g can provide sufficient surface active sites while ensuring solubility and dispersibility, promoting uniform compounding with cobalt and nickel components, forming rich heterogeneous interfaces, and enhancing interfacial polarization and defect polarization loss; an appropriate specific surface area can control the dielectric constant and conductivity loss, which is convenient for broadening the absorption bandwidth and improving the absorption intensity.
[0018] Preferably, the mass ratio of cobalt source, nickel source and modifier in the nanosheet electromagnetic wave absorbing material is (1-4):(1-4):1.
[0019] By employing the above technical solution, this ratio can be adjusted to provide optimization space for cobalt and nickel. By adjusting the degree of electron orbital hybridization, the conductivity and magnetic moment density of the material are balanced, ensuring the enhancement of dielectric loss and magnetic loss. The proportion of the regulator can stably control the nucleation rate and growth direction of the nanosheets. This ratio avoids both the agglomeration caused by excessive metal ions and the structural disorder caused by insufficient regulator, ultimately achieving precise matching of the material's electromagnetic parameters and efficient microwave absorption performance.
[0020] Secondly, this application provides a method for preparing the aforementioned nanosheet electromagnetic wave absorbing material, which adopts the following technical solution: A method for preparing a nanosheet electromagnetic wave absorbing material includes the following steps: S1. Dissolve the polymer in a solvent and obtain a multi-channel carbon fiber matrix through electrospinning and high-temperature annealing processes; S2. Add the multi-channel carbon fiber matrix from step S1 to a mixture of regulator, cobalt source and nickel source, and grow cobalt-nickel hydroxide on the surface of the multi-channel carbon fiber matrix through a hydrothermal process to obtain cobalt-nickel hydroxide fiber. S3. Add the cobalt-nickel hydroxide fiber from step S2 to a tungsten source, and further introduce tungsten elements on the surface through a hydrothermal process. After high-temperature nitriding treatment, a multi-metal nitride nanosheet electromagnetic wave absorbing material is obtained by growing a variety of metal nitride nanosheets on the surface of the one-dimensional fiber.
[0021] By employing the above-mentioned technical solutions, the multi-channel carbon fibers constructed through electrospinning combined with high-temperature annealing not only provide a lightweight, high-specific-surface-area three-dimensional conductive network, but their internal channel structure also effectively extends the transmission path of electromagnetic waves, enhancing multiple scattering and conductivity loss. Hydrothermal in-situ growth of cobalt-nickel hydroxide nanosheets on the fiber surface significantly strengthens interfacial polarization and dipole polarization losses. Simultaneously, the introduction of cobalt-nickel hydroxide provides the material with excellent magnetic loss capability, synergistically enhancing dielectric loss. Finally, by introducing a tungsten source and high-temperature nitriding treatment, metal nitrides are formed on the fiber surface. This modulates the dielectric constant of the material, optimizes impedance matching, and improves the absorption performance of the electromagnetic wave absorbing material.
[0022] Preferably, in step S1, the high-temperature annealing temperature is 700-900℃ and the holding time is 1-4h; in step S3, the high-temperature nitriding temperature is 400-700℃ and the holding time is 1-5h.
[0023] By employing the above technical solutions, high-temperature annealing at 700-900℃ for 1-4 hours ensures the full carbonization of the polymer, constructing a highly conductive multi-channel carbon fiber network and enhancing conductivity and polarization loss. Low-temperature nitriding at 400-700℃ for 1-5 hours forms metal nitride nanosheets in situ on the fiber surface, allowing for appropriate control of the dielectric constant to optimize impedance matching and avoid grain coarsening and interface structure damage caused by high temperatures.
[0024] Application of a nanosheet electromagnetic wave absorbing material in electromagnetic wave radiation and electromagnetic wave pollution.
[0025] In this formula, the ingredients and their functions are as follows: The polymers used are polyacrylonitrile (PA) and polystyrene. PA contains cyano groups, and high-temperature annealing can carbonize it to form a conductive carbon skeleton, providing a one-dimensional fibrous substrate while also possessing resistive loss capabilities. Furthermore, its conductivity can be controlled through annealing to optimize impedance matching. Polystyrene has low thermal stability and decomposes and volatilizes during annealing, forming multi-channel pores within the carbon skeleton. This extends the electromagnetic wave path and enhances reflection loss. Together, these two materials form the basis of high-performance microwave absorbing materials.
[0026] Co(NO3)3·6H2O and Ni(NO3)3·6H2O: These two serve as sources of cobalt and nickel, providing Co and Ni atoms through a hydrothermal process. Under the influence of urea and ammonium fluoride, Co and Ni atoms combine with OH- ions generated by hydrolysis, depositing on the surface of multichannel carbon fibers. First, metal ions adsorb at active sites on the fiber surface, forming initial nuclei. These nuclei then grow along the lowest energy direction to form cobalt-nickel hydroxide nanosheets. This sheet-like structure increases the specific surface area of the material and provides a metal source for subsequent nitriding reactions. The directional loading of the metal-based precursor is achieved through the hydrolytic properties of metal ions and interfacial adsorption on the fiber surface. The 1:1 mass ratio of the two is used to control the proportion of Co and Ni elements, ensuring that the subsequently formed metal nitrides can better optimize dielectric parameters.
[0027] The regulators are urea and ammonium fluoride. Urea hydrolyzes upon heating, providing OH- ions to co-precipitate with metal cations, forming a layered double hydroxide structure. Ammonium fluoride provides F- ions, acting as interlayer anions to regulate interlayer spacing and stability, as well as morphology and dispersibility. By controlling the hydrolysis rate of metal ions and the crystal growth direction, it guides the cobalt-nickel hydroxide to grow into a two-dimensional sheet-like structure.
[0028] The tungsten source is ammonium metatungstate. As a source of tungsten, the high reactivity of tungstate ions is utilized to introduce tungsten onto the surface of existing sheet-like precursors, preparing for the subsequent formation of tungsten-based nitrides. In this invention, the mass ratio of ammonium metatungstate to cobalt-nickel compounds (4-6:1) allows for the introduction of additional polarization centers with an appropriate amount of tungsten, enhancing electromagnetic wave loss. However, an excessive amount may lead to an excessively high dielectric constant, disrupting impedance matching. Therefore, it is necessary to balance the loss capacity and impedance characteristics through proportional control.
[0029] The beneficial effects of this invention are: 1. Compared with the prior art, for the first time in this application, Co, Ni, and W multi-metal nitrides are uniformly anchored on the surface of multi-channel carbon fibers in the form of two-dimensional nanosheets; the synergistic effect of the high dielectric loss and moderate conductivity of the nitrides reduces the reflection loss from -33 dB to -44.5 dB at a thickness of 2 mm, and the effective bandwidth is broadened from 4.9 GHz to 7.5 GHz, with the advantages of light weight, wide frequency band, strong absorption, and weather resistance.
[0030] 2. Compared with the prior art, in this application, processes such as electrospinning, hydrothermal treatment, and nitridation are used to in-situ convert Co, Ni, and W into various nitride nanosheets; at the same time, the two-dimensional sheet layer extends the multiple reflection paths of electromagnetic waves, realizes impedance self-matching, effectively improves the effective absorption bandwidth of the electromagnetic wave absorption material, and thus improves the absorption performance of electromagnetic waves. Description of the Drawings
[0031] Figure 1 X-ray diffraction pattern of a nanosheet electromagnetic wave absorption material prepared in Examples 1, 2, 3 and Comparative Example 1 of this application; Figure 2 Scanning electron microscope image of a nanosheet electromagnetic wave absorption material prepared in Examples 1, 2, 3 and Comparative Example 1 of this application; Figure 3 Reflection loss spectrum of a nanosheet electromagnetic wave absorption material prepared in Example 1 of this application; Figure 4 Reflection loss spectrum of a nanosheet electromagnetic wave absorption material prepared in Example 2 of this application; <Step 1: Place 1g of polyacrylonitrile and 1g of polystyrene in 10mL of N,N-dimethylformamide and stir at 300rpm for 30min; Step 2: Electrospin the solution obtained in Step 1 at a positive voltage of 18kV, a feeding rate of 1mL / h, and a fiber collection device 20cm away from the feeding needle to obtain a fiber membrane. Step 3: The fiber membrane obtained in Step 2 is heated from 25°C to 260°C in a muffle furnace at a heating rate of 2°C / min, and held at 260°C for 2 hours for pre-oxidation treatment. Step 4: Anneal the product from Step 3 at 800°C for 2 hours under an argon atmosphere; Step 5: Weigh the product from Step 4 and 0.25g Co(NO3)3·6H2O, 0.25g Ni(NO3)3·6H2O, 0.2g ammonium fluoride, and 0.4g urea, dissolve them in 35mL of water, stir at 200rpm for 25min, and stir at 200rpm for 6h at 120℃. Step 6: Add the product from Step 5 and 0.08 g of ammonium metatungstate to 35 mL of water, and stir at 180 °C and 200 rpm for 12 h; Step 7: Anneal the product from Step 6 in a tube furnace under an ammonia atmosphere at 600 °C for 3 h to obtain a nanosheet electromagnetic wave absorbing material. (Reference) Figure 1 The curve shows obvious diffraction peaks with a certain intensity, indicating that the sample has a certain degree of crystallinity. From... Figure 2 It can be seen from the data that the corresponding sample is crystalline and has a specific crystalline phase.
[0034] Example 2 A method for preparing a nanosheet electromagnetic wave absorbing material includes the following steps: Step 1: Weigh 1g of polyacrylonitrile and 1g of polystyrene and place them in 10mL of N,N-dimethylformamide, and stir at 300rpm for 30min; Step 2: Electrospin the solution obtained in Step 1 at a positive voltage of 18kV, a feeding rate of 1mL / h, and a fiber collection device 20cm away from the feeding needle to obtain a fiber membrane. Step 3: The fiber membrane obtained in Step 2 is heated from 25°C to 260°C in a muffle furnace at a heating rate of 2°C / min, and held at 260°C for 2 hours for pre-oxidation treatment. Step 4: Anneal the product from Step 3 at 800°C for 2 hours under an argon atmosphere; Step 5: Weigh the product from Step 4 and 0.25g of Co(NO3)2. 3)3Dissolve 0.25g Ni(NO3)3·6H2O, 0.2g ammonium fluoride, and 0.4g urea in 35mL of water, stir at 200rpm for 25min, and then stir at 200rpm for 6h at 120℃. Step 6: Add the product from Step 5 and 0.1 g of ammonium metatungstate to 35 mL of water, and stir at 180 °C and 200 rpm for 12 h; Step 7: Anneal the product from Step 6 in a tube furnace under an ammonia atmosphere at 600 °C for 3 h to obtain a nanosheet electromagnetic wave absorbing material. (Reference) Figure 1 The curve shows obvious diffraction peaks with a certain intensity, indicating that the sample has a certain degree of crystallinity. From... Figure 2 It can be seen from the data that the corresponding sample is crystalline and has a specific crystalline phase.
[0035] Example 3 A method for preparing a nanosheet electromagnetic wave absorbing material includes the following steps: Step 1: Weigh 1g of polyacrylonitrile and 1g of polystyrene and place them in 10mL of N,N-dimethylformamide, and stir at 300rpm for 30min; Step 2: Electrospin the solution obtained in Step 1 at a positive voltage of 18kV, a feeding rate of 1mL / h, and a fiber collection device 20cm away from the feeding needle to obtain a fiber membrane. Step 3: The fiber membrane obtained in Step 2 is heated from 25°C to 260°C in a muffle furnace at a heating rate of 2°C / min, and held at 260°C for 2 hours for pre-oxidation treatment. Step 4: Anneal the product from Step 3 at 800°C for 2 hours under an argon atmosphere; Step 5: Weigh the product from Step 4 and 0.25g Co(NO3)3·6H2O, 0.25g Ni(NO3)3·6H2O, 0.2g ammonium fluoride, and 0.4g urea, dissolve them in 35mL of water, stir at 200rpm for 25min, and stir at 200rpm for 6h at 120℃. Step 6: Add the product from Step 5 and 0.12 g of ammonium metatungstate to 35 mL of water, and stir at 180 °C and 200 rpm for 12 h; Step 7: Anneal the product from Step 6 in a tube furnace under an ammonia atmosphere at 600 °C for 3 h to obtain a nanosheet electromagnetic wave absorbing material. (Reference) Figure 1 The curve shows obvious diffraction peaks with a certain intensity, indicating that the sample has a certain degree of crystallinity. From... Figure 2 It can be seen from the data that the corresponding sample is crystalline and has a specific crystalline phase.
[0036] Comparative Example 1 A method for preparing a nanosheet electromagnetic wave absorbing material includes the following steps: Step 1: Weigh 1g of polyacrylonitrile and 1g of polystyrene and place them in 10mL of N,N-dimethylformamide, and stir at 300rpm for 30min; Step 2: Electrospin the solution obtained in Step 1 at a positive voltage of 18kV, a feeding rate of 1mL / h, and a fiber collection device 20cm away from the feeding needle to obtain a fiber membrane. Step 3: The fiber membrane obtained in Step 2 is heated from 25°C to 260°C in a muffle furnace at a heating rate of 2°C / min, and held at 260°C for 2 hours for pre-oxidation treatment. Step 4: Anneal the product from Step 3 at 800°C for 2 hours under an argon atmosphere; Step 5: Weigh the product from Step 4 and 0.25g Co(NO3)3·6H2O, 0.25g Ni(NO3)3·6H2O, 0.2g ammonium fluoride, and 0.4g urea, dissolve them in 35mL of water, stir at 200rpm for 25min, and stir at 200rpm for 6h at 120℃. Step 6: The product from Step 5 was annealed at 600°C for 3 hours in an ammonia atmosphere in a tube furnace to obtain a nanosheet electromagnetic wave absorbing material. From Figure 1 As can be seen from the curves, except for a strong peak at a certain position, the overall intensity and number of peaks are much less than in Examples 1-3, which may indicate that Comparative Example 1 has a lower degree of crystallinity. Figure 2 It can be seen that it is mainly an amorphous phase / another crystalline phase with low crystallinity.
[0037] Comparative Example 2 A method for preparing a nanosheet electromagnetic wave absorbing material includes the following steps: Step 1: Place 1g of polyacrylonitrile and 1g of polystyrene in 10mL of N,N-dimethylformamide and stir at 300rpm for 30min; Step 2: Electrospin the solution obtained in Step 1 at a positive voltage of 18kV, a feeding rate of 1mL / h, and a fiber collection device 20cm away from the feeding needle to obtain a fiber membrane. Step 3: The fiber membrane obtained in Step 2 is heated from 25°C to 260°C in a muffle furnace at a heating rate of 2°C / min, and held at 260°C for 2 hours for pre-oxidation treatment. Step 4: Anneal the product from Step 3 at 800°C for 2 hours under an argon atmosphere; Step 5: Weigh the product from Step 4 and 0.25g Co(NO3)3·6H2O, 0.25g Ni(NO3)3·6H2O, 0.2g ammonium fluoride, and 0.4g urea, dissolve them in 35mL of water, stir at 200rpm for 25min, and stir at 200rpm for 6h at 120℃. Step 6: Add the product from Step 5 and 0.1g of ferric nitrate nonahydrate to 35mL of water, and stir at 180℃ and 200rpm for 12h. Step 7: Anneal the product from Step 6 at 600°C for 3 hours in an ammonia atmosphere in a tube furnace to obtain a nanosheet electromagnetic wave absorbing material.
[0038] Test case The samples obtained in Examples 1, 2, 3, and Comparative Examples 1 and 2 were mixed with paraffin wax at a mass ratio of 1:5 and pressed into rings with an inner diameter of 3.04 mm, an outer diameter of 7.00 mm, and a thickness of about 2.00 mm using a special mold. The electromagnetic parameters were measured using a vector grid analyzer (E5063A, Keysight). The reflection loss spectrum of the materials in Examples 1-3 and Comparative Example 1 was obtained by simulation calculation. Figure 4-6 The following are reflection loss spectra of samples with a loading of 20%, calculated using the reflection loss formula (below) for Examples 1, 2, 3, and Comparative Examples 1 and 2.
[0039] In the formula, Zin and Z0 are the input impedance and free space impedance of the normalized absorber, respectively, and ε r and μ r denoted as complex permittivity and complex permeability, respectively; f is the frequency; c is the speed of light in free space; and d is the thickness.
[0040] Depend on Figure 3 and Figure 7 It can be seen that the sample obtained in Implementation Case 1 has the lowest reflection loss of -44.54dB within a thickness of 0.1-10mm, and an effective absorption bandwidth of 6.48GHz at 2.3mm; Figure 4 and Figure 7 It can be seen that the minimum reflection loss in Implementation Case 2 is -39.10dB, and the effective absorption bandwidth at 2.0mm is 7.52GHz; Figure 5 and Figure 7 It can be seen that in implementation case 3, the reflection loss value at 3.4mm is -39.83dB, and the effective absorption bandwidth at 2.0mm is 6.16GHz; Figure 6 and Figure 7 It can be seen that Comparative Example 1 has a reflection loss of -33.44 dB at 2.1 mm and an effective absorption bandwidth of 4.88 GHz at 2.2 mm. In Comparative Example 2, the electromagnetic parameters of the sample were measured to show an effective absorption bandwidth of 3.95 GHz at 2.5 mm and a minimum reflection loss of -28.67 dB at a thickness of 2.8 mm.
[0041] Comparative analysis of Examples 1-3 and Comparative Example 1 shows that Example 2 exhibits superior electromagnetic wave absorption performance. The difference in performance is primarily due to variations in the material's phase composition and the content of tungsten, which in turn affects interfacial loss. By adjusting the tungsten content and altering the phase composition, the impedance matching, conduction network, and electron transport behavior within the material can be influenced, ultimately affecting the material's dielectric constant. Figure 7 To compare the dielectric loss capabilities of Implementation Cases 1-3 and Comparative Example 1, Implementation Case 2 demonstrates good dielectric loss performance.
[0042] Analyzing the test results of Example 2 and Comparative Example 2 reveals that the nanosheet electromagnetic wave absorbing material prepared in Example 2 exhibits superior specific surface area and effective absorption bandwidth. This may be due to the formation of metal nitrides such as WN after the introduction of tungsten. Their high dielectric constant and moderate conductivity effectively regulate impedance matching, avoiding the skin effect, while providing strong dielectric loss. In contrast, the Fe-N formed by introducing iron in Comparative Example 2, although enhancing magnetic loss, suffers from severe impedance mismatch due to excessive conductivity, making it difficult for electromagnetic waves to penetrate the material. The synergistic effect of dielectric / magnetic loss between WN and Co-Ni-N is superior, while the strong magnetism and high conductivity of Fe-N easily induce current concentration, weakening polarization loss and compressing the absorption bandwidth. Therefore, Example 2 demonstrates superior performance.
[0043] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A nanosheet electromagnetic wave absorbing material, characterized in that, The nanosheet electromagnetic wave absorbing material comprises: a multichannel carbon fiber matrix, cobalt-nickel hydroxide and a tungsten source grown on the surface of the multichannel carbon fiber matrix; the cobalt-nickel hydroxide comprises: a cobalt source, a nickel source, and a modifier; the modifier is a mixture containing fluorine atoms and capable of hydrolysis reaction and guiding the cobalt source and nickel source to grow into cobalt-nickel hydroxide; the mass ratio of the cobalt-nickel hydroxide to the tungsten source is 1:(4-6); the nanosheet electromagnetic wave absorbing material exhibits a two-dimensional sheet structure.
2. The nanosheet electromagnetic wave absorbing material as described in claim 1, characterized in that, The tungsten source is a soluble tungsten source.
3. The nanosheet electromagnetic wave absorbing material as described in claim 2, characterized in that, The tungsten source is any one of ammonium paratungstate, phosphotungstic acid, or ammonium metatungstate.
4. The nanosheet electromagnetic wave absorbing material as described in claim 3, characterized in that, The tungsten source is ammonium metatungstate.
5. The nanosheet electromagnetic wave absorbing material as described in claim 1, characterized in that, The tungsten source has a particle size of 100-500 nm.
6. The nanosheet electromagnetic wave absorbing material as described in claim 1, characterized in that, The specific surface area of the tungsten source is 10-50 m² / g.
7. The nanosheet electromagnetic wave absorbing material as described in claim 1, characterized in that, The mass ratio of cobalt source, nickel source, and modifier in the nanosheet electromagnetic wave absorbing material is (1-4):(1-4):
1.
8. A method for preparing a nanosheet electromagnetic wave absorbing material, characterized in that, Includes the following steps: S1. Dissolve the polymer in a solvent and obtain a multi-channel carbon fiber matrix through electrospinning and high-temperature annealing processes; S2. Add the multi-channel carbon fiber matrix from step S1 to a mixture of regulator, cobalt source and nickel source, and grow cobalt-nickel hydroxide on the surface of the multi-channel carbon fiber matrix through a hydrothermal process to obtain cobalt-nickel hydroxide fiber. S3. The cobalt-nickel hydroxide fiber from step S2 is added to a tungsten source, and tungsten elements are introduced onto the surface through a hydrothermal process. After high-temperature nitriding treatment, a nanosheet electromagnetic wave absorbing material is obtained.
9. The method for preparing the nanosheet electromagnetic wave absorbing material as described in claim 8, characterized in that, In step S1, the high-temperature annealing temperature is 700-900℃ and the holding time is 1-4h; in step S3, the high-temperature nitriding temperature is 400-700℃ and the holding time is 1-5h.
10. The application of a nanosheet electromagnetic wave absorbing material as described in any one of claims 1-7 in electromagnetic wave radiation and electromagnetic wave pollution.