Preparation method and application of carbon-based magnetic nanocomposite wave-absorbing material

Abstract

The application discloses a preparation method of a carbon-based magnetic nanometer composite wave-absorbing material, which comprises the following steps: mixing a heterocyclic compound with a diamino group, a magnetic metal compound and a template agent NaCl, adding a solvent, and performing ball milling to obtain a viscous mixed slurry; drying the mixed slurry, and then performing high-temperature carbonization; and washing and drying the product to obtain the carbon-based magnetic nanometer composite wave-absorbing material. The preparation method has the advantages of low cost and easy scale production, and the prepared material has very good wave-absorbing performance. The application further discloses a method for preparing a wave-absorbing patch by using the carbon-based magnetic nanometer composite wave-absorbing material. The method has the advantages of low cost, environmentally-friendly material and simple operation, and the prepared wave-absorbing patch has good physical performance and environmental resistance, is wide in functionality, can be widely applied to the wave-absorbing field, and is easy to scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials and relates to a preparation method and application of a carbon-based magnetic nanocomposite wave-absorbing material. Background Art

[0002] Electromagnetic radiation has become a more harmful source of pollution than water, air, noise, and solid waste pollution. Electromagnetic interference (EMI) generated by electromagnetic radiation not only severely disrupts nearby instruments, causing malfunctions and signal interruptions, but also poses a threat to human health, leading to diseases such as cancer and endocrine disorders. Strong electromagnetic radiation can also cause plant inactivation, mutations, and even death. The problem of electromagnetic radiation pollution is a pressing issue for humanity. In the military, many advanced weapons, such as stealth fighters, are primary targets of enemy attack. Electromagnetic stealth technology is a key solution for military equipment to evade detection and attack the enemy. Electromagnetic wave absorbing materials are materials that absorb incident electromagnetic wave energy. Through specialized internal loss mechanisms, these materials convert the electromagnetic waves into heat or other forms of energy, effectively attenuating the electromagnetic waves and preventing the spread of excess electromagnetic waves.

[0003] Over the years, researchers have developed a variety of electromagnetic wave absorbing materials. Materials primarily based on magnetic loss include ferrites (CoFe2O4, MnFe2O4, ZnFe2O4, etc.), magnetic metal oxides (Fe3O4, γ-Fe2O3, CoO, etc.), and magnetic metals (Fe, Co, Ni, and their alloys). Dielectric loss primarily includes conductive polymers, oxides, and carbon-based materials. While these single-component absorbers exhibit some microwave absorption capabilities, their single attenuation mechanism and poor controllability of electromagnetic parameters make them insufficient for ideal microwave absorption devices. Carbon-based absorbers, due to their lightweight, controllable composition and structure, and excellent electrical properties, have become an ideal electromagnetic functional material for addressing key challenges in military and civilian applications, such as radar detection and electromagnetic interference. However, single carbon materials lack magnetic properties, resulting in poor impedance matching and making it difficult to simultaneously achieve the desired combination of thinness, lightness, width, and strength for both electromagnetic wave absorption and shielding. Therefore, there is an urgent need for technology to composite lightweight conductive carbon materials with magnetic materials, which will help improve impedance matching characteristics while maintaining high electromagnetic wave loss intensity, and achieve lightweight, broadband absorption and strong absorption characteristics. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a method for preparing carbon-based magnetic nanocomposite absorbing materials from bottom to top.

[0005] The method for preparing the carbon-based magnetic nanocomposite wave absorbing material provided by the present invention comprises the following steps:

[0006] Step S1, mixing a diamino heterocyclic compound, a magnetic metal compound, and a template agent NaCl, adding anhydrous ethanol as a solvent, and then ball milling to obtain a viscous mixed slurry;

[0007] Step S2, drying the viscous mixed slurry obtained in step S1 to obtain a mixture powder in which the polymer-loaded magnetic metal particles are uniformly coated on the surface of the NaCl crystals;

[0008] Step S3, heating the mixture powder obtained in step S2 to 700-900° C. under a nitrogen atmosphere for carbonization, maintaining the temperature for 1.5-2.5 hours, and then cooling the mixture powder to obtain a dark black carbon-loaded magnetic particle mixture powder;

[0009] Step S4: washing and drying the mixed powder obtained in step S3 to obtain a carbon-based magnetic nanocomposite absorbing material.

[0010] Wherein, the diamino heterocyclic compound in step S1 is m-phenylenediamine, diaminopyridine, diaminopyrimidine, diaminopurine or diaminothiazole.

[0011] Wherein, the magnetic metal compound in step S1 is a magnetic metal chloride or a magnetic metal nitrate; preferably NiCl2·6H2O or CoCl2·6H2O.

[0012] The ball milling condition in step S1 is ball milling at a rotation speed of 500 r / min for 12 h.

[0013] Wherein, in step S1, the mass ratio of the magnetic metal compound, the diamino heterocyclic compound, and the template agent NaCl is 1:10:100.

[0014] The amount of anhydrous ethanol as the solvent added in step S1 is 2.5 mL for every 1 g of template NaCl.

[0015] The drying in step S2 is performed at 80° C. for 12 hours.

[0016] In step S3, the temperature is raised to 700°C, 800°C or 900°C at a rate of 5°C / min for carbonization, maintained for 2 hours and then cooled.

[0017] The washing in step S4 is to mix the mixed powder with deionized water, stir the mixed powder, and then filter and centrifuge to collect the powder. The drying is to dry the mixed powder at 80° C. under vacuum conditions for 12 hours.

[0018] The carbon-based magnetic nanocomposite wave-absorbing material obtained according to the preparation method can be used to absorb electromagnetic waves.

[0019] The present invention also provides a method for preparing a carbon-based magnetic nanocomposite absorbing material absorbing patch using the carbon-based magnetic nanocomposite absorbing material, comprising the following steps:

[0020] (1) mixing the carbon-based magnetic nanocomposite absorbing material and the waterborne polyurethane uniformly, adding an organosilicon defoamer and defoaming under vacuum to obtain a viscous mixture;

[0021] (2) The viscous mixture obtained in step (1) is evenly coated on a flat mold, and the mixture is naturally solidified in a dust-free environment to obtain a magnetic nano-composite absorbing material absorbing patch.

[0022] Wherein, in step (1), the mass ratio of the carbon-based magnetic nanocomposite absorbing material to the waterborne polyurethane is 1:(6-12); the amount of the organic silicon defoaming agent added is 1 g of the organic silicon defoaming agent per 200 g of waterborne polyurethane, and the defoaming time under vacuum is 30 minutes.

[0023] Wherein, in step (2), the solidification time is 24 hours, and the thickness of the absorbing patch based on the magnetic nano-composite absorbing material is 1.4 mm to 2.5 mm; preferably, the thickness of the absorbing patch based on the magnetic nano-composite absorbing material is 1.7 mm.

[0024] Beneficial effects of the present invention

[0025] The present invention provides a method for preparing a carbon-based magnetic nanocomposite absorber. Using a diamino heterocyclic compound as a carbon source, nanomagnetic particles are loaded via a copolymerization and cyclization reaction. These particles are then uniformly coated on a NaCl crystal template via ball milling to synthesize a series of metal complex polymers. The carbon-based magnetic nanocomposite absorber is then carbonized under a nitrogen atmosphere to obtain the material. The material exhibits a three-dimensional network structure, enhancing electromagnetic wave multi-reflection loss. The carbon and magnetic materials enhance the magneto-dielectric synergy, increasing electromagnetic wave loss. This method offers the advantages of low cost and ease of large-scale production. The loading of magnetic particles improves the dispersibility of the flaky carbon material in solution, effectively suppressing the stacking of the flaky carbon material.

[0026] The present invention also provides a method for preparing a carbon-based magnetic nanocomposite absorbing material absorbing patch by a coating method. This method has the advantages of low cost, environmentally friendly materials, and simple operation. The prepared absorbing patch has good physical properties and environmental resistance, wide functionality, can be widely used in the field of absorbing waves, and is easy to produce on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 These are SEM images of the carbon-based magnetic nanocomposite absorbing materials of Examples 1 to 4;

[0028] Figure 2XRD patterns of the carbon-based magnetic nanocomposite absorbing materials of Examples 1 to 4;

[0029] Figure 3 The electromagnetic parameters of the carbon-based magnetic nanocomposite absorbing materials of Examples 1 to 4 vary with frequency. In the figure, (a) is the real part of the dielectric constant, (b) is the imaginary part of the dielectric constant, (c) is the real part of the magnetic permeability, and (d) is the imaginary part of the magnetic permeability;

[0030] Figure 4 is the reflection loss of the absorbing patches of different thicknesses in Examples 8 to 11;

[0031] Figure 5 The impedance matching values ​​and attenuation coefficients of the absorbing patches of different thicknesses in Examples 8 to 11;

[0032] Figure 6 The loss mechanism of the carbon-based magnetic nanocomposite absorbing material of Examples 1 to 4;

[0033] Figure 7 These are the tensile test results of the 1.7 mm thick absorbing patch prepared in Example 8. DETAILED DESCRIPTION

[0034] The following examples further illustrate the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and substance of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0035] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. Unless otherwise specified, the materials, reagents, etc. used in the following examples are all commercially available.

[0036] Example 1 Carbon-based magnetic nanocomposite absorbing material

[0037] (1) 20 g of m-phenylenediamine, 2 g of NiCl2·6H2O, and 200 g of the template agent NaCl were mixed, and 0.5 L of anhydrous ethanol was added. The mixture was ball-milled at a speed of 500 r / min for 12 h to obtain a viscous mixed slurry.

[0038] (2) drying the viscous mixed slurry obtained in step (1) in an oven at 80° C. for 12 h to obtain a mixture powder in which the polymer-loaded magnetic metal particles are uniformly coated on the surface of the NaCl crystals;

[0039] (3) heating the mixture powder obtained in step (2) to 700°C at a rate of 5°C / min under a nitrogen atmosphere for carbonization, maintaining the temperature for 2 hours, and then cooling the mixture powder to obtain a dark black carbon-loaded magnetic particle mixture powder;

[0040] (4) The mixed powder obtained in step (3) was stirred in a deionized water environment for 6 hours, and then filtered and centrifuged to collect the powder, and dried in a vacuum drying oven at 80°C for 12 hours in a vacuum environment to obtain a carbon-based magnetic nanocomposite absorbing material NG@Ni-700.

[0041] Example 2 Carbon-based magnetic nanocomposite absorbing material

[0042] The carbon-based magnetic nanocomposite absorbing material NG@Ni-600 was prepared by the method of Example 1, the carbonization temperature of step (3) was set to 600° C., and the parameters of the other steps were the same as those of Example 1.

[0043] Example 3 Carbon-based magnetic nanocomposite absorbing material

[0044] The carbon-based magnetic nanocomposite absorbing material NG@Ni-800 was prepared by the method of Example 1, the carbonization temperature of step (3) was set to 800° C., and the parameters of the other steps were the same as those of Example 1.

[0045] Example 4 Carbon-based magnetic nanocomposite absorbing material

[0046] The carbon-based magnetic nanocomposite absorbing material NG@Ni-900 was prepared by the method of Example 1, the carbonization temperature of step (3) was set to 900° C., and the parameters of the other steps were the same as those of Example 1.

[0047] Example 5 Scanning electron microscope (SEM) scanning

[0048] The carbon-based magnetic nanocomposite absorbing materials prepared in Examples 1 to 4 were scanned using a scanning electron microscope (SEM). The SEM images are shown in FIG. Figure 1 As shown, from Figure 1 As can be seen, after carbonization, the morphology of all four samples exhibits a flaky three-dimensional network structure, uniformly loaded with nano-magnetic Ni particles. This structure facilitates multiple reflections of incident electromagnetic waves, enhancing their attenuation capabilities.

[0049] Example 6 X-ray diffractometer (XRD) analysis

[0050] The carbon-based magnetic nanocomposite absorbing materials prepared in Examples 1 to 4 were analyzed using an X-ray diffractometer (XRD). The XRD patterns were as follows: Figure 2 As shown, from Figure 2It can be seen that the four sample materials exhibit a protruding broad peak at around 25°, which is caused by the conversion of polymer graphitization into flake graphite during the high-temperature carbonization process. In addition, the X-ray diffraction pattern shows three obvious diffraction peaks at 44.5°, 51.8°, and 76.4°. By comparing with the PDF card of the elemental Ni space group Fm-3m, these characteristic diffraction peaks are completely consistent with the (1,1,1), (2,0,0), and (2,2,0) Ni crystal planes with the space group Fm-3m, respectively, indicating that after high-temperature carbonization, the samples are composed only of graphitized carbon and Ni particles, and no other products are generated.

[0051] Example 7 Electromagnetic parameter test

[0052] The electromagnetic parameters of the carbon-based magnetic nanocomposite absorbing materials prepared in 1 to 4 were tested respectively. The results are as follows Figure 3 As shown, in Figure 3 Middle: (a) real part of dielectric constant; (b) imaginary part of dielectric constant; (c) real part of magnetic permeability and (d) imaginary part of magnetic permeability.

[0053] from Figure 3 It can be seen that within the frequency range of 2 to 18 GHz, the real part of the complex dielectric constant of all samples shows a gradual downward trend, demonstrating excellent dispersion characteristics. Furthermore, with increasing carbonization temperature, both the real and imaginary parts of the dielectric constant increase, indicating enhanced electromagnetic energy storage and dissipation capabilities. This indicates that varying degrees of carbonization can significantly improve the material's conductivity and polarization losses. While the magnetic permeability remains nearly constant with frequency, the curve exhibits consistent undulations in the high-frequency region, indicating the presence of natural resonant electromagnetic loss waves in this region.

[0054] Example 8 Preparation of Carbon-based Magnetic Nanocomposite Wave-Absorbing Patch

[0055] (1) 3 g of the carbon-based magnetic nanocomposite absorbing material NG@Ni-700 prepared in Example 1 was taken and put into a mortar and ground thoroughly. The mixture was then placed into a small beaker, 20 g of waterborne polyurethane and 0.1 g of silicone defoamer (BYK-024 silicone defoamer from Germany) were added. The mixture was stirred on a magnetic stirrer for 30 min to mix evenly. The air in the mixture was then evacuated under vacuum for 30 min to obtain a viscous mixture.

[0056] (2) Pour the viscous mixture obtained in step (1) into a coating machine, adjust the required thickness, and evenly coat the mixture on a glass flat plate mold. Finally, place it in a dust-free environment and naturally solidify for 24 hours to obtain a magnetic nano-composite absorbing material absorbing patch.

[0057] In this embodiment, absorbing patches with thicknesses of 1.7 mm, 2.0 mm, 2.5 mm, 3.0 mm, and 3.5 mm are prepared respectively.

[0058] Example 9 Preparation of Carbon-based Magnetic Nanocomposite Absorbing Patch

[0059] 3 g of the carbon-based magnetic nanocomposite absorbing material NG@Ni-600 prepared in Example 2 was taken, and absorbing patches with thicknesses of 1.7 mm, 2.0 mm, 2.5 mm, 3.0 mm, and 3.5 mm were prepared according to the method of Example 7.

[0060] Example 10 Preparation of carbon-based magnetic nanocomposite absorbing patch

[0061] 3 g of the carbon-based magnetic nanocomposite absorbing material NG@Ni-800 prepared in Example 3 was taken, and absorbing patches with thicknesses of 1.4 mm, 1.7 mm, 2.0 mm, 2.5 mm, and 3.0 mm were prepared according to the method of Example 7.

[0062] Example 11 Preparation of carbon-based magnetic nanocomposite absorbing patch

[0063] 3 g of the carbon-based magnetic nanocomposite absorbing material NG@Ni-900 prepared in Example 4 was taken and absorbing patches with thicknesses of 1.4 mm, 1.7 mm, 2.0 mm, 2.5 mm and 3.0 mm were prepared according to the method of Example 7.

[0064] Example 12 Reflection loss test

[0065] The reflection loss of the absorbing patches of different thicknesses prepared in Examples 8 to 11 was tested respectively. The electromagnetic parameters of the absorbing material can be obtained by a vector network analyzer, mainly including the complex dielectric constant (ε) and the complex magnetic permeability constant (μ), which can be divided into the real part (ε′) and imaginary part (ε″) of the complex dielectric constant and the real part (μ′) and imaginary part (μ″) of the complex magnetic permeability constant. The microwave absorption performance of the material can then be obtained based on the transmission line theory. [1] The strength of a material's absorption can be measured by microwave reflection loss RL (dB). RL can be calculated from the electromagnetic parameters of the material and is generally negative. The more negative the value, the better the material's absorption performance. According to transmission line theory, the RL of a single-layer absorbing material can be calculated using formulas (1-1) and (1-2): [2] get:

[0066]

[0067]

[0068] The relative permittivity and relative permeability can be expressed as:

[0069] ε=ε′-jε″ (1-3)

[0070] μ = μ' - jμ" (1-4)

[0071] The electromagnetic parameters can intuitively reflect the reflection loss of the material at different thicknesses. The RL value of -10 dB indicates that 90% of the microwaves are absorbed, and the RL value of -20 dB indicates that 99% of the microwaves are absorbed.

[0072] The results are shown in Figure 4 Figure 4 The reflection loss of the wave-absorbing patch at different thicknesses and the frequency relationship are reflected. From Figure 4 It can be seen that when the thickness is 1.7 mm, NG@Ni-700 has the best reflection loss at 15.1 GHz, reaching -51.4 dB, and the effective absorption bandwidth (RL≤-10 dB) is 5.2 GHz, which can cover 12.8-18 GHz. When the thickness is 1.4 mm, NG@Ni-800 has the best reflection loss at 15.3 GHz, reaching -40.4 dB, and the effective absorption bandwidth (RL≤-10 dB) is 4.6 GHz, which can cover 13.4-18 GHz. When the thickness is 1.4 mm, NG@Ni-900 has a reflection loss of -24.1 dB at 15.7 GHz, and the effective absorption bandwidth (RL≤-10 dB) is 4.1 GHz, which can cover 13.9-18 GHz. NG@Ni-700, NG@Ni-800 and NG@Ni-900 also exhibit relatively good microwave absorption capacity.

[0073] [1] Wang Y, Gao X, Lin C, et al. Metal organic frameworks-derived Fe-Co nanoporous carbon / graphene composite as a high-performance electromagnetic wave absorber[J]. Journal of Alloys and Compounds, 2019, 785: 765-773.

[0074] [2] Xie P, Li H, He B, et al. Bio-gel derived nickel / carbon nanocomposites with enhanced microwave absorption[J]. Journal of Materials Chemistry C, 2018, 6(32): 8812-8822.

[0075] Example 13 Anti-reflection matching test

[0076] ​The impedance matching parameters of the absorbing patches of different thicknesses prepared in Example 8, Example 10, and Example 11, as well as the attenuation coefficients of the absorbing patches of different thicknesses prepared in Examples 8 to 11, were tested respectively.

[0077] Zin is the standard impedance in air, and Z0 = 377Ω is the impedance of free space. f is the frequency of the incident wave, d is the thickness of the absorbing layer, and c is the speed of light. Furthermore, for electromagnetic wave absorbing materials, it is required that as much of the incident electromagnetic wave as possible enter the material to minimize the amount of reflected electromagnetic wave. Therefore, the concept of impedance matching is introduced, which primarily reflects the absorption and reflection of electromagnetic waves on the material surface. The impedance matching coefficient is a measure of this phenomenon and can be calculated using Formula (1-2).

[0078] In order to comprehensively express the ability of magnetic loss and dielectric loss, the attenuation constant α is introduced. It is a measure of the attenuation strength of the electromagnetic wave intensity passing through the material. It can be calculated using formula (1-5). The larger the attenuation constant, the stronger the material's ability to lose electromagnetic waves.

[0079]

[0080] Impedance matching is considered to be one of the most important parameters in determining microwave absorption performance. The closer the value is to 1, the more incident microwaves are absorbed. Figure 5 As shown, (a) represents NG@Ni-700, (b) represents NG@Ni-800, (c) represents NG@Ni-900, and (d) represents the attenuation coefficient.

[0081] from Figure 5 It can be seen that except for a few thicknesses of NG@Ni-700 sample whose impedance matching is higher than 1, the impedance matching of other thicknesses is almost around 1, which shows that its impedance matching performance is the best and almost all incident microwaves are absorbed. When the thickness of NG@Ni-800 sample is 1.4mm and 1.7mm, the impedance matching is close to 1, corresponding to its best reflection loss. When the thickness of NG@Ni-900 sample is 2.0mm, the impedance matching is close to 1, corresponding to its best reflection loss. The attenuation constant α is usually used to comprehensively evaluate the ability of dielectric loss and magnetic loss. Figure 5 In (d), as the carbonization temperature increases, α gradually increases, indicating that the dielectric loss and magnetic loss capacity increase with increasing temperature.

[0082] Example 14 Loss Mechanism Test

[0083] The loss mechanism of carbon-based magnetic nanocomposite absorbing materials prepared in 1 to 4 was tested respectively.

[0084] A material's ability to resist dielectric and magnetic losses from electromagnetic waves is reflected in the imaginary parts of its dielectric constant and magnetic permeability. Dielectric loss is the loss caused by the interaction between the material and the alternating electric field in electromagnetic waves, while magnetic loss is the loss caused by the interaction between the material and the alternating magnetic field in electromagnetic waves. The dielectric loss tangent, represented by tanε, is equal to the ratio of the real part to the imaginary part of the material's dielectric constant, i.e., tanε = ε′ / ε″; the magnetic loss tangent, represented by tanμ, is equal to the ratio of the real part to the imaginary part of the material's magnetic permeability, i.e., tanμ = μ′ / μ″. The dielectric constant and magnetic permeability of a material are measured using a network vector analyzer.

[0085] To judge the material's attenuation of the alternating magnetic field of electromagnetic waves, the material's dielectric constant ε′-ε″ curve is used for analysis. A Cole-Cole semicircle corresponds to a polarization relaxation process. The more Cole-Cole semicircles there are, the more obvious the dielectric relaxation phenomenon of the material is.

[0086] Analyze the attenuation type of electromagnetic wave alternating magnetic field, generally through C0 = μ "(μ ') -2 f -1 To determine whether there is eddy current loss in the magnetic part of the composite material. If the value of Co is a constant that does not change with frequency, it means that eddy current loss exists in the material.

[0087] See the results Figure 6 In the figure, (a) represents the dielectric loss tangent, (b) represents the magnetic loss tangent, (c) represents the Cole-Cloe diagram, and (d) represents the C0-f curve.

[0088] Cole-Cloe plots can be used to explore the dielectric relaxation process of a material. When a material experiences dipole polarization relaxation loss, a semicircle appears in the Cole-Cloe curve, and the straight line portion of the Cole-Cloe curve represents conductivity loss. (c) The dielectric loss curves of NG@Ni-600, NG@Ni-700, NG@Ni-800, and NG@Ni-900 in the figure all contain semicircles and straight lines, corresponding to the presence of dielectric relaxation and conductivity loss processes. The significant difference in conductivity between graphene and magnetic metals leads to charge accumulation at the interface, generating a large number of dipoles, which in turn enhances the electronic and dipole relaxation polarization near the interface, effectively improving the attenuation capability of carbon-based magnetic nanocomposite absorbers for electromagnetic waves.

[0089] Eddy current loss factor C0 = μ″(μ′) -2 f -1It can reflect the mechanism of magnetic loss. Eddy current loss is a type of energy loss caused by the induced current in the conductor when the conductor moves in a non-uniform magnetic field or is in a time-varying magnetic field. When C0 is a constant, eddy current loss is the main loss mode; if C0 is not a constant, resonance loss plays a dominant role. (d) Figure shows that the C0 value of carbon-based magnetic nanocomposite absorbers remains basically unchanged, and their magnetic loss mechanism is mainly eddy current loss. NG@Ni-800 is basically a constant at 13-18 GHz; NG@Ni-600, NG@Ni-700 and NG@Ni-900 are basically a constant at 11-18 GHz. In these frequency ranges, the magnetic loss is mainly provided by eddy current loss.

[0090] In summary, the dielectric and magnetic losses of carbon-based magnetic nanocomposite absorbing powders increase with increasing carbonization temperature. The dielectric loss tangent decreases from low frequencies to high frequencies, remaining essentially unchanged at high frequencies, while the magnetic loss remains essentially unchanged across the entire frequency range. This indicates that carbon-based magnetic nanocomposite absorbing powders attenuate electromagnetic waves primarily through dielectric and eddy current losses.

[0091] Example 15 Tensile Test

[0092] A tensile test was performed on the 1.7 mm thick absorbing patch prepared in Example 8. The absorbing patch was placed in the fixture of a tensile testing instrument, and a tensile force that varied with time was then applied. The stress condition of the absorbing patch was analyzed using software.

[0093] The results are as follows Figure 7 As shown, in Figure 7 The left picture shows the finished product of the absorbing patch, and the right picture shows the tensile test result. Figure 7 It can be seen that the finished absorbing patch prepared by the present invention has good flexibility. In the tensile test, when the tension is below 11N, the deformation of the absorbing patch does not change significantly with the increase of the tension. When the tension is increased above 11N, the absorbing patch deforms significantly, and the greater the tension, the more obvious the deformation. When the tension is 15.4N, the maximum deformation is 68.1mm, and the deformation area is 1.5mm. 2 , elongation reaches 272.5%, and tensile strength reaches 10.2MPa. The physical and mechanical properties of this absorbing patch meet the requirements of practical use. The preparation process is simple, the materials are environmentally friendly, and it has good development prospects.

[0094] The above examples illustrate the present invention's use of carbon-based materials as carriers loaded with nanomagnetic metal particles. Through pyrolysis and carbonization, the microstructure and composition can be manipulated to produce composite absorbers containing various components of NG-loaded nanomagnetic metal particles. These materials are then mixed with waterborne polyurethane and coated to produce novel carbon-based magnetic nanocomposite absorbers that combine magnetic and electrical losses. The absorbers provided by the present invention feature thin layers, high efficiency, broadband, low frequency, structural integration, and strong functional integration. They utilize environmentally friendly materials, are easy to operate, and can be customized to meet individual production needs through adjustable thickness, effectively connecting the product with its intended application.

Claims

1. A method for preparing a carbon-based magnetic nanocomposite absorbing material, characterized in that: The following steps are involved: Step S1, mixing a diamino heterocyclic compound, a magnetic metal compound, and a template agent NaCl, adding anhydrous ethanol as a solvent, and then ball milling to obtain a viscous mixed slurry; Step S2, drying the viscous mixed slurry obtained in step S1 to obtain a mixture powder in which the polymer-loaded magnetic metal particles are uniformly coated on the surface of the NaCl crystals; Step S3, heating the mixture powder obtained in step S2 to 700-900° C. under a nitrogen atmosphere for carbonization, maintaining the temperature for 1.5-2.5 hours, and then cooling the mixture powder to obtain a dark black carbon-loaded magnetic particle mixture powder; Step S4, washing and drying the mixed powder obtained in step S3 to obtain a carbon-based magnetic nanocomposite absorbing material; Wherein, the diamino heterocyclic compound in step S1 is m-phenylenediamine, diaminopyridine, diaminopyrimidine, diaminopurine or diaminothiazole; Wherein, the magnetic metal compound in step S1 is NiCl2•6H2O or CoCl2•6H2O; the mass ratio of the magnetic metal compound, the diamino heterocyclic compound, and the template agent NaCl is 1:10:

100.

2. The preparation method according to claim 1, characterized in that: The ball milling conditions in step S1 are ball milling at a speed of 500 r / min for 12 h, and the amount of solvent anhydrous ethanol added is 2.5 mL of anhydrous ethanol per 1 g of template NaCl; the drying described in step S2 is drying at 80°C for 12 h; in step S3, the temperature is increased to 700°C, 800°C or 900°C at a rate of 5°C / min for carbonization, maintained for 2 h, and then cooled.

3. A carbon-based magnetic nanocomposite absorbing material prepared according to any one of the preparation methods of claims 1 to 2.

4. A method for preparing a carbon-based magnetic nanocomposite absorbing material absorbing patch using the carbon-based magnetic nanocomposite absorbing material according to claim 3, characterized in that: The following steps are involved: (1) The carbon-based magnetic nanocomposite absorbing material and the waterborne polyurethane are uniformly mixed, and an organic silicon defoaming agent is added to defoam the mixture under vacuum to obtain a viscous mixture; (2) The viscous mixture obtained in step (1) is evenly coated on a flat mold, and the mixture is naturally solidified in a dust-free environment to obtain a magnetic nanocomposite absorbing material-based absorbing patch.

5. The method according to claim 4, characterized in that: In step (1), the mass ratio of the carbon-based magnetic nanocomposite absorbing material to the waterborne polyurethane is 1:6-12; the amount of the organic silicon defoamer added is 1 g of the organic silicon defoamer per 200 g of the waterborne polyurethane, and the defoaming time under vacuum is 30 minutes.

6. The method according to claim 4, characterized in that: In step (2), the solidification time is 24 h, and the thickness of the magnetic nanocomposite absorbing material absorbing patch is 1.4~2.5 mm.

7. A magnetic nanocomposite absorbing material absorbing patch prepared according to any one of claims 4 to 6.

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