Double-gradient synergistic regulation electromagnetic wave absorbing material and preparation method thereof

Abstract

The invention provides a preparation method of a double-gradient synergistic regulation electromagnetic wave absorbing material, which comprises the following steps: dissolving a magnetic metal salt in a solvent to obtain a magnetic metal salt solution, and dispersing a carbon nanomaterial in the solvent to obtain a carbon nanodispersion liquid; the magnetic metal salt solution and the carbon nano dispersion liquid are mixed and stirred evenly to obtain a mixed solution, the mixed solution reacts under the heating condition, a reaction product is obtained after the reaction is completed, and the reaction product is cleaned and dried to obtain the wave-absorbing nano composite material. The absorbing material disclosed by the invention avoids extra load of a coating mode on an aircraft, realizes the characteristics of excellent processability, low density, high specific strength, high temperature resistance and the like, and can tolerate high temperature of 300 DEG C or above.

Description

Technical Field

[0001] The present invention belongs to the field of wave absorption, and in particular relates to a dual-gradient cooperative regulation electromagnetic wave absorption material and a preparation method thereof. Background Technique

[0002] With the rapid development of modern communication technology, the problems of electromagnetic pollution and interference are becoming increasingly serious. Electromagnetic wave absorption materials can convert the energy of electromagnetic waves into heat energy and dissipate it, so they play an important role in civilian and military fields.

[0003] At present, conventional electromagnetic wave absorption materials are those with an electromagnetic wave absorber coated on the surface, that is, coated wave absorption materials. Traditional electromagnetic wave absorption materials are magnetic powder materials such as carbonyl iron powder and ferrite, which are usually compounded with a polymer binder to form a wave absorption coating. They have the advantages of strong absorption ability and convenient application, and mainly work in the microwave frequency band. However, magnetic metal powders such as iron powder have poor chemical stability in complex environments such as humidity and are extremely prone to oxidation, which will greatly weaken the wave absorption performance of the coating and even cause it to fail; on the other hand, due to the large specific gravity and high density of the carbonyl iron absorber, its volume ratio in the coating is generally greater than 40%, so the areal density of this wave absorption coating is relatively large, seriously restricting the lightweight of equipment and reducing the mobility of equipment. At the same time, when an aircraft is flying at high speed, the coated wave absorption material often serves in a harsh high-temperature environment. Especially when the flight speed reaches Mach 3, aerodynamic heating will cause the surface temperature of the aircraft to reach 300 °C, and problems such as cracking and peeling are likely to occur in the wave absorption coating. Therefore, few existing wave absorption materials can meet the requirements.

[0004] The existing wave absorption coatings have disadvantages such as high density, narrow wave absorption frequency band, and low wave absorption intensity, and their applications are greatly restricted. Summary of the Invention

[0005] In view of this, the present invention aims to overcome the defects in the prior art and proposes a dual-gradient cooperative regulation electromagnetic wave absorption material and a preparation method thereof.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A preparation method of a dual-gradient cooperative regulation electromagnetic wave absorption material includes the following steps:

[0008] (1) Dissolve a magnetic metal salt in a solvent to obtain a magnetic metal salt solution, and disperse a carbon nanomaterial in the solvent to obtain a carbon nanodispersion.

[0009] (2) Mix the magnetic metal salt solution and the carbon nanotube dispersion liquid, and after stirring evenly, obtain a mixed solution. React the mixed solution under heating conditions. After the reaction is completed, obtain a reaction product. Wash and dry the reaction product to obtain the wave-absorbing nanocomposite material;

[0010] (3) Heat thermoplastic soft resin materials with different densities until they melt. Add the same mass of the wave-absorbing nanocomposite material obtained above to the thermoplastic soft resin materials with different densities. After mixing evenly, obtain multiple groups of mixed melts. Extrude the mixed melts into water for solidification respectively. After the obtained solidified bodies are mixed, washed, and dried, obtain mixed wave-absorbing resin spheres;

[0011] (4) Mix the mixed wave-absorbing resin spheres and polyetheretherketone evenly to obtain a mixed material. Immerse the mixed material in water, add a foaming agent thereto, and then fill it into a mold for hot pressing and curing to obtain the double-gradient synergistic electromagnetic wave absorption material.

[0012] Furthermore, the magnetic metal salt in the step (1) is at least one of iron salt, cobalt salt, or nickel salt; the solvent in the step (1) is at least one of triethylene glycol, ethylene glycol, or isopropyl alcohol.

[0013] Furthermore, the mass concentration of the magnetic metal salt in the magnetic metal salt solution in the step (1) is 4-6 mg / mL; the mass concentration of the carbon nanomaterial in the carbon nanotube dispersion liquid in the step (1) is 0.4-0.6 mg / mL.

[0014] Furthermore, the volume ratio of the magnetic metal salt solution to the carbon nanotube dispersion liquid in the step (2) is 1-2:1.

[0015] Furthermore, the time of the stirring step in the step (2) is 20-30 minutes; the temperature of the heating step in the step (2) is 160-180 °C; the time of the reaction step in the step (2) is 4-6 hours.

[0016] Furthermore, the thermoplastic soft resin materials with different densities in the step (3) include a first thermoplastic soft resin material, a second thermoplastic soft resin material, and a third thermoplastic soft resin material. The mass ratio of the first thermoplastic soft resin material, the second thermoplastic soft resin material, and the third thermoplastic soft resin material is 1:1:1; the density of the first thermoplastic soft resin material is 0.91-0.94 g / cm 3 , and the first thermoplastic soft resin material is polyethylene; the density of the second thermoplastic soft resin material is 1.10-1.35 g / cm 3, the second thermoplastic soft resin material is polyvinyl chloride, and the density of the third thermoplastic soft resin material is 1.04 - 1.07 g / cm 3 , and the third thermoplastic soft resin material is polystyrene.

[0017] Furthermore, the mass ratio of the first thermoplastic soft resin material to the corresponding wave-absorbing nanocomposite material in step (3) is 10:1; the mass ratio of the second thermoplastic soft resin material to the corresponding wave-absorbing nanocomposite material in step (3) is 1:5; the mass ratio of the third thermoplastic soft resin material to the corresponding wave-absorbing nanocomposite material in step (3) is 1:1; the particle size of the mixed wave-absorbing resin spheres in step (3) is 1 - 2 mm.

[0018] 8. The method for preparing a dual-gradient cooperative electromagnetic wave absorption material according to claim 1, wherein: the mass fraction of the mixed wave-absorbing resin spheres in the mixed material in step (4) is 10 - 50%; preferably, the mass fraction of the mixed wave-absorbing resin spheres in the mixed material in step (4) is 30 - 40%

[0019] Furthermore, the temperature of the hot pressing and curing step in step (4) is 340 - 360 °C, and the time is 30 - 60 min.

[0020] Furthermore, the mass ratio of the foaming agent to the mixed material in step (4) is 0.5 - 5:100; the foaming agent in step (4) is urea.

[0021] The present invention controls the density range of the wave-absorbing resin composite spheres to 0.9 - 2.0 g / cm by adjusting the mass ratio of the thermoplastic soft resin to the wave-absorbing nanocomposite material. 3 . According to the different densities, the composite spheres can naturally form layers in water. The upper layer is a low-density electromagnetic wave transmission layer. The composite spheres in this layer contain a higher proportion of soft resin components and act synergistically with an appropriate amount of wave-absorbing agent and foaming agent. After heat treatment at 360 °C for 30 minutes, the foaming agent decomposes upon heating, causing the formation of a fine pore structure with optimized impedance matching characteristics in this layer, thereby allowing electromagnetic waves to effectively pass through, reducing the amount of wave-absorbing agent used and improving electromagnetic compatibility. The middle layer is an electromagnetic wave absorption layer. The concentration of the wave-absorbing agent is higher than that in the upper layer, and the foaming agent ratio is moderate, which can significantly attenuate the transmitted electromagnetic waves and ensure that the electromagnetic waves are basically absorbed within this layer. The lower layer is a high-density electromagnetic wave reflection layer. The wave-absorbing resin composite spheres in this layer contain the highest content of wave-absorbing agent and the least amount of foaming agent, have strong conductivity, and reflect the residual electromagnetic waves to the middle layer for secondary absorption, thereby achieving excellent electromagnetic wave absorption performance.

[0022] Under the combined action of the variable-mass foaming agent and the self-defect structure of the carbon nanomaterial, the double-gradient cooperative regulation electromagnetic wave absorbing material described in the present invention introduces holes with different quantities and sizes in the upper, middle, and lower layers of the polyether ether ketone matrix, resulting in a decreasing porosity from top to bottom, forming a unique porosity gradient. Moreover, during the layering process, microcapsules with different densities will be distributed at different positions in the material due to different buoyant forces they receive. Those with smaller density occupy the upper layer, and those with larger density occupy the lower layer. During the hot pressing process, the soft resin melts, and the wave-absorbing nanocomposite material (wave absorber) inside it can flow into the gradient holes formed by the foaming agent, forming a wave absorber concentration gradient in the matrix, constructing a unique double-gradient cooperative regulation mode, which can precisely optimize the impedance characteristics of the material, thereby achieving strong absorption of electromagnetic waves in the full frequency band.

[0023] Secondly, due to the special structures of the carbon nanomaterial and the resin matrix, the wave-absorbing nanocomposite material can disperse in the matrix to form three-dimensional cluster islands, two-dimensional conductive sheet layers, and one-dimensional linear conductive chains. This multi-scale structure not only enhances the conductivity but also forms a framework structure, enhancing the scattering effect of electromagnetic waves in the matrix. Moreover, during the hot pressing process, the wave-absorbing nanocomposite material and the resin matrix can form a tighter bond in the form of π-π bond interactions. This interaction not only improves the bonding force between the wave absorber and the resin matrix but also enhances the structural stability and thermal stability of the entire composite material, enabling the material to maintain excellent mechanical and thermal properties even under high temperature or extreme environments, achieving the integration of structure and function.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The double-gradient cooperative regulation electromagnetic wave absorbing material described in the present invention combines the electromagnetic wave absorber with the thermoplastic resin matrix to prepare a composite material with the integration of structure and function, avoiding the additional load on the aircraft caused by the coating method, and achieving excellent processing performance, low density, high specific strength, high temperature resistance, etc., and can withstand high temperatures above 300 °C. At the same time, by adopting the double-gradient cooperative regulation method, strong absorption of electromagnetic waves in the full frequency band is achieved, effectively improving the shortcomings and deficiencies of the coating-type wave-absorbing materials.

[0026] The double-gradient cooperative regulation electromagnetic wave absorbing material described in the present invention adopts the double-gradient cooperative regulation of the concentration gradient and porosity gradient of the wave-absorbing nanocomposite material, enabling the impedance of the material to match the free space impedance at different frequency bands, achieving strong absorption of electromagnetic waves in the full frequency band, and significantly improving the wave-absorbing performance of the material.

[0027] In the dual-gradient cooperative regulation electromagnetic wave absorption material described in the present invention, the carbon nanomaterials used can form bonding interactions such as π-π bonds with the resin matrix, which can significantly improve the binding between the wave-absorbing agent and the resin matrix, enhance the structural stability and thermal stability of the entire composite material, enabling the wave-absorbing material to withstand high temperatures of 300 °C and still maintain excellent mechanical and thermal properties under high-temperature or extreme environments, achieving the integration of structure and function. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram showing the variation of the reflection loss value of the dual-gradient cooperative regulation electromagnetic wave absorption material described in Example 1 of the present invention with thickness and frequency;

[0029] Figure 2 Physical diagram comparing the thermal stability of the dual-gradient cooperative regulation electromagnetic wave absorption material described in Example 1 of the present invention with that of the polyether ether ketone matrix;

[0030] Figure 3 Schematic diagram of the experimental evidence for the formation of π-π bond binding between the wave-absorbing agent and the polyether ether ketone matrix described in Example 1 of the present invention;

[0031] Figure 4 Schematic diagram showing the variation of the reflection loss value of the electromagnetic wave absorption material described in Comparative Example 1 of the present invention with thickness and frequency;

[0032] Figure 5 Schematic diagram showing the variation of the reflection loss value of the electromagnetic wave absorption material described in Comparative Example 2 of the present invention with thickness and frequency;

[0033] Figure 6 Schematic diagram showing the variation of the reflection loss value of the electromagnetic wave absorption material described in Comparative Example 3 of the present invention with thickness and frequency. DETAILED DESCRIPTION OF THE INVENTION

[0034] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; the experimental methods used are all conventional methods unless otherwise specified.

[0035] The present invention will be described in detail below with reference to the examples.

[0036] Example 1

[0037] A preparation method of a dual-gradient cooperative regulation electromagnetic wave absorption material includes the following steps:

[0038] (1) Dissolve 0.202 g of iron(III) nitrate nonahydrate in 30 mL of triethylene glycol. Correspondingly, ultrasonically disperse 30 mg of carbon nanotubes in an equal amount of triethylene glycol. Ultrasonically disperse each of them for 15 min, and then mix and stir the dissolved solution and the dispersion for 20 min.

[0039] (2) Transfer the above solution to the inner lining of a 100 mL polytetrafluoroethylene autoclave, place it in a vacuum drying oven at 180 °C for 4 h. The reaction product is a wave-absorbing nanocomposite material, i.e., a wave absorber. After the reaction is completed, let it stand and cool to room temperature. Centrifuge and wash the cooled composite material, wash it 5 times with deionized water and 5 times with ethanol, and then dry and collect it to obtain the wave-absorbing nanocomposite material, which is stored in a dry environment.

[0040] (3) Mix 10 mg of molten polyethylene with 1 mg of the wave-absorbing nanocomposite material to obtain a first mixed melt with a density of 0.93 g / cm 3 ; mix 2 mg of molten polyvinyl chloride with 10 mg of the wave-absorbing nanocomposite material to obtain a second mixed melt with a density of 1.82 g / cm 3 ; mix 5 mg of molten polystyrene with 5 mg of the wave-absorbing nanocomposite material to obtain a third mixed melt with a density of 1.05 g / cm 3 . Extrude the first mixed melt, the second mixed melt, and the third mixed melt into water respectively to solidify and form solidified bodies with a particle size of 1 - 2 mm. After mixing, washing, and drying the obtained solidified bodies, obtain mixed wave-absorbing resin spheres.

[0041] (4) Mix the above-obtained mixed wave-absorbing resin spheres evenly with 70 mg of polyether ether ketone to obtain a mixed material. Immerse the mixed material in water. After it is layered, add 3 mg of urea to it. After drying, fill it into a mold and perform hot pressing and curing at 360 °C for 30 min to obtain the double-gradient synergistic electromagnetic wave absorption material.

[0042] Comparative Example 1

[0043] The difference from Example 1 is only that: the mass ratio of polyethylene (5 mg) to the wave-absorbing nanocomposite material is 1:1, the mass ratio of polyvinyl chloride (5 mg) to the wave-absorbing nanocomposite material is 1:1, and the mass ratio of polystyrene (5 mg) to the wave-absorbing nanocomposite material is 1:1.

[0044] Comparative Example 2

[0045] The difference from Example 1 is only that: in step (3), mix 15 mg of polyethylene with 15 mg of the wave-absorbing nanocomposite material, then extrude it into water to solidify, and after mixing, washing, and drying the obtained solidified body, obtain mixed wave-absorbing resin spheres with a particle size of 1 - 2 mm.

[0046] Comparative Example 3

[0047] The difference from Example 1 is only that: polyether ether ketone is replaced by epoxy resin, and the curing temperature is 100 °C. The products obtained from Example 1 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0048] Table 1 Result Data

[0049] Example Substrate Minimum reflection loss (dB) Tolerable temperature Example 1 Polyetheretherketone -70.92 300℃ Comparative Example 1 Polyetheretherketone -33.42 300℃ Comparative Example 2 Polyetheretherketone -19.25 300℃ Comparative Example 3 Epoxy resin -32.88 150℃

[0050] As shown in Table 1, Example 1 achieved excellent electromagnetic wave absorption performance through a double-gradient structure, with the minimum reflection loss reaching -70.92 dB, significantly superior to Comparative Examples 1-3, and having excellent thermal stability. In Comparative Example 1, due to the material ratio being adjusted to 1:1, the gradient structure was destroyed, and the minimum reflection loss increased to -33.42 dB; in Comparative Example 2, due to the mixing of a single high-proportion polyethylene, the gradient characteristics were lost, and the minimum reflection loss further increased to -19.25 dB; in Comparative Example 3, due to the matrix being replaced by epoxy resin and the curing temperature being reduced, the minimum reflection loss was -32.88 dB and the thermal stability was poor. As Figure 1 compared with 4 -6 shows, Example 1 has significant absorption peaks in a wide frequency band, while Comparative Examples 1-3 have a narrow effective absorption bandwidth, verifying the key role of the double-gradient structure in electromagnetic wave absorption performance.

[0051] As Figures 2-3 shown, Figure 2 shows the physical comparison between Example 1 and the polyether ether ketone matrix material before and after heat treatment at 400 °C, intuitively verifying its thermal stability: Example 1 still maintains structural integrity at 400 °C, further indicating the applicability of the material at extreme temperatures. Figure 3 The chemical bonding mechanism between the wave absorber and the matrix was revealed through the XPS C1s spectrum: the characteristic peak of the π-π bond (usually corresponding to the interaction between aromatic rings) appearing near 294 eV confirmed that the wave absorber carbon nanotubes and the polyether ether ketone matrix formed a strong interfacial bond through the π-π bond. This bonding not only enhanced the structural stability of the material but also optimized the dispersion of the electromagnetic wave absorber in the matrix, thereby synergistically improving the interfacial polarization and dielectric loss capabilities, providing further experimental evidence for the excellent performance of Example 1.

[0052] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a dual-gradient coordinated electromagnetic wave absorbing material, characterized in that: The steps include: (1) dissolving a magnetic metal salt in a solvent to obtain a magnetic metal salt solution, and dispersing a carbon nanomaterial in the solvent to obtain a carbon nanodispersion liquid; (2) mixing the magnetic metal salt solution and the carbon nano-dispersion solution, stirring them to obtain a mixed solution, reacting the mixed solution under heating conditions, obtaining a reaction product after the reaction is completed, and washing and drying the reaction product to obtain a wave-absorbing nano-composite material; (3) heating thermoplastic soft resin materials of different densities until they are melted, adding the absorbing nanocomposite materials of the same mass to the thermoplastic soft resin materials of different densities, mixing them evenly to obtain a plurality of mixed melts, respectively extruding the mixed melts into water for solidification, and mixing, washing, and drying the obtained solidified bodies to obtain mixed absorbing resin spheres; (4) The mixed absorbing resin spheres are mixed evenly with polyetheretherketone to obtain a mixed material, the mixed material is immersed in water, a foaming agent is added thereto, and then the mixed material is filled into a mold for hot pressing and curing to obtain the dual-gradient synergistically regulated electromagnetic wave absorbing material.

2. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The magnetic metal salt in step (1) is at least one of an iron salt, a cobalt salt or a nickel salt; and the solvent in step (1) is at least one of triethylene glycol, ethylene glycol or isopropanol.

3. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The mass concentration of the magnetic metal salt in the magnetic metal salt solution in step (1) is 4-6 mg / mL; the mass concentration of the carbon nanomaterial in the carbon nano dispersion in step (1) is 0.4-0.6 mg / mL.

4. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The volume ratio of the magnetic metal salt solution to the carbon nano-dispersion solution in the step (2) is 1-2:

1.

5. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The stirring step in step (2) is carried out for 20-30 minutes; the heating step in step (2) is carried out at a temperature of 160-180° C.; and the reaction step in step (2) is carried out for 4-6 hours.

6. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The thermoplastic soft resin materials of different densities in step (3) include a first thermoplastic soft resin material, a second thermoplastic soft resin material and a third thermoplastic soft resin material, wherein the mass ratio of the first thermoplastic soft resin material, the second thermoplastic soft resin material and the third thermoplastic soft resin material is 1:1:1; the density of the first thermoplastic soft resin material is 0.91-0.94 g / cm 3 The first thermoplastic soft resin material is polyethylene; the density of the second thermoplastic soft resin material is 1.10-1.35g / cm 3 The second thermoplastic soft resin material is polyvinyl chloride, and the density of the third thermoplastic soft resin material is 1.04-1.07 g / cm 3 , the third thermoplastic soft resin material is polystyrene.

7. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 6, characterized in that: The mass ratio of the first thermoplastic soft resin material in the step (3) to the corresponding absorbing nano-composite material is 10:1; the mass ratio of the second thermoplastic soft resin material in the step (3) to the corresponding absorbing nano-composite material is 1:5; the mass ratio of the third thermoplastic soft resin material in the step (3) to the corresponding absorbing nano-composite material is 1:1; the particle size of the mixed absorbing resin spheres in the step (3) is 1-2 mm.

8. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The mass fraction of the mixed absorbing resin spheres in the mixed material in step (4) is 10-50%; preferably, the mass fraction of the mixed absorbing resin spheres in the mixed material in step (4) is 30-40%.

9. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The temperature of the hot pressing curing step in step (4) is 340-360° C. and the time is 30-60 minutes.

10. The method for preparing a dual-gradient coordinated electromagnetic wave absorbing material according to claim 1, characterized in that: The mass ratio of the foaming agent to the mixed material in the step (4) is 0.5-5:100; the foaming agent in the step (4) is urea.

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