A radar-infrared multi-spectrum compatible stealth composite material and its preparation method

Abstract

The present invention belongs to the technical field of stealth materials, and relates to a radar-infrared compatible stealth composite material and a preparation method thereof. After separately preparing an infrared shielding and reflecting layer and a wave-absorbing and heat-insulating layer with laser-etched patterns, the two are assembled together with glue to obtain a radar-infrared compatible stealth composite material with a double-layer structure. By redesigning the shape of the periodic unit and cooperating with the size of the periodic unit and the laser etching gap, the present invention realizes the further reduction of the infrared emissivity while further increasing the radar wave transmittance. Further, the present invention uses aerogel as the wave-absorbing and heat-insulating layer of the composite material. The low thermal conductivity of the aerogel can effectively prevent heat transfer, significantly reduce the upper surface temperature of the material and inhibit infrared signal radiation. While improving the infrared stealth effect of the composite material, it also has the function of attenuating the radar wave transmitted from the top layer, realizing efficient radar-infrared compatible stealth performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of stealth materials, and relates to a radar-infrared multi-spectrum compatible stealth composite material and a preparation method thereof. Background Art

[0002] With the rapid development of military reconnaissance technology, the application of surveillance equipment has become increasingly widespread. Among them, multi-spectrum complementary stealth technology, especially radar-infrared compatible stealth technology, has attracted much attention because it can effectively cope with complex and changeable detection systems. Radar stealth technology requires materials to have excellent electromagnetic wave attenuation ability, that is, to achieve high absorption and low reflection; while infrared stealth technology requires materials to have the characteristics of high reflection and low emission. However, there are obvious contradictions in the absorption rate requirements of these two stealth technologies for materials, which brings severe challenges to the development of stealth materials with both advantages.

[0003] Specifically, the radar stealth performance is usually measured by the radar wave transmittance. An ideal material should have a high radar wave transmittance to better absorb the incident electromagnetic waves; while the infrared stealth performance is evaluated by the infrared emissivity. In the two key bands of 3-5μm and 8-14μm, the lower the infrared emissivity, the weaker the infrared radiation of the material. Usually, a value less than 0.3 is used as an excellent evaluation index.

[0004] To meet the requirements of both radar and infrared stealth simultaneously, researchers usually try to design composite materials or layered structures. These designs aim to achieve strong absorption in the radar band and low emission in the infrared band. However, despite many efforts, there are still many difficulties in achieving good multi-spectrum stealth effects.

[0005] As an advanced solution, metamaterials have shown significant advantages in multi-physical field stealth technology. Its core idea is to utilize the difference in radar and infrared wavelengths to manipulate electromagnetic waves by constructing a layered structure. In this design, the infrared stealth top layer usually adopts a frequency-selective surface (i.e., a low-pass filter), which can allow radar waves to pass through while maintaining a low emissivity of the overall structure. The bottom metamaterial absorber is responsible for attenuating and absorbing the radar waves transmitted from the top layer. However, metamaterials still face many challenges in practical applications, including complex processing technology, high cost, poor heat insulation performance, and the need for a large thickness to achieve broadband response. These problems limit the further development and wide application of metamaterials.

[0006] In view of the potential of metamaterials in multi-physical field stealth technology and the challenges they face, the literature (Asymmetricelectric field distribution enhanced hierarchical metamaterials for radar-infrared compatible camouflage[J]. Journal of Materials Science & Technology,2023, 146: 10-18.) prepared an absorbing and heat-insulating layer by mixing carbonyl iron particles, graphene sheets and polyurethane, prepared an infrared shielding and reflecting layer by using a square pattern fabricated by laser etching, and then pasted the infrared shielding and reflecting layer above the absorbing and heat-insulating layer with polyurethane glue to prepare a double-layer compatible stealth material. However, the radar wave transmittance of this material needs to be further improved, and the infrared emissivity also needs to be further reduced. Summary of the Invention

[0007] The object of the present invention is to solve the problems existing in the prior art and provide a radar-infrared multi-spectrum compatible stealth composite material and its preparation method.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A radar-infrared multi-spectrum compatible stealth composite material has a double-layer structure. The upper layer is an infrared shielding and reflecting layer with a periodically patterned fabricated by laser etching, and the lower layer is an absorbing and heat-insulating layer. The shape of the periodic unit (in a periodic structure, the basic unit that can repeat and form the entire structure) of the periodic pattern is a cross-shaped rectangle, a rhombus, a Bagua shape, a cross-shaped circle, a circle or a cross-shaped rectangle;

[0010] The cross-shaped rectangle is composed of a rectangle and 8 line segments located inside it. One end of the 8 line segments is connected to the center point of the rectangle at the same time, and the other end is connected to the 4 vertices of the rectangle and the midpoints of the 4 sides of the rectangle respectively;

[0011] The cross-shaped circle is composed of a circle and 4 line segments located inside it. One end of the 4 line segments is connected to the center of the circle at the same time, and the other end is connected to 4 points evenly distributed on the circle respectively;

[0012] The cross-shaped rectangle is composed of a rectangle and 4 line segments located inside it. One end of the 4 line segments is connected to the center point of the rectangle at the same time, and the other end is connected to the 4 vertices of the rectangle respectively;

[0013] The size of the periodic unit is 0.5-1.0 mm, and the laser etching gap is 35-60 μm.

[0014] When the laser etching gap and the shape of the periodic unit remain unchanged, after reducing the size of the periodic unit, the proportion of the conductive part area will decrease, and the radar wave transmittance will increase. However, the infrared emissivity, which is inversely proportional to the proportion of the conductive part area, will also increase. Therefore, it is difficult to further increase the radar wave transmittance and further reduce the infrared emissivity by simply reducing the size of the periodic unit. In the present invention, by redesigning the shape of the periodic unit and cooperating with the size of the periodic unit and the laser etching gap, it is possible to further increase the radar wave transmittance while further reducing the infrared emissivity.

[0015] As a preferred technical solution:

[0016] For a radar-infrared multi-spectrum compatible stealth composite material as described above, the infrared shielding and reflecting layer includes an infrared shielding material located on the upper layer and a substrate located on the lower layer. The thickness of the infrared shielding material is 0.03 - 0.1 mm, and the thickness of the substrate is 0.1 - 0.2 mm; the infrared shielding material is aluminum foil, copper foil, silver foil, indium tin oxide thin film or conductive paint, and the substrate is a polycarbonate plate.

[0017] For a radar-infrared multi-spectrum compatible stealth composite material as described above, the thickness of the wave-absorbing and heat-insulating layer is 2.5 - 3.5 mm; the wave-absorbing and heat-insulating layer is aerogel, and the skeleton of the aerogel is aramid nanofibers, which are obtained by subjecting short-cut Kevlar fibers to deprotonation and protonation treatments in sequence in a solvent (dimethyl sulfoxide).

[0018] For a radar-infrared multi-spectrum compatible stealth composite material as described above, MXene is attached to the aramid nanofibers. The sheet diameter of MXene is 1 - 20 μm, and MXene is a two-dimensional material. The rich functional groups and lattice defects on MXene and its excellent electrical conductivity provide a transmission path for free electrons for electromagnetic wave attenuation, effectively converting electromagnetic waves into heat energy.

[0019] For a radar-infrared multi-spectrum compatible stealth composite material as described above, Fe3O4@CPPy is also attached to the aramid nanofibers. Fe3O4@CPPy is a chiral nanoparticle with a core-shell structure. Among them, the core is Fe3O4 nanoparticles, and the shell layer is chiral polypyrrole, with an average particle size of 340 - 400 nm. Fe3O4@CPPy is a zero-dimensional material. Compared with ordinary zero-dimensional materials, it has interfacial polarization and dipole polarization, which can further improve the attenuation ability of radar waves.

[0020] For a radar-infrared multi-spectrum compatible stealth composite material as described above, the preparation process of Fe3O4@CPPy is as follows: After preparing Fe3O4 nanoparticles by a hydrothermal method, they are added together with pyrrole monomers to a system containing a chiral dopant or chiral acid for polymerization to obtain Fe3O4@CPPy.

[0021] A radar-infrared multi-spectrum compatible stealth composite material as described above. The preparation process of Fe3O4@CPPy is as follows: Dissolve FeCl3·6H2O, polyethylene glycol, and anhydrous sodium acetate in ethylene glycol, react at 180 - 220 °C for 8 - 10 h. After washing the reactants to obtain Fe3O4 nanoparticles, add the Fe3O4 nanoparticles and pyrrole monomer to an L - camphorsulfonic acid solution with a concentration of 0.5 - 1.5 mol / L, dropwise add ammonium persulfate solution, and polymerize in an ice-water bath for 2 - 4 h. Wash the precipitate to obtain Fe3O4@CPPy.

[0022] A radar-infrared multi-spectrum compatible stealth composite material as described above. In the aerogel, the content of MXene is 20 - 30 wt%, and the content of Fe3O4@CPPy is 10 - 30 wt%. The aerogel has an infrared stealth effect because the porous structure of the aerogel gives it heat insulation performance. The temperature of the upper surface is much lower than that of the lower surface in contact with the heat source, so the radiated infrared signal is suppressed. The evaluation index of the heat insulation performance is mainly the thermal conductivity. The thermal conductivity of the aerogel of the present invention is small, and the heat insulation performance is excellent, which is beneficial to improving the infrared stealth effect of the composite material.

[0023] A radar-infrared multi-spectrum compatible stealth composite material as described above. The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 8.4 - 12.4 GHz in the X-band (8.2 - 12.4 GHz, a specific frequency band in the radar band), a minimum reflection loss of -32.44 ~ -14.4 dB, a thermal conductivity of 0.0274 - 0.0320 W / (m·K) (the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is the thermal conductivity of the wave-absorbing and heat-insulating layer), an average infrared emissivity of 0.18 - 0.28 in the 3 - 5 μm infrared band, an average infrared emissivity of 0.15 - 0.26 in the 8 - 14 μm infrared band, and a surface temperature of 46.6 - 58.6 °C after continuously heating on a 150 °C heating platform for 0.5 h.

[0024] The present invention also provides a method for preparing a radar-infrared multi-spectrum compatible stealth composite material as described in any one of the above. After separately preparing an infrared shielding and reflecting layer and a wave-absorbing and heat-insulating layer with a periodically patterned laser etching, assemble the two together with glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0025] Beneficial effects:

[0026] (1) By redesigning the shape of the periodic unit and cooperating with the periodic unit size and the laser etching gap, the present invention realizes further reducing the infrared emissivity while further increasing the radar wave transmittance.

[0027] (2) The present invention uses aerogel as the wave-absorbing and heat-insulating layer of the radar-infrared multi-spectrum compatible stealth composite material. Due to its unique structure and extremely low density, aerogel has a low thermal conductivity, which can effectively prevent the transfer of heat from bottom to top, significantly reduce the upper surface temperature of the material, thereby suppressing the radiation of infrared signals and enhancing the infrared stealth effect of the composite material.

[0028] (3) The aerogel used in the present invention has the characteristics of increasing the transmission path length of electromagnetic waves inside the material, enhancing the attenuation effect of microwaves and promoting effective scattering, as well as improving the electromagnetic wave absorption and conversion ability due to its high specific surface area, rich porous structure, heterogeneous structure and electron transport ability. Description of the Drawings

[0029] Figure 1 Schematic diagram of the overall structure of the radar-infrared multi-spectrum compatible stealth composite material for Example 1;

[0030] Figure 2 Schematic diagram of the periodic unit size and laser etching gap of different periodic patterns; where, w represents the periodic unit size, p represents the laser etching gap, EMW represents electromagnetic wave, dc represents the thickness of the infrared shielding material, and dt represents the thickness of the substrate;

[0031] Figure 3 SEM of the periodic pattern laser-etched on the infrared shielding material; where, (a) corresponds to Example 1, (b) corresponds to Example 3, (c) corresponds to Example 4, and (d) corresponds to Example 5;

[0032] Figure 4 TEM image of Fe3O4@CPPy for Example 1 (only one particle is selected as an example);

[0033] Figure 5 In (a) is the reflection loss curve obtained from the test of the radar-infrared multi-spectrum compatible stealth composite material for Example 1, Figure 5 In (b) is the transmittance and reflectance diagram of the infrared shielding reflective layer for radar waves in Example 1;

[0034] Figure 6 Infrared reflectance obtained from the test of the radar-infrared multi-spectrum compatible stealth composite material for Example 1;

[0035] Figure 7 In (a) is the SEM image of Fe3O4 for Example 2, Figure 7 In (b) is the reflection loss curve obtained from the test of the radar-infrared multi-spectrum compatible stealth composite material for Example 2;

[0036] Figure 8In (a) is the reflection loss curve obtained by testing the radar-infrared multi-spectrum compatible stealth composite material of Example 3, Figure 8 In (b) is the transmittance and reflectance diagram of the infrared shielding reflective layer of Example 3 for radar waves;

[0037] Figure 9 In (a) is the reflection loss curve obtained by testing the radar-infrared multi-spectrum compatible stealth composite material of Example 4, Figure 9 In (b) is the transmittance and reflectance diagram of the infrared shielding reflective layer of Example 4 for radar waves. Specific Embodiments

[0038] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0039] The following are the test methods for relevant performance indicators in each embodiment:

[0040] Thermal conductivity: Measured using a TPA-2500S type thermal constant analyzer with reference to the standard ISO-22007-2 transient plane heat source method.

[0041] For the absorption performance (absorption bandwidth, reflection loss) of the radar-infrared multi-spectrum compatible stealth composite material in the X-band, and the transmittance and reflectance of the infrared shielding reflective layer for radar waves, mathematical calculations and software simulations of the electromagnetic parameters (complex magnetic permeability, complex permittivity) of the radar-infrared multi-spectrum compatible stealth composite material itself are required; the electromagnetic parameters are obtained using a Keysight E5080B type vector network analyzer with reference to GB / T 35679-2017, where the frequency setting range is 8.2 - 12.4 GHz, and the sample size is 22.85 mm × 10.15 mm;

[0042] The calculation formula for the reflection loss RL (dB) is as follows:

[0043] ;

[0044] ;

[0045] In the formula, is the input impedance (Ω), is the impedance of air (377 Ω), is the thickness (mm) of the radar-infrared multi-spectrum compatible stealth composite material, is the frequency (GHz), is the complex permeability obtained by testing, is the complex permittivity obtained by testing, is the speed of light (3×10 8 m / s);

[0046] The wave absorption bandwidth of the radar-infrared multi-spectrum compatible stealth composite material in the X-band is the calculated frequency range interval of ≤ -10 dB, and the minimum reflection loss is the calculated minimum value;

[0047] The transmittance and reflectivity of the infrared shielding reflective layer to radar waves are obtained by simulation with CST Studio software. Among them, the modeling of the infrared shielding reflective layer is completed using the built-in commands of the software. The electromagnetic parameters of the infrared shielding material and the substrate are selected as the default data in the software material library. The simulation settings are that the direction of the incident electromagnetic field is opposite to the Z-axis, the pattern model is located in the X-O-Y plane, the frequency domain solver and open boundary are selected, and tetrahedral mesh division is performed; the transmittance is the simulated data SZmin(1), Zmax(1), and the reflectivity is the data of SZmax(1), Zmax(1).

[0048] Average infrared emissivity in the 3-5μm infrared band: Use a Nicolet 6700 Fourier infrared spectrometer (with an integrating sphere attachment), and measure the infrared reflectivity and infrared absorptivity of the sample to be tested in the 3-5μm infrared band with reference to the GB / T 21186-2007 standard. Calculate the infrared emissivity of the sample to be tested in the 3-5μm infrared band based on Kirchhoff's law (infrared emissivity = 1 - infrared reflectivity - infrared absorptivity), and obtain the average infrared emissivity of the sample to be tested in the 3-5μm infrared band after processing.

[0049] Average infrared emissivity in the 8-14μm infrared band: Use a Nicolet 6700 Fourier infrared spectrometer (with an integrating sphere attachment), and measure the infrared reflectivity and infrared absorptivity of the sample to be tested in the 8-14μm infrared band with reference to the GB / T 21186-2007 standard. Calculate the infrared emissivity of the sample to be tested in the 8-14μm infrared band based on Kirchhoff's law (infrared emissivity = 1 - infrared reflectivity - infrared absorptivity), and obtain the average infrared emissivity of the sample to be tested in the 8-14μm infrared band after processing.

[0050] Infrared stealth performance: Use a T1050sc type infrared thermal imaging camera to continuously detect the infrared imaging diagram of the sample to be tested, and record its surface temperature after heating on a 150°C heating table for 0.5 h.

[0051] In the following embodiments, when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a cross-square, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (a) therein; when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a cross-square, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (b) therein; when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a rhombus, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (c) therein, and the minimum interior angle of the rhombus is 60°; when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a cross-rectangle, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (d) therein, and the length of the rectangle is ; when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a circle, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (e) therein; when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a cross-circle, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (f) therein; when the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding reflective layer is a bagua shape, the size of the periodic unit of the periodic pattern and the laser etching gap are as shown in Figure 2 (g) therein.

[0052] In the following embodiments, the preparation process of the homogeneous dispersion of aramid nanofibers is as follows: Short Kevlar fibers (manufactured by DuPont, grade 1414), potassium hydroxide, dimethyl sulfoxide, and deionized water are mixed, stirred at a temperature of 20 °C and a rotation speed of 1000 r / min for 6 h, then deionized water is added again, and stirred at a temperature of 20 °C and a rotation speed of 600 r / min for 4 h. A homogeneous dispersion of aramid nanofibers is obtained through a process of repeated suction filtration and washing; wherein, the mass ratio of short Kevlar fibers to potassium hydroxide is 1:1.5, the mass ratio of short Kevlar fibers to dimethyl sulfoxide is 1:250, the mass ratio of dimethyl sulfoxide to the first added deionized water is 25:1, and the volume ratio of the second added deionized water to the first added deionized water is 150:1.

[0053] Example 1

[0054] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, the specific steps are as follows:

[0055] (1) Preparation of raw materials;

[0056] FeCl3-6H2O: CAS No. is 10025-77-1;

[0057] Polyethylene glycol: CAS No. is 25322-68-3;

[0058] Sodium acetate anhydrous: CAS No. is 127-09-3;

[0059] Ethylene glycol: CAS No. is 107-21-1;

[0060] Pyrrole monomer: CAS No. is 109-97-7;

[0061] L - Camphorsulfonic acid solution: concentration is 1 mol / L, and the solvent is deionized water;

[0062] Ammonium persulfate solution: concentration is 1 mol / L, and the solvent is deionized water;

[0063] Infrared shielding material: aluminum foil, with a thickness of 0.05 mm;

[0064] Substrate: polycarbonate board, manufactured by Dongguan Hongyan Plastic Co., Ltd., with a thickness of 0.15 mm;

[0065] Homogeneous dispersion of aramid nanofibers;

[0066] MXene: manufactured by Jiangsu Xianfeng Nano Materials Co., Ltd., with a sheet diameter of 1 - 20 μm;

[0067] Glue: manufactured by Shenzhen Yishangxiang Electronic Materials Co., Ltd., with the product number YS1996;

[0068] (2) Prepare Fe3O4@CPPy;

[0069] Dissolve FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous in ethylene glycol, react at 200 °C for 8 h, wash the reactants to obtain Fe3O4 nanoparticles, and then add the Fe3O4 nanoparticles and pyrrole monomer to L - camphorsulfonic acid solution, dropwise add ammonium persulfate solution, and polymerize in an ice-water bath for 4 h, wash the precipitate to obtain Fe3O4@CPPy with an average particle size of 360 nm; among them, the mass ratio of FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous is 1.3:1:3.6, the mass ratio of ethylene glycol to the total mass of FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous is 10:1, and the mass ratio of Fe3O4 nanoparticles, pyrrole monomer, L - camphorsulfonic acid solution, and ammonium persulfate solution is 2:1:500:200;

[0070] The TEM of the prepared Fe3O4@CPPy is as Figure 4 shown, fromFigure 4 It can be seen that Fe3O4@CPPy has a core-shell structure, where the core is Fe3O4 nanoparticles and the shell is chiral polypyrrole (see the dotted area);

[0071] (3) Prepare the infrared shielding reflection layer and the aerogel respectively;

[0072] The preparation process of the infrared shielding reflection layer is as follows: Stick the infrared shielding material on the substrate through glue, and use a laser marking machine to etch the surface of the infrared shielding material at a laser etching speed of 200 mm / s and an etching power of 80% to obtain an infrared shielding reflection layer with a periodic pattern of laser etching; The shape of the periodic unit of the periodic pattern is a cross-shaped square (SEM as shown in (a) in Figure 3 shown in (a)), the cross-shaped square consists of a square and 8 line segments located inside it. One end of the 8 line segments is connected to the center point of the square at the same time, and the other end is connected to the 4 vertices of the square and the midpoints of the 4 sides of the square respectively. The size of the periodic unit is 1 mm, and the laser etching gap is 35 μm;

[0073] The preparation process of the aerogel is as follows: Mix the homogeneous dispersion of aramid nanofibers, MXene and Fe3O4@CPPy evenly, put it into a mold, freeze it in liquid nitrogen at -80 °C for 12 h, and then dry it at -50 °C to remove the solvent to obtain the aerogel; The thickness of the aerogel is 2.9 mm; The content of MXene in the aerogel is 25 wt%, and the content of Fe3O4@CPPy is 10 wt%;

[0074] (4) Prepare the radar-infrared multi-spectrum compatible stealth composite material;

[0075] Assemble the infrared shielding reflection layer and the aerogel through glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0076] As Figure 1 shown, the finally prepared radar-infrared multi-spectrum compatible stealth composite material consists of an upper infrared shielding reflection layer and a lower aerogel. The infrared shielding reflection layer consists of an upper infrared shielding material and a lower substrate. The upper infrared shielding reflection layer can reflect infrared waves and allow electromagnetic waves to pass through, while the lower aerogel can absorb the electromagnetic waves that may pass through and effectively block the heat transmitted from below;

[0077] The absorption bandwidth of the radar-infrared multi-spectrum compatible stealth composite material in the X band is 8.7 - 12.4 GHz, and the minimum reflection loss is -32.44 dB (the reflection loss curve is as shown in (a) in Figure 5 shown), and the transmittance and reflectance of the infrared shielding reflection layer to radar waves are as shown in Figure 5as shown in Fig. (b); the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0288 W / (m·K); the average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3-5 μm infrared band is 0.23, and the average infrared emissivity in the 8-14 μm infrared band is 0.25 (the infrared reflectivity curve is as Figure 6 shown), and the surface temperature is 50.2 °C after continuously heating on a 150 °C heating table for 0.5 h.

[0078] Comparative Example 1

[0079] A preparation method of a composite material, which is only different from Example 1 in that: the shape of the periodic unit of the periodic pattern is a square, and the size of the square is the same as that of the square constituting the cross-shaped square in Example 1.

[0080] In the finally prepared composite material, the maximum transmittance of the infrared shielding and reflecting layer to radar waves is 74.82%, and the minimum value is 56.25%.

[0081] Compared with Example 1, in the case of keeping the periodic size and the laser etching gap unchanged, the maximum and minimum transmittances of the infrared shielding and reflecting layer in the composite material to radar waves are significantly reduced. This is because the shape of the periodic unit used in Comparative Example 1 is a square. When the periodic unit size is 1 mm, the area ratio of the conductive part is larger, and the coupling with the radar wave is stronger, resulting in more reflection and a decrease in transmittance.

[0082] Example 2

[0083] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, which is only different from Example 1 in that: in step (2), Fe3O4 nanoparticles are prepared, and the specific preparation process is: dissolving FeCl3·6H2O, polyethylene glycol, and anhydrous sodium acetate in ethylene glycol, reacting at 200 °C for 8 h, and washing the reactants to obtain Fe3O4 nanoparticles (SEM is as Figure 7 shown in Fig. (a)); in step (3), when preparing the aerogel, Fe3O4@CPPy is replaced with an equal mass of Fe3O4 nanoparticles.

[0084] The absorption bandwidth of the finally prepared radar-infrared multi-spectrum compatible stealth composite material in the X band is 10.5 - 12.4 GHz, and the minimum reflection loss is -14.4 dB (the reflection loss curve is as Figure 7as shown in Fig. (b)); the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0274 W / (m·K); the average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3-5 μm infrared band is 0.24, the average infrared emissivity in the 8-14 μm infrared band is 0.25, and the surface temperature is 48.8 °C after continuous heating on a 150 °C heating table for 0.5 h.

[0085] Comparing Example 2 with Example 1, it can be seen that compared with the Fe3O4 nanoparticles used in Example 2, the Fe3O4@CPPy used in Example 1 can improve the impedance matching of the material, increase the conductance loss, provide various relaxation losses such as interfacial polarization and dipole polarization, achieve the attenuation and absorption of radar waves, and enhance the radar stealth effect.

[0086] Example 3

[0087] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, which is only different from Example 1 in that: the shape of the periodic unit of the periodic pattern laser-etched on the infrared shielding and reflecting layer is a rhombus (SEM as shown in Fig. (b)), the size of the periodic unit is 0.55 mm, and the laser etching gap is 35 μm. Figure 3 as shown in Fig. (b)), the size of the periodic unit is 0.55 mm, and the laser etching gap is 35 μm.

[0088] The finally prepared radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 9.2 - 12.4 GHz in the X band, and the minimum reflection loss is -32.2 dB (the reflection loss curve is as shown in Fig. (a)), and the transmittance and reflectance of the infrared shielding and reflecting layer to radar waves are as shown in Fig. (b); the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0286 W / (m·K); the average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3-5 μm infrared band is 0.18, the average infrared emissivity in the 8-14 μm infrared band is 0.15, and the surface temperature is 46.6 °C after continuous heating on a 150 °C heating table for 0.5 h. Figure 8 as shown in Fig. (a)), the transmittance and reflectance of the infrared shielding and reflecting layer to radar waves are as shown in Fig. (b); Figure 8 as shown in Fig. (b); the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0286 W / (m·K); the average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3-5 μm infrared band is 0.18, the average infrared emissivity in the 8-14 μm infrared band is 0.15, and the surface temperature is 46.6 °C after continuous heating on a 150 °C heating table for 0.5 h.

[0089] Example 4

[0090] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, the specific steps are as follows:

[0091] (1) Preparation of raw materials;

[0092] FeCl3·6H2O: CAS number is 10025-77-1;

[0093] Polyethylene glycol: CAS number is 25322-68-3;

[0094] Sodium acetate anhydrous: CAS number is 127-09-3;

[0095] Ethylene glycol: CAS No. is 107-21-1;

[0096] Pyrrole monomer: CAS No. is 109-97-7;

[0097] L - Camphorsulfonic acid solution: concentration is 1.5 mol / L, and the solvent is deionized water;

[0098] Ammonium persulfate solution: concentration is 1 mol / L, and the solvent is deionized water;

[0099] Infrared shielding material: silver foil, with a thickness of 0.03 mm;

[0100] Substrate: polycarbonate board, manufactured by Dongguan Hongyan Plastic Co., Ltd., with a thickness of 0.15 mm;

[0101] Homogeneous dispersion of aramid nanofibers;

[0102] MXene: manufactured by Jiangsu Xianfeng Nano Materials Co., Ltd., with a sheet diameter of 1-20 μm;

[0103] Glue: manufactured by Shenzhen Yishangxiang Electronic Materials Co., Ltd., with a grade of YS1996;

[0104] (2) Prepare Fe3O4@CPPy;

[0105] Dissolve FeCl3·6H2O, polyethylene glycol, and anhydrous sodium acetate in ethylene glycol, react at 180 °C for 10 h, wash the reactants to obtain Fe3O4 nanoparticles, and then add the Fe3O4 nanoparticles and pyrrole monomer to L - Camphorsulfonic acid solution, dropwise add ammonium persulfate solution, and polymerize in an ice-water bath for 4 h, wash the precipitate to obtain Fe3O4@CPPy with an average particle size of 400 nm; among them, the mass ratio of FeCl3·6H2O, polyethylene glycol, and anhydrous sodium acetate is 1.2:1:4, and the mass ratio of ethylene glycol to the total mass of FeCl3·6H2O, polyethylene glycol, and anhydrous sodium acetate is 8:1. The mass ratio of Fe3O4 nanoparticles, pyrrole monomer, L - Camphorsulfonic acid solution and ammonium persulfate solution is 2:1.2:500:200;

[0106] (3) Prepare an infrared shielding reflection layer and an aerogel respectively;

[0107] The preparation process of the infrared shielding reflective layer is as follows: Stick the infrared shielding material on the substrate through glue, and use a laser marking machine to etch the surface of the infrared shielding material at a laser etching speed of 220 mm / s and an etching power of 70% to obtain an infrared shielding reflective layer with a periodic pattern formed by laser etching; the shape of the periodic unit of the periodic pattern is a cross circle (as shown in (c) of Figure 3 ), the cross circle is composed of a circle and 4 line segments located inside it. One end of the 4 line segments is connected to the center of the circle at the same time, and the other end is respectively connected to 4 points evenly distributed on the circle. The size of the periodic unit is 0.9 mm, and the laser etching gap is 35 μm;

[0108] The preparation process of the aerogel is as follows: Mix the homogeneous dispersion of aramid nanofibers, MXene and Fe3O4@CPPy evenly, put it into a mold, freeze it in liquid nitrogen at -80 °C for 12 h, and then dry it at -50 °C to remove the solvent to obtain the aerogel; the thickness of the aerogel is 3.1 mm; the content of MXene in the aerogel is 30 wt%, and the content of Fe3O4@CPPy is 15 wt%;

[0109] (4) Prepare the radar-infrared multi-spectrum compatible stealth composite material;

[0110] Assemble the infrared shielding reflective layer and the aerogel through glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0111] The finally prepared radar-infrared multi-spectrum compatible stealth composite material is composed of an upper infrared shielding reflective layer and a lower aerogel. The infrared shielding reflective layer is composed of an upper infrared shielding material and a lower substrate;

[0112] The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 8.4 - 12.3 GHz in the X band, and the minimum reflection loss is -18.2 dB (the reflection loss curve is as shown in (a) of Figure 9 ), the transmittance and reflectance of the infrared shielding reflective layer to radar waves are as shown in (b) of Figure 9 ; the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0308 W / (m·K); the average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3 - 5 μm infrared band is 0.23, the average infrared emissivity in the 8 - 14 μm infrared band is 0.20, and the surface temperature is 51.4 °C after continuous heating on a 150 °C heating table for 0.5 h.

[0113] Example 5

[0114] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, the specific steps are as follows:

[0115] (1) Preparation of raw materials;

[0116] FeCl3 - 6H2O: CAS No. is 10025 - 77 - 1;

[0117] Polyethylene glycol: CAS No. is 25322 - 68 - 3;

[0118] Sodium acetate anhydrous: CAS No. is 127 - 09 - 3;

[0119] Ethylene glycol: CAS No. is 107 - 21 - 1;

[0120] Pyrrole monomer: CAS No. is 109 - 97 - 7;

[0121] L - Camphorsulfonic acid solution: concentration is 1.0 mol / L, and the solvent is deionized water;

[0122] Ammonium persulfate solution: concentration is 0.5 mol / L, and the solvent is deionized water;

[0123] Infrared shielding material: indium tin oxide film, thickness is 0.1 mm;

[0124] Substrate: polycarbonate board, manufacturer is Dongguan Hongyan Plastic Co., Ltd., thickness is 0.15 mm;

[0125] Homogeneous dispersion of aramid nanofibers;

[0126] MXene: manufacturer is Jiangsu Xianfeng Nano Materials Co., Ltd., sheet diameter is 1 - 20 μm;

[0127] Glue: manufacturer is Shenzhen Yishangxiang Electronic Materials Co., Ltd., grade is YS1996;

[0128] (2) Prepare Fe3O4@CPPy;

[0129] Dissolve FeCl3 - 6H2O, polyethylene glycol, and sodium acetate anhydrous in ethylene glycol, react at 190 °C for 9 h, wash the reactants to obtain Fe3O4 nanoparticles, then add the Fe3O4 nanoparticles and pyrrole monomer to L - Camphorsulfonic acid solution, dropwise add ammonium persulfate solution, polymerize in an ice - water bath for 2 h, wash the precipitate to obtain Fe3O4@CPPy with an average particle size of 340 nm; among them, the mass ratio of FeCl3 - 6H2O, polyethylene glycol, and sodium acetate anhydrous is 1.5:1:3, the mass ratio of ethylene glycol to the total mass of FeCl3 - 6H2O, polyethylene glycol, and sodium acetate anhydrous is 12:1, and the mass ratio of Fe3O4 nanoparticles, pyrrole monomer, L - Camphorsulfonic acid solution and ammonium persulfate solution is 2:1:500:150;

[0130] (3)Prepare the infrared shielding reflective layer and the aerogel respectively;

[0131] The preparation process of the infrared shielding reflective layer is as follows: Stick the infrared shielding material on the substrate through glue, and use a laser marking machine to etch the surface of the infrared shielding material at a laser etching speed of 180 mm / s and an etching power of 90% to obtain an infrared shielding reflective layer with a periodic pattern of laser etching; The shape of the periodic unit of the periodic pattern is circular (as shown in (d) in Figure 3 ), the size of the periodic unit is 0.5 mm, and the laser etching gap is 40 μm;

[0132] The preparation process of the aerogel is as follows: Mix the homogeneous dispersion of aramid nanofibers, MXene and Fe3O4@CPPy evenly, put them into a mold, freeze them in liquid nitrogen at -80 °C for 12 h, and then dry to remove the solvent at -50 °C to obtain the aerogel; The thickness of the aerogel is 2.7 mm; The content of MXene in the aerogel is 25 wt%, and the content of Fe3O4@CPPy is 30 wt%;

[0133] (4)Prepare the radar-infrared multi-spectrum compatible stealth composite material;

[0134] Assemble the infrared shielding reflective layer and the aerogel through glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0135] The finally prepared radar-infrared multi-spectrum compatible stealth composite material consists of an upper infrared shielding reflective layer and a lower aerogel. The infrared shielding reflective layer consists of an upper infrared shielding material and a lower substrate;

[0136] The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 10.2 - 12.4 GHz in the X-band, and the minimum reflection loss is -36.1 dB; The maximum transmittance of the infrared shielding reflective layer to radar waves is 96.74%, and the minimum is 93.06%; The thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0318 W / (m·K); The average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3 - 5 μm infrared band is 0.22, in the 8 - 14 μm infrared band is 0.19, and the surface temperature is 52.3 °C after continuous heating on a 150 °C heating table for 0.5 h.

[0137] Example 6

[0138] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, the specific steps are as follows:

[0139] (1)Preparation of raw materials;

[0140] FeCl3-6H2O: CAS No. is 10025-77-1;

[0141] Polyethylene glycol: CAS No. is 25322-68-3;

[0142] Sodium acetate anhydrous: CAS No. is 127-09-3;

[0143] Ethylene glycol: CAS No. is 107-21-1;

[0144] Pyrrole monomer: CAS No. is 109-97-7;

[0145] L - Camphorsulfonic acid solution: concentration is 1 mol / L, and the solvent is deionized water;

[0146] Ammonium persulfate solution: concentration is 1 mol / L, and the solvent is deionized water;

[0147] Infrared shielding material: copper foil, with a thickness of 0.03 mm;

[0148] Substrate: polycarbonate board, manufactured by Dongguan Hongyan Plastic Co., Ltd., with a thickness of 0.15 mm;

[0149] Homogeneous dispersion of aramid nanofibers;

[0150] MXene: manufactured by Jiangsu Xianfeng Nano Materials Co., Ltd., with a flake diameter of 1 - 20 μm;

[0151] Glue: manufactured by Shenzhen Yishangxiang Electronic Materials Co., Ltd., with the product number YS1996;

[0152] (2) Prepare Fe3O4@CPPy;

[0153] Dissolve FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous in ethylene glycol, react at 220 °C for 10 h, wash the reactants to obtain Fe3O4 nanoparticles, and then add the Fe3O4 nanoparticles and pyrrole monomer to L - camphorsulfonic acid solution, dropwise add ammonium persulfate solution, and polymerize in an ice-water bath for 2 h, wash the precipitate to obtain Fe3O4@CPPy with an average particle size of 385 nm; among them, the mass ratio of FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous is 1.5:1:3.6, the mass ratio of ethylene glycol to the total mass of FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous is 8:1, and the mass ratio of Fe3O4 nanoparticles, pyrrole monomer, L - camphorsulfonic acid solution, and ammonium persulfate solution is 2:1.2:400:250;

[0154] (3) Prepare an infrared shielding reflective layer and an aerogel respectively;

[0155] The preparation process of the infrared shielding reflective layer is as follows: Stick the infrared shielding material on the substrate through glue, and use a laser marking machine to etch the surface of the aluminum foil at a laser etching speed of 180 mm / s and an etching power of 90% to obtain an infrared shielding reflective layer with a periodically patterned laser etching; the shape of the periodic unit of the periodic pattern is a cross rectangle, which is composed of a rectangle and 4 line segments inside it. One end of the 4 line segments is connected to the center point of the rectangle at the same time, and the other end is connected to the 4 vertices of the rectangle respectively. The size of the periodic unit is 0.7 mm, and the laser etching gap is 55 μm;

[0156] The preparation process of the aerogel is as follows: Mix the homogeneous dispersion of aramid nanofibers, MXene and Fe3O4@CPPy evenly, put it into a mold, freeze it in liquid nitrogen at -80 °C for 12 h, and then dry it at -50 °C to remove the solvent to obtain the aerogel; the thickness of the aerogel is 2.5 mm; the content of MXene in the aerogel is 20 wt%, and the content of Fe3O4@CPPy is 30 wt%;

[0157] (4)Prepare the radar-infrared multi-spectrum compatible stealth composite material;

[0158] Assemble the infrared shielding reflective layer and the aerogel through glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0159] The finally prepared radar-infrared multi-spectrum compatible stealth composite material is composed of an upper infrared shielding reflective layer and a lower aerogel. The infrared shielding reflective layer is composed of an upper infrared shielding material and a lower substrate;

[0160] The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 11.2 - 12.4 GHz in the X band, and a minimum reflection loss of -17.3 dB; the maximum transmittance of the infrared shielding reflective layer to radar waves is 98.08%, and the minimum is 95.90%; the thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.320 W / (m·K); the average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3 - 5 μm infrared band is 0.28, in the 8 - 14 μm infrared band is 0.26, and the surface temperature is 58.6 °C after continuous heating on a 150 °C heating table for 0.5 h.

[0161] Example 7

[0162] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, the specific steps are as follows:

[0163] (1)Preparation of raw materials;

[0164] FeCl3-6H2O: CAS No. is 10025-77-1;

[0165] Polyethylene glycol: CAS No. is 25322-68-3;

[0166] Sodium acetate anhydrous: CAS No. is 127-09-3;

[0167] Ethylene glycol: CAS No. is 107-21-1;

[0168] Pyrrole monomer: CAS No. is 109-97-7;

[0169] L - Camphorsulfonic acid solution: concentration is 0.5 mol / L, and the solvent is deionized water;

[0170] Ammonium persulfate solution: concentration is 0.5 mol / L, and the solvent is deionized water;

[0171] Infrared shielding material: conductive paint, manufacturer is Shenzhen Jingzhe Technology Co., Ltd., grade is Hailin Star, thickness is 0.03 mm;

[0172] Substrate: polycarbonate sheet, manufacturer is Dongguan Hongyan Plastic Co., Ltd., thickness is 0.15 mm;

[0173] Homogeneous dispersion of aramid nanofibers;

[0174] MXene: manufacturer is Jiangsu Xianfeng Nano Materials Co., Ltd., sheet diameter is 1-20 μm;

[0175] Glue: manufacturer is Shenzhen Yishangxiang Electronic Materials Co., Ltd., grade is YS1996;

[0176] (2) Prepare Fe3O4@CPPy;

[0177] Dissolve FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous in ethylene glycol, react at 180 °C for 8.5 h, wash the reactants to obtain Fe3O4 nanoparticles, and then add the Fe3O4 nanoparticles and pyrrole monomer to L - camphorsulfonic acid solution, dropwise add ammonium persulfate solution, and polymerize in an ice-water bath for 3 h, wash the precipitate to obtain Fe3O4@CPPy with an average particle size of 365 nm; among them, the mass ratio of FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous is 1.2:1:3.6, the mass ratio of ethylene glycol to the total mass of FeCl3-6H2O, polyethylene glycol, and sodium acetate anhydrous is 10:1, and the mass ratio of Fe3O4 nanoparticles, pyrrole monomer, L - camphorsulfonic acid solution and ammonium persulfate solution is 2:1:400:200;

[0178] (3)Prepare the infrared shielding reflective layer and the aerogel respectively;

[0179] The preparation process of the infrared shielding reflective layer is as follows: Stick the infrared shielding material on the substrate through glue, and use a laser marking machine to etch the surface of the aluminum foil at a laser etching speed of 200 mm / s and an etching power of 80% to obtain an infrared shielding reflective layer with a periodic pattern of laser etching; The shape of the periodic unit of the periodic pattern is a cross square, which is composed of a square and 4 line segments inside it. One end of the 4 line segments is connected to the center point of the square at the same time, and the other end is connected to the 4 vertices of the square respectively. The size of the periodic unit is 0.80 mm, and the laser etching gap is 60 μm;

[0180] The preparation process of the aerogel is as follows: Mix the homogeneous dispersion of aramid nanofibers, MXene and Fe3O4@CPPy evenly, put them into a mold, freeze them in liquid nitrogen at -80 °C for 12 h, and then dry to remove the solvent at -50 °C to obtain the aerogel; The thickness of the aerogel is 3.5 mm; The content of MXene in the aerogel is 25 wt%, and the content of Fe3O4@CPPy is 15 wt%;

[0181] (4)Prepare the radar-infrared multi-spectrum compatible stealth composite material;

[0182] Assemble the infrared shielding reflective layer and the aerogel through glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0183] The finally prepared radar-infrared multi-spectrum compatible stealth composite material is composed of an upper infrared shielding reflective layer and a lower aerogel. The infrared shielding reflective layer is composed of an upper infrared shielding material and a lower substrate;

[0184] The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 11.0 - 12.4 GHz in the X band, and the minimum reflection loss is -17.6 dB; The maximum transmittance of the infrared shielding reflective layer to radar waves is 95.70%, and the minimum value is 90.91%; The thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0281 W / (m·K); The average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3 - 5 μm infrared band is 0.27, in the 8 - 14 μm infrared band is 0.24, and the surface temperature is 48.2 °C after continuous heating on a 150 °C heating table for 0.5 h.

[0185] Example 8

[0186] A preparation method of a radar-infrared multi-spectrum compatible stealth composite material, the specific steps are as follows:

[0187] (1)Preparation of raw materials;

[0188] FeCl3 - 6H2O: CAS No. is 10025 - 77 - 1;

[0189] Polyethylene glycol: CAS No. is 25322 - 68 - 3;

[0190] Sodium acetate anhydrous: CAS No. is 127 - 09 - 3;

[0191] Ethylene glycol: CAS No. is 107 - 21 - 1;

[0192] Pyrrole monomer: CAS No. is 109 - 97 - 7;

[0193] L - Camphorsulfonic acid solution: concentration is 1.2 mol / L, and the solvent is deionized water;

[0194] Ammonium persulfate solution: concentration is 1.0 mol / L, and the solvent is deionized water;

[0195] Infrared shielding material: aluminum foil, with a thickness of 0.04 mm;

[0196] Substrate: polycarbonate board, manufactured by Dongguan Hongyan Plastic Co., Ltd., with a thickness of 0.15 mm;

[0197] Homogeneous dispersion of aramid nanofibers;

[0198] MXene: manufactured by Jiangsu Xianfeng Nano Materials Co., Ltd., with a sheet diameter of 1 - 20 μm;

[0199] Glue: manufactured by Shenzhen Yishangxiang Electronic Materials Co., Ltd., with the grade number YS1996;

[0200] (2) Prepare Fe3O4@CPPy;

[0201] Dissolve FeCl3 - 6H2O, polyethylene glycol, and sodium acetate anhydrous in ethylene glycol, react at 220 °C for 10 h, wash the reactants to obtain Fe3O4 nanoparticles, and then add the Fe3O4 nanoparticles and pyrrole monomer to L - Camphorsulfonic acid solution, dropwise add ammonium persulfate solution, polymerize in an ice - water bath for 3 h, wash the precipitate to obtain Fe3O4@CPPy with an average particle size of 390 nm; among them, the mass ratio of FeCl3 - 6H2O, polyethylene glycol, and sodium acetate anhydrous is 1.3:1:3.4, the mass ratio of ethylene glycol to the total mass of FeCl3 - 6H2O, polyethylene glycol, and sodium acetate anhydrous is 10:1, and the mass ratio of Fe3O4 nanoparticles, pyrrole monomer, L - Camphorsulfonic acid solution and ammonium persulfate solution is 2:1.5:500:200;

[0202] (3) Prepare an infrared shielding reflection layer and an aerogel respectively;

[0203] The preparation process of the infrared shielding reflective layer is as follows: Stick the infrared shielding material on the substrate through glue, and use a laser marking machine to etch the surface of the aluminum foil at a laser etching speed of 160 mm / s and an etching power of 85% to obtain an infrared shielding reflective layer with a periodic pattern formed by laser etching; The shape of the periodic unit of the periodic pattern is the Bagua shape, the size of the periodic unit is 1.0 mm, and the laser etching gap is 55 μm;

[0204] The preparation process of the aerogel is as follows: Mix the homogeneous dispersion of aramid nanofibers, MXene and Fe3O4@CPPy evenly, put them into a mold, freeze them in liquid nitrogen at -80 °C for 12 h, and then dry them at -50 °C to remove the solvent to obtain the aerogel; The thickness of the aerogel is 2.5 mm; The content of MXene in the aerogel is 20 wt%, and the content of Fe3O4@CPPy is 25 wt%;

[0205] (4) Prepare a radar-infrared multi-spectrum compatible stealth composite material;

[0206] Assemble the infrared shielding reflective layer and the aerogel through glue to obtain the radar-infrared multi-spectrum compatible stealth composite material.

[0207] The finally prepared radar-infrared multi-spectrum compatible stealth composite material is composed of an upper infrared shielding reflective layer and a lower aerogel, and the infrared shielding reflective layer is composed of an upper infrared shielding material and a lower substrate;

[0208] The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 8.6 - 11.7 GHz in the X band, and the minimum reflection loss is -21.6 dB; The maximum transmittance of the infrared shielding reflective layer to radar waves is 96.29%, and the minimum value is 92.11%; The thermal conductivity of the radar-infrared multi-spectrum compatible stealth composite material is 0.0310 W / (m·K); The average infrared emissivity of the radar-infrared multi-spectrum compatible stealth composite material in the 3 - 5 μm infrared band is 0.28, the average infrared emissivity in the 8 - 14 μm infrared band is 0.26, and the surface temperature is 58.6 °C after continuous heating on a 150 °C heating table for 0.5 h.

Claims

1. A radar-infrared multi-spectrum compatible stealth composite material having a double-layer structure, wherein the upper layer is an infrared shielding reflection layer having a laser-etched periodic pattern, and the lower layer is a wave-absorbing and heat-insulating layer, characterized in that: The periodic unit shape of the periodic pattern is a cross rectangle, a cross circle or a cross rectangle; The cross-shaped rectangle is composed of a rectangle and eight line segments inside it. One end of the eight line segments is connected to the center point of the rectangle at the same time, and the other ends are connected to the four vertices of the rectangle and the midpoints of the four sides of the rectangle respectively. The cross circle is composed of a circle and four line segments inside it. One end of the four line segments is connected to the center of the circle at the same time, and the other end is connected to four points evenly distributed on the circle. The cross rectangle consists of a rectangle and four line segments inside it. One end of the four line segments is connected to the center point of the rectangle at the same time, and the other end is connected to the four vertices of the rectangle respectively. The periodic unit size is 0.5-1.0 mm, and the laser etching gap is 35-60 μm; The thickness of the wave-absorbing and heat-insulating layer is 2.5-3.5 mm; the wave-absorbing and heat-insulating layer is aerogel, the skeleton of the aerogel is aramid nanofiber, and the aramid nanofiber is obtained by deprotonating and protonating short-cut Kevlar fibers in a solvent in sequence; MXene and Fe3O4@CPPy are attached to the aramid nanofibers. The MXene sheet diameter is 1-20 μm. Fe3O4@CPPy is a chiral nanoparticle with a core-shell structure, in which the core is Fe3O4 nanoparticles and the shell is chiral polypyrrole with an average particle size of 340-400 nm. The preparation process of Fe3O4@CPPy is as follows: after Fe3O4 nanoparticles are prepared by a hydrothermal method, they are added together with pyrrole monomers into a system containing a chiral dopant or a chiral acid for polymerization to obtain Fe3O4@CPPy.

2. The radar-infrared multi-spectrum compatible stealth composite material according to claim 1, characterized in that: The infrared shielding reflective layer includes an infrared shielding material located at the upper layer and a substrate located at the lower layer. The thickness of the infrared shielding material is 0.03-0.1mm, and the thickness of the substrate is 0.1-0.2mm. The infrared shielding material is aluminum foil, copper foil, silver foil, indium tin oxide film or conductive spray paint, and the substrate is a polycarbonate board.

3. The radar-infrared multi-spectrum compatible stealth composite material according to claim 1, characterized in that: The preparation process of Fe3O4@CPPy is as follows: FeCl3-6H2O, polyethylene glycol, and anhydrous sodium acetate are dissolved in ethylene glycol, reacted at 180-220°C for 8-10h, the reactant is washed to obtain Fe3O4 nanoparticles, and then the Fe3O4 nanoparticles and pyrrole monomer are added to L-Hydroxypropene with a concentration of 0.5-1.5 mol / L. - Ammonium persulfate solution was added dropwise to the camphorsulfonic acid solution, polymerized in an ice-water bath for 2-4 h, and the precipitate was washed to obtain Fe3O4@CPPy.

4. The radar-infrared multi-spectrum compatible stealth composite material according to claim 1, characterized in that: In the aerogel, the content of MXene is 20-30wt%, and the content of Fe3O4@CPPy is 10-30wt%.

5. The radar-infrared multi-spectrum compatible stealth composite material according to any one of claims 1 to 4, characterized in that: The radar-infrared multi-spectrum compatible stealth composite material has an absorption bandwidth of 8.4-12.4GHz in the X-band, a minimum reflection loss of -32.44~-14.4dB, a thermal conductivity of 0.0274-0.0320W / (mK), an average infrared emissivity of 0.18-0.28 in the 3-5μm infrared band, and an average infrared emissivity of 0.15-0.26 in the 8-14μm infrared band. After continuous heating on a 150℃ heating table for 0.5h, the surface temperature is 46.6-58.6℃.

6. A method for preparing a radar-infrared multi-spectrum compatible stealth composite material as claimed in any one of claims 1 to 5, characterized in that: After separately preparing an infrared shielding reflection layer and a wave-absorbing heat-insulating layer with a laser-etched periodic pattern, the two are assembled together by glue to obtain a radar-infrared multi-spectrum compatible stealth composite material.

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