RGO / Schiff base aerogel as well as preparation method and application thereof

Abstract

The invention provides rGO / Schiffbase aerogel as well as a preparation method and application thereof, and belongs to the technical field of wave-absorbing materials. The preparation method comprises the following steps: uniformly mixing ascorbic acid and a GO suspension, and carrying out a reaction 1 to obtain p-rGO hydrogel; the p-rGO hydrogel is sequentially subjected to freeze thawing, reduction, cleaning and drying, and rGO aerogel is obtained; carrying out a reaction 2 on terephthalaldehyde, p-phenylenediamine and amino siloxane in ethanol; after the reaction 2 is finished, adding alkoxy silane and water into a reaction system, and standing to obtain wet gel; stirring the wet gel until uniform sol is formed, then adding the rGO aerogel, uniformly mixing, aging and drying to obtain the aerogel. The aerogel provided by the invention is low in density, strong in hydrophobicity and relatively good in mechanical property, the effective wave absorbing bandwidth of the aerogel is 9.7 GHz, and the maximum reflectivity of the aerogel is-40.72 dB.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing materials, and particularly relates to an rGO / Schiff base aerogel and a preparation method and application thereof. Background Art

[0002] In recent years, the rapid development of 5G communication and military radar technology has improved social production efficiency and national defense capabilities. However, the resulting electromagnetic pollution problem has become one of the four major public nuisances in the world. Due to the increasingly widespread application of electromagnetic wave absorbing materials in the fields of military, aerospace, communication, electronic devices, etc., the real-time interference of electromagnetic signal transmission has become increasingly prominent. Therefore, researchers at home and abroad are committed to researching and developing new electromagnetic wave absorbing materials that are thin, wide-band, lightweight, have strong absorption performance and are stable, with the goal of reducing the potential threats of electromagnetic pollution to national defense, industry and human health.

[0003] The world's lightest solid, aerogel can even exist at a density lower than that of air, so it is called "blue smoke". Its high porosity and extremely low density result in an ultra-low thermal conductivity. If the mature experience of microwave absorbing materials can be combined with it to make its microwave absorption performance adjustable, aerogel will show great potential. This will effectively solve the limitations of traditional microwave absorbing materials in extreme environments and greatly broaden its application scope, exceeding the performance of traditional materials. Currently, aerogel microwave absorbing materials, as structural materials, have attracted much research due to their strong absorption, wide band, light weight and plasticity, but the complexity of the forming process is a challenge. Microwave absorbing materials are divided into resistive type, dielectric type and magnetic loss type according to the loss mechanism. Resistive type materials such as carbon nanotubes and conductive polymers can generate microcurrents that are converted into heat energy due to their conductivity. However, materials with a single loss mechanism often have low absorption intensity, narrow frequency band or large density, and it is difficult to meet the requirements of modern microwave absorbing materials for the performance of "thin, light, strong, wide". Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an rGO / Schiff base aerogel and a preparation method and application thereof.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention, a preparation method of an rGO / Schiff base aerogel, comprising the following steps:

[0007] Mix ascorbic acid and GO suspension evenly and then carry out Reaction 1 to obtain p-rGO hydrogel;

[0008] Carry out freeze-thawing, reduction, washing and drying on the p-rGO hydrogel in sequence to obtain rGO aerogel;

[0009] React terephthalaldehyde, p-phenylenediamine and amino silicone in ethanol for reaction 2;

[0010] After the end of reaction 2, add alkoxysilane and water to the reaction system, let it stand still to obtain a wet gel;

[0011] Stir the wet gel until a uniform sol is formed, then add the rGO aerogel and mix evenly, age, and dry to obtain the rGO / Schiff base aerogel.

[0012] The second technical solution of the present invention is an rGO / Schiff base aerogel prepared by the above preparation method.

[0013] The third technical solution of the present invention is an application of the above rGO / Schiff base aerogel in the preparation of microwave absorbing materials.

[0014] The fourth technical solution of the present invention is a microwave absorbing material, and the raw materials include the above rGO / Schiff base aerogel.

[0015] The present invention discloses the following technical effects:

[0016] The present invention provides an rGO / Schiff base aerogel with low density, strong hydrophobicity, and good mechanical properties.

[0017] The effective microwave absorption bandwidth of the rGO / Schiff base aerogel provided by the present invention is 9.7 GHz (7.7 - 8.1 GHz and 8.7 - 18 GHz) at 3.0 mm. The RL value first increases and then decreases with the increase of thickness. The RL value is the smallest when the thickness is 3.5 mm and reaches -40.72 dB at 17.2 GHz. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is the scanning electron microscope image (10 μm) of the rGO / Schiff base aerogel of Example 1.

[0020] Figure 2 It is the scanning electron microscope image (1 μm) of the rGO / Schiff base aerogel of Example 1.

[0021] Figure 3In figure (a), it is a photo of rGO / Schiff base aerogel; in figure (b), it is a sectional view of GO aerogel; in figure (c), it is the static contact angle of the liquid on the surface of rGO / Schiff base aerogel after 3 minutes; in figure (d), it is the state diagram of common liquids dropped on the surface of rGO / Schiff base aerogel after two minutes.

[0022] Figure 4 Figure (a) shows the stress-strain curves of Schiff / MTMS-2 aerogel and rGO / Schiff base aerogel under 20% strain for five cyclic compressions, and figure (b) shows the stress-strain curves of rGO aerogel under 50% strain for five cyclic compressions.

[0023] Figure 5 Figure shows the reflectivity curve of Schiff / MTMS-1 aerogel.

[0024] Figure 6 In figure (a), it is the reflectivity curve of Schiff / MTMS-2 aerogel; in figure (b), it is the reflectivity curve of rGO aerogel; in figure (c), it is the reflectivity curve of rGO / Schiff / FeCl3; in figure (d), it is the reflectivity curve of rGO / Schiff base aerogel. Detailed implementation mode

[0025] Now, various exemplary implementation modes of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0026] It should be understood that the terms used in the present invention are only for describing specific implementation modes and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0028] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which will be obvious to those skilled in the art. Other embodiments obtained from the description of the present invention will be obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.

[0029] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0030] Traditional wave-absorbing materials (such as ferrites, carbon blacks) have high density and large weight, while aerogels have ultra-low density (as low as 0.01 g / cm 3 ), which are suitable for lightweight scenarios such as aerospace and wearable devices. The high specific surface area and porous structure of GO enhance the multiple reflections and interfacial polarization of electromagnetic waves. The reduction degree of GO can adjust the conductivity, optimize the impedance matching, and reduce the electromagnetic wave reflection. The GO skeleton endows the aerogel with high mechanical strength and flexibility. The polar C=N bond and modifiability of Schiff base significantly improve the dielectric loss and electro-magnetic synergistic effect. The strong polarity of the C=N bond generates significant dipole polarization in the alternating electromagnetic field, converting electromagnetic energy into heat energy. The three-dimensional multi-level pore structure of the aerogel further optimizes the impedance matching, greatly reducing the electromagnetic wave reflection, and at the same time achieving lightweight and broadband absorption, which is applicable to high-tech fields such as aerospace and 5G communication.

[0031] This material combines functionality and application potential. In scenarios such as military stealth, wearable electronic protection, and new energy electromagnetic shielding, its thermal stability and flexibility advantages are particularly prominent. Future research can focus on multi-component collaborative design, green preparation processes, and optimization of hydrothermal stability to promote its practical application process in extreme environments and intelligent devices.

[0032] The first aspect of the present invention provides a preparation method of rGO / Schiff base aerogel, comprising the following steps:

[0033] Mix ascorbic acid and GO suspension evenly and then carry out Reaction 1 to obtain p-rGO hydrogel;

[0034] Subject the p-rGO hydrogel to freeze-thawing, reduction, washing, and drying in sequence to obtain rGO aerogel;

[0035] React terephthalaldehyde, p-phenylenediamine, and amino siloxane in ethanol for Reaction 2;

[0036] After Reaction 2 ends, add alkoxysilane and water to the reaction system and let it stand to obtain a wet gel;

[0037] Stir the wet gel until a uniform sol is formed, then add the rGO aerogel and mix evenly, followed by aging and drying to obtain the rGO / Schiff base aerogel.

[0038] In some embodiments of the present invention, the concentration of the GO suspension is 0.5 - 10 mg / mL (more preferably 1 - 5 mg / mL, even more preferably 1.5 mg / mL); the mass ratio of ascorbic acid to the GO suspension is 10:1 - 1:1 (more preferably 3 - 5:1, even more preferably 3:1); the reaction temperature of Reaction 1 is 80 - 95 °C (more preferably 90 °C), and the reaction time is 0.5 - 4 h (more preferably 0.5 - 1.5 h, even more preferably 30 min). The present invention does not make special limitations on the preparation method of the GO suspension, and conventional technical means of those skilled in the art can be selected, for example: adding GO powder into deionized water and then ultrasonically dispersing it.

[0039] In some embodiments of the present invention, the freeze-thawing is specifically: freezing at -20 to -80 °C (more preferably -60 °C) for 30 min, and then thawing to room temperature; the reduction is specifically: reducing the p-rGO hydrogel after freeze-thawing at 95 °C for 2 - 24 h (more preferably 4 - 8 h, even more preferably 6 h).

[0040] In some embodiments of the present invention, the amino siloxane is 3-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane or N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane; the molar ratio of the amino functional group to the aldehyde functional group in terephthalaldehyde, p-phenylenediamine and amino siloxane is 1:1; the temperature of Reaction 2 is 20 - 70 °C, and the time is 0.5 - 8 h.

[0041] In some embodiments of the present invention, the alkoxysilane is methyltrimethoxysilane or vinyltriethoxysilane; the molar ratio of the alkoxysilane to terephthalaldehyde is 0.1:1 - 10:1 (more preferably 1 - 2:1); the standing time is 6 - 12 h.

[0042] In some embodiments of the present invention, the volume ratio of ethanol to water is 1:1 - 9:1. If the volume ratio of ethanol to water in the present invention is higher or lower than the above parameters, the gel cannot be formed.

[0043] In some embodiments of the present invention, the parameters of the aging are set as: aging in a water bath at 40 - 80 °C (more preferably 60 °C) for 4 - 24 h (more preferably 6 - 8 h).

[0044] In the present invention, there is no special limitation on the above-mentioned method of mixing evenly, and the conventional technical means of those skilled in the art can be selected, for example: ultrasonic stirring.

[0045] In the process of the rGO / Schiff base aerogel of the present invention, the reaction of terephthalaldehyde and p-phenylenediamine is carried out first, and then the subsequent hydrolysis reaction is carried out, so that the obtained rGO / Schiff base aerogel has good wave-absorbing performance, and the effective absorption bandwidth can reach 9 GHz; if terephthalaldehyde, p-phenylenediamine, water, compound 1 and amino silicone are mixed together first and then reacted, the wave-absorbing performance of the obtained rGO / Schiff base aerogel will be reduced, the effective absorption bandwidth is narrow, and it is much lower than that of the aerogel synthesized step by step.

[0046] The second aspect of the present invention provides an rGO / Schiff base aerogel prepared by the above preparation method.

[0047] The third aspect of the present invention provides an application of the above rGO / Schiff base aerogel in the preparation of wave-absorbing materials.

[0048] The fourth aspect of the present invention provides a wave-absorbing material, the raw materials of which include the above rGO / Schiff base aerogel.

[0049] The technical solutions of the present invention are all conventional solutions in the art unless otherwise specified, and the reagents or raw materials used are all purchased from commercial channels or have been made public unless otherwise specified.

[0050] In order to better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] An rGO / Schiff base aerogel is prepared according to the following steps:

[0053] Step 1. Preparation of rGO aerogel: After mixing 27 mg of ascorbic acid and 9 mg of GO suspension (1.5 mg / mL), keep it at 90 °C for 30 min to obtain p-rGO hydrogel. Then freeze the p-rGO hydrogel at -60 °C for 30 min, thaw it to room temperature and then reduce it at 95 °C for 6 h to form graphene hydrogel; then rinse the graphene hydrogel with distilled water for 24 h to remove the residual ascorbic acid, and then freeze-dry it for 48 h to obtain rGO aerogel.

[0054] Step 2. React 0.115 g of p-phenylenediamine, 0.284 g of p-phthalaldehyde, and 0.5 mL of 3-aminopropyltriethoxysilane in ethanol at 60 °C for 30 min. Subsequently, add 0.3 mL of methyltrimethoxysilane, stir ultrasonically for 10 min, then add 2 mL of distilled water, and let it stand for aging. The mixed solution will slowly form a wet gel. Stir the wet gel until a uniform sol is formed. Then add the rGO aerogel prepared in Step 1 to the uniform clear sol, mix evenly, and age in a water bath at 60 °C for 6 h. After aging is completed, dry to completely remove ethanol and water, and obtain rGO / Schiff base aerogel.

[0055] Comparative Example 1

[0056] A kind of Schiff / MTMS-1 aerogel, the preparation steps are as follows:

[0057] Add 0.284 g of p-phthalaldehyde, 0.115 g of p-phenylenediamine, 0.5 mL of 3-aminopropyltriethoxysilane, and 0.3 mL of methyltrimethoxysilane into a 50 mL glass beaker, stir ultrasonically for 10 min, then add 2 mL of distilled water, and let it stand. The mixed solution will slowly form a wet gel. Then age the wet gel in a water bath at 60 °C for 6 h. After aging is completed, dry to completely remove ethanol and water, and obtain Schiff / MTMS-1 aerogel.

[0058] Comparative Example 2

[0059] A kind of Schiff / MTMS-2 aerogel, the preparation steps are as follows:

[0060] React 0.115 g of p-phenylenediamine, 0.284 g of p-phthalaldehyde, and 0.5 mL of 3-aminopropyltriethoxysilane in ethanol at 60 °C for 30 min. Subsequently, add 0.3 mL of methyltrimethoxysilane, stir ultrasonically for 10 min, then add 2 mL of distilled water, and let it stand. The mixed solution will slowly form a wet gel. Then age the wet gel in a water bath at 60 °C for 6 h. After aging is completed, dry to completely remove ethanol and water, and obtain Schiff / MTMS-2 aerogel.

[0061] Comparative Example 3

[0062] rGO / Schiff / FeCl3 aerogel, the preparation steps are as follows:

[0063] Step. The same as Step 1 of Example 1.

[0064] Step 2. React 0.115 g of p-phenylenediamine, 0.284 g of p-phthalaldehyde, and 0.5 mL of 3-aminopropyltriethoxysilane in ethanol at 60 °C for 30 min. Subsequently, add 0.3 mL of methyltrimethoxysilane and 0.034 g of FeCl3. After ultrasonic stirring for 10 min, add 2 mL of distilled water and let it stand. The mixed solution will slowly form a wet gel. Stir the wet gel until a uniform sol is formed. Then add the rGO aerogel prepared in Step 1 to the uniform clear sol. After mixing evenly, age it in a water bath at 60 °C for 6 h. After aging is completed, dry it to completely dry the ethanol and water, and obtain rGO / Schiff / FeCl3 aerogel (that is, different from Example 1 in that FeCl3 is added to the rGO / Schiff base aerogel).

[0065] Performance characterization:

[0066] 1. Scanning electron microscopy (SEM) test

[0067] As Figure 1 、 2 is the field emission scanning photo of the rGO / Schiff base aerogel. It can be seen from Figure 1 that it has a 3D network porous structure. It can be seen from the enlarged Figure 2 that Schiff base / MTMS particles grow on the surface of rGO.

[0068] 2. Contact angle (CA) test

[0069] From Figure 3 it can be seen that the diameter of the rGO / Schiff base aerogel is 1.5 cm, the thickness is 1.1 cm, and the mass is 0.0839 g. Its density is 43.18 mg / cm -3 ,. When it is placed on the leaf, its contact surface with the leaf is very small, and the leaf does not deform at all, indicating that the rGO / Schiff base aerogel meets the requirements of "light and thin" ( Figure 3 a) in); the cross-section of the rGO aerogel is honeycomb-shaped, so it can play a huge role in wave absorption ( Figure 3 b) in); the static contact angle of water on the surface of the rGO / Schiff base aerogel, and the average contact angle is 136° ( Figure 3 c) in); the wettability of the rGO / Schiff base aerogel to various common liquids such as water, coffee, black tea, cola, and milk ( Figure 3 d) in). The above results show that the rGO / Schiff base aerogel prepared in the present invention meets the requirements of "light and thin", and has hydrophobicity, and all droplets are approximately spherical on the surface of the aerogel.

[0070] 4. Compression Performance Test

[0071] As Figure 4 shown, after five compression cycles, the compression strength of Schiff / MTMS-2 aerogel decreased from the original 226 kPa to 223 kPa, and the compression strength decreased to 1.33% of the original, with a plastic deformation of 5.5%, indicating that its resilience needs to be improved. The reason is that the pores of the aerogel are too large; after five compression cycles, the compression strength of the plastic deformation rGO aerogel decreased from the original 11.3 kPa to 8.9 kPa, and the compression strength decreased to 21.2% of the original, with a plastic deformation of 26.5%, indicating that the compression strength of the rGO aerogel is weak, and the reason is its low bond strength; after five compression cycles, the compression strength of rGO / Schiff base aerogel decreased from the original 13.5 kPa to 8.2 kPa, and the compression strength decreased to 39.2% of the original, with a plastic deformation of 10.8%; the initial strength of Schiff / MTMS-2 aerogel increased after adding rGO compared to Schiff / MTMS-2 aerogel and rGO aerogel.

[0072] 5. Electromagnetic Wave Absorption Performance Test

[0073] Figure 5 The reflectivity curve of Schiff / MTMS-1 aerogel is shown. It can be seen that it has no effective absorption bandwidth, indicating that the wave absorption effect of the aerogel is poor under this synthesis method.

[0074] The reflectivity curve of Schiff / MTMS-2 aerogel is as Figure 6 shown in a of. As the thickness increases, it first increases and then decreases. The effective wave absorption bandwidth at 4.0 mm is 2 GHz (11.3 - 13.3 GHz). The reflectivity (RL) value first increases and then decreases as the thickness increases. The RL value is the smallest when the thickness is 4.0 mm and reaches -42.16 dB at 12.36 GHz; the effective wave absorption bandwidth of rGO aerogel is shown in Figure 6 b of. As the thickness increases, it first increases and then decreases. The effective wave absorption bandwidth at 3.0 mm is 8.5 GHz (8.9 - 17.4 GHz). The RL value first increases and then decreases as the thickness increases. The RL value is the smallest when the thickness is 4.0 mm and reaches -32.35 dB at 9.54 GHz; the effective wave absorption bandwidth of rGO / Schiff / FeCl3 aerogel is shown in Figure 6The c(rGO / Schiff / FeCl3 aerogel is based on Example 1, and FeCl3 is added in Step 2. The result shows that adding other elements such as FeCl3 to the rGO / Schiff aerogel will instead reduce its effective wave absorption bandwidth). As the thickness increases, it first increases and then decreases. The effective wave absorption bandwidth at 3.0 mm is 6.5 GHz (8.5 - 9.0 GHz, 9.4 - 13.6 GHz, and 15.9 - 17.7 GHz). The RL value first increases and then decreases with the increase of thickness. The RL value is the smallest when the thickness is 3.5 mm and reaches -35.54 dB at 15.84 GHz; the effective wave absorption bandwidth of the rGO / Schiffbase aerogel is shown in Figure 6 In d, as the thickness increases, it first increases and then decreases. The effective wave absorption bandwidth at 3.0 mm is 9.7 GHz (7.7 - 8.1 GHz and 8.7 - 18 GHz). The RL value first increases and then decreases with the increase of thickness. The RL value is the smallest when the thickness is 3.5 mm and reaches -40.72 dB at 17.2 GHz. According to the data analysis, the absorption peak of the Schiff / MTMS-2 aerogel is the deepest. rGO provides a relatively large effective absorption bandwidth for rGO / Schiff. After combination, the effective wave absorption bandwidth reaches 9.7 GHz. However, the lowest reflectivity is 2.3 dB different for rGO. This situation shows that after rGO is combined with Schiff / MTMS, through the organic-inorganic hybridization technology, the impedance matching performance of the composite material is significantly improved, and the overall wave absorption performance is greatly enhanced. This results in a wider wave absorption frequency band, and the material thickness required to achieve the same wave absorption effect is significantly reduced, meeting the vision of developing "thin, wide, light, and strong" wave absorption materials.

[0075] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of rGO / Schiffbase aerogel, characterized in that, It includes the following steps: Mix ascorbic acid and GO suspension evenly and then carry out Reaction 1 to obtain p-rGO hydrogel; Subject the p-rGO hydrogel to freeze-thawing, reduction, washing, and drying in sequence to obtain rGO aerogel; React terephthalaldehyde, p-phenylenediamine, and amino siloxane in ethanol in Reaction 2; After Reaction 2 ends, add alkoxysilane and water to the reaction system, and let it stand to obtain a wet gel; Stir the wet gel until a uniform sol is formed, then add the rGO aerogel and mix evenly, age, and dry to obtain rGO / Schiffbase aerogel.

2. The preparation method of the rGO / Schiffbase aerogel according to claim 1, characterized in that The concentration of the GO suspension is 0.5-10 mg / mL; the mass ratio of ascorbic acid to the GO suspension is 10:1-1:1; the reaction temperature of Reaction 1 is 80-95 °C, and the reaction time is 0.5-4 h.

3. The preparation method of the rGO / Schiffbase aerogel according to claim 1, wherein The freeze-thawing specifically is: freeze at -20 to -80 °C for 30 min, and then thaw to room temperature; the reduction specifically is: reduce the p-rGO hydrogel after freeze-thawing at 95 °C for 2-24 h.

4. The preparation method of the rGO / Schiffbase aerogel according to claim 1, characterized in that, The amino siloxane is 3-aminopropyltriethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, or N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane; the molar ratio of amino functional groups to aldehyde functional groups in terephthalaldehyde, p-phenylenediamine, and amino siloxane is 1:1; the temperature of Reaction 2 is 20-70 °C, and the time is 0.5-8 h.

5. The preparation method of the rGO / Schiffbase aerogel according to claim 1, characterized in that, The alkoxysilane is methyltrimethoxysilane or vinyltriethoxysilane; the molar ratio of the alkoxysilane to terephthalaldehyde is 0.1:1-10:1; the standing time is 6-12 h.

6. The preparation method of the rGO / Schiffbase aerogel according to claim 1, characterized in that, The volume ratio of ethanol to water is 1:1-9:

1.

7. The preparation method of the rGO / Schiffbase aerogel according to claim 1, wherein The parameters for aging are set as: water bath aging at 40-80 °C for 4-24 h.

8. An rGO / Schiffbase aerogel prepared by the preparation method according to any one of claims 1-7.

9. An application of the rGO / Schiffbase aerogel according to claim 8 in the preparation of wave-absorbing materials.

10. An electromagnetic wave absorbing material, characterized in that, The raw materials include the rGO / Schiffbase aerogel according to claim 8.

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