A graphene aerogel surface wave-absorbing material loaded with Fe / N co-doped hollow carbon nanospheres and a preparation method thereof

Abstract

This invention discloses a graphene aerogel surface microwave absorbing material supported on Fe / N co-doped hollow carbon nanospheres and its preparation method. First, a reduced graphene oxide aerogel is prepared using graphene oxide as a raw material. Then, hollow Fe3O4 magnetic nanoparticles are prepared via a hydrothermal method using FeCl3·6H2O and ammonium acetate as raw materials. Finally, Fe3O4 / PPy / reduced graphene oxide aerogel is prepared by in-situ polymerization, and the graphene aerogel supported on Fe / N co-doped hollow carbon nanospheres is obtained through high-temperature heat treatment. The graphene aerogel surface microwave absorbing material supported on Fe / N co-doped hollow carbon nanospheres of this invention exhibits excellent dielectric and magnetic losses. Simultaneously, the magnetic Fe nanoparticles in the material can effectively convert electromagnetic wave energy, achieving excellent microwave absorption performance, and showing great potential in next-generation cutting-edge advanced nanocomposite materials.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres and its preparation method. Background Technology

[0002] With the development of the electronic communications industry, electromagnetic waves, as a fundamental means of wireless communication, are ubiquitous, leading to increasingly serious electromagnetic pollution problems. Furthermore, electromagnetic stealth technology in the military field, as an effective means of improving the survivability, penetration, and deep strike capabilities of weapon systems, has become a hot topic among major military powers in the competition for advanced military technologies. Therefore, electromagnetic wave absorbing materials are not only commonly used in the field of electromagnetic transmission and reception, but also crucial materials for achieving radar stealth capabilities in aircraft, warships, armored vehicles, and battlefield facilities.

[0003] It is gradually becoming a research hotspot in the field of functional materials.

[0004] Currently, the main electromagnetic wave absorbing materials available both domestically and internationally include iron-based, carbon-based, and ceramic-based materials. Among these, iron-based materials lose their magnetism and absorption performance at high temperatures, and their high density and poor corrosion resistance limit their application range. Ceramic-based materials are also heavy and not widely applicable. Carbon-based materials, with their advantages of light weight and good conductivity, have become the most widely used electromagnetic wave absorbing materials.

[0005] Among carbon-based microwave absorbing materials, 3D porous graphene aerogel microwave absorbing materials, composed of cross-linked graphene sheets, have proven to be a promising aerogel microwave absorbing material due to their low density, light weight, corrosion resistance, large specific surface area, and excellent conductivity. They can generate dielectric loss under high-frequency electromagnetic fields, thereby dissipating electromagnetic waves. However, due to their simple composition and lack of a polarization loss mechanism, their microwave absorption performance needs further improvement. By combining them with other materials, such as magnetic nanoparticles and polymer molecules, combining magnetic loss with dielectric loss, graphene aerogel microwave absorbing materials with excellent absorption performance can be obtained. Summary of the Invention

[0006] This invention provides a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres and its preparation method, with the aim of providing a high-performance microwave absorbing material to solve the problems brought about by electromagnetic wave applications.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres, comprising the following preparation process:

[0008] Step 1: Preparation of reduced graphene oxide aerogel: (1) Graphene oxide and reducing agent are dispersed in a mixed solution of deionized water and ethanol to carry out a reduction reaction to obtain reduced graphene oxide hydrogel; (2) The reduced graphene oxide hydrogel is placed in a freeze dryer for freeze drying to obtain reduced graphene oxide aerogel.

[0009] Step 2: Preparation of hollow Fe3O4 magnetic nanoparticles: (1) FeCl3·6H2O was dissolved in ethylene glycol and ultrasonically treated to form a transparent yellow solution. Then ammonium acetate was added to the transparent yellow solution and ultrasonically treated for 1 hour. (2) The transparent yellow solution was then transferred to a stainless steel autoclave lined with tetrafluoroethylene and heated at 200°C for 8 hours to obtain a black precipitate. The precipitate was then washed three times by centrifugation with ethanol and vacuum dried at 60°C to obtain hollow Fe3O4 nanoparticles.

[0010] Step 3: Preparation of Fe3O4 / PPy / reduced graphene oxide aerogel: The reduced graphene oxide aerogel was dispersed in deionized water and ultrasonically dispersed for 1 h; then hollow Fe3O4 nanoparticles were added and ultrasonically dispersed for 1 h. Pyrrole monomer (Py) was added dropwise under ultrasonic treatment, and then hydrochloric acid (1 mol / L) was added to make the dispersion acidic. Ultrasonic treatment was continued for 2 h to ensure that pyrrole completely covered the outer and inner surfaces of the hollow Fe3O4 nanospheres. After the reaction was completed, the mixture was cooled to room temperature, and the product was washed three times by centrifugation with ethanol and dried in a vacuum oven at 60 °C for 12 h to obtain Fe3O4 / PPy / reduced graphene oxide aerogel.

[0011] Step 4: Preparation of Fe / N co-doped hollow carbon nanospheres graphene aerogel: The Fe3O4 / PPy / reduced graphene oxide aerogel prepared in step 3 was placed in a tube furnace for heat treatment. During the heat treatment process, Fe / N co-doped hollow carbon nanospheres graphene aerogel was obtained.

[0012] Furthermore, in step 1, the volume ratio of deionized water to ethanol in the mixed solution is 3:1 to 5:1.

[0013] Furthermore, in step 1, the reducing agent is one or more of sodium bisulfite, ascorbic acid, thiourea, sodium sulfide, and hydrazine hydrate, and the mass ratio of graphene oxide to the reducing agent is 1:1 to 1:6.

[0014] Furthermore, in step 1, the reduction reaction is carried out at a temperature controlled between 80°C and 100°C, and the reaction time is controlled between 6 hours and 12 hours.

[0015] Furthermore, in step 1, the freeze-drying process involves a freezing temperature of -20℃ to -100℃ and a freeze-drying time of 5h to 48h.

[0016] Furthermore, in step 2, the mass ratio of FeCl3·6H2O to ammonium acetate is 1:2 to 1:5.

[0017] Furthermore, in step 3, the mass ratio of reduced graphene oxide aerogel, hollow Fe3O4 nanoparticles, and pyrrole monomer (Py) is 100:(5-10):(5-10).

[0018] Furthermore, the heat treatment conditions in step 4 are as follows: under inert gas protection, the temperature is raised to 600℃~800℃, and the heat treatment time is 4h~6h.

[0019] Furthermore, the inert gas is one of nitrogen, argon, and radon.

[0020] The present invention also provides a graphene aerogel surface absorbing material loaded with Fe / N co-doped hollow carbon nanospheres prepared by the above preparation method.

[0021] It should be noted that excellent microwave absorption performance can be obtained by combining the effects of dielectric loss, magnetic loss, and energy conversion of specific nanostructures. The magnetism of nano-iron has a significant impact on magnetic loss, thus enhancing microwave absorption capability. Simultaneously, the synergistic effect of the core / shell structure combined with 0D and 3D nanostructures significantly improves interfacial polarization and enhances dielectric loss. This is because the doping of Fe / N atoms provides more active sites for the transport of charge carriers (space charge) in specific and directional paths. After microwaves penetrate different interfaces, the electromagnetic wave energy is converted into heat energy due to the synergistic effect of conductivity loss, interfacial polarization, dipole polarization, and multiple resonance behavior.

[0022] The graphene aerogel surface microwave absorbing material supported on Fe / N co-doped hollow carbon nanospheres and its preparation method provided by this invention have the following outstanding features and beneficial effects compared with the prior art:

[0023] (1) The graphene aerogel has an interconnected three-dimensional network structure inside. This porous structure can improve the impedance matching between the material and the air, which is beneficial to enhance the dielectric loss of the material to electromagnetic waves.

[0024] (2) The microwave absorbing material of the present invention uses graphene aerogel as a carrier and loads Fe / N co-doped hollow carbon nanospheres through in-situ polymerization reaction. N atoms are introduced into the carbon skeleton structure, which increases the active sites of the structure, makes the charge distribution uneven, which is conducive to generating polarization and improving the dielectric loss capability of the material. At the same time, magnetic Fe nanoparticles are introduced as the main material for magnetic loss. While improving the magnetic loss capability of electromagnetic waves, impedance matching characteristics are also taken into account, resulting in stronger absorption loss and wider effective absorption bandwidth.

[0025] (3) The graphene aerogel surface absorbing material loaded with Fe / N co-doped hollow carbon nanospheres prepared in this invention has excellent properties such as high efficiency, wide bandwidth, ultralight weight and high strength compared with traditional absorbing materials. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The graphene aerosolization supported on Fe / N co-doped hollow carbon nanospheres of the present invention

[0028] Figure label:

[0029] 1. Graphene aerogel main structure; 2. Fe / N co-doped hollow carbon nanospheres; 3. Hollow Fe structure in the inner layer of the nanospheres; 4. N co-doped hollow carbon nanospheres in the outer layer of the nanospheres. Detailed Implementation

[0030] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the invention to the following examples. Various substitutions or modifications made based on ordinary technical knowledge and conventional methods in the art without departing from the above-described methodological spirit of the invention should be included within the scope of the invention.

[0031] Example 1

[0032] This invention provides a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres, comprising the following preparation process:

[0033] Step 1: Preparation of reduced graphene oxide aerogel: (1) Graphene oxide and ascorbic acid reducing agent are dispersed in a mass ratio of 1:1 in a mixed solution of deionized water and ethanol for reduction reaction. The temperature of the reduction reaction is 80℃ and the reaction time is 12h to obtain reduced graphene oxide hydrogel. The volume ratio of deionized water and ethanol is 3:1 and the concentration of the hydrogel is 5mg / mL. (2) The reduced graphene oxide hydrogel is placed in a freeze dryer and freeze-dried at -20℃ for 48h to obtain reduced graphene oxide aerogel.

[0034] Step 2: Preparation of hollow Fe3O4 magnetic nanoparticles: (1) FeCl3·6H2O was dissolved in ethylene glycol and ultrasonically treated to form a transparent yellow solution. Then ammonium acetate was added to the transparent yellow solution and ultrasonically treated continuously for 1 h. The mass ratio of FeCl3·6H2O to ammonium acetate was 1:2. (2) The transparent yellow solution was then transferred to a stainless steel autoclave lined with tetrafluoroethylene and heated at 200°C for 8 hours to obtain a black precipitate. The precipitate was then washed three times by centrifugation with ethanol and vacuum dried at 60°C to obtain hollow Fe3O4 nanoparticles.

[0035] Step 3: Preparation of Fe3O4 / PPy / reduced graphene oxide aerogel: The reduced graphene oxide aerogel was dispersed in deionized water and ultrasonically dispersed for 1 h; then hollow Fe3O4 nanoparticles were added, and ultrasonically dispersed for 1 h. Pyrrole monomer (Py) was then added dropwise under ultrasonic treatment, followed by the addition of hydrochloric acid (1 mol / L) to make the dispersion acidic. Ultrasonic treatment was continued for 2 h to ensure that the pyrrole monomer (Py) completely covered the outer and inner surfaces of the hollow Fe3O4 nanospheres. After the reaction was completed, the mixture was cooled to room temperature, and the product was washed three times by centrifugation with ethanol. It was then dried in a vacuum oven at 60 °C for 12 h to obtain Fe3O4 / PPy / reduced graphene oxide aerogel. The mass ratio of the reduced graphene oxide aerogel, hollow Fe3O4 nanoparticles, and pyrrole monomer (Py) was 100:5:10.

[0036] Step 4: Preparation of Fe / N co-doped hollow carbon nanospheres graphene aerogel: The Fe3O4 / PPy / reduced graphene oxide aerogel prepared in Step 3 was placed in a tube furnace, protected with nitrogen gas, and heated to 600℃ for 6 hours. During the heat treatment, Fe / N co-doped hollow carbon nanospheres graphene aerogel was obtained, with the structure as shown in the figure. Figure 1 As shown.

[0037] The prepared Fe / N co-doped hollow carbon nanosphere graphene aerogel absorbing material was prepared by immersing aerogel slices in molten paraffin using an impregnation method. After cooling and solidification, the aerogel was removed and cut into standard dimensions required for coaxial method testing using a mold: inner diameter 3.04 mm, outer diameter 7.0 mm, and thickness 1 mm to 5 mm. Parameters were measured in the frequency range of 2 GHz to 18 GHz using a vector network analyzer (VNA, Agilent N5224A). The sample prepared in this embodiment exhibited an effective absorption bandwidth (RL < -10 dB) of 12.1 GHz at a thickness of 3 mm, and a minimum reflectivity of -33.8 dB at 11.9 GHz.

[0038] Example 2

[0039] This invention provides a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres, comprising the following preparation process:

[0040] Step 1: Preparation of reduced graphene oxide aerogel: (1) Graphene oxide and sodium bisulfite reducing agent are dispersed in a mass ratio of 1:3 in a mixed solution of deionized water and ethanol for reduction reaction. The temperature of the reduction reaction is 90℃ and the reaction time is 9h to obtain reduced graphene oxide hydrogel. The volume ratio of deionized water and ethanol is 4:1 and the concentration of the hydrogel is 10mg / mL. (2) The reduced graphene oxide hydrogel is placed in a freeze dryer and freeze-dried at -60℃ for 24h to obtain reduced graphene oxide aerogel.

[0041] Step 2: Preparation of hollow Fe3O4 magnetic nanoparticles: (1) FeCl3·6H2O was dissolved in ethylene glycol and ultrasonically treated to form a transparent yellow solution. Then ammonium acetate was added to the transparent yellow solution and ultrasonically treated continuously for 1 h. The mass ratio of FeCl3·6H2O to ammonium acetate was 1:3. (2) The transparent yellow solution was then transferred to a stainless steel autoclave lined with tetrafluoroethylene and heated at 200°C for 8 hours to obtain a black precipitate. The precipitate was then washed three times by centrifugation with ethanol and vacuum dried at 60°C to obtain hollow Fe3O4 nanoparticles.

[0042] Step 3: Preparation of Fe3O4 / PPy / reduced graphene oxide aerogel: The reduced graphene oxide aerogel was dispersed in deionized water and ultrasonically dispersed for 1 h; then hollow Fe3O4 nanoparticles were added, and after ultrasonic dispersion for h, pyrrole monomer (Py) was added dropwise under ultrasonic treatment, and then hydrochloric acid (1 mol / L) was added to make the dispersion acidic. Ultrasonic treatment was continued for 2 h to ensure that the pyrrole monomer (Py) completely covered the outer and inner surfaces of the hollow Fe3O4 nanospheres. After the reaction was completed, the mixture was cooled to room temperature, and the product was washed three times by centrifugation with ethanol and dried in a vacuum oven at 60 °C for 12 h to obtain Fe3O4 / PPy / reduced graphene oxide aerogel. The mass ratio of the reduced graphene oxide aerogel, hollow Fe3O4 nanoparticles and pyrrole monomer (Py) was 100:10:5.

[0043] Step 4: Preparation of Fe / N co-doped hollow carbon nanospheres graphene aerogel: The Fe3O4 / PPy / reduced graphene oxide aerogel prepared in Step 3 was placed in a tube furnace, protected with argon gas, and heated to 700℃ for 5 hours. During the heat treatment, Fe / N co-doped hollow carbon nanospheres graphene aerogel was obtained, with the structure as shown in the figure. Figure 1 As shown.

[0044] The prepared Fe / N co-doped hollow carbon nanosphere graphene aerogel absorbing material was prepared by immersing aerogel slices in molten paraffin using an impregnation method. After cooling and solidification, the aerogel was removed and cut into standard dimensions required for coaxial method testing using a mold: inner diameter 3.04 mm, outer diameter 7.0 mm, and thickness 1 mm to 5 mm. Parameters were measured in the frequency range of 2 GHz to 18 GHz using a vector network analyzer (VNA, Agilent N5224A). The sample prepared in this embodiment exhibited an effective absorption bandwidth (RL < -10 dB) of 13.9 GHz at a thickness of 2 mm, and a minimum reflectivity of -39.6 dB at 12.4 GHz.

[0045] Example 3

[0046] This invention provides a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres, comprising the following preparation process:

[0047] Step 1: Preparation of reduced graphene oxide aerogel: (1) Graphene oxide and hydrazine hydrate reducing agent were dispersed in a mixed solution of deionized water and ethanol at a mass ratio of 1:6 for reduction reaction. The temperature of the reduction reaction was 100℃ and the reaction time was 6h to obtain reduced graphene oxide hydrogel, wherein the volume ratio of deionized water and ethanol was 5:1 and the concentration of the hydrogel was 5mg / mL; (2) The reduced graphene oxide hydrogel was placed in a freeze dryer and freeze-dried at -100℃ for 5h to obtain reduced graphene oxide aerogel, the structure of which is as follows. Figure 1 As shown.

[0048] Step 2: Preparation of hollow Fe3O4 magnetic nanoparticles: (1) FeCl3·6H2O was dissolved in ethylene glycol and ultrasonically treated to form a transparent yellow solution. Then ammonium acetate was added to the transparent yellow solution and ultrasonically treated for 1 hour. The mass ratio of FeCl3·6H2O to ammonium acetate was 1:5. (2) The transparent yellow solution was then transferred to a stainless steel autoclave lined with tetrafluoroethylene and heated at 200°C for 8 hours to obtain a black precipitate. The precipitate was then washed three times by centrifugation with ethanol and vacuum dried at 60°C to obtain hollow Fe3O4 nanoparticles.

[0049] Step 3: Preparation of Fe3O4 / PPy / reduced graphene oxide aerogel: The reduced graphene oxide aerogel was dispersed in deionized water and ultrasonically dispersed for 1 h; then hollow Fe3O4 nanoparticles were added, and ultrasonically dispersed for 1 h. Pyrrole monomer (Py) was then added dropwise under ultrasonic treatment, followed by the addition of hydrochloric acid (1 mol / L) to make the dispersion acidic. Ultrasonic treatment was continued for 2 h to ensure that the pyrrole monomer (Py) completely covered the outer and inner surfaces of the hollow Fe3O4 nanospheres. After the reaction was completed, the mixture was cooled to room temperature, and the product was washed three times by centrifugation with ethanol. It was then dried in a vacuum oven at 60 °C for 12 h to obtain Fe3O4 / PPy / reduced graphene oxide aerogel. The mass ratio of the reduced graphene oxide aerogel, hollow Fe3O4 nanoparticles, and pyrrole monomer (Py) was 100:10:10.

[0050] Step 4: Preparation of Fe / N co-doped hollow carbon nanospheres graphene aerogel: The Fe3O4 / PPy / reduced graphene oxide aerogel prepared in step 3 was placed in a tube furnace, protected by nitrogen gas, and heated to 800℃ for 4 hours. During the heat treatment, Fe / N co-doped hollow carbon nanospheres graphene aerogel was obtained.

[0051] The prepared Fe / N co-doped hollow carbon nanosphere graphene aerogel absorbing material was prepared by immersing aerogel slices in molten paraffin using an impregnation method. After cooling and solidification, the aerogel was removed and cut into standard dimensions required for coaxial method testing using a mold: inner diameter 3.04 mm, outer diameter 7.0 mm, and thickness 1 mm to 5 mm. Parameters were measured in the frequency range of 2 GHz to 18 GHz using a vector network analyzer (VNA, Agilent N5224A). The sample prepared in this embodiment exhibited an effective absorption bandwidth (RL < -10 dB) of 14.1 GHz at a thickness of 2 mm, and a minimum reflectivity of -41.9 dB at 13.8 GHz.

[0052] Comparative Example

[0053] This comparative example is the reduced graphene oxide aerogel prepared in step 1 of Example 1.

[0054] The prepared graphene aerogel absorbing material was prepared by immersing aerogel slices in molten paraffin wax using an impregnation method. After cooling and solidification, the aerogel was removed and cut into standard dimensions required for coaxial testing using a mold: inner diameter 3.04 mm, outer diameter 7.0 mm, and thickness 1 mm to 5 mm. Parameters were measured in the frequency range of 2 GHz to 18 GHz using a vector network analyzer (VNA, Agilent N5224A). The sample prepared in this embodiment exhibited an effective absorption bandwidth (RL < -10 dB) of 9.3 GHz at a thickness of 2 mm, and a minimum reflectivity of -16.6 dB at 11.7 GHz.

[0055] In summary, the Fe / N co-doped hollow carbon nanosphere-based graphene aerogel surface absorbing material of this invention achieves excellent microwave absorption performance by combining the effects of dielectric loss, magnetic loss, and energy conversion of specific nanostructures. The magnetism of the nano-iron significantly influences magnetic loss, enhancing microwave absorption capability. Simultaneously, the synergistic effect of the core / shell structure with 0D and 3D nanostructures significantly improves interfacial polarization and enhances dielectric loss. Because the doping of Fe / N atoms provides more active sites for the transport of charge carriers (space charge) in specific and directional paths, microwaves, after penetrating different interfaces, convert electromagnetic wave energy into heat energy due to the synergistic effect of conductivity loss, interfacial polarization, dipole polarization, and multiple resonance behavior. Compared to the prepared simple reduced graphene oxide aerogel material, the Fe / N co-doped hollow carbon nanosphere-based graphene aerogel of this invention exhibits significantly improved microwave absorption performance.

[0056] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres, characterized in that, The preparation process includes the following: Step 1: Preparation of reduced graphene oxide aerogel: (1) Graphene oxide and reducing agent are dispersed in a mixed solution of deionized water and ethanol to carry out a reduction reaction to obtain reduced graphene oxide hydrogel; (2) The reduced graphene oxide hydrogel is placed in a freeze dryer for freeze drying to obtain reduced graphene oxide aerogel. Step 2: Preparation of hollow Fe3O4 magnetic nanoparticles: (1) FeCl3·6H2O was dissolved in ethylene glycol and ultrasonically treated to form a transparent yellow solution. Then ammonium acetate was added to the transparent yellow solution and ultrasonically treated for 1 hour. (2) The transparent yellow solution was then transferred to a stainless steel autoclave lined with tetrafluoroethylene and heated at 200°C for 8 hours to obtain a black precipitate. The precipitate was then washed three times by centrifugation with ethanol and vacuum dried at 60°C to obtain hollow Fe3O4 nanoparticles. The mass ratio of FeCl3·6H2O to ammonium acetate was 1:2 to 1:

5. Step 3: Preparation of Fe3O4 / PPy / reduced graphene oxide aerogel: The reduced graphene oxide aerogel was dispersed in deionized water and ultrasonically dispersed for 1 h; then hollow Fe3O4 nanoparticles were added and ultrasonically dispersed for 1 h. Pyrrole monomer Py was then added dropwise under ultrasonic treatment, followed by the addition of 1 mol / L hydrochloric acid to make the dispersion acidic. Ultrasonic treatment continued for 2 h to ensure that pyrrole completely covered the outer and inner surfaces of the hollow Fe3O4 nanospheres. After the reaction was completed, the mixture was cooled to room temperature, and the product was washed three times by centrifugation with ethanol and dried in a vacuum oven at 60 °C for 12 h to obtain Fe3O4 / PPy / reduced graphene oxide aerogel. The mass ratio of reduced graphene oxide aerogel, hollow Fe3O4 nanoparticles, and pyrrole monomer Py was 100:(5~10):(5~10). Step 4: Preparation of Fe / N co-doped hollow carbon nanospheres graphene aerogel: The Fe3O4 / PPy / reduced graphene oxide aerogel prepared in step 3 was placed in a tube furnace for heat treatment. During the heat treatment process, Fe / N co-doped hollow carbon nanospheres graphene aerogel was obtained.

2. The method for preparing the graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres according to claim 1, characterized in that, In step 1, the volume ratio of deionized water to ethanol in the mixed solution is 3:1 to 5:

1.

3. The method for preparing the graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres according to claim 1, characterized in that, In step 1, the reducing agent is one or more of sodium bisulfite, ascorbic acid, thiourea, sodium sulfide, and hydrazine hydrate, and the mass ratio of graphene oxide to the reducing agent is 1:1 to 1:

6.

4. The method for preparing the graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres according to claim 1, characterized in that, In step 1, the reduction reaction is carried out at a temperature controlled between 80°C and 100°C, and for a time controlled between 6 hours and 12 hours.

5. The method for preparing the graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres according to claim 1, characterized in that, In step 1, the freeze-drying process involves a freezing temperature of -20℃ to -100℃ and a freeze-drying time of 5h to 48h.

6. The method for preparing the graphene aerogel surface microwave absorbing material supported on Fe / N co-doped hollow carbon nanospheres according to claim 1, characterized in that, The heat treatment conditions in step 4 are as follows: under inert gas protection, the temperature is raised to 600℃~800℃, and the heat treatment time is 4h~6h.

7. The method for preparing the graphene aerogel surface microwave absorbing material loaded with Fe / N co-doped hollow carbon nanospheres according to claim 6, characterized in that, The inert gas is one of nitrogen, argon, or radon.

8. A graphene aerogel surface absorbing material loaded with Fe / N co-doped hollow carbon nanospheres prepared by the preparation method according to any one of claims 1 to 7.

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