Lightweight and efficient three-dimensional graphene-based composite wave-absorbing material and preparation method thereof

Abstract

The invention discloses a lightweight and efficient three-dimensional graphene-based composite wave-absorbing material and a preparation method thereof, and relates to the technical field of microwave absorbing materials, the composite wave-absorbing material comprises reduced graphene oxide, nickel nanoparticles and in-situ growth carbon nanofibers, the nickel nanoparticles are attached to the reduced graphene oxide, and the carbon nanofibers are attached to the reduced graphene oxide. The reduced graphene oxide and the nickel nanoparticles are coated with the in-situ grown carbon nanofibers to form a three-dimensional heterostructure, and the nickel nanoparticles are used for catalyzing the growth of the carbon nanofibers on the reduced graphene oxide. The wave-absorbing material is set to be of a nickel-catalyzed carbon nanofiber-coated reduced graphene oxide (rGO-coated Ni-CNF) three-dimensional heterostructure, so that the purpose of improving the wave-absorbing capacity on the premise of ensuring the light weight of the material is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing materials, and in particular to a lightweight and efficient three-dimensional graphene-based composite absorbing material and a preparation method thereof. Background Art

[0002] With the large-scale application of technologies such as 5G communications and the Internet of Things, electromagnetic pollution caused by the surge in wireless communication devices has become a major issue hindering the development of the information society. The disordered radiation of high-frequency electromagnetic waves in space not only interferes with the operation of precision electronic equipment but also poses a potential threat to human health. In this context, the development of new electromagnetic wave absorbers that combine broadband adaptability, strong loss characteristics, and environmental tolerance has become a key breakthrough in resolving the challenge of electromagnetic compatibility. These new materials must not only possess efficient electromagnetic wave absorption capabilities but also meet the complex requirements of different frequency bands and environments, exhibiting excellent stability, mechanical strength, and processability. Ideal absorbers must achieve dual control over the electromagnetic wave propagation path: first, by optimizing impedance matching (reflection loss RL < -10dB), the reflectivity of the incident wave is reduced, allowing more electromagnetic waves to enter the material; second, through dielectric / magnetic loss mechanisms, the electromagnetic energy is efficiently converted into heat (transmission loss TL < -20dB).

[0003] Traditional absorbers such as ferrite (narrow frequency response), carbon black (high percolation threshold), and metal powders (easy to oxidize and deactivate) are limited by their intrinsic properties and are unable to meet the core requirements of modern electronic devices for absorbers: light, thin, wide, and strong. Current research focuses on constructing multiscale heterogeneous structures. By synergistically optimizing impedance gradient distribution and multiple loss paths through component design and microstructural manipulation, this approach overcomes the performance bottleneck of traditional materials in the 2-18 GHz frequency band. This provides important theoretical support for the development of a new generation of intelligent absorbers. Summary of the Invention

[0004] The purpose of the present invention is to provide a lightweight and efficient three-dimensional graphene-based composite absorbing material and a preparation method thereof, so as to solve the problem in the prior art that electromagnetic wave absorbers cannot simultaneously take into account lightweight, absorption strength and wide bandwidth.

[0005] First, an embodiment of the present invention provides a lightweight and efficient three-dimensional graphene-based composite absorbing material, comprising reduced graphene oxide, nickel nanoparticles, and in-situ grown carbon nanofibers, wherein the nickel nanoparticles are attached to the reduced graphene oxide, and the in-situ grown carbon nanofibers coat the reduced graphene oxide and the nickel nanoparticles to form a three-dimensional heterogeneous structure, and the nickel nanoparticles are used to catalyze the growth of carbon nanofibers on the reduced graphene oxide.

[0006] As an optional embodiment, a material is synthesized from a substrate, a nickel source, a precipitant and a carbon source as raw materials, wherein the substrate comprises graphene oxide, the nickel source comprises NiSO4·6H2O, the precipitant comprises NaOH, and the carbon source comprises ethanol.

[0007] As an optional embodiment, the ratio of graphene oxide, NiSO4•6H2O and NaOH is 0.5g: xmM: xmM, wherein 0 <x<8。

[0008] In order to better solve the above problems, an embodiment of the present invention further provides a method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material, comprising the following steps: S1: Prepare graphene oxide dispersion, NiSO4 solution and NaOH solution using deionized water as solvent; S2: adding NiSO4 solution to the graphene oxide dispersion, mixing, and then adding NaOH solution to obtain a solid product; S3: washing, freeze-drying and grinding the solid product in sequence to obtain graphene oxide precursor powder GO@Ni(OH)2 attached with nickel hydroxide; S4: placing the precursor powder in a CVD tube furnace and heating it in a nitrogen flow environment to reduce GO to rGO and convert NiOH to NiO to form rGO@NiO; S5: Ethanol was introduced into the CVD tube furnace by nitrogen bubbling to obtain rGO@Ni-CNF.

[0009] As an optional embodiment, the concentration of the graphene oxide dispersion is 8 to 12 mg / mL.

[0010] As an optional embodiment, the cleaning method in S3 includes washing with deionized water and anhydrous ethanol alternately until the supernatant becomes colorless.

[0011] As an optional implementation, the gas flow rate of the nitrogen gas in S4 is 50-70 sccm.

[0012] As an optional embodiment, the temperature of the heating reaction in S4 is 600-700° C., and the reaction time is 25-35 min.

[0013] As an optional implementation, the flow rate of nitrogen in S5 is 80-90 sccm.

[0014] As an optional embodiment, the reaction temperature in S5 is 600-700° C., and the reaction time is 1.5-2 h.

[0015] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects: 1. The composite absorbing material of the embodiment of the present invention is a three-dimensional heterostructure of nickel-catalyzed carbon nanofiber-coated reduced graphene oxide (rGO@Ni-CNF). This material is not only lightweight but also has strong absorbing ability.

[0016] 2. The lightweight and efficient three-dimensional graphene-based composite absorbing material and its preparation method provided by the embodiment of the present invention are prepared by using a co-precipitation method to prepare the precursor, Ni 2+ The NiO is anchored on the surface of graphene oxide by exchanging with oxygen-containing functional groups, and then NaOH is added to trigger the Ni 2+ With OH - The reaction occurs, and in situ nucleation forms tightly pinned and uniformly dispersed Ni(OH)2 nanoparticles. After centrifugation, freeze-drying and grinding, GO@Ni(OH)2 precursor powder is obtained. Next, the precursor is heated in a CVD furnace. GO is reduced to rGO by losing oxygen groups, and Ni(OH)2 is dehydrated and converted into NiO. Ethanol vapor, as a carbon source, can effectively reduce NiO to Ni within a specific temperature range and decompose to generate CNF under the catalysis of Ni, forming a three-dimensional heterogeneous network structure of rGO@Ni-CNF. This method is simple, efficient, low-cost, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 is the SEM image of reduced graphene oxide in Comparative Example 1; Figure 2 is the X-ray diffraction pattern (XRD) of the material; Figure 3 is the Raman map of the material; Figure 4 is the reflection loss diagram of the sample in Comparative Example 1; Figure 5 This is a comparison chart of the effective absorption bandwidth of materials; Figure 6 This is a comparison chart of the minimum reflection loss of materials; Figure 7 is the SEM image of Example 1, wherein Figure 7 a is the SEM image of rGNO-2, Figure 7 b is the SEM image of rGNC-2; Figure 8 is the particle size distribution diagram of NiO nanoparticles of rGNO-2 in Example 1; Figure 9 is the reflection loss diagram of the sample in Example 1; Figure 10 is the SEM image of Example 2, wherein Figure 10 a is the SEM image of rGNO-5, Figure 10 b is the SEM image of rGNC-5; Figure 11 is the particle size distribution diagram of NiO nanoparticles of rGNO-5 in Example 2; Figure 12 is the reflection loss diagram of the sample in Example 2; Figure 13 It is the SEM picture of comparative example 2, wherein Figure 13 a is the SEM image of rGNO-8, Figure 13 b is the SEM image of rGNC-8; Figure 14 is the particle size distribution diagram of NiO nanoparticles of rGNO-8 in Comparative Example 2; Figure 15 is the reflection loss diagram of the sample in Comparative Example 2; Figure 16 This is a diagram showing the full-frequency absorption effect of rGNC-5 in Example 2; Figure 17 This is the CST far-field simulation result of the rGNC-5 sample in Example 2; Figure 18 2D graph of the bistatic scattering cross-section at different angles of the CST simulation of the rGNC-5 sample in Example 2.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0022] In the description of the present invention, it should be noted that the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0023] Example The present invention provides a lightweight and efficient three-dimensional graphene-based composite absorbing material and a preparation method thereof, including the following contents: The absorber is composed of reduced graphene oxide (rGO), nickel nanoparticles, and in-situ grown carbon nanofibers (CNFs). Graphene oxide (GO) serves as the substrate, NiSO₄•6H₂O as the nickel source, NaOH as the precipitant, and ethanol as the carbon source to synthesize a nickel-catalyzed three-dimensional heterostructure of reduced graphene oxide-coated carbon nanofibers (rGO@Ni-CNF).

[0024] The preparation method of the above-mentioned rGO@Ni-CNF three-dimensional heterostructure includes the following steps: Step 1: Using graphene oxide, NiSO4•6H2O, and NaOH as raw materials, prepare 50 mL of 10 mg / mL graphene oxide dispersion, 20 mL of 0.05xmol / L NiSO4 solution, and 20 mL of 0.05xmol / L NaOH solution according to the ratio of 0.5 g: xmM: xmM, where 0 <x<8; Step 2: NiSO₄ solution was slowly added to the graphene oxide dispersion. The mixture was magnetically stirred for 6 hours and sonicated for 10 minutes to ensure homogeneity. NaOH solution was then slowly added to the stirring mixture, and stirring was continued for another 6 hours. The resulting product was washed alternately with deionized water and anhydrous ethanol until the supernatant became colorless. Finally, the sample was freeze-dried and ground into a fine powder to obtain graphene oxide precursor powder attached with nickel hydroxide (GO@Ni(OH)₂). Step 3: 0.1 g of the precursor powder was placed in a CVD tube furnace and heated to 650°C under a nitrogen flow (60 sccm) for 30 minutes to reduce GO to rGO and convert NiOH to NiO, forming rGO@NiO, denoted as rGNO-x. Ethanol was then introduced by bubbling nitrogen (85 sccm) and reacted at 650°C for 2 hours to obtain rGO@Ni-CNF, denoted as rGNC-x.

[0025] Comparative Example 1: A method for preparing a graphene-based composite absorbing material is provided, comprising the following steps: Step 1: Using graphene oxide, NiSO4•6H2O, and NaOH as raw materials, prepare 50 mL of 10 mg / mL graphene oxide dispersion, 20 mL of 0.05x mol / L NiSO4 solution, and 20 mL of 0.05x mol / L NaOH solution in a ratio of 0.5 g: x mM: x mM, respectively; take x = 0; Step 2: The graphene oxide dispersion was magnetically stirred for 6 hours and sonicated for 10 minutes to ensure homogeneity. Stirring was continued for an additional 6 hours. The resulting product was washed alternately with deionized water and anhydrous ethanol until the supernatant became colorless. Finally, the sample was freeze-dried and ground into a fine powder to obtain the graphene oxide precursor powder. Step 3: 0.1 g of the precursor powder was placed in a CVD tube furnace and heated to 650 °C for 30 min under a nitrogen flow (60 sccm) to reduce GO to rGO. Example 1: Provided is a lightweight and efficient three-dimensional graphene-based composite absorbing material and a preparation method thereof, comprising the following steps: Step 1: Using graphene oxide, NiSO4•6H2O, and NaOH as raw materials, prepare 50 mL of a 10 mg / mL graphene oxide dispersion, 20 mL of a 0.05x mol / L NiSO4 solution, and 20 mL of a 0.05x mol / L NaOH solution in a ratio of 0.5 g: x mM: x mM, respectively; where x = 2; Step 2: NiSO₄ solution was slowly added to the graphene oxide dispersion. The mixture was magnetically stirred for 6 hours and sonicated for 10 minutes to ensure homogeneity. NaOH solution was then slowly added to the stirring mixture, and stirring was continued for another 6 hours. The resulting product was washed alternately with deionized water and anhydrous ethanol until the supernatant became colorless. Finally, the sample was freeze-dried and ground into a fine powder to obtain a graphene oxide composite powder attached with nickel hydroxide (GO@Ni(OH)₂). Step 3: 0.1 g of the precursor powder was placed in a CVD tube furnace and heated to 650°C under a nitrogen flow (60 sccm) for 30 minutes to reduce GO to rGO and convert NiOH to NiO, forming rGO@NiO, designated as rGNO-2. Ethanol was then introduced by bubbling nitrogen (85 sccm) and reacted at 650°C for 2 hours to obtain rGO@Ni-CNF, designated as rGNC-2.

[0026] Example 2: Provided is a lightweight and efficient three-dimensional graphene-based composite absorbing material and a preparation method thereof, comprising the following steps: Step 1: Using graphene oxide, NiSO4•6H2O, and NaOH as raw materials, prepare 50 mL of 10 mg / mL graphene oxide dispersion, 20 mL of 0.05x mol / L NiSO4 solution, and 20 mL of 0.05x mol / L NaOH solution in a ratio of 0.5 g: x mM: x mM, respectively; take x = 5; Step 2: NiSO₄ solution was slowly added to the graphene oxide dispersion. The mixture was magnetically stirred for 6 hours and sonicated for 10 minutes to ensure homogeneity. NaOH solution was then slowly added to the stirring mixture, and stirring was continued for another 6 hours. The resulting product was washed alternately with deionized water and anhydrous ethanol until the supernatant became colorless. Finally, the sample was freeze-dried and ground into a fine powder to obtain a graphene oxide composite powder attached with nickel hydroxide (GO@Ni(OH)₂). Step 3: 0.1 g of the precursor powder was placed in a CVD tube furnace and heated to 650°C under a nitrogen flow (60 sccm) for 30 minutes to reduce GO to rGO and convert NiOH to NiO, forming rGO@NiO, designated rGNO-5. Ethanol was then introduced by bubbling nitrogen (85 sccm) and reacted at 650°C for 2 hours to obtain rGO@Ni-CNF, designated rGNC-5.

[0027] Comparative Example 2: A method for preparing a graphene-based composite absorbing material is provided, comprising the following steps: Step 1: Using graphene oxide, NiSO4•6H2O, and NaOH as raw materials, prepare 50 mL of a 10 mg / mL graphene oxide dispersion, 20 mL of a 0.05x mol / L NiSO4 solution, and 20 mL of a 0.05x mol / L NaOH solution in a ratio of 0.5 g: x mM: x mM, respectively; where x = 8; Step 2: NiSO₄ solution was slowly added to the graphene oxide dispersion. The mixture was magnetically stirred for 6 hours and sonicated for 10 minutes to ensure homogeneity. NaOH solution was then slowly added to the stirring mixture, and stirring was continued for another 6 hours. The resulting product was washed alternately with deionized water and anhydrous ethanol until the supernatant became colorless. Finally, the sample was freeze-dried and ground into a fine powder to obtain a graphene oxide composite powder attached with nickel hydroxide (GO@Ni(OH)₂). Step 3: 0.1 g of the precursor powder was placed in a CVD tube furnace and heated to 650°C under a nitrogen flow (60 sccm) for 30 minutes to reduce GO to rGO and convert NiOH to NiO, forming rGO@NiO, designated rGNO-8. Ethanol was then introduced by bubbling nitrogen (85 sccm) and reacted at 650°C for 2 hours to obtain rGO@Ni-CNF, designated rGNC-8.

[0028] Testing Method: The samples prepared in Examples 1-2 and Comparative Examples 1-2 were mixed with paraffin wax at a mass fraction of 10 wt%. The mixture was then pressed into concentric rings (7 mm outer diameter, 3 mm inner diameter). The electromagnetic parameters of the samples were measured using a Ceyear 3672E vector network analyzer, and the microwave absorption properties were calculated based on these parameters.

[0029] Test results: Reference Figure 1 The pure rGO sample prepared in Example 1 did not stack and had thin sheets. Figure 2 It can be seen that there is only carbon element in the XRD results, without other impurities, such as Figure 3 It can be seen that the Raman results show that its graphitization degree is the highest. Figure 4 、 Figure 5 and Figure 6 It can be seen that its minimum reflection loss is -16.1dB (12.8GHz) and its maximum absorption bandwidth is 6.08GHz (12.8-18GHz).

[0030] Figure 7 The surface of the product prepared in Example 1 has sparsely grown carbon nanofibers. Figure 2 The XRD results show that there are only carbon and nickel elements, no other impurities, and the Raman results show that the degree of graphitization is the lowest. Figure 9 、 Figure 5 and Figure 6 As shown, the minimum reflection loss is -33.9dB (15.84GHz) and the maximum absorption bandwidth is 4.48GHz (12.4-16.88GHz).

[0031] like Figure 10 As shown, the carbon nanofibers on the surface of the product prepared in Example 2 grow densely, forming a three-dimensional porous network. Figure 2 The XRD results show only carbon and nickel elements, without other impurities. Figure 3 The Raman results show that its graphitization degree is second only to pure rGO. Figure 12 、 Figure 5 and Figure 6As shown in the figure, the minimum reflection loss is -53 dB (11.52 GHz) and the maximum absorption bandwidth is 4.66 GHz (11.74-16.4 GHz).

[0032] like Figure 13 As shown, the carbon nanofibers on the surface of the product prepared in Comparative Example 2 did not grow completely. Figure 2 The XRD results shown show only carbon and nickel elements, without other impurities. Figure 3 The Raman results shown show that its graphitization degree is lower than that of rGNC-5. Figure 15 、 Figure 5 and Figure 6 As shown in Figure 2, the minimum reflection loss is -34.9 dB (16.8 GHz) and the maximum absorption bandwidth is 6.08 GHz (11.44-17.52 GHz).

[0033] It can be seen that in Example 2, when x=5, the rGNC-5 sample prepared has the smallest reflection loss (-53dB) and a higher absorption bandwidth (4.66GHz), and the best comprehensive absorption effect, which confirms that Figure 10 b The carbon nanofibers form a three-dimensional porous network structure, which can effectively enhance the material's wave absorption performance. Figure 16 It shows that by adjusting the thickness of the sample, the full-frequency absorption effect of 2-18 GHz can be achieved. Figure 17 and Figure 18 The results show that the rGNC-5 sample has excellent radar cross section simulation performance and has good practical application potential.

[0034] In general, at a synthesis temperature of 650°C, the three-dimensional morphology of the rGO@Ni-CNF sample in the embodiment of the present invention shows obvious regularity as the amount of NiSO4•6H2O and NaOH added changes. Figure 1 As shown in Figure 2, when x = 0, the sample obtained is a thin, unstacked rGO sheet. Figure 7 and Figure 8 As shown in Figure 2, when x = 2, the average particle size of nickel oxide nanoparticles in rGNO-2 is the smallest, about 23 nm, the carbon nanofibers in rGNC-2 grow sparsely, and the surface of reduced graphene is not fully covered; Figure 10 and Figure 11 As shown in Figure 2, when x = 5, the average particle size of nickel oxide nanoparticles in rGNO-5 is about 27 nm, and carbon nanofibers in rGNC-5 grow densely, constructing a three-dimensional porous network on reduced graphene oxide; Figure 13 and Figure 14 As shown in the figure, when x = 8, the rGNO-8 nickel oxide nanoparticles are densely distributed and even agglomerated, which hinders the further growth of carbon nanofibers. Among them, in the study of the sample's absorption mechanism and performance, the electromagnetic loss performance was improved through the 3D interpenetrating network structure. Specifically, magnetic nickel introduced magnetic loss, while the coupling of CNFs and rGO formed a 3D conductive network, inducing multiple scattering of microwaves and interface polarization. Under the synergistic effect of multiple losses, the absorbing material achieved wide frequency and strong attenuation characteristics. Figure 16 and Figure 6 As shown in Figure 2, when x=5, the composite material exhibits excellent microwave absorption performance at a thickness of 2.4 mm, with a minimum reflection loss (RLmin) of -53 dB (11.52 GHz) and an effective absorption bandwidth (RL ≤ -10 dB) of 4.66 GHz (13.04-17.70 GHz) at a thickness of 2 mm. Figure 17 and Figure 18 As shown in Figure 2, electromagnetic simulation technology was used to analyze the radar cross section (RCS) characteristics of a sample absorbing coating. The coating was applied to a pure electric conductor (PEC) substrate measuring 200 mm x 200 mm and 0.17 mm thick, with a coating thickness of 2.4 mm. The operating frequency bandwidth was 11.52 GHz, and the electromagnetic wave was incident along the z-axis with a variable angle of incidence, θ. The simulation results show that the coating's RCS value remains stable, below -10 dB·m, over a wide range of incident angles (10°-90°). 2 , the minimum value reaches -50dB•m 2 Its performance far outperforms traditional graphene-based materials, and with a filler content of only 10 wt%, it enables a lightweight design. This multidimensional structural coupling method overcomes the limitations of materials with a single loss mechanism and provides an important basis for the development of next-generation lightweight, broadband, and highly efficient microwave absorption materials.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, improvements, and the like made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention. It should be noted that the structures or components illustrated in the accompanying drawings are not necessarily drawn to scale, and that descriptions of known components, processing techniques, and processes are omitted to avoid unnecessarily limiting the present invention.

Claims

1. A lightweight and efficient three-dimensional graphene-based composite absorbing material, characterized in that: The invention comprises reduced graphene oxide, nickel nanoparticles and in-situ grown carbon nanofibers, wherein the nickel nanoparticles are attached to the reduced graphene oxide, the in-situ grown carbon nanofibers cover the reduced graphene oxide and the nickel nanoparticles to form a three-dimensional heterogeneous structure, and the nickel nanoparticles are used to catalyze the growth of the carbon nanofibers on the reduced graphene oxide.

2. A lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 1, characterized in that: The invention comprises a material synthesized from a substrate, a nickel source, a precipitant and a carbon source as raw materials, wherein the substrate comprises graphene oxide, the nickel source comprises NiSO4·6H2O, the precipitant comprises NaOH, and the carbon source comprises ethanol.

3. The lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 2, characterized in that: The ratio of graphene oxide, NiSO4•6H2O and NaOH is 0.5g:xmM:xmM, wherein 0 <x<8。 4. A method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: Prepare graphene oxide dispersion, NiSO4 solution and NaOH solution using deionized water as solvent; S2: adding NiSO4 solution to the graphene oxide dispersion, mixing, and then adding NaOH solution to obtain a mixed product; S3: washing, freeze-drying and grinding the mixed product in sequence to obtain graphene oxide precursor powder GO@Ni(OH)2 attached with nickel hydroxide; S4: placing the precursor powder in a CVD tube furnace and heating it in a nitrogen flow environment to reduce GO to rGO and convert NiOH to NiO to form rGO@NiO; S5: Ethanol was introduced into the CVD tube furnace by nitrogen bubbling to obtain rGO@Ni-CNF.

5. The method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 4, characterized in that: The concentration of the graphene oxide dispersion is 8-12 mg / mL.

6. The method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 4, characterized in that: The washing method in S3 includes washing with deionized water and anhydrous ethanol alternately until the supernatant becomes colorless.

7. The method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 4, characterized in that: The gas flow rate of the nitrogen gas in S4 is 50 to 70 sccm.

8. The method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 4, characterized in that: The temperature of the heating reaction in S4 is 600-700°C, and the reaction time is 25-35 minutes.

9. The method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 4, characterized in that: The flow rate of nitrogen in S5 is 80 to 90 sccm.

10. The method for preparing a lightweight and efficient three-dimensional graphene-based composite absorbing material according to claim 4, characterized in that: The reaction temperature in S5 is 600-700° C., and the reaction time is 1.5-2 h.

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