Three-dimensional graphene composite wave-absorbing material with egg roll structure as well as preparation method and application of three-dimensional graphene composite wave-absorbing material

Abstract

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and relates to a three-dimensional graphene composite wave-absorbing material with an egg roll structure as well as a preparation method and application of the three-dimensional graphene composite wave-absorbing material. The composite wave-absorbing material comprises a surface-modified C-coated Fe3O4 / rGO three-dimensional network and cured epoxy resin compounded with the surface-modified C-coated Fe3O4 / rGO three-dimensional network, wherein the C (at) Fe3O4 is ferroferric oxide nanoparticles wrapped by carbon, and the rGO is reduced graphene oxide compounded with the C (at) Fe3O4. The impedance matching of the composite material is successfully adjusted by using the C-coated Fe3O4 / rGO egg roll core-shell structure, the polarization loss is improved by introducing a rich interface, and the three-dimensional graphene composite wave-absorbing material has relatively high electromagnetic absorption performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic absorbing materials, and specifically relates to a three-dimensional graphene composite absorbing material with an egg-roll structure, a method for preparing a three-dimensional graphene composite absorbing material with an egg-roll structure, a three-dimensional graphene composite absorbing material prepared by the method, and application of the three-dimensional graphene composite absorbing material in preparing an element for absorbing electromagnetic waves. Background Art

[0002] Absorbing materials refer to a type of material that can absorb or weaken electromagnetic waves incident on its surface, thereby reducing or even eliminating electromagnetic wave interference. They can be used in electronic equipment or weapons and equipment to protect against electromagnetic interference or achieve radar electromagnetic stealth effects. With the continuous and rapid development of electronic communication technology, the electromagnetic interference generated between electronic components of lightweight, integrated, and high-power density electronic products continues to increase, affecting the signal reception and processing of electronic equipment. Therefore, there is an urgent need for a new type of electromagnetic absorbing material to enhance the anti-interference ability of electronic components. In addition, with the development of science and technology, radar detection technology can achieve high-precision detection in a higher and wider frequency band. However, the shortcomings of traditional absorbing materials such as high density and narrow absorption band have seriously restricted the development of stealth technology. Therefore, exploring and developing new absorbing materials, further improving the absorption performance of materials for electromagnetic waves, widening the working frequency band, and meeting the technical requirements of "thin, light, wide, and strong" in a higher frequency range have become the research focus in the field of stealth technology.

[0003] Existing absorbing materials, such as ferrite, barium titanate, metal powder, graphite, silicon carbide, conductive fiber, etc., are limited in their wide application in the engineering field due to their high density, poor impedance matching, low absorption efficiency, narrow absorption band, etc. In the prior art, in order to meet the requirements of electromagnetic absorption and use, one solution is to composite dielectrics with magnetic media to meet impedance matching, but the material density is high; another solution is to design a hollow microsphere core-shell structure absorbing material, but the synthesis conditions are harsh and the interface bonding of the core-shell structure is weak, which is not convenient for use. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a three-dimensional graphene composite absorbing material with an egg roll structure in view of the deficiencies in the prior art. The C@Fe3O4 / rGO contained in the material enhances the interface polarization, thereby improving the polarization loss capacity of the material. The introduction of iron oxide with high magnetic permeability improves the magnetic loss capacity of the composite material. Moreover, the material is a fiber fabric with a porous structure, and its higher specific surface area further enhances the interface polarization capacity, enhances the multiple reflections and absorption times of electromagnetic waves inside the material, so that the electromagnetic absorbing material has excellent absorbing performance and also has the advantage of light weight.

[0005] The first aspect of the present invention provides a three-dimensional graphene composite absorbing material with an egg roll structure, which comprises a surface-modified C@Fe3O4 / rGO three-dimensional network and a cured epoxy resin composited therewith; wherein C@Fe3O4 is carbon-encapsulated ferrosoferric oxide nanoparticles, and rGO is reduced graphene oxide composited with C@Fe3O4.

[0006] A second aspect of the present invention provides a method for preparing a three-dimensional graphene composite absorbing material with an egg roll structure, comprising the following steps:

[0007] (1) under nitrogen protection, mixing an organic carbon source with a first mixed solution and heating the mixture to obtain carbon-encapsulated ferroferric oxide nanoparticles, i.e., C@Fe3O4 nanoparticles; the first mixed solution is a mixture of ferric oleate and an organic solvent;

[0008] (2) mixing the C@Fe3O4 nanoparticles obtained in step (1) with graphene oxide slurry, ultrasonically dispersing to obtain a magnetic graphene oxide spinning solution, and sequentially wet spinning, coagulation and fixing, and drying to obtain a C@Fe3O4 / GO non-woven fabric;

[0009] (3) contacting the C@Fe3O4 / GO non-woven fabric obtained in step (2) with a reducing agent for reduction, and washing and drying after the reduction is completed to obtain a C@Fe3O4 / rGO non-woven fabric;

[0010] (4) immersing the C@Fe3O4 / rGO nonwoven fabric obtained in step (3) into a graphene surface modifier solution and heating it, then taking it out, washing it, and drying it to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network;

[0011] (5) Immersing the surface-modified C@Fe3O4 / rGO three-dimensional network obtained in step (4) into a second mixed liquid and using vacuum-assisted impregnation, and then heating and curing it to obtain the composite absorbing material; the second mixed liquid is a mixed liquid containing an epoxy resin, a dispersant and a curing agent.

[0012] The third aspect of the present invention provides a three-dimensional graphene composite absorbing material prepared by the above-mentioned preparation method.

[0013] A fourth aspect of the present invention provides the use of the above-mentioned three-dimensional graphene composite absorbing material in preparing a component for absorbing electromagnetic waves, wherein the frequency band of the electromagnetic waves absorbed by the component is 2 to 18 GHz.

[0014] The beneficial effects of the present invention include:

[0015] (1) The present invention successfully adjusts the impedance matching of the composite material by using the C@Fe3O4 / rGO egg roll core-shell structure, and introduces a rich interface to improve the polarization loss. According to a specific embodiment of the present invention, the three-dimensional graphene composite absorber material finally prepared has a dielectric constant of about 6 and a magnetic permeability of about 2.4 in the 2-18 GHz frequency band, a good electromagnetic matching degree, and a high electromagnetic absorption performance. When the filling amount of the magnetic component ferroferric oxide in the GO composite fiber is 30wt%, the minimum reflection loss value (RL) of the composite material is -44dB (@13.2GHz), and the effective absorption bandwidth (RL<-10dB) of a single thickness (1.5mm) is 7.66GHz.

[0016] (2) The synthesis process of the present invention has good repeatability, low cost, environmental friendliness, cleanness and non-toxicity, and is easy for large-scale production.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0019] Figure 1 This is an electron microscope image of the microstructure of C@Fe3O4 in Example 1 of the present invention.

[0020] Figure 2 This is a test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Example 1 of the present invention.

[0021] Figure 3 This is an electron microscope image of the microstructure of C@Fe3O4 in Example 2 of the present invention.

[0022] Figure 4 This is a test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Example 2 of the present invention.

[0023] Figure 5 This is an electron microscope image of the microstructure of C@Fe3O4 in Example 3 of the present invention.

[0024] Figure 6 This is an electron microscope image of the microstructure of the C@Fe3O4 / rGO non-woven fabric of Example 3 of the present invention.

[0025] Figure 7 This is a test diagram of electromagnetic parameters of the graphene composite absorbing material of Example 3 of the present invention.

[0026] Figure 8 This is a test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Example 3 of the present invention.

[0027] Fig. 9This is an electron microscope image of the microstructure of C@Fe3O4 of Example 4 of the present invention.

[0028] Fig.10 This is a test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Example 4 of the present invention.

[0029] Fig.11 This is a test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0031] The present invention provides an egg-roll structured three-dimensional graphene composite absorbing material, which comprises a surface-modified C@Fe3O4 / rGO three-dimensional network and a cured epoxy resin composited therewith; wherein C@Fe3O4 is carbon-encapsulated ferrosoferric oxide nanoparticles, and rGO is reduced graphene oxide composited with C@Fe3O4.

[0032] According to the present invention, preferably, based on the total weight of the composite absorbing material, the content of C@Fe3O4 is 0.5-8wt%, the content of rGO is 1-8wt%, and the content of epoxy resin is 90-98wt%; the weight content of carbon in C@Fe3O4 is 20-80wt%; more preferably, based on the total weight of the composite absorbing material, the content of C@Fe3O4 is 1-5wt%, the content of rGO is 1-5wt%, and the content of epoxy resin is 90-95wt%; the weight content of carbon in C@Fe3O4 is 30-70wt%.

[0033] According to a specific embodiment of the present invention, the composite absorbing material is prepared by impregnating the surface-modified C@Fe3O4 / rGO three-dimensional network in an epoxy resin impregnation liquid and then heating and curing. The epoxy resin impregnation liquid may contain epoxy resin, a dispersant and a curing agent.

[0034] The surface modification of the present invention is for reducing graphene oxide. Since the surface of the graphene sheet is inert and prone to agglomeration, it is difficult to be evenly dispersed in water and commonly used organic solvents. The surface modification is used to enhance the mixing of rGO and epoxy resin. According to a specific embodiment of the present invention, the surface-modified C@Fe3O4 / rGO three-dimensional network is a coupling agent-surface-modified C@Fe3O4 / rGO three-dimensional network, which is prepared by surface modification of C@Fe3O4 / rGO non-woven fabric with a coupling agent. The present invention can use any coupling agent that can achieve the above-mentioned modification purpose, including but not limited to one or more of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and borate coupling agents. Preferably, the coupling agent is a silane coupling agent, and the lipophilic group in the silane coupling agent is preferably at least one of methyl, vinyl, amino, aminoethyl, aminopropyl, epoxy, mercapto, acryloxypropyl and γ-glycidyloxypropyl; specifically, the silane coupling agent is preferably one or more of aminopropyltriethoxysilane, vinyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0035] According to a specific embodiment of the present invention, the C@Fe3O4 / rGO non-woven fabric is obtained by reducing C@Fe3O4 / GO non-woven fabric.

[0036] According to a specific embodiment of the present invention, the C@Fe3O4 / GO non-woven fabric is obtained by wet spinning, shaping and drying C@Fe3O4 nanoparticles and graphene oxide slurry.

[0037] According to a specific embodiment of the present invention, the C@Fe3O4 nanoparticles are obtained by mixing an organic carbon source and an iron oleate solution and heating them to react.

[0038] The C@Fe3O4 prepared in the present invention has a core-shell structure, a particle size of 10 to 120 nm, preferably 20 to 100 nm, more preferably 40 to 80 nm, and a shell thickness of 5 to 30 nm, preferably 10 to 25 nm, more preferably 15 to 22 nm.

[0039] The C@Fe3O4 / GO non-woven fabric prepared by the present invention has an egg roll structure in microscopic view and a network structure in macroscopic view.

[0040] According to the present invention, the organic carbon source includes but is not limited to one or more of glucose, asphalt and polydopamine.

[0041] The present invention also provides a method for preparing a three-dimensional graphene composite absorbing material with an egg roll structure, comprising the following steps:

[0042] (1) under nitrogen protection, mixing an organic carbon source with a first mixed solution and heating the mixture to obtain carbon-encapsulated ferroferric oxide nanoparticles, i.e., C@Fe3O4 nanoparticles; the first mixed solution is a mixture of ferric oleate and an organic solvent;

[0043] (2) mixing the C@Fe3O4 nanoparticles obtained in step (1) with graphene oxide slurry, ultrasonically dispersing to obtain a magnetic graphene oxide spinning solution, and sequentially wet spinning, coagulation and fixing, and drying to obtain a C@Fe3O4 / GO non-woven fabric;

[0044] (3) contacting the C@Fe3O4 / GO non-woven fabric obtained in step (2) with a reducing agent for reduction, and washing and drying after the reduction is completed to obtain a C@Fe3O4 / rGO non-woven fabric;

[0045] (4) immersing the C@Fe3O4 / rGO nonwoven fabric obtained in step (3) into a graphene surface modifier solution and heating it, then taking it out, washing it, and drying it to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network;

[0046] (5) Immersing the surface-modified C@Fe3O4 / rGO three-dimensional network obtained in step (4) into a second mixed liquid and using vacuum-assisted impregnation, and then heating and curing it to obtain the composite absorbing material; the second mixed liquid is a mixed liquid containing an epoxy resin, a dispersant and a curing agent.

[0047] According to the method of the present invention, in step (1), the iron oleate is used as a precursor, the organic solvent is used as a solvent for dissolving the iron oleate, and the organic carbon source is used as a carbon source for preparing a shell structure.

[0048] Specifically, the organic carbon source is one or more of glucose, asphalt and polydopamine; the organic solvent is one or more of phenyl ether, benzyl ether, tetracosane, dodecylamine, oleylamine, oleic acid, hexadecene and octadecene.

[0049] According to a specific embodiment of the present invention, the concentration of iron oleate in the first mixed solution is 0.1-30 g / mL, preferably 0.15-0.5 g / mL; the mass ratio of iron oleate to organic carbon source is 1:10-10:1, preferably 3:7-7:3.

[0050] According to a preferred embodiment of the present invention, in step (1), the conditions of the heating reaction include: a reaction temperature of 200 to 300° C., and a reaction time of 10 to 360 min;

[0051] The C@Fe3O4 nanoparticles prepared by the above raw materials and reaction conditions have a core-shell structure, a particle size of 20 to 100 nm, and a shell thickness of 10 to 25 nm.

[0052] According to the present invention, in step (2), the graphene oxide slurry includes water and graphene oxide, and can be prepared by mixing water and graphene oxide. The concentration of graphene oxide in the graphene oxide slurry can be 0.1-30 g / mL, preferably 0.15-0.5 g / L; the mass ratio of the C@Fe3O4 nanoparticles to graphene oxide is 0.05-1:1, preferably 0.1-0.5:1.

[0053] According to the present invention, in step (2), the coagulation and fixing step may include: mixing the fiber obtained by wet spinning with a coagulation bath; the coagulation bath is a mixture of acetic acid and ethanol, wherein the volume ratio of acetic acid to ethanol is preferably 1:10 to 10:1, preferably 7:3 to 3:7; the weight ratio of the coagulation bath to the fiber is preferably 100 to 2000:1.

[0054] The C@Fe3O4 / GO non-woven fabric prepared by the above method has an egg-roll structure in the microscopic aspect and a network structure in the macroscopic aspect.

[0055] According to the present invention, in step (3), the reducing agent may be one or more of hydroiodic acid, ascorbic acid, hydrazine hydrate, ammonia, potassium hydroxide, sodium oxide, dimethylhydrazine and hydroquinone; the reducing agent is used in excess to fully reduce the graphene oxide.

[0056] According to the present invention, in step (4), the graphene surface modifier is preferably a coupling agent, which is used to improve the mixing of graphene and epoxy resin. The available coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a phosphate coupling agent, and a borate coupling agent. The mass of the graphene surface modifier is preferably 1 to 5% of the mass of the C@Fe3O4 / rGO non-woven fabric.

[0057] According to a preferred embodiment of the present invention, the graphene surface modifier solution is a silane coupling agent dispersion, which includes a silane coupling agent and an ethanol aqueous solution. The mass ratio of the silane coupling agent to the ethanol aqueous solution is preferably 1:10-99, and the volume ratio of ethanol to water in the ethanol aqueous solution is preferably 5-15:1, preferably 8-10:1; the silane coupling agent is preferably one or more of aminopropyltriethoxysilane, vinyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0058] According to the present invention, in step (4), the heating temperature can be 20 to 80° C., preferably 40 to 60° C., and the heating time can be 2 to 12 hours, preferably 5 to 8 hours.

[0059] According to the present invention, in step (5), the mass ratio of the surface-modified C@Fe3O4 / rGO three-dimensional network to the second mixed liquid can be 1:50 to 1:2, preferably 1:10 to 1:3. The mass ratio of the epoxy resin, dispersant and curing agent is preferably 1:0.1 to 1:0.2 to 0.8.

[0060] In the present invention, the dispersant and curing agent can be the dispersants and curing agents commonly used in the art for use with epoxy resins. For example, the dispersant can be selected from at least one of ethanol, acetone, benzene, toluene and xylene; the curing agent can be selected from at least one of amine curing agents, acid anhydride curing agents and resin curing agents.

[0061] In the impregnation step, the surface-modified C@Fe3O4 / rGO three-dimensional network is completely infiltrated with the second mixed solution; usually, epoxy resin and dispersant are added first, and curing agent is added last. The impregnation time is preferably 10 to 60 minutes. The curing conditions may include: curing temperature of 70 to 90°C and curing time of 3 to 10 hours.

[0062] The present invention also provides a three-dimensional graphene composite wave absorbing material prepared by the above-mentioned preparation method.

[0063] The three-dimensional graphene composite wave-absorbing material of the present invention can be used to prepare a component for absorbing electromagnetic waves, and the frequency band of the electromagnetic waves absorbed by the component is 2 to 18 GHz.

[0064] The present invention will be further described below in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0065] Example 1

[0066] This embodiment is used to illustrate the graphene composite absorbing material of the present invention, and its preparation method comprises the following steps:

[0067] 1) Weigh 36 g of iron oleate and dissolve it in 200 mL of octadecene.

[0068] 2) Weigh 84 g of asphalt powder and put it into a four-necked flask. First, heat the asphalt in an oven to 240°C to soften it. Then transfer the four-necked flask containing the asphalt powder to a heating jacket that has been preheated to 240°C, protect it with nitrogen, and assist with mechanical stirring and gradually increase the rotation speed until the asphalt becomes a liquid with good fluidity.

[0069] 3) The ferric oleate solution in step 1) is slowly added to a four-necked flask and mixed with asphalt, and the temperature is raised to 290°C and kept for 30 minutes. The four-necked flask is taken out from the heating jacket, and stirring is continued. The temperature is rapidly lowered. After the solution is condensed, the sample is taken out to obtain carbon-encapsulated ferroferric oxide (C@Fe3O4) nanoparticles; wherein the weight ratio of carbon to Fe3O4 is 7:3, and the C@Fe3O4 nanoparticles have a core-shell structure, with a particle size of about 30 nm and a shell thickness of about 25 nm. The electron microscope image of the microstructure is as follows Figure 1 shown.

[0070] 4) 0.15 g of C@Fe3O4 nanoparticles was added to 75 mL of 20 g / L graphene oxide slurry, and magnetic graphene oxide spinning solution was obtained by ultrasonic dispersion. C@Fe3O4 / GO fiber was prepared by wet spinning, and after mixing with a coagulation bath for shaping, a C@Fe3O4 / GO non-woven fabric with a microscopic egg roll structure and a macroscopic network structure was obtained by drying; the coagulation bath was a mixture of acetic acid and ethanol in a volume ratio of 1:1, and the weight ratio of the coagulation bath to the C@Fe3O4 / GO fiber was 1000:1.

[0071] 5) The C@Fe3O4 / GO nonwoven fabric was fully reduced in an aqueous solution of ascorbic acid (45 wt%), washed and dried to obtain 1 g of C@Fe3O4 / rGO nonwoven fabric.

[0072] 6) Disperse 1 part of silane coupling agent (aminopropyltriethoxysilane) in a mixed solvent of 98 parts of ethanol and water (the volume ratio of ethanol to water is 9:1), and stir for 20 minutes; add C@Fe3O4 / rGO non-woven fabric (the mass of the silane coupling agent is 2% of the mass of the C@Fe3O4 / rGO non-woven fabric) to the silane coupling agent dispersion, heat in a water bath at 50°C for 6 hours to obtain a C@Fe3O4 / rGO three-dimensional network; take out the C@Fe3O4 / rGO three-dimensional network and wash it repeatedly with ethanol and deionized water to remove unreacted silane coupling agent; dry at 60°C for 12 hours to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network.

[0073] 7) 10 parts of epoxy resin, 1 part of dispersant (ethanol) and 5 parts of curing agent (phenolic modified ethylenediamine curing agent) are mixed to obtain a second mixed solution, 5 parts of surface-modified C@Fe3O4 / rGO three-dimensional network are immersed in the second mixed solution, and placed in a vacuum oven for vacuum-assisted impregnation for 30 minutes to allow the resin to completely infiltrate the internal voids of the graphene, and then heated to 80°C for curing for 6 hours to obtain a C@Fe3O4 / rGO composite absorbing material, wherein the content of C@Fe3O4 in the material is 1wt%, the content of rGO is 5wt%, and the content of epoxy resin is 94wt%.

[0074] Figure 2 The middle curve shows the test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Example 1. Figure 2 It can be seen that the minimum reflection loss value (RL) of the composite absorbing material of Example 1 is -31.7 dB (@12.5 GHz), and the effective absorbing bandwidth (RL<-10 dB) of a single thickness (1.5 mm) is 3.85 GHz, which has certain absorbing performance.

[0075] Example 2

[0076] This embodiment is used to illustrate the graphene composite absorbing material of the present invention, and its preparation method comprises the following steps:

[0077] 1) Weigh 36 g of iron oleate and dissolve it in 200 mL of octadecene.

[0078] 2) Weigh 15.5 g of asphalt powder and put it into a four-necked flask. First, heat the asphalt in an oven to 240°C to soften it. Then transfer the four-necked flask containing the asphalt powder to a heating jacket that has been preheated to 240°C, protect it with nitrogen, and assist with mechanical stirring and gradually increase the rotation speed until the asphalt becomes a liquid with good fluidity.

[0079] 3) The ferric oleate solution in step 1) is slowly added to a four-necked flask and mixed with asphalt, and the temperature is raised to 290°C and kept for 30 minutes. The four-necked flask is taken out from the heating jacket, and stirring is continued. The temperature is rapidly lowered. After the solution is condensed, the sample is taken out to obtain carbon-encapsulated ferroferric oxide (C@Fe3O4) nanoparticles; wherein the weight ratio of carbon to Fe3O4 is 3:7, and the C@Fe3O4 nanoparticles have a core-shell structure, with a particle size of about 100 nm and a shell thickness of about 10 nm. The electron microscope image of the microstructure is as follows: Figure 3 shown.

[0080] 4) adding 0.30 g of C@Fe3O4 nanoparticles to 100 mL of 15 g / L graphene oxide slurry, ultrasonically dispersing to obtain magnetic graphene oxide spinning solution, wet spinning to prepare C@Fe3O4 / GO fibers, mixing with a coagulation bath for shaping, and drying to obtain a C@Fe3O4 / GO non-woven fabric with a microscopic egg roll structure and a macroscopic network structure; the coagulation bath is a mixture of acetic acid and ethanol in a volume ratio of 1:1, and the weight ratio of the coagulation bath to the C@Fe3O4 / GO fiber is 1000:1.

[0081] 5) The C@Fe3O4 / GO nonwoven fabric was fully reduced in an ascorbic acid solution (45 wt%), washed and dried to obtain 1 g of C@Fe3O4 / rGO nonwoven fabric.

[0082] 6) Disperse 5 parts of silane coupling agent (vinyl triethoxysilane) in a mixed solvent of 95 parts of ethanol and water (the volume ratio of ethanol to water is 9:1), and stir for 20 minutes; add C@Fe3O4 / rGO non-woven fabric (the mass of the silane coupling agent is 4% of the mass of the C@Fe3O4 / rGO non-woven fabric) to the silane coupling agent dispersion, heat in a water bath at 50°C for 6 hours to obtain a C@Fe3O4 / rGO three-dimensional network; take out the C@Fe3O4 / rGO three-dimensional network and wash it repeatedly with ethanol and deionized water to remove unreacted silane coupling agent; dry at 60°C for 12 hours to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network.

[0083] 7) 10 parts of epoxy resin, 10 parts of dispersant (ethanol) and 5 parts of curing agent (phenolic modified ethylenediamine curing agent) are mixed to obtain a second mixed solution, 5 parts of surface-modified C@Fe3O4 / rGO three-dimensional network are immersed in the second mixed solution, and placed in a vacuum oven for vacuum-assisted impregnation for 30 minutes to allow the resin to completely infiltrate the internal voids of the graphene, and then heated to 80°C for curing for 6 hours to obtain a C@Fe3O4 / rGO composite absorbing material, wherein the content of C@Fe3O4 in the material is 3wt%, the content of rGO is 2wt%, and the content of epoxy resin is 95wt%.

[0084] Figure 4 The middle curve shows the test diagram of the wave absorbing performance of the graphene composite wave absorbing material of Example 2. Figure 4 It can be seen that the minimum reflection loss value (RL) of the composite absorbing material of Example 2 is -33.1 dB (@15.2 GHz), and the effective absorbing bandwidth (RL<-10 dB) of a single thickness (1.5 mm) is 7.34 GHz, which has certain absorbing performance.

[0085] Example 3

[0086] This embodiment is used to illustrate the graphene composite absorbing material of the present invention, and its preparation method comprises the following steps:

[0087] 1) Weigh 36 g of iron oleate and dissolve it in 200 mL of octadecene.

[0088] 2) Weigh 36 g of asphalt powder and put it into a four-necked flask. First, heat the asphalt in an oven to 240°C to soften it. Then transfer the four-necked flask containing the asphalt powder to a heating jacket that has been preheated to 240°C, protect it with nitrogen, and assist with mechanical stirring and gradually increase the rotation speed until the asphalt becomes a liquid with good fluidity.

[0089] 3) Slowly add the ferric oleate solution in step 1) into a four-necked flask and mix thoroughly with asphalt, heat to 290°C and keep warm for 30 minutes, remove the four-necked flask from the heating jacket, continue stirring, and quickly cool down. After the solution condenses, take out the sample to obtain carbon-encapsulated ferroferric oxide (C@Fe3O4) nanoparticles; wherein the weight ratio of carbon to Fe3O4 is 1:1, and the C@Fe3O4 nanoparticles have a core-shell structure, with a particle size of about 50 nm and a shell thickness of about 20 nm. The electron microscope image of its microstructure is as follows Figure 5 shown.

[0090] 4) adding 0.45 g of C@Fe3O4 nanoparticles to 100 mL of 15 g / L graphene oxide slurry, ultrasonically dispersing to obtain magnetic graphene oxide spinning solution, wet spinning to prepare C@Fe3O4 / GO fibers, mixing with a coagulation bath for shaping, and drying to obtain a C@Fe3O4 / GO non-woven fabric having a microscopic egg roll structure and a macroscopic network structure; the coagulation bath is a mixture of acetic acid and ethanol in a volume ratio of 1:1, and the weight ratio of the coagulation bath to the C@Fe3O4 / GO fibers is 1000:1.

[0091] 5) The C@Fe3O4 / GO nonwoven fabric was fully reduced in an ascorbic acid solution (45 wt%), washed and dried to obtain 1 g of C@Fe3O4 / rGO nonwoven fabric; the microstructure electron microscope image of the C@Fe3O4 / rGO nonwoven fabric is as follows Figure 6 shown.

[0092] 6) Disperse 3 parts of silane coupling agent (γ-glycidyloxypropyltrimethoxysilane) in a mixed solvent of 97 parts of ethanol and water (the volume ratio of ethanol to water is 9:1), and stir for 20 minutes; add C@Fe3O4 / rGO non-woven fabric (the mass of the silane coupling agent is 3% of the mass of the C@Fe3O4 / rGO non-woven fabric) to the silane coupling agent dispersion, heat in a water bath at 50°C for 6 hours to obtain a C@Fe3O4 / rGO three-dimensional network; take out the C@Fe3O4 / rGO three-dimensional network and wash it repeatedly with ethanol and deionized water to remove unreacted silane coupling agent; dry at 60°C for 12 hours to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network.

[0093] 7) 10 parts of epoxy resin, 4 parts of dispersant (ethanol) and 5 parts of curing agent (phenolic modified ethylenediamine curing agent) are mixed to obtain a second mixed solution, 3 parts of surface-modified C@Fe3O4 / rGO three-dimensional network are immersed in the second mixed solution, and placed in a vacuum oven for vacuum-assisted impregnation for 30 minutes to allow the resin to completely infiltrate the internal voids of the graphene, and then heated to 80°C for curing for 6 hours to obtain a C@Fe3O4 / rGO composite absorbing material, wherein the content of C@Fe3O4 in the material is 5wt%, the content of rGO is 2wt%, and the content of epoxy resin is 93wt%.

[0094] Figure 7 The middle curve shows the electromagnetic parameter test diagram of the graphene composite absorbing material of Example 3. It can be seen that the graphene composite absorbing material of Example 3 has a dielectric constant of about 6 and a magnetic permeability of about 2.4 in the 2-18 GHz frequency band, and has a good electromagnetic matching degree.

[0095] Figure 8 The middle curve shows the performance test diagram of the graphene composite absorbing material of Example 3; Figure 8 It can be seen that the minimum reflection loss value (RL) of the composite absorbing material of Example 3 is -44dB (@13.2GHz), and the effective absorbing bandwidth (RL<-10dB) of a single thickness (1.5mm) is 7.66GHz, which has good absorbing performance.

[0096] Example 4

[0097] This embodiment is used to illustrate the graphene composite absorbing material of the present invention, and its preparation method comprises the following steps:

[0098] 1) Weigh 36 g of iron oleate and dissolve it in 50 mL of octadecene.

[0099] 2) Weigh 36 g of asphalt powder and put it into a four-necked flask. First, heat the asphalt in an oven to 240°C to soften it. Then transfer the four-necked flask containing the asphalt powder to a heating jacket that has been preheated to 240°C, protect it with nitrogen, and assist with mechanical stirring and gradually increase the rotation speed until the asphalt becomes a liquid with good fluidity.

[0100] 3) The ferric oleate solution in step 1) is slowly added to a four-necked flask and mixed with asphalt, and the temperature is raised to 290°C and kept for 30 minutes. The four-necked flask is taken out from the heating jacket, and stirring is continued. The temperature is rapidly lowered. After the solution is condensed, the sample is taken out to obtain carbon-encapsulated ferroferric oxide (C@Fe3O4) nanoparticles; wherein the weight ratio of carbon to Fe3O4 is 1:1, and the C@Fe3O4 nanoparticles have a core-shell structure, with a particle size of about 100 nm and a shell thickness of about 10 nm. The electron microscope image of the microstructure is as follows: Fig. 9 shown.

[0101] 4) 0.45 g of C@Fe3O4 nanoparticles was added to 100 mL of 10 g / L graphene oxide slurry, and magnetic graphene oxide spinning solution was obtained by ultrasonic dispersion. C@Fe3O4 / GO fiber was prepared by wet spinning, and after mixing with a coagulation bath for shaping, a C@Fe3O4 / GO non-woven fabric with a microscopic egg roll structure and a macroscopic network structure was obtained by drying; the coagulation bath was a mixture of acetic acid and ethanol in a volume ratio of 1:1, and the weight ratio of the coagulation bath to the C@Fe3O4 / GO fiber was 1000:1.

[0102] 5) The C@Fe3O4 / GO nonwoven fabric was fully reduced in an ascorbic acid solution (45 wt%), washed and dried to obtain 1 g of C@Fe3O4 / rGO nonwoven fabric.

[0103] 6) Disperse 3 parts of silane coupling agent (γ-glycidyloxypropyltrimethoxysilane) in a mixed solvent of 97 parts of ethanol and water (the volume ratio of ethanol to water is 9:1), and stir for 20 minutes; add C@Fe3O4 / rGO non-woven fabric (the mass of the silane coupling agent is 3% of the mass of the C@Fe3O4 / rGO non-woven fabric) to the silane coupling agent dispersion, heat in a water bath at 50°C for 6 hours to obtain a C@Fe3O4 / rGO three-dimensional network; take out the C@Fe3O4 / rGO three-dimensional network and wash it repeatedly with ethanol and deionized water to remove unreacted silane coupling agent; dry at 60°C for 12 hours to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network.

[0104] 7) 10 parts of epoxy resin, 4 parts of dispersant (ethanol) and 5 parts of curing agent (phenolic modified ethylenediamine curing agent) are mixed to obtain a second mixed solution, 3 parts of surface-modified C@Fe3O4 / rGO three-dimensional network are immersed in the second mixed solution, and placed in a vacuum oven for vacuum-assisted impregnation for 30 minutes to allow the resin to completely infiltrate the internal voids of the graphene, and then heated to 80°C for curing for 6 hours to obtain a C@Fe3O4 / rGO composite absorbing material, wherein the content of C@Fe3O4 in the material is 5wt%, the content of rGO is 2wt%, and the content of epoxy resin is 93wt%.

[0105] Fig.10 The middle curve shows the electromagnetic parameter test diagram of the graphene composite absorbing material of Example 4. It can be seen that the graphene composite absorbing material of Example 4 has a minimum reflection loss value (RL) of -27.1dB (@13.4GHz) in the 2-18GHz frequency band, and an effective absorbing bandwidth (RL<-10dB) of 3.3GHz with a single thickness (1.5mm), which has certain absorbing performance.

[0106] Comparative Example 1

[0107] This comparative example is used to illustrate a comparative graphene absorbing material of the present invention, and its preparation method comprises the following steps:

[0108] 1) 100 mL of 15 g / L graphene oxide spinning solution was used to prepare GO fibers by wet spinning, and after shaping treatment, GO non-woven fabric was obtained by drying.

[0109] 2) The GO nonwoven fabric was fully reduced in a hydroiodic acid solution (45 wt%), then washed and dried to obtain rGO nonwoven fabric.

[0110] 3) Disperse 3 parts of silane coupling agent (γ-glycidyloxypropyltrimethoxysilane) in a mixed solvent of 97 parts of ethanol and water (the volume ratio of ethanol to water is 9:1), and stir for 20 minutes; add rGO non-woven fabric (the mass of silane coupling agent is 3% of the mass of C@Fe3O4 / rGO non-woven fabric) to the silane coupling agent dispersion, heat in a water bath at 50°C for 6 hours to obtain an rGO three-dimensional network; take out the rGO three-dimensional network and wash it repeatedly with ethanol and deionized water to remove the unreacted silane coupling agent; dry at 60°C for 12 hours to obtain a surface-modified rGO three-dimensional network;

[0111] 4) 10 parts of epoxy resin, 4 parts of dispersant (ethanol) and 5 parts of curing agent (phenolic modified ethylenediamine curing agent) are mixed to obtain a second mixed solution, 3 parts of surface-modified rGO three-dimensional network are immersed in the second mixed solution, and placed in a vacuum oven for vacuum-assisted impregnation for 30 minutes to allow the resin to completely infiltrate the internal gaps of the graphene, and then heated to 80°C for curing for 6 hours to obtain the rGO epoxy absorbing material.

[0112] Fig.11 The middle curve shows the electromagnetic parameter test diagram of the graphene absorbing material of comparative example 1. The absolute value of the maximum reflection loss (RL) of the graphene composite absorbing material in the frequency band of 2 to 18 GHz is less than 15 dB.

[0113] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0114] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A three-dimensional graphene composite absorbing material with an egg roll structure, characterized in that: The composite wave absorbing material comprises a surface-modified C@Fe3O4 / rGO three-dimensional network and a cured epoxy resin composited therewith; wherein C@Fe3O4 is carbon-wrapped ferrosoferric oxide nanoparticles, and rGO is reduced graphene oxide composited with C@Fe3O4.

2. The three-dimensional graphene composite absorbing material according to claim 1, wherein: Based on the total weight of the composite absorbing material, the content of C@Fe3O4 is 0.5-8wt%, the content of rGO is 1-8wt%, and the content of epoxy resin is 90-98wt%; the weight content of carbon in C@Fe3O4 is 20-80wt%; preferably, based on the total weight of the composite absorbing material, the content of C@Fe3O4 is 1-5wt%, the content of rGO is 1-5wt%, and the content of epoxy resin is 90-95wt%; the weight content of carbon in C@Fe3O4 is 30-70wt%.

3. The three-dimensional graphene composite absorbing material according to claim 1, wherein: The composite absorbing material is prepared by impregnating a surface-modified C@Fe3O4 / rGO three-dimensional network in an epoxy resin impregnation solution and then heating and curing. The surface-modified C@Fe3O4 / rGO three-dimensional network is a coupling agent-surface-modified C@Fe3O4 / rGO three-dimensional network, which is prepared by surface-modifying a C@Fe3O4 / rGO non-woven fabric with a coupling agent; the surface modification is used to enhance the mixing of rGO and epoxy resin; The C@Fe3O4 / rGO non-woven fabric is obtained by reducing the C@Fe3O4 / GO non-woven fabric; The C@Fe3O4 / GO nonwoven fabric is obtained by wet spinning, shaping and drying C@Fe3O4 nanoparticles and graphene oxide slurry; The C@Fe3O4 nanoparticles are obtained by mixing an organic carbon source and an iron oleate solution and heating them for reaction.

4. The three-dimensional graphene composite absorbing material according to claim 3, wherein: The C@Fe3O4 has a core-shell structure, a particle size of 10 to 120 nm, preferably 20 to 100 nm, more preferably 40 to 80 nm, and a shell thickness of 5 to 30 nm, preferably 10 to 25 nm, more preferably 15 to 22 nm; The C@Fe3O4 / GO non-woven fabric has an egg roll structure at the microscopic level and a network structure at the macroscopic level; The organic carbon source is one or more of glucose, asphalt and polydopamine; The epoxy resin impregnation liquid contains epoxy resin, dispersant and curing agent.

5. The three-dimensional graphene composite absorbing material according to claim 3, wherein: The coupling agent is selected from one or more of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a phosphate coupling agent and a borate coupling agent.

6. The three-dimensional graphene composite absorbing material according to claim 5, wherein: The silane coupling agent is one or more of aminopropyltriethoxysilane, vinyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

7. A method for preparing a three-dimensional graphene composite absorbing material with an egg roll structure, characterized in that: The steps include: (1) under nitrogen protection, mixing an organic carbon source with a first mixed solution and heating the mixture to obtain carbon-encapsulated ferroferric oxide nanoparticles, i.e., C@Fe3O4 nanoparticles; the first mixed solution is a mixture of ferric oleate and an organic solvent; (2) mixing the C@Fe3O4 nanoparticles obtained in step (1) with graphene oxide slurry, ultrasonically dispersing to obtain a magnetic graphene oxide spinning solution, and sequentially wet spinning, coagulation and fixing, and drying to obtain a C@Fe3O4 / GO non-woven fabric; (3) contacting the C@Fe3O4 / GO non-woven fabric obtained in step (2) with a reducing agent for reduction, and washing and drying after the reduction is completed to obtain a C@Fe3O4 / rGO non-woven fabric; (4) immersing the C@Fe3O4 / rGO nonwoven fabric obtained in step (3) into a graphene surface modifier solution and heating it, then taking it out, washing it, and drying it to obtain a surface-modified C@Fe3O4 / rGO three-dimensional network; (5) Immersing the surface-modified C@Fe3O4 / rGO three-dimensional network obtained in step (4) into a second mixed liquid and using vacuum-assisted impregnation, and then heating and curing it to obtain the composite absorbing material; the second mixed liquid is a mixed liquid containing an epoxy resin, a dispersant and a curing agent.

8. The preparation method according to claim 7, wherein: In step (1), the organic carbon source is one or more of glucose, asphalt and polydopamine; the organic solvent is one or more of phenyl ether, benzyl ether, tetracosane, dodecylamine, oleylamine, oleic acid, hexadecene and octadecene; the concentration of iron oleate in the first mixed solution is 0.1-30 g / mL, preferably 0.15-0.5 g / mL; the mass ratio of iron oleate to the organic carbon source is 1:10-10:1, preferably 3:7-7:

3.

9. The preparation method according to claim 7, wherein: In step (1), the conditions of the heating reaction include: a reaction temperature of 200 to 300°C and a reaction time of 10 to 360 min; the C@Fe3O4 nanoparticles have a core-shell structure, a particle size of 10 to 120 nm, preferably 20 to 100 nm, more preferably 40 to 80 nm, and a shell thickness of 5 to 30 nm, preferably 10 to 25 nm, more preferably 15 to 22 nm.

10. The preparation method according to claim 7, wherein: In step (2), the graphene oxide slurry comprises water and graphene oxide, the concentration of graphene oxide in the graphene oxide slurry is 1 to 30 g / mL, preferably 10 to 20 g / L; the mass ratio of the C@Fe3O4 nanoparticles to graphene oxide is 0.05-1:1, preferably 0.1-0.5:

1.

11. The preparation method according to claim 7, wherein: In step (2), the coagulation and fixing step comprises: mixing the fiber obtained by wet spinning with a coagulation bath; the coagulation bath is a mixture of acetic acid and ethanol, wherein the volume ratio of acetic acid to ethanol is 1:10 to 10:1, preferably 7:3 to 3:7; the weight ratio of the coagulation bath to the fiber is 100 to 2000:

1.

12. The preparation method according to claim 7, wherein: In step (3), the reducing agent is one or more of hydroiodic acid, ascorbic acid, hydrazine hydrate, ammonia, potassium hydroxide, sodium oxide, dimethylhydrazine and hydroquinone.

13. The preparation method according to claim 7, wherein: In step (4), the graphene surface modifier is a coupling agent, and the coupling agent is preferably selected from one or more of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a phosphate coupling agent and a borate coupling agent; the mass of the graphene surface modifier is 1 to 5% of the mass of the C@Fe3O4 / rGO non-woven fabric.

14. The preparation method according to claim 13, wherein: The graphene surface modifier solution is a silane coupling agent dispersion, which includes a silane coupling agent and an ethanol aqueous solution. The mass ratio of the silane coupling agent to the ethanol aqueous solution is 1:10-99, and the volume ratio of ethanol to water in the ethanol aqueous solution is 5-15:1, preferably 8-10:1; the silane coupling agent is preferably one or more of aminopropyltriethoxysilane, vinyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

15. The preparation method according to claim 7, wherein: In step (4), the heating temperature is 20 to 80° C., preferably 40 to 60° C., and the heating time is 2 to 12 hours, preferably 5 to 8 hours.

16. The preparation method according to claim 7, wherein: In step (5), the mass ratio of the surface-modified C@Fe3O4 / rGO three-dimensional network to the second mixed liquid is 1:50 to 1:2, preferably 1:10 to 1:3; the mass ratio of the epoxy resin, the dispersant and the curing agent is 1:0.1 to 1:0.2 to 0.8; The dispersant is selected from at least one of ethanol, acetone, benzene, toluene and xylene; The curing agent is selected from at least one of an amine curing agent, an acid anhydride curing agent, and a resin curing agent; The surface modified C@Fe3O4 / rGO three-dimensional network is completely infiltrated with the second mixed liquid; the impregnation time is 10 to 60 minutes; the heating and curing conditions include: the curing temperature is 70 to 90°C and the curing time is 3 to 10 hours.

17. A three-dimensional graphene composite absorbing material prepared by the preparation method according to any one of claims 7 to 16.

18. Use of the three-dimensional graphene composite absorbing material according to any one of claims 1 to 6 and 17 in preparing a component for absorbing electromagnetic waves, wherein the frequency band of the electromagnetic waves absorbed by the component is 2 to 18 GHz.

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