Coaxial graphene fiber composite wave-absorbing material and preparation method and application thereof

Abstract

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and relates to a coaxial graphene fiber composite wave-absorbing material and a preparation method and application thereof. The composite wave-absorbing material is surface-modified reduced graphene oxide-ferrite coaxial fibers and cured epoxy resin compounded with the surface-modified reduced graphene oxide-ferrite coaxial fibers. Wherein in the coaxial fiber, the reduced graphene oxide serves as a core layer, and the ferrite serves as a skin layer. The impedance matching of the composite material is successfully adjusted by using the ferrite-reduced graphene oxide coaxial fiber, the polarization loss is improved by introducing a rich interface, and the graphene composite wave-absorbing material is relatively good in electromagnetic matching degree in a frequency band of 2-18 GHz and has relatively good wave-absorbing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic absorbing materials, and specifically relates to a coaxial graphene fiber composite absorbing material, a preparation method of a coaxial graphene fiber composite absorbing material, a coaxial graphene fiber composite absorbing material prepared by the method, and applications of the coaxial graphene fiber composite absorbing material. Background Art

[0002] Since electromagnetic absorbing materials can effectively absorb or weaken the intensity of electromagnetic radiation, they can be used in electronic equipment or weapons to protect against electromagnetic interference or achieve radar electromagnetic stealth. With the widespread application of wireless communication technology and high-frequency electronic devices in modern life, radio electromagnetic wave pollution and electromagnetic wave interference are becoming increasingly serious. 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 electromagnetic wave absorbing materials.

[0003] In the existing absorbing materials and absorbing technologies, problems such as high material density, poor impedance matching, low absorption efficiency, and narrow absorption band are still common. Although carbon-based absorbing materials have properties such as light weight, controllable components and structures, single carbon materials do not have magnetism, resulting in poor impedance matching, and it is difficult to simultaneously meet the comprehensive characteristics of "thin, light, wide, and strong" for electromagnetic wave absorption and shielding. In order to solve the requirements of electromagnetic absorption and use, one solution is to compound carbon materials with magnetic media to meet impedance matching. Among them, commonly used magnetic media such as hexagonal barium ferrite with high magnetocrystalline anisotropy, high resistivity and high magnetic permeability are one of the choices for absorbing materials, especially in the GHz frequency band. However, the shortcomings of barium ferrite absorbing materials such as narrow absorption band, high material density, and thick material thickness at low frequencies limit their wide application in the field of composite materials; another solution is to design absorbing materials with hollow microsphere core-shell structures, 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 reduce the thickness of the material in use in view of the shortcomings of the prior art, and provide a coaxial graphene fiber composite absorbing material and a preparation method thereof. The coaxial graphene fiber composite material prepared by the present invention enhances the interface polarization, thereby improving the polarization loss capacity of the material, and the introduction of hexagonal lamellar ferrite with high magnetic permeability improves the magnetic loss capacity of the composite material; and the fiber fabric has a porous structure, and its high specific surface area further improves the interface polarization capacity, and 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] A first aspect of the present invention provides a coaxial graphene fiber composite absorbing material, wherein the composite absorbing material is a surface-modified reduced graphene oxide-ferrite coaxial fiber and a cured epoxy resin composited therewith; wherein, in the coaxial fiber, the reduced graphene oxide is a core layer and the ferrite is a skin layer.

[0006] A second aspect of the present invention provides a method for preparing a coaxial graphene fiber composite absorbing material, comprising the following steps:

[0007] (1) Hexagonal ferrite flakes are prepared by molten salt method;

[0008] (2) dispersing the hexagonal ferrite obtained in step (1) in a water-soluble polymer aqueous solution to obtain a first mixed solution, and obtaining a ferrite spinning solution after ultrasonic dispersion;

[0009] (3) wet spinning the ferrite spinning solution obtained in step (2) and the graphene oxide slurry, coagulation fixation, and drying to obtain a coaxial fiber with a core layer of graphene oxide and a skin layer of ferrite;

[0010] (4) contacting the coaxial fiber obtained in step (3) with a reducing agent for reduction, washing and drying after the reduction is completed, to obtain a reduced graphene oxide-ferrite coaxial fiber;

[0011] (5) immersing the reduced graphene oxide-ferrite coaxial fiber obtained in step (4) into a graphene surface modifier solution and heating it, then taking it out, washing it, and drying it to obtain a surface-modified reduced graphene oxide-ferrite coaxial fiber;

[0012] (6) adding the surface-modified reduced graphene oxide-ferrite coaxial fiber obtained in step (5) into a second mixed liquid to uniformly disperse the components, and then heating and curing to obtain the composite absorbing material, wherein the second mixed liquid comprises an epoxy resin, a dispersant and a curing agent.

[0013] The third aspect of the present invention provides a coaxial graphene fiber composite absorbing material prepared by the above preparation method.

[0014] A fourth aspect of the present invention provides the use of the above-mentioned coaxial graphene fiber composite absorbing material in the preparation of a component for absorbing electromagnetic waves, wherein the frequency band of the electromagnetic waves absorbed by the component is 2 to 18 GHz.

[0015] The beneficial effects of the present invention include:

[0016] (1) The present invention successfully adjusts the impedance matching of the composite material by using ferrite-reduced graphene oxide coaxial fiber, and introduces rich interfaces to improve polarization loss. According to a specific embodiment of the present invention, the impedance matching coefficient of the graphene composite absorbing material finally prepared is 0.5 (the impedance matching coefficient of perfect matching→1) in the frequency band of 2 to 18 GHz, and the electromagnetic matching degree is good; compared with pure ferrite fiber, the coaxial fiber composite material can achieve effective absorption of low-frequency electromagnetic waves; when the filling amount of coaxial graphene fiber is about 10wt%, the minimum reflection loss value (RL) of the composite material is -35dB (@11GHz), and the effective absorbing bandwidth (RL<-10dB) of a single thickness (1.5mm) is 8.32GHz, which has good absorbing performance.

[0017] (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.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0020] Figure 1 The BaFe of Example 1 of the present invention 12 O 19 / rGO coaxial fiber composite absorbing material wave absorption performance test diagram.

[0021] Figure 2 The BaFe of Example 2 of the present invention 12 O 19 / rGO coaxial fiber composite absorbing material wave absorption performance test diagram.

[0022] Figure 3 The BaFe of Example 3 of the present invention 12 O 19 Impedance matching test diagram of / rGO coaxial fiber composite absorbing material.

[0023] Figure 4 The BaFe of Example 3 of the present invention 12 O 19 / rGO coaxial fiber composite absorbing material wave absorption performance test diagram.

[0024] Figure 5 The hexagonal BaFe 12 O 19 SEM image of ferrite.

[0025] Figure 6 The BaFe of Example 3 of the present invention 12 O 19 SEM image of / rGO coaxial fiber.

[0026] Figure 7 The BaFe of Example 4 of the present invention 12 O 19 / rGO coaxial fiber composite absorbing material wave absorption performance test diagram.

[0027] Figure 8 BaFe of Comparative Example 1 of the present invention 12 O 19 Test diagram of the absorbing performance of fiber composite absorbing material.

[0028] Fig. 9 This is a test diagram of the wave absorbing performance of the rGO fiber composite wave absorbing material of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] The present invention provides a coaxial graphene fiber composite absorbing material, wherein the composite absorbing material is a surface-modified reduced graphene oxide-ferrite coaxial fiber and a cured epoxy resin composited therewith; wherein, in the coaxial fiber, the reduced graphene oxide is a core layer and the ferrite is a skin layer.

[0031] According to the present invention, preferably, based on the total weight of the composite absorbing material, the content of the reduced graphene oxide is 0.5-8wt%, the content of the ferrite is 8-68wt%, and the content of the epoxy resin is 25-90wt%; further preferably, based on the total weight of the composite absorbing material, the content of the reduced graphene oxide is 1-5wt%, the content of the ferrite is 10-60wt%, and the content of the epoxy resin is 30-70wt%; more preferably, based on the total weight of the composite absorbing material, the content of the reduced graphene oxide is 1-5wt%, the content of the ferrite is 30-50wt%, and the content of the epoxy resin is 45-60wt%.

[0032] According to a preferred embodiment of the present invention, the composite absorbing material is prepared by impregnating surface-modified reduced graphene oxide-ferrite coaxial fibers in an epoxy resin impregnation solution and then heating and curing.

[0033] The surface modification of the present invention is for reduced 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, and the surface modification is used to enhance the mixing of rGO and epoxy resin. According to a preferred embodiment of the present invention, the surface-modified reduced graphene oxide-ferrite coaxial fiber is a reduced graphene oxide-ferrite coaxial fiber with a coupling agent surface modification, which is prepared by surface modification of reduced graphene oxide-ferrite coaxial fiber with a coupling agent. The present invention can adopt 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. The above coupling agents are all commercially available, such as silane coupling agent A-172 (vinyltri(β-methoxyethoxy)silane).

[0034] According to a preferred embodiment of the present invention, the reduced graphene oxide-ferrite coaxial fiber is obtained by reducing graphene oxide-ferrite coaxial fiber.

[0035] According to a preferred embodiment of the present invention, the graphene oxide-ferrite coaxial fiber is obtained by wet spinning, shaping and drying a ferrite spinning solution and a graphene oxide slurry.

[0036] According to a preferred embodiment of the present invention, the ferrite spinning solution is obtained by dispersing hexagonal flake ferrite in a water-soluble polymer aqueous solution and then ultrasonically dispersing it.

[0037] According to the present invention, preferably, the hexagonal ferrite is at least one of BaM type, Me2W type, Me2Y type, Me2Z type, Me2X type and Me2U type, Me is a divalent metal ion Sr 2+ , Pb 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ and Cu 2+At least one of the following: the hexagonal ferrite sheet diameter size is 0.1 ~ 8μm, preferably 0.2 ~ 5μm, more preferably 1 ~ 4μm, the sheet thickness is 10 ~ 600nm, preferably 20 ~ 500nm, more preferably 30 ~ 200nm.

[0038] According to the present invention, preferably, the water-soluble polymer is at least one of polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone and polymaleic anhydride; and the epoxy resin impregnation solution contains epoxy resin, dispersant and curing agent.

[0039] The present invention also provides a method for preparing a coaxial graphene fiber composite absorbing material, comprising the following steps:

[0040] (1) Hexagonal ferrite flakes are prepared by molten salt method;

[0041] (2) dispersing the hexagonal ferrite obtained in step (1) in a water-soluble polymer aqueous solution to obtain a first mixed solution, and obtaining a ferrite spinning solution after ultrasonic dispersion;

[0042] (3) wet spinning the ferrite spinning solution obtained in step (2) and the graphene oxide slurry, coagulating and fixing, and drying to obtain a coaxial fiber, the fiber cross section of which has a skin-core structure, the core layer is graphene oxide, and the skin layer is ferrite;

[0043] (4) contacting the coaxial fiber obtained in step (3) with a reducing agent for reduction, washing and drying after the reduction is completed, to obtain a reduced graphene oxide-ferrite coaxial fiber;

[0044] (5) immersing the reduced graphene oxide-ferrite coaxial fiber obtained in step (4) into a graphene surface modifier solution and heating it, then taking it out, washing it, and drying it to obtain a surface-modified reduced graphene oxide-ferrite coaxial fiber;

[0045] (6) adding the surface-modified reduced graphene oxide-ferrite coaxial fiber obtained in step (5) into a second mixed liquid to uniformly disperse the components, and then heating and curing to obtain the composite absorbing material, wherein the second mixed liquid comprises an epoxy resin, a dispersant and a curing agent.

[0046] According to the present invention, preferably, in step (1), the step of preparing hexagonal flake ferrite by the molten salt method comprises: mixing and grinding the molten salt and the ferrite precursor and calcining them.

[0047] The molten salt is preferably at least one of NaCl and KCl; the ferrite precursor is preferably a mixture of iron oxide and at least one composite metal oxide; the mass ratio of the ferrite precursor to the molten salt is preferably 1:10 to 10:1, preferably 1:2 to 5:1, and more preferably 1:1 to 3:1; the composite metal is preferably at least one of Ba, Sr, Pb, Co, Ni, Zn and Cu.

[0048] The hexagonal ferrite prepared by the method of the present invention is preferably at least one of BaM type, Me2W type, Me2Y type, Me2Z type, Me2X type and Me2U type, Me is a divalent metal ion Sr 2+ , Pb 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ and Cu 2+ At least one of the following: the sheet diameter of the hexagonal ferrite is preferably 0.2 to 5 μm, and the sheet thickness is preferably 50 to 500 nm.

[0049] According to the method of the present invention, the calcination conditions preferably include: a temperature range of 800 to 1000° C. and a heat preservation time of 1 to 6 hours.

[0050] The grinding conditions may be ball milling at a speed of 200 to 600 r / min for 6 to 10 hours, drying and sieving after ball milling, then mixing the ferrite precursor with the molten salt, and performing secondary mixing and ball milling, and then drying and sieving, and then calcining.

[0051] According to the method of the present invention, in step (2), the concentration of ferrite in the ferrite spinning solution is preferably 2wt% to 20wt%, and the concentration of the water-soluble polymer in the water-soluble polymer aqueous solution is preferably 5wt% to 20wt%; the water-soluble polymer is preferably at least one of polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone and polymaleic anhydride.

[0052] According to the method of the present invention, in step (3), the graphene oxide slurry may include water and graphene oxide, and the concentration of graphene oxide in the graphene oxide slurry is preferably 5 to 30 g / L, preferably 10 to 15 g / L.

[0053] According to the method of the present invention, the wet spinning step comprises: pushing the ferrite spinning solution and the graphene oxide slurry into a coagulation bath at different spinning speeds respectively, preferably, the spinning speed of the ferrite spinning solution is 5 to 10 times the spinning speed of the graphene oxide slurry; more preferably, the spinning speed of the ferrite spinning solution is 0.2 to 1 mL / min, and the spinning speed of the graphene oxide slurry is 0.02 to 0.2 mL / min.

[0054] According to the method of the present invention, the coagulation bath is preferably at least one of ethanol, acetic acid, CaCl2 solution and hexadecyltrimethylammonium bromide solution, and the concentration of the coagulation bath is preferably 0.05-1 mol / L, preferably 0.1-0.5 mol / L.

[0055] According to the method of the present invention, in step (4), the reducing agent can be one or more of hydroiodic acid, ascorbic acid, hydrazine hydrate, ammonia, potassium hydroxide, sodium oxide, dimethylhydrazine and hydroquinone; preferably, it is a solution of hydroiodic acid in acetic acid, wherein the volume ratio of hydroiodic acid to acetic acid is preferably 1:0.8-1.2.

[0056] According to the method of the present invention, in step (5), the graphene surface modifier is preferably a coupling agent for improving the mixing of graphene and epoxy resin, and the available coupling agent is selected from one or more of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, and borate coupling agents. The concentration of the graphene surface modifier solution is preferably 1wt% to 10wt%; the solid-liquid mass ratio of the coaxial fiber to the graphene surface modifier solution is preferably 1:0.1 to 10, and more preferably 1:3 to 8.

[0057] According to a preferred embodiment of the present invention, the graphene surface modifier solution is a silane coupling agent dispersion, and the silane coupling agent dispersion includes a silane coupling agent and an ethanol aqueous solution, and the mass ratio of ethanol to water in the ethanol aqueous solution is preferably 5 to 15:1, and more preferably 8 to 12:1.

[0058] According to the method of the present invention, the silane coupling agent is preferably at least one of aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-glycidyloxypropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0059] According to the method of the present invention, the heating conditions preferably include: a heating temperature of 80 to 120° C. and a heating time of 0.5 to 6 hours.

[0060] According to the method of the present invention, in step (6), the mass ratio of the epoxy resin, the dispersant and the curing agent is preferably 1:0.1 to 1:0.2 to 0.8.

[0061] 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.

[0062] According to the method of the present invention, in step (6), the mass ratio of the coaxial fiber to the second mixed liquid is preferably 0.05 to 0.5:1, and the epoxy resin and the dispersant are usually added first, and the curing agent is added last. The uniform dispersion is preferably performed by mechanical stirring, and the mechanical stirring time is preferably 10 to 30 minutes; the curing temperature is preferably 80 to 120°C, and the curing time is preferably 0.5 to 2 hours.

[0063] The present invention also provides a coaxial graphene fiber composite wave absorbing material prepared by the above preparation method.

[0064] The coaxial graphene fiber 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.

[0065] 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.

[0066] Example 1

[0067] This embodiment is used to illustrate the coaxial graphene fiber composite absorbing material of the present invention, and the preparation method includes the following steps:

[0068] 1) The raw materials BaCO3 and Fe2O3 were weighed in a ball mill according to a molar ratio of Ba:Fe=1:12, ball milled at a speed of 400r / min for 8h, dried and sieved, and then mixed with molten salt NaCl at a mass ratio of 1:2 for a second time, ball milled, dried and sieved, and the obtained mixed powder was placed in a crucible and calcined at 800°C in a muffle furnace for 6h, then filtered and washed, and dried at 100°C in a blast drying oven for 24h to obtain hexagonal ferrite BaFe 12 O 19 It is of BaM type, with a flake size of about 2 μm and a flake thickness of about 50 nm.

[0069] 2) Weigh 2 parts of the hexagonal ferrite obtained in step 1) and 5 parts of polyvinyl alcohol (PVA), disperse them in 93 parts of water to obtain a first mixed solution, and obtain a ferrite spinning solution with a concentration of 2 wt% after ultrasonic dispersion.

[0070] 3) The ferrite spinning solution in step 2) is added to a syringe, and the syringe is connected to the shell layer of the coaxial needle through a Luer connector. A 10 g / L graphene oxide (GO) solution is added to another syringe, and the other syringe is connected to the core layer of the coaxial needle through a Luer connector. The shell layer and the core layer are pushed into a 0.2 mol / L CaCl2 coagulation bath at a spinning speed of 1 mL / min and 0.2 mL / min, respectively, and coagulated and fixed, and dried to obtain a core layer of GO and a skin layer of BaFe 12 O 19 coaxial fiber.

[0071] 4) adding the coaxial fiber obtained in step 3) into a reducing agent solution having a volume ratio of hydroiodic acid to acetic acid of 1:1 for full reduction, washing and drying after the reduction is completed to obtain a reduced graphene oxide-ferrite coaxial fiber.

[0072] 5) 9 parts of ethanol and 1 part of water were measured in a beaker, 0.1 parts of silane coupling agent A-172 (purchased from New Blue Sky) were added, and the mixture was stirred for 20 minutes to obtain a silane coupling agent dispersion. 2 parts of reduced graphene oxide-ferrite coaxial fiber were weighed and immersed in the silane coupling agent dispersion and heated at 100° C. for 1 hour, and then taken out, washed, and dried to obtain surface-modified reduced graphene oxide-ferrite coaxial fiber.

[0073] 6) 10 parts of epoxy resin and 1 part of dispersant (ethanol) were mixed to obtain a mixed solution, 2 parts of the modified reduced graphene oxide-ferrite coaxial fiber were immersed in the mixed solution, and then 5 parts of curing agent (phenolic modified ethylenediamine curing agent) were added and mechanically stirred for 20 minutes to make the fiber uniformly dispersed, and then transferred to a blast oven for heating and curing at a curing temperature of 100°C and a curing time of 1 hour to obtain BaFe 12 O 19 / rGO coaxial fiber composite absorbing material, wherein the content of reduced graphene oxide is 1wt%, the content of ferrite is 10wt%, and the content of epoxy resin is 89wt%.

[0074] Figure 1 The middle curve shows the BaFe 12 O 19 / rGO coaxial fiber composite absorber wave absorption performance test diagram. Figure 1 It can be seen that the minimum reflection loss value (RL) of the composite material of Example 1 is -26.9 dB (@6.8 GHz), and the effective absorption bandwidth (RL<-10 dB) of a single thickness (2 mm) is 4.24 GHz.

[0075] Example 2

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

[0077] 1) The raw materials BaCO3 and Fe2O3 were weighed in a ball mill according to a molar ratio of Ba:Fe=1:12, ball milled at a speed of 400r / min for 8h, dried and sieved, and then mixed with molten salt NaCl at a mass ratio of 5:1 for a second time, ball milled, dried and sieved, and the obtained mixed powder was placed in a crucible and calcined at 1000°C in a muffle furnace for 1h, then filtered and washed, and dried at 100°C in a blast drying oven for 24h to obtain hexagonal ferrite BaFe 12 O 19 It is of BaM type, with a flake size of about 4.5 μm and a flake thickness of about 150 nm.

[0078] 2) Weigh 20 parts of the hexagonal flake ferrite obtained in step 1) and 20 parts of polyvinyl alcohol (PVA), disperse them in 60 parts of water to obtain a first mixed solution, and obtain a ferrite spinning solution with a concentration of 20 wt% after ultrasonic dispersion.

[0079] 3) The ferrite spinning solution in step 2) is added to a syringe, and the syringe is connected to the shell layer of the coaxial needle through a Luer connector. A 12 g / L graphene oxide (GO) solution is added to another syringe, and the other syringe is connected to the core layer of the coaxial needle through a Luer connector. The shell layer and the core layer are pushed into a 0.2 mol / L CaCl2 coagulation bath at a spinning speed of 0.2 mL / min and 0.02 mL / min, respectively, and coagulated and formed, and dried to obtain a core layer of GO and a skin layer of BaFe 12 O 19 coaxial fiber.

[0080] 4) adding the coaxial fiber obtained in step 3) into a reducing agent solution having a volume ratio of hydroiodic acid to acetic acid of 1:1 for full reduction, washing and drying after the reduction is completed to obtain a reduced graphene oxide-ferrite coaxial fiber.

[0081] 5) 9 parts of ethanol and 1 part of water were measured in a beaker, 1 part of silane coupling agent A-172 was added, and the mixture was stirred for 20 minutes to obtain a silane coupling agent dispersion. 2 parts of reduced graphene oxide-ferrite coaxial fiber were weighed and immersed in the silane coupling agent dispersion and heated at 100° C. for 1 hour. The fiber was then taken out, washed, and dried to obtain a surface-modified reduced graphene oxide-ferrite coaxial fiber.

[0082] 6) 10 parts of epoxy resin and 10 parts of dispersant (ethanol) were mixed to obtain a mixed solution, 2.5 parts of the modified reduced graphene oxide-ferrite coaxial fiber was immersed in the mixed solution, and then 5 parts of curing agent (phenolic modified ethylenediamine curing agent) were added and mechanically stirred for 20 minutes to make the fiber uniformly dispersed, and then transferred to a blast oven for heating and curing at a curing temperature of 100°C and a curing time of 1 hour to obtain BaFe 12 O 19 / rGO coaxial fiber composite absorbing material, wherein the content of reduced graphene oxide is 3wt%, the content of ferrite is 60wt%, and the content of epoxy resin is 37wt%.

[0083] Figure 2 The middle curve shows the BaFe 12 O 19 / rGO coaxial fiber composite absorber wave absorption performance test diagram. Figure 2 It can be seen that the minimum reflection loss value (RL) of the composite material of Example 2 is -27.1 dB (@6.4 GHz), and the effective absorption bandwidth (RL<-10 dB) of a single thickness (2 mm) is 3.92 GHz.

[0084] Example 3

[0085] This embodiment is used to illustrate the coaxial graphene fiber composite absorbing material of the present invention, and the preparation method includes the following steps:

[0086] 1) The raw materials BaCO3 and Fe2O3 were weighed in a ball mill according to a molar ratio of Ba:Fe=1:12, ball milled at a speed of 400r / min for 8h, dried and sieved, and then mixed with molten salt NaCl at a mass ratio of 2:1 for a second time, ball milled, dried and sieved, and the obtained mixed powder was placed in a crucible and calcined at 900°C in a muffle furnace for 2h, then filtered and washed, and dried at 100°C in a blast drying oven for 24h to obtain hexagonal ferrite BaFe 12 O 19 , its SEM picture is as follows Figure 5 As shown by Figure 5 It can be seen that the hexagonal ferrite BaFe 12 O 19 It is of BaM type, with a flake size of about 2.5 μm and a flake thickness of about 50 nm.

[0087] 2) Weigh 15 parts of the hexagonal ferrite obtained in step 1) and 10 parts of polyvinyl alcohol (PVA), disperse them in 75 parts of water to obtain a first mixed solution, and obtain a ferrite spinning solution with a concentration of 15 wt% after ultrasonic dispersion.

[0088] 3) The ferrite spinning solution in step 2) is added to a syringe, and the syringe is connected to the shell layer of the coaxial needle through a Luer connector. A 15 g / L graphene oxide (GO) solution is added to another syringe, and the other syringe is connected to the core layer of the coaxial needle through a Luer connector. The shell layer and the core layer are pushed into a 0.2 mol / L CaCl2 coagulation bath at a spinning speed of 0.5 mL / min and 0.1 mL / min, respectively, and coagulated and formed, and dried to obtain a core layer of GO and a skin layer of BaFe 12 O 19 coaxial fiber.

[0089] 4) adding the coaxial fiber obtained in step 3) into a reducing agent solution having a volume ratio of hydroiodic acid to acetic acid of 1:1 for full reduction, washing and drying after the reduction is completed to obtain a reduced graphene oxide-ferrite coaxial fiber;

[0090] 5) 9 parts of ethanol and 1 part of water were measured in a beaker, 0.5 parts of silane coupling agent A-172 were added, and the mixture was stirred for 20 minutes to obtain a silane coupling agent dispersion. 2 parts of reduced graphene oxide-ferrite coaxial fiber were weighed and immersed in the silane coupling agent dispersion and heated at 100° C. for 1 hour, and then taken out, washed, and dried to obtain surface-modified reduced graphene oxide-ferrite coaxial fiber.

[0091] 6) 10 parts of epoxy resin and 4 parts of dispersant (ethanol) were mixed to obtain a mixed solution, 2 parts of the modified reduced graphene oxide-ferrite coaxial fiber were immersed in the mixed solution, and then 5 parts of curing agent (phenolic modified ethylenediamine curing agent) were added and mechanically stirred for 20 minutes to make the fiber uniformly dispersed, and then transferred to a blast oven for heating and curing at a curing temperature of 100°C and a curing time of 1 hour to obtain BaFe 12 O 19 / rGO coaxial fiber composite absorbing material, wherein the content of reduced graphene oxide is 5wt%, the content of ferrite is 45wt%, and the content of epoxy resin is 50wt%. Figure 6 The BaFe of Example 3 12 O 19 SEM image of / rGO coaxial fiber.

[0092] Figure 3 The BaFe of Example 3 12 O 19 The impedance matching test diagram of the / rGO coaxial fiber composite absorbing material shows that its impedance matching coefficient reaches 0.5 (the impedance matching coefficient of perfect matching →1), and the electromagnetic matching is good. Figure 4 The middle curve shows the BaFe 12 O 19 / rGO coaxial fiber composite absorber wave absorption performance test diagram; Figure 4 It can be seen that the minimum reflection loss value (RL) of the composite material of Example 3 is -35dB (@11GHz), and the effective absorption bandwidth (RL<-10dB) of a single thickness (1.5mm) is 8.32GHz, which has good absorption performance.

[0093] Example 4

[0094] This embodiment is used to illustrate the coaxial graphene fiber composite absorbing material of the present invention, and the preparation method includes the following steps:

[0095] 1) The raw materials BaCO3 and Fe2O3 were weighed in a ball mill according to a molar ratio of Ba:Fe=1:12, ball milled at a speed of 400r / min for 8h, dried and sieved, and then mixed with molten salt NaCl at a mass ratio of 10:1 for a second time, ball milled, dried and sieved, and the obtained mixed powder was placed in a crucible and calcined at 900°C in a muffle furnace for 2h, then filtered and washed, and dried at 100°C in a blast drying oven for 24h to obtain hexagonal ferrite BaFe 12 O 19 , its SEM picture is as follows Figure 4 As shown by Figure 4 It can be seen that the hexagonal ferrite BaFe 12 O 19 It is of BaM type, with a flake size of about 5 μm and a flake thickness of about 500 nm.

[0096] 2) Weigh 15 parts of the hexagonal ferrite obtained in step 1) and 10 parts of polyvinyl alcohol (PVA), disperse them in 75 parts of water to obtain a first mixed solution, and obtain a ferrite spinning solution with a concentration of 15 wt% after ultrasonic dispersion.

[0097] 3) The ferrite spinning solution in step 2) is added to a syringe, and the syringe is connected to the shell layer of the coaxial needle through a Luer connector. 18 g / L of graphene oxide (GO) solution is added to another syringe, and the other syringe is connected to the core layer of the coaxial needle through a Luer connector. The shell layer and the core layer are pushed into a 0.2 mol / L CaCl2 coagulation bath at a spinning speed of 0.5 mL / min and 0.1 mL / min, respectively, and coagulated and formed, and dried to obtain a core layer of GO and a skin layer of BaFe 12 O 19 coaxial fiber.

[0098] 4) adding the coaxial fiber obtained in step 3) into a reducing agent solution having a volume ratio of hydroiodic acid to acetic acid of 1:1 for full reduction, washing and drying after the reduction is completed to obtain a reduced graphene oxide-ferrite coaxial fiber;

[0099] 5) 9 parts of ethanol and 1 part of water were measured in a beaker, 0.5 parts of silane coupling agent A-172 were added, and the mixture was stirred for 20 minutes to obtain a silane coupling agent dispersion. 2 parts of reduced graphene oxide-ferrite coaxial fiber were weighed and immersed in the silane coupling agent dispersion and heated at 100° C. for 1 hour, and then taken out, washed, and dried to obtain surface-modified reduced graphene oxide-ferrite coaxial fiber.

[0100] 6) 10 parts of epoxy resin and 4 parts of dispersant (ethanol) were mixed to obtain a mixed solution, 2 parts of the modified reduced graphene oxide-ferrite coaxial fiber were immersed in the mixed solution, and then 5 parts of curing agent (phenolic modified ethylenediamine curing agent) were added and mechanically stirred for 20 minutes to make the fiber uniformly dispersed, and then transferred to a blast oven for heating and curing at a curing temperature of 100°C and a curing time of 1 hour to obtain BaFe 12 O 19 / rGO coaxial fiber composite absorbing material, wherein the content of reduced graphene oxide is 5wt%, the content of ferrite is 45wt%, and the content of epoxy resin is 50wt%.

[0101] Figure 7 The middle curve shows the BaFe 12 O 19 / rGO coaxial fiber composite absorber wave absorption performance test diagram. The minimum reflection loss value (RL) of the coaxial fiber composite absorber in the 2-18GHz frequency band is -26.5dB (@5.9GHz), and the effective absorption bandwidth (RL<-10dB) of a single thickness (1.5mm) is 3.16GHz. By comparing this embodiment with embodiment 3, it can be seen that the increase in the proportion of molten salt leads to an increase in the thickness of the lamellae. The increased lamellae thickness and high concentration of GO slurry both affect the spinning quality, thereby affecting the performance of the overall absorbent composite material.

[0102] Comparative Example 1

[0103] This embodiment is used to illustrate a comparative composite absorbing material, and the preparation method includes the following steps:

[0104] 1) The raw materials BaCO3 and Fe2O3 were weighed in a ball mill according to a molar ratio of Ba:Fe=1:12, ball milled at a speed of 400r / min for 8h, dried and sieved, and then mixed with molten salt NaCl at a mass ratio of 2:1 for a second time, ball milled, dried and sieved, and the obtained mixed powder was placed in a crucible and calcined at 900°C in a muffle furnace for 2h, then filtered and washed, and dried at 100°C in a blast drying oven for 24h to obtain hexagonal ferrite flake BaFe 12 O 19 The flake size is about 2.5 μm and the flake thickness is about 50 nm.

[0105] 2) Weigh 15 parts of the hexagonal ferrite obtained in step 1) and 10 parts of polyvinyl alcohol (PVA), disperse them in 75 parts of water to obtain a first mixed solution, and obtain a ferrite spinning solution with a concentration of 15 wt% after ultrasonic dispersion.

[0106] 3) The ferrite spinning solution in step 2) is added into a syringe, the syringe and the needle are connected through a Luer connector, and the solution is pushed into a 0.1 mol / L CaCl2 coagulation bath at a spinning speed of 0.5 mL / min, coagulated and fixed, and dried to obtain BaFe 12 O 19 fiber.

[0107] 4) Measure 9 parts of ethanol and 1 part of water into a beaker, add 0.5 parts of silane coupling agent A-172, stir for 20 minutes to prepare a silane coupling agent dispersion, weigh 2 parts of BaFe 12 O 19 The ferrite fiber is immersed in a silane coupling agent dispersion and heated at 100° C. for 1 hour, then taken out, washed, and dried to obtain a surface-modified ferrite fiber.

[0108] 5) 10 parts of epoxy resin and 4 parts of dispersant (ethanol) were mixed to obtain a mixed solution, 2 parts of the modified ferrite fiber were immersed in the mixed solution, and then 5 parts of curing agent (phenolic modified ethylenediamine curing agent) were added and mechanically stirred for 20 minutes to make the fiber uniformly dispersed, and then transferred to a blast oven for heating and curing at a curing temperature of 100°C and a curing time of 1 hour to obtain BaFe 12 O 19 Epoxy composite absorbing material.

[0109] Figure 8 The middle curve shows the BaFe 12 O 19 Test diagram of the wave absorption performance of fiber composite wave absorbing materials. Figure 8 It can be seen that the minimum reflection loss value (RL) of the composite material of Comparative Example 1 is -25.2 dB (@13.1 GHz), and the effective absorption bandwidth (RL<-10 dB) of a single thickness (1.5 mm) is 5.84 GHz.

[0110] Comparative Example 2

[0111] This embodiment is used to illustrate a comparative composite absorbing material, and the preparation method includes the following steps:

[0112] 1) Add 15 g / L graphene oxide (GO) solution into a syringe, connect the syringe and the needle through a Luer connector, push it into a 0.2 mol / L CaCl2 coagulation bath at a spinning speed of 0.1 mL / min, coagulate and shape, and dry to obtain GO fibers.

[0113] 2) adding the GO fiber obtained in step 1) into a reducing agent solution having a volume ratio of hydroiodic acid to acetic acid of 1:1 for full reduction, washing and drying after the reduction is completed to obtain reduced graphene oxide fiber.

[0114] 3) 9 parts of ethanol and 1 part of water were measured in a beaker, 0.5 parts of silane coupling agent A-172 were added, and the mixture was stirred for 20 minutes to obtain a silane coupling agent dispersion. 2 parts of reduced graphene oxide fiber were weighed and immersed in the silane coupling agent dispersion and heated at 100° C. for 1 hour, and then taken out, washed, and dried to obtain surface-modified reduced graphene oxide fiber.

[0115] 4) 10 parts of epoxy resin and 4 parts of dispersant (ethanol) were mixed to obtain a mixed solution, 2 parts of the modified reduced graphene oxide fiber were immersed in the mixed solution, and then 5 parts of curing agent (phenolic modified ethylenediamine curing agent) were added and mechanically stirred for 20 minutes to make the fiber evenly dispersed, and then transferred to a blast oven for heating and curing at a curing temperature of 100°C and a curing time of 1 hour to obtain an rGO epoxy composite absorbing material.

[0116] The rGO epoxy composite absorbing material was subjected to electromagnetic parameter tests and performance tests. Fig. 9 The middle curve shows the BaFe 12 O 19 Test diagram of the wave absorption performance of fiber composite wave absorbing materials. Fig. 9 It can be seen that the minimum reflection loss value (RL) of the rGO epoxy composite absorbing material in the frequency band of 2 to 18 GHz is -24.8 dB (@5.1 GHz), and the effective absorbing bandwidth (RL <-10 dB) of a single thickness (1.5 mm) is 5.52 GHz.

[0117] 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.

[0118] 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 coaxial graphene fiber composite absorbing material, characterized in that: The composite wave absorbing material is a surface-modified reduced graphene oxide-ferrite coaxial fiber and a cured epoxy resin composited therewith; wherein, in the coaxial fiber, the reduced graphene oxide is a core layer and the ferrite is a skin layer.

2. The coaxial graphene fiber composite absorbing material according to claim 1, wherein: Based on the total weight of the composite absorbing material, the content of the reduced graphene oxide is 0.5-8wt%, the content of the ferrite is 8-68wt%, and the content of the epoxy resin is 25-90wt%; preferably, based on the total weight of the composite absorbing material, the content of the reduced graphene oxide is 1-5wt%, the content of the ferrite is 10-60wt%, and the content of the epoxy resin is 30-70wt%; more preferably, based on the total weight of the composite absorbing material, the content of the reduced graphene oxide is 1-5wt%, the content of the ferrite is 30-50wt%, and the content of the epoxy resin is 45-60wt%.

3. The coaxial graphene fiber composite absorbing material according to claim 1, wherein: The composite wave absorbing material is prepared by impregnating surface-modified reduced graphene oxide-ferrite coaxial fibers in an epoxy resin impregnation solution and then heating and curing. The surface-modified reduced graphene oxide-ferrite coaxial fiber is a reduced graphene oxide-ferrite coaxial fiber surface-modified by a coupling agent, which is prepared by surface-modifying the reduced graphene oxide-ferrite coaxial fiber by a coupling agent; The reduced graphene oxide-ferrite coaxial fiber is obtained by reducing the graphene oxide-ferrite coaxial fiber; The graphene oxide-ferrite coaxial fiber is obtained by wet spinning, shaping and drying a ferrite spinning solution and a graphene oxide slurry; The ferrite spinning solution is obtained by dispersing hexagonal ferrite in a water-soluble polymer aqueous solution and then performing ultrasonic dispersion.

4. The coaxial graphene fiber composite absorbing material according to claim 3, wherein: The hexagonal ferrite is at least one of BaM type, Me2W type, Me2Y type, Me2Z type, Me2X type and Me2U type, Me is a divalent metal ion Sr 2+ , Pb 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ and Cu 2+ At least one of the following: the hexagonal ferrite has a sheet diameter of 0.1 to 8 μm, preferably 0.2 to 5 μm, more preferably 1 to 4 μm, and a sheet thickness of 10 to 600 nm, preferably 20 to 500 nm, more preferably 30 to 200 nm; The water-soluble polymer is at least one of polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone and polymaleic anhydride; The epoxy resin impregnation liquid contains epoxy resin, dispersant and curing agent.

5. The coaxial graphene fiber 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 coaxial graphene fiber 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 coaxial graphene fiber composite absorbing material, characterized in that: The steps include: (1) Hexagonal ferrite flakes are prepared by molten salt method; (2) dispersing the hexagonal ferrite obtained in step (1) in a water-soluble polymer aqueous solution to obtain a first mixed solution, and obtaining a ferrite spinning solution after ultrasonic dispersion; (3) wet spinning the ferrite spinning solution obtained in step (2) and the graphene oxide slurry, coagulation fixation, and drying to obtain a coaxial fiber with a core layer of graphene oxide and a skin layer of ferrite; (4) contacting the coaxial fiber obtained in step (3) with a reducing agent for reduction, washing and drying after the reduction is completed, to obtain a reduced graphene oxide-ferrite coaxial fiber; (5) immersing the reduced graphene oxide-ferrite coaxial fiber obtained in step (4) into a graphene surface modifier solution and heating it, then taking it out, washing it, and drying it to obtain a surface-modified reduced graphene oxide-ferrite coaxial fiber; (6) adding the surface-modified reduced graphene oxide-ferrite coaxial fiber obtained in step (5) into a second mixed liquid to uniformly disperse the components, and then heating and curing to obtain the composite absorbing material, wherein the second mixed liquid comprises an epoxy resin, a dispersant and a curing agent.

8. The preparation method according to claim 7, wherein: In step (1), the step of preparing hexagonal flake ferrite by the molten salt method comprises: mixing and grinding the molten salt and the ferrite precursor and calcining; The molten salt is at least one of NaCl and KCl; the ferrite precursor is a mixture of iron oxide and at least one composite metal oxide; the mass ratio of the ferrite precursor to the molten salt is 1:10 to 10:1, preferably 1:2 to 5:1, and more preferably 1:1 to 3:1; the composite metal is at least one of Ba, Sr, Pb, Co, Ni, Zn and Cu; The hexagonal ferrite is at least one of BaM type, Me2W type, Me2Y type, Me2Z type, Me2X type and Me2U type, Me is a divalent metal ion Sr 2+ , Pb 2+ 、Co 2+ 、Ni 2+ 、Zn 2+ and Cu 2+ At least one of the following: the hexagonal ferrite has a sheet diameter of 0.1 to 8 μm, preferably 0.2 to 5 μm, more preferably 1 to 4 μm, and a sheet thickness of 10 to 600 nm, preferably 20 to 500 nm, more preferably 30 to 200 nm; The calcination conditions include: a temperature range of 800 to 1000° C. and a heat preservation time of 1 to 6 hours.

9. The preparation method according to claim 7, wherein: In step (2), the concentration of ferrite in the ferrite spinning solution is 2wt% to 20wt%, and the concentration of the water-soluble polymer in the water-soluble polymer aqueous solution is 5wt% to 20wt%; the water-soluble polymer is at least one of polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone and polymaleic anhydride.

10. The preparation method according to claim 7, wherein: In step (3), the graphene oxide slurry comprises water and graphene oxide, and the concentration of graphene oxide in the graphene oxide slurry is 5 to 30 g / L, preferably 10 to 15 g / L; The wet spinning step comprises: pushing a ferrite spinning solution and a graphene oxide slurry into a coagulation bath at different spinning speeds respectively; preferably, the spinning speed of the ferrite spinning solution is 5 to 10 times the spinning speed of the graphene oxide slurry; more preferably, the spinning speed of the ferrite spinning solution is 0.2 to 1 mL / min, and the spinning speed of the graphene oxide slurry is 0.02 to 0.2 mL / min; The coagulation bath is at least one of ethanol, acetic acid, CaCl2 solution and hexadecyltrimethylammonium bromide solution, and the concentration of the coagulation bath is 0.05-1 mol / L, preferably 0.1-0.5 mol / L.

11. The preparation method according to claim 7, wherein: In step (4), the reducing agent is one or more of hydroiodic acid, ascorbic acid, hydrazine hydrate, ammonia, potassium hydroxide, sodium oxide, dimethylhydrazine and hydroquinone; preferably a solution of hydroiodic acid in acetic acid, wherein the volume ratio of hydroiodic acid to acetic acid is 1:0.8-1.

2.

12. The preparation method according to claim 7, wherein: In step (5), 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 concentration of the graphene surface modifier solution is 1wt% to 10wt%; the solid-liquid mass ratio of the coaxial fiber to the graphene surface modifier solution is 1:0.1 to 10, preferably 1:3 to 8.

13. The preparation method according to claim 12, wherein: The graphene surface modifier solution is a silane coupling agent dispersion, which includes a silane coupling agent and an ethanol aqueous solution, wherein the mass ratio of ethanol to water in the ethanol aqueous solution is 5 to 15:1, preferably 8 to 12:1; The silane coupling agent is preferably at least one of aminopropyltriethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, γ-glycidyloxypropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

14. The preparation method according to claim 7, wherein: In step (5), the heating conditions include: heating temperature of 80 to 120° C., and heating time of 0.5 to 6 h.

15. The preparation method according to claim 7, wherein: In step (6), 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 amine curing agents, acid anhydride curing agents and resin curing agents; the mass ratio of the coaxial fiber to the second mixed liquid is 0.05 to 0.5:

1.

16. The preparation method according to claim 7, wherein: In step (6), the uniform dispersion is carried out by mechanical stirring, and the mechanical stirring time is 10 to 30 minutes; the curing temperature is 80 to 120° C., and the curing time is 0.5 to 2 hours.

17. The coaxial graphene fiber composite absorbing material prepared by the preparation method according to any one of claims 7 to 16.

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

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