Preparation method of wave-absorbing material and wave-absorbing material

Abstract

The embodiment of the invention relates to the technical field of wave-absorbing materials, in particular to a preparation method of a wave-absorbing material and the wave-absorbing material. In the method, the sulfur-nitrogen double-doped graphene is a graphene material of which crystal lattices are doped with sulfur atoms and nitrogen atoms. Heteroatoms such as nitrogen, sulfur and the like are doped into graphene crystal lattices, so that the electronic structure of the graphene can be changed, and the carrier concentration of the graphene can be adjusted; therefore, the sulfur-nitrogen double-doped graphene has stronger absorption and loss capabilities on electromagnetic waves. By doping nitrogen, sulfur and other heteroatoms into graphene crystal lattices, the conductivity of graphene can be reduced, so that sulfur-nitrogen double-doped graphene has better impedance matching characteristics, electromagnetic waves can enter the wave-absorbing material more effectively, reflection of the electromagnetic waves is reduced, and the absorption efficiency of the electromagnetic waves is improved. Meanwhile, MXene and double-doped graphene are combined to form a multi-layer structure, so that more heterogeneous interfaces can be introduced to the wave-absorbing material, the polarization effect of the wave-absorbing material is improved, and the wave-absorbing performance of the wave-absorbing material is further improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of absorbing materials, and in particular to a method for preparing absorbing materials and absorbing materials. Background Art

[0002] With the rapid development of science and technology, a large number of electronic products have flooded into people's daily lives. The electromagnetic radiation pollution caused by electronic products is becoming increasingly serious. The deteriorated electromagnetic environment will not only interfere with the normal operation of electronic and electrical equipment, but also affect human health.

[0003] Absorbing materials, also known as microwave absorbing materials, refer to a type of functional material that can effectively absorb incident electromagnetic waves, convert electromagnetic energy into heat energy and consume it, or cause electromagnetic waves to interfere and destruct, thereby significantly reducing the intensity of reflected electromagnetic waves.

[0004] Graphene is considered to be an efficient microwave absorber due to its high electrical conductivity, high specific surface area, high thermal conductivity and low density. However, the original graphene has a high carrier mobility, which reduces the impedance matching characteristics of the absorbing material and is not conducive to improving the absorbing performance of the absorbing material. Summary of the invention

[0005] In order to improve the absorbing performance of the absorbing material, the embodiment of the present application provides an absorbing material and a preparation method thereof, which can use sulfur-nitrogen dual-doped graphene with lower carrier mobility to prepare the absorbing material and improve the impedance matching characteristics of the absorbing material.

[0006] In a first aspect of the present application, a method for preparing an absorbing material is provided, the method comprising: obtaining a dispersion of sulfur-nitrogen dual-doped graphene; obtaining a dispersion of MXene; filtering the dispersion of the sulfur-nitrogen dual-doped graphene and the dispersion of MXene in sequence by a filtration device to form a filtration product on a filter medium of the filtration device, the filtration product comprising a sulfur-nitrogen dual-doped graphene layer and a MXene layer stacked in sequence; and drying the filtration product to obtain an absorbing material having a laminated structure.

[0007] In the embodiments of the present application, sulfur-nitrogen dual-doped graphene is a graphene material doped with sulfur atoms and nitrogen atoms in the lattice. Doping heteroatoms such as nitrogen and sulfur into the graphene lattice can change the electronic structure of graphene and adjust the carrier concentration of graphene; therefore, sulfur-nitrogen dual-doped graphene has a stronger ability to absorb and lose electromagnetic waves. In addition, doping heteroatoms such as nitrogen and sulfur into the graphene lattice can also reduce the conductivity of graphene, so that sulfur-nitrogen dual-doped graphene has better impedance matching characteristics, so that electromagnetic waves can more effectively enter the interior of the absorbing material, reduce the reflection of electromagnetic waves, and improve the absorption efficiency of electromagnetic waves by the absorbing material. At the same time, combining MXene with dual-doped graphene to form a multilayer structure can introduce more heterogeneous interfaces to the absorbing material, increase the polarization effect of the absorbing material, and further optimize the comprehensive absorbing performance of the absorbing material.

[0008] In some embodiments, before obtaining the dispersion of sulfur-nitrogen dual-doped graphene, the method further includes: preparing sulfur-nitrogen dual-doped graphene; the preparing sulfur-nitrogen dual-doped graphene includes: mixing reduced graphene oxide, thiourea and ethanol to obtain a first mixture; drying the first mixture to obtain a first dried product; and performing a first heat treatment on the first dried product under the protection of an inert gas to decompose the thiourea, and the decomposition product of the thiourea reacts with the reduced graphene oxide to generate sulfur-nitrogen dual-doped graphene.

[0009] In some embodiments, the first heat treatment of the first dried material under the protection of an inert gas includes: heating the first dried material to 500°C to 600°C under the protection of an inert gas, and keeping the temperature at 500°C to 600°C for 1.5h to 2.5h to obtain sulfur-nitrogen dual-doped graphene.

[0010] In some embodiments, the mass ratio of the reduced graphene oxide to thiourea ranges from (1:4) to (1:6).

[0011] In some embodiments, the drying treatment of the first mixture includes: after ultrasonic treatment of the first mixture, placing the first mixture in a fume hood and drying it naturally at room temperature for 11 hours to 13 hours to remove ethanol in the first mixture.

[0012] In some embodiments, before mixing the reduced graphene oxide, thiourea and ethanol, the method further includes: preparing reduced graphene oxide, and the preparing reduced graphene oxide includes: dispersing graphene oxide in deionized water to obtain a graphene oxide dispersion; adding a hydrogen peroxide solution to the graphene oxide dispersion to obtain a second mixture; while stirring the second mixture, heating the second mixture to 95°C to 100°C, and keeping the temperature at 95°C to 100°C for 2.5h to 3h to obtain a reactant; extracting treated graphene oxide from the reactant; and reducing the treated graphene oxide using a solid phase thermal reduction method to obtain reduced graphene oxide.

[0013] In some embodiments, the reduction treatment of the treated graphene oxide by solid phase thermal reduction method comprises: under the protection of inert gas, at 10°C·min -1 The heating rate was 3 °C·min -1 The heat treatment temperature of the treated graphene oxide is increased to 500° C. at a heating rate and maintained at 500° C. for 2 h.

[0014] In some embodiments, after extracting the treated graphene oxide from the reactants and before reducing the treated graphene oxide using a solid-phase thermal reduction method, the method further includes: dispersing the treated graphene oxide in deionized water to obtain a dispersion of treated graphene oxide, and heating the treated graphene oxide dispersion in an oven at 35°C to 45°C for 5.5h to 6.5h to obtain a second dried product; and reducing the treated graphene oxide using a solid-phase thermal reduction method includes: reducing the second dried product using a solid-phase thermal reduction method.

[0015] In some embodiments, the drying treatment of the filtration product includes: placing the filtration product in an oven at 35° C. to 40° C. and drying it for 5.5 to 6.5 hours.

[0016] In the second aspect of the present application, a wave absorbing material is further provided. The wave absorbing material is prepared according to the method described in the first aspect.

[0017] It should be understood that the contents described in the summary of the invention are not intended to limit the key or important features of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 It is a schematic diagram of the process of preparing the absorbing material provided in some embodiments of the present application. DETAILED DESCRIPTION

[0020] The principles and spirit of the present disclosure will be described below with reference to several exemplary embodiments shown in the accompanying drawings. It should be understood that the description of these specific embodiments is only to enable those skilled in the art to better understand and implement the present disclosure, and does not limit the scope of the present disclosure in any way. In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art.

[0021] As used herein, the term "including" and similar terms should be understood as open inclusion, i.e., "including but not limited to". The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first", "second", etc. may refer to different or the same objects, and are only used to distinguish the objects referred to, without implying a specific spatial order, temporal order, order of importance, etc. of the objects referred to.

[0022] Figure 1 is a schematic diagram of a process for preparing an absorbing material provided in some embodiments of the present application, such as Figure 1 As shown, the method comprises the following steps:

[0023] Step 11: Obtain a dispersion of sulfur-nitrogen dual-doped graphene.

[0024] In an embodiment of the present application, the sulfur-nitrogen dual-doped graphene can be dispersed in any suitable solvent (such as ethanol) to obtain a dispersion. Specifically, the sulfur-nitrogen dual-doped graphene and the solvent can be mixed, and the sulfur-nitrogen dual-doped graphene can be evenly dispersed in the solvent by stirring and / or ultrasound to obtain a dispersion of the sulfur-nitrogen dual-doped graphene.

[0025] In some embodiments, before step 11, the method further includes: preparing sulfur-nitrogen dual-doped graphene, and the method for preparing sulfur-nitrogen dual-doped graphene includes: mixing reduced graphene oxide, thiourea and ethanol to obtain a first mixture; drying the first mixture to obtain a first dried product; and performing a first heat treatment on the first dried product under the protection of an inert gas to decompose the thiourea, and the decomposition product of the thiourea reacts with the reduced graphene oxide to generate sulfur-nitrogen dual-doped graphene.

[0026] In some embodiments, under the protection of an inert gas, performing a first heat treatment on the first dried material specifically includes: under the protection of an inert gas, heating the first dried material to 500° C. to 600° C., and keeping the temperature at 500° C. to 600° C. for 1.5 h to 2.5 h to obtain sulfur-nitrogen dual-doped graphene.

[0027] In some embodiments, the method for preparing sulfur-nitrogen co-doped graphene specifically includes: adding rGO and thiourea to ethanol to obtain a first mixture, ultrasonically treating the first mixture, placing the first mixture in a fume hood, and naturally drying it at room temperature for 11 hours to 13 hours to remove the ethanol in the first mixture to obtain a first dried product, which is a black solid; wherein the ultrasonic treatment time can be 85 minutes to 95 minutes, and then, under the protection of an inert gas, at 5°C·min -1 The first mixture is heated to 500° C. to 600° C. at a heating rate of , and is kept at 500° C. to 600° C. for 1.5 h to 2.5 h to obtain sulfur-nitrogen dual-doped graphene.

[0028] In some embodiments, in order to further improve the microwave absorption performance of sulfur-nitrogen dual-doped graphene, the mass ratio of reduced graphene oxide to thiourea is in the range of (1:4) to (1:6).

[0029] In some embodiments, the inert gas may be any suitable inert gas such as nitrogen and / or argon.

[0030] In the embodiments of the present application, reduced graphene oxide (rGO) is used to represent graphene obtained after graphene oxide is reduced. Thiourea is dissolved in ethanol, and reduced graphene oxide, thiourea and ethanol are mixed to obtain a first mixture, and the first mixture is dried to obtain a first dried product, so that the thiourea in the first dried product can be more evenly distributed in rGO, which is beneficial to increase the doping amount of sulfur and nitrogen atoms on sulfur-nitrogen dual-doped graphene and improve the wave absorption performance of sulfur-nitrogen dual-doped graphene. Heat treatment of the first dried product can cause the thiourea in the first dried product to be thermally decomposed, and the decomposition product reacts with the reduced graphene, thereby realizing the doping of sulfur and nitrogen atoms on the surface of the reduced graphene.

[0031] Since rGO is obtained by reducing graphene oxide, there are many structural defects and residual oxygen-containing functional groups inside rGO, which makes rGO more likely to absorb and lose electromagnetic wave energy; however, rGO has a higher carrier mobility, which will cause impedance mismatch in the absorbing material; therefore, the embodiment of the present application obtains sulfur-nitrogen dual-doped graphene by doping sulfur atoms and nitrogen atoms in the rGO lattice to reduce the carrier mobility of rGO and induce dipole polarization of rGO, so that the sulfur-nitrogen dual-doped graphene has better absorbing performance than rGO.

[0032] In the embodiments of the present application, heteroatoms such as nitrogen and sulfur are doped into the graphene lattice to change the electronic structure of graphene and adjust the carrier concentration of graphene; therefore, sulfur-nitrogen co-doped graphene has a stronger ability to absorb and lose electromagnetic waves. In addition, doping heteroatoms such as nitrogen and sulfur into the graphene lattice can also reduce the conductivity of graphene, so that sulfur-nitrogen co-doped graphene has better impedance matching characteristics, allowing electromagnetic waves to more effectively enter the interior of the absorbing material, reducing the reflection of electromagnetic waves, and improving the absorption efficiency of the absorbing material to electromagnetic waves.

[0033] In some embodiments, before mixing reduced graphene oxide, thiourea and ethanol to obtain a first mixture, the method further includes: preparing reduced graphene oxide, and the method for preparing reduced graphene oxide includes: dispersing graphene oxide (GO) in deionized water to obtain a graphene oxide dispersion; adding a hydrogen peroxide solution to the graphene oxide dispersion to obtain a second mixture; while stirring the second mixture, heating the second mixture to 95°C to 100°C, and keeping it at 95°C to 100°C for 2.5h to 3h to obtain a reactant; extracting treated graphene oxide from the reactant; and reducing the treated graphene oxide using a solid phase thermal reduction method to obtain reduced graphene oxide.

[0034] In some embodiments, in order to further improve the wave absorption performance of sulfur-nitrogen dual-doped graphene, in the process of preparing reduced graphene oxide, 100 mg of GO is added to every 100 mL of deionized water. The method of dispersing GO in deionized water includes ultrasonic dispersion. The mass fraction of the solute in the hydrogen peroxide solution is 30%. The amount of hydrogen peroxide solution added for every 100 mg of GO is 10 mL.

[0035] In some embodiments, the method of reducing the treated graphene oxide by solid phase thermal reduction method comprises: under the protection of inert gas, at 10°C·min -1 The heating rate was 3 °C·min -1The heat treatment temperature of the treated graphene oxide is raised to 500° C. at a heating rate of , and kept at 500° C. for 2 hours. The solid phase thermal reduction method can decompose the oxygen-containing functional groups on the surface of the treated graphene oxide and release CO2 and H2O, so as to achieve the purpose of reducing the treated graphene oxide.

[0036] In some embodiments, in order to further improve the wave absorption performance of sulfur-nitrogen dual-doped graphene, after extracting the treated graphene oxide from the reactants, before reducing the treated graphene oxide using a solid-phase thermal reduction method, the method further includes: dispersing the treated graphene oxide in deionized water to obtain a dispersion of treated graphene oxide, placing the treated graphene oxide dispersion in an oven at 35°C to 45°C and heating it for 5.5h to 6.5h to obtain dried treated graphene oxide, i.e., a second dried product. The treated graphene oxide is reduced using a solid-phase thermal reduction method, specifically, the second dried product is reduced using a solid-phase thermal reduction method. Among them, the concentration of the treated graphene oxide in the dispersion of the treated graphene oxide can specifically be 0.5mg·mL -1 ~1.5 mg mL -1 .

[0037] In some embodiments, extracting treated graphene oxide from reactants includes: after the reactants are cooled to room temperature, separating treated graphene oxide (HGO) from the reactants by centrifugation, and then washing the separated HGO multiple times with deionized water to remove impurities in the HGO; the number of washing times can be specifically 3 or 4 times, etc.

[0038] In the embodiments of the present application, the use of hydrogen peroxide to pretreat graphene oxide (GO) has the following two effects: on the one hand, hydrogen peroxide can react with potassium permanganate that may remain in GO; on the other hand, hydrogen peroxide can further oxidize graphene oxide, making the oxidation degree of graphene oxide more sufficient, thereby causing structural defects and residual oxygen-containing functional groups to exist inside the reduced graphene oxide obtained after the reduction of GO. These characteristics make the reduced graphene oxide more likely to absorb and lose electromagnetic wave energy, but the high carrier mobility of the reduced graphene oxide will cause impedance mismatch. In order to reduce the carrier mobility of the reduced graphene oxide and induce dipole polarization, the embodiments of the present application use thiourea to dope the reduced graphene oxide with nitrogen and sulfur.

[0039] Step 12: Obtain a dispersion of MXene.

[0040] In the embodiments of the present application, MXene is a type of metal carbon / nitride with a two-dimensional layered structure, and its chemical formula is M n+1 X n Tx , where (n = 1-3), M represents early transition metals, such as Ti, Zr, V, Mo, etc.; X represents C or N elements, T x It is a surface group, usually -OH, -O, -F or -Cl. It is named MXene because it has a sheet structure similar to graphene. x It has the characteristics of high electrical conductivity, special morphological structure and controllable surface functional groups, which enables it to attenuate electromagnetic waves through conductive loss, multiple reflections, polarization loss and other means.

[0041] Specifically, in some embodiments, MXene can be dispersed in ethanol to obtain a MXene dispersion. In the MXene dispersion, the concentration of MXene can be 0.5 mg·mL -1 ~1.5 mg mL -1 .

[0042] Step 13: Filter the sulfur-nitrogen dual-doped graphene dispersion and the MXene dispersion in sequence through a filtration device to form a filtration product on the filter medium of the filtration device, wherein the filtration product includes a sulfur-nitrogen dual-doped graphene layer and a MXene layer stacked in sequence.

[0043] In some embodiments, the dispersion of sulfur-nitrogen dual-doped graphene can be filtered first, and then the dispersion of MXene can be filtered; or the dispersion of MXene can be filtered first, and then the dispersion of sulfur-nitrogen dual-doped graphene can be filtered. The filter medium can specifically be cellulose paper. For example, the dispersion of sulfur-nitrogen dual-doped graphene can be filtered first by a filtration device, so as to form a sulfur-nitrogen dual-doped graphene layer on the cellulose paper; then, the dispersion of MXene can be filtered, so as to form a MXene layer on the sulfur-nitrogen dual-doped graphene layer.

[0044] Step 14: Dry the filtered product to obtain a wave absorbing material with a laminated structure.

[0045] In some embodiments, after the filtration product is peeled off from the cellulose paper, the filtration product is placed in an oven at 35° C. to 45° C. and dried for 5.5 h to 6.5 h to obtain an absorbing material with a laminated structure.

[0046] Several embodiments of the present application are provided below.

[0047] Example 1

[0048] Step 1: Disperse 100 mg of graphene oxide in deionized water to obtain a GO dispersion; after ultrasonically treating the GO dispersion, add 10 mL of H2O2 with a solute concentration of 30% to the GO dispersion to obtain a second mixture; while stirring the second mixture, heat the second mixture to 100° C. and keep it at 100° C. for 3 hours to obtain a reactant; after the reaction product is cooled to room temperature, extract the treated graphene oxide from the reactant by centrifugation, wash it with deionized water for 3 times, and then re-disperse the treated graphene oxide (the treated graphene oxide is named HGO) in deionized water by ultrasonication to obtain a concentration of 1 mg·mL -1 HGO dispersion.

[0049] Step 2: Take 100 mL of 1 mg mL -1 The HGO dispersion was placed in an oven at 40 °C and heated for 6 hours to obtain dry HGO powder. -1 The heating rate was 3℃·min. -1 The heat treatment temperature of HGO powder was increased to 500°C at a heating rate and kept at 500°C for 2h to obtain reduced graphene oxide.

[0050] Step 3: Add 30 mg of reduced graphene oxide and 120 mg of thiourea to 30 mL of ethanol to obtain a first mixture. After ultrasonic treatment of the first mixture for 90 min, place it in a fume hood and dry it naturally at room temperature for 12 hours to remove the ethanol, thereby obtaining a first dried product (black solid). Subsequently, place the obtained first dried product in a test tube and heat it at 5 °C min under the protection of an inert gas. -1 The first dried material was heated to 500°C at a heating rate and kept at 500°C for 2h to obtain sulfur-nitrogen dual-doped graphene (NSG).

[0051] Step 4: Disperse NSGO in ethanol to obtain a concentration of 1 mg mL -1 MXene was dispersed in ethanol to obtain a concentration of 1 mg mL -1 10 mL of NSG dispersion and 10 mL of MXene dispersion were filtered sequentially by a filtration device to form a filtration product on the cellulose paper (filter medium) of the filtration device, the filtration product comprising a layer of NSG and a layer of MXene stacked sequentially; the filtration product was peeled off from the cellulose paper, and the filtration product was placed in an oven at 40° C. and dried for 6 hours to obtain an absorbing material.

[0052] Example 2

[0053] Step 1 and step 2 in this embodiment are the same as those in embodiment 1. Please refer to embodiment 1 for step 1 and step 2.

[0054] Step 3: Add 30 mg of reduced graphene oxide and 180 mg of thiourea to 30 mL of ethanol to obtain a first mixture. After ultrasonic treatment of the first mixture for 90 min, place it in a fume hood and dry it naturally at room temperature for 12 hours to remove the ethanol, thereby obtaining a first dried product (black solid). Subsequently, place the obtained first dried product in a test tube and heat it at 5 °C min under the protection of an inert gas. -1 The first dried material was heated to 600°C at a heating rate and kept at 600°C for 2h to obtain sulfur-nitrogen dual-doped graphene (NSG).

[0055] Step 4: Disperse NSGO in ethanol to obtain a concentration of 1 mg mL -1 MXene was dispersed in ethanol to obtain a concentration of 1 mg mL -1 15 mL of NSG dispersion and 15 mL of MXene dispersion were filtered sequentially by a filtration device to form a filtration product on the cellulose paper (filter medium) of the filtration device, the filtration product comprising a layer of NSG and a layer of MXene stacked sequentially; the filtration product was peeled off from the cellulose paper, and the filtration product was placed in an oven at 40° C. and dried for 6 hours to obtain an absorbing material.

[0056] Comparative Example 1

[0057] The steps 1 and 2 of the comparative example 1 are the same as those of the embodiment 1. Please refer to the embodiment 1 for the steps 1 and 2.

[0058] Step 3: Disperse the reduced graphene oxide obtained in step 2 in ethanol to obtain a concentration of 1 mg mL -1 MXene was dispersed in ethanol to obtain a concentration of 1 mg mL -1 10 mL of the reduced graphene oxide dispersion and 10 mL of the MXene dispersion are filtered sequentially by a filtration device to form a filtration product on the cellulose paper (filter medium) of the filtration device, the filtration product comprising a layer of reduced graphene oxide and a layer of MXene stacked in sequence; the filtration product is peeled off from the cellulose paper, and the filtration product is placed in an oven at 40° C. and dried for 6 hours to obtain an absorbing material.

[0059] The experimental results of the above embodiments and comparative examples are as follows:

[0060] In Example 1, when the thickness of the absorbing material is 1.52 mm, the minimum reflection loss (RLmin) of the absorbing material is -58.2 dB, and the effective absorption band is as high as 4.50 GHz.

[0061] In Example 2, when the thickness of the absorbing material is 1.75 mm, RLmin is -62.1 dB, and the effective absorption band is as high as 4.80 GHz.

[0062] In Comparative Example 1, when the thickness of the absorbing material is 1.62 mm, RLmin is -35.2 dB.

[0063] The above experimental results show that, compared with the reduced graphene oxide without heteroatom doping provided in Comparative Example 1, the sulfur-nitrogen dual-doped graphene provided in Example 1 and Example 2 can better improve the wave absorbing performance of the wave absorbing material.

[0064] In the embodiments of the present application, heteroatoms such as nitrogen and sulfur are doped into the graphene lattice to change the electronic structure of graphene and adjust the carrier concentration of graphene; therefore, sulfur-nitrogen co-doped graphene has a stronger ability to absorb and lose electromagnetic waves. In addition, doping heteroatoms such as nitrogen and sulfur into the graphene lattice can also reduce the conductivity of graphene, so that the sulfur-nitrogen co-doped graphene has better impedance matching characteristics, allowing electromagnetic waves to more effectively enter the interior of the absorbing material, reducing the reflection of electromagnetic waves and improving the absorption efficiency of the absorbing material for electromagnetic waves. At the same time, combining the MXene layer with the nitrogen-sulfur co-doped graphene layer to form a multilayer absorbing structure can introduce more heterogeneous interfaces into the absorbing material, increase the polarization effect of the absorbing material, and further improve the absorbing performance of the absorbing material.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a microwave absorbing material, characterized in that: The method comprises: obtaining a dispersion of sulfur-nitrogen dual-doped graphene; Obtaining a dispersion of MXene; The dispersion liquid of the sulfur-nitrogen dual-doped graphene and the dispersion liquid of the MXene are sequentially filtered by a filtration device to form a filtration product on a filter medium of the filtration device, wherein the filtration product includes a sulfur-nitrogen dual-doped graphene layer and a MXene layer stacked in sequence; The filtration product is dried to obtain a wave absorbing material with a laminated structure.

2. The method according to claim 1, characterized in that Before obtaining the dispersion of sulfur-nitrogen dual-doped graphene, the method further comprises: preparing sulfur-nitrogen dual-doped graphene; The method for preparing sulfur-nitrogen dual-doped graphene comprises: mixing reduced graphene oxide, thiourea and ethanol to obtain a first mixture; Drying the first mixture to obtain a first dried product; Under the protection of an inert gas, the first dried product is subjected to a first heat treatment to decompose the thiourea, and the decomposition product of the thiourea reacts with the reduced graphene oxide to generate sulfur-nitrogen dual-doped graphene.

3. The method according to claim 2, characterized in that The step of performing a first heat treatment on the first dried product under the protection of an inert gas comprises: Under the protection of an inert gas, the first dried product is heated to 500° C. to 600° C., and kept at 500° C. to 600° C. for 1.5 h to 2.5 h to obtain sulfur-nitrogen dual-doped graphene.

4. The method according to claim 2, characterized in that: The mass ratio of the reduced graphene oxide to thiourea is in the range of (1:4) to (1:6).

5. The method according to claim 2, characterized in that: The step of drying the first mixture comprises: After the first mixture is subjected to ultrasonic treatment, the first mixture is placed in a fume hood and naturally dried at room temperature for 11 h to 13 h to remove ethanol in the first mixture.

6. The method according to any one of claims 1 to 5, characterized in that: Before mixing the reduced graphene oxide, thiourea and ethanol, the method further comprises: preparing reduced graphene oxide, wherein the preparing reduced graphene oxide comprises: dispersing graphene oxide in deionized water to obtain a graphene oxide dispersion; adding a hydrogen peroxide solution to the graphene oxide dispersion to obtain a second mixture; While stirring the second mixture, heating the second mixture to 95° C. to 100° C., and keeping the temperature at 95° C. to 100° C. for 2.5 h to 3 h to obtain a reactant; extracting the treated graphene oxide from the reactants; The treated graphene oxide is reduced by a solid phase thermal reduction method to obtain reduced graphene oxide.

7. The method according to claim 6, characterized in that The method of reducing the treated graphene oxide by solid phase thermal reduction comprises: Under the protection of inert gas, at 10℃·min -1 The heating rate was 3 °C·min -1 The heat treatment temperature of the treated graphene oxide is increased to 500° C. at a heating rate and maintained at 500° C. for 2 h.

8. The method according to claim 6, characterized in that After extracting the treated graphene oxide from the reactants and before reducing the treated graphene oxide using a solid phase thermal reduction method, the method further includes: Dispersing the treated graphene oxide in deionized water to obtain a dispersion of the treated graphene oxide, and heating the dispersion of the treated graphene oxide in an oven at 35° C. to 45° C. for 5.5 h to 6.5 h to obtain a second dried product; The reducing treatment of the treated graphene oxide by solid phase thermal reduction method comprises: reducing the second dried product by solid phase thermal reduction method.

9. The method according to claim 6, characterized in that The drying process of the filtration product comprises: The filtered product was placed in an oven at 35°C to 40°C and dried for 5.5 to 6.5 hours.

10. A wave absorbing material, characterized in that: The absorbing material is prepared according to the method according to any one of claims 1-9.

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