Preparation method of wave-absorbing film, wave-absorbing film and application of wave-absorbing film

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 film, the wave-absorbing film and application of the wave-absorbing film. The wave-absorbing film provided by the embodiment of the invention comprises a carbonized fiber film and flower-like molybdenum disulfide and MOFs derivatives loaded on the carbon fiber film; wherein the carbonized fiber membrane has a multi-pore-channel structure, so that the impedance mismatch phenomenon can be improved, and electromagnetic waves are reflected for multiple times in pore channels so as to be better absorbed; the magnetic metal material in the MOFs derivative has magnetic loss on electromagnetic waves; the flower-shaped molybdenum disulfide is formed by assembling a plurality of molybdenum disulfide nanosheets through Van der Waals force, and the surface of the flower-shaped molybdenum disulfide is of a petal-like lamellar structure. On one hand, the molybdenum disulfide nanosheet can perform dielectric loss on electromagnetic waves; on the other hand, the petal-shaped surface structure of the flower-shaped molybdenum disulfide can promote multiple reflection and scattering of electromagnetic waves on the surface of the flower-shaped molybdenum disulfide, and absorption of the electromagnetic waves by the wave-absorbing film is further promoted.

Description

Technical Field

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

[0002] With the rapid development of modern science and technology, electromagnetic radiation fills people's living space, causing serious electromagnetic pollution. Microwave absorbing materials can absorb the electromagnetic wave energy projected onto their surfaces and convert the electromagnetic wave energy into heat energy or other forms of energy and consume it. Therefore, it is of urgent practical value to study materials with good microwave absorbing properties.

[0003] The key to the research of microwave absorbing materials lies in the preparation of microwave absorbing materials with high absorption rate, thin thickness, wide absorption bandwidth, light weight and low cost. However, traditional magnetic microwave absorbing materials (such as ferrites and metal powders) are difficult to meet the above requirements. Microwave absorbing film materials not only have good electromagnetic wave absorbing energy of traditional microwave absorbing materials, but also have the characteristics of light weight and thin thickness of films. In order to better solve the problem of electromagnetic pollution, modern science and technology put forward higher requirements for the microwave absorbing performance of microwave absorbing film materials. Summary of the Invention

[0004] In order to further improve the microwave absorbing performance of microwave absorbing film materials, the embodiments of the present application provide a preparation method of a microwave absorbing film, the microwave absorbing film and its application.

[0005] To solve the above technical problems, the embodiments of the present application provide the following technical solutions:

[0006] In the first aspect of the present application, a preparation method of a microwave absorbing film is provided. The method includes: taking a spinning solution, where the spinning solution includes an organic solvent and a soluble metal salt and a polymer dissolved in the organic solvent; performing electrospinning using the spinning solution to obtain a first fiber membrane; soaking the first fiber membrane in a solution of dimethylimidazole so that magnetic metal ions in the soluble metal salt on the surface of the fibers of the first fiber membrane react with the dimethylimidazole to generate metal-organic framework crystals, obtaining a second fiber membrane; performing carbonization treatment on the second fiber membrane to obtain a carbonized fiber composite membrane; performing a hydrothermal reaction using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate and thiourea to obtain a carbonized fiber composite membrane modified with flower-like molybdenum disulfide.

[0007] In the embodiments of the present application, when the first fiber membrane is immersed in a dimethylimidazole solution, metal ions in the soluble metal salt on the fiber surface of the first fiber membrane react with dimethylimidazole in the dimethylimidazole solution to form metal-organic framework crystals. Therefore, metal-organic framework (MOFs) crystals are loaded on the fiber surface of the second fiber membrane. After the second fiber membrane is carbonized, a carbonized fiber composite membrane is formed, wherein the MOFs crystals form MOFs derivatives and the polymer matrix forms a carbonized fiber membrane; after a hydrothermal reaction is carried out using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate and thiourea, a flower-like molybdenum disulfide modified carbonized fiber composite membrane, that is, an electromagnetic wave absorbing thin film, is obtained. Therefore, the electromagnetic wave absorbing thin film includes a carbonized fiber membrane, flower-like molybdenum disulfide and MOFs derivatives loaded on the carbon fiber membrane; wherein, the porous channel structure of the carbonized fiber membrane can improve the impedance mismatch phenomenon, enabling electromagnetic waves to be reflected multiple times inside the channels and thus being better absorbed; the magnetic metal materials in the MOFs derivatives have magnetic loss for electromagnetic waves, and there are sufficient interfaces and defects in the MOFs derivative structure, which is beneficial to increasing the loss ability of the electromagnetic wave absorbing thin film for electromagnetic waves; the flower-like molybdenum disulfide is assembled by a number of molybdenum disulfide nanosheets through van der Waals forces, and the surface of the flower-like molybdenum disulfide is a petal-like lamellar structure. On the one hand, the molybdenum disulfide nanosheets can cause dielectric loss to electromagnetic waves; on the other hand, the petal-like surface structure of the flower-like molybdenum disulfide can promote multiple reflections and scattering of electromagnetic waves on the surface of the flower-like molybdenum disulfide, further promoting the absorption of electromagnetic waves by the electromagnetic wave absorbing thin film.

[0008] In some embodiments, the soluble metal salt includes cobalt nitrate hexahydrate.

[0009] In some embodiments, in the spinning solution, the mass ratio of the soluble metal salt to the polymer ranges from (1:1) to (2:1).

[0010] In some embodiments, the immersing of the first fiber membrane in the dimethylimidazole solution includes: at room temperature, placing the first fiber membrane in the dimethylimidazole solution and soaking for 20 h to 30 h; wherein, the concentration of dimethylimidazole in the dimethylimidazole solution is 0.03 g·ml -1 ~0.05 g·ml -1 。

[0011] In some embodiments, before the carbonization treatment of the second fiber membrane, the method further includes: performing a pre-oxidation treatment on the second fiber membrane in an air atmosphere; wherein, the temperature of the pre-oxidation treatment is 220 °C to 240 °C, and the time of the pre-oxidation treatment is 1.5 h to 2.5 h.

[0012] In some embodiments, the carbonization treatment of the second fiber membrane includes: under the protection of an inert gas, placing the second fiber membrane at a temperature of 800°C to 850°C and keeping it warm for 1.5 h to 2.5 h.

[0013] In some embodiments, the hydrothermal reaction using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate, and thiourea includes: dissolving ammonium molybdate tetrahydrate and thiourea in deionized water to obtain an aqueous solution of ammonium molybdate tetrahydrate and thiourea; mixing the carbonized fiber composite membrane and the aqueous solution of ammonium molybdate tetrahydrate and thiourea to obtain the reactants for the hydrothermal reaction; performing the hydrothermal reaction using the reactants; wherein, the temperature of the hydrothermal reaction is 180°C to 220°C, and the time of the hydrothermal reaction is 20 h to 24 h.

[0014] In some embodiments, the mass ratio range of ammonium molybdate tetrahydrate to thiourea is (1:1.5) to (1:2.5).

[0015] In the second aspect of the present application, an absorbing film is further provided, and the absorbing film is prepared according to the method described in the first aspect.

[0016] In the third aspect of the present application, an application of an absorbing film prepared by the method described in the first aspect in the field of electromagnetic wave absorption is further provided.

[0017] It should be understood that the content described in the Summary of the Invention section is not intended to limit the key or important features of the present disclosure, nor 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 drawings required to be used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 is a schematic flowchart of a method for preparing an absorbing film provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[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 for enabling those skilled in the art to better understand and implement the present disclosure, rather than limiting 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 same meaning as commonly understood by those of ordinary skill in the art to which this disclosure belongs.

[0021] As used herein, the term "comprising" and its like terms should be understood as open inclusion, i.e., "including but not limited to". The term "based on" should be understood as "at least partially based 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] Exemplarily, Figure 1 is a schematic flowchart of a method for preparing an electromagnetic wave absorbing film provided by some embodiments of the present application. Please refer to Figure 1 , the method includes the following steps:

[0023] Step 11: Take a spinning solution, which includes an organic solvent, a soluble metal salt, and a polymer.

[0024] In some embodiments, the spinning solution includes an organic solvent, a soluble metal salt, and a polymer, wherein both cobalt chloride hexahydrate and the polymer are soluble in the organic solvent. The polymer can be any suitable polymer applicable to electrospinning. For example, the polymer is polystyrene, polycaprolactone, polyacrylonitrile (PAN), or polymethyl methacrylate; the organic solvent is a mixture of one or more of N,N-dimethylformamide (DMF), chloroform, tetrahydrofuran, and dimethyl sulfoxide. In certain embodiments of the present application, when the polymer is PAN and the organic solvent is DMF, the comprehensive electromagnetic wave absorption performance of the electromagnetic wave absorbing film is better.

[0025] Specifically, in some embodiments, step 11 specifically includes: configuring a spinning solution, and the method for configuring the spinning solution specifically includes: dissolving the soluble metal salt and the polymer in the organic solvent to obtain a spinning solution. Specifically, in some embodiments, the soluble metal salt can be first dissolved in the organic solvent to obtain a first solution, and then the polymer is dissolved in the first solution to obtain a spinning solution. Among them, the method for dissolving the polymer in the first solution can specifically be: adding the polymer to the first solution, and mixing and stirring the polymer and the first solution at a temperature of 55°C to 65°C for 5.5 h to 6.5 h to obtain a spinning solution.

[0026] In some embodiments, to further improve the microwave absorption performance of the microwave absorption film, in the spinning solution, the concentration of the soluble metal salt is 0.12 g·ml -1 , and the concentration of the polymer is 0.1 g·ml -1 . The metal ions in the soluble metal salt are magnetic metal ions, such as Co 2+ and / or Ni 2+ etc. Specifically, the soluble metal salt can be cobalt chloride hexahydrate (CoCl2·6H2O) and / or nickel chloride hexahydrate (NiCl2·6H2O), etc.

[0027] In some embodiments, to improve the comprehensive performance of the microwave absorption film, the mass ratio range of the soluble metal salt to the polymer in the spinning solution is (1:1) to (2:1).

[0028] Step 12: Use the spinning solution for electrospinning to obtain a first fiber membrane.

[0029] In some embodiments, Step 12 specifically includes: loading the spinning solution into the injection syringe of the electrospinning apparatus, performing electrospinning to obtain a first fiber membrane. By applying a high-voltage electrostatic field to the spinning solution through the electrospinning apparatus, the liquid droplets of the spinning solution can be subjected to the action of the electric field force. When the charge repulsion force on the liquid surface is greater than the surface tension of the liquid droplet, a Taylor cone will be formed, and a jet of the polymer will be ejected. A strong electric field intensity is formed between the two electrodes of the electrospinning apparatus due to the high-intensity electric field, and the jet is rapidly stretched into filaments within a short distance. During this process, the organic solvent in the spinning solution volatilizes, and the mixture of the polymer and the soluble metal salt is deposited on the receiver to form a first fiber membrane.

[0030] In the embodiments of the present application, the electrospinning apparatus mainly consists of three parts: a high-voltage power supply, a nozzle and a liquid supply device (generally using a syringe with a needle and a propulsion device), and a fiber receiving device. The main process parameters affecting electrospinning include polymer parameters (such as the relative molecular weight, relative molecular weight distribution, and solubility of the polymer), solvent parameters (such as the volatility and conductivity of the solvent), solution parameters (such as the concentration, viscosity, surface tension, and conductivity of the spinning solution), process control parameters (voltage, flow rate, and receiving distance), and environmental parameters (temperature, humidity, and air flow).

[0031] To further improve the comprehensive microwave absorption performance of the microwave absorption film, the specification of the electrospinning apparatus needle is 21G; the electrospinning voltage is 15 kV to 17 kV, the collection distance is 12 cm to 15 cm, and the injection rate is 0.8 mL·h -1 ~1.8 mL·h -1 .

[0032] Step 13: Immerse the first fiber membrane in a solution of dimethylimidazole so that the magnetic metal ions in the soluble metal salt on the fiber surface of the first fiber membrane react with the dimethylimidazole to form metal-organic framework crystals, obtaining a second fiber membrane.

[0033] In some embodiments, immersing the first fiber membrane in a solution of dimethylimidazole specifically includes: at room temperature, placing the first fiber membrane in a solution of dimethylimidazole and soaking for 20 h to 30 h; wherein, the concentration of dimethylimidazole in the solution of dimethylimidazole is 0.03 g·ml -1 ~0.05 g·ml -1 . The solution of dimethylimidazole can specifically be a methanol solution of dimethylimidazole.

[0034] In some embodiments, Step 13 specifically includes: drying the first fiber membrane, and then placing the first fiber membrane in a dimethylimidazole solution and soaking at room temperature for 20 h to 30 h. For example, the first fiber membrane can first be placed under vacuum drying at a temperature of 55 °C to 65 °C for 5.5 h to 6 h, and then the first fiber membrane is placed in a dimethylimidazole solution and soaked at room temperature for 20 h to 30 h.

[0035] In this embodiment, when the first fiber membrane is immersed in the dimethylimidazole solution, the magnetic metal ions (such as Co 2+ and / or Ni 2+ ) in the soluble metal salt on the fiber surface of the first fiber membrane react with the dimethylimidazole to form metal-organic framework crystals, obtaining a second fiber membrane. For example, Co 2+ can react with dimethylimidazole to form ZIF-67, thereby growing ZIF-67 on the fiber surface of the first fiber membrane to obtain a second fiber membrane.

[0036] Specifically, metal-organic frameworks (MOFs) generally refer to coordination compounds with a periodic structure assembled through coordination bonds, using organic ligands as linkers and metal ions (or metal ion clusters) as nodes. MOFs are materials with a highly ordered porous structure. During the synthesis of MOFs, in addition to the influence of ligands and metal ions, there are other influencing factors, such as reaction temperature, solvent, pH value, pressure, the ratio and concentration of ligands and metal salts, etc. These influencing factors can affect the self-assembly process of MOFs, thereby affecting the structure of MOFs and further affecting the performance of MOFs. Zeolitic Imidazolate Framework (ZIF) belongs to MOFs. In ZIF, organic imidazolate is cross-linked to transition metals to form a tetrahedral framework. ZIF is a new type of porous material that combines the high stability of inorganic zeolites, the high porosity of MOFs, and organic functions. The zeolite-type imidazole-based metal-organic framework ZIF-67 is a porous crystalline material constructed with divalent transition metal Co 2+ and imidazole-based ligands with a zeolite topology.

[0037] Step 14: Carbonize the second fiber membrane to obtain a carbonized fiber composite membrane.

[0038] In some embodiments, the step of carbonizing the second fiber membrane specifically includes: under the protection of an inert gas, place the second fiber membrane at 800°C to 850°C and keep it warm for 1.5 h to 2.5 h. After carbonizing the second fiber membrane, the polymer in the fibers of the second fiber membrane carbonizes to form a carbonized fiber membrane, and the MOF crystals on the surface of the second fiber membrane form MOF derivatives.

[0039] In some embodiments, before step 14, the above method further includes pre-oxidizing the second fiber membrane; wherein, the temperature of the pre-oxidation treatment is 220°C to 240°C, and the time of the pre-oxidation treatment is 1.5 h to 2.5 h. Specifically, the second fiber membrane can be placed in an air atmosphere for pre-oxidation treatment. In this embodiment, the second fiber membrane is first pre-oxidized and then carbonized, and the purpose is to prevent the structure of the second fiber membrane from collapsing during the carbonization process of the second fiber membrane.

[0040] Step 15: Perform a hydrothermal reaction using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate, and thiourea, so that the ammonium molybdate tetrahydrate and the thiourea react to form flower-like molybdenum disulfide, and obtain a flower-like molybdenum disulfide-modified carbonized fiber composite membrane.

[0041] In the embodiments of the present application, ammonium molybdate tetrahydrate and thiourea undergo a hydrothermal reaction to form flower-shaped molybdenum disulfide, and the flower-shaped molybdenum disulfide is loaded on a carbonized fiber composite membrane to form a carbonized fiber composite membrane modified with flower-shaped molybdenum disulfide. The flower-shaped molybdenum disulfide is composed of a number of molybdenum disulfide nanosheets assembled into flower-shaped molybdenum disulfide nanospheres through van der Waals forces; the surface of the flower-shaped molybdenum disulfide is lamellar, similar to flower petals.

[0042] In some embodiments, step 15 specifically includes: dissolving ammonium molybdate tetrahydrate and thiourea in deionized water to obtain an aqueous solution of ammonium molybdate tetrahydrate and thiourea; mixing the carbonized fiber composite membrane and the aqueous solution of ammonium molybdate tetrahydrate and thiourea to obtain a reactant; performing a hydrothermal reaction with the reactant; wherein, the temperature of the hydrothermal reaction is 180°C to 220°C, and the time of the hydrothermal reaction is 20 h to 24 h.

[0043] In some embodiments, in order to further improve the electromagnetic wave absorption performance of the absorbing film, the mass ratio range of ammonium molybdate tetrahydrate to the thiourea is (1:1.5) to (1:2.5).

[0044] The embodiments of the present application also provide an absorbing film, which is prepared according to the preparation method of the absorbing film provided in the above embodiments.

[0045] The embodiments of the present application also provide an application of an absorbing film prepared according to the preparation method of the absorbing film provided in the above embodiments in the field of electromagnetic wave absorption.

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

[0047] Example 1

[0048] Step 1: Dissolve 1.2 g of CoCl2·6H2O in 10 mL of DMF solvent to obtain a cobalt chloride hexahydrate solution. Then, add 1.0 g of PAN powder to the cobalt chloride hexahydrate solution to obtain a first mixed solution. At 60°C, vigorously stir the first mixed solution for 6 h to form a homogeneous spinning solution.

[0049] Step 2: Load the spinning solution into the injection pump of an electrospinning apparatus, and the specification of the needle of the electrospinning apparatus is 21G; perform electrospinning under the conditions of an electrospinning voltage of 15 kV, a collection distance of 15 cm, and an injection rate of 0.8 mL·h -1 to obtain a first fiber membrane.

[0050] Step 3: First, place the first fiber membrane in a vacuum at 60°C for 6 h, and then place the first fiber membrane in a methanol solution containing 4.0 g of dimethylimidazole in 100 mL and soak it at room temperature for 24 h to obtain a second fiber membrane.

[0051] Step 4: After cleaning the second fiber membrane with methanol, dry the second fiber membrane; place the purple second fiber membrane in an air atmosphere at 240 °C for pre-oxidation for 2 h, and then place the pre-oxidized second fiber membrane in an argon atmosphere at 800 °C for heat preservation for 2 h to obtain a carbonized fiber composite membrane.

[0052] Step 5: Add 0.14 g of thiourea and 0.07 g of ammonium molybdate tetrahydrate to 40 mL of deionized water and stir for 30 minutes to uniformly dissolve thiourea and ammonium molybdate tetrahydrate in deionized water to obtain an aqueous solution of thiourea and ammonium molybdate tetrahydrate. Subsequently, mix 80 mg of the carbonized fiber composite membrane with the aqueous solution of thiourea and ammonium molybdate tetrahydrate to obtain a reactant. Place the reactant in a hydrothermal reactor and heat it at 200 °C for 22 h to obtain a black reaction product. Wash the reaction product repeatedly with ethanol and deionized water, and then place the reaction product in a vacuum oven at 60 °C for drying for 6 h to obtain a flower-like molybdenum disulfide modified carbonized fiber composite membrane (i.e., the microwave absorbing thin film).

[0053] Example 2

[0054] Step 1: Dissolve 0.6 g of CoCl2·6H2O and 0.6 g of NiCl2·6H2O in 10 mL of DMF solvent to obtain a cobalt chloride hexahydrate solution. Then, add 1.0 g of PAN powder to the cobalt chloride hexahydrate solution to obtain a first mixture. Stir the first mixture vigorously at 60 °C for 6 h to form a homogeneous spinning solution.

[0055] Step 2: Load the spinning solution into the injection pump of an electrospinning instrument, and the specification of the needle of the electrospinning instrument is 21G; perform electrospinning under the conditions of an electrospinning voltage of 17 kV, a collection distance of 12 cm, and an injection rate of 1.8 mL·h -1 to obtain a first fiber membrane.

[0056] Step 3: First, place the first fiber membrane in a vacuum drying oven at 60 °C for 6 h, and then place the first fiber membrane in a methanol solution containing 4.0 g of dimethylimidazole in 100 mL and soak it at room temperature for 24 h to obtain a second fiber membrane.

[0057] Step 4: After cleaning the second fiber membrane with methanol, dry the second fiber membrane; place the purple second fiber membrane in an air atmosphere at 220 °C for pre-oxidation for 2 h, and then place the pre-oxidized second fiber membrane in an argon atmosphere at 850 °C for heat preservation for 2 h to obtain a carbonized fiber composite membrane.

[0058] Step 5: Add 0.16 g of thiourea and 0.08 g of ammonium molybdate tetrahydrate to 40 mL of deionized water and stir for 30 minutes to uniformly dissolve thiourea and ammonium molybdate tetrahydrate in deionized water, obtaining an aqueous solution of thiourea and ammonium molybdate tetrahydrate. Subsequently, mix 80 mg of the carbonized fiber composite membrane with the aqueous solution of thiourea and ammonium molybdate tetrahydrate to obtain a reactant. Place the reactant in a hydrothermal reactor and heat it at 200 °C for 22 h to obtain a black reaction product. Wash the reaction product repeatedly with ethanol and deionized water, and then place the reaction product in a vacuum oven at 60 °C and dry it for 6 h to obtain a flower-like molybdenum disulfide-modified carbonized fiber composite membrane (i.e., the microwave absorption thin film).

[0059] Comparative Example 1

[0060] Step 1: Dissolve 1.0 g of PAN powder in 10 mL of DMF solvent; at 60 °C, vigorously stir the mixture of PAN powder and DMF for 6 h to form a homogeneous spinning solution.

[0061] Step 2: Load the spinning solution into the syringe pump of an electrospinning instrument, and the specification of the needle of the electrospinning instrument is 21G; perform electrospinning under the conditions of an electrospinning voltage of 15 kV, a collection distance of 15 cm, and an injection rate of 0.8 mL·h -1 to obtain a first fiber membrane.

[0062] Step 3: Place the first fiber membrane in a vacuum drying oven at 60 °C and dry it for 6 h.

[0063] Step 4: Place the first fiber membrane in an air atmosphere at 240 °C and pre-oxidize it for 2 h, and then place the second fiber membrane after the pre-oxidation treatment in an argon atmosphere at 800 °C and keep it warm for 2 h to obtain a carbonized fiber membrane.

[0064] Step 5: Add 0.14 g of thiourea and 0.07 g of ammonium molybdate tetrahydrate to 40 mL of deionized water and stir for 30 minutes to uniformly dissolve thiourea and ammonium molybdate tetrahydrate in deionized water, obtaining an aqueous solution of thiourea and ammonium molybdate tetrahydrate. Subsequently, mix 80 mg of the carbonized fiber membrane with the aqueous solution of thiourea and ammonium molybdate tetrahydrate to obtain a reactant. Place the reactant in a hydrothermal reactor and heat it at 200 °C for 22 h to obtain a black reaction product. Wash the reaction product repeatedly with ethanol and deionized water, and then place the reaction product in a vacuum oven at 60 °C and dry it for 6 h to obtain a flower-like molybdenum disulfide-modified carbonized fiber membrane (i.e., the microwave absorption thin film).

[0065] Test the electromagnetic shielding performance of the microwave absorption thin films provided in Example 1, Example 2, and Comparative Example 1 respectively, and the test results are shown in Table 1. Among them, the absorption bandwidth refers to the frequency range in which the microwave absorption thin film can effectively absorb electromagnetic waves.

[0066] Table 1

[0067] Absorption loss (dB) Absorption bandwidth (GHz) Example 1 -67.42 6.43 Example 2 -58.59 5.95 Comparative Example 1 -45.35 3.75

[0068] As can be seen from Table 1, the absorption loss and absorption bandwidth of the microwave absorption films provided in Example 1 and Example 2 for electromagnetic waves are both higher than those in Comparative Example 1. Therefore, compared with Comparative Example 1, the microwave absorption films provided in Example 1 and Example 2 have better electromagnetic shielding performance.

[0069] In the embodiments of the present application, when the first fiber membrane is immersed in a dimethylimidazole solution, metal ions in the soluble metal salt on the fiber surface of the first fiber membrane react with dimethylimidazole in the dimethylimidazole solution to form metal-organic framework crystals. Therefore, metal-organic framework (MOFs) crystals are loaded on the fiber surface of the second fiber membrane. After the second fiber membrane is subjected to carbonization treatment, a carbonized fiber composite membrane is formed, wherein the MOFs crystals form MOFs derivatives and the polymer matrix forms a carbonized fiber membrane; after a hydrothermal reaction is carried out using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate, and thiourea, a flower-like molybdenum disulfide-modified carbonized fiber composite membrane, that is, a microwave absorption film, is obtained. Therefore, the microwave absorption film includes a carbonized fiber membrane, flower-like molybdenum disulfide, and MOFs derivatives loaded on the carbon fiber membrane; wherein, the porous channel structure of the carbonized fiber membrane can improve the impedance mismatch phenomenon, enabling electromagnetic waves to be reflected multiple times inside the channels and thus being better absorbed; the magnetic metal materials (such as nickel and / or cobalt) in the MOFs derivatives have magnetic loss for electromagnetic waves, and there are sufficient interfaces and defects in the MOFs derivative structure, which is beneficial to increasing the loss ability of the microwave absorption film for electromagnetic waves; the flower-like molybdenum disulfide is assembled by a number of molybdenum disulfide nanosheets through van der Waals forces, and the surface of the flower-like molybdenum disulfide is a petal-like lamellar structure. On the one hand, the molybdenum disulfide nanosheets can cause dielectric loss to electromagnetic waves; on the other hand, the petal-like surface structure of the flower-like molybdenum disulfide can promote multiple reflections and scattering of electromagnetic waves on the surface of the flower-like molybdenum disulfide, further promoting the absorption of electromagnetic waves by the microwave absorption film.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; under the idea of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of an electromagnetic wave absorbing thin film, characterized in that, The method includes: Taking a spinning solution, the spinning solution includes an organic solvent and a soluble metal salt and a polymer dissolved in the organic solvent; Performing electrospinning using the spinning solution to obtain a first fiber membrane; Soaking the first fiber membrane in a solution of dimethylimidazole so that magnetic metal ions in the soluble metal salt on the fiber surface of the first fiber membrane react with the dimethylimidazole to generate metal-organic framework crystals, obtaining a second fiber membrane; Performing carbonization treatment on the second fiber membrane to obtain a carbonized fiber composite membrane; Performing a hydrothermal reaction using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate, and thiourea so that the ammonium molybdate tetrahydrate and the thiourea react to generate flower-like molybdenum disulfide, obtaining a flower-like molybdenum disulfide modified carbonized fiber composite membrane.

2. The method according to claim 1, wherein The soluble metal salt includes cobalt nitrate hexahydrate.

3. The method according to claim 2, wherein In the spinning solution, the mass ratio range of the soluble metal salt to the polymer is (1:1) to (2:1).

4. The method according to claim 1, characterized in that, The soaking of the first fiber membrane in the dimethylimidazole solution includes: At room temperature, placing the first fiber membrane in the dimethylimidazole solution and soaking for 20h to 30h; Among them, the concentration of the 2-methylimidazole in the solution of 2-methylimidazole is 0.03 g·ml -1 ~0.05 g·ml -1 .

5. The method according to claim 1, wherein Before performing the carbonization treatment on the second fiber membrane, the method further includes: Performing a pre-oxidation treatment on the second fiber membrane in an air atmosphere; Wherein, the temperature of the pre-oxidation treatment is 220°C to 240°C, and the time of the pre-oxidation treatment is 1.5h to 2.5h.

6. The method according to claim 1, characterized in that The carbonization treatment of the second fiber membrane includes: Under the protection of an inert gas, placing the second fiber membrane at a temperature of 800°C to 850°C and holding for 1.5h to 2.5h.

7. The method according to any one of claims 1-6, characterized in that The hydrothermal reaction using the carbonized fiber composite membrane, ammonium molybdate tetrahydrate, and thiourea includes: Dissolving ammonium molybdate tetrahydrate and thiourea in deionized water to obtain an aqueous solution of ammonium molybdate tetrahydrate and thiourea; Mixing the carbonized fiber composite membrane and the aqueous solution of ammonium molybdate tetrahydrate and thiourea to obtain a reactant for the hydrothermal reaction; Performing a hydrothermal reaction using the reactant; Wherein, the temperature of the hydrothermal reaction is 180°C to 220°C, and the time of the hydrothermal reaction is 20h to 24h.

8. The method according to any one of claims 1-6, characterized in that, The mass ratio range of the ammonium molybdate tetrahydrate to the thiourea is (1:1.5) to (1:2.5).

9. An absorbing film, characterized in that, The absorbing thin film is prepared by the method according to any one of claims 1-8.

10. Application of an absorbing thin film prepared by the method according to any one of claims 1-8 in the field of electromagnetic wave absorption.

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