Electromagnetic shielding film having an electromagnetic alternating structure and method for manufacturing and use thereof

Abstract

The application discloses an electromagnetic shielding film with an electromagnetic alternating structure and a preparation method thereof, and the electromagnetic shielding film is composed of cellulose nanofibers, modified metal organic framework compounds and single-layer MXene, and the electromagnetic shielding film is a multilayer structure. The electromagnetic shielding film not only has excellent gigahertz and terahertz shielding efficiency, but also has excellent light-heat conversion performance, and has great application potential in the fields of multifunctional electromagnetic shielding composites, special facility protection and electronic equipment. The multilayer structure of the electromagnetic shielding film brings good electromagnetic shielding effect, and the multilayer structure can make incident electromagnetic waves be scattered and reflected at alternating interfaces for multiple times, and enhance the interface polarization effect of the material. The alternating structure design also endows the material with a large number of electric / magnetic dipoles, and further enhances the electromagnetic shielding capacity of the material.

Description

Technical Field

[0001] This invention belongs to the field of materials, specifically relating to an electromagnetic shielding film with an electromagnetic alternation structure and its preparation method. The electromagnetic shielding film prepared by this method not only has excellent gigahertz and terahertz shielding efficiency, but also excellent photothermal conversion performance, and has great application potential in the fields of multifunctional electromagnetic shielding composite materials, special facility protection and electronic equipment. Background Technology

[0002] Electromagnetic shielding materials can absorb or reflect electromagnetic waves emitted by electronic devices, thus not only ensuring the normal operation of these devices but also preventing the human body from being harmed by electromagnetic radiation. In recent years, an increasing number of researchers have devoted themselves to studying various types of electromagnetic shielding materials. For example, Huang et al. successfully prepared a metal-cotton composite fabric with electromagnetic shielding effect by loading Ag-Cu metal onto cotton cloth using chemical plating (HJTong, JJWan, SLWang, Y.Yu, WQZhang, R.Liu, JJHuang, J.Mater.Sci:Mater.Electron.2023,34,1299); Yang et al. prepared a novel electromagnetic shielding material by composite Ag and Si3N4 ceramics using an impregnation and calcination strategy (CBCheng, YLJiang, X.Sun, JXShen, TLWang, GHFan, RHFan, Compos.Part A-Appl.S.2020,130,105753); Liu et al. proposed to prepare a composite foam with electromagnetic shielding effect by using chemical electroplating and electrodeposition methods to prepare CNTs and Cu-Ni (D.Wang, Z.Wu, FX). Li, XPGan, JMTao, JHYi, YCLiu, Nanomaterials, 2021, 11, 1772); These electromagnetic shielding materials all have good shielding effects, but their applications are limited due to their high density and complicated preparation process. To address these issues, Shahzad et al. proposed a novel two-dimensional material, MXene, to prepare a highly conductive electromagnetic shielding film, achieving excellent electromagnetic shielding performance with low thickness and low density. (F. Shahzad, M. Alhabeb, CB Hatter, B. Anasori, SM Hong, CMKoo, Y. Gogotsi, Science, 2016, 353, 1137-1140)

[0003] However, the electromagnetic shielding materials mentioned above have limited electromagnetic loss mechanisms, single functions, and poor adjustability of electromagnetic shielding performance. With the increasing demand for electromagnetic shielding materials in today's society, they are difficult to apply to high-precision fields such as wearable flexible electromagnetic shielding devices and the protection of special electronic equipment. Therefore, it is still necessary to develop a multifunctional and efficient electromagnetic shielding material with a reasonable structural design to further improve its application value. Summary of the Invention

[0004] To address the problems of traditional methods, according to one aspect of the present invention, one objective of the present invention is to provide an electromagnetic shielding film with an electromagnetic alternation structure, which not only has high shielding efficiency, but also has certain photothermal conversion capability, cutability and stability, and has great application potential in the fields of multifunctional flexible electronic devices and electromagnetic shielding composite materials.

[0005] An electromagnetic shielding membrane with an alternating electromagnetic structure is provided. The electromagnetic shielding membrane is composed of cellulose nanofibers, modified metal-organic framework compounds and a single layer of MXene. The electromagnetic shielding membrane has a multilayer structure with 1 to 9 layers, preferably 3 to 7 layers, and more preferably 5 layers.

[0006] Preferably, in the electromagnetic shielding film according to the present invention, the contents of each component in each layer, such as cellulose nanofibers, modified metal-organic framework compounds and monolayer MXene, are the same or different, and more preferably, the contents of each component in each layer are different.

[0007] Preferably, in the electromagnetic shielding film according to the present invention, the content of cellulose nanofibers gradually decreases from bottom to top.

[0008] Preferably, in the electromagnetic shielding film according to the present invention, the content of modified metal-organic framework compounds gradually decreases from bottom to top.

[0009] Preferably, in the electromagnetic shielding film according to the present invention, the content of monolayer MXene gradually increases from bottom to top.

[0010] Preferably, in the electromagnetic shielding film according to the present invention, the total weight ratio of the cellulose nanofibers and the modified metal-organic framework compound is 2:1 and 0.5:1, more preferably 2:1.

[0011] Preferably, in the electromagnetic shielding film according to the present invention, the total weight ratio of the modified metal-organic framework compound and the monolayer MXene is 1:1 to 1:4, more preferably 1:3 to 1:4, and even more preferably 1:4.

[0012] According to another aspect of the present invention, an object of the present invention is to provide a method for preparing an electromagnetic shielding film having an electromagnetic alternation structure, comprising the following steps:

[0013] 1) Preparation of monolayer MXene solution

[0014] Dissolve 1 part by weight of LiF in 20 parts by weight of 9M hydrochloric acid, then add 1 part by weight of Ti3AlC2 powder and stir for 24 to 60 hours. After the reaction, the resulting suspension is centrifuged at 3500 r / min for 5 minutes and washed with deionized water until the pH of the supernatant is ≥5. The supernatant is then discarded. The resulting precipitate is dispersed in 20-30 parts by weight of deionized water, sonicated in an ice bath for 0.5 to 2 hours, and then centrifuged at 3500 r / min for 1 hour. The supernatant is collected to obtain a monolayer MXene solution.

[0015] 2) Preparation of modified metal-organic framework compounds

[0016] Under stirring conditions, 5 to 10 parts by weight of zinc nitrate hexahydrate and 5 to 10 parts by weight of 2-methylimidazole were added to 50 to 200 parts by weight of methanol. The mixture was stirred at room temperature for 24 hours, and ZIF-8 was obtained after centrifugation and washing at 8000 r / min. Under stirring conditions, 0.1 to 1.5 parts by weight of the synthesized ZIF-8 were added to 50 to 200 parts by weight of anhydrous methanol containing 5 to 10 parts by weight of cobalt nitrate hexahydrate. The mixture was stirred at room temperature for 1 hour, and then 5 to 10 parts by weight of 2-methylimidazole were added. ZIF-8@ZIF-67 was obtained by centrifugation and washing at 8000 r / min in 50 to 200 parts by weight of methanol containing azole. The synthesized ZIF-8@ZIF-67 was dried under vacuum at 80 degrees Celsius and placed in a tube furnace under nitrogen atmosphere protection. The temperature was increased to 800 degrees Celsius at a heating rate of 1 to 5 degrees Celsius per minute for carbonization for 1 to 5 hours. Then, the surface was modified with 0.05 to 0.2 parts by weight of hexadecyltrimethylammonium bromide based on the carbonization product to form a modified metal-organic framework compound.

[0017] 3) Electromagnetic shielding film with alternating electromagnetic structure

[0018] Under stirring conditions, the modified metal-organic framework compound obtained in step 2) above is dispersed in a 0.2% aqueous solution of cellulose nanofibers at a solid content ratio of 1:2 to 2:1 and divided into corresponding parts by weight. The monolayer MXene obtained in step 1) above is divided into corresponding parts by weight ratio of 1:1 to 1:4 of the modified metal-organic framework compound and then alternately vacuum filtered onto a filter membrane. The electromagnetic shielding membrane with alternating electromagnetic structure prepared has 1 to 9 layers. The number of layers is controlled by dividing the above solution into corresponding parts and filtration.

[0019] Preferably, the stirring time in step 1) is 12-72 hours, more preferably 24-60 hours, and even more preferably 48 hours; the weight of the dispersed deionized water is 20 to 30 parts by weight, more preferably 25 parts by weight; and the ice bath ultrasonic time is 0.5-2 hours, more preferably 1-1.5 hours, and even more preferably 1 hour.

[0020] Preferably, in step 2), 5 to 10 parts by weight of zinc nitrate hexahydrate and 5 to 10 parts by weight of 2-methylimidazole are added to 50 to 200 parts by weight of methanol, stirred at room temperature for 1 hour, and then added to 50 to 200 parts by weight of methanol containing 5 to 10 parts by weight of 2-methylimidazole.

[0021] More preferably, 6 parts by weight of zinc nitrate hexahydrate and 6 parts by weight of 2-methylimidazole are added to 100 parts by weight of methanol;

[0022] Preferably, in step 2), 0.1 to 1.5 parts by weight of the synthesized ZIF-8 are added to 50 to 200 parts by weight of methanol containing 5 to 10 parts by weight of cobalt nitrate hexahydrate, stirred at room temperature for 1 hour, and then added to 50 to 200 parts by weight of methanol containing 5 to 10 parts by weight of 2-methylimidazole.

[0023] More preferably, 0.5 parts by weight of the synthesized ZIF-8 are added to 100 parts by weight of methanol containing 6 parts by weight of cobalt nitrate hexahydrate, stirred at room temperature for 1 hour, and then added to 100 parts by weight of methanol containing 6 parts by weight of 2-methylimidazole.

[0024] Preferably, in step 2), the temperature is increased to 800 degrees Celsius at a heating rate of 1 to 5 degrees Celsius per minute for carbonization for 1 to 5 hours, and then the surface is modified with 0.05 to 0.2 parts by weight of hexadecyltrimethylammonium bromide based on the above carbonization product.

[0025] More preferably, the temperature is increased to 800 degrees Celsius at a heating rate of 2 degrees Celsius per minute for carbonization for 2 hours, and then the surface is modified with 0.1 parts by weight of hexadecyltrimethylammonium bromide based on the above carbonization product.

[0026] Preferably, the modified metal-organic framework compound in step 3) is dispersed in the cellulose nanofiber dispersion at a weight ratio of 1:2 to 2:1, and more preferably at a weight ratio of 1:2; the monolayer MXene is dispersed in the cellulose nanofiber dispersion at a weight ratio of 1:1 to 1:4 of the modified metal-organic framework compound, and more preferably at a weight ratio of 1:4.

[0027] The electromagnetic shielding film of the electromagnetic alternating structure has 1 to 9 layers, preferably 3 to 7 layers, and more preferably 5 layers;

[0028] The preparation method according to the present invention includes the following steps:

[0029] 1) Preparation of monolayer MXene

[0030] One part by weight of LiF was dissolved in 20 parts by weight of 9M hydrochloric acid, and then one part by weight of Ti3AlC2 powder was added and stirred for 48 hours. The resulting suspension was centrifuged at 3500 r / min for 5 minutes and washed with deionized water until the pH of the supernatant was ≥5. The supernatant was then discarded. The resulting precipitate was dispersed in 25 parts by weight of deionized water, sonicated in an ice bath for 1 hour, and then centrifuged at 3500 r / min for 1 hour. The supernatant was collected to obtain a monolayer MXene solution.

[0031] 2) Preparation of modified metal-organic framework compounds

[0032] Under stirring conditions, 6 parts by weight of zinc nitrate hexahydrate and 6 parts by weight of 2-methylimidazole were added to 100 parts by weight of methanol. The mixture was stirred at room temperature for 24 hours, and after centrifugation and washing at 8000 r / min, ZIF-8 was obtained. Under stirring conditions, 0.5 parts by weight of the synthesized ZIF-8 were added to 100 parts by weight of methanol containing 6 parts by weight of cobalt nitrate hexahydrate. The mixture was stirred at room temperature for 1 hour, and then 100 parts by weight of methanol containing 6 parts by weight of 2-methylimidazole were added. After centrifugation and washing at 8000 r / min, ZIF-8@ZIF-67 was obtained. The synthesized ZIF-8@ZIF-67 was dried under vacuum at 80 degrees Celsius and placed in a tube furnace under nitrogen atmosphere protection. The temperature was increased to 800 degrees Celsius at a heating rate of 2 degrees Celsius per minute for 2 hours for carbonization. Then, the surface was modified with 0.1 parts by weight of hexadecyltrimethylammonium bromide based on the carbonization product to form a modified metal-organic framework compound.

[0033] 4) Electromagnetic shielding film with alternating electromagnetic structure

[0034] Under stirring conditions, the modified metal-organic framework compound obtained in step 2) above is dispersed in a 0.2% cellulose nanofiber aqueous solution at a solid content ratio of 1:2, and then vacuum filtered to form a membrane. The monolayer MXene solution obtained in step 1) above is alternately vacuum filtered onto the membrane at a solid content weight ratio of 1:4 for the modified metal-organic framework compound. The electromagnetic shielding membrane with alternating electromagnetic structures prepared has 5 layers. The number of layers is controlled by dividing the modified metal-organic framework compound / cellulose nanofiber solution monolayer MXene solution into corresponding portions for vacuum filtration. Specifically:

[0035] The prepared modified metal-organic framework / cellulose nanofiber solution was divided into three parts (containing 16.7%, 33.3%, and 50.0% of the total modified metal-organic framework / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into two parts (containing 33.3% and 66.7% of the total monolayer MXene, respectively). First, a 50.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, a 33.3% monolayer MXene solution was vacuum filtered onto the 50.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 33.3% monolayer MXene membrane. Then, a 66.7% monolayer MXene solution was vacuum filtered onto a 33.3% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 16.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 66.7% monolayer MXene membrane.

[0036] According to another aspect of the invention, another object of the invention is to provide the use of the electromagnetic shielding film having an electromagnetic alternation structure in the cryogenic protection environment of advanced electromagnetic interference protection devices and electronic equipment for future sixth-generation communications.

[0037] Beneficial effects

[0038] 1. The method for preparing the electromagnetic shielding film according to the present invention is simple and has a wide range of applications;

[0039] 2. The electromagnetic shielding film prepared according to the present invention has the characteristics of low density, thin thickness, and good stability;

[0040] 3. The electromagnetic shielding film prepared according to the present invention has excellent gigahertz and terahertz electromagnetic shielding performance, and also has excellent photothermal performance.

[0041] 4. The electromagnetic shielding film prepared according to the present invention exhibits good performance in actual simulated electromagnetic shielding tests;

[0042] 5. The key feature of this invention is that the electromagnetic shielding film has a multi-layered structure. This multi-layered structure brings about the aforementioned excellent electromagnetic shielding effect. The multi-layered structure allows incident electromagnetic waves to undergo multiple scattering and reflection at the alternating interfaces, enhancing the interfacial polarization of the material. The alternating structural design also endows the material with a large number of electric / magnetic dipoles, further enhancing the material's electromagnetic shielding capability. Attached Figure Description

[0043] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating the preparation process of the electromagnetic shielding film according to the present invention.

[0045] Figure 2 X-ray diffraction patterns of the electromagnetic shielding film, monolayer MXene, modified metal-organic framework compound, and cellulose nanofiber prepared according to Example 1.

[0046] Figure 3 Transmission electron microscopy (TEM) images of monolayer MXene, modified metal-organic framework compounds, and cellulose nanofibers prepared according to Example 1.

[0047] Figure 4 Fourier transform infrared spectra of the electromagnetic shielding film, monolayer MXene, modified metal-organic framework compound, and cellulose nanofiber prepared according to Example 1.

[0048] Figure 5 X-ray photoelectron spectroscopy (XPS) analysis of the monolayer MXene and modified metal-organic framework compound prepared according to Example 1.

[0049] Figure 6 The images show scanning electron microscope (SEM) images and energy dispersive spectroscopy (EDS) spectra of the electromagnetic shielding film prepared according to Example 1.

[0050] Figure 7 The electrical and magnetic properties of each layer of the electromagnetic shielding film prepared according to Example 1 were tested.

[0051] Figure 8 This study aims to test the gigahertz electromagnetic shielding performance of the electromagnetic shielding films prepared according to Examples 1-5 and Comparative Examples 2-3.

[0052] Figure 9 The terahertz electromagnetic shielding performance of the electromagnetic shielding film prepared according to Example 1 was tested.

[0053] Figure 10 This is a test to simulate the actual electromagnetic shielding of the electromagnetic shielding film prepared according to Example 1.

[0054] Figure 11 This experiment was conducted to test the solar photothermal conversion performance and stability of the electromagnetic shielding film prepared according to Example 1.

[0055] Figure 12This experiment was conducted to test the photothermal conversion performance and stability of the electromagnetic shielding film prepared according to Example 1 using 808 infrared laser.

[0056] Figure 13 Ultrasonic stability test experiment of the electromagnetic shielding film prepared according to Example 1 and Comparative Example 1.

[0057] Figure 14 This is a cuttable experiment of the electromagnetic shielding film prepared according to Example 1. Detailed Implementation

[0058] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0059] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0060] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0061] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0062] An electromagnetic shielding film with an alternating electromagnetic structure prepared according to the method of the present invention not only has excellent gigahertz and terahertz electromagnetic shielding performance and photothermal conversion capability, but also has good cutability and stability. Figure 1 This is a flowchart illustrating the preparation process of the electromagnetic shielding film according to the present invention.

[0063] In the preparation method according to the present invention, the weight ratio of the cellulose nanofibers and the modified metal-organic framework compound is 2:1 and 1:2, more preferably 2:1. When the ratio of cellulose nanofibers to the modified metal-organic framework compound is 1:2, the film-forming ability deteriorates, making it difficult to form a stable film structure.

[0064] In the preparation method according to the present invention, the weight ratio of the modified metal-organic framework compound to the monolayer MXene is 1:1 to 1:4, more preferably 1:3 to 1:4, and even more preferably 1:4. When the weight ratio of the modified metal-organic framework compound to the monolayer MXene is greater than 1:4, the electromagnetic shielding performance will decrease.

[0065] In the preparation method according to the present invention, the electromagnetic shielding film of the electromagnetic alternation structure has 1 to 9 layers, further optimized to 3 to 7 layers, and even more preferably 5 layers. When the number of electromagnetic shielding film layers is too small, the structural design has little effect on the electromagnetic shielding performance. When the number of electromagnetic shielding film layers is too large, the thickness between each layer is too low, resulting in severe interpenetration between electromagnetic components, leading to a decrease in electromagnetic shielding capability. Therefore, the structural design has little effect on the electromagnetic shielding performance.

[0066] Specifically, depending on the number of layers of the electromagnetic shielding film of the electromagnetic alternating structure, step 3) of the preparation method of the electromagnetic shielding film of the electromagnetic alternating structure is carried out as follows. The following is only an example of step 3), and the specific implementation of step 3) is not limited to this.

[0067] Under stirring conditions, the modified metal-organic framework compound obtained in step 2) is dispersed in a 0.2% cellulose nanofiber aqueous solution at a solid content ratio of 1:2 to 2:1, and divided into corresponding parts by weight. The monolayer MXene obtained in step 1) is divided into corresponding parts by weight at a ratio of 1:1 to 1:4 of the modified metal-organic framework compound, and then alternately vacuum filtered onto a filter membrane. The electromagnetic shielding membrane with alternating electromagnetic structures prepared has 1 to 9 layers. The number of layers is controlled by dividing the above solution into corresponding parts and filtration. The specific implementation method according to the number of layers is as follows:

[0068] Electromagnetic shielding membrane with 1 layer: The prepared modified metal-organic framework compound / cellulose nanofiber solution is mixed with a single layer of MXene and then vacuum filtered to form a membrane.

[0069] Electromagnetic shielding membrane with 3 layers: The prepared modified metal-organic framework / cellulose nanofiber solution was divided into two portions (containing 33.3% and 66.7% of the total modified metal-organic framework / cellulose nanofiber, respectively), and a single-layer MXene was divided into one portion (100.0% of the total). First, the 66.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, the 100.0% single-layer MXene solution was vacuum filtered onto the 66.7% modified metal-organic framework / cellulose nanofiber membrane. Finally, the 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the 100% single-layer MXene membrane.

[0070] Electromagnetic shielding film with 5 layers: The prepared modified metal-organic framework compound / cellulose nanofiber solution was divided into 3 parts (containing 16.7%, 33.3% and 50.0% of the total modified metal-organic framework compound / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into 2 parts (containing 33.3% and 66.7% of the total monolayer MXene, respectively). First, a 50.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a membrane. Then, a 33.3% monolayer MXene solution was vacuum filtered onto the 50.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 33.3% monolayer MXene membrane. Then, a 66.7% monolayer MXene solution was vacuum filtered onto a 33.3% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 16.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 66.7% monolayer MXene membrane.

[0071] Electromagnetic shielding film with 7 layers: The prepared modified metal-organic framework compound / cellulose nanofiber solution was divided into 4 parts (containing 10.0%, 20.0%, 30.0%, and 40.0% of the total modified metal-organic framework compound / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into 3 parts (containing 16.7%, 33.3%, and 50.0% of the total monolayer MXene, respectively). First, a 40.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a membrane. Then, a 16.7% monolayer MXene solution was vacuum filtered onto a 50.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 30.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 16.7% monolayer MXene membrane. Then, a 33.3% monolayer MXene solution was vacuum filtered onto a 30.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 20.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 33.3% monolayer MXene membrane. Then, a 16.7% monolayer MXene solution was vacuum filtered onto a 20.0% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 10.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 16.7% monolayer MXene membrane.

[0072] Electromagnetic shielding film with 9 layers: The prepared modified metal-organic framework compound / cellulose nanofiber solution was divided into 5 parts (containing 6.7%, 13.3%, 20.0%, 26.7% and 33.3% of the total modified metal-organic framework compound / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into 4 parts (containing 10.0%, 20.0%, 30.0% and 40.0% of the total monolayer MXene, respectively). First, a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a membrane. Then, a 10.0% monolayer MXene solution was vacuum filtered onto the 33.3% modified metal-organic framework / cellulose nanofiber membrane. Next, a 26.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the 10.0% monolayer MXene membrane. Then, a 20.0% monolayer MXene solution was vacuum filtered onto the 26.7% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 20.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the membrane. The solution was then filtered through an air filter onto a 20.0% monolayer MXene membrane. Next, a 30.0% monolayer MXene solution was filtered through an air filter onto a 20.0% modified metal-organic framework / cellulose nanofiber membrane. Then, a 13.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered through an air filter onto a 30.0% monolayer MXene membrane. Finally, a 40.0% monolayer MXene solution was vacuum filtered through an air filter onto a 13.3% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 6.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered through an air filter onto a 40.0% monolayer MXene membrane.

[0073] In short, taking a 5-layer structure as an example, the specific details are as follows: in order from bottom to top, the first layer contains 50.0% modified metal-organic framework compounds / cellulose nanofibers, the second layer contains 33.3% monolayer MXene, the third layer contains 33.3% modified metal-organic framework compounds / cellulose nanofibers, the fourth layer contains 66.7% monolayer MXene, and the fifth layer contains 16.7% modified metal-organic framework compounds / cellulose nanofibers.

[0074] Electromagnetic shielding performance typically depends on magnetic and electrical loss capabilities, electric / magnetic dipoles, and multiple interfaces. Monolayer MXene and modified metal-organic framework materials exhibit strong magnetic and electrical loss capabilities, and the alternating structural design leads to the polarization of electric / magnetic dipoles. Materials with asymmetric charge distributions form interacting dipoles. Alternating multilayer structures construct multiple interfaces.

[0075] The electromagnetic shielding film prepared by the method of the present invention has excellent electromagnetic shielding performance, with an average electromagnetic shielding capability of 66.8 dB in the gigahertz range and 114.6 dB in the terahertz range.

[0076] The electromagnetic shielding film prepared by the method of the present invention has excellent photothermal conversion capability. Under the irradiation of two suns, the surface temperature can reach 104.6 degrees Celsius, and under the irradiation of an 808 infrared laser lamp with a power of 0.8 milliwatts per square centimeter, the surface temperature can reach 235.4 degrees Celsius.

[0077] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0078] Example 1

[0079] 1) Preparation of monolayer MXene

[0080] One part by weight of LiF was dissolved in 20 parts by weight of 9M hydrochloric acid, and then one part by weight of Ti3AlC2 powder was added and stirred for 48 hours. The resulting suspension was centrifuged at 3500 r / min for 5 minutes and washed with deionized water until the pH of the supernatant was ≥5. The supernatant was then discarded. The resulting precipitate was dispersed in 25 parts by weight of deionized water, sonicated in an ice bath for 1 hour, and then centrifuged at 3500 r / min for 1 hour. The supernatant was collected to obtain a monolayer MXene solution.

[0081] 2) Preparation of modified metal-organic framework compounds

[0082] Under stirring conditions, 6 parts by weight of zinc nitrate hexahydrate and 6 parts by weight of 2-methylimidazole were added to 100 parts by weight of methanol. The mixture was stirred at room temperature for 24 hours, and after centrifugation and washing at 8000 r / min, ZIF-8 was obtained. Under stirring conditions, 0.5 parts by weight of the synthesized ZIF-8 were added to 100 parts by weight of methanol containing 6 parts by weight of cobalt nitrate hexahydrate. The mixture was stirred at room temperature for 1 hour, and then 100 parts by weight of methanol containing 6 parts by weight of 2-methylimidazole were added. After centrifugation and washing at 8000 r / min, ZIF-8@ZIF-67 was obtained. The synthesized ZIF-8@ZIF-67 was dried under vacuum at 80 degrees Celsius and placed in a tube furnace under nitrogen atmosphere protection. The temperature was increased to 800 degrees Celsius at a heating rate of 2 degrees Celsius per minute for 2 hours for carbonization. Then, the surface was modified with 0.1 parts by weight of hexadecyltrimethylammonium bromide based on the carbonization product to form a modified metal-organic framework compound.

[0083] 3) Electromagnetic shielding film with alternating electromagnetic structure

[0084] Under stirring conditions, the modified metal-organic framework compound obtained in step 2) above is dispersed in a 0.2% cellulose nanofiber aqueous solution at a solid content ratio of 1:2, and then vacuum filtered to form a membrane. The monolayer MXene obtained in step 1) above is vacuum filtered onto the above membrane at a weight ratio of 1:4 of the modified metal-organic framework compound. The electromagnetic shielding membrane with an alternating electromagnetic structure prepared has 5 layers. The number of layers is controlled by dividing the above solution into corresponding portions and filtering them. Specifically, as follows:

[0085] The prepared modified metal-organic framework / cellulose nanofiber solution was divided into three parts (containing 16.7%, 33.3%, and 50.0% of the total modified metal-organic framework / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into two parts (containing 33.3% and 66.7% of the total monolayer MXene, respectively). First, a 50.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, a 33.3% monolayer MXene solution was vacuum filtered onto the 50.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 33.3% monolayer MXene membrane. Then, a 66.7% monolayer MXene solution was vacuum filtered onto a 33.3% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 16.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 66.7% monolayer MXene membrane.

[0086] like Figure 2 As shown, the prepared electromagnetic shielding film was analyzed using X-ray diffraction (XRD). The diffraction peaks of each component of the electromagnetic shielding film were obvious, proving the successful preparation of the composite material.

[0087] like Figure 3 As shown, the cellulose nanofibers, monolayer MXene, and modified metal-organic framework were characterized by transmission electron microscopy (TEM), further demonstrating the successful synthesis of the raw materials.

[0088] like Figure 4 As shown, the Fourier transform infrared (FTIR) spectra of the prepared electromagnetic shielding film and the raw materials show that the infrared characteristic peaks of each component of the electromagnetic shielding film are obvious, proving the successful preparation of the composite material.

[0089] like Figure 5As shown, X-ray photoelectron spectroscopy (XPS) was used to analyze the prepared monolayer MXene and modified metal-organic framework compounds, proving the successful synthesis and modification of the materials.

[0090] like Figure 6 As shown, the electromagnetic shielding film prepared in Example 1 was analyzed using a scanning electron microscope (SEM), which further proved the successful preparation of its alternating structure.

[0091] like Figure 7 As shown, the conductivity and permeability of the electromagnetic shielding film prepared in Example 1 were tested, and it can be seen that there is an electromagnetic alternation structure between the layers.

[0092] Example 2

[0093] Except for the electromagnetic shielding film of the electromagnetic alternating structure, which is controlled to have 1 layer, the electromagnetic shielding film (HMN-1L-57.1%) was prepared according to the same preparation steps as in Example 1.

[0094] Example 3

[0095] Except for the electromagnetic shielding membrane with the alternating electromagnetic structure having 3 layers for adjustment, the electromagnetic shielding membrane (HMN-3L-57.1%) was prepared according to the same preparation steps as in Example 1. Specifically, the prepared modified metal-organic framework / cellulose nanofiber solution was divided into two portions (containing 33.3% and 66.7% of the total modified metal-organic framework / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into one portion (containing 100.0% of the total monolayer MXene). First, the 66.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, the 100.0% monolayer MXene solution was vacuum filtered onto the 66.7% modified metal-organic framework / cellulose nanofiber membrane. Finally, the 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the monolayer MXene membrane.

[0096] Example 4

[0097] Except for the electromagnetic shielding film of the electromagnetic alternation structure, which was adjusted to have 7 layers, the electromagnetic shielding film (HMN-7L-57.1%) was prepared according to the same preparation steps as in Example 1. Specifically, the prepared modified metal-organic framework compound / cellulose nanofiber solution was divided into 4 parts (containing 10.0%, 20.0%, 30.0%, and 40.0% of the total modified metal-organic framework compound / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into 3 parts (containing 16.7%, 33.3%, and 50.0% of the total monolayer MXene, respectively). First, a 40.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, a 16.7% monolayer MXene solution was vacuum filtered onto a 50.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 30.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 16.7% monolayer MXene membrane. Then, a 33.3% monolayer MXene solution was vacuum filtered onto a 30.0% modified metal-organic framework / cellulose nanofiber membrane. Next, a 20.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 33.3% monolayer MXene membrane. Then, a 16.7% monolayer MXene solution was vacuum filtered onto a 20.0% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 10.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 16.7% monolayer MXene membrane.

[0098] Example 5

[0099] Except for the electromagnetic shielding film with the alternating electromagnetic structure having 9 layers for adjustment, the electromagnetic shielding film (HMN-9L-57.1%) was prepared according to the same preparation steps as in Example 1. Specifically, the prepared modified metal-organic framework compound / cellulose nanofiber solution was divided into 5 parts (containing 6.7%, 13.3%, 20.0%, 26.7%, and 33.3% of the total modified metal-organic framework compound / cellulose nanofiber, respectively), and the monolayer MXene solution was divided into 4 parts (containing 10.0%, 20.0%, 30.0%, and 40.0% of the total monolayer MXene, respectively). First, a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, a 10.0% monolayer MXene solution was vacuum filtered onto the 33.3% modified metal-organic framework / cellulose nanofiber membrane. Next, a 26.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the 10.0% monolayer MXene membrane. Then, a 20.0% monolayer MXene solution was vacuum filtered onto the 26.7% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 20.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered... The solution was filtered onto a 20.0% monolayer MXene membrane, then a 30.0% monolayer MXene solution was vacuum filtered onto a 20.0% modified metal-organic framework / cellulose nanofiber membrane, then a 13.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 30.0% monolayer MXene membrane, then a 40.0% monolayer MXene solution was vacuum filtered onto a 13.3% modified metal-organic framework / cellulose nanofiber membrane, and finally a 6.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 40.0% monolayer MXene membrane.

[0100] Comparative Example 1

[0101] An electromagnetic shielding film (pure MXene film) was prepared by using only a single layer of MXene following the same preparation steps as in Example 1. Details are as follows:

[0102] First, 66.7% monolayer MXene was vacuum filtered into a membrane, and then 33.3% monolayer MXene was vacuum filtered onto the 66.7% monolayer MXene membrane.

[0103] Comparative Example 2

[0104] An electromagnetic shielding film (pure TOCNF film) was prepared using only cellulose nanofibers following a similar preparation procedure to that in Example 1. Details are as follows:

[0105] First, a 50.0% cellulose nanofiber solution was vacuum filtered to form a membrane. Then, a 33.3% cellulose nanofiber solution was vacuum filtered onto the 50.0% cellulose nanofiber membrane. Finally, a 16.7% cellulose nanofiber solution was vacuum filtered onto the 33.3% cellulose nanofiber membrane.

[0106] Comparative Example 3

[0107] An electromagnetic shielding film (HMN-5L-0.0%) was prepared by simply using a modified metal-organic framework compound / cellulose nanofiber solution following a similar preparation procedure to Example 1. Details are as follows:

[0108] First, a 50.0% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered to form a membrane. Then, a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the 50.0% modified metal-organic framework / cellulose nanofiber membrane. Finally, a 16.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto the 33.3% modified metal-organic framework / cellulose nanofiber membrane.

[0109] Experiment Example 1: Gigahertz Electromagnetic Shielding Experiment

[0110] The electromagnetic shielding films prepared in Examples 1-5 and Comparative Examples 2-3 were cut to the appropriate size for the waveguide cavity of the vector network analyzer. Electromagnetic waves were emitted from below. For upward transmission, the S-parameters before and after electromagnetic wave transmission are calculated under electromagnetic wave radiation at frequencies of 8.2-40 GHz, and the electromagnetic shielding efficiency is obtained from the S-parameters.

[0111] Figure 8 The test results are for the electromagnetic shielding efficiency of the electromagnetic shielding films prepared in Examples 1-5 and Comparative Examples 2-3. The test results show that Example 1 has the best electromagnetic shielding performance and excellent shielding capability in the range of 8.2-40 GHz.

[0112] Experiment Example 2: Terahertz Electromagnetic Shielding Experiment

[0113] The electromagnetic shielding film prepared in Example 1 is cut to a size suitable for the terahertz time-domain spectrum. Electromagnetic waves are transmitted from bottom to top. The time-domain spectral signals before and after electromagnetic wave transmission are calculated under electromagnetic wave radiation at frequencies of 0.1-4 terahertz. The frequency domain signal is obtained by Fourier transformation from the time-domain spectral signal, and the electromagnetic shielding efficiency is calculated from the frequency domain signal.

[0114] Figure 9 The transmission signal and shielding performance of the electromagnetic shielding film prepared in Example 1 are shown in the test results. The test results show that the electromagnetic shielding film with alternating structure can effectively shield terahertz electromagnetic waves.

[0115] Experimental Example 3: Simulation of Actual Electromagnetic Shielding

[0116] The electromagnetic shielding membrane and cellulose filter membrane prepared in Example 1 were placed near a Tesla coil, and the electromagnetic shielding capability was tested by observing the changes in the electromagnetic radiation instrument (LZT-1000) and the small light bulb.

[0117] Figure 10 The figures show the actual electromagnetic shielding simulation test results of the electromagnetic shielding membrane and cellulose filter membrane prepared in Example 1. The figures demonstrate that the electromagnetic shielding membrane prepared in Example 1 exhibits good shielding performance against electromagnetic waves, while the cellulose filter membrane shows very poor shielding performance.

[0118] Experimental Example 4: Photothermal Performance Test

[0119] Example 1 was placed on a flat surface and the electromagnetic shielding film was irradiated with sunlight of different intensities and an 808nm near-infrared laser. The surface temperature change was monitored using an infrared thermal imager (FLIR A325SC camera).

[0120] Figure 11 The figure shows the solar thermal test results of Example 1. It can be seen from the figure that under sunlight irradiation, the electromagnetic shielding film of Example 1 can reach a maximum temperature of approximately 104.6 degrees Celsius. Furthermore, it also exhibits good stability in the cyclic illumination experiment, indicating excellent solar thermal performance and stability.

[0121] Figure 12 The figure shows the photothermal test results of the 808nm near-infrared laser in Example 1. It can be seen from the figure that under irradiation with the 808nm near-infrared laser, the electromagnetic shielding film of Example 1 can reach a maximum temperature of approximately 235.4 degrees Celsius. Furthermore, it exhibits good stability in the cyclic heating and cooling light irradiation experiment, indicating excellent photothermal performance and stability with the 808nm near-infrared laser.

[0122] Experimental Example 5: Stability Test

[0123] The electromagnetic shielding films prepared in Example 1 and Comparative Example 1 were cut into the same size, placed in water, and subjected to continuous ultrasonic treatment under 180W water bath ultrasonic conditions.

[0124] Figure 13 The electromagnetic shielding membranes prepared according to Example 1 and Comparative Example 1 show that the electromagnetic shielding membrane in Example 1 remained intact after being sonicated at 180W for 30 minutes, while the electromagnetic shielding membrane in Comparative Example 1 dispersed rapidly in water, indicating the excellent stability of its electromagnetic shielding membrane with alternating electromagnetic structure.

[0125] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An electromagnetic shielding membrane with an alternating electromagnetic structure, the electromagnetic shielding membrane being composed of cellulose nanofibers, modified metal-organic framework compounds and a single layer of MXene, wherein the electromagnetic shielding membrane has a multilayer structure with 1 to 9 layers; In the electromagnetic shielding film, the total weight ratio of the cellulose nanofibers and the modified metal-organic framework compound is 2:

1. The total weight ratio of the modified metal-organic framework compound to the monolayer MXene is 1:

4.

2. The electromagnetic shielding film with an alternating electromagnetic structure according to claim 1, characterized in that, The electromagnetic shielding film contains the same or different amounts of cellulose nanofibers, modified metal-organic framework compounds, and monolayer MXene in each layer.

3. The electromagnetic shielding film with an alternating electromagnetic structure according to claim 1, characterized in that, The content of cellulose nanofibers in the electromagnetic shielding film gradually decreases from bottom to top.

4. The electromagnetic shielding film with an alternating electromagnetic structure according to claim 1, characterized in that, The electromagnetic shielding film has a multi-layer structure with 3-7 layers.

5. The electromagnetic shielding film with an alternating electromagnetic structure according to claim 1, characterized in that, The electromagnetic shielding film has a multi-layer structure with 5 layers.

6. The electromagnetic shielding film with an alternating electromagnetic structure according to claim 3, characterized in that, The content of modified metal-organic framework compounds gradually decreases from bottom to top in the electromagnetic shielding film.

7. The electromagnetic shielding film with an alternating electromagnetic structure according to claim 3, characterized in that, In the electromagnetic shielding film, the content of MXene in a single layer gradually increases from bottom to top.

8. A method for preparing an electromagnetic shielding film with an alternating electromagnetic structure, characterized in that, The method specifically includes the following steps: 1) Preparation of monolayer MXene 1 g of LiF was dissolved in 20 g of 9 M hydrochloric acid, and then 1 g of Ti3AlC2 powder was added and stirred for 48 h. The resulting suspension was centrifuged at 3500 r / min for 5 min and washed with deionized water until the pH of the supernatant was ≥ 5. The supernatant was then discarded. The resulting precipitate was dispersed in 25 g of deionized water, sonicated in an ice bath for 1 h, and then centrifuged at 3500 r / min for 1 h. The supernatant was collected to obtain a monolayer MXene solution. 2) Preparation of modified metal-organic framework compounds Under stirring conditions, 6g of zinc nitrate hexahydrate and 6g of 2-methylimidazole were added to 100g of methanol and stirred at room temperature for 24 hours. After centrifugation and washing at 8000r / min, ZIF-8 was obtained. Under stirring conditions, 0.5g of the above ZIF-8 was added to 100g of methanol containing 6g of cobalt nitrate hexahydrate and stirred at room temperature for 1 hour. Then, 100g of methanol containing 6g of 2-methylimidazole was added and centrifuged at 8000r / min to obtain ZIF-8@ZIF-67. The above ZIF-8@ZIF-67 was dried under vacuum at 80 degrees Celsius and placed in a tube furnace under nitrogen atmosphere protection. The temperature was increased to 800 degrees Celsius at a heating rate of 2 degrees Celsius per minute for 2 hours to obtain a carbonized product. Then, the surface was modified with 0.1g of hexadecyltrimethylammonium bromide based on the above carbonized product to form a modified metal-organic framework compound. 3) Electromagnetic shielding film with alternating electromagnetic structure Under stirring conditions, the modified metal-organic framework compound obtained in step 2) above is dispersed in a 0.2% cellulose nanofiber aqueous solution at a solid content ratio of 1:2, and then vacuum filtered to form a membrane. The monolayer MXene solution obtained in step 1) above is alternately vacuum filtered onto the above membrane at a solid content weight ratio of 1:

4. The electromagnetic shielding membrane with alternating electromagnetic structures prepared has 5 layers. The number of layers is controlled by dividing the modified metal-organic framework compound / cellulose nanofiber solution and monolayer MXene solution into corresponding portions for filtration. The prepared modified metal-organic framework compound / cellulose nanofiber solution is divided into 3 portions, containing 16.7%, 33.3%, and 50.0% of the total modified metal-organic framework compound / cellulose nanofiber, respectively. The monolayer MXene solution is divided into 2 portions, containing 33.3% and 66.7% of the total monolayer MXene, respectively. First, the 50.0% modified metal-organic framework compound / cellulose nanofiber solution is vacuum filtered to form a membrane, and then the 33.3%... A monolayer MXene solution was vacuum filtered onto a 50.0% modified metal-organic framework / cellulose nanofiber membrane, then a 33.3% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 33.3% monolayer MXene membrane, then a 66.7% monolayer MXene solution was vacuum filtered onto a 33.3% modified metal-organic framework / cellulose nanofiber membrane, and finally a 16.7% modified metal-organic framework / cellulose nanofiber solution was vacuum filtered onto a 66.7% monolayer MXene membrane.

9. The use of the electromagnetic shielding film with an alternating electromagnetic structure according to any one of claims 1 to 7 in advanced electromagnetic interference protection devices for future sixth-generation communications.

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