A composite electromagnetic metamaterial film, a preparation method and application thereof

Abstract

This invention provides a composite electromagnetic metamaterial film, its preparation method, and its application. The preparation method includes: pre-treating one side surface of a polymer film with plasma to obtain a pre-treated surface; the step of setting the electromagnetic metamaterial layer includes: depositing a metallic absorbing material onto the pre-treated surface using a coating process to form an electromagnetic metamaterial layer, thereby obtaining a composite electromagnetic metamaterial film including the electromagnetic metamaterial layer; the composite electromagnetic metamaterial film has a length direction, and the electromagnetic wave transmittance gradually increases from -40dB to -20dB to -2dB to -0.1dB along the length direction of the composite electromagnetic metamaterial film. This invention, through the coating process, achieves a good composite between the electromagnetic metamaterial layer formed by the electromagnetic material and the polymer film, thereby achieving a linear gradient in transmittance, greatly broadening the acceptable transmittance range, and resulting in a better match of electromagnetic performance.

Description

Technical Field

[0001] This invention relates to the fields of metamaterials and microwave absorbing materials, and more specifically, to a composite electromagnetic metamaterial film, its preparation method, and its application. Background Technology

[0002] Electromagnetic metamaterial films are an important innovative achievement in the field of modern materials science. They are meticulously designed by researchers and possess extraordinary electromagnetic properties, bringing new possibilities to many fields.

[0003] The electromagnetic metamaterial membrane is prepared using a flexible substrate, which can be seamlessly integrated with composite material manufacturing processes, reducing process difficulty and cost while improving production efficiency and quality. Its performance meets the requirements of modern microwave absorbing materials for being "wide, thin, light, and strong," and satisfies the practical application requirements of integrated structure and function. It has broad application prospects in the aerospace field, and can be used in aircraft stealth design and electromagnetic protection of avionics equipment, potentially improving aircraft performance and safety and promoting the development of the aviation industry.

[0004] However, traditional electromagnetic metamaterial films are limited by their manufacturing processes, making it difficult to meet increasingly diverse design requirements. The traditional manufacturing process for electromagnetic metamaterial films primarily relies on screen printing, specifically printing absorbing materials onto the film surface using a customized screen to form an electromagnetic metamaterial layer, thereby achieving the electromagnetic properties of the film. Therefore, it is inevitably constrained by the screen printing process, preventing traditional electromagnetic metamaterial films from achieving superior and more flexible electromagnetic performance, and also hindering the effective improvement of the interfacial strength between the electromagnetic metamaterial layer and the substrate surface.

[0005] Based on the above, how to provide a method for preparing an electromagnetic metamaterial film that achieves a linear gradient in transmittance and matches better electromagnetic performance, so as to effectively broaden the range of transmittance and improve the bonding force between the metamaterial layer and the polymer substrate surface, is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0006] The main objective of this invention is to provide a composite electromagnetic metamaterial film, its preparation method, and its application, in order to solve the problems of poor overall mechanical properties of composite electromagnetic metamaterial films obtained by existing preparation methods, such as the inability to achieve linear changes in wave transmittance, a small range of wave transmittance, and poor bonding force between the electromagnetic metamaterial layer and the surface of the polymer substrate.

[0007] To achieve the above objectives, the present invention provides a method for preparing a composite electromagnetic metamaterial film, comprising the step of depositing an electromagnetic metamaterial layer on one side surface of a polymer film. Before depositing the electromagnetic metamaterial layer, the preparation method includes: pre-treating one side surface of the polymer film with plasma to obtain a pre-treated surface; the step of depositing the electromagnetic metamaterial layer includes: depositing a metal absorbing material on the pre-treated surface using a coating process to form an electromagnetic metamaterial layer, thereby obtaining a composite electromagnetic metamaterial film including the electromagnetic metamaterial layer; the composite electromagnetic metamaterial film has a length direction, and the electromagnetic wave transmittance gradually increases from -40dB to -20dB to -2dB to -0.1dB along the length direction of the composite electromagnetic metamaterial film.

[0008] Further, the metal absorbing material is a nickel-chromium alloy and / or a nickel-copper alloy; preferably, when the metal absorbing material is a nickel-chromium alloy, the electromagnetic wave transmittance gradually increases from -30dB to -20dB to -2dB to -0.1dB along the length direction of the composite electromagnetic metamaterial film; or, when the metal absorbing material is a nickel-copper alloy, the electromagnetic wave transmittance gradually increases from -40dB to -30dB to -2dB to -0.5dB along the length direction of the composite electromagnetic metamaterial film.

[0009] Furthermore, the coating process includes the following steps performed sequentially: a first coating stage with an initial coating speed of V1, a second coating stage with an initial coating speed of V2, a third coating stage with an initial coating speed of V3, and a fourth coating stage with an initial coating speed of V4, wherein: V1 is 0.1 m / min to 0.5 m / min; V2 is 1.0 m / min to 3.0 m / min; V3 is 1.5 m / min to 4.0 m / min; and V4 is 2.0 m / min to 5.0 m / min.

[0010] Further, the first coating stage includes the following stages performed sequentially: a first uniform speed stage and a first uniform acceleration stage, both with an initial coating speed of V1, and the duration of the first uniform speed stage is 20s to 60s; and / or, the second coating stage includes the following stages performed sequentially: a second uniform speed stage and a second uniform acceleration stage, both with an initial coating speed of V2, and the duration of the second uniform speed stage is 1s to 3s; and / or, the third coating stage includes the following stages performed sequentially: a third uniform speed stage and a third uniform acceleration stage, both with an initial coating speed of V3, and the duration of the third uniform speed stage is 1s to 3s; and / or, the fourth coating stage includes a fourth uniform speed stage, and the duration of the fourth uniform speed stage is 1s to 3s; preferably, when the final speed of the first uniform acceleration stage in the first coating stage is V2, the second coating stage is performed; when the final speed of the second uniform acceleration stage in the second coating stage is V3, the third coating stage is performed; when the final speed of the third uniform acceleration stage in the third coating stage is V4, the fourth coating stage is performed.

[0011] Furthermore, the accelerations in the first, second, and third uniform acceleration stages are each independently 0.2 m / min to 0.5 m / min per second.

[0012] Furthermore, the coating power of the first coating stage is 10kW to 12kW; and / or, the coating power of the second coating stage is 2kW to 10kW; and / or, the coating power of the third coating stage is 1kW to 5kW; and / or, the coating power of the fourth coating stage is 0.5kW to 2kW.

[0013] Furthermore, the plasma pretreatment has a processing power of 30W to 100W and a processing speed of 0.1m / min to 5m / min; preferably, the plasma pretreatment is carried out in an inert atmosphere.

[0014] Furthermore, the polymer membrane is selected from one or more of polyaniline membrane, polypyrrole membrane, polythiophene membrane and polyimide membrane; more preferably, it is a polyimide membrane.

[0015] Another aspect of the present invention provides a composite electromagnetic metamaterial membrane, which is prepared by the above-described method for preparing a composite electromagnetic metamaterial membrane, and the composite electromagnetic metamaterial membrane includes a polymer membrane and an electromagnetic metamaterial layer disposed on one side surface of the polymer membrane; preferably, the thickness of the polymer membrane is 23 μm to 53 μm, and the thickness of the electromagnetic metamaterial layer is 0.03 μm to 0.8 μm.

[0016] Another aspect of the present invention provides an application of the above-mentioned composite electromagnetic metamaterial film as a microwave absorbing electromagnetic film in the aerospace field.

[0017] By applying the technical solution of this invention, a good composite of the electromagnetic metamaterial layer formed by the electromagnetic material and the polymer film is achieved through a coating process, thereby realizing a linear gradient of transmittance and greatly expanding the range of acceptable transmittance, resulting in a better match of electromagnetic performance. Simultaneously, by pre-treating the surface of the polymer substrate with plasma, the bonding force between the electromagnetic metamaterial layer and the polymer film substrate surface is greatly improved, enhancing the mechanical properties of the resulting composite electromagnetic metamaterial film, while also effectively reducing its thickness and ensuring its flexibility. Attached Figure Description

[0018] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0019] Figure 1 The curves showing the electromagnetic wave transmittance versus composite film length variation of the composite electromagnetic metamaterial films obtained in Example 1 and Comparative Example 6 are shown. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0021] As described in the background art, existing methods for preparing composite electromagnetic metamaterial films suffer from problems such as the inability to achieve linear changes in transmittance, a small range of transmittance, and poor overall mechanical properties due to weak bonding between the electromagnetic metamaterial layer and the polymer substrate surface. To address these technical problems, this invention provides a method for preparing a composite electromagnetic metamaterial film, comprising the step of depositing an electromagnetic metamaterial layer on one side surface of a polymer film. Before depositing the electromagnetic metamaterial layer, the method includes: pre-treating one side surface of the polymer film with plasma to obtain a pre-treated surface; the step of depositing the electromagnetic metamaterial layer includes: depositing a metallic absorbing material onto the pre-treated surface using a coating process to form the electromagnetic metamaterial layer, thereby obtaining a composite electromagnetic metamaterial film including the electromagnetic metamaterial layer; the composite electromagnetic metamaterial film has a length direction, and the electromagnetic wave transmittance gradually increases from -40dB to -20dB to -2dB to -0.1dB along the length direction of the composite electromagnetic metamaterial film.

[0022] The method for preparing composite electromagnetic metamaterial films provided by this invention can not only improve the bonding force between the electromagnetic metamaterial layer and the polymer film substrate and enhance the tensile strength of the resulting composite electromagnetic metamaterial film, but also effectively reduce the thickness of the resulting composite electromagnetic metamaterial layer and ensure its flexibility.

[0023] Specifically, the first surface of the polymer film is pretreated by plasma treatment to clean it and increase active groups, thereby improving the adhesion between the polymer film surface and the subsequent metal absorbing material. Then, a coating process is used to deposit the metal absorbing material onto the pretreated surface, forming an electromagnetic metamaterial layer. The magnetic loss and / or dielectric loss of the two materials are utilized to enhance the absorption capability of the resulting composite electromagnetic metamaterial film. Compared to the screen printing process commonly used in the art, the coating process used in this invention is better suited to the composite electromagnetic metamaterial film system formed by the metal absorbing material and the polymer, improving the bonding force between the two, as well as the density and uniformity of the metal absorbing material deposited on the polymer film, thus improving the mechanical properties of the resulting composite electromagnetic metamaterial film. More importantly, for the formed composite electromagnetic metamaterial layer, compared to the screen printing process, the coating process provided by this invention can achieve a special distribution of the electromagnetic metamaterial layer on the polymer film surface, ultimately resulting in a composite electromagnetic metamaterial film with a linearly gradual change in transmittance over a wider range. Meanwhile, the method provided by this invention can more effectively control the thickness of the resulting composite film, preventing it from becoming brittle due to excessive thickness and improving the overall flexibility of the composite film. Furthermore, in actual production, the preparation method provided by this invention is adaptable to polymer film substrates of various sizes, offering greater versatility.

[0024] To effectively improve the microwave absorption performance of the final electromagnetic metamaterial film, the metal absorbing material is further selected as a nickel-chromium alloy and / or a nickel-copper alloy. Through extensive experimentation, the inventors optimized the type of metal material forming the electromagnetic metamaterial layer. Compared to other suitable metal absorbing materials, the aforementioned two types of metal materials exhibit better microwave absorption performance and better compatibility with the polymer matrix film, thereby more effectively improving the mechanical properties of the resulting electromagnetic metamaterial film.

[0025] In several typical embodiments, when the metal absorbing material is a nickel-chromium alloy, the electromagnetic wave transmittance gradually increases from -30dB to -20dB to -2dB to -0.1dB along the length of the composite electromagnetic metamaterial film; or, when the metal absorbing material is a nickel-copper alloy, the electromagnetic wave transmittance gradually increases from -40dB to -30dB to -2dB to -0.5dB along the length of the composite electromagnetic metamaterial film. This invention is based on different types of metal absorbing materials and designs the absorption performance of the composite electromagnetic metamaterial films formed from them, resulting in the above-mentioned scheme. This achieves a more effective bonding between the electromagnetic metamaterial layer formed by the metal absorbing material and the polymer film substrate, thereby obtaining a composite electromagnetic metamaterial film with stronger mechanical properties, a wider range of electromagnetic wave transmittance, and a gradual change in transmittance.

[0026] Furthermore, the coating process includes the following sequentially performed stages: a first coating stage with an initial coating speed of V1, a second coating stage with an initial coating speed of V2, a third coating stage with an initial coating speed of V3, and a fourth coating stage with an initial coating speed of V4, wherein: V1 is 0.1 m / min to 0.5 m / min; V2 is 1.0 m / min to 3.0 m / min; V3 is 1.5 m / min to 4.0 m / min; and V4 is 2.0 m / min to 5.0 m / min. Through extensive experimentation, the inventors set the coating process into four sequential stages and optimized the relevant parameters for each stage, resulting in the aforementioned process parameter settings. Within the above conditions, using metallic materials as the component of the electromagnetic metamaterial layer for coating results in a more compact and structurally complete electromagnetic metamaterial layer, while also allowing for more effective thickness reduction, thus leading to superior mechanical properties. In order to better adapt the initial velocities of each stage and to more significantly optimize the microstructure and mechanical properties of the resulting electromagnetic metamaterial layer, the velocities are further set as follows: V1 is 0.1 m / min to 0.5 m / min; V2 is 1.5 m / min to 2.0 m / min; V3 is 3.0 m / min to 3.5 m / min; and V4 is 4.0 m / min to 5.0 m / min.

[0027] Furthermore, in order to improve the gradient characteristics of the electromagnetic wave transmittance of the obtained composite electromagnetic metamaterial film and enhance its mechanical properties, the first coating stage preferably includes the following sequential stages: a first uniform speed stage and a first uniform acceleration stage, both with an initial coating speed of V1, and the duration of the first uniform speed stage is 20s to 60s; and / or, the second coating stage includes the following sequential stages: a second uniform speed stage and a second uniform acceleration stage, both with an initial coating speed of V2, and the duration of the second uniform speed stage is 1s to 3s; and / or, the third coating stage includes the following sequential stages: a third uniform speed stage and a third uniform acceleration stage, both with an initial coating speed of V3, and the duration of the third uniform speed stage is 1s to 3s; and / or, the fourth coating stage includes a fourth uniform speed stage, and the duration of the fourth uniform speed stage is 1s to 3s.

[0028] Furthermore, to better adapt to the production process and improve manufacturing efficiency and quality, in several typical embodiments, when the final velocity of the first uniform acceleration stage in the first coating stage is V2, the second coating stage is performed; when the final velocity of the second uniform acceleration stage in the second coating stage is V3, the third coating stage is performed; and when the final velocity of the third uniform acceleration stage in the third coating stage is V4, the fourth coating stage is performed. That is, in the coating process method provided by this invention, the first, second, third, and fourth coating stages are all continuous processes with good transitions between stages, resulting in a more superior overall performance of the obtained composite electromagnetic metamaterial film.

[0029] In order to more effectively realize the characteristic of gradual change in electromagnetic wave transmittance along the length of the obtained composite electromagnetic metamaterial film and make it exhibit more flexible application features, it is preferable that the acceleration of the first uniform acceleration stage, the second uniform acceleration stage and the third uniform acceleration stage are each independently 0.2 m / min to 0.5 m / min.

[0030] In several typical embodiments, based on the kinetic conditions of the four coating stages described above, the inventors, through extensive experiments, have correspondingly optimized their respective power parameters: the coating power of the first coating stage is 10kW to 12kW; and / or, the coating power of the second coating stage is 2kW to 10kW; and / or, the coating power of the third coating stage is 1kW to 5kW; and / or, the coating power of the fourth coating stage is 0.5kW to 2kW. The optimization and setting of the above coating power correspond to the coating speed of each stage, in order to obtain a composite electromagnetic metamaterial film with a wider transmittance range and a more uniform gradient effect. In several more typical embodiments, it is further preferred that the coating power of the first coating stage is 10kW to 12kW; and / or, the coating power of the second coating stage is 4kW to 6kW; and / or, the coating power of the third coating stage is 1kW to 2kW; and / or, the coating power of the fourth coating stage is 0.5kW to 1kW, thereby obtaining a composite electromagnetic metamaterial film with a more stable structure and better mechanical properties.

[0031] The method provided by this invention includes an indispensable step of plasma pretreatment of the polymer film. In a typical embodiment, the plasma pretreatment power is 30W to 100W, more preferably 30W to 50W, and the treatment speed is 0.1m / min to 5m / min. Specifically for the material system in the synthesis method provided by this invention, the plasma pretreatment step encompasses multiple processes such as ablation, crosslinking, and activation. On the one hand, it cleans the polymer surface; on the other hand, it forms a structure similar to "dangling bonds" on the surface, thereby better achieving its bonding with the metal material. Therefore, regarding the various process parameters involved in this pretreatment, the inventors screened and optimized them through numerous experiments to obtain the above-mentioned process conditions and ranges. They found that plasma pretreatment of the polymer surface according to the above parameters can better improve its surface bonding ability, thereby obtaining a composite electromagnetic metamaterial film structure with a more stable structure and better overall performance. Furthermore, it is preferable to carry out the plasma pretreatment in an inert atmosphere to avoid the ionization of components in the air into other plasmas that may damage the bonding of the film surface, thus affecting the effective composite of the electromagnetic metamaterial layer and the polymer film.

[0032] In particular, in several typical embodiments, in order to obtain a composite electromagnetic metamaterial film with better gradient effect, the plasma pretreatment process is preferably a uniform acceleration process with an acceleration of 0.2 m / min to 0.5 m / min per second.

[0033] In particular, to enable the above-mentioned coating process to be carried out more effectively, the polymer film is preferably selected from one or more of polyaniline film, polypyrrole film, polythiophene film, and polyimide film. Theoretically, the polymer film can be any functional polymer commonly used in the art, but since the present invention also involves pretreatment and coating processes, there are certain requirements for its surface characteristics and internal structure. Through extensive experiments and comparisons, the inventors have preferred polyimide film, and found that when polyimide film is used as the polymer film base layer, in addition to maximizing the flexibility of the resulting electromagnetic metamaterial film, the polyimide film also has a special segment -CO-NR-CO- in its main chain structure, which allows for better bonding between metal materials when in contact with it. The structural integrity and consistency of the resulting composite electromagnetic metamaterial film are thus significantly improved, and the coating is less likely to separate from the film before failure, resulting in higher safety during service.

[0034] Another aspect of the present invention provides a composite electromagnetic metamaterial film, which is prepared by the above-described method for preparing composite electromagnetic metamaterial films. The composite electromagnetic metamaterial film includes a polymer film and an electromagnetic metamaterial layer disposed on one surface of the polymer film. The resulting composite electromagnetic metamaterial film exhibits better flexibility and tensile strength due to the thinner thickness of the electromagnetic metamaterial layer and its strong adhesion to the polymer layer. Furthermore, the composite electromagnetic metamaterial film obtained by the above-described preparation method possesses a wider range of electromagnetic wave transmittance and exhibits a linear increase in electromagnetic wave transmittance along its length, thus broadening its application range.

[0035] Furthermore, in the obtained composite electromagnetic metamaterial film, the thickness of the polymer film is 23 μm to 53 μm, and the thickness of the electromagnetic metamaterial layer is 0.03 μm to 0.8 μm. This thickness matching not only allows the intrinsic flexibility of the polymer film to be brought into greater use, but also more effectively promotes the bonding between the electromagnetic metamaterial layer and the polymer film with stronger strength, so as to obtain a composite electromagnetic metamaterial film with more significant improvement in wave absorption performance and higher overall mechanical properties.

[0036] Another aspect of the present invention provides an application of the above-mentioned composite electromagnetic metamaterial film as a microwave absorbing electromagnetic film in the aerospace field. Because the obtained electromagnetic metamaterial film has higher flexibility and tensile strength, and also possesses the characteristic of linearly gradual change in electromagnetic wave transmittance, it can better meet various performance requirements when used as a microwave absorbing electromagnetic film in the aerospace field, with wider application conditions and a longer service life.

[0037] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0038] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0039] Example 1

[0040] a) Substrate selection:

[0041] A 50 μm thick polyimide film was selected as the polymer film substrate for the composite electromagnetic metamaterial membrane.

[0042] b) Selection of coating materials:

[0043] Nickel-chromium alloy was chosen as the absorbing material to form the electromagnetic metamaterial layer.

[0044] c) Substrate surface pretreatment:

[0045] Start the equipment and reduce the vacuum level in the equipment chamber. Once the equipment's working environment meets production conditions, fill it with inert gas, set the plasma treatment power to 50W, and begin winding for surface treatment. During treatment, use an initial processing speed of 0.1 m / min, accelerate to 5 m / min at a rate of 0.2 m / min per second, then decelerate to 0.1 m / min at a rate of 0.2 m / min per second, repeating this cycle to complete the plasma pretreatment of the polyimide film surface.

[0046] d) Coating:

[0047] The coating process is set up in four stages, namely:

[0048] The initial coating speed was set to 0.1 m / min, and the power was set to 10 kW for the first coating stage. In this stage, a first uniform speed process was performed for 60 seconds; then a first uniform acceleration process was performed at an acceleration of 0.2 m / min per second until the speed was accelerated to 2 m / min.

[0049] When the coating speed reaches 2 m / min, the power is set to 6 kW to proceed to the second coating stage. In this stage, a second uniform speed process lasting 1 second is performed first; then a second uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 3 m / min.

[0050] When the coating speed reaches 3 m / min, the power is set to 1 kW to proceed to the third coating stage. In this stage, a third uniform speed process lasting 1 second is performed first; then a third uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 5 m / min.

[0051] When the coating speed reaches 5 m / min, the power is set to 0.5 kW to proceed to the fourth coating stage. In this stage, a fourth uniform speed process lasting 1 second is performed.

[0052] After filling with inert gas and starting the winding process, the power supply is turned on, and the coating process described above is followed to begin coating, ultimately obtaining a composite electromagnetic metamaterial film. Its electromagnetic transmittance increases approximately linearly from -30dB to -0.1dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.05μm to 0.7μm.

[0053] Example 2

[0054] a) Substrate selection:

[0055] A 25 μm thick polyimide film was selected as the polymer film substrate for the composite electromagnetic metamaterial film.

[0056] b) Selection of coating materials:

[0057] Nickel-chromium alloy was chosen as the absorbing material to form the electromagnetic metamaterial layer.

[0058] c) Substrate surface pretreatment:

[0059] Start the equipment and reduce the vacuum level in the equipment chamber. Once the equipment's working environment meets production conditions, fill it with inert gas, set the plasma treatment power to 50W, and begin winding for surface treatment. During treatment, use an initial processing speed of 0.1 m / min, accelerate to 5 m / min at a rate of 0.5 m / min per second, then decelerate to 0.1 m / min at a rate of 0.5 m / min per second, repeating this cycle to complete the plasma pretreatment of the polyimide film surface.

[0060] d) Coating:

[0061] The coating process is set up in four stages, namely:

[0062] The initial coating speed was set to 0.5 m / min, and the power was set to 12 kW for the first coating stage. In this stage, a first uniform speed process was performed for 20 seconds; then a first uniform acceleration process was performed at an acceleration of 0.5 m / min per second until the speed was accelerated to 1.5 m / min.

[0063] When the coating speed reaches 1.5 m / min, the power is set to 4 kW to proceed to the second coating stage. In this stage, a second uniform speed process is first performed for 2 seconds; then a second uniform acceleration process is performed at an acceleration of 0.5 m / min per second until the speed is accelerated to 3 m / min.

[0064] When the coating speed reaches 3 m / min, the power is set to 2 kW to proceed to the third coating stage. In this stage, a third uniform speed process lasting 1 second is performed first; then a third uniform acceleration process is performed at an acceleration of 0.5 m / min per second until the speed is accelerated to 4 m / min.

[0065] When the coating speed reaches 4 m / min, the power is set to 1 kW to proceed to the fourth coating stage. In this stage, a fourth uniform speed process lasting 1 second is performed.

[0066] After filling with inert gas and starting the winding process, the power supply is turned on, and the coating process described above is followed to begin coating, ultimately obtaining a composite electromagnetic metamaterial film. Its electromagnetic transmittance increases approximately linearly from -24dB to -1.5dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.03μm to 0.4μm.

[0067] Example 3

[0068] A method for preparing a composite electromagnetic metamaterial membrane:

[0069] The only difference between this embodiment and Embodiment 1 is that the absorbing material, nickel-chromium alloy, is replaced with nickel-copper alloy to obtain a composite electromagnetic metamaterial film. Its electromagnetic transmittance increases approximately linearly from -40dB to -0.5dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.03μm to 0.6μm.

[0070] Example 4

[0071] A method for preparing a composite electromagnetic metamaterial membrane:

[0072] The difference between this embodiment and Embodiment 1 lies only in the process settings at each stage of the coating process, specifically:

[0073] The coating process is set up in four stages, namely:

[0074] The initial coating speed was set to 0.05 m / min, and the power was set to 15 kW for the first coating stage. In this stage, a first uniform speed process lasting 80 seconds was performed first; then a first uniform acceleration process was performed at an acceleration of 0.2 m / min per second until the speed was accelerated to 1 m / min.

[0075] When the coating speed reaches 1 m / min, the power is set to 1 kW to proceed to the second coating stage. In this stage, a second uniform speed process lasting 1 second is performed first; then a second uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 2.5 m / min.

[0076] When the coating speed reaches 2.5 m / min, the power is set to 3 kW to proceed to the third coating stage. In this stage, a third uniform speed process is first performed for 4 seconds; then a third uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 3 m / min.

[0077] When the coating speed reaches 3 m / min, the power is set to 0.2 kW to proceed to the fourth coating stage. This stage involves a fourth uniform speed process lasting 1 second.

[0078] Example 5

[0079] A method for preparing a composite electromagnetic metamaterial membrane:

[0080] The difference between this embodiment and Embodiment 1 lies only in the process settings at each stage of the coating process, specifically:

[0081] The coating process is set up in four stages, namely:

[0082] The initial coating speed is set to 1 m / min, and the power is set to 5 kW for the first coating stage. In this stage, a first uniform speed process lasting 10 s is performed first; then a first uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 1 m / min.

[0083] When the coating speed reaches 1.5 m / min, the power is set to 5 kW to proceed to the second coating stage. In this stage, a second uniform speed process is first performed for 4 seconds; then a second uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 4.5 m / min.

[0084] When the coating speed reaches 4.5 m / min, the power is set to 0.5 kW to proceed to the third coating stage. In this stage, a third uniform speed process lasting 1 second is performed first; then a third uniform acceleration process is performed at an acceleration of 0.2 m / min per second until the speed is accelerated to 6 m / min.

[0085] When the coating speed reaches 6 m / min, the power is set to 1.5 kW to proceed to the fourth coating stage. This stage involves a fourth uniform speed process lasting 4 seconds.

[0086] Example 6

[0087] A method for preparing a composite electromagnetic metamaterial membrane:

[0088] The only difference between this embodiment and Embodiment 1 is that in the coating process, only the first coating stage and the fourth coating stage are performed.

[0089] Example 7

[0090] A method for preparing a composite electromagnetic metamaterial membrane:

[0091] The only difference between this embodiment and Embodiment 1 is that, in the coating process, the acceleration of each uniform acceleration stage is changed to 0.1 m / min per second.

[0092] Under the conditions of this embodiment, a composite electromagnetic metamaterial film with good electromagnetic wave transmittance variation range, bonding force, and mechanical properties can be obtained. However, since the acceleration of each uniform acceleration stage is changed, the curve of electromagnetic wave transmittance changing with the length direction is no longer nearly linear, that is, the gradual change effect is slightly worse.

[0093] Example 8

[0094] A method for preparing a composite electromagnetic metamaterial membrane:

[0095] The only difference between this embodiment and Embodiment 1 is that, in the coating process, the acceleration of each uniform acceleration stage is changed to 0.8 m / min per second.

[0096] Similarly, in this embodiment, the gradient effect of the resulting composite electromagnetic metamaterial film is slightly inferior due to the change in the acceleration of each uniform acceleration stage. However, the range of electromagnetic wave transmittance variation, bonding strength, and mechanical properties still exhibit excellent performance.

[0097] Example 9

[0098] A method for preparing a composite electromagnetic metamaterial membrane:

[0099] The only difference between this embodiment and Embodiment 1 is that the power of the plasma treatment is set to 100W during the pretreatment of the substrate surface.

[0100] Example 10

[0101] A method for preparing a composite electromagnetic metamaterial membrane:

[0102] The only difference between this embodiment and Embodiment 1 is that, during the pretreatment of the substrate surface, the plasma treatment process is changed to a uniform process, and the processing speed is maintained at 2.5 m / min.

[0103] Comparative Example 1

[0104] A method for preparing a composite electromagnetic metamaterial membrane:

[0105] The only difference between this comparative example and Example 1 is that: in the coating process, only the first coating stage is performed, and the composite electromagnetic metamaterial film is finally obtained. Its electromagnetic transmittance increases approximately linearly from -30dB to -6dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.1μm to 0.2μm.

[0106] Comparative Example 2

[0107] A method for preparing a composite electromagnetic metamaterial membrane:

[0108] The only difference between this comparative example and Example 2 is that only the fourth coating stage is performed during the coating process, and a composite electromagnetic metamaterial film is finally obtained. Its electromagnetic transmittance increases approximately linearly from -2dB to -0.6dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.05μm to 0.1μm.

[0109] Comparative Example 3

[0110] A method for preparing a composite electromagnetic metamaterial membrane:

[0111] The only difference between this comparative example and Comparative Example 1 is that: in the coating process, only the first coating stage is performed, and the coating power of the first coating stage is changed to 20kW, and the composite electromagnetic metamaterial film is finally obtained. Its electromagnetic transmittance increases approximately linearly from -40dB to -6dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.4μm to 0.6μm.

[0112] Comparative Example 4

[0113] A method for preparing a composite electromagnetic metamaterial membrane:

[0114] The only difference between this comparative example and Comparative Example 1 is that: in the coating process, only the first coating stage is performed, and the coating power of the first coating stage is changed to 15kW, and the composite electromagnetic metamaterial film is finally obtained. Its electromagnetic transmittance increases approximately linearly from -35dB to -6dB along the length direction, and the thickness of the electromagnetic metamaterial layer on it ranges from 0.3μm to 0.4μm.

[0115] Comparative Example 5

[0116] A method for preparing a composite electromagnetic metamaterial membrane:

[0117] The only difference between this comparative example and Example 1 is that the polyimide film was not pretreated on the substrate surface; instead, the nickel-chromium alloy was directly deposited onto one side of the untreated polyimide film using a coating process.

[0118] Comparative Example 6

[0119] A method for preparing a composite electromagnetic metamaterial membrane:

[0120] This comparative example uses screen printing instead of coating to produce electromagnetic metamaterial films, specifically:

[0121] a) Ink thawing:

[0122] The ink is left to stand at 25℃±3℃ to return to room temperature before use.

[0123] b) Ink mixing:

[0124] Remove the ink from the can and add the additives, then use an ink mixing knife to thoroughly mix it.

[0125] c) Printing:

[0126] Pour an appropriate amount of ink onto the screen; place the PI film for adjusting the printing plate on the printing platform to fully fill the mesh with ink, adjust the squeegee pressure, and begin printing.

[0127] d) Baking:

[0128] The printed electromagnetic metamaterial film is placed in an oven for baking.

[0129] e) Detection:

[0130] Due to the limitations of screen printing technology, the lower the required transmittance, the thicker the printed electromagnetic metamaterial layer will be. When the required transmittance is below -15dB, the electromagnetic metamaterial layer will be too thick. After baking, the electromagnetic metamaterial layer will become brittle, resulting in the electromagnetic metamaterial film having too low mechanical properties and failing to meet the performance requirements of the sample.

[0131] Test methods

[0132] Electromagnetic wave transmittance: Tested according to GJB 7954B.

[0133] Mechanical properties, i.e. tensile strength: tested according to GB / T 5210, with 10 parallel samples taken for each material sample to obtain the maximum, minimum and average values.

[0134] Failure mode: Tested according to GB / T 5210. Before the test: Apply adhesive film evenly and smoothly to both sides of the composite electromagnetic metamaterial film sample to be tested, and then align and attach the loading head to the adhesive film on both sides; cut off the excess part along the edge of the loading head, and after curing, conduct mechanical testing under dry conditions at room temperature, and observe the fracture mode with the naked eye.

[0135] The composite electromagnetic metamaterial film samples prepared in each embodiment and comparative example were subjected to the above tests, and the results are shown in Table 1. Furthermore, the electromagnetic wave transmittance versus composite film length variation curves for Example 1 and Comparative Example 6 are shown in Table 1. Figure 1 .

[0136] from Figure 1 As can be seen, the technical solution provided by this invention changes the production process of the electromagnetic metamaterial layer from screen printing to coating, and designs the coating process. The transmittance of the prepared electromagnetic metamaterial film can achieve a continuous, near-linear gradual change, and the performance curve can be further diversified. At the same time, it broadens the transmittance range that the electromagnetic metamaterial film can meet. In contrast, electromagnetic metamaterial films prepared using screen printing cannot achieve a continuous gradual change in transmittance, and have a narrower electromagnetic wave transmittance range, limiting their applications.

[0137] Table 1

[0138]

[0139] As can be seen from the above description, the embodiments of the present invention rely on the coating process to significantly broaden the electromagnetic wave transmittance range of the obtained composite electromagnetic metamaterial film, improve its mechanical properties, and achieve the advantage of linearly increasing electromagnetic wave transmittance in the length direction, which can meet more design and application requirements.

[0140] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate, so that the embodiments of this application described herein can be implemented, for example, in orders other than those described herein.

[0141] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite electromagnetic metamaterial film, comprising the step of depositing an electromagnetic metamaterial layer on one side surface of a polymer film, characterized in that, Before setting the electromagnetic metamaterial layer, the preparation method includes: pre-treating one side surface of the polymer film with plasma to obtain a pre-treated surface; The steps of setting the electromagnetic metamaterial layer include: depositing a metal absorbing material on the pretreated surface using a coating process to form the electromagnetic metamaterial layer, thereby obtaining the composite electromagnetic metamaterial film including the electromagnetic metamaterial layer. The coating process includes the following steps performed sequentially: The coating process includes a first coating stage with an initial coating speed of V1, a second coating stage with an initial coating speed of V2, a third coating stage with an initial coating speed of V3, and a fourth coating stage with an initial coating speed of V4, wherein: The speed V1 is 0.1 m / min to 0.5 m / min; the speed V2 is 1.5 m / min to 2.0 m / min; the speed V3 is 3.0 m / min to 3.5 m / min; and the speed V4 is 4.0 m / min to 5.0 m / min. The composite electromagnetic metamaterial film has a length direction, and the electromagnetic wave transmittance of the composite electromagnetic metamaterial film gradually increases from -40dB to -20dB to -2dB to -0.1dB along the length direction of the composite electromagnetic metamaterial film.

2. The method for preparing the composite electromagnetic metamaterial film according to claim 1, characterized in that, The metal absorbing material is a nickel-chromium alloy and / or a nickel-copper alloy.

3. The method for preparing the composite electromagnetic metamaterial film according to claim 2, characterized in that, When the metal absorbing material is a nickel-chromium alloy, the electromagnetic wave transmittance of the composite electromagnetic metamaterial film gradually increases from -30dB to -20dB to -2dB to -0.1dB along the length direction of the composite electromagnetic metamaterial film. Alternatively, when the metal absorbing material is a nickel-copper alloy, the electromagnetic wave transmittance of the composite electromagnetic metamaterial film gradually increases from -40dB to -30dB to -2dB to -0.5dB along the length direction of the composite electromagnetic metamaterial film.

4. The method for preparing the composite electromagnetic metamaterial film according to claim 1, characterized in that, The first coating stage includes the following sequential stages: a first uniform speed stage and a first uniform acceleration stage, both with an initial coating speed of V1, wherein the duration of the first uniform speed stage is 20s~60s; and / or, The second coating stage includes the following sequential stages: a second uniform speed stage and a second uniform acceleration stage, both with an initial coating speed of V2, wherein the duration of the second uniform speed stage is 1s to 3s; and / or, The third coating stage includes the following sequential stages: a third uniform speed stage and a third uniform acceleration stage, both with an initial coating speed of V3, and the duration of the third uniform speed stage is 1s to 3s; and / or, The fourth coating stage includes a fourth uniform speed stage, and the duration of the fourth uniform speed stage is 1s to 3s.

5. The method for preparing the composite electromagnetic metamaterial film according to claim 4, characterized in that, When the final velocity of the first uniform acceleration stage in the first coating stage is V2, the second coating stage is performed; when the final velocity of the second uniform acceleration stage in the second coating stage is V3, the third coating stage is performed; when the final velocity of the third uniform acceleration stage in the third coating stage is V4, the fourth coating stage is performed.

6. The method for preparing the composite electromagnetic metamaterial film according to claim 4, characterized in that, The accelerations of the first uniform acceleration phase, the second uniform acceleration phase, and the third uniform acceleration phase are each independently 0.2 m / min to 0.5 m / min per second.

7. The method for preparing the composite electromagnetic metamaterial film according to claim 1 or 6, characterized in that, The coating power in the first coating stage is 10kW~12kW; and / or, The coating power in the second coating stage is 2kW~10kW; and / or, The coating power of the third coating stage is 1kW~5kW; and / or, The coating power of the fourth coating stage is 0.5kW to 2kW.

8. The method for preparing the composite electromagnetic metamaterial film according to any one of claims 1 to 6, characterized in that, The plasma pretreatment has a processing power of 30W~100W and a processing speed of 0.1m / min~5m / min.

9. The method for preparing the composite electromagnetic metamaterial film according to any one of claims 1 to 6, characterized in that, The plasma pretreatment is performed in an inert atmosphere.

10. The method for preparing the composite electromagnetic metamaterial film according to any one of claims 1 to 6, characterized in that, The polymer film is selected from one or more of polyaniline film, polypyrrole film, polythiophene film and polyimide film.

11. The method for preparing the composite electromagnetic metamaterial film according to any one of claims 1 to 6, characterized in that, The polymer film is a polyimide film.

12. A composite electromagnetic metamaterial membrane, characterized in that, The composite electromagnetic metamaterial membrane is prepared by the method for preparing the composite electromagnetic metamaterial membrane according to any one of claims 1 to 11, and the composite electromagnetic metamaterial membrane includes the polymer membrane and the electromagnetic metamaterial layer disposed on one side surface of the polymer membrane.

13. The composite electromagnetic metamaterial membrane according to claim 12, characterized in that, The thickness of the polymer film is 23μm~53μm, and the thickness of the electromagnetic metamaterial layer is 0.03μm~0.8μm.

14. The application of the composite electromagnetic metamaterial membrane according to claim 12 or 13 as a wave-absorbing electromagnetic membrane in the aerospace field.

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