Composite electromagnetic metamaterial membrane as well as preparation method and application thereof

Abstract

The invention provides a composite electromagnetic metamaterial membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out plasma pretreatment on the surface of one side of the polymer film in advance to obtain a pretreated surface; the step of arranging the electromagnetic metamaterial layer comprises the following steps: depositing a metal wave-absorbing material on the pretreated surface by adopting a coating process to form the electromagnetic metamaterial layer, and further obtaining a composite electromagnetic metamaterial film comprising the electromagnetic metamaterial layer; the composite electromagnetic metamaterial film has a length direction, and the electromagnetic wave transmissivity is gradually increased from-40dB to-20dB to-2dB to-0.1 dB along the length direction of the composite electromagnetic metamaterial film. According to the invention, through the coating process, the good compounding of the electromagnetic metamaterial layer formed by the electromagnetic material and the polymer film is realized, the linear gradual change of the wave transmission rate is further realized, the satisfactory wave transmission rate range is greatly widened, and the electromagnetic performance is better matched.

Description

Technical Field

[0001] The present invention relates to the fields of metamaterials and wave-absorbing materials, and in particular to a composite electromagnetic metamaterial film, a preparation method thereof, and applications thereof. Background Art

[0002] Electromagnetic metamaterial film is an important innovative achievement in the field of modern materials science. It is carefully designed by scientific researchers and has extraordinary electromagnetic properties, bringing new possibilities to many fields.

[0003] Electromagnetic metamaterial films are manufactured using flexible substrates, enabling seamless integration with composite material manufacturing processes, reducing complexity and costs while improving production efficiency and quality. Their performance aligns with the requirements of modern absorbing materials for wide, thin, light, and strong applications, meeting the practical requirements of integrated structural and functional design. They hold broad application prospects in the aviation sector, including applications in aircraft stealth design and electromagnetic shielding for avionics equipment. They are expected to enhance aircraft performance and safety, ultimately driving the development of the aviation industry.

[0004] However, due to limitations in manufacturing processes, traditional electromagnetic metamaterial films struggle to meet increasingly diverse design requirements. Traditionally, these films rely on screen printing, where an absorbing material is printed onto the film surface using a custom screen, forming the electromagnetic metamaterial layer and achieving the desired electromagnetic properties. Consequently, these films are inevitably constrained by the screen printing process, preventing them from achieving superior and more flexible electromagnetic properties, and effectively improving the interface strength between the electromagnetic metamaterial layer and the substrate surface.

[0005] Based on the above content, how to provide a method for preparing an electromagnetic metamaterial film to achieve a linear gradient of transmittance and match better electromagnetic performance to effectively broaden the range of transmittance satisfaction while improving 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 purpose of the present invention is to provide a composite electromagnetic metamaterial film, a preparation method and application thereof, so as to solve the problems that the composite electromagnetic metamaterial film obtained by the preparation method in the prior art cannot achieve linear change in the transmittance, the transmittance range is small, and the bonding force between the electromagnetic metamaterial layer and the polymer substrate surface in its structure is poor, resulting in poor overall mechanical properties of the composite electromagnetic metamaterial film.

[0007] To achieve the above-mentioned objectives, the present invention provides, on one hand, a method for preparing a composite electromagnetic metamaterial film, comprising the step of providing an electromagnetic metamaterial layer on one side surface of a polymer film. Prior to providing the electromagnetic metamaterial layer, the preparation method comprises: pre-processing one side surface of the polymer film with plasma to obtain a pretreated surface; providing the electromagnetic metamaterial layer comprises: depositing a metal absorbing material on the pretreated 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] Furthermore, 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: 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, and: V1 is 0.1m / min~0.5m / min; V2 is 1.0m / min~3.0m / min; V3 is 1.5m / min~4.0m / min; V4 is 2.0m / min~5.0m / min.

[0010] Further, the first coating stage includes the following stages that are carried out successively: a first uniform speed stage and a first uniform acceleration stage, both of which have an initial coating speed of V1, and the time of the first uniform speed stage is 20s to 60s; and / or, the second coating stage includes the following stages that are carried out successively: a second uniform speed stage and a second uniform acceleration stage, both of which have an initial coating speed of V2, and the time of the second uniform speed stage is 1s to 3s; and / or, the third coating stage includes the following stages that are carried out successively: a third uniform speed stage and a third uniform acceleration stage, both of which have an initial coating speed of V3, and the time of the third uniform speed stage is 1s to 3s; and / or, the fourth coating stage includes a fourth uniform speed stage, and the time of the fourth uniform speed stage is 1s to 3s; preferably, when in the first coating stage, the final speed of the first uniform acceleration stage is V2, the second coating stage is carried out; when in the second coating stage, the final speed of the second uniform acceleration stage is V3, the third coating stage is carried out; when in the third coating stage, the final speed of the third uniform acceleration stage is V4, the fourth coating stage is carried out.

[0011] Furthermore, the accelerations of the first uniform acceleration stage, the second uniform acceleration stage, and the third uniform acceleration stage are independently 0.2 m / min to 0.5 m / min.

[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 processing power of the plasma pretreatment is 30W to 100W, and the processing speed is 0.1m / min to 5m / min; preferably, the plasma pretreatment is performed in an inert atmosphere.

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

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

[0016] Another aspect of the present invention provides an application of the composite electromagnetic metamaterial film as a wave-absorbing electromagnetic film in the aviation field.

[0017] The technical solution of the present invention achieves a good composite of the electromagnetic metamaterial layer formed by the electromagnetic material and the polymer film through a coating process, thereby achieving a linear gradient of transmittance, greatly broadening the acceptable transmittance range and achieving a better match of electromagnetic performance. Furthermore, by pre-plasma treatment of the polymer substrate surface, the bonding between the electromagnetic metamaterial layer and the polymer film substrate is greatly improved, strengthening the mechanical properties of the resulting composite electromagnetic metamaterial film while also effectively reducing its thickness and ensuring its flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0019] Figure 1 1 and 2 are curves showing the change in electromagnetic wave transmittance versus composite film length of the composite electromagnetic metamaterial films obtained in Example 1 and Comparative Example 6. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0021] As described in the background art, the composite electromagnetic metamaterial film obtained by the existing preparation method has the problem that the transmittance cannot achieve linear change, the transmittance range is small, and the bonding force between the electromagnetic metamaterial layer and the polymer substrate surface in its structure is poor, resulting in poor overall mechanical properties of the composite electromagnetic metamaterial film. In order to solve the above technical problems, the present invention provides a preparation method of a composite electromagnetic metamaterial film, including the step of providing an electromagnetic metamaterial layer on one side surface of a polymer film. Before providing the electromagnetic metamaterial layer, the preparation method includes: pre-processing one side surface of the polymer film with plasma to obtain a pre-treated surface; providing 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.

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

[0023] Specifically, the first surface of the polymer film is pretreated by plasma treatment to clean and increase the active groups, thereby improving the bonding between the polymer film surface and the subsequent metal absorbing material. A coating process is then used to deposit the metal absorbing material on the pretreated surface to form an electromagnetic metamaterial layer, and the magnetic loss and / or dielectric loss of the two are utilized to improve the absorbing ability of the resulting composite electromagnetic metamaterial film. Compared with the silk-screen printing process commonly used in this field, the coating process used in the present invention can better adapt to the composite electromagnetic metamaterial film system formed by the metal absorbing material and the polymer, improve the bonding force between the two, and the density and uniformity of the metal absorbing material deposited on the polymer film, thereby improving the mechanical properties of the resulting composite electromagnetic metamaterial film. More importantly, for the composite electromagnetic metamaterial layer formed, compared with the silk-screen printing process, the coating process provided by the present invention can achieve a special distribution of the electromagnetic metamaterial layer on the surface of the polymer film, and ultimately obtain a composite electromagnetic metamaterial film with a linear gradient in transmittance over a larger range. The method provided by the present invention also effectively controls the thickness of the resulting composite film, preventing it from becoming brittle due to excessive thickness and improving its overall flexibility. Furthermore, in actual production, the preparation method provided by the present invention is adaptable to polymer film substrates of various sizes, demonstrating greater universality.

[0024] To effectively enhance the absorbing performance of the resulting electromagnetic metamaterial film, the metal absorbing material is a nickel-chromium alloy and / or a nickel-copper alloy. The inventors conducted extensive experiments to optimize the metal material type used to form the electromagnetic metamaterial layer. Compared to other metal absorbing materials, the aforementioned two metal materials exhibit superior absorbing performance and improved compatibility with the polymer matrix film, effectively enhancing 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. The present invention is based on different types of metal absorbing materials and designs the absorbing properties of the composite electromagnetic metamaterial films formed therefrom, resulting in the above-mentioned solution. This achieves a more effective combination of 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 gradient.

[0026] Furthermore, the coating process includes the following: 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 0.1m / min to 0.5m / min; V2 is 1.0m / min to 3.0m / min; V3 is 1.5m / min to 4.0m / min; and V4 is 2.0m / min to 5.0m / min. After extensive experiments, the inventors set the coating process to four sequential stages and optimized the relevant parameters to obtain the above process parameter settings. Within the above conditions, coating the electromagnetic metamaterial layer with metal materials as the components of the electromagnetic metamaterial layer results in a denser and more complete structure, while also enabling more effective thickness reduction, resulting in superior mechanical properties. In order to better adapt the initial speed of each stage and to more significantly optimize the microstructure and mechanical properties of the obtained electromagnetic metamaterial layer, V1 is further set to 0.1m / min~0.5m / min; V2 is set to 1.5m / min~2.0m / min; V3 is set to 3.0m / min~3.5m / min; and V4 is set to 4.0m / min~5.0m / min.

[0027] Furthermore, in order to make the gradual change characteristics of the electromagnetic wave transmittance of the obtained composite electromagnetic metamaterial film better and the mechanical properties better, it is preferred that the first coating stage includes the following stages that are carried out successively: the first uniform speed stage and the first uniform acceleration stage, both of which have an initial coating speed of V1, and the time of the first uniform speed stage is 20s to 60s; and / or, the second coating stage includes the following stages that are carried out successively: the second uniform speed stage and the second uniform acceleration stage, both of which have an initial coating speed of V2, and the time of the second uniform speed stage is 1s to 3s; and / or, the third coating stage includes the following stages that are carried out successively: the third uniform speed stage and the third uniform acceleration stage, both of which have an initial coating speed of V3, and the time of the third uniform speed stage is 1s to 3s; and / or, the fourth coating stage includes the fourth uniform speed stage, and the time of the fourth uniform speed stage is 1s to 3s.

[0028] Furthermore, to better adapt to production processes 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 provided by the present invention, the first coating stage, the second coating stage, the third coating stage, and the fourth coating stage are all continuous processes, with each stage well connected, and the overall performance of the resulting composite electromagnetic metamaterial film is also better.

[0029] In order to more effectively realize the characteristic of gradual change of electromagnetic wave transmittance in the length direction of the obtained composite electromagnetic metamaterial film and make it exhibit more flexible application characteristics, it is preferred that the accelerations 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 per second.

[0030] In several typical embodiments, based on the dynamic conditions of the four coating stages described above, the inventors, after extensive experiments, have correspondingly optimized their respective power parameters, namely: 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 above-mentioned preferred coating powers and settings correspond to the coating speeds of each stage, so as 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 the present invention includes the 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 processing speed is 0.1m / min to 5m / min. Regarding the material system in the synthesis method provided by the present invention, since the plasma pretreatment step covers multiple processes such as ablation, crosslinking, and activation, it can not only clean the polymer surface, but also form a structure similar to "dangling bonds" on its surface, thereby better achieving its bonding with the metal material. Therefore, for the various process parameters involved in this pretreatment, the inventors screened and optimized them through extensive experiments to obtain the above process conditions and ranges. They found that plasma pretreatment of the polymer surface according to the above parameters can better enhance its surface bonding ability, thereby obtaining a composite electromagnetic metamaterial membrane structure with more stable structure and better overall performance. It is further preferred that the plasma pretreatment be carried out in an inert atmosphere to prevent components in the air from being ionized into other plasmas that may destroy the bonding of the membrane surface and affect the effective bonding of the electromagnetic metamaterial layer and the polymer membrane.

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

[0033] In particular, in order to make the above-mentioned coating process more efficient, the type of polymer film is preferably selected from one or more of polyaniline film, polypyrrole film, polythiophene film and polyimide film. In theory, the type of polymer film can be a functional polymer commonly used in the art, but because the present invention also involves the process steps of pre-treatment and coating, there are certain requirements for its surface characteristics and internal structure. After a large number of experiments and comparisons, the inventors preferred polyimide film and found that when polyimide film is used as the polymer film base, in addition to being able to maximize the flexibility of the obtained electromagnetic metamaterial film, the polyimide film also has a special segment -CO-NR-CO- in its main chain structure. When the metal material comes into contact with it, it can better combine with it. The structural integrity and consistency of the composite electromagnetic metamaterial film finally obtained are thus more significantly improved, and it is not easy for the coating and the film to separate before failure, and the safety during service is higher.

[0034] Another aspect of the present invention provides a composite electromagnetic metamaterial film, which is prepared by the above-mentioned composite electromagnetic metamaterial film preparation method, and 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 improved flexibility and flat tensile strength due to the thinner thickness of the electromagnetic metamaterial layer in its structure and good bonding with the polymer layer. Furthermore, the composite electromagnetic metamaterial film obtained by the above-mentioned preparation method has a larger electromagnetic wave transmittance range and exhibits a linear increase in electromagnetic wave transmittance along the length direction, thus having a wider range of applications.

[0035] Furthermore, in the resulting composite electromagnetic metamaterial film, the polymer film has a thickness of 23 to 53 μm, while the electromagnetic metamaterial layer has a thickness of 0.03 to 0.8 μm. This thickness matching not only maximizes the inherent flexibility of the polymer film but also more effectively promotes a stronger bond between the electromagnetic metamaterial layer and the polymer film, resulting in a composite electromagnetic metamaterial film with significantly improved wave absorption performance and higher overall mechanical properties.

[0036] Another aspect of the present invention provides the use of the composite electromagnetic metamaterial film as an electromagnetic absorbing film in the aviation field. Because the resulting electromagnetic metamaterial film has enhanced flexibility and tensile strength, as well as a linear gradient in electromagnetic wave transmittance, it can better meet various performance requirements, has a wider range of operating conditions, and a longer service life when used as an electromagnetic absorbing film in the aviation field.

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

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

[0039] Example 1

[0040] a) Substrate selection:

[0041] A polyimide film with a thickness of 50 μm was selected as the polymer film substrate of the composite electromagnetic metamaterial film.

[0042] b) Coating material selection:

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

[0044] c) Substrate surface pretreatment:

[0045] The equipment was started and the vacuum level in the chamber was reduced. Once the operating environment reached production conditions, inert gas was introduced, the plasma treatment power was set to 50W, and the winding was turned on for surface treatment. The treatment started at 0.1 m / min, accelerated at 0.2 m / min per second to 5 m / min, and then decelerated at 0.2 m / min per second to 0.1 m / min. This cycle was repeated to complete the plasma pretreatment of the polyimide film surface.

[0046] d) Coating:

[0047] The coating process is divided into four stages, namely:

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

[0049] When the coating speed reaches 2m / min, the power is set to 6KW and the second coating stage is carried out. In this stage, the second uniform speed process is carried out for 1s; then the second uniform acceleration process is carried out at an acceleration of 0.2m / min per second until the speed is accelerated to 3m / min.

[0050] When the coating speed reaches 3m / min, the power is set to 1KW and the third coating stage is carried out. In this stage, the third uniform speed process is carried out for 1s; then the third uniform acceleration process is carried out at an acceleration of 0.2m / min per second until the speed is accelerated to 5m / min.

[0051] When the coating speed reaches 5 m / min, the power is set to 0.5 kW and the fourth coating stage is performed, in which the fourth uniform speed process is performed for 1 s.

[0052] After filling with inert gas and unwinding, the power supply is turned on and the coating process is carried out according to the above coating process, and finally a composite electromagnetic metamaterial film is obtained. Its electromagnetic transmittance increases roughly linearly from -30dB to -0.1dB along the length direction, and the thickness of the electromagnetic metamaterial layer thereon ranges from 0.05μm to 0.7μm.

[0053] Example 2

[0054] a) Substrate selection:

[0055] A polyimide film with a thickness of 25 μm was selected as the polymer film substrate of the composite electromagnetic metamaterial film.

[0056] b) Coating material selection:

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

[0058] c) Substrate surface pretreatment:

[0059] The equipment was started and the vacuum level in the chamber was reduced. Once the operating environment reached production conditions, inert gas was introduced, the plasma treatment power was set to 50W, and the winding was turned on for surface treatment. The treatment cycle was repeated with an initial speed of 0.1 m / min, then accelerated at 0.5 m / min per second to 5 m / min, and then decelerated at 0.5 m / min per second to 0.1 m / min. This cycle completed the plasma pretreatment of the polyimide film surface.

[0060] d) Coating:

[0061] The coating process is divided into four stages, namely:

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

[0063] When the coating speed reaches 1.5m / min, the power is set to 4KW and the second coating stage is carried out. In this stage, the second uniform speed process is carried out for 2s; then the second uniform acceleration process is carried out at an acceleration of 0.5m / min per second until the speed is accelerated to 3m / min.

[0064] When the coating speed reaches 3m / min, the power is set to 2KW and the third coating stage is carried out. In this stage, the third uniform speed process is carried out for 1s; then the third uniform acceleration process is carried out at an acceleration of 0.5m / min per second until the speed is accelerated to 4m / min.

[0065] When the coating speed reaches 4 m / min, the power is set to 1 kW and the fourth coating stage is carried out. In this stage, the fourth uniform speed process is carried out for 1 s.

[0066] After filling with inert gas and unwinding, the power supply is turned on and the coating process is carried out according to the above coating process. Finally, a composite electromagnetic metamaterial film is obtained, whose electromagnetic transmittance increases roughly linearly from -24dB to -1.5dB along the length direction, and the thickness of the electromagnetic metamaterial layer thereon ranges from 0.03μm to 0.4μm.

[0067] Example 3

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

[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, whose electromagnetic transmittance increases approximately linearly from -40dB to -0.5dB along the length direction, and the thickness of the electromagnetic metamaterial layer thereon ranges from 0.03μm to 0.6μm.

[0070] Example 4

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

[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 divided into four stages, namely:

[0074] The first coating stage was set at an initial coating speed of 0.05 m / min and a power of 15 kW. During this stage, a first uniform speed process was performed for 80 seconds, followed by a first uniform acceleration process at an acceleration of 0.2 m / min per second until the speed reached 1 m / min.

[0075] When the coating speed reaches 1m / min, the power is set to 1KW and the second coating stage is carried out. In this stage, the second uniform speed process is carried out for 1s; then the second uniform acceleration process is carried out at an acceleration of 0.2m / min per second until the speed is accelerated to 2.5m / min.

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

[0077] When the coating speed reaches 3 m / min, the power is set to 0.2 kW and the fourth coating stage is carried out. In this stage, the fourth uniform speed process is carried out for 1 s.

[0078] Example 5

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

[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 divided into four stages, namely:

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

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

[0084] When the coating speed reaches 4.5m / min, the power is set to 0.5KW and the third coating stage is carried out. In this stage, the third uniform speed process is carried out for 1s; then the third uniform acceleration process is carried out at an acceleration of 0.2m / min per second until the speed is accelerated to 6m / min.

[0085] When the coating speed reaches 6 m / min, the power is set to 1.5 kW and the fourth coating stage is carried out, in which a fourth uniform speed process of 4 s is carried out.

[0086] Example 6

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

[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 film:

[0091] The only difference between this embodiment and embodiment 1 is that in the coating process, the acceleration in 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 excellent electromagnetic wave transmittance variation range, bonding strength, and mechanical properties can be obtained. However, due to the change in the acceleration of each uniform acceleration stage, the curve of electromagnetic wave transmittance variation along the longitudinal direction is no longer nearly linear, that is, the gradient effect is slightly poor.

[0093] Example 8

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

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

[0096] In this embodiment, the acceleration of each uniform acceleration stage is changed, so the gradient effect of the composite electromagnetic metamaterial film is slightly worse. However, the electromagnetic wave transmittance variation range, bonding strength and mechanical properties are still excellent.

[0097] Example 9

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

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

[0100] Example 10

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

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

[0103] Comparative Example 1

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

[0105] The only difference between this comparative example and Example 1 is that during 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 -30 dB to -6 dB along the length direction, and the thickness of the electromagnetic metamaterial layer thereon ranges from 0.1 μm to 0.2 μm.

[0106] Comparative Example 2

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

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

[0109] Comparative Example 3

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

[0111] The only difference between this comparative example and comparative example 1 is that during the coating process, only the first coating stage is performed, and the coating power of the first coating stage is changed to 20 kW. Finally, a composite electromagnetic metamaterial film is obtained, whose electromagnetic transmittance increases approximately linearly from -40 dB to -6 dB along the length direction, and the thickness of the electromagnetic metamaterial layer thereon ranges from 0.4 μm to 0.6 μm.

[0112] Comparative Example 4

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

[0114] The only difference between this comparative example and comparative example 1 is that during the coating process, only the first coating stage is performed, and the coating power of the first coating stage is changed to 15 kW. Finally, a composite electromagnetic metamaterial film is obtained, whose electromagnetic transmittance increases approximately linearly from -35 dB to -6 dB along the length direction, and the thickness of the electromagnetic metamaterial layer thereon ranges from 0.3 μm to 0.4 μm.

[0115] Comparative Example 5

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

[0117] The only difference between this comparative example and Example 1 is that the polyimide film is not subjected to a substrate surface pretreatment step, but the nickel-chromium alloy is directly deposited on one side of the untreated polyimide film through a plating process.

[0118] Comparative Example 6

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

[0120] This comparative example uses a silk screen printing process instead of a coating process to produce an electromagnetic metamaterial film. Specifically:

[0121] a) Thawing of ink:

[0122] The ink should be placed in an environment of 25℃±3℃ and allowed to return to room temperature before use.

[0123] b) Ink stirring:

[0124] Remove the ink from the can and add the additive, stirring it thoroughly with an ink spatula.

[0125] c) Printing:

[0126] Pour an appropriate amount of ink on the screen; place the PI film used for adjusting the machine on the printing platform, fill the mesh holes with ink, adjust the scraping pressure, and start printing.

[0127] d) Baking:

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

[0129] e) Testing:

[0130] Due to the constraints of the screen printing process, the lower the required transmittance, the thicker the printed electromagnetic metamaterial layer will be; when the required transmittance is lower than -15dB, the electromagnetic metamaterial layer will be too thick, and the electromagnetic metamaterial layer will become brittle after baking, resulting in the mechanical properties of the electromagnetic metamaterial film being too low to meet the sample performance requirements.

[0131] Test Method

[0132] Electromagnetic wave transmittance: tested in accordance with GJB 7954B.

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

[0134] Failure mode: Tested in accordance with GB / T 5210. Before testing: Apply adhesive film evenly and evenly to both sides of the composite electromagnetic metamaterial film sample to be tested. Then, align and attach a loading head to the films on both sides. Trim off the excess along the edge of the loading head. After curing, perform mechanical testing in a dry state at room temperature, and visually observe the fracture mode.

[0135] The above test was performed on the composite electromagnetic metamaterial film samples prepared in each embodiment and comparative example, and the results are shown in Table 1. In addition, the electromagnetic wave transmittance-composite film length change curves of embodiment 1 and comparative example 6 obtained by the test are shown in Table 1. Figure 1 .

[0136] from Figure 1 As can be seen in the figure, the technical solution provided by the present invention changes the production process of the electromagnetic metamaterial layer from a silk screen printing process to a coating process, and the coating process is designed. The transmittance of the prepared electromagnetic metamaterial film can achieve a continuous, nearly linear gradient, and the performance curve can be further diversified. At the same time, the transmittance range that the electromagnetic metamaterial film can meet is expanded. In contrast, the transmittance of electromagnetic metamaterial films prepared using the silk screen process cannot achieve a continuous gradient, and the electromagnetic wave transmittance range is narrower, which limits their application.

[0137] Table 1

[0138]

[0139] From the above description, it can be seen that the above-mentioned 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 at the same time achieve the advantage of a linear increase in electromagnetic wave transmittance in the length direction, which can meet more design and use requirements.

[0140] It should be noted that the terms "first," "second," and the like 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 precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0141] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a composite electromagnetic metamaterial film, comprising the step of providing an electromagnetic metamaterial layer on one surface of a polymer film, characterized in that: Before providing the electromagnetic metamaterial layer, the preparation method includes: pre-processing one side surface of the polymer film with plasma to obtain a pre-processed surface; The step of providing the electromagnetic metamaterial layer comprises: depositing a metal absorbing material on the pretreated surface by a coating process to form the electromagnetic metamaterial layer, thereby obtaining the 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.

2. The method for preparing a composite electromagnetic metamaterial film according to claim 1, wherein: The metal absorbing material is nickel-chromium alloy and / or nickel-copper alloy; Preferably, when the metal absorbing material is a nickel-chromium alloy, the electromagnetic wave transmittance gradually increases from -30 dB to -20 dB to -2 dB to -0.1 dB 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 gradually increases from -40 dB to -30 dB to -2 dB to -0.5 dB along the length direction of the composite electromagnetic metamaterial film.

3. The method for preparing a composite electromagnetic metamaterial film according to claim 1 or 2, characterized in that: The coating process includes the following steps: 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, and: The V1 is 0.1m / min to 0.5m / min; the V2 is 1.0m / min to 3.0m / min; the V3 is 1.5m / min to 4.0m / min; and the V4 is 2.0m / min to 5.0m / min.

4. The method for preparing a composite electromagnetic metamaterial film according to claim 3, wherein: The first coating stage includes the following stages that are performed successively: a first uniform speed stage and a first uniform acceleration stage, both of which have 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 that are performed successively: a second uniform speed stage and a second uniform acceleration stage, both of which have 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 that are performed successively: a third uniform speed stage and a third uniform acceleration stage, both of which have 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 in the first coating stage, the final velocity of the first uniform acceleration stage is V2, the second coating stage is carried out; when in the second coating stage, the final velocity of the second uniform acceleration stage is V3, the third coating stage is carried out; when in the third coating stage, the final velocity of the third uniform acceleration stage is V4, the fourth coating stage is carried out.

5. The method for preparing a composite electromagnetic metamaterial film according to claim 4, wherein: The accelerations of the first uniform acceleration stage, the second uniform acceleration stage, and the third uniform acceleration stage are independently 0.2 m / min to 0.5 m / min.

6. The method for preparing the composite electromagnetic metamaterial film according to claim 4 or 5, characterized in that: 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.

7. The method for preparing a composite electromagnetic metamaterial film according to any one of claims 1 to 6, characterized in that: The processing power of the plasma pretreatment is 30W to 100W, and the processing speed is 0.1m / min to 5m / min; Preferably, the plasma pretreatment is performed in an inert atmosphere.

8. The method for preparing a composite electromagnetic metamaterial film according to any one of claims 1 to 7, characterized in that: The polymer film is selected from one or more of polyaniline film, polypyrrole film, polythiophene film and polyimide film, and is preferably a polyimide film.

9. A composite electromagnetic metamaterial film, characterized in that: The composite electromagnetic metamaterial film is prepared by the method for preparing a composite electromagnetic metamaterial film according to any one of claims 1 to 8, and the composite electromagnetic metamaterial film comprises the polymer film and the electromagnetic metamaterial layer provided on one surface of the polymer film; Preferably, 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.

10. Use of the composite electromagnetic metamaterial film according to claim 9 as a wave-absorbing electromagnetic film in the aviation field.

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