Stretchable carbon nanotube electromagnetic shielding material with medium-high frequency and preparation method and application thereof

Abstract

The application discloses a kind of medium-high frequency stretchable carbon nanotube electromagnetic shielding materials and its preparation method and application.The preparation method includes: high-conductivity metal, antioxidant metal is combined with carbon nanotube film in sequence, to form high-conductivity metal layer, antioxidant metal layer on the surface of the carbon nanotube film, obtain nanometer metal carbon nanotube composite film;Stretching force is applied to elastic substrate, and its surface is combined with the nanometer metal carbon nanotube composite film, then water-based resin is applied to the other side surface of the elastic substrate, then the stretching force applied to the elastic substrate is released, and the elastic substrate drives nanometer metal carbon nanotube composite film to retract, to obtain medium-high frequency stretchable carbon nanotube electromagnetic shielding material with wrinkle structure.The application combines carbon nanotube film with metal-based shielding layer, adjusts shielding efficiency by flexibly changing the thickness of nanometer metal layer and wrinkle structure design, and can realize 8-40GHz medium-high frequency electromagnetic shielding effect.

Description

Technical Field

[0001] The present invention relates to a method for preparing an electromagnetic shielding material, and in particular to a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material and a preparation method and application thereof, belonging to the technical field of composite materials. Background Art

[0002] With the development of science and technology, electromagnetic waves have been widely used in communications, aerospace, military and other fields. Around the world, various network information transmits countless military, political, economic and other information and intelligence. However, the electromagnetic interference (EMI) problem caused by it is also becoming increasingly serious, plaguing people's daily lives and threatening the country's military defense system, seriously restricting the international competitiveness of my country's electronic products and equipment, and also polluting the environment. Long-term exposure to high-frequency electromagnetic radiation can also cause damage to the human body, causing nervous disorders, behavioral disorders, etc., which endangers human health.

[0003] To date, carbon nanotubes (CNTs) are considered the strongest and hardest carbon structures ever invented. Extensive research efforts are devoted to effectively connecting carbon nanotubes using binders such as resins to create next-generation advanced composite materials. Metals and metal alloys are common EMI shielding materials due to their excellent electrical conductivity. However, metals suffer from poor ductility and flexibility, are heavy, susceptible to corrosion, and are difficult to process, further limiting their application in modern EMI shielding materials. Conductive nanoparticles are dispersed at an appropriate concentration within an insulating polymer matrix. The particles form a conductive network within the polymer, reflecting and absorbing incoming electromagnetic waves, creating a composite electromagnetic shielding material. However, achieving high electromagnetic shielding effectiveness requires a high loading of conductive nanoparticles. This high loading leads to particle aggregation, which degrades the mechanical properties of the shielding material. Consequently, conventional metal shielding materials cannot meet lightweight requirements. Therefore, the development of efficient electromagnetic shielding materials to prevent electromagnetic interference and electromagnetic compatibility issues caused by electromagnetic waves is crucial for improving the safety and reliability of electronic products and equipment, enhancing international competitiveness, and ensuring the security and smooth operation of information and communication systems, network systems, and transmission systems.

[0004] Further, the conventional metal shielding materials in the prior art also have the following disadvantages: 1) the metal materials with high electromagnetic shielding efficiency are limited in further application due to their high density and high cost; 2) the existing light shielding materials usually use conductive fillers in the materials to achieve the shielding effect, although such materials have small density and good ductility, the shielding efficiency is low and the shielding frequency band has limitations; 3) the conventional conductive layer is usually prepared by chemical deposition method for better interface bonding, which is not suitable for practical application and easy to cause environmental pollution; 4) the existing stretchable flexible shielding material has low stretching and rebound rate, limited preparation size, large test frequency band limitation, and uneven tension distribution. SUMMARY

[0005] The main purpose of the present application is to provide a middle-high frequency stretchable carbon nanotube electromagnetic shielding material and a preparation method thereof to overcome the deficiencies in the prior art.

[0006] Another purpose of the present application is to provide an application of the middle-high frequency stretchable carbon nanotube electromagnetic shielding material.

[0007] To achieve the above-mentioned purposes, the technical solutions adopted by the present application include:

[0008] The present application provides a preparation method of a middle-high frequency stretchable carbon nanotube electromagnetic shielding material, which includes:

[0009] The high-conductivity metal and the oxidation-resistant metal are sequentially combined with the carbon nanotube film, so that a high-conductivity metal layer and an oxidation-resistant metal layer are sequentially formed on the first surface and the second surface of the carbon nanotube film, and a nanometal carbon nanotube composite film is obtained, wherein the first surface and the second surface are oppositely arranged;

[0010] An elastic substrate is provided, a stretching force is applied to the elastic substrate, then the third surface of the stretched elastic substrate is combined with the nanometal carbon nanotube composite film, and a water-based resin is applied to the fourth surface of the elastic substrate, wherein the third surface and the fourth surface are oppositely arranged;

[0011] The stretching force applied to the elastic substrate is released, and the elastic substrate drives the nanometal carbon nanotube composite film to shrink, thereby obtaining a middle-high frequency stretchable carbon nanotube electromagnetic shielding material with a wrinkle structure.

[0012] In some embodiments, the preparation method specifically includes:

[0013] At least one of vacuum electron beam evaporation, electron beam evaporation, and magnetron sputtering is used to first evaporate a highly conductive metal on the first surface and the second surface of the carbon nanotube film to form a highly conductive metal layer, and then an anti-oxidation metal is evaporated on the highly conductive metal layer to form an anti-oxidation metal layer, thereby obtaining a dense and continuous nano-metal layer, thereby obtaining a nano-metal carbon nanotube composite film.

[0014] In some embodiments, the preparation method specifically comprises:

[0015] A plurality of elastic and retractable elastic threads are arranged in parallel as the elastic base.

[0016] A stretching force is applied to the elastic substrate, and the stretching rate is maintained at 100-600%. Then, an elastic adhesive is sprayed on the third surface of the stretched elastic substrate, and the nano-metal carbon nanotube composite film is pressed onto the elastic substrate sprayed with the elastic adhesive, so that the elastic filaments therein are tightly adhered to the nano-metal carbon nanotube composite film.

[0017] In some embodiments, the preparation method specifically comprises:

[0018] A solution containing an aqueous resin is evenly sprayed on the fourth surface of the elastic substrate, and then formed into a film, so that at least part of the aqueous resin enters between the elastic filaments and the carbon nanotube fibers and metal particles contained in the nano-metal carbon nanotube composite film, and covers the metal particles and carbon nanotube fibers.

[0019] An embodiment of the present invention also provides a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material prepared by the aforementioned method, wherein the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material includes an aqueous resin layer, an elastic substrate, an elastic adhesive layer, and a nano-metal carbon nanotube composite film stacked in sequence in the thickness direction, and the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material has a pleated structure.

[0020] Furthermore, in the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material, there are micro-wrinkles between the elastic substrate and the nano-metal carbon nanotube composite film, and there are wrinkles between the elastic filaments contained in the elastic substrate.

[0021] Furthermore, the medium and high frequency stretchable carbon nanotube electromagnetic shielding material has a shielding effectiveness that can simultaneously shield electromagnetic fields from low frequency to high frequency, preferably in the medium and high frequency bands of 8 to 40 GHz.

[0022] The embodiments of the present invention also provide applications of the aforementioned medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material in fields such as functional intelligent devices, electromagnetic shielding clothing, or aerospace.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The preparation method of the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material provided by the present invention has low metal content through vacuum electron beam evaporation, low density of the carbon nanotube composite film, good stretchability, and the metal is attached to the surface of the carbon nanotube film without changing the quality and flexibility. It has good shielding effectiveness and avoids oxidation of the metal layer, extending the service life. The preparation process is simple and pollution-free;

[0025] 2) The preparation method provided by the present invention can produce elastic fibers of larger sizes, which is easy to apply in actual production. The elastic fibers have the same tension and will not experience necking phenomenon like elastic films, which would cause uneven wrinkle distribution and other problems.

[0026] 3) The medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material prepared by the present invention combines a carbon nanotube film with a traditional metal-based shielding layer. The thickness of the nanometal layer can be flexibly changed according to the shielding effectiveness requirements. The shielding effectiveness can be adjusted through an ultra-thin laminate design, and can achieve electromagnetic shielding in the medium- and high-frequency bands of 8-40 GHz.

[0027] 4) Combining carbon nanotube composite film with elastic filaments to create a highly elastic structure allows for flexible adjustment of the elongation of the stretchable composite film based on actual needs. Shielding effectiveness can also be adjusted by designing the elongation and arrangement density of the elastic filaments. The flexible, stretchable electromagnetic shielding film can be expanded 2-3 times its radial area without applying excessive external force during application. Furthermore, the shielding effectiveness of the electromagnetic shielding material can be precisely controlled by controlling its draw-down ratio.

[0028] 5) The medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material of the present invention has potential application value in functional intelligent devices, electromagnetic shielding clothing, aerospace, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1a and Figure 1b This is an SEM image of a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material in a typical embodiment of the present invention;

[0031] Figure 2 This is a schematic structural diagram of a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material in a typical embodiment of the present invention;

[0032] Figure 3 Schematic diagram of shielding effectiveness results at 8-40 GHz of the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material at different stretching rates described in some typical embodiments of the present invention;

[0033] Figure 4 This is a schematic diagram of the shielding effectiveness results at 8-40 GHz of medium- and high-frequency stretchable carbon nanotube electromagnetic shielding materials made of nano-metal layers composited with carbon nanotube films of different thicknesses in some typical embodiments of the present invention. DETAILED DESCRIPTION

[0034] In light of the shortcomings of the existing technology, the inventors of this case, after extensive research and extensive practice, have come up with the technical solution of the present invention, which primarily provides a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material and a method for preparing the same. The following further explains this technical solution, its implementation process, and its principles.

[0035] Carbon nanotube films possess a unique structure and numerous excellent properties, including light weight, superior mechanical properties, structural flexibility, chemical stability, and high-temperature resistance. Of particular note, carbon nanotubes are the best electromagnetic shielding material compared to other materials. Currently, industry researchers are focusing extensive research efforts on effectively connecting carbon nanotubes using binders such as resins to create next-generation advanced composite materials. Metals and metal alloys, due to their excellent electrical conductivity, are attractive EMI shielding materials. By dispersing metal nanoparticles at an appropriate concentration on the surface of a material, the conductive particles further reflect and absorb electromagnetic waves, creating a composite electromagnetic shielding material.

[0036] The present invention utilizes a carbon nanotube film obtained by directly drawing a spinnable carbon nanotube array, combines the carbon nanotube film with nanometal, and then compounds it with highly elastic and retractable elastic wire to obtain a composite electromagnetic shielding material that can simultaneously shield wide-band interference from low frequency to high frequency.

[0037] One aspect of an embodiment of the present invention provides a method for preparing a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material, comprising:

[0038] Combining a highly conductive metal and an anti-oxidation metal with the carbon nanotube film in sequence, thereby forming a highly conductive metal layer and an anti-oxidation metal layer in sequence on a first surface and a second surface of the carbon nanotube film to obtain a nano-metal carbon nanotube composite film, wherein the first surface and the second surface are arranged in opposite directions;

[0039] Providing an elastic substrate, applying a stretching force to the elastic substrate, then bonding the nano-metal carbon nanotube composite film to a third surface of the stretched elastic substrate, and applying a water-based resin to a fourth surface of the elastic substrate, wherein the third surface and the fourth surface are disposed opposite to each other;

[0040] The stretching force applied to the elastic substrate is released, so that the elastic substrate drives the nano-metal carbon nanotube composite film to retract, thereby obtaining a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material with a pleated structure.

[0041] The first surface may be understood as the upper surface of the carbon nanotube film, and the second surface may be understood as the lower surface of the carbon nanotube film.

[0042] Likewise, the third surface may be understood as the upper surface of the elastic base, and the fourth surface may be understood as the lower surface of the elastic base.

[0043] In some embodiments, the carbon nanotube film is a carbon nanotube film obtained by directly drawing a spinnable carbon nanotube array.

[0044] Furthermore, the carbon nanotube film has a thickness of 50 to 3000 nm.

[0045] In some embodiments, the preparation method specifically comprises:

[0046] At least one of vacuum electron beam evaporation, electron beam evaporation, and magnetron sputtering is used to first evaporate a highly conductive metal on the first surface and the second surface of the carbon nanotube film to form a highly conductive metal layer, and then an anti-oxidation metal is evaporated on the highly conductive metal layer to form an anti-oxidation metal layer, thereby obtaining a dense and continuous nano-metal layer, thereby obtaining a nano-metal carbon nanotube composite film.

[0047] Furthermore, to improve the conductivity of the carbon nanotube film, multiple layers of highly conductive metal and oxidation-resistant metal are deposited on the surface of the carbon nanotube film using electron beam vacuum deposition. The vacuum deposition method can be electron beam evaporation or magnetron sputtering, where metal layers are deposited on both sides of the carbon nanotube film.

[0048] Furthermore, the present invention achieves better shielding effectiveness by combining a low-content, low-density, highly conductive metal layer (inner layer) and an anti-oxidation metal layer (outer layer) through vacuum electron beam evaporation, while avoiding oxidation of the metal layer and extending the service life.

[0049] Furthermore, the present invention combines carbon nanotube film with traditional metal-based shielding layer, and can flexibly change the thickness of the nanometal layer according to the shielding effectiveness requirements. The shielding effectiveness can be adjusted through ultra-thin laminated design, and electromagnetic shielding effect in the medium and high frequency bands of 8-40GHz can be achieved.

[0050] Furthermore, the thickness of the nanometal layer is 200 to 1100 nm, preferably 200 to 1000 nm.

[0051] Furthermore, the thickness of the highly conductive metal layer is 150 to 1000 nm, and the thickness of the anti-oxidation metal layer is 50 to 100 nm.

[0052] Furthermore, the material of the highly conductive metal may include any one or a combination of two or more of copper, gold, silver, etc., but is not limited thereto.

[0053] Furthermore, the material of the oxidation-resistant metal includes any one or a combination of two or more of nickel, titanium, stainless steel, etc., but is not limited thereto.

[0054] Furthermore, without considering the cost, the inner layer of each metal layer mentioned in the present invention can be preferably replaced by gold or silver, and the outer layer can be preferably made of metals with good oxidation resistance such as titanium or stainless steel.

[0055] Furthermore, the process conditions adopted by the vacuum electron beam evaporation method include: a vacuum value higher than 1×10 4 , the coating rate is 1~3nm / min.

[0056] Furthermore, the electrical conductivity of the nano-metal carbon nanotube composite film is higher than 2.5×10 6 s / m.

[0057] In some embodiments, the preparation method specifically comprises:

[0058] A plurality of elastic and retractable elastic threads are arranged in parallel as the elastic base.

[0059] A stretching force is applied to the elastic substrate, and the stretching rate is maintained at 100-600%. Then, an elastic adhesive is sprayed on the third surface of the stretched elastic substrate, and the nano-metal carbon nanotube composite film is pressed onto the elastic substrate sprayed with the elastic adhesive, so that the elastic filaments therein are tightly adhered to the nano-metal carbon nanotube composite film.

[0060] Furthermore, the size of the elastic thread is 20D to 140D.

[0061] Furthermore, the distance between two adjacent elastic threads is 0.5 to 2 mm.

[0062] Furthermore, the elastic yarn includes spandex yarn, but is not limited thereto.

[0063] Furthermore, the elastic adhesive includes polyurethane and modified polyurethane adhesives, but is not limited thereto.

[0064] Further, the preparation method can specifically include: selecting an elastic filament with a diameter of 20D-140D as an elastic base, passing the elastic filament through parallel fixed steel reeds (reed number 50-210), fixing two sections of the elastic filament, obtaining an elastic base with a certain interval and parallel arrangement, fixing the elastic filament after stretching to a certain length, and spraying an elastic adhesive on the surface of the elastic filament.

[0065] In some embodiments, the preparation method specifically includes:

[0066] uniformly spraying a solution containing an aqueous resin on the fourth surface of the elastic base, and then forming a film, so that at least part of the aqueous resin in the solution enters between the elastic filament and the carbon nanotube fibers and metal particles contained in the nanometal carbon nanotube composite film, and the metal particles are coated with the carbon nanotube fibers.

[0067] Further, the aqueous resin includes an aqueous polyurethane resin, but is not limited thereto.

[0068] Further, the concentration of the aqueous resin in the solution containing the aqueous resin is 40wt%-60wt%.

[0069] In some more specific embodiments, the specific preparation steps of the medium-high frequency stretchable carbon nanotube electromagnetic shielding material can be as follows:

[0070] (1) A vacuum electron beam evaporation machine is used to first deposit a metal with good conductivity on a flexible carbon nanotube film, and then deposit a metal with good oxidation resistance, to form a nanometal layer with a thickness of 200-1100nm, and the evaporation process is as follows: the vacuum value is higher than 1x10 4 , and the film deposition rate is 1-3nm / min;

[0071] (2) Select an elastic filament with a diameter of 20D-140D as an elastic base, pass the elastic filament through parallel fixed steel reeds (reed number 50-210), fix two sections of the elastic filament, obtain an elastic base with a certain interval and parallel arrangement, fix the elastic filament after stretching to a certain length, and spray an elastic adhesive on the surface of the elastic filament;

[0072] (3) Pressing the nano-metal carbon nanotube composite film with the nano-metal layer deposited thereon onto the upper side of the elastic wire coated with the adhesive, spraying the aqueous resin solution onto the lower side of the elastic wire, and waiting for the film to form to prevent the metal layer from oxidizing, then releasing the tension applied to the elastic wire to cause the nano-metal carbon nanotube composite film to retract, thereby obtaining the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material (hereinafter also referred to as "stretchable nano-metal electromagnetic shielding composite film"), the elongation of which can be controlled to be below 300%. When the nano-metal layer is generally deposited on a carbon nanotube film, the carbon nanotube film and the nano-metal layer are planar structures. Under the action of external forces, the metal layer is very easy to break and peel off. In the present invention, after the nano-metal layer is formed on the planar structure of the carbon nanotube film, it is compounded with the aqueous polyurethane resin. It can be seen from the surface of the composite film that part of the resin enters between the carbon nanotube fibers and the metal particles, coating the metal particles and the carbon nanotube fibers, thereby preventing the metal from peeling off from the carbon nanotube film.

[0073] In summary, the preparation method of medium and high frequency stretchable carbon nanotube electromagnetic shielding material provided by the present invention has low metal content through vacuum electron beam evaporation, low density of carbon nanotube composite film, good stretchability, and metal attached to the surface of carbon nanotube film without changing the quality and flexibility. It has good shielding performance and avoids oxidation of the metal layer, extending the service life. The preparation process is simple and pollution-free.

[0074] The preparation method provided by the present invention can prepare elastic fibers of larger size and is easy to apply in actual production. The elastic fibers have the same tension and will not experience necking phenomenon like elastic films, which causes problems such as uneven wrinkle distribution.

[0075] Another aspect of the embodiments of the present invention further provides a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material prepared by the aforementioned method.

[0076] See also Figure 2 As shown, another aspect of an embodiment of the present invention further provides a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material, which includes an aqueous resin layer, an elastic substrate, an elastic adhesive layer and a nano-metal carbon nanotube composite film stacked in sequence in the thickness direction, and the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material has a pleated structure.

[0077] Furthermore, the thickness of the nano-metal-carbon nanotube composite film is 200-1100 nm, preferably 200-1000 nm.

[0078] Furthermore, at least part of the aqueous resin in the aqueous resin layer is also distributed between the elastic filaments and the carbon nanotube fibers and metal particles contained in the nano-metal carbon nanotube composite film, and covers the metal particles and carbon nanotube fibers.

[0079] Further, the stretchable carbon nanotube electromagnetic shielding material has micro-creases between the elastic base and the nanometal carbon nanotube composite film, and the elastic filaments contained in the elastic base have creases between the elastic filaments.

[0080] In the stretchable carbon nanotube electromagnetic shielding material, the higher the degree of creases, the greater the reflection loss of the electromagnetic wave material interface, and the higher the shielding effectiveness. The creases include: 1) micro-creases between the elastic filament retraction and the carbon nanotube film, which can be controlled by the draft of the elastic filament; and 2) creases between the elastic filaments, which control the crease density of the carbon nanotube by changing the elastic filament spacing (selecting steel reeds of different counts). In application, the degree of creases is increased according to the demand for the size of the shielding effectiveness. The higher the degree of creases, the higher the content of metal and carbon nanotubes per unit area.

[0081] Further, the density of the stretchable carbon nanotube electromagnetic shielding material is less than 1 g / cm 3 .

[0082] Further, the stretchable carbon nanotube electromagnetic shielding material has a shielding effectiveness that can simultaneously shield electromagnetic waves from low frequency to high frequency, preferably in the medium and high frequency band of 8-40 GHz. The present application combines the nanometal carbon nanotube composite film with the elastic filament, adds a high-elasticity structure design, and can flexibly change the elongation of the stretchable composite film according to actual needs. The shielding effectiveness can also be adjusted by designing the elongation and arrangement density of the elastic filament.

[0083] Further, the radial area of the stretchable carbon nanotube electromagnetic shielding material can be increased by 2-3 times after being stretched. That is, the flexible stretchable carbon nanotube electromagnetic shielding material of the present application can be stretched by 2-3 times in the radial direction without applying excessive external force, which is not achievable by ordinary elastic fabrics.

[0084] Another aspect of the embodiment of the present application also provides the aforementioned stretchable carbon nanotube electromagnetic shielding material for use in the fields of functional smart devices, electromagnetic shielding clothing, aerospace, etc.

[0085] In summary, the present application combines the carbon nanotube film with the metal-based shielding layer, adjusts the shielding effectiveness by flexibly changing the thickness of the nanometal layer and the ultra-thin layer design, and realizes electromagnetic shielding in the medium and high frequency band of 8-40 GHz. The preparation process is simple, and the prepared stretchable carbon nanotube electromagnetic shielding material has potential application value in the fields of functional smart devices, electromagnetic shielding clothing, aerospace, etc.

[0086] The present application will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings. Detailed embodiments of the application are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the application, which can be embodied in various forms. Therefore, specific functional details disclosed herein are not to be interpreted as limiting, but only as a representative basis for teaching one skilled in the art to employ the present application in virtually any appropriate detailed embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The data of high frequency band in the following examples are obtained by waveguide method to test the shielding effectiveness of the material from 8-40GHz.

[0088] As shown in Example 1, a preparation method of a stretchable carbon nanotube electromagnetic shielding material in a medium-high frequency band includes the following specific technical steps: Figure 2

[0089] In this embodiment, in order to improve the conductivity of the carbon nanotube film, a multi-layer metal layer is evaporated on the surface of the carbon nanotube film by using an electron beam vacuum coating method, and the evaporation process is as follows: the vacuum value is 1x10 4 , and the rate is 1-3 nm / min. The above-mentioned vacuum coating method can be electron beam evaporation or magnetron sputtering method, and the double-sided metal layer covering the carbon nanotube film, and the thickness of the nanometer metal layer is 200-1000 nm. As shown in Table 1, the shielding effectiveness of different metal coating thicknesses is controlled to be less than 1 g / cm Figure 4 , and the density of the stretchable nanometer metal electromagnetic shielding composite film is less than 1 g / cm 3 , and the nanometer metal layer is a composite metal film with high-conductivity copper in the inner layer and oxidation-resistant nickel or stainless steel in the outer layer.

[0090] In another preferred embodiment, a copper layer with a thickness of 500 nm is first evaporated on the surface of the carbon nanotube film by using a vacuum electron beam, and then a 50 nm nickel layer is evaporated. Similarly, a copper layer with a thickness of 500 nm is evaporated on the lower surface of the carbon nanotube film, and then a 50 nm nickel layer is evaporated, so as to obtain a nanometer metal carbon nanotube composite film with a conductivity of 2.5x10 6 s / m. Further, as shown in FIGS. 2 and 3, which are SEM images of the surface of the nanometer metal carbon nanotube composite film prepared in the above-mentioned embodiment, it is proved that a dense and continuous nanometer metal layer is formed on the surface of the carbon nanotube film. In addition, it can be seen from the SEM images of the surface of the composite film that part of the resin enters the fiber and the metal particles, so as to coat the metal particles and the carbon nanotube fiber, and avoid the peeling of the metal and the carbon nanotube film. Figure 1a Figure 1b In another preferred embodiment, a copper layer with a thickness of 500 nm is first evaporated on the surface of the carbon nanotube film by using a vacuum electron beam, and then a 50 nm nickel layer is evaporated. Similarly, a copper layer with a thickness of 500 nm is evaporated on the lower surface of the carbon nanotube film, and then a 50 nm nickel layer is evaporated, so as to obtain a nanometer metal carbon nanotube composite film with a conductivity of 2.5x10 6 s / m. Further, as shown in FIGS. 2 and 3, which are SEM images of the surface of the nanometer metal carbon nanotube composite film prepared in the above-mentioned embodiment, it is proved that a dense and continuous nanometer metal layer is formed on the surface of the carbon nanotube film. In addition, it can be seen from the SEM images of the surface of the composite film that part of the resin enters the fiber and the metal particles, so as to coat the metal particles and the carbon nanotube fiber, and avoid the peeling of the metal and the carbon nanotube film.

[0091] In this embodiment, the material of the highly conductive metal may be gold, silver, etc. in addition to copper. The material of the anti-oxidation metal may be titanium, stainless steel, etc. in addition to nickel.

[0092] In this embodiment, a group of 140D spandex yarns are passed through two parallel fixed 100 # A steel reed (a textile machine accessory) is used, the length of the steel reed is greater than the width of the carbon film, and the distance between the two steel reeds is greater than the length of the nano-metal carbon nanotube composite film, to obtain a parallel-arranged spandex yarn substrate (with a spacing of 1 mm). The spandex yarn substrate is stretched 100-600% and then fixed again.

[0093] Spray polyurethane adhesive on the above-mentioned spandex yarn base, cover the nano-metal carbon nanotube composite film on the top of the spandex yarn base, and evenly spray an aqueous polyurethane resin solution under the spandex yarn base. After it forms a film, the medium and high frequency stretchable carbon nanotube electromagnetic shielding material, that is, the stretchable nano-metal electromagnetic shielding composite film, is obtained.

[0094] Further integration Figure 1a and Figure 1b The figure shows an electron microscope image of the upper surface of the stretchable nano-metal electromagnetic shielding composite film prepared above, which proves that the spandex yarn and the nano-metal carbon nanotube composite film are tightly attached and a wrinkle structure is formed at the microscopic level. By stretching the above-mentioned stretchable nano-metal electromagnetic shielding composite film to different lengths (i.e. different stretching ratios), different shielding effectiveness can be obtained. When used, the degree of wrinkling is increased according to the demand for the shielding effectiveness. The higher the degree of wrinkling, the higher the content of metal and carbon nanotubes per unit area. Figure 3 As shown in the figure, after the electromagnetic shielding film is unfolded (0%), the shielding effectiveness can reach 70dB. As the external force decreases, that is, the degree of wrinkling increases (50%), the shielding effectiveness increases to 85dB. The shielding effectiveness of the electromagnetic shielding film can be precisely controlled by the stretching rate, as shown in the figure. Figure 3 The figure shows the shielding effectiveness of different draw-down ratios in X-band, KU-band, K-band and Ka-band. When applied, the draw-down ratio and the thickness of the nano-metal layer ( Figure 4 ) can achieve different shielding effects.

[0095] The medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material of the above-mentioned embodiment has potential application value in functional intelligent devices, electromagnetic shielding clothing, aerospace, etc.

[0096] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and are not intended to limit the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0097] The use of headings and sections in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.

[0098] Throughout this disclosure, where compositions are described as having, comprising, or including particular components, or where processes are described as having, comprising, or including particular process steps, it is contemplated that the compositions taught by the present invention also consist essentially of, or consist of, the recited components, and that the processes taught by the present invention also consist essentially of, or consist of, the recited process steps.

[0099] Unless specifically stated otherwise, use of the terms "include," "includes," "including," "have," "has," or "having" should generally be construed as open ended and non-limiting.

[0100] Should be understood that, the order of each step or the order in which specific action is performed is not very important, as long as the present invention teachings remain operable.In addition, two or more steps or actions can be performed simultaneously.

[0101] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0102] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantial equivalents may be substituted for the elements of the embodiments without departing from the spirit and scope of the present invention. Additionally, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the scope of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for carrying out the present invention, but rather to include all embodiments within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for preparing a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material, characterized in that include: A highly conductive metal and an anti-oxidation metal are sequentially combined with a carbon nanotube film, thereby sequentially forming a highly conductive metal layer and an anti-oxidation metal layer on the first surface and the second surface of the carbon nanotube film to obtain a nano-metal carbon nanotube composite film, wherein the first surface and the second surface are arranged opposite to each other, the highly conductive metal is selected from any one or a combination of two or more of copper, gold, and silver, and the anti-oxidation metal is selected from any one or a combination of two or more of nickel, titanium, and stainless steel, and the electrical conductivity of the nano-metal carbon nanotube composite film is higher than 2.5×10 6 s / m; A plurality of elastic and retractable elastic threads are arranged in parallel as the elastic base. Applying a stretching force to the elastic substrate while maintaining a stretching ratio of 100-600%, spraying an elastic adhesive on the third surface of the stretched elastic substrate, and then pressing the nano-metal carbon nanotube composite film onto the elastic substrate sprayed with the elastic adhesive, so that the elastic filaments therein are tightly adhered to the nano-metal carbon nanotube composite film; A solution containing an aqueous resin is uniformly sprayed on the fourth surface of the elastic substrate to form a film, so that at least a portion of the aqueous resin enters between the elastic filaments and the carbon nanotube fibers and metal particles contained in the nano-metal carbon nanotube composite film, thereby coating the metal particles and carbon nanotube fibers; the third surface and the fourth surface are arranged to face each other; Releasing the stretching force applied to the elastic substrate, so that the elastic substrate drives the nano-metal carbon nanotube composite film to retract, thereby obtaining a medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material with a pleated structure; The medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material includes an aqueous resin layer, an elastic substrate, an elastic adhesive layer, and a nano-metal carbon nanotube composite film stacked in sequence in the thickness direction, and the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material has a wrinkled structure; in the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material, micro-wrinkles are present between the elastic substrate and the nano-metal carbon nanotube composite film, and wrinkles are present between the elastic filaments contained in the elastic substrate; at least part of the aqueous resin in the aqueous resin layer is also distributed between the elastic filaments and the carbon nanotube fibers and metal particles contained in the nano-metal carbon nanotube composite film, and covers the metal particles and the carbon nanotube fibers; The medium and high frequency stretchable carbon nanotube electromagnetic shielding material has a shielding effectiveness that can simultaneously shield electromagnetic shielding effects in the medium and high frequency bands of 8 to 40 GHz; After the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material is unfolded, its radial area can be increased by 2 to 3 times.

2. The preparation method according to claim 1, wherein: The carbon nanotube film is a carbon nanotube film obtained by directly drawing a film using a spinnable carbon nanotube array method.

3. The preparation method according to claim 1, wherein: The thickness of the carbon nanotube film is 50-3000 nm.

4. The preparation method according to claim 1 or 2, characterized in that Specifically include: At least one of vacuum electron beam evaporation, electron beam evaporation, and magnetron sputtering is used to first evaporate a highly conductive metal on the first surface and the second surface of the carbon nanotube film to form a highly conductive metal layer, and then an anti-oxidation metal is evaporated on the highly conductive metal layer to form an anti-oxidation metal layer, thereby obtaining a dense and continuous nano-metal layer, thereby obtaining a nano-metal carbon nanotube composite film.

5. The preparation method according to claim 4, characterized in that: The thickness of the nanometal layer is 200-1100 nm.

6. The preparation method according to claim 5, characterized in that: The thickness of the nanometal layer is 200-1000 nm.

7. The preparation method according to claim 4, characterized in that: The thickness of the highly conductive metal layer is 150-1000 nm.

8. The preparation method according to claim 4, characterized in that: The thickness of the anti-oxidation metal layer is 50-100 nm.

9. The preparation method according to claim 4, characterized in that The process conditions adopted by the vacuum electron beam evaporation method include: a vacuum value higher than 1×10 -4 , the coating rate is 1~3nm / min.

10. The preparation method according to claim 1, characterized in that: The size of the elastic thread is 20D~140D.

11. The preparation method according to claim 1, characterized in that: The distance between two adjacent elastic threads is 0.5-2 mm.

12. The preparation method according to claim 1, characterized in that: The elastic yarn is spandex yarn.

13. The preparation method according to claim 1, wherein: The elastic adhesive is selected from polyurethane and / or modified polyurethane adhesives.

14. The preparation method according to claim 1, characterized in that: The water-based resin is a water-based polyurethane resin.

15. The preparation method according to claim 1, characterized in that: The concentration of the aqueous resin in the solution containing the aqueous resin is 40 wt % to 60 wt %.

16. The preparation method according to claim 1, characterized in that: The density of the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material is less than 1g / cm 3 .

17. Application of the medium- and high-frequency stretchable carbon nanotube electromagnetic shielding material prepared by the preparation method according to any one of claims 1 to 16 in functional intelligent devices, electromagnetic shielding clothing, or aerospace fields.

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