CN114161795B

CN114161795B - Silver nanotube network film based on electromagnetic interference shielding and preparation method thereof

Info

Publication number: CN114161795B
Application number: CN202111318363.6A
Authority: CN
Inventors: 江诚鸣; 夏嘉临; 孙楠; 徐睿文; 陶志远; 彭艳; 曾丽君; 谭东宸
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2021-11-09
Filing date: 2021-11-09
Publication date: 2022-09-27
Anticipated expiration: 2041-11-09
Also published as: CN114161795A

Abstract

The invention belongs to the technical field of electromagnetic shielding materials, and particularly relates to a silver nanotube network film based on electromagnetic interference shielding and a preparation method thereof. Based on a uniform and large-scale nanofiber framework, the high-performance silver nanotube network film with stability and integrated interconnection is prepared by adopting a physical deposition technology. The simple integrated preparation process can bring high comprehensive performance to a large-scale AgNTs network. These results indicate that flexible transparent EMI shielding films based on AgNTs networks have great potential in aerospace and industrial optical systems and hold great market prospects.

Description

Silver nanotube network film based on electromagnetic interference shielding and preparation method thereof

Technical Field

The invention belongs to the technical field of electromagnetic shielding materials, and particularly relates to a silver nanotube network film based on electromagnetic interference shielding and a preparation method thereof.

Background

With the advancement of society, there is an urgent need to develop flexible transparent electromagnetic interference (EMI) shielding materials having an excellent combination of properties as visual windows and display devices for aviation, industry, medical and research institutions. This is decisive for the design and manufacture of the flexible transparent electromagnetic interference shielding material. The improvement of the performance of flexible transparent electromagnetic interference shielding materials is particularly important as an integral part of visual windows and display devices. Indium Tin Oxide (ITO) thin films are widely used as commercial EMI shielding materials because of their acceptable EMI SE and transmittance. However, with the increasing demand for screen size in recent years, ITO has the disadvantages of brittle quality, large processing difficulty, and poor flexibility. Therefore, the development of batch preparation of other materials capable of replacing ITO (indium tin oxide), and the flexible transparent electromagnetic interference shielding material with low cost becomes a focus of attention in recent years.

To address these issues, recent developments have proposed many transparent materials with EMI shielding properties, such as graphene, Reduced Graphene Oxide (RGO), Carbon Nanotubes (CNT), conductive polymers and MXene, as well as metal-based materials. However, their use is limited by unsatisfactory EMI SE or low light transmittance throughout the preparation process. There are few reports on their mechanical properties, while they have no light transmission and limited mechanical properties. The use of silver nanowires (AgNWs) breaks this impasse because they have inherently superior electrical properties, facilitating light transmittance of the physical structure and good mechanical properties. However, the contact resistance between AgNWs has a severe impact on the EMI SE and mechanical performance of the entire network. AgNWs requires two strengthening by perfect welding techniques or strong surface coatings, which is certainly a complex problem and difficult to mass produce. Therefore, the development of a large-area flexible transparent electromagnetic interference shielding material with simple preparation process and excellent performance has very important significance.

Disclosure of Invention

In order to solve the problems, the invention provides a silver nanotube network film based on electromagnetic interference shielding and a preparation method thereof.

The technical scheme of the invention is as follows:

a silver nanotube network film based on electromagnetic interference shielding comprises an AgNTs (silver nanotube) network inner layer 1, a PET (polyethylene terephthalate) substrate outer layer 2 and a PDMS (polydimethylsiloxane) protective layer 3, wherein the AgNTs network inner layer 1 is positioned between the PET substrate outer layer 2 and the PDMS protective layer 3.

The AgNTs network inner layer 1 is formed by a plurality of AgNTs network pipes 6 which are arranged in a line and are lapped into a whole, and the interconnected AgNTs network pipes 6 form a compact and uniform network; the AgNTs network tube 6 consists of an outer Ag layer 4 and a PVA (polyvinyl alcohol) core 5.

The aperture set of the AgNTs network pipe 6 is 5-30 μm, and the aperture depends on the working time of electrostatic spinning.

The thickness of the silver nanotube network film based on electromagnetic interference shielding is 0.5mm-0.8mm, wherein the thickness of the inner layer 1 of the AgNTs network is 0.3mm-0.4mm, the thickness of the outer layer 2 of the PET substrate is 0.1mm-0.2mm, and the thickness of the PDMS protective layer 3 is 0.1mm-0.2 mm.

The outer Ag layer 4 of the AgNTs network tube 6, silver (Ag) is selected as the outer material because the inert metal group, graphene, Reduced Graphene Oxide (RGO) are all weaker than silver (Ag) in conductivity and bending resistance, and are also higher than silver (Ag) in price, manufacturing difficulty, cost, and the like; moreover, the chemical stability of some active metals, transition metals, Carbon Nano Tubes (CNT), conductive polymers, MXene and metal-based materials is higher than that of silver (Ag), and the materials are more easily oxidized in the subsequent process of manufacturing the nano tube materials to cause the deterioration of the materials and influence the experimental effect; meanwhile, the texture of the nanotube made of the material is not as good as that of a silver (Ag) nanotube, so Ag is selected as the outer metal because of the best conductivity and texture. Meanwhile, when materials such as graphene, Reduced Graphene Oxide (RGO), Carbon Nano Tubes (CNT), conductive polymers and the like are used as AgNTs cores, the graphene and the Reduced Graphene Oxide (RGO) have high brittleness and are easy to break under the condition of high bending degree; the mechanical stability of materials such as Carbon Nanotubes (CNTs) and conductive polymers at high temperatures and during the fabrication of the electrolyte solution can be greatly reduced, thereby affecting the quality of the final product.

The PVA core 5 of the AgNTs network pipe 6 is an important premise for AgNTs interconnection by the integrated lapping of the PVA framework, and is also a foundation for forming a large-scale AgNTs network. Due to the micron-sized pores of the AgNTs network, the size of the AgNTs network is far smaller than one fourth of the wavelength of the high-frequency electromagnetic wave; electromagnetic waves can be reflected back and forth between the pores, and then are gradually attenuated by electric absorption due to the action of the AgNTs pores, and trap metal interconnection formed by the integrated AgNTs network can directly and obviously enhance corresponding electromagnetic wave absorption. In the manufacturing process, the PVA material has unique strong adhesiveness and involucra flexibility, and is superior to other materials in smoothness, oil resistance, solvent resistance, protective colloid property, gas barrier property, wear resistance and water resistance after special treatment. The aqueous solution of the PVA material has good adhesion and film-forming property, and can resist most organic solvents such as oils, lubricants, hydrocarbons and the like; has chemical properties of long-chain polyol esterification, etherification, acetalization and the like. The PVA material is therefore chosen as the core because of its good flexibility and resistance to oil and wear compared to other materials.

A preparation method of a silver nanotube network film based on electromagnetic interference shielding comprises the steps of forming interconnection of AgNTs networks by integrated overlapping of PVA frameworks on a PVA core 5, plating an external Ag layer 4 on the surface of the PVA core 5, and obtaining a high-performance AgNTs network inner layer 1 with stable and integrated interconnection; then, synthesizing a PET substrate outer layer 2 and a PDMS protective layer 3 by using polyethylene glycol terephthalate and a polydimethylsiloxane material through electrostatic spinning; finally, the nanofibers are mutually connected through the action of vacuum heating and sputtering deposition, the obtained AgNTs network inner layer 1 is adsorbed on the PET substrate outer layer 2, and the surface of the AgNTs network inner layer 1 is covered by the PDMS protective layer 3, so that a large-area transparent flexible electromagnetic interference shielding film is obtained; the whole preparation process is in a vacuum environment. The method comprises the following specific steps:

dissolving PVA particles in deionized water to prepare 10-15 mass percent PVA solution, stirring and heating at 65-75 ℃ and 1300-1500rpm for 12-24 hours to obtain PVA spinning solution, cooling the PVA spinning solution to room temperature and injecting the PVA spinning solution into electrostatic spinning equipment.

Step (2) connecting a spinning nozzle of the electrostatic spinning equipment with the positive electrode of a high-voltage power supply, and maintaining the working voltage at 12-18 kV; during electrostatic spinning, the working distance between the spinning nozzle and the receiving ring is kept between 12 and 18 centimeters; PVA cores 5 arranged in a line are prepared to obtain the PVA nanofiber membrane.

And (3) placing the PVA nanofiber membrane in an oven with the dryness of 80-90% and heating for 550-650s at 65-75 ℃ to dissolve the combined part of the PVA nanofiber, and then heating for 550-650s at 65-75 ℃ in a vacuum and non-humid environment to remove moisture so as to connect the nanofibers.

Preparing an external Ag layer 4 on the surface of the PVA nanofiber membrane by a sputtering deposition technology to form an AgNTs network inner layer 1 which is formed by a plurality of AgNTs6 which are arranged in a line and are lapped into a whole; the working power of the sputtering deposition is 90-110W, and the time is 550-650 s.

In the step (5), the outer layer 2 of the PET substrate adopts a PET film, and the PDMS protective layer 3 adopts a PDMS film; adsorbing the AgNTs network inner layer 1 obtained in the step (4) on a PET film, and covering the surface of the AgNTs network inner layer 1 with a PDMS film; and then drying the film for 8 to 12 hours in a vacuum oven at the temperature of between 65 and 75 ℃ to obtain the silver nanotube network film based on the electromagnetic interference shielding.

The AgNTs film with the overlapped PVA nanofibers and the high-uniformity (< 10% diameter deviation) integrated fibers is prepared by an electrostatic spinning technology and a physical deposition technology, is a flexible transparent silver nanotube network film based on an AgNTs network, has excellent comprehensive performance and based on electromagnetic interference shielding, and can realize the sheet resistance of 1.0 omega/sq and the light transmittance of 90%; its EMI SE can reach 35dB, has excellent mechanical stability, and change after 5000 bending and twisting cycles is negligible. The simple integrated preparation process can bring high comprehensive performance to a large-scale AgNTs network.

The invention has the beneficial effects that:

1. according to the invention, a large-area high-quality conductive network is formed by the AgNTs which are connected with each other, and the micron-sized pores of the AgNTs network block electromagnetic waves and allow visible light waves to pass through. Currently, there are graphene, Reduced Graphene Oxide (RGO), Carbon Nanotubes (CNTs), and the like. Graphene and Reduced Graphene Oxide (RGO) are brittle and easily broken when bent to a large degree; the mechanical stability of materials such as Carbon Nanotubes (CNTs) and conductive polymers at high temperatures and during the fabrication of the electrolyte solution can be greatly reduced, thereby affecting the quality of the final product. The outer layer of the PET substrate and the PDMS protective layer have better performances than those of a conductive polymer, MXene and a metal-based material in the aspects of flexibility and chemical and mechanical stability under a high-temperature electrolyte environment. Not only plays a role of protection, but also plays a role of a buffer layer so as to ensure that the AgNTs network is damaged minimally in the mechanical deformation process.

2. The diameter (<200nm) of AgNTs in the invention is far smaller than the wavelength of visible light (400- & gt 800nm), and the AgNTs is allowed to pass through, so that the intensity and the reflective interference of light are reduced to the maximum extent, and serious visual impairment is avoided. Moreover, this unique structure enables AgNTs networks to achieve conductivities (1.0 Ω/sq, > 90% transmittance) that are an order of magnitude higher than the transmittances of previous materials such as graphene, Reduced Graphene Oxide (RGO), Carbon Nanotubes (CNT), conductive polymers and MXene, and metal-based materials (0.2-0.4 Ω/sq, > 20-30% transmittance) and maintain < 10% change when randomly deformed (>5000 times).

3. The invention can directly and obviously enhance the absorption of corresponding electromagnetic waves. Micron-sized pores of the AgNTs network, the size of which is far less than one fourth of the wavelength of the high-frequency electromagnetic wave; due to the action of the AgNTs pores, electromagnetic waves can reflect back and forth between the pores and then be gradually attenuated by electro-absorption. Furthermore, the good metal interconnections formed by the integrated AgNTs network can also directly and significantly enhance the corresponding absorption of electromagnetic waves.

4. The invention enables the overlong AgNTs to be interconnected to form an integral network, reduces the barrier of contact resistance, greatly reduces the possibility of fracture during mechanical deformation, and enables the durability of the AgNTs network to be greatly superior to that of an AgNWs network.

5. The invention has large scale, low cost and simple preparation process. The network has significant advantages in terms of integrity, procedurality, uniformity and stability. These excellent properties give AgNTs shielding films great potential for future flexible transparent scenarios.

Drawings

FIG. 1 is a schematic view of the overall structure of the film of the present invention.

Fig. 2(a) and 2(b) are schematic cross-sectional structures of the layered and AgNTs network tube of the present invention.

In the figure: the device comprises an AgNTs network inner layer 1, a PET substrate outer layer 2, a PDMS protective layer 3, an external Ag layer 4, a PVA core 5 and an AgNTs network pipe 6.

Fig. 3, fig. 4 and fig. 5 are implementation process diagrams of three embodiments.

Fig. 6, 7 and 8 are electron micrographs of AgNTs network tubes prepared by three examples.

Fig. 9 is an enlarged view of fig. 7.

Detailed Description

The following further describes a specific embodiment of the present invention with reference to the drawings and technical solutions.

The electromagnetic interference shielding-based large-area flexible transparent silver nanotube network film comprises an AgNTs network inner layer 1, a PET substrate outer layer 2 and a PDMS protective layer 3, wherein the AgNTs network inner layer 1 is composed of a plurality of AgNTs network tubes 6, and each AgNTs network tube 6 is composed of an external Ag layer 4 and a PVA core 5, as shown in figure 1, figure 2(a) and figure 2 (b).

The invention relates to a preparation method of a large-area flexible transparent silver nanotube network film based on electromagnetic interference shielding, which comprises the steps of dissolving PVA particles with certain mass in deionized water with certain volume to form a PVA solution with the mass fraction of 10-15%, stirring and heating for 12-24 hours at the temperature range of 65-75 ℃ and the rotating speed of 1300-1500rpm, keeping the working voltage at 12-18kV, spinning to obtain a PVA nanofiber film, and then placing the PVA film in an oven with the dryness of 80-90% and heating for 550-75 ℃ for 650 seconds to ensure that nanofibers are perfectly connected with each other. And finally drying the film for 8 to 12 hours in a vacuum oven at the temperature of between 65 and 75 ℃ to obtain the large-area transparent flexible AgNTs network film.

The method comprises the following specific steps:

example 1:

(1) the 10% by mass PVA solution was heated at 65 ℃ and 1300rpm with stirring for 12 hours, cooled to room temperature and injected into an electrospinning device. The spinning nozzle is connected with the positive pole of a high-voltage power supply, the working voltage is maintained at 12kV, and the working distance between the spinning nozzle and the receiving ring is kept at 12 cm. PVA cores 5 arranged in a line are prepared to obtain the PVA nanofiber membrane. The electrospinning time directly determines the mass density of the AgNTs network, thereby affecting EMI SE and transmittance.

(2) And (2) putting the PVA nanofiber membrane obtained in the step (1) in an 80% RH oven for 550s at 65 ℃ to dissolve the combined part of the PVA nanofibers, and then heating the PVA nanofiber membrane for 550s at 65 ℃ in a vacuum and non-humid environment to remove moisture so as to perfectly connect the nanofibers with each other.

(3) Preparing an external Ag layer 4 on the surface of the PVA nanofiber network obtained in the step (2) through a sputtering technology to form an AgNTs network inner layer 1. The working power is 90W and the time is 550 s.

(4) And (4) loading the AgNTs network inner layer 1 obtained in the step (3) on the PET substrate outer layer 2 and covering the PET substrate outer layer with a PDMS protective layer 3. After drying in a vacuum oven at 65 ℃ for 8 hours, a large-area transparent flexible AgNTs network film is obtained.

Example 2:

(1) the 12% by mass PVA solution was heated at 75 ℃ and 1500rpm with stirring for 21 hours, cooled to room temperature and injected into an electrospinning device. The spinning nozzle is connected with the positive pole of a high-voltage power supply, the working voltage is maintained at 15kV, and the working distance between the spinning nozzle and the receiving ring is kept at 15 cm. PVA cores 5 arranged in a line are prepared to obtain the PVA nanofiber membrane. The electrospinning time directly determines the mass density of the AgNTs network, thereby affecting EMI SE and transmittance.

(2) Placing the PVA nanofiber membrane obtained in the step (1) in an 85% RH oven at 75 ℃ for 650s to dissolve the combined part of the PVA nanofibers, and then heating at 75 ℃ for 650s in a vacuum and non-humid environment to remove moisture so that the nanofibers are perfectly connected with each other.

(3) Preparing an external Ag layer 4 on the surface of the PVA nanofiber network obtained in the step (2) through a sputtering technology to form an AgNTs network inner layer 1. The working power is 100W and the time is 650 s.

(4) And (4) loading the AgNTs network inner layer 1 obtained in the step (3) on the PPET substrate outer layer 2 and covering the PPET substrate outer layer with a PDMS protective layer 3. After drying in a vacuum oven at 75 ℃ for 12 hours, large-area transparent flexible AgNTs network films were obtained.

Example 3:

(1) the 15% by mass PVA solution was heated at 70 ℃ and 1400rpm with stirring for 24 hours, cooled to room temperature and injected into an electrospinning device. The spinning nozzle is connected with the positive pole of a high-voltage power supply, the working voltage is maintained at 18kV, and the working distance between the spinning nozzle and the receiving ring is kept at 18 cm. PVA cores 5 arranged in a line are prepared to obtain the PVA nanofiber membrane. The electrospinning time directly determines the mass density of the AgNTs network, thereby affecting EMI SE and transmittance.

(2) And (2) putting the PVA nanofiber membrane obtained in the step (1) in a 90% RH oven for 600s at 70 ℃ to dissolve the combined part of the PVA nanofibers, and then heating for 600s at 70 ℃ in a vacuum and non-humid environment to remove moisture so as to perfectly connect the nanofibers with each other.

(3) Preparing an external Ag layer 4 on the surface of the PVA nanofiber network obtained in the step (2) through a sputtering technology to form an AgNTs network inner layer 1. The working power is 110W, and the time is 600 s.

(4) And (4) loading the AgNTs network inner layer 1 obtained in the step (3) on a PET substrate outer layer 2 and covering the PET substrate outer layer with a PDMS protective layer 3. After drying in a vacuum oven at 70 ℃ for 10 hours, large-area transparent flexible AgNTs network films were obtained.

The interconnected AgNTs form a large-area high-quality conductive network, and the AgNTs network pipe 6 can effectively block electromagnetic waves and allow visible light waves to pass through. The outer layer 2 of the PET substrate and the PDMS protective layer 3 not only play a role of protection, but also play a role of a buffer layer so as to ensure that the AgNTs network is damaged minimally in the mechanical deformation process.

Comparative analysis of results

Fig. 3, 4 and 5 are diagrams of processes for manufacturing flexible transparent silver nanotube network films for electromagnetic interference shielding in three embodiments.

FIG. 6, FIG. 7, FIG. 8 are scanning electron micrographs of the AgNTs integral structure on the nanofiber film surface obtained by heating at 65-75 ℃ for 12min and magnifying by 5-15 times in three examples; FIG. 9 is a scanning electron micrograph of the cross-linking AgNTs in the nanofiber film surface obtained in example 2 at 75 ℃ for 12min under 100-fold magnification. As can be seen from the figure, the prepared AgNTs line is straight in transparent fiber and compact in film appearance at the specific intersection, and can be used for preparing a large-area AgNTs network film for shielding electromagnetic interference.

According to the technical scheme, the AgNTs network is an EMI shielding film with excellent comprehensive performance, can achieve the EMI SE of a 1.0 omega/sq sheet resistance and a 90% light transmittance AgNTs film to reach 35dB, has excellent mechanical stability, and can change negligibly after 5000 bending and twisting cycles. The simple integrated preparation process can bring high comprehensive performance to a large-scale AgNTs network. These results show that the silver nanotube network film based on electromagnetic interference shielding prepared by the invention has great potential in aviation and industrial optical systems and has good market prospect.

Claims

1. The preparation method of the silver nanotube network film based on electromagnetic interference shielding is characterized in that the film comprises an AgNTs network inner layer (1), a PET substrate outer layer (2) and a PDMS protective layer (3), wherein the AgNTs network inner layer (1) is positioned between the PET substrate outer layer (2) and the PDMS protective layer (3); the AgNTs network inner layer (1) is formed by a plurality of AgNTs network pipes (6) which are arranged in a line and are lapped into a whole, and the interconnected AgNTs network pipes (6) form a compact and uniform network; the AgNTs network pipe (6) consists of an external Ag layer (4) and a PVA core (5); during preparation, the PVA skeleton on the PVA core (5) is integrated and lapped to form the interconnection of the AgNTs network, and the surface of the PVA core (5) is plated with an external Ag layer (4) to obtain a high-performance AgNTs network inner layer (1) with stable and integrated interconnection; then, synthesizing a PET substrate outer layer (2) and a PDMS protective layer (3) by using polyethylene terephthalate and a polydimethylsiloxane material through electrostatic spinning; finally, the nano fibers are mutually connected through vacuum heating and sputtering deposition, the obtained AgNTs network inner layer (1) is adsorbed on the PET substrate outer layer (2), and the surface of the AgNTs network inner layer (1) is covered by a PDMS protective layer (3), so that the large-area transparent flexible silver nanotube network film based on electromagnetic interference shielding is obtained; the whole preparation process is in a vacuum environment;

the method comprises the following specific steps:

dissolving PVA particles in deionized water to prepare 10-15 mass percent PVA solution, stirring and heating the PVA solution at the temperature of 65-75 ℃ and the rotating speed of 1300-1500rpm for 12-24 hours to obtain PVA spinning solution, cooling the PVA spinning solution to room temperature and injecting the PVA spinning solution into electrostatic spinning equipment;

step (2) connecting a spinning nozzle of the electrostatic spinning equipment with the positive electrode of a high-voltage power supply, and maintaining the working voltage at 12-18 kV; during electrostatic spinning, the working distance between the spinning nozzle and the receiving ring is kept between 12 and 18 centimeters; preparing PVA cores (5) which are arranged in a straight line to obtain a PVA nanofiber membrane;

step (3) placing the PVA nanofiber membrane in an oven with the dryness of 80-90% and heating the PVA nanofiber membrane for 550-75 ℃ for 650s to dissolve the combined part of the PVA nanofiber, and then heating the PVA nanofiber membrane for 550-75 ℃ for 650s in a vacuum and non-humid environment to remove moisture so as to connect the nanofibers with each other;

preparing an external Ag layer (4) on the surface of the PVA nanofiber membrane by a sputtering deposition technology to form an AgNTs network inner layer (1) which is formed by arranging and overlapping a plurality of AgNTs into a whole in a straight line; the working power of the sputtering deposition is 90-110W, and the time is 550-650 s;

step (5), adopting a PET film as the PET substrate outer layer (2), and adopting a PDMS film as the PDMS protective layer (3); adsorbing the AgNTs network inner layer (1) obtained in the step (4) on a PET film, and covering the surface of the AgNTs network inner layer (1) with a PDMS film; and then drying the film for 8 to 12 hours in a vacuum oven at the temperature of between 65 and 75 ℃ to obtain the silver nanotube network film based on the electromagnetic interference shielding.

2. The method for preparing the silver nanotube network film based on electromagnetic interference shielding according to claim 1, wherein the pore size set of the AgNTs network tube (6) is 5-30 μm.

3. The method for preparing the EMI shielding-based silver nanotube network film according to claim 1 or 2, wherein the EMI shielding-based flexible transparent silver nanotube network film has a thickness of 0.5mm-0.8mm, wherein the thickness of the AgNTs network inner layer (1) is 0.3mm-0.4mm, the thickness of the PET substrate outer layer (2) is 0.1mm-0.2mm, and the thickness of the PDMS protective layer (3) is 0.1mm-0.2 mm.