High-light-transmittance and self-repairing AgNW-based composite electromagnetic shielding film and preparation method thereof

Abstract

The invention discloses a high-light-transmittance and self-repairing AgNW-based composite electromagnetic shielding film and a preparation method thereof, and belongs to the technical field of photoelectric materials. The method comprises the following steps: preparing an AgNW / MXene composite film; preparing a CMC / CNF gel; and transferring the prepared CMC / CNF gel to the surface of the AgNW / MXene composite film, and drying to obtain the CNF / AgNW / MXene composite electromagnetic shielding film. Two-dimensional MXene is compounded with one-dimensional AgNW and cellulose nanofiber (CNF) nanopaper to form a line-plane interconnection structure, so that the CNF / AgNW / MXene composite electromagnetic shielding film is obtained, and absorption and scattering of electromagnetic waves are enhanced through a layered structure; the CNF / CMC composite structure can utilize the nanostructure of CNF and surface carboxyl to form a hydrogen bond to enhance the mechanical property of cellulose nanopaper and utilize the mobility of CMC to enhance the self-repairing performance, and finally the multifunctional integrated transparent flexible film with high light transmittance, strong electromagnetic shielding capability, high mechanical strength and a self-repairing function is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic materials, and in particular relates to a highly light-transmitting, self-repairable AgNW-based composite electromagnetic shielding film and a preparation method thereof. Background Art

[0002] With the rapid development of electronic communication technology, electromagnetic pollution is becoming increasingly serious, which not only poses a huge challenge to the normal operation of electronic equipment, but also threatens people's lives and health. Electronic equipment releases electromagnetic signals during operation. These signals are used for communication and data transmission and may be interfered with by external factors such as power lines of other devices and electromagnetic radiation sources. This interference may not only weaken the performance of the equipment, but also lead to an increase in equipment failure rate, increase the noise inside the electronic equipment, and even cause the equipment to malfunction or completely fail. Therefore, the management and protection of electromagnetic radiation is particularly important. At present, electromagnetic shielding materials have been increasingly used in the fields of electronic product manufacturing, aerospace, medical equipment manufacturing, etc. Traditional electromagnetic shielding materials often have problems such as insufficient light transmittance and inability to self-repair, which to a certain extent limit their scope of application. Therefore, it is necessary to develop a composite electromagnetic shielding material with high light transmittance and self-repairability.

[0003] Silver nanowires, as a new nanomaterial, possess excellent optoelectronic properties. Metallic silver exhibits excellent electrical conductivity and electromagnetic shielding properties. Furthermore, their nanowire morphology provides a good window for visible light transmission, leading to their widespread application in high-transmittance electromagnetic shielding materials. However, the presence of voids in one-dimensional AgNW films hinders their electromagnetic shielding performance. Furthermore, the application of silver nanowire films is limited by the poor mechanical properties of the substrate material. Traditional metal sheets, due to their material properties, often exhibit poor light transmittance and are heavy, increasing the cost of transport and installation while also limiting their potential for applications requiring good visible light transmittance. While some substrate materials, such as PET substrates, exhibit excellent visible light transmittance, their mechanical properties are less than ideal. Once the material breaks or breaks, its lack of self-repair means the damage persists and is difficult to recover through its own mechanisms. Summary of the Invention

[0004] The present invention provides a highly transmittance, self-repairable AgNW-based composite electromagnetic shielding film and its preparation method. The two-dimensional electromagnetic shielding material MXene is used to cover the gaps in the AgNW, thereby improving local conductivity and electromagnetic shielding performance. The self-repairing performance of the material is achieved by utilizing the hydrogen bond network constructed by the carboxyl groups on the surface of the CNF and CMC composite structure and the excellent fluidity.

[0005] To achieve the above objectives, the present invention adopts the following technical solutions: A method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film comprises the following steps: (1) After the substrate was washed several times with deionized water and ethanol and dried, it was irradiated with UV ozone cleaning machine for 5 minutes; (2) Take an AgNW / Mxene ethanol dispersion with a mass concentration of 20-80% and spray the AgNW / Mxene ethanol dispersion on the substrate surface with a spraying amount of 200-600 mg / m 2 ; (3) Cellulose nanofiber (CNF) powder is fully dispersed in deionized water to prepare a CNF suspension with a mass percentage concentration of 1%-5%; carboxymethyl cellulose (CMC) powder is dissolved in deionized water to prepare a solution with a mass percentage concentration of 1%-5%; the CNF suspension and the CMC solution are mixed so that the mass percentage of the CNF suspension during mixing is 35%-85% to prepare a CNF / CMC mixed solution; (4) The CMC / CNF mixture is poured into a mold and placed in an oven to dry until it is in a gel state. The gel is then transferred to the AgNW / MXene surface. After drying at 40-60°C for 36-72 hours, the substrate is peeled off. The CMC in the molecular chain state is fully filled into the pores of the CNF skeleton to obtain a CNF / AgNW / MXene composite electromagnetic shielding film.

[0006] A highly transparent, self-repairable AgNW-based composite electromagnetic shielding film, wherein the upper layer of the film is a CNF / CMC composite layer, and the lower layer is an AgNW / MXene layer; the CNF / CMC composite produces a hydrogen bond network, and the CMC fills the pores of the CNF skeleton; the MXene covers the voids in the AgNW to form a line-surface interconnected structure.

[0007] Beneficial effects: The present invention provides a highly transmittance, self-repairable AgNW-based composite electromagnetic shielding film and its preparation method, which has good visible light transmittance, self-repair and electromagnetic shielding performance: a traditional two-dimensional MXene material with good electromagnetic shielding performance is combined with a one-dimensional AgNW to form a conductive film with a line-surface interconnected structure, which solves the problem that the silver nanowire film has difficulty improving its electromagnetic shielding performance due to the presence of gaps; at the same time, CNF / CMC has self-repairing properties, and the CNF / CMC composite structure can utilize the hydrogen bonds formed by the nanostructure and surface carboxyl groups of CNF to enhance the mechanical properties of cellulose nanopaper, and CMC can utilize its own fluidity to enhance its self-repairing performance. The CNF nanopaper layer is bonded to AgNW / MXene during the transfer experiment through the rich polar groups of cellulose, which can take into account both self-repair and electromagnetic shielding, and relies on the polar groups to assist in the repair of the electromagnetic shielding line-surface network during the self-repair process, thereby reducing the loss of electromagnetic shielding performance; finally, a multifunctional integrated transparent flexible film with high transmittance, strong electromagnetic shielding capability, high mechanical strength and self-repairing function is obtained. At a surface density of 400mg / m 2 , when the ratio of AgNW / MXene is 75%, the maximum electromagnetic shielding effectiveness is 32.1 dB. The layered structure of the present invention enhances the absorption and scattering of electromagnetic waves. Even after the complete tearing and self-repairing operation, the X-band electromagnetic shielding effectiveness is maintained at a relatively stable level. At a CNF / CMC concentration of 60%, the maximum tensile strength of the repaired nanopaper is 79.3MPa, slightly lower than the 82.5MPa before repair. At the same time, thanks to the good visible light transmittance of AgNW (550nm, 80%) and CNF (550nm, 86%), the CNF / AgNW / MXene film achieves high light transmittance, self-repairability and electromagnetic shielding performance; in addition, the preparation process of the present invention is simple and easy to operate, the production cost is low, and it can be widely used in electromagnetic shielding engineering applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 400 mg / m in Example 1 of the present invention 2 , XRD pattern of 75% AgNW / MXene film; Figure 2 XPS spectra of the AgNW / MXene composite film in Example 1 of the present invention (a) total spectrum, (b) Ti 2p spectrum, (c) C 1s spectrum, and (d) O 1s spectrum; Figure 3 400 mg / m in Example 1 of the present invention 2 , stress-strain curves of 75% AgNW / MXene, 40% CNF / CMC composite films before and after self-healing; Figure 4 400 mg / m in Example 1 of the present invention2 , electromagnetic shielding performance diagram of 75% AgNW / MXene, 40% CNF / CMC composite electromagnetic shielding film; Figure 5 400 mg / m in Example 1 of the present invention 2 , visible light transmittance graph of 75% AgNW / MXene, 40% CNF / CMC composite electromagnetic shielding film; Figure 6 400 mg / m in Example 1 of the present invention 2 , 75% AgNW / MXene, 40% CNF / CMC composite electromagnetic shielding film before and after repair comparison chart; Figure 7 200 mg / m in Example 2 of the present invention 2 , XRD pattern of 50% AgNW / MXene film; Figure 8 200 mg / m in Example 2 of the present invention 2 , stress-strain curves of 50% AgNW / MXene, 60% CNF / CMC composite films before and after self-healing; Figure 9 200 mg / m in Example 2 of the present invention 2 , electromagnetic shielding performance diagram of 50% AgNW / MXene, 60% CNF / CMC composite electromagnetic shielding film; Figure 10 200 mg / m in Example 2 of the present invention 2 , visible light transmittance graph of 50% AgNW / MXene, 60% CNF / CMC composite electromagnetic shielding film; Figure 11 200 mg / m in Example 2 of the present invention 2 , electromagnetic shielding performance comparison of 50% AgNW / MXene and 60% CNF / CMC composite electromagnetic shielding films before and after repair; Figure 12 600 mg / m in Example 3 of the present invention 2 , XRD pattern of 75% AgNW / MXene film; Figure 13 600 mg / m in Example 3 of the present invention 2 , stress-strain curves of 75% AgNW / MXene, 80% CNF / CMC composite films before and after self-healing; Figure 14 600 mg / m in Example 3 of the present invention 2 , electromagnetic shielding performance diagram of 75% AgNW / MXene, 80% CNF / CMC composite electromagnetic shielding film; Figure 15 600 mg / m in Example 3 of the present invention 2 , visible light transmittance graph of 75% AgNW / MXene, 80% CNF / CMC composite electromagnetic shielding film; Figure 16 600 mg / m in Example 3 of the present invention 2 , electromagnetic shielding performance comparison of 75% AgNW / MXene and 80% CNF / CMC composite electromagnetic shielding films before and after repair; Figure 17 A real-life picture of the self-repair process of the present invention (left side is before repair, right side is after repair); Figure 18 This is a flow chart for preparing the highly transparent, self-repairable AgNW-based composite electromagnetic shielding film of the present invention. DETAILED DESCRIPTION

[0009] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments: Example 1

[0010] like Figure 18 As shown, a method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film comprises the following steps: Step (1): Cut the PET substrate into 3×2cm 2 Size, washed with deionized water and ethanol several times and dried, then irradiated with UV ozone cleaning machine for 5 minutes; Step (2): Take a 75% AgNW / Mxene ethanol dispersion, set the spray gun pressure to 0.3 MPa, set the distance between the spray gun and the PET to 10 cm, and spray the AgNW / Mxene ethanol dispersion on the surface of the PET substrate. The spraying amount is 400 mg / m 2 ,spare; Step (3): Disperse CNF dry powder in deionized water and use an ultrasonic cell disruptor to crush the CNF for 1.5 h to fully disperse the CNF, thereby preparing a CNF suspension with a concentration of 2%; dissolve CMC dry powder in deionized water to similarly prepare a solution with a concentration of 2%, and mix the 2% CNF suspension and the 2% CMC solution to obtain a mixed solution with a solute mass of 0.6 g and a CNF concentration of 40%; Step (4): Pour the CMC / CNF mixture into a mold and place it in an oven to dry until it is in a gel state. Then carefully transfer the gel to the AgNW / MXene surface and peel it off after drying at 40°C for 60 hours to obtain a CNF / AgNW / MXene composite electromagnetic shielding film.

[0011] like Figure 1As shown in the figure, the XRD image of the 75% AgNW / Mxene composite film after spraying is visible, in which AgNW has five characteristic diffraction peaks at 38.1°, 44.3°, 64.5°, 77.4° and 81.6°, corresponding to the (111), (200), (220), (311) and (222) crystal planes of silver, respectively. There is no obvious XRD signal of the few-layer Mxene, but with the increase of Mxene content, the characteristic peak intensity of silver in the XRD graph gradually weakens until it disappears. like Figure 2 As shown in Figure 2, XPS spectrum was used to characterize and analyze the chemical composition of the composite film, indicating that the composite of AgNW and MXene was achieved. Figure 2 As shown in (b), the high-resolution Ti 2p spectrum is composed of the previously reported TiO2 and titanium atoms (Ti, Ti 2+ 、Ti 3+ ) fitting; Figure 2 As shown in (c), the high-resolution C1 spectrum is fitted by three peaks with a binding energy of 281.2 eV. The peak corresponding to C−Ti−T x , the other two peaks (284.6 and 286.5 eV) correspond to graphite C−C and C−O, which may be derived from the selective dissolution of Ti during etching; high-resolution O spectrum ( Figure 2 d) Fitted by three peaks, corresponding to the binding energy of TiO2 at 528.9 eV, C−Ti−O at 530.9 eV, and x and C−Ti(OH) at 532.6 eV x ; C−Ti−(OH) x The binding energy also shifted from 532.1 eV to a higher binding energy. The change in chemical environment proved that there were a large number of hydrogen bonds between the nanosheets, which helped to enhance the interfacial adhesion and mechanical properties and improve the stability of the film. like Figure 3 As shown in the stress-strain curves of the composite film before and after self-repair, the tensile strength after repair decreased slightly. The maximum tensile strength of the repaired nanopaper was 74.2 MPa, slightly lower than the 82.4 MPa before repair. The mechanical properties remained basically stable before and after repair. like Figure 4 As shown, the vector network analyzer measured 400mg / m 2 , 75% AgNW / MXene, 40% CNF / CMC composite electromagnetic shielding films have certain electromagnetic shielding effectiveness in the X-band, with an average total electromagnetic shielding effectiveness of 32.1dB; like Figure 5 As shown, 400 mg / m 2, 75% AgNW / MXene, 40% CNF / CMC composite electromagnetic shielding films have good transmittance in the visible light range, and the transmittance at 550nm is 84.5%; like Figure 6 As shown, 400 mg / m 2 , 75% AgNW / MXene, 40% CNF / CMC composite electromagnetic shielding film still maintains stable electromagnetic shielding effectiveness in the X-band after self-repair, with an average total electromagnetic shielding effectiveness of 22.8dB. Example 2

[0012] like Figure 18 As shown, a method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film comprises the following steps: Step (1): Cut the PET substrate into 3×2cm 2 Size, washed with deionized water and ethanol several times and dried, then irradiated with UV ozone cleaning machine for 5 minutes; Step (2): Take 50% AgNW / Mxene ethanol dispersion, set the spray gun pressure to 0.3 MPa, the distance between the spray gun and the PET to 10 cm, and spray the AgNW / Mxene ethanol dispersion on the surface of the PET substrate. The spraying amount is 200 mg / m 2 ;spare; Step (3): Disperse CNF dry powder in deionized water and use an ultrasonic cell disruptor to crush the CNF for 1 hour to fully disperse the CNF, thereby preparing a 1% CNF suspension. Dissolve CMC dry powder in deionized water and similarly prepare a 1% solution. Mix the 1% CNF suspension and the 1% CMC solution to obtain a mixed solution with a solute mass of 0.5 g and a CNF concentration of 60%. Step (4): Pour the CMC / CNF mixture into a mold and place it in an oven to dry until it is in a gel state. Then carefully transfer the gel to the AgNW / MXene surface and peel it off after drying at 50°C for 48 hours to obtain a CNF / AgNW / MXene composite electromagnetic shielding film.

[0013] like Figure 7 As shown in Figure 2, the XRD pattern of the 50% AgNW / Mxene composite film after spraying shows that AgNW has five characteristic diffraction peaks at 38.1°, 44.3°, 64.5°, 77.4° and 81.6°, corresponding to the (111), (200), (220), (311) and (222) crystal planes of silver, respectively. As the MXene content increases, the XRD peaks of the AgNW / Mxene composite film increase with the increase of MXene content. Figure 1 ), the characteristic peak of silver is slightly weakened, and Figure 2XPS characterization results show that AgNW / MXene composite film was successfully prepared after spraying; like Figure 8 As shown in the stress-strain curves of the composite film before and after self-repair, the tensile strength after repair decreased slightly. The maximum tensile strength of the repaired nanopaper was 79.3 MPa, slightly lower than the 82.5 MPa before repair. The mechanical properties remained basically stable before and after repair. like Figure 9 As shown, the vector network analyzer measured 200mg / m 2 , 50% AgNW / MXene, 60% CNF / CMC composite electromagnetic shielding films have certain electromagnetic shielding effectiveness in the X-band, and the average total electromagnetic shielding effectiveness is 16.4dB; like Figure 10 As shown, 200 mg / m 2 , 50% AgNW / MXene, 60% CNF / CMC composite electromagnetic shielding films have good transmittance in the visible light range, and the transmittance at 550nm is 86.3%; like Figure 11 As shown, 200 mg / m 2 , 50% AgNW / MXene, 60% CNF / CMC composite electromagnetic shielding film still maintains stable electromagnetic shielding effectiveness in the X-band after self-repair, with an average total electromagnetic shielding effectiveness of 13.7dB. Example 3

[0014] like Figure 18 As shown, a method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film comprises the following steps: Step (1): Cut the PET substrate into 3×2cm 2 Size, washed with deionized water and ethanol several times and dried, then irradiated with UV ozone cleaning machine for 5 minutes; Step (2): Take a 75% AgNW / Mxene ethanol dispersion, set the spray gun pressure to 0.3 MPa, set the distance between the spray gun and the PET to 10 cm, and spray the AgNW / Mxene ethanol dispersion on the surface of the PET substrate. The spraying amount is 600 mg / m 2 ;spare; Step (3): Disperse CNF dry powder in deionized water and use an ultrasonic cell disruptor to crush the CNF for 3 hours to fully disperse the CNF, thereby preparing a 4% CNF suspension. Dissolve CMC dry powder in deionized water and similarly prepare a 4% solution. Mix the 4% CNF suspension and the 4% CMC solution to obtain a mixed solution with a solute mass of 0.6 g and a CNF concentration of 80%. Step (4): Pour the CMC / CNF mixture into a mold and place it in an oven to dry until it is in a gel state. Then carefully transfer the gel to the AgNW / MXene surface and peel it off after drying at 55°C for 72 hours to obtain a CNF / AgNW / MXene composite electromagnetic shielding film.

[0015] like Figure 12 As shown in Figure 2, the XRD pattern of the 75% AgNW / Mxene composite film after spraying shows that AgNW has five characteristic diffraction peaks at 38.1°, 44.3°, 64.5°, 77.4° and 81.6°, corresponding to the (111), (200), (220), (311) and (222) crystal planes of silver, respectively. Figure 2 XPS characterization results show that AgNW / MXene composite film was successfully prepared after spraying; like Figure 13 As shown in the stress-strain curves of the composite film before and after self-repair, the tensile strength after repair decreased slightly. The maximum tensile strength of the repaired nanopaper was 74.8 MPa, slightly lower than the 77.9 MPa before repair. The mechanical properties remained basically stable before and after repair. like Figure 14 As shown, the vector network analyzer measured 600mg / m 2 , 75% AgNW / MXene, 80% CNF / CMC composite electromagnetic shielding films have certain electromagnetic shielding effectiveness in the X-band, and the average total electromagnetic shielding effectiveness is 31.9dB; like Figure 15 As shown, 600 mg / m 2 , 75% AgNW / MXene, and 80% CNF / CMC composite electromagnetic shielding films have good transmittance in the visible light range, and the transmittance at 550nm is 85.5%.

[0016] like Figure 16 As shown, 600 mg / m 2 , 75% AgNW / MXene, 80% CNF / CMC composite electromagnetic shielding film still maintains stable electromagnetic shielding effectiveness in the X-band after self-repair, with an average total electromagnetic shielding effectiveness of 24.2dB.

[0017] like Figure 17 As shown in the figure, the process is a real photo of the self-repair of the film. The two torn parts of the film are immersed in a water tank, picked up and spliced ​​together. The glass plate carrying the film is placed in the room to dry naturally for 24 hours and then peeled off to obtain the repaired nanopaper, which proves that the composite electromagnetic shielding film of the present invention has good self-repair performance.

[0018] The above description is only a preferred embodiment of the present invention. It should be pointed out that those skilled in the art can make corresponding changes and adjustments to the technology of the present invention without departing from the basic principles of the present invention. These changes and adjustments are all within the scope of protection of the present invention.

Claims

1. A highly transparent, self-repairable AgNW-based composite electromagnetic shielding film, characterized in that: The upper layer of the film is a CNF / CMC composite layer, and the lower layer is an AgNW / Mxene layer; the CNF / CMC composite produces a hydrogen bond network, in which the CMC in a molecular chain state is fully filled into the pores of the CNF skeleton; the MXene covers the gaps in the AgNW to form a line-surface network structure; the polar groups in the CNF / CMC act to assist in the repair of the electromagnetic shielding line-surface network.

2. A method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film, characterized in that The following steps are involved: Preparation of AgNW / MXene composite films; Preparation of CMC / CNF gel; The prepared CMC / CNF gel was transferred to the surface of the AgNW / MXene composite film, and after drying, a CNF / AgNW / MXene composite electromagnetic shielding film was obtained.

3. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 2, characterized in that: The specific process of preparing the AgNW / MXene composite film is as follows: take an AgNW / MXene ethanol dispersion with a mass concentration of 20-80%, and spray the AgNW / MXene ethanol dispersion on the surface of the substrate.

4. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 3, characterized in that: The spraying amount is 200-600mg / m2 2 .

5. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 3 or 4, characterized in that: During spraying, the air pressure of the spray gun was set to 0.3 MPa, and the distance between the spray gun and the substrate was 10 cm.

6. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 3, characterized in that: The pre-treatment process of the substrate is as follows: cutting the substrate into a suitable size, washing it with deionized water and ethanol for several times and drying it, and then irradiating it with an ultraviolet ozone cleaning machine for 5 minutes.

7. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 2, characterized in that: The process of preparing CMC / CNF gel is as follows: prepare a CNF suspension with a mass concentration of 1%-5% and a CMC solution with a mass concentration of 1%-5% respectively, mix the CNF suspension and the CMC solution to prepare a CMC / CNF mixed solution; pour the CMC / CNF mixed solution into a mold and dry it to a gel state.

8. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 7, characterized in that: When the CNF suspension and the CMC solution are mixed, the mass proportion of the CNF suspension is 35%-85%.

9. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 7 or 8, characterized in that: When preparing CNF suspension, CNF dry powder was dispersed in deionized water and crushed using an ultrasonic cell disruptor for 1-3 h to allow CNF to be fully dispersed.

10. The method for preparing a highly transparent, self-repairable AgNW-based composite electromagnetic shielding film according to claim 2, wherein: The CMC / CNF gel was transferred to the AgNW / MXene surface and the substrate was peeled off after drying at 40-60°C for 36-72 hours. The CMC in the molecular chain state was fully filled into the pores of the CNF skeleton to obtain a CNF / AgNW / MXene composite electromagnetic shielding film.

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