PMXene-CNT / ANF electromagnetic shielding composite film and preparation method and application thereof
Through gradient centrifugation and dopamine modification technology, the mechanical and conductive properties of MXene nanosheets are improved and assembled with the CNT/ANF layer, the problem of insufficient mechanical and electromagnetic shielding performance of MXene matrix composite films is solved, and efficient electromagnetic shielding and long-term stable composite films are achieved.
Patent Information
- Application Number
- CN202510236612.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2025-05-30
AI Technical Summary
The existing MXene-based electromagnetic shielding composite films are difficult to take into account excellent mechanical properties and electromagnetic shielding properties, and MXene nanosheets exposed to the surface are prone to oxidation, affecting long-term effectiveness and stability.
Gradient centrifugation technology was used to screen large-scale MXene nanosheets, and their environmental stability and conductivity were improved through dopamine modification. The modified PMXene nanosheets were assembled with the CNT/ANF layer to form a PMXene-CNT/ANF composite gel, and an electromagnetic shielded composite film was obtained after vacuum drying.
The composite film has achieved excellent electromagnetic shielding performance, environmental stability and mechanical properties, extended its service life, and has shown broad application prospects in the fields of electromagnetic shielding, sensing, electric thermal deicing, etc.
Smart Images
Figure CN120059253A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of electromagnetic shielding materials, and particularly relates to a PMXene-CNT / ANF electromagnetic shielding composite film, a preparation method thereof, and an application thereof. Background Art
[0002] With the wide application of radio communication and 5G technology, the social production level and the quality of human life have been greatly improved; however, the resulting large-scale electromagnetic wave radiation interference poses a serious threat to the life and health of humans and animals and the safe operation and service life of electronic facilities; due to the high integration and miniaturization of modern electronic devices, traditional metal materials (such as stainless steel or solid copper) can no longer meet the requirements of high-performance electromagnetic interference shielding materials for light weight, ultrathin, flexibility, and high mechanical properties.
[0003] In recent years, transition metal carbides / nitrides (MXene) have been widely studied due to their excellent electrical conductivity, strong microwave attenuation ability, unique two-dimensional sheet structure, large specific surface area, and high processability in aqueous solutions; however, due to the weak interlayer interaction and loose structure of MXene nanosheets, the mechanical properties of MXene films are poor, and the application scenarios are limited; to solve this problem, polymers are often introduced into MXene in the prior art to improve its mechanical properties; however, the simple homogeneous structure makes it difficult for the composite material to balance excellent mechanical properties and electromagnetic shielding properties; in addition, the MXene nanosheets exposed on the surface layer will face the problem of oxidation failure when exposed to air for a long time, which seriously affects the long-term effectiveness and stability of MXene-based electromagnetic shielding composite films and increases the safety risk during the application process; therefore, improving the environmental stability and mechanical properties of MXene-based composite films has important practical significance for their in-depth application in the new generation of flexible electronic products. Summary of the Invention
[0004] Aiming at the technical problems existing in the prior art, the present invention provides a PMXene-CNT / ANF electromagnetic shielding composite film, a preparation method thereof, and an application thereof, so as to solve the technical problems that the existing MXene-based electromagnetic shielding composite films are difficult to balance excellent mechanical properties and electromagnetic shielding properties, and the MXene nanosheets exposed on the surface layer will face the problem of oxidation failure when exposed to air for a long time, which is likely to affect the long-term effectiveness and stability of MXene-based electromagnetic shielding composite films.
[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a preparation method of a PMXene-CNT / ANF electromagnetic shielding composite film, comprising: The ANF / DMSO dispersion is subjected to proton reduction treatment using a carbon nanotube aqueous dispersion to obtain a CNT / ANF aqueous dispersion; Using gradient centrifugation technology, for Ti 3 C 2 T x The MXene nanosheets are centrifuged to obtain large-scale MXene nanosheets; among them, the diameter size of the large-scale MXene nanosheets is greater than 2 μm; The large-scale MXene nanosheets are modified using dopamine to obtain PMXene nanosheets; The CNT / ANF aqueous dispersion and the PMXene nanosheets are assembled to obtain a PMXene-CNT / ANF composite gel; The PMXene-CNT / ANF composite gel is vacuum dried to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0006] Furthermore, in the process of subjecting the ANF / DMSO dispersion to proton reduction treatment using a carbon nanotube aqueous dispersion to obtain a CNT / ANF aqueous dispersion, the mass concentration of the carbon nanotube aqueous dispersion is 0.1% - 0.4%, and the mass fraction of carbon nanotubes compared to ANF is 0.5 wt.% - 3 wt.%.
[0007] Furthermore, the process of using gradient centrifugation technology to centrifuge the Ti 3 C 2 T x MXene nanosheets to obtain large-scale MXene nanosheets includes: Under the first preset centrifugation conditions, the Ti 3 C 2 T x MXene nanosheets are centrifuged, the upper layer dispersion is collected to obtain a first gradient product; Under the second preset centrifugation conditions, the first gradient product is centrifuged, the lower layer precipitate is collected to obtain a second gradient product; Under the third preset centrifugation conditions, the second product is centrifuged, the precipitate is collected and dispersed in water to obtain large-scale MXene nanosheets.
[0008] Furthermore, the first preset centrifugation conditions include: the centrifugation speed is 2000 - 3500 rpm, and the centrifugation time is 10 - 30 min; the second preset centrifugation conditions include: the centrifugation speed is 3000 - 3500 rpm, and the centrifugation time is 10 - 30 min; the third preset centrifugation conditions include: the centrifugation speed is 2000 - 4000 rpm, and the centrifugation time is 10 - 30 min.
[0009] Further, during the process of modifying large-scale MXene nanosheets with dopamine to obtain PMXene nanosheets, the mass fraction of the large-scale MXene nanosheets is 0.05% - 0.2%, and the mass fraction of dopamine relative to the large-scale MXene nanosheets is 0.5 wt.% - 10 wt.%.
[0010] Further, the process of assembling the CNT / ANF aqueous dispersion and PMXene nanosheets to obtain the PMXene-CNT / ANF composite gel includes: Performing vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable layer-by-layer assembly of CNT / ANF, and using CNT to regulate the molecular chains and intermolecular interactions of ANF to obtain an enhanced CNT / ANF gel; Stacking PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain the PMXene-CNT / ANF composite gel.
[0011] Further, the mass fraction of the PMXene nanosheets relative to the enhanced CNT / ANF gel is 5 wt.% - 75 wt.%.
[0012] Further, during the process of vacuum drying the PMXene-CNT / ANF composite gel to obtain the PMXene-CNT / ANF electromagnetic shielding composite film, the vacuum drying temperature is 80 - 120 °C, and the time is 10 - 30 min.
[0013] The present invention also provides a PMXene-CNT / ANF electromagnetic shielding composite film, which is prepared by using the preparation method of the PMXene-CNT / ANF electromagnetic shielding composite film described above.
[0014] The present invention also provides an application of the PMXene-CNT / ANF electromagnetic shielding composite film, that is, the application of the PMXene-CNT / ANF electromagnetic shielding composite film as an electromagnetic interference shielding material in electronic devices.
[0015] Compared with the prior art, the beneficial effects of the present invention are: The PMXene-CNT / ANF electromagnetic shielding composite film provided by the present invention, its preparation method and application use ANF enhanced by CNT as a flexible substrate independently to provide mechanical support for the composite film; gradient centrifugal screening and PDA-modified PMXene nanosheets are used as the conductive layer, which further enhances the conductivity on the basis of improving the antioxidant property, enabling the composite film to have excellent electromagnetic shielding performance, environmental stability and mechanical properties, and having broad application prospects in the fields of electromagnetic shielding, sensing, electrothermal de-icing, etc.; wherein, introducing PDA changes the surface properties of MXene nanosheets and enhances the environmental stability of MXene lamellae; at the same time, introducing PDA can optimize the interlayer interaction of the MXene film, improve the arrangement orientation and tightness between the layers of the MXene film, greatly eliminate the interlayer defects, improve the electron transport efficiency, and thus improve the electromagnetic shielding performance; in addition, the modified PMXene nanosheets can form a good interfacial bond with the CNT / ANF layer, and can effectively transfer stress during the stress process, further improving the mechanical properties of the composite film. Brief Description of the Drawings
[0016] Figure 1 It is the cross-sectional SEM images of large-scale MXene nanosheets and PMXene nanosheets in Example 1; wherein, Figure 1 (a) is the cross-sectional SEM image of large-scale MXene nanosheets, Figure 1 (b) is the cross-sectional SEM image of PMXene nanosheets; Figure 2 It is the optical photos of the aqueous dispersions of large-scale MXene nanosheets and PMXene nanosheets in Example 1 before and after being placed at room temperature for 45 days; Figure 3 It is the photos of the films of large-scale MXene nanosheets and PMXene nanosheets in Example 1 exposed in the air; Figure 4 It is the curve graph of the surface resistance change of large-scale MXene nanosheets and PMXene nanosheets in Example 1 during the 45-day placement; Figure 5 It is the curve graph of the electromagnetic shielding performance of the PMXene-CNT / ANF electromagnetic shielding composite film in Example 1 before and after being placed for 45 days. Detailed Embodiments
[0017] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention clearer, the following specific embodiments are used to further elaborate on the present invention in detail. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0018] This embodiment provides a method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film, comprising the following steps: Step 1: Prepare an aramid nanofiber (ANF) / DMSO dispersion using the chemical splitting method; specifically, add 1.5 g of potassium hydroxide (KOH) and 1.0 g of para-aramid short fibers (PPTA) to 499.0 g of dimethyl sulfoxide (DMSO) solvent in sequence, and continuously stir to obtain the ANF / DMSO dispersion.
[0019] Step 2: Prepare a carbon nanotube (CNT) aqueous dispersion; use the CNT aqueous dispersion to perform a protonation reduction treatment on the ANF / DMSO dispersion to obtain a CNT / ANF aqueous dispersion; wherein, the mass concentration of the CNT aqueous dispersion is 0.1% - 0.4%, and the mass fraction of CNT compared to ANF is 0.5 wt.% - 3 wt.%.
[0020] Step 3: Prepare a fluorine-containing solution to selectively etch the MAX precursor, and prepare Ti 3 C 2 T x MXene (abbreviated as MXene) nanosheets through washing and ultrasonic treatment; the specific process is as follows: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of lithium fluoride (LiF), and stir until completely dissolved to obtain a fluorine-containing solution; then slowly add 3 g of the MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system; subsequently, wash the post-reaction mixed system to neutrality and let it stand and swell; wherein, the standing temperature is 4 °C and the standing time is 12 - 36 h; finally, perform vortex oscillation to obtain MXene nanosheets; wherein, the vortex rotation speed is 2000 - 4000 rpm and the oscillation time is 20 - 120 min.
[0021] Step 4: Use gradient centrifugation technology to perform centrifugation treatment on Ti 3 C 2 T x Mxene nanosheets to obtain large-scale MXene nanosheets; wherein, the diameter size of the large-scale MXene nanosheets is greater than 2 μm; the specific process is as follows: Under the first preset centrifugation conditions, perform centrifugation on Ti 3 C 2 T xThe MXene nanosheets are centrifuged, and the upper-layer dispersion is collected to obtain the first-gradient product. Among them, the first preset centrifugation conditions include: the centrifugation speed is 2000 - 3500 rpm, and the centrifugation time is 10 - 30 min. Under the second preset centrifugation conditions, the first-gradient product is centrifuged, and the lower-layer precipitate is collected to obtain the second-gradient product. Among them, the second preset centrifugation conditions include: the centrifugation speed is 3000 - 3500 rpm, and the centrifugation time is 10 - 30 min. Under the third preset centrifugation conditions, the second product is centrifuged, and the precipitate is collected and dispersed in water to obtain large-scale MXene nanosheets. Among them, the third preset centrifugation conditions include: the centrifugation speed is 2000 - 4000 rpm, and the centrifugation time is 10 - 30 min.
[0022] Step 5: Modify the large-scale MXene nanosheets with dopamine (PDA) to obtain PMXene nanosheets. The specific process is as follows: Add the dopamine solution to the large-scale MXene nanosheets, and stir and react at room temperature for 20 - 60 min to obtain PMXene nanosheets. Among them, the mass fraction of the large-scale MXene nanosheets is 0.05% - 0.2%, and the mass fraction of dopamine relative to the large-scale MXene nanosheets is 0.5 wt.% - 10 wt.%.
[0023] Step 6: Assemble the CNT / ANF aqueous dispersion and PMXene nanosheets to obtain the PMXene-CNT / ANF composite gel. The specific process is as follows: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chains and intermolecular interactions of ANF to obtain an enhanced CNT / ANF gel. Based on the hydrogen bond interaction between PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain the PMXene-CNT / ANF composite gel. Among them, the mass fraction of PMXene nanosheets relative to the enhanced CNT / ANF gel is 5 wt.% - 75 wt.%.
[0024] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel to obtain the PMXene-CNT / ANF electromagnetic shielding composite film. Among them, the vacuum-drying temperature is 80 - 120 °C, and the time is 10 - 30 min.
[0025] Preparation principle: The preparation method of the PMXene-CNT / ANF electromagnetic shielding composite film described in the present invention uses a carbon nanotube aqueous dispersion to perform a proton reduction treatment on the ANF / DMSO dispersion, and uses aramid nanofibers (ANF) enhanced by carbon nanotubes (CNT) as a matrix to provide mechanical properties; by 3 C 2 T x performing gradient centrifugation on Mxene nanosheets to obtain large-scale Mxene nanosheets, which is beneficial to improving the conductivity of the Mxene nanosheet film; secondly, using dopamine to modify the large-scale Mxene nanosheets to introduce PDA to change the surface properties of the Mxene nanosheets and enhance the environmental stability of the Mxene lamellae; at the same time, PDA can optimize the interlayer interaction of the Mxene film, improve the arrangement orientation and compactness between the layers of the Mxene film, greatly eliminate the interlayer defects, improve the electron transport efficiency, and thus improve the electromagnetic shielding performance; assembling the CNT / ANF aqueous dispersion and the PMXene nanosheets enables the PMXene nanosheets to form a good interfacial bond with the CNT / ANF layer, and can perform effective stress transfer during the stress process, further improving the mechanical properties of the composite film.
[0026] In the present invention, CNT-reinforced ANF is independently used as a flexible substrate to provide mechanical support for the composite film; using an interface engineering strategy to assemble the CNT / ANF aqueous dispersion and the PMXene nanosheets, the modified PMXene nanosheets can form a good interfacial bond with the CNT / ANF layer, and can perform effective stress transfer during the stress process, further improving the mechanical properties of the composite film; the composite film has excellent electromagnetic shielding performance, environmental stability and mechanical properties, and has broad application prospects in the fields of electromagnetic shielding, sensing, electrothermal de-icing, etc.
[0027] Example 1 This Example 1 provides a preparation method of a PMXene-CNT / ANF electromagnetic shielding composite film, comprising the following steps: Step 1: Add 1.5 g of KOH and 1.0 g of PPTA to 499.0 g of DMSO in sequence, and continuously stir for 7 d to prepare an ANF / DMSO dispersion.
[0028] Step 2: Prepare a CNT aqueous dispersion; use the CNT aqueous dispersion to perform a proton reduction treatment on the ANF / DMSO dispersion to prepare a CNT / ANF aqueous dispersion; wherein, the mass concentration of the CNT aqueous dispersion is 0.1%, and the mass fraction of CNT compared to ANF during the proton reduction process is 1 wt.%.
[0029] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF, and stir thoroughly until completely dissolved to obtain a fluorine-containing solution. Then slowly add 3 g of the MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system. Subsequently, wash the post-reaction mixed system until neutral, then let it stand and swell at 4 °C for 24 h. Finally, perform vortex oscillation to obtain MXene nanosheets; among them, the vortex rotation speed is 4000 rpm, and the oscillation time is 120 min.
[0030] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 3500 rpm for 15 min, collect the upper dispersion liquid to obtain a first-gradient product. Centrifuge the first-gradient product at a centrifugal speed of 3000 rpm for 30 min, collect the lower precipitate to obtain a second-gradient product. Centrifuge the second-gradient product at a centrifugal speed of 2000 rpm for 60 min, collect the precipitate and disperse it in water to obtain large-scale MXene nanosheets; among them, the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0031] Step 5: Add the dopamine solution to the large-scale MXene nanosheets and stir and react at room temperature for 60 min to obtain PMXene nanosheets; among them, the mass fraction of the large-scale MXene nanosheets is 0.2%, and the mass fraction of dopamine compared to the large-scale MXene nanosheets is 4 wt.%.
[0032] Step 6: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chain and interlayer interaction of ANF to obtain an enhanced CNT / ANF gel. Based on the hydrogen bond interaction between the PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel; among them, the mass fraction of the PMXene nanosheets compared to the enhanced CNT / ANF gel is 75 wt.%.
[0033] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at a temperature of 105 °C for 15 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0034] Performance testing: Perform performance testing on the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 1 of this embodiment, and the test results are as follows: The tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film is 257.8 MPa, and the toughness is 29.4 MJ·m -3, the conductivity is 3548.8 S·cm -1 , the electromagnetic shielding effectiveness is 55.1 dB; under an applied voltage of 2.5 V, the surface temperature of the composite film can reach 150.4 °C, showing excellent mechanical properties, electromagnetic shielding properties and Joule heat performance.
[0035] As shown in the Figure 1 appendix, Figure 1 the cross-sectional SEM images of large-scale MXene nanosheets and PMXene nanosheets in Example 1 are given; among them, Figure 1 (a) is the cross-sectional SEM image of large-scale MXene nanosheets, Figure 1 (b) is the cross-sectional SEM image of PMXene nanosheets; it can be seen from the Figure 1 appendix that the cross-section of large-scale MXene nanosheets is irregularly layered, and there are large gaps between layers, resulting in a loose structure; while after being modified by PDA, the interlayer defects of PMXene nanosheets are significantly reduced. More importantly, the PMXene nanosheet layers show obvious orientation, and the density and regularity between layers are also significantly increased; the above shows that dopamine modification can effectively improve the distribution structure of MXene nanosheet layers, and may also affect the chemical structure and physical properties of the film.
[0036] As shown in the Figure 2 appendix, Figure 2 the optical photos of the aqueous dispersions of large-scale MXene nanosheets and PMXene nanosheets before and after being placed at room temperature for 45 days are given; among them, the left attached figure in the Figure 2 appendix is the optical photo of the aqueous dispersions of large-scale MXene nanosheets and PMXene nanosheets at room temperature; the right attached figure in the Figure 2 appendix is the optical photo of the aqueous dispersions of large-scale MXene nanosheets and PMXene nanosheets after being placed at room temperature for 45 days; it can be seen from the Figure 2 appendix that the color of large-scale MXene nanosheets turns grayish white after being placed for 45 days, and the color of the optical photo of the aqueous dispersion of PMXene nanosheets hardly changes after being placed at room temperature for 45 days; the reason is the result of the oxidation of MXene nanosheets after long-term contact with water and oxygen.
[0037] As shown in the Figure 3 , 4 appendix, Figure 3 the photos of large-scale MXene nanosheets and PMXene nanosheet films in Example 1 placed naked in the air are given, and the Figure 4 appendix gives the surface resistance change curve of large-scale MXene nanosheets and PMXene nanosheets in Example 1 during the 45-day placement; it can be seen from the Figure 3-4It can be seen that the surface resistance of the modified PMXene film only slightly increases during placement, while the surface resistance of the pure MXene film significantly increases with the increase of the placement time, indicating that PDA modification significantly increases the antioxidant property of MXene nanosheets.
[0038] As shown in the Figure 5 appendix, the Figure 5 electromagnetic shielding performance curve graphs of the PMXene-CNT / ANF electromagnetic shielding composite film in Example 1 before and after being placed for 45 days are given; it can be seen from the Figure 5 appendix that after being placed for 45 days, the electromagnetic shielding performance only slightly decreases, indicating that dopamine modification is beneficial to the stability and long-term effectiveness of the conductivity and electromagnetic shielding performance of the composite film.
[0039] Example 2 This Example 2 provides a preparation method of a PMXene-CNT / ANF electromagnetic shielding composite film, including the following steps: Step 1: Add 1.5 g of KOH and 1.0 g of PPTA into 499.0 g of DMSO in sequence, and continuously stir for 7 d to prepare an ANF / DMSO dispersion liquid.
[0040] Step 2: Prepare a CNT aqueous dispersion liquid; use the CNT aqueous dispersion liquid to perform a proton reduction treatment on the ANF / DMSO dispersion liquid to prepare a CNT / ANF aqueous dispersion liquid; wherein, the mass concentration of the CNT aqueous dispersion liquid is 0.4%, and the mass fraction of CNT compared to ANF during the proton reduction process is 3 wt.%.
[0041] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF and stir until completely dissolved to obtain a fluorine-containing solution; then slowly add 3 g of MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system; subsequently, wash the post-reaction mixed system to neutrality, then let it stand and swell at 4 °C for 12 h; finally, perform vortex oscillation to obtain MXene nanosheets; wherein, the vortex rotation speed is 3000 rpm and the oscillation time is 60 min.
[0042] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 3000 rpm for 10 min, collect the upper-layer dispersion liquid to obtain a first-gradient product; centrifuge the first-gradient product at a centrifugal speed of 3500 rpm for 10 min, collect the lower-layer precipitate to obtain a second-gradient product; centrifuge the second-gradient product at a centrifugal speed of 3500 rpm for 30 min, collect the precipitate and disperse it with water to obtain large-scale MXene nanosheets; wherein, the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0043] Step 5: Add the dopamine solution to the large-scale MXene nanosheets and stir at room temperature for 20 min to obtain PMXene nanosheets; wherein, the mass fraction of the large-scale MXene nanosheets is 0.05%, and the mass fraction of dopamine relative to the large-scale MXene nanosheets is 0.5 wt.%.
[0044] Step 6: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chains and interlayer interactions of ANF to obtain an enhanced CNT / ANF gel; based on the hydrogen bond interaction between the PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel; wherein, the mass fraction of the PMXene nanosheets relative to the enhanced CNT / ANF gel is 10 wt.%.
[0045] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at 80 °C for 30 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0046] Performance detection: Perform performance detection on the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 2, and the detection results are as follows: the tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film is 366.8 MPa, the toughness is 69.3 MJ·m -3 , and the conductivity is 1942.4 S·cm -1 , the electromagnetic shielding effectiveness is 32.6 dB, and under an external voltage of 2.5 V, the surface temperature of the composite film can reach 50.1 °C, showing excellent mechanical properties, electromagnetic shielding properties, and Joule heat properties.
[0047] Example 3 This Example 3 provides a method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film, including the following steps: Step 1: Add 1.5 g of KOH and 1.0 g of PPTA to 499.0 g of DMSO in sequence and continuously stir for 7 d to prepare an ANF / DMSO dispersion.
[0048] Step 2: Prepare a CNT aqueous dispersion; use the CNT aqueous dispersion to perform a protonation treatment on the ANF / DMSO dispersion to prepare a CNT / ANF aqueous dispersion; wherein, the mass concentration of the CNT aqueous dispersion is 0.2%, and the mass fraction of CNT relative to ANF during the protonation process is 0.5 wt.%.
[0049] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF, and stir thoroughly until completely dissolved to obtain a fluorine-containing solution; then slowly add 3 g of the MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system; subsequently, wash the post-reaction mixed system until neutral, and then let it stand and swell at 4 °C for 36 h; finally, perform vortex oscillation to obtain MXene nanosheets; among them, the vortex rotation speed is 2000 rpm, and the oscillation time is 120 min.
[0050] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 2000 rpm for 30 min, collect the upper-layer dispersion liquid to obtain a first-gradient product; centrifuge the first-gradient product at a centrifugal speed of 5000 rpm for 15 min, collect the lower-layer precipitate to obtain a second-gradient product; centrifuge the second-gradient product at a centrifugal speed of 2500 rpm for 10 min, collect the precipitate and disperse it with water to obtain large-scale MXene nanosheets; among them, the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0051] Step 5: Add the dopamine solution to the large-scale MXene nanosheets and stir and react at room temperature for 40 min to obtain PMXene nanosheets; among them, the mass fraction of the large-scale MXene nanosheets is 0.15%, and the mass fraction of dopamine compared to the large-scale MXene nanosheets is 8 wt.%.
[0052] Step 6: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chains and interlayer interactions of ANF to obtain an enhanced CNT / ANF gel; based on the hydrogen bond interaction between the PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel; among them, the mass fraction of the PMXene nanosheets compared to the enhanced CNT / ANF gel is 35 wt.%.
[0053] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at a temperature of 120 °C for 20 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0054] Performance detection: The performance of the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 3 was tested, and the test results were as follows: the tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film was 302.1 MPa, the toughness was 42.7 MJ·m -3 , the conductivity was 2567.4 S·cm -1 , the electromagnetic shielding effectiveness was 45.9 dB. Under an applied voltage of 2.5 V, the surface temperature of the composite film could reach 83.6 °C, showing excellent mechanical properties, electromagnetic shielding properties, and Joule heat performance.
[0055] Example 4 Example 4 provides a method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film, which includes the following steps: Step 1: Add 1.5 g of KOH and 1.0 g of PPTA to 499.0 g of DMSO in sequence, and continuously stir for 7 days to prepare an ANF / DMSO dispersion.
[0056] Step 2: Prepare a CNT aqueous dispersion; use the CNT aqueous dispersion to perform a proton reduction treatment on the ANF / DMSO dispersion to obtain a CNT / ANF aqueous dispersion; wherein, the mass concentration of the CNT aqueous dispersion is 0.1%, and the mass fraction of CNT compared to ANF during the proton reduction process is 3 wt.%.
[0057] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF and stir until completely dissolved to obtain a fluorine-containing solution; then slowly add 3 g of MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a reaction mixture system; subsequently, wash the reaction mixture system to neutrality, then let it stand and swell at 4 °C for 24 h; finally, perform vortex oscillation to obtain MXene nanosheets; wherein, the vortex rotation speed is 4000 rpm and the oscillation time is 60 min.
[0058] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 2500 rpm for 25 min, collect the upper-layer dispersion to obtain a first-gradient product; centrifuge the first-gradient product at a centrifugal speed of 4000 rpm for 10 min, collect the lower-layer precipitate to obtain a second-gradient product; centrifuge the second-gradient product at a centrifugal speed of 2500 rpm for 10 min, collect the precipitate and disperse it in water to obtain large-scale MXene nanosheets; wherein, the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0059] Step 5: Add the dopamine solution to the large-scale MXene nanosheets and stir at room temperature for 60 min to obtain PMXene nanosheets; among them, the mass fraction of the large-scale MXene nanosheets is 0.05%, and the mass fraction of dopamine relative to the large-scale MXene nanosheets is 2 wt.%.
[0060] Step 6: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the intermolecular chain and interlayer interaction of ANF to obtain an enhanced CNT / ANF gel; based on the hydrogen bond interaction between the PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel; among them, the mass fraction of the PMXene nanosheets relative to the enhanced CNT / ANF gel is 5 wt.%.
[0061] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at 90 °C for 10 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0062] Performance detection: Perform performance detection on the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 4, and the detection results are as follows: the tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film is 310.9 MPa, the toughness is 69.3 MJ·m -3 , the conductivity is 1192.3 S·cm -1 , the electromagnetic shielding effectiveness is 23.9 dB, and under an applied voltage of 2.5 V, the surface temperature of the composite film can reach 39.6 °C, showing excellent mechanical properties, electromagnetic shielding properties, and Joule heat properties.
[0063] Example 5 This Example 5 provides a preparation method of a PMXene-CNT / ANF electromagnetic shielding composite film, including the following steps: Step 1: Add 1.5 g of KOH and 1.0 g of PPTA to 499.0 g of DMSO in sequence and continuously stir for 7 d to prepare an ANF / DMSO dispersion.
[0064] Step 2: Prepare a CNT aqueous dispersion; perform a protonation treatment on the ANF / DMSO dispersion with the CNT aqueous dispersion to prepare a CNT / ANF aqueous dispersion; among them, the mass concentration of the CNT aqueous dispersion is 0.3%, and the mass fraction of CNT relative to ANF during the protonation process is 2 wt.%.
[0065] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF, and stir thoroughly until completely dissolved to obtain a fluorine-containing solution. Then, slowly add 3 g of the MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system. Subsequently, wash the post-reaction mixed system until neutral, and then let it stand and swell at 4 °C for 30 h. Finally, perform vortex oscillation to obtain MXene nanosheets; among them, the vortex rotation speed is 3500 rpm, and the oscillation time is 90 min.
[0066] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 2500 rpm for 20 min, collect the upper-layer dispersion liquid to obtain a first-gradient product. Centrifuge the first-gradient product at a centrifugal speed of 4000 rpm for 20 min, collect the lower-layer precipitate to obtain a second-gradient product. Centrifuge the second-gradient product at a centrifugal speed of 3000 rpm for 20 min, collect the precipitate and disperse it with water to obtain large-scale MXene nanosheets; among them, the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0067] Step 5: Add the dopamine solution to the large-scale MXene nanosheets, and stir and react at room temperature for 30 min to obtain PMXene nanosheets; among them, the mass fraction of the large-scale MXene nanosheets is 0.1%, and the mass fraction of dopamine relative to the large-scale MXene nanosheets is 10 wt.%.
[0068] Step 6: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion liquid to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chains and intermolecular interactions of ANF to obtain an enhanced CNT / ANF gel. Based on the hydrogen bond interaction between the PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel; among them, the mass fraction of the PMXene nanosheets relative to the enhanced CNT / ANF gel is 55 wt.%.
[0069] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at a temperature of 110 °C for 10 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0070] Performance detection: Perform performance detection on the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 5 of this embodiment, and the detection results are as follows: the tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film is 278.6 MPa, and the toughness is 34.6 MJ·m-3 , with a conductivity of 3025.4 S·cm -1 , the electromagnetic shielding effectiveness is 49.3 dB. Under an applied voltage of 2.5 V, the surface temperature of the composite film can reach 114.3 °C, demonstrating excellent mechanical properties, electromagnetic shielding performance, and Joule heating performance.
[0071] Example 6 This Example 6 provides a method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film, including the following steps: Step 1: Add 1.5 g of KOH and 1.0 g of PPTA to 499.0 g of DMSO in sequence, and continuously stir for 7 days to prepare an ANF / DMSO dispersion.
[0072] Step 2: Prepare a CNT aqueous dispersion; use the CNT aqueous dispersion to perform a proton reduction treatment on the ANF / DMSO dispersion to prepare a CNT / ANF aqueous dispersion; wherein, the mass concentration of the CNT aqueous dispersion is 0.3%, and the mass fraction of CNT compared to ANF during the proton reduction process is 1 wt.%.
[0073] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF and stir until completely dissolved to obtain a fluorine-containing solution; then slowly add 3 g of MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system; subsequently, wash the post-reaction mixed system to neutral, then let it stand and swell at 4 °C for 24 h; finally, perform vortex oscillation to obtain MXene nanosheets; wherein, the vortex rotation speed is 4000 rpm and the oscillation time is 90 min.
[0074] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 3500 rpm for 15 min, collect the upper-layer dispersion to obtain a first-gradient product; centrifuge the first-gradient product at a centrifugal speed of 3000 rpm for 30 min, collect the lower-layer precipitate to obtain a second-gradient product; centrifuge the second-gradient product at a centrifugal speed of 2500 rpm for 15 min, collect the precipitate and disperse it in water to obtain large-scale MXene nanosheets; wherein, the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0075] Step 5: Add the dopamine solution to the large-scale MXene nanosheets and stir and react at room temperature for 60 min to obtain PMXene nanosheets; wherein, the mass fraction of the large-scale MXene nanosheets is 0.2%, and the mass fraction of dopamine compared to the large-scale MXene nanosheets is 6 wt.%.
[0076] Step 6: Perform vacuum-assisted suction filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chains and intermolecular interactions of ANF to obtain an enhanced CNT / ANF gel; based on the hydrogen bond interaction between PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel; wherein, the mass fraction of PMXene nanosheets compared to the enhanced CNT / ANF gel is 20 wt.%.
[0077] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at a temperature of 110 °C for 30 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0078] Performance testing: Perform performance testing on the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 6. The test results are as follows: the tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film is 340.3 MPa, the toughness is 60.1 MJ·m -3 , the conductivity is 2269.9 S·cm -1 , the electromagnetic shielding effectiveness is 39.6 dB. Under an applied voltage of 2.5 V, the surface temperature of the composite film can reach 62.3 °C, showing excellent mechanical properties, electromagnetic shielding properties, and Joule heat properties.
[0079] Example 7 This Example 7 provides a method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film, including the following steps: Step 1: Sequentially add 1.5 g of KOH and 1.0 g of PPTA to 499.0 g of DMSO, and continuously stir for 7 d to prepare an ANF / DMSO dispersion.
[0080] Step 2: Prepare a CNT aqueous dispersion; perform a reprotonation treatment on the ANF / DMSO dispersion using the CNT aqueous dispersion to prepare a CNT / ANF aqueous dispersion; wherein, the mass concentration of the CNT aqueous dispersion is 0.4%, and the mass fraction of CNT compared to ANF during the reprotonation process is 0.5 wt.%.
[0081] Step 3: Prepare 60 mL of 9 mol / L hydrochloric acid solution, add 4.8 g of LiF, and stir well until completely dissolved to obtain a fluorine-containing solution. Then slowly add 3 g of the MAX precursor to the fluorine-containing solution, and stir and etch at 35 °C for 48 h to obtain a post-reaction mixed system. Subsequently, wash the post-reaction mixed system until neutral, and then let it stand and swell at 4 °C for 12 h. Finally, perform vortex oscillation to obtain MXene nanosheets, where the vortex rotation speed is 3000 rpm and the oscillation time is 120 min.
[0082] Step 4: Centrifuge the MXene nanosheets at a centrifugal speed of 3000 rpm for 25 min, collect the upper dispersion liquid to obtain a first-gradient product. Centrifuge the first-gradient product at a centrifugal speed of 4000 rpm for 20 min, collect the lower precipitate to obtain a second-gradient product. Centrifuge the second-gradient product at a centrifugal speed of 2000 rpm for 30 min, collect the precipitate and disperse it with water to obtain large-scale MXene nanosheets, where the diameter size of the large-scale MXene nanosheets is greater than 2 μm.
[0083] Step 5: Add the dopamine solution to the large-scale MXene nanosheets and stir and react at room temperature for 40 min to obtain PMXene nanosheets. Among them, the mass fraction of the large-scale MXene nanosheets is 0.15%, and the mass fraction of dopamine compared to the large-scale MXene nanosheets is 2 wt.%.
[0084] Step 6: Perform vacuum-assisted filtration on the CNT / ANF aqueous dispersion to enable the layer-by-layer assembly of CNT / ANF, and use CNT to regulate the molecular chains and intermolecular interactions of ANF to obtain an enhanced CNT / ANF gel. Based on the hydrogen bond interaction between the PMXene nanosheets and ANF and CNT, stack the PMXene nanosheets on the surface of the enhanced CNT / ANF gel for sealing filtration to obtain a PMXene-CNT / ANF composite gel. Among them, the mass fraction of the PMXene nanosheets compared to the enhanced CNT / ANF gel is 35 wt.%.
[0085] Step 7: Vacuum-dry the PMXene-CNT / ANF composite gel at a temperature of 105 °C for 10 min to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
[0086] Performance detection: Perform performance detection on the PMXene-CNT / ANF electromagnetic shielding composite film prepared in Example 7 of this embodiment. The detection results are as follows: The tensile strength of the PMXene-CNT / ANF electromagnetic shielding composite film is 302.1 MPa, and the toughness is 42.7 MJ·m -3, the conductivity is 2567.4 S·cm -1 , the electromagnetic shielding effectiveness is 45.9 dB. Under an external voltage of 2.5 V, the surface temperature of the composite film can reach 83.6 °C, demonstrating excellent mechanical properties, electromagnetic shielding properties, and Joule heating properties.
[0087] The preparation method of the PMXene-CNT / ANF electromagnetic shielding composite film described in the present invention screens out large-size MXene nanosheets through selective etching and gradient centrifugation, which is beneficial to improving the conductivity of the MXene nanosheet film; and modifies the MXene nanosheets to optimize their surface and interfacial interactions, further enhancing the conductivity on the basis of improving the antioxidant property; among them, using PDA modification endows MXene with antioxidant property and regulates the interlayer interaction and micro-orientation of the MXene layer, further enhancing the conductivity of the MXene layer; in addition, ANF reinforced by CNT independently serves as a flexible substrate to provide mechanical support for the composite film, enabling the composite film to have excellent electromagnetic shielding properties, environmental stability, and mechanical properties, and having broad application prospects in the fields of electromagnetic shielding, sensing, electrothermal de-icing, etc.
[0088] In the present invention, by introducing PDA, the surface properties of MXene nanosheets are changed, enhancing the environmental stability of the MXene sheets; secondly, PDA can optimize the interlayer interaction of the MXene film, improving the arrangement orientation and compactness between the layers of the MXene film, greatly eliminating the interlayer defects, enhancing the electron transport efficiency, and thus improving the electromagnetic shielding property; using interface engineering technology combined with a two-step assembly strategy, the CNT / ANF aqueous dispersion and PMXene nanosheets are assembled. The modified PMXene nanosheets can form a good interfacial bond with the CNT / ANF layer and can effectively transfer stress during the stress process, further enhancing the mechanical properties of the composite film; the PMXene-CNT / ANF electromagnetic shielding composite film prepared by the present invention has excellent mechanical properties, environmental stability, electromagnetic interference shielding, and Joule heating properties, and has broad application prospects in flexible electronics, defense equipment, and polar exploration equipment.
[0089] The above embodiments are only one of the implementation manners capable of implementing the technical solution of the present invention. The scope of protection required by the present invention is not limited only by this embodiment, but also includes any changes, substitutions, and other implementation manners that are easily conceivable by any person skilled in the art within the technical scope disclosed by the present invention.
Claims
1. A method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film, characterized in that: include: Using the carbon nanotube aqueous dispersion to perform protonation treatment on the ANF / DMSO dispersion to obtain a CNT / ANF aqueous dispersion; Using gradient centrifugation technique, Ti3C2T x The MXene nanosheets are centrifuged to obtain large-scale MXene nanosheets; wherein the diameter of the large-scale MXene nanosheets is greater than 2 μm; Large-scale MXene nanosheets were modified with dopamine to obtain PMXene nanosheets; Assembling CNT / ANF aqueous dispersion and PMXene nanosheets to obtain PMXene-CNT / ANF composite gel; The PMXene-CNT / ANF composite gel is vacuum dried to obtain a PMXene-CNT / ANF electromagnetic shielding composite film.
2. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 1, characterized in that: In the process of protonating the ANF / DMSO dispersion using the carbon nanotube aqueous dispersion to obtain the CNT / ANF aqueous dispersion, the mass concentration of the carbon nanotube aqueous dispersion is 0.1%-0.4%, and the mass fraction of the carbon nanotubes compared to ANF is 0.5wt.%-3wt.%.
3. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 1, characterized in that: Using gradient centrifugation technique, Ti3C2T x The process of centrifuging MXene nanosheets to obtain large-scale MXene nanosheets includes: Under the first preset centrifugal condition, Ti3C2T x The MXene nanosheets are centrifuged, and the upper dispersion is collected to obtain the first gradient product; Under the second preset centrifugation condition, the first gradient product is centrifuged, and the lower layer of precipitate is collected to obtain a second gradient product; Under the third preset centrifugal condition, the second product is centrifuged, the precipitate is collected and dispersed in water to obtain large-scale MXene nanosheets.
4. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 1, characterized in that: The first preset centrifugal condition includes: a centrifugal speed of 2000-3500rpm, and a centrifugal time of 10-30min; the second preset centrifugal condition includes: a centrifugal speed of 3000-3500rpm, and a centrifugal time of 10-30min; the third preset centrifugal condition includes: a centrifugal speed of 2000-4000rpm, and a centrifugal time of 10-30min.
5. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 1, characterized in that: In the process of modifying large-scale MXene nanosheets with dopamine to obtain PMXene nanosheets, the mass fraction of large-scale MXene nanosheets is 0.05%-0.2%, and the mass fraction of dopamine compared to large-scale MXene nanosheets is 0.5wt.%-10wt.%.
6. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 1, characterized in that: The process of assembling CNT / ANF aqueous dispersion and PMXene nanosheets to obtain PMXene-CNT / ANF composite gel includes: The CNT / ANF aqueous dispersion is vacuum-assisted filtered to assemble the CNT / ANF layer by layer, and the CNT is used to regulate the ANF molecular chain and the interlayer interaction to obtain an enhanced CNT / ANF gel; The PMXene nanosheets were superimposed on the surface of the enhanced CNT / ANF gel for sealing and filtration to obtain the PMXene-CNT / ANF composite gel.
7. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 6, characterized in that: The mass fraction of PMXene nanosheets compared to the reinforced CNT / ANF gel is 5wt.%-75wt.%.
8. The method for preparing a PMXene-CNT / ANF electromagnetic shielding composite film according to claim 1, characterized in that: In the process of vacuum drying the PMXene-CNT / ANF composite gel to obtain the PMXene-CNT / ANF electromagnetic shielding composite film, the vacuum drying temperature is 80-120° C. and the time is 10-30 min.
9. A PMXene-CNT / ANF electromagnetic shielding composite film, characterized in that: The film is prepared by the method for preparing the PMXene-CNT / ANF electromagnetic shielding composite film as described in any one of claims 1 to 8.
10. The use of the PMXene-CNT / ANF electromagnetic shielding composite film according to claim 9, characterized in that: Application of PMXene-CNT / ANF electromagnetic shielding composite film as electromagnetic interference shielding material in electronic equipment.