Preparation And Performance On Multifunctional Organic/Inorganic Electromagnetic Shielding Composite Membranes

Since the 21st century,with the rapid development of electronic information technology,5G and 6G communication technologies have become increasingly mature,resulting in increasingly serious electromagnetic radiation problems.Electromagnetic shielding materials with flexibility,lightweight and high performance have attracted much attention in recent years.Nanofiber membranes prepared by electrospinning have large porosity,specific surface area and nano-size effect,showing great application potential in the field of electromagnetic shielding.Nanofiber membrane was combined with conductive matrix filler to achieve ideal electromagnetic shielding effect by regulating the content and distribution of conductive filler.At the same time,it is urgent to develop multi-functional electromagnetic shielding materials that can be applied in multiple scenarios for different types of electromagnetic waves and protection requirements.In this paper,from the perspective of designing and constructing multi-functional composite electromagnetic shielding fiber membrane,it is expected that through the strategy of combining organic fiber membrane skeleton with inorganic nanomaterials,based on electrospinning technology,combined with modification methods such as modification treatment,chemical deposition method and spraying process,the multi-functional application of composite fiber membrane can be realized while giving excellent electromagnetic shielding performance.Moreover,the related mechanism is explored.This paper mainly includes the following two parts:（1）In order to realize the long-term use of outdoor all-weather electrical equipment in harsh environments and prolong its service life,the silver nanocluster structure was grown on the PAN fiber after alkali etching by electrospinning combined with surface modification and chemical deposition.After low surface energy material-stearic acid（SA）modification,the APAN-Ag-SA electromagnetic shielding fiber membrane with superhydrophobic and corrosion resistance was prepared.The composite membrane showed excellent electromagnetic shielding performance.With the extension of chemical deposition time,silver particles grew compactly on the fiber membrane,forming a perfect conductive network,and its shielding performance gradually increased.When the deposition time was 1.5 h,the conductivity of SA modified membrane was 57319.2 S cm^-1.Due to the porous structure and interfacial polarization,the electromagnetic shielding effectiveness of the composite membrane was 90.14 d B（average thickness was 31μm）,the SSE value was 44.18 d B cm³ g^-1,and the SSE/t value was 14253 d B cm² g^-1.Simultaneously,the composite membrane had good mechanical property.After 2000 times bending,the EMI SE value was 87.68 d B,only3.55%loss.The wettability was analyzed,and the water contact angle could reach156.7°,and the contact angle values were all greater than 150°in the simulated harsh environment,showing excellent superhydrophobic property.Finally,the salt spray box was used to analyze its corrosion resistance.It was found that after 40 days of long-term storage,the water contact angle was 150.6°,and EMI SE was reduced by 5.94 d B,showing the shielding stability of APAN-Ag-SA composite fiber membrane.（2）In order to realize the feasibility of wearable electromagnetic shielding skin and realize the monitoring of human physiological signals as an electronic skin,so as to provide help for the collection and upgrading of Internet of Things information.The MXenes nanosheets and Fe3O4 nanoparticles（NPs）were modified to the fiber membrane by electrospinning combined with surface modification and spraying process,and polydopamine（PDA）was used as the adhesion agent.The PPAN-M-Fe3O4 electromagnetic shielding fiber membrane was successfully prepared,which was constructed by 0D-1D-2D hierarchical structure and had pressure sensitivity.Due to its good porous structure,the magnetic loss of Fe3O4 NPs and the dielectric loss of MXene,this composite membrane（thickness of 33μm）had good electromagnetic shielding performance in the broad band（8～26.5 GHz）,with EMI SE value of 43.83 d B and SSE/t value of 9221.21 d B cm² g^-1;the fiber membrane has good mechanical property.After 2000 times bending,EMI SE was 87.68 d B,only 3.55%loss.The flexible fiber membrane was used as a piezoresistive sensor.The sensitivity was 5.53 k Pa^-1 and the response time is 62.2 ms in the pressure range（0～2.5 k Pa）.It had good durability and could withstand more than 2500 pressure cycles.Simultaneously,it could not only detect strong human signals such as knee flexion,but also accurately monitored small physiological signals such as wrist pulse beating and throat vocalization.