Structure Design And Properties Of Polymer Based Electromagnetic Interference Shielding Composite Film

With the rapid development of electronic information and communication technology,all kinds of electronic and electrical equipment used in hospitals,military,commercial and scientific departments have increased rapidly,and the electromagnetic radiation hazards have increased significantly.Therefore,high-performance flexible polymer electromagnetic interference shielding composites have become one of the most effective ways to reduce electromagnetic wave pollution.Due to the conductive network formed by the filler in the matrix,the shielding efficiency of the conductive polymer electromagnetic interference shielding composites can be significantly improved.The research work of this thesis mainly includes the following three parts:（1）A commercial polyethylene terephthalate（PET）film was coated with a high conductivity Ti₃C₂T_xMXene,Ag NWs and conductive polymer PEDOT:PSS composite conductive ink by a simple drip coating process to develop a flexible and multifunctional MXene/Ag NWs/PEDOT:PSS conductive composite film.Without the action of other binders,the obtained MXene/Ag NWs/PEDOT:PSS-PET can achieve certain shape bending and distortion.Combined with the advantages of Ag NWs and MXene,the film shows excellent electrical conductivity（3900 S/m）at a thickness of 10μm and extraordinary electromagnetic shielding performance(EMI SE=31.5 d B,SSE/t=10161.29 d B cm²g^-1).The high conductivity and local surface plasmonic resonance（LSPR）effect of MXene and Ag NWs make the films have good Joule heating properties and photothermal conversion effect under low pressure driving and simulated illumination conditions.In addition,MXene/Ag NWs/PEDOT:PSS-PET has excellent hydrophobicity before and after surface modification of trimethoxy（1H,1H,2H,2H-heptafluorodecyl）silanes（TMHFS）.Our work provides an important reference for the development of multifunctional EMI shielding membranes in complex environments.（2）Hydrothermal synthesis of multi-interface cattail-like Mo S₂@Si C hybrids for Electromagnetic interference shielding impedance matching layer.An asymmetric Mo S₂@Si C/MXene hybrid film was prepared by vacuum-assisted filtration.The effects of different content of Mo S₂@Si C hybrids on thermal conductivity,Electromagnetic interference shielding properties,and electromagnetic parameters of Mo S₂@Si C/MXene hybrid films were studied.With the increase of Mo S₂@Si C content,the thermal conductivity of Mo S₂@Si C/MXene through-plane measured by hot-wire method is 0.31 W/m K,which is100.45%higher than that of pure CNF film.EMI SE is more than 38.8 d B,which can shield more than 99.987%of electromagnetic waves,meaning that the transmission rate of the incident electromagnetic wave is only 0.013%.In addition,the R coefficient is effectively reduced by introducing Mo S₂@Si C.（3）The Mo S₂@Si C-Fe₃O₄/CNT/MXene composites were prepared by the combination of step hot pressing and freeze-drying,the introduction of Fe₃O₄magnetic particles,and the conductivity gradient of CNT and MXene.After changing the mass ratio of Mo S₂@Si C and Fe₃O₄,10Mo S₂@Si C-0Fe₃O₄/CNT/MXene foam,5Mo S₂@Si C-5Fe₃O₄/CNT/MXene foam and 0Mo S₂@Si C-10Fe₃O₄/CNT/MXene foam composites have EMI SE_Tof 36.1d B,34.1d B,and 35.8 d B,respectively,and SE_Rof 3.7 d B,1.5 d B,and 2.8 d B,respectively.SE_A/SE_T（%）values were 89.7%,95.6%and 92.1%,respectively.After constructing the foam structure,5Mo S₂@Si C-5Fe₃O₄/CNT/MXene foam drops from R=0.71 at film structure to 0.21 at foam structure.In addition,electromagnetic waves incident from different directions,the electromagnetic interference shielding effectiveness of Mo S₂@Si C-Fe₃O₄/CNT/MXene composites is basically equal,and the R constant changes obviously.The synergistic effect of Fe₃O₄and foam structure can effectively reduce the reflection of electromagnetic waves and the secondary pollution of the electromagnetic wave to the environment.