Study On Fabrication And Electromagnetic Shieding Properties Of Multi-Layered Graphene Nanocomposites

With the development of miniaturization and high frequency of electronic products,the accompanying electromagnetic pollution is seriously affecting the normal operation of nearby electronic equipment and human health.The use of electromagnetic interference(EMI)shielding materials has become a common method to tackle this problem.Compared to traditional metal-based electromagnetic shielding materials,conductive polymer composites(CPCs)have been viewed as advanced candidates for EMI shielding due to their advantages of good corrosion resistance,processing advantages,low density,and adjustable performance.However,conventional CPCs usually require high filler content or a large shielding thickness to achieve desired EMI shielding effectiveness(EMI SE),which limits their practical applications in the aerospace sector and communication devices with highly integrated circuits to a large extent and cannot satisfy the growing narrow space for electronic packing.The construction of the multi-layered structure is conducive to form an "absorption-reflection-reabsorption" propagation process,which can effectively increase internal reflection and scattering,and thus obtaining high EMI SE at low filler content and small size.Therefore,in this work,we carried out a systematic study on the design of CPCs with layered structure and its specific influence on EMI SE.The main contents are as follows:(1)By employing graphene nanosheets(GNSs)that providing dielectric loss and Fe3O4 that providing magnetic loss as fillers to fabricate GNSs-Fe3O4/Cyanate ester(CE)composites with layered structure and homogeneous structure via facile solution mixing and subsequently hot-pressing process.And the EMI shielding performance of multi-layered structure is compared with that of homogeneous structure.The corresponding results showed that the composites with multi-layered structure exhibited higher electrical conductivity and EMI SE than that of the homogeneous structure under the same filler loading and thickness.For instance,multi-layered structure composite possessed the EMI SE value of 45.7 dB,higher than that of the homogeneous structure(39.8 dB)at 5 wt%GNSs content and the15 wt%Fe3O4 content.(2)Owing to the specific relationship between the number of layers and EMI SE is still unclear in the multi-layered structure composites.Therefore,GNSs and Fe3O4 were selected as fillers,Poly(vinylidene fluoride)(PVDF)with good flexibility and excellent film formation properties was used as matrix.Multi-layered CPCs with the same filler content and thickness,but different numbers of layers(three-layer structure(T type)and five-layer structure(F type))were constructed by layer-by-layer coating.The resultant composites were investigated,and the results showed that more multi-layered structure was beneficial for enhancing the EMI SE of CPCs.This work laid the foundation for the further development of multi-layered EMI shielding composites.