Flexible Polyimide Foams Coated with Graphene Nanoplatelets/Fe₃O₄ for Absorption-Dominated Electromagnetic Interference Shielding, Broad-Band Microwave Absorption, and Sensor Applications

With the rapid development of 5G communication technologies,thehigh-performance electromagnetic interference (EMI) shielding materialswith less secondary reflection for electronic devices have becomean urgent demand in recent years. In this study, flexible open-cellpolyimide (PI) foams containing graphene nanoplatelets (GN)/Fe3O4 coatings for absorption-dominated EMI shieldingwere fabricated. The result shows that the EMI shielding efficient(EMI SE) of composite foam PI/GN/Fe3O4 (PF/GN/Fe3O4) can achieve 60.6 dB with a thickness of 6.0mm along with an absorption coefficient (A) of 0.4-0.6,indicating excellent EMI shielding and a low reflection property.Furthermore, the optimal reflection loss (R (L)) of PF/GN/Fe3O4 with a low GN loading canbe up to -35 dB at 5.0 mm and less than or equal to -10dB in the whole X-band with a thickness of & GE;4.5 mm. In addition,the prepared composite foam PI/GN (PF/GN) exhibits good electricalconductivity of 2.5 x 10(3) S/m and sensing stability.Notably, this research systematically studied the application performanceof the composite foam in EMI shielding, electromagnetic wave (EW)absorption, and sensing monitoring. The prepared composite foam canbe applied as "Green" EMI shielding materials for flexibleelectronic devices due to the remarkable EW absorption properties.