Magnetic-electric module design and fabrication of high performance electromagnetic interference shielding sandwich structure melamine foam composites with ultra-low reflection.

The development of an efficient electromagnetic interference (EMI) shielding material that balances the paradoxical relationship between low thickness and ultra-low reflectivity is highly significant for mitigating secondary electromagnetic wave pollution. In this work, a sandwich structure consisting of thermoplastic composite, porous foam, and conductive film was meticulously designed, employing a modular assembly strategy. This design aims to tackle the challenge by optimally leveraging the inherent advantages of each individual layer, thereby enhancing the overall performance and functionality of the structure. The core design features a melamine foam framework impregnated with discontinuous copper/silver nanoparticles and carbonyl iron magnetic nanosheets serving as the middle layer which offers abundant pores and interfaces, contributing to dielectric and magnetic losses for electromagnetic waves. The synergistic effect between the top layer (thermoplastic polyurethane/carbonyl iron), the middle layer and the bottom layer (a conductive polyester fiber@copper@nickel) was investigated in terms of impedance matching and magnetic loss as well as reflective shielding. The composite exhibited a shielding effectiveness of 78.01 dB across the X-band (8.2-12.4 GHz) with a thickness of only 2.26 mm. A low-reflection bandwidth (R < 0.1) of 2.69 GHz was obtained which constitutes 64.04 % of the X-band. Importantly, the composite achieved a remarkably low reflectivity of 0.818 %, corresponding to a reflecting shielding effectiveness (SE) of merely 0.035 dB. A finite element analysis was conducted to elucidate the wave shielding mechanism. This research provides a dependable and straightforward approach for creating EMI composites with low thickness, ultra-low reflection, and robust shielding efficiency.