Asymmetric magnetic-electric dual-functional composite foams for ultra-efficient electromagnetic interference shielding with unprecedented low reflection

Abstract

• Magnetic-electric dual-functional network is constructed in TPU by Fe 3 O 4 @rGO and CNT via scCO 2 foaming. • TPU/CNT/Fe 3 O 4 @rGO composite foam exhibits high EM wave absorption property with an RL min of -46.8 dB. • EMI shielding and EM wave absorption are further improved by introducing an Ag reflection layer. • Asymmetric TPU/CNT/Fe 3 O 4 @rGO/Ag composites possess a high EMI SE of 89.2 dB and the lowest reflection of 0.001. Asymmetric composite foams comprised of iron oxide decorated reduced graphene oxide (Fe 3 O 4 @rGO)/carbon nanotube (CNT)/thermoplastic polyurethane (TPU) foams and a silver layer were developed by vacuum-assisted hot-pressing and supercritical carbon dioxide (scCO 2 ) foaming. The magnetic-electric dual-functional network constructed by Fe 3 O 4 @rGO and CNT nanofillers rendered the foam excellent impedance matching and wave attenuation capability, achieving -46.8 dB reflection loss at ∼2 mm sample thickness. With the reflective silver layer, the asymmetric composite foam realized a unique “low reflection-absorption-reflection-reabsorption” EM wave depletion mechanism and reached preeminent total shielding effectiveness (SE T ) of 89.2-103.5 dB with a reflection shielding effectiveness (SE R ) of 0.24-0.83 dB. The optimized composite foam achieved a low reflectivity (R) of 0.05 (Average value) and a minimum value of 0.001, which holds the lowest record among EMI shielding materials with comparable SE. This work provides new insights into the design of high-efficiency shielding materials with ultra-low reflection features for cutting-edge EMI shielding applications.