Light-weight and flexible silicone rubber/MWCNTs/Fe3O4 nanocomposite foams for efficient electromagnetic interference shielding and microwave absorption

Light-weight and flexible methyl vinyl silicon rubber (VMQ)/multi-walled carbon nanotubes (MWCNTs)/ferriferrous oxide (Fe3O4) nanocomposite foams with efficient electromagnetic interference (EMI) shielding performance were firstly prepared by supercritical carbon dioxide (Sc-CO2) foaming process. The microwave-absorbing ability of the VMQ/MWCNTs/Fe3O4 foams has been greatly improved owing to the existence of cellular structure and magnetic Fe3O4 nanoparticles, thus significantly reducing the secondary EM wave pollution caused by reflection. These nanocomposite foams with density of ∼0.48 g−1 cm3 exhibited an EMI shielding effectiveness (SE) of 27.5 dB, and its average absorption ratio can reach up to 64% in the frequency range of 8.2–12.4 GHz. Such highly conductive (∼14.6 S/m) and specific EMI SE (∼72 dB·g−1cm3) can be obtained with filler loading of 1.78 vol%. Moreover, the flexible silicone rubber foams present excellent EMI shielding stability after repeated bending. The shielding mechanism of the composite foams was also discussed, and the results show that the main shielding mechanism of the foams was absorption with the addition of Fe3O4 nanoparticles. Furthermore, the foams exhibits excellent superparamagnetic and thermal properties, the maximum onset decomposition temperature can reach 467 °C. In view of the uncomplicated, low-cost and environmental protection preparation procedure, the light-weight, flexible, magnetic and highly conductive silicone rubber nanocomposite foams are expected to be used in lightweight and flexible electromagnetic shielding materials.