Absorption dominated high-performance electromagnetic interference shielding epoxy/functionalized reduced graphene oxide/Ni-chains microcellular foam with asymmetric conductive structure

In order to develop high-performance electromagnetic interference (EMI) shielding materials for the increasingly complex electromagnetic (EM) environment, in this work, the epoxy/functionalized reduced graphene oxide/Ni-chains microcellular foams with asymmetrical conductive structure (a-EP/f-RGO/Ni-chains microcellular foams) are prepared through a thermal compressing method and then followed by a supercritical carbon dioxide (scCO₂) foaming process. Benefiting from the construction of asymmetrical conductive structure which is assembled from the f-RGO-rich layer and Ni-chains-rich layer, the a-EP/f-RGO/Ni-chains microcellular foam with 5 vol% f-RGO and 5 vol% Ni-chains content exhibits better electrical conductivity of ∼10⁻¹ S/m and higher EMI shielding effectiveness (EMI SE) of 40.82 dB in X-band compared with the homogeneous conductive structured EP/f-RGO/Ni-chains (h-EP/f-RGO/Ni-chains) microcellular foam in same filler content. In addition, the maximum difference of reflection coefficient (R) up to ∼0.5 is achieved by actively regulating the EMI shielding process from reflection-absorption to absorption-reflection-reabsorption in different directions of EM wave incidence on the foams. Moreover, the compressive strength of microcellular foam is up to 24.58 MPa. Combined with excellent EMI shielding property and outstanding compressive property, the a-EP/f-RGO/Ni-chains microcellular foams prepared in this work display significant application advantages as high-performance EMI shielding materials.