▎ 摘　　要

Recently, the three-dimensional (3D) porous cellular foam derived from poly (vinylidene fluoride) (PVDF) via a simple CO2-assisted procedure has been widely applied as electromagnetic (EM) wave absorbing materials due to its one-step preparation process and high void fraction. However, delicate control of 3D microcellular structure by decoration of dielectric/magnetic components is still virgin. Herein, the hierarchical structure of 3D PVDF foam decorated with an ultra-low content of graphene nanoplates (5.0 wt%) and Ni nanochains (2.4 wt%) was successfully fabricated. The correlation between microcellular structure, and electrical conductivity/microwave absorption was systematically investigated. After introducing the conductive and magnetic components, a strong enhancement of dielectric loss, coming from the presence of conduction loss and polarization loss of 3D network, and magnetic loss, originating from strong eddy current loss and the natural resonance, was observed. Mean-while, a high void fraction (similar to 92%) greatly optimized the impedance matching of incident waves and favored the multi-scattering. As a result, the superior microwave absorption was obtained, in which the effective absorption bandwidth (frequency with 90% microwave dissipation) can cover the whole K band (18-26.5 GHz) under the thickness of 3 mm. Overall, this work provides an ameliorated strategy for porous foams applied in microwave absorption.