Controllable synthesis of porous Fe3O4@ZnO sphere decorated graphene for extraordinary electromagnetic wave absorption.

For the first time, mesoporous Fe3O4@ZnO sphere decorated graphene (GN-pFe3O4@ZnO) composites with uniform size, considerable porosity, high magnetization and extraordinary electromagnetic (EM) wave absorption properties were synthesized by a simple and efficient three-step method. Structure and morphology details were characterized by X-ray diffraction, transmission electron microscopy, high-resolution electron microscopy and field-emission scanning electron microscopy. Electron microscopy images reveal that pFe3O4@ZnO spheres with obvious porous and core-shell structures are uniformly coated on both sides of the GN sheets without significant numbers of vacancies or apparent aggregation. EM wave absorption properties of epoxy containing 30 wt% GN-pFe3O4@ZnO were investigated at room temperature in the frequency region of 0.2-18 GHz. The absorption bandwidth with reflection loss (RL) values less than -10 dB is up to 11.4 GHz, and the minimal RL is almost -40 dB. The intrinsic physical and chemical properties of the materials, the synergy of Fe3O4 and ZnO, and particularly the unique multi-interfaces are fundamental to the enhancement of EM absorption properties. The as-prepared GN-pFe3O4@ZnO composites are shown to be lightweight, have strong absorption, and broad frequency bandwidth EM absorbers.