Enhanced electromagnetic wave absorption properties integrating diverse loss mechanism of 3D porous Ni/NiO microspheres

The research and development of electromagnetic wave absorbing materials with light weight, thin thickness, powerful absorption, and wide frequency bandwidth is a long-term pursuing. Here, Ni/NiO microspheres were synthesized through hydrothermal reaction followed by thermal reduction process. The experimental results indicated that the electromagnetic parameters and electromagnetic wave absorption performance were seriously affected by the morphology, composition and loading of Ni/NiO microspheres. When the reduction temperature rose to 550 °C, Ni/NiO550 showed a special porous-microsphere structure which assembled by irregular Ni/NiO core-shell nanorods. The micro-size combination of porous and core-shell structures, the affluent surface area, sufficient NiO-Ni interface, high-concentration active sites were conducive to the impedance matching and diverse loss mechanism including conductive loss, interfacial polarization, dipole polarization, natural/exchange resonance and multiple scattering. Finally, 45 wt% porous Ni/NiO/paraffin composite exhibited high reflection loss (− 52.15 dB) and broad effective frequency bandwidth (3.22 GHz) at a thickness of 2.17 mm.