Porous NiO/Ni foam composites for improved impedance match and electromagnetic wave absorption through a simple in-situ calcination process

Light weight is a significant target for the magnetic metal-based electromagnetic wave (EMW) absorbents. Constructing foams with porous structure and low density has been proved to be a feasible way. However, the high conductivity of the metal foam will bring a poor impedance match, which hinders the EMW absorbing property. Herein, we reported a facile one-step calcination strategy for the magnetic metal foams toward improved impedance match. The NiO/Ni foam composites were obtained with NiO particles in situ grown on the surface of foams. Greatly enhanced EMW absorption performance was obtained with minimum reflection loss (RLmin) of −39.71 dB at a frequency of 13.6 GHz and a thickness of 2.0 mm. Meanwhile, the effective absorption bandwidth (EAB) could reach 5.15 GHz. The introduction of surface NiO weakens the conductivity of pure metals and the abundant pore structures of NiO as well as the inherent three-dimensional (3D) networks of metal foams further promote the multiple reflections and scattering of the EMWs. Consequently, this work provides a feasible and convenient way for the massive production of magnetic metal foams as excellent EMW absorbents.