Metallic Nanowires for Electromagnetic Interference Shielding

In this study, metallic nanowires electrodeposited onto commercially available porous alumina membranes are employed to enhance electromagnetic interference (EMI) shielding. Three samples were utilized: a commercial porous alumina membrane (Al2O3@Au), serving as the reference; an alumina membrane embedded with cobalt nanowires (Al2O3@Au@Co); and an alumina membrane with nickel/cobalt nanowires (Al2O3@Au@NiCo). Morphological analyses demonstrated uniform distribution of nanowires within the membrane pores. The Al2O3@Au@NiCo sample exhibited nanowires with diameter variations attributed to the membrane pore geometry. Nanowire lengths were determined, with Al2O3@Au@NiCo featuring longer nanowires due to a higher concentration of metal ions in the electrolyte. X-ray diffraction analysis unveiled distinct crystalline structures for the samples: the Al2O3@Au@Co sample presented cobalt wires with a hexagonal structure, while Al2O3@Au@NiCo exhibited nickel/cobalt wires, both metals having a cubic structure. Energy dispersive X-ray spectroscopy (EDS) analysis confirmed the cobalt and nickel concentrations in the samples. The ferromagnetic resonance (FMR) technique revealed the presence of an anisotropy field in the samples, indicating a directional preference in magnetization. EMI shielding evaluation demonstrated that all samples containing metallic nanowires outperformed the Al2O3@Au reference sample across the X-band frequency range (8.0–12.0 GHz). Notably, the Al2O3@Au@Co sample exhibited the highest performance, providing 13.7 dB of shielding.