Polyol derived Ni and NiFe alloys for effective shielding of electromagnetic interference

Abstract

Ni and NiFe alloys with different compositions have been successfully synthesized using a simple, surfactant-free polyol method. The morphological analysis demonstrated a uniform spherical nature of the alloys, with size range ∼10–30 nm. A very thin oxide layer was found to form over the alloy nanoparticles (NPs) which is weakly visible in TEM and later confirmed by XPS analysis. The magnetic properties of the Ni and NiFe NPs were measured using a vibrating sample magnetometer (VSM) at room temperature. The saturation magnetization value was found to be lowest in Ni and keeps on increasing with increasing Fe content in the composition. The resistivity, as revealed from I–V characteristics, was shown to be lowest for the permalloy (Ni80Fe20) phase, while the values increase with further increment in the Fe content. The microwave shielding properties of the Ni and its Fe alloy NPs were investigated in the Ku band range. The lower EM wave transmittance with good reflection and absorption coefficients is responsible for the high shielding values. All of the alloys tested in this investigation showed excellent microwave shielding properties ranging from −21 to −41 dB in the entire Ku band, for ∼1 mm thick samples. The lowest EMI shielding range (−21 to −29 dB) was noted for Ni NPs while the highest was observed in the case of permalloy (−30 to −41 dB). The rest of the NiFe combinations show intermediate shielding effectiveness as compared to Ni and permalloy. Certainly, all of the NiFe alloy combinations we tested showed excellent EMI shielding above −30 dB, with significant enhancements in the absorption shielding efficiency. These alloys are good candidates for EMI shielding having the ability to attenuate 99.9% of electromagnetic radiation.