Multilayered effects of Fe on EMI shielding of Sn–Al architectural powder

Abstract

No evident effect on shielding efficiency was observed when electromagnetic wave-absorbing coating materials were applied in single layers because of the dispersing nature of the powder. When coating was increased to two layers, shielding effects were evident at both high and low frequencies, with greater shielding efficiency at low frequencies than at high frequencies. It is worth noting that when coating was increased to three layers, as the weight percentage of powdered iron (Fe) increased from 5 to 8%, the shielding efficiency of the powdered iron composite material was raised to −35 dB. This shows that as the weight percentage becomes higher, the powder shows the resonance phenomenon of permeability spectrum, and at high frequencies, the electromagnetic wave shielding efficiency of the composite materials was greatly increased. As the weight percentage of the powdered iron was increased to 8%, the powder could not be spread evenly in the epoxy because of the dispersing characteristic of the electromagnetic properties of iron and the anisotropic and heterogeneous nature of the powdered composite material. During production, the powder aggregates often resulted in greater heterogeneity in the materials and, consequently, lowered shielding efficiency at 3 GHz.