Electromagnetic interference shielding effectiveness of amorphous and nanocomposite soft magnetic ribbons

The electromagnetic interference shielding effectiveness (EMI SE) of amorphous and annealed melt-spun ribbons having typical composition of Co72.5Si12.5B15, (Fe0.65Co0.35)83Si1.3B11.7Nb3Cu1, Fe80Si8B12 and Fe83Si2B13Nb2 were studied in the 0.2–8.5 GHz microwave range. The amorphous nature of the as-quenched ribbons was confirmed by X-ray diffraction patterns and differential scanning calorimetry (DSC). The flexible electromagnetic wave absorber ribbons of CoSiB, FeSiB, and FeCoSiBNbCu based alloys exhibit ∼99.99% attenuation of electromagnetic waves in the entire 0.2–8.5 GHz (L, S and C-band) range. Both as-quenched and annealed amorphous ribbons of Co72.5Si12.5B15 and Fe80Si8B12 are electromagnetically active and total electromagnetic shielding effectiveness (SET) of ribbons found to be ∼36 dB, ∼34 dB throughout the test range. The EMI shielding properties deteriorates for FeCoSiBNbCu and FeSiBNb based nanocomposite ribbons achieved by in-situ crystallization annealing. The electromagnetic shielding of magnetic ribbons is effected mainly by absorption mechanism due to high electrical resistivity and magnetic permeability. The CoSiB and FeSiB melt-spun ribbons can be a potential magnetic filler for military and stealth applications in L, S and C-band range.