Influence of alloy components on electromagnetic characteristics of core/shell-type Fe–Ni nanoparticles

Fe–Ni alloy nanoparticles with various alloy components were fabricated by a direct current arc-discharge method. By dispersing the nanoparticles homogeneously into a paraffin matrix, the complex permittivity $\left({\epsilon }_r={\epsilon }_r^{\prime }+i{\epsilon }_r^{″}\right)$ and permeability $\left({\mu }_r={\mu }_r^{\prime }+i{\mu }_r^{″}\right)$ of the nanoparticles have been investigated in the frequency range of 2–18 GHz and the effects of alloy components on the electromagnetic parameters were discussed. It is found that the permittivities of the nanoparticles are lower than those of the microscale counterparts and almost independent of frequency. The magnetic loss is attributed to natural resonance and the resonance peak shifts to high frequency range with the increase in Fe content. Better microwave absorption performances can be obtained by adjusting the composition and tailoring the core/shell structures to balance the electromagnetic parameters. The calculated results indicate that the Fe–Ni nanoparticles with $49\text{wt}\%$ Ni exhibit excellent electromagnetic wave (EMW) absorption properties (reflection loss $<-20\text{dB}$ ) over the range of 7.6–16.0 GHz in the thickness of 1.02–1.70 mm. The mechanism of effective EMW introduction and attenuation is discussed on the basis of the experimental results.