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

Abstract

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 (εr=εr′+iεr″) and permeability (μr=μr′+iμr″) 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 wt % Ni exhibit excellent electromagnetic wave (EMW) absorption properties (reflection loss <−20 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.

Microwave absorption and flexural properties of Fe nanoparticle/carbon fiber/epoxy resin composite plates

“…8(a) Core-shell type Fe NPs are used as absorbent due to their excellent microwave absorption ability because of high magnetic and dielectric losses as shown in our previous work [6,7,13,31]. Either the only magnetic loss or only dielectric loss may cause a weak microwave wave absorption property due to dissymmetry of the electromagnetic match.…”

Facile solvothermal synthesis of novel hetero-structured CoNi–CuO composites with excellent microwave absorption performance

“…8, the C 0 values of all samples drastically decrease at the lower frequency range of 2-5 GHz and it is mainly caused by the natural resonance. 44 Natural resonance could be calculated by the following equation: where g means the gyromagnetic ratio, H a represents the anisotropy energy, and |K| represents the anisotropy coefficient. Commonly, the resonance frequency depends on the anisotropy eld, which is closely related to the coercivity value of the materials.…”

Time-sensitivity for the preparation and microwave absorption properties of core–shell structured Ni/TiO2 composite microspheres

“…5c, d. The real parts (l 0 ) of the three samples decline with increasing frequency. Notably, the decrease trends of Ni/TiO 2 samples prepared at 20 and 36 h are slower than those of Ni/TiO 2 composites prepared at 5 and 15 h, which stemming from the eddy current loss was effectively suppressed by the outer TiO 2 shell [12]. As for the l 00 (Fig.…”

“…Due to the high saturation magnetization, high initial permeability of nickel, the previous work mainly investigated the effects of various Ni-based composites with dielectric shells on the microwave absorption performances [10,[12][13][14]. Ni-based core-shell structure with the semiconductor TiO 2 shells have been rarely focused on [15,16].…”