Nanocomposites α-Fe/Fe3B/Y2O3 were prepared by a melt-spun technique, and the electromagnetic wave absorption properties were measured in the 0.05–20.05 GHz range. Compared with α-Fe/Y2O3 composites, the resonance frequency (fr) of α-Fe/Fe3B/Y2O3 shifted to a higher frequency range due to the large anisotropy field (HA) of tetragonal Fe3B (∼0.4 MA/m). The relative permittivity (εr=εr′−jεr″) was constantly low over the 0.5–10 GHz region, which indicates that the composite powders have a high resistivity (ρ=∼100 Ω m). The effective electromagnetic wave absorption (reflection loss <−20 dB) was obtained in a frequency range of 2.7–6.5 GHz on resin composites of 80 wt % α-Fe/Fe3B/Y2O3 powders, with thickness of 6–3 mm, respectively. A minimum reflection loss of −33 dB was observed at 4.5 GHz with an absorber thickness of 4 mm.

The saturation magnetization values (Ms) of α-Fe∕Ba3Co1.8Fe23.6Cr0.6O41 nanocomposites prepared by mechanically alloying α-Fe with Ba3Co1.8Fe23.6Cr0.6O41 powders increased with increasing the concentration of α-Fe. α-Fe∕Ba3Co1.8Fe23.6Cr0.6O41 nanocomposites showed higher coercivity values than α-Fe and Ba3Co1.8Fe23.6Cr0.6O41 because of the effects of shape anisotropy and exchange bias. The resin compacts with 33.5 vol % α-Fe∕Ba3Co1.8Fe23.6Cr0.6O41 (38, 70, 85 vol % α-Fe) powders provided good electromagnetic wave absorption performances in ranges of 7.5–16.0, 5.4–10.5, and 4.3–8.3 GHz over the absorber thicknesses of 1.3–2.5, 1.6–3.0, and 1.7–3.2 mm, respectively.

Nanocomposite magnetic materials α-Fe∕C(a), Fe2B∕C(a), and Fe1.4Co0.6B∕C(a) were prepared by mechanically grinding α-Fe, Fe2B, or Fe1.4Co0.6B with amorphous carbon [C(a)] powders. Complex permittivity, permeability, and electromagnetic wave absorption properties of resin compacts containing 40-vol% composite powders of α-Fe∕C(a), Fe2B∕C(a), and Fe1.4Co0.6B∕C(a) were characterized according to a conventional reflection/transmission technique. The real part (εr′) and imaginary part (εr″) of the relative permittivity are low and almost independent of frequency between 0.05 and 40GHz. The Imaginary part (μr″) of the relative permeability exhibited wide peaks in the 1–9-GHz range for α-Fe∕C(a), in the 2–18-GHz range for Fe2B∕C(a), and in the 18–40-GHz range for Fe1.4Co0.6B∕C(a) owing to their different magnetocrystalline anisotropy field (HA) values. Consequently, the resin compacts of 40-vol% α-Fe∕C(a), Fe2B∕C(a), and Fe1.4Co0.6B∕C(a) powders provided good electromagnetic (em) wave absorption performances (reflection loss<−20dB) in ranges of 4.3–8.2GHz (G band), 7.5–16.0GHz (X band), and 26.5–40GHz (Q band) over absorber thicknesses of 1.8–3.3, 1.2–2.2, and 0.63–0.82mm, respectively. Our experimental results demonstrate that the amorphous-carbon-based magnetic nanocomposites are promising for the application to produce thin and light EM wave absorbers.

Nanocomposite materials of α-Fe/Y2O3 prepared by melt-spun technique exhibited good electromagnetic wave absorption properties (RL<−20 dB) in a 2.0-3.5 GHz range as absorbers with thickness ranging from 3 to 5 mm, and a minimum reflection loss of −36 dB was obtained at 2.6 GHz with an absorber thickness of 4 mm.

The complex permittivity, permeability and electromagnetic (EM) wave absorption properties have been investigated for resin compacts containing 75 wt% composite powders of α-Fe/C(a) and Fe2B/C(a). The real and imaginary parts ( and εr′) of relative permittivity for the resin composites remained almost constant in the 0.05–20.05 GHz range. The imaginary part of the relative permeability (μr′) exhibited a wide peak in the 1–9 GHz range for α-Fe/C(a) and in the 2–18 GHz range for Fe2B/C(a). Both resin composites exhibited good EM wave absorption properties (RL < −20 dB) in the 4.4–8.3 GHz range with an absorber thickness of 1.9–3.4 mm, and in the 7.5–16 GHz range for an absorber thickness of 1.2–2.2 mm, respectively.