Iron based carbon nanocomposites for electromagnetic wave absorber with wide bandwidth in GHz range

The electromagnetic wave absorption properties of resin compacts containing 40 vol. % composite powders of α-Fe/C(a), and Fe₃C/C(a) were characterized in a frequency range of 0.05–26.5 GHz, according to a conventional reflection/transmission technique. The real part (ε_r ^′) and the imaginary part (ε_r ^′′) of relative permittivity were constantly low in the 2–14 GHz (ε_r ^′= ∼12.4 and ε_r ^′′= ∼0.6) for α-Fe/C(a) resin composites, and in the 1–26.5 GHz (ε_r ^′= ∼9.6 and ε_r ^′′= ∼0.8) for Fe₃C/C(a) ones. The imaginary part (μ_r ^′′) of relative permeability exhibited wide peaks in the 1–9 GHz range for α-Fe/C(a), and in the 2–26.5 GHz range for Fe₃C/C(a) owing to their different magnetocrystalline anisotropy field values. Consequently, the resin compacts with 40 vol. % α-Fe/C(a), and Fe₃C/C(a) powders provided good electromagnetic wave absorption performances (reflection loss <-20 dB) in ranges of 4.3–8.2 GHz, and 9–26.5 GHz over absorber thicknesses of 1.8–3.3 mm, and 1.0–2.4 mm, respectively. PACS 76.50.+g; 61.46.+w; 75.50.Bb; 75.30.Gw; 75.20.En