Fig. 1. SEM images of (a) the starting amorphous gas atomized FeSi-based powders, (b, c) flakes milled for 14 h (see text for details), (d) milled flakes after an anneal at 400 °C for 1 h in flowing Ar gas, (e) sieved flakes with effective diameters <25 μm, and (f) sieved flakes with effective diameters >45 μm.

Fig. 2. (a) XRD patterns of gas atomized FeSi-based powders (green), powders milled for 14 h (see text for details) (red), and those in red after annealing at 400 °C for 1 h in Ar gas (black). (b) DC conductivity measured for spheroidal- and flake-based composites.

Fig. 3. Hysteresis loops of gas atomized FeSi-based powder and flakes milled for 14 h with annealing in an Ar gas using different conditions. The inset plot shows an expanded view of the zero-crossing region with an applied field from -2000 to 2000 A/m.

Fig. 4. Real (a) and imaginary (b) parts of the complex permeability μ, the real (c) and imaginary (d) parts of the complex permittivity ε for FeSi-based gas atomized powders and high aspect ratio flakes obtained after ball milling said powders for 14 h followed by anneal and loading in paraffin measured over the frequency range of 0.1-18 GHz. Several samples are measured reflecting different loading volume fractions.

Fig. 5. EMI shielding properties (reflection loss RL and shielding effectiveness SE) of amorphous FeSi-based fillers suspended in a paraffin wax matrix with various shape, aspect ratios, loading factors and thicknesses over the frequency range of 0.1-18 GHz.