Tuning microwave absorption properties by hybriding heterogeneous components for core@shell structural Fe@SiC flakes

Flake-like Fe@SiC composites were synthesized by a combined approach consisting of ball-milling and heat-assisted surface adhesion processes. The experimental results indicate that the Fe micropowders with an initial size of 30-40 μm can be completely milled into a flake-like shape with the diameter of 35 μm and the thickness of 10 μm after 5 h ball-milling, and then the flakes would be further fractured to smaller pieces as increasing the milling time. The as-made Fe flakes were subsequently encapsulated within SiC nanopowders by high-speed mixing at 120 °C for 2 h under nitrogen atmosphere. By turning the ball-milling time and the Fe/SiC ratios, the reflection loss (RL) could be optimized to −10 dB in the frequency ranges of 21.5-22.3 GHz and 20.1-26.5 GHz for the absorber thicknesses of 0.3 mm and 0.5 mm, respectively. In particular, the maximum RL peaks for the flake-like Fe@SiC composites shifted to higher frequencies compared with the spherical Fe@SiC composite due to the increased magnetic anisotropy. The enhanced microwave absorption properties are a synergistic effect of magnetic loss and dielectric loss, resulting from the heterogeneous components, and their proper electromagnetic impedance matching.