High frequency properties of Fe-Si nano-powder/epoxy films

Composites of Fe93.5Si6.5 powder and epoxy (diglycidyl ether of bisphenol A type) were prepared using an electron beam irradiation process. Scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and network analyzer were used to analyze the structure, electromagnetic properties and micro wave absorption of the composites. Results show that the saturation magnetization depends on the fraction of the Fe93.5Si6.5 powder in the composite, which affects initial permeability. It is believed that the eddy current loss is a dominant factor over 1 GHz and that the resonance frequency of the composite decreases with increasing fractions of Fe93.5Si6.5 powder. Finally, reflection loss was calculated from the permeability and permittivity of these composites. Composite with 50 wt% Fe93.5Si6.5 powder fractions and 5 mm thickness showed reflection loss below -20 dB from 3.66 GHz to 4.16 GHz. Therefore, it is believed that thin Fe-Si/epoxy composites may be a good candidate for microwave absorption application.