GHz microwave properties of melt spun Fe–Si alloys

The structural and microwave properties of melt spun Fe100−xSix (x = 10, 20, 30) nanocomposites were investigated. The phases varied with Si content in FeSi alloys. It is found that the Fe3Si and FeSi phases could be obtained with Si content up to 20 at.%. The X-ray absorption fine structure (XAFS) spectra of Fe K-edges show that the local structures around Fe atoms in melt spun Fe–Si alloys become more disordered with increasing Si content when compared with that of α -Fe. The complex permittivity–frequency and permeability–frequency properties were determined in the microwave frequency regime of 2–18 GHz by vector network analysis. It is found that flake-like FeSi powder composite has the largest values of μ′ and μ″ at 2 GHz. The reflection loss shifts to the higher frequency with the Si content increasing for melt spun FeSi alloys. A minimum reflection loss of −16.5 dB is obtained at 13.9 GHz for composition Fe70Si30 with the thickness of 1.5 mm. However, for composition Fe70Si30, the minimum reflection loss shifts to lower frequency and larger value with the thickness increasing. The results suggest a new design for microwave absorbers based on electromagnetic wave-absorbing materials.