Iron-based soft magnetic composites with Al2O3 insulation coating produced using sol-gel method

The alumina sol was obtained using Al(C3H7O)(3) as a precursor. Pure Fe particles were coated with Al2O3 using a sol-gelmethod and subsequently calcinated at 1100 degrees C. The resulting softmagnetic compositeswere investigatedwhile varying the treating temperature. Scanning electronmicroscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analyses revealed that the surface of the Fe powder particles comprised a thin alpha-Al2O3 insulating layer uniformly distributed after calcination at 1100 degrees C for 1 h. The permeability increased with the treating temperature, reaching a stable value of 93 from675 degrees C to 725 degrees C. The hysteresis losses decreased, whereas the eddy losses increased with the treating temperature in the range of 650-725 degrees C. The core losses (P-cv) decreased (lowest value: 10.2 kW/m(3)) up to 675 degrees C and increased thereafter. The permeability of the material annealed at 675 degrees C remained stable with changes in the frequency, whereas P-cv remained low over the 5-100 kHz range. A noticeable insulation layer separating the different Fe particles was observed by SEM for the samples annealed below 700 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.