Structural and magnetic properties of Fe–Al2O3 soft magnetic composites prepared using the sol–gel method

Abstract

Abstract In this work, powder metallurgy was performed for preparation of iron-based soft magnetic composites (SMCs). For this purpose, iron powders were coated with a thin alumina insulating layer using the sol–gel process, and then compacted for characterization. Microstructural analysis confirmed the formation of an alumina insulating layer with high thermal stability and uniform coverage on the powder surfaces. The alumina coating increased the magnetic permeability of the composites at high frequencies as a result of increased electrical resistivity and decreased eddy current loss. In addition, the different components of the total loss factor were calculated by means of a loss separation method. It was found that by addition of 8 wt.% insulation, the hysteresis loss coefficient increased from 2.7 × 10−3 to 4 × 10−3 while the eddy current loss coefficient decreased from 3.00 × 10−6 to 1.53 × 10−6 as compared with pure iron compacts.