Analysis of the Preparation and Magnetic Properties of Fe/SiO2 Soft Magnetic Composites

Soft magnetic composites are valuable materials due to their impressive magnetic properties. The aim of this research is to investigate the influence of the ball-to-powder ratio during mechanical milling and an innovative powder surface treatment on the magnetic properties of these materials. Six powder samples of pure Fe (99.98% purity) were prepared by mechanical milling with different ball-to-power ratios (BPR 3:1, BPR 6:1, BPR 9:1) and by the surface smoothing process. Magnetic properties were evaluated by measured hysteresis loops and initial magnetization curves. The results show that the best soft magnetic properties at 200 and 300 K — based on the shape of the hysteresis loops, maximum magnetization, and initial magnetization curve — were exhibited by the sample with BPR 3:1 and with powder surface treatment. The sample with a high magnetic moment is the one with BPR 9:1 and we can expect that increasing the ball-to-powder ratio causes the formation of many internal structural defects during mechanical milling, but it also creates a larger amount of small particles, which generally means smaller domain walls. We can confirm that mechanical milling and subsequently surface treatment of milled powder is a suitable precursor for preparing powdered material for further hot or cold compaction and to obtain of the required shape of soft magnetic material with excellent magnetic properties.