Soft magnetic composites based on Fe fibres and powders prepared by cold sintering process
B.V. Neamţu, Florin Popa, Traian Florin Marinca, I. Chicinaş
Abstract
The manuscript provides a new strategy for preparation of soft magnetic composites that involves the consolidation of the ferromagnetic phase (fibres or powders), which is first covered with an insulating layer, via the cold sintering process. The manuscript reports on the preparation and characterisation of cold sintered compacts based on Fe fibres and Fe powders coated with ZnO and sintered at the temperature of 200 °C for 60 min under the pressure of 600 MPa. The amount of ZnO used as dielectric phase was 10 and 20 wt%. The absence of any reaction between phases that compose the compacts (Fe fibres or powders and ZnO) during the cold sintering process was proved by X-ray diffraction (XRD). Electron microscopy and X-ray micro-analysis (SEM-EDX) were used for morphology and chemical analysis of the cold sintered compacts. The influence of the type of ferromagnetic phase (fibres or particles), as well as the influence of the amount of dielectric phase on the saturation induction (Bs), the coercive field (Hc), and the maximum relative permeability (µrmax) of the cold sintered magnetic cores, was investigated and discussed. The effect of the same factors on the total core power losses (P) and the initial relative permeability (µri) of the cold sintered compacts, upon increasing the frequency of the magnetising field up to 10 kHz, was analysed. The feasibility of applying a heat treatment at the temperature of 450 °C for 1 h was investigated, leading to the enhancement of both DC and AC magnetic properties of the cold sintered compacts.