Properties of soft magnetic composites based on Fe fibres coated with SiO2 by hydrothermal method

• Published in: Journal of alloys and compounds 2020-06, Vol.826, p.154222, Article 154222
• Main Authors: Neamţu, B.V., Belea, A., Popa, F., Ware, E., Marinca, T.F., Vintiloiu, I., Badea, C., Pszola, M., Nasui, M.
• Format: Article
• Language: English
• Subjects: Addition polymerization; Annealing; Coated fibers; Cold pressing; Compacts; Core loss; Diffusion coating; Diffusion layers; Eddy currents; Ferromagnetism; Fibres based composites; Hybrid coating; Hydrothermal coating; Iron; Magnetic properties; Particulate composites; Polymers; Silicon dioxide; SiO2 coating; Soft magnetic composites; Thickness
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.154222

The paper reports on the preparation and characterisation of a new type of soft magnetic composites in which the ferromagnetic particles are replaced by Fe fibres. The fibres were coated via hydrothermal method with a SiO2 layer having a thickness of 150–200 nm. Also, a hybrid coating was developed by adding a supplementary layer of polymer on top of the SiO2 layer. The coated fibres were compacted via cold pressing at the pressure of 700 MPa. Our results indicate that using only SiO2 as the insulating layer leads to compacts characterised by lower hysteresis losses. However, it seems that during compaction, the SiO2 layer is damaged leading to the development of large eddy currents at high frequencies. Conversely, the additional polymer layer manages to prevent the development of excessive eddy currents in the compact, but with a significant increase of the hysteresis losses of the compacts being observed. A significant improvement of the magnetic characteristics of the fibre-based soft magnetic composites can be achieved by an annealing treatment with the condition of maintaining the integrity of the insulating layer, or minimising the diffusion between the fibres and the SiO2 coating during the annealing. [Display omitted] •Fibres based soft magnetic composites (FSMC) were prepared and characterised.•The Fe fibres were coated with a SiO2 layer via hydrothermal method.•The thickness of the SiO2 layer is 150–200 nm.•A hybrid coating was developed by adding a polymeric layer on top of SiO2 layer.•AC and DC characterisation showed the potential of FSMCs for further applications.