Fibres based soft magnetic composites prepared by cold pressing and spark plasma sintering

ABSTRACT

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The aim of this project is to develop a new family of SMC that is Fibres based Soft Magnetic Composites (FSMC). The main idea consists in the replacement of ferromagnetic particles by long and thin Fe fibres (ranging from few cm to tens of cm). This new family of materials should have lower core losses as compared to magnetic cores based on Fe-Si laminates and higher magnetic permeability and mechanical strength as compared to SMC`s. Pure Fe fibres available under the form of iron wool will be used. The Fe fibres will be covered by an insulating layer, compacted into toroidal shapes and then characterised from morphological, chemical, mechanical and electromagnetic point of view. Concerning the insulating layer, we propose a systematic approach that will lead to three different FSMC compacts: (i) compacts prepared from Fe fibres coated with silicon-based resin cold pressed; (ii) compacts prepared by fibres coated by a hybrid insulating layer that consist of an inorganic layer (phosphate, surface oxidised, SiO2) and a silicon-based resin layer. The two coatings should complement each other; (iii) spark plasma sintered (SPS) compacts based on Fe fibres coated with NiZn or MnZn ferrites. The use of ferrites as the coating material is justified by their high electrical resistivity and the fact that they have also magnetic properties. In such a case, the loss of magnetic permeability and saturation induction that is induced by insulating layer in classic SMC is partially eliminated. As compaction techniques, we propose uniaxial cold pressing (for first two types of compacts) and SPS (for the third type). SPS will be used to produce high-density compacts and to reduce/eliminate the reaction of the ferrite shell with the Fe core. It will be investigated the influence processing parameters on the electromagnetic characteristics of the compacts (permeability, core loss, saturation induction, coercivity, cutting frequency etc.) and mechanical strength.

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This research was founded by The Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI), project number TE 133/2018, project code PN-III-P1-1.1-TE-2016-0649.