Permeability Of Soft Magnetic Composites Research Articles

Evaluation of Equivalent Permeability of Soft Magnetic Composites Considering Manufacturing Process

A method for evaluating the equivalent permeability of soft magnetic composites is presented. Firstly, a new microstructural characterization model of soft magnetic composites is proposed, which introduces the concepts of pores and gaps. The effect of these two structures on the magnetic properties of composites is analyzed, and an analytical model is derived from the microstructural parameters. Secondly, the compaction process is numerically simulated by discrete element method and powder particle 3D reconstruction technique. The microstructure models of soft magnetic composites under different compaction conditions are established. Finally, the magnetic field characteristics of the microstructure model are analyzed by finite element method, and the equivalent permeability is accurately evaluated. The correctness and feasibility of the simulation method proposed in this paper is verified by comparing with the measured results.

Improved high-frequency magnetic properties of FeSiBCCr amorphous soft magnetic composites by adding carbonyl iron powders

The rapid development of mobile communication, electronics and electronics has put forward higher requirements on the permeability, core loss and DC bias performance of soft magnetic materials. In order to prepare soft magnetic materials with excellent high-frequency properties, FeSiBCCr amorphous powders produced by gas-water combined atomization were mixed with the CIP (carbonyl iron powder), and the toroidal SMCs (soft magnetic composites) were prepared by the phosphate and EP (epoxy resin) co-coated FeSiBCCr/CIP hybrid powders. The effects of EP and CIP content on soft magnetic properties of the SMCs were investigated. When the EP content was increased from 1 to 3wt%, the insulated coating effect and density of SMCs were significantly improved, resulting in decreased core losses and increased permeability. Although the DC bias performance of SMCs deteriorated slightly after adding the small-size CIP, the consequent reduction in the air gaps between amorphous particles led to a significant increase in the density and permeability of SMCs. When the CIP content was 0∼20wt%, core losses decreased with the increase of CIP due to the decreased average particle size; when the CIP content was 20∼70wt%, core losses increased rapidly with the increase of CIP content due to the continuous decrease of resistance and the increase of coercivity. Under the condition of 20wt% CIP and 3wt% EP, the FeSiBCCr/CIP SMCs exhibited a high permeability of 30.9 ± 0.6 and a high DC bias% of 91.8 ± 0.2 at a DC magnetic field of 71.25 Oe. Core losses of the SMCs were 50.6 ± 13.4 mW·cm–3 (at 0.05 T and 100 kHz) and 850.0 ± 11.8 mW·cm–3 (at 0.02 T and 1000 kHz), which were decreased by 64.8% and 27.9% compared to that without adding CIP. The FeSiBCCr/CIP SMCs shows excellent DC bias performance and low core losses, which indicates great potential in the electronic and electrical application.

High permeability and low core loss Fe-based soft magnetic composites with Co-Ba composite ferrite insulation layer obtained by sol-gel method

To balance the core loss and permeability of soft magnetic composites (SMCs), a Co-Ba composite ferrite insulation layer was employed to clad the surface of reduced iron powder by sol-gel method. The successful preparation of the honeycomb-like Co-Ba composite ferrite coating layer was verified by scanning electron microscopy (SEM), the composition of the coating was determined by X-ray diffraction (XRD), and the magnetic properties were tested with a B-H curve analyzer. BSEM images of the polished cross-section and core loss separation results confirmed that an excessively high annealing temperature causes the composite ferrite insulation layer to fail. A high effective permeability of up to 121 at 300 kHz and low core loss (Pcv) of 129 kW/m3 at 100 kHz and 0.02 T were obtained in prepared samples at the optimized annealing temperature of 500 °C. Subsequently, simulation analysis based on the Clausius-Maxwell formula model was used to confirm the feasibility of the enhancement on effective permeability in Fe@Co-Ba composite ferrite theoretically. The agreement between simulation and experimental results further indicated that a good balance between the core loss and permeability of Fe-based SMCs was achieved by Co-Ba composite ferrite cladding.

Effect of defects on the complex permeability of soft magnetic composites

To calculate the complex permeability of soft magnetic composites, two-dimensional analytical models with and without the defects were used for the complex case. The relation of the complex permeability with the frequency, component size ratio δ and inclusion particle size is deduced. The results show that the effect of the defects is even more pronounced for the complex permeability. The complex permeability is a function of the component size ratio δ and the size of the inclusion. Increasing the component size ratio δ causes a decrease of the complex permeability at the same frequency. With the increase of inclusion particle size when the component size ratio keeps constant 0.01, both of the real and imaginary parts increase. In addition, the theoretical method is tested by the experimental results, which can be used to design parameters before the experiment.

Theoretical and experimental approach to characteristic magnetic measurement data of polymer bonded soft magnetic composites

Soft magnetic composites consisting of an organic binder and FeCoV particles have been produced and examined afterward regarding the dependence of magnetic field H at polarization J on filler content C. In general, the applied magnetic field to achieve a certain value of polarization is proportional to the inverse filler content, following H∼1∕C, and the polarization is directly proportional to the filler content, following J∼C. With use of the evaluated material data and the inner demagnetization factor Ni a model for calculating the permeability of soft magnetic composites has been derived. As input values the permeability of the soft magnetic particles μ, the filler content C, and the geometric demagnetization factor of the particles Np are used. The elaborated approach shows an excellent agreement with experimental permeability data of the FeCoV composites.

Influence of demagnetizing field on the permeability of soft magnetic composites

The influence of demagnetizing field on the effective permeability of magnetic composites has been investigated. A theoretical expression of the effective permeability has been obtained and discussed according to four typical composites with spheres, needles, flakes, and aligned prolate ellipsoidal particles. The results indicate that the demagnetizing field within the particles can reduce the effective permeability significantly. In order to increase the effective permeability, it is necessary to decrease the demagnetizing field within the particles. A linear relationship between effective permeability and volume fraction is also observed for composites filled with spherical particles at low volume fraction.

Permeability of soft magnetic composites from flakes of nanocrystalline ribbon

The permeability of powder cores is usually modeled using a nonmagnetic grain boundary model (NMGB), which is not satisfying in the case of composites based on ground nanocrystalline ribbon, especially for particles larger than several 100 /spl mu/m. An improvement of the NMGB model is proposed where both in plane and perpendicular reluctances are taken into account. This model is consistent with our experimental results as well as other authors' results in a very large range of packing fractions (30%-92%) and particle sizes (80-1000 /spl mu/m).