Microwave Sintered Fe/MgO Soft Magnetic Composite

Micro/nano soft magnetic composite based on the Fe microparticles and the MgO nanoparticles was prepared by cold pressing followed by microwave sintering. Magnetic and mechanical properties of the green compact as well as sintered samples were measured. Coercivity, permeability, resistivity, elastic modulus and transverse rupture strength values in dependence on MgO content were investigated. The influence of MgO content ratio on properties was different in the case of as pressed green samples in comparison to sintered bodies. Microstructure formation and its influence on mechanical and magnetic properties are discussed. The coercivity of the green compacts with 1-5 wt% of MgO exhibits approximately 460 A/m and after sintering decreases to approximately 290 A/m. The real part of complex permeability at the frequency of 100 kHz exhibits a maximum for 2 wt% of MgO in green compacts, while for 10 wt% in sintered samples. It was observed that increase of the content of MgO causes decrease of the permeability. Properties of the sintered composite are related to formation of magnesium ferrite as well as volume distribution of residual MgO in dependence on initial MgO ratio

Magnetic Properties of Sintered Fe₅₀Co₅₀ Powder Cores

We investigated coercivity, total losses and complex permeability of sintered Fe-Co powder cores to detect magnetization processes performing in ac magnetic field. The Fe-Co solid solution alloy powders with 50:50 wt% ratio were prepared by 1, 15, and 20 h alloyed mixture of pure chemical elements in planetary ball mill. The resulting powder was subsequently sintered into a disk form. The compaction was performed at a pressure of 800 MPa for 5 min at temperatures of 400°C, 500°C and 600°C in vacuum oxidation protective atmosphere, with pressure of 5×10¯³ Pa. The best magnetic properties exhibit sample prepared from 1 h alloyed powder, compacted at 600°C

DC Magnetic Properties and Complex Permeability of Ni-Fe Based Composites

We have investigated soft magnetic composite materials to better understand the influence of binder (resin) content on the DC magnetic properties and the complex permeability. Soft magnetic composite samples were composed from NiFe powder with phenol formaldehyde resin (ATM). Ferromagnetic magnetic powder for ring-shaped samples was obtained by milling of small pieces cut of NiFe sheets. The obtained powder was annealed to partially remove structural defects. The prepared powder was mixed with phenol-formaldehyde resin in different vol.%. The mixtures were pressed into the ring-shape samples. Complex permeability and DC magnetic properties (initial magnetization curves, anhysteretic curves and hysteresis loops) were measured. Higher inner demagnetizing fields in the resin containing samples were responsible for higher coercivity and hysteresis losses, but the permeability was stable up to much higher frequencies, compared to the sample without the resin