Effect of the shape and content for added iron powder on properties of nanocrystalline soft magnetic composites

The objective of this work is to investigate the difference of the shape and content for iron powders on properties of nanocrystalline SMCs prepared under the low baking temperature and molding pressure. The results show that both irregular reduced iron powders (RIP) and spherical carbonyl iron powders (CIP) can effectively improve the relative density (ρr), saturation magnetization and effective permeability (μe) of nanocrystalline SMCs, but the optimization effect of RIP on the ρr and μe is higher when the content is less than 50 wt.%. Because RIP is more easily filled between nanocrystalline particles and coupled and agglomerated to form new magnetic path. The SMCs prepared by adding CIP has higher DC-bias characteristics (> 94% at 100 Oe), frequency stability and lower total losses (Pcv). When the content of CIP is 30 wt.%, the Pcv is 748.4 mW/cm3 (20 mT, 1 MHz), which is 6.5% lower than nanocrystalline SMCs and 18.6% lower than RIP mixed SMCs. This is due to the fact that CIP has a slight deformation during the molding process, which has low damage to the insulation coating layers. The present work provides reference for the application of nanocrystalline powders in the field of molding inductors.