To explore a new preparation process of powder cores,Fe73.5Cu1Nb3Si13.5B9 nanocrystalline alloy cores were used as raw material and powdered by mechanical crushing method.Subsequently,seven kinds of nanocrystalline alloy powder cores with different particle size ratios were prepared by super-gravity percolation process.The morphology,structure,and magnetic properties of powder were characterized by SEM,XRD,and VSM,respectively.And the effect of particle size ratio on the morphology,density,effective permeability,core loss and quality factor of powder cores were studied.The results show that the powder prepared by mechanical crushing has low coercivity despite its sharp corners,and the powder surface of powder cores prepared by super-gravity percolation process are essentially solely covered by resin.Moreover,with proper particle size ratio,it is found that the best performance of the powder core's particle size ratio is:100～200 mesh powder accounting for 60％,200～400 mesh powder accounting for 20％,400～1 000 mesh powder accounting for 20％.The density of the core is 4.46 g/cm3 and the effective permeability is relatively stable in the frequency range from 100 kHz to 3 000 kHz,reaching 28.2 at 3 000 kHz.The core loss is only 99.1 W/kg at the magnetic induction strength of 20 mT and the frequency of 500 kHz.Furthermore,this process can produce low-loss powder cores at frequencies above MHz according to the experiment results.
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