An Investigation of the Magnetic Properties of Iron-based Soft Magnetic Composites Coated by Sodium Silicate Insulator

In this study, iron powder (~45 μm) with the minimum purity of 99% was insulated by the 1 to 4 wt% sodium silicate insulator (SiO2.3Na2O solution in 40 wt% water) and the 0.5 wt% zinc stearate. Insulated powders were pressed in a die with a toroidal shape at the pressure of 320 MPa. The effects of insulator percentage and annealing temperature on the magnetic permeability, core loss tangent, and the total loss were investigated. The results indicated that the sodium silicate insulator could be suitable for insulating iron powders used in iron powder cores for high frequencies up to 1000 kHz. Also, this insulator could be stable against heat up to 450 °C.