Microstructure and magnetic properties of novel powder cores composed of iron-based amorphous alloy and PTFE

The temperature resistance of a magnetic powder core is determined by the organic resin in it, while the conventionally used phenolic resin and epoxy resin are sensitive to temperature. Herein, iron-based amorphous powder cores with heat-resisting polytetrafluoroethylene (PTFE) insulating layers were fabricated by processes of ball-milling mixing, cold pressing, simultaneously sintering, and annealing, and the effect of different PTFE contents on magnetic properties was analyzed. The PTFE played the roles of lubricant, insulating layer, and binder in the fabrication of magnetic powder cores. The high lubricity and deformability of PTFE well protected the amorphous powder from ball-milling or cold-pressing damage, making it feasible for mixing amorphous powder with PTFE. In the sintering process, melting PTFE could fill the air gaps among powders and endow the powder cores with available strength. The analysis of microstructure showed that the amorphous powders could be well coated by PTFE, and the tests of magnetic properties showed that the PTFE content had a fluctuating influence on the total core losses of the powder cores. Owing to the better microstructure homogeneity and more proper compositions, the powder cores with 2.4% and 3.6% mass fractions of PTFE show relatively high effective permeabilities above 25 under 100 kHz, and relatively low total core losses of 1448 and 1402 kW/m(3) respectively under 100 kHz, 100 mT. Moreover, all the prepared magnetic powder cores exhibit superior DC-bias properties, the percentages of incremental permeability are as high as 83-90% under a direct magnetic field of 100 Oe. [GRAPHICS] .