Process Improvement and Characterization of Fe-Si-Al Soft Magnetic Composites for High Frequency Applications
In order to improve the anti-saturation and solve the problem of high core loss at high frequency of Fe-Si-Al soft magnetic composites,the process of preparing soft magnetic composites by alumina coated small particle size Fe-Si-Al powder was conducted by Al3+hydrolysis method.The effects of alumina content in aluminum sources solution and pressing pressure on the high frequency magnetic properties of soft magnetic composites were studied.The micro-morphology of the powder coated with different amounts of alumina was observed by a scanning electron microscope(SEM),and the chemical composition of the coating was analyzed by a Fourier transform infrared spectrometer(FTIR).The experimental results indicate that with the increase of alumina content,the permeability of soft magnetic composites is reduced,but the DC-bias performance is improved.The reason is that the structural demagnetization caused by the coating increases gradually.The forming pressure mainly affects the magnetic properties by affecting the internal air gap rate and the quality of the coating.The greater the pressure is,the smaller the air gap rate and the greater the magnetic permeability is.However,the surface coating of the powder will be damaged and the magnetic properties will be deteriorated because of excessive pressure.It shows that when the dosage of alumina is 2.0 wt%and the molding pressure is 1 860 MPa,the permeability of the soft magnetic composites is about 60,the%μe of the powder core is up to 63.84%at 8 000 A/m DC magnetic field and the core loss is 235.7 mW/cm3 at 200 kHz/50 mT.
Fe-Si-Al soft magnetic compositesHigh-frequencyInsulation coatingCore lossAnti-seturetion
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