Study On Preparation Process And Properties Of Iron-based Magnetic Powder Core With Low Magmetic Loss

The global communications industry and electronic technologyhas developed rapidly in recent years.Integration,miniaturization and lightweight becomes the new standards for electronic products in the current application market.The iron-based magnetic powder cores are commonly used as the raw material for integrated inductor due to their excellent saturation magnetic induction strength and favor cost.The iron-based magnetic cores have high magnetic loss at high frequency,which limits their applications at medium and high frequencies.The purpose of this paperis is to reduce the magnetic loss of the iron-based magnetic powder cores at high frequencies.The specific research content includes optimization of phosphating process parameters secondary acidification to reduce the magnetic loss of the alloy magnetic powder core at high frequency.Furthmore,the researchers granulated high-sphericity carbonyl iron powder to optimize the particle size distribution of the secondary particles to reduce the high-frequency magnetic loss of the Fe powder core.The original Fe Si Cr alloy powder prepared by water atomization exhibits irregular shapes,which lead to excellent press forming property.The saturation magnetization?M_s?of Fe Si Cr alloy powder is proportional to the atomic ratio of Fe element.The self-corrosion potential of Fe Si Cr alloy powder body increases with the increase of Fe content,which indicates the alloy powder?s corrosion resistance improved.When the content of Cr is 5.55 at.%,the self-corrosion current density of the Fe Si Cr alloy powder body is 9.34×10^-5 A/cm²which is lower than other compositions?self-corrosion current density.Surface phosphating?first acidification?has been used to produce phosphate insulation coating on the surface of Fe Si Cr alloy powder.The phosphating temperature and phosphating solution concentration can affect the thickness of the insulating layer.The real part magnetic permeability and high frequency loss factor of Fe Si Cr alloy powder core decrease with increasing the concentration of phosphating solution.Fe Si Cr alloy powder reacts slowly with H3PO4 at room temperature lead to the relatively thin insulating layer formed.The phosphating reaction rate increases with increased phosphating temperature.Furthermore,the M_s and loss factor of Fe Si Cr alloy powder decreased significantly.The optimal pressing pressure of organic-coated Fe Si Cr alloy magnetic powder core is 800 MPa.The incomplete insulating coating formed on the surface of Fe Si Cr alloy powder via phosphating.The secondary acidification process can promote the further passivation of the Fe Si Cr alloy powder surface and form an insulating layer containing phosphate and chloride on the surface.Excessive HCl addition and secondary acidification time will deteriorate the alloy powder?s properties.The Fe Si Cr powder core treated with 2.0 wt.%HCl ethanol solution for 2 h have the higher volume resistivity and lower loss factor at high frequencies.A reasonable secondary particle size distribution plays an important role in optimizing the internal structure of the Fe powder core and reducing this loss at high frequencies.The content of the insulating agent in the secondary particles decreases as the secondary particle size increases.The density,magnetic permeability and loss factor of Fe powder core decrease with the increase of secondary particles.For the cores prepared from the secondary particles with bimodal size distribution.The minimum magnetic loss factor value is obtained at the coarse/fine secondary particles volume ratio of 7:3.