Preparation And Properties Of Fe-based Nanocrystalline Soft Magnetic Powder Cores

As a new type of functional composite material,magnetic powder core is widely used in current applications.Due to its high effective permeability and low loss,the magnetic powder core is widely used in the field of electronic communication.With the advancement of technology,devices are becoming more and more compact and efficient,and people have higher expectations for such soft magnetic materials,such as higher magnetic permeability and saturation magnetic induction.As an emerging soft magnetic alloy,Fe-based nanocrystalline alloys replaces traditional magnets in many applications and further enhances the functionality and sensitivity of the device due to its excellent soft magnetic properties,low cost,and environmentally friendly production process.The most valuable soft magnetic material recognized in terms of functionality and sensitivity.In order to finally prepare Fe-based nanocrystalline soft magnetic powder cores with excellent properties,the following contents were studied and the corresponding results were obtained.Firstly,in order to obtain a suitable Fe-based nanocrystalline alloy,the composition of(Fe0.76Si0.09B0.1P0.05)99.3-xNbxCu0.7(x = 0～1.5)alloys were studied.The variation of amorphous forming ability and soft magnetic properties of Nb in alloys was studied.The study obtained a series of Fe-based nanocrystalline alloys with high amorphous forming ability(Dcr = 1～2.5 mm),high saturation magnetic induction(Bs=1.42～1.51T),high magnetic permeability(μe=15,000～18,500)and low coercivity(Hc=1 A/m).By observing the changes of microstructure during crystallization and the calculation of the crystallization kinetics process,the relationship between the crystallization process and the soft magnetic properties of the alloy were revealed.It is found that as the crystallization process progresses,the nano-scale α-Fe(Si)phase first precipitates and grows,while the soft magnetic properties of the alloy including coercivity,magnetic permeability and saturation magnetic induction are continuously optimized,however,as the hard magnetic phase Fe3(B,P)precipitates,the soft magnetic properties of the alloy deteriorate rapidly.Secondly,the amorphous alloy powder prepared by gas atomization method is obtained by gas atomization method.The nanocrystalline magnetic powder cores with excellent performance were obtained by coating,pressing and nanocrystallization annealing.And the effect of nanocrystallization annealing process on the performance of magnetic powder cores was systematically studied.The alloy with the highest amorphous forming ability(Fe0.76Si0.09B0.1P0.05)99.3Nb1Cu0.7 was used as the base material,and the amorphous alloy powder prepared by gas atomization method was mixed with 2 wt.%epoxy resin,0.5 wt.%zinc stearate and 0.5 wt.%ethylene bisstearyl(EBS),it was pressed into a ring under the pressure of 1800 MPa for 1 minute.After appropriate annealing treatment,the obtained nanocrystalline magnetic powder cores have good magnetic permeability frequency stability of 63 at 1 MHz,and low loss less than 700 mW/cm3 at 0.1 T and 100 kHz.It is found that with the a-Fe(Si)phase gradually precipitated,the magnetic permeability of the magnetic powder core is increased and the loss is reduced.After the precipitation of the Fe3(B,P)phase,the performance of the magnetic powder core deteriorates rapidly.Thirdly,in order to further improve the magnetic permeability and saturation magnetic induction of the magnetic powder core,the corresponding magnetic powder cores were prepared by mixing the nano-NiZn-Fe2O4 and using high-saturation magnetic induction alloy composition.It is found that the coated nano-ferrite can significantly improve the magnetic permeability of the magnetic powder core,and the DC-bias performance of the magnetic powder core prepared by the alloy composition with high saturation magnetic induction is significantly improved.This is important for the application of high frequency and miniaturization of devices.