Study On Microwave Absorption Properties Of Fe-Si-B-Nb-Cu Amorphous And Nanocrystalline Powders

The increasingly serious electromagnetic pollution problem caused by the development of power electronics industry and the demand of military stealth technology put forward higher requirements for electromagnetic absorption materials.So it is urgent to develop electromagnetic absorption materials with excellent performance.Fe-Si-B-Nb-Cu amorphous and nanocrystalline alloys are new soft magnetic materials,which have excellent soft magnetic properties such as high permeability,low coercivity,low iron loss and so on.Therefore,they are expected to be excellent electromagnetic absorption materials.In this paper,amorphous nanocrystalline alloy with Fe_73.2Si_16.2B_6.6Nb₃Cu₁ composition was designed,and amorphous,nanocrystalline alloy powders and nanocrystalline alloy-carboxyl carbon nanotube composite powders were prepared respectively.The microstructure morphology,soft magnetic properties and electromagnetic absorption properties of the powders were observed.The effects of ball milling time on the microstructure,morphology,soft magnetic properties and electromagnetic absorption properties of amorphous and nanocrystalline alloy powders,and the effects of carboxyl carbon nanotubes content on the electromagnetic absorption properties of nanocrystalline alloy composite powders were studied.The results show that:The soft magnetic properties of the amorphous alloy are improved by the formation of?-(Fe,Si)soft magnetic phase after ball milling.While the nanocrystalline alloy remains amorphous and nanocrystalline complex structure.With the increase of ball-milling time,the content of?-(Fe,Si)phase gradually decreases,and the saturation magnetization of the alloy shows a trend of first increasing and then decreasing.The amorphous alloy powders were elliptic and the nanocrystalline alloy powders were flaky.The minimum average particle size of amorphous alloy powder and nanocrystalline alloy powder is 8.42?m and 6.87?m,respectively.The reduction of particle size improves the electromagnetic wave absorption performance,and the reduction of particle size of nanocrystalline alloy powder is beneficial to enhance the high frequency electromagnetic wave absorption performance of alloy powder.Both amorphous and nanocrystalline alloy powders have excellent electromagnetic wave absorption performance.The nanocrystalline alloy powders have better magnetic loss performance,while the amorphous alloy powders have better dielectric loss performance.The minimum reflection loss of amorphous and nanocrystalline alloys is-42.26d B and-46.15d B,respectively,and the maximum effective absorption bandwidth is up to 5.78GHz and7.22GHz,respectively.The addition of carboxyl carbon nanotubes can effectively improve the dielectric loss capacity of the composite powder,and the minimum reflection loss of composite powder reaches-53.51d B.