Preparation And Electromagnetic Shielding Properties Of Iron-based FeSiBPCu Amorphous/nanocrystalline Composite Powders

With the rapid development of modern electronic industry and information industry,theharm caused by electromagnetic radiation can not be ignored.Exploring efficient electromagnetic shielding materials has become an urgent problem to be solved.High permeability(μ)and saturation magnetization(Ms)are prerequisites for high-efficiency electromagnetic shielding materials.The iron-based Fe Si BPCu nanocrystalline alloys developed in recent years have excellent soft magnetic properties such as high Ms,high μ,and low loss,but little research has been conducted on their electromagnetic shielding properties.In this paper,the high-iron-content Fe83.3Si4B8P4Cu0.7 alloy powders were prepared by high-energy ball milling,and the effect of milling time and annealing process on the structure,morphology and electromagnetic properties were investigated.The alloy powders with an amorphous/nanocrystalline composite structure and excellent electromagnetic shielding performance was obtained.The microstructure and morphology were characterized by X-ray diffraction(XRD)and scanning electron microscope(SEM),respectively.The thermal and magnetic properties were determined by differential scanning calorimetry(DSC),and vibrating sample magnetometer(VSM),respectively.The electromagnetic parameters were tested by vector network analyzer and the reflection losses(RL)were calculated according to transmission line theory.The results are summarized as following:The micron-sized Fe83.3Si4B8P4Cu0.7 alloy powders with an amorphous/α-Fe nanocrystalline composite structure can be formed after milling.With the increase of the milling time,the particle size of the powders gradually decreased,and the α-Fe grain size first decreased and then remained at about 6 nm.The Ms of the alloy powders increased first and then decreased with the increase of the milling time,while the coercive(Hc)showed a conversed tendency.The powders after milling for 100 h had the best soft magnetic properties,and the Ms reached a maximum value of 182.3emu/g.The real part of the complex permeability and complex permittivity of the powders gradually increased with the increase of the milling time.The imaginary part of the complex permeability all had a large value at high frequency,and the imaginary part of the complex permittivity was almost zero,indicating that the powders were mainly based on magnetic loss.Under the perfect matching condition,the thickness of the sample gradually became thinner,the peak of the RL corresponding to the frequency shifted to high frequency,the frequency width of RL <-10 d B gradually widened,and the minimum RL corresponding to the sample with a thickness of 2 mm reached-44 d B after 100 h milling.After annealed at 573 K for 30 min,the α-Fe grain size and Ms changed slightly,while the Hc decreased significantly.Under the perfect matching condition,the thickness of the sample changed slightly,and the minimum RL decreased to-54 d B.After annealing at 773 K,the grain size increased significantly,and the soft magnetic properties electromagnetic shielding performance were deteriorated.