Study On Electromagnetic Properties Of Iron Base Absorbent Made By Mechanical Alloying

The iron-based alloy powders were processed by high-energy ball mill method. Firstly, the characterizations properties of water atomized Fesy.sSi7Al5.5(Wt.%) alloy processed by ball-milling and Fe-Co-Ni alloy made by mechanical alloying. The morphology, microstructure, and electromagnetic properties were measured by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and vector network analyzer (VNA). Moreover, Moreover, the magnetic property was calculated in a theoretical perspective using the first principle based density functional theory (DFT), and the effect of the changes in electronic structure on the saturation magnetization was investigated. The results show that:The analysis results showed that the Fe87.5Si7Al5.5(Wt.%) powders shape became flaky from fusiform. The powders showed a reduction of the average grain size and the increase of the internal strain, and then presented an adverse variation trend after55h milling. The powders that milled10h had the largest saturation magnetization Ms (131emu/g). The value10of the powders decreased with increasing milling time at relatively lower frequency (2-8GHz), but opposite variation tendency happened at higher frequency (8-18GHz). Also, only short time milling can enhance the value of100in the test frequency. The powders after10h milling showed excellent microwave absorption (RL≤10dB) at the frequency9.0-15.6GHz and the absorption peak shifted regularly to the high frequency as the increased milling time.The Fe-Co-Ni alloy was made by mechanical alloying method. The systematically discussion about microstructures (morphology, phase, grain size, internal strain, etc.) and electromagnetic properties including saturation magnetization (Ms), coercivity (Hc), electromagnetic parameter (μ=μ’-jμ,", ε=ε’-jε") and microwave absorption ability (RL) were carried out and found those related properties changed in the alloying process with the extension of milling time (Oh,25h,40h,55h and90h). The α-Fe (Co) powders obtained after milling25h had the maximum Ms (153emu/g). The microwave absorbing characteristic was enhanced with milling process, and the minimum RL (-32.4dB) was obtained at about9GHz after90h milling.The electronic configurations and magnetic properties were investigated using the first-principle method based on the density functional theory (DFT). The supercell (5×1×1) of Fe, Fe7Co1, Fe6Co2, Fe9Ni1and Fe8Ni2were constructed. The results showed that Ni or Co doping changed the electronic configuration of Fe atoms, resulting in the enhancement of spin polarization of Fe and the larger Bohr magnetic moment in Fe-(Ni, Co) alloys. The Bohr magnetons of Fe supercell (5×1×1), Fe9Ni1and Fe8Ni2were23.14,23.34and22.61μB, respectively, showing that the proper Ni impurity in α-Fe favored the enhancement of magnetic moment.