Preparation Of Fe-based/C Nanofibers By Electrospinning And Their Electromagnetic Wave Absorption Performance

One-dimensional nanocrystalline/carbon material with large aspect ratio can easily assemble into a three-dimensional network structure,which is conducive to improve the electron transmission ability and accelerate the heat energy dissipation.Electrospinning is a simple,low-cost and efficient method for preparing nanocrystalline/carbon nanofibers.Compared with ferrites,FeCo and Fe₃C have larger saturation magnetization,which is expected to provide higher magnetic permeability.Based on these considerations,we prepared FeCo/C and Fe₃C/C nanofibers by electrospinning,and investigated their electromagnetic wave absorption properties.The main results are as follows:1. FeCo alloy is an excellent magnetic loss material,which shows high saturation magnetization,low coercivity,high Curie temperature and low magnetocrystalline anisotropy.The FeCo/C nanofibers were fabricated by electrospinning technique,which show a density of 1.1 g/cm³.The dielectric carbon nanofibers were uniformly decorated by tiny magnetic FeCo nanocrystals.The FeCo/nanofibers show good impedance matching conditions and high attenuation ability when the mass fraction is 40 wt%,which perform excellent electromagnetic wave absorption performance.The optimal FeCo/C nanofibers have a minimum RL value of-59.9 d B with broad absorption bandwidth of 6.0 GHz at13.2 GHz,when the thickness is only 2.6 mm.Investigations show that the boosting microwave absorption performance of FeCo/C nanofibers is mainly originated synergistic effects caused by nature resonance,exchange resonance,dipole polarization,interface polarization and micro-current.2. The crystallinity and chemical compositions of microwave absorption materials play an important role on the complex permittivity and permeability.We prepared a series of Fe_xCo_1-x/C nanofibers with different element ratios and crystallinity by changing the raw material ratios and annealing temperatures,and investigated their electromagnetic wave absorption performance.The precursor fibers were treated at 600?,700?,800?,and900?,respectively.The rusults show that the grain size of FeCo increases as the temperature increases,and the carbon component converts into crystalline phase when the temperature rises above 800?.FeCo/C nanofibers prepared at high temperature reveal excellent electromagnetic wave absorption performance,even when the mass fraction is small.The optimal FeCo/C nanofibers have a minimum RL value of-58.8 d B with broad absorption bandwidth of 4.2 GHz at 1.6 mm,when the the mass fraction of FeCo/C nanofibers is only 20 wt%.Four kinds of nanofibers including Fe_0.3Co_0.7/C,Fe_1/3Co_2/3/C,Fe_0.5Co_0.5/C and Fe_0.7Co_0.3/C,were prepared by changing the raw material ratio of Fe/Co.The ratio of Fe/Co can adjust the electromagnetic parameters,which can achieve effective electromagnetic wave absorption performance at a lower thickness.Among them,the Fe_0.5Co_0.5/C nanofibers have a minimum RL value of-18.9 d B,when the the thickness is1.5 mm.3. The anti-oxidation ability of electromagnetic wave absorption material directly affects their practical application.During the research,we found that the FeCo alloy can be oxidized at 200?.Herein,we prepared Fe₃C/C nanofibers by electrospinning with iron acetylacetonate as the iron source.The crystal phase did not change at 200?,revealing a good thermal stability.Electromagnetic wave absorption performance investigations show that the Fe₃C/C nanofibers have a minimum RL value of-54.5 d B with broad absorption bandwidth of 2.7 GHz at 17.8 GHz,when the thickness is only 1.5 mm.Meanwhile,the Fe₃C/C nanofibers have a RL value of-57.9 d B at 5.8 GHz with broad absorption bandwidth ranging from 4.8 to 7.0 GHz,which located in the C band.The Fe₃C/C nanofibers show high thermal stability,good oxidation resistance and remarkable electromagnetic wave absorption performance in the C band,which have broad application prospects in the fields of satellite TV broadcasting,weather radar and civil aviation communication.