Synthesis and enhanced electromagnetic wave absorption performance of amorphous CoxFe10-x alloys

Using NaBH4 as reductant, a fast reduction method was developed to synthesize CoxFe10-x alloys nanochains with different Fe molar fractions. XRD and SAED investigations reveal as-prepared nanostructures have amorphous features. By annealing at 500 degrees C, crystalline CoxFe10-x alloy nanostructures with similar morphology can be obtained. Magnetic properties reveal that the saturation magnetization and coercivity of the samples strongly depend on the Co/ Fe ratio, and the amorphous samples perform lower coercivity and remarkable soft magnetic behavior. The amorphous samples can hold good complementarities between the dielectric loss and the magnetic loss, which are beneficial for the impedance matching. Therefore, the amorphous samples have dramatic enhancement of electromagnetic wave absorption properties compared to the crystallized samples with similar chemical components. In particular, with a thickness of 2 mm, the strongest reflection loss (RL) of amorphous Co4Fe6 alloy based sample is up to -38.7 dB at 15.1 GHz, the effective absorption (RL < -10 dB) bandwidth can reach 6.9 GHz (10.1-17.0 GHz). These results suggest that the amorphous nanostructures may be promising candidates as high efficient electromagnetic wave absorbing materials. (C) 2017 Elsevier B.V. All rights reserved.