Thermal phase transition controlling electromagnetic wave absorption behavior of PAN fiber derived porous magnetic absorber

The increasing excess electromagnetic wave (EMW) energies causes potential electromagnetic radiation pollution. It gives rise to more and more attention on designing environmentally friendly, efficient and suitable for large-scale industrial production of daily EMW absorbers. Carbon matrix composites modified with magnetic particles occupy the majority of these candidate absorbers. How-ever, the preparation is still in its infancy. Here, wecreatively mixed Fe(acac)(3) with polyacrylonitrile (PAN) spinning solution, and then prepared magnetic carbon-based composites by in-situ pyrolysis of the obtained electrospun fibers (Fe(acac)(3)/PAN) at different temperatures. The SEM images display a fractured fibrous material with porous structure and uniform distribution of magnetic particles on the outer surface and inside. The XRD and XPS results indicate the composites consist of Fe3O4, Fe3C and carbon matrix. Besides, the thermal phase transition occurs with the pyrolysis temperature increasing from 300 to 1000 degrees C, and the formed Fe3O4 reacts with the carbon matrix to form Fe3C. As a result, the corresponding magnetic properties and electromagnetic properties improve. MCF-1000 exhibits enhanced EMW absorption performance with a minimum RL (RLmin) value of - 29.27 dB at a matching frequency (f(m)) of 11.68 GHz, a matching thickness (t(m)) as low as 1.50 mm, and an effective frequency bandwidth as broad as 4.50 GHz from 13.50 to 18.00 GHz at a fixed thickness as thin as 1.13 mm. Further investigations indicate that such good EMW absorption behavior is attributed to the optimal impedance matching and the weakened eddy current effect which are both benefited by the thermal phase transition effect. The results provide theoretical and practical experience for the industrial large-scale preparation of a kind of EMW absorbers.

Automated summary

By creatively mixing Fe(acac)(3) with polyacrylonitrile (PAN) spinning solution, magnetic carbon-based composites were prepared in this study. It was found that the increase in pyrolysis temperature caused thermal phase transition resulting in the formation of Fe3C, improving the magnetic and electromagnetic properties. The results provide theoretical and practical experience for the industrial large-scale preparation of a kind of EMW absorbers.