Electron energy-loss spectroscopy characterization and microwave absorption of iron-filled carbon-nitrogen nanotubes

Iron-filled carbon-nitrogen ( Fe/CNx) nanotubes and iron-filled carbon ( Fe/C) nanotubes were synthesized at 900 degrees C through a pyrolysis reaction of ferrocene/acetonitrile and ferrocene/xylene, respectively. The differences of structure and composition between the Fe/CNx nanotubes and Fe/C nanotubes were investigated by transmission electron microscopy and electron energy-loss spectroscopy ( EELS). It was found that the morphology of Fe/CNx nanotubes is more corrugated than that of the Fe/C nanotubes due to the incorporation of nitrogen. By comparing the Fe L-2,L-3 electron energy-loss spectra of Fe/CNx nanotubes to those of the Fe/C nanotubes, the electron states at the interface between Fe and the tubular wall of both Fe/CNx nanotubes and Fe/C nanotubes were investigated. At the boundary between Fe and the wall of a CNx nanotube, the additional electrons contributed from the doped 'pyridinic-like' nitrogen might transfer to the empty 3d orbital of the encapsulated iron, therefore leading to an intensity suppression of the iron L-2,L-3 edge and an intensity enhancement of the carbon K edge. However, such an effect could not be found in Fe/C nanotubes. Microwave absorption properties of both Fe/CNx and Fe/C nanocomposites at 2-18 GHz band were studied.