FMR study of nanocarbon materials obtained by carburisation of nanocrystalline iron.

Samples of nanocrystalline iron were carburised with ethylene and next reduced with hydrogen. Both carburisation and reduction were monitored by the thermogravimetry. The obtained samples were characterised using X-ray diffraction, high-resolution transmission electron microscopy and ferromagnetic resonance. The samples after carburisation contained cementite (Fe₃C) and carbon deposit (nanofibres and nanotubes). As the result of reduction with hydrogen at 450 or 500 °C cementite was reduced to iron. A major part of carbon was also hydrogenated, only thin carbon nanotubes remained. The FMR spectra of the prepared samples were recorded at room temperature. The sample after carburisation has shown a wide FMR line with weak intensity while the resonance field has been shifted to lower magnetic field. This spectrum has been attributed to the presence of cementite. The FMR lines corresponding to samples after reduction are more intense and are connected with the presence of a-Fe nanoparticle conglomerates. [ABSTRACT FROM AUTHOR]