| The methane decomposition on nanocrystalline iron, promoted with small amounts of calcium, aluminum and potassium oxides, was studied. The iron nanocrystallites are bridged by the promoters. The carburization process was carried out in differential tubular reactor with thermogravimetric measurement of mass changes. The carburization was investigated for a reduced iron catalyst with pure methane at temperature 650 °C under atmospheric pressure during several different carburizing levels. The carburized samples contained nanocrystalline forms of iron carbide (Fe3C), iron and graphite, what was evidenced by XRD measurements. Ferromagnetic resonance (FMR) spectra of Fe3C and α-Fe nanoparticles have been recorded at room temperature in samples subjected to different carburization levels. The FMR spectra have been analyzed in terms of four components having Callen lineshape and revealed anisotropic magnetic interaction in two types of nanoparticles. The anisotropic resonance fields (parallel and perpendicular) were used to determine the magnitude of the anisotropy fields for both types of nanoparticles while the dipol-dipol interaction between nanoparticles was responsible for the linewidths of the spectral components. |
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