Investigation of disorder in carbon encapsulated core-shell Fe/Fe3C nanoparticles synthesized by one-step pyrolysis

Abstract

Fe/Fe3C (core) - graphite (shell) nanoparticles embedded in micron sized amorphous carbon globules were synthesized by pyrolysis route in a closed reactor. A large number of such nanoparticles were observed to be distributed in the inner section of each globule covered by amorphous carbon in the outer regions. The distribution of nanoparticles varies according to the reaction-temperature-profile of the furnace during the synthesis process. These particles catalyze the formation of the graphitic coating on their surface, due to metastable nature of Fe3C. The globules which contain smaller catalyst particles were found to contain defective- and less amount of graphitic carbon and large amount of amorphous carbon. We observed that for low synthesis temperature conditions the globules contain a thicker shell of amorphous carbon (without any catalyst particle). Furthermore, the amount of disorder in the graphitic layer is determined by the number and size of the (Fe/Fe3C) catalyst particles and reaction-temperature. The disorder in the graphitic layer on the particles can be potentially important for the catalytic behaviour of these particles.