Magnetic carbon nanocomposites via the graphitization of glucose and their induction heating

Carbon nanocomposites containing iron-based nanoparticles are attractive materials for the catalyst sup-ports used for magnetic (induction) heating catalysis. The metallic, soft-magnetic iron nanoparticles pro-vide local heating of the support in an alternating magnetic field and ensure rapid magnetic separation of the nanocomposite particles from reaction suspensions. In this work, magnetic carbon nanocomposites were prepared by annealing the precursor particles consisting of iron-oxide nanoparticles dispersed in a carbohydrate matrix. The annealing was conducted at 600 degrees C and 750 degrees C in an Ar atmosphere. At both temperatures the carbothermal reduction of iron oxide to Fe/Fe3C was observed; however, at the lower temperature the rate of reduction and the growth of the nanoparticles were considerably slower. The Fe3C was formed in negligible amounts only after a prolonged period of annealing at 600 degrees C. A detailed structural analysis showed that the Fe/Fe3C nanoparticles catalyze the graphitization of the carbonaceous precursor material already at 600 degrees C, resulting in the formation of a graphitic shell that surrounds them. This shell is tight enough to prevent the areal oxidation of the encapsulated Fe nanoparticles; their magnetic properties remained unchanged even after 1 year of storage under ambient conditions. At the higher annealing temperature, the growth of the Fe/Fe3C nanoparticles caused bursting of the graphitic shell and thus par-tially exposed their surfaces to the atmosphere. All the nanocomposites exhibited ferromagnetic behavior in accordance with their compositions. The nanocomposite that was predominantly composed of a graphitic shell, encapsulated Fe nanoparticles and a negligible amount of Fe3C, showed the highest specific ab-sorption rate (760 W/gFe at 274 kHz), even at a relatively low AC-field amplitude (88 mT).(c) 2023 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).