Preparation of carbon-encapsulated iron nanoparticles by co-carbonization of aromatic heavy oil and ferrocene

Carbon-encapsulated iron nanoparticles with uniform diameters have been synthesized on a large scale by co-carbonization of an aromatic heavy oil and ferrocene at 480 °C under autogenous pressure. The morphologies and structural features of the iron/carbon composites were investigated using TEM, HREM and XRD measurements. It was found that, by increasing the amount of ferrocene added from 2 wt.% to 45 wt.%, the size of the nanoparticles increased from 15 nm to 50 nm and the morphologies of the resulting products changed from spherical-type to iron-filled carbon nanorods when the ferrocene loading was higher than 30 wt.%. The iron particles pyrolyzed from ferrocene exist mainly in the form of α-Fe and small amounts of Fe₃C were also formed when the ferrocene content was higher than 20 wt.%. The formation mechanism of carbon-encapsulated iron nanoparticles is discussed briefly. This novel and simple approach constitutes a more practical method to prepare carbon-encapsulated metal nanoparticles than those reported to date.