The electronic state of carbon in the products of co-carbonization of an aromatic heavy oil and ferrocene in an autoclave has been studied by X-ray emission spectroscopy. Analysis of the C K alpha-spectra revealed that the proportion of graphite-like component in the samples containing ferric spherical and tubular nanoparticles is about 55% and 65%, respectively. An average size of graphitic sheets forming the coating on metallic cores and the carbon matrix was estimated by the results of quantum-chemical calculations on graphene fragments to be similar to 2 nm. The field electron emission properties of the studied carbon materials were found to be dependent on the graphitization degree, not on the aspect ratio of constituting nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.