During the experiments aimed at understanding the evolution mechanism by which vapor grown carbon nanofibers (VGCNFs) nucleate and grow, a series of carbon nanomaterials were synthesized by chemical vapor deposition (CVD) using deoiled asphalt (DOA) as carbon source and ferrocene as catalyst precursor with an experimental strategy developed to quench the CVD at different deposition times (3-30 min). The morphology and microstructure of the products were investigated by field emission scanning electron microscope, high resolution transmission electron microscope and X-ray powder diffractometer. The formation of hollow/metal-encapsulating carbon nanoparticles at short deposition time (3 min) of CVD and the subsequent evolution of these nanoparticles into carbon nanotubes/nanofibers at longer deposition time suggest a multi-step growth model for VGCNFs, which includes the stages of (1) pyrolysis and aggregation, (2) nucleation, coalescence and self-assembly, and (3) development and maturation. At first, C, Fe and Fe/C clusters are produced by decomposition and agglomeration of C and Fe species from the pyrolysis of DOA and ferrocene; second, the carbon nanoparticles are self-assembled into nanowires with dispersive metal nanoparticles, which are further developed into nanotubes for structural stability and minimum surface energy, meanwhile fishbone-like CNFs might be formed by rearranging carbon layers at an angle against the tube axis under the nucleation of small graphitic layers on certain crystal orientation of the metal particles: finally. CNFs are formed by the synergistic action of metal catalysis and continuous rearrangement of graphitic layers. (C) 2010 Elsevier B.V. All rights reserved.