Modeling of fishbone-type carbon nanofibers with cone-helix structures Original Research Article

Proposing a plausible model for fishbone-type carbon nanofiber (f-CNF) proves to be a challenge. A practical approach to the construction of a cone-helix model is suggested on the basis of early experimental observations and from a geometric perspective. With the introduction of disclination angle and overlap angle into graphene sheets, the resultant helical cones have variable morphologies which rationalize the broad distribution of the f-CNF apex angles. A fraction of overlap angles can produce energetically favorable cone-helix models with high densities of coincident lattice points. Once the nearest coincident points to the apex is identified, both the overlap angle and the degree of graphitic alignment can be obtained. Periodic boundary conditions are imposed on the cone-helix models to depict the f-CNF morphologies along the principal axes. The lattice strain induced by the multi-layered model is found to have a negative effect on the structural stability. After the central parts of f-CNFs are removed, the lattice strain around the cone tips is eliminated, and the cone-helix model of more graphite layers is energetically more favorable. X-ray diffraction simulations are finally conducted to evaluate the reliability of the proposed models and to reveal the identity of the reflections at the diffraction angle of 44.5°.