The graphitization of carbon nanofibers produced by the catalytic decomposition of natural gas

Fishbone carbon nanofibers (CNFs) were produced by methane decomposition in a fluidized bed reactor using nickel–copper based catalysts that were prepared with different promoters (SiO2, Al2O3, TiO2, MgO). The CNFs were subjected to heat treatment (HT) in the temperature range 2400–2800 °C to explore their ability to graphitize. The influence of treatment temperature and CNF metal content on the structural and textural parameters of the resulting heat treated carbon nanofibers was studied. More-ordering was achieved in CNFs containing Si and Ti because of the catalytic effect of these metals. Since titanium carbide appeared after the HT, the formation of graphitic material by carbide decomposition seems to be a plausible mechanism to explain the catalytic graphitization of the CNFs. A parallel evolution of the structural and textural properties of the nanofibers during HT was found, suggesting that a decrease of the specific surface area is caused by the removal of structural defects and an increase of crystallite size.