Impaction of precursor gas-induced catalyst change on morphology, growth kinetics and field emission property of carbon nanofibers

Abstract

Three types of carbon nanofiber (CNF): filamentous CNF, chain-like CNF and thick CNF were successfully synthesized from three hydrocarbon precursor gases of ethylene (C₂H₄), n-hexane (n-C₆H₁₄) and n-dodecane (n-C₁₂H₂₆) on iron catalyst at 1073 K. A detailed study implied that the nucleation of iron catalyst in the incubation period varied with the type of the precursor gas, which intensively affected the morphology, structure and growth kinetics of the CNFs. A thermodynamic basis of carbon diffusion in iron particle for the catalyst activity was derived. Various characterizations demonstrated that the typical filamentous CNFs (∼50 nm), developed from C₂H₄ with relatively large aspect ratios and highly ordered graphene layers, possessed the highest field emission enhancement factor (β). By contrast, the chain-like CNFs (∼80 nm), developed from n-C₆H₁₄ with non-sequence graphene layers, and the thick CNFs (∼500 nm), developed from n-C₁₂H₂₆ with numerous micropores and mesopores in the disordered graphene layers, possessed the lower values of β.