Influence of reaction parameters on the attachment of a carbon nanofiber layer on Ni foils

Abstract

Dense carbon (C) and entangled carbon nanofiber (CNF) layers were deposited on nickel foils by decomposition of ethylene in presence of different H2 concentrations at 450°C for different reaction times. Both C and CNF layer thicknesses increase with time, but samples pre-oxidized at 500°C normally lead to thinner CNF layers and thicker C layers, as compared to samples pre-oxidized and reduced at 700°C. The mechanical stability of CNFs decreases with growth time, especially for oxidized-reduced samples. The addition of H2 creates a maximum in the CNF thickness that coincides with a minimum in the C layer thickness, at 5% H2 for samples oxidized at 500°C and at 20% H2 for samples oxidized-reduced at 700°C. CNF layer stability increases with C layer thickness but decreases with CNF layer thickness. The ratio between the C layer thickness and the CNF thickness determines in the end the mechanical stability of the CNF layer.