Formation of bamboo-like nanocarbon and evidence for the quasi-liquid state of nanosized metal particles at moderate temperatures

Abstract

Carbon nano-filament formation in hydrocarbon and syngas based catalytic processes is fatal for supported metal catalysts as this leads to deactivation and crushing, and hence limitation of carbon deposition has been a major topic in catalysis.^1–5 Recently, the deliberate preparation of catalytically grown nanocarbons has been investigated because of their specific structure and potential for application in many fields.^6–8 Many nanocarbon conformations have been reported, such as tubular, coiled, helical, branched, octopus, etc. and have been found to be sensitive to the reaction conditions and catalyst properties.^9–14 Catalytic hydrocarbon decomposition^9–13 or arc-discharge evaporation of graphite^14–18 have been often used as preparation methods, though in the latter case, the presence of a metal is necessary as catalyst in the form of either vapor or droplets of melt. The selective preparation of a given formation is a challenge to catalysis researchers. Here, several nanocarbon conformations are shown to be formed with high morphological purity from methane on a copper–nickel–alumina catalyst, and some interesting phenomena related to the nanosized metal are reported.