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

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 decompositiong-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.