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On the graphitisation role of oxide supports in carbon nanotube CVD synthesis

Abstract:

In this contribution we present various data from CNT grown from supported catalysts. The observed data are in agreement with the catalyst volume to surface area model developed for floating catalysts and which pbkp_redicts a direct CNT diameter and number of wall dependence on the catalyst size. Further, our studies point to the root of a CNT lying at the support rather than the catalyst. Additional supporting studies point to oxygen playing a critical role in the growth of CNT, viz. the CNT can grow from an oxide support rather than the catalyst. In this scenario the catalysts role is twofold; to precipitate carbon from the catalyst-carbon eutectic upon supersaturation and thus form the embryonic caps and to form circular defect sites at its circumference on the oxide support. These circular defect sites enable continued CNT growth directly from the support. Our findings point to catalytic processes very reminiscent of many other heterogeneous catalytic processes. (Figure Presented) © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.