The role of the hydrocarbon source on the growth of carbon materials Review Article

In recent years extensive studies on carbon nanotubes has led to the synthesis and characterization of other carbons with a wide range of morphologies. Current understanding is that the carbon reagents decompose in the presence of a catalyst to give C atoms that then combine or extrude into carbon nanotubes, fibers (or spheres). This mechanism does not indicate how the structure of the carbon source can impact on a material’s growth, in particular at low temperatures. In this paper we show that evidence exists to indicate that the structure of hydrocarbons (and other carbon reagents) has the ability to influence the carbon growth process. This can be achieved by catalyst–reactant effects (and subsequent catalyst reconstruction) that are influenced by both the production of carbon fragments and radicals produced in the gas phase or by direct reaction of the carbon source with the metal particle. A modification of the current Baker carbon growth model, to show the metal–catalyst interactions, that takes this information into account (particularly at temperatures lower than 500 °C) is proposed.