Experimental study of thiophene and ferrocene in synthesis of single-walled carbon nanotubes in rich premixed hydrogen/air flames

Abstract

The effects of varying concentrations of ferrocene and thiophene on the synthesis of carbon nanotubes (CNT) in a floating catalyst, flame-based reaction system were investigated. Pre-vapourised ethanol and a surrounding premixed H2/air flame were used as carbon feedstock and heat source. Samples of the synthesised material were collected and analysed using Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and X-ray diffraction to determine their compostitions and properties. Sulphur to iron mass ratios mS/Fe were varied from 0 up to 10.1, by changing the relative amounts of thiophene and ferrocene. The latter was found to marginally improve the yield of CNTs, but rather led to an enhanced yield of iron oxide nanoparticles. In comparison, the addition of sulphur resulted in an improved production of CNTs in terms of number density and lengths. An optimum window of mass ratios mS/Fe for CNT production was identified as 0.1–2. A numerical model for the diffusion of species coupled with an equilibrium chemical model for the resulting species has been constructed to understand the mechanisms of the synthesis process, which demonstrates the range of elemental proportion conditions and residence times favourable to high yield of CNTs.