Synthesis of single-walled carbon nanotubes in rich hydrogen/air flames

Abstract

We explore the production of single-walled carbon nanotubes (CNTs) in a stream surrounded by rich premixedlaminar H2/air flames using a feedstock containing ethanol and ferrocene. The as-produced nanomaterialswere characterised by Raman spectroscopy, transmission electron microscopy, scanning electron microscopyand X-ray diffraction. A formation window of equivalence ratios of 1.00–1.20 was identified, and single-walledCNT bundles with individual CNTs of an average diameter of 1 nm were observed. The formation of CNTswas accompanied by the production of highly crystalline Fe3O4nanoparticles of a size of 20–100 nm. Theinvestigation of the limiting factors for the CNT synthesis was carried out systematically, assisted by numericalmodelling. We conclude that the key factors affecting CNT synthesis are the surrounding flame temperatures and the concentration of carbon available for CNT nucleation.