On the correlation between CVD growth conditions and crystalline quality and abundance of multi-walled carbon nanotubes

INFM, Dipartimento di Meccanica e Materiali, Facoltà di Ingegneria, Università “Mediterranea”, Località Feo di Vito, 89060 Reggio Calabria, Italy

Corresponding author: saveria.santangelo@unirc.it

Received: 30 October 2007
Accepted: 15 January 2008
Published online: 9 April 2008

Abstract

Multiwalled carbon nanotubes (MWCNTs) were synthesised by chemical vapour deposition (CVD) in a C₂H₆+H₂ atmosphere over 20%Fe/SiO₂ catalysts. The influence of synthesis temperature, flow-rate and flow ratio of the reactant gases, the amount of catalyst employed and the catalyst reduction temperature on the abundance and crystalline perfection of product was analysed by scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The changes in yield and crystalline perfection, as monitored by Raman G' band relative intensity, were correlated with the variations of synthesis temperature, the diverse catalyst surface area and H₂/C supply ratio attained by varying growth conditions. In the range examined, the lowering of catalyst reduction-temperature turns out to be beneficial for both yield and crystalline perfection of the MWCNTs. All the other growth parameters produce opposite effects so the best compromise has to be sought.