A comparative study of the morphology of carbon nanotubes synthesized from organometallic precursors in

M. M. ESCOBAR; D. ZILLI; S. N. GOYANES; P. BOZZANO; G. R. RUBIOLO; A. L. CUKIERMAN

Buenos Aires, Argentina

Workshop; Seventh J.J. Giambiagi Winter School; 2005

Depto de Fisica FCEyN UBA

Among the different synthesis routes leading to the production of carbon nanotubes (CNTs), the chemical vapor deposition (CVD) process is currently conceived as one of the most interesting alternatives towards an economically viable upscale. In turn, the CVD of organometallic compounds, as starting materials, in hydrogen atmosphere is particularly attractive since it provides both the metallic nanoparticles acting as catalyst and the carbon source required for nucleation and growth of the CNTs, thus avoiding tedious work involved in the preparation of the former ones. Though studies in the literature have been devoted to explore the use of different organometallic precursors,  the influence of process variables has been scarcely investigated. Within this context, the present work aims at examining comparatively the effect of main operating conditions on the morphology of CNTs arising from CVD of organometallic compounds involving two different transition metals. Nickel phtalocyanine and iron phtalocyanine are used as precursors. For each precursor, the synthesis process is carried out in a semi-continuous quartz tubular reactor within a two-zone furnace, operated under a flow of H2 and Ar. Quartz substrates are conveniently placed inside the reactor for nucleation and growth of CNTs. Process variables examined systematically include the reaction temperature, total gas flow rate, gas composition, and reaction time. The CNTs synthesized from both precursors for the different experimental conditions are characterized by scanning and transmission electron microscopy. Large arrays of self-aligned CNTs are obtained on the quartz substrates. The effect of the operating conditions on the diameter, length, alignment, and compactness of the grown CNTs is analyzed accounting for the metallic species composing the organometallic precursor.