ORIGINAL PAPER Effect of hydrocarbon gas on synthesis and diameter of carbon nanotubes F Taleshi 1 *, A A Hosseini 2 , M Mohammadi 2 and M Pashaee 2 1 Department of Applied Science, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran 2 Department of Physics, Faculty of Sciences, Mazandaran University, P.O. Box 47416-95447, Babolsar, Iran Received: 07 March 2013 / Accepted: 14 May 2013 Abstract: In this study, effect of ethylene and acetylene on synthesis and diameter of carbon nanotubes has been examined. The synthesis of carbon nanotubes has been carried out by chemical vapor deposition method on iron catalyst nanoparticles, at 925 °C under atmospheric pressure. Iron oxide nanoparticles have been prepared in alcohol solution containing MgO powder as a support, with a combination of 10–40 wt% by impregnation method. During synthesis of carbon nanotubes, temperature, carrier gas flow and hydrocarbon gases have been kept constant. The produced materials have been characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Keywords: Carbon nanotubes; Catalyst nanoparticles; CVD method; Impregnation method PACS Nos.: 61.46.-w; 61.46.Fg; 61.48.De 1. Introduction Due to their unique structural and physical properties car- bon nanotubes (CNTs) are promising candidates for applications ranging from nanocomposites, gas storage, sensors, nanoelectronics, field emission displays and elec- trochemical devices [1–4]. CNTs’ properties and conse- quently, their potential applications strongly depend on CNTs structural characteristics such as length, number of layers, diameter or presence of defects on sidewall and cap. Thus, a very strict control of experimental parameters is required during CNTs production. Carbon nanotubes can be produced by different tech- niques, mainly by arc-discharge [5], laser ablation [6] and thermal chemical vapor deposition (TCVD) [7–9]. In recent years, many efforts have been carried out to control the growth process of CNTs by CVD method, because of its versatility, low cost, high purity, size selectivity and high production yield [7–11]. In CVD method, the types of carbon precursors, furnace temperature, types and size of catalyst particles and support material greatly affect the growth rate of carbon nanotubes [7, 10–13]. Control of the diameter of CNTs has been a key issue. Carbon precursors play a key role in affecting the structural properties of carbon deposits. Several hydrocarbons have been used as precursors for the CVD growth of carbon nanotubes [14– 16]. Investigation of carbon precursors used within the same reaction system is thus crucial towards understanding the formation of nanotube influenced by the features of carbon precursors. In the present study, we have addressed this issue by selecting two hydrocarbons ethylene and acetylene, which are relatively chemically stable at high temperature and easily decomposable for the catalytic decomposition stud- ies with fixed-bed growth model. 2. Experimental details Carbon nanotubes were synthesized by chemical vapor deposition of hydrocarbons over MgO supported Fe 2 O 3 catalyst, which was prepared by chemical impregnation method [10, 17]. Fe 2 O 3 /MgO catalysts were prepared with different contents ranging from 10, 20, 30 and 40 wt% of iron oxide. In a typical synthesis procedure, 1 g of light weight MgO powder ( [ 99.0 % purity, Aldrich) was dis- persed in 30 ml of ethanol and the suspension was soni- cated, followed by stirring for 10 min in order to get a *Corresponding author, E-mail: far.taleshi@gmail.com Indian J Phys DOI 10.1007/s12648-013-0319-z Ó 2013 IACS