Carbon nanotubes (CNTs) represent an important group of nanomaterials with attractive geometrical, electrical and chemical properties and are synthesized using a variety of techniques. CNTs have been extensively studied in our previous works and in this study were fabricated by arc discharge full automatic set up in liquid which does not require vacuum equipment, heat exchange system, active or inert gases. This technique was full automatic which enabled the controlling of gap between the two electrodes. The effect of the kind of catalyst on quantity of synthesized CNTs was studied herein. Carbon nanotubes were fabricated between two graphite electrodes which were submerged in the LiCl 0.25N as a solution and with a voltage of 25v. For comparative studies, Ni, Mo, Fe and Ni‐Mo were exploited as metallic or bimetallic catalysts and the results were subsequently analyzed, compared and discussed. In order to analyze the morphology of the synthesized products a scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) study were employed. Based on Mo‐Ni as catalysts in carbon electrode, high‐crystalline and alonged multi walled carbon nanotubes (MWCNTs), single walled carbon nanotubes (SWCNTs) and spring‐like carbon nanotubes (SCNTs) were synthesized by using this unique technique. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Well graphitised nanocarbons including onion-like fullerenes and single-and multi-walled carbon nanotubes (CNTs) were synthesised in high yield by automatic arc-discharge method in solution. This technique is considered a low-cost method since it does not require any expensive equipment. Herein, an arc discharge full automatic set-up was used for fabrication of CNTs which enables controlling of the gap between the two electrodes and the voltage as well. Carbon nanostructures under a controlled amount of voltage (from 10 to 30 V) were synthesised where Ni : Mo as a catalyst and LiCl 0.25 M as a solution were used. Subsequently, a modified acid treatment method was applied as purification stage of the products. The production rate of CNTs was as high as 7.7 mg min À1 while the voltage was set at 30 V. Scanning electron microscopy and transmission electron microscopy as well as Raman spectroscopy were employed to study the morphology of these carbon nanostructures. The results indicated that CNTs synthesised at a voltage of 30 V had the best quality and elongated straight structures. The mechanism of the voltage conditions for preparing nanocarbons as well as their characterisation are discussed.

Carbon nanotubes (CNTs) are fascinating structures with a wide range of applications and several methods have been developed for their fabrication. The arc‐discharge in liquid method is a new technique for synthesis of nanocarbon structures and is recognized as a low‐cost method. In this work, this method was used for fabrication of carbon nanotubes, and subsequently a modified acid treatment method was applied as a purification stage. In order to optimize the process, a statistical design of experimental (Taguchi method with L9 orthogonal array robust design) was implemented in this study. As the result of Taguchi analysis in this study, voltage, ratio of catalyst and solution were the most influencing parameters on the yield product of carbon nanotubes (7.9 mg/min purified CNTs). The maximum product yield of CNTs was obtained at a voltage of 25 V, NaCl 0.2N as a salt in solution, Ni/Fe as a catalyst and a 1:1 catalyst ratio. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) as well as Raman spectra were utilized to study the morphology and purity of these carbon nanotubes. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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