Production of Multi-walled Carbon Nanotubes via Catalytic Decomposition of Methane in the Chemical Vapor Decomposition process GHAZALEH ALLAEDINI 1* , SITI MASRINDA TASIRIN 1 , PAYAM AMINAYI 2 , ZAHIRA YAAKOB 1 , MEOR ZAINAL MEOR TALIB 1 1 Department of Chemical and Process Engineering, University of Kebangsaan Malaysia, UKM Bangi, Selangor, Malaysia 2 Chemical and Paper Engineering, Western Michigan University, Kalamazoo, Michigan, USA * Corresponding author email: jiny_ghazaleh@yahoo.com,masrinda@eng.ukm.my , phone: +603- 89218428 Abstract: In this paper, carbon nanotubes (CNTs) were synthesized via vapor deposition of methane as a carbon source in the presence of Ni/MgO catalyst. The catalyst crystallinity and morphology was examined by XRD and SEM and its superior size distribution and crystallinity was confirmed. The catalytic methane decomposition was conducted in a chemical vapor deposition reactor at 900 °C. Methane, with the flow rate of 600 ml/min, was used as a carbonous gas and hydrogen and nitrogen were used at the flow rate of 500 ml/min. The obtained carbon was characterized by transmission electron microscopy (TEM) and recognized to be multi-walled carbon nanotubes with an average diameter of ~8.6 nm. The Raman spectrum confirmed a high graphitization degree of the obtained CNTs with an I D /I G ratio of 2.05, indicative of high crystallinity with few structural defects. Moreover, the thermal analysis showed the high oxidation stability of the multi-walled carbon nanotubes. It was concluded that Ni/MgO catalyst can be used as an active catalyst in the production of multi-walled carbon nanotubes (MWCNTs) in the vapor phase deposition process. Keywords: Ni/MgO catalyst, methane decomposition, multi-walled carbon nanotubes. I . INTRODUCTION Multi-walled carbon nanotubes (MWCNT) were discovered by Iijima in 1991[1]. Later in 1993, single-walled carbon nanotubes (SWCNT) were discovered by the same researcher[2]. Carbon nanotubes with form of Bamboo shaped has been reported as well.[3] Since the discovery, research about the different methods of production, properties and applications of carbon nanotubes has been continued. Although all carbon nano structures, including fullerenes, graphene and nanotubes are of great interest, CNTs have many unique physical and electrical properties [4] which make them an ideal candidate for numerous applications from field emission sources[5] to anti- cancer agent[6]. There are a number of methods to produce carbon nanotubes, including arc discharge, chemical vapor deposition, plasma enhanced chemical vapor deposition, laser ablation, and high-pressure CO conversion production[7] and CO2 conversion [8]. However, chemical vapor deposition (CVD) is still the most dominant method of high-volume carbon nano structures production [9] which typically utilizes a fluidized bed reactor that enables a uniform gas diffusion and heat transfer to the metallic catalyst nanoparticles employed in the CNT production[10]. In a CVD process, CNTs are produced via the decomposition of a gaseous carbon-containing hydrocarbon source at an elevated temperature in the presence of a transition metal catalyst [11]. A high nanotubes production yield can be achieved using this method. In addition, the product obtained using this approach tends to posses high purity and the growth of the carbon nanotubes requires a lower temperature in the range of 550-1000 °C when compared to other methods. This renders the process cheap, easy for lab scale production, and suitable form as production for commercial applications[12]. Finally, when catalyst is supported with a substrate, the growth of nanotubes can be controlled in a desired direction with respect to the substrate[13, 14]. As mentioned earlier common transition metals such as Ni, Co, Fe have been used in the production of carbon nanotubes. Despite the fact that MgO has been shown to be a superior support in the production of carbon nanotubes [15], there are no comprehensive reports which examines the utilization of such materials in the production of carbon nanotubes via chemical vapor deposition of methane gas. In this work MgO supported nickel was used as a novel catalyst in the production of INTERNATIONAL JOURNAL OF MATERIALS Volume 2, 2015 ISSN: 2313-0555 48