Contents - Akademi Sains Malaysia

NitrogengasAcetylene gasFume hoodGas trapASM Science Journal, Volume 7(1), 2013Cr 2 O 3NdCr(O 3 )NiOLin (Cps)29282726252423222120191817161514131211109876543210Nd 2 O 2 (O 2 )NiMn 2 O 4NiOCuO Nd 4 (CuNi)O 8Ni 19 CuO 2020 30 40 5060 70 80 902-Theta - Scale(a)(b)(c)Figure 2. XRD patterns for series of hybrid catalysts: (a) Ni:Cr/Nd, (b) Ni:Mn/Nd and (c) Ni:Cu/Nd catalysts.Thermal Gravimetric AnalysisThermal gravimetric analysis (TGA) is one of thefundamental studies to differentiate the types of carbonnanomaterials. Its purity can be determined by calculatingthe percentage of mass loss during the heat treatment. Thedecomposition temperatures in Table 1 shows that theCNTs synthesized using the respected Ni:Cr/Nd, Ni:Mn/Nd and Ni:Cu/Nd hybrid catalysts gave one region of massloss. This was an indication for the complete combustion ofthe specific form of CNTs with high purity, produced fromthe respected hybrid catalyst formulated.It was found that, CNTs synthesized using Ni:Cr/Nd catalyst had the lowest decomposition temperatureat 500°C with 90.64% of mass loss, which indicated thatthe diameter of the as-synthesized CNTs was the smallestcompared to the other two hybrid catalysts formulated(Table 1). Small diameter CNTs usually decomposed atlower temperature compared to that of the larger diameterCNTs (Li et al. 2009). This result was in good agreementwith the FESEM analysis of CNTs showed in Figure2a. Whereas, the decomposition temperature for the assynthesizedCNTs from Ni:Mn/Nd catalyst occurred at thehighest temperature of 630°C with 96.98% of mass loss.This observation as attributed to the presence of largerdiameter CNTs and the presence of other form of carbonnanomaterials and was in agreement with the FESEManalysis showed in Figure 2b. The as-synthesized CNTsdominated was identified as MWCNTs and depicted highquality and purity when using Ni:Cr/Nd. However, whenusing Ni:Cu/Nd and Ni:Mn/Nd the CNTs produced werehighly dense.CONCLUSIONSeries of new hybrid catalysts of Ni:Mn/Nd, Ni:Cr/Ndand Ni:Cu/Nd, have been successfully formulated for theproduction of MWCNTs with the average diameter of 30nm. The presence of the oxide phases, identified as spinaland ternary oxides in the hybrid catalyst formulation, werethe active phases which had enhanced the growth of CNTs.The metal-metal interactions in the catalyst had stronglyinfluenced the growth of the CNTs, specifically with highpurity and density. The Cr, Mn and Cu transition metalsintroduced in the Ni based hybrid catalysts formulationwere acting as the promoter towards the formation of theactive oxide phases as well as the dispersant to enhancethe production of CNTs; whereas, the addition of Ndhad enhanced the formation of nanoparticle catalyst withuniform size.4