Contents - Akademi Sains Malaysia

B. Nor Aziah and I. Fatiha: New Formulated Hybrid Catalysts for the Synthesis of Carbon NanotubesMicro-reactorN 2 flowmeterTube furnaceN 2regulatorAcetyleneregulatorMixing chamberAcetyleneflow meterCatalystNitrogengasAcetylene gasFume hoodGas trapFigure 1. Diagram of the fixed-bed CCVD reactor.Crof the Cr, Mn and Cu, in the hybrid catalyst formulations 2 O 3NdCr(O(Philippe 2009), and as 3 )NiOfor the larger diameter CNTs theaffected 29the catalytic performance of the respected catalyst. applications was more to the fabrication of advanced28It also proved that Ni was acting as the active species while composite materials.27Cr was acting 26 as the dispersant to hinder the aggregation of The Ni:Mn/Nd catalyst gave the highest density of25Ni particle, so as to control the particle size of the catalyst, CNTs, whereas the Ni:Cr/Nd catalyst exhibited (a) better24and it was23in agreement with the work done by Chen and quality CNTs. The Ni:Mn/Nd and Ni:Cu/Nd hybridWu (2005). 22 The agglomeration and aggregation process catalysts gave non-uniform CNTs with the mixture of21among the Ni particles were further hindered by the addition different forms of carbon nanomaterials (Figure 3b and 3c).20Nd 2 O 2 (O 2 )NiMn 2 O 4NiOof small 19amounts of Nd as the dopant, hence, it stabilized The small diameter CNTs was observed when using Ni:Cr/18the size of the particles of catalyst in the nanometer range. Nd (Figure 3a) due to the presence of small sized particles17In addition, 16 with the assistance of the respected Mn and Cr of catalyst which were assigned earlier as amorphous in thein the Ni 15 based hybrid catalysts formulation, the reduced XRD analysis.14(b)environment during the synthesis was sustained. Thus,13it contributed 12 towards the controlled production of the The presence of spinal NiMn 2 O 4 compound in the11specific form of CNTs.Ni:Mn/Nd hybrid catalyst formulation gave the highest10CuO Nddensity of 4 (CuNi)Oproduction 8 Niof as-synthesized 19 CuO 209CNTs. The8common active species, NiO had catalyzed the growth of76CHARACTERIZATION OF THE AS-CNTs in Ni:Mn/Nd and Ni:Cr/Nd hybrid catalysts. TheSYNTHESIZED 5CARBON NANOTUBES combination of Ni:Cu/Nd hybrid catalyst resulted in the4formation of ternary oxide of Nd 4 (CuNi)O(c)8 . This ternary3Micrograph 2 of FESEMcompound had initiated the formation of the mixture of1carbon nanomaterials with the large diameter of 50 nm0FESEM micrographs in Figure 3 confirmed the morphology (Figure 3c). The presence of the specific oxide phases in20 30 40 5060 70 80 90of all carbon nanomaterials obtained by the decomposition the hybrid catalysts identified from the XRD analysis had2-Theta - Scaleof acetylene at 700ºC over Ni:Cr/Nd, Ni:Mn/Nd and clearly explained its contribution towards the morphologyNi:Cu/Nd hybrid catalysts are the CNTs. This proved that of the as-synthesized CNTs observed from the FESEM.each of the hybrid catalysts were able to produce CNTsbut they differed in term of the quality. The diameter of From the micrographs of the FESEM, it was noted thatCNTs obtained was within the range of 10 nm to 50 nm. the growth mechanism of MWCNT followed the basedThe smaller diameter CNTs plays an important role, growth model, indicated by the absence of white spots atspecifically in the gas storage application and bio-sensors the tips of the CNTs floss (Anne-Claire 2005).Lin (Cps)3