| Multi walled carbon nanotubes (MWNTs) were synthesized via methane chemical vapor decomposition using low-cost activated carbon (AC) as support for Fe and Ni catalyst. Maximum methane conversions of 98% and 42% were observed on Fe and Ni catalysts respectively at reaction temperature of 750 °C by on-line gas chromatography. Bundles of MWNTs with an average internal dia ~ 20nm at 850 °C over Ni catalyst and thin-walled CNTs (dia ~ 8 nm) formed over Fe catalysts were confirmed by morphological studies by transmission electron microscopy. CNTs formed over Fe catalyst illustrated a typical tip-growth phenomenon. The formation of MWNTs was further supported with the data obtained from thermogravimetric analysis. The ideal condition for CNTs growth was noticed under N2/CH4 gas flow ratio of 2:1 rather than H2/CH4 atmosphere. CH4 atmosphere. |
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