Effect of processing conditions on unsupported Ni-based catalysts for graphitic-nanofibre formation

Graphitic nanofibres (GNFs) were successfully synthesised at low temperatures (below 400 °C) using NiO powder as the catalyst precursor and a H2/C2H4 gas mixture with a high yield, around 57ggcatalyst-1h-1. The yield was found to vary with temperature with the optimum yield at 500 °C. XRD patterns confirm that during GNF formation the NiO was reduced forming either metallic Ni and or Ni3C phase. TEM study confirmed the formation of a graphitic phase in the form of GNFs and that the diameter was dependent on the synthesis temperature, varying from 500 nm to 20 nm. The sample surface area was found to increase from 49 to 252 m2 g−1, with lowering of the synthesis temperature.