Growth Conditions for Carbon Nanotubes and Helical Nanofibers on Copper Substrates Using Sparked Catalysts

Abstract

Carbon nanotubes (CNTs) and helical nanofibers (HNFs) were selectively grown on copper substrates by chemical vapor deposition using acetylene as a carbon source. The experiments were carried out by using Ni, Fe and Co as single and co-catalysts which were deposited onto the substrates by a sparking method. The catalyst-coated copper substrates were heated at 750°C in a mixed-gas-flowing tube furnace, at an argon flow rate of 100 ml/min and various acetylene flow rates of 3, 5 and 10 ml/min. The larger diameter of HNFs was grown only on Ni and Ni-Fe catalysts at the acetylene flow rates of 5 and 10 ml/min whereas the uniform smaller diameter of CNTs was preferentially grown on Fe-Co and Ni-Fe catalysts at the flow rate of 3 ml/min. We suggest that Co likely prevents the formation of HNFs whereas Ni promotes.