The growth mechanism of carbon nanotubes from thermal cracking of acetylene over nickel catalyst supported on alumina

Carbon nanotubes (CNTs) were grown on Ni/Al2O3 catalyst by thermal cracking of C2H2/H-2(N-2) at 600 degreesC for 30 min with a gas flow rate of 10/100 seem. The Ni/Al2O3 catalyst was prepared by mechanically mixing fine Ni an d alpha -Al2O3 powders. The growth of CNTs in C2H2/H-2 medium is higher tha n that in C2H2/N-2 medium. The grown CNTs is a mixture of single-wall carbo n nanotubes (SWNTs) and multi-wall carbon nanotubes (MWNTs). The gas-phase reaction was studied by analyzing gas species generated from the cracked C2 H2/H-2 (N-2) media during the CNTs growth. C2H2 is not decomposed in gas-ph ase even at the growth temperature 600 degreesC, but is catalytically disso ciated on the Ni surface to produce a reactive carbonic species. The growth mechanism of CNTs was intensively discussed in detail in this paper based on the experimental observations. (C) 2001 Elsevier Science B.V. All rights reserved.