Synthesis of narrow-diameter carbon nanotubes from acetylene decomposition over an iron–nickel catalyst supported on alumina Original Research Article

Carbon nanotubes (CNTs) were synthesized by the catalytic decomposition of acetylene over 40Fe:60Al2O3, 40Ni:60Al2O3 and 20Fe:20Ni:60Al2O3 catalysts. High density CNTs of 20 nm diameter were grown over the 20Fe:20Ni:60Al2O3 catalyst, whereas low growth density CNTs of 40 and 50 nm diameter were found over 40Fe:60Al2O3 and 40Ni:60Al2O3 catalysts. Smaller catalyst particles enabled the synthesis of highly dense, long and narrow-diameter CNTs. It was found that a homogeneous dispersion of the catalyst was an essential factor in achieving high growth density. The carbon yield and the quality of CNTs increased with increasing temperature. For the 20Fe:20Ni:60Al2O3 catalyst, the carbon yield reached 121% after 90 min at 700 °C. The CNTs were grown according to the tip growth mode. Based on reports regarding hydrocarbon adsorption and decomposition over different faces of Ni and Fe, the growth mechanism of CNTs over the 20Fe:20Ni:60Al2O3 catalyst are discussed.