Carbon nanotubes and onions from methane decomposition using Ni/Al catalysts

Abstract: Ni/Al catalysts with different Ni concentrations have been used successfully for the synthesis of carbon nanotubes and onions from methane by chemical vapor deposition. The catalyst nanoparticles were produced by a deposition–precipitation method, and the carbon products by the catalytic decomposition of methane at 600°C. Carbon nanotubes (CNTs) were formed in the presence of a Ni/Al composite catalyst containing 20wt.% nickel. The CNTs were multi-walled, 10–20nm in diameter and up to 15μm long. Hollow carbon onions were produced in the presence of a Ni/Al composite catalyst containing 80wt.% nickel. The carbon onions were from 5 to 50nm in diameter and consisted of several concentric carbon layers surrounding a hollow core. The mechanisms for the formation of both the CNTs and carbon onions were discussed on the basis of the experimental results. [Copyright &y& Elsevier]