A combinatorial technique was used to determine the optimum catalyst combin
ation for the efficient synthesis of carbon nanotubes (CNTs). The morpholog
y, length and yield of CNTs greatly differ depending on the catalyst combin
ations. Among 20 different compositions of mixed catalysts, CNTs of good st
ructure were obtained when the volume ratios of the three precursor solutio
ns-Co(NO3)(2), Ni(NO3)(2) and Fe(NO3)(3)-were 4 : 2 : 4 (island #7) and 1 :
5 : 4 (island # 18).