We investigated the effects of parametric synthesis conditions of catalysts such as sintering
temperature, sorts of supports and compositions of catalysts on alignment and length-control
of carbon nanotubes (CNTs) using catalyst powders. To obtain aligned CNTs, several parameters
were changed such as amount of citric acid, calcination temperature of catalysts,
and the sorts of supports using the combustion method as well as to prepare catalyst. CNTs
with different lengths were synthesized as portions of molybdenum and iron using a chemical
vapor deposition reactor. In this work, the mechanisms of alignment of CNTs and of the
length-control of CNTs are discussed.