Icicle-like carbon nanotube (CNT) forest, i.e., discrete bundles of CNTs in free standing forms, can be synthesized at a tip surface of tungsten wire via heterogeneous catalysis together with corona discharge in H-2-C2H4 mixture at atmospheric pressure. The influences of several parameters in the synthesis condition on the product structures were investigated. It was found that there was an optimized temperature-range to synthesize the icicle-like structure,400-600 degrees C, and the increase of temperature caused the increase of CNT-diameter. It was observed that the discharge current affected the straightness of CNTs. It was also found that the increase of the ethylene flow rate caused the increase of the height of the CNTs bundles. The lengths of CNTs bundles were limited even when their growth process was continued due to the limited lifetime of the catalyst. (c) 2007 Published by Elsevier B.V.