A new approach to synthesize carbon nanotube (CNT) powders has been achieved by using the floating catalyst method below atmospheric pressure. Scanning electron microscopy, Raman spectroscopy and high-resolution transmission electron microscopy were utilized to characterize the CNTs samples. Using ferrocene (FeC10H10) as catalyst precursor, cyclohexane (C6H12) as carbon source, H-2 as carrier gas and thiophene (C4H4S) as promoter, it is found that the pressure of 15 kPa, temperature of 650 degrees C and H-2 flow rate of 60 sccrn would be the optimization condition for synthesis of high quality CNTs. This method is economical and easily scalable for synthesis of CNTs. (c) 2005 Elsevier B.V. All rights reserved.