Investigation on preparation of multiwalled carbon nanotubes by DC arc discharge under N-2 atmosphere

MWCNTs and SWCNT bands were prepared and carbon nanostructures were formed by DC arc discharge under N-2 atmosphere. The effects of nitrogen pressure and flow rate on the yield and morphology of CNTs, and morphology of carbon nanostructures were investigated separately. SEM, HR-TEM, EDX in SEM and TEM, and XRD were performed to characterize the products. It was found that MWCNTs and SWCNTs bands exist in the inner core of the cathode deposit, but the former one is the main product. The suitable N-2 atmosphere should be in the region of 200-300 Torr, and the N-2 flow rate should be smaller than 350 mL/min. The inner diameter and the length of growth of MWCNTs obviously increases with the increase of the N-2 pressure from 0 to 900 Torr, but the change of outside diameter of MWCNTs does not show a good regularity. Both the inner and outside diameters of MWCNTs slightly decrease with the increase of the N-2 flow rate from 0 to 1000 mL/min. Right angle structure of SWCNT band and graphite layers in MWCNT was observed. It is very possible that a little amount of nitrogen atoms has doped into MWCNTs. Several different carbon nanostructures were observed in the products collected from the different parts in the DC arc discharge apparatus. (C) 2004 Elsevier Ltd. All rights reserved.