Template synthesis of carbon nanotubes

The template synthesis and characterization of carbon nanotubes (CNTs) formed in porous alumina membranes (PAM) by the thermal chemical vapor decomposition (CVD) of propylene (Pr) gas are described We found that the graphitic character of CNTs improved as CVD temperature was increased from 500 to 800 degrees C. Samples showed progressive increases in metallic appearance and layered tube wall structure and decreases in electrical resistance. No further enhancement of graphitization was observed among samples formed crt 800 900 and 1000 degrees C. X-ray diffraction (XRD) indicated that long-range order was absent in all CNTs tested. Localized crystalline domains of graphitic carbon, however, were detected by Raman spectroscopy and seen in light and darkfield transmission electron microscopy (TEM) images. CNTs formed in the presence of catalytic Fe and Co particles at 600 and 700 degrees C with a Pr/N-2 flow rate of 94 seem (standard cubic centimeters per minute) showed slightly lower electrical resistance than CNTs formed in control experiments. The catalytic effects of Fe and Co were observed for samples made at 800 degrees C with a 50 seem Pr/N-2 flow rate as "nanotubes within nanotubes" were formed. No major differences were found between catalyst-containing and control samples formed at temperatures greater than or equal to 800 degrees C at 94 seem. (C) 1999 Acta Metallurgica Inc.