Template synthesis of carbon nanotubes

The template synthesis and characterization of carbon nanotubes (CNTs) form ed in porous alumina membranes (PAM) by the thermal chemical vapor decompos ition (CVD) of propylene (Pr) gas are described We found that the graphitic character of CNTs improved as CVD temperature was increased from 500 to 80 0 degrees C. Samples showed progressive increases in metallic appearance an d layered tube wall structure and decreases in electrical resistance. No fu rther enhancement of graphitization was observed among samples formed crt 8 00 900 and 1000 degrees C. X-ray diffraction (XRD) indicated that long-rang e order was absent in all CNTs tested. Localized crystalline domains of gra phitic carbon, however, were detected by Raman spectroscopy and seen in lig ht 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 exp eriments. 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 nano tubes" were formed. No major differences were found between catalyst-contai ning and control samples formed at temperatures greater than or equal to 80 0 degrees C at 94 seem. (C) 1999 Acta Metallurgica Inc.