Chemical vapor deposition based synthesis of carbon nanotubes and nanofibers using a template method

We have developed a new approach for preparing graphitic carbon nanofiber and nanotube ensembles. This approach entails chemical vapor deposition (CVD) based synthesis of carbon within the pores of an alumina template membrane with or without a Ni catalyst. Ethylene or pyrene was used in the CVD process with reactor temperatures of 545 degrees C for Ni-catalyzed CVD and 900 degrees C for the uncatalyzed process. The resultant carbon nanostructures were uniform hollow tubes with open ends. Increasing the deposition time converted the carbon nanotubes into carbon nanofibers. Transmission electron microscopy and electron diffraction data show the as deposited graphitic carbon nanofibers synthesized with the Ni catalyst were not highly ordered. Heating the carbon-containing membrane at 500 degrees C for 36 h, however, converts the carbon nanofibers into highly ordered graphite. The electron diffraction data show a spotted diffraction pattern characteristic of single-crystal graphite with the graphitic planes parallel to the long axis of the nanofibers.