Effects of ammonia on the alignment of carbon nanotubes in metal-assisted thermal chemical vapor deposition

The effects of ammonia on alignment of carbon nanotubes in an atmospheric pressure thermal chemical vapor deposition assisted by Ni were investigated. It was confirmed that ammonia is critical to the alignment of nanotubes at temperatures of 800-950 degreesC. Both synthesis by C2H2 after ammonia pretreatment and synthesis by NH3/C2H2 mixture flow could establish alignment. Alignment of carbon nanotubes due to ammonia was realized not by its influence on the morphology of the metal particles, but by its role of inhibiting a formation of amorphous carbon during the synthesis, particularly in its initial stage. (C) 2001 Published by Elsevier Science Ltd.