Effect of gas pressure on the growth and structure of carbon nanotubes by chemical vapor deposition

The effect of gas pressure on the structure of carbon nanotubes (CNTs) has been systematically investigated in the chemical vapor deposition process. The yield of CNTs (defined as the weight ratio of CNTs vs. catalyst) increa ses significantly with the gas pressure, reaches 600% at 600 Torr, then dec reases with further increase of gas pressure. At low reacting gas pressure the CNTs have completely hollow cores, whereas at high pressure the CNTs ha ve a bamboo structure, The density of the compartments in the bamboo-struct ured CNTs increases dramatically with the increase of the gas pressure. Thi s result shows that the structure and yield of carbon nanotubes are strongl y affected by the growth gas pressure.