Open-Air Synthesis of Carbon Nanotubes by Laser-Induced Chemical Vapor Deposition

Carbon nanotubes have unique mechanical, electronic and thermal properties with applications ranging from reinforced composite materials to micro-scale electronic devices, and are considered one of the next generation advanced engineering materials. In this study, a laser-induced chemical vapor deposition (LCVD) process has been developed that is capable of depositing carbon nanotubes in open-air from a gas mixture consisting of propane and hydrogen. A CO₂ laser is used to irradiate the substrate covered with metal nanoparticles, subsequently resulting in the growth of multi-wall carbon nanotubes. The effect of laser power and reactant gas flow configuration on carbon nanotube growth kinetics is experimentally investigated. Results indicate that carbon nanotube synthesis is highly dependent on the laser-induced temperature distribution and the carbon radical concentration. Transmission electron microscopy, scanning electron microscopy and Raman spectroscopy are used to relate the composition, microstructure and growth kinetics to the process conditions of carbon nanotubes deposited in this study.