Vertically aligned carbon nanotubes synthesized by the thermal pyrolysis with an ultrasonic evaporator

Thermal pyrolysis process is a catalytic chemical vapor deposition (CVD) based method, involving pyrolysis of mixed solution composed of liquid carbon sources and catalysts. This paper is focused on the synthesis of carbon nanotubes (CNTs) by the thermal pyrolysis process with an ultrasonic evaporator that atomizes the mixed liquid solution. The merit of this approach is that the apparatus can produce aligned and clean CNTs which can be easily controlled in a cost-effective manner. CNT samples synthesized by introducing the atomized solution into the pyrolysis furnace were analyzed to understand and characterize the growth mechanism. HRTEM and high magnification SEM analysis indicate that the samples are multiwalled carbon nanotubes (MWNTs) grown through tip growth mechanism. The results were confirmed by Raman spectrum curve. In addition, the effects of experimental parameters on the structure of CNTs were investigated by SEM images and themogravimetric analysis. The results reveal that synthesis time and temperature have a key influence on the size of CNTs, and the concentration of catalyst determines the amount of the filling yield in the inner part of CNTs.