The effect of temperature on the TCVD growth of CNTs from LPG over Pd nanoparticles prepared by laser ablation

TCVD growth of multiwalled carbon nanotubes (MWCNTs) was reported by catalytic decomposition of liquefied petroleum gas (LPG) at a temperature range of 580–800 °C. Laser ablation was employed as a simple and rapid technique to produce Pd nanoparticles which possess effective catalytic activities for CNT synthesis. UV–visible spectroscopy and TEM images confirmed that the Pd nanoparticles are stable for a long time and have rather spherical shape with average size of 7 nm. SEM and TEM observations and Raman spectroscopy demonstrated that the CNTs have a wavy structure, dense morphology and acceptable crystallinity. Since Pd nanoparticles are inactivated or agglomerated at extremes of the investigated temperature range, the best result of CNT synthesis was obtained at moderate temperatures. It was found that by increasing the growth temperature, crystallinity of grown CNTs is improved; however, strong agglomeration of Pd nanoparticles at high growth temperature prevents further improvement. The grown CNTs can be classified into two categories: one category includes straighter CNTs with smaller diameters and the other includes CNTs with more wavy morphology and larger diameters. The results provide a low cost, versatile and flexible growth of carbon nanotubes over Pd nanocatalysts.