Synthesis of carbon nanotubes by microwave heating: Influence of diameter of catalytic Ni nanoparticles on diameter of CNTs

Abstract

We rapidly synthesized multi walled carbon nanotubes (MWCNTs) by calcination of granulated polystyrene with nickel nanoparticles having different average diameter (D_Ni = 10, 20, 50 or 90 nm) under nitrogen gas at a certain temperature and time (700 °C, 15 min or 800 °C, 10 min), using a domestic microwave oven in order to systematically investigate the influence of the diameter of nickel nanoparticles on the diameter of MWCNTs. The MWCNTs synthesized here were characterized by a transmission electron microscope, a Raman spectrophotometer and a wide angle X-ray diffractometer. We found that for the calcination condition of (800 °C, 10 min), a relationship between the outer diameter of the resulted carbon nanotubes (D_CNT) and the diameter of catalytic nickel nanoparticles (D_Ni) can be described as a linear function, D_CNT = 1.01D_Ni + 14.79 nm with the correlation coefficient R = 0.99, and that for the calcination condition of 700 °C, 15 min, D_CNT = 1.12D_Ni + 7.80 nm with R = 0.95. Thus, we revealed that when the diameter of the catalytic nickel nanoparticles (D_Ni) increases by 1 nm, the outer diameter of the obtained MWCNTs (D_CNT) increases by about 1 nm.