Abstract
Fly ash is a by-product, generated due to the use of heavy oil or coal as a fuel in power plants. Recently, carbon-rich fly ash is found to have ideal compositions as a catalyst and precursor for carbon nanotube (CNTs) growth by the chemical vapor deposition method. The existing methods have a limitation on producing CNTs in a large scale. In this work, the parameters effecting the growth of CNTs of fly ash were investigated. These include temperature, gas pressure, growth time, and gas flow rate. The produced samples were characterized by different techniques. Consistent results are demonstrated in terms of CNT uniformity, conversion and lengths as produced under optimized values. The optimum values provide multiwall CNTs with diameters in the 20-40 nm range. Raman spectrum shows G and D bands (the G/D intensity ratio ∼1.4). The as-grown CNTs displayed peaks of sp
2
and sp
3
carbons in the X-ray photoelectron spectroscopy spectrum with an intensity ratio 7.5 eV. Two small bands are also observed at 288.2 and 290.5 eV, which could be assigned to -COO group and π-π* transition carbon. A proposed mechanism for CNT growth is also presented. The goal of this method is to develop a large-scale production of CNTs using fly ash for various applications.