Growth of CNTs over Fe–Co/Nanometric TiO2 Catalyst by CVD: The Effects of Catalyst Composition and Growth Temperature

   In this research carbon nanotubes were produced by chemical vapor deposition of acetylene over a mixture of iron and cobalt catalysts supported on nanometric TiO2 and the influences of two synthesis parameters: growth temperature and catalyst composition ratio on properties of end-product carbon nanotubes were investigated. The catalytic basis was prepared by wet impregnation method with different wt% mass ratio of Fe-Co/TiO2=20-0/80, 15-5/80, 10-10/80, 5-15/80 and 0-20/80 wt%. The nanomaterials (catalysts and carbon nanotubes) were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray map of elemental distribution (Xmap) and Raman spectroscopy. The results confirmed that by increasing the growth temperature from 650°C to 800°C; the growth rate, the average diameter and the amount of impurities of grown carbon nanotubes increase and their length and density decrease. Furthermore, it was observed that in comparison with monometallic Fe or Co, bimetallic compositions of these metals exhibit better catalytic activity in growth of carbon nanotubes. The highest yield of carbon nanotubes possessing minimum average diameter was obtained on Fe-Co/TiO2 catalyst with a mass ratio of 10-10/80 wt%.