Carbon-nanotube growth over iron nanoparticles formed on CaCO₃ support by using hydrogen reduction

Carbon nanotubes (CNTs) were grown by chemical vapor deposition on a mixture of iron salt and CaCO₃. Salt mixtures of Fe(NO ₃)₃·9H₂O/CaCO₃ and FeCl ₃·6H₂O/CaCO₃ with various Fe weight contents were used as catalysts for growing the CNTs. A scanning electron microscope study revealed that the CNTs were densely grown on the Fe(NO ₃)₃·9H₂O/CaCO₃ catalyst containing 5 wt.% Fe. The effect of growth temperature on the segregation of Fe nanoparticles formed by hydrogen reduction is discussed. The result shows that 800 °C is the optimal temperature for the formation of Fe nanoparticles over which CNTs grow with the highest yield of 78.61 %. A raman spectroscope and a scanning transmission electron microscope were utilized to characterize the multiwall structure of the CNTs. The 92.16 % purity of the CNTs was determined by using thermal gravimetric analysis.