In situ fabrication of carbon nanotube–MgAl2O4 nanocomposite powders through hydrogen-free CCVD

Carbon nanotube–MgAl2O4 composite powders were successfully prepared through solution combustion synthesis (SCS) followed by catalytic chemical vapor deposition (CCVD) of methane. Catalyst powders were synthesized starting with the stoichiometric ratios of metal nitrates and urea with a small amount of water and different Fe contents followed by subjecting the solution to heat. The obtained powders were placed in a silica tube to react with methane and form carbon nanotubes. It is noteworthy that no hydrogen was used throughout the whole process. Catalysts and composite powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The quality of products were evaluated by ID/IG ratio obtained from G and D bands intensities in Raman spectra of samples having 10 and 15 wt.% iron. The final product mostly comprised a mixture of single- and double-walled nanotubes on the catalyst containing 10 wt.% Fe, while no carbon product was formed on the catalyst with 5 wt.% Fe.