Synthesis of High-Quality Single- and Double-Walled Carbon Nanotubes on Fe/MgO Catalysts

Abstract

In this study, Fe/MgO catalysts with three different iron contents (5, 10, and 15 wt.%) were prepared by three catalyst preparation methods: impregnation, solution combustion synthesis, and co-calcination of metal nitrates. The resulting catalysts were subjected to methane at 900°C in order to grow carbon nanotubes (CNTs). The powders and products were then studied by X-ray diffraction (XRD), differential thermal analysis (DTA), scanning and transmission electron microscopy (SEM and TEM), and Raman spectroscopy. Formation of MgFe2O4 upon heating the catalysts to 900°C was confirmed by XRD. After the growth step, corresponding peaks of MgFe2O4 disappeared and metallic iron peaks appeared, indicating that MgFe2O4 is the responsible phase for production of iron nanoparticles. HRTEM images showed that the product on the 5 wt.% catalysts was mostly SWNTs and DWNTs with no evidence of carbon nanofibres or multi-walled carbon nanotubes on the co-calcination catalyst. Furthermore, ID/IG ratios obtained from Raman...