Characterization and magnetic properties of helical carbon nanotubes and carbon nanobelts synthesized in acetylene decomposition Over Fe-Cu nanoparticles at 450 °C

Over Fe-Cu nanoparticles derived from sol-gel synthesis followed by hydrogen reduction at 400 °C, helical carbon nanotubes (HCNTs) and carbon nanobelts (CNBs) were synthesized in large quantities in acetylene decomposition at 450 °C. The two carbon species could be separated easily as they deposited on different locations of the ceramic plate in which the Fe-Cu nanoparticles were placed. The advantages of this synthetic method are that the approach is simple and environmentally friendly and there is no need of using dilute gas such as argon or nitrogen. Field-emission and transmission electron microscopic investigations reveal that the selectivity to HCNTs (ca. 85%) or to CNBs (ca. 90%) is high. The corresponding yield of carbon species and CNBs is about 27 307% and 9867%, respectively, higher than any of those reported in the literature. It was found that the variation of reduction temperature (from 400 to 450 or 500 °C) of Fe₂O₃/CuO catalyst precursor and the temperature gradient during acetylene decomposition have profound influence on the morphology and yield of HCNTs and CNBs. The magnetic properties and the possible reaction mechanism of HCNTs and CNBs were also investigated in this study.