In situ synthesis of multi-walled carbon nanorings by catalytic chemical vapor deposition process

Carbon nanorings (CNRs) are found to be the most promising nanostructure for the application of nanoscale devices. The CNRs are synthesized by many post-treatment processes such as ultrasonication and acid treatment. The post-treatment process may alter the properties of the rings. Hence, in this investigation, an attempt has been made to synthesize multi-walled carbon nanorings in a single-step process (as-synthesized condition itself). The CNRs are synthesized by catalytic chemical vapor deposition process using NiO/Al₂O₃ as catalyst material, and acetylene was used as the precursor gas. FESEM confirms the as-grown ring structure and HRTEM reveals the effect of the isolation process. The rings typically have thickness ranges from 7 to 17 nm, and diameter ranges from 10 to 190 nm. In addition, FTIR, Raman spectroscopy was used to evaluate the functionality and structure of the rings, respectively. The scientific justification behind the growth mechanism to the CNRs and open rings was discussed in this paper. The agglomerated morphology of catalyst particles has a significant effect on the growth of ring structure.