Flame Synthesis of Carbon Nanotubes and Nano-Onions in a Rotating Opposed-Jets Flow

Abstract

The influence of flow rotation on the synthesis of carbon nano-structures using rotating opposed flow ethylene diffusion flames and a catalytic Ni substrate was investigated. In the experiments, the flame parameter was kept constant with fuel and oxidizer compositions of 20%C2H2+80%N2 and 40%O2+60%N2 in the upper and lower burners, respectively, whereas the strain rate was varied by adjusting the rotation speed. Stain rate affects carbon nano-structures synthesis either through the residence time of the flow or carbon sources available for the growth of carbon nanotubes (CNTs) and onions. A diffusion flame at low strain rate is stronger than a weak flame at high strain rate and produces more carbon sources because of the longer residence time of the flow. At a higher strain rate, curved and entangled tubular multi-walled CNTs were harvested, however, at a lower strain rate carbon nano-onions (CNOs) were synthesized. It is verified that flow rotation associated with residence time plays an important role in the synthesis of carbon nanostructures.