Ring formation mechanism of single-walled carbon nanotubes: Energy conservation between curvature elasticity and inter-tube adhesion

► Examine the ring formation mechanism in terms of energy conservation. ► The energy includes increased curvature energy and inherent inter-tube adhesion. ► Ring's diameter D and width δ match dimensions of original SWNTs or the bundles. ► Thinner bundles form small rings and bigger ones are resulted from thicker bundles. ► Smaller rings have relatively wider width.