Experimental observation on the flow-induced assembly of Carbon nanotube suspensions to form helical bands

This paper describes optical observations on the way aggregates of multi-walled carbon nanotubes (CNTs) in an epoxy matrix can form unusual helical bands (HBs) that are aligned perpendicular to the shear flow. By applying specific flow conditions, HBs were formed from isotropic aggregates of CNTs suspended in an essentially Newtonian epoxy matrix. Both optical and matching rheological data are presented together with a schematic model of the way HBs are formed. It was discovered that the steady shear rheology of the CNT suspension did not substantially change during the observed micro-structure change. The HB structure may have relevance in terms of potential applications for CNTs.