Paper Number
SC36 

Session
Suspensions, Colloids and Granular Systems

Title
Orientation dynamics of dilute graphene suspensions: Dichroism and modeling

Presentation Date and Time
October 12, 2017 (Thursday) 9:05

Track / Room
Track 3 / Crystal C

Authors (Click on name to view author profile)

1. Natale, Giovanniantonio (University of Calgary)
2. Reddy, Naveen K. (Hasselt University)
3. Vermant, Jan (ETH Zurich)

Author and Affiliation Lines (in printed abstract book)
Giovanniantonio Natale¹, Naveen K. Reddy², and Jan Vermant^3
1University of Calgary, Calgary, Canada; ²Hasselt University, Hasselt, Belgium; ³ETH Zurich, Zurich, Switzerland

Speaker / Presenter 
Natale, Giovanniantonio

Text of Abstract
Graphene sheets are two-dimensional structures made of carbon atoms, which are electrically and thermally conductive and have unique mechanical properties. They have potential applications in many fields, including organic electronics, reinforced and electrically conducting composites and even new types of biological sensors and devices. Promising processing routes involve suspensions of graphene flakes. However, to fully exploit graphene suspensions, control of the microstructure evolution during flow is required. Specifically, a full understanding of the orientation behaviour of the graphene flakes during flow is necessary. In this work, we analyse the orientation dynamics of graphene suspensions in the dilute regime by examining their rheo-optical response. Dichroism is obtained in a Couette flow geometry which allows direct measurement of the average orientation angle (χ) of the particles with respect to the flow direction. Micrometer sized and functionalized graphene flakes were dispersed in a Newtonian mineral oil. The orientation of the system is studied in simple shear flow at steady state and using large amplitude oscillatory shear (LAOS) as a prototype transient flows. In LAOS, the suspensions present an interesting double peaked χ response at large strains during oscillation. To explain flow behaviour of graphene suspensions in simple steady shear and in LAOS, the particles are modelled as oblate spheroids and the suspension orientation dynamics are captured by a single particle Smoluchowski equation. This simple model captures surprisingly well, especially given the strong approximation of particle shape, the suspensions dynamics without the need of additional fitting parameters.