Yield stress, thixotropy and shear banding in a dilute aqueous suspension of few layer graphene oxide platelets

Abstract

We demonstrate a rigidity percolation transition and the onset of yield stress in a dilute aqueous dispersion of graphene oxide platelets (aspect ratio $5000) above a critical volume fraction of 3.75 Â 10 À4 with a percolation exponent of 2.4 AE 0.1. The viscoelastic moduli of the gel at rest measured as a function of time indicate the absence of structural evolution of the 3D percolated network of disks. However a shear-induced aging giving rise to a compact jammed state and shear rejuvenation indicating a homogenous flow is observed when a steady shear stress (s) is imposed in creep experiments. We construct a shear diagram (s vs. volume fraction f) and the critical stress above which shear rejuvenation occurs is identified as the yield stress s y of the gel. The minimum steady state shear rate _ g m obtained from creep experiments agrees well with the end of the plateau region in a controlled shear rate flow curve, indicating a shear localization below _ g m . A steady state shear banding in the plateau region of the flow curve observed in particle velocimetry measurements in a Couette geometry confirms that the dilute suspensions of GO platelets form a thixotropic yield stress fluid.

Rheological Characterization of Carbopol® Dispersions in Water and in Water/Glycerol Solutions

“…The same behavior was later reported by [79] for shear-stress controlled experiments. On the other hand, the transient shear banding phenomenon was not observed by [80] under similar conditions for a yield stress fluid. Ref.…”

Dynamics of Colloidal Glasses and Gels

“…Moorcroft et al (111) developed a criterion for the observation of shear banding for such transient flows that solely depends on the shape of the rheological response function. Shear banding has been reported for Carbopol gels (112), clay suspensions (113,114), emulsions and foams (109,115), graphene oxide dispersion (116), and cement pastes (41) in recent reviews including discussions on the physical behavior (108) and probes (67). Recently, Besseling et al (117) reported the presence of shear banding in hard-sphere suspension owing to the concentration variations arising from migration of particles toward domains of low shear rate.…”

Relationship between structures and rheological properties of plate-like particle suspensions

“…It was reported that the microstructure of materials, the dispersion state and the orientation of plates, and the interaction between plate and matrix affected the rheological properties of plate-like particle suspensions [4][5]. Although the rheological properties of plate-like particle suspensions are widely studied [4][5][6][7][8], some questions still remain unsolved. For example, negative normal stress differences (ΔN) during shear experiments were reported in the concentrated kaolin aqueous solutions [7], clay/polymer suspensions [8] and graphene oxide (GO)/polymer composites [9].…”