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

Vasu, KS and Krishnaswamy, Rema and Sampath, S and Sood, AK (2013) Yield stress, thixotropy and shear banding in a dilute aqueous suspension of few layer graphene oxide platelets. In: Soft Matter, 9 (25). pp. 5874-5882.

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Abstract

We demonstrate a rigidity percolation transition and the onset of yield stress in a dilute aqueous dispersion of graphene oxide platelets (aspect ratio similar to 5000) above a critical volume fraction of 3.75 x 10(-4) with a percolation exponent of 2.4 +/- 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 (sigma) is imposed in creep experiments. We construct a shear diagram (sigma vs. volume fraction phi) and the critical stress above which shear rejuvenation occurs is identified as the yield stress sigma(y) of the gel. The minimum steady state shear rate (gamma) over dot(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 (gamma) over dot(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.

Item Type:	Journal Article
Publication:	Soft Matter
Publisher:	Royal Society of Chemistry
Additional Information:	Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry Division of Physical & Mathematical Sciences > Physics
Date Deposited:	15 Jul 2013 10:01
Last Modified:	15 Jul 2013 10:01
URI:	http://eprints.iisc.ac.in/id/eprint/46889

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