Discontinuous shear thickening in confined dilute carbon nanotube suspensions

Majumdar, Sayantan and Krishnaswamy, Rema and Sood, AK (2011) Discontinuous shear thickening in confined dilute carbon nanotube suspensions. In: PNAS, 108 (22). pp. 8996-9001.

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Abstract

A monotonic decrease in viscosity with increasing shear stress is a known rheological response to shear flow in complex fluids in general and for flocculated suspensions in particular. Here we demonstrate a discontinuous shear-thickening transition on varying shear stress where the viscosity jumps sharply by four to six orders of magnitude in flocculated suspensions of multiwalled carbon nanotubes (MWNT) at very low weight fractions (approximately 0.5%). Rheooptical observations reveal the shear-thickened state as a percolated structure of MWNT flocs spanning the system size. We present a dynamic phase diagram of the non-Brownian MWNT dispersions revealing a starting jammed state followed by shear-thinning and shear-thickened states. The present study further suggests that the shear-thickened state obtained as a function of shear stress is likely to be a generic feature of fractal clusters under flow, albeit under confinement. An understanding of the shear-thickening phenomena in confined geometries is pertinent for flow-controlled fabrication techniques in enhancing the mechanical strength and transport properties of thin films and wires of nanostructured composites as well as in lubrication issues.

Item Type:	Journal Article
Publication:	PNAS
Publisher:	National Academy of Sciences
Additional Information:	Copyright of this article belongs to National Academy of Sciences.
Keywords:	rheology;jamming;shear diagram
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	15 Jun 2011 04:47
Last Modified:	15 Jun 2011 04:47
URI:	http://eprints.iisc.ac.in/id/eprint/38239

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