J. Phys. I France
Volume 6, Numéro 2, February 1996
Page(s) 237 - 244
DOI: 10.1051/jp1:1996145
J. Phys. I France 6 (1996) 237-244

Multiphase Coexistence and Non-linear Rheology of Colloidal. Dispersions as Observed in a Model Capillary Viscosimeter

Thomas Palberg and Mathias Würth

University of Konstanz, Faculty of Physics, Postfach 5560 M675, 78434 Kontanz, Germany

(Received 13 July 1995, revised 26 October 1995, accepted 6 November 1995)

Investigations of the flow properties of colloidal substances by viscometry and rheometry are a valuable tool in understanding many transport processes of importance in biology, medicine and industrial treatment of materials. The streaming of cytoplasm, blood, micellar solutions or crude oil emulsions are but some obvious examples. One of the most intriguing properties of colloidal systems is their ability of thinning or thickening under shear. To characterise this non-Newtonian flow behaviour different visco- and rheometric experiments have been devised, the capillary viscometer being one of the classical instruments. The underlying physical mechanisms of non-linear rheometry are the shear-induced formation and destruction of long range positional and orientational order. Since only in rare cases comprehensive structure and velocity information is accessible from inside a viscosimeter, generally, homogeneous samples are assumed. However, there are indications of a geometry dependent evolution of inhomogeneous phase and flow behaviour from recent experiments on colloidal model systems, in particular for denser systems of strongly interacting particles. We here present investigations performed on a well characterised suspension of spherical particles interacting via a screened electrostatic potential. We give a detailed study of the local structures and shear rates in an optical model capillary viscosimeter. As a function of the overall flux several different flow scenarios are observed within the viscosimeter and the most striking feature is the simultaneous existence of up to four concentrically arranged phases under conditions of stationary flow.

© Les Editions de Physique 1996

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.