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Identifier

000405245

Title

Microscopic Dynamics and Rheology of Colloidal Gels

Alternative Title

Αργή δυναμική και γήρανση κολλοειδών υάλων και πηκτωμάτων

Author

Moghimi, Esmaeel

Thesis advisor

Πετεκίδης, Γεώργιος

Reviewer

Φυτάς, Γεώργιος
Βλασσόπουλος, Δημήτριος
Βαμβακάκη, Μαρία
Benoit, Loppinet
Philippe, Coussot
Stefan, Egelhaaf

Abstract

In this dissertation we examine both linear and nonlinear response rheology of concentrated colloidal suspensions with attractive interactions using a combination of experiments and Brownian Dynamics (BD) simulations with the view towards understanding the link between microstructure and mechanical properties. The experimental model system is depletion colloid-polymer mixture comprising of a hard sphere (PMMA particles) colloidal suspension with the addition of non adsorbing linear polymer chains as depletant. We study a range of particle volume factions and attraction strengths exploring from a low particle volume fraction gel to highly dense attractive glassy state. We also perform Brownian Dynamics (BD) simulations in order to get both rheological and detailed structural information. We have studied four topics in this work: We first examine yielding of attractive glasses during start-up shear flow. For a fixed volume fraction of φ = 0.62, a wide range of attraction strengths and the ranges of attraction is investigated. We second, examine both linear and nonlinear response rheology of colloidal gels. A range of volume fractions, gel ages, and bond strengths are investigated. In the third part, we study by rheology and Brownian dynamics (BD) simulations the decay of stress over time after shear cessation of a well-developed steady shear flow in an intermediate volume fraction particle gel (φ = 0.44). In the last part, we interrogate both structural and mechanical properties of the gel during flow and its time evolution after shear cessation for both steady and oscillatory shear flow by a combination of experiments and BD simulations providing a link between structural and mechanical properties of the gel.

Language

English

Subject

Attractive colloidal glasses

Brownian Dynamics simulations

Προσομοιώσεις Brownian δυναμικής

Issue date

2017-02-10

Collection

School/Department--School of Sciences and Engineering--Department of Materials Science and Technology--Doctoral theses

Type of Work--Doctoral theses

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