Linking Single Particle Dynamics to Macroscopic Phenomena in Colloidal Gels
Gopalakrishnan, Vijay
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https://hdl.handle.net/2142/82384
Description
Title
Linking Single Particle Dynamics to Macroscopic Phenomena in Colloidal Gels
Author(s)
Gopalakrishnan, Vijay
Issue Date
2006
Doctoral Committee Chair(s)
Zukoski, Charles F.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical and Biomolecular Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Language
eng
Abstract
In this thesis, we investigate the role of colloidal dynamics in governing diverse macroscopic phenomena in colloidal gels. The ability to design materials using predictive tools requires that we understand how the desired properties depend on the various system parameters that govern particle dynamics in solution and this remains an outstanding problem of academic and industrial interest. We perform systematic experiments on well-characterized colloidal gels to observe the impact of parameters such as the colloid size, volume fraction, the strength and range of attraction between the colloids on the microstructure and macroscopic response of colloidal gels to external perturbations. We initially investigate links between the morphologies of stable particle-clusters in weak depletion systems and the microstructure of space-spanning gels. Next, we test the hypothesis that thermally activated-particle dynamics governs the delayed-collapse of weak depletion gels under gravity and investigate the role of particle size in setting this time scale for delayed-collapse. We then focus on experiments that examine how stress weakens colloidal gels and leads to a decrease in the gel elastic modulus. We compare our observations for the characteristic stress that initiates gel-softening with that predicted by a recently developed theory that incorporates a stress-induced weakening of particle localization in gels and links it with the macroscopic elastic modulus. Finally, we investigate a delayed-flow response in creep experiments on thermo-reversible gels. We explain the non-linear response in this system by proposing a phenomenological model that describes the evolution of particle-localization as the result of competing stress-induced bond-breakage and bond-reformation processes.
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