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Title: Low-shear rheology and delayed sedimentation of colloidal systems
Author: Meeker, Steven Paul
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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Low-shear viscometry and visual observation are used to study the rheology and sedimentation behaviour of colloid-polymer transient gels. The delay to sedimentation (or latency time) exhibited by the transient gels increases strongly with both polymer concentration and colloid volume fraction. Two distinct categories of transient gel are discovered; those displaying a latency time independent of sample height (lower polymer concentration), and those for which latency time strongly decreases with increasing sample height (higher polymer concentration). The transient gel displays power-law fluid behaviour for low shear rates (Pe π 1), the viscosity strongly increasing as the shear stress is reduced. It is suggested that the strongly shear-thinning rheological behaviour of the transient gel is the principal mechanism behind the abruptness of the transient gel collapse. Rheological observations suggest that the strength of the transient gel structure significantly increases then decreases during the latency period, the decrease coinciding with the collapse. Measurements of the low shear rate viscosity of a model hard-sphere suspension are also presented. Suspension volume fractions are calibrated with respect to the thermodynamic disorder to order, or crystallization, transition. At freezing, the low-shear suspension viscosity is found to be ≈ 53 times that of the solvent, significantly different to values measured in previous studies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available