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Title: The Use of Two-Dimensional Suspensions for the Fundamental Study of the Dynamics of Colloidal Suspensions and their Technological Applications (Gebruik van twee-dimensionale suspensies voor fundamentele studies van de dynamica van colloidale systemen en hun technologische toepassingen)
Other Titles: The Use of Two-Dimensional Suspensions for the Fundamental Study of the Dynamics of Colloidal Suspensions and their Technological Applications
Authors: Masschaele, Kasper
Issue Date: 30-Oct-2009
Abstract: De invloed van uitwendige velden op colloidale deeltjes aan vloeistof-vloeistof interfasen worden bestudeerd in dit werk. De interactie potentiaal tussen twee deeltjes die gepind zijn aan een interfase is experimenteel bepaald. Wanneer aggregatie word geinduceerd, bekomt men een model systeem dat gebruikt kan worden om typische eigenschappen van colloidale dispersies te bestuderen, zoals yielden, thixotropie en het onstaan van ansiotropie. De structurele organsiatie van de colloidale deeltjes onder invloed van electrische velden worden bestudeerd.
Table of Contents: Contents
Acknowledgements i
Contents iii
Samenvatting xi
Summary xiii
List of symbols xv
1 Introduction 1
1.1 Motivation for studying particles at interfaces . . . . . . . . . . . . 1
1.1.1 Colloidal systems . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 Colloids as model systems . . . . . . . . . . . . . . . . . . . 1
1.1.3 Stabilization of mixtures of immiscible fluids . . . . . . . . 3
1.1.4 High quality products . . . . . . . . . . . . . . . . . . . . . 5
1.2 Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Materials and methods 7
2.1 Model monolayer experiments . . . . . . . . . . . . . . . . . . . . . 7
2.2 Two-dimensional flow fields . . . . . . . . . . . . . . . . . . . . . . 10
2.2.1 Shear flow fields . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.2 Extensional and rotational flow fields . . . . . . . . . . . . . 12
2.2.3 Converging and capillary flow fields . . . . . . . . . . . . . 14
2.3 2D Rheology experiments . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 2D Electric Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.4.1 Normal electric fields . . . . . . . . . . . . . . . . . . . . . . 17
2.4.2 In-plane electric fields . . . . . . . . . . . . . . . . . . . . . 18
2.5 Image analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5.1 Local structural descriptors . . . . . . . . . . . . . . . . . . 20
2.5.2 Global structural descriptors . . . . . . . . . . . . . . . . . 23
2.5.3 Overview of parameters and IDL routines . . . . . . . . . . 25
iii
3 Colloids at interfaces: interactions 27
3.1 Colloids in bulk: overview . . . . . . . . . . . . . . . . . . . . . . . 27
3.2 Colloids at interfaces: state of the art . . . . . . . . . . . . . . . . 30
3.2.1 Static properties . . . . . . . . . . . . . . . . . . . . . . . . 30
3.2.2 Forces between particles at interfaces . . . . . . . . . . . . . 31
3.2.3 What changes for nano-particles at interfaces? . . . . . . . 39
3.3 Pair interactions at liquid interfaces . . . . . . . . . . . . . . . . . 40
3.3.1 Contact-angle measurements . . . . . . . . . . . . . . . . . 40
3.3.2 Repulsive interactions . . . . . . . . . . . . . . . . . . . . . 41
3.3.3 Attractive interactions . . . . . . . . . . . . . . . . . . . . . 57
3.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.5 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
4 Colloids at interfaces: effect of flow fields 67
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.1.1 Structure of suspensions . . . . . . . . . . . . . . . . . . . . 67
4.1.2 Suspension rheology and modeling . . . . . . . . . . . . . . 76
4.1.3 Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.2 Yielding in shear flow . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 84
4.2.2 Characterization of the initial microstructure . . . . . . . . 84
4.2.3 Characteristic length scales under quiescent conditions . . . 86
4.2.4 Structural rearrangements under shear flow start-up . . . . 90
4.2.5 Comparison with theoretical models . . . . . . . . . . . . . 101
4.3 Yielding in complex flows . . . . . . . . . . . . . . . . . . . . . . . 105
4.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 105
4.3.2 Behavior in shear flow of a pre-sheared network . . . . . . . 106
4.3.3 Behavior in rotational flow . . . . . . . . . . . . . . . . . . 106
4.3.4 Behavior in extensional flow . . . . . . . . . . . . . . . . . . 109
4.3.5 Converging flow . . . . . . . . . . . . . . . . . . . . . . . . 114
4.3.6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
4.4 Flow-induced structures and anisotropy . . . . . . . . . . . . . . . 122
4.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 122
4.4.2 Results and discussion . . . . . . . . . . . . . . . . . . . . . 123
4.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
5 Colloids at interfaces: effect of electric fields 145
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
5.2 Field lines normal to the interface . . . . . . . . . . . . . . . . . . 148
5.2.1 Determination of the electric fields . . . . . . . . . . . . . . 148
5.2.2 Forces induced by an electric field . . . . . . . . . . . . . . 150
5.2.3 Uncharged particles . . . . . . . . . . . . . . . . . . . . . . 153
5.2.4 Charged particles . . . . . . . . . . . . . . . . . . . . . . . . 159
iv
5.2.5 Mixtures of particles . . . . . . . . . . . . . . . . . . . . . . 162
5.3 Field lines parallel to the interface . . . . . . . . . . . . . . . . . . 170
5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
6 Conclusions and outlook 179
Notes and references 183
List of publications 203
Curriculum Vitae 205
ISBN: 978-94-6018-137-5
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Soft Matter, Rheology and Technology Section
Chemical and Extractive Metallurgy Section (-)
Chemical Engineering - miscellaneous
Department of Materials Engineering - miscellaneous
Centre for Surface Chemistry and Catalysis

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