Download or read book Colloidal Suspensions in Confined Geometries written by Clemens Bechinger and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charged Colloidal Suspensions in Confined Geometries written by Ana Barreira Fontecha and published by . This book was released on 2009 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Charged Colloidal Suspensions in Confined Geometries written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the behaviour of charged colloidal suspensions under geometrical confinement is studied. We use different wedge-like geometries which allow a continuous variation of the distance between the plates. At low salt concentrations the confinement of suspensions in fluid phase cells reveal that the particles accumulate in the cusp of the wedge forming crystalline ordered structures. We present systematic experiments to understand the accumulation effect in the narrow part of the cell. We conclude that the effect is due to electrostatic trapping, which is confirmed by a simple theoretical model proposed by Löwen et al. Crystalline structures appear forming a characteristic sequence with increasing plate distance. This structural sequence has been already observed previously in confinement at wedge geometries; however, the small wedge angles achieved in our experiments allow the observation of new structures. Some of these new structures show exotic arrangements that have no atomic counterpart. We also propose different transition mechanism models between the different structures based on the experimental observations. For that we assume that the particles behave as hard spheres subject to a high pressure. Finally, a cell with variable height was designed in order to study the complete phase behaviour of charged spheres confined between parallel plates. The preliminary results are compared with theoretical predictions.

Download or read book Confined Flow of Attractive Colloidal Suspensions written by Rahul Pandey and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Attractive particulate fluids flowing through complex confined geometries are frequently used in technological applications. While the flow properties of hard-sphere suspensions in micro-scale geometries have been studied extensively, the effects of interparticle attractions and particle size dispersity on the confined flow properties of particulate suspensions are not well understood. We used confocal microscopy, particle tracking, and bulk rheology to study the confined structure, dynamics, and flow properties of colloid-polymer mixtures, which serve as simple models of attractive particulate suspensions. We employed poly(methyl-methacrylate) spheres that were suspended in a refractive-index and density- matched solvent, and induced a controlled short-range depletion attraction between particles by adding non-absorbing linear polystyrene. First, we investigated the effects of particle size dispersity on confinement-induced solidification of colloid-polymer mixtures. We formulated mixtures of polymer and bidispersed colloids with particle size ratio aS/aL ≈ 0.49 at a constant total volume fraction fT and measured the dynamics of the large particles as a function of the volume fraction of large particles. The dynamics of large particles became slower as the volume fraction of large particles r=fL/fT was decreased or the confinement thickness was decreased, indicating increasingly solid-like behavior. Second, we investigated the effects of variation in particle size dispersity r on the rheology and microstructure of mixtures of polymer and bidispersed colloids. Significant changes in rheology and microstructure were observed only at high volume fractions of large particles. By contrast, dense suspensions fT = 0.40 were strong gels at all concentration of large particles and exhibited only modest rheological and microstructural changes. Finally, we investigated the effects of variation in interparticle attractions on the microchannel flow of colloid-polymer mixtures. In suspensions with weak interparticle attractions, the number density of particles increased downstream in the channel due to shear-induced migration and consolidation by compression. In suspensions with stronger interparticle attractions, an interconnected network of particles suppressed these mechanisms and prevented the increase in density downstream. Together, our results indicate that the confined structure, dynamics, and flow properties of attractive colloidal suspensions can be controllably tuned from fluid-like to solid-like by varying the interparticle attractions and the particle size dispersity.

Download or read book Theoretical Studies on Colloid Suspensions in Confined Geometry written by Xinliang Xu and published by . This book was released on 2007 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: When a colloidal system is constrained to occupy confined spaces, it displays many interesting new static and dynamic properties.

Download or read book Colloids in Confined Geometries Hydrodynamics Simulation and Rheology written by James W. Swan and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The hydrodynamics of colloids in confined geometries is studied hierarchically beginning with the exact solutions for a spherical particle translating, rotating and deforming in the presence of a plane wall at low Reynolds number. The many-bodied hydrodynamic interactions among a collection of spherical particles near a plane wall are computed and used to study the Brownian motion of confined suspensions. The method of reflections is used to describe the motion of a single spherical particle embedded in the fluid constrained by two, parallel plane walls. From this, tables which are independent of the channel width are generated describing the particle's response to various force moments. This same approach is expanded to describe the hydrodynamic interactions among the particles comprising a colloidal dispersion confined in a channel. The simulations arising from this theory depict the short-time self-diffusivity, sedimentation rate and high frequency viscosity of suspensions of varying volume fractions in channels of varying widths. A theory for the scattering of evanescent waves by colloidal dispersions is developed and cast in the form of the diffusivity measured by classical light scattering. A series of simulations is conducted to predict the short- time self-diffusivity and the collective diffusivity measured by evanescent wave dynamic light scattering. The thesis concludes with a discussion of how the developed simulations and theories can be extended to make dynamic measurements as well as a brief consideration of some remaining, open questions.

Download or read book Phase Behavior and Effective Interactions in Colloidal Suspensions written by and published by Cuvillier Verlag. This book was released on 2007-04-25 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal suspensions describe particles with size from typically a few nanometers to a few microns which are dispersed in a medium. In physics, in chemistry, and in biology colloids play an important role and the study of colloidal systems underwent a recent renaissance. This is based on the development of experimental techniques, the availability of extensive computer simulations and well-developed theoretical approaches. From a technological point of view, the relevance of micro- and nanostructured materials and the presence of colloids in nature and everyday life motivates study of this rich field. In this thesis the phase behavior and the effective interactions of colloidal suspensions in bulk, in contact with surfaces, and in confined geometry are studied. For mixtures of particles with hard-core interactions the model introduced by Asakura, Oosawa and Vrij provides an appropriate starting-point. Based on that model the free-volume theory and the density functional theory are employed. In experimental systems one faces particles with properties such as the size or the shape which are described by a distribution. To capture that issue a generalized approach based on free-volume theory for treating mixtures of colloids and a polydisperse depletion agent is presented. Within that approach it is possible to treat size and morphology polydispersity. A depletion agent with a bimodal distribution possessing two length scales can be studied. Though the Asakura-Oosawa-Vrij model describes a simple fluid - a mixture of hard spheres and ideal polymer - the phenomenology is rather rich: in contact with a wall one finds layering and wetting effects and in confined geometry of a narrow pore one finds capillary condensation. The competition between both effects manifests itself in thermodynamic properties like the excess colloid adsorption and the solvation force between the two confining walls. Solvent phase separation complicates the evaluation of interparticle interactions between the solute particles. We address this question for the wall-colloid and the colloid-colloid geometry. For a non-spherical particle the effect of curvature on thermodynamic quantities is studied.

Download or read book Structure and Diffusion in Dense Confined Colloidal Suspensions written by Bianxiao Cui and published by . This book was released on 2002 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloidal Interactions Under Applied Fields in Confined Geometries written by Laura A. Schafer and published by . This book was released on 2002 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Complex Fluids in Confined Geometries written by Jonghoon Lee and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: The hydrodynamic interaction among constituents of a complex fluid is sensitive to any change in the boundary conditions. Hence the response of a confined complex fluid to the applied stress is quite different from that of an unbounded complex fluid. In this thesis, using numerical simulations, we investigate the dynamics of suspensions in two different types of confinement. The rheology of dense colloidal suspensions changes drastically upon the modification in the surface properties of the particles. We used lattice Boltzmann simulations to investigate the the effects of polymer coatings on the squeezing flow between parallel plates. In this study, we used random arrays of stationary and mobile particles as the simplest models of the polymer coat.

Download or read book Suspensions of Colloidal Particles and Aggregates written by Frank Babick and published by Springer. This book was released on 2016-04-04 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses the properties of particles in colloidal suspensions. It has a focus on particle aggregates and the dependency of their physical behaviour on morphological parameters. For this purpose, relevant theories and methodological tools are reviewed and applied to selected examples. The book is divided into four main chapters. The first of them introduces important measurement techniques for the determination of particle size and interfacial properties in colloidal suspensions. A further chapter is devoted to the physico-chemical properties of colloidal particles—highlighting the interfacial phenomena and the corresponding interactions between particles. The book’s central chapter examines the structure-property relations of colloidal aggregates. This comprises concepts to quantify size and structure of aggregates, models and numerical tools for calculating the (light) scattering and hydrodynamic properties of aggregates, and a discussion on van-der-Waals and double layer interactions between aggregates. It is illustrated how such knowledge may significantly enhance the characterisation of colloidal suspensions. The final part of the book refers to the information, ideas and concepts already presented in order to address technical aspects of the preparation of colloidal suspensions—in particular the performance of relevant dispersion techniques and the stability of colloidal suspensions.

Download or read book Field induced Phase Behavior of Colloidal Systems in Confined Geometries written by Tieying Gong and published by . This book was released on 2002 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Supramolecular Structure in Confined Geometries written by Srinivas Manne and published by . This book was released on 1999 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of confinement on the surfaces of aggregates in 100-1000 oA size range is an emerging field in condensed matter physics and chemistry. This volume collects work from a range of scientists who are studying the same general kinds of molecular behavior and seeks to draw connections between different approaches.

Download or read book Colloidal Dispersions Under Slit Pore Confinement written by Yan Zeng and published by Springer Science & Business Media. This book was released on 2012-12-28 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation contributes to the understanding of fundamental issues in the highly interdisciplinary field of colloidal science. Beyond colloid science, the system also serves as a model for studying interactions in biological matter. This work quantitatively investigated the scaling laws of the characteristic lengths of the structuring of colloidal dispersions and tested the generality of these laws, thereby explaining and resolving some long-standing contradictions in literature. It revealed the effect of confinement on the structuring, independently of specific properties of the confining interfaces. In addition, it resolved the influence of roughness and charge of the confining interfaces on the structuring and as well providing a method to measure the effect of surface deformability on colloidal structuring.

Download or read book Non equilibrium Dynamics of Confined Colloidal Suspensions in Shear flow written by Sascha Gerloff and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shear Behavior and Microstructures of Confined Colloidal Suspensions written by John Eric Hug and published by . This book was released on 1995 with total page 662 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rheological properties and microstructures of concentrated charge-stabilized suspensions confined to gap sizes on the order of a few particle diameters are investigated by molecular dynamics computer simulations. Suspensions of uniform spheres at volume fractions ranging from 0.28 to 0.53 covering the crystalline phase are studied. The suspensions are modeled as spheres interacting via a repulsive short-ranged electrostatic potential. Stress versus shear rate behavior is examined as a function of particle volume fraction, gap size, and shear history. Microstructures for systems at equilibrium and under shear are investigated by direct observation of particle configurations and by scattering patterns generated from structure factor calculations. The observed shear behavior and microstructures compare favorably with experimental shear studies of bulk colloidal suspensions. The shear response and stresses marking rheological transitions scale on the equilibrium modulus in a universal manner. Small changes in gap size result in significant differences in the equilibrium properties which in turn can affect the observed rheological response. Gap size also plays an important role at shear rates where catastrophic shear thinning and shear thickening occur. Qualitative differences in shear behavior between experiments and simulations are observed at high shear rates suggesting that particle interactions dominate the shear behavior at low shear rates and hydrodynamics becomes important at high shear rates.

Download or read book Encyclopedia of Surface and Colloid Science written by Arthur T. Hubbard and published by CRC Press. This book was released on 2002-07-18 with total page 1580 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive reference collects fundamental theories and recent research from a wide range of fields including biology, biochemistry, physics, applied mathematics, and computer, materials, surface, and colloid science-providing key references, tools, and analytical techniques for practical applications in industrial, agricultural, and forensic processes, as well as in the production of natural and synthetic compounds such as foods, minerals, paints, proteins, pharmaceuticals, polymers, and soaps.