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 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 Geometry and Phase Transitions in Colloids and Polymers written by William Kung and published by World Scientific. This book was released on 2009 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph represents an extension of the author''s original PhD thesis and includes a more thorough discussion on the concepts and mathematics behind his research works on the foam model, as applied to studying issues of phase stability and elasticity for various non-closed packed structures found in fuzzy and colloidal crystals, as well as on a renormalization-group analysis regarding the critical behavior of loop polymers upon which topological constraints are imposed. The common thread behind these two research works is their demonstration of the importance and effectiveness of utilizing geometrical and topological concepts for modeling and understanding soft systems undergoing phase transitions.

Download or read book Structure and Functional Properties of Colloidal Systems written by Roque Hidalgo-Alvarez and published by CRC Press. This book was released on 2009-11-18 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt: Integrating fundamental research with the technical applications of this rapidly evolving field, Structure and Functional Properties of Colloidal Systems clearly presents the connections between structure and functional aspects in colloid and interface science. It explores the physical fundamentals of colloid science, new developments of synthesis

Download or read book Colloids and the Depletion Interaction written by Henk N. W. Lekkerkerker and published by Springer Nature. This book was released on with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Colloids and the Depletion Interaction written by Henk N.W. Lekkerkerker and published by Springer Science & Business Media. This book was released on 2011-05-12 with total page 245 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloids are submicron particles that are ubiquitous in nature (milk, clay, blood) and industrial products (paints, drilling fluids, food). In recent decades it has become clear that adding depletants such as polymers or small colloids to colloidal dispersions allows one to tune the interactions between the colloids and in this way control the stability, structure and rheological properties of colloidal dispersions. This book offers a concise introduction to the fundamentals of depletion effects and their influence on the phase behavior of colloidal dispersions. Throughout the book, conceptual explanations are accompanied by experimental and computer simulation results. From the review by Kurt Binder: "They have succeeded in writing a monograph that is a very well balanced compromise between a very pedagogic introduction, suitable for students and other newcomers, and reviews of the advanced research trends in the field. Thus each chapter contains many and up to date references, but in the initial sections of the chapters, there are suggested exercises which will help the interested reader to recapitulate the main points of the treatment and to deepen his understanding of the subject. Only elementary knowledge of statistical thermodynamics is needed as a background for understanding the derivations presented in this book; thus this text is suitable also for advanced teaching purposes, useful of courses which deal with the physics for soft condensed matter. There does not yet exist any other book with a similar scope..... The readability of this book is furthermore enhanced by a list of symbols, and index of keywords, and last not least by a large number of figures, including many pedagogic sketches which were specifically prepared for this book. Thus, this book promises to be very useful for students and related applied sciences alike." Eur. Phys. J. E (2015) 38: 73

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 Computational Methods in Surface and Colloid Science written by Malgorzata Borowko and published by CRC Press. This book was released on 2019-04-23 with total page 625 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents computer simulation methods and mathematical modelling of physical processes used in surface science research. It offers in-depth analysis of advanced theoretical approaches to behaviours of fluids in contact with porous, semiporous and nonporous solid surfaces. The book also explores interfacial systems for a wide variety of p

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 Interactions Between Colloidal Particles at Oil water Interfaces written by Bum Jun Park and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The behavior of colloidal particles at two-dimensional interfaces is of considerable interests in terms of industrial applications and model systems for research. To systematically study colloidal particle behaviors at 2D interfaces, we directly measure interaction forces between particle pairs, dynamics of a confined particle in a fixed geometry, and micromechanical properties of aggregates or percolated networks. For doing this, we use multiple time-shared optical traps which enable us to measure forces in the piconewton range (0.1-100 pN). First, the trapping forces for a single ray at the interface were calculated while varying the particle position at the 2D interfaces. The trapping force is described by the contributions of reflected and refracted rays with their corresponding powers, which are determined by Fresnel reflection and transmission coefficients. Based on the Ashkin's calculation in the 3D aqueous phase, we found that the trapping and scattering forces are mainly determined by the first reflection of the incident ray and the next three refractions to the medium. At 2D interfaces, the trapping force is considered for two geometries; (a) when the incident ray is incident on a particle in the aqueous phase, (b) when a transmitted ray at the liquid interface enters into a particle in the oil phase. In the first geometry, the trapping forces do not change, regardless of the refraction orders if the second refracted ray is to the oil phase. The dimensionless factors Q g and Q s of the gradient force and the scattering force decrease compared to those in the 3D aqueous space, and Q s decreases more than Q g . This suggests that the presence of the interface provides good trapping conditions. In the second geometry, the magnitude of dimensionless factors is consistent with those calculated in the first geometry when the incident angle is in the range of 0

Download or read book Encyclopedia of Surface and Colloid Science 2004 Update Supplement written by P. Somasundaran and published by CRC Press. This book was released on 2004-08-11 with total page 714 pages. Available in PDF, EPUB and Kindle. Book excerpt: Appending the Encyclopedia of Surface and Colloid Science by 42 entries as well as 3800 new citations, 1012 equations, and 485 illustrations and chemical structures, this important supplement summarizes a constellation of new theoretical and experimental findings related to chemical characterization, mechanisms, interfacial behavior, methods and modeling, and applications.

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 Phase Behavior Microstructure and Transitions in Self assembled Colloidal Systems written by Xiangbing Li and published by . This book was released on 1996 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Structural Properties and Phase Behavior in Colloidal Suspensions written by Stephen A. Barr and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation I present my research on the effective interactions of colloidal particles induced by a smaller species, as well as the structure of colloidal particles undergoing freeze casting. In this research I have used a wide variety of computational techniques in order to understand these systems. Specifically, in Chapter 2 I study nanoparticle haloing in a system of silica microspheres and highly charged polystyrene nanoparticles. Computer simulations are employed to determine the effective microsphere0́3 microsphere potential induced by the nanoparticles. From these simulations I am also able to determine the degree of nanoparticle adsorption on the microsphere surface. In Chapter 3 I investigate the depletion interaction in a system of charged microspheres and rigid rods. The effect of both rod concentration and screening length is explored. In Chapter 4 I study the effective interactions between charged colloids in the presence of multivalent counterions. The role of colloid charge is investigated and the onset of like-charged attraction is determined and compared with theoretical predictions. In order to study this system, I extended the geometric cluster algorithm to efficiently simulate systems interacting through the Coulomb potential. In Chapter 5 computer simulations are employed to elucidate the experimentally observed crystal phases of the Q and MS-2 virus particles in solution with multivalent salt and non-adsorbing polymer. Freeze casting is studied in Chapter 6. In this process colloidal particles are pushed by an advancing ice front. I use molecular dynamics simulations to study the dynamics of the colloidal particles and the resulting structures formed. iii

Download or read book Two dimensional Colloid Systems written by Thomas O. E. Skinner and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The behaviour of colloidal particles in two-dimensional (2D) systems is addressed in real space and time using magnetic fields, optical tweezers and optical vi£t~(inicroscopy. First, the fluctuations of a grain boundary in a 2D colloidal crystal are analysed. A real space analogue of the capillary fluctuation method is derived and successfully employed to extract the key param- eters that characterise the grain boundary. Good agreement is also found with a fluctuation- dissipation based method recently suggested in simulation. Following on from analysis of the interface fluctuations, the properties of the individual grain boundary particles are analysed to investigate the long standing hypothesis that suggests that grain boundary particle dynam- ics are similar to those in supercooled liquids. The grain boundary particle dynamics display cage breaking at long times, highly heterogeneous particle dynamics and the formation of co- operatively moving regions along the interface, all typical behaviour of a supercooled liquid. Next, the frustration induced by confining colloidal particles inside a pentagonal environment is investigated. The state of the system is adjusted via two separate control parameters: the inter-particle interaction potential and the number density. A gradual crystalline to confined liquid-like transition is observed as the repulsive inter-particle interaction potential is decreased. In contrast, re-entrant orientational ordering and dynamical effects result as the number den- sity of the confined colloidal particles is increased. Finally, the dynamics of colloidal particles distributed amongst a random array of fixed obstacle particles is probed as a function of both the mobile particle and fixed obstacle particle number densities. Increasing the mobile and the obstacle particle number density drives the system towards a glass transition. The dynamics of the free particles are shown to behave in a similar way to the normal glass transition at low obstacle density and more analogous to a localisation glass transition at high obstacle density.

Download or read book The Dynamics and Phase Behavior of Suspensions of Stimuli responsive Colloids written by Jae Kyu Cho and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The studies of the dynamics, phase behavior, interparticle interactions, and hydrodynamics of stimuli-responsive pNIPAm-co-AAc microgels were described in this thesis. Due to their responsiveness to external stimuli, these colloidal particles serve as excellent model systems to probe the relationship between colloidal interactions and phase behavior. As a first step, we established our core experimental methodology, by demonstrating that particle tracking video microscopy is an effective technique to quantify various parameters in colloidal systems. Then we used the technique in combination with a microfluidic device that provides in situ control over sample pH to probe the phase behavior of pNIPAm-co-AAc microgel suspensions. In essence, the experimental set-up enables changes in effective particle volume fractions by changing pH, which can be used to construct the phase diagram. In order to explain the unique features of the microgel phase diagram, we measured the underlying pairwise interparticle potential of pNIPAm-co-AAc microgels directly in quasi-2D suspension and proved that the interactions are pH dependent and can range from weakly attractive to soft repulsive. Finally, the hindered Brownian diffusion due of colloidal particles confined by hard walls was investigated systematically and striking differences between hard sphere and soft sphere were found, with soft pNIPAm-co-AAc microgels showing surprising mobility even under strong confinement.