Download or read book Interactions and Micromechanics of Colloidal Aggregates written by John Peter Pantina and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal gels exhibit rheological properties, such as yield stress and viscoelasticity, which arise from the manner in which stress is transmitted through the microstructure. Insight into the mechanisms of stress transmission is critical in developing a full understanding of the rheological properties of these materials. Paramount to this is a thorough knowledge of the interparticle interactions. To systematically study the influence of nanoscale particle interactions on gel elasticity and yield stress, we use multiple time-shared optical traps to direct the assembly of colloidal aggregates consisting of dozens of particles. This novel technique provides a direct method of measuring the micromechanical properties and near contact interactions of aggregates that mimic the gel backbone as a function of physicochemical conditions, such as the ionic strength, ionic species, and the presence of surfactant additives. We begin by measuring the response of chain aggregates composed of colloidal PMMA in adhesive contact, due to the presence of inorganic salts in solution, to an applied bending moment. The aggregates were found to exhibit an elastic response below a critical bending moment. The simplified geometry of the aggregate allows us determine the single-bond rigidity from the measured chain elasticity, which is then related to the work of adhesion, W SL, through the Johnson-Kendall-Roberts (JKR) theory of adhesion. Next, we study the effect surfactant additives have on the micromechanics of aggregates. It is observed that both the single-bond elasticity, and the critical bending moment decreases as the surfactant concentration increases. However, ionic surfactants do so more efficiently than non-ionic surfactants. This is a consequence of the greater particle surface charge that arises from the adsorption of ionic surfactants, which in turn results in a larger Columbic repulsion between the particles. Finally, we measure the interactions and micromechanics of colloidal particles confined to an oil-water interface. A very long ranged repulsion is initially observed between particles, in agreement with theoretical descriptions of an electrostatic dipole arising from a small number of dissociated charge groups on the particle surface in the oil phase. As the sample ages, however, the repulsion is found to decrease until the particles are capable of aggregating. The results from this work are expected to aid in the development of improved microrheological models of colloidal gels by providing better descriptions of the near-contact interactions between particles, as well as greater insight into the manner in which stress is transmitted through the gel backbone. These models will permit a greater degree of rational engineering to be incorporated into the development of colloidal gels for industrial applications. (Abstract shortened by UMI.).
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 Structure and Dynamics of Strongly Interacting Colloids and Supramolecular Aggregates in Solution written by Sow-Hsin Chen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the last decade, various powerful experimental tools have been developed, such as small angle X-ray and neutron scattering, X-ray and neutron reflection from interfaces, neutron spin-echo spectroscopy and quasi-elastic multiple light scattering and large scale computer simulations. Due to the rapid progress brought about by these techniques, one witnesses a resurgence of interest in the physicochemical properties of colloids, surfactants and macromolecules in solution. Although these disciplines have a long history, they are at present rapidly transforming into a new, interdisciplinary research area generally known as complex liquids or soft condensed matter physics: names that reflect the considerable involvement of the chemical and condensed matter physicists. This book is based on lectures given at a NATO ASI held in the summer of 1991 and discusses these new developments, both in theory and experiment. It constitutes the most up-to-date and comprehensive summary of the entire field.
Download or read book Particle Stabilized Emulsions and Colloids written by To Ngai and published by Royal Society of Chemistry. This book was released on 2014-11-13 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been much scientific interest in the behaviour of colloidal particles at liquid interfaces. From a research aspect they provide model systems for fundamental studies of condensed matter physics. From a commercial aspect they provide applications for making new materials in the cosmetics, food and paint industries. In many cases of colloidal particles at interfaces, the mechanism of particle interactions is still unknown. Particle-Stabilized Emulsions and Colloids looks at recent studies on the behaviour of particles at liquid interfaces. The book first introduces the basic concepts and principles of colloidal particles at liquid-liquid interfaces including the interactions and conformations. The book then discusses the latest advances in emulsions and bicontinuous emulsions stabilized by both solid and soft particles and finally the book covers applications in food science and oil extraction. With contributions from leading experts in these fields, this book will provide a background to academic researchers, engineers, and graduate students in chemistry, physics and materials science. The commercial aspects will also be of interest to those working in the cosmetics, food and oil industry.
Download or read book Colloidal Particles Surface Properties Interactions and Aggregation Kinetics written by Sven Holger Behrens and published by . This book was released on 1999 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Optical Trapping and Scattering Studies of Field induced Micromechanics Interactions and Dynamics in a Colloidal Suspension written by Eric Matthew Furst and published by . This book was released on 2000 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Microstructure and Microrheology of Colloidal Gels written by Myung Han Lee and published by ProQuest. This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal gels are of considerable interest for both research and industry, within ceramic coatings, pharmaceutical formulations, and mineral recovery. External forces and fields, including shear deformation and gravitational sedimentation, lead to microstructural transitions, which depend on the nature and strength of interparticle interactions and on the connectedness and topology of the gel. Characterizations of the microstructure and its response to such perturbations enable us to understand and control the rheology of gels. In this dissertation, we report direct measurements of microscopic structure and mechanical response of gels with the ultimate aim of establishing fundamental relationships between the microstructure and rheological properties. We achieve this through the combined use of confocal microscopy and optical tweezers. First, we study the microscopic mechanical response of colloidal gels by manipulating single probe particles within the network. For this work, we use a refractive index and density matched suspension of polymethylmethacrylate (PMMA) particles with non-adsorbing polymer. As polymer concentration increases, a dynamically arrested, space-filling network is formed, exhibiting structural transitions from a cluster-like to a more homogeneous string-like gel phase. In a gel, probe particles are oscillated with an optical trap, creating the local strain field in the network. We find that the micromechanics correlate strongly with the gel structure. At high polymer concentration, strain fields scale as 1/ r to a distance quite close to the probe particle, as expected for a purely elastic material. In contrast, at low polymer concentrations, gels exhibit anomalous strain fields in the near-field; the strain plateaus, indicating that many particles move together with the probe. By rescaling the probe size in the theoretical model, we obtain a micromechanical gel correlation length, which is consistent with the structural difference in terms of "cluster-like" and "string-like". Next, we observe the gel elasticity and particle rearrangements in the same system. The gel microelasticity from Stokes equation monotonically increases with polymer concentration, corresponding to the aggregate internal stiffness. Then, we correct for the structural heterogeneity based on the micromechanical correlation length in gels using a prefactor suggested by Schweizer and coworkers. The revised elasticity is non-monotonically dependent on polymer concentration and is in better agreement with the bulk measurements. We also examine local elastic and plastic deformations in gels with the probe oscillation. The rearrangements strongly depend on the strength of attraction. Finally, we investigate the coupled aggregation and sedimentation phenomena of colloidal particles as functions of the strength of attraction and initial volume fraction. For this work, we use a refractive index matched and density mismatched suspension of fluorescent core-shell silica particles with a non-adsorbing polymer, polystyrene. Silica particles with a fluorescent core and non-fluorescent shell are synthesized using a modified Stober method in the presence of sodium dodecyl sulfate (SDS). For high gravitational Peclet numbers (Pe g>1), we find that the strong coupling between aggregation and sedimentation determines the growth of clusters and evolution of the suspension. Early in the aggregation process, the suspension structure depends on the attractive well depth and initial volume fraction with the functional form that resembles thermally activated barrier hopping processes in colloidal systems, such as the delayed sedimentation of gels. The aggregation behavior prior to sedimentation determines the final structure of the suspension. Finally, we find that compaction and rearrangements in the sediment correlate strongly with the depth of attraction, but not with the sediment structure. The results from this work are expected to provide a better understanding of the role of the local structure and particle interactions in micromechanics and rheology of gels. Such an understanding will ultimately lead to more accurate predictions and a better control of gel processing and properties.
Download or read book Colloidal Suspension Rheology written by Jan Mewis and published by Cambridge University Press. This book was released on 2012 with total page 417 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented in an accessible and introductory manner, this is the first book devoted to the comprehensive study of colloidal suspensions.
Download or read book Effect of Colloidal Interactions on Formation of Glasses Gels Stable Clusters and Structured Films written by Anand Kumar Atmuri and published by . This book was released on 2013 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal suspensions are ubiquitous because of their vast industrial and household usage. We demonstrate that interactions between colloidal particles play a crucial role in manipulating the phase behavior and thereby the macroscopic properties of a variety of colloidal materials, including structured films, gels, glasses and stable clusters. First, we examined films comprised of two different colloidal particles and investigated the impact of colloidal interactions in manipulating the extent of segregation in the dried films. A transport model was used to predict the volume fraction profiles of the particles as a function of film thickness, which showed that segregation could be altered by changing the particle interactions. Experimental studies were carried out using different charged latex particles and varying the pH to change the interactions, and the results from experiments and model show a very good agreement to capture the extent of segregation. Second, we studied the effect of adding low molecular weight adsorbing and non-adsorbing polymers to suspensions to modify the interparticle interactions. We studied the structural dynamics and bulk rheology of a disk-shaped clay colloid, laponite®, and polymer. Under basic conditions laponite® forms a repulsive colloidal glass. We show that low concentrations of an adsorbing polymer retards glass formation, whereas at higher concentrations an attractive glass is formed. Thus, we obtain a type of re-entrant glass transition, which is a first of its kind observed in anisotropic colloids with adsorbing polymer. On the other hand addition of a non-adsorbing polymer to laponite® suspensions triggers the formation of particle clusters, and increasing the concentration of polymer increases the strength of attraction between the particles and the size of the clusters. To further understand formation of stable clusters, we utilized population balance equations (PBE) models to study aggregation of charged colloids under quiescent conditions. We considered particles with a DLVO-type potential, where the interactions are a sum of van der Waals attraction and electrostatic repulsion. Under certain conditions, the net repulsion between large aggregates and a single particle acts as a barrier against further aggregation, and clusters reach a stable size. The PBE model was used to map out regimes of uncontrolled aggregation, controlled aggregation, and no aggregation as a function of ionic strength and colloid weight fraction. The model was tested using experimental data on charged latex particles with different colloid weight fractions and ionic strengths. The model was able to predict the regime of controlled aggregation and final size of aggregates very well. However, the rate of aggregation predicted by the model was much faster than observed experimentally. Finally, we explored aggregation of latex particles in a shear environment similar to that used in industrial toner production processes. We studied the effect of temperature, pH and coagulant concentration on aggregation and showed that there is a optimum variable space to have aggregates of controlled size and distribution.
Download or read book Theory and Applications of Colloidal Suspension Rheology written by Norman J. Wagner and published by Cambridge University Press. This book was released on 2021-04-15 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: An essential text on practical application, theory and simulation, written by an international coalition of experts in the field and edited by the authors of Colloidal Suspension Rheology. This up-to-date work builds upon the prior work as a valuable guide to formulation and processing, as well as fundamental rheology of colloidal suspensions. Thematically, theory and simulation are connected to industrial application by consideration of colloidal interactions, particle properties, and suspension microstructure. Important classes of model suspensions including gels, glasses and soft particles are covered so as to develop a deeper understanding of industrial systems ranging from carbon black slurries, paints and coatings, asphalt, cement, and mine tailings, to natural suspensions such as biocolloids, protein solutions, and blood. Systematically presenting the established facts in this multidisciplinary field, this book is the perfect aid for academic researchers, graduate students, and industrial practitioners alike.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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. This book was released on 2024-04-07 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This open access book provides a detailed exploration of the phase behaviour of, and interfacial properties in, complex colloidal mixtures (e.g., clay, milk, blood). Insights into colloids have been at the heart of many innovations in different industries. The big question underlying these innovations is how can colloidal systems be formulated and designed towards the desired properties? To do this, the forces between the colloidal particles need to be controlled. Adding depletants (non-adsorbing polymers or small colloids) is key to controlling the attractive interactions. Colloids and the Depletion Interaction provides the qualitative insights and quantitative tools to understand and predict such forces in colloidal dispersions. It offers a concise introduction to the history and fundamentals of the depletion interaction in, and phase behaviour of, colloidal dispersions. Why does adding polymers lead to attractive forces between colloidal particles? What determines the phase stability of multi-component colloidal systems? These include colloid—polymer mixtures, binary colloidal mixtures, and anisotropic particles such as clay platelets, cubes and rod-like viruses. Conceptual explanations are accompanied by experimental and computer simulation results throughout. Illustrations of depletion effects in colloid science, biology and technology demonstrate its wider significance. The concluding outlook provides the scope of challenges and possibilities in this exciting field of science. This second updated and enlarged edition contains 12 Chapters. It is an ideal book for advanced undergraduates and graduate students in physical chemistry, chemical engineering and soft matter physics. Besides providing a fundamental understanding of depletion interactions in colloidal mixtures, it gives background information on colloidal stability and phase behaviour in general. For experienced scientists and engineers working on mixtures of colloids and non-adsorbing (bio)polymers or colloidal particles, this book serves as a reference for understanding depletion interactions in systems of their specific interest.
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 Colloid Polymer Interactions written by Raymond S. Farinato and published by Wiley-Interscience. This book was released on 1999-06-15 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: P>Of related interest . . . THE COLLOIDAL DOMAIN Second Edition Where Physics, Chemistry, Biology, and Technology Meet D. Fennell Evans and Håkan Wennerström Fully updated and revised, this new edition of the critically acclaimed book incorporates information on key developments in colloid science and technology in the twentieth century. It provides a unified treatment of colloid theory, methods, and applications to specific systems, complete with concept maps, new worked examples, and more than 250 illustrations. 1999 (0-471-24247-0) 672 pp. FUNDAMENTALS OF INTERFACIAL ENGINEERING Robert J. Stokes and D. Fennell Evans This book emphasizes the importance of the intermolecular forces that hold materials together within a bulk phase or across an interface. It examines the fundamentals of the intermolecular interactions along with the properties, processing, and behavior of fluid interfacial systems. Solid surfaces and interfaces are also discussed. 1996 (0-471-18647-3) 736 pp. POLYMER HANDBOOK Fourth Edition Edited by J. Brandrup, E. H. Immergut, and E. A. Grulke Now in a fourth edition, the Polymer Handbook is one of the most comprehensive resources of fundamental, validated property data of polymeric materials necessary for polymer research. This edition boasts over 30% new material, covering such advances as the new pvt relationships and copolymer reactivity parameters. Improved nomenclature for better indexing and search and retrieval is also provided. 1999 (0-471-16628-6) 2336 pp.
Download or read book A Mathematical Model for Colloidal Aggregation written by Colleen S. O'Brien and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: The total particle interaction energy necessary for the calculation of stability ratios is represented by the summation of electrostatic and van der Waals interactions. The electrostatic interactions are modeled using DLVO theory, the linear Poisson-Boltzmann equation, and a numerical solution for the non-linear Poisson-Boltzmann Equation, while the van der Waals interactions are represented by Hamaker theory. The mathematical model is solved using an adjustable discretion technique, which is tested against a specific analytic solution, and yields an assessment of the error intrinsic in the discretization method. The basis of the mathematical model is a population balance framework. The model developed in this study is general in many respects, but could be readily applied to many different aggregation systems with minor modification.
Download or read book Hydrodynamics written by Harry Schulz and published by BoD – Books on Demand. This book was released on 2011-12-22 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: The phenomena related to the flow of fluids are generally complex, and difficult to quantify. New approaches - considering points of view still not explored - may introduce useful tools in the study of Hydrodynamics and the related transport phenomena. The details of the flows and the properties of the fluids must be considered on a very small scale perspective. Consequently, new concepts and tools are generated to better describe the fluids and their properties. This volume presents conclusions about advanced topics of calculated and observed flows. It contains eighteen chapters, organized in five sections: 1) Mathematical Models in Fluid Mechanics, 2) Biological Applications and Biohydrodynamics, 3) Detailed Experimental Analyses of Fluids and Flows, 4) Radiation-, Electro-, Magnetohydrodynamics, and Magnetorheology, 5) Special Topics on Simulations and Experimental Data. These chapters present new points of view about methods and tools used in Hydrodynamics.
