Download or read book Influence of Particle Shape on the Structure and Dynamics of Colloidal Glasses and Gels written by Mukta Tripathy and published by . This book was released on 2008 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Effects of Particle Shape Size and Interaction on Colloidal Glasses and Gels written by Ryan C. Kramb and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Particle Shape on the Structure and Rheology of Colloidal Suspensions and Gels written by Ali Mohraz and published by . This book was released on 2004 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Structure And Dynamics Of Charged Colloidal Disks In Colloid Polymer Mixtures written by Suhasini Kishore and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Complex fluid mixtures of colloids and polymers are extensively used in several conventional and emerging technological applications. Particles self-assemble under different conditions to form colloidal glasses and gels and it often leads to the development of unusual viscoelastic features. In the case of aspherical particles, shape anisotropy and physical aging effects add to the existing complexities so the implementation of a strategic formulation method to improve performance and stability remains a critical challenge. This thesis presents a comprehensive analysis of particle interactions in mixtures of charged disk-shaped colloids and weakly-adsorbing polymers like poly(ethylene oxide) (PEO). Here, we discuss the behavior of suspensions containing laponite® and PEO of molecular weights (Mw) varying between 4.6 and 300 kg/mol and at concentrations within the dilute through concentrated regimes. Techniques such as rheology, light (DLS) and x-ray scattering (XPCS and USAXS) were used to understand and characterize the effect of chain number and length on the macroscopic behavior, microstructure and dynamics of particles in these colloid-polymer mixtures. Laponite® suspensions gradually transition from a homogeneous fluid to a structurally arrested phase. With the addition of polymers, rheological measurements show that in addition to the typical re-entrant behavior observed in the dilute polymer phase, there is another onset of stabilization close to the semi dilute polymer regime. While DLS and XPCS results show three different regimes in the microstructural dynamics along these transitions, USAXS measurements indicate the presence of only finite sized ellipsoidal structures that are directed by polymer-particle interactions. We believe that the arrested phase is a glassy system as no large scale structure is observed. On the other hand, adding high Mw PEO results in the formation of strong colloidal gels where laponite® particles act as junctions in the colloid-polymer network. Nanometer to micron-sized clusters form with the addition of PEO chains larger than the minimum required for polymer-clay bridging. Increasing the concentration of PEO changes the density of clusters and this directly affects the bulk elasticity of the material. The results thus serve as an excellent benchmark to understand how to effectively formulate an anisotropic colloid-polymer mixture for an application.
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 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: Essential text on the practical application and theory of colloidal suspension rheology, written by an international coalition of experts.
Download or read book Colloidal Crystals of Spheres and Cubes in Real and Reciprocal Space written by Janne-Mieke Meijer and published by Springer. This book was released on 2015-06-11 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an in-depth study on the effect of colloidal particle shape and formation mechanism on self-organization and the final crystal symmetries that can be achieved. It demonstrates how state-of-the-art X-ray diffraction techniques can be used to produce detailed characterizations of colloidal crystal structures prepared using different self-assembly techniques, and how smart systems can be used to investigate defect formation and diffusion in-situ. One of the most remarkable phenomena exhibited by concentrated suspensions of colloidal particles is the spontaneous self-organization into structures with long-range spatial and/or orientational orders. The study also reveals the subtle structural variations that arise by changing the particle shape from spherical to that of a rounded cube. In particular, the roundness of the cube corners, when combined with the self-organization pathway, convective assembly or sedimentation, was shown to influence the final crystal symmetries.
Download or read book Dynamical Heterogeneities in Glasses Colloids and Granular Media written by Ludovic Berthier and published by OUP Oxford. This book was released on 2011-07-14 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of the solid materials we use in everyday life, from plastics to cosmetic gels exist under a non-crystalline, amorphous form: they are glasses. Yet, we are still seeking a fundamental explanation as to what glasses really are and to why they form. In this book, we survey the most recent theoretical and experimental research dealing with glassy physics, from molecular to colloidal glasses and granular media. Leading experts in this field present broad and original perspectives on one of the deepest mysteries of condensed matter physics, with an emphasis on the key role played by heterogeneities in the dynamics of glassiness.
Download or read book Direct Observation of Correlated Motions in Colloidal Gels and Glasses written by Yongxiang Gao and published by . This book was released on 2008 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamical Heterogeneities in Glasses Colloids and Granular Media written by Ludovic Berthier and published by Oxford University Press. This book was released on 2011-07-14 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most everyday solid materials, from plastics to cosmetic gels, exist in a non-crystalline, amorphous form: they are glasses. Yet we are still seeking an explanation as to what glasses really are and to why they form. In this book, leading experts present broad and original perspectives on one of the deepest mysteries of condensed matter physics.
Download or read book Non equilibrium Transitions in Colloidal Glasses and Gels written by and published by . This book was released on 2016 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis, we study the structure dynamics and mechanical response of colloidal glasses and gels in the presence of applied stresses and aging. We follow the dynamics and three-dimensional structures of the glass and gel in real time using confocal microscopy and X-ray scattering. The main purpose of this study is to motivate a new conceptual approach in terms of a dynamic first-order transition in response to applied stress or even upon aging of the glass. This topic is poorly understood due to the difficulty of investigating these driven systems over a wide range of length and time scales, and the lack of theoretical models to describe the non-affine displacements of the particles under shear, and of an appropriate dynamic order parameter to describe dynamic states in a disordered glassy system. Recent development of X-ray scattering and confocal microscopy, and a new conceptual idea of a dynamical phase transition allows us to investigate this challenging topic. Here, we can contribute to the understanding of the new non-equilibrium first-order phase transition by connecting the non-affine motion of the glassy particles to their free energy under deformation. We also evaluate experimentally the newly proposed order parameter characterizing the trajectories of mobile and immobile particles in the presence of a shearing field and aging."--Samenvatting auteur.
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 Origins of Heterogeneous Dynamics in Colloidal Gels written by Clare J. Dibble and published by . This book was released on 2006 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Improved Models of Colloidal Gels written by Zsigmond Varga (Ph. D.) and published by . This book was released on 2018 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal gels, composed of sub-micron, mutually attractive particles that aggregate to form a system spanning network, are the most abundant and diverse soft matter in society with numerous familiar, yet also many exotic applications, ranging from common dairy products to novel medical implants. Despite this profusion, the link between network microstructure and macroscopic behavior and function remains a mystery. Computational models of the microstructural evolution of colloidal gels present one opportunity to efficiently study the emergence of bulk material properties. However, these simulations often fail to match experimental results and are unable to reproduce landmark observations set as benchmarks. This thesis is concerned with the systematic study of the influence of hydrodynamic interactions on colloidal gelation to explain the prevailing experimental-theoretical mismatch in the literature. The novel insights drive the development of improved models that can accurately describe the physics of colloidal gels. A series of computational studies carefully investigate the role of hydrodynamic interactions in determining the conditions for kinetic arrest of attractive dispersions. The collective dynamics enabled by fluid mechanics are shown to enhance coagulation leading to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic forces. Simulations with long-ranged hydrodynamic interactions are found to faithfully reproduce experimental phase diagrams. This is shown to hold true both for purely attractive dispersions as well as in systems with repulsive barriers. Perturbation analysis is used to study the rheology of semi-dilute, attractive colloidal dispersions and it is demonstrated that both hydrodynamic interactions and the interparticle potential critically affect the viscoelasticity of the material. A normal mode analysis on colloidal gels is conducted using different models of the hydrodynamic interactions between suspended particles to investigate the relaxation rates and energy dissipation in the network. It is established that computational models neglecting long-ranged hydrodynamic interactions critically fail to compute accurate values of rheological properties of interest. These findings are then integrated to study experimentally observed instabilities of attractive dispersions under shear and during sedimentation. Models accounting for the prevalent hydrodynamic forces are used to demonstrate that the phenomena of vorticity alignment and log-rolling are fluid mechanical in origin. Experimental measurements of density fluctuations and shear anisotropy are accurately recovered in simulations for the first time. Finally, a theory is developed to quantitatively predict the collapse dynamics of freely settling colloidal gels and new engineering strategies for extending the process lifetime of gel networks are presented. The observations and results discussed in this thesis leave no doubt that the properties and the mechanical response of gels are fundamentally altered by many-body hydrodynamics. These will have to be properly accounted for in the first generation of predictive computational models employed in the engineering design of colloidal gels.
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 Multiscale Probing of Colloidal Gelation Dynamics written by Jae Hyung Cho (S. M.) and published by . This book was released on 2018 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal gels are viscoelastic materials characterized by the collective behavior of particles that form a space-spanning network. Although the network structure embodies the aggregation process of the particles, the kinetic pathway from a stable suspension to such a complex microstructure remains poorly understood. In this work, we explore the evolution of microscopic structure and dynamics of home-made colloidal particles in the early phase of gelation, by extending the applicability of Differential Dynamic Microscopy (DDM) to non-ergodic media. We demonstrate uncoupled development of the structure and dynamics that reveals an intermediate stage of gel formation, and compare the DDM results with the rheological features of evolving gels. We finally show how understanding the gelation at multiple length and time scales via DDM and rheology opens new ways to tune the mechanical properties of colloidal gels that bear inherent versatility.
Download or read book Linking Microstructure and Macroscopic Properties in Colloidal Gels and Glasses written by Eric Schwen and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal suspensions are ubiquitous in consumer products and industry, but the details of how particle structures and interactions lead to their macroscopic properties are often not well understood. In this thesis, we show methods for using shear or compression to modify the microstructure of colloidal suspensions and relate these modifications to system-scale changes. In colloidal gels, we investigate the use of oscillatory shear protocols to embed a memory of the applied shear. This method is able to modify the yield strain of the gel without changing any of the constituent components or interactions. By combining our shear protocols with confocal microscopy, we are able to identify which particles in the gel are rearranging the most and correlate these changes with a lower number of neighboring particles. Analysis of the local microstructure also reveals that the bond angle distribution remains isotropic even as the gel structures rearrange to support increased strains. This lack of directionality in the gel bond structure helps explain the other main finding of our gel experiments: when trained along one axis, the same shear memory can be measured along an orthogonal axis. Our study of colloidal glasses utilizes a similar combination of macroscopic manipulation and confocal microscopy to investigate the Gardner transition. The Gardner transition is a critical phase transition occurring deep within the glass phase where glass states break into a multitude of marginally stable states with vanishingly small energy barriers between them. In our three-dimensional glass, the Gardner phase is expected to emerge as caged glass particles become trapped in subcages of their neighbors. We apply cycles of compression to a colloidal glass and track particle positions and cage properties over time to look for the signatures of the Gardner transition. This study is one of the first experimental explorations of marginal states in a three-dimensional glass and can help to clarify the nature and characteristics of the Gardner transition in physical dimensions. Together, these experiments on colloidal gels and glasses provide insight into the local microstructural changes that occur as colloidal suspensions are subjected to macroscopic manipulations.
