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 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 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 Supramolecular And Colloidal Structures In Biomaterials And Biosubstrates written by Moti Lal and published by World Scientific. This book was released on 2000-05-12 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt: Of central importance in personal care, food, pharmaceutics, and biotechnology, biomaterials and biosubstrates formed the subject of the fifth meeting of the Royal Society-Unilever INDO-UK Forum in Materials Science and Engineering. The programme for this meeting dwelt on two principal foci: (i) new advances in the measurement of the supramolecular and colloidal structures, and (ii) the relationship of these structures to the functional properties of the materials.This volume is a compilation of selected papers presented at the meeting by world-renowned scientists who included, among others, Prof E D T Atkins (Bristol, UK), Prof N Chandrakumar (Chennai, India), Dr A M Hermansson (Goteborg, Sweden), Dr V J Morris (Norwich, UK), Prof P Walstra (Wageningen, The Netherlands), Dr V Prakash (Mysore, India), Prof S B Ross-Murphy (King's College, London, UK), Prof G E Rogers (Adelaide, Australia), Dr T Kealey (Cambridge, UK) and Prof N Appaji Rao (Bangalore, India)./a
Download or read book Microgel Suspensions written by Alberto Fernandez-Nieves and published by John Wiley & Sons. This book was released on 2011-01-11 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: Providing a vital link between chemistry and physics on the nanoscale, this book offers concise coverage of the entire topic in five major sections, beginning with synthesis of microgel particles and continuing with their physical properties. The phase behavior and dynamics of resulting microgel suspensions feature in the third section, followed by their mechanical properties. It concludes with detailed accounts of numerous industrial, commercial and medical applications. Edited by David Weitz, Professor at Harvard and one of the world's pre-eminent experts in the field.
Download or read book Food Polymers Gels and Colloids written by Eric Dickinson and published by . This book was released on 1991 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Microscopic Characterization of Macroscopic Colloidal Gel Rheology written by Jae Hyung Cho (Scientist in mechanical engineering) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: When attracted to one another, colloids, particles of size ranging from a few nanometers to a few microns suspended in a liquid, form a colloidal gel. The squishiness of a colloidal gel stems from its elastic space-spanning network of aggregated particles in a viscous liquid, which allows the gel to resist deformations like a solid under low stress, but to flow like a liquid under high stress. Owing to such mechanical versatility, colloidal gels are found in every corner of our lives as personal care products, dairy products, pharmaceuticals, and construction materials. Colloidal gels composed of functionalized particles are utilized for novel energy storage devices and biomedical applications. Engineering the mechanical behaviors of colloidal gels, however, remains a challenge due to our limited understanding of the link between microscopic particle interactions and macroscopic rheological properties. The state of thermodynamic nonequilibrium and the structural disorder of the network due to kinetic arrest of the attractive particles call for comprehensive investigation of colloidal gel rheology. In this thesis, we develop a better physical understanding of key rheological characteristics of a model colloidal gel via optical microscopy and rheometry. We employ differential dynamic microscopy to quantify the thermal fluctuations of the gel network across multiple length and timescales and rotational rheometry to characterize macroscopic strain and stress responses under shear. Use of the two complementary techniques enables us to show how the elasticity, the viscoelasticity, and the viscoplasticity of the gel on macroscopic scales arise from the microscopic structure and dynamics of the gel network while addressing different stages of the system from its gelation to yield or fluidization. Our findings suggest ways to systematically control the deformation and the flow of colloidal gels by tuning particle interactions or by adjusting external loadings.
Download or read book Colloid Chemistry written by Clemens K. Weiss and published by MDPI. This book was released on 2019-01-15 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Colloid Chemistry" that was published in Gels
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 Chemical Methods written by Abdolhossein Hemmati-Sarapardeh and published by Gulf Professional Publishing. This book was released on 2021-11-30 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemical Methods, a new release in the Enhanced Oil Recovery series, helps engineers focus on the latest developments in one fast-growing area. Different techniques are described in addition to the latest technologies in data mining and hybrid processes. Beginning with an introduction to chemical concepts and polymer flooding, the book then focuses on more complex content, guiding readers into newer topics involving smart water injection and ionic liquids for EOR. Supported field case studies illustrate a bridge between research and practical application, thus making the book useful for academics and practicing engineers. This series delivers a multi-volume approach that addresses the latest research on various types of EOR. Supported by a full spectrum of contributors, this book gives petroleum engineers and researchers the latest developments and field applications to drive innovation for the future of energy. - Presents the latest research and practical applications specific to chemical enhanced oil recovery methods - Helps users understand new research on available technology, including chemical flooding specific to unconventional reservoirs and hybrid chemical options - Includes additional methods, such as data mining applications and economic and environmental considerations
Download or read book Aerogels Handbook written by Michel Andre Aegerter and published by Springer Science & Business Media. This book was released on 2011-06-10 with total page 929 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerogels are the lightest solids known. Up to 1000 times lighter than glass and with a density as low as only four times that of air, they show very high thermal, electrical and acoustic insulation values and hold many entries in Guinness World Records. Originally based on silica, R&D efforts have extended this class of materials to non-silicate inorganic oxides, natural and synthetic organic polymers, carbon, metal and ceramic materials, etc. Composite systems involving polymer-crosslinked aerogels and interpenetrating hybrid networks have been developed and exhibit remarkable mechanical strength and flexibility. Even more exotic aerogels based on clays, chalcogenides, phosphides, quantum dots, and biopolymers such as chitosan are opening new applications for the construction, transportation, energy, defense and healthcare industries. Applications in electronics, chemistry, mechanics, engineering, energy production and storage, sensors, medicine, nanotechnology, military and aerospace, oil and gas recovery, thermal insulation and household uses are being developed with an estimated annual market growth rate of around 70% until 2015. The Aerogels Handbook summarizes state-of-the-art developments and processing of inorganic, organic, and composite aerogels, including the most important methods of synthesis, characterization as well as their typical applications and their possible market impact. Readers will find an exhaustive overview of all aerogel materials known today, their fabrication, upscaling aspects, physical and chemical properties, and most recent advances towards applications and commercial products, some of which are commercially available today. Key Features: •Edited and written by recognized worldwide leaders in the field •Appeals to a broad audience of materials scientists, chemists, and engineers in academic research and industrial R&D •Covers inorganic, organic, and composite aerogels •Describes military, aerospace, building industry, household, environmental, energy, and biomedical applications among others
Download or read book Nanosized Drug Delivery Systems Colloids and Gels for Site Specific Targeting written by Francesco Cellesi and published by Frontiers Media SA. This book was released on 2020-09-17 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.
Download or read book Physical Gels from Biological and Synthetic Polymers written by Madeleine Djabourov and published by Cambridge University Press. This book was released on 2013-05-16 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting a unique perspective on state-of-the-art physical gels, this interdisciplinary guide provides a complete, critical analysis of the field and highlights recent developments. It shows the interconnections between the key aspects of gels, from molecules and structure through to rheological and functional properties, with each chapter focusing on a different class of gel. There is also a final chapter covering innovative systems and applications, providing the information needed to understand current and future practical applications of gels in the pharmaceutical, agricultural, cosmetic, chemical and food industries. Many research teams are involved in the field of gels, including theoreticians, experimentalists and chemical engineers, but this interdisciplinary book collates and rationalises the many different points of view to provide a clear understanding of these complex systems for researchers and graduate students.
Download or read book Special Issue on Colloidal Gels written by George Petekidis and published by . This book was released on 2014 with total page 531 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gels Handbook Fundamentals Properties Applications In 3 Volumes written by and published by World Scientific. This book was released on 2016-01-25 with total page 1170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogels are made from a three-dimensional network of cross linked hydrophilic polymers or colloidal particles that contain a large fraction of water. In recent years, hydrogels have attracted significant attention for a variety of applications in biology and medicine. This has resulted in significant advances in the design and engineering of hydrogels to meet the needs of these applications. This handbook explores significant development of hydrogels from characterization and applications. Volume 1 covers state-of-art knowledge and techniques of fundamental aspects of hydrogel physics and chemistry with an eye on bioengineering applications. Volume 2 explores the use of hydrogels in the interdisciplinary field of tissue engineering. Lastly volume 3 focuses on two important aspects of hydrogels, that is, drug delivery and biosensing. Contains 50 colour pages.
Download or read book Rheokinetics written by A. Ya. Malkin and published by John Wiley & Sons. This book was released on 2008-09-26 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:
