Download or read book Hydrodynamic Simulations of Colloidal Gels written by Michael Dean Bybee and published by ProQuest. This book was released on 2009 with total page 209 pages. Available in PDF, EPUB and Kindle. Book excerpt: BD simulations are also performed, and the results are compared with those of the FLD simulations. Remarkable agreement is observed for both the microstructure and dynamics, suggesting that the structural evolution and dynamics of colloidal suspensions with short-range attraction and long-range repulsion under quiescent conditions may not be very sensitive to the effects of hydrodynamic interactions.
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 Micromechanics and Rheology of Colloidal Gels Via Dynamic Simulation written by Lilian Challingsworth Johnson and published by . This book was released on 2018 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal gels are soft solids comprising a viscoelastic, networked structure embedded in solvent. This network forms from microscopically small particles initially dispersed in a solvent which self-assemble into a hierarchical, space-spanning network of particles connected by physical bonds. When subjected to external forces, colloidal gels exhibit a solid-to-liquid transition yet regain elastic character when forcing is removed. Their tunable mechanical properties and ability to flow enable colloidal gels to serve as the foundation of a multitude of applications ranging from everyday products, like yogurt, to biomedical applications, such as injectable therapeutics. The nonlinear rheology of colloidal gels underlies their utility in nearly every application, for example, spreading, injecting, or pouring. The transition from rest to steady flow of colloidal gels is characterized by one or more stress overshoots indicative of gel yield. In strongly-bonded, dilute colloidal gels, yield is hypothesized to result from the catastrophic loss of the network structure. Solid-like fracture leading to fluidization of strongly bonded gels may not be relevant where particle strands are not single-particle thick chains but rather bicontinuous and time-evolving due to reversible bonds. The connections between gel yield and the structural evolution of dense, bicontinuous gels remains poorly understood due to the difficulty of imaging of the internal structure of dense particulate gels with sufficient time resolution in experiments and due to the large system size required in computational studies. Here we report large-scale dynamic simulation to study reversible colloidal gels to elucidate the micromechanical underpinnings of non-Newtonian behavior of soft materials and to understand ongoing phase separation. First, we show that the startup of a fixed strain rate reveals that colloidal gel yield, separating the short-time solid-like response from the long-time liquid-like response, can be framed as a transition in energy storage. Contrary to prior hypotheses connecting yield to loss of network connectivity, the network persists after flow startup and a predictive model connecting hierarchical structure to early-time stress growth is presented. We devised a novel approach to monitor bond stretching, compression, formation, and loss alongside macroscopic deformation. We find that changes in structure that underlie the stress growth and post-yield relaxation, as monitored by bond dynamics, indicate the switch from energy storage to release. After rheological yield, energy release continues if flow is sufficiently strong; however, when imposed flow is weak, energy release reverses after yield, and the gel densifies. This gives the important result that yield under weak flow can be viewed as a release from kinetic arrest, permitting the gel to evolve toward more complete phase separation. This supports our view that yield of weakly sheared gels is a `non-equilibrium phase transition'. Second, we compare our simulations to experimental measurements of colloidal gel rheology to study the influence of bond strength, volume fraction, and network morphology on the viscoelastic moduli. Strong agreement is found between linear viscoelasticity from sim...
Download or read book Hydrodynamic Simulations of Colloidal Suspensions with Short range Attraction and Long range Repulsion written by Michael Dean Bybee and published by . This book was released on 2007 with total page 126 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 Microstructural Dynamics of Colloidal Gels written by and published by . This book was released on 2020 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Advances in Mechanics of Non Newtonian Fluids written by Wei-Tao Wu and published by MDPI. This book was released on 2020-02-21 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Non-Newtonian (non-linear) fluids are common in nature, for example, in mud and honey, but also in many chemical, biological, food, pharmaceutical, and personal care processing industries. This Special Issue of Fluids is dedicated to the recent advances in the mathematical and physical modeling of non-linear fluids with industrial applications, especially those concerned with CFD studies. These fluids include traditional non-Newtonian fluid models, electro- or magneto-rheological fluids, granular materials, slurries, drilling fluids, polymers, blood and other biofluids, mixtures of fluids and particles, etc.
Download or read book Linking Single Particle Dynamics to Macroscopic Phenomena in Colloidal Gels written by Vijay Gopalakrishnan and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Inherent Structure Approach to Yield Behaviors in Colloidal Gels written by Stacy C. Pyett and published by . This book was released on 2003 with total page 242 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 Response of Dilute Colloidal Gels to Shear Deformation written by Bharath Rajaram and published by . This book was released on 2011 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal gels are often subject to transient shear deformation during steps involved in their manufacturing, processing and handling. Understanding the microstructural and rheological implications of this deformation is of critical importance to a wide host of technologies that use these materials as feedstock, including the food processing and ceramic industries, and in emerging technologies such as direct write assembly. For these systems, the rheology and microstructural evolution are coupled by a circular interplay between the interparticle and hydrodynamic interactions at the micro- and nano- scale, and the macroscopically imposed stresses or strains making their predictions from theoretical models difficult. In this study, we directly probe the shear-induced evolution of the microstructure, dynamics and rheology of dilute, depletion-induced colloidal gels suspended in a refractive index- and density- matched solvent mixture. The real time response of the gel network to shear flow is quantified using a fast scanning confocal microscope coupled with a custom-built cone-and-plate shear cell. Our results capture, for the first time in real space, local dynamic and structural information during the gel's evolution to the applied shear. Broadly, the particle dynamics evolve through three prominent regimes: (i) a period of movement immediately following the imposition of shear, (ii) an intermediate interval characterized by a predominantly immobilized microstructure, albeit with sporadic local rearrangements and, (iii) a final regime consisting of disconnected clusters advecting along the shear flow direction with a plug-like flow profile. Here, the intermediate interval is associated with transient heterogeneities in the particle dynamics and the appearance of chain-like domains oriented along the extensional axis of the flow field. We also unveil a secondary yield point previously unforseen in such dilute systems. Remarkably, the onset of gel rupture is progressively delayed at positions closer to the center of the cone; the microstructural and rheological signatures of this behavior are interrogated and a unified theory accounting for hydrodynamic contributions is proposed. Finally, the terminal microstructure of the sheared gels is investigated by systematically varying the strength and range of the attractive interactions, and the rate of deformation, and the implications on the phase behavior of colloidal gels are discussed.
Download or read book Trends in Colloid and Interface Science V written by M. Corti and published by Springer. This book was released on 2007-12-11 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aggregation and Gelation of Concentrated Colloidal Suspensions written by Sara Romer and published by Herbert Utz Verlag. This book was released on 2001 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Journal of the Physical Society of Japan written by and published by . This book was released on 2009-03 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Computer Simulations of Gel Formation in Colloidal Systems of Sticky Rods written by Johannes Krotz and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
