Download or read book Microstructure and Rheology of Concentrated Colloidal Suspensions with Varying Nanotribological Interactions written by Yu-Fan Lee and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is divided into two research aims: The first aim, presented in Chapters 3 and 4, is to test the theoretical framework of friction contact models with rheological and nanotribological measurements on model suspensions with controlled surface properties. In Chapter 3, we first present comprehensive experimental tests of a friction contact model based on correlating simulation results against rheological measurements for both model and industrial colloidal dispersions complemented by independent estimates of the particle-scale friction coefficients from literature surveys. The comparisons emphasize the sensitivity of the first normal stress difference can distinguish between states of shear thickening dominated by hydrodynamic friction or contact friction. Based on the findings in Chapter 3, a systematic exploration of nanotribological measurements using lateral force microscopy (LFM) is presented in Chapter 4. Our systematic studies qualitatively agree with the Stribeck relationship regardless of the solvent environment. It is also confirmed that the friction coefficient obtained from the bulk rheology lies in the high Sommerfeld number regime, suggesting that directly applying the friction coefficient obtained from the nanotribological measurements for predicting the rheology using the friction contact model is not quantitative.

Download or read book Microstructure and Rheology of Concentrated Suspensions of Near Hard sphere Colloids written by Dennis P. Kalman and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The relationship between colloidal suspension microstructure and rheology is investigated to provide a solid understanding of the nonlinear rheology of concentrated suspensions, with a focus on shear thickening. These suspensions are also studied as a treatment to woven fabric in body-armor applications, where the insight from microstructural measurements is used to attempt to improve the application. The colloid and suspension properties are characterized via SEM, DLS, SANS, USANS, and rheometry. The rheology is mapped onto an effective hard-sphere model with the addition of a yield stress. An additional excluded volume shell, as measured by SANS and USANS structural measurements, accounts for interparticle interactions due to surface forces arising from the stabilizing layer on the particles. The microstructure of these near hard-sphere concentrated, shear-thickening colloidal dispersions are measured via SANS and USANS as a function of volume fraction, shear rate, and particle size. Special Rheo-SANS, flow-SANS, and flow-USANS instruments are developed and validated to measure microstructure in flowing systems. Structures measured via USANS show a cluster peak that arises from hydrocluster formation in concentrated, shear thickening suspensions. Structure measurements in SANS via 1-d averaged analysis and analysis of the 2-d structure corresponds to that expected from Stokesian Dynamics simulations. Micromechanics theory via a Stress-SANS law is used to calculate rheology from the microstructure for comparison. As the rheology calculated from the SANS data qualitatively agrees with that of the suspension and the structures seen correspond to those expected from simulations, strong confirmation of the hydrocluster mechanism for shear thickening is observed. This improved knowledge of the hydrocluster structure is used to develop an elastohydrodynamic theory for the limiting viscosity at high shear stresses due to particle deformations in the hydrocluster. Measurements of particle modulus give consistent application of this elastohydrodynamic model to suspensions studied in this thesis. In addition, the model is applied to widely varying suspensions, including those of hard mineral particles, polymer particles, microgels, and emulsions and consistent results are seen. The results of these fundamental studies of how particle size, concentration, and hardness affect suspension microstructure and rheology are used to engineer shear thickening fluid treated textiles, suitable for various types of protective devices.

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 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 The Effects of Particle Anisotropy on the Rheology and Microstructure of Concentrated Colloidal Suspensions Through the Shear Thickening Transition written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Though suspensions comprised of anisotropic particles are ubiquitous in industry, little has been done to elucidate the effects of particle anisotropy on concentrated suspension rheology, or the mechanism responsible for the reversible shear thickening observed in these systems. This dissertation explores the rheology and shear-induced microstructure of anisotropic particle suspensions through the shear thickening transition, and provides the first account of anisotropic particle alignment during shear thickening. For this investigation, Poly(ethylene glycol) (PEG)-based suspensions of acicular precipitated calcium carbonate (PCC) particles of varying particle aspect ratio (nominal L/D & sim; 2, 4, 7) are generated that demonstrate both continuous and discontinuous reversible shear thickening with increasing applied shear rate or stress. The critical volume fraction for the onset of discontinuous shear thickening decreases as the average particle aspect ratio is increased. However, the critical stress for shear thickening is found to be independent of particle anisotropy and volume fraction, and can be predicted based on the minor axis dimension of the particles in agreement with the critical stress scaling for hard-sphere suspensions. Small angle neutron scattering during shear flow (Rheo-SANS) demonstrates that long-axis particle alignment with the flow direction is maintained throughout the range of shear stresses investigated, including the shear thickening regimes for both continuous and discontinuous shear thickening PCC/PEG suspensions. Investigations of particle flow alignment following flow cessation provide evidence that the critical volume fraction for shear thickening may be associated with an isotropic-nematic transition within the anisotropic particle suspensions. Rheo-SANS investigations of concentrated kaolin clay suspensions demonstrate that disk-shaped particles exhibit particle alignment with the face surfaces orthogonal to the gradient direction during both continuous and discontinuous shear thickening. The critical stress at the onset of shear thickening for discontinuous shear thickening clay suspensions is observed to scale with the particle thickness dimension. The rheology and Rheo-SANS observations for both the acicular PCC and disk-like kaolin clay suspensions invalidate earlier hypothesis suggesting that shear thickening behavior in anisotropic particle dispersions results from increased particle rotations out of flow alignment potentially leading to particle jamming. Rather, the observations suggest that shear thickening in anisotropic particle suspensions is a consequence of short range hydrodynamic lubrication forces resulting in the formation of hydroclusters at higher shear rates, analogous to the behavior established for spherical particle suspensions. Lastly, anisotropic particle suspensions are used to successfully develop of shear thickening fluid (STF)/ballistic fabric composites. Shape anisotropy imparts the advantage of lower solids loading required to achieve energy dissipative improvements compared to spherical particle STFs. The observed improvements in ballistic and stab resistance response of these composites over that of ballistic fabrics alone suggests that they could potentially be used in the development of personal body armors with improved, multi-threat protective capabilities.

Download or read book Rheology and Microstructure of Concentrated Suspensions of Plate Shaped Colloidal Particles written by Suzanne Michelle Jogun and published by . This book was released on 1998 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructure and Rheology of Concentrated Colloids at High Rates of Shear written by Alan Arthur Catherall and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 The Rheology of Attractive Suspensions written by Derek Eusean Huang and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Complex fluids form a broad class of materials, examples of which include foodstuffs, personal care products, biological fluids, industrial compounds, and geological materials. Detailed knowledge of their flow behavior is therefore key to understanding and predicting natural phenomena or developing new materials. In the past century, major advances in both experimental and theoretical methods have enabled greater understanding of the connection between the microscopic physical structure of complex fluids and their material response. Traditional rheology involves imposing deformation on a macroscopic sample of fluid and measuring the stress response. However, an increasing need to interrogate microscopically-small fluid samples, and a heightened interest in the colloid-level physics of biology, have motivated the development of techniques to interrogate microliter-size samples and resolve micron-length heterogeneities. One of these experimental techniques is active microrheology, where a microscopically small probe particle is driven through the material of interest. Constitutive relations between the force required to drive the probe and the speed with which it moves allow one to infer the effective viscosity of the material, and more recent expansions of the theory of active microrheology allow the direct measurement of suspension stress by monitoring the mean and fluctuating motion of the probe. Theoretical models that connect probe motion to material and flow properties have enjoyed great expansion in the last decade for the study of complex fluids of particles interacting hydrodynamically, or with repulsive forces. However, many systems of interest, including biological cells, comprise colloidal suspensions that experience attractive forces not previously represented in theoretical models. This work presents a theoretical study of the impact of attractive forces on the microstructure, microviscosity, and nonequilibrium osmotic pressure of colloidal suspensions as measured by active microrheology. In active microrheology, the probe distorts the surrounding microstructure from its equilibrium configuration. The degree of this distortion is set by the strength of external forcing relative to entropic restoring forces; interparticle attractions and repulsions also influence this evolution. Although the effects of repulsions are well-studied in prior literature, a theoretical understanding of attraction-induced effects on nonequilibrium rheology is lacking. To examine how this interplay between different microscopic forces influences rheology, we formulate a Smoluchowski equation governing pair configuration as it evolves with flow strength, interparticle attractions, and hydrodynamic interactions. We determine its solution and compute microviscosity and nonequilibrium osmotic pressure from the structure via statistical mechanics. When the probe is subject to external forcing, attractions speed upstream probe-bath encounters and slow downstream detachment, transferring particle density downstream. This sets both the strength and direction of dipolar disturbance under weak forcing and the boundary-layer and wake structure under strong forcing. These attraction-induced structural changes affect rheology: both attraction-thinning and attraction-thickening are observed in the weak-forcing limit, while sufficiently strong forcing breaks attractive bonds and leads to flow-thinning or, in the presence of hydrodynamic interactions, flow-thickening. We find that the equilibrium osmotic pressure, described by the second virial coefficient B2, accurately predicts structural and rheological behavior in the weak-forcing limit regardless of specific attractive potential, but that the secondary length scale that arises under strong forcing precludes potential-agnostic observations far from equilibrium. The structural transitions and non-monotonic rheology in active microrheology show that tuning surface stickiness can either enhance or hinder probe motion and provide a means by which proteins or other macromolecules may change their surface chemistry to alter the viscosity of the surrounding medium, either speeding or slowing their own motion. Attractive forces are known to reduce the equilibrium osmotic pressure; as the second virial coefficient becomes more strongly negative, it is possible for phase separation to occur. This behavior changes away from equilibrium, where we find that the flow-induced nonequilibrium osmotic pressure reaches a minimum at a critical value of B2 before increasing with attraction strength. Hydrodynamic interactions suppress the nonequilibrium osmotic pressure and, at certain attraction strengths, can give rise to a flow-induced reduction in osmotic pressure below its equilibrium value. This denotes a flow-induced destabilization of attractive suspensions that may lead to phase separation in more concentrated systems, suggesting that self-assembly of active particles in biological suspensions may be driven by both attractive forces and hydrodynamic interactions

Download or read book Rheology of Non spherical Particle Suspensions written by Francisco Chinesta and published by Elsevier. This book was released on 2015-10-06 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a review of the current understanding of the behavior of non-spherical particle suspensions providing experimental results, rheological models and numerical modeling. In recent years, new models have been developed for suspension rheology and as a result applications for nanocomposites have increased. The authors tackle issues within experimental, model and numerical simulations of the behavior of particle suspensions. Applications of non-spherical particle suspension rheology are widespread and can be found in organic matrix composites, nanocomposites, biocomposites, fiber-filled fresh concrete flow, blood and biologic fluids. - Understand how to model and predict the final microstructure and properties of particle suspensions - Explores nano, micro, meso and macro scales - Rheology, thermomechanical and electromagnetic physics are discussed

Download or read book Hydrosols and Rheology written by Milton Kerker and published by Academic Press. This book was released on 2014-05-10 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloid and Interface Science, Volume IV: Hydrosols and Rheology is the fourth volume of papers presented at the International Conference on Colloids and Surfaces, held in San Juan, Puerto Rico on June 21-25, 1976. This volume contains 57 chapters and begins with reviews on colloidal dispersions, interacting latex particles, reversible adsorption of hydrosols, and stability of colloidal kaolinite suspensions. The next chapters deal with determination of colloidal stability, the microstructure of latex particles, instrumentation, and analytical methods for rheology measurement. These topics are followed by discussions of polymer adsorption, kinetic aspects of rheology, and measurement of important parameters in adsorption. This text also explores the properties of surface rheological models, the analysis of sedimentation velocity, and the application of hydrodynamic chromatography. The remaining chapters look into the colloid chemical aspects of drilling fluid rheology, the rheology of dilute polymer solutions, colloidal sol flow, and the shear thickening of colloidal dispersions, This book will prove useful to chemical engineers and other related professions who are interested in colloidal dispersion, rheology, and hydrosols.

Download or read book Rheology of Concentrated Colloidal Suspensions and Comparison with Mode Coupling Theory written by Miriam Isabell Siebenbürger and published by . This book was released on 2010 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rheology and Microstructure of Concentrated Near Hard Sphere Colloidal Dispersions at the Shear Thickening Transition written by Brent J. Maranzano and published by . This book was released on 2001 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Active Microrheology of Colloidal Suspensions written by Indira Sriram and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Typically, rheology is measured using bulk rheological techniques, which give information about the macroscopic properties of the fluid, such as viscosity, and elastic modulus. However, the recent advances in sensitive microscopic and optical techniques have led to the emergence of a new field, known as microrheology. Microrheological measurements are capable of resolving forces on the order of piconewtons, and can obtain very localized structural information in the test fluid. All microrheological techniques utilize embedded probe particles to determine the surrounding fluid properties. The most common form of microrheology is "passive" microrheology, wherein the probe particles execute purely Brownian or thermal motion. Alternatively, in "active" microrheology, probe particles are manipulated using an external source of force, such as laser tweezers or magnetic tweezers. Both techniques present specific advantages. Passive microrheology has been widely adopted because the design and implementation of experiments is relatively straightforward. However, since passive microrheology is constrained to rely on purely thermal motion, the recovered fluid behavior is always in a linear response regime. The goal of the present work is to adapt active microrheology to measure non-linear fluid properties such as shear thinning, and to determine the conditions where such measurements agree with bulk rheology. We begin by developing a small amplitude, oscillatory active microrheological technique, where a single probe particle is trapped and oscillated in a suspension of small bath particles, whose diameter that is approximately twenty times smaller than that of the probe diameter. The suspension microviscosity is recovered across a frequency range of 5-1000 Hz, and applied amplitudes which are approximately 10% of the probe diameter. We find that the suspension exhibits thinning behavior with increasing frequency. In addition, we obtain quantitative agreement between our microrheological measurements, drag microrheology measurements, and bulk rheology, suggesting that this technique is capable of recovering bulk viscosity values. Finally, we compare our results to a new theoretical model that accounts for the three sources of stress in active microrheological measurements of colloidal suspensions: (i) direct interactions between the probe and bath particles (ii) indirect interactions between bath particles, and (iii) Einstein stresses that arise from the particles' inability to shear in the same manner as the surrounding fluid. Notably, while indirect interactions and Einstein stresses are present in macroscopic techniques, direct interactions have no macroscopic analog. Therefore, if indirect interactions dominate in the measurements, the bulk suspension viscosity can be recovered. We find that indirect interactions dominate in the limit that the probe particle is far larger than the surrounding bath particles, and therefore determine both experimentally and analytically that our measurements recover the bulk suspension viscosity. Next, we analyze single probe drag measurements in a suspension of fluorescently labeled bath particles. We recover the suspension microviscosity, and directly correlate this to the microstructural deformation in the bath suspension. We find that the suspension exhibits thinning behavior as the velocity of the probe increases. In addition, the measured microviscosity is found to be in good agreement with recent computational studies in the "direct" collision limit, which is a measurement artifact when considering the bulk, non-linear response in a suspension. In addition, we find some departure between our experimental results, and recently performed theoretical studies, which we attribute to the presence of hydrodynamic interactions in our system. We further characterize the anisotropic, non-linear structures formed in the direct probe limit by performing two probe experiments in a colloidal suspension. We hypothesize that these structures could potentially lead to interprobe interactions. First, we hold two particles such that the line joining their centers is normal to the flow direction, and then conduct measurements as a function of probe velocity and interparticle separation. Both the drag force and microstructural deformation surrounding the particles are recovered. Intriguingly, we find that the microstructure induces a slight attraction between the probe particles, particularly at close separations, constituting a "non-equilibrium" depletion interaction. We then conduct two point measurements with the line joining the particles aligned parallel to the flow direction, and reexamine the forces on the probes, and the microstructural effects in the bath suspension. We find that the drag force experienced by both particles is the same, despite their orientation to the flow direction. In addition, we find several microstructural effects that differ from both the single probe and perpendicular case.

Download or read book The Rheology of Concentrated Polymer Colloidal Suspensions written by Babak Kaffashi and published by . This book was released on 1994 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Flow and Microstructure of Dense Suspensions Volume 289 written by Leslie J. Struble and published by . This book was released on 1993-05-28 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.

Download or read book Colloidal Suspension Rheology written by Jan Mewis and published by . This book was released on 2012 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Colloidal suspensions are encountered in a multitude of natural, biological, and industrially relevant products and processes. Understanding what affects the flow behavior, or rheology, of colloid particles, and how these suspensions can be manipulated, is important for successful formulation of products such as paint, polymers, foods, and harmaceuticals. This book is the first devoted to the study of colloidal rheology in all its aspects. With material presented in an introductory manner, and complex mathematical derivations kept to a minimum, the reader will gain a strong grasp of the basic principles of colloid science and rheology. Beginning with purely hydrodynamic effects, the contributions of Brownian motion and interparticle forces are covered, before the reader is guided through specific problem areas such as thixotropy and shear thickening; special classes of colloid suspensions are also treated. An essential guide for academic and industrial researchers, this book is also ideal for graduate course use"--Résumé de l'éditeur.