Author: Ali Mohraz
Publisher:
ISBN:
Category :
Languages : en
Pages : 444

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Book Description

Author: Norman J. Wagner
Publisher: Cambridge University Press
ISBN: 1108423035
Category : Science
Languages : en
Pages : 437

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Book Description
Essential text on the practical application and theory of colloidal suspension rheology, written by an international coalition of experts.

Author: Jan Mewis
Publisher: Cambridge University Press
ISBN: 0521515998
Category : Science
Languages : en
Pages : 417

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Book Description
Presented in an accessible and introductory manner, this is the first book devoted to the comprehensive study of colloidal suspensions.

Author: Mukta Tripathy
Publisher:
ISBN:
Category :
Languages : en
Pages : 272

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Author: Guangjun Yin
Publisher:
ISBN:
Category :
Languages : en
Pages : 276

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Book Description

Author: Rajesh Kumar Mallavajula
Publisher:
ISBN:
Category :
Languages : en
Pages : 138

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Book Description
It is well known that the shape of particles is an important factor that determines the fluid flow behavior of suspensions. Interactions of cubic particles with one another and with the flow medium are unique because of their sharp edges, corners and flat surfaces. Using theory, simulations and experiments, the structure and flow properties of cube-shaped particles in suspension over a range of volume fractions is studied to understand the effect of shape on fluid structure and rheology. At very low volume fractions, the sharp edges and corners of cubes are found to profoundly alter the velocity field around the cube. The stresslet-strain relationship for a cube is anisotropic and depends on the orientation of the cube with respect to the velocity flow field. The effective viscosity of the suspension in a simple shear flow is obtained by computing the orientationaly averaged stresslet acting on cubes. These calculations yield a universal intrinsic viscosity, [[eta]] = 3.1 for sharp cubes, which is higher than the corresponding value for spheres [[eta]] = 5/2. Using the 2D velocity flow profile around sharp corners we further find that the pressure becomes singular near the edges of the cube, which results in the increased value of stress and hence the higher viscosity when compared with spherical particles. In the presence of an external torque acting on each cube, the orientation distribution is no longer isotropic. This can be achieved by using magnetic cubes in magnetic field. The general expression for the stress in a suspension of mag- netic cubes subjected to linear velocity field in presence of an external magnetic field is calculated. We find that the intrinsic viscosity for the weakly Brownian suspension in a simple shear flow can be varied between [[eta]] = 3.25 to [[eta]] = 5.5 by changing the strength and the direction of the applied magnetic field. At low to moderate volume fractions, Brownian dynamics simulations were carried out to study the structure and flow behavior of suspensions. Simulations were performed over a wide range of volume fractions and Pe to study its rheological properties. Our equilibrium results show that cubic particles behave like spheres interacting with a soft repulsion potential function for volume fractions less than 0.25. This soft repulsion potential captures the orientationally averaged excluded volume of the cubes and produces identical probability distributions as that of for cubes at very low volume fractions. For higher volume fractions, cubic particles starts to lose their orientational freedom resulting in the deviation of equilibrium properties from that of soft spheres. We also found that suspension of cubic particles when subjected to simple shear will produce higher viscosity when compared with spherical particles in suspensions with equivalent volume. We show that the suspension rheology in this regime can be discussed in terms of ordering and collisions among hard cubic particles. In order to gain insights from experiments, cubic particles of varying sizes (10nm to 5 micron sized cubes) and chemistries (PbT e, Fe3 O4 and MnCO3) were synthesized. Polymer brushes were also attached on the surfaces of PbT e and Fe3 O4 nanocubes to characterize the effect of particle surface chemistry on flow behavior. MnCO3 spherical particles of similar sizes as that of MnCO3 cubes were also synthesized and their suspension behavior studied to empirically characterize the effects of shape. A key result from this study is that irrespective of the cube size, size distribution, and surface chemistry, the intrinsic viscosity([[eta]]) for cube-shaped particles is [[eta]] = 3.1 ± 0.2 which agrees well with the value estimated from theory.

Author: Ulrich Bröckel
Publisher: John Wiley & Sons
ISBN: 3527654763
Category : Technology & Engineering
Languages : en
Pages : 367

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Book Description
Covering the whole value chain - from product requirements and properties via process technologies and equipment to real-world applications - this reference represents a comprehensive overview of the topic. The editors and majority of the authors are members of the European Federation of Chemical Engineering, with backgrounds from academia as well as industry. Therefore, this multifaceted area is highlighted from different angles: essential physico-chemical background, latest measurement and prediction techniques, and numerous applications from cosmetic up to food industry. Recommended reading for process, pharma and chemical engineers, chemists in industry, and those working in the pharmaceutical, food, cosmetics, dyes and pigments industries.

Author: Anand Kumar Atmuri
Publisher:
ISBN:
Category : Colloids
Languages : en
Pages : 107

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Book Description
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.

Author: Norman J. Wagner
Publisher: Cambridge University Press
ISBN: 1108503624
Category : Technology & Engineering
Languages : en
Pages : 438

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Book Description
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.

Author:
Publisher:
ISBN: 9780542458071
Category : Anisotropy
Languages : en
Pages :

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Book Description
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.