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Letteratura scientifica selezionata sul tema "Colloidal pastes"

Autore: Grafiati

Pubblicato: 25 gennaio 2025

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Articoli di riviste sul tema "Colloidal pastes"

Madeline, J. B., M. Meireles, J. Persello, C. Martin, R. Botet, R. Schweins e B. Cabane. "From colloidal dispersions to colloidal pastes through solid-liquid separation processes". Pure and Applied Chemistry 77, n. 8 (1 gennaio 2005): 1369–94. http://dx.doi.org/10.1351/pac200577081369.

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Solid-liquid separation is an operation that starts with a dispersion of solid particles in a liquid and removes some of the liquid from the particles, producing a concentrated solid paste and a clean liquid phase. It is similar to thermodynamic processes where pressure is applied to a system in order to reduce its volume. In dispersions, the resistance to this osmotic compression depends on interactions between the dispersed particles.The first part of this work deals with dispersions of repelling particles, which are either silica nanoparticles or synthetic clay platelets, dispersed in aqueous solutions. In these conditions, each particle is surrounded by an ionic layer, which repels other ionic layers. This results in a structure with strong short-range order. At high particle volume fractions, the overlap of ionic layers generates large osmotic pressures; these pressures may be calculated, through the cell model, as the cost of reducing the volume of each cell. The variation of osmotic pressure with volume fraction is the equation of state of the dispersion. The second part of this work deals with dispersions of aggregated particles, which are silica nanoparticles, dispersed in water and flocculated by multivalent cations. This produces large bushy aggregates, with fractal structures that are maintained through interparticle surface-surface bonds. As the paste is submitted to osmotic pressures, small relative displacements of the aggregated particles lead to structural collapse. The final structure is made of a dense skeleton immersed in a nearly homogeneous matrix of aggregated particles. The variation of osmotic resistance with volume fraction is the compression law of the paste; it may be calculated through a numerical model that takes into account the noncentral interparticle forces. According to this model, the response of aggregated pastes to applied stress may be controlled through the manipulation of interparticle adhesion.

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Poon, Wilson C. K. "Colloidal Glasses". MRS Bulletin 29, n. 2 (febbraio 2004): 96–99. http://dx.doi.org/10.1557/mrs2004.35.

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AbstractThis article reviews recent advances in understanding amorphous glassy states in dense colloidal suspensions with or without short-range interparticle attractions. Experiments, theory, and simulation show that two kinds of glassy states are possible, dominated respectively by repulsion and attraction. Under suitable conditions, a small change in the interparticle potential can lead to a transition between these two kinds of colloidal glasses that entails sharp changes in material properties such as the shear modulus. This may provide novel routes for fine-tuning the properties of industrial pastes and slurries.

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Dewitte, Charlotte, Alexandra Bertron, Mejdi Neji, Laurie Lacarrière e Alexandre Dauzères. "Chemical and Microstructural Properties of Designed Cohesive M-S-H Pastes". Materials 15, n. 2 (12 gennaio 2022): 547. http://dx.doi.org/10.3390/ma15020547.

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Concretes can be exposed to a magnesium attack in several environments leading to the formation of magnesium silicate hydrates (M-S-H) and brucite (MH). The formation of M-S-H is likely to alter the properties of the cement matrix because it is linked to the decalcification of C-S-H. However, relatively few data on M-S-H exist in the literature. In order to characterize, physically and mechanically, the M-S-H phase, pure M-S-H cohesive pastes are needed. This work studies the formation of cohesive M-S-H pastes made with MgO-to-SiO2 atomic ratios of 0.78, 1 and 1.3, from two types of silica (silica fume or colloidal silica) and under 20 °C and 50 °C thermal curing. X-ray diffraction and thermogravimetric analyses confirmed that the consumption of brucite and the formation of M-S-H were quicker with a 50 °C curing. Energy-dispersive X-ray spectroscopy and microtomography showed that colloidal silica enabled a better distribution of the particles than silica fume. Microstructural characterizations were conducted under the protocol with colloidal silica and 50 °C thermal curing. Porosity investigations allowed to describe the M-S-H pastes as highly porous materials with a low content of micropores in comparison with mesopores. The type of mixing influenced the mesopore size distribution.

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Athira, K., e T. Shanmugapriya. "Investigation on effect of colloidal nano-silica on the strength and durability characteristics of red mud blended Portland cement paste through tortuosity". Materiales de Construcción 72, n. 347 (5 settembre 2022): e293. http://dx.doi.org/10.3989/mc.2022.01922.

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A novel binder system for cement-based composites depending upon the strength and durability characteristics is introduced in this study. The possibility of calcined red mud cement pastes with and without colloidal nano-silica (CNS) over Ordinary Portland Cement paste (OPC) at three W/B ratios (0.3, 0.4, 0.5) is evaluated. The optimum percentage of cement replacement by red mud (15%) was selected from compressive strength values of different cement replacements (5%, 10%, 15%, and 20%). Colloidal nano-silica (CNS) was added at 0.5%, 1%, 1.5%, and 2 % to the selected red mud cement paste. Water absorption, sorptivity, resistance to sulfate attack, and resistance to acid attack tests were conducted for optimum red mud cement paste with and without CNS. The experimental results are explained based on tortuosity with empirical formulas and mathematical models of pore network distribution. The tortuosity is directly proportional to the inter-connectivity of the pores. The mixes with 15% calcined red mud and 1.5% CNS replacement performed better strength and durability at all W/B ratios. The mix (R15NS1.5) with minimum tortuosity value results in the higher overall performance of the paste. The mixes with a 0.3 W/B ratio give high-performance cement paste compared to higher W/B ratios.

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Kunz, Simon, Maria Pawlik, Wolfgang Schärtl e Sebastian Seiffert. "Polymer- vs. colloidal-type viscoelastic mechanics of microgel pastes". Colloid and Polymer Science 296, n. 8 (24 giugno 2018): 1341–52. http://dx.doi.org/10.1007/s00396-018-4352-5.

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Yune, Jeremy H., Inna Karatchevtseva, Peter J. Evans, Klaudia Wagner, Matthew J. Griffith, David Officer e Gerry Triani. "A versatile binder-free TiO2 paste for dye-sensitized solar cells". RSC Advances 5, n. 37 (2015): 29513–23. http://dx.doi.org/10.1039/c4ra14247k.

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In this study, binder-free TiO₂ colloidal pastes have been prepared using a variety of heterocyclic bases with diverse characteristics to produce robust photoanodes for dye-sensitized solar cells (DSSC) from a single cast film thickness of 5 micron.

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Zemánek, David, e Lenka Nevřivová. "Development and Testing of Castables with Low Content of Calcium Oxide". Materials 15, n. 17 (26 agosto 2022): 5918. http://dx.doi.org/10.3390/ma15175918.

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Colloidal silica is used in many kinds of industry. It is an aqueous dispersion of SiO2 nanoparticles. SiO2 colloidal solutions are commercially available in different concentrations, with different particle sizes and are stabilized with different ions. Colloidal SiO2 was used in this study as a cement replacement in refractory castable. The present study, in its first stage, offers an assessment of five different SiO2 colloidal solutions. The particle size of the solutions was 15 nm, the particle concentration was 30% and 40% and the colloidal solutions were stabilized with Na+, OH− and Cl− ions. The effect of the colloidal solutions on selected characteristics of the refractory pastes and on their mineralogical composition after firing at 1000 °C and 1500 °C was described. The most suitable SiO2 colloidal solution from the first stage was subsequently used for the refractory castable test samples’ preparation in the second stage. Refractory castables, unlike paste, contain a coarse aggregate (grog) up to a grain size of 6 mm. Four types of coarse refractory grog were evaluated. Their effect on selected characteristics of the refractory castable and on its mineralogical composition after firing at 1000 °C and 1500 °C was described. The selected characteristics, within the scope of this study, include bulk density, apparent porosity, cold modulus of rupture and linear changes after firing. Finally, the study describes the effect of the sol particle concentration and the effect of pore size distribution on corrosion resistance and on the internal structure of the material. Mineral and chemical compositions and microstructures of both the raw materials and designed aggregates were thoroughly investigated by the means of X-ray fluorescence spectroscopy, powder X-ray diffraction and scanning electron microscopy. An analysis of the transition zone between corrosive media (K2CO3) and tested castables showed better corrosion resistance for a sol-gel castable than an ultra-low cement castable.

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Avery, Michael P., Susanne Klein, Robert Richardson, Paul Bartlett, Guy Adams, Fraser Dickin e Steve Simske. "The Rheology of Dense Colloidal Pastes Used in 3D-Printing". NIP & Digital Fabrication Conference 30, n. 1 (1 gennaio 2014): 140–45. http://dx.doi.org/10.2352/issn.2169-4451.2014.30.1.art00036_1.

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Sikora, Pawel, Krzysztof Cendrowski, Mohamed Abd Elrahman, Sang-Yeop Chung, Ewa Mijowska e Dietmar Stephan. "The effects of seawater on the hydration, microstructure and strength development of Portland cement pastes incorporating colloidal silica". Applied Nanoscience 10, n. 8 (4 marzo 2019): 2627–38. http://dx.doi.org/10.1007/s13204-019-00993-8.

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AbstractThis contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial effect of seawater was reflected in an improvement in compressive strength for up to 14 days of hydration, while in the 28 days compressive strength values were comparable to that of cement pastes produced with demineralized water. The combination of seawater and NS significantly promotes cement hydration kinetics due to a synergistic effect, resulting in higher calcium hydroxide (CH) production. NS can thus react with the available CH through the pozzolanic reaction and produce more calcium silicate hydrate (C-S-H) gel. A noticeable improvement of strength development, as the result of the synergistic effect of NS and seawater, was therefore observed. In addition, mercury intrusion porosimetry (MIP) tests confirmed significant improvements in microstructure when NS and seawater were combined, resulting in the production of a more compact and dense hardened paste structure. The optimal amount of NS to be mixed with seawater, was found to be 3 wt% of cement.

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Hou, Lixia, Cuicui Li e Xuede Wang. "The Colloidal and Oxidative Stability of the Sesame Pastes during Storage". Journal of Oleo Science 69, n. 3 (2020): 191–97. http://dx.doi.org/10.5650/jos.ess19214.

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Più fonti

Tesi sul tema "Colloidal pastes"

O'Keefe, Samantha Jane. "A study of the rheological properties of polymer modified cement pastes". Thesis, University of the West of England, Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293326.

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The work outlined in this thesis describes how rheological techniques can be used to gain insight into the behaviour of complex hydrating systems. These techniques are currently used to elucidate interparticle interactions of concentrated colloidal dispersions. Those used here were stress relaxation, pulse shearometry and oscillation. These enabled parameters such as the dynamic moduli, relaxation moduli, relaxation spectrum and limiting moduli to be obtained. These all give a measure of the strength of interaction of the colloidal system under different conditions, without reducing these interactions by inducing flow. Calorimetric data was obtained for a hydrating cement paste. The particle and floc size of this cement was also measured. The data were found to be in accord with one another, and with current theories of the hydration processes of cement. In combination with the rheological parameters measured this enabled the extent and strength of attraction between the particles of a cement paste to be determined, as a function of the age of the paste. The adsorption characteristics of surfactant on cement were measured, as was the effect of surfactant on the particle and floc size of hydrating cement. Coupled with a measure of the rheological parameters of the cement-surfactant system, an understanding of the effect of surfactant on a hydrating cement paste was obtained. Similarly the effect of the addition of styrene-butadiene polymer latex particles, with and without excess added surfactant, was able to be determined. This information was obtained for hydrating cement pastes, both in the presence and absence of added polymer, at both ambient and non-ambient temperatures.

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Auxois, Mathilde. "Identification et étude de descripteurs du malaxage d’une pâte de boehmite pour la conception de nouveaux solides". Electronic Thesis or Diss., Lyon, École normale supérieure, 2024. http://www.theses.fr/2024ENSL0066.

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Le contrôle des propriétés mécaniques et texturales des supports de catalyseurs hétérogènes est essentiel pour la conception de matériaux catalytiques innovants et efficaces. En particulier, la microstructure poreuse du support affecte fortement le transport de masse et la résistance mécanique. Industriellement, la fabrication de supports en alumine peut être mise en œuvre par un procédé de malaxage-extrusion, qui vise à passer d’une poudre de précurseur aluminique (la boehmite) à des objets micrométriques (taille finale du support). Ce procédé permet également d'optimiser les propriétés mécaniques et texturales du support en jouant sur les conditions opératoires de chacune des opérations unitaires. Le but de cette thèse est d’abord de caractériser l’influence du malaxage sur les propriétés des pâtes de boehmite. En particulier, les effets de la vitesse et de la durée de malaxage, ainsi que celui de la composition des pâtes, sont quantifiés sur leurs propriétés mécaniques et texturales des pâtes de boehmite. Cette étude expérimentale, réalisée sur un malaxeur pilote, a permis d’identifier deux paramètres de contrôle des propriétés analysées : le pH des pâtes et la déformation cumulée, équivalente au nombre de tours appliqués pendant le malaxage. Ensuite, une modélisation des pâtes de boehmite a été élaborée grâce à une méthode par éléments discrets, afin de représenter leur microstructure (difficile à caractériser expérimentalement) et de simuler leur comportement mécanique. Dans ce modèle, les pâtes sont représentées comme des empilements de sphères dures polydisperses, et les propriétés mécaniques dépendent de paramètres numériques élastiques et visqueux. Ces derniers, tout comme la taille des sphères, ont été ajustés itérativement pour reproduire au mieux les caractérisations expérimentales
Controlling the mechanical and textural properties of heterogeneous catalyst supports is essential for the design of innovative and efficient catalytic materials. In particular, the porous microstructure of the support strongly affects mass transport and mechanical strength. Industrially, alumina supports are manufactured using a knead-extrusion process, which aims to go from an alumina precursor powder (boehmite) to micrometric objects (the final size of the support). This process also enables the mechanical and textural properties of the substrate to be optimized by adjusting the operating conditions for each of the unit operations. The aim of this thesis is to characterize the influence of mixing on the properties of boehmite pastes. In particular, the effects of mixing speed and duration, as well as paste composition, are quantified on the mechanical and textural properties of boehmite pastes. This experimental study, carried out on a pilot mixer, identified two parameters controlling the properties analyzed: paste pH and cumulative deformation, equivalent to the number of revolutions applied during kneading. Then, a discrete-element model of boehmite pastes was developed to represent their microstructure (difficult to characterize experimentally) and simulate their mechanical behavior. In this model, pastes are represented as stacks of polydisperse hard spheres, and mechanical properties depend on numerical elastic and viscous parameters. The latter, like the size of the spheres, have been iteratively adjusted to reproduce experimental characterizations as closely as possible

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Viasnoff, Virgile. "Influence d'un cisaillement oscillant sur la dynamique de vieillissement microscopique d'un verre colloidal". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2003. http://pastel.archives-ouvertes.fr/pastel-00000272.

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Ce travail expérimental cherche à mieux caractériser les effets du cisaillement sur le vieillissement d'un verre colloidal au niveau microscopique. La dynamique des réarrangements d'un tel système est étudiée au moyen d'une technique de diffusion multiple de la lumière (MSDWS) développée au cours de cette thèse. Nous montrons que la cessation d'un cisaillement de forte amplitude est, au niveau microscopique, l'équivalent pour ces systèmes d'une trempe thermique pour d'autres systèmes vitreux. Notre système est en effet rajeuni par un fort cisaillement puis présente un comportement de vieillissent classique à la cessation de celui-ci. De surcroît, nous montrons qu'un cisaillement de faible amplitude permet au système de vieillir plus vite. Nous appelons ce comportement le survieillissement. Ces deux effets antagonistes (rajeunissement et survieillissement) sont aussi observés sur des polymères vitreux soumis à des marches de température. Nous montrons enfin que le modèle SGR fournit une description unifiée de ces comportements similaires pour différents types de perturbation. Ceux-ci mettent en lumière l'élargissement de la distribution de temps de relaxation au sein de ce type de matériaux soumis à des perturbations extérieures.

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Ramiandrisoa, Donatien. "Adsorption de protéines sur des colloïdes et agrégation induite". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://pastel.archives-ouvertes.fr/pastel-00997448.

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Les colloïdes sont utilisés dans de nombreuses applications médicales tels les agents de contraste en IRM ou l'immuno-agglutination magnétique dans le diagnostic. Pour en améliorer leurs performances, l'interaction entre les particules et les milieux biologiques - en particulier les protéines - a été étudiée depuis plus de 150 ans ; mais ce phénomène n'est toujours pas correctement décrit. La première partie de cette thèse est dédiée à une des applications des colloïdes : la détection de protéines cible. Basée sur l'orientation d'agrégats magnétiques anisotropes, une nouvelle méthode a été mise au point, permettant de mesurer un signal d'agrégation uniquement proportionnel à la quantité de protéines à doser, la limite de détection est donc abaissée. Cette technique a été validée sur un système réel : la protéine C-réactive. La seconde partie de cette thèse est consacrée à l'adsorption des protéines sur les colloïdes. Le premier objectif a été la mise au point d'un protocole de mesure capable de fournir des données fiables ; l'adsorption a ainsi pu être caractérisée sur un système modèle, l'albumine de sérum bovin sur la silice. Les mesures obtenues ont ainsi permis de lever certains paradoxes et de proposer un nouveau modèle d'adsorption. Enfin, ces connaissances ont permis de comprendre comment des protéines, en s'adsorbant sur deux particules, agrègent les colloïdes. En quantité suffisante, elles peuvent également les protéger de l'agrégation, ouvrant la voie à une nouvelle méthode de stabilisation des particules.

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Wyart, Matthieu. "Sur la rigidité des solides amorphes. Fluctuation des prix, conventions et microstructure des marchés financiers". Phd thesis, Ecole Polytechnique X, 2005. http://pastel.archives-ouvertes.fr/pastel-00001919.

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Sur la Rigidité des Solides Amorphes: On comprend mal les propriétés microscopiques des solides amorphes, comme le transport, la propagation des forces ou la nature de leur rigidité mécanique. Ces questions semblent liées à la présence d'un excès de modes vibratoires à basse fréquence, le ''pic boson". On explique la nature de ces modes dans les systèmes répulsifs à courte portée. On argumente que cette description s'applique aussi aux milieux granulaires, à la silice, et aux verres colloïdaux. Fluctuations des prix, Conventions et Microstructure des marches Financiers: Les fluctuations des cours de la bourse ont des propriétés étonnantes. La volatilité (l'amplitude de ces fluctuations) est environ un ordre de grandeur plus grand que les prédictions de la théorie des marches efficients, et est corrèlee sur des échelles de temps très longs. Les agents sur réagissent aux informations. On montre que ces propriétés apparaissent lorsque les agents agissent en fonction de leur expérience et du passé du marché. On étudie aussi la microstructure des marchés, qui régulent les échanges aux temps courts. On explique pourquoi le prix est diffusif bien que les ordres marchés (les chocs subis par les prix) soient très corrélés. On évalue la fourchette des prix par des arguments de symétrie.

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Rondon, Loic. "Effondrement granulaire : couplages fluide-grains". Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10209/document.

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Nous étudions expérimentalement l'effondrement d'une colonne granulaire dans un liquide visqueux. Contrairement au cas sec, la morphologie des dépôts n'est principalement plus contrôlée par le rapport d'aspect initial du tas mais par la fraction volumique initiale de la masse granulaire. Deux régimes différents sont identifiés selon l'empilement initial. L'empilement lâche donne lieu à des dépôts minces et longs et la dynamique est rapide. Une surpression du liquide est mesurée sous de la colonne. Pour l'empilement dense, l'étalement final est deux fois moindre, le mouvement est lent et une dépression interstitielle est mesurée. Ces observations suggèrent que la dynamique de l'effondrement granulaire dans un fluide est fortement affectée par le comportement de la dilatance du milieu granulaire.Nous développons ensuite un modèle théorique basé sur des équations diphasiques moyennées dans l’épaisseur prenant en compte les mécanismes de dilatance. L’étude dimensionnelle de notre modèle permet de montrer que l’effondrement d’une colonne est contrôlé par trois paramètres sans dimension : le rapport d’aspect de la colonne, la fraction volumique initiale, et le nombre de grains dans l’épaisseur. On montre également que le temps caractéristique met en compétition le frottement visqueux et la gravité.De ce modèle, nous développons un algorithme de résolution lagrangien. Cette approche, grossière mais robuste, permet d’implanter s sans trop de difficulté. Le code est validé sur des configurations simples sur plan incliné avant de simuler l’effondrement de colonnes granulaires immergées dans la même gamme de paramètres que nos expériences
Nous étudions expérimentalement l'effondrement d'une colonne granulaire dans un liquide visqueux. Contrairement au cas sec, la morphologie des dépôts n'est principalement plus contrôlée par le rapport d'aspect initial du tas mais par la fraction volumique initiale de la masse granulaire. Deux régimes différents sont identifiés selon l'empilement initial. L'empilement lâche donne lieu à des dépôts minces et longs et la dynamique est rapide. Une surpression du liquide est mesurée sous de la colonne. Pour l'empilement dense, l'étalement final est deux fois moindre, le mouvement est lent et une dépression interstitielle est mesurée. Ces observations suggèrent que la dynamique de l'effondrement granulaire dans un fluide est fortement affectée par le comportement de la dilatance du milieu granulaire.Nous développons ensuite un modèle théorique basé sur des équations diphasiques moyennées dans l’épaisseur prenant en compte les mécanismes de dilatance. L’étude dimensionnelle de notre modèle permet de montrer que l’effondrement d’une colonne est contrôlé par trois paramètres sans dimension : le rapport d’aspect de la colonne, la fraction volumique initiale, et le nombre de grains dans l’épaisseur. On montre également que le temps caractéristique met en compétition le frottement visqueux et la gravité.De ce modèle, nous développons un algorithme de résolution lagrangien. Cette approche, grossière mais robuste, permet d’implanter s sans trop de difficulté. Le code est validé sur des configurations simples sur plan incliné avant de simuler l’effondrement de colonnes granulaires immergées dans la même gamme de paramètres que nos expériences

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Kim, Jongwook. "Elaboration, Propriétés optiques et applications de suspensions colloïdales de nanobâtonnets de LaPO4". Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00948255.

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Le contrôle de la synthèse et de l'assemblage de nanobâtonnets est un enjeu important pour l'étude de dispositifs présentant des propriétés physiques anisotropes, notamment dans le domaine de l'optique ou du magnétisme. L'objectif de cette thèse était d'étudier un système particulier, le phosphate de lanthane (LaPO4), dont on a montré qu'il peut être fabriqué sous forme de nanobâtonnets en solution jusqu'à des concentrations remarquablement élevées. Comme les cristaux liquides organiques, ces bâtonnets s'organisent spontanément en solution et leur orientation peut être contrôlée en appliquant un champ électrique. Par ailleurs, il est possible de déposer ces bâtonnets sur des substrats de verre et les couches minces obtenues présentent une remarquable biréfringence. Enfin, le dopage des bâtonnets avec des ions europium les rend luminescents, avec un signal qui dépend de l'orientation du bâtonnet. Une application originale est l'utilisation de ces nanobâtonnets comme capteurs du débit d'un liquide.

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Seth, Jyoti Ravishanker 1981. "On the rheology of dense pastes of soft particles". 2008. http://hdl.handle.net/2152/18287.

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Many concentrated paste-like materials are composed of deformable particles randomly packed into a dense suspension. Examples of the constituent soft particles include polyelectrolyte microgels, emulsion droplets, polymer coated colloids, and star polymers. These materials share in common many properties such as yield stress, shear thinning, non-zero normal stresses, wall-slip, shear-banding, memory and aging (similar to that in structural, spin and polymer glasses). Their unique properties make soft particle pastes (SPPs) scientifically interesting and extremely useful in industrial applications (as rheological modifiers). In this dissertation particle simulations, theoretical models and experiments are used to study the flow dynamics and rheological behavior of SPPs near confining surfaces - wall-slip and shear flow, and in the bulk - elasticity at small stresses and the non-linear shear rheology. In the study of slip near smooth surfaces, rheological measurements are shown that identify the influence of the chemical nature of the shearing boundary on slip at the shearing boundary. A modified elastohydrodynamic model is presented that incorporates attractive and repulsive short range interactions between the paste particles and captures the corresponding suppression and promotion of slip at the wall. Further, fluorescence microscopy and particle tracking velocimetry is used to visualize slip and flow of pastes near smooth boundaries and study the sensitivity of the bulk flow profile to the nature of the shearing surface. In the study of elastic properties of pastes, SPPs are modeled as three-dimensional systems of randomly packed elastic spheres. Simulations are performed wherein the packing is subject to small deformations to compute the high- and low-frequency shear moduli. The simulation results are compared with the data from experiments on microgel pastes. This model is extended to study paste dynamics under simple shear with added pairwise elastohydrodynamic lubrication interactions between the densely packed soft particles. The shear and normal stress differences generated during simple hear flow are calculated that compare well with the experimental data. In addition, the pair distribution function of the initial isotropic configuration, the elastically deformed and the steady sheared configurations is investigated. A semi-empirical analysis of the microstructure and its evolution due to shearing is presented.
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Capitoli di libri sul tema "Colloidal pastes"

Jennings, H. "The Colloid/Nanogranular Nature of Cement Paste and Properties". In Nanotechnology in Construction 3, 27–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-00980-8_3.

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Nan, Bo, Francisco J. Galindo-Rosales e José M. Ferreira. "Large Amplitude Oscillatory Shear (LAOS) Experiments on Colloidal Ceramic Paste Formulated for Robocasting Applications". In Springer Proceedings in Materials, 139–43. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-27701-7_29.

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Ortiz-Caballero, Z. K., A. Covarrubias-Muñoz, M. E. Montero-Cabrera e M. Rentería-Villalobos. "Distribution of Uranium and Thorium Isotopes in Colloidal and Dissolved Fraction of Water from San Marcos Dam, Chihuahua, Mexico". In Uranium - Past and Future Challenges, 635–42. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-11059-2_72.

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Steeneken, P. A. M., e A. J. J. Woodman. "Stringiness of Aqueous Starch Pastes". In Food Colloids and Polymers, 147–56. Elsevier, 2005. http://dx.doi.org/10.1533/9781845698270.147.

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"Ceramic Pastes and Ceramics". In Encyclopedia of Colloid and Interface Science, 83. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-20665-8_100016.

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BARSHAD, ISAAC. "X-RAY ANALYSIS OF SOIL COLLOIDS BY A MODIFIED SALTED PASTE METHOD". In Clays and Clay Minerals, 350–64. Elsevier, 2013. http://dx.doi.org/10.1016/b978-0-08-009235-5.50029-2.

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Rovira, Miguel, e Christopher Giordano. "Fluid Therapy and Homeostasis". In Advanced Anesthesia Review, a cura di Alaa Abd-Elsayed, 432—C165.S6. Oxford University PressNew York, 2023. http://dx.doi.org/10.1093/med/9780197584521.003.0164.

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Abstract This chapter covers the basics of fluid homeostasis and fluids that are employed to maintain homeostasis in the perioperative setting. It begins with a basic review of human physiology in relation to fluids, age, and gender. Historical background is also provided on the 4–2–1 rule, the method of choice for determining fluid rate administration that has been passed on from generation to generation of physicians. Then it transitions into how the homeostasis is maintained in the perioperative setting. Particular emphasis is given to the most commonly administered fluids, such as PlasmaLyte, lactated Ringer’s, normal saline (crystalloids), and albumin (colloids). The reader will learn what these fluids are made of, what makes them different, as well as how and why certain fluids should be given and when they could be potentially dangerous.

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"Fig. 31 Internals of colloid mill. (From Ref. 29.) colloid mills, typically equipped with rotor diameters of 10-30 cm, provide flow rates in the area of 4000-6000 L/hr, depending upon the viscosity. The key operating requirements of colloid mills are to feed the mill with a well-blended premix and to set the gap at the correct and reproducible setting. There is of-ten some difficulty with setting the gap at exactly the required distance, since the cali-bration of the gap can only be done at the manufacturer. This is less of a problem if the mill is well made and the product is not abrasive. If abrasive wear attacks the ro-tor or stator, the gap may become larger than the setting on the machine indicates. Colloid mills are generally used as "polishing" machines for emulsions or sus-pensions. That is, after the product has been totally and uniformly blended, the batch is passed through the colloid mill one or two times to further reduce the droplet or particle size. Whether or not multiple recycling passes are required depends on prod-uct requirements. Generally speaking, the colloid mill produces emulsions and suspen-sions with particle-size distributions smaller than the particle sizes obtainable using fixed gap rotor/stator mixers. They do represent an extra step in the process, and their use is suggested only when it is found that this added ability to disperse is necessary to produce a fine enough particle- or droplet-size product to enhance a product's stabil-ity. 3. Piston Homogenizers The most powerful device for producing emulsions and suspensions is the piston ho-mogenizer or high-pressure homogenizer. This device uses a high-power positive dis-placement piston-type pump to produce pressures of 3000-10,000 psig and then force". In Pharmaceutical Dosage Forms, 361–63. CRC Press, 1998. http://dx.doi.org/10.1201/9781420000955-52.

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"colloid mills, piston homogenizers, rotor/stator mixers, Microfluidizer™ (a registered trademark of Microfluidics International Corp.) technologies, ultrasonic mixers, and hybrid devices. Each uses a unique processing technique to shear a mixture or com-bine the flows of materials in order to form an emulsion or suspensions. Most of the time these devices are not used in a truly continuous process. Rather, after the compo-nents of a dispersed delivery system are combined and blended in a batch vessel, the components in the mixture are passed through the device, and the shearing and mixing that take place inside the device affect particle size reduction, dispersion, and emulsi-fication. 1. Rotor/Stator Mixer Disperser Emulsifiers "All mixers pump and all pumps mix." This is reflected in the earlier-shown power equation, Eq. (3). A type of in-line device that is very similar to a rotor/stator batch mixer is the rotor/stator continuous mixer disperser emulsifier. Indeed, most of the designs of this type of in-line high-shear device are essentially identical to the batch equipment designs of a given manufacturer. Since rotor/stator batch mixers are acting as submerged pumps, a design can be made that places the rotor/stator in a pump hous-ing and allows for product to be pumped through itself (Fig. 27). During the time the product is inside the rotor/stator mixing pump, the droplets and particles are subjected to a wide variety of high shear rates. All pumps of any kind impart some level of shear to the product that passes through the pump. Rotor/stator mixing pumps are designed with fine tolerance rotor/stator gaps that promote the high shear rates and high amounts of shear per pass through. Shear rates in a rotor/stator in-line mixer are equal to those in rotor/stator batch mixers. The maximum shear rates occur in the gap between the high-speed rotating Fig. 27 Rotor/stator in-line mixer disperser emulsifier. (From Ref. 31.)". In Pharmaceutical Dosage Forms, 356. CRC Press, 1998. http://dx.doi.org/10.1201/9781420000955-49.

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Atti di convegni sul tema "Colloidal pastes"

Davidson, Drew A., e Gary L. Lehmann. "Squeeze Flow Study of a Colloidal Paste". In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73394.

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Crucial to the development and characterization of thermal interface materials (TIMs) is an understanding of the squeeze flow process that is commonly used to form thin bond layers in micro-electronic assemblies. A single model TIM, a dense, fairly monomodal suspension of submicron alumina particles suspended in a silicone-based resin, is first characterized as a Bingham fluid using a parallel disk rotational viscometer. Next, the model TIM is squeezed from ∼1 mm initial thickness to ∼.01 mm limiting thickness under nominally constant applied load (68 to 345 kPa) between 20 mm diameter aluminum plates in an axial compression test apparatus (the type commonly used for materials testing). The test plates are flat (∼10 μm flatness deviation over the plate) and smooth (Ra ∼ 20 nm), and are fixed in the test column with epoxy for optimum parallelism. Bond layer thickness is estimated using the LVDT built into the compression tester. The thickness measurement resolution is limited by LVDT noise of 10–20 microns. Squeezing forces are well above the ∼.02 N noise level of the 100 N load cell. Of the test system compliance, inertia, and friction, only the compliance is significant to our testing, and is corrected for. Squeeze flow tests of Newtonian standards are used to qualify the test process. In the case of the model paste, Bingham fluid model parameters from rotational viscometry are used in a lubrication model of squeeze flow that shows good agreement with the measured gap vs. time behavior during squeezing. Improved agreement is obtained by including plate flatness deviation and time-dependent force in the lubrication model. Parallel disk viscometry and squeeze flow testing of the base resin of the model TIM shows Newtonian behavior.

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Ballesta, Pierre. "Temporal heterogeneity of the slow dynamics of a colloidal paste". In SLOW DYNAMICS IN COMPLEX SYSTEMS: 3rd International Symposium on Slow Dynamics in Complex Systems. AIP, 2004. http://dx.doi.org/10.1063/1.1764063.

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Botet, R., B. Cabane, M. Clifton, M. Meireles, R. Seto, Michio Tokuyama, Irwin Oppenheim e Hideya Nishiyama. "How a Colloidal Paste Flows—Scaling Behaviors in Dispersions of Aggregated Particles under Mechanical Stress—". In COMPLEX SYSTEMS: 5th International Workshop on Complex Systems. AIP, 2008. http://dx.doi.org/10.1063/1.2897806.

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Vladu, Alina, Emilia Visileanu, Alina Popescu e Roxana Rodica Constantinescu. "Antimicrobial treatments of undergarments designed for the combat-protective clothing of soldiers". In AHFE 2023 Hawaii Edition. AHFE International, 2023. http://dx.doi.org/10.54941/ahfe1004210.

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Military forces around the world must be equipped with combat-protective clothing made from the best technical textiles available that must provide sufficient protection, increased comfort, and even antimicrobial protection, especially for underwear pieces. Antibacterial treatments for textile materials include the use of various substances such as chitosan, silver, collagen and so on. Chitosan is a polysaccharide that promotes changes in the permeability properties of the membrane wall causing internal osmotic imbalances and consequently inhibits the growth of microorganisms. Silver can also damage the bacterial RNA and DNA, eventually leading to the bacteria`s death. Moreover, collagen, a fibrous natural protein, has an intrinsic ability to fight infection and contributes to keeping the infection site sterile.This paper focuses on the functionalization of four variants of textile materials with different compositions to increase their antibacterial properties. The variants were treated through two different technologies: exhaustion (30 min at 40°C, 500 rpm) and padding (3 consecutive passes). V1-V4 were functionalized with colloidal silver and V1-V3 with a mixture of collagen hydrolysate and colloidal silver through exhaustion. Variants V1-V3 were also treated through the padding technique using 0.5% chitosan, 1% collagen hydrolysate and a mixture of chitosan and colloidal silver. Untreated textile variants were evaluated regarding their physical-mechanical characteristics. Moreover, the functionalized variants were characterised according to their pH, loading degree with active substances (%), wettability by drop test and contact angle methods, thermal resistance (m2K/W) and vapour resistance (m2Pa/W) according to ISO 11092. Treated textile samples were also investigated relating to their antimicrobial resistance using two methods according to ISO 20743/2013 and SR EN ISO 20645/2005. The evaluation of antibacterial resistance using the standards SR EN ISO 20645/2005 and SR EN ISO 20645/2005 demonstrated the effectiveness of treatments with active substances for approx. 95% of the tested variants.

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Saab, Joseph, Ramy Abou Naccoul, Juliette Stephan, Rosette Ouaini, Jacques Jose e Naim Ouaini. "Dynamic Fluid Saturation Method for Hydrocarbons Thermodynamics’ Properties Determination". In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37114.

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Low solubility compounds suffer from lack of data, leading to an impoverishment in thermodynamic parameters such as Gibbs free energy (ΔG), enthalpy of dissolution (ΔH), entropy (ΔS), infinite dilution coefficient (γ∞) and isobaric heat capacity (Cp) of utmost practical importance for industrial optimization processes. Dynamic fluid method is a novel technique for low solubility (expressed as molar fraction χ) determination based on the saturation of a specific heated fluid passing through a saturation cell. The heated components are kept inside a chromatographic oven maintained at a constant temperature to within ± 0.05°C by means of a PID temperature controller. A regular stream of fluid, using a constant flow pump, passes through the saturation cell packed with an inert stationary phase (Gaz chrom R 60/80) pre-coated with the organic compound. The solute transported by the fluid is subsequently trapped in a specific extraction column (inverse phase). The organic compound is removed by back flushing using the appropriate solvent in order to dissolve and carry out the totality. A low flow of fluid through the generator column is to be set to avoid safely the formation of colloidal dispersion, to increase the contact time and to keep small pressure drops across the generator/extractor column. The gas chromatography coupled to mass spectrometer detector is used in order to quantify the solute. The validation of this apparatus was achieved by comparison of our values with the ones extracted from previous papers using the static method to determine aqueous solubility of the ethylbenzene, and a precision of our solubility measurements was established to be better than 0.2%. In continuous, aqueous solubility and thermodynamics properties of perfluorocarbons compounds were determined in the range of temperature from 273 K to 333 K. Considering the contribution of chromatographic, calibration and other operational errors, the combined measurement uncertainty (standard deviation) was established to be less than 3%.

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Hale, Jack S., Alison Harris, Qilin Li e Brent C. Houchens. "The Fluid Mechanics of Membrane Filtration". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43656.

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Reverse osmosis and nanofiltration membranes remove colloids, macromolecules, salts, bacteria and even some viruses from water. In crossflow filtration, contaminated water is driven parallel to the membrane, and clean permeate passes through. A large pressure gradient exists across the membrane, with permeate flow rates two to three orders of magnitude smaller than that of the crossflow. Membrane filtration is hindered by two mechanisms, concentration polarization and caking. During filtration, the concentration of rejected particles increases near the membrane surface, forming a concentration polarization layer. Both diffusive and convective transport drive particles back into the bulk flow. However, the increase of the apparent viscosity in the concentration polarization layer hinders diffusion of particles back into the bulk and results in a small reduction in permeate flux. Depending on the number and type of particles present in the contaminated water, the concentration polarization will either reach a quasi-steady state or particles will begin to deposit onto the membrane. In the later case, a cake layer eventually forms on the membrane, significantly reducing the permeate flux. Contradictive theories suggest that the cake layer is either a porous solid or a very viscous (yield stress) fluid. New and refined models that shed light on these theories are presented.

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Kobayashi, Isao, e Mitsutoshi Nakajima. "Micro/Nanochannel Emulsification for Generating Monosize Droplets". In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75238.

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Emulsification is an important process in various fields including foods, pharmaceuticals, cosmetics, and chemicals. Emulsification operation is commonly conducted using conventional emulsification devices, such as high-speed blenders, colloid mills, high-pressure homogenizers, and ultrasonic homogenizers. However, these emulsification devices result in the production of polydisperse emulsions with wide droplet size distributions and poor controllability in droplet size and its distribution. In contrast, monodisperse emulsions consisting of monosize droplets have received a great deal of attentions over the past decade due to their high-tech applications, e.g., monosize microparticles as spacers for electronic devices and monosize micro-carriers for drug delivery systems (DDS). Our group proposed microchannel (MC) emulsification as a promising technique to produce monodisperse emulsions in the mid 1990s. Micro/Nanochannel (MNC) emulsification enables generating monosize droplets with the smallest coefficient of variation (CV) of below 5% using MC and nanochannel (NC) arrays of unique geometry. The resultant droplet size, which ranged from 0.5 to 200 μm, can be precisely controlled by channel geometry. Droplet generation for MNC emulsification is very mild and does not require any external shear stress; a dispersed phase that passed through channels is transformed spontaneously into monosize droplets inside a continuous-phase domain. The aim of this paper is to present recent developments in MNC emulsification chips, particularly focusing on asymmetric straight-through MC arrays for large-scale production of monodisperse emulsions. Asymmetric straight-through MC array chips were fabricated using a silicon-on-insulator wafer. Numerous asymmetric straight-through MCs each consisting of a microslot and a narrow MC were positioned in the central region of the chip. Monosize droplets were stably generated via asymmetric straight-through MCs at high production rates. Below a critical droplet production rate, monosize droplets were generated via asymmetric straight-through MCs, with droplet size and size distribution independent of the droplet productivity. The use of a large asymmetric straight-through MC array chip achieved the mass production of monosize tetradecane oil droplets at ∼1 L/h. The simulation results using CFD (computational fluid dynamics) agreed well with the experimental results and provided useful information, such as the movement of the oil-water interface during droplet generation. Monosize submicron droplets were also obtained using NC emulsification chips made of single-crystal silicon.

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Nnanna, A. G. Agwu, Chenguang Sheng, Kimberly Conrad e Greg Crowley. "Performance Assessment of Pre-Filtration Strainer of an Ultrafiltration Membrane System by Particle Size Analysis". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53447.

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One of the industrial applications of ultrafiltration membrane system is water purification and wastewater treatment. Membranes act as physical barriers by eliminating particles such as pollen, yeast, bacteria, colloids, viruses, and macromolecules from feed water. The effectiveness of the membrane to separate particles is determined by its molecular weight cut-off and feed water characteristics. Typically, pre-filtration strainers are installed upstream of an ultrafiltration membrane system to separate large particles from the flow stream. The criteria for selection of the strainer pore size is unclear and is often determined by the feed water average particle size distribution. This paper is motivated by the hydraulic loading failure of a 125 μm strainer by average feed water particle size of 1.6 μm when the volumetric flow is at or greater than 40% of the rated design flow capacity. The objective of this paper are to: a) determine if the feed particle size distribution is a sufficient parameter for selection of pre-filtration strainer, b) evaluate the effect of feed flow velocity on strainer performance, and c) enhance strainer performance using vortex generator. In this experimental study, a Single Particle Optical Sensing, Accusizer, was used to analyze particle size distribution of five water samples collected at strainer feed, strainer filtrate, and strainer backwash. All samples were analyzed using a lower detection limit of 0.5 μm. In order to capture more counts of the larger particles present in the sample, a second analysis was done for each sample at a higher detection limit, 5.09 μm for feed sample, and 2.15 μm for the rest of the samples. Particle size data based on individual detection limits were statistically combined to generate comprehensive blended results of total number and total volume. The volume was determined based on assumption that each particle is spherically shaped. The Particle Size Distribution Measurement Accuracy is ±0.035 μm. Results showed that the feed particle size diameter and volume was insufficient to determine strainer size. Particle size distribution is needed at the feed, filtrate, and backwash to evaluate the strainer particle separation efficiency. It was observed that the total particle count in the filtrate (4.4 × 106) was an order of magnitude higher than the feed (3.2 × 105). Specifically, the total count for particles with diameter less than 7.22 μm were higher in the filtrate while larger particle size ≥ 7.22 μm were more in the feed stream. It appears that the large particles in the feed breaks down into smaller particles at the strainer interface and the small particles (≤ 7.22μm) passed through the pore into the filtrate. The particle breakdown, detachment of particles in the strainer pore into the filtrate, and particle to particle interactions are enhanced by increase in flow velocity hence increasing the hydrodynamic shear that acts on attached particles. A vortex generator inserted in to the strainer reduced pore clogging and pressure drop.

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