Suspensions, suspension colloids

Monovoukas Y and Cast A P 1989 The experimental phase diagram of charged colloidal suspensions J. Colloid Interface Sol. 128 533-48... 

Turbidimetry and nephelometry are two related techniques in which an incident source of radiation is elastically scattered by a suspension of colloidal particles. In turbidimetry, the detector is placed in line with the radiation source, and the... 

Mixing. In method 1, a suspension of colloidal powders, or sol, is formed by mechanical mixing of colloidal particles in water at a pH that prevents precipitation (step A in Fig. 1) (8). In method 2 or 3, a Hquid alkoxide precursor such as Si(OR)4, where R is CH (TMOS), C2H (TEOS), or C Hy, is hydrolyzed by mixing with water (eq. 2). 

Sol-gel is one of the most useful techniques for preparation of inorganic membranes with fine pores in the nanometer range (1-5 nm). The sol is a stable suspension of colloidal solid particles within soft uniform solution. The gel was obtained by hydrolysis with open reflux in 24 hours at 85-90 °C. The advantage of sol-gel technology is the ability to produce... 

Comprehension of the interactions among microstructures composed of tethered chains is central to the understanding of many of their important properties. Their ability to impart stability against flocculation to suspensions of colloidal particles [52, 124, 125] or to induce repulsions that lead to colloidal crystallization [126] are examples of practical properties arising from interactions among tethered chains many more are conceivable but not yet realized, such as effects on adhesion, entanglement or on the assembly of new block copolymer microstructures. We will be rather brief in our treatment of interactions between tethered chains since a comprehensive review has been published recently of direct force measurements on interacting layers of tethered chains [127]. 

Clusters of metal atoms can form colloidal suspensions. Colloidal clusters of copper, silver, and gold in glass are responsible for some of the vivid colors of stained glass in medieval cathedrals. Even aqueous suspensions of metal clusters are known (Fig. 8.45). 

The examples in Table 12-3 illustrate the diversity of colloidal suspensions. Colloidal suspensions are commonly found in nature, and humans have learned how to make useful suspensions. Some of these are foods such as butter, Ice cream, and whipped cream. Others are personal care items like shampoos, shaving creams, and hair sprays. 

D. Jiao and M. M. Sharma. Mechanism of cake buildup in crossflow filtration of colloidal suspensions. J Colloid Interface Sci, 162(2) 454-462, February 1994. 

Another fluid standard used in the literature is a suspension of colloidal noble-metal particles in a solvent [96]. The method is explained starting on p. 134. The application of such calibration methods is in particular feasible, if polymer solutions are studied and thus the measurement of a calibration fluid does not require to modify the setup. 

The typical viscous behavior for many non-Newtonian fluids (e.g., polymeric fluids, flocculated suspensions, colloids, foams, gels) is illustrated by the curves labeled structural in Figs. 3-5 and 3-6. These fluids exhibit Newtonian behavior at very low and very high shear rates, with shear thinning or pseudoplastic behavior at intermediate shear rates. In some materials this can be attributed to a reversible structure or network that forms in the rest or equilibrium state. When the material is sheared, the structure breaks down, resulting in a shear-dependent (shear thinning) behavior. Some real examples of this type of behavior are shown in Fig. 3-7. These show that structural viscosity behavior is exhibited by fluids as diverse as polymer solutions, blood, latex emulsions, and mud (sediment). Equations (i.e., models) that represent this type of behavior are described below. 

Westesen and Siekmann [11] used suspensions of colloidal solid lipid particles as well as lyophilizates as delivery systems for the parenteral administration of the drug for its particle morphology determination. 

Thus the study of surfaces has emerged as an important focus in the chemical sciences, and the relationship between surfaces of small systems and their performance has emerged as a major technological issue. Flow in microfluidic systems—for example, in micromechanical systems with potential problems of stiction (sticking and adhesion) and for chemistry on gene chips—depends on the properties of system surfaces. Complex heterogeneous phases with high surface areas—suspensions of colloids and liquid crystals—have developed substantial... 

By using this technique only water insoluble monomers can be polymerised. In this process, the monomer is suspended as discrete droplets (0.1 to 1.0 mm diameter) in dilute aqueous solution containing protective colloids like polyvinyl alcohol and surfactants, etc. The droplets have large surface area and can readily transfer heat to water. Suspension is brought about by agitating the suspension. Protective colloids prevent coalescence of the droplets. A monomer soluble initiator is used. The product is obtained by filtration or spray drying. This process cannot be carried out yet in a continuous process hence batch processing has to be used. 

Colloidal gold A suspension (or colloid) of submicrometer-sized particles of gold in a fluid, usually water. A colloidal gold conjugate consists of gold particles coated with a selected protein or macromolecule, such as an antibody, protein A or protein G. Because of their high electron density, the gold particles are visible in the electron microscope without further treatment. 

Fig. 7.1 gives a size spectrum of water-borne particles. Particles with diameters less than 10 pm have been called colloids. In soils, the clay-sized and fine silt-sized particles are classified as colloids. Colloids do not dissolve, but instead remain as a solid phase in suspension. Colloids usually remain suspended because their gravitational settling is less than 10 2 cm s 1. Under simplifying conditions (spherical particles, low Reynolds numbers), Stokes law gives for the settling velocity, vs... 

Relaxation studies have shown that the attachment of an ion to a surface is very fast, but the establishment of equilibrium in wel1-dispersed suspensions of colloidal particles is much slower. Adsorption of cations by hydrous oxides may approach equilibrium within a matter of minutes in some systems (39-40). However, cation and anion sorption processes often exhibit a rapid initial stage of adsorption that is followed by a much slower rate of uptake (24,41-43). Several studies of short-term isotopic exchange of phosphate ions between aqueous solutions and oxide surfaces have demonstrated that the kinetics of phosphate desorption are very slow (43-45). Numerous hypotheses have been suggested for this slow attainment of equilibrium including 1) the formation of binuclear complexes on the surface (44) 2) dynamic particle-particle interactions in which an adsorbing ion enhances contact adhesion between particles (43,45-46) 3) diffusion of ions into adsorbents (47) and 4) surface precipitation (48-50). 

Practically, the phase delay and the modulation ratio mR of the light emitted by the scattering solution (solution of glycogen or suspension of colloidal silica) are measured with respect to the signal detected by the reference photomultiplier. Then, after rotation of the turret, the phase delay r/ F and the modulation ratio mF for the sample fluorescence are measured with respect to the signal detected by the reference photomultiplier. The absolute phase shift and modulation ratio of the sample are then — [Pg.179]

The method has been developed particularly for the treatment of dilute industrial effluents, including suspensions and colloids, especially those containing small quantities of organic materials. It allows the dilute suspension to be separated into a concentrated slurry and a clear liquid and, at the same time, permits oxidation of unwanted organic materials at the positive electrode. 

Micelle, An electrically charged aggregation of large organic molecules in suspension (a colloid), typically in water if its an emulsion polymerization process. The colloid is electrically charged and forms the site where polymerization takes place, even as the micelle stays in suspension. 

A.P. Gast, C.K. Hall, and W.B. Russel Polymer-Induced Phase Separations in Nonaqueous Colloidal Suspensions. J. Colloid Interface Sci. 96, 251 (1983). 

Note A colloidal suspension is colloidal dispersion of a solid in a liquid. 

Navarrete, R.C. Scriven, L.E. Macosko, C.W. (1996) Rheology and structure of flocculated iron oxide suspensions. J. Colloid Interface Sd. 180 200-211... 

Sugimoto,T. Waki, S. Itoh, H. Muramatsu, A. (1996) Preparation of monodisperse platelet type particles from a highly condensed K-FeOOH suspension. Colloids Surfaces 109 155-165. 

In this system RuO, powders were coated with the water insoluble polymer complex (i8) and used as suspensions. Ru02 colloids were stabilized by the water soluble Ru complex prepared from poly(Vbpy) and used (see also Sect. 3.4). 

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