Colloidal salt stability

In addition to surfactant-stabilized colloids, there has been work on forming metal colloids without stabilizers. Lee et al. have shown that direct reduction of mefal chloride salts in tetrahydrofuran with LiBH4 gives small nanoparticles that can be impregnated onto carbon. No further treatment is required after the removal of the solvent. This route was applied to the preparation of PfRu, PtNi, PtMo, and PtW particles. 

Use of Enological Additives for Colloid and Tartrate Salt Stabilization in White Wines and for Improvement of Sparkling Wine Foaming Properties... 

Use of Enological Additives for Colloid and Tartrate Salt Stabilization... 

Bimetallic particles with layered structures have opened fascinating prospects for the design of new catalysts. Schmid et al. [10m] have applied the classical seed-growth method [20] to synthesize layered bimetallic Au/Pd and Pd/Au colloids in the size range of 20-56 nm. The sequential reduction of gold salts and palladium salts with sodium citrate allows the gold core to be coated with Pd. This layered bimetallic colloid is stabilized by trisulfonated triphenylphosphane and sodium sulfanilate. More than 90% metal can be isolated in the solid state and is redispersable in water in high concentrations. 

Schema 8.1 Electrochemical fabrication of nanosized transition metal colloids (the stabilizer is usually a tetraalkylammonium salt) [25],...

Another application concerns the fabrication of metallic and bimetallic nanostructures on surfaces by electron beam induced metallization of the RjN Br"-stabilized Pd and Pd/Pt colloids [48]. In a simple three-step process, namely dip-coating, electron beam writing of patterns (e.g. lines) and rinsing, lines having a thickness of only 30 nm were achieved. This technique is of potential interest in lithography and catalysis. Finally, tetraalkylammonium salt-stabilized transition... 

Scheme 7.6 Thermal preparation of ammonium salt-stabilized palladium colloids.

Stabilising agents for use in water borne coatings are discussed with reference to the three classes dispersants, surfactants, and protective colloids. Salts are also examined as an aid to colloidal stability in the formulation, and defoamers as related species are also discussed. Each are described with hints on improving performance. 7 refs. EUROPE-GENERAL Accession no.584582... 

Casein is utilized in diverse ways, as an adhesive, as a binder, and as a protective colloid and stabilizer for emulsified adhesive systems. Casein is sold as a raw material, and casein adhesives are sold in both the dry and liquid forms. The useful wood adhesive known as casein glue, which is formulated with lime and sodium salts, will be addressed later. This section will cover other uses of casein, for which the solubilization of the casein is generally accomplished with the use of heat, and at lower pH s than for the lime-containing glues. 

Colloidal silica dispersions are sensitive to the presence of salts. Addition of a salt to a colloidal silica dispersion leads to a shrinkage of the thickness of the diffuse part of the electrical double layer which is surrounding each particle in the dispersion [56]. However, silane-modified silica dispersions are expected to be much more resistant towards addition to salt as such dispersions are not primarily stabihzed by electrostatic forces. In order to evaluate the salt stability of silane-modified silica dispersions, various amounts of sodium chloride were added to two different types of unmodified and silane-modified silica dispersions. After addition of sodium chloride to the different silica dispersions, the gel time was measured. The definition of gel time in this context is the time it takes to obtain a rigid gel, i.e., the... 

Li, Na, K these are obtained very easily by the reaction between the metal and the alcohol with which they form an ionic salt. They do not give any condensation and by virtue of their RO" group basic and nucleophilic, they can modify the reactivity of other cations. These ions remain in solution or get adsorbed in the colloids formed by the condensation of other cations. But this adsorption has to be limited for avoiding the flocculation of these colloids by stabilizing them with polymers or by adjusting the surface charge with an appropriate pH. 

For a more complete understanding of colloid stability, we need to address the kinetics of aggregation. The theory discussed here was developed to describe coagulation of charged colloids, but it does apply to other cases as well. First, we consider the case of so-called rapid coagulation, which means that two particles will aggregate as soon as they meet (at high salt concentration, for instance). This was considered by von Smoluchowski 1561 here we follow [39, 57]. 

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