Colloidal nucleation

The experimental results show that a simultaneous resemblance of ephedrine and Ca on the one side and of acetylcholine and K on the other side is present neither in sulphate colloids (agar) nor its substitute (Si02), nor in carboxyl colloids (pectinate) nor in the phosphate colloid nucleate but only in phosphatides. 

Now carrageen, pectate and nucleate have not, it is true, the same equivalent weights, but these are at least of the same order of magnitude and the observed differences in intensity of the tricomplex flocculation (strong, weak, absent) can indeed hardly be attributed to this. An explanation is however found in the different polaris-ability of the ionised groups of these colloids (carrageen = sulphate colloid pectate == carboxyl colloid nucleate = phosphate colloid). 

Silver-Colloid-Nucleated ( ytochromc c Superstructures Encapsulated in Silica Nanoarchitectures. Langmuir 20 (21) 9276 9281... 

S. Briat, C. Gauthier, G. Vigier, J. Perez, Composite polymer colloid nucleated by fimctionalized silica in Hybrid Organic-Inorganic Composites, Chap. 10, pp. 112-124, J.E. Mark, C.Y.-C. Lee, P.A. Bianconi (Eds.), ACS Symposium Series 585, Washington DC, 1995. 

The entropically driven disorder-order transition in hard-sphere fluids was originally discovered in computer simulations [58, 59]. The development of colloidal suspensions behaving as hard spheres (i.e., having negligible Hamaker constants, see Section VI-3) provided the means to experimentally verify the transition. Experimental data on the nucleation of hard-sphere colloidal crystals [60] allows one to extract the hard-sphere solid-liquid interfacial tension, 7 = 0.55 0.02k T/o, where a is the hard-sphere diameter [61]. This value agrees well with that found from density functional theory, 7 = 0.6 0.02k r/a 2 [21] (Section IX-2A). 

Two nucleation processes important to many people (including some surface scientists ) occur in the formation of gallstones in human bile and kidney stones in urine. Cholesterol crystallization in bile causes the formation of gallstones. Cryotransmission microscopy (Chapter VIII) studies of human bile reveal vesicles, micelles, and potential early crystallites indicating that the cholesterol crystallization in bile is not cooperative and the true nucleation time may be much shorter than that found by standard clinical analysis by light microscopy [75]. Kidney stones often form from crystals of calcium oxalates in urine. Inhibitors can prevent nucleation and influence the solid phase and intercrystallite interactions [76, 77]. Citrate, for example, is an important physiological inhibitor to the formation of calcium renal stones. Electrokinetic studies (see Section V-6) have shown the effect of various inhibitors on the surface potential and colloidal stability of micrometer-sized dispersions of calcium oxalate crystals formed in synthetic urine [78, 79]. 

Sol-Gel Techniques. Sol-gel powders (2,13,15,17) are produced as a suspension or sol of coUoidal particles or polymer molecules mixed with a Hquid that polymerizes to form a gel (see Colloids SoL-GELtechnology). Typically, formation of a sol is foUowed by hydrolysis, polymerization, nucleation, and growth. Drying, low temperature calciaation, and light milling are subsequently required to produce a powder. Sol-gel synthesis yields fine, reactive, pseudo-crystalline powders that can be siatered at temperatures hundreds of degrees below conventionally prepared, crystalline powders. 

This paper presents the physical mechanism and the structure of a comprehensive dynamic Emulsion Polymerization Model (EPM). EPM combines the theory of coagulative nucleation of homogeneously nucleated precursors with detailed species material and energy balances to calculate the time evolution of the concentration, size, and colloidal characteristics of latex particles, the monomer conversions, the copolymer composition, and molecular weight in an emulsion system. The capabilities of EPM are demonstrated by comparisons of its predictions with experimental data from the literature covering styrene and styrene/methyl methacrylate polymerizations. EPM can successfully simulate continuous and batch reactors over a wide range of initiator and added surfactant concentrations. 

Turkevich, J., Stevenson, P.C. and Hillier, J. (1951) A study of the nucleation and growth processes in the synthesis of colloidal gold. Discussions of the Faraday Society, 11, 55-75. 

Turkevich who established the first reproducible standard procedure for the preparation of metal colloids [44] also proposed a mechanism for the stepwise formation of nanoclusters based on nucleation, growth, and agglomeration [45,46]. This model, refined by data from modern analydical techniques and results from thermodynamic and kinetic studies, is in essence stiU valid today (Figure 2) [82]. 

Auer, S. and Frenkel, D. Numerical Simulation of Crystal Nucleation in Colloids. Vol. 173, pp. 149-208. 

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