Growth of silica

Hubert DHW, Jung M, Frederick PM, Bomans PHH, Meuldijk J, German AL (2000) Vesicle-directed growth of silica. Adv Mater 12(17) 1286-1290... 

In fact, such biomimetic molecules demonstrate the ability to tailor the growth of silica nanoparticles in a way that is very similar to diatom-extracted species. However, they demonstrate the same limitations in terms of morphological control of nanoparticle assembly. This is because the diatom shell architecture results not only from interactions of silica precursors with templating molecules but also benefits from a cell-driven molding of the vesicular compartment where silicification occurs [29]. Thus, it is very likely that diatom-like synthetic silica will only be achieved when such confinement/molding effects are taken into account in the design of biomimetic experiments [30]. 

Gautier, C., Lopez, P.J., Hemadi, M., Livage and J., Coradin, T. (2006) Biomimetic growth of silica tubes in confined media. Langmuir, 22, 9092-9095. 

The small aggregates of SiOn so formed are considered to be the template for the nucleation and growth of silica. 

Growth of Silica and its Controlling of Pore-opening Size on CVD Zeolites... 

This difference In growth of silica due to the composition of zeolites may be explained simply by the similarity of reagent deposited and basal surface. Because silica grows on the surface through the slloxane bond -0-S1-0-), layers with the same properties and structure can be grown on the siliceous surface. 

Difference In surface concentrations required for achieving the shape-selectivity indicates fornatlon of silica with different surface conditions. The relationship between shape-selectivity and surface silicon concentration, however, does not largely depend on the Included cation, proton or sodium, but rather on the composition of zeolites. Strong dependence on the composition was confirmed on the dealumlnated mordenlte, since the behavior was not in agreement with those on the native species but with those expected from the composition. Therefore, growth of silica and pore size enclosure can be summarized. 

Keefer Structure and Growth of Silica Condensation Polymers... 

Jansen JC and van Rosmalen GM. Oriented growth of silica molecular-sieve crystals as supported films. J Crystal Growth 1993 128(1 ) 1150-1156. 

Van Blaaderen and Vrij s chapter (Chapter 4) constitutes an excellent contribution to the understanding of the mechanisms of nucleation and growth of silica spheres in the alcohol-ammonia-water system to achieve particle sizes much larger than those of the classic silica sols synthesized in water. Kozuka and Sakka (Chapter 6) provide detailed conditions and the mechanism of formation of micrometer-sized particles of gels synthesized in highly acidic solutions of tetramethoxysilane (TMOS). 

Philipse (5) also assumed that fast hydrolysis created an active monomer bulk. He studied the growth of silica nuclei, already synthesized, after extra addition of different amounts of TES with static light scattering. To explain his growth curves (radius versus time), he used a diffusion-controlled particle growth in a finite bulk of monomers or subparticles. The model contained equations from classical flocculation theories. It takes into account the exhaustion of the monomer bulk and the retarding influence of an (unscreened) electrostatic repulsion between growing spheres and monomers. 

Schaefer and Keefer (14, 19, 34, 35) used a model developed by Eden to describe the growth of cell colonies to explain their X-ray scattering experiments. They used this simple model of nucleation and chemical limited growth to mimic the growth of silica structures in TES solutions (1... 

The kinetics of silica formation from TEOS in non-ionic reverse microemulsions has been studied by Chang and Fogler. They concluded that the growth of silica particles is controlled by the rate of TEOS hydrolysis, which is found to be first order with respect to the aqueous ammonia concentration, approximately zero order with respect to water concentration and roughly one-half order with respect to the concentration of surfactant. 

A sol (Section 9.2.1) is a fluid colloidal dispersion with free particles, subject to Brownian motion. Siliceous earths are stable, concentrated aqueous suspensions of non-aggregated particles of silica produced by the in situ growth of silica microcrystals. Particles of different sizes are obtained by controlling their growth. They are byproducts of the glass industry. 

The above-referred growth of silica particles by further accretion of silica as taught by the prior art is carried out in hot solution, that is, 50-100°C, for a variety of reasons ... 

To permit the growth of silica particles by accretion of silica from alkali metal silicate to a size sufficiently larger that the sol can be subsequently concentrated to a stiU higher silica content and remain stable, the growth step, like the transition step, is carried out in such manner as to avoid the formation of any substantial number of new particles as described hereinabove. 

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