Synthesis nanosilica

The specific surface area (Sbet) °f silicas produced by burning of SiCl4 in an 02/H2/N2 flame can be varied over a large range from 50-500 m2/g (Table l).6,7 Features of the flame synthesis and the nature of amorphous nanosilicas cause certain generic characteristics (i) a roughly spherical shape of nonporous... 

The structure of secondary particles of nanosilicas is random and loose with an empty volume V, = pbx - pbx > 10 cm3/g.6"9 Changes in synthesis conditions allow one to vary the structure of contacts between adjacent primary particles in aggregates6,7, which affect the properties of powders and dispersions. Different treatments of the powders and suspensions result in changes in particle-particle interactions in aggregates, that leads to variation of the adsorption capacity for various adsorbates.1 16 From the textural characteristics (Table 1 and Figure 1) one can surmise that the structures of... 

The aim of this contribution is to present experimental data concerning the synthesis, physicochemical properties and bio-activity of several nanosilica-based composites tested by interaction with native red blood cells (RBCs). The investigations include (i) synthesis of nanocomposites by adsorption of BSA, fructose and glucose on a fumed silica surface, and (ii) analysis of the adsorption properties of composites and their bio-activity. It is known that both glucose and fructose do not individually adsorb on fumed silica therefore, bovine serum albumin was used as a mediator to bind the monosaccharides to the fumed silica surface. 

Synthesis Conditions and Characteristics of Nanosilicas (Second Series)... 

Synthesis Conditions and Hydration Degree of Nanosilicas (Third Series) with Different Hydrophilicity... 

Thus, the structural and adsorption properties of nanosilicas depend on the synthesis conditions such as the ratio of reactants (SiCl4, O2, and H2), temperature, flow velocity, turbulence and length of the flame, and additional external actions (e.g., electrostatic field). These structural features of nanosilicas can affect the interactions with water, described later. 

Characteristics of Two Samples of Nanosilica A-300 Differently Hydrated Due to Synthesis Conditions... 

For one of nanosilica A-300 samples shown in Table 1.30, synthesis conditions corresponded to 30% excess of oxygen and hydrogen in comparison with their stoichiometric contents in respect to SiCl4 to provide a high degree of hydration of particles (No 1, Table 1.30). 

Silochrome is a silica maCToporous material with broad pores and much higher bulk density than that of the nanosilica powder. However, HTT (during Silochrome synthesis) can lead to formation of not only broad pores but also shallow and narrow pores, which can provide appropriate conditions for appearance of WAW (Gun ko et al. 2005d). Additionally, low amounts of adsorbed water can provide the H NMR spectra with visible signal of WAW. The temperature effect on the H NMR spectra of water adsorbed on the surface of Silochrome (Sbet 120 mVg) at Chjo =31 mg/g is depicted in Figure 1.248. 

A third field where the anionic polymerization of CL has been applied to advantage is the in situ preparation of nanocomposites from nanosilica, uniformly dispersed in the monomer. Some recent publications describe the fundamental steps of the synthesis and underline the most significant property improvements, especially when chemical bonds between surface-functionalized silica particles and anionic PA6 chains are formed. ... 

Synthesis of Symmetric and Asymmetric Nanosilica for Materials, Optical and Medical Applications... 

The benefit of this division can be illustrated from several perspectives. From a synthetic point of view, the division is significant as synthesis normally results in the production of symmetric materials. Hence, the synthesis of asymmetric nanosilica and molecular species are quite unique by themselves. The division can thus be viewed as a helpful hint to understanding the synthesis of helical materials and other asymmetric nanomaterials. The origin of the production of asymmetric nanosilica is believed to be the nature of the different catalysts or templates involved, while the exact growth mechanism depends on the structure of these catalysts or templates. To date, asymmetric nanosihca has not been prepared without these two assisting species. 

Table 2.1 Synthesis of nanosilica. The data relate to the types of material synthesized, symmetry of the material, whether it is made via catalytic processes, a brief description of the method, and the appropriate reference.

Figure 2.4 Three typical growth models for the catalytic synthesis of nanosilica, (a) VLS = vapor-liquid-solid ...

Figure 2.5 A typical method for the synthesis of nanosilica, without using catalysts or catalysts in the traditional sense. In this case, TEOS is condensed to form nanotubes on the surface of cylindrical micelles. After removal of the micelles and treatment of the TEOS nanotubes, silica nanotubes are formed. (Adopted from Ref [JO].)...

---