Nanosilica shapes

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... 

Nanosilicas with a spherical shape of nonporous nanoparticles, controlled particle size distribution (PaSD), and specific surface area (Sbet) are appropriate nanosized materials to study the interfacial phenomena (without the strong distorting effects in nanopores) in different dispersion media. Nanosilicas are fully amorphous and can possess a larger 5bet value from 50 up to 500 mVg and a narrow PaSD (which becomes narrower at a greater Sbet value Her 1979, Ulrich 1984, Degussa 1997, Barthel et al. 1998a,b, Kammler and Pratsinis 2000, Kammler et al. 2004, Cabot Corporation 2011). 

Nanosilica is composed of primary nanoparticles of a spherical shape, which form aggregates (Figure 1.29a) characterized by the textural porosity (Figure 1.58). 

The shape of radial dependence of the adhesion forces shown in Figure 1.92 for nanosilica in the aqueous medium differs significantly from similar dependences measured directly as forces between two crossed cylinders (Claesson et al. 1995, Atkins et al. 1997, Spalla and Kekicheff 1997). Clearly from these results (Figure 1.92), the adhesion force value decreases practically linearly with the distance (not far from the surface). At the same time, the interaction force between two cylinders changes in the sign at a short distance between them due to too much decrease in the liquid layer thickness and can be described as follows f=jr . When x is smaller than the adsorbed layer, the work is made against the adsorption forces, and the structure of this... 

FIGURE 1.102 Effect of the pretreatment procedure of nanosilica A-300 on the shape of (a) radial function of variation in the free energy of adsorbed water and (b) adhesion forces for aqueous suspensions of nanosilica. (Adapted from Colloids Surf. B Biointerfaces, 8, Turov and Barvinchenko, Structurally ordered surface layers of water at the Si02/ice interface and influence of adsorbed molecules of protein hydrolysate on them, 125-132, 1997. Copyright 1997, with permission from Elsevier.)... 

FIGURE 1.189 IPSDforinitialandMCA-treatedwettedpowdersforl and 6 h with respect to the pore volume calculated using (a) DFT/PaSD for the model of voids between spherical particles, (b) the self-consistent model of mixture of pores (slit-shaped and cylindrical pores and voids), and (c) NLDFT (cylindrical pores). (Adapted from J. Colloid Interface Sci., 355, Gun ko, V.M., Voronin, E.F., Nosach, L.V. et al.. Structural, textural and adsorption characteristics of nanosilica mechanochemically activated in different media, 300-311, 201 le. Copyright 2011, with permission from Elsevier.)... 

The sol-gel technique to generate nanosilica particles within a polymer matrix has been a useful process which gives specific interphase impact between the organic matrix and inorganic component. The incorporation of the filler particles into polymers using this process avoids the aggregation of the nanofiller within the polymer matrix [17]. The polymer-silica interaction depends on the size and shape of the nanofiller particles, their volume fraction, and the interparticle interaction [18]. What s more, these parameters also strongly influence the properties of the nanocomposites. 

Later, Goren et al. (2010) eonducted a more systanatic study on the size effect using nanoparticles with the same base geometrical shape (spherical). They prepared PMMA silica nanocomposite foams using two nanosilica of different sizes... 

Figure 2.1 The shapes of nanosilica. The top (e) channels] [5]. The lower panel shows...

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