Surface electric and titration behaviour of fumed oxides

Morphology and surface properties of fumed silicas

“…Thus, fumed oxides of different chemical composition can possess close particle morphology if they have close specific surface area. However, the surface properties such as surface charge density, ζ potential, secondary particle size distribution in the gaseous and liquid dispersion media, adsorption of low and high molecular compounds [15,16,21] or metal ions [18] can be very different not only because of the different total contents of oxide components but also due to different distributions of these oxides in the volume and at the surface of primary particles. Controlled changes in the mentioned parameters as well as in the size of patches with the second oxide and the content of terminal and bridging surface hydroxyls [13][14][15][16]18,21,24,40] allow one to produce morphologically close materials possessing very different surface chemical properties.…”

“…Changes in synthesis conditions allow one to vary the structure of contacts between adjacent primary particles in their aggregates [12,13], which affect the structural and adsorption properties of the powders and the suspensions. Additionally, different types of treatment of the powders and the suspensions allow one to change particle-particle interaction in aggregates, which also results in variation of the adsorption capacity with respect to both polar and nonpolar low molecular adsorbates and polymers [14][15][16][17][18][19][20][21]. Certain aspects of these effects will be analyzed below.…”

“…The Lennard-Jones potential was used for cylindrical pores and gaps between spherical particles [12,18,22]. This method gives better results than that used previously for complex adsorbents with one distribution function for all the pore shape models because of the use of independent f V,j (R p ) functions for each pore type.…”

“…However, variations in the S BET value and the number of nanosilicas in these series were not as significant as possible. Additionally, these investigations were devoted to analysis of only certain properties of nanosilicas, e.g., their hydrophilicity dependent on synthesis conditions [12,13], hydrothermal treatment [14], heating and mechanochemical activation [17], the behavior of nanosilicas in aqueous media [15], and the influence of adsorption of metal ions [18], polymers and biomacromolecules [12,13,[19][20][21], chemical modification of nanosilica surface [22][23][24], and carbonization of different precursors on structural and adsorption characteristics on nanosilicas [16]. These investigations stimulated us to maximum widen nanosilica series with respect to the specific surface area, to vary precursors, and to analyze changes in the properties of nanosilicas during synthesis for elucidation of regularities in the properties of nanosilicas that are of interest and importance from practical and theoretical points of view.…”

TSDC spectroscopy of relaxational and interfacial phenomena

“…This feature, as well as changes in the specific surface area ( Table 1, S BET ), i.e. in the size of primary particles, and Brönsted and Lewis acidity of fumed oxides [18,76] affect interfacial phenomena such as the adsorption of water, metal ions [84] and proteins [23,85], and haemolysis of red blood cells by these oxides [86,87]. One can expect that the interfacial relaxation phenomena at the surface of these oxides depend on the surface composition.…”