Relationships between surface compositions and properties of surfaces of mixed fumed oxides

Titania deposits on nanosilicas

“…More significant changes in the PSDs are observed at R > 5 nm because of changes in the organization of aggregates and agglomerates occurring in the titania synthesis and sample treatments as well as the formation of titania particles in large voids between silica nanoparticles. The deviations in the pore shape from the model as voids between the spherical particles randomly packed in aggregates (this deviation corresponds to that of the particle shape from a spherical one) are larger for titania/silica based on A-50 and A-100 than A-300 or A-380 in the synthesis in 2-propanol because the shape of larger primary particles of fumed silicas can be less spherical because of features of the flame synthesis [4,5,[51][52][53][54]. Therefore, the synthesis technique and the amounts of titania affect these deviations differently depending on the type of the silica matrix.…”

“…Water desorption from nanooxides was studied by the OPTPDMS method (chamber pressure ∼ 10−7 Torr, sample weight ~5 mg, heating rate 2 K/s, ∼ 0.5 cm distance between the sample and the MS detector), with a MSC-3 (Electron, Sumy, Ukraine) time-of-flight mass spectrometer (sensitivity 2.2 × 10 −5 A Torr −1 , accelerating voltage 0.5 kV, pulse frequency 3 kHz). Application of this technique to water desorption from various fumed oxides was described in detail elsewhere [31,[52][53][54].…”

“…The interaction of TiX 4 with silanols, subsequent hydrolysis and aggregation of grafted titania in nanoparticles were studied in detail for different matrices with unmodified [26][27][28][29][30][31][32]37] and modified [50] fumed silica, unmodified silica gel [33,35,36] and silylated silicas [40,50]. Notice that structural, adsorption and catalytic properties of grafted TiO 2 /fumed silica and fumed ST materials significantly differ and this difference depends on the titania content, phase composition and titania distribution [51][52][53][54]. The influence of features of the textural porosity of fumed silica on the formation of titania deposits is not so clear as in the case of silica gels with rigid granules and a relatively narrow pore size distribution [26][27][28][29][30][31][32][33][34][35]50].…”

Heating effects on morphological and textural characteristics of individual and composite nanooxides

“…(1-2 nm), primary (5-100 nm), secondary (<0.1-1 μm), ternary (1-10 μm) and quaternary (>10 μm) particles depend on flame synthesis conditions (flame temperature, its gradient, flame length, flow velocity and turbulence, ratio of reactant concentrations), phase distributions for composite oxides, amount of adsorbed water, and sample history (Iler 1979;Legrand 1998;Basic Characteristics of Aerosil 1997;Gun'ko et al 2003Gun'ko et al , 2004Gun'ko et al , 2005Gun'ko et al , 2007aGun'ko et al , 2007bGun'ko et al , 2007c. These characteristics are of importance to control the adsorption of various adsorbates (water, metal ions, low-molecular organics, polymers, proteins, etc.…”

Characteristics of surface and electrochemical properties of composites with fumed metal oxides and hydroxyapatite

“…Such five fumed oxides as ST20 (20 % TiO 2 ; 80 % SiO 2 ); A300 (100 % SiO 2 ); A90 (100 % SiO 2 ); alumina (100 % Al 2 O 3 ); AST1 (89 % Al 2 O 3 ; 10 % SiO 2 ; 1 % TiO 2 ) (pilot plant of the Chuiko Institute of Surface Chemistry, Kalush, Ukraine) were used (these fumed oxides were described in detail elsewhere (Gun'ko et al 2007(Gun'ko et al , 2009). The prepared composites were washed many times to clean them from impurities.…”