Fumed Silicas Possessing Different Morphology and Hydrophilicity

Fumed silicas synthesized under varied conditions (stoichiometric or nonstoichiometric amounts of reactants SiCl4, O2 (mixed with N2), and H2, different burner diameter, flow velocity and turbulence, flame temperature, etc.) were studied using adsorption of nitrogen, argon, and water, infrared (IR)...

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Bibliographic Details
Published in:	Journal of colloid and interface science Vol. 242; no. 1; pp. 90 - 103
Main Authors:	Gun'ko, V.M., Mironyuk, I.F., Zarko, V.I., Turov, V.V., Voronin, E.F., Pakhlov, E.M., Goncharuk, E.V., Leboda, R., Skubiszewska-Ziȩba, J., Janusz, W., Chibowski, S., Levchuk, Yu.N., Klyueva, A.V.
Format:	Journal Article
Language:	English
Published:	San Diego, CA Elsevier Inc 01-10-2001 Elsevier
Subjects:	1H NMR aqueous suspension Chemistry electrophoretic mobility Elements and non-metal compounds (oxides, hydroxides, hydrides, sulfides, carbides, ...) Exact sciences and technology fumed silica Inorganic chemistry and origins of life particle morphology particle size distribution photon correlation spectroscopy Preparations and properties synthesis condition impact water adsorption aqueous suspension fumed silica photon correlation spectroscopy electrophoretic mobility 1H NMR particle morphology particle size distribution synthesis condition impact water adsorption Adsorption isotherm Particle suspension Experimental study Texture Operating conditions Hydrophily Particle size distribution Electrophoretic mobility Morphology Preparation Silicon Oxides Water absorption Aqueous solution Surface area
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Summary:	Fumed silicas synthesized under varied conditions (stoichiometric or nonstoichiometric amounts of reactants SiCl4, O2 (mixed with N2), and H2, different burner diameter, flow velocity and turbulence, flame temperature, etc.) were studied using adsorption of nitrogen, argon, and water, infrared (IR) and photon correlation spectroscopy, 1H NMR, and electrokinetic methods. Prepared silicas posses different specific surface area (SAr=85–512 m2/g), structures of primary particles and their swarms, concentrations of silanols (COH=1.9–5.2 μmol/m2), and weakly (Cw,105=0.4–2.4 wt%) and strongly (Cw,900=0.4–2.2 wt%) bound waters. There is correlation between the specific surface area (S) of fumed silica and the flow velocity vf(S∼ln vf at vf<25–30 m/s). A decrease in the amounts of hydrogen/oxygen in the flame and elevating synthesis temperature or flame turbulence (due to an increase in the burner diameter or changes in the reactant amounts) enhances the size of primary particles, which become slightly micropous on addition of hydrogen (though an annular nozzle) reacting at the flame periphery. Dividing of the flow in the burner to several smaller flows reducing the turbulence without changes in other synthesis conditions significantly enhances the specific surface area. The concentration of silanols increases with growing primary particle size, and the hydrophilicity (Cw,105+Cw,900) decreases at oxygen deficiency on the synthesis.
ISSN:	0021-9797 1095-7103
DOI:	10.1006/jcis.2001.7736