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) 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