Preparation of spherical silica particles in reverse micro emulsions using silicon tetrachloride as precursor

Abstract

Silica powders with spherical shape have been prepared by precipitation reaction of silicon tetrachloride with de-ionized water in the micro emulsion system. Two kinds of micro emulsion systems were used. One was cyclohexane/polyoxyethylene nonyl phenyl ether (NP-5)/de-ionized water system, and the other was heptane e/NP-5/de-ionized water. Transmission electron microscope (TEM), thermo gravimetric analysis (TG), X-ray diffraction (XRD) patterns, infrared spectrum (IR) were employed to characterize the micro structure, shape, thermal properties, phase, and molecular structure of the obtained silica. The results show that silica featuring spherical shapes and uniform characteristics was yielded by the precipitation method using silicon tetrachloride with de-ionized water in the micro emulsion system. A decreased tendency for silica particles agglomeration could be achieved by using lower mole ratio of water and SiCl4, and the particle size was 5.74nm when mole ratio of water and SiCl4 was 4 in NP-5/cyclohexane/deionized water micro emulsion system. The silica prepared by these two systems was amorphous silica and thermally stable after 600°C treatment. The structures of silica prepared from the different micro emulsion systems were similar; organic molecules can be removed completely from the silica through 600°C treatment.