서강대학교

목차

Preparation of silica nanoparticles by flame spray pyrolysis from two different precursor solutions was investigated. Tetraehyl orthosilicate (TEOS) and aqueous silicic acid were chosen as the precursor and these precursor solutions were sprayed by an ultrasonic atomizer. The precursor concentration, the maximum flame temperature, and the residence time were selected as experimental variables.
The specific surface areas of as-prepared particles were analyzed by BET method and average particle sizes were calculated from them. Transmission electron microscope (TEM) was used for characterization of morphology. Crystal structure and chemical bonding of as-prepared powder were characterized by an X-ray diffractometer and a Fourier transform infrared (FT-IR) spectrometer, respectively.
In the case of TEOS, amorphous silica nanoparticles ranging 9-47 nm were synthesized by the flame spray pyrolysis. Average particle size increased as the precursor concentration increased. Average particle size also decreased with respect to increase of the maximum flame. Two kinds of mechanisms, vapor phase reaction and intradroplet reaction, were suggested for generation and growth of silica nanoparticles by the flame spray pyrolysis from TEOS based on these experimental results.
On the other hand, when the aqueous silicic acid was used as precursor, much larger amorphous silica particles, ranging 304-685 nm, were prepared by the flame spray pyrolysis. Average size of as-prepared powder from the aqueous silicic acid increased with respect to increase of precursor concentration. However, the average particle size was not changed clearly while the maximum flame temperature was changed. It was suggested on the basis of the experimental results that the silica nanoparticles from the aqueous silicic acid was formed through only the intradroplet reaction.