DYNAMIC LIGHT-SCATTERING-STUDIES OF THE STABILITY AND GROWTH OF SILICA PARTICLES

The kinetics of silica sol growth under different chemical conditions was observed by measuring the particle size of sols using dynamic ligh t scattering (DLS). An oscillatory non-linear behavior of sol growth d ynamics was obtained. The particle size profile shows damped and perio dic oscillations until a steady state condition is reached. This oscil latory behavior of the profile is associated with the unstable charact er of the chemical reaction. The instability arises because one reacti on of the process is auto-catalytic. This instability produces a wide variety of possible structures that are formed during this part of the reaction. By appropriately changing some chemical parameters such as pH, concentration, temperature, etc., it was possible to obtain a stab le reaction from the beginning of the process. All the predictions of the effect of growth parameters on the stability of the reaction were fulfilled, thus giving good support to the assumptions about the unsta ble character of the chemical reaction.