INFLUENCE OF STIRRING SPEED ON KINETIC AND MORPHOLOGICAL PARAMETERS OF GROWTH OF AMORPHOUS SILICA NANOSPHERES OBTAINED BY THE STOBER METHOD

Calorimetric and conductometric analysis methods in online mode for the synthesis of silica globules have been used. The dependence of the initial reaction rate of sol synthesis on the stirring rate of the reaction mixture was obtained. The stirring regions corresponding to diffusive and kinetic character of synthesis at the ratio of components Si(O_C2H₅)₄ : H₂O : NH₃H₂O – 0.2 : 18.9 : 2.0 (mol l⁻¹) have been revealed. The kinetic region lies in the stirring frequency range of 7–23 Hz, which is characterized by a constant process rate and quality of the grown nanospheres, and the diffusive one up to 7 Hz with varying synthesis parameters. SEM-photographs of samples with determination of average sizes and deviation of sizes at different stirring speeds were analyzed. Morphological defects of nanospheres grown in the diffusion synthesis mode have been observed.

kinetic curve, thermal analysis, SiO₂ nanospheres, stirring speed, kinetic mode