Particle Growth in Acidic Solution

In the early stages of conversion of silica to particles, where the concentrations of oligomers are decreasing, it is probable that once a certain concentration of nuclei has been reached, they remain constant in number as they grow in size. When oligomers have been consumed, the particles then grow in size at the expense of the smaller particles, and thus decrease in number. 

In alkaline solution above pH 7, all these early stages of polymerization occur very rapidly and particle growth by Ostwald ripening continues as the charged particles remain as sol. 

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