Examination of the regime controlling sol–gel based colloidal silica aggregation

• The size distribution of colloidal silica during aggregation was studied.
• The effecting parameters were altered to elucidate the aggregation regime.
• We found a mixed regime of both diffusion and reaction limited aggregation.
• We unveiled the empirical kernel of the system for the first time.
• We found that the empirical kernel shows a curiosity arousing difference with the classical kernel.

The behavior of the size distribution of colloidal silica during aggregation was studied. The effecting parameters including: pH, temperature, colloidal concentration, and electrolyte concentration were altered to elucidate the nature of the aggregation kinetic regime. Size distribution was measured by Dynamic Light Scattering monitoring the progress of the reaction.We found clear evidences for a mixed regime of both diffusion limited and reaction limited cluster aggregation. In addition, using computer simulations, we compared the empirical behavior to the theory. This enabled us unveiling the empirical kernel of the system for the first time. The empirical kernel shows a curiosity arousing difference with the classical kernel.