Aggregation of colloidal nickel hydroxycarbonate studied by light scattering

The aggregation kinetics of nickel hydroxycarbonate particles in aqueous solution have been studied using dynamic and static light-scattering techniques. Different aggregation kinetics were observed, which depended on the concentration of electrolyte dissolved in the dispersion. At low concentration, slow reaction-limited aggregation and an exponential increase of aggregate size over time was found. The aggregates are characterized by a fractal dimension D = 2.0–2.1. At high electrolyte concentration fast diffusion-limited aggregation behavior was observed as was an increase in aggregate size over time described by a power law. The aggregates are characterized by a fractal dimension D = 1.7–1.8. Crossover from reaction-limited to diffusion-limited aggregation behavior was observed for large clusters. Under shear flow a drastic change of fractal dimension was noted. It was most pronounced for aggregates grown at low electrolyte concentration, where D increased from 2.0 at zero shear to D = 2.7 at a shear rate of 200 s−1. This is more drastic than computer simulations predict. At high electrolyte concentration, D increases from 1.7 at zero shear to D = 2.2 at a shear rate of 200 s−1, which is in line with results of computer simulation.

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