Aggregation of nanoparticles in high ionic strength suspensions: Effect of Hamaker constant and particle concentration

The kinetics of aggregation of nanocolloidal particles in suspensions has been studied using computer simulations based on Discrete Element Method. This study presents the analysis of the influence of Hamaker constant, Brownian forces and particle concentration on the aggregation time of nanoparticles in high ionic strength suspensions. Particle adhesion and cohesion were simulated using the van der Waals force equation. Half the particles were assigned a Hamaker constant of 9.0 × 10−20 J and the other half of the particles had the Hamaker constant varied from case to case with values between 1.0 × 10−20 and 9.0 × 10−20 J. Aggregation times obtained from analysing the number of interparticle contacts and number of singlets in the suspensions have been used to characterise the speed of the aggregation process. The simulation results show that when the strength of the van der Waals interaction increases the aggregation time decreases following a power law. In addition, the presence of Brownian forces speeds up the aggregation process. Finally, the relationship between packing fraction and aggregation times for singlets and contacts has been very well expressed by power laws.

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► We present a study of the kinetics of aggregation of colloidal suspensions.
► Aggregation time follows a power law.
► A decrease in particle packing produces an increase in aggregation time.
► The final aggregate structure is influenced by the initial particle concentration.