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Flow-induced aggregation of colloidal particles in viscoelastic fluids
Donglin Xie1, Greg G Qiao1, Dave E Dunstan1
1Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, Victoria 3010, Australia.
Physical Review. E
|September 15, 2016
Summary
Flowing polystyrene nanoparticles aggregate in solutions. Elasticity hinders aggregation, while viscosity promotes it, following a revised Smoluchowski equation. This impacts colloidal science and material design.
Area of Science:
- Colloidal Science
- Rheology
- Nanoparticle Dynamics
Background:
- Understanding nanoparticle aggregation is crucial for controlling material properties.
- Flow dynamics significantly influence colloidal particle interactions and aggregation behavior.
- The role of fluid viscoelasticity in nanoparticle aggregation remains an active research area.
Purpose of the Study:
- To investigate the flow-induced aggregation of polystyrene nanoparticles in various media.
- To elucidate the impact of fluid rheological properties (viscosity and elasticity) on aggregation kinetics.
- To validate numerical models describing nanoparticle coagulation under flow.
Main Methods:
- A rheo-optical technique was employed using a quartz Couette cell.
- Real-time aggregation was monitored by measuring optical absorption and scattering.
- Numerical simulations were performed to model the aggregation process.
Main Results:
- Observed decreases in absorbance indicate flow-induced nanoparticle coagulation.
- Aggregation kinetics were found to follow a revised Smoluchowski coagulation equation.
- Fluid elasticity was shown to reduce aggregation rates, while increased viscosity enhanced them.
Conclusions:
- Fluid rheology is a critical factor governing flow-induced nanoparticle aggregation.
- Elasticity acts as a stabilizing mechanism, suppressing aggregation, whereas viscosity promotes it.
- The findings provide insights into controlling nanoparticle assembly in complex fluids.
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