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The effects of added nanoparticles on aqueous kaolinite suspensions II. Rheological effects
1Department of Chemical Engineering, Yale University, PO Box 208286, New Haven, CT 06520, USA.
Journal of Colloid and Interface Science
|December 5, 2006
Summary
Adding silica nanoparticles and salt stabilizes kaolinite suspensions, forming a gel with a yield stress. Higher concentrations of nanoparticles or salt increase this yield stress, demonstrating controlled rheological behavior.
Area of Science:
- Materials Science
- Colloid Science
- Rheology
Background:
- Kaolinite suspensions typically aggregate and settle without additives.
- Previous work focused on structural changes induced by silica nanoparticles.
Purpose of the Study:
- To investigate the rheological behavior of kaolinite suspensions with added silica nanoparticles.
- To understand the gelation process and yield stress development.
Main Methods:
- Rheological measurements of kaolinite suspensions with varying silica nanoparticle and NaCl concentrations.
- Analysis of complex viscosity and phase lag over time.
Main Results:
- Addition of silica nanoparticles and salt stabilizes kaolinite suspensions.
- Gelation and yield stress development occur above critical concentrations of nanoparticles and salt.
- Yield stress increases with higher nanoparticle or salt concentrations, exceeding 3500 Pa in some cases.
- Gelation exhibits two time scales: rapid initial increase in viscosity, followed by gradual rise.
- Phase lag measurements indicate transitions between viscous and elastic states.
Conclusions:
- Silica nanoparticles and salt act as stabilizers for kaolinite suspensions.
- Controlled gelation and tunable yield stress are achievable by adjusting nanoparticle and salt concentrations.
- The rheological transitions are characterized by distinct time-dependent viscosity changes and phase behaviors.
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