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Microstructure evolution in magnetorheological suspensions governed by Mason number
Sonia Melle1, Oscar G Calderón, Miguel A Rubio
1Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, USA.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 20, 2003
Summary
In dilute colloidal suspensions, high Mason numbers prevent particle chaining under rotating magnetic fields, leading to isotropic clusters. This behavior is independent of particle concentration, as confirmed by simulations and experiments.
Area of Science:
- Colloid science
- Soft matter physics
- Magnetohydrodynamics
Background:
- Polarizable colloidal suspensions exhibit complex structures under external fields.
- Understanding particle aggregation dynamics is crucial for material science applications.
Purpose of the Study:
- To investigate the spatiotemporal evolution of field-induced structures in colloidal suspensions.
- To determine the influence of rotating magnetic fields and Mason number on particle aggregation.
- To explore the role of volume fraction in suspension dynamics.
Main Methods:
- Experimental study using video microscopy.
- Scattering dichroism experiments for concentrated and dilute suspensions.
- Brownian particle dynamics simulations.
Main Results:
- A crossover Mason number was identified, above which particle chaining is suppressed.
- Higher Mason numbers promote the formation of isotropic clusters and isolated particles.
- The observed dynamics and crossover Mason number are independent of the volume fraction.
Conclusions:
- Rotating magnetic fields can control particle assembly in colloidal suspensions.
- The dynamics of field-induced structures are largely independent of suspension concentration.
- Simulations validate experimental findings on particle aggregation behavior.