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Periodic ice banding in freezing colloidal dispersions
Anthony M Anderson1, M Grae Worster
1Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
Langmuir : the ACS Journal of Surfaces and Colloids
|November 1, 2012
Summary
Directional solidification of alumina colloids reveals two distinct ice banding modes. Increasing freezing rates reduce ice band spacing, influencing particle aggregation and potential frozen fringe formation.
Area of Science:
- Materials Science
- Physical Chemistry
- Geophysics
Background:
- Colloidal dispersions are susceptible to phase transitions during freezing.
- Understanding ice formation in suspensions is crucial for material processing and geological phenomena.
Purpose of the Study:
- To investigate the effects of freezing rate and temperature gradient on ice banding in concentrated colloidal alumina.
- To characterize the microstructural evolution and segregation patterns during directional solidification.
Main Methods:
- Directional solidification apparatus with independent control of freezing rate and temperature gradient.
- Microscopic observation of ice segregation and particle aggregation.
- Quantitative modeling of freezing behavior and undercooling.
Main Results:
- Two distinct steady-state modes of periodic ice banding were observed.
- Ice band wavelength decreased with increasing freezing rate.
- At low rates, cracklike ice lenses formed with structured particle layers, suggesting cryosuction and frozen fringes.
- At high rates, a new, non-cracklike banding mode emerged without visible structure ahead of the bands.
Conclusions:
- Experimental findings provide insights into the mechanisms of ice lensing and particle segregation in colloidal systems.
- The study highlights the influence of freezing dynamics on the formation of ordered structures in frozen suspensions.
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