Grand Séminaire d'Institut

Vendredi 14 Septembre 2018 à 11h00.

Objects interacting with solidification fronts: from materials science to geophysics and biology

''The processing of porous materials by ice-templating has received a great deal of attention during the past decade. This simple process, where a material suspension is simply frozen and then sublimated, provides materials with unique porous architectures, where the porosity is almost a direct replica of the ice crystals. The basic principle of ice-templating is the assembly of a second phase, usually particles, triggered by their progressive concentration increase in the inter-crystal space. This concentration mechanism can be used to induce ordering or self-assembly of various types of building blocks between the ice crystals, providing thus materials with an increasingly elaborate architecture with improved functional properties. I will present first a few examples of such materials and phenomena investigated in our group.
The interaction of objects with a moving solidification front is nevertheless a common feature of many industrial and natural processes such as metal processing, the growth of single crystals, the cryopreservation of cells, or the formation of sea ice. Interaction of solidification fronts with objects leads to different outcomes, from total rejection of the objects to their complete engulfment. It is however still fundamentally difficult to track in situ the development of 3D solidification microstructures where objects interact with a solid/liquid interface, even more so in the presence of solute effects. I will discuss how the recent developments in the lab with cryoconfocal microscopy, such as freezing emulsions, help us make progress in these domains and revisit some of these old but still relevant problems.
References:
- Deville, S. (2017). Freezing colloids: observations, principles, control, and use: applications in materials science, life science, earth science, food science, and engineering. Springer.
- Freezing-induced self-assembly of amphiphilic molecules. Soft Matter (2017)
- Five-dimensional imaging of freezing emulsions with solute effects. Science (2018)
- A temperature-controlled stage for laser scanning confocal microscopy and case studies in materials science. Ultramicroscopy (2018)
- Multiphase imaging of freezing particle suspensions by confocal microscopy. Journal of the European Ceramic Society (2018)
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