Micro-tomographie d’un borosilicate de baryum démixé : du mûrissement à la fragmentation

Abstract : We use a barium borosilicate glass as a model system to study phase separation in liquids. We consider here the coarsening process in the viscous hydrodynamical regime, where the characteristic length scale grows linearly with time : ∼ (γ/η)t, with η the viscosity and γ the interfacial tension. The system is initially bicontinuous, which is mandatory for this growth regime.X-ray microtomography experiments are performed in situ at the ID19 beamline of the European Synchrotron Radiation Facility (ESRF) in order to obtain the morphology of the domains. We developed dedicated image processing routines for the analysis of the 3D images. We computed the volumes and surface areas of the domains, chord-length distributions, the Euler characteristic as well as local mean and Gaussian curvatures. Dynamic scaling hypothesis predicts a self-similar growth, which served as a basis for the discussion of these measurements. The glass separates in two phases with a very high viscosity contrast (several orders of magnitude). The main control parameter in our experiments is then the volume fraction of the less viscous phase. When this low-viscosity phase is the minority one, it undergoes a gradual fragmentation that eventually stops the coarsening. This fragmentation process bears self-similar features, which result in a wide distribution of domains sizes. We indeed predict a power-law distribution. More generally, we observed that the coarsening process follows the dynamic scaling hypothesis as long as fragmentation remains insignificant.
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David Bouttes. Micro-tomographie d’un borosilicate de baryum démixé : du mûrissement à la fragmentation. Chimie-Physique [physics.chem-ph]. Université Pierre et Marie Curie - Paris VI, 2014. Français. ⟨NNT : 2014PA066302⟩. ⟨tel-01078337v3⟩

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