BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Memento EPFL//
BEGIN:VEVENT
SUMMARY:Transport phenomena in silicate melts: chemical diffusion and phas
 e separation
DTSTART:20160404T131500
DTEND:20160404T141500
DTSTAMP:20260930T201959Z
UID:4c415f3dd8f97ba1258e926d51a677c8275481ac0a1f8454a5b04481
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Emmanuelle Gouillard\, Saint Gobain Recherche\, Aubervil
 liers France\nCo-authors: Ekaterina Burov\, Marie-Hélène Chopinet\, Cori
 nne Claireaux (SVI)\, David Bouttes et Damien Vandembroucq\, PMMH (ESPCI)\
 , Michael Toplis (Observatoire Midi-Pyrénées)\nIn this lecture\, I will 
 present two different studies of transport phenomena conducted at high tem
 perature in silicate melts.\nThe structure of silicate melts is that of a 
 strongly polymerized network of silica tetrahedra\, with additional degree
 s of freedom given by cations known as network modifiers. In such a constr
 ained system\, the diffusion of chemical species cannot be considered inde
 pendent\, and couplings between species have to be taken into account. Ins
 tead of independent diffusion coefficients\, one has to consider a diffusi
 on matrix\, which relates the flux of one element to the gradients of all 
 elements. We\nstudied chemical diffusion in the quaternary system Na2O - C
 aO - SiO2 - Al2O3\, of interest to industrial glass melting as well as geo
 chemistry. Diffusion experiments between melts of different initial compos
 itions were realized\, and chemical profiles were measured thanks to elect
 ron microprobe. The set of all chemical profiles is used to determine the 
 complete diffusion matrix. From the diffusion matrix\, eigenvectors and ei
 genvalues can be extracted. They are interpreted respectively as combinati
 ons of elements that rearrange cooperatively for diffusion to proceed\, an
 d as the probabilities of such exchanges. Eigenvalues of strikingly differ
 ent magnitudes are found\, confirming that fast and very slow diffusion pr
 ocesses operate simultaneously in the melts.\nSecondly\, we studied the ki
 netics and the morphology of phase-separated domains during coarsening in 
 barium borosilicate melts\, using in situ synchrotron  microtomography to
  characterize the 3-D microstructure of the phases. Quantitative geometric
 al measurements and direct observations demonstrate that  viscous coarsen
 ing is the dominant mechanism governing the evolution of the bicontinuous 
 structure. This mechanism results in a linear growth of domain size with t
 ime\, much faster than the t^1/3 growth associated to diffusive mechanisms
 \, that have been observed so far in silicates. Complementary experiments 
 show that diffusive mechanisms\nare negligible compared to viscous coarsen
 ing at such high temperatures\, in contrast to experiments of the literatu
 re performed closer to the glass transition. Furthermore\, we observe a pr
 ogressive fragmentation of one of the percolating phases\, that we relate 
 to the important viscosity contrast between phases.\nBio: Emmanuelle Gouil
 lart is currently the head of the joint unit CNRS/Saint-Gobain Surface of 
 Glass and Interfaces\, a lab dedicated to basic research on topics relevan
 t for the industry.\nAfter graduating in theoretical physics at Ecole Norm
 ale Supérieure in Paris\, she did her PhD on chaotic mixing in viscous fl
 uids between Imperial College and CEA Saclay and graduated in 2007. In 200
 8\, she joined the R&D center Saint-Gobain Recherche to work in their join
 t unit with CNRS (an academic lab)\, and start a research program on glass
  melting. She took over the direction of the joint unit in 2013.\nHer rese
 arch activities are on glass melting\, phase separation and diffusion in s
 ilicate glass. She is a frequent user of synchrotron ultrafast microtomogr
 aphy\, an imaging technique used to study the evolution of phases in mater
 ials such as silicate melts\, in situ at high temperature. Her strong focu
 s on imaging techniques led her to contribute to and develop scikit-image\
 , a major open-source image processing library for the Python language.
LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201
STATUS:CONFIRMED
END:VEVENT
END:VCALENDAR