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| Titel |
Diffusion of water in the mesoporosity of a dry clay: an experimental study using space and time resolved X-ray diffraction |
| VerfasserIn |
Henrik Hemmen, Lars Ramstad Alme, Jon Fossum, Yves Meheust |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056643
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| Zusammenfassung |
| We use space- and time-resolved X-ray diffraction as a tool for imaging the humidity content
of a clay sample in situ, in a non-invasive manner. Imposing a humidity gradient between the
two ends of a quasi-onedimensional temperature controlled weakly-hydrated sample of
synthetic swelling clay, we follow the transport of water by monitoring the individual particle
swelling.
Indeed, the swelling clay grains are nano-layered, that is, they consist of stacks of
individual 1 nm-thick clay particles. They have the ability to incorporate water molecules in
the nano-porosity between the layers, causing the interlayer repetition distance (d-spacing) of
the stacks to depend on temperature and on the humidity present in the surrounding
meso-porosity. A first experiment performed under controlled constant temperature and
controlled humidity level all around the sample, varying the ambient relative humidity by
steps, allows us to map the monotonous evolution of the d-spacing as a function of the
relative humidity surrounding the clay.
The reproducibility and reliability of this relative humidity-controlled d-shift enables
us to use d as a measure of the local humidity surrounding the clay particles in
the second experiment, which addresses quasi-onedimensional water transport in
the clay. In this second experiment, we map the d-spacing in space and time as
water progresses along the sample, and are able to extract profiles of the relative
humidity along the sample length. Their time evolution describes the transport of
water through the mesoporous space inside the clay: An analysis of the measured
humidity profiles based on the Boltzmann transform, under certain simplifying
assumptions, yields a diffusive behavior that is either normal or possibly weakly
anomalous.
References:
G. Løvoll, B. Sandnes, Y. Méheust, K. J. Måløy, J. O. Fossum, G. J. da Silva,
M. S. P. Mundim, R. Droppa, D. M. Fonseca, Dynamics of water intercalation
fronts in a nano-layered synthetic silicate: a synchrotron X-ray scattering study,
Physica B 370, 90-98 (2005).
Y. Méheust, G. Løvoll, B. Sandnes, K. J. Måløy, J. O. Fossum, G. J. da Silva, M.
S. P. Mundim, R. Droppa, D. M. Fonseca, Using synchrotron X-ray scattering
to study the diffusion of water in a weakly hydrated clay sample, Clay Science
12(Supp. 2), 66-70 (2006).
H. Hemmen, L. R. Alme, J. O. Fossum, Y. Méheust, X-ray studies of interlayer
water absorption and mesoporous water transport in a weakly hydrated clay,
Phys. Rev. E 82, 036315 (2010). |
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