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| Titel |
Low-temperature dielectric measurements of confined water in porous granites |
| VerfasserIn |
Hugo Gonçalves da Silva, Pedro Prezas, Ana Vinagre, Manuel F. Graça, Jorge H. Monteiro, Mouhaydine Tlemçani, Patrícia Moita, António Pinho, Mourad Bezzeghoud, Sushil K. Mendiratta, Rui N. Rosa |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250097082
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| Publikation (Nr.) |
 EGU/EGU2014-12625.pdf |
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| Zusammenfassung |
| Three different granitic rocks extracted from Évora (in the south of Portugal) where used to
perform dielectric measurements in the frequency range from 100 Hz to 1 MHz and
temperatures 100 - 350 K. Thin cylindrical samples were prepared and circular electrodes
were established using silver conductive paint. A clear anomaly appears, for T ~ 200 - 220
K, in the dielectric measurements of the samples studied. This anomaly occurs
in different materials and coincides with a phase transition of supercooled water.
Tightly bounded water confined in the pores of the rock do not crystallize at 273 K,
but form a metastable liquid down to 200 - 220 K increasing water polarization.
Below this temperature water molecules solidify and polarizability decreases. The
rock presenting the most sizeable anomaly has a very low specific surface area, ~
0.09 m2g-1, and connected porosity, ~ 1.10 %. In addition, geochemical analyses
reveal almost inexistence of water molecules in its structure confirming the role of
confined water in the anomaly. Comparison between saturated, oven dried, and
vacuum dried samples is done. Finally, a logarithmic dependency of the critical
temperature for the supercooled water phase transition with the measuring frequency is
found.
The authors acknowledge the support of FCT (Portuguese Science and Technology
Foundation) through the project PTDC/GEO-FIQ/4178/2012. |
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