Low-temperature dielectric measurements of confined water in porous granites

• Main Author: Silva, Hugo
• Publication Date: 2014
• Other Authors: Prezas, Pedro, Vinagre, Ana, Graça, Manuel F., Monteiro, Jorge H., Tlemçami, Mouhadyne, Moita, Patrícia, Pinho, António, Bezzeghoud, Mourad, Sushil, Mendiratta, Rosa, Rui
• Format: Conference object
• Language: por
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10174/13624
• topic: dielectric measurements; granites

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