Issue Eur. Phys. J. AP Volume 22, Number 1, April 2003 Page(s) 21 - 28 Section Plasmas, Discharges and Processes DOI 10.1051/epjap:2003011 Published online 25 February 2003

Eur. Phys. J. AP 22, 21-28 (2003)
DOI: 10.1051/epjap:2003011

Differential scanning calorimetry and X-ray diffraction study of water confined in silica gel for several levels of hydration

A. Fouzri, R. Dorbez-Sridi and M. Oumezzine

Laboratoire de Physico-Chimie structurale, Département de Physique, Faculté des Sciences de Monastir, 5019 Monastir, Tunisia

habfay@yahoo.fr

(Received: 15 November 2001 / Revised in final form: 28 May 2002 / Accepted: 12 December 2002 Published online: 25 February 2003 )

Abstract
Differential scanning calorimetry (DSC) and X-ray scattering measurements on water confined in silica gel is studied for several levels of hydration at room temperature and down to 77 K. The DSC analysis of water confined in silica gel in function of the level of hydration shows that the solidification of water inside the pore is sensitive to the pore opening but the fusion is closely related to the curve of the pore. The X-ray pair correlation function showed the presence of a distorted tetrahedral-like hydrogen-bonded network of water characterized by the peaks at ~2.8, ~4.1 and ~4.9 Å. This distortion is caused by the competition between confinement effect and silica-water interaction. To eliminate the contribution of the water-silica gel interaction we have determined the structure of confined water by subtraction of the feebly hydrated silica gel from that strongly hydrated sample. The pair correlation function of extracted water show an oxygen-oxygen correlation at 3.8 Å. A similar peak is observed in the case of water confined in polyHEMA, in charcoal and at vicinity of myoglobin.

PACS
61.20.-p - Structure of liquids.
61.30.Pq - Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems.
64.70.Dv - Solid-liquid transitions.

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