Studies of water and ice in hydrophilic and hydrophobic mesoporous silicas: pore characterisation and phase transformations.

Jelassi, J. and Castricum, H.L. and Bellissent-Funel, M-C. and Dore, J.C. and Webber, J.B.W. and Sridi-Dorbez, R. (2010) Studies of water and ice in hydrophilic and hydrophobic mesoporous silicas: pore characterisation and phase transformations. Physical Chemistry Chemical Physics, 12 . pp. 2838-2849. ISSN 1463-9076. (Access to this publication is restricted)

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Abstract

A study has been made as a function of temperature of the phase transformation of water and ice in two samples of mesoporous silica gel with pore diameters of B50 A ˚ . One sample was modified by coating with a layer of trimethylchlorosilane, giving a predominantly hydrophobic internal surface, whereas the unmodified sample has a hydrophilic interface. The pore structure was characterised by nitrogen gas adsorption and NMR cryoporometry and the melting/freezing behaviour of water and ice in the pores was studied by DSC and neutron diffraction for cooling and heating cycles, covering a range of 200 to 300 K. Measurements were made for several filling-factors in the range 0.2 to 0.9. The results show a systematic difference in the form of ice created in each of the samples. The non-modified sample gives similar results to previous studies with hydrophilic silicas, exhibiting a defective form of cubic ice superimposed on a more disordered pattern that changes with temperature and has been characterised as ‘plastic’ ice [Liu et al., 2006, Webber et al., 2007]. The modified sample has similar general features but displays important variability in the ice transformation features, particularly for the case of the low filling-factor (f = 0.2). The results exhibit a complex temperature-dependent variation of the crystalline and disordered components that are substantially altered for the different filling-factors.

Item Type: Article
Subjects: Q Science > QC Physics > QC176.8.N35 Nanoscience, nanotechnology
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group
Depositing User: J.B.W. Webber
Date Deposited: 26 Oct 2010 13:51
Last Modified: 04 May 2012 14:36
Resource URI: http://kar.kent.ac.uk/id/eprint/25820 (The current URI for this page, for reference purposes)
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