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

Jelassi, Jahwar, Castricum, Hessel L., Bellissent-Funel, Marie-Claire, Dore, John C., Webber, J. Beau W., Sridi-Dorbez, Rachida (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. (doi:10.1039/b908400b) (KAR id:25820)

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http://dx.doi.org/10.1039/b908400b

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
DOI/Identification number: 10.1039/b908400b
Subjects: Q Science > QC Physics > QC176.8.N35 Nanoscience, nanotechnology
Divisions: Divisions > Division of Natural Sciences > Physics and Astronomy
Depositing User: J.B.W. Webber
Date Deposited: 26 Oct 2010 13:51 UTC
Last Modified: 16 Nov 2021 10:04 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/25820 (The current URI for this page, for reference purposes)
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