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Issue 12, 2010
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Studies of water and ice in hydrophilic and hydrophobic mesoporous silicas: pore characterisation and phase transformations

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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 ∼50 Å. 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.

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

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Article information


Submitted
27 Apr 2009
Accepted
10 Dec 2009
First published
28 Jan 2010

Phys. Chem. Chem. Phys., 2010,12, 2838-2849
Article type
Paper

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

J. Jelassi, H. L. Castricum, M. Bellissent-Funel, J. Dore, J. B. W. Webber and R. Sridi-Dorbez, Phys. Chem. Chem. Phys., 2010, 12, 2838
DOI: 10.1039/B908400B

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