Studies of water and ice in hydrophilic and hydrophobic mesoporous silicas: pore characterisation and phase transformations
- 28 January 2010
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 12 (12), 2838-2849
- https://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 ∼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.Keywords
This publication has 25 references indexed in Scilit:
- Studies of nano-structured liquids in confined geometries and at surfacesProgress in Nuclear Magnetic Resonance Spectroscopy, 2010
- Hydration water rotational motion as a source of configurational entropy driving protein dynamics. Crossovers at 150 and 220 KPhysical Chemistry Chemical Physics, 2008
- Solid−Liquid Interfacial Free Energy of Water: A Molecular Dynamics Simulation StudyJournal of Chemical Theory and Computation, 2007
- The Three-Dimensional Structure of Water Confined in Nanoporous Vycor GlassThe Journal of Physical Chemistry B, 2007
- Curvature-dependent metastability of the solid phase and the freezing-melting hysteresis in poresPhysical Review E, 2006
- Increasing the hydrothermal stability of mesoporous SiO2 with methylchlorosilanes—a ‘structural’ studyMicroporous and Mesoporous Materials, 2006
- Organic nanocrystals: an NMR study of cyclohexane in porous silicaMolecular Physics, 1998
- The Scattering of Neutrons by Systems of Heavy NucleiPhysical Review B, 1952
- The Determination of Pore Volume and Area Distributions in Porous Substances. I. Computations from Nitrogen IsothermsJournal of the American Chemical Society, 1951
- Adsorption of Gases in Multimolecular LayersJournal of the American Chemical Society, 1938