Liu, E. and Dore, J.C. and Webber, J.B.W. and Khushalani, S. and Findenegg, G.H. and Hansen, T. (2006) Neutron diffraction and NMR relaxation studies of structural variation and phase transformations for water/ice in SBA-15 silica: I. The over-filled case. Journal of Physics-condensed Matter, 18 (44). pp. 10009-10028. ISSN 0953-8984.
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| Official URL http://www.iop.org/EJ/abstract/0953-8984/18/44/003... |
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Abstract
Neutron diffraction and NMR relaxation measurements have been made of water/ice in SBA-15, a mesoporous silica constituting an ordered array of cylindrical mesopores of pore diameter similar to 86 angstrom, over the temperature range 180-300 K in a cooling and heating cycle. The over-filled sample shows the initial formation of hexagonal ice on the outside of the silica grains, followed by the nucleation of cubic ice inside the pores at a lower temperature. Neutron scattering profiles for the cubic ice peaks are significantly broadened and indicate a defective structure, as observed in previous experiments on ice formation in sol-gel and MCM-type silicas. Below the pore freezing temperature the intensity of the cubic ice peaks exhibit a significant increase, down to the lowest experimental temperature, indicating a reversible conversion of defective ice to ordered ice crystals. The peak profile analysis for the two ice patterns indicates a systematic variation in the position as a function of temperature, giving values of the expansion coefficients that are slightly lower than other measurements for the bulk phase. NMR results on proton relaxation as a function of temperature indicate the presence of a mobile phase for temperatures below pore freezing that supports the view that there is interconversion between brittle and plastic phases of ice.
| Item Type: | Article |
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| Subjects: | Q Science > QC Physics |
| Divisions: | Faculties > Science Technology and Medical Studies > School of Physical Sciences > Functional Materials Group |
| Depositing User: | J.B.W. Webber |
| Date Deposited: | 17 Mar 2009 20:06 |
| Last Modified: | 06 Sep 2011 01:07 |
| Resource URI: | http://kar.kent.ac.uk/id/eprint/13464 (The current URI for this page, for reference purposes) |
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