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. (Access to this publication is restricted)
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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.
|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)|