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Small‐angle neutron scattering studies of water and ice in porous Vycor glass
Author(s) -
Li J.C.,
Ross D. K.,
Benham M. J.
Publication year - 1991
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889891001929
Subject(s) - scattering , small angle neutron scattering , neutron scattering , capillary condensation , adsorption , hysteresis , materials science , desorption , porous glass , porosity , porous medium , small angle scattering , chemistry , chemical physics , analytical chemistry (journal) , mineralogy , optics , condensed matter physics , composite material , chromatography , physics
Small‐angle neutron scattering has been used to study both water condensation and freezing/ defreezing processes in porous Vycor glass. When the system is partially saturated with a matched D 2 O/H 2 O water mixture, an interesting new feature appears in the scattering which gives a straight line on a log‐log plot of scattering intensity versus scattering vector, Q . This feature extends over about one and half orders of magnitude in Q , but with a substantially different gradient for desorption and adsorption, the gradients being 1.75 ± 0.1 and 0.5 ± 0.1 respectively. The overall form of the scattering is modelled in terms of a percolating system of empty pores connected to the surface during desorption and of a random distribution of clusters of filled pores on adsorption. Further, when water in porous Vycor undergoes a freezing/defreezing cycle, the density of the water changes gradually over a large temperature range and there is also ~ 10 K hysteresis between the freezing and defreezing processes.