Neutron spin echo measurements of monolayer and capillary condensed water in MCM-41 at low temperatures

Neutron spin echo measurements of monolayer and capillary condensed heavy water (D2O) confined in MCM-41 C10 (pore diameter 2.10 nm) were performed in a temperature range of 190-298 K. The intermediate scattering functions were analyzed by the Kohlrausch-Williams-Watts stretched exponential function...

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Bibliographic Details
Published in:Journal of physics. Condensed matter 2012-02, Vol.24 (6), p.064101-20
Main Authors: Yoshida, K, Yamaguchi, T, Kittaka, S, Bellissent-Funel, M-C, Fouquet, P
Format: Article
Language:English
Subjects:
Capillarity
Condensed matter
Condensing
Crossovers
Deuterium Oxide - chemistry
Dynamics
Mathematical analysis
Monolayers
Neutrons
Porosity
Silicon Dioxide - chemistry
Temperature
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Summary:Neutron spin echo measurements of monolayer and capillary condensed heavy water (D2O) confined in MCM-41 C10 (pore diameter 2.10 nm) were performed in a temperature range of 190-298 K. The intermediate scattering functions were analyzed by the Kohlrausch-Williams-Watts stretched exponential function. The relaxation times of confined D2O in the capillary condensed state follow remarkably well the Vogel-Fulcher-Tammann equation between 298 and 220 K, whereas below 220 K they show an Arrhenius type behavior. That is, the fragile-to-strong (FTS) dynamic crossover occurs, which has never been seen in experiments on bulk water. On the other hand, for monolayer D2O, the FTS dynamic crossover was not observed in the temperature range measured. The FTS dynamic crossover observed in capillary condensed water would take place in the central region of the pore, not near the pore surface. Because the tetrahedral-like water structure in the central region of the pore is more preserved than that near the pore surface, the FTS dynamic crossover would be concerned with the tetrahedral-like water structure.
ISSN:0953-8984
1361-648X
DOI:10.1088/0953-8984/24/6/064101