2006 Fiscal Year Final Research Report Summary
Studies on the critical crystallite size of ice and glassy states in mesoporous confinement
| Project/Area Number |
17550022
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Okayama University of Science |
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Principal Investigator |
KITTAKA Shigeharu Okayama University of Science, Faculty of Science, Professor, 理学部, 教授 (60068905)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAHARA Shuichi Okayama University of Science, Faculty of Science, Lecturer, 理学部, 講師 (20289135)
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| Project Period (FY) |
2005 – 2006
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| Keywords | physical properties of the surface / water / dynamics / porous materials / nanostructure / glassy water / critical size / liquid-liquid transition |
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| Research Abstract |
When the water is condensed in fine pores, it is frozen and molten at the temperatures lower than those of bulk water. Effect of pore size on this phenomenon has been explained by classical Gibbs-Thomson relation. Present work has investigated this phenomena in detail through DSC measurements by use of mesoporous silica, MCM-41 and SBA-15, which have well-regulated pore sizes, and suggested the limit of applicability of the relation. Furthermore, thermodynamic analysis of the heat of melting presented an interfacial free energy change indicating a phase change in the supercooled water around at 230 K. It was also confirmed that water molecules does not freeze to crystalline ice in the pores below 2.1 nm, that is, they are frozen as glassy ice.
Dynamic property (translational motion) of heavy water confined in the pore of MCM-41 (d=2.1 nm) was investigated by using neutron spin echo measurement. It was found that water molecules are mobile at temperatures down to 200 K. Relaxation times of translational motion analyzed by KWW function changed the mode of temperature dependence around at 229 K, above which it obeys the Vogel Fulcher Tamman relation and below which the Arrhenius relation. This fact suggests that supercooled water in fine pores represents a liquid-liquid transition. The transition has been suggested just by molecular dynamic simulation in the noman's land region of temperatures and has not been realized by experiments with bulk water. And thus, we can conclude that one can prepare the noman's land in water in confinement.
Critical minimum size of ice crystallite was estimated to be 2.2 nm in the acetonitrile-water mixture confined in the MCM-41 mesopore of 2.4
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Research Products
(19 results)
