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Dec 5, 2008 4:00 pm - 5:00 pm (Friday)
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By: Chemistry, Department of
Cost: Free Location: Corcoran 101 The fast scanning calorimetry (FSC) apparatus was employed to investigate glass transition phenomena in vapor deposi...
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Event details: Fast Scanning Calorimetry Studies of Amorphous Solid Water
Description
By: Chemistry, Department of
Cost: Free
Location: Corcoran 101
The fast scanning calorimetry (FSC) apparatus was employed to investigate glass transition phenomena in vapor deposited amorphous solid water (ASW) films doped with acetic acid, pentanol, and carbon tetrachloride. In all three cases, FSC thermograms of doped ASW films show well pronounced glass transitions at temperatures near 177 K. Systematic FSC measurements of the glass transition temperature and the excess heat capacity dependence on the concentration of impurities indicate the possible existence of two distinct non-crystalline phases of H2O in binary aqueous solutions. According to our conjecture, bulk pure ASW is a glass at temperatures up to its crystallization at temperatures near 205 K. However, a guest molecule in the ASW matrix may be enveloped in ultraviscous liquid water at temperatures as low as 136 K. In the case of CH3COOH, we estimate that such a viscous shell contains approximately 25 H2O molecules. This seminar will discuss the implications of these findings for past studies of molecular kinetics in pure vitreous water and in binary aqueous solutions.
Cost: Free
Location: Corcoran 101
The fast scanning calorimetry (FSC) apparatus was employed to investigate glass transition phenomena in vapor deposited amorphous solid water (ASW) films doped with acetic acid, pentanol, and carbon tetrachloride. In all three cases, FSC thermograms of doped ASW films show well pronounced glass transitions at temperatures near 177 K. Systematic FSC measurements of the glass transition temperature and the excess heat capacity dependence on the concentration of impurities indicate the possible existence of two distinct non-crystalline phases of H2O in binary aqueous solutions. According to our conjecture, bulk pure ASW is a glass at temperatures up to its crystallization at temperatures near 205 K. However, a guest molecule in the ASW matrix may be enveloped in ultraviscous liquid water at temperatures as low as 136 K. In the case of CH3COOH, we estimate that such a viscous shell contains approximately 25 H2O molecules. This seminar will discuss the implications of these findings for past studies of molecular kinetics in pure vitreous water and in binary aqueous solutions.
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