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| 2. |
- Andersson, Ove, et al.
(författare)
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Glass Transitions in Pressure-Collapsed Ice Clathrates and Implications for Cold Water
- 2012
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Ingår i: The Journal of Physical Chemistry Letters. - Washington : American Chemical Society (ACS). - 1948-7185. ; 3:15, s. 1951-1955
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Tidskriftsartikel (refereegranskat)abstract
- Ice is known to collapse to amorphous ice upon pressurization at low temperatures and shows the unusual feature of multiple distinct solid amorphous water states, which have inspired models of liquid water’s structure and unusual properties.Here, we use heat capacity Cp measurements to show that similarly collapsed ice clathrates display identical glass behavior as amorphous ice but that crystallization above the glass transition temperature Tg of ∼140 K at 1 GPa is inhibited. This effect of the homogeneously distributed “guest molecules” in water reveals a relatively strong reversible Cp increase above Tg but no further transition before crystallization at ∼190 K.This is consistent with a glass−liquid transition of water at Tg, which suggests a new path to study an ultraviscous liquid water network and evaluate water models
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| 3. |
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| 4. |
- Andersson, Ove, et al.
(författare)
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Unusual Grüneisen and Bridgman parameters of low-density amorphous ice and their implications on pressure induced amorphization
- 2005
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 122:12, s. 124710-
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Tidskriftsartikel (refereegranskat)abstract
- The low-temperature limiting value of the Grüneisen parameter for low-frequency phonons and the density dependence of the thermal conductivity (Bridgman parameter) of low-density amorphous (LDA) ice, high-density amorphous (HDA) ice, hexagonal ice Ih, and cubic ice Ic were calculated from high-pressure sound velocity and thermal conductivity measurements, yielding negative values for all states except HDA ice. LDA ice is the first amorphous state to exhibit a negative Bridgman parameter, and negative Grüneisen parameters are relatively unusual. Since Ih, Ic, and LDA ice all transform to HDA upon pressurization at low temperatures and share the unusual feature of negative Grüneisen parameters, this seems to be a prerequisite for pressure induced amorphization. We estimate that the Grüneisen parameter increases at the ice Ih to XI transition, and may become positive in ice XI, which indicates that proton-ordered ice XI does not amorphize like ice Ih on pressurization.
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| 5. |
- Inaba, Akira, et al.
(författare)
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Multiple glass transitions and two step crystallization for the binary system of water and glycerol
- 2007
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Ingår i: Thermochimica Acta 461, issue 1-2. - : Elsevier BV. ; , s. 44-49
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Konferensbidrag (refereegranskat)abstract
- Glass formation/crystallization phenomena were studied in water and glycerol mixtures using adiabatic calorimetry. The sample was cooled rapidly from room temperature and its thermal response was followed on heating from 80 to 300 K. The binary mixtures with the glycerol contents more than 55% (w/w) (19 mol%) yielded the homogeneous glassy states, consisting of randomly mixed water and glycerol molecules. Their glass transition temperatures showed the composition dependence of the Gordon-Taylor equation, and extrapolated exactly to that of pure water (135 K). The mixtures in the 0-55% (w/w) glycerol range crystallized partly on cooling and exhibited three anomalies in the temperature drift rate on heating. The first of these three is associated with the onset of reorientational motions of water molecules in the hexagonal ice which increases from 107 to 120 K on increasing the glycerol composition. The second is the composition independent temperature of 164 K that corresponds to the mixture with 76% (w/w) glycerol (38 mol%, known as the maximally freeze-concentrated solution), which is the mixture with the maximum composition of water that can be cooled without crystallization. The third is associated with the ice crystallization followed by ice dissolution in the range 185-202 K. In addition, the sample with 60% (w/w) glycerol composition (23 mol%) exhibited two distinguishable exothermic peaks on heating. The initial one is large and is attributed to crystallization into a novel two-dimensionally ordered structure of ice, and the second is due to the transformation of the layered structures into the hexagonal ice.
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| 6. |
- Palacios, Oscar D. Camacho, et al.
(författare)
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Low-temperature heat capacity of a two-dimensionally ordered structure of ice crystallized from glycerol aqueous solutions
- 2010
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Ingår i: Thermochimica Acta. - : Elsevier BV. - 0040-6031 .- 1872-762X. ; 500:1-2, s. 106-110
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensionally ordered structure of ice crystallized from a glycerol 55% (w/w) aqueous matrix has been studied by adiabatic calorimetry. Its heat capacity was measured between T = 5 K and T = 15 K and found to be consistently larger than that of hexagonal ice (ice Ih) by an average of 1.3%. The composition and the heat capacity of the maximally freeze-concentrated solution, i.e. the non-crystallizing glycerol-rich phase that remains after water's partial crystallization, were also investigated.
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| 7. |
- Sundqvist, Bertil, et al.
(författare)
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Physical properties of pressure polymerized C60
- 1996
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Ingår i: Fullerenes: Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, volume 3. - Pennington, NJ : The Electrochemical Society. - 1566771625 ; , s. 1014-1028
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Konferensbidrag (refereegranskat)abstract
- We present in this paper an overview of the physical properties of the high pressure polymerized C60 phase commonly known as "soft fcc". This phase has been studied by several methods over wide ranges in temperature T and/or pressure, p. We present here experimental information about the specific heat capacity, the thermal expansion coefficient, the lattice structure, and the thermal conductivity, and we also show results obtained by NMR and Raman spectroscopy. All data presented agree with the accepted model that the individual molecules in this phase are covalently bound to form linear molecular chains. In particular, the NMR data show clearly the presence of covalent bonds, and the Raman data exhibit several new lines at very low energies connected with chain vibrations. Thermal conductivity data obtained during polymerization show both the time dependence of the process and that polymerization occurs at lower p and T than observed previously for this phase.
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