| 1. |
- Andersson, Ove, et al.
(författare)
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Phase behavior and thermal conductivity of urea at pressures up to 1 GPa and at temperatures in the range 50–370 K
- 1994
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Ingår i: International journal of thermophysics. - : Plenum Publishing. - 0195-928X .- 1572-9567. ; 15:3, s. 513-524
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity of the solid phases I and III of urea was measured at temperatures in the range 50-370 K for pressures up to 1 GPa. Phase III, previously detected only at pressures above 0.5 GPa, was observed here at low pressures (< 0.07 GPa) below about 230 K. Extrapolation of the I-III phase line indicates that phase III might be obtained at 218 K at atmospheric pressure and, consequently, that urea might exhibit two solid phases at atmospheric pressure. The temperature dependence of the thermal conductivity of both phase I and phase III could be described by the Debye model for thermal conductivity assuming phonon scattering by three phonon umklapp processes only. Despite a volume decrease at the I --> III transition, the thermal conductivity decreased by about 20%. Normally, thermal conductivity increases at a phase transition at which volume decreases. This rather unusual behavior of urea might be due to an increase in the nearest-neighbor distance at the I --> III transition.
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| 2. |
- Andersson, Ove, et al.
(författare)
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Thermal conductivity of low-density amorphous ice
- 1994
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Ingår i: Solid State Communications. - : Elsevier. - 0038-1098 .- 1879-2766. ; 91:12, s. 985-988
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ of low-density amorphous ice was measured using the transient hot-wire method in the temperature range 70–135 K at a pressure of 0.1 GPa. The amorphous state was formed at 135 K by pressurising hexagonal ice up to about 1 GPa. The results for λ are roughly temperature and pressure independent and in magnitude about 0.6 W m−1 K−1, which is roughly equal to λ for water. These results for λ of amorphous ice are several orders of magnitude larger than those reported recently for a specimen prepared by a vapour deposition technique.
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| 3. |
- Andersson, Ove, et al.
(författare)
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Thermal conductivity of the Ih and XI phases of ice
- 1994
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Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 50:10, s. 6583-6588
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ of KOH-doped ice was measured using the transient hot-wire method at temperatures in the range 55–250 K and at pressures up to 0.15 GPa. With an isobaric increase of temperature at 0.08 GPa, λ decreased 17% at about 74 K. This decrease is associated with the known transition from ordered phase XI to phase Ih which exhibits orientational disorder of H2O. A model for λ indicates that the decrease of λ at the transition is due to an increase of the lattice anharmonicity which might be caused by the disorder in phase Ih. It was inferred from the temperature dependence of λ that phonon scattering in both phases Ih and XI is dominated by three phonon umklapp processes. At 58 K, λ of supercooled phase Ih decreased slightly with increasing pressure whereas λ of phase XI was independent of pressure.
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| 4. |
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| 5. |
- Sundqvist, Bertil, et al.
(författare)
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Structure, disorder, and phase diagram of C60 up to 1 GPa and below 300 K
- 1994
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Ingår i: High Pressure in Material Science and Geoscience. - Praha, Czech Republic : Prometheus. - 8085849933 ; , s. 109-112
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Konferensbidrag (refereegranskat)abstract
- We have measured the compressibility and the thermal conductivity of C60 in the range below 300 K and up to 1 GPa (10 kbar). From the data obtained we have deduced the p-T phase diagram of C60. Literature data show that the ratio of pentagon-to-hexagon oriented molecules in the orientationally ordered phase decreases with increasing pressure, and from our data we conclude that C60 forms a new, completely "hexagon oriented" phase above 0.6 GPa at 150 K, or 1.2 GPa at 300 K. The glass transition temperature (90 K at atmospheric pressure) is found to increase by 54 K/GPa.
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