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| 2. |
- Andersson, Per, et al.
(författare)
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Effect of guest molecule size on the thermal conductivity and heat capacity of clathrate hydrates
- 1983
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Ingår i: Journal of Physics C: Solid State Physics. - : Institute of Physics Publishing (IOPP). - 0022-3719. ; 16:8, s. 1423-1432
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Tidskriftsartikel (refereegranskat)abstract
- Using the transient hot-wire method, we have measured both the thermal conductivity, lambda, and the heat capacity per unit volume, rho cp, for structure II clathrate hydrates of 1,3-dioxolane (DO) and cyclobutanone (CB), and compared the results with similar previous measurements for tetrahydrofuran (THF). All three clathrate hydrates showed a glass-like temperature dependence of lambda. The magnitude of lambda was small, about the same as liquid water, and decreased in the sequence DO-THF-CB which corresponds to an increase in the size of the guest molecule. There was some evidence to support the suggestion that the dominant process in the thermal resistivity was associated with excitation of rotational vibrations of the guest molecules. In all cases, the pressure dependence of lambda was unusually small. We found evidence that there was a phase transition on the CB clathrate hydrate (and almost certainly also in the DO clathrate) at 135K and 1 GPa, which are essentially the same conditions under which we previously found an analogous transition for THF. In each case, the resultant presumably metastable phase may be a new type of clathrate hydrate arising from densification of the host structure. For the three clathrates, our results for rho cp did not depend on the nature of the guest species, and at 0.1 GPa, were the same as previously found for ice Ih.
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| 3. |
- Andersson, Per, et al.
(författare)
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Thermal resistivity of ice Ih near the melting point
- 1980
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Ingår i: Journal of Physics C: Solid State Physics. - : Institute of Physics Publishing (IOPP). - 0022-3719 .- 1747-3802. ; 13:4, s. L73-L76
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Tidskriftsartikel (refereegranskat)abstract
- The thermal resistivity r(T) of ice Ih has been re-measured from 120K to as close as practicable to melting. Measurements were made under isobaric conditions at a pressure of 0.07 GPa, and corrected to isochoric conditions. The resultant deviation from the simple theoretical prediction, r/T=constant, has been plausibly accounted for by interaction between optic and acoustic phonons. Thermal resistivity arising from the presence of point defects has been shown to be of negligible importance.
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| 4. |
- Fransson, Åke, et al.
(författare)
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Thermal conductivity, heat capacity and phase stability of solid sodium chlorate (NaClO3) under pressure
- 1983
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Ingår i: Journal of Physics C: Solid State Physics. - : Institute of Physics Publishing (IOPP). - 0022-3719. ; 16:15, s. 2861-2869
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity, lambda, and the specific heat capacity at constant pressure, cp, have been measured for solid sodium chlorate (NaClO3) in the temperature range 100-300K. Differential scanning calorimetry (DSC) was used to measure cp at atmospheric pressure, whilst the transient hot-wire method was used to measure simultaneously both lambda and the heat capacity per unit volume, rho cp, up to a pressure of 2 GPa. We found that our measured DSC values of cp exceeded those previously predicted from a lattice dynamical model, consistent with a previous prediction of disorder in Cl atom positions at high temperatures. However, such disorder, if it exists, did not affect the transport of heat, since we found that lambda (T) under isochoric conditions appeared to be determined entirely by three-phonon umklapp interactions. We found no evidence for a phase transition in NaClO3 up to 2 GPa at 300K, contrary to some previous results. However, we did observe an explosive chemical instability to occur at about 1 GPa and 130K.
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| 5. |
- Håkansson, Björn, et al.
(författare)
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Thermal conductivity and heat capacity of solid LiBr and RbF under pressure
- 1989
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 1:25, s. 3977-3985
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity λ and the heat capacity ρcp per unit volume of solid LiBr and RbF have been measured over the temperature T range 100-400 K and at pressures p up to 2 GPa, using the transient hot-wire method. The results are compared with recent theoretical calculations. A predicted drop of λ(T) below T-1 dependence is observed for LiBr.
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