| 31. |
|
|
| 32. |
- Andersson, Ove, et al.
(författare)
-
A high-pressure study of PMMA-based gels with and without TiO2 nano-particle filler: a filler induced change in the activation volume
- 2005
-
Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 50:16-17, s. 3217-3223
-
Tidskriftsartikel (refereegranskat)abstract
- The ionic conductivity σ of PMMA-based gels with and without nano-particle filler has been investigated at elevated pressure up to 0.9 GPa and in the temperature range 220-330 K to determine the effect of pressure and to obtain the activation volume. Both gels had molar ratios: EC:PC:LiClO 4 :PMMA 53.9:22:5.2:18.9, and one gel contained 8 wt.% TiO 2 nano-particles. At room temperature and atmospheric pressure, the conductivity of the gel with filler is almost the same as that for the gel without filler. At increasing pressure p, σ(p) for both gels exhibits an abrupt change, which is associated with a transition, and consequently there is a pressure induced change in the activation volume for both gels. The activation volume ΔV * in low-pressure state is the same for the gels with and without filler and about 14 cm 3 mol -1 at room temperature, which is typical liquid-like behaviour. In the high-pressure state, ΔV * = 42 and 45.3 cm 3 mol -1 at 294 K for the gels with and without filler, respectively. The results show that the ionic movements are restricted by the rigid environment of the high-pressure state and that the filler affects ΔV * under this condition. In particular, the filler appears to improve the cation transport number as a results of a decreased mobility of large-sized ions in the rigid environment of the high-pressure state. © 2004 Elsevier Ltd. All rights reserved.
|
|
| 33. |
- Andersson, Ove, et al.
(författare)
-
A low-temperature high-pressure apparatus with a temperature control system
- 1992
-
Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 10:4, s. 599-606
-
Tidskriftsartikel (refereegranskat)abstract
- A low-temperature high-pressure apparatus was designed using commercial cryogenic equipment. Pressures up to 1 GPa and temperatures down to 40 K can be obtained in a volume of up to 30 cm3. The apparatus is of the piston-cylinder type with a piston diameter of 45 mm, and the pressure can be varied at all temperatures, An adaptive temperature control system keeps the temperature inside the pressure cylinder constant to within ±0.1 K.
|
|
| 34. |
- Andersson, Ove, et al.
(författare)
-
A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates
- 2018
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 122:15, s. 4376-4384
-
Tidskriftsartikel (refereegranskat)abstract
- Type II clathrate hydrates (CHs) M-17 H2O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to similar to 1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass liquid glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.
|
|
| 35. |
- Andersson, Ove, et al.
(författare)
-
An ice phase of lowest thermal conductivity
- 2004
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:20, s. 9612-9617
-
Tidskriftsartikel (refereegranskat)abstract
- On pressurizing at temperatures near 130 K, hexagonal and cubic ices transform implosively at 0.8–1 GPa. The phase produced on transformation has the lowest thermal conductivity among the known crystalline ices and its value decreases on increase in temperature. An ice phase of similar thermal conductivity is produced also when high-density amorphous ice kept at 1 GPa transforms on slow heating when the temperature reaches ∼155 K. These unusual formation conditions, the density and its distinguished thermal conductivity, all indicate that a distinct crystal phase of ice has been produced.
|
|
| 36. |
- Andersson, Ove, et al.
(författare)
-
Chirality and the thermophysical properties of molecular solid phases under pressure: (+)- and (±)-camphor
- 1990
-
Ingår i: Molecular Physics. - : Taylor & Francis Group. - 0026-8976 .- 1362-3028. ; 70:6, s. 1065-1083
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal conductivity λ, heat capacity per unit volume pcP and P-T phase diagrams are investigated for both (+)- and (±)-camphor. The transient hotwire method is used at temperatures in the range 100–430 K and at pressures up to 1·75 GPa. We detect solid phases I-IV for (+)-camphor and I′-V′ for (±)-camphor. We conclude that λ is independent of enantiomeric composition for plastic-crystal phase pairs I-I′, II-II′ and IV-IV′. Phase V′ also appears to be a plastic-crystal phase. Non-plastic phases III and III′ show a variation of λ with T that differ considerably from that expected for a simple crystal, with the greatest such difference being observed for the racemic compound III′. An unannealed specimen of the racemic compound III′ is probably chirally disordered and shows a variation of λ with T for T < 130 K, which may indicate phonon-assisted fracton hopping.
|
|
| 37. |
- Andersson, Ove, et al.
(författare)
-
Collapse of an ice clathrate under pressure observed via thermal conductivity measurements
- 2008
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 78, s. 174201-
-
Tidskriftsartikel (refereegranskat)abstract
- Irreversible transformation of the tetrahydrofuran ice clathrate at 130 K was studied by measuring thermal conductivity k with increase in pressure p. Initially, k increases slowly with p up to 0.75 GPa where it levels off, is roughly constant up to 0.95 GPa, then decreases up to 1.05 GPa. Pressure collapses the clathrate structure, plausibly beginning with lattice distortion, and k increases at 1.05 GPa in a sharp sigmoid-shape manner due to large densification until the transformation is complete at 1.25 GPa. This is the opposite of that found for ice whose k decreases first slowly with increase in p and then rapidly in an inverted sigmoidshape manner [O. Andersson and H. Suga, Phys. Rev. B 65, 140201 (2002)]. At 1.08 GPa and 131 K, k increases with time t (s) according to exp(t /2945), which is also the opposite of the collapse of ice [G. P. Johari and O. Andersson, Phys. Rev. B 70, 184108 (2004)]. The difference in its behavior is attributed to strong phonon scattering from the tetrahydrofuran guest molecules. k of the collapsed clathrate is 30% less than that for the collapsed ice, which is comparable with the 25% lesser k of the tetrahydrofuran-water solution from k of water at ambient pressure. On depressurizing at 130 K, k decreases progressively more rapidly and k of the collapsed state at 0.3 GPa is slightly lower than that of the as-made clathrate, showing that its original structure is not recovered.
|
|
| 38. |
|
|
| 39. |
|
|
| 40. |
- Andersson, Ove
(författare)
-
Dielectric relaxation of the amorphous ices
- 2008
-
Ingår i: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 20
-
Tidskriftsartikel (refereegranskat)abstract
- The dielectric properties of the low and high density amorphous ices are discussed in terms of those for supercooled water and crystalline ices, and also used to evaluate the transition behaviour upon pressure cycling at 130 K. The dielectric relaxation of the high density amorphous ice is described well by the symmetrical Cole–Cole function with an almost pressure independent relaxation time τ ∼ 2 s at 133 K and a relaxation time distribution factor of 0.7. At the high to low density amorphous ice transition, the dielectric relaxation time increases by about two orders of magnitude despite a ∼30% decrease in density, and τ of the low density amorphous ice is in the range 102–103 s at 130 K. The relaxation time behaviour of the high density amorphous ice is similar to that of supercooled liquid water, whereas τ of the low density amorphous ice appears to be prolonged by the ice rules, in correspondence to that of the crystalline ices.
|
|
