| 61. |
- Danilchenko, Boris A., et al.
(författare)
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Stability of the Tomonaga-Luttinger liquid state in gamma-irradiated carbon nanotube bundles
- 2013
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Ingår i: Journal of Physics. - : Institute of Physics Publishing (IOPP). - 0953-8984 .- 1361-648X. ; 25:47, s. 475302-
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental results for the changes in conductivity of single-wall carbon nanotube bundles when irradiated by Co-60 gamma-rays in various environments. In the current study the samples investigated were irradiated in hermetic cells, either evacuated (0.1 Pa) or filled with hydrogen or deuterium at atmospheric pressure. In situ measurements of the resistance change as a function of irradiation dose at room temperature are presented. It was found that, for all irradiation conditions, the normalized resistance versus irradiation dose demonstrates a logarithmic behaviour. A phenomenological model for the observed dependence is derived. The current-voltage characteristics of the irradiated samples were measured in the temperature range from 4.5 to 300 K using short (10 ns) electric pulses, and the results demonstrate a scaling behaviour. This scaling occurs in the universal coordinates that correspond to the Tomonaga-Luttinger liquid concept. Our results confirm the existence of the Tomonaga-Luttinger liquid phase up to room temperature in carbon nanotubes after gamma-irradiation to a dose of 5 x10(7) rad in vacuum, 1 : 7 x 10(7) rad in hydrogen and 1 : 24 x 10(8) rad in deuterium.
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| 62. |
- Diederichs, J., et al.
(författare)
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Critical currents in Tl-2122 and Y-124 sinters under high hydrostatic pressure
- 1991
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Ingår i: Superconductor Science and Technology, volume 4, Special Issue 1S. - Bristol : Adam Hilger. - 0750301082 ; , s. S97-S99
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Konferensbidrag (refereegranskat)abstract
- Utilizing AC susceptibility measurements the authors have investigated the inter and intragranular properties of selected bulk materials under hydrostatic pressures to 3.5 GPa. A single phase Tl2CaBa2Cu2O8 sample with superconducting transition temperature Tc approximately=107 K shows a clear maximum in Tc(P) at approximately 2.2 GPa coupled with a nearly twofold increase to 3 GPa of the intergranular critical current density JcJ near Tc. The second sample, a YBa2Cu4O8 sinter, shows a large linear increase in Tc with pressure (+5.5 K/GPa) as well as a fivefold increase JcJ to 3 GPa. Applying a critical state model, the authors find that Tc(P) varies as lambda g-2(P), where lambda g is the intragranular (London) penetration depth.
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| 63. |
- Dmitriev, Vladimir, et al.
(författare)
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Pressure-temperature phase diagram of LiBH4: Synchrotron x-ray diffraction experiments and theoretical analysis
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 77:17
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Tidskriftsartikel (refereegranskat)abstract
- An in situ combined high-temperature high-pressure synchrotron radiation diffraction study has been carried out on LiBH4. The phase diagram of LiBH4 is mapped to 10 GPa and 500 K, and four phases are identified. The corresponding structural distortions are analyzed in terms of symmetry-breaking atomic position shifts and anion ordering. Group-theoretical and crystal-chemical considerations reveal a nontrivial layered structure of LiBH4. The layers and their deformations define the structural stability of the observed phases.
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| 64. |
- Dolbin, Alexander Vitoldovich, et al.
(författare)
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Influence of dissolved oxygen on the thermal expansion and polyamorphism of fullerite C60
- 2007
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 33:5, s. 465-471
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of the coefficient of linear thermal expansion alpha of O-2-C-60 solutions with 20% and 80% filling of the octahedral cavities with oxygen is investigated in the temperature interval 2.2-24 K. Hysteresis of alpha(T) is observed, attesting to the coexistence of two orientational glasses in these solutions. A comparison of the behavior of these glasses is made. The characteristic times for reorientation of the C-60 molecules and for the phase transformations in the solutions are determined. When the temperature of the O-2-C-60 solution with 20 mol.% oxygen is increased to 450 degrees C, a chemical interaction of the oxygen with the C-60 molecules is manifested. It proves possible to separate the influences of the chemical and physical sorption of oxygen on the thermal expansion of polycrystalline fullerite C-60.
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| 65. |
- Dolbin, Alexander V., et al.
(författare)
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Low-temperature radial thermal expansion of single-walled carbon nanotube bundles saturated with nitrogen
- 2010
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 36:5, s. 365-369
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a N2 impurity on the radial thermal expansion coefficient αr of single-walled carbon nanotube bundles has been investigated in the temperature interval 2.2–43 K by the dilatometric method. Saturation of nanotube bundles with N2 caused a sharp increase in the positive magnitudes of αr in the whole temperature range used and a very high and wide maximum in the thermal expansion coefficient αr(T) at T ~ 28 K. The low temperature desorption of the impurity from the N2-saturated powder of bundles of single-walled carbon nanotubes with open and closed ends has been investigated.
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| 66. |
- Dolbin, Alexander V., et al.
(författare)
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Quantum effects in the radial thermal expansion of bundles of single-walled carbon nanotubes doped with 4He
- 2010
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - Woodbury, N.Y. : American Institute of Physics. - 1063-777X .- 1090-6517. ; 36:7, s. 635-637
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Tidskriftsartikel (refereegranskat)abstract
- The radial thermal expansion αr of bundles of single-walled carbon nanotubes saturated with 4He impurities to the molar concentration 9.4% has been investigated in the interval 2.5–9.5 K using the dilatometric method. In the interval 2.1–3.7 K αr is negative and is several times higher than the negative αr for pure nanotube bundles. This most likely points to 4He atom tunneling between different positions in the nanotube bundle system. The excess expansion was reduced with decreasing 4He concentration.
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| 67. |
- Dolbin, Alexander V., et al.
(författare)
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Quantum phenomena in the radial thermal expansion of bundles of single-walled carbon nanotubes doped with 3He. A giant isotope effect
- 2011
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics (AIP). - 1063-777X .- 1090-6517. ; 37:6, s. 544-546
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Tidskriftsartikel (refereegranskat)abstract
- The radial thermal expansion αr of bundles of single-walled carbon nanotubes saturated with 3He up to the molar concentration 9.4% has been investigated in the temperature interval 2.1–9.5 K by high-sensitivity capacitance dilatometry. In the interval 2.1–7 K a negative αr was observed, with a magnitude which exceeded the largest negative αr values of pure and 4He-saturated nanotubes by three and two orders of magnitude, respectively. The contributions of the two He isotope impurities to the negative thermal expansion of the nanotube bundles are most likely connected with the spatial redistribution of 4He and 3He atoms by tunneling at the surface and inside nanotube bundles. The isotope effect turned out to be huge, probably owing to the higher tunneling probability of 3He atoms.
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| 68. |
- Dolbin, Alexander V., et al.
(författare)
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Radial thermal expansion of pure and Xe-saturated bundles of single-walled carbon nanotubes at low temperatures
- 2009
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 35:6, s. 484-490
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Tidskriftsartikel (refereegranskat)abstract
- The radial thermal expansion coefficient alphar of pure and Xe-saturated bundles of single-walled carbon nanotubes (CNTs) is measured in the interval 2.2–120 K. The coefficient is positive above T=5.5 K and negative at lower temperatures. The experiment was done using a low-temperature capacitance dilatometer with a sensitivity of 2×10−9 cm, and the sample was prepared by compacting a CNT powder in such a way that the pressure applied oriented the nanotube axes perpendicular to the axis of the cylindrical sample. The data show that individual nanotubes have a negative thermal expansion, while the solid compacted material has a positive expansion coefficient due to expansion of the intertube volume in the bundles. Doping the nanotubes with Xe caused a sharp increase in the magnitude of alphar in the whole range of temperatures used and gave rise to a peak in the dependence alphar(T) in the interval 50–65 K. A subsequent decrease in the Xe concentration lowered the peak considerably but had little effect on the thermal expansion coefficient of the sample outside the region of the peak. The features revealed are explained qualitatively.
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| 69. |
- Dolbin, Alexander V, et al.
(författare)
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Radial thermal expansion of single-walled carbon nanotube bundles at low temperatures.
- 2008
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Ingår i: Fizika Nizkikh Temperatur. - : AIP Publishing. - 0132-6414. ; 34:8, s. 860-862
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, the linear coefficient of radial thermal expansion is measured on a system of carbon single-walled nanotube (SWNT) bundles at low temperatures (2.2–120 K). The measurements are performed using a dilatometer with a sensitivity of 2×10−9 cm. A cylindrical sample 7 mm high and 10 mm in diameter was obtained by compressing powder. The resulting bundles of nanotubes are oriented perpendicular to the sample axis. The starting powder consisted of over 90% SWNTs with outer diameter 1.1 nm, the length varying in the range 5–30 µm. A change of sign of the radial thermal expansion coefficient at 5.5 K is observed.
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| 70. |
- Dolbin, Alexander V., et al.
(författare)
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Specific features of thermal expansion and polyamorphism in CH4 – C60 solutions at low temperatures
- 2007
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 33:12, s. 1068-1072
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of the linear thermal expansion coefficient alpha(T) is investigated in the temperature range of 2.5 to 23 K for two different CH4-C-60 solutions in which CH4 molecules occupy 24 and 50% of the octahedral interstitial sites of the C-60 lattice. In both cases, alpha(T) exhibits hysteresis, suggesting the existence of two types of orientational glass associated with these solutions. The temperature of the first-order phase transition between these two glasses is estimated, and the behavior of these two glasses is compared. The characteristic times of thermalization tau(1), reorientation of the C-60 molecules tau(2), and of the phase transformation between the glasses tau('), are estimated for these solutions. Both the temperature dependence of alpha(T) and the characteristic thermalization time tau(1) are found to have features near the phase transition temperature, and an explanation is put forward to explain these observed features.
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