| 1. |
- Aleksandrovskii, A. N., et al.
(författare)
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Effect of argon on the thermal expansion of fullerite C60 at helium temperatures
- 2001
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics. - 1063-777X .- 1090-6517. ; 27:3, s. 245-246
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Tidskriftsartikel (refereegranskat)abstract
- The linear thermal expansion of compacted Ar-doped fullerite C60(ArxC60) is investigated at 2–12 K using a dilatometric method. The thermal expansion of ArxC60 is also studied after partial desaturation of argon from fullerite. It is revealed that argon doping resulted in a considerable change of the temperature dependence of the thermal expansion of fullerite. An explanation of the observed effects is proposed.
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| 2. |
- Aleksandrovskii, A. N., et al.
(författare)
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Low-temperature thermal expansion of pure and inert gas-doped fullerite C60
- 2003
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Ingår i: Fizika Nizkikh Temperatur (Kharkov). - : AIP Publishing. - 0132-6414 .- 1816-0328. ; 29:4, s. 432-442
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Tidskriftsartikel (refereegranskat)abstract
- The low temperature (2–24 K) thermal expansion of pure (single-crystal and polycrystalline) C60 and polycrystalline C60 intercalated with He, Ne, Ar, and Kr has been investigated using the high-resolution capacitance dilatometer. The investigation of the time dependence of the sample length variations deltaL(t) on heating by deltaT shows that the thermal expansion is determined by the sum of positive and negative contributions, which have different relaxation times. The negative thermal expansion usually prevails at helium temperatures. The positive expansion is connected with the phonon thermalization of the system. The negative expansion is caused by reorientation of the C60 molecules. It is assumed that the reorientation is of a quantum character. The inert gas impurities affect the reorientation of the C60 molecules very strongly, especially at liquid helium temperatures. A temperature hysteresis of the thermal expansion coefficient of Kr– and He–C60 solutions has been revealed. The hysteresis is attributed to orientational polyamorphous transformation in these systems.
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| 3. |
- Aleksandrovskii, A. N., et al.
(författare)
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Negative thermal expansion of fullerite C60 at helium temperatures
- 1997
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 23:11, s. 943-946
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of fullerite C60 has been measured in the temperature range 2–9 K. A compacted fullerite sample with a diameter of about 6 mm and height of 2.4 mm was used. It was found that at temperatures below ~ 3.4 K the linear thermal expansion coefficient becomes negative. At temperatures above 5 K our results are in good agreement with the available literature data. A qualitative explanation of the results is proposed
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| 4. |
- Aleksandrovskii, A.N., et al.
(författare)
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On the polyamorphism of fullerite-based orientational glasses.
- 2005
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Ingår i: Low Temperature Physics. - : AIP Publishing. - 1063-777X .- 1090-6517. ; 31:5, s. 429-444
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Tidskriftsartikel (refereegranskat)abstract
- The dilatometric investigation in the temperature range of 2–28 K shows that a first-orderpolyamorphous transition occurs in the orientational glasses based on C60 doped with H2, D2 andXe. A polyamorphous transition was also detected in C60 doped with Kr and He. It is observed thatthe hysteresis of thermal expansion caused by the polyamorphous transition (and, hence, the transitiontemperature) is essentially dependent on the type of doping gas. Both positive and negativecontributions to the thermal expansion were observed in the low-temperature phase of the glasses.The relaxation time of the negative contribution occurs to be much longer than that of the positivecontribution. The positive contribution is found to be due to phonon and libron modes, whilst thenegative contribution is attributed to tunneling states of the C60 molecules. The characteristictime of the phase transformation from the low-T phase to the high-T phase has been found for theC60–H2 system at 12 K. A theoretical model is proposed to interpret these observed phenomena.The theoretical model proposed, includes a consideration of the nature of polyamorphism inglasses, as well as the thermodynamics and kinetics of the transition. A model of noninteractingtunneling states is used to explain the negative contribution to the thermal expansion. The experimentaldata obtained is considered within the framework of the theoretical model. From the theoreticalmodel the order of magnitude of the polyamorphous transition temperature has been estimated.It is found that the late stage of the polyamorphous transformation is described well by theKolmogorov law with an exponent of n = 1. At this stage of the transformation, the two-dimensionalphase boundary moves along the normal, and the nucleation is not important.
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| 5. |
- Aleksandrovskii, A.N., et al.
(författare)
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Thermal expansion of fullerite C60 alloyed with argon and neon
- 2001
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - Woodbury : American Institute of Physics. - 1063-777X .- 1090-6517. ; 27:12, s. 1033-1036
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Tidskriftsartikel (refereegranskat)abstract
- The linear thermal expansion of compacted fullerite C60 alloyed with argon (ArxC60) and neon (NexC60) are investigated by a dilatometric method. The experimental temperature is 2–12 K. In the same temperature interval the thermal expansion of ArxC60 and NexC60 are examined after partial desaturation of the gases from fullerite. It is found that Ar and Ne alloying affects the temperature dependence of the thermal expansion coefficient of C60 quite appreciably. The libration and translation contributions to the thermal expansion of pure C60 are separated. The experimental results on the thermal expansion are used to obtain the Debye temperature of pure C60. The effects observed are tentatively interpreted.
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| 6. |
- Aleksandrovskii, A. N., et al.
(författare)
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Thermal expansion of single-crystal fullerite C60 at helium temperatures
- 2000
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 26:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The thermal expansion of single-crystal fullerite C60 has been studied in the range of liquid-helium temperatures (2–10 K). At temperatures below ~4.5 K the thermal expansion of fullerite C60 becomes negative, in agreement with the previous results on polycrystalline materials. A qualitative explanation of the results is proposed.
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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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| 10. |
- 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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