V. B. Esel’son

Low-temperature thermal expansion of pure and inert gas-doped fullerite C60

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-res ...

Radial thermal expansion of pure and Xe-saturated bundles of single-walled carbon nanotubes at low temperatures

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 ...

Radial thermal expansion of single-walled carbon nanotube bundles at low temperatures

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 (2.2–120K). The measurements are performed using a dilatometer with a sensitivity of 2×10−9cm. A cylindrical sample 7mm high and 10mm 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 1.1nm, the length varying in the range 5–30μm. A change of sign of the radial thermal expansion coefficient at 5.5K is observed.

Thermal expansion and polyamorphism of N2–C60 solutions

The linear coefficients alpha(T) of N-2-C-60 solutions with 9.9% and 100% of the C-60 lattice thermal expansion interstitials filled with N-2 are investigated in the interval 2.2-24 K. The dependen ...

Specific features of thermal expansion and polyamorphism in CH4–C60 solutions at low temperatures

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 o ...

Kinetics of the sorption of 3He by C60 fullerite. The quantum diffusion of 3He and 4He in fullerite

The kinetics of the sorption and subsequent desorption of gaseous 3He in a C60 fullerite powder has been studied in the temperature range of 2–292 K. The temperature dependences of the diffusion coefficients of 3He and 4He impurities in fullerite have been plotted using the measured characteristic times of filling of octahedral and tetrahedral interstices, as well as previous data. These temperature dependences of the diffusion coefficients of 3He and 4He impurities in fullerite are qualitatively similar. A decrease in the temperature from 292 to 79 K is accompanied by a decrease in the diffusion coefficients, which corresponds to the dominance of the thermally activated diffusion of helium isotopes in fullerite. A further decrease in the temperature to 8–10 K leads to an increase in the diffusion coefficients by more than an order of magnitude. The diffusion coefficients of 3He and 4He are independent of the temperature below 8 K, indicating the tunnel character of the diffusion of helium in C60 fullerite. The isotope effect is manifested in the difference between the absolute values of the diffusion coefficients of 3He and 4He atoms at the same temperatures.

Kinetics of He4 gas sorption by fullerite C60. Quantum effects

The kinetics of helium gas sorption by C60 powder and subsequent desorption of the He4 impurity from the saturated powder is studied in the temperature interval 2–292K. Evidence is obtained supporting the existence of two stages in the temperature dependences of sorption and desorption. These stages originate in different times taken by helium to occupy octahedral and tetrahedral interstices in the C60 lattice. The characteristic times of sorption and desorption coincide. It is found that the temperature dependences of the characteristic times for occupying the octahedral and tetrahedral interstices are nonmonotonic. When the temperature is lowered from 292to79.3K, the characteristic times increase, which indicates thermally activated diffusion of helium in C60. With a further reduction to T=10K, the characteristic times decrease by more than an order of magnitude. Below 8K the characteristic times of sorption and desorption are temperature-independent. This suggests tunnel diffusion of He4 in C60.

Influence of dissolved oxygen on the thermal expansion and polyamorphism of fullerite C60

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 temperat ...

Low-temperature thermal expansion of fullerite C60 alloyed with argon and neon

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.

Thermal expansion of single-crystal fullerite C60 at liquid-helium temperatures

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 becom ...