The effect of O2 impurities on the low-temperature radial thermal expansion of bundles of closed single-walled carbon nanotubes (original) (raw)
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Radial thermal expansion of single-walled carbon nanotube bundles at low temperatures
For the first time the linear coefficient of the radial thermal expansion has been measured on a system of SWNT bundles at low temperatures (2.2-120 K). The measurements were performed using a dilatometer with a sensitivity of 2•10-9 cm. The cylindrical sample 7 mm high and 10 mm in diameter was obtained by compressing powder. The resulting bundles of the nanotubes were oriented perpendicular to the sample axis. The starting powder contained over 90% of SWNTs with the outer diameter 1.1 nm, the length varying within 5-30 mm. The change of sign of the radial thermal expansion coefficient at 5.5 K was observed. PACS: 65.80.+n Thermal properties of small particles, nanocrystals, and nanotubes.
2009
The radial thermal expansion coefficient (a)r of pure and Xe-saturated bundles of single-walled carbon nanotubes has been 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 made using a low temperature capacitance dilatometer with a sensitivity of 2x10-9 cm and the sample was prepared by compacting a CNT powder such 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 (a)r in the whole range of temperatures used, and a peak in the dependence (a)r (T) in the interval 50-65 K. A subsequent decrease in the Xe concentration lowered the peak considerably but had little effect on the...
The specific heat and the radial thermal expansion of bundles of single-walled carbon nanotubes
2013
The specific heat at constant pressure C(T) of bundles of single-walled carbon nanotubes (SWNTs) closed at their ends has been investigated in a temperature interval of 2-120 K. It is found that the curve C(T) has features near 5 K, 36 K, 80 K and 100 K. The experimental results on the C(T) and the radial thermal expansion coefficient R (T) of bundles of SWNTs oriented perpendicular to the sample axis have been compared. It is found that the curves C(T) and R (T) exhibit a similar temperature behavior at T>10 K. The temperature dependence of the Gruneisen coefficient (Т) has been calculated. The curve (Т) also has a feature near 36 K. Above 36 K the Gruneisen coefficient is practically independent of temperature (4). Below 36 K (Т) decreases monotonically with lowering temperature and becomes negative at T< 6 K. PACS: 65.40.Ba Heat capacity; 65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems; 81.07.De Nanotubes.