A specific heat anomaly in multiwall carbon nanotubes as a possible sign of orientational order–disorder transition

GUILLERMO A. JORGE; V. BEKERIS; M. M. ESCOBAR; S. GOYANES; D. ZILLI; A. L. CUKIERMAN; R. J. CANDAL

CARBON

Elsevier

Año: 2010 vol. 48 p. 525 - 530

0008-6223

We present micro-calorimetric specific heat measurements on different multiwall carbonnanotubes of large outer diameter, as a function of temperature in the range 10–120 K. Aclear anomaly at 60 K with the shape of a peak is present in two of the samples, and boththe height and the characteristic temperature of the peak are independent of magnetic fieldand do not exhibit thermal hysteresis, discarding magnetic degrees of freedom related to Feseeds or contributions from adsorbed gases. These features suggest that the anomaly maybe caused by a structural change. As the anomaly is also unaffected by induced intertubedisorder, it may be related with a melting of orientational dislocations of individual tubeswithin multiwall nanotubes, an effect that was theoretically predicted to occur in carbonnanotubes and represents a distinctive feature of asymmetric molecular systems