Anelastic spectroscopy experiments in HiPco carbon nanotubes from room temperature to 3 K displayed a thermally activated relaxation process at about 25 K for frequencies in the kHz range. The activation energy obtained by the peak shift with frequency is E-a = 635 K and reveals the presence of a very mobile species performing about 10(3) jumps/s at the peak temperature. The derived value of the pre-exponential factor of the Arrhenius law for the relaxation time, tau(0) = 10(-14) s, is typical of point defect relaxation and suggests that the process is originated by the dynamics of hydrogen or H complexes. The peak is much broader than a single Debye-relaxation process, indicating the presence of intense elastic interactions in the highly disordered bundle structure. There are clear, but not conclusive, indications that the relaxation process is governed by a quantum mechanism. (c) 2005 Elsevier B.V All rights reserved.
Hydrogen dynamics in HiPco carbon nanotubes / Cantelli, Rosario; A., Paolone; S., Roth; U., Dettlaff. - In: JOURNAL OF ALLOYS AND COMPOUNDS. - ISSN 0925-8388. - STAMPA. - 404:SPEC. ISS.(2005), pp. 630-633. (Intervento presentato al convegno 9th International Symposium on Metal-Hydrogen Systems, Fundamentals and Applications tenutosi a Cracow, POLAND nel SEP 05-10, 2004) [10.1016/j.jallcom.2004.11.102].
Hydrogen dynamics in HiPco carbon nanotubes
CANTELLI, Rosario;
2005
Abstract
Anelastic spectroscopy experiments in HiPco carbon nanotubes from room temperature to 3 K displayed a thermally activated relaxation process at about 25 K for frequencies in the kHz range. The activation energy obtained by the peak shift with frequency is E-a = 635 K and reveals the presence of a very mobile species performing about 10(3) jumps/s at the peak temperature. The derived value of the pre-exponential factor of the Arrhenius law for the relaxation time, tau(0) = 10(-14) s, is typical of point defect relaxation and suggests that the process is originated by the dynamics of hydrogen or H complexes. The peak is much broader than a single Debye-relaxation process, indicating the presence of intense elastic interactions in the highly disordered bundle structure. There are clear, but not conclusive, indications that the relaxation process is governed by a quantum mechanism. (c) 2005 Elsevier B.V All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
