Acoustic and thermal transport properties of hard carbon formed from C_60 fullerene

Lasjaunias, J. C. and Saint-Paul, M. and Bilušić, A. and Smontara, Ana and Gradečak, S. and Tonejc, Anđelka and Tonejc, Antun and Kitamura, N. (2002) Acoustic and thermal transport properties of hard carbon formed from C_60 fullerene. Physical Review B, 66 (1). pp. 14302-11. ISSN 1098-0121

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We report on extended investigation of the thermal transport and acoustical properties on hard carbon samples obtained by pressurization of C60 fullerene. Structural investigations performed by different techniques on the same samples indicate a very inhomogeneous structure at different scales, based on fractal-like amorphous clusters on the micrometer to submillimeter scale, which act as strong acoustic scatterers, and scarce microcrystallites on the nanometer scale. Ultrasonic experiments show a rapid increase in the attenuation with frequency, corresponding to a decrease in the localization length for vibrations. The data give evidence for a crossover from extended phonon excitations to localized fracton excitations. The thermal conductivity is characterized by a monotonous increase versus temperature, power law T1.4, for T ranging from 0.1 to 10 K, without any well-defined plateau, and a strictly linear-in-T variation between 20 and 300 K. The latter has to be related to the linear-in-T decrease of the sound velocity between 4 and 100 K, both linear regimes being characteristic of disordered or generally aperiodic structures, which can be analyzed by the “phonon-fracton hopping” model developed for fractal and amorphous structures.

Item Type: Article
Keywords: fullerene and related materials, X-ray difraction, high resolution transsmision electron microscope, transport properties, acoustic propeties
Date: July 2002
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2002) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Project code: 0035013, 0119252
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 22 May 2014 19:15
Last Modified: 22 May 2014 19:15

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