Acoustic and thermal transport properties of hard carbon formed from C-60 fullerene

Article

关键词: AMORPHOUS SOLIDS;    SILICA AEROGELS;    ELASTIC PROPERTIES;    HIGH-PRESSURE;    CONDUCTIVITY;    TEMPERATURE;    PLATEAU;    HEAT;    SCATTERING;    SAMPLES;   

DOI  :  10.1103/PhysRevB.66.014302

来源: SCIE

【 摘 要 】

We report on extended investigation of the thermal transport and acoustical properties on hard carbon samples obtained by pressurization of C-60 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 T-1.4, 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.

【 授权许可】

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