Phonon attenuation in vitreous silica and silica porous systems

Year: 2004

Authors: Caponi S., Benassi P., Eramo R., Giugni A., Nardone M., Fontana A., Sampoli M., Terki F., Woignier T.

Autors Affiliation: Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Università di L’Aquila, L’Aquila, I-67100, Italy; Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Università di Trento, Povo, Trento, I-38050, Italy; Dipartimento di Energetica, Istituto Nazionale per la Fisica della Materia, Laboratorio Europeo di Spettroscopia Non Lineare Università di Firenze, Italy; Université Montpellier II, Montpellier Cedex, F34095, France

Abstract: The mechanisms responsible for phonon attenuation in glasses and in porous systems have been investigated. The acoustic attenuation has been measured by Brillouin light scattering using a Fabry-Pérot apparatus and a new ultraviolet spectrometer. In particular, melt-quenched vitreous silica (?=2200 kgm-3), silica xerogels with different densities (?=510±50, 770±80, 1380±140 and 2190±200 kgm-3), and silica aerogel (?=670±80 kgm-3) have been studied. The porosities of the samples have been measured by nitrogen adsorption–desorption techniques. The Brillouin linewidth is found to increase with increasing pore size, being related to the effect of the growing structural disorder. Comparison between the acoustic attenuation obtained by the two wavelengths shows the existence of a crossover length a* which identifies the wave-vector values above which the disorder induced by the pore size starts to be the dominant cause of absorption. The position of the crossover is found to be frequency dependent.


Volume: 84 (13/16)      Pages from: 1423  to: 1431

More Information: This work was supported by Ministero dell Universita e dellas ricerca Scientifica e Tecnologica Progetto di Ricerca di Interesse Nazionale.
KeyWords: Absorption; Aerogels; Attenuation; Brillouin scattering; Crystalline materials; Frequencies; Molecular dynamics; Phonons; Pore size; Porous materials; Quenching; Relaxation processes; Spectrometers, Disordered systems; Phonon attenuation; Structural disorders; Vibrational dynamics, Silica
DOI: 10.1080/14786430310001644170

Citations: 7
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