A low frequency Raman study of fractons in partially densified silica aerogels

We report on a low-frequency Raman scattering study of base-catalyzed silica aerogels (BCSA) and partially densified BCSA prepared by heat treatment (HT), hydrostatic pressure (HP) and uniaxial pressure (UP). Low-frequency Raman susceptibility scales with frequency, χ( ω)∼ ω − φ , within a large ran...

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Bibliographic Details
Published in:Journal of non-crystalline solids 1998-04, Vol.225 (1-3), p.248-253
Main Authors: Anglaret, Eric, Beurroies, Isabelle, Duffours, Laurent, Levelut, Claire, Foret, Marie, Delord, Pierre, Woignier, Thierry, Phalippou, Jean, Pelous, Jacques
Format: Article
Language:English
Subjects:
Aerogels
Chemistry
Colloidal gels. Colloidal sols
Colloidal state and disperse state
Densification
Exact sciences and technology
General and physical chemistry
Hydrostatic pressure
Raman study
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Summary:We report on a low-frequency Raman scattering study of base-catalyzed silica aerogels (BCSA) and partially densified BCSA prepared by heat treatment (HT), hydrostatic pressure (HP) and uniaxial pressure (UP). Low-frequency Raman susceptibility scales with frequency, χ( ω)∼ ω − φ , within a large range of frequencies whose extent decreases with densification. Changes in the spectra are correlated with densification-induced changes in structure and connectivity of BCSA. φ is a constant independent of density for all as-prepared samples, in agreement with their mutual self-similarity. φ also remains essentially constant for HT samples while it decreases for HP and UP samples. φ values are discussed in terms of fractal and spectral dimensions of the samples in the light of the theoretical predictions of Alexander, Courtens and Vacher (ACV) and recent Brillouin scattering results.
ISSN:0022-3093
1873-4812
DOI:10.1016/S0022-3093(98)00323-8