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Various Scale Levels of the Gel‐to‐Glass Transformation
Author(s) -
Chmel Alexandre,
Krivda Alexy,
Mazurina Ekatherina,
Shashkin Victor,
Zhizhenkov Valery
Publication year - 1993
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1993.tb03940.x
Subject(s) - transformation (genetics) , materials science , scale (ratio) , mineralogy , composite material , chemical engineering , chemistry , physics , engineering , quantum mechanics , biochemistry , gene
The gel‐to‐glass transition in SiO 2 xerogels prepared by inorganic sol‐gel synthesis was studied. The evolution of the molecular structure is traced using the infrared and lowfrequency Raman spectroscopy methods. The elastic moduli of the samples as well as the pore wall moduli at various stages of heat treatment are determined from the data on Brillouin scattering. The formation of monolithic glass on the macroscopic level manifests itself within a narrow temperature range by the dramatic increase of Young's modulus to the accepted value for fused silica. This phenomenon coincides with structural transformations on the molecular scale: (i) the definite correlation radius (the long‐range order sphere) appears; (ii) local distortions of the silica network relax. The presence of structural defects influences the kinetics of vitreous SiO 2 formation during xerogel heat treatment.