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Three Anisotropies in Vitreous Silica
Author(s) -
NASSAU K.,
SHIEVER J. W.
Publication year - 1976
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.1151-2916.1976.tb10947.x
Subject(s) - anisotropy , annealing (glass) , quartz , materials science , perpendicular , electron paramagnetic resonance , analytical chemistry (journal) , composite material , mineralogy , crystallography , chemistry , nuclear magnetic resonance , optics , chromatography , physics , geometry , mathematics
Plasma‐torch fused‐silica boules of low OH content showed an optical anisotropy in the as‐grown state which disappeared after annealing in O 2 ; this behavior was related to an EPR anisotropy which also depended on annealing, probably involving Fe 2+ and Fe 3+ , respectively. High‐temperature (1200° to 1500°C) deformation experiments performed in a modified DTA machine on slabs cut parallel and perpendicular to the preparation symmetry axis also showed an anisotropy, corresponding approximately to a factor of 2 in the viscosity. This anisotropy was also observed in commercial worked fused silica of high and low OH (water) content, made from purified Si compounds or natural quartz, and was not removed by annealing for 5 days at 1200°C in O 2 . The deformation rate of fused silica decreases as water content is reduced from high to medium, but there is little further change when water content is decreased to a very low level.