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Ion Exchange in Sodium Borosilicate Glasses
Author(s) -
VARSHNEYA A. K.,
MILBERG M. E.
Publication year - 1974
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.1151-2916.1974.tb10846.x
Subject(s) - borosilicate glass , activation energy , aluminosilicate , alkali metal , ionic bonding , sodium aluminosilicate , sodium , electron microprobe , ion exchange , analytical chemistry (journal) , chemistry , mineralogy , ion , materials science , thermodynamics , inorganic chemistry , composite material , metallurgy , biochemistry , physics , organic chemistry , chromatography , catalysis
The kinetics of K + ‐Na + exchange in sodium borosilicate glasses containing 20 mol% Na 2 O were studied as a function of glass composition and exchange time and temperature. The distribution of K in the glass after exchange in molten KNO 3 was determined using an electron microprobe. In those specimens which were not chemically attacked by the molten salt, the K profiles were consistent with Fickean behavior. The calculated interdiffusion coefficients varied with local composition in each specimen. This composition dependence and its variation with temperature could be fitted approximately to a mixed‐alkali model using the Nernst‐Planck relation for diffusive fluxes. However, some deviation from this behavior, presumably as a result of the generation of microscopic stresses around an exchange site, was observed. The dependence of the apparent activation energy, Ẽ, on the B/Si ratio was analogous to that of the activation energy for ionic conduction in these glasses: Ẽ decreased with increasing fraction of nonbridging oxygen. This result disagrees with the presumed behavior in sodium aluminosilicate glasses.