Jf. Stebbins et S. Sen, MICROSCOPIC DYNAMICS AND VISCOUS-FLOW IN A BOROSILICATE GLASS-FORMINGLIQUID, Journal of non-crystalline solids, 224(1), 1998, pp. 80-85
The connections between microscopic dynamical processes and macroscopi
c viscous transport are not well known in multi-component oxide liquid
s, despite their importance in the glass industry and in the earth sci
ences. Here, rates of exchange among both silicate and berate network
species in an alkali borosilicate liquid are derived from high tempera
ture boron-ll and silicon-29 magic angle spinning nuclear magnetic res
onance spectroscopy. About 80 degrees C above the glass transition, ex
change rates of both types of units are close to the shear relaxation
time calculated from the bulk viscosity. However, at lower temperature
s, the silicon exchange rates decouple from the viscosity curve, possi
bly because of the development of intermediate-range compositional het
erogeneities. (C) 1998 Elsevier Science B.V.