"The concentration of nuclei (Nv) in a Li2O·2SiO2 (LS2) glass was measured using a newly developed DTA technique, after densifying the glass at 1, 3, or 6 GPa pressure at 400° C for 20 min. Ny increased from 38 x 1012 m-3 for an as-melted glass to 82 x 1012 m-3 for a glass subjected to a pressure of 1 GPa, and then remained nearly constant with increasing pressure up to 6 GPa. This increase in Ny is equivalent to nucleating this LS2 glass for 2 h at the temperature (455° C) where its nucleation rate is a maximum The average effective activation energy for crystallization for the densified glasses, 292 ±10 kJ/mol, was also the same as that of the (undensified) glass nucleated at 455° C for 2 h, but was significantly smaller than that (358 ±10 kJ/mol) for an as-melted (undensified and unnucleated) glass. The present results show that applying an external pressure on this LS2 glass shifts its nucleation curve to lower temperatures causing nuclei to form at temperatures as low as 400° C. A decrease in viscosity at all temperatures with the application of pressure is suspected to be a reason for the enhanced nucleation observed for this LS2 glass.
Day, D. E.
Brow, Richard K.
Switzer, Jay A., 1950-
Ray, C. S.
Materials Science and Engineering
M.S. in Ceramic Engineering
University of Missouri--Rolla
x, 46 pages
© 2002 Tihana Fuss, All rights reserved.
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Fuss, Tihana, "Pressure induced nucleation in Li₂O·2SiO₂ glass" (2002). Masters Theses. 2169.
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