RECENT RESEARCH RESULTS OF THE DIECKMANN GROUP
Sodium Tracer Diffusion in an Alkaline-Earth Boroaluminosilicate Glass1
Lei Tian and Rüdiger Dieckmann
Department of Materials Science and
Engineering, Cornell University, Bard Hall, Ithaca, NY 14853-1501, U.S.A.
Abstract
Sodium tracer diffusion coefficients, D*Na, have been measured in an alkaline-earth boroaluminosilicate glass (Corning Code 1737) in the temperature range from 500 to 800 °C by using the radioactive isotope Na-22. It was found that the temperature dependence of D*Na could not be described by a simple Arrhenius-type function over the entire temperature range denoted above. A change in the activation energy occurs near the strain point (= 666 °C). Below 664 °C D*Na = 10(-2.21±0.07)·exp(-(129.9±1.2 kJ/mol)/R·T) cm2/s and above 664 oC D*Na = 10(-0.23±0.15)·exp(-(165.5±3.0 kJ/mol)/R·T) cm2/s.
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1 Corning Code 1737 glass
Experimental data for the diffusion of Na-22 in
the alkaline-earth boroaluminosilicate glass investigated (Corning Code 1737)
in air as a function of the temperature.
(Journal of Non-Crystalline Solids, 265 (1-2) [2000] 36-40)
Sodium Tracer
Diffusion in a Glass-Ceramic Containing Nano-Sized Spinel Crystals
Lei Tian and Rüdiger Dieckmann
Department of Materials Science and
Engineering, Cornell University, Bard Hall, Ithaca, NY 14853-1501, U.S.A.
Abstract
Tracer diffusion coefficients of sodium have
been measured at temperatures between 400 and 800 °C in a
glass-ceramic containing nano-crystalline spinel by employing the radioactive
tracer Na-22. Diffusion profiles of Na-22 obtained in this two-phase
glass-ceramic can be evaluated very well by assuming a single tracer diffusion
coefficient for describing the diffusion on a macroscopic length scale. The
values of the tracer diffusion coefficients obtained range from 4·10-10 to 3·10-7 cm2/s.
A simple Arrhenius equation, D*Na = 10(-1.89±0.08)·exp(-(96.7±12.1 kJ/mol)/R·T) cm2/s, summarizes
the data very well. Based on the results from separate sodium tracer diffusion
experiments in spinel it is concluded that sodium ions diffuse practically only
in the silica-rich glass matrix of the glass-ceramic and that the dispersed
nano-sized spinel particles practically do not contribute to the diffusion of
sodium ions.
Arrhenius plot of sodium
tracer diffusion coefficients measured with the radioactive isotope Na-22
diffusing in the glass-ceramic with nano-sized spinel inclusions.
(submitted for publication 08/15/2000)
Effect of Water
Incorporation on the Diffusion of Sodium in an Alkaline-Earth
Boroaluminosilicate
Glass1
Lei Tian and Rüdiger Dieckmann
Department of Materials Science and
Engineering, Cornell University, Bard Hall
Ithaca, NY 14853-1501, U.S.A.
Chung-Yuen Hui
Department of Theoretical and Applied
Mechanics, Cornell University, Thurston Hall
Ithaca, NY 14853-1501, U.S.A.
J. Greg Couillard
Corning Incorporated
Corning, NY 14831, U.S.A.
Abstract
Tracer
diffusion coefficients of sodium ions diffusing in an alkaline-earth boro-
aluminosilicate glass1 were measured
by using Na-22 as a radioactive tracer. It was found
that the presence of a significant amount of
water vapor in the atmosphere surrounding
a diffusion sample during diffusion annealing
reduces considerably the mobility of sodium
in the near-surface region of the glass. This
partial immobilization of Na is attributed to
an interaction between water dissolved into the
glass and diffusing sodium ions.
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1 Corning Code 1737 glass
(submitted for publication 09/01/2000)
Effect of Water Incorporation on the Diffusion of Sodium in Type I Silica Glass1
Lei Tian and Rüdiger Dieckmann
Department of Materials Science and
Engineering, Cornell University, Bard Hall
Ithaca, NY 14853-1501, U.S.A.
Chung-Yuen Hui and Yu-Yun Lin
Department of Theoretical and Applied
Mechanics, Cornell University, Thurston Hall
Ithaca, NY 14853-1501, U.S.A.
J. Greg Couillard
Corning Incorporated
Corning, NY 14831, U.S.A.
Abstract
The diffusion of sodium ions in
Type I silica glass1 was studied experimentally by
using Na-22 as a radioactive tracer at
temperatures between 400 and 700 °C. It was
found that the sodium tracer diffusion
coefficient in as-received glass was well described
by an Arrhenius equation. All residual
radioactivity profiles observed after pre-annealing
glass samples in common and wet air at
temperatures between 900 and 1100 °C and
performing diffusion anneals at 650 °C cannot be
described by a single diffusion
coefficient. A strong residual radioactivity
decrease occurred near the surface, which was
followed by a much smaller decrease in the bulk
below. This type of profile was attributed
to the generation of a near-surface region with
a reduced sodium mobility during the pre-
annealing. A mathematical model for the
analysis of the observed profiles was developed
and used to determine sodium tracer diffusion
coefficients in the near-surface region and
in the bulk. It was found that the sodium
tracer diffusion coefficient in the near-surface
region was by about two orders of magnitude
smaller than that in the bulk. This
immobilization of Na is believed to de due to a
water-induced structural relaxation in the
near-surface region during pre-annealing.
1 Heraeus-Amersil Infrasil 302
(submitted for publication 09/08/2000)
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last update: 09/08/2000