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Laboratory of Glass Chemistry and
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 Vapor Hydration Testing (VHT)
In recent years, a significant effort has been
applied towards the understanding of the mechanism of hydration and alteration
of glasses by aqueous conditions. One of the reasons to study these processes
are humid repository environments, like
Yucca Mountain repository, where hydration of glass surfaces may be an
important aging mechanism of vitrified waste forms. To understand the mechanism
and related processes that occur during the reaction with an aqueous
environment, it is necessary to accelerate the reaction progress and form
secondary alteration products. Vapor hydration is a method that can be used to:
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Determine if a glass is likely to corrode at
an extreme rate,�
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Obtain secondary alteration products within
a short time period
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Measure the apparent dissolution rate at
elevated temperatures.�
Conducting VHT
Figure 1
displays the apparatus for conducting VHT. Specimens with dimensions of 10x10x1.5
mm are prepared using a diamond-impregnated saw. All sides are� polished to a
600-grit surface finish with water-lubricated SiC paper. Specimens, stainless
steel vessels, lids, and supports are cleaned and specimens suspended from
stainless steel supports on a Pt wire. The support with the specimen are placed
inside the vessel, together with a given amount of deionized water. The sealed
vessel is held at constant temperature in a convection oven for a preset time.
After the test termination, the specimen is removed from the vessel and examined
for the presence of alteration products. The alteration products are
identified with scanning electron microscopy (SEM) with energy dispersive
spectroscopy (EDS) and X-ray diffraction (XRD).
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