Lau, John (1980) Transparent glass-ceramics and interaction with alkali metal vapours. PhD thesis, University of Warwick.

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Abstract

The aims of the project were to investigate the fundamental
processes involved when a glass is exposed to sodium vapour, and
to examine the different ways of improving the resistance towards
sodium attack.
With regard to the interaction of glasses with sodium, the
silicates were studied in most detail. The discolouration of the
silicate glasses by sodium was treated as a surface phenomenon and
techniques such as ESCA, MRS and ESR were used to investigate the
interaction. The results from, these various techniques all point
to the same conclusion, that the mechanism of sodium attack is the
progressive breaking of Si-O bonds to form Si-0- bonds. The
reaction between borate glasses and sodium showed certain similarities
with the silicates. This led to the suggestion that the same mechanism
of attack might also apply to the borates.
In attempting to improve the resistance of transparent materials
towards sodium attack, two methods were considered. The first approach
was to change the chemical composition by selecting components of a
glass which are inert to sodium. The chemical compatibilities of the
components were assessed using an equilibrium thermodynamic argument
to consider the possible reactions with sodium, and a number of
materials have been suggested to be inert in this way.
The second method of improving the resistance was to rearrange
the structure of a glass by crystallisation. The crystallisation
behaviour and the microstructures of two glass compositions -
MgBAl (3-2) and CAl (6) were studied in detail, and transparent
glass-ceramics were derived from them. It was found that the
improvement in resistance towards sodium attack was only marginal
in the case of crystallising the glasses in bulk. However,
substantial improvements were observed in the case of surface
crystallisation.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Sodium vapor, Glass -- Reactivity, Borates -- Reactivity, Transparent solids -- Reactivity
Official Date:	July 1980
Dates:	Date Event July 1980 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	McMillan, P. W. (Peter Warwick)
Extent:	[13], 149 leaves
Language:	eng

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