Jones, R. W. (1977) The development and properties of glass-ceramic fibres. PhD thesis, University of Warwick.

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Abstract

Fibres were produced from glasses with the following compositions:
A= 25% Li20
74% SiO2 1% P205
B= 29% LiO2
68% SiO2 1% P205 1% ZnO 1% K20
by drawing the fibres from a single tip platinum bushing. The fibres,
in the form of tows, were then subjected to a series of heat
treatments in which the nucleation and crystallization temperatures
and times were varied. The tensile strength and elastic modulus
was determined for each sample of fibres and use was made of
microscopy and X-ray diffraction to determine the microstructure
resulting from the subsequent heat treatments. The data obtained
from the tests performed in this investigation required a statistical
analysis because of the variance in any one measured parameter.
This is often found to be the case when investigating small volumes
of material such as fibres. A model was proposed, for each composition,
relating the strength to crytallization time and an attempt
was made to justify each model on the basis of the empirical
data obtained and indirect evidence arising from the statistical
interpretation of this data.
The strength of crystallized fibres produced from composition
A. decreased with crystallization time. This was explained by
assuming that the strength controlling flaws were introduced by
the appearance of a surface crystal layer and that the flaw size
was proportional to the thickness of the layer. Evidence was
produced to reinforce this argument. Two proposals regarding the
elastic modulus, were tested and it was found that observed moduli
could beat be described by considering the fibre to be a composite
cylinder with an outer annulus of lithium disilicate surrounding a
core of glass.
Glass B. fibres did not behave in the same way as A. after
crystallization except at high crystallization temperature. In
general the strength would decrease thenincrease again slightly
before finally decreasing. This behaviour was explained by assuming
that the mean intercrystal spacing controlled flaw size until the
depth of the surface crystal layer became large enough to dominate.
Some research is described in which an attempt is made to
inhibit surface nucleation/crystallization by using a vapour phase
ion-exchange treatment. This work remains incomplete but there
was some indication that it would be successful in allowing higher
strengths to be achieved in glass-ceramic fibres after prolonged
crystallization.

Item Type:	Thesis (PhD)
Subjects:	T Technology > TP Chemical technology
Library of Congress Subject Headings (LCSH):	Glass fibers, Glass-ceramics, Crystallization
Official Date:	December 1977
Dates:	Date Event December 1977 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	McMillan, P. W. (Peter Warwick)
Sponsors:	Science Research Council (Great Britain) (SRC)
Extent:	189 leaves
Language:	eng

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