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Title: The development and properties of glass-ceramic fibres
Author: Jones, Ronald William
ISNI:       0000 0001 3592 7699
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1977
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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.
Supervisor: Not available Sponsor: Science Research Council (Great Britain) (SRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TP Chemical technology