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Recycled colourless soda-lime-silica glass as an alternative flux in whitewares.

Tarvornpanich, Tarnkamol (2007) Recycled colourless soda-lime-silica glass as an alternative flux in whitewares. PhD thesis, University of Sheffield.

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Abstract

The most common type of container glass which is landfilled in the UK is soda-limesilica glass, comprising typically 7I-75wt% silica, 12-I6wt% soda and 1O-15wt% lime. Considering its chemical similarity to that of the fluxing materials commonly used in whiteware bodies, it is sensible to investigate the use of SLS waste glass as replacement for these fluxes in whitewares. The present study aimed at the incorporation of colourless SLS waste glass into a standard whiteware formulation (Le. 50wt% kaolinite clay, 25wt% quartz and 25wt% nepheline syenite) as a flux, and at the examination of the microstructural development on firing. Bulk samples with two (e.g. clay and quartz, SLS glass and clay, etc.), three (standard and fully SLS-fluxed whiteware) and four (mixed nepheline syenite SLS glass as flux system) components were studied in depth. After firing 3h at 1100°C, batches containing 6.25wt% SLS glass and 18.75wt% nepheline syenite attained open-pore closure and a bulk density of 2.40 g/cm3 , comparable to that of the standard body fired at 1200°C. SLS glass softens and melts, conferring early densification and overfiring on whitewares fired at commercially-applied firing temperatures. Severe bloating ruled out the use of higher amounts of SLS glass. The microstructural evolution examined using XRD, SEMlEDS, and TEMIEDS revealed the formation of a variable composition plagioclase, wollastonite, and cristobalite in batches containing SLS glass, in addition to primary and secondary mullites, partially dissolved quartz, and a glassy matrix as found in the standard whiteware. Na+ and Ca2+ions from SLS glass migrate towards clay mineral relicts to form plagioclase, limiting the extent of mullite crystallization in SLS containing batches. Wollastonite and cristobalite crystallize from the devitrification of SLS glass. The flexural strength of the body containing 6.25wt% SLS glass fired at 1l00°C (-71.2 MPa) was higher, modulus of elasticity slightly lower, and fracture toughness comparable to those of the standard whiteware body fired at 1200°C. The Weibull modulus of the partially SLS-fluxed whiteware was lower due to the presence of crystals inhomogeneously distributed over a complex microstructure. From the physical and mechanical properties investigated in this study, SLS glass can be used as part of the fluxing system of some fully densified whitewares.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Materials Science and Engineering (Sheffield)
Identification Number/EthosID: uk.bl.ethos.485068
Depositing User: EThOS Import Sheffield
Date Deposited: 13 Dec 2016 15:18
Last Modified: 13 Dec 2016 15:18
URI: http://etheses.whiterose.ac.uk/id/eprint/14505

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