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Investigating the formulation of silica-based ceramic core materials for investment casting

Wilson, Paul James (2011)
Eng.D. thesis, University of Birmingham.

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Abstract

An investigation has been performed into the formulation of silica-based ceramic core materials for investment casting. The formulation of 3 materials that are currently used by Ross Ceramics was investigated in detail and the data from this used to determine the elements of the formulation that should be investigated in more detail. The techniques used included a variety of mechanical tests at both room and high temperatures, dilatometry, phase analysis by XRD and chemical analysis by XRF, pore analysis by simple Archimedes tests and mercury porosimetry and both scanning electron and transmitted light microscopy. A large number of materials were created with different formulations and the various characterisation techniques employed were used to determine the function of the different constituent.
It was determined that the function of zircon was to prevent grain boundary movement at elevated temperatures via the Zener effect, by acting as a non-reactive secondary phase. The zircon also had an additional consequence from the inherent contamination, with alumina, from the ball-mill procedure performed by the supplier. This had the effect of significantly affecting several high temperature properties. The effect of several dopant materials: TiO2, Al2O3, MgO, cristobalite seed and Molochite addition was also investigated. The latter two were determined to function mainly by their inherent contamination. The other additives affected the materials in different ways depending on the amount used and the presence of any phase eutectics that had detrimental effects on the high temperature material properties. The particle size distribution of the materials was also investigated. It was determined from the experiments that the D20 was an important factor for deterring final material properties and that most materials obeyed a modified Griffith’s crack theory relation, with the exception of materials with a larger zircon particle size than that of the main silica constituent.
From this work new materials could be created using the knowledge gained and material properties could be optimised to meet specific requirements by changing zircon quantity, dopant levels and particle size.

Type of Work:Eng.D. thesis.
Supervisor(s):Blackburn, Stuart and Greenwood, Richard
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemical Engineering
Additional Information:

Thesis is embargoed until 1 Feb 2016

Subjects:Q Science (General)
TS Manufactures
Institution:University of Birmingham
ID Code:2829
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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