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Fabrication of porous ceramics and composites by a novel freeze casting process

Liu, Gang (2011)
Ph.D. thesis, University of Birmingham.

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Abstract

Porous ceramics have been widely used in many fields. Among the fabrication techniques for porous ceramic, freeze casting has recently attracted much attention as being a versatile, low cost and environmental friendly process. In this study, alumina and Al\(_2\)O\(_3\)-ZrO\(_2\) were utilized as model materials to investigate the preparation technique of freeze casting. Basic factors such as initial solids loading, cooling rate, and sintering temperature that would affect the final morphologies and the effect of additives have been studied. Porous alumina ceramics with lamellar microstructure exhibited compressive strengths up to 123 MPa for 33% porosity and 55 MPa for 42% porosity, making them suitable to be considered for potential load-bearing applications. In a two-phase system (Al\(_2\)O\(_3\)-ZrO\(_2\)), the choice of particle size of the ceramic powder was of great significance, which can lead to engulfment and phase segregation. BaTiO\(_3\) and Lead zirconate titanate (PZT) were employed to demonstrate the application of the freeze casting technique. BaTiO\(_3\)-epoxy composites exhibited modest piezoelectric constant but the dielectric constant was 1 order of magnitude higher than conventional composites with randomly distributed ceramic particles. For the 2-2 PZT-epoxy composites, with an increase of initial solids loading from 11 vol.% to 25 vol.%, the volume of ceramic phase in the composite gradually increased from about 30 vol.% to 50 vol.%, the piezoelectric constant \(d_{33}\) increased from about 103 pC/N to 203 pC/N, demonstrating the potential applications of this technique for the fabrication of 2-2 piezocomposites.

Type of Work:Ph.D. thesis.
Supervisor(s):Button, Timothy W.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Metallurgy and Materials
Keywords:freeze casting, porous ceramic, composite
Subjects:T Technology (General)
Institution:University of Birmingham
ID Code:1532
This unpublished thesis/dissertation is copyright of the author and/or third parties.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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