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Title: Electroacoustic and rheological measurements of concentrated inorganic suspensions
Author: Sykes, Caroline.
Awarding Body: University of Keele
Current Institution: Keele University
Date of Award: 2004
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The use of composite ceramic materials is increasingly important in industry as a consequence of their enhanced physical and chemical properties. However, a number of problems are associated with the production of multicomponent systems manufactured from an intermediate suspension of solids; a protocol commonly adopted in the genesis of ceramics. Specifically, the behaviour of the individual components within such a suspension is poorly understood and consequently the control of defect formation is a challenge. Several methods that can be employed to interrogate mixed suspensions include rheology and the determination of Zeta Potential (s potential). The recent development of electroacoustic spectroscopy as a tool for interrogating concentrated particulate suspensions has attracted much interest. This is due to the ability of the instrumentation to interrogate industrially relevant (Le. high solids volume) systems without the need for dilution, a factor which has limited the utility of historical data. With the advent of this new technique, a significant amount of research has focused upon homogeneous suspensions however very little effort has been devoted to mixed identity systems. In this thesis, mixed identity particulate systems have been investigated using electroacoustic spectroscopy and the results have been correlated with complementary rheological, mass titration and sedimentation experiments with a view to determining the feasibility of using this new technique for on-line measurements and process control. The mixed systems under investigation were micro (one dimension of the particulate being less than 10-6m) alumina with micro silica, micro alumina and nano (one dimension of the particulate being less than 1a-sm) silica and micro alumina and micro iron oxide (haematite). The first observation is the fact that the interpretation of the spectroscopic data secured from mixed systems is not a simple task. The summative influences of particle chemistry, size and dynamic mobility are not easily resolved, and at high solids loading, these cumulative influences have an impact upon the ability of the instrumentation to compute a s potential value. Several explanations for the deviance of the results have been given; physical or chemical coating, and the dampening of particle movement due to the high solid loadings and/or the interaction of oppositely charged particles are major factors. These conclusions are reinforced by the data secured from complementary analysis, namely mass titration, rheology and sedimentation. The research programme has provided an increased understanding of how electroacoustic spectroscopy can be used to interrogate mixed concentration systems. It can be concluded from the research however, that the Acoustosizer and O'Brien's theory cannot be employed for on-line measurements of mixed concentration suspensions as the Acoustosizer results do not provide zeta potential measurements that are meaningful to how the suspension behaves. One potential use for the Acoustosizer for on-line measurements however, would be to provide a simple quality control test with a very well defined suspension were the chemistry of the powder and the raw materials will not be altered significantly. This will have a rather limited industrial use.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available