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Abstract:In this study, electrophoretic deposition (EPD) technique was used to deposit titanium dioxide (TiO 2 ) thin films on conducting glass substrates for application in water purification from organic contaminants. Phenol was used as a model pollutant. The EPD suspension related parameters and deposition conditions were first optimized for good quality film deposits. The suspension stability and deposition conditions that result in good adherence of TiO 2 particles to the substrate with homogeneous film coatings, is ethanol with a pH of 3.0, a TiO 2 solid loading of 4.0 wt%, a 0.2 wt% iodine concentration in the solvent and a deposition voltage of 20.0V in a time of 210.0s. The photocatalytic activity of TiO 2 thin films decreases exponentially with the ultraviolet light (UV) illumination time and it is also dependent on film thickness, sintering temperature and the intensity of the UV light. Highest rate of photocatalytic activity is observed at an optimal film thickness of 95.0 ± 2.0µm sintered at 300.0°C. The implications of these results are discussed for design of inexpensive waste water purification systems for light industries before discharge into the ecosystem.

several sintered materials. He observed, with the exceptions of the data on Al 2 O 3 and porcelain, that the ultrasonic T he eVect of pore geometry on the elastic modulusvelocity in porous sintered materials was satisfactorily porosity relationship of a triaxial porcelain has been modelled by oblate spheroidal pores, and that various studied using the experimentally measured aspect ratio sintering processes of the same material yielded different as a fitting parameter. T he experimental elastic moduaspect ratios for the spheroidal pores at comparable porositlus data have been compared with those predicted from ies. For every category of material studied by Phani, a theoretical models based on self-consistency spheroidal single value of a (effective aspect ratio) was used to fit all inclusion theory and analytically derived expressions the data over the entire porosity range. The failure of this of Boccaccini et al., Anderson, and Sudduth. A good model to fit the experimental data for Al 2 O 3 and porcelain fit was obtained with Boccaccini 's equation using the was attributed to lack of information/details about the experimentally determined aspect ratio at each level of pore structure. In practice, however, complexities such as porosity, and with Anderson's equation. Failure of the rearrangement of particles or grains during sintering occurs self-consistent scheme based theory to predict the which consequently alters the co-ordination number and experimental results over the porosity range of interest structure of the compact,8 resulting in a variable aspect was attributed to the fact that this theory is best suited ratio within the samples. Therefore the assumption that all for single phase materials rather than multiphase materpores are described by a single porosity aspect ratio may ials such as triaxial porcelain.BCT /390 not always be true. It is for this reason that Martin et al.9have advocated analysis of the modulus-porosity data on T he authors are in the Department of Physics, a point by point basis, that is, determining the modulus at University of Nairobi, PO Box 30197, Nairobi, Kenya.each porosity and the value of the aspect ratio which Manuscript received 2 July 1999; in final form provides the best fit with the theoretical prediction. 12 April 2000.Martin et al.9 showed that, by assigning each datum point a specific aspect ratio, and applying the Mori-Tanaka

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This paper presents the results of a combined experimental and theoretical study of microstructure and thermal shock resistance of an aluminosilicate ceramic. Shock-induced crack growth is studied in sintered structures produced from powders with different particle size ranges. The underlying crack/microstructure interactions and toughening mechanisms are elucidated via scanning electron microscopy (SEM). The resulting crack-tip shielding levels (due to viscoelastic crack bridging) are estimated using fracture mechanics concepts. The implications of the work are discussed for the design of high refractory ceramics against thermal shock.