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Abstract:
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The present thesis develops from the point of view of titania sol-gel chemistry and an attempt is made to address the modification of the process for better photoactive titania
by selective doping and also demonstration of utilization of the process for the
preparation of supported membranes and self cleaning films.A general introduction to nanomaterials, nanocrystalline titania and sol-gel
chemistry are presented in the first chapter. A brief and updated literature review on
sol-gel titania, with special emphasis on catalytic and photocatalytic properties and
anatase to rutile transformation are covered. Based on critical assessment of the reported
information the present research problem has been defined.The second chapter describes a new aqueous sol-gel method for the preparation
of nanocrystalline titania using titanyl sulphate as precursor. This approach is novel
since no earlier work has been reported in the same lines proposed here. The sol-gel
process has been followed at each step using particle size, zeta potential measurements
on the sol and thermal analysis of the resultant gel. The prepared powders were then
characterized using X-ray diffraction, FTIR, BET surface area analysis and transmission
electron microscopy.The third chapter presents a detailed discussion on the physico-chemical
characterization of the aqueous sol-gel derived doped titania. The effect of dopants such
as tantalum, gadolinium and ytterbium on the anatase to rutile phase transformation,
surface area as well as their influence on photoactivity is also included.
The fourth chapter demonstrates application of the aqueous sol-gel method in
developing titania coatings on porous alumina substrates for controlling the poresize for
use as membrane elements in ultrafiltration. Thin coatings having ~50 nm thickness and
transparency of ~90% developed on glass surface were tested successfully for self
cleaning applications. |