Shape preserving conversion reactions of alumina structures using metal halides: Structures, kinetics, and applications
Shapero, Taylor McLachlan
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Porous anodic aluminum oxide nanostructures provide hexagonally ordered arrays of pores with periodic distribution and tunable size and length. The research in this dissertation introduces a new process for partially converting the chemistry of the aluminum oxide nanostructure to titanium dioxide while retaining shape through a gaseous metal halide (TiF4) reactive conversion process. By this process, oriented single and multi-wall titania nanotube arrays with tailored structures can be formed. This vapor-based process allows titania formation within small pores inaccessible to liquid-based approaches through an intermediary TiOF2 product. The research explores applications of converted titania structures, including dye-sensitized solar cells. The reactive conversion kinetics of Al2O3 into TiOF2 was studied to reveal two kinetic regimes likely limited by chemical reaction and solid-state diffusion allowing a stronger understanding of how the conversion reaction might be optimized in future applications. Other metal fluoride reactions with anodic aluminum oxide (Al2O3) are also studied (including the successful conversion of Al2O3 into Nb2O5) showing the versatility of converting anodic aluminum oxide for applications requiring certain other oxide materials.