Preparation of $TiO_2/Ti$ and $TiO_2/Al$ bilayer composites and hydrogen transport through $TiO_2/Pd$ and $Ta_2 O5/Ta$ bilayer composites

Abstract

The present work is concerned with the preparation of $TiO_2$/Ti and $TiO_2$/Al bilayer composites and hydrogen transport through $TiO_2$/Pd and $Ta_2O_5$/Ta bilayer composites In chapter III, the relationship between interfacial reaction and adhesion at the PVD-$TiO_2$ film/titanium or aluminum interfaces was investigated as a function of substrate temperature using Auger electron spectroscopy, scanning electron microscopy and scratch adhesion test. $TiO_2$ films were prepared by reactive rf- magnetron sputtering onto titanium and aluminum at substrate temperatures ranging from 313K to 523K. Scanning electron microscopy suggested that any compound formation hardly occurred, but interdiffusion layer was formed at the $TiO_2$/Ti interface. As against to this, Auger electron spectroscopy depth profile and scanning electron microscopy revealed the formation of aluminum oxide at the $TiO_2$/Al interface. The fracture mode of $TiO_2$ films on titanium changed predominantly from the chipping manner below 388 K to the cohesive type above 438 K. In contrast, the $TiO_2$ film on aluminum fractured in fully-adhesive type only at the substrate temperatures higher than 438K. Variations in adhesion of the $TiO_2$ films on titanium and aluminum were explained with substrate temperature as related to interfacial reaction. In chapter IV, the CNLS data fitting method allowed us to quantitatively determine the circuit elements from the proposed equivalent circuit at the PECVD-$TiO_2$ film/0.1 M NaOH solution interface. The substantial difference between the circuit elements determined from the classical and proposed equivalent circuits, accounted for the occurrence of slow relaxation processes near the flatband potential. The appearance of the minimum value of adsorption capacitance close at the flatband potential has been considered with respect to hydrogen adsorption/absorption into the $TiO_2$ film. In chapter V, hydrogen adsorption/absorption reaction and transport through $...