Electrochemical properties, chemical composition and thickness of passive film formed on novel Ti–20Nb–10Zr–5Ta alloy

Ellipsometric study of bovine serum albumin adsorbed onto Ti/TiO2 electrodes

Photoelectrochemical characterization of thin anodic oxide films on zirconium metal

Influence of the forming electrolyte on the electrical properties of anodic zirconium oxide films: Part II. Ac impedance investigation

Anodic zirconium oxide films were grown potentiodynamically at a constant sweep rate up to the breakdown potential on rod electrodes made of 99.8% metallic zirconium. Different media of different pH were tested, namely 0.5 M H2SO4 (pH 0.3), 0.1 M Na2SO4 (pH 9) and 0.1 M NaOH (pH 13). By electrochemical impedance spectroscopy and scanning electron microscopy the oxide film thickness was monitored during the voltage scan. The behaviour was found to be different in the presence and absence of sulphate anions. In the presence of SO4) , the films were dense but breakdown occurred at 300–340 nm. In NaOH, two relaxations appeared above 50 V and were ascribed to a bi-layered coating structure and the maximum layer thickness was 720 nm before breakdown.

Impedance spectroscopy study of anodic growth of thick zirconium oxide films in H2SO4, Na2SO4 and NaOH solutions

The anodic oxidation of zirconium was studied by in situ ellipsometry together with capacity measurements. The oxides were grown under potentiodynamic, galvanostatic, and potentiostatic conditions up to final potentials of 100 V in 0.5M H[sub 2]SO[sub 4] solution. The refractive index of the oxides changes depending on the growth current. The films were slightly absorbing but their absorption coefficient was independent of the oxide growth conditions. Different methods of surface preparation including etching in hydrofluoric acid-based mixtures, electropolishing and mechanical polishing were used. The surfaces and oxides were characterized by SEM examination and XPS measurements. The surface pretreatment affects both the substrate and the oxide optical constants as well as the rate of oxide growth. The density and dielectric constant of the oxides were calculated performing simultaneous ellipsometric, coulometric, and capacity measurements.

E. M. Patrito

Papers

Ellipsometric Investigation of Anodic Zirconium Oxide Films