In-situ determination of thickness and electrochemical properties of barrier oxide film on impure aluminium in aqueous solution

Lead is present as a trace element (ppm level) in nearly all commercial aluminium alloys. The objective of this work is to investigate the changes incurred by the presence of a small amount (20 ppm) of alloyed Pb and heat treatment on the properties of the barrier oxide in relation to those on pure aluminium, in chloride free acetate buffer. The potential range of interest was − 1.1 to − 0.1 V versus saturated Hg/Hg2SO4. The methods used were electrochemical impedance spectroscopy (EIS) and chronoamperometry. The film growth data obtained by chronoamperometry was analysed by use of Cabrera–Mott inverse square logarithmic law. The activation energy for film growth, obtained from this analysis, decreased with increasing heat treatment time and temperature, along with deleterious changes in the electrochemical properties of the oxide, indicating reduced passivity. The steady state data obtained by EIS showed decreasing oxide resistivity with increasing heat-treatment temperature of the samples in the range 300–600 °C. These changes were attributed to reduced passivity caused by increased segregation of Pb at the aluminium substrate-film interface

Optical and magnetooptical properties of bismuth and gallium substituted iron garnet films

Contains fulltext : 60235.pdf (publisher's version ) (Open Access)A series of iron garnet films of composition Lu3-xBixFe5-yGayO12 grown on (100) oriented GGG substrates have been studied using variable angle spectroscopic ellipsometry and polar Keff spectroscopy (MOKE). The diagonal and off-diagonal components of the permittivity tensor have been determined in the range 1-5 eV Our results seem to be in accordance with previously reported measurements on similar systems. We find that the optical absorption is reduced as the gallium content is increased. With increased Ga doping we also see an increase in the real part of epsilon(0) above 3.7 eV, but a decrease for lower energies. In the spectra of the off-diagonal permittivity tensor components we observe bismuth enhancement and gallium dilution effects. (C) 2003 Elsevier B.V. All rights reserved