Abstract
Photoelectrochemical and ESCA methods were applied to the passive films formed on a variety of amorphous NiTi alloys and pure titanium in a deaerated sulfuric acid at 303 K polarized at various anodic potentials. Photocurrents were measured as a function of wavelength, potential and alloy composition. All the specimens showed positive photocurrent. From the photocurrent spectra, a band-gap energy of 3.2 eV was determined for the passive films on pure titanium and amorphous NiTi alloys. The photocurrent increased linearly with the Ti content in the alloys. The passive films on Ni40Ti alloy were enriched with Ti in all the potential regions examined in comparison with bulk alloy composition. Dilution of photoactive Ti ions in the passive film by the presence of Ni ions, therefore, results in a negative effect more than that expected from the passive film composition.
Published Version
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