Characterisation of surface oxidation of nickel–titanium alloy by ion-beam and electrochemical techniques
2004; Elsevier BV; Volume: 50; Issue: 1 Linguagem: Inglês
10.1016/j.electacta.2004.07.007
ISSN1873-3859
AutoresSimona Barison, Sandro Cattarin, S. Daolio, Marco Musiani, Ausonio Tuissi,
Tópico(s)Anodic Oxide Films and Nanostructures
ResumoThe passivating effects produced on Ni49Ti51 (at.%) shape memory alloy by electropolishing in methanol–sulphuric acid electrolyte or thermal treatment in air are investigated with ion-beam techniques (secondary ion mass spectrometry (SIMS) and mass resolved ion scattering spectrometry (MARISS)) and electrochemical techniques (polarisation curves, photocurrent spectroscopy and impedance). Electropolishing produces a limited passivation due to formation of a thin layer of amorphous TiO2, which causes only a slight hindrance to the oxygen evolution reaction. Thermal treatment in air at 450 °C causes a more substantial passivation due to formation of a thick oxide layer, estimated at about 80 nm for a 16 h treatment on the basis of weight increase, disregarding roughness. Data indicate that the film produced by thermal oxidation has probably a duplex structure, with a porous outer layer with inclusions of Ni species and a compact inner layer, in contact with the substrate, consisting of (essentially) nickel free TiO2 rutile.
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