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Surface conditions of Nitinol wires, tubing, and as‐cast alloys. The effect of chemical etching, aging in boiling water, and heat treatment
Author(s) -
Shabalovskaya S. A.,
Anderegg J.,
Laab F.,
Thiel P. A.,
Rondelli G.
Publication year - 2003
Publication title -
journal of biomedical materials research part b: applied biomaterials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.665
H-Index - 108
eISSN - 1552-4981
pISSN - 1552-4973
DOI - 10.1002/jbm.b.10001
Subject(s) - materials science , boiling , x ray photoelectron spectroscopy , auger electron spectroscopy , isotropic etching , scanning electron microscope , chemical state , etching (microfabrication) , oxide , metallurgy , contact angle , titanium , composite material , chemical engineering , chemistry , layer (electronics) , physics , organic chemistry , nuclear physics , engineering
The surface conditions of Nitinol wires and tubing were evaluated with the use of X‐ray photoelectron spectroscopy, high‐resolution Auger spectroscopy, electron backscattering, and scanning‐electron microscopy. Samples were studied in the as‐received state as well as after chemical etching, aging in boiling water, and heat treatment, and compared to a mechanically polished 600‐grit‐finish Nitinol surface treated similarly. General regularities in surface behavior induced by the examined surface treatments are similar for wires, tubing, and studied as‐cast alloy, though certain differences in surface Ni concentration were observed. Nitinol wires and tubing from various suppliers demonstrated great variability in Ni surface concentration (0.5–15 at.%) and Ti/Ni ratio (0.4–35). The wires in the as‐received state, with the exception of those with a black oxide originating in the processing procedure, revealed nickel and titanium on the surface in both elemental and oxidized states, indicating a nonpassive surface. Shape‐setting heat treatment at 500 °C for 15 min resulted in tremendous increase in the surface Ni concentration and complete Ni oxidation. Preliminary chemical etching and boiling in water successfully prevented surface enrichment in Ni, initially resulting from heat treatment. A stoichiometric uniformly amorphous TiO 2 oxide generated during chemical etching and aging in boiling water was reconstructed at 700 °C, revealing rutile structure. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 193–203, 2003