Nature of oxide layer formed on NiTi by anodic oxidation in methanol

F. T. Cheng, P. Shi, Hau Chung Man

Research output: Journal article publicationJournal articleAcademic researchpeer-review

50 Citations (Scopus)


NiTi was galvanostatically anodized in a methanolic electrolyte to form a thick (more than 10 μm) and uniform oxide layer. The oxide layer was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), thin-film X-ray diffractometry (TF-XRD), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The layer was composed of a mixture of TiO2and metallic Ni while the surface of the layer contained non-stoichiometric nickel titanate (NiTiO3-x). The as-prepared coating was free of cracks and composed of very fine crystallites. Vickers indentation showed that the as-prepared layer was ductile, with a low Vickers hardness of about 1.50 GPa. The high room-temperature ductility of the oxide coating was attributable to the nanosized crystallites in the coating.
Original languageEnglish
Pages (from-to)1516-1520
Number of pages5
JournalMaterials Letters
Issue number12
Publication statusPublished - 1 May 2005


  • Indentation
  • NiTi
  • Oxidation
  • Shape memory alloy
  • Thick coating
  • TiO 2

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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