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Surface chemistry and topographical changes of an electropolished NiTi shape memory alloy
Author(s) -
Neelakantan Lakshman,
Valtiner Markus,
Eggeler Gunther,
Hassel Achim Walter
Publication year - 2010
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200983312
Subject(s) - electropolishing , x ray photoelectron spectroscopy , materials science , nickel titanium , shape memory alloy , metallurgy , surface roughness , surface finish , alloy , phase (matter) , sulfuric acid , chemical engineering , chemistry , composite material , organic chemistry , electrode , engineering , electrolyte
Electropolishing and its mechanism for NiTi shape memory alloy in methanolic sulfuric acid have been investigated recently. In the current study, X‐ray photoelectron spectroscopy was carried out to characterize the chemical nature of the electropolished surface. The electropolished surface is covered by a thin layer of TiO 2 . For an electropolished specimen, the Ni:Ti ratio at surface (∼1 nm) was 0.31, whereas for a mechanically polished specimen the ratio was 0.70. The second aspect of this work is the attempt to characterize the salt film formed during electropolishing. The characterization of salt‐film showed sulfide and sulfate compounds of Ni and/or Ti. The crystallographic and topographical changes caused due to thermally induced phase transformation on an electropolished NiTi was followed by in situ XRD and AFM. AFM studies revealed significant changes in the surface features due to phase transformation. The surface roughness value increased by a factor of 2.