Effects of H2O2 pretreatment on surface characteristics and bioactivity of NaOH-treated NiTi shape memory alloy

The effects of H2O2 pretreatment on the surface characteristics and bioactivity of NaOH-treated NiTi shape memory alloy(SMA) were investigated by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectra, Fourier transform infrared spectroscopy as well as a simulated body fluid(SBF) soaking test. It is found that the H2O2 pretreatment can lead to the direct creation of more Ti OH groups and the decrease in the amount of Ni2O3, Na2TiO3 and remnant NiTi phases on the surfaces of bioactive NiTi SMA prepared by NaOH treatment. As a result, the induction period of apatite formation is shortened by dispensing with the slow kinetic formation process of Ti OH groups via an exchange of Na+ ions from Na2TiO3 phase with H3O+ ions in SBF, which indicates that the bioactivity of NaOH-treated NiTi SMA can be further improved by the H2O2 pretreatment.