Fig. 4. XRD patterns of (a) uncoated, (b) (Ti, O, N)/Ti coated, and (Si, O, N)/(Ti, O, N)/Ti coated NiTi SMA samples.Figure optionsDownload full-size imageDownload as PowerPoint slide
The chemical composition of the (Si, O, N)/(Ti, O, N)/Ti coating surface BAY 80-6946 shown in Table 1. Si, O and N were major components on the surface of (Si, O, N)/(Ti, O, N)/Ti coating. Low carbon content was detected due to contamination by air exposure or handling. SiN, SiO and ON were reported to exhibit in silicon oxynitride coatings  and . Not only Ni but also Ti was depleted from surface, revealing that a Si containing outer layer formed on (Ti, O, N)/Ti inner layer, and that Ni-free surface was achieved. Heat treatment of NiTi SMA at 3 × 10−2 mbar and 400 °C for 150 min resulted in an almost Ni-free surface . For PIII treatment in the oxygen atmosphere, Ni ions and compound such as NiO, which is strong carcinogens, could still be detected on the surface of NiTi SMA through XPS analysis . In this study, Ni was not detected on the surface of (Si, O, N)/(Ti, O, N)/Ti coated NiTi SMA by XPS and EDX analysis (Table 2).