مشخصات پژوهش

عنوان	In-situ formation of TiN-TiO2 composite layer on NiTi shape memory alloy via fluidized bed reactor
نوع پژوهش	مقاله چاپ‌شده در مجلات علمی
کلیدواژه‌ها	NiTi Shape memory alloy, Gaseous oxynitriding, Microstructural assessment, Phase analysis, Electrochemical behavior, Biocompatibility
چکیده	In this work, the NiTi alloy was oxynitrided in a fluidized bed reactor to attain an in-situ TiN-TiO2 protective composite layer. Samples were treated at 540 ± 10 °C for various holding times ranging between 0 h and 8 h. Microstructural evolution on the surface was analyzed by scanning electron microscopy, X-ray diffraction, hardness test, electrochemical behavior, Ni ion release, and bioactivity. Quantitative phase analysis from X-ray diffraction pattern of the treated sample for 8 h showed that TiN (71.3%) and TiO2 (23.0%) were dominant phases on surface. Hardness results revealed as the oxynitriding time increased from 0 h to 8 h, hardness values increased from 263.4 HV0.1 to 1227.4 HV0.1. Scanning electron microscopy observation and energy dispersive X-ray spectroscopy mapping micrographs showed that the grown of TiN with dendritic branches was hindered by Ni-rich regions. Electrochemical measurements using polarization and electrochemical impedance spectroscopy analysis revealed corrosion resistance of the oxynitrided samples was increased by ~170% from 173.3 kΩ cm2 for the bare NiTi alloy to 473.1 kΩ cm2 for the treated NiTi sample for 8 h. It was found that concentration of the released Ni ions decreased from 0.070 (bare NiTi) mg/l to 0.028 mg/l (treated for 8 h) after oxynitriding treatment. Enhanced biocompatibility of the surface treated sample for 8 h was explained by formation of thick and homogenous TiN-TiO2 composite layer. Finally, bioactive behavior of the oxynitrided samples were studied using simulated body fluid.
پژوهشگران	امیر مصطفایی (نفر پنجم)، محمد خوشقدم پیریوسفان (نفر چهارم)، جعفر خلیل علافی (نفر سوم)، احد محمدزاده (نفر دوم)، میلاد بدر (نفر اول)