论文部分内容阅读
NiTi samples were hydrothermally treated in NaOH at 200℃ with different soaking times. The morphology of the surface layer formed was studied by scanning electron microscopy (SEM). The composition of the layer and the major phases present were determined by energy-dispersive spectroscopy (EDS) and X-ray diffractometry (XRD), respectively. In contrast to the results reported by some authors,the surface layer was essentially Ni(OH)2 instead of being TiO2. The electrochemical behavior of the samples was studied by electrochemical impedance spectroscopy (EIS) in 3.5% NaCI solution at 23℃,and analyzed using a simplified Randle circuit consisting of a resistance R and a capacitance C in parallel. After hydrothermal treatment, R was increased by a factor ranging from 1.5 to 5.0 times, depending on the treatment time. The value of R of all the samples became steady within a period of less than 15 h. Results of the present study indicate that alkaline treatment leads to the growth of an insulating layer on NiT
NiTi samples were hydrothermally treated in NaOH at 200 ° C with different soaking times. The morphology of the surface layer formed was studied by scanning electron microscopy (SEM). The composition of the layer and the major phases present were determined by energy-dispersive spectroscopy ( EDS) and X-ray diffractometry (XRD), respectively. In contrast to the results reported by some authors, the surface layer was essentially Ni (OH) 2 instead of being TiO2. The electrochemical behavior of the samples was studied by electrochemical impedance spectroscopy (EIS) in 3.5% NaCI solution at 23 ° C, and analyzed using a simplified Randle circuit consisting of a resistance R and a capacitance C in parallel. After hydrothermal treatment, R was increased by a factor ranging from 1.5 to 5.0 times, depending on the treatment time. The value of R of all the samples was steady within a period of less than 15 h. Results of the present study indicate that alkaline treatment leads to the growth of an ins ulating layer on NiT