Lin Changjian

Electrochemical Construction and Biological Performance of Micropatterned CaP Films

National Natural Science Foundation of China [20620130427, 20773100]; National Key Basic Research Program of China (973) [2007CB935603]; Ministry of Science and Technology of China [2007DFC40440]

The Fe-doped TiO2 nanotube arrays as a photoanode for cathodic protection of stainless steel

A highly ordered Fe-doped TiO2 nanotube layer was fabricated by potentiostatic anodization of pure titanium in fluorinated electrolyte solutions containing iron ions. The structure and composition of the as-prepared TiO2 nanotubes were characterized by SEM, XRD, UV-Vis, and XPS. The effects of temperature, time, dopant content on the morphologies, structure and photochemical properties of the TiO2 nanotube arrays were investigated systemically. The performances of photogenerated cathodic protection and the photoelectrochemical response for the Fe-doped TiO2 nanotube layers under illumination and dark conditions were evaluated through the electrochemical measurements. It was found that Fe ions in the TiO2 nanotube arrays could suppress the recombination of photogenerated hole-electron. The Fe-doped TiO2 nanotubes showed a stronger absorption in the 410650 nm range. The open-circuit potentials of 316L SS (stainless steel) coupled with the Fe-doped TiO2 nanotubes layers shifted negatively under visible light irradiation (!>400 nm), and maintained negatively for a period even in dark condition. It was indicated that the Fe-doped TiO2 nanotubes layers were able to create effectively a photogenerated cathodic protection for metals under regular sunlight conditions.

CORRELATION BETWEEN COMPOSITION OF REINFORCING STEEL SURFACE FILM AND STEEL CORROSION BEHAVIOR IN SIMULATED CONCRETE PORE SOLUTIONS

National Natural Science Foundation of China [21073151, 50731004]; National High Technology Research and Development Program of China [2009AA03Z327]

Electrical transport properties of individual TiO2 nanowire in one dimension

The anatase TiO2 nanowire arrays with 60 nm diameter and 20 nm diameter were prepared within the nanochannels of anodic aluminum oxide (AAO) template by an electrochemically induced sol-gel method. Atomic force microscopy (AFM) technique was applied to map topographic image at half-contact mode and to measure current-voltage characteristics of individual TiO2 nanowire at contact mode. The I-V characteristics of individual TiO2 nanowire by AFM revealed semiconductor characteristics. The bias voltage resulting in a measurable current on individual TiO2 nanowire was much lower than that on the bulk TiO2 materials,and its value increased with the diameter of individual nanowire decreasing.

EFFECT OF NO2- AND Cl- ON THE CORROSION BEHAVIOR OF REINFORCING STEEL IN SIMULATED CONCRETE PORE SOLUTIONS

应用极化曲线法和电化学阻抗技术研究了NO2^-和Cl^-对钢筋在不同pH值的模拟混凝土孔隙液中的腐蚀行为,结果表明,钢筋耐蚀性与溶液的pH值,以及NO2^-和Cl^-的浓度相关,pH值的降低和Cl^-浓度的增高都会使钢筋的耐蚀性降低。在含Cl^-的模拟液中,随着NO2^-浓度升高,钢筋腐蚀速率降低,在pH值为12.50和10.50的溶液中,当[NO2^-]/[Cl^-]≥0.4时,NO2^-对钢筋具有良好的阻锈作用。Under normal conditions, reinforcing steel in concrete maintains its passivity because of the high alkalinity of the concrete pore solution. However, steel passivity may be broken and the steel corrosion takes place due to concrete carbonation and/or chloride ingress. In fact, premature failure of reinforced concrete structures due to the steel corrosion has been a major problem in civil engineering. Therefore, the study of corrosion and protection of reinforcing steel is of indispensable importance to prolonging the service life of reinforced concrete structures. The application of inhibitors is an effective and economical method to prevent the corrosion of reinforcing steel. NaNO2 is a notable corrosion inhibitor which is effective in the steel corrosion control by reacting with ferrous ions to form a protective ferric oxide film on the steel surface, but unfortunately it can also accelerate the steel corrosion when the amount of nitrite is insufficient in amedium. In the present work, the linear polarization and electrochemical impedance spectroscopy were used to study the effect of nitrite and chloride ions on the corrosion behavior of reinforcing steel in simulated concrete pore solutions with different pH values. The results showed that the corrosion resistance of reinforcing steel is related with the pH value of the solution, nitrite ion concentrations and chloride ion concentrations. The drop of pH value and the increase of chloride ion concentration would result in the decline of corrosion resistance of reinforcing steel in the solution. The corrosion rate of reinforcing steel decreased with the NO 2 concentration increasing in the simulated concrete pore solutions with Cl , and the NO 2 ions had a good inhibiting effect on the steel when the concentration ratio of NO 2 and Cl was 0.4 or higher for the solutions of pH=12.50 or pH=10.50.