Interferometric Sensor for Electrochemical Studies of Metallic Alloys in Aqueuos Solution

In a previous study a mathematical model relating surface and bulk behaviors of metals in aqueous solution was developed. The model was established based on principles of holographic interferometry for measuring microsurface dissolution, i.e., mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e., corrosion current. In the present work, an interferometric sensor was built based on the above model, and the corrosion current density of coated copper and brass in seawater were obtained using this sensor. The interferometric sensor was also utilized for the first time to measure the initial stage of the anodization process (oxidation) of aluminium samples in aqueous solution. This was carried out chemically in different acid concentrations (3.125–25% H₂SO₄) at room temperature. The sensor was further used for observation of catalytic activities, i.e., pitting corrosion, which occurred subsequent to the anodization of the aluminium samples in aqueous solutions, after an oxide film had been formed.     

Measurement of the double layer capacitance of aluminium samples by holographic interferometry

In the present investigation, holographic interferometry was utilized for the first time to measure the double layer capacitance of aluminium samples during the initial stage of anodization processes in an aqueous solution without any physical contact. The anodization process (oxidation) of the aluminium samples was carried out chemically in different sulphuric acid concentrations (0.5–3.125% H₂S0₄) at room temperature. In the meantime, a method of holographic interferometry was used to measure the thickness of anodization (oxide film) of the aluminium samples in aqueous solutions. Along with the holographic measurement, a mathematical model was derived in order to correlate the double layer capacitance of the aluminium samples in solutions to the thickness of the oxide film of the aluminium samples which forms due to the chemical oxidation. The thickness of the oxide film of the aluminium samples was measured by real-time holographic interferometry. Consequently, holographic interferometry is found to be very useful for surface finish industries, especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film as well as the double layer capacitance of the aluminium samples can be determined in situ. In addition, a comparison was made between the obtained data of the double layer capacitance from the holographic measurements and the double layer capacitance data obtained from measurements of electrochemical impedance spectroscopy. The comparison indicates that there is good agreement between the data from both techniques.     

两步离子交换玻璃光功分器的折射率分布

介绍了在用两步离子交换方法制作光功分器中，在高斯分布为初始条件下采用平均法求出非线性两步离子扩散方程的折射率分布，与实验测出的折射率分布符合得很好。该法尤其对单模光功分器求其折射率更为简单和实用。     

Fabrication and characterization of ZnO-coated TiO2 nanotube arrays

In this study, we prepared highly ordered TiO₂ nanotube arrays on Ti through an anodizing process. Then, utilizing its proven antibacterial properties, we coated our TiO₂ nanotubes (TiO₂-NTs) with ZnO using the sol–gel method. We characterized the morphology, structure, and composition of the ZnO-coated TiO₂ nanotubes (ZnO-TNTs) using field-emission scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy, respectively. We investigated surface topography and roughness of the coatings by atomic force microscopy operated in the tapping mode. Our results revealed impurity-free, anatase-phase TiO₂ nanotubes that are uniformly coated with a ZnO layer. Finally, we tested the antibacterial activity of ZnO-TNTs against Staphylococcus aureus, and found ZnO-TNTs significantly improved the antibacterial properties of Ti implants. We conclude that ZnO-TNTs provide Ti with antibacterial activity, which highlights its potential in orthopedic and dental implants.     

强烈阳极氧化法快速制备多孔氧化铝模板

In the electrolyte of oxalic acid/alcohol/aqueous solution, highly-ordered porous anodic aluminum oxide(AAO) template was fabricated by hard anodization. The surface morphology and the structure of AAO template were characterized by Field-Emission Scanning Electron Microscope(FE-SEM) and XRD, respectively. The effects of different factors including alcohol type, ratio of alcohol to water, and oxalic acid concentration on the ordering degree and pore diameter of AAO template were investigated. Under the glycol to water ratio of 1∶1(by volume) with an oxalic acid concentration of 0.5 mol·L^-1, and voltage at 160 V, the obtained AAO template was hexangular arrangement with pore diameter of 80 nm and pores spacing of 120 nm, the growth rate was 51.9 μm·h^-1.     

Effect of surface finishing on the formation of nanostructure and corrosion behavior of Ni–Ti alloy

In the present work, we have investigated the formation of nanostructured oxide layers by anodic oxidation on different surface finished (mirror finished, 600 and 400 grit polished) nickel–titanium alloy (Ni–Ti) in electrolyte solution containing ethylene glycol and NH₄F_. The anodized surface has been characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X‐ray photoelectron spectroscopy (XPS). The corrosion behaviors of the Ni–Ti substrate and anodized samples have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in simulated body fluid (Hanks' solution). The results show that the native oxide on the substrate is replaced by nanostructures through anodization process. XPS of Ni–Ti substrate shows the presence of Ni⁰, NiO, Ti⁰ and TiO₂ species, whereas Ni₂O₃ and Ni(OH)₂ and TiO₂ are observed in the samples after anodization. Corrosion resistance of the anodized sample is comparable with that of the untreated sample. Copyright © 2016 John Wiley & Sons, Ltd.     

Double‐Side Co‐Catalytic Activation of Anodic TiO2 Nanotube Membranes with Sputter‐Coated Pt for Photocatalytic H2 Generation from Water/Methanol Mixtures

Self‐standing TiO₂ nanotube layers in the form of membranes are fabricated by self‐organizing anodization of Ti metal and a potential shock technique. The membranes are then decorated by sputtering different Pt amounts i) only at the top, ii) only at the bottom or iii) at both top and bottom of the tube layers. The Pt‐decorated membranes are transferred either in tube top‐up or in tube top‐down configuration onto FTO slides and are investigated, after crystallization, as photocatalysts for H₂ generation using either front or back‐side light irradiation. Double‐side Pt‐decoration of the tube membranes leads to higher H₂ generation rates (independently of tube and light‐irradiation configuration) compared to membranes decorated at only one side with similar overall Pt amounts. The results suggest that this effect cannot be only ascribed to the overall amount of Pt co‐catalyst as such but also to its distribution at both tube extremities. This leads to optimized light absorption and electron diffusion/transfer dynamics: the central part of the membranes acts as light‐harvesting zone and electrons therein generated can diffuse towards the Pt/TiO₂ active zones (tube extremities) where they can react with the environment and generate H₂.     

Single‐Walled TiO2 Nanotubes: Enhanced Carrier‐Transport Properties by TiCl4 Treatment

In the present work we report significant enhancement of the photoelectrochemical properties of self‐ organized TiO₂ nanotubes by a combined “de‐coring” of classic nanotubes followed by an appropiate TiCl4 treatment. We show that, except for the expected particle decoration, a key effect of the TiCl4 treatment is that the electron transport characteristics in TiO₂ nanotubes can be drastically improved, for example, we observe an enhancement of up to 70 % in electron‐transport times.     

碱/酸两步催化法制备耐候性SiO2增透膜的研究

以正硅酸乙酯(TEOS)为先驱体,采用碱/酸两步催化溶胶-凝胶法制备出一种兼具碱催化增透膜的高透过率和酸催化增透膜的良好耐摩擦性能的优点的SiO2增透膜。对酸碱催化SiO2相对比例及酸催化时水含量的系统研究表明,当酸催化SiO2的含量为50%时,增透膜综合性能最好,即具有高透过率和高耐摩擦性;当nH2O/nHCl=1∶0.0010时,增透膜的透过率最高。碱/酸两步催化法制备的增透膜与水的接触角仅为11.3°,本文进一步用六甲基二硅氧烷(HMDS)对增透膜表面进行了修饰,修饰后增透膜的接触角提高至52.5°,增透膜的疏水性及环境稳定性得到较大的提高。     

TiO2 nanotubes: synthesis and applications

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.