Foil Anode Research Articles

Preparation and photocatalytic activity of BiOX–TiO2 composite films (X=Cl, Br, I)

Being able to separate electron–hole pairs effectively, semiconductor compound systems can exhibit outstanding photocatalytic activity. Based on this consideration, BiOX–TiO2 composite films were prepared in this work. Firstly, TiO2 nanotube arrays were prepared through anodization of titanium foils; then BiOX (X=Cl, Br, I) was deposited into the TiO2 nanotube arrays by vacuum impregnation and chemical precipitation to obtain the required BiOX–TiO2 composite films. The morphologies, phase components, and photocatalytic activities of the samples were characterized by using scanning electron microscopy, X-ray diffractometry, and UV–vis spectrophotometry, respectively. Results showed that the bonding between BiOX and TiO2 decreased in the order X=Cl, Br and I, as did the photocatalytic activity. The BiOCl–TiO2 composite film exhibited better photocatalytic activity than those of the other samples due to effective transportation and long lifetime of the photo-induced electrons. Further experiments indicated that with BiOCl–TiO2 composite film as photocatalysts, the decolorization ratio of methyl orange solution reached 99.7% under xenon-light irradiation for 8h.

Simple and Rapid Spectrophotometric Determination of Titanium on Etched Aluminum Foils

Introduction of titanium oxides with high permittivity on etched aluminum foils’ surface has been successfully utilized to increase specific capacitance of anode foils for aluminum electrolytic capacitors. In order to quantify the concentration of titanium (IV) on the etched aluminum foil precisely, a simple and rapid spectrophotometric procedure has been developed. After optimizing a series of variables including absorbance wavelength, concentration of nitric acid, concentration of hydrogen peroxide, nitration time and developing time, analytical precision and accuracy were tested by using standard working solution containing known amount of titanium (IV). The results showed that Lambert-Beer’s law was obeyed in the range of 0.01 to 3.00 mmol·L﹣1. The relative standard deviation (RSD) ranged from 0.67% to 1.09% (n = 6), and the recovery was between 99.17% - 100.03%. Investigation on effect of Al3+ ion indicated that there was no interference in the absorbance of titanium (IV) at 410 nm. The proposed procedure was applied to real samples for the determination of titanium (IV), and the results were in a good agreement with the values certified by inductively coupled plasma-atomic emission spectrometry (ICP-AES).

A design optimization methodology for Li+ batteries

Design optimization for functionally graded battery electrodes is shown to improve the usable energy capacity of Li batteries predicted by computational simulations and numerically optimizing the electrode porosities and particle radii. A multi-scale battery model which accounts for nonlinear transient transport processes, electrochemical reactions, and mechanical deformations is used to predict the usable energy storage capacity of the battery over a range of discharge rates. A multi-objective formulation of the design problem is introduced to maximize the usable capacity over a range of discharge rates while limiting the mechanical stresses. The optimization problem is solved via a gradient based optimization. A LiMn2O4 cathode is simulated with a PEO–LiCF3SO3 electrolyte and both a Li Foil (half cell) and LiC6 anode. Studies were performed on both half and full cell configurations resulting in distinctly different optimal electrode designs. The numerical results show that the highest rate discharge drives the simulations and the optimal designs are dominated by Li+ transport rates. The results also suggest that spatially varying electrode porosities and active particle sizes provides an efficient approach to improve the power-to-energy density of Li+ batteries. For the half cell configuration, the optimal design improves the discharge capacity by 29% while for the full cell the discharge capacity was improved 61% relative to an initial design with a uniform electrode structure. Most of the improvement in capacity was due to the spatially varying porosity, with up to 5% of the gains attributed to the particle radii design variables.

Fabrication of multilayer Nb2O5 nanoporous film by anodization of niobium foils

Multilayer Nb2O5 nanoporous films were successfully synthesized on Nb surfaces by the control anodization process in ethylene glycol containing 4 vol% HF and 2 vol% H2O2 electrolyte. The nanoporous films are characterized in detail by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The Nb2O5 nanoporous films have a multilayer morphology with the side wall thickness of ~5 nm, irregular pores with a diameter of ~25 nm, and a length of up to 7.39 μm, depending on the anodization time. A mechanism for the multilayer Nb2O5 nanoporous formation was also discussed. These nanoporous materials can be very useful in the fields of solar cells, gas sensors, catalysts, optical filters, and capacitors.

Anodized Preparation of Titanium Dioxide Nanotube Arrays and Photocatalytic Degradation of Chloramine Phosphorus

Anodic oxidation processing titanium foil in an aqueous solution of hydrofluoric acid+ glacial acetic acid+polyethylene glycol constant pressure, Synthesized by high-density ordered TiO2nanotube arrays. Calculate the degradation rate of chloramine phosphorus, TiO2nanotubes catalytic performance test.The use of scanning electron microscopy (SEM) and X-ray diffraction (XRD) to characterize the morphology and structure of the nanotubes, Visits oxidation time on the morphology and size of the nanotube arrays, mapping and analysis of current - time curve. An average particle diameter d of the sample may be calculated the strongest diffraction peak of the plane FWHM ,So chloramine phosphorus selection of organic phosphorus drugs for the photocatalytic degradation object, Molybdenum blue spectrophotometry measured and calculated degradation rate, Study of heat treatment temperature and anodizing time photocatalytic degradation, And the sol - gel prepared TiO2 thin film and photocatalytic comparative experiments.

Erratum: Nanocontainers made of Various Materials with Tunable Shape and Size

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications.

Acceleration of Ions by an Electron Beam Injected Into a Closed Conducting Cavity

In a pinched-beam ion diode, an intense electron beam focuses on-axis at the center of the anode and passes through the thin anode foil into a beam dump region behind the anode foil. The beam dump usually consists of an evacuated cylindrical anode-can. Because of energy deposition from the intense electron beam, the interior surfaces of the anode-can are expected to be space-charge-limited emitters. Therefore, the electron space charge from the beam in the anode-can will draw ions off these surfaces. There is evidence from nuclear activation which suggests that ions exist in the anode-can with energies that significantly exceed those associated with the diode voltage. Analysis and particle-in-cell simulations show that a virtual cathode can form in the anode-can that accelerates ions up to the energy associated with the diode voltage. Additionally, a subset of these ions can form current bursts that are driven to the outer wall of the anode-can with ion energies as high as a few times the energy associated with the diode voltage.

Nanocontainers made of Various Materials with Tunable Shape and Size

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications.

Charge-induced reversible bending in nanoporous alumina-aluminum composite

Upon electrical charging, reversible bending was found in nanoporous anodic alumina-aluminum foil composites, as directly observed by an optical microscope and detected by in situ nanoindentation. The bending is thought to be the result of charge-induced surface stresses in the nanoporous alumina. The results suggest the possibility of a type of composite foil materials for applications as micro-scale actuators to transform electrical energy into mechanical energy.

Breakdown of gas gaps in a nonuniform electric field at a subnanosecond voltage pulse rise time

The influence of the nitrogen pressure on the breakdown voltage in a nonuniform electric field is studied. Voltage pulses with nanosecond and subnanosecond rise times are applied to the gas gap. Simultaneously with the application of voltage pulses, supershort avalanche electron beam pulses are observed behind a foil anode. It is found that, when a runaway electron beam is generated and voltage pulses have a subnano-second rise time, the breakdown voltage rises as the nitrogen pressure decreases from 9 × 104 to 1 × 102 Pa. Experimental data are in good agreement with pulsed breakdown analytical curves.

Ag2SO4 decorated with fluorescent Agn nanoclusters

Here we report on the production of an Ag2SO4/Ag2O mixed-grain powder during the anodization of Ag foil in a HF-H2SO4 electrolyte. We propose that there are three competing reactions during the anodization process: (i) the production of Ag2O at the Ag foil anode surface from the presence of water in the electrolyte, (ii) the dissolution of the Ag2O in the presence of HF releasing Ag+ ions, (iii) the precipitation of Ag+ and SO42− ions, as Ag2SO4 on the Ag foil anode surface. This co-precipitation/dissolution process ultimately results in a mixed-grain powder. We then show that the Ag2O embedded within the mixed-grain is photo-decomposed to produce highly fluorescent silver nanoclusters (Agn) which decorate the Ag2SO4 crystals. The Ag2SO4 salt offers a stable matrix for the photo-decomposed Agn nanoclusters to emit their strong fluorescence.

Titania nanotube porosity controls dissolution rate of sputter deposited calcium phosphate (CaP) thin film coatings

Calcium phosphate (CaP) coatings are of continuing significant interest due to their ability to directly promote bone cell differentiation. Whereas sputter deposited CaP coatings have much to offer in this regard, in the as-deposited state they are inherently amorphous and readily undergo rapid dissolution. This behaviour severely limits their ability to support bone cell adhesion and the subsequent events of proliferation and/or differentiation without subsequent processing such as thermal annealing. Removal of the need for this additional processing step would significantly increase their utility. This paper reports a study of the use of nano-porous titania substrates to directly control the rate of dissolution of thin amorphous as-deposited CaP sputter coatings. Titania nanotubes with different pore sizes were prepared by electrochemical anodization of titanium foils and sputter coated with CaP. Dissolution studies were performed on the as-deposited CaP layers in cell culture media for periods of up to 21 days. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis confirmed the potential of the nanotubes to prolong the rate of loss of CaP over the entire 21 day period as compared to coatings prepared on flat polished titanium surfaces, which dissolved completely in less than 48 h. The CaP coated titania nanotube surfaces showed high levels of osteoblast attachment and proliferation with no signs of cell death. Alkaline phosphatase (ALP) activity measurements at 21 days indicated that the highest levels of osteoblast differentiation occurred on CaP thin films deposited onto titania nanotubes with an average pore size of 30 ± 7.5 nm and tube length of 1.3 ± 0.2 μm. These results indicate that prolonged availability of the as-deposited sputtered CaP can be provided for by use of a substrate surface comprising titania nanotubes. Moreover, nanotube pore size and tube length affect the rate of CaP dissolution and attendant cell behaviour thereon.

Vanadium pentoxide cathode materials for high-performance lithium-ion batteries enabled by a hierarchical nanoflower structure via an electrochemical process

Hierarchical vanadium oxide nanoflowers (V10O24·nH2O) were synthesized via a simple, high throughput method employing a fast electrochemical reaction of vanadium foil in NaCl aqueous solution, followed by an aging treatment at room temperature. During the electrochemical process, the anodic vanadium foil is dissolved in the form of multi-valence vanadium ions into the solution, driven by the applied electrical field. After being oxidized, the VO2+ and VO2+ ions instantly react with the OH− in the electrolyte to form uniformly distributed vanadium oxide nanoparticles at a high solution temperature due to the exothermic nature of the reaction. Finally, nucleation and growth of one dimensional nanoribbons takes place on the surface of the nanoparticles during the aging process to form unique hierarchical V10O24·nH2O nanoflowers. Upon heat treatment, the hierarchical architecture of the vanadium pentoxide nanoflower morphology is maintained. Such a material provides porous channels, which facilitate fast ion diffusion and effective strain relaxation upon Li ion charge–discharge cycling. The electrochemical tests reveal that the V2O5 nanoflowers cathode could deliver high reversible specific capacities with 100% coulombic efficiency, especially at high C rates (e.g., 140 mAh g−1 at 10 C).

Effect of the electrolyte temperature on the formation and structure of porous anodic titania film

The porous titania growth during electrochemical anodization of titanium films and foils in the 0.1M ammonium fluoride (FNH4) solution in ethyleneglycol has been studied in the temperature range from −5°C to +20°C. Titania films with a smooth tubular morphology was found to be formed at the electrolyte temperatures below 0°C. The growth rate was as high as 1.5μm/min provided that the tube diameters were up to 300nm and the film porosity was less than 1%. Porous titanium anodization at the electrolyte temperature of 0°C and below induces formation of porous titania with a structure close to ideal packed hexagonal prisms with a smooth tubular surface. The mechanism of the appearance of such structure is discussed.

Preparation and photocatalytic activity for water splitting of Pt–Na2Ta2O6 nanotube arrays

Na2Ta2O6 nanotube arrays were prepared by hydrothermal method from Ta2O5 nanotube arrays, obtained by anodization of Ta foils, in Na2CO3 solution at 150°C. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV–vis diffuse reflectance spectra (UV-DRS) and X-ray photoelectron spectroscopy (XPS). Analysis results show that pyrochlore structure Na2Ta2O6 nanotube arrays have been successfully fabricated. The diameters and lengths of Na2Ta2O6 nanotube arrays are 50nm and 4μm, respectively. The photocatalytic hydrogen production activities of the as-synthesized Na2Ta2O6 nanotube arrays are highly dependent on the hydrothermal reaction time and Na2CO3 concentration, optimized reaction parameters are obtained. To further improve the photocatalytic activity for hydrogen evolution, Pt loaded Na2Ta2O6 nanotube arrays are prepared by photochemical reduction method. The Pt loaded samples exhibit much higher activity for hydrogen evolution than pure Na2Ta2O6 nanotube arrays. Moreover, the photocatalytic hydrogen properties are rather stable.

Experimental and numerical investigation of two mechanisms underlying runaway electron beam formation

The electrical breakdown of a gas-filled diode with a highly nonuniform electric field is studied in the case when a 25-kV voltage pulse generates runaway electron beams with time-separated maxima of different duration behind anode foil. Experimental data are analyzed and numerically simulated using the PIC/MC code OOPIC-Pro. It is shown that, in terms of the model used, both beams arise at the cathode but their formation mechanisms differ. The first runaway electron beam no longer than 500 ps is attributed to the ionization mechanism; the second one, which may last several nanoseconds, is due to emission.

Structural and photoelectrochemical characterization of TiO2 nanowire/nanotube electrodes by electrochemical etching

TiO2 nanowire/nanotube electrodes were synthesized by anodization of titanium foils in ethylene glycol solution containing 0.5 wt% NH4F and 1 wt% water at 60 V for 6 h. The microstructure and morphology of the asprepared electrodes were investigated by XRD and SEM. A possible formation mechanism and oxidation parameters of nanocomposite structure were discussed. The relationship between structural characteristics of TiO2 nanowire/nanotube electrodes and its photoelectrochemical characterization were evaluated by electrochemical analyzer and photocatalytic degradation of methylene blue (MB) solution. Furthermore, these TiO2 nanowire/nanotube electrodes promoted the photoelectrochemical characterization due to the larger surface areas, enhanced light harvesting and electron transport rate. The results show that photocurrent density of 1.44mA/cm2 and photocatalytic degradation of 95.51% was achieved for TiO2 nanowire/nanotube electrodes, which were 0.55mA/cm2 and 20.52% higher than the TiO2 nanotube electrodes under a similar condition, respectively.

Synthesis of Various Generations Titania Nanotube Arrays by Electrochemical Anodization for H2 Production

The synthesis of second, third and fourth generation of highly ordered titania nanotubular photoanodes by electrochemical anodization of Ti thin foils in different electrolytes is reported. Field emission gun scanning electron microscope analysis indicated that films composed by nanotubes have a high porous tubular morphology. X-ray diffraction results confirmed that annealed titania nanotubes have anatase/rutile phase. Diffuse reflectance UV-Vis spectra analysis indicated that the band gap for various generation titania nanotube arrays as 3.0, 2.8 and 2.5eV. The hydrogen generation of second, third and fourth generation titania nanotube arrays at an illumination of 10 mW/cm2 for 1h is 0.10, 0.28 and 0.36mL respectively.

Impact of mechanical bending on the electrochemical performance of bendable lithium batteries with paper-like free-standing V2O5–polypyrrole cathodes

Highly flexible, paper-like, free-standing V2O5 and V2O5–polypyrrole (PPy) films were prepared via the vacuum filtration method. The films are soft, lightweight, and mechanically robust. The electrochemical performance of the free-standing pure V2O5 electrode was improved by incorporating conducting polypyrrole. A bendable cell with a novel design was fabricated, consisting of a free-standing V2O5–PPy cathode film, gel electrolyte, and a lithium foil anode. The cell was tested under repeated bending conditions for several cycles. The results show that the battery performance of the repeatedly bent cell was similar to that of the conventional cell.

Gradient TiO2 Nanotube Arrays via Asymmetric Anodization

Gradient self-organized TiO2 nanotube arrays with the tube diameters and length gradually changing along the sample plane are conveniently fabricated. The fabrication method is based on asymmetric anodization with the point cathode placed close to the edge of the titanium foil anode. Mechanism study reveals that the drastic variance in the voltage drop over the tube bottom at different locations along the film is responsible for the formation of the gradient morphology. Experimentally, moderate electrolyte conductivities and sufficiently high anodization voltages are necessary to enable the desired gradient TiO2 nanotube arrays. Moreover, the structural features of the fabricated gradient TiO2 nanotube arrays can be further adjusted by controlling the imperfection level of the titanium substrate.