Anodic Oxidation Process Research Articles

An electrochemical study of two self-dopable water-soluble aniline derivatives: electrochemical deposition of copolymers.

An electrochemical study of two water-soluble aniline derivatives, N-(3-sulfopropyl) aniline (AnPS) and N-(3-sulfopropyl) p-aminodiphenylamine (DAnPS), in aqueous acidic electrolytic solutions containing different kinds of doping anions (Cl −, SO4 2−, and ClO4 −) was carried out. At sufficiently high anodic potential, the sulfonated aniline derivatives undergo oxidation processes yielding cation-radical and dimer intermediates, but no polymer deposition was observed on the working electrode surface. Experimental results showed that both aniline derivatives are electroactive compounds exhibiting redox behaviour in the range of potential of −0.2 V–1.6 V. Due to the self-doping effect induced by sulfonic groups, AnPS and DAnPS compounds have good electroactivity even in neat water solution. By adding a small amount of aniline into electrolytic system, thin layers of copolymers were deposited on the working electrode surface. The copolymer layers formed on the electrodes show a highly orientational and positional order, confirmed by AFM and XRD spectroscopic techniques. During the anodic oxidation processes some distinct colour changes were observed.

Redox processes in silicon dioxide thin films using copper microelectrodes

Although SiO2 is a typical insulator, we demonstrate an electrochemical characteristic of the Cu/Cu+ oxidation at the interface with 30 nm thick silicon dioxide thin films studied by cyclic voltammetry. This study reveals the process of anodic oxidation and subsequent reduction of oxidized Cu ions injected in the SiO2 layer with special attention to the kinetics of the redox process. We estimated the diffusion coefficient and the mobility of Cu ions in SiO2. The results gain deeper insight in the processes involved during resistive switching of Cu/SiO2 based nonvolatile memory devices.

Effect of the electrolyte composition on the anatase fraction of photocatalytic active TiO2 coatings prepared by plasma assisted anodic oxidation

Titanium dioxide is one of the most commonly used semiconductors for photocatalytic applications. In the majority of experimental studies, titanium dioxide is used in a powder form. In the present investigations titanium dioxide layers were formed by the plasma assisted anodic oxidation process SOLECTRO®. In this process a titanium substrate (anode) is dipped into an electrolyte bath containing a titanium precursor. Impressing a voltage greater than 100V, a titanium dioxide layer is deposited on the substrate in several minutes. The titanium dioxide is formed from the constituents of the electrolyte. For this reason, the composition of the electrolyte influences the deposition process and also the phase fractions and the layer morphology. It is known that the photocatalytic activity of titanium dioxide layers depends strongly on the anatase volume fraction, the layer morphology and therefore the specific surface area. The standard SOLECTRO® process generates titanium dioxide layers consisting of nearly 25vol.% anatase and 75vol.% rutile. In the present study, the electrolyte's constituents, especially the chelating agent, were varied to increase the anatase percentage. The results show that the anatase fraction and the specific surface area can be increased by substitution of ethylendiammintetraacetic acid by dieethylenetriaminepentaacetic acid. The anatase fraction amounts to 44vol.% using the new electrolyte composition.

Fe 3 C和珠光体对低碳铁素体钢腐蚀电化学行为的影响

The microstructure of X80 pipeline steel welding joint, consisted of Fe3C and de- generated pearlite, was simulated by carburizing treatment. The effects of Fe3C and pearlite on the electrochemical properties of bainitic ferrite steel and localized corrosion occurrence regularity in Ying- tan soil simulation solution were investigated by scanning Kelvin probe (SKP), scanning vibrating probe (SVP) and local electrochemical impedance spectroscopy (LEIS), combined with immersion test. It is demonstrated that the corrosion potential of degenerated pearlite is lower than bainitic ferrite, and decreases with increasing Fe3C content. Localized corrosion occurs on the surface of the carburized sample in Yingtan soil simulation solution. The anodic oxidation process is observed to be initiated on the carburized degenerated pearlite, whereas the cathodic reaction involving dissolved H + is on bainitic ferrite, and the anodic current density increases with increasing Fe3C concentration. As the ion contents of the soil simulation solution doubled, the anodic dissolution of degenerated pearlite increases, and the local impedance of the electrode decreases.

Dithiocarbamate Derivative as an Efficient Inhibitor for Copper

The corrosion inhibition behaviors for the self-assembled monolayers (SAMs) of ammonium pyrrolidine dithiocarbamate（APDTC） on the copper surface in HCl and NaCl solutions had been investigated by polarization curve, respectively. Prone to be adsorbed on the copper surface, the APDTC SAMs restrain both anodic oxidation and cathodic reduction process. The results indicated that APDTC SAMs had good corrosion inhibition effects on copper in both HCl and NaCl solutions.

Fabrication of Photofunctional Nanoporous Membrane and Its Photoinactivation Effect of Vesicular Stomatitis Virus

Fabrication and photophysical study of photofunctional nanoporous alumina membrane (PNAM) were performed, and its application of photodynamic antimicrobial chemotherapy (PACT) was investigated. Nanoporous alumina membrane (NAM) was fabricated by two‐step aluminium anodic oxidation process. Surface of the fabricated NAM was modified with organo‐silane agent to induce covalent bonding between NAM and a photosensitizer (PtCP: [5,10,15‐triphenyl‐20‐(4‐methoxycarbonylphenyl)‐porphyrin] platinum). PtCP was covalently bonded to the surface of the modified NAM by nucleophilic acyl substitution reaction process. The morphology and the photophysical properties of the fabricated PNAM were confirmed with field emission scanning electron microscope (FE‐SEM), steady‐state spectroscopies, and nanosecond laser‐induced time‐resolved spectroscopy. For the efficacy study of PNAM in PACT, an enveloped animal virus, vesicular stomatitis virus (VSV), was utilized as a target organism. Antiviral effect of the PNAM‐PACT was measured by the extent of suppression of plaque‐forming units (PFU) after the light irradiation. In the cultures inoculated with PACT‐treated VSV, the suppression of PFU was prominent, which demonstrates that PNAM is a potential bio clean‐up tool.

Processing Ti-25Ta-5Zr Bioalloy via Anodic Oxidation Procedure at High Voltage

The current paper reports the processing of Ti-25Ta-5Zr bioalloy via anodic oxidation in NH4BF4 solution under constant potentiostatic conditions at high voltage to obtain more suitable properties for biomedical application. The maximum efficiency of the procedure is reached at highest applied voltage, when the corrosion rate in Hank’s solution is decreased approxomately six times. The topography of the anodic layer has been studied using atomic force microscopy (AFM), and the results indicated that the anodic oxidation process increases the surface roughness. The AFM images indicated a different porosity for the anodized surfaces as well. After anodizing, the hydrophilic character of Ti-25Ta-5Zr samples has increased. A good correlation between corrosion rate obtained from potentiodynamic curves and corrosion rate from ions release analysis was obtained.

Studies on the oxidation rate of metallic inert anodes by measuring the oxygen evolved in low-temperature aluminium electrolysis

The rate of oxygen evolution on metallic inert anodes was measured as a function of current density during electrolysis of a low-melting NaF(12)–KF–AlF3 bath ([NaF + KF]/[AlF3] = 1.5 mol mol−1) at 800 °C. The oxidation rate of the anode substrate (A cm−2) was calculated. The anode oxidation process was depressed at the potentials of oxygen evolution. The dynamics of the decrease in the oxidation rate, which were obtained in previous study by the change in geometrical size of the metallic part of the specimen, was reproduced both by the technique proposed and also in potentiostatic electrolysis at potentials below that of oxygen evolution, in some cases, depending on prepolarisation.

Effect of electropolishing on electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al

The electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al after electropolishing in a self-developed electrolyte in comparison with conventional grinding were studied by electrochemical impedance spectroscopy (EIS). Optical microscopy (OM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the surface characteristics of the alloy. It was found from the EIS experiments that the polarization resistance (Rp) was increased, the double layer capacitance (Qc) was decreased and the electrochemical impedance of the alloy was enhanced by electropolishing. The electropolished surface was flat, smooth and bright and its roughness was 3.310 nm. To underline the advantage of electropolishing process against grinding to provide the anodic oxidation process with a higher quality substrate, the ground and electropolished titanium alloys were anodized in parallel under the same conditions. The corrosion behaviours of the two kinds of anodized titanium alloys were compared. It was revealed that electropolishing generated a high quality substrate and improved the corrosion resistance of anodic oxide film formed on titanium alloy Ti-10V-2Fe-3Al. Furthermore, the mechanism of electropolishing improving the corrosion resistance of the anodic oxide film was proposed.

Study on anode oxidation process of aluminum alloy foams and microwave absorbing properties

Porous aluminum anodizing film was prepared on aluminum alloy foams in oxalic acid solution by electrochemical method, Al-alloy foams were tested according to the Standard GJB 2038-94 “Method to test the reflectivity of radar absorbing materials”, i.e., the RCS (radar cross-section) method. Micromorphology and crystal structure of the oxide films were analyzed by scanning electron microscopy (SEM). The influence of oxalic acid solution consistency, oxidizing current density and temperature on the structure of porous aluminum anodizing film was investigated, and making a comparison between porous aluminum anodizing film produced by one step and two steps. The results show that microporous on the oxide film are equally distributed and the size of aperture is nearly same, porous aluminum anodizing film produced by one step anodic oxidation method is more superior than two step and the microwave absorbing properties of aluminum foams are enhance obviously after anodic oxidation.

陽極酸化プロセスによる硝酸、硫酸、リン酸を用いた共ドープナノポーラス酸化チタン粉末の合成と評価

陽極酸化プロセスによる硝酸、硫酸、リン酸を用いた共ドープナノポーラス酸化チタン粉末の合成と評価

Electrochemical Characterization of Anodic Tin Oxides with Nano-Porous Structure

A nano-porous structure of tin oxide was prepared using an anodic oxidation process and the sample's electrochemical properties were evaluated for application as an anode in a rechargeable lithium battery. Microscopic images of the as-anodized sample indicated that it has a nano-porous structure with an average pore size of several tens of nanometers and a pore wall size of about 10 nanometers; the structural/compositional analyses proved that it is amorphous stannous oxide (SnO). The powder form of the as-anodized specimen was satisfactorily lithiated and delithiated as the anode in a lithium battery. Furthermore, it showed high initial reversible capacity and superior rate performance when compared to previous fabrication attempts. Its excellent electrode performance is probably due to the effective alleviation of strain arising from a cycling-induced large volume change and the short diffusion length of lithium through the nano-structured sample. To further enhance the rate performance, the attempt was made to create porous tin oxide film on copper substrate by anodizing the electrodeposited tin. Nevertheless, the full anodization of tin film on a copper substrate led to the mechanical disintegration of the anodic tin oxide, due most likely to the vigorous gas evolution and the surface oxidation of copper substrate. The adhesion of anodic tin oxide to the substrate, together with the initial reversibility and cycling stability, needs to be further improved for its application to high-power electrode materials in lithium batteries.

Effects of Anodic Oxidation Process on Transmittance of Porous Alumina on Glass Substrate

Aluminum films were deposited on glass substrate by electron beam heat evaporation, and porous alumina films with high transmittance were prepared by means of anodic oxidation under different anodizing conditions in oxalic acid solution or phosphoric acid solution respectively. Thus the morphology of these porous alumina films was characterized by different structural. he optical transmittance spectrum at normal incidence over the 300~1000nm spectra region were obtained by spectrophotometer, which shows, in visible and ultraviolet light region, the transmittance of porous alumina films prepared in oxalic acid solution is much better than that prepared in phosphoric acid solution. The SEM analysis results showed that the pores are circular and uniform in porous alumina prepared in oxalic acid but irregular and non-uniform in that prepared in phosphoric acid, which affected the surface roughness of alumina films.

Fabrication of titanium dioxide nanofibers via anodic oxidation

In this work, titanium dioxide (TiO2) nanofibers were obtained from anodic oxidation process. A piece of titanium sheet was anodized in 1.0M sodium chloride (NaCl) solution, at 30V. The as-anodized sample was calcinated at 400°C for one hour. Subsequently the sample was characterized using field-emission scanning electron microscopy (FE-SEM), high resolution X-ray diffraction (HR-XRD), and Raman spectroscopy. Interestingly, results showed rutile phase dominates over anatase phase, which is rarely reported. In addition, the possible chemical reactions that lead to the formation of nanofibers were proposed. It was found that the nanofibers having an average length of 3μm, also diameter of 83nm.

Mineralization of antibiotic sulfamethoxazole by photoelectro-Fenton treatment using activated carbon fiber cathode and under UVA irradiation

The mineralization of antibiotic sulfamethoxazole (SMX) of concentrations up to 300mgL−1 was examined by photoelectro-Fenton (PEF) using an activated carbon fiber (ACF) cathode with UVA (365nm) irradiation. Comparative mineralization has been studied by different methods: RuO2/Ti anodic oxidation (AO), AO in the presence of electrogenerated H2O2 (AO-H2O2), AO-H2O2 in the presence of UVA (AO-H2O2-UVA), and both the electro-Fenton (EF) and PEF processes. PEF treatment at a low applied current of 0.36A yields a faster and more complete depollution with 80% of the TOC removed after 6h of electrolysis. The higher oxidative ability of the PEF process can be attributed to the additional hydroxyl radicals (OH) produced by the photo-Fenton reaction. The 63% mineralization in the case of EF treatment was due to the formation of short intermediates, such as carboxylic acids, which were difficult to oxidise with OH. In the AO-H2O2-UVA process, about 36% of the TOC was removed after 6h electrolysis, while 28% of the TOC was removed in the AO-H2O2 process. SMX is only slightly mineralized by the AO process, with only 25% of the TOC removed. HPLC–MS analysis allowed for up to six aromatic reaction products to be identified during the SMX degradation in the PEF process, mainly formed from the hydroxylation of the aromatic ring or/and isoxazole ring, accompanied by the substitution of the amine group (on aromatic cycle) or methyl group (on isoxazole ring) by OH. The carboxylic acids generated, including oxalic, maleic, oxamic, formic and acetic acids, were detected by ion-exclusion chromatography. The initial organic nitrogen was mainly converted into NH4+ along with a very small proportion of NO3− ion. Considering all the oxidation intermediates and end products for SMX degradation in the PEF process, a general mineralization mechanism by OH and UVA was proposed.

CuO-loaded nano-porous SnO 2 films fabricated by anodic oxidation and RIE process and their gas sensing properties

The fabrication of nano-porous SnO 2 films with 1-D nano-channels by anodic oxidation has been a challenge due to a collapse of pore structure during annealing process and an existence of non-porous upper barrier layer. A new approach is developed to synthesize the nano-porous SnO 2 films by employing Sn thin film instead of Sn foil and a reactive ion etching (RIE) process. The integrity of nano-porous structure was maintained by anodizing the Sn thin film deposited on SiO 2/Si substrate, and 1-D nano-channels were opened up by removing the non-porous layer by RIE. As a potential application to gas sensor, CuO was impregnated to the nano-porous SnO 2 films and their gas sensing properties were investigated. The nano-porous CuO–SnO 2 film sensors exhibited the enhanced sensitivity and selectivity toward H 2S gas, and their H 2S sensing mechanism was discussed in terms of the formation/disruption of resistive p-CuO/n-SnO 2 junction based on the variation of XPS binding energy and electrical resistance during gas exposure.

Electrochemical abatement of the antibiotic sulfamethoxazole from water

The electrochemical abatement of the antibiotic sulfamethoxazole (SMX) from aqueous solutions at pH 3.0 has been carried out by anodic oxidation and electro-Fenton (EF) processes with H 2O 2 electrogeneration. The electrolyses have been performed using a small, undivided cell equipped with a Pt or thin film boron-doped diamond (BDD) anode and a carbon-felt cathode. The higher performance of the EF process with 0.2 mM Fe 2+ in a BDD/carbon felt cell is demonstrated. This is due to the higher production of OH radicals, as well as to the simultaneous degradation at the anode surface and in the bulk solution. At low current, the oxidation at the anode was predominant; at high current, SMX was pre-eminently degraded in the bulk. SMX was quickly destroyed under all the conditions tested, following pseudo first-order kinetics; however, the almost total removal of the total organic carbon was only achieved in the BDD/carbon felt cell. The reaction by-products were quantified by chromatographic techniques and thus, the reaction pathway for the mineralization of SMX by EF has been elucidated. Hydroxylation of SMX on the sulfanilic ring is suggested as the first step, followed by the formation of p-benzoquinone and 3-amino-5-methylisoxazole. Their oxidative cleavage led to the formation of five carboxylic acids that were finally mineralized to CO 2; the release of NH 4 + , NO 3 - , and SO 4 2 - accounted for almost 100% of the initial nitrogen and sulfur content. The absolute rate constants for the oxidative degradation of SMX and the detected aromatic by-products have also been determined.

The study on the thickness change of tantalum oxide as voltage drop in electrolyte

Tantalum oxide (<TEX>$Ta_2O_5$</TEX>) films are of considerable interest for a range of application, including optical waveguide devices, high temperature resistors, and oxygen sensors. In this paper, we establish an anode oxidation process of tantalum thin film. The voltage drop in the electrolyte is affected not in voltage change but in current change. If the voltage drop in the electrolyte is same with cathode oxidation voltage, the current changes logarithmically in proportion to the voltage drop in interface of tantalum oxide and electrolyte. As a result of the measurement on the electrical property of tantalum oxide thin film, when the thickness of the insulator film is <TEX>$1500{\AA}$</TEX>, the breakdown voltage is 350volts and dielectric constant is 29.

Fabrication and photophysical properties of singlet oxygen generating nanoporous membrane

The nanoporous alumina membranes (NAMs) were fabricated by a two-step aluminium anodic oxidation process. The fabricated NAMs have controllable pore diameters (40–80 nm) and unidirectionally ordered pore direction. The surface of the NAM was modified with the organo-silane agent (APTES: (aminopropyl)triethoxysilane) to induce ionic bonding between the NAM and the photosensitizer (TSPP: tetrakis(p-sulfonatophenyl)porphyrin). The morphology and chemical nature of the surface modified NAM were studied by field emission scanning electron microscope (FE-SEM), FT-IR spectra, and thermo gravimetric analysis (TGA). Furthermore, this singlet oxygen generating nanoporous membranes (SGNMs) were investigated, in detail, to understand their photophysical properties and the singlet oxygen generation efficiency which were the essential factors for their applications. Steady-state spectroscopies and nanosecond laser induced time-resolved spectroscopy were applied to get information on all photophysical properties including the lifetime of singlet oxygen which depended on the pore diameter of the SGNM.

SILICON NANOWIRE TRANSISTOR FABRICATED BY AFM NANOLITHOGRAPHY FOLLOWED BY WET CHEMICAL ETCHING PROCESS

Atomic force microscope (AFM) nanolithography was performed to create nanowire transistor pattern via local anodic oxidation process on surface of silicon-on-insulator (SOI) wafer. This nanoscale oxide pattern is used as a mask system for chemical etching to produce silicon nanowire transistor. The device with component structures of a silicon nanowire (SiNW) as channel with source, drain, and gate pads had been drawn at 9 V tip voltage, 6 μm/s writing speed with humidity 55.8–68.9%RH. The designed device was etched with tetramethylammonium hydroxide (TMAH) to remove uncovered silicon layer but oxide pattern remains. In order to obtain SiNW transistor, sample was etched using hydrogen fluoride (HF) to remove oxide layer. From the AFM and field emission scanning electron microscope (FESEM) observation found that the SiNW transistor with wire size of 92.65 nm in wire thickness, 90.83 nm wire width and 10.30 μm in length with contact pads size of about 5 μ m × 5 μ m has been successfully fabricated.