Anodic Oxidation Process Research Articles

含Y形Cu纳米线多孔铝膜的偏振特性

Porous anodic alumina (PAA) templates with branch structure are fabricated by the two-step anodic oxidation processes, and then the Y-branched Cu nanowires are synthesized in the templates using an alternating current (AC) deposition method. We observe the morphology image of the samples by scanning electron microscopy (SEM), and measure the transmission spectrum and the polarization spectrum of the samples by the spectrophotometer. The results show that PAA films with Y-branched Cu nanowires have better transmittance in the near infrared region. An extinction ratio of 15~18 dB and an insertion loss of 0.1~0.4 dB are obtained in this region. Therefore PAA with Y-branched Cu nanowires can be used as a near-infrared micropolarizer, and this kind of micropolarizer would have a promising future in the field of photoelectricity integration.

Ruthenium Complexes with Vinyl, Styryl, and Vinylpyrenyl Ligands: A Case of Non-innocence in Organometallic Chemistry

We herein describe a systematic account of mononuclear ruthenium vinyl complexes L-{Ru}-CH=CH-R where the phosphine ligands at the (PR'3)2Ru(CO)Cl={Ru} moiety, the coordination number at the metal (L = 4-ethylisonicotinate or a vacant coordination site) and the substituent R (R = nbutyl, phenyl, 1-pyrenyl) have been varied. Structures of the enynyl complex Ru(CO)Cl(PPh3)2(eta1:eta2-nBuHC=CHCCnBu), which results from the coupling of the hexenyl ligand of complex 1a with another molecule of 1-hexyne, of the hexenyl complexes (nBuCH=CH)Ru(CO)Cl(PiPr3)2 (1c) and (nBuCH=CH)Ru(CO)Cl(PPh3)2(NC5H4COOEt-4) (1b), and of the pyrenyl complexes (1-Pyr-CH=CH)Ru(CO)Cl(PiPr3)2 (3c) and (1-Pyr-CH=CH)Ru(CO)Cl(PPh3)3 (3a-P) have been established by X-ray crystallography. All vinyl complexes undergo a one-electron oxidation at fairly low potentials and a second oxidation at more positive potentials. Anodic half-wave or peak potentials show a progressive shift to lower values as pi-conjugation within the vinyl ligand increases. Carbonyl band shifts of the metal-bonded CO ligand upon monooxidation are significantly smaller than is expected of a metal-centered oxidation process and are further diminished as the vinyl CH=CH entity is incorporated into a more extended pi-system. ESR spectra of the electrogenerated radical cations display negligible g-value anisotropies and small deviations of the average g-value from that of the free electron. The vinyl ligands thus strongly contribute to or even dominate the anodic oxidation processes. This renders them a class of truly "non-innocent" ligands in organometallic ruthenium chemistry. Experimental findings are fully supported by quantum chemical calculations: The contribution of the vinyl ligand to the HOMO increases from 46% (Ru-vinyl delocalized) to 84% (vinyl dominated) as R changes from nbutyl to 1-pyrenyl.

Controllable Synthesis of PbO Nano/Microstructures Using a Porous Alumina Template

Porous anodic aluminum oxide (AAO) templates were prepared by a two-step aluminum anodic oxidation process. Nanowires, microspheres, and hexagonal nanoplates of PbO were successfully prepared by an improved sol–gel method combined with AAO templates. On the anodized external surface and the surface-dissolved barrier layer of AAO, hexagonal nanoplates of PbO with a diameter of 2 μm and a thickness of 100 nm and microspheres of PbO with a diameter of 400 nm were obtained, respectively, where hexagonal patterns and circular patterns of the external surface appearance of AAO acted as templates. Nanowires with a diameter of 80 nm and a length of 10 μm were also synthesized within the pores of AAO, consistent with the diameters and thicknesses of the pores. All of the samples were characterized by field emission scanning electron microscopy and powder X-ray diffraction pattern.

Synthesis and Characterization of S-Doped TiO2 Made by Anodic Oxidation of Titanium in Sulfuric Acid

Abstract TiO2 coating doped with S ions was made by the anodic oxidation process of the titanium sheet in sulfuric acid. TiO2 coating on titanium plate prepared by the anodic oxidation possessed many nanohole-like pores. XPS results showed that S6+ and S2− were incorporated in TiO2 coating after anodic oxidation. These S-doped TiO2 coatings showed the high photocatalytic activity.

Support effect, thermal stability, and structure feature of toluene combustion catalyst

A novel 0.01%Pt–0.02%Pd/stainless steel catalyst was prepared by using stainless steel as support and pretreatment via an anodic oxidation process. The total oxidation temperature over the prepared catalyst toward toluene was achieved at 210 °C as the catalyst was calcined at 1000 °C. The results indicate that the design of anodic oxidation process in the support preparation was quite effective in increase of catalytic activity. In special, the stainless steel support has proven to be effective for preventing the catalyst deactivation after high temperature calcination. In addition, the stability test on the catalyst was also investigated.

Investigating corrosion processes in the micrometric range: A SVET study of the galvanic corrosion of zinc coupled with iron

Abstract The galvanic corrosion of an iron/zinc pair immersed in aqueous 0.1 M Na 2 SO 4 solution has been investigated by using the scanning vibrating electrode technique (SVET). In this way, investigations in the micrometer range of the progress of the electrochemical reactions involved in galvanic process were performed. The anodic oxidation process is observed to be initiated on the zinc sample in a localized manner, whereas the cathodic reaction involving the electroreduction of dissolved oxygen is homogeneously distributed over the iron sample. This later process is the rate determining step in the overall corrosion process, as demonstrated by the changes in the ionic and galvanic currents measured in the system when the area of the iron specimen is varied relative to that of zinc. The occurrence of coupled chemical reactions in the solution phase involving the products of the corrosion reactions could also be deduced from the integration of the ionic currents measured for each half-reaction during a SVET scan. Thus, the corrosion processes involved in the galvanic coupling of iron and zinc have been further understood by using this microelectrochemical technique appropriately, helping to better interpret large scale measurements.

Structural evolution and adhesion of titanium oxide film containing phosphorus and calcium on titanium by anodic oxidation

This study investigated the microstructure evolution and defects of the titanium oxide layer containing calcium (Ca) and phosphorus (P) formed by anodic oxidation in a solution containing Ca and P compounds. Results show that the anodic film exhibited a two-layer structure: a pore-containing amorphous titanium oxide layer dispersed with nano-sized crystallites formed prior to sparking, and a porous overlay dotted with craters formed after sparking. Ca and P were predominantly incorporated in the porous overlay, in which the amorphous region contained more Ca and P than the crystalline region regardless of the anodizing voltages. Moreover, the ratio of amorphous to crystalline regions in the porous overlay changed insignificantly with anodizing voltage. Increasing anodizing voltage enhanced the incorporation of Ca and P in the anodic film, but deteriorated the adhesion of the anodic film to the substrate. This deterioration was related to two inherent adhesive weaknesses: the aligned pores in the titanium oxide layer and the craters in the major overlay, signifying that a new anodic oxidation process that can produce high Ca- and P-containing oxide film at relatively-low anodizing voltages, i.e. approximately 200 V, is a necessity.

Long-time anodisation of titanium in sulphuric acid

The long-time behaviour of CP titanium in 1 M H 2SO 4 has been investigated. The authors revealed electrochemical behaviour during the long-time chrono-amperometric experiments. The ex-situ observations (EIS, ellipsometry, SEM and optical microscopy) brought out information concerning morphological changes of the surface as well as the change in the oxide thickness during the anodic oxidation process. From the obtained data, the authors developed a hypothesis describing the potentiostatic anodisation of titanium at voltages (up to 15 V) in 1 M H 2SO 4 with respect to time of anodisation.

Synthesis and Evaluation of Novel Titanium Oxide by Anodic Oxidation Process

Synthesis and Evaluation of Novel Titanium Oxide by Anodic Oxidation Process

High Voltage Pulse Anodization of a NiTi Shape Memory Alloy

In an attempt to improve the corrosion resistance of a NiTi shape memory alloy, thick oxide films were fabricated on the surface by an anodic oxidation process. High-voltage square shape pulse anodization was carried out in various electrolytes over the whole range of pH values from sulfuric acid, acetate buffer, ammonium pentaborate, sodium diphospho heptoxide, sodium aluminate, and potassium hydroxide. Microscopic observation showed that the films are porous or tile structured in nature and the structural analyses by X-ray diffraction and Raman spectroscopy demonstrated their amorphous nature. From the chemical analyses, the oxide films were determined to consist mainly of titanium as the metal component, whereas the nickel content of the oxide films depends on the pH value of the electrolyte as well as the amount of anions incorporated from the electrolyte. The application of an asymmetrical rectangle waveform was effective in increasing the density of the films. An electrochemical technique was used for screening the corrosion resistance of the anodized films and demonstrating the improvement in the resistance against localized corrosion of NiTi.

Optical properties of alumina membranes prepared by anodic oxidation process

The luminescence property of anodic alumina membranes (AAMs) with ordered nanopore arrays prepared by electrochemically anodizing aluminum in oxalic acid solutions have been investigated. Photoluminescence emission (PL) measurement shows that a blue PL band occurs in the wavelength ranges of 300–600 nm. The PL intensity and peak position of AAMs depend markedly on the excitation wavelength. A new peak located at 518 nm can be observed under a monitoring wavelength at 429 nm in the photoluminescence excitation (PLE) spectra. Convincing evidences have been presented that the PLE would be associated with the residual aluminum ions in the membrane. The PLE and PL of AAMs, as a function of anodizing times, have been discussed. It is found that the oxalic impurities incorporated in the AAMs would have important influences on the optical properties of AAMs in the initial stage of anodization. The PL and PLE spectra obtained show that there are three optical centers, of which the first is originated from the F + centers in AAMs, the second is correlated with the oxalic impurities incorporated in the AAMs, and the third is associated with the excess aluminum ions in the membrane.

Capacitance characteristics and structure of anodic oxide films grown on rapidly quenched aluminum alloys

Anodic oxide films grown on rapidly quenched aluminum alloys containing 2 at% Ti, Zr, Ta, Nb or Hf were characterized. The capacitance of the film on each alloy was found to be related to the dielectric constant of the alloying metal oxide film. In addition, the capacitance was found to depend on the degree of the exposure of the alloyed metal to the electrolyte, due to aluminum dissolution during the anodic oxidation. Capacitance varied with time, temperature and pH of the electrolyte in the anodic oxidation process. An oxide film of the barrier type was observed on Al3Zr by TEM, whereas the oxidation film of the Al–Ti alloy had a dual structure consisting of an inner layer with lower TiO2 content and an outer one with higher TiO2 content. It is considered that these phenomena were caused by the preferential dissociation of aluminum in the anodic oxidation process.

二酸化チタンを電着した二層構造アルミニウム陽極酸化皮膜の作製と抗菌性評価

Aluminum anodic oxide film with a two-layer structure was successfully prepared by a two-step anodic oxidation process in two solutions of phosphoric acid (H3PO4) and sulfuric acid (H2SO4). The two-layer structure consists of the upper layer with wide pores and the lower layer with narrow pores. Subsequently, titanium dioxide (TiO2) was electrodeposited into wide pores in upper layer. The TiO2 content in the obtained sample depended on the concentration of TiO2 sol, pH and the migration voltage during electrodeposition. The hardness, corrosion resistance and sealing degree of the sample with TiO2 were almost the same as that of the sealed sample without TiO2. On the other hand, the electron spin resonance (ESR) measurement indicated that hydroxyl radicals (·OH) were generated from the prepared sample by the irradiation of ultraviolet light. Furthermore, antimicrobial activity to Escherichia coli of the anodic oxide film of aluminum electrodeposited TiO2 was higher than that without TiO2. These results suggested that the two-layered anodic oxide film of aluminum electrodeposited with TiO2 would be a novel photocatalytic antimicrobial material.

High Voltage Anodization of a NiTi Shape Memory Alloy

In order to improve the corrosion resistance of a NiTi shape memory alloy, thick oxide films were fabricated on the surface by an anodic oxidation process. The microscopic observation showed the films had a porous nature and the structural analyses indicated that the films are amorphous. From the chemical analyses, the oxide films mainly contained titanium as metal component, the nickel content of the oxide films depends on pH of the electrolyte and anions could be incorporated from the electrolyte into the films. The asymmetrically rectangle waveform was effective to increase the density of the films. The electrochemical technique showed that the corrosion resistance of the anodised films could improve the resistance against localized corrosion of NiTi.

Changes in mass and stress during anodic oxidation and cathodic reduction of the Cu/Cu 2O multilayer film

The anodic oxidation and cathodic reduction processes of the Cu/Cu 2O multilayer film and pure Cu film in pH 8.4 borate buffer solution were analyzed by electrochemical quartz crystal microbalance (EQCM) for gravimetry and bending beam method (BBM) for stress measurement. The mass loss of the multilayer film during anodic oxidation at 0.8 V (SHE) in the passive region was less than that of the pure Cu film. The comparison between current transients and mass changes during anodic oxidation has succeeded in separating the anodic current density into two partial current densities of oxide film growth, i O 2 - , and of Cu 2+ dissolution through the passive film, i Cu 2 + . As a result, in the case of the pure Cu film, the anodic current density was mainly due to i Cu 2 + , while in the case of the multilayer film, i Cu 2 + was almost equal to i O 2 - . The compressive stress for the multilayer film was generated during anodic oxidation, while the tensile stress for the pure Cu film was generated. The mass loss of the multilayer film during cathodic reduction at a constant current density ( i c = −20 μA cm −2) was significantly less than that estimated from coulometry, suggesting that H 2O produced by cathodic reduction remained in the multilayer film. The compressive stress was generated during cathodic reduction of the multilayer film, which was ascribed to H 2O remained in the multilayer film.

Degradation of bisphenol A in aqueous solution by H 2O 2-assisted photoelectrocatalytic oxidation

A series of titanium dioxide (TiO 2/Ti) film electrodes were prepared from titanium (Ti) metal mesh by an improved anodic oxidation process and were further modified by photochemically depositing gold (Au) on the TiO 2 film surface as Au–TiO 2/Ti film electrodes. The morphological characteristics, crystal structure and photoelectroreactivity of both the TiO 2/Ti and Au–TiO 2/Ti electrodes were studied. The experiments confirmed that the gold modification of TiO 2 film could enhance the efficiency of e −/h + separation on the TiO 2 conduction band and resulted in the higher photocatalytic (PC) and photoelectrocatalytic (PEC) activity under UV or visible illumination. To further enhance the TiO 2 PEC reaction, a reticulated vitreous carbon (RVC) electrode was applied in the same reaction system as the cathode to electrically generate H 2O 2 in the aqueous solution. The experiments demonstrated that such a H 2O 2-assisted TiO 2 PEC reaction system could achieve a much better performance of BPA degradation in aqueous solution due to an interactive effect among TiO 2, Au, and H 2O 2. It may have good potential for application in water and wastewater treatment in the future.

Electrochemical synthesis and physical–chemical characterization of the low-oxidized graphite fluoroxide materials

A process of anodic oxidation of purified natural graphite in aqueous 11–45% HF solutions has been studied at constant voltages 5–7 V. New types of low-oxidized graphite fluoroxide materials (FOG-E) were isolated, prepared under electrochemical synthesis conditions only. Electrochemical oxidation of graphite should include in a first step the reaction of evolving oxygen and O-containing groups with surface carbon atoms on graphite particles and a subsequent formation of C–OH bonds, and in a second step, a partial substitution of the latter groups into C–F groups. Chemical and physical–chemical study of FOG-E showed that they are multiphasic materials. The low-oxidized graphite fluoroxide materials are excellent precursors for the preparation of thermally expanded graphite (TEG).

Preparation and characterization of TiO2/Ti film electrodes by anodization at low voltage for photoelectrocatalytic application

Multiporous TiO2/Ti film electrodes were prepared by different anodic oxidation processes at low voltage, in which the micro-structured TiO2 thick films were prepared in H2SO4–H2O2–H3PO4–HF solution for 2 h and the nano-structured TiO2 thin films were prepared in H3PO4–HF solution for 30 min with post-calcination. Both types of TiO2/Ti films were characterized by scanning electron microscopy and X-ray diffraction analysis. The photocatalytic (PC) and photoelectrocatalytic (PEC) reactivity of the TiO2/Ti electrodes were evaluated in terms of bisphenol A (BPA) degradation in aqueous solution. The experimental results demonstrated that the nano-structured TiO2/Ti thin-film electrodes had higher reactivity in the BPA degradation reaction. The PEC degradation of BPA was further studied using different cathodes, either a reticulated vitreous carbon (RVC) electrode or a platinum (Pt) electrode. The experimental results confirmed that the efficiency of BPA degradation could be significantly enhanced in the TiO2/Ti–RVC reaction system due to the generation of H2O2 on the RVC cathode. It is believed that such a H2O2-assisted TiO2 PEC oxidation process may have good potential for water and wastewater treatment.

Obtaining of high surface roughness copper deposits by electroless plating technique

The use of pyridine-2,6-dicarboxylic and 4-hydroxypyridine-2,6-dicarboxylic acids as copper(II) ligands in formaldehyde-containing alkaline electroless copper plating solutions allowed to obtain copper layers with extremely high surface roughness factor reaching approximately 120. The Cu deposits of higher surface area were formed at highly negative open-circuit (mixed) potentials; the correlation between copper electrode overpotential and roughness of the deposit was found and discussed. The copper films obtained demonstrate a high electrocatalytic activity in anodic formaldehyde oxidation process, the oxidation rate reaches 40 mA cm −2 and exceeds considerably that for other copper surfaces.

Protective action towards aluminium corrosion by silanes with a long aliphatic chain

A noticeable and persistent protective action towards aluminium corrosion can be obtained by treatments with silane molecules containing a long aliphatic chain (e.g., n-octadecyl-trimethoxy-silane, C18), which can markedly increase the barrier properties of the silanic coating. At variance with other silanic compounds, the layer of C18, although not uniform, tends to cover the whole aluminium surface completely and, in fact, its EIS spectra initially present one time constant only. It is likely that v.d.Waals interactions between the alkyl chains of C18 can lead to the formation of a polymolecular layer. The aqueous salt solutions may permeate through this layer, but with greater difficulties than in the case of an efficient di-silyl derivative (e.g., 1,2-bis-trioxymethyl-silyl-ethane, BTSE). C18 coatings noticeably retard not only the cathodic oxygen reduction reaction, but also the anodic metal oxidation process. A very prolonged action is also found towards the pitting process in the particularly aggressive chloride solution.