Effects of anodic spark oxidation by pulse power on titanium substrates

The characteristics of the oxide layer of titanium generated by anodic spark oxidation are affected significantly by the process variables. In this study, electrochemical treatments were performed while applying a direct current, a pulse current, and a reverse pulse current during anodic spark oxidation. A mixed solution of 0.015 M DL‐α‐GP (DL‐α‐glycerophosphate disodium salt) and 0.2 M CA (calcium acetate) was used as the electrolyte. The pore size generated after anodic spark oxidation was smallest in the group exposed to the reverse pulse current followed in order by the pulse current and direct current. Anatase was the major crystal phase of the TiO₂ produced on the surfaces subjected to 280 V, and the rutile phase was additionally detected in the group subjected to 320 V. The crystals precipitated on the surface after the hydrothermal treatment were hydroxyapatite (HA) crystals that had a polygonal bar‐shaped needle structure. Good activity was observed in the 320‐V pulse treated group, in which very thin needle‐shaped crystals were observed after immersing the samples in Hanks' solution for 4 weeks. The cell viability was increased greatly by anodic spark oxidation, and the surface roughness was also increased. It is believed that the surface treated using a pulse current has excellent characteristics, making it suitable for applications in biomaterials. Copyright © 2010 John Wiley & Sons, Ltd.     

Rearrangement oftrans-stilbene into diphenylacetaldehyde acetals induced by direct anodic oxidation

Direct anodic oxidation oftrans-stilbene in lower alcohols and in some other solvents in the presence of KF or Bu₄NBF₄ is accompanied by its electrooxidatve rearrangement into diphenylacetaldehyde acetals; a competing reaction yields 1,2-dialkoxy-1,2-diphenylethanes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2202–2205, December, 1997.     

Synthesis of silver nanotubes by electroless deposition in porous anodic aluminium oxide templates

An electroless deposition method has been employed for the synthesis of silver nanotubes using porous anodic aluminium oxide as templates, by which high-yield silver nanotubes with length over ten microns have been synthesized.     

Fast migration of fluoride ions in growing anodic titanium oxide

The rapid inward migration of fluoride ions in growing anodic titanium oxide under a high electric field has been elucidated by anodizing a Ti–12 at% silicon alloy, where film growth proceeds at nearly 100% efficiency in selected electrolytes. Further, incorporated silicon species in the anodic film are immobile, acting as marker species. The migration rate of fluoride ions is determined precisely by three-stage anodizing, consisting of initial anodic film formation at a constant current density to 50 V in ammonium pentaborate electrolyte, subsequent incorporation of fluoride ions by reanodizing to 55 V in ammonium fluoride electrolyte and, finally, anodizing again in ammonium pentaborate electrolyte at high current efficiency. The resultant films were analyzed by glow discharge optical emission spectroscopy to reveal the depth distribution of fluoride ions and the location of the silicon marker species. The fluoride ions migrate inward at twice the rate of O²⁻ ions. Consequently, anodizing of titanium in fluoride-containing electrolytes develops a fluoride-rich layer that separates the alloy substrate from the anodic oxide, with eventual detachment of the film from the substrate.     

Gravity assisted growth of self-organized anodic oxide nanotubes on titanium

The present work investigates the anodic growth of self-organized TiO₂ nanotube arrays under different gravity fields. It is found that the aspect ratio of the nanotubes can be strongly affected by the orientation of the growing tubes within the natural gravity field or by high artificial gravitational fields in a centrifuge. Particularly remarkable is that under identical electrochemical growth conditions, the length of the nanotubes can be extended from 0.8 μm to 1.8 μm arranging the tube growth direction with or against the gravity field, or even extended up to 6.0 μm under high centrifugal forces (3220g).This strong effect is ascribed to gravity effects on the mass transport processes under diffusion controlled tube growth conditions.     

Synthesis of titanium nitride by anodic polarization of titanium

Possibility of forming titanium nitride by anodic polarization of the surface of titanium in water-containing organic electrolytes in the presence of NH₄F at potentials of 2–14 V was demonstrated and substantiated. The method of cyclic voltammetry was used to study electrochemical processes in electrolytes based on ethylene glycol and glycerol. Results obtained in an analysis of the structural, chemical, and physicomechanical properties of the titanium nitride layers obtained in the study are presented.     

Creation of thin oxide coatings and oxide nanopowders by anodic oxidation of metals in molten salts

We studied the feasibility of synthesizing ultrafine oxide powders by anodic oxidation of metals, such as zirconium and tantalum, in chloride + nitrate melts at temperatures above 830K. We showed that, varying the electrolyte composition, oxidation temperature, and anodic current density, one obtains either compact protective coatings on the specified metals or oxide powders with particle sizes of 50 to 200 nm.     

Area-selective microscale metallization on porous anodic oxide film of aluminium

A new method for micropatterning of metallic patterns on porous anodic oxide film of aluminium is described. The porous anodic oxide film was impregnated with organic dye and palladium ions before the hydrothermal pore-sealing. The surface layers formed during the pore-sealing, i.e. outer acicular hydroxide layer and a compact intermediate sub-layer trap the palladium ion underneath the layers. Exposing the palladium enriched area by the help of laser beam followed by electroless nickel deposition results the deposition of nickel on the laser-exposed part. Thickness of the deposits can be up to about 2–3 μm, after about the 20 min of immersion in electroless nickel plating bath. The metallic micropatterns, formed by the method are crack free, smooth and uniform over extended length.     

Intercalation of cobaltammine complex ions into layered manganese oxide

The intercalation of Co(2+), [Co(NH(3))(6)](3+), and [Co(NH(3))(5)Cl](2+) ions into layered manganese oxide (birnessite) was studied by chemical, XRD, SEM, IR, and DTA-TG analyses. The intercalation reaction progressed by a 2:1 or 3:1 ion-exchange mechanism depending on the valence of the starting ions. The oxidation state of cobalt did not change with the intercalation reaction. The intercalation of [Co(NH(3))(6)](3+) ions resulted in an increase of basal spacing from 0.716 to 0.956 nm, giving a layered structure material consisting mainly of platelike particles. The chemical analysis results showed that the structure of [Co(NH(3))(6)](3+) ions was maintained in the interlayer. On the other hand, an H(2)O/NH(3) ligand exchange reaction progressed for the intercalation of [Co(NH(3))(5)Cl](2+) ions, resulting in an increase in the basal spacing from 0.716 to 0.956 nm.     

Syntheses of rare-earth metal oxide nanotubes by the sol-gel method assisted with porous anodic aluminum oxide templates

In this paper, we report a versatile synthetic method of ordered rare-earth metal (RE) oxide nanotubes. RE (RE=Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) oxide nanotubes were successfully prepared from corresponding RE nitrate solution via the sol-gel method assisted with porous anodic aluminum oxide (AAO) templates. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM, and X-ray diffraction (XRD) have been employed to characterize the morphology and composition of the as-prepared nanotubes. It is found that as-prepared RE oxides evolve into bamboo-like nanotubes and entirely hollow nanotubes. A new possible formation mechanism of RE oxide nanotubes in the AAO channels is proposed. These high-quantity RE oxide nanotubes are expected to have promising applications in many areas such as luminescent materials, catalysts, magnets, etc.     

Multi-method characterization of anodic oxidation of a titanium alloy in fluoride-containing electrolytes

Journal of Solid State Electrochemistry - Anodic film growth on a Ti alloy in water-containing ethylene glycol electrolyte with addition of fluoride...     

Electrochemical oxidation of alcohols: Part II preparative anodic oxidation of secondary alkanols employing lithium nitrate

The nitrate-mediated oxidation of simple alkanols to the corresponding ketones is described. Except for compounds containing several tertiary hydrogens the procedure is simple to perform and gives clean products in high current yield.     

多孔阳极氧化铝膜的制备研究

在直流恒压下,在不同的酸性溶液中对铝片实施两步阳极氧化制备多孔氧化铝膜,在磷酸溶液中制得的模板孔径大,并且电解时间缩短,加快了制备模板的过程。同时利用阳极氧化初期电流密度的变化,分析了多孔氧化铝膜的形成机理。     

First aromatic ring acetamidation by anodic oxidation

Anodic oxidation of 1-(trifluoromethyl)benzene in dry acetonitrile/Bu₄NBF₄ under constant potential conditions led to 2-(trifluoromethyl) acetanilide in 86% yield. Other experimental conditions, as the use of constant current or the change in the supporting electrolyte were considered.     

Fabrication of three dimensional interconnected porous carbons from branched anodic aluminum oxide template

In this communication, the morphology of double branched anodic aluminum oxide (AAO) templates from linear down or step down function of anodizing voltage is discussed. The interconnected AAO film is obtained when the thin pore wall at the final branched channels is dissolved by chemical etching. The three-dimensional interconnected porous carbons are fabricated by carbonization of polyimide film which is negative replicated from the layered interconnected AAO template.     

Kinetics of the growth of the oxide layer during anodic oxidation of aluminum

Experimental plots of anode current density against time obtained for various electrolytes over a temperature range from 5 to 60°C have been compared with a theoretical model which describes the kinetics of the growth of the oxide film during anodic oxidation of aluminum. It is concluded from differences in the kinetic parameters for ammonium benzoate and ammonium adipate that the oxidative destruction of the corresponding carboxylate anion is involved in a rate determining step of the process. V. I. Vernadskii Institute of General and Inorganic Chemistry, Ukraine Academy of Sciences, 32/34 Academician Palladin Prosp., 252680 Kiev-142, Ukraine. Translated from Teoreticheskiya i éksperimental’naya Khimii, Vol. 33, No. 1, pp. 58–61, January–February, 1997.     

Formation of porous Al particles by anisotropic anodic etching

Porous Al particles were prepared by anisotropic anodic etching of small Al particles. The anisotropic anodic etching was carried out in a Cl⁻ containing electrolyte using a close-packed Al particle structure in which particles were electrically connected through the contact points between them. Anisotropic tunnel pits in the 〈100〉 direction of the Al crystal lattice were formed in the particles. After the etching, the porous Al particles could be dispersed from the close-packed structure easily. The average depth of the etching pits was ca. 25 μm. The obtained porous Al particles will be useful for various functional devices which require large surface area, such as substrates for catalysts and electrodes for electrolytic capacitors.     

阳极氧化条件对氧化钛纳米管阵列形貌及光催化性能的影响

以阳极氧化法制备了高度有序的TiO2纳米管阵列,采用扫描电镜观察了不同制备条件下得到的TiO2纳米管阵列的微观形貌,分别考察了电解时间、电压、电解液组成对TiO2纳米管阵列形貌的影响;此外,以酸性红3R染料作为标志物,测定了制得的TiO2纳米管阵列片的光催化性能.结果表明,以0.5%NH4F(质量分数)和乙二醇与水按体积比5∶1混合得到的溶液作为电解液,在15V电压下电解2h,得到的TiO2纳米管阵列的纳米管管径适中(60nm)、大小均一、排列整齐.所制备的TiO2纳米管阵列对染料的降解率显著优于纳米TiO2水溶胶的,且其光催化性能与形貌、电解时间及煅烧温度等密切相关.