Structures and magnetic properties of iron- and cobalt-containing oxide coatings on an aluminum alloy formed in electrolytes via plasma electrolytic oxidation

The effect of the nature of the supporting electrolyte in the composition of electrolytic suspensions containing dispersed particles of Fe(III) and Co(II) hydroxides, and of anodic and bipolar anodic-cathodic polarization on features of the formation, composition, and magnetic characteristics of oxide coatings is studied. In all cases, iron and cobalt are incorporated into the coatings and are concentrated predominantly in pores. The pores of the coatings include particles consisting of the reduced metals, presumably surrounded by oxide or hydroxide shells. The electrolyte composition affects the concentration and ratio of the metals in the particles. A correlation is observed between the ferro- or ferrimagnetism of the coatings and the content and ratio of cobalt and iron in the pores.     

Use of Mother Liquor from Fluorplastic Production for Preparing Composite Coatings

The composition and properties of mother liquor from production of F4D fluoroplastic were studied. Nickel-fluoroplastic cathodic and aluminum oxide-fluoroplastic anodic composite coatings were prepared. Aluminum oxide-fluoroplastic composite coatings were obtained by thermal treatment of aluminum oxide coatings impregnated with the mother liquor.     

Ta-containing oxide coatings on titanium for biomedical application

Bioinert, biocompatible, chemical-resistant oxide coatings containing Ta₂O₅, which are promising to be applied to titanium implants, were produced on titanium by plasma electrolytic oxidation in an aqueous electrolyte. An effect of formation conditions on the elemental and phase composition, thickness, and roughness of the coatings was researched. It was found that an addition of polyethylene glycol to electrolyte without affecting the elemental composition and the thickness causes a change in the porosity and an increase in the roughness of the formed oxide layer. Changing the surface arrangement may allow affecting an adhesion of biotissues to titanium implants with coatings and accumulating drugs by the coatings.     

稀土盐对铝合金阳极化过程的影响

在阳极化溶液中添加稀土盐得到的铝合金氧化膜在腐蚀试验中表现出优良的耐蚀性能,现场椭圆法对阳极氧化过程的研究结果表明,稀土盐的加入,对椭圆编振参数的振荡方式没有显著影响,但却使振荡的周期和振幅发生了一些变化,由此可以推知,稀土盐的加入并未改变氧化膜的组成,但却在一定程度上影响了成膜过程,使膜的结构发生了变化。对椭圆数据进行定量分析的结果进一步表明：加入稀土盐后,氧化膜多孔层生长速率加快,阻挡层厚度增加,多孔部分变得更加致密,这种结构上的变化是阳极化膜耐蚀性能得以提高的主要原因,EDAX和TEM分析结果也证实了椭圆法研究的结果。     

Plasma-electrochemical formation of oxide layers on titanium in aqueous electrolytes with trilonate complexes of manganese

Layered oxide coatings catalyzing oxidation of CO to CO₂ by plasma-electrolytic oxidation in aqueous electrolytes with trilonate complexes of manganese were studied. Data on the elemental composition of their surface and deep layers, phase composition, and specific features of growth were obtained.     

Electrodeposition and physicomechanical properties of coatings and foil of copper reinforced with nanosize aluminum oxide

Method of electrosynthesis of composite coatings and foil composed of copper reinforced with nanosize aluminum oxide is described. A method for chemical dispersion of aluminum oxide by the top-down principle and an electrolyte composition are suggested, which provide synthesis of composite materials with varied content of the modifying phase. The results of mechanical tests indicate that the plasticity, strength, and a number of other physicomechanical properties of thus synthesized composite materials are improved.     

Quantum-chemical approach to optimization of the synthesis conditions of two-component phosphorus-titanium oxide structures on silica surface

The features of formation of a two-component phosphorus-titanium oxide coating on the silica surface by sequential treatment of the substrate with POCl₃ and TiCl₄ vapors were analyzed with application of quantum-chemical approaches. An experimental synthesis of two-component coatings under conditions selected on the basis of theoretical calculations yielded coatings whose composition corresponded to the model predictions. The structure of the resulting coatings was studied by Fourier-transform IR spectroscopy, electronic diffuse reflectance spectroscopy, and chemical analysis.     

On the quantification of SNMS analyses of silicate glasses and oxide coatings

The new high frequency mode (HFM) of the SNMS apparatus, type INA3, is especially suited for the analysis of electrically non-conducting materials. Experiments were carried out with glasses and various oxide coatings in order to demonstrate the quantifiability of HFM analyses with respect to these materials. The influence of the composition of the samples and the selected parameters of the HFM, such as accelerating voltage, duty cycle and frequency, on the quantifiability of the measurements are discussed. It is shown that quantification is possible within certain limits of composition.     

Solid-Phase Complex Compounds and Composites of Metal Oxides,Fluorides, and Chalcogenides as Materials for Interference Coatings: A Review

Theoretical and Experimental Chemistry - The development of composition optimization methods of oxide, fluoride, and chalcogenide materials for interference coatings using the valence state of...     

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.     

铱钽钛金属氧化物阳极的电化学特性

采用热分解方法在钛基体上制备铱钽钛金属氧化物阳极 ,用扫描电镜对阳极涂层显微形貌进行分析 ,通过强化电解寿命试验、开路电位测试、消耗率试验及循环伏安曲线研究了金属氧化物阳极的电化学性能 .SEM分析结果表明铱钽钛金属氧化物阳极涂层呈现多孔多裂纹形貌结构 .随阳极涂层组成不同 ,涂层显微形貌表现出很大差异 ,这种差异直接影响阳极电化学性能 .电化学性能试验结果表明铱钽钛金属氧化物阳极在酸性介质和海水中具有良好的电化学稳定性和电化学活性 .此外 ,铱钽钛金属氧化物阳极在海水中的消耗率很低 ,属于不溶性的阳极材料 ,作为外加电流阴极保护用辅助阳极具有广泛的应用前景 .     

Reinforcement of metal-ceramic coatings in the course of their partial fusion

Factors and mechanisms responsible for the appearance of layered structures of variable cross section in protective coatings based on self-fluxing alloys were studied. A number of structural fragments of composite coatings based on safe-fluxing PG-10K-01 and PG-SR3 alloys (initial formulations and those reinforced with oxide ceramic particles), formed by sputtering in a plasma flux and then partially fused in a furnace, by a gas-oxygen flame, and with laser and electron beams, were revealed and studied. The relationships of the element distribution across the coating layer as a whole and in separate phases were determined. The effect exerted on the chemical composition and microhardness of coatings by the size, structure, and arrangement of inclusions in the coating cross section was demonstrated.     

Sol-gel alumina coatings on stainless steel for wear protection

The aluminium oxide films on austenitic steel are prepared from sols of re-dispersed boehmite nano powders in water. After dip-coating of the sol, a heat treatment including drying, calcination and annealing in vacuum at temperatures up to 1100°C is performed to obtain crack-free coatings of a thickness up to 6 μm. XRD measurements detect α- and γ-alumina, a TiO_x-phase at the metal/coating interface and a gradient of phase formation in the coating. The strong adhesion on the substrates is due to the layered assembly and gradient composition of the coating caused by an inter-diffusion of metal cations and oxygen in the metal/oxide interface during heat treatment. Residual stress measurements by X-rays result in compressive stresses of 2–4 GPa in the alumina coatings. The pin-on-disc test shows a remarkable improvement of wear resistance obtained by sol-gel coatings. The α-alumina content and the compressive stress of the coatings correlate with wear resistance of the coatings.     

Anticorrosion composite coatings on biodegradable Mg alloys: Electrochemical studies

Calcium phosphate coatings consisting of magnesium oxide and hydroxyapatite, which accelerates osteogenesis (bone formation), were formed on magnesium alloys of the Mg–Mn–Ce and Mg–Zn–Zr systems by plasma electrolytic oxidation (PEO). The phase and elemental composition, morphology, and anticorrosion properties of the coatings were studied. Approaches to the formation of composite protective coatings on the basis of the PEO layer using superdispersed polytetrafluoroethylene were developed. Treatment of the PEO-coating with a polymer material reduces the adverse effect of different-level defects. After a single polymer deposition, corrosion protection effect of the composite layer substantially (by more than three orders of magnitude) increases with respect to the base PEO coating.     

Role of the interaction between forming nanocrystals and glass surface on the structure and properties of ZnO-based films

The interaction between glass surface and forming nanocrystals plays the important role in the formation of thin ZnO coatings crystal structure. The comparative study of the crystal structure of thin ZnO-based films and powders having similar chemical compositions was performed with the use of SEM, XRD analysis, optical, and luminescent spectroscopy. The influence of different coatings parameters (chemical composition, thickness) on the spectroscopic and morphological properties of thin films and powders reveals the structural features of the interaction between forming ZnO nanocrystals and glass surface. ZnO–SnO₂ coatings and powders were prepared by liquid polymer-salt technique. This method provides the close contact between the coatings’ precursors with a surface of the glass during both the nucleation and the initial growth stage of forming oxide crystals. The interaction of nanocrystals and substrate surface is responsible for the texture formation in the ZnO films and determines some features of their optical properties.     

Anodic oxide-film of the Co—Sn—O composition

Properties and electrocatalytic activity of thin-film (∼2 μm) oxide coatings on aTi support are considered by the example of the anodic chlorine evolution reaction. The coatings are obtained by thermally decomposing Co and Sn chloride solutions of different compositions on a Ti plate. The Co and Sn oxides are present in all studied compositions as individual phases and form no compounds or solid solutions. The oxide coating containing 70 at. % Co and 30 at. % Sn reveals a maximum electrocatalytic activity. The existence of the optimum composition is attributed to a favorable effect tin dioxide has on the formation of a transition layer between the Ti support and oxide coating. Tin dioxide hampers the Ti diffusion in the main coating and its subsequent oxidation, thus diminishing the negative impact titanium oxides have on the coating     

Synthesis of anodic silicon oxide films in water-organic solutions containing orthophosphoric acid

Variations in electrophysical properties of anodic silicon oxide at the surface of semiconductor silicon are studied as a function of the composition of electrolytic solutions containing orthophosphoric acid and the conditions of reaching the final formation potential. The optimum conditions for the formation of anodic SiO₂ coatings that include phosphorus-containing admixtures are determined, the coatings being intended for application as diffusates in nanoelectronics.     

The influence of clay minerals,oxides, and humic matter on the methylation and demethylation of mercury by micro-organisms in freshwater sediments

Laboratory experiments and analysis of field samples showed that clay minerals, Fe and Mn oxides, and humic matter (colloids) have complex and often dramatic effects on the microbial methylation and demethylation of Hg, and on other microbial activities, in lake sediments. Depending on the nature, abundance, and surface chemistry of the colloids, the source of the sediment, the nature of the microbes, and synergistic/antagonistic effects of environmental variables, the colloids either strongly inhibited or stimulated the Hg transformations, had little or no effect, or alternated in their effects. Most of the results suggest specific effects on particular kinds of microbes, and are not attributable to general inhibition or stimulation of microbial growth or to effects due to the binding of Hg by the colloids. The colloids probably alter the species composition of the microbial community and affect the course of ecological succession, upsetting the dynamic balance between methylation and demethylation and causing alternate increases and decreases in methyl mercury (CH₃Hg⁺) levels along with changes in other indicators of microbial activity [CO₂ and CH₄ production and oxidationreduction potential (Eh)]. The role of clays was critically dependent on surface coatings. Clays often interfered with methylation (while in some cases strongly promoting subsequent demethylation); but iron oxide (FeOOH) often promoted methylation, and FeOOH coatings on clay tended to counterbalance the negative influence of the clay. Removal of oxide coatings depressed both methylation and demethylation. Manganese oxide (MnOOH) coatings sometimes promoted methylation, but larger amounts of MnOOH (unlike FeOOH) strongly suppressed methylation. On addition of organic nutrients, oxide coatings enhanced methylation and impeded demethylation; without nutrient enrichment, the reverse tended to occur. Humic matter in solution tended to stimulate methylation; but humic coatings on clay impeded methylation and fostered demethylation. Thus, the effects of natural colloids on Hg speciation are vitally important but variable, inconsistent, and not altogether predictable.     

Al 6061/SiCp稀土转化膜的组成、结构及性能

铝金属基复合材料以其多方面的优异性能在航空、航天、汽车、电子和光学等工业领域中显示出了十分广泛的应用前景［１ ,２］．某些种类的（如ＳｉＣ颗粒增强）铝金属基复合材料已经开始走向工业规模的应用［３］．然而,在铝金属基复合材料中由于增强体的存在使其内部组织结构极不均匀,在使用环境中极易形成腐蚀微电池而遭受点蚀、剥蚀、磨蚀等等腐蚀形式的破坏［４ ,５］ ．适用于常规铝合金防腐处理方法的阳极氧化法和铬酸盐化学氧化法（Ａｌｏｄｉｎｅ法）存在着下述弊端而不能对铝金属基复合材料起到有效的防腐作用：１）铝金属基复合…     

Catalytic Activity of Complex-Oxide Perovskite-containing Compositions in Reactions of Oxidation of CO and Organic Compounds

The catalytic activity of composites constituted by a porous metallic or ceramic support, intermediate layers of oxide nature, and perovskite coatings, including those doped with silver, was studied in reactions of deep oxidation of CO and organic compounds of various classes. The relationship between the catalytic activity of a composite and its composition and nature of substances being oxidized was analyzed.