Dependence of physicomechanical properties of a nickel-cobalt-aluminum oxide composite electrolytic coating on the dispersity of the alloying component

Effect of the dispersity of aluminum oxide on the microhardness, wear, internal stresses, and porosity of nickel-cobalt-aluminum oxide composite electrolytic coatings deposited from a chloride electrolyte and the dependence of the content of aluminum oxide in the coating on the agitation rate and working duration of the electrolyte were studied.     

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.     

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.     

Formation of Protective Coatings on Graphite by a Microspark Oxidation Method

Models, mechanisms, and criteria of formation of protective coatings on graphite by a microspark oxidation method (MSO) are considered. It is established that a prerequisite for the graphite MSO is the deposition of a barrier film of a valve metal oxide at the graphite surface. Optimum regimes of the graphite MSO in aqueous solutions of sodium aluminate are determined. Protective coatings on graphite comprising α-phase aluminum oxide are obtained. It is concluded that the graphite MSO should be viewed as a version of MSO of metals, which involves the electrochemical deposition (at high voltages that cause the anode to microspark) of oxide films consisting of electrolyte components on graphite, as opposed to a version of MSO of metals, which involves the formation of an anodic film consisting of electrolyte components and the intrinsic oxide.     

The influence of electrolyte on photocatalytic activity of PEO coatings with incorporated Ce-ZSM5 formed on aluminum

Journal of Solid State Electrochemistry - The preparation and characterization of oxide coatings made by plasma electrolytic oxidation (PEO) process on aluminum in two different electrolyte...     

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.     

Fabrication of polytetrafluoroethylene- and graphite-containing oxide layers on aluminum and titanium and their structure

Stable aqueous electrolyte emulsions with negatively charged micelles containing dispersed particles of polytetrafluoroethylene (PTFE) or graphite are obtained using siloxane-acrylate emulsion as an emulsifier. The oxide coatings formed in such electrolytes contain carbon, polytetrafluoroethylene, or graphite. The coatings with PTFE particles are similar to monolithic polytetrafluoroethylene with respect to its hydrophobic characteristics. According to X-ray photoelectron spectroscopy data, the surface of the formed coatings predominantly contains aliphatic carbon (C-C and C-H bonds) and some fraction of oxidized (or, in the case of PTFE-containing electrolytes, fluorinated) carbon.     

Deposition of protective-decorative coatings onto aluminum alloys

Technique for deposition of a nickel coating onto various aluminum alloys was developed. This coating can be used both independently and as a sublayer under multilayer coatings and, in particular, under those of nickel, tin–bismuth, lustrous nickel, and lustrous chromium. The technique includes anodization, chemical treatment, and electrodeposition of nickel in a special solution. The working modes of the anodization electrolyte were chosen and the necessity for a preliminary chemical treatment of the oxide film being formed was substantiated. A composition of the acid electrolyte for the subsequent nickel plating was developed with buffer and improving additives. The thus deposited electroplated nickel coatings exhibit a high adhesion to the aluminum base without additional thermal treatment. This makes it possible not only to reduce the technological time for deposition of the subsequent multilayer coatings, but also to fully automate the whole process.     

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.     

Titanium-supported nickel-copper oxide catalysts for oxidation of carbon(II) oxide

Nickel-copper compositions for catalytic oxidation of carbon(II) oxide to carbon(IV) oxide were prepared by impregnation of oxide films on titanium surface, obtained by plasma electrolytic oxidation followed by annealing. Plasma electrolysis oxide coatings with a layer thickness of 5 to 50 μm were generated using different electrolytes. The compositions were studied by X-ray powder diffraction, X-ray spectral analysis, and electron microscopy, and moisture absorption of the initial plasma electrolytic structures was estimated. A linear correlation was found between the overall concentration of nickel and copper (4 to 25 mol %) in the surface layer of ∼2–5-μm compositions and their catalytic activity. The overall concentration of nickel and copper was found to increase in parallel with the moisture absorption of plasma electrolytic oxidation coatings. Nickel-copper compositions based on plasma electrolytic oxidation coatings generated in a silicate electrolyte displayed the best catalytic, mechanical, and adhesion properties.     

(NaPO3)6对AZ91D镁合金微弧氧化陶瓷层电化学腐蚀特性的影响

在Na2SiO3-KOH电解液体系中添加一定量的(NaPO3)6, 利用微弧氧化(MAO)技术在AZ91D 镁合金表面制备了原位生长的陶瓷层. 采用动电位极化和电化学阻抗谱(EIS)技术研究了添加(NaPO3)6前后, 制备的陶瓷层在3.5%(w) NaCl溶液中的室温电化学行为. 结果表明, 添加(NaPO3)6后, 陶瓷层的自腐蚀电位显著上升, 自腐蚀电流密度明显减小. 这主要是由于(NaPO3)6增加了反应过程中基体镁合金表面的“氧空位”和溶液中PO3-4的含量, 促使元素Mg在金属/膜层(M/F)界面上快速形成相应氧化物, 从而增加了陶瓷层的厚度和致密性. 根据电化学反应体系和陶瓷层的特殊结构, 建立了合理的等效电路, 并结合EIS 数据, 分析了添加(NaPO3)6提高陶瓷层耐电化学腐蚀性能的机理.     

Anodic oxidation of complex shaped items of aluminum and aluminum alloys with subsequent electrodeposition of copper coatings

It was shown that the method of anodization of aluminum and aluminum alloys can be applied for subsequent plating of highly adherent copper coating instead of the known zincate treatment with additional annealing. Fluorine-containing additives in anodizing electrolyte were proposed as activator of oxide film. The parameters of the anodic film (thickness, porosity, and microroughness) were calculated. The plated quality copper coatings have high adhesion to the aluminum support, and no additional heat treatment is required. This considerably reduces the processing time for deposition of multilayer coatings and decreases the material costs.     

Improvement in corrosion resistance of micro arc oxidation coating formed on AZ91D magnesium alloy via applying a nano-crystalline sol–gel layer

Although magnesium is used in many industries, it is reactive and requires protection against aggressive environments. In this study, oxide coating was formed on AZ91D magnesium alloy using micro-arc oxidation (MAO) process in an alkaline electrolyte. Then, in order to seal the pores in the oxide film, a sol–gel layer was applied to the surface of the MAO coating by dipping. For investigation of heat treatment temperature of the sol–gel layer on the properties of the coatings, two different temperatures (150 and 350 °C) were chosen. Surface morphologies and compositions of the coatings were analyzed by Scanning Electron Microscope and X-ray Diffraction (XRD). Surface roughness of the coatings was also measured. The corrosion behavior of the coatings was evaluated with Electrochemical Impedance Spectroscopy and potentiodynamic polarization tests in 3.5 wt%NaCl solution. The porosity percent of the coatings was measured by potentiodynamic polarization tests results. It is found that the sol–gel layers successfully cover the pores of the MAO coatings. The results of the corrosion tests show that the sol–gel layers significantly increase the corrosion resistance of the substrate by reducing the percent of the porosity. The grain size measurements by XRD analysis shows that the grain size of the sol–gel layer heated in 350 °C is about 50 nm.     

Properties of nickel-cobalt-diamond composite coating deposited from a chloride electrolyte

Effect of electrolysis modes and electrolyte composition on physicomechanical properties of nickel-cobalt-diamond composite electroplated coatings deposited from a chloride electrolyte with introduction of an ultradispersed diamond suspension was studied and the possibility of replacement of wear-resistant chromium coatings with these composite coatings was demonstrated.     

X-ray photoelectron and scanning Auger electron spectroscopy study of electrodeposited ZnCr coatings on steel

Zn–Cr alloyed coatings electrochemically deposited are of high interest for leading steel manufacturing companies because of their novel properties and high corrosion resistance compared with conventional Zn coatings on steel. For tuning and optimizing the properties of the electrodeposited Zn–Cr coatings, a broad range of the deposition conditions must be studied. For this reason, two different types of material were investigated in this study, one with a low electrolyte temperature and one with an elevated electrolyte pH, compared with the standard values. Because different corrosion performance and delamination behaviour of the layers were observed for the two types, advanced surface analysis was conducted to understand the origin of this behaviour and to discover differences in the formation of the coatings. The topmost surface, the shallow subsurface region, and the whole bulk down to the coating–steel interface surface were analysed in detail by X-ray photoelectron spectroscopy (XPS) and high-resolution scanning Auger electron spectroscopy to determine the elemental and the chemical composition. For better understanding of the resulting layer structure, multiple reference samples and materials were measured and their Auger and XPS spectra were fitted to the experimental data. The results showed that one coating type is composed of metallic Zn and Cr, with oxide residing only on the surface and interface, whereas the other type contains significant amounts of Zn and Cr oxides throughout the whole coating thickness.     

Recent Advances in Surface Coatings of Layered Cathode Materials for High-Performance Sodium-Ion Batteries

Layered transition metal oxides (layered materials) have the advantages of simple synthesis methods, high average operating voltages, and good specific capacity, and are therefore promising cathode materials for sodium-ion batteries (SIBs). However, the capacity retention of these materials is poor due to the dissolution of transition metals caused by the detrimental reactions of the electrode with the electrolyte and the rupture of the electrode due to volume expansion during cycling. Studies have discovered that surface modification can effectively improve the aforementioned problems. This paper reviews the effects of different coating materials (e. g., carbon coatings, metal oxide coatings, phosphate coatings, etc.) on the performances of layered cathode materials and analyzes the reasons for the improved performance. In addition, the limitations of different coating materials and coating methods are presented, and future developments are proposed.     

钌镧氧化物涂层在NaCl 溶液中的电化学阻抗谱(EIS)研究

测量了钌镧氧化物涂层的电化学阻抗谱(EIS), 结合循环伏安(CV)及扫描电子显微镜形貌分析, 研究了钌镧氧化物涂层阳极在3.5% NaCl 溶液中电化学表面结构及电化学行为. 在非析氯反应区间, 该涂层EIS 数据的最佳拟合等效电路是R_s(R_ctQ_dl), 在析氯反应区间, 其等效电路为R_s(R_fQ_f)(R_ctWQ_dl). 高频段阻抗行为对应涂层的物理阻抗, 低频段对应涂层与溶液界面的电化学反应阻抗. 实验结果表明, 随着La 浓度增加, 氧化膜及双电层的伪电容增大, 且在La 含量30mol%时达到最大值, 与CV实验结果一致, 证明了加入La 能提高RuO₂涂层的电催化活性. 但在析氯反应区间, 涂层氧化膜的导电性在含La 大于30 mol%之后迅速下降, 在低频段产生Warburg 阻抗, 与其表面钝化和特性吸附现象有关,这是导致含La 70 mol%时电催化活性急剧下降的原因.     

Preparation and characterization of oxides of Ni-Cu: anode material for methanol oxidative fuel cells

Oxides of Ni-Cu were electrodeposited and characterized by SEM, IR and XPS techniques. These studies indicate that the coatings are mostly amorphous, made up of tiny particles of copper metal or a very low alloy with nickel in non-metallic phases with non-stoichiometric compositions. The deposited oxide films exhibit low overvoltages at 303 K for methanol oxidation and act as effective anode materials. Electrocatalytic activity of the deposited films depends on the composition of the coating. Under working conditions the deposits exhibit good corrosion resistance towards the electrolyte medium.     

水热电沉积羟基磷灰石涂层的研究

在0.0105mol/LCa(NO₃)₂,0.0063mol/LNH₄H₂PO₄,0.1mol/LNaNO₃,pH=4.6的电解液中,控制温度60～200℃,恒电流0.4mA/cm²,通过水热电沉积法制备羟基磷灰石涂层.实验结果表明,涂层晶体端面呈六边形棒状结构,涂层组分为缺钙磷灰石Ca_10-x(HPO₄)_x(PO₄)_6-x(OH)_2-x.经800℃烧结后涂层分解为HA和β-TCP的混合物.随温度升高,涂层n(Ca)/n(P)不断增大,涂层组分逐渐接近计量比的HA.涂层质量和结合强度随温度升高先增后减,在160℃时达到最大值16.7MPa     

Effect of electrolyte components on the magnetic and magnetoresistive characteristics of Fe-containing plasma electrolytic oxide coatings on titanium

The effect replacing Na₃PO₄ with Na₂HPO₄ in aqueous phosphate–borate–tungstate electrolyte that additionally contains Fe₂(C₂O₄)₃ on the magnetic and magnetoresistive characteristics of oxide coating/ titanium composites formed by means of plasma electrolytic oxidation (PEO) is investigated. It is established that PEO coatings with ferromagnetic characteristics form on titanium in an electrolyte containing Na₃PO₄ (pH ~ 11) upon adding iron(III) oxalate, while replacing Na₃PO₄ with Na₂HPO₄ and the respective drop in the pH of the base electrolyte down to 9.8 results in the formation of coatings with different magnetic characteristics. The correlation between changes in the values of the charge carriers’ activation energy and the magnetic susceptibility is demonstrated for the latter. An increase in the electric resistance of coatings in a magnetic field is observed, and the type of the magnetic resistance temperature dependence is established.