Compositions of Composite Polymer-Oxide Coatings on Aluminum from Pyrolytic Gas Chromatography Mass-Spectrometry Data

Data on the composition of the external polymer part of the composite polytetrafluoroethylene (PTFE) oxide coatings obtained on an aluminum substrate by plasma electrolytic oxidation (PEO) within a single stage are presented. The coatings were formed in an aqueous silicate electrolyte with addition of PTFE dispersed powder in a siloxane–acrylate emulsion. It has been established that the external polymer-like layer of the PTFE/PEO coatings does not represent a physical mixture of the siloxane–acrylate copolymer and PTFE particles, but is composed of fragments of them. A partial substitution of fluorine by hydrogen in fluorocarbons contained in the coatings has been revealed. The obtained data are crucial for expanding knowledge on the formation, structure, composition, and properties of the composite polymer-containing oxide coatings formed within a single stage by means of plasma electrolytic oxidation on the valve metal surface.     

电解液成分对等离子体电解氧化TC4合金腐蚀行为和摩擦学性能的影响（英文）

在TC4合金表面制备4种典型等离子体电解氧化(PEO)涂层,研究电解质组成对PEO涂层腐蚀行为和摩擦学性能的影响。结果表明,PEO涂层的腐蚀行为和摩擦学性能与电解质成分密切相关。在含NaH₂PO₂的电解液中制备的PEO涂层由于内氧化膜较致密而具有最好的耐蚀性能,而在含NaAlO₂的电解液中制备的PEO涂层由于含有Al₂O₃而具有最好的摩擦学性能。为制备具有良好耐蚀性和耐磨性的PEO涂层,以NaH₂PO₂和NaAlO₂为电解液主要成分制备了复合PEO涂层。     

The Effect of Iron Precursors in an Electrolyte on the Formation,Composition, and Magnetic Properties of Oxide Coatings on Titanium

The effect of iron sulfate and citrate addition into the base alkaline phosphate-borate-tungstate electrolyte on the peculiarities of plasma-electrolytic formation of coatings on titanium, their thickness, surface morphology, composition, and magnetic characteristics has been investigated. In the first electrolyte, dispersed particles of iron hydroxides and hydroxo salts are formed, whereas the second one comprises a true solution. Numerous Fe-containing crystallites of a size of ~50 nm united into agglomerates have been found in the suspension electrolyte with FeSO₄. Such coatings manifest ferromagnetic properties: coercive force Hc of the samples is 62 and 148 Oe at 300 and 2 K, respectively. In pores of the coatings obtained in the electrolyte with FeC₆H₅O₇ (true solution), the presence of crystallites is less clearly expressed, while crystallites themselves are larger and molten to a higher degree. At room temperature, such coatings are paramagnetic; at 2 K, they manifest ferromagnetic behavior with the Н _с value of up to 200 Oe. The available data enable one to associate ferromagnetic properties of the formed coatings with metals concentrated in pores.     

Chemical deposition of metal composite coatings on plastics

Recently interest in electroless deposition of metal dispersion coatings on plastics has increased. These coatings are obtained through incorporation of solid dispersoids in the deposited metal matrix. Thin coatings with incorporated nanoscaled particles have gained a special interest with a view to their application in microtechniques.

The present review summarises the data available in the literature concerning chemically deposited nickel-phosphorus and copper dispersion coatings on ABS polymers from alkaline electrolytes. The studied dispersoids are SiC and Polyamide (PA) with particle size of 1 μm and TiO₂ and SiO₂ with particle sizes in the nanoscale range. The effects of the nature and size of dispersoid particles and their concentration in the base electrolyte, as well as the influence of electrolyte components and experimental conditions on the process kinetics, on the structure of dispersion coatings produced and on the degree of incorporation of dispersoids in both metal matrices have been established.     

Effect of electrolyte on mechanical properties of AZ31B Mg alloy in electrolytic plasma processing

Coatings on Mg alloys were prepared using NaOH + Na₂SiO₃ as basic electrolyte containing electrolyte of Na₂SiF₆ or NaF. EPP treatment was carried out on AZ31 Mg alloys matrix under a hybrid voltage of AC of 200 V combined with DC of 260 V for 30 min. Structural and morphological analyses of ceramic coatings were analyzed by XRD and SEM. Wear and hardness of coatings were measured by pin-on disk test and Vickers hardness test. The coatings formed in Na₂SiF₆ and NaF electrolytes were mainly composed of MgO and Mg₂SiO₄. The measured micro-hardness of coating formed in Na₂SiF₆ electrolyte was found to be over HV 1100, while, coating formed in NaF electrolyte possessed micro-hardness of HV ～900. These results show that the mechanical properties of AZ31B Mg alloys can be enhanced by the proper selection of electrolyte agent.     

Characterization of plasma electrolytic oxidation coatings formed on Mg–Li alloy in an alkaline silicate electrolyte containing silica sol

We investigate the influence of silica sol addition on the ceramic coatings of Mg–Li alloy by plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte. Scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and energy dispersive spectroscopy are employed to characterize the microstructure and composition of the ceramic coatings. The anti‐corrosion behavior of the ceramic coatings is evaluated by potentiodynamic polarization measurements in conjunction with electrochemical impedance analysis. The ceramic coating formed in the electrolyte containing silica sol contains SiO₂ and Mg₂SiO₄ phase and has more uniform morphology and higher corrosion resistance than that formed in the electrolyte without addition of silica sol.     

The Microstructure and Wear Resistance of Microarc Oxidation Composite Coatings Containing Nano-Hexagonal Boron Nitride (HBN) Particles

The composite coatings containing HBN were prepared on 2024 aluminum alloy by microarc oxidation in the electrolyte with nano-HBN particles. The microstructure, surface roughness, phase composition, hardness, adhesion strength and wear resistance of composite coatings were analyzed by SEM, EDS, laser confocal microscope, XRD, Vickers hardness tester, scratch test and ball-on-disc abrasive tests. The results revealed that composite coatings were mainly composed of γ-Al₂O₃, α-Al₂O₃, mullite and HBN. With increasing the content of HBN particles in the electrolyte, the size and number of the pores on the surface of composite coatings decreased significantly. Compared to the MAO coatings without HBN, the composite coatings exhibited better wear resistance, as demonstrated by the lower friction coefficient and the lower wear rate.     

Influence of aluminum phosphate on the tribocorrosion performance of chemically bonded phosphate ceramic coatings

In this study, chemically bonded phosphate ceramic coatings (CBPCCs) with different contents of aluminum phosphate (AP) are prepared on stainless steel (AISI 304L). Differential scanning calorimetry, X-ray diffraction, contact angle test, and a tribocorrosion experiment are carried out to clarify the role of AP in the tribocorrosion performance of CBPCCs. The results show that, with the increase in the AP content, the enthalpy of curing increases because of the greater formation of the bonding phase AlPO₄. Both in static corrosion and in tribocorrosion, the corrosion current density of CBPCCs achieves the lowest value when the weight ratio of AP to polytetrafluoroethylene is about 0.78. Additionally, the influence mechanism of AP on tribocorrosion is clarified. AlPO₄ from the reaction between AP and Al₂O₃ has excellent mechanical properties and can enhance the wear resistance of CBPCCs by reducing the mechanical wear and the increased wear due to corrosion. The alumina particles wrapped by AlPO₄ can form a dense and smooth surface and change the direction of electrolyte propagation, which leads to the increase in the tribocorrosion resistance of CBPCCs.     

Producing and investigating oxide coatings containing manganese and nickel compounds on titanium from electrolyte suspensions

Elemental and phase compositions, as well as the surface structure of oxide coatings formed on titanium by plasma-electrolytic oxidation in aqueous electrolyte suspensions containing dispersed MnO₂, NiO, and Mn₂O₃ particles with sizes of 5–10 μm, are determined. The coatings are investigated using X-ray spectral analysis, X-ray photoelectron spectroscopy, and X-ray phase analysis, as well as electron and atomic force microscopy. The amount of transient metals contained in the surface layer of the coatings is found to be determined by the concentration of oxide particles added to the solution, their nature, and the nature of the base solution. The relations discovered can be used when carrying out a directional formation of coatings containing the necessary oxide systems, including their mixtures with particular component ratios.     

Effects of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Nano-Particles on Corrosion Performance of Plasma Electrolytic Oxidation Coatings Formed on 6061 Aluminum Alloy

Corrosion resistance improvement of plasma electrolyte oxidation coatings on 6061 aluminum alloy in silicate electrolyte containing Al₂O₃ nano-particles was studied, with particular emphasis on the microstructure, coating growth, and corrosion behavior in 3.5 wt.% NaCl solution. The microstructure of coatings, their thickness, and phase composition were characterized using scanning electron microscopy and x-ray diffraction. All characterization data showed that the maximum coating thickness and lowest amount of porosity were obtained in a low concentration of KOH, a high concentration of Na₂SiO₃, and moderate concentration of Al₂O₃ nano-particles in the electrolyte. This combination describes the optimum plasma electrolytic oxidation electrolyte, which has the best conductivity and oxidizing state, as well as the highest incorporation of electrolyte components in the coating growth process. On the other hand, incorporation and co-deposition of Al₂O₃ nano-particles were more pronounced than SiO₃ ^2? ions in some level of molar concentration, which is due to the higher impact of electron discharge force on the adsorption of Al₂O₃ nano-particles. The electrochemical results showed that the best protective behavior was obtained in the sample having a coat with the lowest porosity and highest thickness.     

Effect of surfactant on the co-electrodeposition of the nano-sized ceria particle in the nickel matrix

The nickel–ceria (Ni–CeO₂) nanocomposite coatings have been pulse electrodeposited from a Watts-type electrolyte containing nano-sized CeO₂ particles produced by high-energy ball milling technique (HEBM). Sodium Lauryl Sulphate (SLS) has been added in the electrolyte as a cationic surfactant. The effects of the surfactant on the zeta potential, co-deposition and distribution of ceria particles in the nickel matrix and hardness of composite coatings have been investigated. Experimental results show that the addition of SLS up to 0.10 g/l increases the amount of co-deposited ceria particles in the nickel matrix and microhardness of the nanocomposite. However, when the amount of SLS in the electrolyte is more than 0.1 g/l, there is a tendency to form agglomerates of ceria particles in the nickel matrix resulting no further increase in hardness of the Ni–CeO₂ nanocomposite coatings.     

Plasma-electrolytic formation of Ta-containing oxide coatings on titanium. Their composition and properties

Coatings with a thickness of 2–18 μm that contain up to 20 at % tantalum and Ta₂O₅ oxide phase are formed in an aqueous NH₄[TaF₆]-containing electrolyte for 2 min. The coatings are pierced with pores with a size of from 0.5 to 2 μm. The number of pores in the coatings can be decreased by additionally applying a Ta-containing paste to the surface. The contact angle of the coatings in distilled water is 68°–85°. This approach is promising for application of Ta-containing coatings on titanium implants and stents for increasing their corrosion resistance, chemical inertness, and biocompatibility.     

The influence of sodium tungstate concentration and anodizing conditions on microarc oxidation (MAO) coatings for aluminum alloy

Microarc oxidation (MAO) coatings on 5052 aluminum alloy are prepared in silicate–hypophosphite electrolytes with sodium tungstate. The effects of sodium tungstate concentrations and current density on the surface morphology, phase composition and properties of the coatings are investigated. With the addition of sodium tungstate in the electrolyte and increase of current density, the final voltage at the microarc discharge process increases. The results also show that the MAO coatings are composed mainly of α-Al₂O₃ and γ-Al₂O₃ and the proportion of α-Al₂O₃ and γ-Al₂O₃, pore size, surface roughness as well as thickness of the coatings strongly depend on the sodium tungstate concentration and current density. Thus, the hardness, friction coefficient and corrosion resistance of the coatings are significantly influenced by the magnitude of the current density and sodium tungstate concentration. These oxide films on aluminum were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thickness gage, and polarization curves, respectively.     

Plasma-electrolytic oxidation of valve metals in Zr(IV)-containing electrolytes

The studies devoted to the production of Zr-containing coatings on valve metals (Ti, Al, and Mg) using plasma-electrolytic oxidation are reviewed. The coatings are formed from aqueous electrolyte suspensions containing dispersed ZrO₂ particles, as well as Zr(IV) fluorocomplexes, polyphosphate, and tartrate complexes, and from Zr(SO₄)₂ electrolytes. The layers that contain both zirconium oxide in either monoclinic or tetragonal modification and zirconium pyrophosphate and layers containing simple and complex zirconium phosphates are obtained. The described approaches enable one to produce protective layers and can form the basis of the technique for obtaining surface structures with a complex chemical composition, as well as coatings that contain certain compounds with specific characteristics.     

Effect of Gun Current on Electrical Properties of Atmospheric Plasma-Sprayed Lanthanum Silicate Coatings

Apatite-type lanthanum silicate (ATLS) electrolyte coatings for use in intermediate-temperature solid oxide fuel cells were deposited by atmospheric plasma spraying (APS). Plasma-sprayed coatings with typical composition La₁₀(SiO₄)₆O₃ exhibiting good densification and high oxide ionic conductivity were obtained by properly adjusting the spraying parameters, particularly the gun current. The highest obtained ionic conductivity value of 3.3 mS/cm at 1,173 K in air is comparable to other ATLS conductors. This work demonstrated empirically that utilization of the APS technique is feasible to synthesize dense La₁₀(SiO₄)₆O₃ electrolyte coatings using gun currents within an unusually broad range.     

纳米 SiO2添加剂对铸造铝铜合金微弧氧化陶瓷层耐磨性的影响

采用Na3PO4基础电解液,添加不同量的纳米SiO2,对铸造铝铜合金进行微弧氧化处理,分析了纳米SiO2用量对微弧氧化膜层厚度、硬度、物相组成、微观表面形貌及耐磨性能的影响。分析表明:纳米SiO2参与了微弧氧化反应过程,并进入微弧氧化膜层,当其添加量为3 g/L时,膜层的耐磨性能最佳。     

Potentiodynamic Study of Electroplating of Zn–Ni Alloy

It is found that, at a certain Zn⁺⁺concentration in the electrolyte, the cathodic current (i _c) peaks are observed in the potentiodynamic curves; the peak's height depends on the electrolyte composition and the cathodic potential sweep rate. At an elevated electrolyte temperature, no i _cpeaks are observed in the potentiodynamic curves. It is found that high-quality Zn–Ni alloy coatings are plated under the conditions, when the i _cpeaks are present in the potentiodynamic curves. Acetates negatively affect the quality of alloy electroplates.     

MO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>–ZrO<Subscript>2</Subscript> coatings with M=Al,Mg, Zr,Ti, and Nb on valve metals

Coatings formed on aluminum, titanium, magnesium, zirconium, and niobium by means of plasma-electrolytic oxidation in an aqueous electrolyte containing MgZrF are studied. All elements involved in the composition of the complex compound are present in the coatings. Contents of the elements involved in the inner sphere are the largest. Phase and elementary compositions of the coatings depend on the nature of the valve metal. All coatings contain ZrO₂ in either cubic or monoclinic modifications. The main phase of the coatings formed on magnesium is MgF₂. According to the surface structure, the coatings can be divided into three groups: large-pore (on Mg, Al, and Ti), small-pore (on Nb), and compact with a wavy surface (on Zr).     

黄铜在含磷酸二氢钠或硅酸钠的铝酸盐电解液中的等离子电解氧化行为和耐腐蚀性能（英文）

采用等离子电解氧化(PEO)技术对黄铜进行表面处理,研究其在铝酸盐电解液中分别加入NaH₂PO₄ (S1)和Na₂SiO₃(S2)添加剂对涂层形成和耐腐蚀性能的影响。在S1电解液中进行PEO处理的初始阶段,黄铜表面形成AlPO₄和Al₂O₃的混合涂层,导致快速产生等离子体火花放电现象并形成由Al₂O₃、CuO、Cu₂O和ZnO组成的黑色涂层。然而,在S2电解液中,等离子体火花放电行为延迟产生。由于产生较多的Cu₂O,S2涂层显示为深红棕色。Mott-Schottky测试表明,S1涂层为p型半导体;S2涂层具有n型和p型半导体可调性。动电位极化和电化学阻抗谱(EIS)测试表明,PEO处理能显著提高黄铜的耐腐蚀性,腐蚀防护效率可达91.50%,S1涂层电荷转移电阻最大可达59.95 kΩ·cm²。     

Microstructure and texture investigation of chemically deposited copper coatings

Abstract

This work reports electron microscopy and X-ray investigations of the structure and texture of thin copper coatings that were chemically deposited (_chemCu) from trilonic electolytes. The relationships between the structure and texture of _chemCu, and the structure and texture of electrochemically deposited copper coatings have been established. It has been determined that chemically deposited copper coatings have very fine crystal structure, with areas of coherent scattering that are orders of magnitude smaller than their counterparts in matt copper coatings (_mattCu) that are electrochemically deposited from simple (non-complex) sulphuric-acid electrolyte. Additionally, in _chemCu, the axis of preferred orientation is in the <111> direction, while in _mattCu it is in the <110> direction. Alternatively, bright copper coatings (_brightCu) (electrodeposited from similar sulphuric acid electrolyte but with brightener additives), which are also characterised with extremely fine crystal structure have mixed <311> plus <110> texture, at a <311> dominant axis of preferable orientation. The values of microhardness of the copper coatings are arranged in the following sequence: HV_mattCu<HV_chemCu<HV_brightCu, opposite to the crystal size (D) and the internal stress (rms) in these three types of coatings – D_mattCu> D_chemCu>D_brightCu and rms_mattCu>rms_chemCu≧rms_brightCu. The data obtained for D and rms are in good agreement with the Hall–Petch rule on HV-grain size relationship.