Surface Engineering and Applied Electrochemistry最新文献

The effect of anodic boriding modes on the structure of the modified layer and the tribological characteristics of the treated titanium alloy has been studied. The structure, phase, and elemental compositions of the layer have been studied by X-ray diffraction analysis and electron microscopy with energy dispersive X-ray spectroscopy analysis. Surface roughness and microhardness distribution have been measured by the standard methods. The tribological characteristics of the borided alloy have been studied under dry friction conditions using a counterbody made of bearing steel. It has been found that the modified layer contains titanium dioxide (rutile) and a solid solution of boron in titanium with precipitates of the beta phase. A fivefold increase in the wear resistance of the alloy due to an increase in hardness and a decrease in the roughness has been achieved owing to boriding in a solution of boric acid and ammonium chloride at temperatures of 850–900°C for 5 min.

Factors leading to size-dependent surface properties of electroplated coatings obtained by induced codeposition of iron group metals and tungsten are investigated. The size effect in microhardness described in earlier studies and the size effect in the corrosion resistance revealed in this work are shown to stem from a common origin, which is the formation of surface oxides. Removing surface oxides by abrasive processing leads to a higher corrosion rate and cancels the size effect in microhardness. Factors contributing to the formation of surface oxide layers during induced codeposition of considered alloys are studied.

An experimental study has been carried out on the surface characteristics of hot-dip aluminized (HDA) C45 carbon steel. The coated specimens were also tested thrice by cycling heat between the ambient temperature and 700°C inside an electrical resistance furnace. Both the as-coated and the oxidized samples were analyzed by scanning electron microscopy, energy dispersive spectrometry, and elemental mapping. Microstructural features and other important characteristics (compositional changes, chemical elemental distributions, growth of the intermetallic phases, the formation of micro-voids, etc.) were investigated. Under the high temperature tested conditions, the HDA coated C45 carbon steel close-to-surface top-layer almost entirely converted to iron-aluminum intermetallics, with Fe to Al atomic ratios of 1 to 2 corresponding to the phases FeAl and FeAl₂. However, the innermost intermetallic phase (FeAl) formed between the finger-like structure and the steel substrate appeared quite compact and sound (without voids, micro-crack, and internal iron oxide scale), which is a convincing sign and an experimental proof of a high chemical and mechanical stability of such type of surface coatings. The results confirm that even inexpensive carbon steel, if properly aluminized, can provide sufficient protection against excessive oxide scale formation in the air at high temperatures.

The article considers the technological aspects of temperature estimation in an aluminum specimen with the possible formation of an aluminum-containing coating on its surface using the combined technology of cold gas dynamic deposition and microarc oxidation. The experimental results for the temperature flow distribution over the thickness of the metal surface under the cold gas dynamic deposition are presented. The temperature of the heat flow during spraying was varied from 200 to 600°C. It was found that the operating temperature of the aluminum substrate with a thickness of 8 mm at the standard thermal deposition modes is not more than 120°C, which is one of the advantages of the used technology over the known methods of plasma and magnetron sputtering. The temperature effect of the microarc oxidation on the surface of a specimen depending on various technological modes is estimated. It was found that the surface temperature of the specimen oxidized in an alkaline electrolyte with liquid glass additives at current densities of 20–30 A/dm² is not more than 90°C, which shows the absence of thermal transformations.

The use of different pore sizes (0.42–0.76 μm) in track membranes for the anodic and cathodic space separation upon the induced codeposition of Fe–W coatings from a citrate bath is described. This allows a twofold increase in the current efficiency without increasing the process’s power capacity as well as ensuring the constancy of the coating properties (microhardness) upon a lengthy electrolysis. Limited abilities of the membranes are emphasized since they serve only as the microfilters and lack the properties of ion exchangers.

The electrochemical behavior of cobalt and molybdenum oxides in molten carbamide at 135°C has been studied. The potentials and limiting discharge currents of cobalt and molybdenum have been determined by the cyclic voltammetry method. According to the results of the studies, an electrolysis mode for the formation of cobalt–molybdenum coatings has been selected.

Cu₂ZnSnSe₄ (CZTSe) based solar cells, containing abundant elements, with Ag alloying have recently reached efficiency of 10.2%. The open circuit voltage in CZTSe devices is believed to be limited, in between other factors, by strong band tailing caused by an exceptionally high density of Cu/Zn antisites. By replacing Cu in CZTSe with Ag, whose covalent radius is 15% larger than that of Cu and Zn, the density of I–II antisite defects (e.g., Cu–Zn disorder) is predicted to drop. In the present work, (Ag_xCu_1 – x)₂ZnSnS₄ (ACZTS) heterostructures in three different architectures were investigated. The 5 and 10% silver substituted CZTS absorber layers were obtained by low-cost spray pyrolysis technique, as well as three different methods for the CdS layer deposition were tested in order to optimize the ACZTS heterostructure efficiency.

The aim of the present work was to evaluate the inhibition effect of cinnamon essential oil (CEO) on mild steel corrosion in 1.0 M HCl. Its antioxidant activity was also analyzed. The CEO characteristics were studied using a chromatography-flame ionization detector, gas chromatography-mass spectrometry analysis, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and weight loss measurements, the results achieved via different techniques were in excellent agreement. The inhibition efficiency of CEO exceeded 92% at 1.0 g/L at 298 K and increased with increasing the oil concentration but decreased slightly with an increase of temperature. The adsorption of the inhibitor on the surface of mild steel followed best the Langmuir isotherm model. The scanning electron microscopy and energy dispersive X-ray spectroscopy data confirmed the formation of a protective film on the surface of the mild steel.

The results regarding formation of ITO/c-Si junctions interface through the oxidation of the silicon wafer are described. Thus, the formation by this method of the thin layers with a thickness of about ~1 nm is demonstrated, which allows to obtain a photovoltaic conversion efficiency up to 15.3%. By depositing the luminescent layer on the front side of the ITO/c-Si junctions, which is active in the region of the solar cells sensitivity to the action of UV irradiation, their functionality in the range of 300–1100 nm of the solar spectrum is demonstrated.

This study reports the preparation and performance of a smart material—a carbon paste electrode combined with TiO₂ semiconductor (CPE/TiO₂) as electrochemical sensor for detecting profenofos—a toxic organophosphates group insecticide widely used in agriculture. Such techniques as real samples tests and electrochemical tests were used to investigate the following parameters: a scan rate, an electrode response, a limit of detection (LoD), and repeatability. Based on the obtained results, the best mass composition of TiO₂ combined with CPE was found to be in a ratio of 1 : 1 : 5, with an anodic peak current (I_pa) of 150 μA, an anodic peak potential (E_pa) of 0.87 V, and an optimal scan rate measurement of 0.5 V s^–1. The LoD based on a linearity curve with a value of 4.0 × 10^–5 μM was also observed, and a repeatability test against the working electrode was performed until the 30th day, using the Horwitz ratio of 0.16. A good electrochemical performance of the working electrode tested against a real sample showed the specifically detected profenofos with I_pa value of 7.0 × 10^–5 μM.