Surface Engineering and Applied Electrochemistry最新文献

AZ31 alloy has excellent properties like ultra-low density, good energy absorption, and high damping performance but has poor corrosion resistance. The influence of media pH on the corrosion of AZ31 alloy in chloride and sulphate media was investigated using such electrochemical techniques as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The tests were carried out by varying pH in different concentrations (0.05–0.25M) of the media. The surface morphologies and surface compositions of the corroded alloy surfaces were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. Conclusively, the recorded results reflect a trend of a higher corrosion rate at higher concentrations of the media; and an increase in the corrosion rate on decreasing the pH of the media. In the studied pH range, the alloy showed a higher corrosion resistance at pH 11 and a lower corrosion resistance at pH 3.

A method for the electrophoretic deposition of nanocluster coatings from a colloidal silver solution onto the receiving surface of silicon photovoltaic converters (PVCs) has been proposed. It has been shown that the resulting coatings exhibit a surface plasmon resonance (SPR) effect. A phenomenological model to assess the effect of nonmetallic impurities that can be incorporated during coating deposition on the occurrence of the SPR effect has been proposed. Calculations in the COMSOL 5.5 Multiphysics environment have shown that, in the absence of impurities, the SPR condition is satisfied in a wavelength range of 270–370 nm. The presence of nonmetallic impurities decreases the probability of the occurrence of an SPR and makes it impossible at impurity concentrations of approximately 0.1 at %. The experiment has shown full compliance with the calculations.

The peculiar features in the manifestation of the properties of topological insulators (TIs) and quantum size effects on the longitudinal magnetoresistance (LM) (H ||I) of Bi–17 at % Sb single-crystal semiconductor wires prepared by liquid phase casting (Ulitovsky method) having orientation ((10vec {1}1)) along the axis and diameters of 75–1000 nm have been studied. At high temperatures (T > 50 K), the quantum size effect is evident as an increase in the energy gap of ΔE ~ d^–1 of the Bi-17 at % Sb semiconductor wires with a decrease in the wire diameter d. A decrease in temperature (T < 50 K) leads to a transition from the semiconductor dependence R(T) to the metallic dependence with a decrease in the wire diameter d; the transition indicates the presence of the surface states characteristic of TIs. In a diameter range of 200–350 nm, the Shubnikov de Haas (SdH) oscillations are observed on the longitudinal magnetoresistance H ||I in weak magnetic fields (H < 3 T); they are used to calculate the Dingle temperature, cyclotron masses, carrier mean free path, and charge carrier mobilities μ = 11 × 10³ cm²/s. On the LM of the Bi–17 at % Sb wires at 4.2 K, a singularity in the form of phase shift of the Landau levels’ index on the SdH oscillations and anomalous maximum in the thickness dependence of the LM at 4.2 K is observed; it is associated with the semiconductor-metal transition due to a significant contribution of the surface states of the TI to the conductivity. Taken together, the singularities on the LM, the phase shift of the SdH oscillations, high mobility and anisotropy of charge carriers, and an increase in conductivity with a decrease in the wire diameter d indicate the presence of surface states in thin semiconductor Bi_{1 – x}Sb_x wires with a Fermi energy of the “Dirac cone” type, which are highly sensitive to the wire diameter, temperature, and the magnitude and direction of the magnetic field and lead to new peculiar features of the transport properties of topological insulators in the low-dimensional structures.

The mechanisms of electrification of various solids in contact or friction, as well as in the interaction of liquid media with conductive and dielectric materials, are described and analyzed. The output characteristics of nanogenerators based on the phenomenon of electrification of solids and liquids are considered. The design and the study results of an electrostatic nanogenerator based on the electrification of a glass porous structure when a dielectric fluid passes through it are presented.

In this study the wear properties of chromium deposit were improved by using the nickel electrodeposited middle layers. The nickel middle layers were formed by direct current (DC) and pulse current (PC) power supplies. The results showed that the surface morphology of a chromium layer in Ni/Cr coating (DC deposited) and Ni (duty cycle = 30%, frequency = 20 Hz, PC deposited) were compact, with small nodules. Also in these coatings the crack networks density of the chromium layer decreased when compared other coatings. The hardness step value profiles with the highest value of the chromium layer and the lowest value of the nickel middle layer occurred in the studied five samples. The compact surface morphology and the appropriate hardness step value profiles of the layers were two main reasons for improving the wear resistance of the chromium layer coated on the top of the nickel layers produced by DC and PC (duty cycle = 30% and frequency = 20 Hz) currents.

In this study, ZnFe₂O₄ magnetic nanoparticles were used to modify a screen printed electrode. The modified electrode decreased the over-potential of vitamin C (70 mV) and prominently increased its oxidation peak current (3.3%). Under optimum conditions, the electrode provided a linear response based on the vitamin C concentrations between 0.5–500.0 μM, with a detection limit of 0.15 µM, by using the differential pulse voltammetric method. The modified electrode exhibited excellent electrochemical performance, including a good linear range and a micromolar detection limit, high sensitivity, and desirable stability and repeatability. Particularly, the practical applicability was revealed by quantifying the vitamin C concentrations in real samples.

The inhibitory effect of a new derivative of the indazole family, namely, (Z)-2-(1-methyl-5-nitro-1H-indazol-4-yl)-3-(3-nitrophenyl) acrylonitrile (51K2) against corrosion of carbon steel in 1 M HCl medium at a temperature of 25°C has been evaluated by different techniques such as gravimetric methods, potential-intensity curves, and electrochemical impedance spectroscopy. The impact of the concentration on the inhibition efficiency was also studied. The results of weight loss measurements and electrochemical analyses obtained showed that the addition of 51K2 increases the inhibition efficiency by decreasing the corrosion rate, with a maximum inhibitory efficacy of 80%. In other words, 51K2 is a good anodic-type corrosion inhibitor of carbon steel in 1 M HCl.

Sargassum latifolium extract was used as new extract for the protection of Al dissolution using chemical and electrochemical methods. It was extracted, tested, and its high inhibition quality with addition of 1 × 10^–2 M KI at 298 K for 300 ppm in 1M hydrochloric acid was recorded. The adsorption mechanism agreed with the Temkin isotherm from the weight loss procedure. From Tafel extrapolations showed that the used extract acts as mixed inhibitor. The thermodynamic parameters were organized and clarified. The attenuated total reflectance-Fourier transform infrared spectroscopy and atomic forced microscopy were performed for the Al surface analyses and a good decrease in the surface roughness was reached. The used extract has also demonstrated a satisfying biological activity against bacterial growth.