Surface Engineering and Applied Electrochemistry最新文献

The current study was conducted to measure the concentrations of nitrite by a glassy carbon electrode modified with MXene/La³⁺ doped ZnO/hemoglobin (Hb) nanocomposite as a new voltammetric sensor. Chronoamperometry, differential pulse voltammetry, and cyclic voltammetry were employed to characterize the modification of the electrode surface. According to the analytical results, the glassy carbon electrode incorporated with MXene/La³⁺ doped ZnO/Hb nanocomposite was able to detect the presence of different concentrations of nitrite (0.1–700.0 μM), with the detection limit of 4.0 × 10^–8 M. The proposed sensor can be proposed as acceptable electrochemical detector of nitrite in real samples.

Abrasive water jet (AWJ) cutting is an emerging material processing technology with significant advantages, such as no thermal deformation, high processing versatility, high flexibility, and low cutting force. It is used in various applications including machining, cleaning, surface preparation, and material cutting. The main concerns during the AWJ cutting process are the surface roughness and the kerf geometry. This study aimed to successfully predict the surface roughness and the kerf geometry during low pressure AWJ machining to cut metal sheets at low and high water pressures when cutting the stainless steel and copper specimens. The experimental results show that a low water pressure indicates fewer variations between the surface roughness and the kerf angle. At various pressures, the roughness values ranged from 3.087 to 4.817 µm. A regression model was developed to predict the surface roughness and the kerf angle. As a result, the effect of water pressure can only increase the kinetic energy but cannot affect other processing parameters separately. Scanning electron microscopy revealed micro-cracks during the AWJ cutting process.

Based on mathematical modeling of the process of electrohydraulic sheet stamping, the influence of a pressure plate on the deformation of a workpiece rigidly clamped along its outer contour was studied. The influence of the thickness of the pressure plate and its internal diameter, in relation to the diameter of the cavity of the cylindrical discharge chamber, on the energy of plastic deformation of the workpiece and the shape of its deflection; parameters of the pressure plate on the pressure of hydrodynamic waves on the workpiece; and the shape of its deflection and the efficiency of using the energy stored in the capacitor bank for plastic deformation of the workpiece have been established.

The surface plasmon resonance (SPR) of metal nanoparticles (NPs) plays a crucial role in designing numerous chemical and biomolecule sensors. Therefore, in this work, gold (Au) NPs thin films were deposited on a glass substrate at the substrate temperature of 300°C using the pulsed laser deposition method. The effect of the number of laser pulses on the morphology and optical properties of Au NPs was investigated through scanning electron microscopy, ultraviolet-visible spectroscopy, and photoluminescence studies. Scanning electron microscopy revealed that the particle size increased from 14 to 28 nm whereas the inter-particle distance decreased from 19 to 8 nm with an increase of the number of laser pulses from 1000 to 5000, but the thickness of the Au NPs film increased from 107.5 to 132.4 nm. The observance of the SPR peak around 565–586 nm in absorption spectroscopy confirmed the formation of Au NPs. The red shift of the SPR peak position at higher numbers of laser pulses could be attributed to the simultaneous enhancement in the particle size and the reduction of the inter-particle distance. Further, the trend of the full-width half maxima in the intrinsic and extrinsic particle size region was studied, and the phenomena behind the SPR broadening was briefly explained. The photoluminescence spectrum has also shown a strong emission band at 530 nm, with a corresponding energy band gap of 2.34 eV, and the band position was in good agreement with the SPR peak position. This study suggests that the SPR properties of Au NPs can be tuned by varying the number of laser pulses as it strongly affects the morphology of Au NPs.

It has been shown that the response of the functional property of the deposit on the action of dimensional factors of electrolysis conditions equally determines the dimensional property of the electrolyte. It has been established that the most universal assessment methods of dimensional effects can be formed based on the correlation of dimensionless quantities for a number of specified and directional values of the size factor with a number of corresponding values of the functional parameter of the sediment. It is shown that studying the dimensional properties of electrolytes and deposits, depending on the type of dimensional factors and their scale scales, will expand the capabilities of the electrolytes used, increase the controllability of the formation of the functional parameter of the deposit, obtain new information about the process of deposition of nanostructured deposits, and reveal the factors which previously did not attract attention. A determination method and cell for quantifying the dimensional properties of the precipitate and electrolyte are presented.

Research into self-oscillatory processes in semiconductors and semiconductor structures makes it possible to formulate the physical mechanism of these unique phenomena and create solid-state generators and sensors of physical quantities with frequency-amplitude output. It was established that the excitation conditions and parameters of self-oscillations of the current were studied in more detail only in silicon doped with manganese and zinc atoms, as well as in semiconductor compounds CdSe, CdS, InGa and in some structures, while the boundary regions of existence of these current instabilities depending on external factors were not very accurately determined in other materials. This led to the lack of reproducible results and a discrepancy in the correlation between the electrical parameters of the material and the parameters of self-oscillations of the current (amplitude, frequency). In this regard, the results of comprehensive studies of self-oscillations of current in silicon doped with impurity atoms of manganese, zinc, sulfur, and selenium are presented. A physical mechanism of current self-oscillations is proposed, which is in good agreement with the known experimental results obtained.

In this study, new synthesized triazole-containing copolymer derivatives were investigated. The title compounds were identified using Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and carbon-13 nuclear magnetic resonance spectroscopy. The inhibitory effects of the synthesized compounds (1, 2, and 5) on the corrosion of mild steel in a solution containing 0.5 M H₂SO₄ were studied using also the electrochemical polarization technique (Tafel plots). The resulted values of corrosion parameters showed the efficacy of corrosion inhibition by raising the concentration of organic corrosion inhibitors of mild steel in 0.5 M H₂SO₄ solution at 295 K.

Approximate calculations were made to identify the main features of the propagation of standing transverse electromagnetic waves (EMWs) and standing longitudinal de Broglie electron waves in a homogeneous non-massive non-magnetic metallic conductor of finite dimensions (radius r₀ and length l₀ ⪢ r₀) with axial alternative conduction current i₀(t) of different amplitude–time parameters. Relations were obtained for the calculation estimation of averaged propagation velocities of standing transverse EMWs and standing longitudinal de Broglie electron waves in the metal (alloy) of the specified conductor. It was demonstrated that quantized standing transverse EMWs emerging in the finite-sized metallic conductor significantly differ from ordinary transverse EMWs propagating in conducting media of unlimited dimensions. An important characteristic of the standing transverse EMWs in the considered conductor is that their axial electric field intensity leads in phase their azimuthal magnetic field intensity by an angle of π/2. It was found that, in the standing transverse EMWs in the investigated conductor, the energy of the electric field is only converted into the energy of their magnetic field and vice versa. Therefore, the standing transverse EMWs do not transfer electromagnetic energy fluxes along the metal (alloy) of the considered conductor.

The aluminum metal matrix composite (AMMC) is now occupying an irreplaceable space in various industries due its advantages such as a great strength to the weight ratio, good wear resistance, and a reduced density. In this paper, the AMMC was developed using aluminum 7075 reinforced with 5 and 10% boron carbide. The L₁₈ orthogonal array was used for conducting the electrochemical micromachining experiments. The AMMC was a wire cut into thin sheets; and specimen 1 designates the AMMC with 5% boron carbide, and specimen 2 designates the AMMC with 10% boron carbide. The tool electrode was of a diameter of 0.5 mm, and sodium nitrate was used as an electrolyte. The technique for order of preference by similarity to ideal solution and the principal component analysis were utilised in order to find out the best parameter combination on the machining speed, the diametral overcut, and the delamination factor. The electrolyte concentration of 35 g/L, the voltage of 11 V, and the duty cycle of 70% were found to be the optimal combination for the machining speed, the diametral overcut, and the delamination factor in specimen 1. The ANOVA analysis results showed that the duty cycle is a significant factor, with its 53.5% contribution.

The results of experimental and theoretical studies of the electrical conductivity of weakly concentrated solutions of liquid dielectrics (LDs) with a chemically active impurity and associated electrohydrodynamic (EHD) flows are presented. The studies are carried out on the basis of a multi-ion model of electrical conductivity, which makes it possible to adequately describe both the dissociation–recombination interactions of ions and the electrochemical injection of ions from the electrode surface. It is shown that the recombination processes in the volume of the LD lead to a slow disappearance of the space charge with a characteristic time of hours and days, which does not allow for significantly reducing the distribution of the space charge in the LD that reduces the intensity of EHD flows. Numerical calculations based on the obtained theoretical and experimental data on the electrical conductivity were carried out, and they confirmed the results of observations concerning the development and structure of EHD flows and current characteristics.