Surface Engineering and Applied Electrochemistry最新文献

The comparative corrosion resistance in acidic, alkaline, and neutral environments of pure metals (steel, nickel, titanium) and of nickel and titanium coatings produced on steel using electrospark alloying with a high-frequency vibrator is investigated. It is established that the phase structure, roughness, and porosity of received coatings depend on the electrode material and on the modes of coating application that affect the corrosion behavior. A positive influence of the high-frequency alloying with nickel and titanium on an increase in the corrosion resistance of the steel surface is shown.

The effect of the addition of graphene oxide (GO) particles to the chromium electroplated coating on the surface of commercially pure aluminum (Al 1100) was studied in this paper. The synthesized coatings microhardness was characterized by the atomic force microscopy, field emission scanning electron microscopy, and the corrosion behavior was evaluated by using polarization and electrochemical impedance spectroscopy in the 3.5 wt % NaCl solution. The obtained Cr/GO nanocomposite shows remarkable improvement in the value of the surface microhardness, and the highest value achieved at the sample composed with 10 wt % of GO equals 1526 HV_0.5. The results gained from polarization and electrochemical impedance microscopy demonstrated that the sample with the 5 wt % of GO has better corrosion resistance, which is due to the coating compactness and active galvanic couples.

In this study, calcium phosphate/nano silica (CaP/SiO₂) composite coatings with different concentrations of silica were developed on the pretreated titanium using pulsed co-electrodeposition to improve their biocompatibility. The scanning electron microscopy images showed that silica nano-particles could act as nucleators for the CaP crystals during electrodeposition; therefore, all composite coatings showed different morphologies, in comparison with the pure CaP one. Increasing the concentration of silica particles in bath to 1 g/L changed the morphology of the composite coatings from the clove-like structure to the sunflower-like one. Next, the composite coating obtained from the bath containing 1 g/L silica revealed poor coverability, and some uncoated areas were found on the surface of the pretreated titanium substrate. In addition, the results of cell culture test demonstrated that the coated areas were more biocompatible so that the fibroblast cells were only adhered onto the areas covered with the CaP-based coating.

This paper discusses the essence and technological characteristics of the process of electrospark deposition (ESD), its advantages and disadvantages with a view to its application for improving the tribological properties of titanium and its alloys. A summary of the available data and results in the literature devoted on the ESD of titanium and its alloys has been made. Based on the published data, a comparative analysis of the technical parameters and technological capabilities of the most common equipment, including contactless ESD, is presented. The geometrical and physico-mechanical characteristics of the coatings obtained with different equipment and the nature of their change depending on the technological parameters of the ESD mode and the type of the anode and cathode materials are shown. A summary of the data on the wear resistance of the coatings obtained with different electrode materials and modes are given. It has been demonstrated that ESD can be successfully applied to improve the wear resistance of titanium surfaces. Suitable electrode materials and process parameters for ESD on titanium alloys are indicated.

The article is devoted to studying the electrical discharge cavitation development in a liquid working medium (water, aqueous electrolytes) placed in an external magnetic field. The main stages of an electrical discharge in an aqueous medium under the influence of an external magnetic field on the discharge gap are considered. A theoretical analysis of the preconditions for the magnetic field’s influence on the development of an electrical discharge in aqueous media is implemented. The experimental data obtained using high-speed photographic recording and measuring the cavitation intensity by the iodometric method allowed the authors to propose a concept for controlling the electrical discharge cavitation processes by external magnetic fields.

High capacity (>200 F/g) supercapacitor electrodes have been fabricated by blending high surface area microporous carbon and polyaniline. The incorporation of a conducting polymer is expected to stabilize the microporous graphitic layers to form a conductive porous composite to increase the capacitance. Well-organized nano- and micropores are believed to facilitate rapid ion diffusion especially when the micropore size is comparable to the ionic radii in the electrolyte solution thereby greatly boosting the capacitance. The initial capacitance of ~110 F/g of the microporous carbon network was found to increase to ~224 F/g (>100% increase) after the incorporation of polyaniline in the 1 M H₂SO₄ aqueous electrolyte. The non-linear behavior in the charge/discharge galvanostatic curve and the appearance of additional redox peaks in the capacitance-voltage curves confirm the presence of pseudocapacitance in the microporous carbon/ polyaniline composite in addition to the electrical double layer capacitance of pristine microporous carbon. The composite material shows the capacitance retention percentage over 80% after 1000 cycles implying a promise for novel supercapacitors with long-lasting ultra-high capacitance and power density.

The pressure field in the limited volume discharge chambers with deformable walls markedly affects the technological process efficiency of sheet alloys’ deformation; therefore, its determination is of great importance. Resulting from the electrical discharge in liquid, which fills the discharge chamber, a cavity is formed in the latter with a higher compressibility than that of the liquid in the chamber. Its pulsations create the field of pressure in the discharge chamber. At present, the role of the gas-vapor cavity is studied slightly as to the formation of the field of pressure in the discharge chamber with a deformable wall. Its definition is the aim of this work. The research is based on the earlier developed mathematical model of the electric discharge in water, which is supplemented in this work with correlations that significantly enhance the calculation precision of the discharge channel resistance and the energy released in it. It was determined that the pulsations of the gas-vapor cavity ensure pressure oscillations in it in a counter-phase with an average pressure in the liquid. They decay slowly in the discharge chamber with rigid walls, whereas the presence of the deformable wall makes the decay of the pressure oscillation to be rapid. In the mathematical model developed earlier, a change in the plasma optical transparency and its substantial effect on the pressure in the cavity as well as the pressure field in the liquid were taken into account.

The composites consisting of similar or dissimilar metallic layers with different physical properties are vastly applicable. Among various methods for producing these composites, cold roll bonding (CRB) is considered to be more efficient and more cost-effective than other bonding processes. Nowadays, Al-Cu layer composite bonds are favorable in different industries due to their low price, well conductibility, high corrosion resistance, high deformation, and good electrical conduction. This review paper deals with the investigations of the Al-Cu cold rolling process, of the bonding mechanism of metallic layers during CRB, and of the effect of the roll bond strength parameters such as initial thickness, for one. Roll bonding has three levels: (1) physical touch; (2) activating surfaces in touch; (3) interaction between bonding metals. CRB is supposed to be an in-plane strain, and the normal stress distributed on the top and bottom rollers is homogeneous. Annealing before and after rolling, the direction and speed of rolling, the amount of thickness reduction, and the lubrication conditions on the Al–Cu bond through the roll bonding process were studied. The effect of different annealing conditions on the produced intermetallic compounds at the Al–Cu rolling bond interface and the growth of the intermetallic phases and their impact on the CRB parameters was examined. The thickness of intermetallic compounds, thickness reduction under the rolling process, the rolling speed, the annealing temperature, and time affected the bond strength. The effect of the rolling speed on the bond strength depends on the touching time between the sheets during rolling, which means that the touching time between two surfaces of Al and Cu sheets reduces at higher rolling speeds. As a result, the chance for proper bonding is lost, and, therefore, the bond strength is decreased.

ZnO nanorods and Al:ZnO nanosheets have been successfully synthesized via two chemical methods: electrodeposition and successive ionic layer adsorption and reaction (SILAR). The present study reports their structural, morphological, and optical properties. All samples annealed at 350°C were polycrystalline, with a hexagonal wurtzite structure. The morphological analyses show two different nanostructures of hexagonal nanorods and hexagonal nanosheets which are attributed to pure ZnO and Al:ZnO, respectively. Moreover, the average size and the vertical orientation of the obtained nanorods and nanosheets depend on the used synthesis methods. Furthermore, the UV-Vis analyses performed on the obtained films revealed transmittance over 70% in the UV-Vis region. In fact, the electrodeposition method allows depositing a ZnO film with a transparence higher than 13% compared to that obtained via SILAR method. The obtained band gap values are approximately 3.25 and 3.28 eV for the ZnO synthesized by electrodeposition and SILAR, respectively.

A highly sensitive method is proposed for the simultaneous determination of dopamine and tyrosine using a Ti₃C₂ nano layer modified screen printed electrode. The electro-oxidation of dopamine at the surface of the modified electrode was studied using cyclic voltammetry, chrono-amperometry, and differential pulse voltammetry. Under the optimized conditions, the differential pulse voltammetric peak current of dopamine increased linearly with dopamine concentrations in the ranges of 0.5–600.0 µM, and the detection limit of 0.15 µM was obtained for dopamine.