Open Access
Access granted
Subscription Access
Vol 55, No 1 (2019)
- Year: 2019
- Articles: 13
- URL: https://bakhtiniada.ru/1068-3755/issue/view/14305
Article
Plasma Electrolytic Boriding of Steels and Titanium Alloys
Abstract
Results of diffusion saturation of steels and titanium alloys with boron and other elements under cathodic and anodic electrolysis plasma are considered. Processing regimes and electrolytes compositions, structural features of modified layers, their microhardness, surface roughness, as well as data of tribological and corrosion tests in various environments are presented. The treatment conditions are found to significantly increase the wear resistance and corrosion resistance of structural steels and titanium alloys. A conclusion is made on the prospects of electrolytic-plasma treatment; plasma electrolytic boriding has proven its potential; the advantages and limitations of the method are noted, including promising areas for further research.
1-30
Deposition of Nanostructured Carbon Coatings on Metal Surfaces with the Electric-Discharge Method in a Hydrocarbon Medium
Abstract
An experimental setup for depositing nanostructured carbon coatings on structural materials is described; it exploits the principle of the electric-discharge destruction of gaseous hydrocarbons to deposit the carbon nanoparticles onto a metal surface. The results of optical metallography, atomic force microscopy, and X-ray diffraction analysis suggest that a nanostructured amorphous carbon layer with a grain size of 50–80 nm and an arithmetic average roughness of 35–40 nm and that is capable of absorbing X-rays is present on the sample surface. The coating thickness can achieve 20–40 μm. The characteristics and growth mechanisms of the coatings depend on the ability of the substrate material to interact with carbon.
31-37
Impact of Electrolyte Composition and Modes of Operation on the Structure, Morphology, and Properties of Oxide Ceramic Coatings Fabricated by Microarc Oxidation
Abstract
The formation of oxide coatings on D16 aluminum alloy by microarc oxidation (MAO) treatment in the anodal-cathodal mode with discharge interruption in the basic silicate-alkali electrolyte (composed of three solutions) and in the mode without charge interruption in a silicate-alkali electrolyte of similar composition is studied. We find that the mechanism of formation of oxide ceramic coatings depends on the mode of MAO treatment. Addition of sodium tetraborate to the electrolyte has an impact on the properties of oxide ceramic coatings fabricated using the mentioned treatment modes. We demonstrate that MAO treatment in the anodal-cathodal mode with discharge interruption gives rise to a higher content of high-temperature aluminum oxide phase (α-Al2O3) in coatings and enables the formation of thin (up to 25 μm) oxide ceramic coatings that retain all unique properties of this type of coatings.
38-45
Macroscopic Size Effect on the Microhardness of Electroplated Iron Group Metal—Tungsten Alloy Coatings: Impact of Electrode Potential and Oxygen-Containing Impurities
Abstract
The cause of the microscopic size effect in the microhardness of electroplated binary alloys between iron group metals and tungsten is identified by studying electrodeposition of Co-W alloys. The effect is caused by the presence of oxygen-containing impurities in electroplated alloys, the impurity content growing with increasing the volume current density, which leads to a reduction in the coating microhardness. We find that the nature of anodes used affects the properties of deposited coatings, in particular, microhardness, because a deposition-inducing metal complex, which is a complex of an iron group metal, is consumed during electrolysis not only at the cathode, but it may also undergo oxidation at the anode, which identifies the way the anode affects the coating properties.
46-52
Peculiarities of Distribution of Electromagnetic and Hydrodynamic Fields for Conductive Electric Current Treatment of Melts in Different Modes
Abstract
The peculiarities of the redistribution of electromagnetic and hydrodynamic fields for conductive electric current treatment in different modes and with various electrode systems are shown. Mathematical simulation is performed to determine that, depending on the type of the electrode system and the mode of the electric current passing through the melt, qualitatively different configurations and distributions of electric, magnetic, and hydrodynamic fields are realized in the macrovolume of the melt. The character of the distribution determines the area and degree of the impact on the object under treatment, which is decisive in the design of technologies for the electric current treatment of melts.
53-64
Characteristics of High-Current Pulse Discharge in Air with Ectonic Mechanism of Copper Vapor Injection into a Discharge Gap
Abstract
The characteristics of bipolar high-current nanosecond discharge in the air between the copper electrodes is described. With an inter-electrode gap of 1–2 mm and the air pressure of 0.05–3.0 atm the conditions for obtaining a homogeneous volume discharge in the inhomogeneous electric field, associated with the generation of a beam of a runaway electron and concomitant X-ray radiation, are realized. It is shown that this discharge is a simple point source of radiation in the spectral range of 200–230 nm on the transitions of singly charged copper ions. The results of the optimization of the UV-emitter depending on the pump conditions and parameters of the discharge medium are provided. It is found that under the influence of a discharge, a deposition of thin nanostructured membranes made of electrodes erosion products and products of dissociation of air molecules is possible.
65-69
Effect of Electron Irradiation on Charge Transfer in 2D Gallium Monosulfide
Abstract
The features of the effect of electron irradiation with an energy of 4 MeV and a dose of 2 × 1012-1013 cm−2 on the dielectric properties and AC-conductivity in alternating current of a 2D layered single GaS crystal in a frequency range of 5 × 104−3.5 × 107 Hz are established. It is shown that the electron irradiation of a single GaS crystal increases the real component of the complex dielectric constant, decreases its imaginary component, causes the dielectric loss tangent and AC-conductivity across the layers. Both before and after the electron irradiation, the conductivity varies according to a law characteristic of the hopping mechanism of charge transfer over states localized near the Fermi level. It is shown that at 140–238 K in the layered single GaS crystals across their natural layers in the constant electric field there is also a hopping conductivity (DC-conductivity) with a variable jump length along the states localized near the Fermi level. The effect of electron irradiation on the electrical conductivity of single GaS crystals and the parameters of the states localized in their forbidden gap was studied. Taking into account the experimental data obtained in alternating and direct currents the density of states near the Fermi level and their energy spread, average hopping distances in the area of activation hopping conductivity, as well as the activation energy of jumps, are estimated in both pure and electron irradiated GaS crystals.
70-76
Hydrogen Evolution Reaction in an Alkaline Solution via ε-Fe3N Phase Formation on AISI 316 Stainless Steel by Plasma Treatment
Abstract
Surface modification techniques can be used to enhance the use of low-cost materials in water electrolysis applications, improving their hydrogen evolution efficiency and life. In this work, a well-known AISI 316 stainless steel was treated with nitrogen direct current glow discharge plasma for the periods of 2, 3, 4, and 5 hours. The ε-Fe3N phase was created from the first plasma treatment period, as detected by the X-ray powder diffraction and X-ray photo-electron spectroscopy investigations. To understand the effect of the ε-Fe3N phase formation and growth on the hydrogen evolution rate and mechanism both the electrochemical and electro-chemical impedance spectroscopy measurements were done. Advanced plasma treatment over time and enhanced ε-Fe3N phase growth were found to decrease the Tafel slope, over-potential, and polarization resistance, which contributes to improving the hydrogen evolution reaction properties of AISI 316 stainless steel. A lab scale electrolyzer equipped with a distilled water displacement attachment was prepared to evaluate the HER practically. The contact angle was measured to find an evidence on the effect of the advanced plasma treatment on the surface hydrophilicity.
77-83
Effect of Parameters of Liquids on Amplitudes of Pressure Waves Generated by Electric Discharge
Abstract
An experimental study is performed on the effect of hydrostatic pressure, temperature and specific electric conductivity of a liquid on the amplitude of a pressure wave generated by an electric discharge in a liquid during the electric discharge treatment of oil wells. The results show that with an increase in hydrostatic pressure the amplitude of the generated pressure wave decreases. The use of a fluid with a conductivity of 0.53 S/m as a working medium (which is close to the value of a specific conductivity of the produced water) decreases (up to 67%) the amplitude of the pressure wave. During the treatment of the oil wells using the electric discharge immersion device, it is necessary to use a scheme with a closed electrode system, since in this case the treatment efficiency is independent of the electric conductivity of the downhole fluid.
84-88
Influence of Some Axially Symmetric Stepped Forms of Discharge Chambers on the Efficiency of Electrohydraulic Forming
Abstract
A mathematical simulation of the electrohydraulic forming using some types of stepped axisymmetric discharge chambers is performed. The mathematical model is tested on the basis of experimental data obtained using the optical method of measuring the deflection of a plate. It is shown that a change in the shape of the discharge chamber can significantly affect the efficiency of electrohydraulic forming with the same parameters of the discharge circuit. It is found that the conical discharge chamber provides the highest forming efficiency.
89-96
The Inhibitive Action of Some Diazole Derivatives on the Corrosion of 304 Stainless Steel in HCl Solution
Abstract
The effect of the addition of some diazole derivatives on the corrosion of stainless steel 304 (SS 304) in hydrochloric acid (HCl) was investigated using such methods as weight loss (WL), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS) and electrochemical frequency modulation (EFM) measurements. The inhibition efficiency (% IE) increases with increasing the inhibitor concentration, but decreases with increasing the temperature. The studied compounds are adsorbed chemically on the SS 304 surface following the Langmuir adsorption isotherm. Potentiodynamic polarization studies showed that those compounds are mixed type inhibitors. The quantum chemical calculation was applied to elucidate the adsorption mode of the inhibitor molecule onto the SS 304 surface. The results obtained from different techniques are in good agreement.
97-108
Sodium Titanate for Sodium-Ion Batteries
Abstract
First research related to the intercalation of sodium atoms into the structure of the host material emerged in the early 1980s. Since that time, the development of sodium-ion batteries continues. In the last decade, a considerable attention is aimed at sodium-ion batteries with the context of renewable energy sources. The consumption of non-renewable resources like oil or coal resulted in an increasing problem related to the production of greenhouse gases. The main solution to this problem is the generation of energy by renewable energy sources like wind, sun, or hydropower. Solar and wind energies are among non-dispatchable energy sources, i.e. the energy cannot be dispatched at a request of the power grid or the plant owner according to current needs. Renewable energy sources need energy storage devices for energy accumulation. Batteries play a crucial role in that application. Sodium-ion batteries present a promising solution that can deliver low-cost, environmentally friendly energy storage for sustainable development of the human society. This manuscript provides a brief introduction into the field of sodium-ion batteries and describes a simple preparation method of a negative electrode material for sodium-ion batteries that is based on sodium-titanate ceramics—NaTiO.
109-113
Electrophysical Characteristics of Composite Nonlinear Resistors Based on Polymer and Silicon
Abstract
This work presents the results of studies of the volt-ampere characteristic, resistivity, as well as infra-red spectra and X-ray diffraction patterns of composite resistors (varistors) based on polypropylene and monocrystalline silicon. The effect of the composition of the components of the composite on the voltampere characteristics, the resistivity values, and the nature of the infrared and X-ray spectra was found.
114-117