Surface Engineering and Applied Electrochemistry最新文献

In blade-to-plane electrostatic precipitators at variable temperatures, the electric field and the current density distributions of the negative DC corona were experimentally analyzed, and the corona discharge was used as the source of ionization. In this research, an experimental cell was designed and built to adjust the temperature from 20 to 46°C within the cell. The current density-voltage characteristic and the radial distance distribution of the current density of an electrostatic blade-to-plane precipitator were measured over a temperature interval. Based on the Tassicker and Townsend models, the electric field and the onset voltage were determined. With the rise in temperature, the corona current obtained at the collector plate has been observed to increase, but the onset voltage decreased. The applied voltage and temperature greatly affected the corona current density characteristics and the electrical field. If an exponent of 4.6 to 5 for a negative corona discharge is taken, the DC density distribution is satisfied, then the current density distribution follows the well-known Warburg theorem.

The existence of the phenomenon of the electrochemical phase formation in metals and alloys via a supercooled liquid state stage is further discussed. In order to experimentally verify the existence of the phenomenon in point, the density of metal deposits subjected to the action of a centrifugal force applied perpendicular to the crystallization front during the electrodeposition process was studied. For this purpose, an installation and electrochemical cells were developed and manufactured, which ensures of metals electrodeposition under the conditions of a low force impact, in the field of a centrifugal force, in particular. The performed experiments identified the effect of an increase in the density of metal deposits under a low force superimposed perpendicular to the crystallization front during the electrochemical phase formation. This effect was confirmed by a decrease in porosity and a decline in the intensity of the X-ray diffraction maxima from the metal electrodeposits obtained under the impact of the conditions mentioned above. The identified effect is another proof for the existence of the phenomenon under discussion.

The paper deals with a symmetric problem on the basis of physically substantiated estimates of the processes of electromagnetic-acoustic transformations (EMAT) of energy during the flow of an electric current through a melt and the key parameters of the open problem of the system “Power source parameters–Parameters of the magnetic field and magnetic pressure of the skin layer–Parameters of acoustic disturbances.” When formulating the EMAT problem in technological applications, it was shown that the key parameter is the geometry of the container with the object of processing and the material of the mold. When solving the problem, it is the parameter of the skin layer and the time dependence of the discharge current. It was established that the part of energy during the formation of the magnetic pressure in the skin layer from the amount of the energy stored in the capacitor bank of the pulse current generator is approximately 10^–4–10^–2. The value of this part depends on the period of the discharge current and is proportional to the (sqrt T ). When acoustic disturbances propagate in the melt, the main share of energy losses is determined by the difference in the acoustic rigidity of the melt and the shape of materials. The frequency spectra of the pressure of sound waves at the parameters selected for the analysis can cover the range of up to hundreds kHz, which is a good reason for the realization of resonance effects and the active formation of dissipative structures. Attention is focused on the fact that the EMAT effects are manifested in the melt not only under the influence of an acoustic field but also under that of an electromagnetic one in the skin layer. They are separated in time, but the acoustic field can occupy the entire volume of the melt and its effect is longer in time.

The conceptual directions of creating functional composites based on polymer matrices for metal–polymer systems are considered. An algorithm has been developed to develop a methodology for the implementation of the nanostate phenomenon in materials science and technology of composites and metal–polymer systems. The methodological principles of the implementation of the nanostate phenomenon in materials science and the technology of functional materials based on polymer matrices for metal–polymer systems with high performance characteristics are proposed.

Potentiodynamic polarization, electrochemical impedance spectroscopy, mass loss, and hydrogen evolutions techniques were used to investigate the effect of the plant extract Cystoseira myrica as corrosion inhibitor for aluminum in 1 M HCl. All those measurements showed that the effectiveness of inhibition increased with an increase in the extract dose and in temperature. The inhibition efficiency of the extract reached 93.7% at 300 ppm, 25°C. Thermodynamic parameters of activation and adsorption were computed and discussed. Polarization curves showed that the extract studied behaves as mixed kind inhibitor. The Langmuir adsorption isotherm was obtained for the adsorption of the extract on the Al surface. Using the mass loss technique, it was revealed that adding KI enhances inhibitory efficiency from 77.3 to 91.6% owing to the synergistic effect. The surface analysis of aluminum was performed using different techniques. All other data approached were compatible and in line with each other.

The corrosion rate of mild steel in hydrochloric acid and in sulphuric acid was determined by potentiodynamic polarization and electrochemical impedance spectroscopy in 0.5 M concentrations of HCl and of H₂SO₄ using 4-hydroxy n-[2-methoxy naphthalene methylidene] benzohydrazide (HNBH) as an inhibitor The inhibition efficiency of HNBH for the corrosion mitigation of mild steel was studied by varying the concentration of the inhibitor and temperature. It was found that the inhibition efficiency of HNBH increased with increase in the inhibitor concentration in both media. The maximum of 80% inhibition efficiency at the optimum inhibitor concentration of 2.5 × 10^–4 M was achieved. However, with an increase in temperature, the inhibition efficiency decreased. The corrosion inhibition by HNBH took place through physisorption. The adsorption isotherm fitting with the experimental data was identified to find out the mechanism of inhibition. The results indicated that HNBH functions as mixed type inhibitor and follows the Langmuir adsorption isotherm. The surface of the specimen was analyzed using scanning electron microscopy.

The analysis of dielectric materials that can be used as a working dielectric of a monoblock multifunctional high-voltage pulse capacitor is carried out. In particular, the properties of liquid dielectrics that can be used as an impregnating dielectric are considered. The properties of a polypropylene film, which is recommended for manufacturing capacitors with a high repetition rate of charges-discharges, are studied as well. Some recommendations are made for the use of dielectrics for the dielectric system of a monoblock multifunctional high-voltage pulse capacitor.

Diabetes is a chronic condition in which the body cannot produce or effectively utilize the produced insulin. Insulin is a hormone that regulates the blood glucose level (BGL). The long-term increased BGL can have serious health effects. Time-based monitoring of BGL is necessary for diabetic patients to avoid severe health conditions. For this purpose, a non-enzymatic electrochemical sensor for the non-invasive detection of glucose was prepared and tested in the framework of this research. The sensor was developed by combining the features of a molecularly imprinted polymer (MIP) and the highly conductive nature of polyaniline (PANI) and copper oxide nanoparticles (CuONPs). The CuONPs were electrodeposited onto the bare graphite electrode in the presence of 1.8 M H₂SO₄ solution. Using aniline as the monomer in presence of 0.5 M H₂SO₄, the copper oxide-coated pencil graphite electrode was electropolymerized to obtain a non-imprinted polyaniline/copper oxide-coated graphite electrode. Glucose was added to the electrolytic solution for the preparation of a molecularly imprinted polymer electrode. Cyclic voltammetry and amperometry were used to characterize the electrochemical response of the modified electrode in the presence and in the absence of glucose, as well as the selectivity of the sensor towards glucose detection in the presence of the interfering species. The morphological characterization of the fabricated electrode was investigated using scanning electron microscopy, Fourier transform-infrared spectroscopy, 3D surface profilometry, X-ray diffraction spectroscopy, and goniometry. From the electrochemical and morphological characterization results, it was inferred that the modified graphite electrode possesses imprinted sites, which helps to increase selectivity towards glucose sensing.

The results of experimental study of pressure waves produced during electrical discharges in water initiated with a thin-layer copper conductor in the form of a nylon thread coated with a thin copper layer are presented. The experiments are performed in two different modes that provide discharges of shorter and longer periods. Use of the thread with a thin copper layer is a promising approach to initiating electrical discharges in water because it allows the shorter prebreakdown stage, lower prebreakdown energy losses, spatially more stable discharges, and improved effectiveness of discharge impact. The amplitude of pressure waves produced during short electrical discharges is comparable to that observed when using a thin solid copper conductor for initiation, with the amplitude of generated pressure wave growing exponentially with the wire length: more than a twofold increase in the amplitude is observed as the wire length increases from 20 to 50 mm. Similarly, it is shown that the thread with thin copper layer has a good stability under the conditions prevailing during electrical discharges in water.