Electrophysical Properties Research Articles

The effect of the carbon material content on the electrophysical and optical properties of NiMoO4/C composites

The aim of the work is to establish the dependences of the electrophysical and optical characteristics of NiMoO4/C composites from the content of carbon material. Experimental data and their analysis by Raman and impedance spectroscopy were used to achieve these goals. As a result of studies the numerical values of electrical conductivity at direct current and activation energy of the materials under study have been determined. The shift of the maximum G-band of composites to the high-frequency region in Raman spectra testifies to the formation of interfacial covalent bonds between NiMoO4 and carbon material in the process of hydrothermal synthesis.

Point Defects of Bismuth in TlInTe2 Crystals: Electrophysical and Dielectric Properties of Solid Solutions

Point Defects of Bismuth in TlInTe2 Crystals: Electrophysical and Dielectric Properties of Solid Solutions

Electric Tunable Structures Based on BaZr<sub>x</sub>Ti<sub>1–x </sub>O<sub>3</sub> and BaSn<sub>x</sub>Ti<sub>1–x</sub>O<sub>3</sub> Solid Solutions for Microwave Applications

Introduction. An experimental study of the structural and electrophysical properties of multicomponent films of solid solutions of barium titanate-zirconate and barium titanate-stannate on sapphire substrates has been carried out. These materials are an alternative to the more studied barium-strontium titanate for use in microwave technology, due to the relatively high controllability. In this paper, it is shown that when using post-post high-temperature annealing, films with a component composition close to the composition of the sprayed targets are formed on the substrate. Optimal deposition temperatures of thin films of barium titanate-zirconate and barium titanate-stannate have been determined to obtain the best electrophysical parameters.Aim. Investigation of structural and microwave properties of BaZrxTi1-xO3 (BZT) and BaSnxTi1–xO3 (BSnT) films on dielectric substrates. These ferroelectric materials are promising in terms of losses and nonlinearity, and the formation of planar structures based on these materials on a dielectric substrate allows for a significantly higher level of operating power of the microwave device.Materials and methods. The crystal structure and phase composition of the obtained films were studied by X-ray diffraction using a DRON-6 diffractometer on the emission spectral line CuKa1 (λ = 1.5406 Å). Capacitance C and Q-factor (Q = 1/tg δ) of capacitors were measured at frequencies of 1 and 3 GHz using a resonator and an HP 8719C vector analyzer.Results. It is established that high-temperature annealing after film deposition has a significant effect on the crystal structure, phase composition of films and their electrical characteristics. For the first time, a low level of dielectric losses of planar capacitive elements based on titanate-stannate and barium titanate-zirconate films in the frequency range of 1…60 GHz with acceptable controllability has been demonstrated.Conclusion. The results obtained indicate the prospects of using thin ferroelectric films of BaSn0.5Ti0.5O3 and BaZr0.5Ti0.5O3 solid solutions in microwave devices.

Hydrothermally synthesized hierarchical Ce1-xSmxO2-δ oxides for additive manufacturing of planar solid electrolytes

This paper studies the hydrothermal synthesis of Ce1-xSmxO2-δ (x = 0.20, 0.25 and 0.30) oxides in the form of hierarchically structured nanopowders (the crystallite size was 9–11 nm). The thermal behaviour of cerium and samarium hydroxocarbonates, formed as intermediate products, was studied using synchronous TGA/DSC/DTA analysis; and with the help of an X-ray diffraction analysis (XRD), and infrared spectroscopy, their transformation process, which resulted in the formation of target oxides, was evaluated. It was shown that an increase in the samarium concentration leads to a change in the type of microstructure from nanorods to microspheres partially or fully covered by nanosheets. The influence of the particle size and shape of the nanopowders obtained on the microstructure of the coatings (porosity, degree of roughness, and height difference), formed using microextrusion printing, were investigated by atomic force (AFM) and scanning electron (SEM) microscopy. The electrophysical properties of the oxide coating surface were evaluated using specialized semi-contact AFM techniques. The use of impedance spectroscopy made it possible to evaluate the effect of dopant concentration on the electrical conductivity of hierarchically organized solid electrolytes, and to show that microextrusion printing can be effectively used in the additive creation of planar components for alternative energy devices.

Obtaining Al–Zr-Hf wire using electromagnetic casting, combined rolling-extrusion, and drawing

The article presents the results of obtaining an aluminum electrical wire with a diameter of 0.5 mm from alloys of the Al–Zr-Hf system used in aircraft. Alloys of three compositions were cast in the form of a billet with a diameter of 12 mm using the method of electromagnetic crystallization. Next, the rheological characteristics of billets from experimental alloys were studied. The obtained data were used to simulate the process of combined rolling-extrusion when obtaining a rod with a diameter of 5 mm from a billet with a diameter of 12 mm using the Deform 3D program. A comparison of the experimental forces and forces during the simulation is made for the forces acting on the rolls and the die of the CRE-200 unit. At the next stage, experimental studies were carried out to obtain rods based on simulation data. The obtained rods with a diameter of 5 mm were subjected to drawing or sectional rolling with drawing and intermediate annealing to obtain a wire with a diameter of 0.5 mm. At all stages, the mechanical (ultimate tensile strength, yield strength, elongation to failure and area reduction) and electrophysical properties (electrical resistivity) of the obtained deformed semi-finished products were studied.

Fluorographene and Its Composites: Fundamentals, Electrophysical Properties, DFT Studies, and Advanced Applications

AbstractFluorographenes (FGs) are the youngest family of graphene derivatives 2D layer‐structure, which has changed the hybridization state from sp2‐to‐sp3 carbon and unique CF bonds impacting physical and chemical properties. Due to various types of CF bonds, wide bandgap, tunable F/C ratios, and unique nanostructure, the FGs show attractive physicochemical properties. Owing to the extraordinary properties, the researchers have recently paid attention to exploring FGs into fluorographene composites (FG‐Cs) as a potential candidate for fundamental advances in the field of the energy system, optoelectronic, biomedical, and aeronautics. Despite their promise, in‐depth experimental and theoretical studies of FGs over FG‐Cs are not explored systematically. This review focuses on the recent experimental developments on FGs and FG‐Cs, including fundamentals and electrophysical properties, synthesis methods, conductivity, hydrophobicity, and magnetic nature. Further, for the validation, the theoretical studies, first‐principle study/density functional theory emphasize their real intrinsic activity, stability, and effects of F content, defects, and doping mechanism. Finally, the wide applications, energy systems to biomedical and optoelectronics to the aerospace industry, along with challenges and future perspectives, are also discussed. This review aims to conclude valuable insights into the fundamental science and perspective toward highly efficient FG‐C‐based catalysts engineering in advanced applications.

Interaction of components of the mineral part of Kansko-Achinsk coals in chamber combustion technologies with regard to thermodynamic and kinetic factors

The paper considers the physical and chemical properties of ash and slag waste generated in boilers of different types. Various literature sources and the results of industrial research conducted by the author are analyzed. Factors, influencing the properties of ash and slag wastes are formulated and considered. Issues to be solved for additional use of ash from Kansko-Achinsk coals (KAC) are formulated and partially considered in terms of reducing sulphur dioxide emissions. The article shows the possibility and expediency of low-temperature flaring of KAC (at temperatures of 1450 K) and the additional use of ash in technologies of chamber combustion, as well as the necessity of taking into account the changes in the electrophysical properties of ash produced during combustion with a high fraction of SO2 binding is shown. For the sulfur dioxide (SO2) binding reaction, the kinetic and differential equations are compiled and solved. Based on the solved equations, the efficiency of ash recirculation to the upper part of the cooling chamber of the BKZ 320-140 boiler was evaluated.

Impurity-impurity interaction during the growth of UMG-Si-based mc-Si

This article investigates the relationship between the chemical composition and electrophysical properties of p- and n-type multicrystalline silicon ingots based on metallurgical silicon with a purity of 99.99 at.%. In particular, the role of impurity-impurity interactions in the production of multisilicon by the Bridgman vertical method is evaluated in order to identify approaches to controlling this process effectively. The phase equilibrium calculations in the “silicon–all impurities” and “silicon-impurity-oxygen” systems were carried out based on the Gibbs energy minimization in the Selector software package. The study investigates the rank correlations of the concentrations of various impurities with each other, as well as with the specified electrical resistivity (SER) and the lifetime of nonequilibrium charge carriers (NCC) in the direction of crystal growth. Pair correlations of the element distribution profiles were considered based on the role of the main factor represented by the ratio of individual impurity solubilities in solid or liquid silicon (k0), as well as from the standpoint of direct interaction between two elements. It was found that the k0 value for two individual impurities in silicon does not automatically lead to the pair correlation of their distribution profiles in the ingot. A significant effect on the distribution profiles of impurities in multisilicon with k0→0 has the factor of binding some part of the impurity into such a form that this impurity can be incorporated easily into a growing crystal. Binding may be induced by the interaction of the impurity in the melt with the oxygen background, its segregation at the grain boundaries, and its capture by the crystallization front in the composition of the liquid inclusion. Significant correlations of impurity distribution profiles in the ingot were demonstrated by the pairs whose elements interact without the formation of chemical compounds in the 25–1413 °C temperature range. The conducted phase equilibrium calculations for the “silicon–all impurities” system revealed the possibility of forming the VB2, TiB2, ZrB2, and MgTiO4 solid phases in the melt.

Modification of Electrophysical Properties of Dense Anodic Alumina by Surfactant Addition to Anodizing Electrolyte

Modification of Electrophysical Properties of Dense Anodic Alumina by Surfactant Addition to Anodizing Electrolyte

Influence of Electrohydrodynamic Flows on the Intensification of the Heat- and Mass Trasfer Processes. Part 2. One- and Multistage Electrohydrodynamic Pumps

The one-stage electrohydrodynamic (EHD) pumps with electrodes “a diaphragm – a plate with a hole” and “a wire – a plate with a hole” are studied. It is established that with the help of flow-limiting diaphragms, the pump characteristics can be significantly improved. It is indicated that in the main multi-stage EHD pumps, it is preferable to use lattice-type electrodes made of bare and perforated insulated wires. Optimal geometrical parameters of electrodes, flow-limiting diaphragms, dielectric coatings, and interelectrode distances are determined. The influence of the electrophysical properties of the working medium and galvanically isolated high voltage sources on the performance of a multistage pump is considered. Possible ways to reduce the mutual influence of steps on its output parameters are shown. Formulas have been obtained that reliably fully reflect the physical nature of the results of studies of the characteristics of EHD pumps. It was found out that organosilicon liquid has the best characteristics and considering the stability of its properties under the influence of an electric field, micro-discharges, and temperature, it is recommended to use it as a coolant in EHD heat exchangers. The reasons for the deterioration of the pump characteristics during prolonged operation are identified, and ways to reduce the influence of these factors on the output parameters are noted.

ENSURING ELECTROMAGNETIC COMPATIBILITY OF MICROPROCESSOR DEVICES

The research is devoted to the problem of electromagnetic compatibility of toroidal chokes with microprocessor elements of printed circuit boards. The scientific novelty of the work lies in the determination of the most favorable option for the location of the chokes through the minimization function. The analysis of target vector functions and the most effective option is carried out. The purpose of the study is to determine the permissible location of the chokes, at which the electromagnetic interference, they create for the microprocessor elements of the printed circuit board, will be minimal. The object of the study is a printed circuit board of a microprocessor-based device for measuring the grounding resistance of supports of high-voltage power lines, in the power circuit of which toroidal chokes are used. The subject of this work is the electrophysical properties of toroidal chokes, which are sources of electromagnetic interference for microprocessor elements of control and measuring instruments. The research methodology consists in carrying out numerical experiments to calculate the electromagnetic field with subsequent analysis of the obtained vector functions of the magnetic field strength H on the board surface. The assessment of the influence of interference caused by chokes is carried out using the developed mathematical model and numerical methods for calculating the electromagnetic field. For computational calculations, the authors have developed a software algorithm implemented using the Delphi programming language. The choice of the mutual arrangement of the chokes on the microprocessor integrated circuit is carried out as a result of solving the optimization problem by the gradient method, taking into account the given restrictions on the condition of electromagnetic compatibility. To assess electromagnetic compatibility, a design model of a printed circuit board of a microprocessor device with toroidal chokes was developed. As a result of a numerical experiment, a method for automated determination of the location of toroidal chokes within an integrated microcircuit of resistance devices of the proposed control of electrodes of overhead power transmission line supports was tested. As a result of research, it was found that for electromagnetic compatibility of microelectronic devices, it is sufficient to place the toroidal chokes of power circuits closer to the corners of the printed circuit board. In other design cases, the EMC class 1 requirement is not met.

ELECTROMAGNETIC COMPATIBILITY OF CONTROL AND MEASURING CABLES IN NON-STATIONARY MODES

The article deals with questions of researching and analysis of voltages induced in protective shields of three-phase shielded conductor in modes of asymmetric short circuits external to generators of power station. The development of recommendations and measures to ensure electromagnetic compatibility of measuring circuits of microprocessor devices is an urgent research task, since it is generally determined by the electrophysical properties of the interference source and the analog-digital element base of the measuring part of the devices. The scientific novelty of the work consists in the development of measures to eliminate the induced electromagnetic influence on control and measuring cables switched to current and voltage measuring transformers. The purpose of the study is to assess the electromagnetic effect of the industrial frequency field on control and measuring cables laid near a phase-shielded current pipeline, as well as to develop measures to ensure their electromagnetic compatibility. The paper presents a method for calculating the distribution of the intensity modulus H of a magnetic field induced by an industrial frequency current from a generator at an electric power station. For the modes of single-phase, two-phase and two-phase short circuits to the ground, patterns of the distribution of the magnetic field intensity modulus H are constructed, a stiffness class is assigned according to the magnetic field effect on control and measuring cables in accordance with the classification. Recommendations to reduce the level of exposure to the magnetic field intensity H are given. In case of using the screen, a repeated calculation was performed to compare and determine the effectiveness of this event. As a result of numerical experiments, the effectiveness of the use of an additional screen as one of the measures to ensure electromagnetic compatibility is justified. The use of an additional steel shield makes it possible to reduce the magnetic field strength on the surface of control and measuring cables to acceptable values and, as a result, ensure reliable operation of microprocessor control, protection and automation devices.

Electrophysical properties of compensated n-Germanium

Measurements of the transverse magnetoresistance and the Hall effect of compensated n-Ge crystals in the weak and strong magnetic fields at liquid nitrogen temperature have been carried out. It was revealed that in crystals with a sufficiently high degree of compensation, the space charge regions play a significant role in the scattering of charge carriers, which cause an increase in the transverse magnetoresistance (with increasing H) and its linear dependence on H in the region of strong magnetic fields. It was shown that in sufficiently strongly compensated crystals, the scattering of current carriers by the space charge regions is practically isotropic. It was found that thermal annealing (350 °C; 60 h) of compensated oxygen-containing n-Ge, which significantly reduces the compensation degree due to the arising donor-type oxygen complexes, leads to a decrease in the slope of the field dependences of the transverse magnetoresistance in the quantizing magnetic fields.

Study of the effect of continuous loading and compaction on the electrical resistance of powder materials

The electrical conductivity of powder media depends on the composition, impurities, oxide films, morphology and the nature of the contact surface. We present the results of studying the electrical resistance of powder materials and their compounds under continuous loading by the four-contact method. The electrical resistance is determined using a special experimental cell. Industrial powders Al (ASD-1), Ti (PTK), Hf (GFM-1), soot and their mixtures, as well as TaC and HfC powders obtained by self-propagating high-temperature synthesis were studied. It is shown that an increase in the mechanical pressure up to 80 MPa leads to a decrease in the electrical resistance of the materials under study. The morphology of the particles (spherical or fragmentary shape), their dispersion affects the quality of the contact surface and, accordingly, the magnitude of the electrical resistance. Moreover, the electrical resistance of the material depends on the degree of cleaning of the particle surface from oxide films. The proposed method in combination with other analytical methods used for studying powder media allows us to reveal the regularities of this relationship, characteristic of all morphological features, composition and electrophysical properties of powders of various compositions under loading conditions. The results obtained can be used to select the optimal characteristics of consolidation by electric current depending on the initial pressure, as well as in case of high-voltage electric pulse consolidation of powder materials by spark plasma sintering and electrothermal explosion methods.

Changes in the crystal structure and electro physical properties of polycrystalline indium oxide when heated in air

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Silicon nanowire arrays synthesized using the modified MACE process: Integration into chemical sensors and solar cells

In this work, the influence of the technological process for metal-assisted chemical etching on surface morphology and electrophysical properties of obtained nanostructures has been investigated. It has been demonstrated that the obtained structures with a high aspect ratio could be used both in sensors and solar cells. It has been shown that application of the metal-assisted chemical etching (MACE) process enables to significantly improve the short-circuit current density in silicon solar cells (up to 29 mA/cm2). Also, the possibility of detection of hydrogen peroxide and glucose (via enzymatic reaction) by resistor-like sensors with nanostructured silicon as the sensitive area has been demonstrated with the sensitivity up to 2.5…2.75 mA/V•%.

Нелинейные эффекты в ячейке с твёрдым электролитом на основе протонированного полититаната калия

In this paper, the electrochemical and electrophysical properties of protonated potassium polytitanate synthesized at pH values varying from 3.11 to 8.88 depending on the magnitude of the polarization voltage and the magnitude of the measured signal were studied by the method of impedance spectroscopy. The values of effective conductivity, relaxation times, frequency dependences of the loss tangent, and dielectric permittivity are determined.

RELATİONSHİP BETWEEN ELECTRICAL AND CATALYTIC IN THE REACTION OF CONVERSION OF ETHANOL TO ACETONE

Low molecular weight ketones are among the most important products widely used in industry, however, the existing methods for their production are multistage. The significant disadvantages of these methods include the implementation of individual stages at high temperatures and pressures. As a result, the development of more economical and easy-to-implement processes is presented as an actual task for the basic organic synthesis industry. Recently, ethanol has been considered as a possible feedstock for the production of acetone. The prospect of using ethanol as a feedstock is due to the large renewable resources for its production. The growing interest in recent years in the production of ethanol by processing agricultural products and waste from the food and woodworking industries will undoubtedly stimulate further development of the method of producing acetone from ethanol. The catalytic conversion of ethanol to acetone is a relatively new method for producing acetone and, naturally, the number of publications devoted to this process is relatively small. In previously published works, as a rule, the issues of the mechanism of the process, as well as the relationship between the physicochemical and catalytic properties of the proposed active systems in these reactions, are not considered in detail. Active and selective catalysts were selected for the conversion reaction of ethanol to acetone, the mechanism of the process and the relationship between the physicochemical and catalytic properties of the activated sample were studied. The experiments were carried out on an active catalyst with the composition ZnO:CaO=9:1 The main provisions of the electronic theory of catalysis are developed in application to semi¬con-ductors, since, firstly, the theory of semiconductors is now more developed, and secondly, most of the catalysts used in practice belong to semiconductors. The surface of a semiconductor is the protection of two phases: a solid body-gas. The approach to this boundary from the side of the gaseous environment is essential for catalysis. The environment affects the surface and volume of the solid body. The influence of the environment is carried out through adsorption, as a result, the Fermi level shifts, and the electrophysical pro¬pert¬ies of catalysts change in the processes of adsorption and catalysis. Reactions of heterogeneous-catalytic transformation of low molecular weight alcohols are of great practical importance. The relevance of catalytic transformations of ethanol into various valuable products is the most important task of modern catalytic chemistry. To elucidate the mechanism of these reactions, a necessary step is to study the nature of the electronic interaction of reactants with a solid body, since the vast majority of catalysts of heterogeneous-catalytic oxidation - metal oxides, semiconductors, so especially promising is to involve methods for studying the electro physical properties of the surface. Changing these properties and studying the nature of their change in the atmosphere of the reactants, it is possible obtain valuable information about the nature of the electronic interaction of the reactant-catalyst. The works carried out in this direction showed that in most cases the process of chemisorption is accompanied by the appearance of an additional surface potential, indicating the charging of the surface in the presence of a particular reactant. The electrical and catalytic properties of a series of active zinc-calcium oxide catalysts were studied (their activity was also studied in previous experiments). The study of the electrical properties of the catalyst is of the greatest interest for elucidating the mechanism of reactions, since they can provide information about the nature of electronic transitions that limit the course of the reaction. The number of different factors determines the catalytic activity of a solid body. Each of these factors can correlate with certain properties of a solid body. When comparing catalytic and electrophysical properties electrical conductivity is most often measured. Measuring on the same catalyst sample under the same conditions of conductivity change can provide useful information about mechanism of action of the catalyst and the course of the catalytic reaction. Studies of the electrical conductivity of the synthesized catalysts have shown that all the catalysts studied are semiconductors. This article shows the relationship between the electrical and catalytic properties of zinc-calcium oxide catalysts. Keywords: catalyst, electrical conductivity, activation energy, adsorption, ethanol, acetone.

Effect of chemical modifications and coating with Cu-based nanoparticles on the electro-physical properties of jute fabrics in a condition of high humidity

The electro-physical properties of raw, alkali and oxidatively modified jute fabrics were investigated as complex phenomena of the interactions between the fabrics’ chemical composition, carboxyl group content, crystallinity, structural characteristics, moisture sorption, and frequency of the electric field. At 80% relative air humidity, chemically modified jute fabrics have 38–179% and 1.7–5.4 times higher dielectric loss tangent and effective relative dielectric permeability compared to unmodified. To further improve these properties, fabrics were treated with CuSO4 and Cu-based nanoparticles were in situ synthesized on their surfaces by reduction. A few smaller agglomerates of Cu-based nanoparticles were observed across the alkali modified fabric’s surface, while smaller irregularly shaped and larger agglomerates were distributed over the oxidatively modified fabric’s surface. Regardless of the type of synthesized nanostructures (metallic Cu, copper oxide (Cu2O or CuO) or their mixtures), excellent fabrics’ effective relative dielectric permeability is guaranteed. Precisely, exploitation in specific conditions that contribute to copper reduction will make jute fabrics able to store 21–163 times more energy from an external electric field than before the exploitation, which will extend their lifetime. On the other hand, with increasing the total content of Cu after the reduction and formation of agglomerates of Cu-based nanoparticles, the movements of cellulose, hemicelluloses, and lignin molecules become difficult resulting in lower energy dissipation within the chemically modified than within unmodified fabric. Applied chemical modification and coating with Cu-based nanoparticles enables designing fabrics with predictable electro-physical properties, which is very important from the application point of view.

Changes in the Crystal Structure and Electrophysical Properties of Polycrystalline Indium Oxide When Heated in Air

Changes in the Crystal Structure and Electrophysical Properties of Polycrystalline Indium Oxide When Heated in Air