Investigation of the influence of the mode of heat treatment of the initial powder on the efficiency of sintering zirconium ceramics by dilatometry

Using methods of synchronous thermal and X-ray structural analyzes applied to zirconium dioxide powders partially stabilized with yttrium obtained by chemical coprecipitation the processes of dehydration of these powders during annealing in air have been investigated. Using the dilatometry method, the regularities of compaction of powder compacts have been investigated with thermal sintering. It was found that the resulting powders mainly consist of the tetragonal modification zirconium dioxide and are nano-sized. The average particle size was 25 nm. The resulting powders are characterized by a high degree of agglomeration. It is shown that an increase in the thermal annealing temperature from 500 to 700ºС leads to partial baking of individual particles inside the agglomerate, and causes the formation of hard agglomerates, the presence of which complicates the processes of compaction and subsequent sintering. The presence of such agglomerates prevents the production of ceramics with high mechanical characteristics: density and porosity. Thermal annealing temperature increase leads to a decrease in the density of the sintered ceramic and a decrease in its hardness.

Prototyping of a concrete maturity sensor with a hermetically sealed housing made of two-component plastic

The construction industry, traditionally considered quite conservative, is now going through a marked change. With competition intensifying, companies have begun to gradually adopt various digital technologies to reduce construction costs, such as the wireless concrete monitoring sensors, which implement a temperature-strength monitoring method for concrete. Each device has its technological features, which are considered in the development of the concepts. Enclosure design is the most important stage of product development. An enclosure made in-house has many advantages and disadvantages. The most important part of the design of an electronic device enclosure is the preliminary research stage. This article presents features of wireless monitoring sensor enclosure design. A data acquisition station (DAS), also referred to in the network topology as a “gateway”, will be used to collect data from the wireless monitoring sensor over the selected protocol. The server application was created based on HTML, PHP, CSS, JavaScript. Testing of the wireless monitoring sensor, SDS, and the server application working together showed full functionality. A study is also given on the determination of concrete strength using the developed sensor according to the ASTM method and using the IPS MG 4.0 by GOST.

Determination of the reduced electric field in surface dielectric barrier discharge plasmas

In this paper, the experimental determination of the reduced electric field (E/n) in plasma of dielectric coplanar surface barrier discharge (DCSBD) at atmospheric pressure was demonstrated. The plasma characteristics and the experimental setup properties were described, and the optical emission spectrum of the plasma was also measured. The results of optical emission spectroscopy showed the presence of nitrogen molecular bands in the emission spectrum of DCSBD. In particular, the second positive and the first negative systems, as well as low intensity OH and NO lines were identified. The main transport properties of electrons, such as mobility, mean average energy, and diffusion coefficients were calculated using the BOLSIG+ open source software. The dependence of the ratio of intensities of the nitrogen spectral lines on the reduced electric field, the dependence of the E/n on plasma power, and the dependence of the electron energy distribution function (EEDF) on E/n were obtained. An algorithm in the form of a block diagram for determining the reduced electric field by the BOLSIG + program and experimentally measured spectral line intensities are presented. The utilized method is quite simple, accessible and versatile.

High entropic coatings FeCrNiTiZrAl and their properties

In our proposed empirical model, the anisotropy of the surface energy and the thickness of the surface layer of the high-entropy FeCrNiTiZrAl alloy are calculated. The thickness of the surface layer of this alloy is about 2 nm, which is an order of magnitude greater than the thickness of the surface layer of complex crystals, but is of the same order of magnitude as that of metallic glasses. The hardness and other properties of the high-entropy alloy are the same as for metallic glasses, but are 2-3 times higher than the hardness of stainless steels. The surface energy of the high-entropy FeCrNiTiZrAl alloy is about 2 J/m2, which corresponds to the surface energy of magnesium oxide and other crystals with a high melting point. However, unlike these crystals, the friction coefficients of a high-entropy alloy (~ 0.06) are much lower than that of ordinary steels (~ 0.8). We have theoretically shown that the friction coefficient is proportionally dependent on the surface energy and inversely proportional to the Gibbs energy, which significantly decreases for a high-entropy alloy, leading to low friction. The high hardness and low coefficient of friction of the high-entropy alloy facilitates the deposition of coatings from them on structural metal products, which contributes to their widespread use.

Photocatalytic water splitting of nanocomposite materials based on TiO2 and rGO nanorods

The paper presents the results of a study of films formed by titanium dioxide nanorods and deposited on their surface of reduced graphene oxide by electrochemical deposition. Nanostructured films based on TiO2 nanorods were prepared in a 100 ml stainless steel autoclave with a fluoroplastic insert from a solution containing 35 ml of deionized water (H2O), 35 ml of hydrochloric acid (HCl) (36.5 %, Sigma–Aldrich) and 0.25 ml of titanium butylate C16H36O4Ti (97 %, Sigma–Aldrich). The addition of reduced graphene oxide to the structure of titanium dioxide nanorods increases the specific surface area of nanostructures from 29.3 m2 /g to 63.1 m2 /g. Calculations based on the film impedance spectra have shown that the optimal deposition time of reduced graphene oxide on the surface of TiO2 nanorods is 3 minutes, since it has a low recombination coefficient and a long electron lifetime. Studies of the photocatalytic activity of nanomaterials and registration of the released hydrogen and oxygen gases have shown that when the films are irradiated for 5 hours, the amount of hydrogen released varies from 50 to 225 mmol/cm2 .

Processing of industrial waste by plasma-chemical method

In this paper, the results of the processing of magnesium fluoride by plasma-chemical method to obtain periclase and a solution of hydrogen fluoride (hydrofluoric acid) were presented. For the industrial implementation of plasma technologies, it is necessary to study the main parameters of plasma processes for obtaining reducing gases and processing metal oxides with them, to solve the issues of their hardware design, to increase the service life of plasma torches for their use in continuous metallurgical processes. The purpose of this work was to determine the conditions for the plasma-chemical process of processing magnesium fluoride. Thermal analysis of magnesium fluoride on a TGA/DSC2 thermogravimetric analyzer was performed. Thermogravimetric analysis showed that in the temperature range under consideration the process is endothermic, and at a temperature of ~1280°C a phase transition of the 1st kind is observed due to the melting of magnesium fluoride. The fractional composition of MgF2 and MgO powders was studied using the Analysette-22 Nanotech laser diffraction analyzer. The results of the evaluation of the fractional composition of powders have a significant difference. At the same time, the convergence of the data obtained using laser diffraction and electron microscopy methods was found.

Acoustic-electrical testing of defects in the cement-sand and cement-glass model samples

A complex method of acoustic-electrical testing of defects in dielectric samples made from cement-sand and cement-glass mixtures is discussed. The paper reports the results of studies of changes in the parameters of electromagnetic responses and their spectra under pulsed deterministic acoustic excitation of model samples with defects in the form of solid-state inclusions. The results of mathematical calculations of the time variation in the stress-strain state induced in a defective dielectric model sample by deterministic acoustic pulse are presented. The relationship is shown between the parameters of the acoustic excitation and the electromagnetic response to the impact in a magnetic field. The study revealed that the specific electrical resistance of the cement-sand and cement-glass mixtures differs significantly. Excitation of electrical double layers by acoustic pulses causes an electromagnetic signal, parameters of which depend on the parameters of the acoustic impact and acoustic and electrical properties of the material. As a result, a reduced specific electrical resistance of the mixture increases its conductivity. The numerical calculation of the propagation of the deterministic acoustic pulse showed that its parameters change when it passes through a defect with acoustic impedance different from that of the mixture used.

Influence of surface structure and morphology of PEDOT: PSS on its optical and electrophysical characteristics

This paper presents the results of a study of the effect of modification of the structure of the PEDOT: PSS polymer with hole conductivity on the optical and electrophysical properties of an organic solar cell. It was found that the modification of a polymer film with ethyl and isopropyl alcohols leads to a change in the morphology and roughness of the film surface. It has been determined that annealing of films in alcohol vapor promotes the formation of more uniform films. It is shown that upon modification of the PEDOT: PSS film in alcohol vapor the absorption spectrum shifts the absorption maximum of PEDOT to the short-wavelength region of the spectrum, the absorption of the aromatic PSS fragment decrease. X-ray phase analysis showed that after surface modification with alcohol vapor, the PEDOT and PSS chains change their structure. It is shown that the structural features of the surface morphology of PEDOT: PSS affect the electrophysical parameters of the films, such as the effective extraction rate and the effective time of flight of charge carriers. It was found that the modification of the surface of the PEDOT: PSS film leads to an improvement in the electrical transport properties of the films.

Influence of a rough surface on the aerodynamic characteristics of a rotating cylinder

The article considers the influence of the relative roughness of a cylindrical blade on aerodynamic characteristics. It is known that the operation basis of blades under consideration is the Magnus effect, which is characterized by appearance of a lifting force (Magnus force), when the cylinders rotate in a transverse flow. This force is used to rotate the wind wheel, similar to lifting force, but can have a much larger value when selecting optimal conditions, both geometric and aerodynamic. The authors conducted a comparative analysis of cylinder layout with a relative roughness (0.005 ÷ 0.02). Experimental studies of aerodynamics process of rotating cylinders were carried out in the aerodynamic laboratory using the T-1-M wind tunnel at an air flow value of 5 to 15 m/s. Graphs of dependences of rotating cylinder's lifting force and drag force on the changing air flow velocity and on relative roughness, k/d, are obtained. For further study experimental cylinder layout’s aerodynamic parameters, the most optimal is the variant with a relative roughness value of 0.02, which had high indicators, was selected. In the course of experimental studies, graphs of the dependence of the values of lift and drag force on the angles of attack of a single rotating cylinder with a rough surface on the speed and angle of attack of the wind flow (0°, 30° and 60°) were obtained. It is established that the effective angle of attack is 0°, at which aerodynamic characteristics’s maximum values were obtained.

Statistical evaluation of morphological parameters of porous nanostructures on the synthesized indium phosphide surface

A constructive method for estimating the surface morphology of nanostructured semiconductors, which consists in determining the main statistical characteristics of the aggregate structure of nanoscale objects on their synthesized surface is presented. In terms of the indium phosphide semiconductor with a synthesized porous layer on its surface, it is shown that the evaluation of the main statistical characteristics allows a deeper understanding of the kinetics of the pore formation process during typical electrochemical treatment of the crystal. The determination of the main statistical metrologically based characteristics (indicators of the distribution center, variation, and shape of the distribution) allows us to understand in more detail view the processes occurring during electrochemical processing of crystals. In the long run, this will make it possible to create nanostructures with predetermined properties, which will become the basis for the industrial production of high-quality nanostructured semiconductors.